Abstract:
A pressure control valve arrangement for controlling a fluid pressure in an ABS brake system of a vehicle so that, while there is a tendency of individual wheels of the vehicle to lock, the brake pressure in at least one associated brake cylinder can be adaptively adjusted, including: a housing; and at least one diaphragm valve is accommodated in the housing, the diaphragm valve having a diaphragm as the valve body, which diaphragm can be acted upon by introducing pressure medium into a control chamber that is covered on the outside of the housing by a cover so that the control chamber is formed between the diaphragm and the cover, wherein at least one pressure medium channel carrying pressure medium is formed in the housing in the region of the cover, wherein at least one cover has at least one projection projecting into the pressure medium channel in the housing, a pressure medium guiding surface for directing the flow of the pressure medium carried in the pressure medium channel being formed on the projection.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a pressure control valve arrangement for controlling the fluid pressure in an ABS brake system of a vehicle in such a way that, while there is a tendency of individual wheels of the vehicle to lock, the brake pressure in at least one associated brake cylinder can be adaptively adjusted, wherein at least one diaphragm valve is accommodated in a housing of the pressure control valve arrangement, the diaphragm valve having a diaphragm as the valve body, which diaphragm can be acted upon by introducing pressure medium into a control chamber that is covered on the outside of the housing by a cover in such a way that the control chamber is formed between the diaphragm and the cover, and wherein at least one pressure medium channel carrying pressure medium is formed in the housing in the region of the cover, in accordance with the features described herein. 
       BACKGROUND INFORMATION 
       [0002]    ABS (antilock brake system) prevents wheels from locking and comes into operation when a higher friction coefficient between a tire and the road is demanded than can be transmitted, i.e. when the driver brakes too hard. In the case of excessively hard braking, the central electronic control unit of the ABS brake system detects the tendency for one or more wheels to lock from rotational speed detector signals and, from these signals, calculates the activation of the pressure control valve arrangement acting on the associated brake cylinder. The brake pressure is then adjusted to an optimum slip of the pressure control valve arrangement, which lowers, holds or builds up the pressure in accordance with the wheel behavior and hence with the friction conditions between the tire(s) and the road. 
         [0003]    ABS pressure control valve arrangements without a relay action, to which the exemplary embodiments and/or exemplary methods of the present invention relate, are used on vehicles such as commercial vehicles, buses, semitrailer trucks and trailers. Pressure control valve arrangements without a relay action generally have 3/2-way solenoid valves as pilot control valves for diaphragm valves, wherein an electronic control device activates the 3/2-way solenoid valves to enable the functions required for ABS operation, “pressure holding”, “pressure reduction” and “pressure buildup”, to be carried out. During a braking operation which does not involve a response by the ABS (no tendency for a wheel to lock), the pressure medium, generally air, flows through the pressure control valve arrangements unhindered in both directions during air admission to and venting from the brake cylinders. This ensures that the operation of the service brake system is not affected by the ABS pressure control valve arrangement. 
         [0004]    Within the housing, pressure control valves of the type in question in the form of single-channel pressure control valves for antilock systems of motor vehicles have respective diaphragm valves as a holding valve and an outlet valve and respective solenoid control valves for the holding valve and the outlet valve. The two diaphragm valves each contain a diaphragm, which can be acted upon by the pressure in a control chamber, wherein the control chamber is closed off from the outside by a cover secured on the housing. 
         [0005]    A pressure control valve arrangement of the type in question for an ABS brake system is known from EP 0 266 555 A1, for example. In the prior-art pressure control valve arrangements, the two diaphragm valves are generally arranged on the side of the housing, wherein the corresponding pilot control spaces are closed off by covers secured on the side of the housing. These covers are produced by primary forming processes such as injection molding. Pressure medium channels are furthermore formed in the housing in order to carry pressure medium within the housing to and from the various connections of the pressure control valve arrangement and to and from the diaphragm valves and to and from the solenoid valves controlling the above valves. 
         [0006]    The pressure medium channels may run in a vertical and/or horizontal direction within the housing because then the housing does not have to be re-clamped during the machining of the pressure medium channels of a machining center, for example. A change in the direction of such a pressure medium channel is problematic in terms of flow engineering because the deflection of the flow in the pressure medium channel concerned is then generally 90 degrees (deflection from the vertical to the horizontal or vice versa) and this results in relatively high flow losses due to the abrupt deflection in such a pressure medium channel elbow. However, because a high dynamic response is required in pressure control valve arrangements for ABS/ASR systems and as rapid as possible venting of the brake cylinder concerned is required, for example, in the context of the “pressure lowering” function when the permissible wheel slip is exceeded, such flow losses caused by deflections must be kept as small as possible. 
         [0007]    Because the installation dimensions of such a pressure control valve arrangement, especially the installation width thereof, are standardized and invariable owing to restricted space conditions, a solution to this problem cannot consist in enlarging the flow cross sections of the pressure medium channels. 
         [0008]    Given this situation, it is the underlying object of the invention to develop a pressure control valve arrangement of the type mentioned at the outset in such a way that the flow losses or flow resistance, especially in pressure medium channels deflecting a pressure medium flow, are reduced. At the same time, the outlay on the production and finishing of the manner for achieving this object should be as low as possible. 
       SUMMARY OF THE INVENTION 
       [0009]    According to the present invention, this object may be achieved by the features described herein. 
         [0010]    The exemplary embodiments and/or exemplary methods of the present invention provide that at least one cover has at least one projection projecting into the pressure medium channel in the housing, a pressure medium guiding surface for directing the flow of the pressure medium carried in the pressure medium channel being formed on the projection. 
         [0011]    Since such a cover is present in any case for the purpose of covering and/or sealing off a control chamber of a diaphragm valve of the pressure control valve arrangement and, according to an additional function, it is now also the carrier of a projection with a pressure medium guiding surface which guides the flow or, in the case of a deflection, deflects the flow, it advantageously performs a dual function in a single component. 
         [0012]    In this case, the flow-guiding or flow-deflecting pressure medium guiding surface of the projection projecting into the pressure medium channel is advantageously configured in such a way that the flow losses or flow resistance of the pressure medium channel concerned, excluding the surface in the pressure medium channel, is/are reduced. 
         [0013]    Owing to the reduced flow resistance, the pressure control valve arrangement consequently has an improved dynamic response without a change in the flow cross section of the pressure medium channel concerned, and this has a positive effect in terms of the required rapid succession of pressure reduction, pressure holding and pressure increasing phases. 
         [0014]    Advantageous developments and improvements of the exemplary embodiments and/or exemplary methods of the present invention indicated herein are possible of the measures presented in the further description herein. 
         [0015]    The projection having the pressure medium guiding surface may project into the pressure medium channel at a location at which deflection of the flow of the pressure medium within the pressure medium channel from a section of the pressure medium channel which leads in one direction into a section of the pressure medium channel which leads in another direction is envisaged. In order to achieve this, one or the other section of the pressure medium channel can, for example, extend as far as an aperture in a side face of the housing, into which opening the projection of the cover then projects in the manner of a spigot. 
         [0016]    The deflection of the flow of the pressure medium within the pressure medium channel may be substantially 90 degrees, wherein the pressure medium guiding surface of the projection is designed to deflect the flow of the pressure medium from one direction to the other. 
         [0017]    According to a development, the pressure medium channel is a vent channel, which carries compressed air from a diaphragm valve designed as an outlet valve to a vent of the pressure control valve arrangement. In this case, a central area of the cover may serve to cover the control chamber of the diaphragm valve designed as an outlet valve, and the at least one projection having the pressure medium guiding surface is formed at the edge of a nose of the cover. 
         [0018]    If the cover provided with the projection and the pressure medium guiding surface is designed as an integral injection molding made of plastic or metal, production and assembly costs are advantageously low. 
         [0019]    Further measures that improve the exemplary embodiments and/or exemplary methods of the present invention are explained in greater detail below together with the description of an embodiment of the invention with reference to the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  shows a diagrammatic representation of an ABS brake system as a general layout of a four-sensor/4-channel ABS brake system of a vehicle. 
           [0021]      FIG. 2   a  shows a schematic representation of a pressure control valve arrangement which controls a brake cylinder, in the open state (pressure buildup). 
           [0022]      FIG. 2   b  shows a schematic representation of the pressure control valve arrangement in  FIG. 2   a  in the closed state (pressure reduction). 
           [0023]      FIG. 3  shows a side view of a specific embodiment of the pressure control valve arrangement in  FIG. 2   a  and  FIG. 2   b  in accordance with an exemplary embodiment of the invention. 
           [0024]      FIG. 4  shows a sectional representation along the line IV-IV in  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    According to  FIG. 1 , a vehicle fitted with an ABS brake system has a front axle  1  and a rear axle  2 . Wheels  3   a  and  3   b  are arranged on the front axle  1 ; the rear axle  2  has wheels  4   a  and  4   b,  each fitted with twin tires, for example. In this case, the ABS brake system used to brake these wheels  3   a,    3   b  and  4   a,    4   b  is in the form of a four-sensor/4-channel system. This means that, in this case, a total of four rotational speed sensors  5   a - 5   b  and four pressure control valve arrangements  7   a - 7   d  are available. The pressure control valve arrangements  7   a - 7   d  are used to control respectively associated brake cylinders  6   a - 6   d.  All the pressure control valve arrangements  7   a - 7   d  are connected to a foot brake valve  9  by a branching pneumatic brake pressure line  8 . 
         [0026]    In actuating the foot brake valve  9 , the driver generates a brake pressure, which, passing through the pressure control valve arrangements  7   a - 7   d  via the pneumatic brake pressure line  8 , is transmitted to the brake cylinders  6   a - 6   d  associated with wheels  3   a,    3   b  and wheels  4   a,    4   b.    
         [0027]    The pressure control valve arrangements  7   a - 7   d  can be activated by integrated solenoid valves  15   a,    15   b,  shown in  FIG. 2   a ,  FIG. 2   b  and  FIG. 4 , and, for this purpose, are connected electrically to a central electronic control unit  10 . On the input side, the electronic control unit  10  is connected to the four rotational speed sensors  5   a - 5   b  that detect the wheel speeds. If a wheel  3   a - 3   d  locks, the brake pressure input by the driver via the foot brake valve  9  is reduced by the corresponding pressure control valve arrangement  7   a - 7   d  in an ABS control operation under the command of the electronic control unit  10  until locking has been eliminated. The ABS brake system in the embodiment under consideration furthermore comprises an ASR function, which comprises an ASR unit  11  for reducing the engine torque, an ASR solenoid valve  12  and a shuttle valve  13 . 
         [0028]    Here, the pressure control valve arrangement  7  used for the purpose of ABS control as part of the ABS brake system in accordance with  FIG. 2   a  is constructed in the manner of a single-channel pressure control valve arrangement and essentially comprises two integrated diaphragm valves  14   a  and  14   b  and two spring-loaded solenoid valves  15   a,    15   b,  which control the diaphragm valves. The diaphragm valves  14   a  and  14   b  are each biased in the closing direction by spring elements  16   a,    16   b  and are pilot-controlled of the respectively associated solenoid valves  15   a  and  15   b.    
         [0029]    In  FIG. 2   a , the pressure control valve arrangement  7  is shown in the open position thereof, in which a pressure buildup to the connected brake cylinder  6  takes place. In this case, neither of the solenoid valves  15   a  and  15   b  is electrically activated. In the position shown, the compressed air coming from the foot brake valve  9  pushes open diaphragm valve  14   a,  which is designed as an inlet valve. The normally closed solenoid valve  15   a  prevents the associated diaphragm valve  14   a  from being closed again. Via the normally open second solenoid valve  15   b,  the brake pressure coming from the foot brake valve  9  closes the second diaphragm valve  14   b,  which serves as an outlet valve. The compressed air thus passes unhindered through the pressure control valve arrangement  7 . The pressure control valve arrangement  7  is in this state also when there is no ABS control taking place. 
         [0030]    To hold the brake pressure constant in a brake cylinder  6   a  to  6   d,  all that is required is to energize solenoid valve  15   a,  as a result of which the valve opens and, as a consequence, the brake pressure coming from the foot brake valve  9  pushes shut the inlet-side diaphragm valve  14   a.  The pressure on the right hand side and the left hand side of diaphragm valve  14   a  is now equal. However, since the effective area on the left hand side of diaphragm valve  14   a  is larger, diaphragm valve  14   a  is closed. The same applies to the outlet-side diaphragm valve  14   b  controlled by solenoid valve  15   b.  To hold the pressure constant, the pressure control valve arrangement  7  thus closes the pneumatic brake pressure line  8  running from the foot brake valve  9  to the brake cylinder  6 . 
         [0031]    According to  FIG. 2   b , a pressure reduction in a brake cylinder  6   a  to  6   d  is achieved by energizing both solenoid valves  15   a  and  15   b.  The statements made above on maintaining the pressure apply to solenoid valve  15   a  and the associated inlet-side diaphragm valve  15   a.  The other solenoid valve  15   b,  on the other hand, is closed due to energization. The pressure coming from the brake cylinder  6  therefore pushes the outlet-side diaphragm valve  14   b  open, and the brake cylinder  6  is vented. 
         [0032]    The above-described functions of the pressure control valve arrangement  7  are carried out in the manner described at the outset as part of an ABS/ASR control operation under the command of the electronic control unit  10 . 
         [0033]    In  FIG. 3  and  FIG. 4 , the pressure control valve arrangement  7  illustrated only schematically in  FIG. 2   a  and  FIG. 2   b  is shown in a specific embodiment in the installed position, i.e. the components described above are at the top. In this embodiment, the two solenoid valves  15   a,    15   b  for pilot control of the diaphragm valves  14   a,    14   b  are combined in a dual solenoid valve, although it operates in a manner similar to individual valves  15   a,    15   b.    
         [0034]    The two solenoid valves  15   a,    15   b  have a double magnet  18  housed in a block  17 , having two magnet coils, which interact with two solenoid valve seats. Magnet armatures, which interact with the solenoid valve seats of the solenoid valves  15   a,    15   b  and are not shown explicitly here, are operated as valve closing members by energizing the magnet coils. 
         [0035]    The block  17  surrounding the double magnet  18  is secured on a housing  21  of the pressure control valve arrangement  7 , which may be on the front side, and has a plug connection  22  for supplying power to the double magnet  18 . This housing  21  furthermore has a pressure medium connection  23  for supplying pressure to and/or relieving pressure from the pressure control valve arrangement  7 , and a working connection  24  for connection of the brake cylinder  6  ( FIG. 3 ). 
         [0036]    As  FIG. 2   a  and  FIG. 2   b  show, the pressure medium connection  23  is connected to the foot or service brake valve  9  of the fluid-pressure-actuated braking device by the brake pressure line  8  and is supplied with air or vented in accordance with an actuation of the foot brake valve  9 . 
         [0037]    As is apparent especially from  FIG. 3 , the housing  21  is provided with at least one and, in this case, for example, two through holes  20   a,    20   b  opening into both side faces  19   a,    19   b  of the housing  21 , through which holes holding arrangements, e.g. screws, for holding the pressure control valve arrangement on a support, e.g. on a chassis of the vehicle, project. The center lines of the two through holes  20   a,    20   b  may be parallel to each other. The axial length of the through holes  20   a,    20   b  applies as a standardized installation dimension of the pressure control valve arrangement  7  and, for reasons of space, is fixed and invariable, defining the maximum permissible width B of the housing  21 . 
         [0038]    One diaphragm valve  14   a  may be arranged on the side of the housing  21 , and the other diaphragm valve  14   b  may be arranged on the bottom of the housing  21 , as  FIG. 4  shows. As a valve body, a diaphragm valve  14   a,    14   b  of this kind has a diaphragm  25   a,    25   b,  which can be acted upon by introducing pressure medium into a control chamber  26   a,    26   b,  each of which is covered on the outside of the housing by a cover  27   a,    27   b  produced by a primary forming process, such as injection molding, which is secured on the housing  21 . In this arrangement, the control chamber  26   a,    26   b  is formed between the diaphragm  25   a,    25   b  and the cover  27   a,    27   b.    
         [0039]    As is apparent especially from  FIG. 4 , the cover  27   a  closing the control chamber  26   a  of the diaphragm valve  14   a  arranged on the side has a projection or spigot  28  which projects from the outside into an aperture  29  of a pressure medium channel  30  in the housing. A pressure medium guiding surface  31  for directing the flow of the pressure medium carried in the pressure medium channel  30  is formed on the projection  28 . 
         [0040]    The pressure medium channel  30  may be intended to bring about deflection of the flow of the pressure medium from an upstream part of the pressure medium channel  30 , which leads in one direction, into a downstream part of the pressure medium channel  30 , which leads in another direction. 
         [0041]    In the exemplary embodiment, for example, the pressure medium channel  30  brings about a 90-degree deflection of the flow of the pressure medium from a first section  32  of the pressure medium channel  30 , the section being vertical in  FIG. 4  and having a flow connection to a valve seat of the diaphragm valve  14   a  acting as an outlet valve, the control chamber  26   a  of which is covered by the cover  27   a,  into a section  33  of the pressure medium channel  30 , the section being horizontal in  FIG. 4  and having a flow connection to a vent connection (not explicitly visible here) formed on the housing  21 , as the arrow  34  in  FIG. 4  symbolizing the direction of flow illustrates. 
         [0042]    As seen from the interior of the housing  21 , the horizontal section  33  of the pressure medium channel is extended as far as the aperture  29  in the side face  19   a  of the housing  21 . The projection  28  of the cover  27   a  projects into this aperture  29  in the manner of a spigot. 
         [0043]    In the present case, the pressure medium channel  30  therefore may be a vent channel, which carries compressed air from the working connection  24 , which is connected to a brake cylinder, via the outlet valve embodied as a diaphragm valve  14   a,  to a vent of the pressure control valve arrangement  7 . 
         [0044]    The pressure medium guiding surface  31  of the projection  28  is designed to deflect the flow of the pressure medium from one direction (in this case the vertical direction) to the other (in this case the horizontal direction) or to assist such a deflection, which may be by a spherical surface. 
         [0045]    In a particular embodiment, the cover  27   a  provided with the projection  28  and the pressure medium guiding surface  31  is designed as an integral injection molding made of plastic or metal. 
         [0046]    In a particular embodiment, the central area of the cover  27   a  serves to cover the control chamber  26   a,  and the projection  28  having the pressure medium guiding surface  31  is formed at the edge of the cover  27   a,  e.g. on a nose  35  of the cover  27   a,  as illustrated by  FIG. 3 . A corresponding seal  36  in the region of the aperture  29  ensures that the pressure medium channel  30  is sealed off from the outside. 
         [0047]    A cover  27   a  having a projection  28  and a pressure medium guiding surface  31  is not necessarily restricted to use for a pressure medium channel  30  having a 90-degree deflection of the direction of flow. On the contrary, such a cover  27   a  can be used for any kind of pressure medium channel  30 , especially for those without flow deflection, in which a reduction in the flow resistance can be achieved by a pressure medium guiding surface. 
       LIST OF REFERENCE SIGNS 
       [0000]    
       
           1  front axle 
           2  rear axle 
           3  wheel 
           4  wheel 
           5  rotational speed sensor 
           6  brake cylinder 
           7  pressure control valve arrangement 
           8  brake pressure line 
           9  foot brake valve 
           10  control unit 
           11  ASR unit 
           12  ASR solenoid valve 
           13  shuttle valve 
           14   a/b  diaphragm valve 
           15   a/b  solenoid valve 
           16   a/b  spring element 
           17  block 
           18  double magnet 
           19   a/b  side face 
           20   a/b  through hole 
           21  housing 
           22  plug connection 
           23  pressure medium connection 
           24  working connection 
           25   a/b  diaphragm 
           26   a/b  control chamber 
           27   a/b  cover 
           28  projection 
           29  aperture 
           30  pressure medium channel 
           31  pressure medium guiding surface 
           32  section 
           33  section 
           34  arrow 
           35  nose 
           36  seal