DE102011100735B4 - Method for producing a toothed wheel and toothed wheel produced thereby - Google Patents

Abstract

Method for producing a toothed wheel, in particular for a seat adjustment gear, in which the toothed wheel (1) having a toothed region (2) with a plurality of teeth (3) is cut from an output sheet by means of at least one cutting laser beam (12), the cutting laser beam ( 12) along the toothing region (2) of the toothed wheel (1) is moved at different speeds (v1, v2), wherein the cutting laser beam (12) in areas (4) of the toothed wheel (1) loaded with rolling contact or loaded with rolling contact Speed (v2) is driven than in other areas of the gear (1), wherein the cutting laser beam (12) during curing at the low speed (v1) performs a cure by local heating, so that the teeth (3) in on rolling contact loaded or loadable areas (4) have a different surface finish than in other areas (8, 10, 6).

Description

The invention relates to a gear wheel, which can be used in particular for a Sitzverstellgetriebe.

Gears made of sheet metal, which are also used in particular for seat adjustments, generally can not be formed by simple, inexpensive processes such as punching, since the achievable thereby surface qualities are often not sufficient. To achieve higher surface qualities, on the one hand, a fine blanking process can be used in which the starting sheet is first clamped in the tool and cutting knives are guided from below and above. By such fine cutting processes, the z. B. in the GB 2 235 888 A and GB 2 214 110 A are described, higher surface qualities can be formed, which can be measured, for example, on the surface roughness. As a result, better operating conditions and performance characteristics of the gear can be realized. In order to increase the surface hardness, the gear can subsequently be placed in another machine in which it is subjected to a heat treatment.

The DE 4228740 C2 describes a laser processing apparatus and a method of operating the same, wherein a laser beam from a laser beam generator may optionally be supplied to one of a plurality of different processing heads intended for cutting, welding and curing. The processing heads are each structured differently.

The US 2007/0095804 A1 describes a method for producing sprockets by means of a laser beam. Here, the gear made of sheet steel is cut out with a toothed area with several teeth. A pre-hardened steel plate is used which is cut out in the gearing area under an oxygen atmosphere and in other areas subsequently under a nitrogen atmosphere so that the surface finish in the gearing area is different than in the other areas.

The US 4,250,372 A describes the heat treatment of surfaces of steel products by means of a laser beam.

The GB 13 46 174 describes an abrasive surface treatment with electrochemical machining.

In addition to fineblanking processes, laser cutting processes can also be used. The surface quality of the cut surface depends to a large extent on the speed with which the cutting laser is driven. To achieve a high surface quality, a low laser cutting speed is generally needed so that the productivity is again reduced.

The FR 2 698 302 A1 describes a laser cutting process in which the travel speed of the cutting laser is varied depending on the thickness and the material in order to achieve a uniform surface quality. The US 2006/0207977 A1 describes another laser cutting process.

The invention has for its object to provide a method for producing a gear, which is particularly suitable for a Sitzverstellgetriebe used, which allows a relatively low cost high quality of the gear.

This object is achieved by a method according to claim 1 and a gear according to claim 4. The dependent claims describe preferred developments. Here, the seat adjustment is provided with a plurality of such gears.

According to the invention thus the gear is formed in its rolling contact loaded or loadable areas with a different surface finish than in other areas.

According to the invention, the teeth are hardened in these loaded areas by a heating process. With such a heating process, in particular locally a martensite precipitate can form, which leads to a significant hardening of the surface. The areas subjected to rolling contact can, in particular, be tooth flank areas in which the toothings, in particular involute toothings of two intermeshing toothed wheels, come into rolling contact.

The invention is thus based on the finding that a significant improvement in the quality can be achieved in a surprisingly simple manner in which the surface texture is improved locally in the areas loaded or loadable on rolling contact. In other areas, i. In particular, in the tooth base between the teeth and in tooth tip areas, according to the invention, a different surface texture, i. in particular a lower quality or a higher surface roughness and / or lower hardness allowed.

The gears according to the invention are produced by laser cutting processes. For this purpose, the cutting laser beam is driven along the toothing of the gear at different speeds. In the loaded or loadable on Wälzkontakt areas of the laser beam is driven at a lower speed, and in the other areas at a higher speed.

Thus, a relatively high productivity can again be achieved in a surprisingly simple manner and still the quality can be kept high, since the areas relevant for the rolling contact can be formed by a lower process speed with a better quality, in particular less roughness.

According to a particularly preferred embodiment, the areas subjected to rolling contact are again hardened by a heating process. This is done by the cutting laser beam itself, which already causes a hardening at the low process speed.

Thus, according to the inventive method, the formation of the gear in a single tool possible. It is no longer necessary to move the gear after a fine blanking process or laser cutting process for curing in another machine. It turns out that a high surface hardness can be achieved by this surprisingly simple solution. In particular, can be sought by the local heating in these areas on Wälzkontakt charged areas a higher Martensitausscheidung than when the gear is heated as a whole in an oven later, as in such a heating process in a furnace and other areas of the gear are changed with, not should have too high a brittleness.

• 1 einen Verzahnungsbereich eines erfindungsgemäßen Zahnrades;
• 2 den Wälzkontakt des Zahnrades beim Kämmen mit einer weiteren Verzahnung;
• 3 ein Flussdiagramm eines erfindungsgemäßen Herstellungsverfahrens.

The invention will be explained in more detail below with reference to an embodiment with reference to the accompanying drawings. Show it:

• 1 a toothed portion of a gear according to the invention;
• 2 the rolling contact of the gear when combing with a further toothing;
• 3 a flow chart of a manufacturing method according to the invention.

An inventive gear 1 is as external gear with an external toothing 2 thus formed by individual teeth 3 is formed. In 1 . 2 is an involute gearing 2 shown. The teeth 3 have tooth flank areas 4 on, according to 2 with teeth of an engaged further gear or a rack engage. According to 2 is the tooth flank area 4 each between a starting point 4a and an endpoint 4b the Wälzkontaktes or the rolling process defined; in 1 is a tooth flank area 4 illustrated by a dash-dotted line.

Thus, a rolling contact with the other gear is only in the tooth flank areas 4 in front; Alternatively, but z. B. with corresponding tooth geometries and a contact in other areas outside the tooth flank areas 4 be present, in which case these other areas may not be charged.

The gear 1 is made of sheet steel and is formed by laser cutting from an output plate.

According to the invention, the tooth flank areas 4 formed with a different surface finish than other areas of the external teeth 2 of the gear 1 , eg the tooth tips 6 and the tooth base 8th , but preferably also as further tooth flank areas 10 , which are closer to the base of the tooth, for example. Preferably, the tooth flank area 4 harder than the areas 6 . 8th . 10 , eg with a higher martensite precipitation of the steel material.

For this purpose, in particular the laser beam during the cutting process at different speeds along the contour of the external toothing 2 be guided. In areas 8th . 10 and 6 , which are not loaded on rolling contact, the in 1 indicated and by a laser head 14 output laser beam 12 driven at a higher first speed v1. In the tooth flank area loaded on rolling contact 4 however, the laser beam becomes 12 driven at a lower speed v2 <v1. This initially increases the quality of the surface and reduces the roughness, since a more accurate cutting process is made possible with slow process control.

In this case, in the machine or the tool also several laser heads 14 are used, which thus cut simultaneously.

According to the invention, the laser beam 12 in the tooth flank areas 4 be performed so slowly, that by the local heating already a significant Martensitausscheidung and thus hardening of the surface area 4a of the gear 1 takes place, which thus improves the mechanical hardness and abrasion resistance, but the base material of the gear 1 otherwise not significantly affected.

The inventive method thus comprises the steps according to 3 : Start in st0 , below laser cutting of the gear 1 in step St1 by means of a laser 12 , already with hardening of the tooth flank area 4 until the procedure in step St3 is finished and the gear 1 is issued.

Claims (9)

Method for producing a toothed wheel, in particular for a Sitzverstellgetriebe, in which the toothed wheel (1) having a toothed region (2) with a plurality of teeth (3) is cut from an output sheet by means of at least one cutting laser beam (12), wherein the cutting laser beam (12) is driven along the toothing region (2) of the toothed wheel (1) at different speeds (v1, v2), wherein the cutting laser beam (12) is moved at rolling-contact or loadable areas (4) of the toothed wheel (1) at a lower speed (v2) than in other areas of the toothed wheel (1), wherein the cutting laser beam (12) performs a local heating cure during low speed cutting (v1) such that the teeth (3) have a different surface finish in rolling contact loaded or loadable areas (4) than in other areas (8) , 10, 6). Method according to Claim 1 characterized in that martensite precipitation is formed by the local heating as the cutting laser beam (12) is driven at the lower velocity (v2). Method according to Claim 1 or 2 , characterized in that the entire laser cutting and hardening process takes place in a single machine. Gear, in particular for a Sitzverstellgetriebe, which is produced by a method according to any one of the preceding claims. Gear after Claim 4 , characterized in that the rolling contact loaded areas tooth flank regions (4). Gear after Claim 4 or 5 , characterized in that the rolling contact loaded areas (4) have a Martensitausscheidung. Gear after one of the Claims 4 to 6 , characterized in that the rolling contact loaded areas (4) have a lower surface roughness than the other areas (8, 10, 6). Gear after one of the Claims 4 to 7 , characterized in that the toothed region (2) is or has an involute toothing. Sitzverstellgetriebe with several, intermeshing gears (1) after one or more of the Claims 4 to 8th ,

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