Abstract:
A measuring device is proposed whose sensors ( 12 ) and circuit holders ( 14 ) are combined into a compactly structured measuring device ( 10 ). This measuring device ( 10 ) has a console ( 11 ), which is used for containing circuit holders ( 14 ) and sensors ( 12 ). The measuring device ( 10 ), which can be fastened anywhere and is therefore easily accessible, permits a relatively short, direct line routing and consequently, to the greatest extent possible, prevents the accumulation of function-impairing air cushions in the measuring circuits, particularly in pressure measurements. specially embodied bushings ( 35 ) that are connected in an airtight fashion to the measuring cells ( 30 ) of the pressure sensors ( 12 ) reduce the interior space of the cup-shaped pressure sensors ( 12 ) so that air cushions are also to a large extent prevented in these components.

Description:
BACKGROUND OF THE INVENTION 
     The invention is based on a measuring device. Measuring devices are used for example in brake systems of motor vehicles, which are electrohydraulically actuated or regulated. Known applications are antilock brake systems or brake systems without mechanical coupling between the brake actuation pedal and the master cylinder. 
     The main parameters for regulating these electrohydraulic brake systems are the operating pressures that occur in the brake circuits. These can be detected by brake sensors, converted into electrical signals, and, together with other sensors signals, can be processed in a control unit into control signals for the brake assembly. This requires a relatively large number of individual parts, which must be separately fastened and connected by way of hydraulic or electric lines. When routing hydraulic lines, in particular a possible production of air cushions in the measuring circuits must be prevented because air conditions of this kind can cause incorrect measurements and in the extreme case, can lead to malfunctions of the brake system. A production of air cushions is particularly encouraged when conventional, inexpensive pressure sensors with cup-shaped measuring cells are used. 
     SUMMARY OF THE INVENTION 
     In keeping with these objects, one feature of present invention resides, briefly stated in a measuring device, in which at least one sensor and at least one circuit holder are combined into a measuring unit with the aid of a console. 
     A measuring device with these characterizing features has the advantage over the prior art of a measuring device that is combined into a separate assembly, which in particular can be fastened to the hydraulic block of a brake assembly and as a result, has a relatively compact structure. The necessary electric and hydraulic line routing from or to the measuring device can therefore take place in a comparatively short and direct manner so that to a large extent, hollow chambers that are not flowed through in the measuring circuits can be prevented. Also, the hollow chambers required by the cup-shaped embodiment of the pressure sensors are reduced to an obligatory minimum in the measuring device according to the invention. The measuring device has a particularly embodied console with recesses for the sensors and the circuit holders. As a result, the console also protects these sensitive components against mechanical and thermal stresses. The measuring device is also easily accessible when serviced and can be replaced with a small number of operations and using a standard tool. 
     The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     Exemplary embodiments of the invention are shown in the drawings and will be explained in more detail in the subsequent description. 
     FIG. 1 is a perspective view that shows a first exemplary embodiment of a measuring device, 
     FIG. 2 shows the measuring device according to FIG. 1 in a cross section along the cutting line II—II in FIG.  1 . 
     FIG. 3 shows a perspective view of a second exemplary embodiment; 
     FIGS. 4 and 5 show cross sections along the line IV—IV in FIG. 3, which disclose different possibilities for routing the measuring tube to the sensors. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a measuring device  10 , which is essentially comprised of a console  11 , for example six pressure sensors  12  disposed on the console  11 , and a circuit holder  14  associated with each of the pressure sensors  12 . The console  11  is embodied in the form of a bridge and in the exemplary embodiment has a total of three supports  15 , which are connected to each other by means of a lateral cross bars  16 . The supports  15  divide the cross bars  16  into two cross bar sections  17 . In the vicinity of one cross bar sections  17 , for example, three recesses  18  are provided (FIG. 2) into which the pressure sensors  12  are inserted. The pressure sensors  12  in this connection are disposed parallel to the longitudinal direction of the supports  15 . On their ends protruding from the cross bar  16 , the pressure sensors  12  respectively have a resistance bridge circuit  20  that is for measurement value detection and is connected by means of contact lines  21  to the circuit holders  14 , which are positioned on the console  11  lateral to the pressure sensors  12  and process the measurement values. The strip conductors  19  of the circuit holders  14  continue on a printed circuit board  22  which is fastened at right angles to the circuit holders  14  on the console  11 . This printed circuit board  22  has a plug device  13  in order to convey the measurement results to external control electronics, not shown. In order to measure pressures at different measurement points of a brake system, the pressure sensors  12  are coupled by means of measuring tubes  24  to the corresponding pressure measurement points. The measuring tubes  24 , only sections of which can be seen in FIG. 1, are accordingly filled with pressure medium, which is at the pressure level to be detected, and feed into the pressure sensors  12  opposite from their ends protruding from the cross bar  16  (FIG.  2 ). 
     FIG. 1 also shows that the console  11  has through bores  25  in the vicinity of its supports  15 . These through bores  25  contain fastening elements  26 —screws in the exemplary embodiment—via which the measuring device  10  can be fastened preferably to an electrohydraulically controllable hydraulic block, not shown, of a brake assembly. 
     It is clear from the cross section of the measuring device  10  depicted in FIG. 2 that the continuous recesses  18  of the cross bar  16  are offset once in their inner diameter. The smaller inner diameter is disposed on the side of the console  11  remote from the supports  15  (FIG.  1 ). The transition from the smaller inner diameter to the larger one is embodied at right angles so that a circumferential contact shoulder  28  is formed. A pressure sensor  12 , which is available as a mass-produced item, rests against the contact shoulder  28  and is comprised of a measuring cell  30  and a resistance bridge circuit  20  that is affixed to this cell. The measuring cell  30  of the pressure sensor  12  is embodied as hat-shaped for safety reasons among other things and is correspondingly comprised of a cover plate  30   a,  a wall  30   b,  and a collar  30   c  which cooperates with the contact shoulder  28  of the recess  18 . The resistance bridge circuit  20  is fastened to the outside of the cover plate  30   c  of the measuring cell  30  protruding from the recess  18  and, by means of contact lines  21 , is electrically coupled to a circuit holder  14 , which is laterally affixed to the console  11  and processes the measurement results. The circuit holders  14  have contact pins  34 , which are embodied on their circumference side oriented toward the printed circuit board  22 , protrude through plug bores, not shown, in the printed circuit board  22  fastened at right angles to the circuit holders  14  on the console  11 , and are conductively connected to this printed circuit board  22 . 
     FIG. 2 also shows that the inside region of the measuring cell  30  is filled up by a bushing  35  except for a narrow measuring gap  36  extending parallel to the cover plate  30   a.  The bushing  35  has a likewise hat-shaped outer contour, is dimensionally matched to the inner diameter of the measuring cell  30 , and has a straight measuring tube  24  passing through it along its longitudinal axis. The first end of this measuring tube  24  feeds into the measuring gap  36  while the second end, not shown, disposed opposite this ends at a pressure measurement point of a hydraulic circuit. Among other things, the bushing  35  has the function of sealing the measuring gap  36  in relation to the outside. To this end, the bushing  35  has an airtight connection  27  with the measuring cell  30  and also with the measuring tube  24 . This connection  27  can be embodied for example as a solder or a weld, in particular as a laser weld. This ensures that the pressure level in the measuring gap  26  is identical to that of the pressure measurement point and can be reliably measured. Because the size of the measuring gap  36  has been reduced by the bushing  35  to an obligatory minimum, there is the additional assurance that larger portions of residual air possibly present in the hydraulic circuits to be measured or in the measuring tubes  24 , which could distort the pressure measurement, cannot collect in the measuring gap  36 . 
     FIG. 3 shows a measuring device  10 . 1  as a second exemplary embodiment, which is essentially comprised of the same component parts as the measuring device  10  described above. Identical components are therefore provided below with the same reference numerals while structurally altered components are indicated by having the index  1  added to their reference numerals. In contrast to the measuring device  10 , the measuring device  10 . 1  has pressure sensors  12  which are disposed at right angles to the longitudinal direction of the supports  15  (FIG.  1 ). The pressure sensors  12  thereby protrude with their ends which have the resistance bridge circuit  20  through corresponding bores  37  in a printed circuit board  22 . 1 . The printed circuit board  22 . 1  is fastened to the console  11 . 1  with the aid of screw connections  38 . Advantageously, the pressure sensors  12  can thus contact the printed circuit board  22 . 1  directly. In addition to the plug device  13 , the evaluation circuits for the resistance bridge circuits  20  in the form of integrated circuits  39  are also placed on the printed circuit board  22 . 1 . The measuring device  10 . 1  is therefore distinguished by a considerably smaller number of individual parts since the circuit holders  14  which were required in the first exemplary embodiment and their contact lines  21  can thus be eliminated without being replaced. As a result, the assembly expense for the measuring device  10 . 1  is reduced along with a simultaneous increase in its reliability. The embodiment of the measuring tube  24  is also slightly different in the measuring device  10 . 1 . FIGS. 4 and 5 show two embodiments for this that can be produced in a comparatively inexpensive manner. 
     According to FIG. 4, a bushing  35  that is embodied identically to the one in the first exemplary embodiment is inserted into the measuring cell  30  of the pressure sensor  12  disposed at right angles to the supports  15  and is affixed by way of an airtight connection  27 . Due to the altered position of the pressure sensor  12 , the measuring tube  24 . 1 , which is at first routed parallel to the supports  15 , has a bend  40  before it feeds into the bushing  35 . If such a band  40  of the measuring tube  24 . 1  were to be undesirable for certain applications for stability or cost reasons, an embodiment that has been improved in this regard is shown in FIG.  5 . 
     According to FIG. 5, instead of adapting the measuring tube  24 . 1  to the altered position of the pressure sensor  12 , the proposal is made to adapt the bushing  35 . 1  that is inserted into the measuring cell  30 . To this end, the bushing  35 . 1  is lengthened until its end remote from the measuring cell  30  of the pressure sensor  12  protrudes past the console  11 . A blind bore  42  is embodied in the bushing  35 . 1  and extends from its opening, which feeds into the measuring gap  26 , into the vicinity of the end of the bushing  35 . 1  that protrudes beyond the console  11 . A radial bore  43  is disposed in the protruding region of the bushing  35 . 1  and continues the blind bore  42  toward the outside. The measuring tube  24  is fixed in this radial bore  43  by way of the airtight connection  27 . This measuring tube  24  can consequently still be routed parallel to the supports  15  and thereby be embodied as straight despite a position of the pressure sensors  12  which is offset at right angles to that of the supports  15 . 
     Naturally it is possible for there to be changes or additions to the above-described exemplary embodiment of a measuring device  10  without departing from the fundamental concept of the invention. For example, it is therefore conceivable to also use a measuring device  10  of this kind for measurement tasks outside the automotive field. These applications are also not limited to pressure measurements since the pressure sensors  12  can also be replaced by arbitrary other sensors.