An electromagnetically actuatable valve for hydraulic control devices in motor vehicles is embodied as a pressure-equalized seat valve in a mode of construction comprising a hydraulic part with a valve dome and an electrical part that can be slipped onto the valve dome. In a magnet valve that is normally open, the tubular tappet that supports the closing member is supported at one point in a first bearing point, in terms of the longitudinal direction, that is embodied as a slide bearing, and a bearing ring that forms the sealing point accomplishes the hydraulic pressure equilibrium with the effective sealing diameter of the closing member that together with the valve seat forms the second bearing point. With the valve, very short switching times, in particular less than 0.5 ms, can be achieved with an economical mode of construction.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is directed to an improved electromagnetically actuatable valve for a hydraulic control device for a motor vehicle.

2. Description of the Prior Art

One electromagnetically actuatable valve of the type with which this invention is concerned is known from German Patent Disclosure DE 195 36 619 A1 and is suitable for hydraulic controls in traction-controlled brake systems. For economical mass production, this valve is provided with simple parts by providing that the magnet valve has a hydraulic part with a valve dome, onto the outside of which valve dome the electrical part of the valve with the electromagnet is slipped. To embody this valve for high pressures and fast switching, it is embodied as a pressure-equalized seat valve. For the pressure equilibrium, in this magnet valve, the tappet that carries the actual closing member is hollow and embodied with a continuous longitudinal bore, in which a pin is guided with a relatively narrow gap and thus tightly; the pin diameter and the effective sealing diameter at the closing member are of equal size, in order to achieve the pressure equilibrium. Moreover, over a long axial range, the tappet is guided with its jacket face in a housing bore in such a way that a gap for transmitting pressure from an outflow opening into a pressure chamber of the valve dome is available for the pressure equilibrium of the seat valve. Although this valve is already economical in construction and makes a fast switching time possible, these sealing provisions on the piston principle, with long pistons and bores and with sealing gaps and leakage gaps, mean that the switching times are technologically limited and are therefore unsuitable for some applications that involve especially short switching times. Moreover, this valve is embodied only as a magnet valve that is normally open and does not make a valve construction that is normally closed possible. The pin in the tubular, longitudinally movable tappet is braced against the housing and also makes for a complicated construction, which is moreover less well suited to miniaturization of valves.

From European Patent Disclosure EP 0 720 551 B1, an electromagnetically actuatable valve is also known which by its simple construction is suitable for economical mass production and can be embodied as either a normally closed or a normally open magnet valve of the seat valve type. However, in this valve, there are different ratios of surface area in the hydraulic region, and hence this valve is not pressure-equalized; moreover, it has relatively long sealing provisions based on the piston principle, with a leakage gap between the piston and the bore, so that these valves too are limited in terms of the pressure that can be switched and their switching times to such an extent that they cannot meet especially stringent demands. This is above all true if switching times in the range of a millisecond or less are required.

From German Patent Disclosure DE 38 02 648 A1, an electromagnetically actuated valve is also known, which with a compact construction is embodied as a fast-switching, pressure-equalized seat valve. In this valve, through which the flow can be in both directions, the armature itself forms the movable closing member and is embodied for that purpose as a sleeve, which is disposed longitudinally displaceably on a guide pin that is structurally connected to the housing. Once again, the guide pin operates with axially relatively long seals on the piston principle, or seals with an O-ring are employed. Particularly the O-ring or an elastomer seal, because of their radial contact pressure, cause friction and thus problems that stand in the way of shortening the switching time. Also, this valve has a special structural form, which cannot be derived from valves, produced in large-scale mass-production, for traction-controlled brake systems.

OBJECT AND SUMMARY OF THE INVENTION

The electromagnetically actuatable valve of the invention has the advantage over the prior art that with it, given a simple, economical construction, the switching times can be reduced still further, making it possible to meet even especially stringent demands. Thus fast-switching valves can be achieved whose switching times are less than a millisecond and in particular less than 0.5 ms, since hydraulic contrary forces and damping are reduced to a minimum. Simple components that are already in mass production and economical seat valves can be employed. Moreover, both a normally open and a normally closed magnet valve can be realized. In this way, the valves can be used in an electrohydraulic valve controller for gas exchange valves in the inlet and outlet region of gasoline or Diesel engines, and because of the especially short switching times, even high engine speeds can be mastered.

By the provisions described below advantageous refinements of and improvements to the valve defined by the main claim are possible. A kind of two-point bearing is especially advantageous, so that axially long piston seals with leak fuel gaps are omitted entirely. Because of the radial bearing of the closing member means at only two points, which are as far apart as possible, a low-friction slide bearing is the result, which on the one hand assures an adequate pressure equilibrium and on the other permits very short switching times. In addition, centering the closing member in the sealing seat requires no additional effort or expense. In one embodiment of the valve, both production and design of the pressure equilibrium precisely in small valves can be favorably achieved. It is also advantageous if the valve is embodied with relatively great radial play in the housing; an interfering influence of alignment and angular errors of the tappet or armature can then be avoided in a simple way. Hydraulic damping is also avoided and a simple construction is favored. In an especially favorable embodiment despite component alignment errors and with simple production, a tight valve can always be achieved. Especially economical production is obtained if the bearing ring is formed directly onto the closing member means or is partially ground, thus dispensing with one additional component. Other embodiments are also practical for favoring simple mass production, by using a type of construction as in magnet valves for traction-controlled brake systems. A magnet valve that is normally open can be realized.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1shows a longitudinal section through an electromagnetically actuatable valve10in a simplified view; it is embodied a fast-switching seat valve of pressure-equalized construction and as a normally open magnet valve. Valve10comprises a hydraulic part11with an electrical part12slipped onto it. For that purpose, the hydraulic part11has a valve housing13, in which a cup-shaped, thin-walled capsule17and a pot-shaped valve sleeve18are secured tightly and firmly to a tubular valve insert14on the opposite ends15,16of the valve housing. Part of the valve insert14, together with the capsule17, in this way forms a pressure-tight valve dome19, in which magnetically operative elements such as an armature21and a magnet core22are received. The armature21is supported longitudinally movably in the capsule17.

The electrical part12of the valve10is slipped onto this valve dome19in a manner known per se. An annular magnet coil23surrounds the valve dome19. The magnet coil23is surrounded by a bell-shaped magnet housing24, which on one end engages the capsule17and on the other rests on a yoke disk25, which closes a magnetic circuit of the electrical part12via the valve insert14. The yoke disk25can be firmly built into the magnet housing24and can contact the valve insert14closely, so that it can be slipped onto the valve dome19together with the electrical part12.

The valve insert14also has an annular flange26on its outer circumference, with which flange the valve10can be inserted into a stepped bore, not identified by reference numeral, in a valve block and then, by wedging or crimping of the material comprising the valve block, which in particular is of lightweight metal, can be secured tightly and firmly, as is taught in particular by EP 0 720 551 B1 cited at the outset, in which this type of fastening is described in further detail for magnet valves for traction-controlled brake systems.

The valve sleeve18is tightly fastened to the lower end16of the valve insert14by an annular welding point27; in this valve sleeve18, an inflow opening28is disposed on the bottom and an outflow opening29is disposed radially. Between these openings28,29, an annular valve body31, which centrally has a conical valve seat32, is press-fitted tightly and firmly in the interior of the valve sleeve18.

The tubular valve insert14has a continuous longitudinal bore33, in which a tubular tappet34is disposed. This longitudinal bore33is stepped in the region of the upper end15and therefore forms a relatively short bearing bore35of smaller diameter, in which the tappet34is guided slidingly in the longitudinal direction by a bearing ring36on the outside. The bearing bore35and the bearing ring36extend axially over only a very short range, so that it can be said to be a kind of pointlike bearing point37here. While this first bearing point37is embodied on the end toward the armature of the tubular tappet34that penetrates the entire valve insert14longitudinally, a second bearing point38for the tappet34is located as far away from it as possible. For that purpose, on its end toward the valve seat32, the tappet34has a closing member39. This closing member39has a sealing face41, embodied in the form of a spherical segment, which is located facing the conical valve seat32and is associated with it, so as to form the seat valve42that is connected between the inflow opening28and the outflow opening29. This sealing face41annularly surrounds a central opening43of a conduit44that penetrates the tubular tappet34and causes both of its ends to communicate hydraulically with one another, so that by way of this conduit, an unhindered pressure equilibrium can be effected. Since the stroke of the tappet34is relatively short, the closing member39always remains inside the guide through the conical valve seat32and thus forms the second bearing point38.

The effective sealing diameter of the closing member39in the valve seat32is embodied such that it is essentially the same size as the outside diameter of the bearing ring36, which with the bearing bore35forms a slide bearing. In addition, the bearing ring36also provides a sealing point, which divides the chamber45, communicating with the outflow opening29, from the pressure chamber46in the capsule17in which armature21is received. This pressure chamber46, via a transverse groove47in the tappet34, is always in communication with the conduit44. Because of this embodiment of the bearing points37,38, which at the same time function as sealing points, a hydraulically effective equilibrium in terms of area is created, which results in a valve construction that is pressure-equalized to both sides.

To compensate for production variations or errors in oblique positioning or axial errors, the bearing ring36secured to the tappet34is embodied on the outside in the form of a spherical segment, so that the sealing point is embodied essentially linearly. Via this linear sealing point of the first bearing point37, a limited leak fuel flow can build up, but it can be reduced toward the respective other, pressureless connection.

In the region of the valve sleeve18, a support ring48is pressed onto the tappet34, near the closing member39. A compression spring49surrounding the tappet34is braced on one end on this support ring48and on the other on the valve body31and thus keeps the seat valve32,39open, resulting in a normally open magnet valve. In addition, the tappet34is adapted in terms of its outer diameter to the inner diameter of the longitudinal bore33in such a way that there is a relatively large annular gap51; through this annular gap51, an undamped pressure buildup can be achieved, and a situation in which, in the event of axial errors, two components touch one another outside the two bearing points37,38and create problematic friction is averted. The tappet34is pressed by the compression spring49against the armature21, which in turn is braced on the capsule17in a manner structurally connected to the housing. In the present valve10of the normally open type, the armature21is disconnected from the tappet34, so that there are two different components. The two components21,24are together referred to as closing member means52, which are electromagnetically actuatable.

The mode of operation of the valve10will now be explained as follows, on the assumption that the basic function of such two-way seat valves is known per se.

The valve10is embodied as a valve that is open when without current and that furthermore functions as a pressure-equalized seat valve. A pressure fluid stream to be controlled can therefore flow from the inflow opening28to the outflow opening29or in the opposite direction through the seat valve. Any pressure difference that might occur in the flow between the valve seat32and the closing member39acts not only on the effective sealing face41but also on the counterpart pressure face of the same size at the first bearing point37. Thus the pressure from the inflow opening28can build up unhindered in the tappet34and in the pressure chamber46via the conduit44and from the pressure chamber can act upon the bearing ring36from above, while the pressure in the outflow opening29can propagate unhindered via the annular gap51and can act upon the bearing ring36from below. Because of equal-sized hydraulically effective surface areas, the tappet34is hydraulically pressure-equalized. Depending on the pressure difference, a limited leak fuel flow through the sealing point37toward the lower pressure level can arise, but this leak fuel flow does not problematically affect the pressure equilibrium.

If the valve10is to be closed, the magnet coil23is excited and the armature21is thus moved, and the tappet34contacting the armature is deflected mechanically downward; the tappet34is moved, counter only to the force of the compression spring49, until its sealing face41rests tightly on the valve seat32. Because of the pointlike bearing points37,38, at which major friction resistances do not occur, especially fast reciprocating motions are made possible as a result, since there are no seals on the piston principle with long leakage gaps, nor are there any radial forces, causing friction, from O-rings or elastomer seals. In this way, switching times of less than 1 ms and in particular less than 0.5 ms can be attained. The valve10can therefore be used especially advantageously in electrohydraulic valve controllers of gas exchange valves in the inlet and outlet region of gasoline or Diesel engines, where high engine speeds as well as highly variable temperatures must be taken into account. The valves function with strokes of only approximately 0.3 to 0.6 mm.

If the valve10is switched by excitation of the magnet coil23, then the armature21is pulled downward by the magnet core22and, via the tappet34, presses the closing member39tightly against the valve seat32counter to the force of the compression spring49; the seat valve is closed. If high pressure should thereafter prevail at the outflow opening29while the inflow opening28is relieved, then a leak fuel flow, flowing out via the bearing ring36, can reach the pressure chamber46and flow onward away to the inflow opening28via the transverse groove47and the conduit44. The situation is correspondingly the reverse if with the seat valve closed, pressure occurs at the inflow opening28, and the outflow opening29is relieved. In both cases, the closing member means52remain pressure-balanced, so that with the valve10, high pressures and short switching times can be controlled.

FIG. 2shows a longitudinal section through a second valve60, which differs from the first valve ofFIG. 1as follows, using the same reference numerals for the same structural elements.

In principle, the second valve60has the same makeup, comprising a hydraulic part11and an electrical part12, but is embodied as a normally closed valve. For this purpose, the hydraulic part11has a different valve housing61, in which a thin-walled housing sleeve62, a pole core63, and a valve body64are tightly secured to the opposite ends. The inflow opening28and the valve seat32are embodied on the hollow-cylindrical valve body64, which is joined tightly and firmly to the housing sleeve62by a wedged feature65. Because of the thin-walled housing sleeve62, a reinforced annular flange66is provided for securing the hydraulic part11in a valve block. The valve dome19is now formed by the pole core63and part of the thin-walled housing sleeve62, onto which part the electrical part12is slipped. The pole core63now has a central blind bore67, which is open toward the valve body64and in which the pressure chamber46is embodied, and in which a compression spring68is now disposed.

The closing member means69are disposed longitudinally movably in the interior of the valve housing61, and these closing member means69are embodied in one piece and essentially form the armature71. On its upper end, the armature71has an integral stepped bolt72of lesser diameter, which protrudes into the blind bore67, where with the aid of the first bearing point37it forms a slide bearing and a sealing point. For forming the first bearing point37, the bearing ring36is formed integrally onto the closing member means69; an annular bead74is partially ground on the jacket face of the stepped bolt72and in cross section has a spherical outer contour, so as to perform the functions of both a slide bearing and a sealing point. This one-piece mode of construction is especially economical for relatively large numbers of mass-produced items. On the opposite end of the armature71, there is a closing member73which cooperates in a corresponding way with the valve seat32and at the same time forms the second bearing point38. The armature71is penetrated by the conduit44, so that by way of this conduit the inflow opening28is made to communicate hydraulically with the pressure chamber46. The outflow opening29is now disposed in the thin-walled housing sleeve62itself.

The second valve60is thus embodied in a corresponding fashion to the first valve10ofFIG. 1, such that the one-piece closing member means69, namely the armature71, is guided at only two pointlike bearing points37and38. In addition, the area ratios at the closing member73and in the bearing point37are adapted to one another such that a hydraulically pressure-equalized seat valve is created. The armature71is disposed with a relatively great gap between its outer circumference and the thin-walled housing sleeve62, so that no problematic friction occurs upon a motion of the armature. The mode of operation of the second valve60is logically equivalent to that of the first valve10, with the difference that it is embodied as a normally closed valve.

It is understood that in the exemplary embodiments shown, variations may be made without departing from the concept of the invention. For instance, instead of the bearing ring36shown inFIG. 1, a spherical component that is pressed onto the tappet may be used. A bearing ring of this type can also be dispensed with entirely, if its guide face is ground directly on the moving part, that is, the tappet or the armature. Moreover, it is possible to transpose the components of the first bearing point kinematically and to provide the function of the former bearing ring in the component that is structurally connected to the housing. It could also be advantageous, for instance in the pole core ofFIG. 2, to press-fit a suitable bearing of its own into the pole core. Still other changes may be made without departing from the concept of the invention.

The valve can be used as both a switching valve and a regulating valve. Because the effective surface areas are designed to be of unequal size hydraulically, the valve can be designed to open or close with slight pressure reinforcement. As a result, the valve can additionally be influenced in terms of its switching speed.