WO2004074687A2

WO2004074687A2 - Vacuum pump with a plastic blade

Info

Publication number: WO2004074687A2
Application number: PCT/DE2004/000294
Authority: WO
Inventors: Friedrich Schuler; Ulrich Pabst; Rolf-Albrecht Schmidt; Robert Deipenwisch; Ulrich Hiltemann; Carsten Sczesny; David Ribaric
Original assignee: Luk Automobiltechnik Gmbh & Co. Kg
Priority date: 2003-02-20
Filing date: 2004-02-18
Publication date: 2004-09-02
Also published as: WO2004074687A3

Abstract

The invention relates to vacuum pumps provided with plastic vanes or blades and used, in particular for a brake booster in motor vehicles.

Description

vacuum pump

The invention relates to a vacuum pump, in particular for brake booster systems for motor vehicles, with a plastic slide or wing, which, for. B. is known as a mono-wing type. The previously known plastic slide valves for vane pumps are mostly solid, which leads to relatively long cycle times in injection molding and to high costs in the production as an injection molded part. In addition, the weight leads to high inertial forces and thus to an increased load and wear on the pumps. Furthermore, plastic slides are known, which are provided with open-edge cavities and are ribbed. The open structure has little stability. There is also a risk that weak spots may arise from weld lines, sink marks and strongly anisotropic material properties. In addition, the use of cores means that the injection molding tool is relatively complex and not very robust.

The invention further relates to a vacuum pump with a plastic slide or wing, the plastic slide or wing being made of a thermoset material, in particular a high-strength thermoset material. The known thermoset wing has caps at its ends, which are made from an expensive high-performance thermoplastic, such as PEEK.

It is therefore an object of the invention to present an improved vacuum pump.

The object is achieved by a vacuum vane cell pump with a plastic slide or vane, which is characterized in that the slide or vane has one or more cavities on the inside, the cavities being closed to the outside except for one injection opening each. According to the invention, the cavities of the plastic slide are produced in an injection molding process by injecting a fluid (gas or liquid) under pressure (internal pressure injection molding). A plastic slide is preferred in which the injection opening is arranged centrally on one of the two wide side surfaces.

Furthermore, a vacuum pump with a plastic slide is preferred, in which the injection opening is arranged centrally on one of the two narrow side surfaces.

A vacuum pump according to the invention with a plastic slide is characterized in that the injection opening can be closed after the fluid injection has ended, for. B. by melt that is added during the injection molding process, or a poured or pressed or clipped or welded or screwed or riveted or glued in plug or by subsequent melting of the injection site.

The object is further achieved by a vacuum pump with a plastic slide or wing, in particular for brake booster systems for motor vehicles, the slide or wing having a foamed, porous material structure on the inside, while having a compact, closed outer skin on its surface. This has the advantage that a so-called sandwich structure with high strength and relatively low weight is created.

Furthermore, a vacuum pump with a plastic slide is preferred, in which the foamed material structure is produced in an injection molding process by admixing a gas. This has the advantage that when the plastic cools, a dense structure forms on the housing wall, while a porous structure is created on the inside. A gas pressure builds up in the material, which largely prevents the part from shrinking when cooling down and sink marks are formed.

A vacuum pump according to the invention is characterized in that a gas is added chemically by adding a gas generator. The has the advantage that the gas generator decomposes when heated in the injection molding machine and releases gas.

Another vacuum pump according to the invention is characterized in that the admixing of a gas is carried out by blowing gas into the liquid plastic mass. This method has the advantage of a simple physical process. A vacuum pump is also preferred, in which a gas is admixed by injecting a liquid which evaporates and thus causes the foaming process.

A vacuum pump according to the invention is characterized in that the slide or wing has a low degree of foaming, for example 1.5% to 10%. This has the advantage that the dimensional accuracy of the slide is increased and sink marks are avoided.

Another vacuum pump according to the invention is characterized in that the slide or wing has a high degree of foaming of 10 to 80%. This has the advantage that the weight of the wing is significantly reduced.

Another vacuum pump according to the invention has separate caps on one or both ends of the slide, which represent sliding sealing surfaces with respect to a housing contour of the vane vacuum pump. According to the invention, the caps represent wear protection caps and / or low-friction sliding caps and / or sealing caps.

Another vacuum pump according to the invention is characterized in that the caps are made of a different material than the plastic slide.

The object is further achieved by a vacuum pump with a plastic slide or wing, the plastic slide or wing made of a thermoset material, in particular special high-strength thermoset material is shown, the caps being made of a wear-resistant, low-friction thermoset material.

A vacuum pump is also preferred, in which the caps can be firmly connected to the slide by casting or welding or gluing or clipping on or pressing on. This has the advantage that no relative movement between the slide and the caps can occur during operation.

Furthermore, a vacuum pump is preferred in which the caps are attached and a relative movement is possible between the slide and the caps. This allows function-related and production-related games to be compensated for.

A vacuum pump according to the invention is characterized in that the caps are placed on the tapered slide ends from the outside. A vacuum pump is also preferred, in which the caps are pushed axially (from the side) onto the slide. Furthermore, a vacuum pump is preferred in which the plastic slide or vane is made of a high-strength thermoset material and the entire surface of the slide is extrusion-coated with a wear-resistant, low-friction thermoset.

The invention will now be described with reference to the figures.

Figure 1 shows a one-piece slide.

Figure 2 shows a slide with firmly connected caps. Figure 3 shows a slide with attached caps.

Figure 4 shows a foamed one-piece slide.

Figure 5 shows a foamed slider with firmly connected caps.

Figure 6 shows a foamed slider with attached caps.

Figure 7 shows a completely overmolded slide. Figure 8 shows a slide with attached caps.

Figure 9 shows another slide with attached caps. Figure 10 shows a further cap arrangement.

Figure 11 also shows another cap arrangement.

In Figure 1c, a plastic slide 1 is shown in perspective. The outer surface of the slide consists of two wide side surfaces 3, two narrow side surfaces 5 and two head surfaces 7, which serve as sliding surfaces with respect to a housing contour of the pump. The slider 1 is completely closed at its edges and surfaces except for an injection opening 11 which can be arranged centrally on one of the large side surfaces 3 or alternatively can be arranged centrally as an injection opening 13 on one of the two narrow side surfaces 5. After introducing the plastic into the injection mold, a fluid is injected under pressure through the injection opening 11 or 13, which presses the liquid plastic against the walls of the injection mold, from which the solidification process then spreads by cooling. The fluid pressure is maintained until the plastic solidifies and cools down, as a result of which a high degree of dimensional accuracy is achieved and sink marks can be largely avoided. This process creates a slide 1 with a light structure and high rigidity. The hollow design ensures a low weight. Because the fluid pressure is maintained until the plastic solidifies and cools down, there is no risk of sink marks occurring during cooling, so that a high manufacturing accuracy of the slide can be cost-effectively represented. According to the invention, a plate-shaped component with large functional areas with high demands on flatness and dimensional accuracy can thus be produced with the method.

Figures 1 a and 1 b show in cross section a one-piece slide without attached caps. 1 shows the injection opening 13 in one of the two narrow side faces 5. The other side face 5 and the two end faces 7, like the wide side faces 3, are completely closed. The corresponding fluid is introduced under pressure into the filled plastic mold through the injection opening 13 in such a way that it enters the plastic mass in the middle of the injection mold and from there builds up a pressure volume uniformly on all sides, which the plastic presses the material against the injection molding wall and from there, by progressively cooling, guarantees an evenly uniform layer build-up. As already described above, the fluid pressure is maintained until the liquid plastic has evenly accumulated on the inside of the solidified plastic mass and has solidified by cooling and thus forms a uniform wall thickness. The corresponding fluid pressure is only lowered after the plastic mass has cooled completely, so that sink marks can no longer occur due to cooling.

Figure 2 shows a slide 1 with firmly connected caps. To avoid repetitions, only the differences from FIG. 1 are discussed here. The two end faces 7 of the slider 1 are firmly overlaid here with plastic caps 9, which can be made of a different material than the rest of the slider material, so as to meet special requirements with regard to sliding properties, low friction, wear and sealing effect. The valve body itself, on the other hand, must primarily have properties such as rigidity and mechanical strength as well as low weight and high stability. The caps 9 can therefore consist of a different material than the slide 1, which is preferably made of thermoplastic. The caps 9 can be firmly connected to the slider 1 by casting or welding or gluing or clipping on or pressing on, so that no relative movement between the slider 1 and the caps 9 can occur during operation.

Figure 3 shows a further embodiment of a slide 1, which has attached caps 15. The end faces 7 of the slide 1 show cams 17 which serve as a form-fitting hold for the caps 15. The cams additionally have two protruding strips 21 which can engage in corresponding grooves 23 within the caps 15. The caps 15 can in turn be made of a different material than the slide 1 in order to achieve the different properties described above. Depending on the design of the strips 21 and grooves 23, a relative movement in the longitudinal direction of the slide is now possible between the slide 1 and the caps 15, as a result of which play and play-related play within the vane vacuum pump can be compensated. FIG. 4 shows a one-piece slide, as has already been shown in a similar form in FIG. 1. The difference is that the slide does not have a uniform cavity, but instead has a material structure provided with pores 30 on the inside. In Figure 4a, this porous material structure is shown schematically by a section through the slide. It can also be seen that the slide walls 3, 7 have a dense plastic structure, while inside the pores 30 form a light structure which is, however, firmly connected to one another by the pore walls and is therefore highly rigid. The introduction of a gas generator or the injection of gas or the injection of a liquid which evaporates is preferably introduced in the center of the plastic injection mold, as in the previously described embodiments, so that the pore formation can spread evenly from the center of the slide to the edges. This method does not leave an injection opening, since after the gas or liquid injection has been completed, the outer skin of the plastic wing is closed by the formation of pores from the inside.

FIG. 5 shows, analogously to FIG. 2, a slide 1 with firmly connected caps. The difference from FIG. 1 again consists in the fact that this is a slide with a foamed-out material structure. All other explanations can be found in the description of FIG. 2.

Similarly, FIG. 6 shows, analogously to FIG. 3, a slide with attached caps, the slide in FIG. 6 again showing a material structure produced by foaming. All other features of the slide in FIG. 6 correspond to the description of the slide in FIG. 3.

A slide 30 is shown in FIG. 7, which has a base body 32, preferably made of high-strength thermoset, which is overmolded at the ends and possibly also on the sides with a wear-resistant thermoset 34. The advantage of a thermoset wing is that better tolerances are maintained due to the significantly lower shrinkage during injection molding compared to thermoplastics can and thus additional processing can be omitted. The expensive cap material made of thermoplastic materials used in the prior art is replaced here according to the invention by an inexpensive thermoset material which is designed as a wear-optimized material for the surfaces subject to wear. Good crosslinking of the two materials during spraying enables an inexpensive, wear-resistant wing with high mechanical strength to be achieved. The slide in FIG. 7 has a plurality of cavities 36, which serve to lighten the weight and promote a more uniform curing process of the thermosetting plastic. Furthermore, the slide 30 has two through openings 38, which serve to equalize the pressure between the two long sides of the wing.

A slide 40 is shown in FIG. 8, which is also preferably made of a high-strength thermoset material. In this illustration, the slide is not completely surrounded by a second, wear-resistant thermoset body, but has two slide caps 42, which can be made of a wear-resistant thermoset and are fastened to the base body 40, for example, by clipping or similar fastening methods, as previously described. The caps cover the entire wing width in area 44, but then become narrower in area 46 and then taper in area 48. The base body 40 has tapered sections 50 at its ends, which can accommodate the caps 42 accordingly. Analogously to FIG. 7, the base body again has cavities 36 and through openings 38.

A further slide 52 is shown in FIG. 9, which differs from the previously described slide by a somewhat different cap design. The caps 5A have openings 56 into which strips 58 attached to the slide 52 can snap. A certain axial play in the longitudinal direction of the slide can be provided between the strips 58 and the openings 56 in order to be able to maintain appropriate sealing tolerances within the vacuum pump. The caps 54 are thus fastened on the slide base body 52 with axial play and thus axially movable. Figure 10 has a further design example for the slide body and the caps. The slide main body 60 has an indentation 62, in which hook-shaped configurations 66 of the cap 64 engage. In this design example, the cap can be pushed laterally over the slide main body 60 and is secured against lateral displacement after the entire wing has been introduced into the pump.

FIG. 11 shows a variant of the design from FIG. 10, the indentation 72 of the slide main body having no axial longitudinal extent and thus being connected to the cap 76 essentially axially without play, whereas the illustration in FIG. 10 between the cap 64 and the main body 60 is clear recognizable axial play allows. The game is chosen so large that gap compensation using centrifugal force is retained.

The invention thus leads to a plastic slide valve or vane for vane pumps, in particular vane vacuum pumps, with one or more vanes, which have a high stability and a low weight. They are inexpensive to manufacture with high manufacturing accuracy. The slide or slides is / are used in pumps for conveying preferably gaseous media. The pumps are either fluid lubricated (e.g. with oil, water or similar) or run dry. What is new in the production of a plastic slide is that a plate-shaped component with large functional surfaces with high demands on flatness and dimensional accuracy can be produced using the methods presented.

Claims

claims

1. Vacuum pump with plastic slide or wing, in particular for brake booster systems for motor vehicles, characterized in that the slide 1 or wing 1 has one or more cavities inside, the cavities except for one injection opening 11, 13 to the outside are closed all around.

2. Vacuum pump according to claim 1, characterized in that the cavities are produced in an injection molding process by injecting a fluid (gas or liquid) under pressure (internal pressure injection molding).

3. Vacuum pump according to claim 1 or claim 2, characterized in that the injection opening 11 is arranged centrally on one of the two wide side surfaces 3.

4. Vacuum pump according to claim 1 or claim 2, characterized in that the injection opening 13 is arranged centrally on one of the two narrow side surfaces 5.

5. Vacuum pump according to one of the preceding claims, characterized in that the injection opening 11, 13 can be closed after the end of the fluid injection, for. B. by melt that is replenished during the injection molding process, by a cast or pressed in or clipped in or welded or screwed or riveted or glued in plug or by subsequent melting of the injection site.

6. Vacuum pump with a plastic slide or wing, in particular for brake booster systems for motor vehicles, characterized in that the slide 1 or wing has a foamed, porous material structure 30 inside, while it has a compact, closed outer skin on its surface.

7. Vacuum pump according to claim 6, characterized in that the foamed material structure 30 is produced in an injection molding process by admixing a gas.

8. Vacuum pump according to claim 7, characterized in that the admixing of a gas takes place chemically by adding a gas generator.

9. Vacuum pump according to claim 7, characterized in that the admixing of a gas is carried out by blowing gas into the liquid plastic mass.

10. Vacuum pump according to claim 7, characterized in that the admixing of a gas is carried out by injecting a liquid which evaporates.

11. Vacuum pump according to one of the preceding claims, characterized in that the slide 1 or wing 1 has a degree of foaming of 1.5-10%.

12. Vacuum pump according to one of the preceding claims, characterized in that the slide 1 or wing 1 has a degree of foaming of 10-80%.

13. Vacuum pump according to one of the preceding claims, characterized in that the plastic slide 1 has separate caps 9, 15, 42, 54, 64, 76 at one or both ends, which represent sliding sealing surfaces with respect to a housing contour.

14. Vacuum pump according to one of the preceding claims, characterized in that the caps represent 9,15,42,54,64,76 wear protection caps and / or low-friction sliding caps and / or sealing caps.

15. Vacuum pump according to one of the preceding claims, characterized in that the caps 9,15,42,54,64,76 are made of a different material than the plastic slide.

16. Vacuum pump with plastic slide 1, 20, 40, 52 or wing, the plastic slide 1, 30, 40, 52 or wing made of a thermoset material, in particular a high-strength thermoset material, characterized in that the

Caps 9, 15, 42, 54, 64, 76 made of a wear-resistant, low-friction thermoset material are shown.

17. Vacuum pump according to claim 13 to claim 16, characterized in that the caps 9,15,42,54,64,76 can be firmly connected to the slide by casting, welding, gluing, clipping or pressing.

18. Vacuum pump according to claim 13 to claim 16, characterized in that the caps 9, 15, 42, 54, 64, 76 are fitted in such a way that a relative movement is possible between the slide and the caps.

19. Vacuum pump according to one of the preceding claims, characterized in that the caps 9, 15, 42, 54, 64, 74 are placed on the outside on tapered slide ends 17, 50, 62, 74.

20. Vacuum pump according to one of the preceding claims, characterized in that the caps 64, 76 are pushed onto the slide 60, 70 from the side.

2 I. Vacuum pump with plastic slide 30 or wing 30, wherein the plastic slide 30 or wing 30 is shown made of a thermoset material, in particular a high-strength thermoset material, characterized in that the entire surface of the slide 30 with a wear-resistant, low-friction Du - molded plastic.

22. A method for producing a plastic slide or wing with one or more of the features of the preceding claims.