Title of Invention

ELECTROMAGNETICALLY OPERATED VALVE, ESPECIALLY FOR HYDRAULIC BRAKING SYSTEMS IN MOTOR VEHICLES

Abstract

ABSTRACT (IN/PCT/2002/00689/CHE) "Electromagnetically operated valve, in particular for hydraulic braking systems in motor vehicles" The valve has a seat valve with a hollow conical valve seat and a hemispherical closing element. An inlet flow bore, which is connected to a pressure medium inlet opens centrally in the valve seat. A magnet armature which acts on the seat valve to open it and which interacts with a pole core in accordance with the flat armature principle acts on a plunger which has the closing element. A priestesses restoring spring, which acts on the seat valve to close it, is arranged between the pole core and the magnet armature.

Full Text

The invention is based on an electromagnetically operated valve. A valve such as this is already known (DE 41 34 490 Al) which is in the form of a proportional pressure control valve In order to achieve a good control response the known pressure control valve, which is equipped with a seat valve which is closed with no current flowing is designed in accordance with the plunger-type armature principle, that is to say the pole core has a depression at the end, which the essentially cylindrical magnet armature enters to a greater or lesser depth as a function of an electric current which is supplied to an electrical winding which surrounds the pole core. In this case, the magnetic force acting on the magnet armature is assisted by a hydraulic force in the sense of opening the seat valve, while the force of the restoring spring counteracts these forces. However, the known valve has the disadvantage that the plunger-type armature principle requires increased complexity for the physical design of the pole core and magnet armature. In particular, tight radial tolerances are required between the magnet armature and the pole core, in order to ensure that the air gaps alongside them are small. This in turn demands complex guidance for the magnet armature with small guide clearances, since transverse forces on the magnet armature can lead to functional defects. The known valve is thus expensive to manufacture. Furthermore, DE 196 04 317 Al discloses an electromagnetically operated valve which operates in accordance with the flat armature principle and has a seat valve which is open when no current is flowing. Although this known valve is in the form of a two- position valve (open, closed valve), it is possible, by controlling the magnetic force which counteracts the force of a restoring spring and a hydraulic force, for it to be moved like a proportional valve with short travels to any desired number of intermediate positions without, however, needing to have the complex design of a proportional valve. The shape of the seat valve and the matching on the magnetic force characteristic and restoring spring make a significant contribution to this. Advantages of the invention The electromagnetically operated valve according to the invention has, in contrast to the proportional valve mentioned initially, the advantage that it has the simple configuration of a two-position valve with a flat armature, but behaves like a proportional valve. Since, in the case of the flat armature, the lines of force of the magnetic circuit in the operating air gap essentially run between the mutually facing, planar end surfaces of the pole core and magnetic armature, radial tolerances have little influence in this embodiment. Furthermore, the shape of the seat valve and plunger region contributes to the valve according to the invention, which operates as a pressure control valve, having a stable control response: the pressure on one side of the pressure medium inlet assists the magnetic force when opening the seat valve. Pressure medium which emerges from the valve seat is carried along the closing element and the plunger without any turbulence toward the magnet armature, and exerts an opening effect. As the pressure difference between the pressure medium inlet and the pressure medium outlet decreases, this force is reduced, and the valve adopts a stable final position of the seat valve, on reaching the pressure at the outlet that is set as a function of the current. This control process takes place with a dynamic response and control quality that are adequate for many applications. Drawing One exemplary embodiment of the invention is illustrated in simplified form in the drawing, and will be explained in more detail in the following description. Figure 1 shows a longitudinal section through an electromagnetically operated valve having a seat valve, Figure 2 shows the seat valve which is located in the closed position when no current is flowing, on a scale that is larger than that in Figure 1, and Figure 3 shows a diagram of the forces acting in the valve over the valve opening travel. Description of the exemplary embodiment An electromagnetically operated valve 10, which is illustrated in Figure 1 of the drawing, for hydraulic braking systems for motor vehicles, for example external force braking systems according to DE 195 46 647 Al, essentially comprises two assemblies: a hydraulic part 13 which is mounted in a stepped bore 11 in a valve block 12, and an electrical part 14 which is plugged onto the hydraulic part. The hydraulic part 13 of the valve 10 has a valve body 16, which is connected to an armature guide sleeve 17 and has a hole bored through it longitudinally. The valve body 16 and the armature guide sleeve 17 are secured by means of a first staked connection 18 in the stepped bore 11 in the valve block 12. The valve body 16 has a pressure medium inlet 19 for the valve 10, which is connected to an inlet flow channel 20 for the pressure medium, which opens at the base of the stepped bore 11. A filter disk 21 is held in the stepped bore 11, between the pressure medium inlet 19 and the inlet flow channel 20. In the region facing away from the base of the bore, the valve body 16 is provided with an inlet flow bore 23, which merges into a hollow conical valve seat 24. The valve seat 24 has an associated hemispherical closing element 26, which is formed on a plunger 25. The valve seat 24 and the closing element 26 form a seat valve 27, which will be described in more detail further below with reference to Figure 2. In the armature guide sleeve 17, there is a valve chamber 29 adjacent to the valve body 16, in which a magnet armature 30 is guided such that it can move longitudinally. The magnet armature 30 is essentially in the form of a straight circular cylinder with radially running end surfaces 31 and 32. The plunger 25 originates from the end surface 31 facing the valve body 16, and has a pin 33 which is pressed into the magnet armature 20. That part of the valve chamber 29 which is located between the valve body 16 and the magnet armature 30 is connected through an opening 34 in the armature guide sleeve 17 to a pressure medium outlet 35 from the valve 10 and, furthermore, to an outlet flow channel 36, which opens into the stepped bore 11, in the valve block 12. Apart from the plunger 25, that part of the valve chamber 29 which is located between the valve body 16 and the magnet armature 30 is free of fittings. The magnet armature 30 has a relatively large amount of radial play with respect to the armature guide sleeve 17. It is provided with two longitudinal grooves 18, which run over its entire length. A restoring spring 39 in the form of a helical compression spring is held in the magnet armature 30, in the region of its end surface 32 facing away from the valve body 16. This restoring spring 39 is relatively stiff and is prestressed to act on a residual air gap disk 40 which is supported on a radially running end surface 41 of a pole core 42. Part of the length of the pole core 42 engages in the armature guide sleeve 17, to which it is connected forming a seal for the pressure medium. An operating air gap 43, which governs the opening travel of the valve 10, is located between the end surface 32 of the magnet armature 30 and the residual air gap disk 40. A filter sleeve 45, which is arranged between the pressure medium outlet 35 and the outlet flow channel 36, is held on the outside of the armature guide sleeve 17 in the stepped bore 11 in the valve block 12. This is followed, towards the opening of the stepped bore 11, by a sealing ring 46, a disk 47 and a bush 48, which is secured by means of a second staked connection 49 in the stepped bore 11 of the valve block 12. The electrical part 14, which is plugged onto the hydraulic part 13 of the valve, has a coil 52 which is enclosed by a housing 50 having an annular disk 51 and has an electrical winding 53. While the housing 50 is connected radially on the inside to the pole core 42, the annular disk 51 produces a connection for the bush 48. The magnet armature 30, the pole core 42, the bush 48, the housing 50 and the annular disk 51 are composed of magnetically permeable material, while the armature guide sleeve 17 and the residual air gap disk 40 are magnetically impermeable. A magnetic circuit which is produced when current flows through the electrical winding 53 runs via the pole core 42, the residual air gap disk 40, the magnet armature 30, the armature guide sleeve 17, the annular disk 51 and the housing 50 of the electrical part 14. In this case, the magnetic armature 30 and the pole core 42 interact in accordance with the flat armature principle. That region of the seat valve 27 which is important for operation of the valve 10 as a pressure control valve has the following design features, which will be described with reference to Figure 2: The hollow conical valve seat 24 has a cone angle a, which is at most 75°. The valve seat 24 is bounded with respect to the valve chamber 29 by a planar depression 55 in the valve body 16 with sharp edges. The radius Ri of the hemispherical closing element 26 is matched to the valve seat 24 such that the diameter Di of the inlet flow bore 23 corresponds approximately to the sealing diameter D2 of the seat valve 27. The closing element 26 is followed by a relatively short cylindrical section 56 of the plunger 25. The cylindrical section 56 has a diameter D3, which corresponds to twice the radius Ri of the closing element 26. The cylindrical section 56 is followed, towards the magnet armature 30, by a conical section 57 of the plunger 25, without any discontinuities. This has a cone angle p of approximately 35°, and merges with a rounded transition with the radius R2 into the end surface 31 of the magnet armature 30, with no discontinuities. The pressure in the inlet flow bore 23 is pi and, when the valve 10 is used in the external force braking system mentioned above, this pressure pi is produced by a high-pressure pump or by a pressure medium reservoir. The pressure p2 in the valve chamber 29 may be between the value 0 and pi. The electromagnetically operated valve 10 operates as follows: Initially, it is assumed that no current is flowing in the electrical winding 53, so that the seat valve 27 has assumed its closed position (as shown in Figures 1 and 2) . There is a relatively high pressure pi on the inlet flow side of the seat valve 27, and a very low pressure p2 on the outlet flow side. The preloaded restoring spring 39 exerts a force f on the magnet armature 30 and on the plunger 25, which holds the seat valve 27 in the closed position up to a maximum permissible value of the pressure pi. In the diagram in Figure 3, which shows the profile of the forces F acting in the valve 10 plotted against the valve opening travel H, namely the spring force Fp, the magnetic force FM and the hydraulic force Fp, this preloading force f of the spring 39 is indicated on the ordinate for zero travel. The diagram shows the profile of the spring force FF produced by the restoring spring 39 as a straight line, which has a profile that rises monotonally as the valve opening travel increases. The relatively steep gradient of the spring force characteristic is governed by the high stiffness of the restoring spring 39. The second characteristic shows the profile of the magnetic force FM and hydraulic force Fp, which are additively linked to one another, for a constant current I and a constant pressure difference 5p between the pressures pi and p2. The characteristic FM + Mp has a profile which rises monotonally as the valve opening travel H increases, but whose gradient is less than that of the characteristic FF. This relatively flat profile of the characteristic FM + Fp is essentially achieved by the design of the magnetic circuit, to be precise by means of a relatively large operating air gap 43 and a relatively thick residual air disk 40. Furthermore, the influence of the hydraulic force Fp on the plunger 25 and on the magnet armature 30 is kept low since the sealing diameter D2 is relatively small, and the magnet armature 30 is washed by the pressure medium on all sides. The operating point AP of the valve 10 at which the seat valve 27 assumes an operating travel h is located in the intersection of the two characteristics. The characteristic FM + Fp can be shifted in the diagram by varying the current I flowing through the electrical winding 53 of the coil 52, so that the operating point AP can be set to a different travel h. When current flows through the electrical winding 53 of the coil 52, the magnetic force FM acts on the magnet armature 30, in the sense of opening it. The hydraulic force Fp which results from the differential pressure Pi - p2 also has an opening effect on the plunger 25. The force FF of the restoring spring 30, which in contrast has a closing effect, is overcome provided the current I is sufficiently high, and the seat valve 27 opens. Pressure medium flows from the pressure medium inlet 19 to the pressure medium outlet 35 of the valve 10. In the process, pressure medium flows along the plunger 25 to the end surface 31 of the plunger and magnet armature 30, and exerts an opening effect on them. As the pressure p2 in the valve chamber 29 rises, a pressure imbalance occurs across the magnet armature 30, which reduces the hydraulic force Fp, which has an opening affect. The spring force FF produced by the restoring spring 30 moves the seat valve 27 to the closed position when the pressure P2 on the outlet flow side associated with the electric current I is reached. Owing to the design of the valve 10, the pressure P2 on the outlet flow side is proportional to the current I flowing in the electrical winding 53. The electromagnetically operated valve 10 is self-stabilizing in response to small disturbances: The operating point AP of the valve 10 is assumed when there is a force equilibrium between the magnetic force FM, the hydraulic force F and the spring force Fp. Disturbances to this force equilibrium, for example caused by fluctuations in the hydraulic force Fp, lead only to the operating point AP being shifted briefly: for example, an increase in the hydraulic force Fp leads to an increase in the valve opening travel H, with the consequence that the spring force Fp rises at the same time. Although this initially results in the operating point AP being displaced on the spring force characteristic Fp, this is compensated for, however, once the hydraulic disturbance has ceased by the magnet armature 30 being moved back by the spring force Fp to the operating travel h. When no current is flowing, the valve 10 can also be used as a pressure limiting valve: In the case of pressures pi at the pressure medium inlet 19 which produce a hydraulic force Fp, which has an opening effect, less than the preloading force f of the restoring spring 39, the seat valve 27 is locked in its closed position. If, on the other hand, in the event of higher pressures, the preloading force f of the restoring spring 39 is overcome, then the seat valve 27 opens and the pressure medium can flow away from the pressure medium inlet 19 of the valve 10 to its pressure medium outlet 35, thus limiting the pressure. WE CLAIM: 1. Electromagnetically operated valve (10), in particular for hydraulic braking systems in motor vehicles, having the following features: - a seat valve (27) , which is closed with no current flowing, is provided between a pressure medium inlet (19) and a pressure medium outlet (35), - the seat valve (27) has a hollow conical valve seat (24) and a hemispherical closing element (26) formed on a plunger (25), - an inlet flow bore (23), which is connected to the pressure medium inlet (19), opens centrally into the valve seat (24) - a magnet admixture (30) which acts on the seat valve (27) to open it and has an associated pole core (42) facing away from the plunger, acts on the plunger (25), - a prestressed restoring spring (39) , which acts on the seat valve (27) to close it, is supported on the magnet armature (30), characterized by the features: - the diameter (DO of the inlet flow bore (23) corresponds nearly to the sealing diameter (D2) of the seat valve (27), - the cone angle (a) of the valve seat (24) is at most 75°, - pressure medium emerging from the valve seat (24) is capable of being carried without any discontinuities along the plunger (25) to a radially running largely planar end surface (31) of the magnet armature (30) with a rounded transition between the plunger (25) and the magnet armature (30), - the magnet armature (30) and the pole core (42) interact in accordance with the flat armature principle, the magnetic circuit of the valve (10) is provided such that the magnetic force (F^) which is exerted on the magnet armature (30) and is transmitted to the closing element (26) is capable of being varied without any discontinuities, with its profile rising monotonally, as the valve opening travel (H) increases, together with a hydraulic force (Fp) which is produced by the pressure medium and acts on the closing element (26) and the magnet armature (30), and - the force (Fp) which is produced by the restoring spring (39) is matched to the closing element (26) such that it has a profile which rises monotonally as the valve opening travel (H) increases and whose positive gradient is greater than that of the magnetic and hydraulic force profile. 2. The valve according to Claim 1, wherein the hemispherical closing element (26) is integrally formed on a cylindrical section (56) of the plunger (25) without any discontinuities, which is followed without any discontinuities, facing away from the valve seat, by a conical section (57) ofthe plunger (25) with less iconicity which is followed, after a transition radius (Ra), by a radially running end surface (31) ofthe plunger (25) or ofthe magnet armature (30).

Documents:

in-pct-2002-0689-che abstract-duplicate.pdf

in-pct-2002-0689-che abstract.jpg

in-pct-2002-0689-che abstract.pdf

in-pct-2002-0689-che claims-duplicate.pdf

in-pct-2002-0689-che claims.pdf

in-pct-2002-0689-che correspondence-others.pdf

in-pct-2002-0689-che correspondence-po.pdf

in-pct-2002-0689-che description(complete)-duplicate.pdf

in-pct-2002-0689-che description(complete).pdf

in-pct-2002-0689-che drawings-duplicate.pdf

in-pct-2002-0689-che drawings.pdf

in-pct-2002-0689-che form-1.pdf

in-pct-2002-0689-che form-18.pdf

in-pct-2002-0689-che form-26.pdf

in-pct-2002-0689-che form-3.pdf

in-pct-2002-0689-che form-5.pdf

in-pct-2002-0689-che pct.pdf

in-pct-2002-0689-che petition.pdf