Plastic housing for steering gears, method for manufacturing and assembling a plastic housing

Abstract

Method for manufacturing a plastic housing (10, 30) for a steering gear housing, in which, in a first step, a base body (12, 32) and at least one closure element (14, 34) are manufactured in a process, such that the base body (12, 32) and the at least one closure element (14, 34) are each connected via a web (16), and in which, in a further step, an elastomer layer (42) is applied which connects the base body (12, 32) and the at least one closure element (14, 34) together, wherein, in the method, the at least one web (16) is broken by a relative movement between the base body (12, 32) and the at least one closure element (14, 34).

Description

[0001] The invention relates to a method for producing a plastic housing for a steering gear of a steering system, in particular a steering system for a motor vehicle, a plastic housing for a steering gear of a steering system and a method for assembling such a plastic housing.

[0002] A steering mechanism is a device used, for example, in motor vehicles to influence the direction of travel. A steering movement initiated by the driver at the steering wheel is transmitted to the articulated wheels via a steering gear, among other things. These steering mechanisms are usually enclosed in a housing.

[0003] Steering gear housings and steering boxes are largely made of die-cast aluminum, which is supplemented by injection-molded plastic housings. The connection between the aluminum housing and the plastic housing is made by screws. The holes in the plastic housing are reinforced with metal sleeves to prevent plastic creep and to ensure expansion in the screw over its service life. An O-ring is often used to seal the plastic housing to the aluminum housing, as this type of sealing is technically sophisticated. For the O-ring seal to function reliably in the typical vehicle temperature range of -40 °C to +120 °C, the plastic must have a similar thermal expansion to that of the aluminum. The plastic must also meet the strength requirements of the vehicle's steering system. For this reason, the plastics are often reinforced with fillers.

[0004] Plastic housings are also secured using snap-in elements in a groove in the aluminum housing. However, the fillers in the plastic, which are necessary for the O-ring seal, reduce the plastic's expansion. This means that the snap-in elements are large enough to avoid exceeding the permissible expansion. Such large snap-in elements are often too large to fit within the vehicle's installation space. This makes inexpensive snap-in solutions unsuitable in many cases.

[0005] From the publication DE 10 2012 110 363 A1, a housing for a steering gear is known, comprising a steering housing and a plastic housing. The plastic housing has a base body made of a plastic, an elastomer layer, and at least one closure element.

[0006] The publication DE 10 2012 110 373 A1 describes a method for producing a plastic housing for a steering gear housing. In a first step, a base body and at least one closure element are produced. In a second step, an elastomer layer is applied over at least one gate point in a gate process, which connects the base body and the at least one closure element.

[0007] US Pat. No. 4,717,034 A discloses a closure for a container having a plurality of vertical ribs on its inner wall that come into contact with the thread of the container. Furthermore, the closure has a seal, which can be made of foamed polyethylene.

[0008] US Pat. No. 4,489,844 A discloses a closure for closing carbonated beverage containers. The closure consists of an internally threaded sleeve with a fitting located therein that seals against the neck of the beverage container. The sleeve and the fitting are made of different plastic materials and are injection-molded in different parts of the same mold.

[0009] The object of the invention is to provide a plastic housing and a method for manufacturing and assembling the plastic housing, which avoids the aforementioned disadvantages. In particular, the closure elements of the plastic housing are to be made smaller in accordance with the available installation space in a vehicle, while still ensuring the permissible expansion.

[0010] Against this background, a method according to claim 1, a plastic housing with the features of claim 11, and a method for assembling such a plastic housing according to claim 14 are presented. Further details emerge from the dependent claims and the description.

[0011] The presented method is used to manufacture a plastic housing for a steering gear housing. In a first step, a base body and at least one closure element are produced in a single process, typically a casting process, such as an injection molding process. This process is carried out in such a way that the base body and the at least one closure element are each connected to one another via at least one web. This web, also referred to as a sprue web, can have a round or rectangular cross-section. For a round cross-section, the diameter is, for example, 1 mm. For a rectangular cross-section, the cross-sectional area can be 1 mm. 2 be.

[0012] The method presented here involves applying an elastomer layer in a further step, which connects the base body and the at least one closure element. This elastomer layer can be made of, for example, a thermoplastic elastomer or a silicone material.

[0013] In one embodiment, the elastomer layer is applied via at least one gate point in a gate process. In one embodiment, the elastomer layer is applied via exactly one gate point. This can be done, for example, using a shield gate or a bar gate. In one embodiment, the elastomer layer is applied or attached continuously over the entire circumference of the base body. Alternatively, the elastomer layer can be provided only in areas of closure elements. The at least one closure element can be designed as a snap element or as a locking element.

[0014] In a further embodiment, the at least one web is broken by a relative movement between the base body and the at least one closure element. This relative movement causes shearing and thus breaking of the at least one web, which represents a predetermined breaking point.

[0015] It can be provided that the at least one web is broken, for example, with a tool, before the further step of applying the elastomer layer, typically in the casting tool, e.g., the injection molding tool, with which the first process is carried out. Thus, the breaking of the at least one web can be effected before the elastomer layer is applied.

[0016] In an alternative embodiment, the at least one web is broken after the further step of applying the elastomer layer. This can occur, for example, in a casting tool or during assembly, during which the plastic housing is attached to or in the housing of the steering gear. This creates a relative movement between the base body, which is typically made of plastic, and the at least one closure element, which is designed, for example, as a snap element or locking element, which causes the at least one web to shear or break.

[0017] The breaking of the web can, whenever this is done, be done by lifting the associated closure element away from the base body or by moving the closure element radially inwards, especially during assembly.

[0018] Also presented is a plastic housing for a steering gear housing, which comprises a base body, typically a plastic base body, and at least one closure element, each of which is connected via a web. The plastic housing comprises an elastomer layer that connects the base body and the at least one closure element to one another. This plastic housing is manufactured, in particular, by a method described above.

[0019] In this plastic housing, the at least one closure element can be designed as a snap-in element or a locking element. However, other closure elements are also conceivable.

[0020] The presented method for assembling a plastic housing to a housing of a steering gear uses a plastic housing of the type described above and thus a plastic housing having a base body, typically a plastic base body, and at least one closure element, each of which is connected via a web, and wherein the plastic housing has an elastomer layer that connects the base body and the at least one closure element to one another. During assembly of the plastic housing to or in the housing of a steering gear, the at least one web is broken by a relative movement between the base body and the at least one closure element. This relative movement can occur during the assembly itself, by hand, or using a tool.

[0021] During the manufacturing process, an elastomer layer is applied between the base body and the snap element, ensuring the permissible expansion within a small installation space. To manufacture this structure cost-effectively, the base body and the snap elements are manufactured or molded in a first process, e.g., an injection molding process, and the elastomer is injected between the base body and the snap element in a further process, e.g., an injection molding process. This creates a thin sprue made of brittle, filler-reinforced plastic between the base body and the snap element. This is necessary for any O-ring that may be provided, which has a similar thermal expansion.

[0022] In one embodiment, this web or sprue web breaks during assembly of the plastic housing into the aluminum housing, exceeding the permissible elongation. The strength of the connection between the base body and the at least one snap-in element is ensured by the elastomer layer. In this case, the breakage of the web to the snap-in element is compensated for by the bond of the elastomer layer between the base body and the snap-in element. This allows the plastic housing to be manufactured in a simple two-component injection molding process with a filler-reinforced plastic base body including closure elements, e.g., snap-in elements, and the elastomer layer, without any assembly process.

[0023] Due to production using the two-component injection molding process, the temperature of filler-reinforced plastic is high when the elastomer is injected, which ensures a good material bond between the plastics.

[0024] This achieves two advantages, at least in some of the designs. It makes it possible to produce a single component, the plastic housing, cost-effectively. Furthermore, the connection between the plastic components is very strong.

[0025] In one embodiment, the at least one closure element and the base body are injection-molded in a single pass, leaving a thin sprue between the two components. The elastomer is then injected onto the component while it is still at a good temperature, ensuring a good bond. During assembly of the component into the aluminum housing or into or onto the housing, which can be made of aluminum, plastic, steel, etc., the sprue is broken by the movement of the closure element relative to the base body, as the permissible elongation is exceeded. The bond between the elastomer and the base body and the snap element ensures the strength of the assembly.

[0026] In the two-component injection molding process, a positive fit can also be created by injecting the elastomer between the closure element, the elastomer, and the base body. This is achieved, for example, by a conical bore in the base body and / or the snap-in element, which is filled with the elastomer. However, the strength of the component primarily comes from the bond between the elastomer and the plastic.

[0027] Additional ribs can be added to the base body to improve the centering of the cover when joining it into the housing.

[0028] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

[0029] The invention is illustrated schematically in the drawing using embodiment(s) and is described schematically and in detail with reference to the drawing. Fig. 1 shows a perspective view of a design of the plastic housing. Fig. 2 shows a perspective view of another version of the plastic housing. Fig. 3 shows the plastic housing made of Fig. 1 in a different view. Fig. 4 shows a section through the plastic housing of Fig. 1. Fig. 5 shows a section through the plastic housing of Fig. 2. Fig. 6 shows a section of Fig. 5.

[0030] The invention is illustrated schematically in the drawing using exemplary embodiments and is described in detail below with reference to the drawing.

[0031] Fig. Figure 1 shows a plastic housing, designated overall by reference numeral 10. This plastic housing 10 comprises a base body 12, which is circular in cross-section and made of a high-strength plastic. This base body 12 carries four closure elements 14 on one side in the area of ​​the outer circumference, distributed at equal intervals around the circumference. These closure elements are made of the same plastic material as the base body 12. This is achieved by manufacturing the base body 12 and the closure elements 14 in a single process, typically an injection molding process.

[0032] This process is carried out in such a way, or the casting tool used for the process is designed in such a way that between each of the closure elements 14, which in this case are designed as snap elements, a web 16 is formed, which connects the respective closure element 14 to the base body 12. Furthermore, the illustration shows four insertion aids 18, which are also distributed over the circumference of the base body between the closure elements 14. These can also be manufactured together with the base body 12 and the closure elements 14 in a single process. The insertion aids 18 are intended to facilitate assembly of the plastic housing 10 on a housing of a steering gear. To support this, the insertion aids each have a bevel 20. The closure elements 14 can also have corresponding bevels.In one embodiment, it can be provided that the closure elements 14 are each connected to the base body by more than one web.

[0033] It should be noted that the plastic housing 10 shown does not yet have an elastomer layer, which is applied in a subsequent step. It may now be provided that the webs 16 are broken before the elastomer layer is applied. This can be done with a tool while the plastic housing is still held in the casting tool. This tool causes a relative movement of the closure elements 14 to the base body 12, typically a lifting of the closure elements 14 away from the base body 12.

[0034] Fig. 2 shows a plastic housing comparable to the plastic housing 10 of Fig. 1 with a base body 32, closure elements 34 and insertion aids 38. Webs are not visible in this illustration, since in the embodiment shown the elastomer layer 42 is already formed between the closure elements 34 and the base body 32.

[0035] Fig. 3 shows the plastic housing 10 from Fig. 1 in a different view. The base body 12, the closure elements 14, the webs 16, and the insertion aids 18 with bevels 20 are visible.

[0036] Fig. 4 shows a section through the plastic housing 10 of Fig. 1. The illustration shows the base body 12, the webs 16, the closure elements 14, which are connected to the base body 12 via the webs 16, and the insertion aids 18. Furthermore, the illustration shows a circumferential groove 22 for receiving an O-ring, which in turn ensures that the housing is tight after the plastic housing 10 has been assembled.

[0037] Fig. 5 shows a section through the plastic housing 30 of Fig. 2. The illustration shows the base body 32 and the closure elements 34, which are each connected via the elastomer layer 42, which in this case is only formed in the area of ​​the closure elements 34.

[0038] Fig. 6 shows a section of Fig. 5 and thus a section of the plastic housing 30 shown. The base body 32 and a closure element 34 can be seen, which are connected to one another via the elastomer layer 42. Furthermore, the illustration shows a conical bore 50 in the base body 32 and a conical bore 52 in the closure element 34, each of which is filled by the elastomer layer 42. This ensures not only a material connection but also a positive connection between the base body 32 and the closure element 34. List of reference symbols 10 plastic housings 12 basic bodies 14 locking elements 16 jetty 18 insertion aids 20 slopes 22 grooves 30 plastic housings 32 basic bodies 34 locking elements 38 insertion aids 42 Elastomer layer 50 Conical bore 52 Conical bore

Claims

[1] Method for producing a plastic housing (10, 30) for a housing of a steering gear, in which, in a first step, a base body (12, 32) and at least one closure element (14, 34) are produced in one process, in such a way that the base body (12, 32) and the at least one closure element (14, 34) are each connected via a web (16), and in which, in a further step, an elastomer layer (42) is applied which connects the base body (12, 32) and the at least one closure element (14, 34) to one another, wherein, in the method, the at least one web (16) is broken by a relative movement between the base body (12, 32) and the at least one closure element (14, 34). [2] Method according to claim 1, wherein the base body (12, 32) and the at least one closure element (14, 34) are produced in an injection molding process. [3] Method according to claim 1 or 2, wherein the elastomer layer (42) is applied via at least one gate point in a gate process. [4] Method according to one of claims 1 to 3, wherein the at least one web (16) is broken in a casting tool before the further step of applying the elastomer layer (42). [5] Method according to one of claims 1 to 3, wherein the at least one web (16) is broken after the further step of applying the elastomer layer (42). [6] Method according to claim 5, wherein the at least one web (16) is broken in a casting tool. [7] Method according to claim 5, wherein the at least one web (16) is broken during assembly of the plastic housing (10, 30) on the steering gear. [8] Method according to one of claims 1 to 7, in which a conical bore (50) is introduced into the base body and / or a conical bore (52) is introduced into the at least one snap element, which are filled by the elastomer. [9] Method according to one of claims 1 to 8, in which ribs are attached to the base body (12, 32). [10] Plastic housing (10, 30) for a housing of a steering gear, which has a base body (12, 32) and at least one closure element (14, 34), which are each connected via a web (16), wherein the plastic housing (10, 30) has an elastomer layer (42) which connects the base body (12, 32) and the at least one closure element (14, 34) to one another, and wherein the at least one closure element (14, 34) is designed as a snap element. [11] Method for assembling a plastic housing (10, 30) according to claim 10 on a housing of a steering gear, in which the at least one web (16) is broken by a relative movement between the base body (12, 32) and the at least one closure element (14, 34). [12] Method according to claim 11, wherein the relative movement is effected by a tool.

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