Vacuum system for a brake booster

A vacuum system for the brake booster of a motor vehicle includes a demand-driven vacuum pump and a vacuum line connected on one end to the vacuum chamber of the brake booster and connected on another end to an intake port of the demand-driven vacuum pump. The vacuum system may include a discharge device arranged on an exhaust air opening of the vacuum system for ensuring bidirectional air volume flow between the external surroundings of the discharge device and the exhaust air opening of the vacuum system, which preventing liquids from reaching the exhaust air opening of the vacuum system as an air volume flows from the exterior surroundings into the exhaust air opening of the vacuum system. The vacuum system may also include a check valve arranged between the intake port of the demand-driven vacuum pump and the connection to a vacuum chamber of the brake booster.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to German Patent Application No. 202016007448.3, filed Dec. 7, 2016, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

This application pertains to a vacuum system for a brake booster of a motor vehicle.

BACKGROUND

Vacuum brake boosters are well established in automotive engineering and widely used, in particular, in a passenger cars and light-duty commercial vehicles. When the brake pedal is actuated, such brake boosters generate an auxiliary force that boosts an actuating force exerted upon the brake cylinder by the brake pedal. This auxiliary force is generated by a pressure differential between two chambers in the brake booster, which are separated from one another by a movable diaphragm. During such a pedal actuation, atmospheric pressure, i.e. an ambient pressure of the surrounding air, is adjusted in the first chamber by a valve control. A vacuum is generated in the second chamber or so-called vacuum chamber.

The intake section of an internal combustion engine, in which a vacuum is generated, for example by an air volume flow while a throttle valve is closed, conventionally serves as a vacuum source for the vacuum in the vacuum chamber. To this end, the intake section and the vacuum chamber are connected to one another by a vacuum line and corresponding check valves.

In modern engines such as diesel engines or hybrid drive systems, the air volume flow in the intake section of the internal combustion engine may be either insufficient or not permanently available as a vacuum source depending on the operating state of the drive system. As a result, it has become common practice to provide an alternative or supplementary vacuum source for brake boosters in an increasing number of vehicles.

An alternative or supplementary vacuum source may be realized in the form of a vacuum system with a demand-driven vacuum pump having an electric vacuum pump. In addition to the demand-driven vacuum pump, such a vacuum system includes at least one vacuum line, one check valve and, if applicable, an exhaust air line. The exhaust air line may be realized in the form of an exhaust air hose that is installed in the engine compartment of a motor vehicle. The exhaust air line is connected to an exhaust port of the demand-driven vacuum pump with its first end. Its second end is routed to a desired location in the engine compartment.

The vacuum line and the check valve enable the demand-driven vacuum pump to convey an air volume from the vacuum chamber into the engine compartment and therefore into the external surroundings of the vacuum system through the second end of the exhaust air line such that a vacuum relative to the external surroundings, i.e. the atmosphere, is generated in the vacuum chamber.

The demand-driven vacuum pump or an electric vacuum pump can be activated and/or deactivated as needed by a pressure sensor or a pressure switch that monitors the vacuum in the vacuum chamber. When the demand-driven vacuum pump is deactivated, the vacuum in the vacuum chamber is initially maintained by the check valve until the vacuum is consumed, for example, as a result of corresponding brake boosting processes.

At the deactivation moment of the demand-driven vacuum pump, the vacuum prevailing at the check valve is essentially identical to the vacuum in the vacuum chamber. The ambient or atmospheric pressure simultaneously prevails at the second end of the exhaust air line. After the air volume flow conveyed by the demand-driven vacuum pump has been interrupted, the pressure gradient between the check valve and the second end of the exhaust air line causes the vacuum system to be ventilated with ambient air from the second end of the exhaust air line up to the check valve via the demand-driven vacuum pump. In other words, the air required for ventilating the vacuum system is taken in from the engine compartment of the respective motor vehicle through the second end of the exhaust air line.

Investigations have shown that splash water, which enters the engine compartment of a motor vehicle while it is driven in heavy rain, through water or under similar operating conditions, can be taken in by the vacuum system during such a ventilation process. These investigations have furthermore shown that splash water taken in through the second end of the exhaust air line can damage the demand-driven vacuum pump. The same problem also arises if the vacuum system does not include an exhaust air line such that splash water would in this configuration be directly taken in by the exhaust port of the demand-driven vacuum pump.

SUMMARY

The present disclosure provides a vacuum system for a brake booster of a motor vehicle with a demand-driven vacuum pump, in which the intake of splash water can be suppressed.

According to an embodiment of the present disclosure, a vacuum system for the brake booster of a motor vehicle includes a demand-driven vacuum pump and a vacuum line. The vacuum line is configured to be connected to the vacuum chamber of the brake booster and connected to an intake port of the demand-driven vacuum pump.

According to an embodiment of the present disclosure, the vacuum system may include a discharge device that is arranged on an exhaust air opening of the vacuum system. The discharge device is configured to ensure a bidirectional air volume flow between the external surroundings of the discharge device and the exhaust air opening of the vacuum system. The discharge device is configured to prevent liquids from reaching the exhaust air opening of the vacuum system while an air volume flows from the exterior surroundings into the exhaust air opening of the vacuum system. In this regard, the discharge device therefore makes it possible to ventilate, in particular, the vacuum pump with air from the exterior surroundings after a deactivation.

According to another aspect of the present disclosure, a check valve may be arranged between the intake port of the demand-driven vacuum pump and the connection to a vacuum chamber of the brake booster. To this end, the vacuum line may be divided into two vacuum line sections. The check valve is integrated into the vacuum system between the vacuum line sections in this case. The check valve may alternatively also be arranged on the intake port of the demand-driven vacuum pump such that the vacuum line is indirectly connected to the intake port of the demand-driven vacuum pump via the check valve. The check valve is configured to allow an air volume flow from the connection to a vacuum chamber of the brake booster in the direction of the demand-driven vacuum pump and for blocking an oppositely directed air volume flow. The admission of an air volume flow with the ambient pressure into a vacuum chamber of the brake booster, which is connected to the vacuum line, is thereby prevented.

According to another aspect of the present disclosure, the discharge device may include a housing that encloses a chamber. The chamber of the discharge device forms an air volume reservoir and therefore makes available an air volume that suffices for ventilating the vacuum system between the exhaust air opening of the vacuum system and the check valve as soon as the demand-driven vacuum pump is deactivated. The chamber provides the sufficient air volume for partially ventilating the vacuum system irrespective of a potential intake of splash water at the exhaust air opening of the vacuum system.

According to another aspect of the present disclosure, a first volume corresponding to the chamber of the discharge device is larger than or equal to a second volume corresponding to a working volume of a section of the vacuum system, which extends between the check valve and the exhaust air opening of the vacuum system. The term working volume refers to a fluidically active internal volume of the vacuum system that, for example but not conclusively, is defined by the inside diameter and line lengths of the vacuum line and, according to an enhancement of the present disclosure, an exhaust air line, as well as the internal volume of a conveying device of the demand-driven vacuum pump.

If the first volume is chosen greater than or equal to the second volume, sufficient air for ventilating the vacuum system between the exhaust air opening of the vacuum system and the check valve is also available if the region of the second end of the exhaust air line is completely immersed in water during the entire ventilation time.

According to another aspect of the present disclosure, the vacuum system may include an exhaust air line that is configured to be installed in the motor vehicle. A first end of the exhaust air line can therefore be connected to an exhaust port of the demand-driven vacuum pump. In this embodiment of the present disclosure, a second end of the exhaust air line forms the exhaust air opening of the vacuum system, which is connected to the discharge device. The discharge device may alternatively also be connected to the exhaust port of the demand-driven vacuum pump such that an additional exhaust air line can be eliminated. In this case, the exhaust port of the demand-driven vacuum pump forms the exhaust air opening of the vacuum system.

According to another aspect of the present disclosure, a connection piece for being connected to the exhaust air line or for being connected to the exhaust port of the demand-driven vacuum pump may be arranged on a first side of the housing. In this way, the discharge device and the exhaust air line can be exchanged separately of one another. In an alternative embodiment of the present disclosure, the discharge device may be integrated into a housing of the demand-driven vacuum pump.

According to another aspect, at least one opening or a number of openings may be arranged on a second side of the housing and fluidically connected to the chamber and the external surroundings of the discharge device. The housing of the discharge device may furthermore include a hollow-cylindrical housing section.

According to another embodiment, the second side of the housing may be defined by a base of the hollow-cylindrical housing section, wherein the openings may in this embodiment be arranged in a cylinder wall of the hollow-cylindrical housing section adjacent to the base. A plurality of openings may be arranged in the cylinder wall such that they are uniformly spaced apart from one another in the circumferential direction of the hollow-cylindrical housing section. In the case of a moderate entry of splash water, this plurality of openings, which are uniformly distributed in the circumferential direction, makes it possible to ensure with sufficient probability that water does not infiltrate all openings simultaneously. Consequently, the vacuum system can still be provided with ventilation air from the external surroundings through openings, which are not affected by a moderate entry of splash water.

According to another embodiment, the second side of the housing may be closed with a cover inserted into the hollow-cylindrical housing section. Such a two-piece design of the housing on the one hand allows a simple manufacture of the cylindrical housing section, for example, by an injection molding process. In addition, a two-piece housing can also be opened, for example, for cleaning purposes.

According to another aspect, a conically tapered housing section may be connected to the hollow-cylindrical housing section on the first side of the housing. The conically tapered housing section preferably reduces the diameter of the hollow-cylindrical housing section to the diameter of the connection piece such that the corresponding housing sections and the connection piece can be realized in one piece. In addition, the conically tapered housing section causes a reduced flow speed of the air volume flow in this housing section. In this way, an entrainment of liquid drops can either be suppressed or at least reduced while an air volume flows into the vacuum system for ventilation purposes.

Other characteristics and details can be gathered from the following description, in which at least one exemplary embodiment is elucidated in greater detail—if applicable with reference to the drawings. Described and/or graphically illustrated characteristics form the object of the present disclosure individually or in any sensible combination, if applicable also independently of the claims, and particularly may also form the object of one or more separate application/s. Identical, similar and/or functionally identical components are identified by the same reference symbols.

DETAILED DESCRIPTION

FIG. 1shows a fluidic diagram with a vacuum brake booster, which is simply referred to as brake booster50below, and with a vacuum system1, which is connected to the brake booster50in order to generate a vacuum in a vacuum chamber51by an electric vacuum pump30. Instead of using the electric vacuum pump30, it would also be possible to provide a different type of demand-driven vacuum pump such as a mechanical vacuum pump, which can be coupled to a drive unit by a controllable coupling element.

A vacuum connection or fluidic connection between the vacuum chamber51and the electric vacuum pump20is produced by a vacuum line. In the present exemplary embodiment, the vacuum line includes two pieces—a first vacuum line section41and a second vacuum line section42, which are connected to one another by a check valve30. The vacuum line or the two vacuum line sections41,42may be respectively realized, for example, in the form of a vacuum hose.

As an alternative to the embodiment illustrated inFIG. 1, the check valve30may also be arranged on the intake port21of the electric vacuum pump20or on a connector of the vacuum chamber51for connecting the vacuum line. The intake port21of the electric vacuum pump20and the vacuum chamber51of the brake booster50are connected to one another by a one-piece or multi-piece vacuum line41,42and at least one check valve30. The check valve30is configured to allow an air volume flow in the flow direction from the brake booster50to the electric vacuum pump20and for blocking an air volume flow in the opposite flow direction.

The electric vacuum pump20may include a positive-displacement pump such as a reciprocating pump or a diaphragm pump that is driven by an electric motor. The electric vacuum pump20is configured to convey an air volume from the intake port21to the exhaust port22. A vacuum available for boosting a brake force is generated in the vacuum chamber51during the at least partial evacuation of the air volume contained in the vacuum chamber51of the brake booster50.

An exhaust air line10is connected to the exhaust port22with its first end11and preferably realized in the form of an exhaust air hose. The exhaust air line10may be routed from the exhaust port22of the electric vacuum pump20to a desired location in the engine compartment such that the air evacuated from the vacuum chamber51by the electric vacuum pump20can be discharged into the engine compartment at this location through the second end12of the exhaust air line10.

A discharge device60is arranged on the second end12of the exhaust air line10and configured to ensure a bidirectional air volume flow between the external surroundings and the exhaust air line10. Bidirectional means that an air volume conveyed by the electric vacuum pump20can flow from the exhaust air line10into the surrounding atmosphere. In addition, an air volume can also flow from the surrounding atmosphere into the exhaust air line10after the electric vacuum pump20has been deactivated such that the vacuum system1is ventilated in a section between the discharge device60and the check valve30. In other words, a vacuum is equalized in front of the intake port21of the electric vacuum pump20.

An exemplary embodiment of the discharge device60is illustrated in greater detail inFIGS. 2 and 3. The discharge device60includes a housing68with a cylindrical base body. The cross section according toFIG. 2shows that a chamber66is formed in the interior of the housing68. The housing68includes a hollow-cylindrical section with a cylindrical wall67. A conically tapered section is provided on the first side61of the housing66and tapered from the diameter of the cylinder wall67to the diameter of a connection piece63.

The connection piece63may be realized in the form of a hose connector, to which an exhaust air line10in the form of an exhaust air hose can be or is attached. The connection piece63ensures a fluidic connection between the exhaust air line10illustrated inFIG. 1and the chamber66. A different connecting point to the opening on the first side61housing68, which ensures a connection between the chamber66and the interior of the exhaust air line10, would basically also be sufficient.

The second side62of the housing68is closed with a cover64that is inserted into the hollow-cylindrical housing section. According toFIGS. 2 and 3, the cover64may be clipped into the hollow-cylindrical section of the housing by a tongue-and-groove joint. Alternatively, a screw-type cover and/or an adhesive cover may also be provided in this case.

FIG. 3, in particular, shows that the second side62of the housing68is provided with a plurality of openings65that are arranged in the cylinder wall67. The openings65are uniformly spaced apart from one another in the circumferential direction of the cylindrical housing section and border on the cover64. The openings66provide a fluidic connection between the chamber66and the external surroundings of the separating device, i.e. the surrounding atmosphere of the separating device and of the entire vacuum system.

An air volume is evacuated from the vacuum chamber51by the electric vacuum pump20as soon as the vacuum system1is activated, for example, by a vacuum switch or pressure sensor on the brake booster50. The resulting air volume flow is conveyed through the exhaust air line10and reaches the chamber66through the connection piece63on the first side61of the housing68. The air volume conveyed into the chamber66can escape into the engine compartment of a motor vehicle, i.e. into the atmosphere, through the openings65on the second side62of the housing68.

The air volume flow conveyed by the electric vacuum pump20ceases as soon as the vacuum system1is deactivated by a vacuum switch or pressure sensor on the brake booster50. At such a deactivation moment, a vacuum prevails at the outlet32of the check valve30, whereas atmospheric pressure prevails at the openings65of the discharge device60. The pressure gradient between the openings65of the discharge device60and the outlet32of the check valve30attempts to generate a volume flow that is directed opposite to the pumping direction of the electric vacuum pump30until the pressure gradient is compensated and the vacuum system1is ventilated in the section between the openings of the discharge device60and the check valve30.

During this ventilation process, air is taken in from the surrounding atmosphere through the openings65of the discharge device60. The discharge device60is arranged in the engine compartment of a motor vehicle and therefore exposed to splash water, which can enter the engine compartment, for example, in heavy rain or while driving through water. Under these circumstances, water may also be taken in through the openings65of the discharge device60during the intake of the air for ventilating the vacuum system1and therefore reach the chamber66of the discharge device60.

The volume of the chamber66is dimensioned in such a way that it stores a sufficient air volume for ventilating a section of the vacuum system1, which is respectively formed between the second end of the exhaust air line or the connection piece63of the discharge device60and the outlet32of the check valve. The ventilation process can be completed with the air volume stored in the chamber before the water taken into the chamber reaches the exhaust air line.

The chamber volume of the chamber66preferably corresponds to the volume, which is altogether enclosed by the exhaust air line10, the working volume of the electric vacuum pump20and the first section of the vacuum line41. In this way, complete ventilation can also be ensured if all of the openings65of the discharge device60are exposed to or submersed in water. No further air volume flow takes place as soon as the pressure gradient in the vacuum system1has been compensated after the completion of the ventilation process. Any water taken into the chamber66of the discharge device60can subsequently drain through at least one of the openings65of the discharge device60under the force of gravity. Air from the atmosphere for compensating the drained water volume can simultaneously reach the chamber66through at least one other opening65in the discharge device60such that a sufficient air volume for another ventilation process is once again available in the chamber66. In addition, any potentially remaining water in the chamber66can be ejected through the openings65in the discharge device60when the electric vacuum pump is activated again.