Abstract:
An electromagnetic valve is provided with an elongated tappet guided axially displaceably in a tappet guide, and with a sealing body, embodied on the tappet, that can seal against a sealing seat. So that the valve can be produced more economically yet can be regulated more precisely, the sealing seat and the tappet guide are embodied in one piece. The adjustability of the valve is assured in particular by an adjusting ring.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a 35 USC 371 application of PCT/EP 2004/053413 filed on Dec. 13, 2004. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to an electromagnetic valve, in particular for a brake system of a motor vehicle, having an elongated tappet, which is guided axially displaceably in a tappet guide, and having a sealing body, embodied on the tappet, that can seal against a sealing seat. 
   2. Description of the Prior Art 
   In known brake systems, electromagnetic valves are used particularly as inlet or switchover valves, in order to furnish anti-lock, traction control or electronic stability program functions for brakes of an associated motor vehicle. Known electromagnetic valves have an elongated tappet, which is guided axially displaceably in a substantially hollow-cylindrical tappet guide. A likewise hollow-cylindrical sealing seat is press-fitted into the hollow-cylindrical tappet guide, and a sealing body located on one end of the tappet can then strike this sealing seat and hence provide sealing. The press-fitting of the sealing seat into the tappet guide can change the geometry of the entire arrangement for adapting and adjusting the desired valve function. In particular, when the sealing seat is open, an existing air gap in the axial direction between the tappet and the tappet guide can be adjusted. 
   With such an open sealing seat, an operating medium, such as a brake fluid, flows through the sealing seat into the interior of the tappet guide, where after a deflection by an angle of 180° it is then fed onward, through as a rule three longitudinal grooves embodied in the tappet guide and six further radial grooves, then after a further deflection by an angle of 180° it is fed in the direction of a radial filter, and after flowing through the radial filter and after a final deflection by an angle of 90°, it is fed into the associated hydraulic unit of the electromagnetic valve. 
   OBJECTS AND SUMMARY OF THE INVENTION 
   The object of the invention is to furnish an electromagnetic valve, particularly for a brake system of a motor vehicle, which in comparison to known valves can be produced more economically and in particular can also be regulated better. 
   This object is attained according to the invention with an electromagnetic valve as described at the outset, in which the sealing seat and the tappet guide are embodied in one piece. The invention is based on the recognition that in known valves, their most important function, namely sealing and regulating pressure, are done with a sealing body and a sealing seat that are linked with one another via a comparatively large number of interfaces. Each of these interfaces involves dimensional, shape and positional tolerances, which impairs the replicability of the position of the tappet that is important for regulating pressure. 
   According to the invention, the number of interfaces between the sealing body and the sealing seat is reduced to a minimum, and in contrast to known electromagnetic valves, a plurality of components are combined into a single one. As a result, according to the invention, the number of unknowns are restricted, and the position of the tappet can be better reproduced. This improvement is expressed in every individual valve. It moreover gains in importance when a plurality of valves are controlled with adaptation to one another, as in brake systems today. 
   Despite this improvement, in the electromagnetic valve of the invention, the possibility of adjusting the sealing and pressure regulating functions is still preserved. In fact, as will be described in further detail below, in the valve of the invention geometric differences among parts can still be advantageously compensated for. 
   As noted, it is the nucleus of the invention that the sealing seat, or a valve body, is embodied in one piece with the tappet guide, or a valve insert. Based on this design according to the invention, the guide of the tappet can be made comparatively narrow, so that the tappet and its sealing body replicably strike in or on the sealing seat. 
   In an advantageous refinement of the electromagnetic valve of the invention, it is purposefully wanted, and that both the tappet guide and the tappet are accordingly designed, that the sealing body strikes the sealing seat centrally. Alternatively, this striking action can be purposefully done eccentrically. Both possibilities can be attained with the one-piece sealing seat-tappet guide component of the invention, at comparatively little effort or expense. In the valve of the invention, the location of the sealing seat can be machined especially precisely, particularly in the radial direction, inside the tappet guide. Therefore the position of the tappet and of its sealing body in proportion to the sealing seat in this radial direction is also comparatively precise. 
   In the tappet guide of the invention, an adjusting device is also advantageously provided, by means of which an air gap can be adjusted in the axial direction between the tappet and the tappet guide. With the adjusting device, tolerances in length of the aforementioned individual parts can be compensated for, and the width of the air gap, existing when the sealing seat is closed, between the sealing body and the sealing seat can be adjusted. 
   An adjusting device of this kind is especially advantageously designed as an adjusting ring, which is located particularly on the tappet guide. As a result, the tappet guide overall takes on a triple function, because it has the sealing seat, it guides the tappet, and it forms the basis for the adjusting device. In this way, the aforementioned air gap can be adjusted for instance by a simple displacement of the adjusting ring on the tappet guide. 
   Especially advantageously, the adjusting ring is fixed on the tappet guide with the aid of a radial compression. The radial compression can be embodied comparatively precisely and simply during the adjustment of the valve function, and the length ratios adjusted in the process no longer change in subsequent operation of the electromagnetic valve. 
   Alternatively or in addition, the adjusting device may be designed as an adjusting ring, which is fixed by means of a laser-welded seam, in particular on the jacket face of a substantially cylindrical tappet guide. The laser-welded seam assures a durable, fluid-tight and positionally accurate connection between the adjusting ring and the tappet guide. 
   A cap can advantageously be placed on the tappet guide and/or the adjusting ring and can then be fixed inexpensively on the adjusting ring by means of a further laser-welded seam. Once the cap is slipped onto the adjusting ring, the maximum deflection of the tappet in the tappet guide can be defined. 
   In an electromagnetic valve according to the invention embodied in this way, the magnetic flux passes from the tappet guide radially to the adjusting ring and from it axially into an armature, located on the tappet, of the valve. In the process, the adjusting ring as a rule does not take on any guide function for the tappet. 
   Advantages in the assembly of the parts of the tappet with its armature, the cap, and the adjusting ring are also obtained as a result of the one-piece sealing seat-tappet guide component provided according to the invention. Thus during assembly, the tappet stroke can be set by simply varying the relative position of the adjusting ring on the tappet guide by means of the radial compression. The air gap between the armature of the tappet and the adjusting ring can subsequently be adjusted by varying the relative position of the cap or capsule on the adjusting ring, again with the aid of a radial compression. Both relative positions and the tightness of the entire valve are then assured by the aforementioned double laser-welded seam. The electromagnetic valve of the invention can therefore be produced and assembled inexpensively. Moreover, there are advantages in terms of the regulatability of the valve. 
   A sealing seat is not press-fitted into the tappet guide of the invention, and thus the tappet guide need not absorb corresponding pressure forces and can optionally be embodied as comparatively thin in the region of the sealing seat. This saves material, weight and expenses. Moreover, at least one radial bore can advantageously be embodied on the tappet guide of the invention, in the region of the sealing seat, by which bore a fluid flowing through the sealing seat can be carried away to the outside of the tappet guide. In this outflow of the fluid, its flow is deflected only once, by an angle of 90°. The flow resistance is correspondingly reduced. Furthermore, the tappet guide then also takes on the function of “conducting the outflow”, so that other components of the electromagnetic valve of the invention, which have previously taken on this function, can be embodied correspondingly more simply. For instance, a plastic insert, provided in known valves, on the side of the sealing seat facing away from the tappet can be designed correspondingly simply. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments of an electromagnetic valve according to the invention are described in further detail below in conjunction with the accompanying schematic drawings. Shown are: 
       FIG. 1 , a longitudinal section through an electromagnetic valve of the prior art; 
       FIG. 2 , a longitudinal section through a first exemplary embodiment of an electromagnetic valve of the invention; 
       FIG. 3 , a view of the magnetic flux and of the flow of the operating medium in the electromagnetic valve of the invention as shown in  FIG. 2 ; and 
       FIG. 4 , a longitudinal section through a second exemplary embodiment of an electromagnetic valve of the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   In  FIG. 1 , an electromagnetic valve  10  of the prior art is shown. As its central component, the valve  10  has a substantially hollow-cylindrical tappet guide  12 , or valve insert, on the outside of which a collar  14  is embodied approximately in the middle of its length and a through opening  16  is embodied in the longitudinal direction in the interior. In the through opening  16 , a substantially circular-cylindrical tappet  18  is supported displaceably in the longitudinal direction of the tappet guide  12 . On the lower end of the tappet  18 , in terms of  FIG. 1 , a sealing body  20  is provided, which has a spherical-segment-shaped surface  22  that bulges downward. 
   Diametrically opposite the sealing body  20 , there is a sealing seat  24  or sealing body which is designed essentially hollow-cylindrically and which has a frustoconical surface  26  opposite the spherical-segment-shaped surface  22 . A spiral spring  28 , which acts as a compression spring and is braced on the sealing seat  24 , is thrust onto the lower part of the tappet  18 , which—as can be seen from FIG.  1 —is designed with a smaller diameter. 
   On the face end, facing away from this spiral spring  28 , of the substantially hollow-cylindrical sealing seat  24 , there is a virtually disk-shaped insert body  30 , with a check ball valve  32  embodied eccentrically in it. A slightly cup-shaped axial filter  34  is located on the lower face end, in terms of  FIG. 1 , of this insert body  30 . 
   A through bore  36  is embodied in the insert body  30 , and a through bore  38  adjoining this through bore  36  is embodied in the longitudinal direction in the sealing seat  24 . Through these through bores  36  and  38 , a fluid operating medium or fluid delivered through the axial filter  34  can reach the conical-segment-shaped surface  26  of the sealing seat  24 . In the operating state shown, the sealing body  20  does not rest on the sealing seat  24 . The operating medium is therefore capable of getting into the chamber in and around the spiral spring  28 , and from there it can flow out through one or more longitudinal grooves  40  embodied in the tappet guide  12 , a plurality of radial grooves  42  embodied in the insert body  30 , and a radial filter  44  located on the jacket face of the tappet guide  12 . 
   So that this flow of operating medium through the sealing seat  24  can also be interrupted by the valve  10 , the tappet  18 , on its upward end portion in terms of  FIG. 1 , has an electromagnetic armature  46 . This armature can be moved with the aid of an electromagnet, not shown, so that the tappet  18  is displaced in the tappet guide  12  and the spherical-segment-shaped surface  22  is guided toward the conical-segment-shaped surface  26 . 
   In order to enable this motion of the tappet  18 , an air gap  48  is embodied between the upper end face, in terms of  FIG. 1 , of the substantially hollow-cylindrical tappet guide  12  and the lower end face of the armature  46 . A substantially cup-shaped cap  50  is also fitted over the armature  46  and is fixed on the outer jacket face of the tappet guide  12  with the aid of a circumferential welded seam  52 . 
   In  FIG. 2 , an exemplary embodiment of an electromagnetic valve  10  of the invention is shown. In contrast to the valve  10  shown in  FIG. 1 , the valve of  FIG. 2  has a one-piece sealing seat-tappet guide component  54 , which takes on both the function of a tappet guide and the function of a sealing seat. 
   As a further innovation compared to the valve  10  shown in  FIG. 1 , the valve  10  of  FIG. 2 , in the upper end region in terms of  FIG. 2 , has an adjusting ring  56  of L-shaped cross section, which is fixed on the tappet guide  12  with the aid of a press fit or radial compression  58 . The adjusting ring  56  has no guidance function for the tappet  18  and instead serves to adjust the air gap  48 , which now, in the valve  10  of  FIG. 2 , is formed between the upper end face of the adjusting ring  56  and the lower end face of the armature  46 . 
   In the valve  10  of  FIG. 2 , a cap  50  is fitted over the adjusting ring  56  and the upper region, in terms of  FIG. 2 , of the tappet guide  12 ; it is firmly slipped onto the tappet guide  12  with the aid of a press fit or radial compression  60  and is then fixed on the outer circumference of the tappet guide  12  with a laser-welded seam  62 . 
   Besides these innovations, in the sealing seat-tappet guide component  54  of the valve  10  of  FIG. 2 , two or more diametrically opposed radial bores  64  are embodied above the conical-segment-shaped surface  26  of the sealing seat portion of the sealing seat-tappet guide component  54 . An operating medium flowing through the sealing seat portion of the sealing seat-tappet guide component  54  can flow through these radial bores  64 , deflected only twice at an angle of 90° each, to the radial filter  44  located on the outer jacket face of the tappet guide  12 . In  FIG. 3 , this primary direction of the flow of the operating medium through the radial bores  64  is illustrated by an arrow  66 . 
   In  FIG. 3 , the primary line  68  of the magnetic flux in or on the valve  10  of  FIG. 2  is also shown. As can be seen, the magnetic flux passes from the tappet guide  12  radially toward a leg of the adjusting ring  56  of L-shaped cross section and from it axially into the armature  46 . The cap  50  comprises material that conducts magnetic flux, and it closes the magnetic circuit between the sealing seat-tappet guide component  54  and the armature  46 . An electric coil that generates the magnetic field or flux is not shown. It can be assumed that this coil is slipped onto the magnet valve and surrounds both the armature  46  and the tappet guide  12  as far as the collar  14 . 
   In the valve  10  shown in  FIGS. 2 and 3 , the insert body  30  is designed precisely the same as that in  FIG. 1 , although the radial grooves  42  in the insert body  30  are no longer necessary and can therefore be omitted. 
   In  FIG. 4 , a second exemplary embodiment of an electromagnetic valve  10  of the invention is shown, which in terms of the sealing seat-tappet guide component  54  and the one-piece design thus attained of the sealing seat and tappet guide is designed like the sealing seat-tappet guide component  54  shown in  FIGS. 2 and 3 . 
   However, in the region of the adjusting ring  56 , the valve  10  of  FIG. 4  is modified. Here the adjusting ring  56  is embodied as comparatively long in the longitudinal direction, and between the lower end region, in terms of  FIG. 4 , of the this long adjusting ring  56  and the upper end region of the sealing seat-tappet guide component  54 , a radial compression  70  and an extensive laser-welded seam  72  are embodied. Onto the remaining jacket face of the long adjusting ring  56 , the cap  50  is slipped onto the adjusting ring  56  at a radial compression  74  and then likewise fixed with a laser-welded seam  76 ; the two laser-welded seams  72  and  76  may be made in a single operation. Alternatively, the laser-welded seams  72  and  76  may be made in succession and possibly even at different work stations. 
   The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.