Pole tube for an actuator

Abstract

The invention relates to a pole tube (1) for an actuator (2) designed as a valve magnet, at least comprising a pole core section (3) and a tube section (5) which directly adjoins the pole core section (3) along an axial direction (4) and in which an armature (6) of the actuator (2) can be arranged so as to be movable along the axial direction (4), wherein the pole core section (3) and the tube section (5) are formed together in a single piece and are made of a magnetisable material, wherein the tube section (5) is free of sections in which the wall thickness (7) of the tube section (5) is designed to be locally tapered in order to influence a magnetic force characteristic curve of the actuator (2).

Description

[0001] R.416541

[0002] Robert Bosch GmbH

[0003] 416541 - Baumann

[0004] Polar tube for an actuator

[0005] The invention relates to a pole tube for an actuator designed as a valve magnet.

[0006] A solenoid valve consists of a pressure-tight pole tube in which an armature moves along an axial direction, with a magnetic coil extending around the pole tube. The pole tube transmits the magnetization generated by the magnetic coil to the armature. Simultaneously, it separates the armature from the magnetic coil and serves as a guide for the armature's movement relative to the pole tube and the magnetic coil.

[0007] Different designs of polar tubes are known.

[0008] To generate and influence a magnetic force characteristic (force-displacement characteristic), the pole tube has a recess or (in the case of internally pressurized pole tubes) a non-magnetic section, also known as a magnetic break. This section is made of a non-magnetizable material and is inserted into the pole tube, for example, by soldering or welding.

[0009] Such a polar tube is known, for example, from DE 10 2017 213 456 A1.

[0010] To reduce manufacturing costs, one-piece pole tubes are sometimes used, which contain a thinly machined section. Here, the field lines are guided towards the armature via the magnetic saturation in this thinly machined area, thus influencing the magnetic force distribution.

[0011] Such a polar tube is known, for example, from DE 10 2013 218 766 A1.

[0012] These polar tubes, or those manufactured in this way, have the disadvantage that they can only be used for low (thin-turned) and medium pressures (by means of thermal joining).

[0013] In order to guarantee the required pressure resistance at high pressures up to, for example, 900 bar, the use of a thick-walled pole tube is necessary, which therefore does not have the aforementioned non-magnetic section.

[0014] Page 1 of 12 R.416541

[0015] A pole tube of this type is also known. It consists of three metallic components and a seal. A non-magnetizable material is used for the pressure-loaded section of the pole tube in which the armature is movably mounted. A constriction or section for force control is not possible here due to the material and the pressures involved. Because of the non-magnetic material, the parasitic gap between the magnetizable components—coil housing and armature—is very large, resulting in a low achievable magnetic force at the armature.

[0016] To enable the generation of a magnetic force, a magnetizable pole section is required. This section extends from one end of the pipe section into the pipe itself and forms a seal against the pipe. This seal is subjected to considerable stress due to the high pressures and the resulting widening of the gap between the pipe section and the pole section, which is caused by these high pressures. Consequently, the seal's service life is limited.

[0017] To attach and fix the pole area to the pipe section, a magnetizable nut is also required, which connects to the pipe section along the axial direction and into which the pole area extends.

[0018] This design of a pole tube comprises numerous components that must be manufactured individually and then assembled. Manufacturing costs are therefore high. Additionally, a wear-prone seal is required, and the magnetic force at the armature is limited by the design.

[0019] Based on this, the object of the invention is to at least partially alleviate the problems described with reference to the prior art and, in particular, to provide a polar tube that is suitable for high pressure loads and can be manufactured cost-effectively. Furthermore, a high actuating force of the armature housed in the polar tube should be achievable.

[0020] These problems are solved by the subject matter of the independent claims. Preferred embodiments are found in the dependent claims. The features specified in the claims can be combined with each other and / or with features of the description in any technologically meaningful way. The description, particularly in conjunction with the figures, explains the invention and provides further embodiments.

[0021] This is achieved through a pole tube for an actuator designed as a valve solenoid. The pole tube comprises at least (in particular exclusively) a pole core section and a [missing information - likely a specific component].

[0022] Page 2 of 12 R.416541 A pipe section immediately adjoining the pole core section along an axial direction, in which an armature of the actuator can be movably arranged along the axial direction. The pole core section and the pipe section are formed in one piece and made of a magnetizable material. The pipe section is free of sections in which the wall thickness of the pipe section is locally tapered to influence a magnetic force characteristic of the actuator.

[0023] In particular, the pole core section and the tube section are manufactured together in one piece by a primary forming process (casting or powder metallurgical production) or a forming process (compression, tensile-compression, tensile, bending, shear forming; i.e. e.g. bending, pressing, deep drawing, stretch drawing, upsetting, forging).

[0024] "One-piece" here means that the polar tube is already provided as a semi-finished product in a geometry that (essentially) corresponds to the final form. The geometry of the polar tube is therefore not created by thermal joining (welding, brazing) of individual components. In particular, this means that the polar tube is not enlarged between its provision as a semi-finished product and its final form with regard to its geometry (volume of the material of the polar tube).

[0025] This excludes, in particular, a coating of the polar tube that only slightly increases the volume of the material (less than 1 vol%).

[0026] The term "semi-finished product" refers to a workpiece produced by primary forming or forming.

[0027] Starting with the semi-finished product, further processing can be carried out until the polar tube reaches its final form (in which it can be used in an actuator), e.g., machining or heat treatment. A coating can also be applied to the polar tube if necessary.

[0028] The magnetizable material is, in particular, a metallic material.

[0029] The polar tube or semi-finished product consists in particular of a single material or has the same material composition or material specification extending over the entire volume (excluding any coating that may be present).

[0030] In particular, the material is a soft magnetic material or a ferromagnetic material (possibly then not soft magnetic or not annealed).

[0031] Page 3 of 12 R.416541

[0032] In particular, the material is a high-alloy material or a ferritic stainless steel. This allows the polar tube or actuator to be used in hydrogen-containing environments. In non-corrosive environments, a low-alloy material can also be used.

[0033] In particular, the material is a 1.4105 material or X6CrMoS17 (according to DIN EN 10088-3, valid as of October 2024; or according to JIS: SUS430F, valid as of October 2024), especially with the following chemical composition:

[0034] C: 0 to 0.08 mass %;

[0035] Si: 0 to 1.5 mass %;

[0036] Mn: 0 to 1.5 mass %;

[0037] P: 0 to 0.04 mass %;

[0038] S: 0.150 to 0.350 mass %;

[0039] Cr: 16.00 to 18.00 wt%;

[0040] Mo: 0.20 to 0.60 mass %;

[0041] Fe: Rest.

[0042] The tube section is specifically designed without any sections where the wall thickness is locally reduced to influence the actuator's magnetic force characteristic. In particular, the geometry deliberately avoids influencing the magnetic force profile. While the pole tube, and especially the tube section, does form a path for the magnetic flux parallel to the axial direction, thus reducing the potential force on the magnetic armature, the magnetic force build-up in the armature results from the pole tube achieving magnetic saturation, which then intensifies the magnetic flux on the armature. The achievable magnetic force is higher than with conventional pole tubes due to the use of a magnetizable pole tube and the associated significant reduction in the parasitic gap.

[0043] Sections with varying wall thicknesses may therefore be included in the pipe section. These obviously serve purposes such as the arrangement or fastening of components, or are included for manufacturing reasons.

[0044] In particular, such sections are not provided to influence a magnetic force characteristic of the actuator, but the pole tube or tube section is made of a magnetizable material so that the parasitic gap is as small as possible.

[0045] In particular, the thick-walled polar tube is suitable for a pressure of at least 800 bar occurring in the tube section when used as required, especially as shown on page 4 of 12 R.416541

[0046] Suitable for use at 850 bar, preferably at least 900 bar. Literature specifies "thin-walled" as having a wall thickness to outer diameter ratio of ≤0.06, sometimes ≤0.1. "Thick-walled" is defined as having a wall thickness to outer diameter ratio >0.1. Preferably, the wall thickness to outer diameter ratio can be 0.15; more preferably, a wall thickness to outer diameter ratio of >0.1 to 0.3 can be selected.

[0047] The one-piece design of the polar tube allows for the incorporation of radii that increase compressive strength and reduce stress concentrations. Specifically, edges on the polar tube (especially those located inside) are rounded to reduce stress concentrations. Radii of at least 2.0 millimeters are provided. Only the edges located inside the polar tube are rounded. The radius on the polar tube (or on a stop surface of the polar tube for an anchor) is slightly smaller than on the opposite edge of an anchor that can be installed in the polar tube, so that the intended axial movement of the anchor is not restricted.

[0048] Furthermore, an actuator assembly is proposed, comprising at least the described pole tube and an armature that is movably arranged within the tube section of the pole tube along the axial direction. The armature is made of a magnetizable material.

[0049] The armature moves, particularly along the axial direction, into the pole tube until it reaches a stop surface on the pole tube. A spring element can be arranged in the stop surface between the armature and the pole tube in a known manner.

[0050] The anchor has a coating on at least one surface that is in sliding contact with the pipe section. In particular, the coating serves to prevent the anchor from seizing within the pipe section. Such seizing (the surfaces bonding together) can occur especially when the anchor and pipe section are made of the same or very similar materials.

[0051] In particular, the coating is a (generally known) DLC coating (diamond like carbon - DLC) or another friction- and wear-reducing coating.

[0052] Alternatively or additionally, the surface of the pipe section can also have the coating.

[0053] In particular, the pole tube and the armature are made of a soft-annealed material X6CrMoS17 (as described above).

[0054] Page 5 of 12 R.416541

[0055] Furthermore, an actuator is proposed, at least comprising the described actuator assembly and additionally a coil for actuating the armature, which extends along a circumferential direction (in a known manner or completely) around the pole tube.

[0056] The explanations regarding the polar tube apply equally to the actuator assembly and the actuator, and vice versa.

[0057] The use of indefinite articles (“a”, “an”, “one”, and “one”), particularly in the claims and the description reproducing them, is to be understood as such and not as a numeral. Accordingly, terms or components introduced by these articles are to be understood as existing at least once and, in particular, as potentially existing multiple times. Insofar as a component can occur multiple times (“at least one”), the description of one of these components may apply equally to all or some of the multiple components, but this is not mandatory.

[0058] The invention and its technical context will now be explained in more detail with reference to the figures, without these explanations limiting the invention itself. Unless explicitly excluded below, partial aspects or individual features shown in the figures can also be combined with each other and / or with the features of the claims or the preceding description. Where components in different figures are designated with the same reference numeral, their descriptions apply analogously to all such components, unless explicitly stated otherwise. The figures schematically depict:

[0059] Fig. 1 shows a first embodiment of an actuator according to DE 10 2017 213 456 A1 ,

[0060] Fig. 2 shows a second embodiment of an actuator according to DE 10 2013 218 766 A1 ,

[0061] Fig. 3 shows a third embodiment of an actuator according to the prior art, and

[0062] Fig. 4 shows an actuator.

[0063] Fig. 1 shows a first embodiment of an actuator 2 according to DE 10 2017 213 456 A1. The actuator 2 comprises an actuator assembly 8, with a pole tube 1 and an armature 6, as well as a coil 11 for actuating the armature 6. The coil 11 extends circumferentially 12 completely around the pole tube 1. The coil 11 is arranged in a (coil) housing 13 of the actuator 2.

[0064] Page 6 of 12 R.416541

[0065] To generate and influence a magnetic force characteristic, the pole tube 1 has a recess or a non-magnetic section 14, which is also referred to as a magnetic break. This section 14 is made of a non-magnetizable material and is inserted into the pole tube 1, for example, by soldering or welding.

[0066] Fig. 2 shows a second embodiment of an actuator 2 according to DE 10 2013 218 766 A1. Reference is made to the descriptions in Fig. 1. In contrast to the first embodiment according to Fig. 1, the pole tube 1 is made in one piece. The pole tube 1 has a thin-turned section 14 through which the field lines are guided via the magnetic saturation in this thin-turned area towards the armature 6, thus influencing the magnetic force distribution.

[0067] Fig. 3 shows a third embodiment of an actuator 2 according to the prior art. Reference is made to the descriptions in Figs. 1 and 2.

[0068] The pole tubes 1 shown in Figures 1 and 2 have the disadvantage that they can only be used for low (thin-turned) and medium pressures (by thermal joining). To ensure the required pressure resistance at very high pressures up to, for example, 900 bar, the use of a thick-walled pole tube 1 is necessary, i.e., without the aforementioned non-magnetic section 14. In the thick-walled pole tube, the ratio of wall thickness to outer diameter is > 0.1. The ratio of

[0069] The wall thickness / outer diameter ratio can preferably be 0.15; more preferably, a ratio of wall thickness / outer diameter of > 0.1 to 0.3 can be chosen.

[0070] A pole tube 1 of this type is also known. It consists of three metallic components 15, 16, 17 and a seal 18. A non-magnetizable material is used for the pressure-loaded tube section 15 of the pole tube 1, in which the armature 6 is movably arranged. A constriction or section 14 for force control is not possible here due to the material and the pressures. Because of the non-magnetic material, the parasitic gap 21 between the magnetizable components (coil housing 13) and the armature 6 is very large, resulting in a low achievable magnetic force at the armature 6.

[0071] To enable the generation of a magnetic force, a magnetizable pole area 16 is required, which extends from one end of the tube section 15 into the tube section 15 and has a seal 18 towards the tube section 15. This seal 18 is subjected to high stress due to the widening of the gap between the tube section 15 and the pole area 16 under the high pressures that occur.

[0072] Page 7 of 12 R.416541

[0073] To fasten and fix the pole area 16 to the pipe section 15, a magnetizable nut 17 is also required, which connects to the pipe section 15 along the axial direction 4 and into which the pole area 16 extends.

[0074] Fig. 4 shows an actuator 2. Reference is made to the descriptions of Figs. 1 to 3.

[0075] The actuator 2 comprises an actuator assembly 8 with a pole tube 1 and an armature 6, as well as a coil 11 for actuating the armature 6. The coil 11 extends circumferentially 12 completely around the pole tube 1. The coil 11 is arranged in a housing 13 of the actuator 2.

[0076] The pole tube 1 comprises a pole core section 3 and a tube section 5 extending along an axial direction 4 directly adjacent to the pole core section 3, in which an armature 6 of the actuator 2 can be movably arranged along the axial direction 4. The pole core section 3 and the tube section 5 are formed in one piece and made of a magnetizable material. The tube section 5 is free of sections in which a wall thickness 7 of the tube section 5 is locally tapered to influence a magnetic force characteristic of the actuator 2.

[0077] The polar tube 1 consists in particular of a single material and has a uniform material composition or material specification throughout the entire volume of the polar tube 1 (except for the coating 10).

[0078] The material of the pole tube 1 is a soft magnetic material or a ferromagnetic material (possibly then not soft magnetic or not annealed).

[0079] Pipe section 5 is free of sections (sections 14, see Figs. 1 and 2) in which the wall thickness 7 of pipe section 5 is locally tapered to influence the magnetic force characteristic of the actuator 2. Thus, there is no deliberate manipulation of the magnetic force profile. The pole tube 1, and specifically pipe section 5, forms a path for the magnetic flux parallel to the axial direction 4.

[0080] Sections 14 with varying wall thicknesses 7 are provided on the pipe section 5 outside the force-generating or force-influencing area. These obviously serve, for example, for the arrangement or fastening of components (here, a thickening of the wall thickness 7 forms a stop for the housing 13).

[0081] Page 8 of 12 R.416541

[0082] In the pole tube 1, such sections for influencing a magnetic force characteristic of the actuator 2 are therefore not provided, but the pole tube 1 or the tube section 5 is made of a magnetizable material so that the parasitic gap 21 is as small as possible.

[0083] The polar tube 1 can be used for a pressure of at least 800 bar occurring in the tube section 5 in a needs-based application (i.e. intended for operation or a specific application).

[0084] The edges 19 located within the polar tube 1 are rounded to reduce stress concentrations. These edges 19 have radii of at least 2.0 millimeters. The rounding of the edge 19 at a stop surface 20 of the polar tube 1 for an anchor 6 is slightly smaller than the rounding on the opposite edge 19 of the anchor 6 located in the polar tube 1, so that the intended lifting movement of the anchor 6 along the axial direction 4 is not restricted.

[0085] The anchor 6 has a coating 10 on a surface 9 that is in sliding contact with the pipe section 5. The coating 10 is a (generally known) DLC coating or another friction- and wear-reducing coating.

[0086] Page 9 of 12

Claims

R.416541 Claims 1. Pole tube (1) for an actuator (2) designed as a valve magnet, comprising at least a pole core section (3) and a tube section (5) extending along an axial direction (4) directly adjacent to the pole core section (3), in which an armature (6) of the actuator (2) can be movably arranged along the axial direction (4), wherein the pole core section (3) and the tube section (5) are formed in one piece and made of a magnetizable material, wherein the tube section (5) is free of sections in which a wall thickness (7) of the tube section (5) is locally tapered to influence a magnetic force characteristic of the actuator (2).

2. Polar tube (1) according to claim 1, wherein the polar core section (3) and the tube section (5) are manufactured together in one piece by a primary forming process or a forming process.

3. Polar tube (1) according to one of the preceding claims, wherein the material is a soft magnetic material or a ferromagnetic material.

4. Polar tube (1) according to one of the preceding claims, wherein the material is a stainless steel material.

5. Polar tube (1 ) according to one of the preceding claims, wherein the polar tube (1 ) is designed with a wall thickness, in particular of the tube section, which allows the polar tube to be used at a pressure of at least 800 bar occurring in the tube section (5 ).

6. Actuator assembly (8), comprising at least a pole tube (1) according to one of the preceding claims and an armature (6) which is arranged to be movably arranged in the tube section (5) of the pole tube (1) along the axial direction (4), wherein the armature (6) is made of a magnetizable material.

7. Actuator assembly (8) according to claim 6, wherein the anchor (6) has a coating (10) at least on one surface (9) in sliding contact with the pipe section (5).

8. Actuator assembly (8) according to claim 7, wherein the coating (10) is a DLC coating.

9. Actuator assembly (8) according to any one of the preceding claims 6 to 8, wherein the pole tube (1) and the armature (6) are made of a soft annealed material X6CrMoS17. Page 10 of 12 R.416541 10. Actuator (2), comprising at least an actuator assembly (8) according to any one of the preceding claims 6 to 9 and additionally a coil (11) for actuating the armature (6), which extends along a circumferential direction (12) around the pole tube (1). Page 11 of 12

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