Two-stage solenoid valve

Abstract

A valve for controlling fluids, in particular hydraulic fluid, includes a first connector opening and a second connector opening, a preliminary stage with a first valve seat and a first displaceable closing body, and a main stage with a second valve seat and a second displaceable closing body. The first valve seat is assigned to a through opening of the second closing body. A filtering gap is formed in a flow path from the first connector opening to the preliminary stage by way of a constriction of the flow path.

Claims

1. A valve for controlling fluids, comprising: a first port and a second port; a preliminary stage with a first valve seat and a first displaceable closing body; a main stage with a second valve seat and a second displaceable closing body; and an actuating element arranged axially displaceably in a valve sleeve and configured to selectively engage with the first closing body, wherein: the second closing body is arranged axially displaceably in the valve sleeve, the second closing body has a passage opening and the first valve seat is assigned to the passage opening, a filtration gap is formed in a flow path from the first port to the preliminary stage by a constriction of the flow path, the actuating element has at least one groove formed in a radially outwardly facing surface of the actuating element, and the at least one groove forms a portion of the flow path and is upstream of the filtration gap.

2. The valve as claimed in claim 1, wherein: the first valve seat lies inside the valve sleeve, and the flow path leads through at least one radial opening formed in the valve sleeve.

3. The valve as claimed in claim 1, wherein: the at least one groove is an axial groove, and the flow path leads through at least one radial opening formed axially at the level of the actuating element.

4. The valve as claimed in claim 1, wherein: the filtration gap is formed radially between the actuating element and the valve sleeve.

5. The valve as claimed in claim 1, wherein the filtration gap lies adjacent to an axial air gap between the actuating element and the second closing body.

6. The valve as claimed in claim 4, wherein the filtration gap lies adjacent to an axial air gap between the actuating element and the second closing body.

7. The valve as claimed in claim 1, wherein the at least one groove is an annular groove.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The disclosure is now explained in more detail with reference to several exemplary embodiments. The drawings show:

(2) FIG. 1 a two-stage solenoid valve from the prior art in a longitudinal section view,

(3) FIG. 2 a first exemplary embodiment of an advantageous valve in a longitudinal section view,

(4) FIG. 3 a detail view of the first exemplary embodiment,

(5) FIG. 4 a second exemplary embodiment of the valve in a longitudinal section view,

(6) FIG. 5 the second exemplary embodiment in a cross section view,

(7) FIG. 6 a third exemplary embodiment of the valve in a longitudinal section view,

(8) FIG. 7 a fourth exemplary embodiment of the valve in a longitudinal section view, and

(9) FIG. 8 a fifth exemplary embodiment of the valve in a longitudinal section view.

DETAILED DESCRIPTION

(10) FIG. 1 shows, in a simplified longitudinal section view, a two-stage valve 1 which is formed as a high-pressure switching valve for a brake system of a motor vehicle. The valve 1 has a preliminary stage 2 and a main stage 3, wherein the preliminary stage 2 and the main stage 3 are both arranged between a first port 4 and a second port 5 of the valve 1. The port 4 serves to connect the valve 1 to a primary circuit of a brake system, such as for example a master brake cylinder, and the second port 5 serves to connect it to a secondary circuit, such as for example a pump device.

(11) The preliminary stage 2 is formed by a first closing body 6, in this case formed as a valve ball, and a first valve seat 7. The valve body 6 is fixedly connected to an actuating element 8 which is displaceable axially in a first valve sleeve 9.

(12) To displace the actuating element 8, a pole piece 10 is arranged axially spaced therefrom in the valve sleeve 9, to which piece a magnetic coil (not shown here) is assigned. When the magnetic coil is powered, a magnetic field is generated by means of the pole piece 10 which draws the actuating element 8which is formed as an armature accordinglyin the direction of the pole piece 10. A compression spring 11, in this case in the form of a coil spring, is arranged pre-tensioned between the pole piece 10 and the actuating element 8, against which spring the actuating element is drawn for actuating the valve 1. To this extent, the valve 1 constitutes a normally closed solenoid valve. In the unactuated state, the coil spring 11 presses the first closing body 6 against the first valve seat 7 by means of the actuating element 8. The actuating element 8 here protrudes axially in regions into a second valve sleeve 12, in which the preliminary stage 2 or the first valve seat 7 lies.

(13) The first valve seat 7 is formed by a second closing body 13 which is arranged axially displaceably in the second valve sleeve 12. A further compression spring 14, in this case in the form of a coil spring, is provided in the second closing body 13 and presses the second closing body 13 in the direction of the actuating element 8. The second closing body 13 has a passage opening 15 which is assigned to the first valve seat 7. The first closing body 6 thus closes the passage opening 15 when the solenoid valve 1 is in the unactuated state.

(14) The second closing body 13 has an axial portion 16 which protrudes through a face-side opening 17 of the valve sleeve 12. The valve 1 furthermore has a third valve sleeve 18 which is formed in multiple stages, in particular in the manner of a deep-drawn component. The valve sleeve 12 and the axial portion 16 protrude into the third valve sleeve 18, wherein the third valve sleeve 18 forms a second valve seat 19 which cooperates with the closing body 13 to form the main stage 3. The valve sleeve 18 has the port 5 at its free end. The valve sleeve 18 is here arranged in a valve housing 20 which radially comprises the port 4. The valve sleeve 18 has a plurality of radial openings 21 arranged distributed over the periphery of the valve sleeve 13 and lying axially at the level of the port 4.

(15) A filter 22 is also assigned to the port 4 and is configured to retain large dirt particles.

(16) If the pressure in the secondary circuit is greater than in the primary circuit, the hydraulic medium lifts the closing body 13 from the second valve seat 19 and thus flows to the port 4 through the filter 22, as indicated by an arrow 23, wherein any large dirt particles are retained in the filter 22. If the valve 1 is actuated in that the first closing body 6 is drawn away from the first valve seat 7 by means of the actuating element 8, hydraulic medium flows from the primary circuit into the secondary circuit, as indicated by an arrow 24. The dirt particles thus removed again from the filter 22 can lead to blockage of the preliminary stage 2.

(17) FIG. 2 shows a first exemplary embodiment of an advantageous refinement of the valve 1 which securely prevents seizing or clogging of the preliminary stage 2. For this, FIG. 2 shows a detail of the valve 1 in an enlarged longitudinal section view.

(18) At the level of the actuating element 8, a plurality of radial openings 25 is arranged in the valve sleeve 12, distributed over the periphery of the valve sleeve 12. The hydraulic medium flows through these radial openings 25 from the port 4 into the valve sleeve 12. At its end assigned to the closing bodies 6, 13, the actuating element 8 has an annular groove 26 in its outer casing surface which extends over the entire periphery of the actuating element 8. In at least one actuating position of the actuating element 8, in particular the rest position as shown, the annular groove 26 is located in the region of the radial opening. The annular groove 26 forms a flow deflection 27, as shown in an enlarged view in FIG. 3. Preferably, the annular groove 26 is configured such that it has vertical side walls to ensure a flow deflection by 90.

(19) In the flow direction shown by arrow 24, the annular groove 26 is followed by a constriction of the flow path. The outer diameter of the actuating element 8 relative to the inner diameter of the valve sleeve 12 is here selected such that a narrow filtration gap 28 is formed radially between the actuating element 8 and the valve sleeve 12. Preferably, the filtration gap 28 is dimensioned such that it has a filtration effect similar to or the same as that of the filter 22, in order also to prevent large dirt particles, which become detached from the filter 22 and are flushed back, from passing in the direction of the preliminary stage 2. The filtration gap 28 here extends over the entire periphery of the actuating element 8 and is thus configured as an annular filtration gap. The annular groove 26 upstream of the filtration gap 28 leads firstly to dirt particles being expelled from the hydraulic medium by the flow deflection before reaching the filtration gap 28, and secondly in particular to dirt particles retained by the filtration gap 28 being collected in the annular groove 26 without clogging the filtration gap 28.

(20) Due to the advantageous configuration, the dirt particles retained by the filter 22 are therefore prevented from reaching the preliminary stage 2 and there for example becoming seized between the first closing body 6 and the first valve seat 7, which would lead to malfunction of the valve 1.

(21) According to this exemplary embodiment, the second closing body 13 is arranged preferably radially tightly on the valve body 12.

(22) FIG. 4 shows a second exemplary embodiment of the valve 1 in a longitudinal section view. In the exemplary embodiments described below, essentially only differences from preceding exemplary embodiments are discussed, and to this extent the same elements carry the same reference numerals and in this respect reference is made to the description above.

(23) The second exemplary embodiment according to FIG. 4 differs from the first exemplary embodiment according to FIGS. 2 and 3 in that the radial openings 25 are not formed as radial bores, but as recesses 29 open at the edge on the face of the valve sleeve 12 facing the actuating element 8.

(24) In this case, the actuating element 8 preferably has a plurality of axial grooves 30 arranged distributed over the periphery, which deflect the flow path 24 along the actuating element 8. The axial grooves 30 are in communicative connection with the recesses 29. The recesses 29 may be formed by an axial spacing of the valve sleeve 12 and the actuating element 8, which extends over the entire periphery of the valve sleeve 12. Both the annular groove 26 and the axial grooves 30 may have a square, round, curved or polygonal cross section. The respective filtration gap 28 may also be formed as peripheral segments, so that it extends not over the entire periphery but only over one or more peripheral segments. In this case, preferably several filtration gaps are provided, arranged distributed over the periphery. The axial grooves 30 (longitudinal grooves) may be formed by material removal or by cold-forming (cold beating). FIG. 5 for this shows a cross section through the valve 1 along line A-A of FIG. 4.

(25) FIG. 6 shows a third exemplary embodiment of the valve 1 which differs from the preceding exemplary embodiments in that the radial openings 25 of the valve sleeve 12 are provided axially as radial bores/through bores at the level of the second closing body 13. In this way, the hydraulic medium enters the valve sleeve 12 in the region of the second closing body 13. In this case, the end of the closing body 13 facing the actuating element 8 has on its outer periphery a diameter which is smaller than the diameter of the valve sleeve 12, so that a filtration gap 31 is formed between the flow body 13 and the valve sleeve 12, the form and function of which correspond to that of the filtration gap 28. Large dirt particles can also be retained accordingly by the filtration gap 31, so they cannot enter the preliminary stage 2. Preferably, a flow deflection 32 corresponding to the flow deflection 27 is located upstream of the filtration gap 31 as viewed in the flow direction.

(26) FIG. 7 shows a fourth exemplary embodiment of the valve 1 which differs from the exemplary embodiment in FIG. 6 in that there are no radial openings 25. Instead, the diameter of the opening 17 of the valve sleeve 12 and the outer diameter of the axial portion 16 of the closing body 13 are selected such that an annular opening 33 is formed, through which the hydraulic medium coming from the radial openings 21 can flow into the valve sleeve 12.

(27) FIG. 8 shows a fifth exemplary embodiment of the valve 1 in a longitudinal section view, wherein this exemplary embodiment differs from the preceding exemplary embodiment in that the annular opening 33 and the filtration gap 31 are exchanged. For this, the outer diameter of the axial portion 16 of the closing body 13 and the inner diameter of the opening 17 of the valve sleeve 12 are selected such that the filtration gap 31 is formed between them. At the same time, the end of the closing body 13 facing the actuating element 8 is formed on its outer periphery such that the annular opening 33 is formed between the end and the valve sleeve 12. The annular opening 33 differs from the filtration gap 31 in that the constriction it forms in the flow path is lesser, and in particular a lower back-pressure is built up in operation, and dirt particles are not filtered at this point. Evidently, it would however also be conceivable to form the annular opening 33 as a filtration gap, in order to increase the overall filtration effect. It is also conceivable to provide the valve 1 with more than just the two valve stages shown and depicted here. Equally, it is conceivable to arrange the first and/or the second closing body not axially, but for example radially, displaceably and/or twistably.