Abstract:
A pressure control valve arrangement is described for controlling the fluid pressure in an ABS brake system of a vehicle so that, during a tendency of individual wheels of the vehicle to lock, the brake pressure in at least one assigned brake cylinder can be matched adaptively, a) two diaphragm valves and two electromagnetic control valves, activatable by an electronic control device, for the pilot control of the diaphragm valves being provided in the housing of the pressure control valve arrangement, b) the two electro-magnetic control valves having a double magnet with two magnet coils and also magnet armatures cooperating with solenoid valve seats and actuable by current being applied to the magnet coils, c) the housing having at least one pressure medium connection, connected to a service brake valve, for acting with pressure upon and/or relieving the pressure of the pressure control valve arrangement and also at least one working connection for connecting to the brake cylinder, characterized in that d) a plane of symmetry of the mid-axes of the magnet coils of the double magnet of the electromagnetic control valves is arranged parallel, and offset by the amount of an eccentricity, with respect to a mid-axis of the pressure medium connection.

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. 
       BACKGROUND INFORMATION 
       [0002]    ABS (antilock system) prevents the wheels from locking and comes into operation when greater adhesion than is transferable is demanded between a tire and the road, that is to say when the driver overbrakes. In overbraking, the central electronic control apparatus of the ABS brake system detects from rotational speed sensor signals the tendency of one or more wheels to lock and from this calculates the activation of the pressure control valve arrangement acting upon the assigned brake cylinder. The brake pressure is then set to optimal slip by the pressure control valve arrangement by lowering, holding or building up the brake pressure according to the wheel behavior and therefore the frictional conditions between the tire and 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 in vehicles, such as, for example, utility vehicles, omnibuses, tractors and trailers. Pressure control valve arrangements without a relay action mostly have 3/2 way solenoid valves as the pilot control valves of diaphragm valves, an electronic control device activating the  3 / 2  way solenoid valves so that the “pressure holding”, “pressure reduction” and the “pressure build-up” functions necessary for ABS operation can be carried out. During braking without the response of the ABS (no tendency of a wheel to lock), the pressure medium, mostly air, flows, unimpeded, through the pressure control valve arrangements in both directions when the brake cylinders are being ventilated and bled. This ensures that the functioning of the service brake system is not influenced by the ABS pressure control valve arrangement. 
         [0004]    Pressure control valves of the generic type, as 1-channel pressure control valves for antilock systems in motor vehicles, have in each case, inside the housing, a diaphragm valve as a holding valve and as an outlet valve and also in each case an electromagnetic control valve for the holding valve and the outlet valve. The two diaphragm valves contain in each case a diaphragm capable of being acted upon by the pressure in a pilot control space, the pilot control space being closed outwardly by a cover fastened to the housing. A generic pressure control valve arrangement of an ABS brake system is known, for example, from EP 0 266 555 A1 or from DE-A 2 855 876. In the pressure control valve arrangements of the prior art, the housing has a pressure medium connection for the action of pressure and/or the relief of pressure, which is connected to a foot-operated brake valve. Furthermore, the two diaphragm valves are arranged laterally on the housing, the corresponding pilot control spaces being closed by covers fastened laterally to the housing, that is to say, there, surface normals on the diaphragms of both diaphragm valves are arranged perpendicularly to the mid-axis of the pressure medium connection. 
         [0005]    Furthermore, in the published references, particularly according to  FIG. 1  of DE-A-2 855 876, a plane of symmetry of the mid-axes of the magnet coils of the double magnet of the two electromagnetic control valves is arranged centrically with respect to a mid-axis of the pressure medium connection (there, the pressure medium inlet). In this case, the mid-axes of the two magnet coils at the same time also define the positions of the valve seats of the electromagnetic control valves of the pressure control valve arrangement, because the mid-axes of the magnet coils are arranged coaxially with the valve seats and with the magnet armatures. Furthermore, the valve seats of the electromagnetic control valves are connected to the pressure medium connection or issue into this via pressure medium ducts. These pressure medium ducts may be made coaxially with the mid-axes of the magnet coils by cutting manufacture, such as drilling, in order for reasons of cost to avoid having to rechuck the housing in order to make obliquely running pressure medium ducts or housing bores. The pressure medium ducts consequently run parallel to one another in a vertical direction. 
         [0006]    So that the pressure medium ducts emanating from the valve seats of the electromagnetic control valves can therefore be manufactured in a vertical direction in the housing by cutting and at the same time both of them can issue into the pressure medium connection, the inside diameter of the pressure medium connection has to be relatively large, especially since the magnet coils also cannot undershoot a certain diameter. However, because a correspondingly large diameter of the pressure medium connection is unfavorable in flow terms, in practice a reducing sleeve which reduces the effective flow diameter is inserted into the pressure medium connection. 
         [0007]    However, this procedure entails additional costs for producing and mounting the reducing sleeve, and, in view of the large number of pressure control valve arrangements delivered by a supplier of vehicles, this amounts in total to a relatively high sum. 
       SUMMARY OF THE INVENTION 
       [0008]    The subject on which the exemplary embodiments and/or exemplary methods of the present invention are based is to develop a pressure control valve arrangement of the type initially mentioned in such a way that it can be manufactured and assembled more simply and more cost-effectively. 
         [0009]    This object may be achieved, according to the exemplary embodiments and/or exemplary methods of the present invention, by the features described herein. 
         [0010]    As explained initially, the mid-axes of the magnet coils are coaxial with the valve seats of the electromagnetic control valves, and in each case one valve seat is formed at one end of a pressure medium duct which connects the respective valve seat to the pressure medium connection. Since two electromagnetic control valves are present, two pressure medium ducts formed in the housing must consequently lead from the respective valve seats coaxial with the mid-axes of the magnet coils into the pressure medium connection. In this case, pressure medium ducts running obliquely, that is to say deviatingly from a vertical or from a horizontal, are to be avoided, so as to avoid having to rechuck the housing during manufacture. 
         [0011]    The exemplary embodiments and/or exemplary methods of the present invention achieve this object by providing that a plane of symmetry of the mid-axes of the magnet coils of the double magnet of the two electromagnetic control valves is arranged parallel and eccentrically with respect to a mid-axis of the pressure medium connection. 
         [0012]    The distance between the mouth of the connecting duct, arranged in the housing, in the pressure medium connection between the valve seat of one of the electromagnetic control valves and the pressure medium connection, on the one hand, and the mid-axis of the pressure medium connection, on the other hand, is then reduced, as compared with the prior art, because the mid-axis of one of the magnet coils of the double magnet and therefore also the valve seat, coaxial thereto, of the respective electromagnetic control valve and, too, the respective pressure medium duct can then be moved nearer to the mid-axis of the pressure medium connection and consequently issue into the pressure medium connection at a shorter distance from this mid-axis. The other pressure medium duct emanating from the valve seat of the other electromagnetic control valve then no longer needs to run parallel to the first, for example vertical pressure medium duct, but instead can issue, for example running in a horizontal direction, into an annular duct which is formed in a housing and which is connected in turn to the pressure medium connection. The pressure medium ducts then run in a vertical and a horizontal direction, so that the housing does not have to be rechucked during manufacture. The diameter of the pressure medium connection can thus be smaller and therefore more favorable in flow terms. In particular, a reducing sleeve can be dispensed with. 
         [0013]    Advantageous developments and improvements of the exemplary embodiments and/or exemplary methods of the present invention specified herein are possible as a result of the measures listed in the further descriptions herein. 
         [0014]    Especially, the housing may be provided with at least one through bore which issues in side faces of the housing and which is intended as a holding arrangement for holding the pressure control valve arrangement on a carrier body, the plane of symmetry of the mid-axes of the magnet coils of the double magnet of the two electromagnetic control valves being arranged, offset by the amount of the eccentricity with respect to a plane of symmetry of the through bore, said plane of symmetry being arranged perpendicularly to a mid-axis of the through bore. As a result, the eccentric arrangement of the double magnet acquires an additional reference to a relevant geometric quantity of the pressure control valve arrangement, because the length of the through, bore is fixed, for reasons of space, as a standardized installation dimension of the pressure control valve arrangement and is invariable. It defines the maximum width of the housing. 
         [0015]    According to a development, in one diaphragm valve of the two diaphragm valves, the surface normal running perpendicularly with respect to the assigned diaphragm is arranged parallel to the mid-axis of the through bore and perpendicularly to the mid-axis of the pressure medium connection, and, in the other diaphragm valve, the surface normal running perpendicularly with respect to the assigned diaphragm is arranged perpendicularly to the mid-axis of the through bore and perpendicularly to the mid-axis of the pressure medium connection. This may be implemented, for example, in that one diaphragm valve is arranged laterally and the other diaphragm valve on the bottom side or head side on the housing. 
         [0016]    If a cover closing a pilot control space of one diaphragm valve, for example arranged laterally on a housing, with respect to the outside and fastened to the housing is then composed of at least one plastic, the wall thickness of this cover can be greater than in the prior art, in which both diaphragm valves are arranged laterally on the housing and, because of the standardized overall width of the housing, the thickness of the covers has to be smaller. The plastic cover which is thicker, as compared with the prior art, is then more rigid. The tendency of the cover to deformation therefore decreases, and so the safety of the respective diaphragm valve against leakage of the pilot control space is increased. 
         [0017]    A cover closing a pilot control space of the other diaphragm valve with respect to the outside and fastened to the housing may likewise be composed of a plastic. 
         [0018]    In this case, at least one of the covers may at the same time, with the effect of an advantageous double function, close a pressure medium duct formed in the housing and separated from the respective pilot control space. 
         [0019]    The pressure medium connection may be provided, in particular, for connection to a service brake valve of a pressure medium-actuated brake apparatus of a vehicle. 
         [0020]    Further measures improving the exemplary embodiments and/or exemplary methods of the present invention are illustrated in more detail below, together with the description of an exemplary embodiment of the present invention, by the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  shows a basic illustration of an ABS brake system as a general diagram of a 4S/4C ABS brake system of a vehicle. 
           [0022]      FIG. 2   a  shows a diagrammatical illustration of a pressure control valve arrangement activating a brake cylinder, in the open state (pressure build-up). 
           [0023]      FIG. 2   b  shows a diagrammatic illustration of the pressure control valve arrangement of  FIG. 2   a  in the closed state (pressure reduction). 
           [0024]      FIG. 3  shows a front view of an actual version of the pressure control valve arrangement of  FIG. 2   a  and  FIG. 2   b  according to an exemplary embodiment of the present invention. 
           [0025]      FIG. 4  shows a side view of the pressure control valve arrangement of  FIG. 3 . 
           [0026]      FIG. 5  shows a sectional illustration along the line V-V of  FIG. 4 . 
           [0027]      FIG. 6  shows the other side view of the pressure control valve arrangement of  FIG. 3 . 
           [0028]      FIG. 7  shows a sectional illustration along the line VII-VII of  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    According to  FIG. 1 , a vehicle equipped 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, for example, wheels  4   a  and  4   b  in each case equipped with twin tires. The ABS brake system serving for braking these wheels  3   a ,  3   b  and  4   a ,  4   b  is designed here in the manner of a 4S/4C system (four sensors, four channels). This means that, overall, four rotational speed sensors  5   a - 5   d  and four pressure control valve arrangements  7   a - 7   d  are available here. The pressure control valve arrangements  7   a - 7   d  serve for the activation of respectively assigned brake cylinders  6   a - 6   d . All the pressure control valve arrangements  7   a - 7   d  are connected to a foot-operated brake valve  9  via a branching pneumatic brake pressure line  8 . 
         [0030]    The driver, when actuating the foot-operated brake valve  9 , generates a brake pressure which, passing through the pressure control valve arrangements  7   a - 7   d , is transferred by the pneumatic brake pressure line  8  to the brake cylinders  6   a - 6   d  assigned to the wheels  3   a ,  3   b  and to the wheels  4   a ,  4   b.    
         [0031]    The pressure control valve arrangements  7   a - 7   d  are activatable via integrated electromagnetic 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 . The electronic control unit  10  is connected on the input side to the four rotational speed sensors  5   a - 5   b  determining the wheel speeds. In the event of the locking of a wheel  3   a - 3   d , the brake pressure selected by the driver via the foot-operated brake valve  9  is lowered correspondingly to an ABS control, according to the electronic control unit  10 , by the corresponding pressure control valve arrangements  7   a - 7   d  until locking is eliminated. The ABS brake system of the present exemplary embodiment comprises, furthermore, an ASR function which comprises an ASR unit  11  for reducing the engine torque, such as an ASR solenoid valve  12  and a shuttle valve  13 . 
         [0032]    The pressure control valve arrangement  7  used according to  FIG. 2   a  within the framework of the ABS brake system for the purpose of ABS control is constructed here in the manner of a 1-channel pressure control valve arrangement and is composed essentially of two integrated diaphragm valves  14   a  and  14   b  and of two spring-loaded electromagnetic valves  15   a ,  15   b  activating these. The diaphragm valves  14   a  and  14   b  are in each case loaded in the closing direction by spring elements  16   a ,  16   b  and are pilot-controlled via the respectively assigned electromagnetic valves  15   a  and  15   b.    
         [0033]    A pressure control valve arrangement  7  is shown in  FIG. 2   a  in its open position, in which a build-up of pressure to the connected brake cylinder  6  takes place. In this case, neither of the solenoid valves  15   a  and  15   b  is activated electrically. In the position shown, the compressed air coming from the foot-operated brake valve  9  presses onto the diaphragm valve  14   a  designed as an inlet valve. The normally closed electromagnetic valve  15   a  prevents the assigned diaphragm valve  14   a  from being closed again. By the normally open second electromagnetic valve  15   b , the brake pressure coming from the foot-operated brake valve  9  closes the second diaphragm valve  14   b  serving as an outlet valve. The compressed air thus runs, unimpeded, through the pressure control valve arrangement  7 . The pressure control valve arrangement  7  is in this state even when ABS control does not take place. 
         [0034]    To keep the brake pressure constant in a brake cylinder  6   a  to  6   d , current merely has to be applied to the electromagnetic valve  15   a , with the result that this opens and consequently the brake pressure coming from the foot-operated brake valves  9  presses the inlet-side diaphragm valve  14   a  shut. The pressure on the right and the left side of the diaphragm valve  14   a  is then equal. However, since the active surface on the left side of the diaphragm valve  14   a  is greater, the diaphragm valve  14   a  is closed. The same applies correspondingly to the outlet-side diaphragm valve  14   b  activated via the electromagnetic valve  15   b . To keep the pressure constant, therefore, the pressure control valve arrangement  7  closes the pneumatic brake pressure line  8  running from the foot-operated brake valve  9  to the brake cylinder  6 . 
         [0035]    According to  FIG. 2   b , a pressure reduction in a brake cylinder  6   a  to  6   d  is achieved in that current is applied to both electromagnetic valves  15   a  and  15   b . What was described above for holding the pressure applies to the electromagnetic valve  15   a  and the assigned inlet-side diaphragm valve  15   a . By contrast, the other electromagnetic valve  15   b , by having current applied to it, is closed. The pressure coming from the brake cylinder  6  therefore presses the outlet-side diaphragm valve  14   b  open and the brake cylinder  6  is bled. 
         [0036]    The above-described functions of the pressure control valve arrangement  7  are carried out according to the electronic control unit  10 , within the framework of ABS/ASR control, in the way described initially. 
         [0037]      FIG. 3  to  FIG. 5  show the pressure control valve arrangement  7  illustrated merely diagrammatically in  FIG. 2   a  and  FIG. 2   b  in an actual embodiment in the installation position, that is to say the components illustrated at the top are located at the top. In this embodiment, the two electromagnetic valves  15   a ,  15   b  for the pilot control of the diaphragm valves  14   a ,  14   b  are combined in a double solenoid valve, the function of which, however, is analogous to that of the individual valves  15   a ,  15   b.    
         [0038]    The two electromagnetic valves  15   a ,  15   b  have a double magnet  18  combined in a block  17  and having two magnet coils  19   a ,  19   b  which cooperate with two solenoid valves seats  20   a ,  20   b . As may be gathered clearly from  FIG. 5 , magnet armatures  36   a ,  36   b  cooperating with the solenoid valves seats  20   a ,  20   b  of the electromagnetic valves  15   a ,  15   b  are actuated as valve closing members by current being applied to the magnet coils  19   a ,  19   b.    
         [0039]    The block  17  comprising the double magnet  18  is fastened, which may be on the front side, to a housing  21  of the pressure control valve arrangement  7  and has a plug connection  22  for supplying current to the double magnet  18 . This housing  21  has, furthermore, a pressure medium connection  23  for the action of pressure upon and/or the relief of pressure of the pressure control valve arrangement  7 , and also a working connection  24 , as can be seen in  FIG. 4 , for connecting the brake cylinder  6 . 
         [0040]    As shown in  FIG. 2   a  and  FIG. 2   b , the pressure medium connection  23  is connected via the brake pressure line  8  to the foot-operated or service brake valve  9  of the pressure medium-actuated brake apparatus and is ventilated or bled according to actuation of the foot-operated brake valve  9 . 
         [0041]    As many be gathered particularly from  FIG. 5 , the mid-axes  25   a ,  25   b  of the magnet coils  19   a ,  19   b  are coaxial with the solenoid valve seats  20   a ,  20   b  of the electromagnetic valves  15   a ,  15   b , and in each case one solenoid valve seat  20   a ,  20   b  is formed at one end of a pressure medium duct  26   a ,  26   b  which connects the respective solenoid valve seat  20   a ,  20   b  to the pressure medium connection  23 . 
         [0042]    A plane of symmetry  27 , shown in  FIG. 3 , of the mid-axes  25   a ,  25   b  of the magnet coils  19   a ,  19   b  of the double magnet  18  of the two electromagnetic valves  15   a ,  15   b  is arranged, offset eccentrically by the amount of an eccentricity e with respect to a mid-axis  28  of the pressure medium connection  23 . The mid-axis  28  of the pressure medium connection  23  is parallel with respect to this plane of symmetry  27 . 
         [0043]    The distance between the mouth of, for example, the pressure medium duct  26  in the pressure medium connection  23  and the mid-axis  28  of the pressure medium connection  23  is then reduced, because the mid-axis  25   a  of one of the magnet coils  19   a  of the double magnet  18  and consequently also the solenoid valve seat  20   a  of the respective electromagnetic valve  15   a  and also the respective pressure medium duct  26   a  are then moved nearer to the mid-axis  28  of the pressure medium connection  23 , and consequently the pressure medium duct  26   a  can then issue into the pressure medium connection  23  at a shorter distance from said mid-axis, as shown clearly in  FIG. 5 . Of course, the double magnet  18  may also be arranged, offset by the amount of an eccentricity e, in the other direction, in  FIG. 3  to the right with respect to the mid-axis  28  of the pressure medium connection  23 . 
         [0044]    According to the eccentricity e, however, the distance of the other pressure medium duct  26   b  emanating from the solenoid valve seat  20   b  of the other electromagnetic valve  15   b  from the mid-axis  28  of the pressure medium connection  23  is increased. This pressure medium duct  26   b  therefore does not issue directly into the pressure medium connection  23 , but instead first, for example, into an annular duct  29  which is formed in the housing  21  and which is connected, in turn, to the pressure medium connection  23 . The eccentricity may amount to more than 1 mm. 
         [0045]    The housing  21  is provided with at least one, here, for example, two, through bores  31   a ,  31   b  which issue into the two side faces  30   a ,  30   b  of the housing  21  and through which a project holding arrangement, for example screws, for holding the pressure control valve arrangement on a carrier body, for example on a chassis of the vehicle. The mid-axes  32   a ,  32   b  of the two through bores  31   a ,  31   b  may be parallel to one another. 
         [0046]    In this case, the plane of symmetry  27  of the mid-axes  25   a ,  25   b  of the magnet coils  19   a ,  19   b  of the double magnet  18  of the two electromagnetic valves  15   a ,  15   b  is arranged eccentrically with respect to a plane of symmetry  33  arranged perpendicularly to the mid-axes  32   a ,  32   b  of the through bores  31   a ,  31   b , as may be gathered from  FIG. 3 . In this case, the mid-axis  28  of the pressure medium connection  23  lies in this plane of symmetry. The axial length of the through bores  31   a ,  31   b  is deemed a standardized installation dimension of the pressure control valve arrangement  7  and, for reasons of space, is fixed and invariable, and it defines the maximum permissible width B of the housing  21 . 
         [0047]    One diaphragm valve  14   a  may be arranged laterally and the other diaphragm valve  14   b  may be arranged on the bottom side on the housing  21 , as shown in  FIG. 4  and  FIG. 7 . 
         [0048]    Such a diaphragm valve  14   a ,  14   b  has, as a valve body, a diaphragm  34   a ,  34   b  which can be acted upon by pressure medium being introduced into a control chamber  38   a ,  38   b  which is covered in each case on the housing outside by a cover  35   a ,  35   b  which is produced by primary forming, such as injection molding, and which is fastened to the housing  21 . In this case, the control chamber  38   a ,  38   b  is formed between the diaphragm  34   a ,  34   b  and the cover  35   a ,  35   b . The covers  35   a ,  35   b  may be composed of at least one plastic. 
         [0049]    At least one of the covers  35   a ,  35   b  may be designed such that, in addition to its function as a closing body for the assigned control chamber  38   a ,  38   b , it at the same time closes a bore which is formed in the housing  21  and is not intended for connection to the control chamber  38   a ,  38   b  and which issues into a side face  30   a ,  30   b  of the housing  21 . 
         [0050]    With regard to one diaphragm valve  14   a  of the two diaphragm valves  14   a ,  14   b , the surface normal running perpendicularly with respect to the assigned diaphragm  34   a  may be parallel to the mid-axes  32   a ,  32   b  of the through bores  31   a ,  31   b  and perpendicular to the mid-axis  28  of the pressure medium connection  23 , as can easily be imagined from  FIG. 3 . As regards the other diaphragm valve  14   b , by contrast, the surface normal running perpendicularly with respect to the assigned diaphragm  34   b  is arranged perpendicularly to the mid-axes  32   a ,  32   b  of the through bores  31   a ,  31   b  and perpendicularly to the mid-axis  28  of the pressure medium connection  23 . In other words, in the view of  FIG. 3 , one diaphragm valve  14   a  is then arranged laterally and the other diaphragm valve  14   b  on the bottom side or, alternatively, on the head side on the housing  21 . 
       THE LIST OF REFERENCE SYMBOLS IS AS FOLLOWS  
       [0051]      1  Front axle 
         [0052]      2  Rear axle 
         [0053]      3  Wheel 
         [0054]      4  Wheel 
         [0055]      5  Rotational speed sensor 
         [0056]      6  Brake cylinder 
         [0057]      7  Pressure control valve arrangement 
         [0058]      8  Brake pressure line 
         [0059]      9  Foot-operated brake valve 
         [0060]      10  Control unit 
         [0061]      11  ASR unit 
         [0062]      12  ASR solenoid valve 
         [0063]      13  Shuttle valve 
         [0064]      14   a/b  Diaphragm valve 
         [0065]      15   a/b  Electromagnetic valve 
         [0066]      16   a/b  Spring element 
         [0067]      17  Block 
         [0068]      18  Double magnet 
         [0069]      19   a/b  Magnet coils 
         [0070]      20   a/b  Solenoid valve seats 
         [0071]      21  Housing 
         [0072]      22  Plug connection 
         [0073]      23  Pressure medium connection 
         [0074]      24  Working connection 
         [0075]      25   a/b  Mid-axes magnet coils 
         [0076]      26   a/b  Pressure medium duct 
         [0077]      27  Plane of symmetry 
         [0078]      28  Mid-axis 
         [0079]      29  Annular duct 
         [0080]      30   a/b  Side faces 
         [0081]      31   a/b  Through bores 
         [0082]      32   a/b  Mid-axes 
         [0083]      33  Plane of symmetry 
         [0084]      34   a/b  Diaphragm 
         [0085]      35   a/b  Cover 
         [0086]      36   a/b  Magnet armature 
         [0087]      38   a/b  Control chamber