The invention relates to a valve, in particular a proportional pressure regulating valve, comprising a valve housing (10) and a valve piston (12) which is arranged in the valve housing in a longitudinal a movable manner and which can be actuated by means of an actuation magnet (14) so as to produce either a fluidic connection between a pressure supply connection (P) and a load connection (A) or between the load connection (A) and a return connection (T) in the valve housing (10), wherein the valve piston (12) is permanently fluidically connected to the return connection (T) at the opposing end faces (44, 46) of the valve piston. The invention is characterized in that the valve piston (12) has a pressure-active measuring surface (50) in the region of the load connection (A), said pressure-active measuring surface providing the respective fluid pressure at the load connection (A) as a counterforce to the actuation force of the actuation magnet (14) when the actuation magnet (14) is energized in order to produce a fluidic connection between the pressure supply connection (P) and the load connection (A).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to German Patent Application No. DE 10 2021 003 039.7, filed on Jun. 12, 2021 with the German Patent and Trademark Office. The contents of the aforesaid Patent Application are incorporated herein for all purposes.

TECHNICAL FIELD

The disclosure relates to a valve, in particular a proportional pressure reducing valve, having a valve housing and a valve piston, which is arranged therein so as to be longitudinally movable and which can be actuated by means of an actuating solenoid to produce either a fluid-conducting connection between a pressure supply port and a consumer port or between this consumer port and a return port in the valve housing, the valve piston being permanently connected to the return port on its opposing end faces in a fluid-conducting manner.

BACKGROUND

One proportional pressure reducing valve, in particular for hydraulically controllable clutches, can be ordered and purchased from the applicant/proprietor under catalogue number PDMC05S30A-50. This is a direct-acting proportional pressure reducing valve, having a valve housing and a valve piston, which is arranged therein so as to be longitudinally movable and which can be actuated in turn by means of an actuating solenoid to produce either a fluid-conducting connection between a pressure supply port and a consumer port or between this consumer port and a tank or return port in the valve housing, the valve piston being permanently connected to the return port on its opposing end faces in a fluid-conducting manner. Viewed in ascending order towards the actuating solenoid, the tank or return port is arranged first on the end face in the valve housing, following in turn from this the consumer port is installed in the radial direction, and again following in the radial direction is the pressure supply port in the form of at least one transverse drilled hole, regularly in the form of a pump supply port. Furthermore, a longitudinal drilled hole with a relatively small diameter is additionally incorporated in the valve housing in the axial direction, which diameter permanently connects a valve chamber, above the pressure supply port and opening towards the valve piston, in a fluid-conducting manner to the consumer port which can consist of a plurality of drilled holes of a row of drilled holes. In the region of the valve chamber, the valve piston has a small change in diameter and in this respect the resulting annular surface forms a pressure-active measuring surface on the valve piston because the opposing end faces of the valve piston are permanently connected to the tank or return port via a central drilled hole as the fluid-conducting connection.

The control pressure occurring during operation then acts in this respect against the said annular or measuring surface and causes an axial force which counteracts a magnetic force of the actuating solenoid in the energised state. Thus, the control pressure can be changed proportionally depending on the magnetic force applied in each case. If the control pressure is less than the magnetic force, the piston moves towards the return or tank port and in this respect opens a fluid connection from the pressure supply port towards the consumer port. If, on the other hand, the pressure is too high, the valve piston moves in the opposite direction and a fluid-conducting connection is created from the consumer port to the tank or return port. The solution thus known has proven extremely successful in practice; however, the production of the longitudinal drilled hole, which is small in cross-section, requires a relatively long machining time and is therefore cost-intensive to produce.

SUMMARY

A need exists to provide a cost-effective way of producing a valve in a functionally reliable design. The need is addressed by the subject matter of the independent claim(s). Embodiments of the invention are described in the dependent claims, the following description, and the drawings.

DESCRIPTION

In some embodiments, a valve piston of a valve has a pressure-active measuring surface in the region of the consumer port which, when the actuating solenoid is energized, compares the fluid pressure prevailing in each case at the consumer port as a counterforce to the actuating force of the actuating solenoid in order to establish a fluid-conducting connection between the pressure supply port and the consumer port, the above-mentioned change in diameter in the region of the rear valve chamber of the valve piston is now shifted directly to the position of the consumer port, so that in this respect it is possible to dispense completely with the longitudinal drilled hole in the valve housing, which is costly to produce.

The valve concept addressed here is able to switch quickly during a cold start at a viscosity of more than 2,000 cST and in this respect, by eliminating the long throttling point in the form of the longitudinal drilled hole, the cold start behaviour for the valve improves. Furthermore, with the omission of the longitudinal drilled hole, which is kept small in diameter, the diameter of the valve piston itself can be significantly increased so that in such a way the flow resistance of the oil is considerably reduced without increasing the installation space necessary for the valve or the valve piston.

The solution discussed herein implements a directly controlled proportional pressure reducing valve which, when used for hydraulically controlled clutches, makes it possible to generate very large opening cross-sections when the clutch is released in a cost-effective and functionally reliable manner, and thus to ensure rapid disconnection of the clutch without the need for very large and expensive actuating devices in the form of actuating solenoids in addition to valves with large flow cross-sections. However, use of the valve is not limited to clutch applications. Further beneficial configurations of the valve are the subject matter of the dependent claims.

Reference will now be made to the drawings in which the various elements of embodiments will be given numerical designations and in which further embodiments will be discussed.

Specific references to components, process steps, and other elements are not intended to be limiting. Further, it is understood that like parts bear the same or similar reference numerals when referring to alternate FIGS.

The proportional pressure reducing valve shown inFIG.1can be purchased from the applicant/proprietor as a catalogue item under order no. PDMC05S30A-50. A large number of these valves are being used by customers, particularly in the context of operating hydraulically controlled clutches. The solution comprises a valve housing10with a valve piston12arranged therein so as to be longitudinally movable, which can be actuated by means of an energizable actuating solenoid14. In the usual design (DE 10 2013 014 558 A1), the actuating solenoid14comprises an actuatable solenoid armature16as well as an electric coil bobbin18which can be energised by means of a plug connector part20. If the actuating solenoid14is energised via the coil bobbin18, the solenoid armature16, viewed in the direction ofFIG.1, moves downwards from its neutral position shown inFIG.1to an actuating position and at the same time takes with it the valve piston12in contact with it in the same actuating direction, against the action of an energy accumulator in the form of a compression spring22. If no current is applied, the compression spring22mentioned returns the solenoid armature16to its initial position according toFIG.1. In this non-actuated position, a consumer port A in the valve housing10is connected to a tank or return port T in a fluid-conducting manner. This tank or return port T is incorporated into the valve housing10on the face end, whereas the consumer port A is formed from a row of drilled holes23with at least two radial transverse drilled holes which open into the valve housing10transverse to the longitudinal or actuating axis24of the valve. In the embodiment shown according toFIG.1, at least two, but for example six, transverse drilled holes which, arranged radially transverse to the longitudinal axis24of the valve, pass through the valve housing10, are part of the row of drilled holes23.

Viewed in the direction ofFIG.1, at least one further transverse drilled hole26is incorporated above it, which forms a pressure supply port P and is connected to a pressure source, such as a hydraulic pump which is not shown in greater detail. The consumer port A, on the other hand, is connected to a hydraulic consumer, such as a hydraulically actuatable clutch device (not shown). The corresponding connection structure is common, with the result that it will not be discussed in greater detail at this point.

In addition, the valve piston12has a cylindrical recess28on the outer circumference, the axial length of which is dimensioned in such a manner that when the actuating solenoid14is energised, the solenoid armature16drives the valve piston12downwards in such a manner that a fluid-conducting connection is created between the pressure supply port P and the consumer port A while simultaneously shutting off both of the aforementioned ports P, A with respect to the tank or return port T.

As also emerges fromFIG.1, on the right-hand side there is a longitudinal drilled hole30which permanently connects the consumer port A to an annular valve chamber32in a pressure and fluid-conducting manner, which valve chamber opens out towards the valve piston12, the valve piston12being reduced in diameter in this region and to this extent forming an annular surface34as a so-called measuring surface or pressure-active surface. This longitudinal drilled hole30is small in diameter for space-saving reasons and opens out into one of the transverse drilled holes of the row of holes23viewed in the axial direction.

Furthermore, a longitudinal drilled hole36is incorporated in the valve piston12coaxial with the longitudinal axis24, which opens out into the tank or return port T on the lower free end face and into a transverse drilled hole38in the valve piston12on the opposing face, which transverse drilled hole is overlapped by the compression spring22. This transverse drilled hole38discharges into a spring chamber40through which the valve piston12passes and which accommodates the compression spring22, one free lower end of which is supported in the region of the chamber40on a shoulder of the valve housing10and on the opposing side on a shoulder-like widening on the valve piston12.

The valve is designed as an insert valve solution for a valve block not shown in greater detail and has a locating plate42in the manner of a connecting flange for this purpose. The control pressure can now be directed into the valve chamber32above the pressure supply port P via the consumer port A and the longitudinal drilled hole30which is small in diameter. As already mentioned, the valve piston12has a small change in diameter there and in this respect the annular surface34resulting therefrom forms a pressure-active measuring surface on the valve piston12which furthermore is permanently connected with its opposing end faces top and bottom to the tank or return port T via the longitudinal drilled hole36.

The control pressure mentioned acts in this respect against this annular or measuring surface34, thereby causing an axial force which counteracts the magnetic force of the actuating solenoid14in the energised state. Thus, the control pressure can be changed proportionally depending on the magnetic force applied in each case. That is, if the control pressure is less than the magnetic force, then the valve piston moves downwards and opens the flow of fluid from the pressure supply port P to the consumer port A via the cylindrical recess28on the valve piston12. If, on the other hand, the control pressure is too high, the valve piston12moves upwards and a pressure-relieving flow of fluid is created from the consumer port A to the return or tank port T.

The valve solution according to the teachings herein as shown inFIGS.2to4will now be discussed insofar as it differs substantially fromFIG.1, the statements made so far also applying to the new valve solution and the same components being provided with the same reference numbers as in the solution according toFIG.1.

FIG.2shows the valve according to the teachings herein in the form of a proportional pressure reducing valve in one of its control positions. In accordance with the valve solution according toFIG.1, the valve according to the teachings herein also has a valve housing10and a valve piston12, which is arranged therein so as to be longitudinally movable and which can be actuated by means of an actuating solenoid14to produce either a fluid-conducting connection between a pressure supply port P and a consumer port A or between this consumer port A and a return port T in the valve housing10. The return or tank port T regularly leads to a fluid storage tank, whereas the pressure supply port is connected to a pressure supply source, such as a hydraulic pump; neither of which are shown. As further emerges fromFIG.2and comparable to the prior art solution according toFIG.1, the valve piston12is provided with the longitudinal drilled hole36so that the valve piston12is permanently connected to the return port T on its opposing end faces44,46in a fluid-conducting manner and is therefore pressure balanced.

According to the illustration shown inFIG.2, the top end face46of the valve piston12is in contact with an actuating rod48which can be controlled by the solenoid armature16. For this purpose, the actuating solenoid14likewise has an energizable coil bobbin18and when the coil bobbin18is energised via a plug connector part20, not shown in greater detail inFIGS.2to4, the solenoid armature16moves downwards against the action of the compression spring22. In the control position, at least a partial fluid-conducting connection is created between the pressure supply port P and the consumer port A, whereas the return port T is shut off by the valve piston12. Thus, in the fully energised state of the actuating solenoid14, the valve piston12assumes a switching position according toFIG.4in which there is full flow through the valve from the pressure supply port P to the consumer port A. In the de-energised state, however, the compression spring22returns the solenoid armature16to its maximum initial position in the upward direction of travel according to the illustration shown inFIG.3and a full flow of fluid is enabled between the consumer port A and the return port T.

As also emerges fromFIGS.2to4, the valve piston12has a pressure-active measuring surface50in the region of the consumer port A which forms a circumferential annular surface.

For the valve concept according to the teachings herein, it is particularly significant that the consumer port A consists of a plurality of rows of drilled holes23,25,27arranged one behind the other when viewed in the direction of travel of the valve piston12, of which one row of drilled holes23serves to establish the fluid-conducting connection between the pressure supply port P and the consumer port A and a second row of drilled holes25serves to transfer the pressure from the consumer port A to the measuring surface50of the valve piston12. The third row of drilled holes27is used in turn to establish a fluid-conducting connection between the consumer port A and the return port T (cf.FIG.3). In principle, the middle row of drilled holes25needs only to consist of a single drilled hole, since it in this respect it only serves as a measuring port for transferring the pressure at the consumer port A to the annular measuring surface50on the valve piston12.

However, to simplify production, it is also possible to equip all three rows of drilled holes23,25and27with the same number of transverse drilled holes with the same drilled hole diameter.

At least when the actuating solenoid14is de-energised, the valve piston12assumes a position according to the illustration shown inFIG.3in which the two rows of adjacent drilled holes23,25are in communication with each other in a fluid-conducting manner via a recess52in the valve piston12, which forms the measuring surface50by forming a step, and the third row of drilled holes27located below is separated from the other two rows of said drilled holes23,25by means of the valve piston12in the valve housing10. As emerges in particular fromFIG.2, the transverse drilled holes of the top row of drilled holes23form a first control edge at this point with the valve piston12; likewise the bottom row of drilled holes27.

It is also particularly significant for the valve solution according to embodiments that, between the second25and third 27 row of drilled holes of the valve housing10, there is a separating wall54which protrudes into the interior of the valve housing, the surface area of which corresponds to the size of the measuring surface50on the valve piston12, and is for example larger by a slight amount. In this respect, the separating wall54forms a diaphragm-like ring-shaped surface and ensures in every travel position of the valve piston12that fluid cannot escape unintentionally from the row of drilled holes25into the lower row of drilled holes27, so that in this respect it is always ensured that the fluid pressure present in the row of drilled holes25is permanently present, as the measuring pressure originating from consumer port A, at the measuring surface50of the valve piston12.

As further emerges fromFIGS.2to4, the valve piston12is configured in a stepped manner due to a reduction in diameter on its side directed towards the return port T, with a first step56which has the measuring surface50and with a second step58merging into the first step56, formed by a recess, the largest external diameter of which corresponds to the internal diameter of the separating wall54and to the internal diameter of the valve housing10at the location of the return port T. This second step58opens out on the underside of the valve piston12towards an annular extension60which protrudes towards the return port T; in this respect, extension60and step-shaped recess58form the lower end face44of the valve piston12. For the fluid flow from consumer port A to return port T, the valve piston12, as emerges from the illustration according toFIG.3, forms a further control edge with the valve piston12.

For the control to be explained in greater detail, it is significant that the effective pressure surfaces, in particular on the opposing end faces44,46of the valve piston12, differ by the annular surface which is formed by the first step56and consequently by the measuring surface50. In accordance with the prior art, the valve solution according to the teachings herein also has a cylindrical, hollow-chamber-like recess28in the region of the pressure supply port P, into which the pressure supply port P discharges with its transverse drilled holes in each travel position of the valve piston12. The end face boundaries of this recess28seen in the projection transverse to the direction of travel of the valve piston12have the same surface area in terms of pressure compensation. Overall, the valve design is characterised by a rotationally symmetrical structure.

AsFIG.2in particular illustrates, the control pressure at the consumer port A thus acts against the annular measuring surface50on the valve piston12and causes an axial force which counteracts the magnetic force of the actuating solenoid14. Thus, the control pressure can be changed proportionally depending on the magnetic force applied in each case.

Due to the fact that the pressure-active surfaces on the two end faces44,46of the valve piston differ from each other, precisely by the annular surface at the change in diameter in the form of the first step56of the piston, which forms the measuring surface50, the working pressure at the consumer port A can be converted at precisely this point into a force which counteracts the magnetic force of the actuating solenoid14. In this respect, the valve according to the teachings herein can control the pressure proportionally because the pressure is always in balance with the magnetic force.

Accordingly, if the pressure is less than the magnetic force, the piston12moves downwards as viewed in the direction ofFIGS.2to4and opens the flow of fluid from the pressure supply port P to the consumer port A, which is shown inFIG.4. If the pressure is too high, the valve piston12moves upwards and in turn a flow of fluid is created from the consumer port A to the return port, which is the subject matter of the illustration according toFIG.3.

The valve according to the teachings herein can also switch quickly during a cold start, due to the relatively large free flow cross-sections available between the valve piston12and the valve housing10. Furthermore, the valve piston12can be significantly enlarged in diameter which considerably reduces the flow resistance for the oil, without increasing the valve installation space at the same time. This thus has no equivalent in prior art.

The term “exemplary” used throughout the specification means “serving as an example, instance, or exemplification” and does not mean “preferred” or “having advantages” over other embodiments. The term “in particular” and “particularly” used throughout the specification means “for example” or “for instance”.