ELECTROMAGNET FOR A HYDRAULIC SYSTEM

Abstract

An electromagnetic valve for a hydraulic system for an automatic transmission of a vehicle. An armature chamber is filled with hydraulic medium and fluidically connected to hydraulic lines of the hydraulic system. An armature is mounted in the armature chamber such that its stroke is adjustable. The armature includes a shut-off body and divides the armature chamber into an opening-side chamber facing the flow opening and into an inner chamber facing away from the flow opening. During a stroke of the armature, an oil exchange occurs, and a displacement volume of the hydraulic medium overflows from the opening-side chamber into the inner chamber. A hydraulic line leading to the opening-side chamber or to the inner chamber of the armature chamber includes a dirt collecting element that is designed as a permanent magnet and that retains contaminations in the hydraulic medium that flows through the hydraulic line during an oil exchange.

Claims

1-10. (canceled)

11. An electromagnetic valve for a hydraulic system, comprising: an armature chamber filled with a hydraulic medium and fluidically connected to hydraulic lines of the hydraulic system; an armature mounted in the armature chamber such that its stroke is adjustable, the armature having a shut-off body and dividing the armature chamber into an opening-side chamber facing a flow opening and an inner chamber facing away from the flow opening, wherein during a stroke movement of the armature, an oil exchange occurs, during which a displacement volume of the hydraulic medium overflows from the opening-side chamber into the inner chamber, wherein a hydraulic line leading to the opening-side chamber or to the inner chamber of the armature chamber has at least one dirt collecting element that is designed as a permanent magnet and that retains contaminations in the hydraulic medium that flows through the hydraulic line during an oil exchange, wherein the dirt collecting element is a dirt collecting contour that is formed on an inner wall of the hydraulic line and has elevations and depressions.

12. The electromagnetic valve according to claim 11, wherein a bottom of the depressions is magnetic.

13. The electromagnetic valve according to claim 11, wherein in order to provide the displacement volume of the hydraulic medium that overflows into the inner chamber, the electromagnetic valve has a hydraulic medium reservoir, the hydraulic medium of which has a higher degree of purity than the hydraulic medium in the hydraulic lines and which is fluidically connected to the opening-side chamber, wherein the hydraulic medium reservoir is at least partially filled with a gap-filtered hydraulic medium.

14. The electromagnetic valve according to claim 13, wherein the flow opening between a partial line leading to a working connection of the electromagnetic valve and a partial line leading to a pan-side tank connection is controlled by means of the shut-off body, wherein the hydraulic medium reservoir is formed by expanding the cross-section of the partial line leading to the pan-side tank connection.

15. The electromagnetic valve according to claim 14, wherein the electromagnetic valve comprises a flow interrupter that prevents a return flow of contaminated hydraulic medium from the hydraulic medium pan into the tank connection and into the opening-side chamber during the oil exchange from the opening-side chamber into the inner chamber.

16. The electromagnetic valve according to claim 15, wherein, in order to form the flow interrupter, the partial line leading to the pan-side tank connection is conducted upward in a vertical duct in a vertical direction of the device, and that the pan-side tank connection is arranged at a height offset geodetically above the hydraulic medium pan, wherein the tank connection is in flow connection with the hydraulic medium pan via an interposed free ventilation space.

17. The electromagnetic valve according to claim 16, wherein the shut-off body of the armature is adjustably guided in a hydraulic chamber while forming between the hydraulic chamber, wherein a valve gap provides a bearing clearance, the hydraulic chamber is connected to a hydraulic medium reservoir via a hydraulic line so that a leakage of the gap-filtered hydraulic medium into the hydraulic chamber takes place through the valve gap, and wherein the hydraulic medium reservoir is filled with the gap-filtered hydraulic medium.

18. The electromagnetic valve according to claim 17, wherein the hydraulic medium reservoir is formed by expanding the cross-section of the hydraulic chamber and the drain line, and that the hydraulic chamber and the drain line is connected to the opening-side chamber or the inner chamber via a connecting line, wherein the displacement volume of the hydraulic medium is at least partially conducted via the connecting line during the oil exchange, and the dirt collecting element is associated in particular with the connecting line.

19. The electromagnetic valve according to claim 11, wherein the opening-side chamber of the armature chamber is separated from the hydraulic line via a valve housing wall, the valve housing wall has a bearing opening through which the shut-off body is guided while forming a valve gap providing a bearing clearance, wherein the opening-side chamber is connected to the hydraulic line by means of a connecting line, the displacement volume of the hydraulic medium is at least partially conducted via the connecting line during the oil exchange, and the dirt collecting element is associated with the connecting line.

20. The electromagnetic valve according to claim 11, wherein the shut-off body of the armature is an axially movable piston with at least a first annular collar and a second annular collar, wherein depending on the axial position of the piston, a control edge of the second annular collar opens or closes a flow opening between the pressure connection of a pressure source and a working connection, wherein a control edge of the first annular collar opens or closes a flow opening between a tank connection and the working connection.

Description

[0023] The invention and its advantageous embodiments and/or further developments as well as their advantages are explained in more detail below with reference to the drawings.

[0024] The figures show:

[0025] FIGS. 1a, 1b, and 1c an electromagnetic valve not included in the invention in different operating states in a rough schematic illustration;

[0026] FIGS. 2 to 5 respectively views corresponding to FIG. 1b, which respectively show different exemplary embodiments of the electromagnetic valve according to the invention;

[0027] FIG. 6 a connecting line leading to the opening-side chamber of the armature chamber, with a dirt collecting element in a detailed view;

[0028] FIGS. 7 to 10 respectively views corresponding to FIG. 6 with alternative dirt collecting elements.

[0029] FIGS. 1a and 1b first show a comparative example not included in the invention for easier comprehension of the invention, in which an electromagnetic valve 1 is arranged in a partially shown hydraulic system of an automatic transmission. The hydraulic system comprises a hydraulic pump 3 that is connected on the suction side to an oil pan 5 and on the pressure side via a pressure line 7 to a pressure connection P of the electromagnetic valve 1. The electromagnetic valve 1 additionally comprises a working connection A, which is connected to a hydraulic component of the transmission, such as a clutch or an actuator to engage gears, via a working line not shown. The electromagnetic valve 1 also comprises a tank connection T, which is also fluidically connected to the oil pan 5. In order to remove contaminating particles from the hydraulic oil, a filter 9 is arranged in the pressure line 7.

[0030] In FIGS. 1a and 1b, the electromagnetic valve is, for example, a directly controlled pressure control valve with an armature 11 that has an axially adjustable stroke and is extended by a piston 13. The armature 11 is guided stroke-adjustably in an armature chamber 15 that is filled with hydraulic oil and fluidically connected to the hydraulic path in the electromagnetic valve 1. The armature chamber 15 is delimited by a valve housing 17 indicated shaded, wherein outside the armature chamber 15 is arranged an electromagnet coil (not shown), which can be controlled by a transmission control device in order to adjust the armature 11 using electromagnetic force.

[0031] In FIGS. 1a and 1b, the piston 13 of the armature 11 comprises a first annular collar 19 and a second annular collar 21 with a smaller diameter, which are spaced apart axially and formed on the piston 13. The front face of the piston 13 facing away from the armature 11 is supported by a return spring 23 that is positioned in a spring chamber 25.

[0032] Depending on the axial position of the piston 13, a control edge of the first annular collar 19 more or less covers a flow opening 33 between a partial line 29 leading to the working connection A and a partial line 31 leading to the tank connection T. Accordingly, depending on the axial position of the piston, the control edge of the second annular collar more or less covers the flow opening 27 between the partial line 35 leading to the pressure connection P and the partial line 29 leading to the working connection A.

[0033] As can also be seen in FIGS. 1a and 1b, the armature chamber 15 is divided by means of the stroke-adjustable armature 11 into a chamber 37 facing the flow openings 27, 33 and an inner chamber 39 facing away from them. The flow-side chamber 37 is separated from the partial line 31 leading to the tank connection T by means of a separating wall 41 on the valve housing side. The separating wall 41 comprises a bearing opening 43, in which the annular collar 19 of the piston 13 is mounted while forming a valve gap 45 providing a bearing clearance. In addition, the separating wall 41 comprises a connecting line 47, via which the opening-side chamber 37 and the partial line 31 leading to the tank connection T are connected to one another.

[0034] The second annular collar 21 with the smaller diameter is adjustably mounted in the spring chamber 25 while forming another valve gap 49 providing a bearing clearance. Moreover, a drain line 51 leads from the spring chamber 25 to the oil pan 5, via which ambient pressure is applied to the spring chamber 25.

[0035] During a stroke displacement h.sub.1, h.sub.2 of the armature 11 as a result of a corresponding controlling of the coil part of the electromagnetic valve, an oil exchange takes place between the flow-side chamber 37 and the inner chamber 39. Exemplarily, the armature 11 in FIG. 1a is moved into the armature chamber 15 by means of a stroke displacement h.sub.1. As a result, a displacement volume of the hydraulic oil is conducted from the inner chamber 39 via a compensation line 53 (shown dashed) in the armature 11 to the flow-side chamber 37. Said flow-side chamber however has a smaller volume than the inner chamber 39 so that the displacement volume is at least partially conducted via the connecting line 47 and via the partial line 31 to the oil pan 5 as indicated by arrows in FIG. 1a.

[0036] On the other hand, in FIG. 1b, the armature 11 is moved out of the armature chamber 15 by means of a stroke displacement h.sub.2. During such an oil exchange, the problem exists in FIG. 1b that contaminated hydraulic oil is sucked from the oil pan 5 through the tank connection T, the partial line 31, and the connecting line 47 into the flow-side chamber 37 and from there further through the compensation line 53 into the inner chamber 39, whereby contaminating particles can accumulate in the inner chamber 39.

[0037] The problem described above also applies to the valve shown in FIG. 1c, which valve is basically constructed in the same manner as the valve shown in FIGS. 1a and 1b. In contrast to FIGS. 1a and 1b, the opening-side chamber 37 in FIG. 1c is connected directly to the oil pain 5 via a drain line 52 so that during the stroke displacement h.sub.2, the contaminated hydraulic oil directly finds its way from the oil pan 5 through the drain line 52 into the opening-side chamber 37.

[0038] In order to avoid such a displacement suction of contaminated hydraulic oil into the inner chamber 39, the electromagnetic valve 1 in FIG. 2 comprises an oil reservoir 55, in which is stored hydraulic oil that has a higher degree of purity than the hydraulic oil in the hydraulic lines 29, 31, 35, i.e. it is less interspersed with contaminating particles. The oil reservoir 55 in FIG. 2 is designed in the manner of a pocket-shaped recess in the inner wall of the partial line 31 leading to the tank connection T. In this case, the oil reservoir 55 forms a dead zone, in which the hydraulic oil only moves at a limited flow velocity, whereby contaminating particles can sediment. In this way, the degree of purity of the hydraulic oil contained therein increases. The degree of purity of the hydraulic oil stored in the oil reservoir 55 is further increased by the following factor: During hydraulic operation, the oil reservoir 55 is not filled with contaminated hydraulic oil from the oil pan 5 but rather is filled when the hydraulic oil 5, which is pre-filtered by means of the filter 9, is conducted via the line 31 leading to the tank connection T into the oil pan 5 in order to reduce pressure.

[0039] During an oil change (due to the stroke displacement h.sub.2) indicated in FIG. 2 by arrows, the hydraulic oil that was purified by sedimentation and filtering (by means of filter 9), and not the highly contaminated hydraulic oil from the oil pan 5, is thus for the most part provided as displacement volume that is displaced into the inner chamber 39 during the oil exchange.

[0040] In FIG. 3, the electromagnetic valve 1 additionally comprises a flow interrupter 57, which interrupts a flow connection to the oil pan 5 during the oil exchange from the opening-side chamber 37 into the inner chamber 39 (see arrows in FIG. 3), whereby a return flow of contaminated hydraulic oil into the opening-side chamber 37 and further into the inner chamber 39 is prevented. In order to form the flow interrupter 57, the partial line 31 leading to the pan-side tank connection T is guided upward in FIG. 3 in a vertical duct in the vertical direction z of the device. The tank connection T in FIG. 3 is realized by means of an upwardly open, free outlet opening that is arranged at a height offset z geodetically above the oil pan 5. Between the tank connection T (i.e. the free outlet opening) and the oil pan 5, a free ventilation space 59 is also arranged, which prevents the aforementioned return flow. The partial line 31 leading to the tank connection T is formed in FIG. 3 by the oil reservoir 55.

[0041] FIG. 3 shows a valve position, in which the annular collar 19 of the shut-off body 13 closes the chimney-like oil reservoir 55. In this operating state, a gap filtration occurs, in which the hydraulic oil is supplied through the valve gap at the annular collar 19 of the shut-off body 13 to the opening-side chamber 37 and thus fills the chimney-like oil reservoir 55.

[0042] The oil reservoir is also filled when the annular collar 19 of the shut-off body 13 opens a flow gap to the oil reservoir 55. In this case, the oil already filtered by the filter 9 is supplied to the oil reservoir 55.

[0043] FIG. 5a shows another design variant, the basic design of which is identical to that of FIG. 3. In FIG. 5a, the hydraulic oil that flows through the valve gap 45 into the spring chamber 25 as part of the basic leakage, i.e. the hydraulic oil that is already gap-filtered, is provided for the oil exchange mentioned above. For this purpose, the drain line 51 no longer leads to the oil pan 5 directly but rather via the interposed partial line 31 leading to the tank connection T, because the drain line 51 leads to a branch point 61 in the preferably chimney-like partial line 31 being used as oil reservoir 55.

[0044] The valve shown in FIG. 5b is substantially constructed in the same manner as the valve shown in FIG. 5a. In contrast to FIG. 5a, a second tank connection T is provided in FIG. 5b. In FIG. 5b, the oil reservoir 55 is filled by means of a gap leakage, in which gap-filtered leakage oil is supplied from the spring chamber 25 to the oil reservoir 55. The oil reservoir 55 in FIG. 5b is thus exclusively filled with gap-filtered oil, whereby the degree of purity of the oil stored in the oil reservoir 55 is further increased.

[0045] In FIG. 4, the gap-filtered hydraulic oil flowing into the spring chamber 25 is also used as displacement volume for the oil exchange. Consequently, the drain line 51 branching off from the spring chamber 25 is connected to the oil pan 5 via the interposed oil reservoir 55. In addition, a connecting line 65 that leads directly to the flow-side chamber 37 is branched off at a branch point 63 between the spring chamber 25 and the oil reservoir 55. The displacement volume required during the oil exchange is thus completely provided by means of the gap-filtered hydraulic oil. In the arrangement of the lines shown in FIG. 4, the connecting line 47 that connects the partial line 31 to the flow-side chamber 37 can be dispensed with, as is the case in the previous FIGS. 1 to 3 and 5.

[0046] The following FIGS. 6 to 10 show different exemplary embodiments of the connecting lines 47, 65. According to FIG. 6, a rod-like permanent magnet 67 is arranged in the connecting line 47, 65. The permanent magnet acts as a dirt collecting element, with which ferromagnetic contaminating particles can be removed from the hydraulic oil flowing past. Alternatively, the dirt collecting element in FIG. 7 is not a rod-like permanent magnet but rather a flow-permeable mesh, through which the hydraulic oil can flow. The mesh can preferably be made from a magnetic material.

[0047] In FIG. 8, the dirt collecting element is a dirt collecting contour with elevations 69 and depressions 71. In FIG. 8, the dirt collecting contour 67 is made from a magnetic material. In FIG. 9, the dirt collecting element is also designed as a dirt collecting contour with elevations 69 and depressions 71. In contrast to FIG. 8, however, only the bottoms 73 of the depressions 71 are magnetic in FIG. 9.

[0048] FIG. 10 shows an exemplary embodiment, in which the dirt collecting element is a web that is placed on the bottom side in the connecting line in the manner of a doormat. During hydraulic operation, dirt particles from the oil sediment in the web and are trapped there.