A morphological abrasive tool and its manufacturing process, and a method for retouching at least one tooth of a mechanical transmission part with such a tool

Abstract

The present invention relates to a tool (30) for reworking a mechanical transmission part (20). The tool (30) is a morphological abrasive tool comprising a body (40) shaped to an objective inter-tooth volume (13) and an abrasive (50) cooperating with the body (40). The body (40) and the abrasive (50) are configured to remove a defect in a tooth (56) that does not conform to a theoretical definition by displacement within an inter-tooth volume of the mechanical transmission part (20) delimited by this non-conforming tooth. (Shorthand figure: Figure 2)

Description

Title of the invention: Morphological abrasive tool and its manufacturing process, and method for retouching at least one tooth of a mechanical transmission part with such a tool

[0001] The present invention relates to a morphological abrasive tool, a method for manufacturing such a tool, and a method for retouching at least one tooth of a toothed mechanical transmission part with such a tool.

[0002] Such a mechanical transmission component may take the form of a wheel or a shaft, for example. Furthermore, such a toothed mechanical transmission component has teeth for transmitting mechanical torque.

[0003] Mechanical transmission systems can be manufactured taking into account extremely stringent dimensional, geometric, and surface quality requirements with tight tolerances. For example, a helicopter power transmission gearbox may include a mechanical transmission component with complexly shaped teeth that must be manufactured with tolerances of 4 to 25 micrometers. Manufacturing a mechanical transmission component with such complex shapes and precision proves difficult.

[0004] By way of illustration, the manufacture of such a mechanical transmission component can involve several dozen operations, including material shaping, processing, welding, three-dimensional precision control, and visual inspection, for example. The teeth are usually formed during the final manufacturing stages. Precision machines make it possible to manufacture such a mechanical transmission component with the required accuracy. Precision inspection machines can be used to inspect a mechanical transmission component to verify, in particular, that all the teeth have the required dimensional, geometric, and surface finish characteristics.

[0005] However, geometric and surface defects such as pitting, dents, and scratches may appear on one or more teeth. Such defects are unacceptable in the functional areas of the part, and particularly in the contact areas of the teeth. To avoid discarding the mechanical transmission part, an operator may attempt to rework the non-standard tooth or teeth. Rework may also be considered as a repair on an existing mechanical transmission part during a maintenance operation.

[0006] Retouching a tooth can only be performed if there is sufficient material available, and the success rate is uncertain or even low. If the material available is too small, for example less than 25 micrometers, then the retouching is If the modification is impossible and the part must be scrapped, then the part must also be scrapped. If the modification does not achieve the required dimensional, geometric and surface quality characteristics, then the part must also be scrapped.

[0007] To reshape a tooth with high precision, a known technique involves manually polishing the tooth with felt and abrasive paste, a stone, or cloth. Manual treatment of a tooth is unpredictable. Furthermore, on concave or convex surfaces, this technique can create localized contact points that distort the tooth's geometry. Defects in depressions are also accentuated.

[0008] Other techniques can be implemented using machines.

[0009] Thus, one of these machine-assisted techniques involves honing by honing and lapping. This technique is not applicable for teeth with complex surfaces, for example, for a tooth with an involute profile.

[0010] One of these machine-assisted techniques includes smuritropy tribofinishing or vibratory abrasion. This technique has the disadvantage of treating the entire part, which can accentuate recessed defects. Furthermore, this technique only allows for the removal of a thin layer of material, on the order of 0.001 millimeters at most.

[0011] One of these machine-assisted techniques involves abrasive flow polishing. This technique is not suitable for external shapes, is likely to accentuate recessed defects, and can generate non-uniform material removal with the required precision.

[0012] One of these machine-assisted techniques involves electrolytic polishing. This technique is suitable for stainless steels, but not for case-hardened or nitrided steels used in the power transmission systems of a helicopter, for example.

[0013] Abrasive processes such as smuritropy tribofinishing, abrasive flow polishing, or electrolytic polishing treat a part globally, which can tend to accentuate recessed defects. To remedy this, an operator can locally mask the part, but such an operation is delicate on complex shapes and produces unpredictable results.

[0014] Regardless of the technique used, reworking a tooth on a precision mechanical transmission component proves to be a delicate task. Precision mechanical transmission components requiring reworking often end up being scrapped due to the lack of a long-awaited solution.

[0015] The invention thus relates to a tool for reworking a mechanical transmission part, the mechanical transmission part to be reworked comprising a plurality of teeth, each of which must conform to a theoretical definition, each tooth having an upstream flank and a downstream flank connected by a ridge, a first tooth and a second Adjacent teeth that conform to the aforementioned theoretical definition, delimiting an objective inter-tooth volume between them, the objective inter-tooth volume being delimited by the downstream flank of the first tooth, the upstream flank of the second tooth, and a tooth root connecting the downstream flank of the first tooth to the upstream flank of the second tooth. The first and second teeth may belong to the mechanical transmission part to be reworked or to a reference part.

[0016] This tool comprises a body shaped to the objective inter-tooth volume, the body being configured to eliminate a defect of a tooth to be retouched not conforming to said theoretical definition by self-centering and displacement in an inter-tooth volume of the mechanical transmission part to be retouched delimited by this tooth to be retouched by cooperating with an abrasive.

[0017] The expression "inter-tooth volume" refers to a volume circumferentially delimited by two flanks of two teeth.

[0018] For example, the teeth are teeth having an involute profile. For example, the mechanical transmission part to be modified is a part with a complex spiral conical tooth profile.

[0019] The tool is thus a morphological abrasive tool comprising a body having the shape of the objective inter-dental volume, namely the inter-dental volume conforming to the theoretical definition, for removing material from the tooth to be retouched.

[0020] The expression "conforming to the theoretical definition" means that the associated object meets the dimensional (i.e., dimensions between two points), geometric (i.e., general shape), and surface constraints imposed by the theoretical definition. In other words, on a flawless mechanical transmission part, the body perfectly and completely conforms to the inter-tooth volume, having the same profile as the downstream flank, the upstream flank, and the root of the tooth that define this inter-tooth volume, accurate to the micrometer, for example. The morphological body represents a negative, accurate to the micrometer, of the inter-tooth volume of a flawless mechanical transmission part.

[0021] To retouch an upstream or downstream flank of a non-conforming tooth on a mechanical transmission part, an operator positions the body within an inter-tooth volume defined by the flank to be retouched. The abrasive is either integrated into the body, placed on the body, or placed on the tooth to be retouched. By moving and, ideally, sliding within this inter-tooth volume, the body allows the abrasive to be precisely rubbed against the tooth to be retouched, thus removing material from the tooth until it conforms to its theoretical definition. The body's conformation to the target inter-tooth volume allows the tool to self-center within a groove in the teeth defined by the tooth to be retouched, ensuring contact and positioning parallel to the surface to be retouched. The body is necessarily well positioned which allows the tooth in question to be retouched by removing material without creating a geometric defect on the tooth and its profile.

[0022] This tool does not tend to deepen defects, but to correct such defects.

[0023] Consequently, and surprisingly, such an abrasive tool may tend to solve a problem encountered throughout history in the manufacture of precision mechanical parts by increasing the chances of retouching a tooth that does not conform to its theoretical definition.

[0024] The tool may include one or more of the following features, taken alone or in combination.

[0025] According to one possibility, the body may include a material sufficiently elastic so as not to unduly damage a tooth.

[0026] Thus, the body may comprise a material from the silicone group.

[0027] Such a material allows for the precise fabrication of the body. Furthermore, this material is unlikely to scratch the teeth or generate significant stress on them during retouching.

[0028] According to a possibility compatible with the preceding ones, the tool includes the abrasive.

[0029] This abrasive can be integrated into the body or independent of the body.

[0030] According to one embodiment, the abrasive may have grains incorporated into the body. The nature and / or size of the abrasive grains may be chosen according to, for example, the material of the tooth or the depth of the defect to be corrected.

[0031] According to another variant, an abrasive paste can be placed on the body or tooth to be retouched.

[0032] According to a possibility compatible with the previous ones, the body can be shaped into a form delimited by the downstream side of the first tooth as well as the upstream side of the second tooth and the tooth bottom connecting the downstream side of the first tooth to the upstream side of the second tooth.

[0033] According to a possibility compatible with the preceding ones, the body may include at least one edge shaped to the crest of the first or second tooth.

[0034] The crest of a tooth is not usually functional. However, the body may have an edge shaped like a crest, for example to allow an operator to check that the tool is correctly positioned before moving it to perform a retouch.

[0035] In addition to a tool, the invention relates to a method for manufacturing such a tool for reworking a mechanical transmission part, the mechanical transmission part to be reworked comprising a plurality of teeth, each of which must conform to a theoretical definition, each tooth having an upstream flank and a downstream flank connected by a ridge, a first tooth and a second adjacent tooth conforming to said theoretical definition delimiting an objective inter-tooth volume between them, the target inter-tooth volume being delimited by the downstream side of the first tooth as well as the upstream side of the second tooth and a tooth bottom connecting the downstream side of the first tooth to the upstream side of the second tooth.

[0036] The manufacturing process includes manufacturing a body shaped to the target inter-tooth volume so that it can be self-centered and moved within an inter-tooth volume of the mechanical transmission part to be reworked, delimited by a tooth to be reworked.

[0037] This method may include one or more of the following features, taken alone or in combination.

[0038] According to one possibility, the process for manufacturing a tool may include the design of an abrasive, said design of an abrasive being carried out independently of said manufacturing of the body or during said manufacturing of the body.

[0039] The abrasive may comprise grains. The nature and / or size of the abrasive grains may be chosen according to, for example, the material of the tooth and / or the depth of the defect to be corrected. For example, the process includes determining the grains to be used according to the depth of the defect to be corrected and / or the material of the tooth to be corrected, possibly using a nomogram or equivalent established by trial and error.

[0040] Several different tools can have different grits. For example, a first tool with coarse grits is used initially to retouch a tooth in a first pass, then a second tool with finer grits is used subsequently for finer retouching.

[0041] According to a possibility compatible with the preceding ones, said manufacture may include a molding of said body by placing a material of the body in an inter-tooth volume of a reference part, present between two teeth conforming to said theoretical definition.

[0042] An operator can easily manufacture a body on a reference part. For example, the operator pours a mixture of silicone, a suitable catalyst for the polymerization of silicone, and possibly an abrasive, into an inter-tooth volume of the reference part.

[0043] Alternatively, said manufacture may include a molding of said body by placing a material of the body in an inter-tooth volume of the mechanical transmission part to be retouched, present between two teeth conforming to said theoretical definition.

[0044] This alternative is particularly interesting and innovative. The mechanical transmission part to be retouched itself then serves as a mold for manufacturing the morphological tool. Indeed, a mechanical transmission part to be retouched usually has only a limited number of teeth to be retouched. It is then possible to use the volume between two teeth conforming to the theoretical definition to mold the body of a morphological tool. For example, the operator pours a mixture of silicone, a suitable catalyst for silicone polymerization, and possibly an abrasive into the inter-tooth volume of the mechanical transmission part to be modified, located between two teeth conforming to the theoretical definition.

[0045] This solution is advantageous because all teeth then have essentially the same definition after retouching. In particular, this solution is especially suitable for maintenance to ensure that all teeth are substantially equivalent.

[0046] Alternatively, said manufacturing may include modeling the objective interdental volume with a scanner on a reference piece, and manufacturing said body using said modeling.

[0047] The inter-tooth volume of a reference part can be modeled with a scanner. The body can then be produced in various ways, via a mold conforming to the model or by an additive manufacturing method by superimposing layers of material such as three-dimensional printing for example.

[0048] Alternatively, said manufacturing may include modeling the objective interdental volume with a scanner on the mechanical transmission part to be reworked, and making said body using said modeling.

[0049] An inter-tooth volume, deemed to conform to the theoretical definition, of the mechanical transmission part to be modified itself can be modeled with a scanner. The body can then be produced in various ways, via a mold conforming to the model or by an additive manufacturing method by superimposing layers of material such as three-dimensional printing for example.

[0050] Alternatively, said fabrication may include making said body using a definition plan for said objective inter-tooth volume.

[0051] The body can then be produced in various ways, via a mold conforming to the definition plan or by an additive manufacturing method by superimposing layers of material such as three-dimensional printing for example.

[0052] The invention also relates to a retouching method for retouching a mechanical transmission part to be retouched, the mechanical transmission part to be retouched comprising a plurality of teeth, each of which must comply with a theoretical definition, each tooth having an upstream flank and a downstream flank connected by a ridge, a first tooth and a second tooth adjacent which conform to said theoretical definition delimiting an objective inter-tooth volume between them, the objective inter-tooth volume being delimited by the downstream flank of the first tooth as well as the upstream flank of the second tooth and a tooth root connecting the downstream flank of the first tooth to the upstream flank of the second tooth.

[0053] The retouching process involves sliding a tool comprising a body shaped to the objective inter-tooth volume and an abrasive, for example by going back and forth, in a non-conforming inter-tooth volume of the mechanical transmission part to be retouched between a tooth to be retouched that does not conform to said theoretical definition and an adjacent tooth.

[0054] The sliding can be performed manually by an operator. Alternatively, a conventional robot carries the tool and moves it within the non-conforming inter-tooth volume of the mechanical transmission part to be reworked.

[0055] Following the sliding, the retouching process may include a check of the conformity of the tooth to be retouched with respect to the theoretical definition, and a new sliding of said tool by going back and forth in the non-conforming inter-tooth volume if the tooth to be retouched is still not in conformity with the theoretical definition.

[0056] The retouching can be carried out precisely using several successive material removal and verification operations. The verification can be performed using conventional tooth-verifying machines.

[0057] The invention and its advantages will become apparent in more detail in the following description, with illustrative examples given by reference to the accompanying figures, which represent:

[0058] [Fig. 1], a view of a mechanical transmission part having two teeth conforming to a theoretical definition,

[0059] [Fig. 2], a view of a morphological abrasive tool according to the invention,

[0060] [Fig. 3], a view illustrating the manufacture of a morphological abrasive tool according to the invention on a reference part or the mechanical transmission part to be reworked,

[0061] [Fig.4], a view illustrating the manufacture of a morphological abrasive tool according to the invention using a model of a reference part or of the mechanical transmission part to be reworked,

[0062] [Fig. 5], a view illustrating the manufacture of a morphological abrasive tool according to the invention using a definition drawing, and

[0063] the [Fig.6], a view explaining a method of retouching a tooth of a mechanical transmission part to be retouched using a morphological abrasive tool according to the invention.

[0064] Elements present in several separate figures are assigned one and the same reference.

[0065] Figure 1 shows a mechanical transmission part 10 comprising a first tooth 11 and a second tooth 12, both conforming to a theoretical definition. The theoretical definition defines the shape that each tooth must have, namely its dimensions in several directions, within a tolerance of approximately 4 to 25 micrometers. These dimensions allow us to obtain the desired geometry and surface finish.

[0066] The first tooth 11 and the second tooth 12 each comprise a downstream flank 112, 122, an upstream flank 111, 121, and a crest 113, 123 connecting its downstream flank 112, 122 and its upstream flank 111, 121. The terms "downstream" and "upstream" are to be considered with regard to the direction of rotation ROT of the mechanical transmission part 10 relative to a housing not shown, the upstream flank of a tooth being behind the downstream flank of that tooth according to this direction of rotation.

[0067] The downstream flank 112 of the first tooth 11 is further connected by a tooth bottom 131 to the upstream flank 121 of the second tooth 12.

[0068] The mechanical transmission part 10 includes a volume called "target inter-tooth volume 13" between the first tooth 11 and the second tooth 12. This target inter-tooth volume 13 is delimited by the downstream flank 112 of the first tooth 11 as well as the tooth root 131 and the upstream flank 121 of the second tooth 12.

[0069] This target inter-tooth volume 13 represents a target inter-tooth volume to be achieved between all the teeth of a mechanical transmission part 10, the first tooth 11 and the second tooth 12 both conforming to the theoretical definition.

[0070] However, at least one tooth of a mechanical transmission part, referred to as a "mechanical transmission part requiring reworking," normally identical to the first or second tooth conforming to the theoretical definition, may have a defect. Such a tooth is called a "tooth requiring reworking" insofar as it does not conform to the theoretical definition. The mechanical transmission part requiring reworking may be mechanical transmission part 10 or may be normally identical to this mechanical transmission part 10, within tolerances.

[0071] [Fig.2] shows a tool 30 for retouching a retouching tooth 56 of such a retouching mechanical transmission part 20. The teeth of this retouching mechanical transmission part 20 must comply with the theoretical definition of the first tooth and the second tooth of [Fig.1].

[0072] Tool 30 is a morphological abrasive tool used to remove material from the tooth to be retouched 56.

[0073] This tool 30 has a body 40 shaped to the objective interdental volume 13. This body 40 has the shape that the non-conforming interdental volume delimited by the tooth to be retouched 56 should normally have, namely the shape of the objective interdental volume 13 of [Fig.1].

[0074] Thus, the body 40 is shaped by a form delimited by the downstream flank 112 of the first tooth 11, the upstream flank 121 of the second tooth 12, and the tooth root 131, conforming to the theoretical definition. This body 40 thus comprises a downstream face 42 identical to the upstream side 121, an upstream face 41 identical to the downstream side 112, and a base 43 identical to the tooth bottom 131 which extends from the downstream face 42 to the upstream face 41.

[0075] Optionally, the body 40 may include at least one edge 44, 45 shaped to at least one of the ridges 113, 123 of the first tooth 11 and / or the second tooth 12. According to the illustrated example, the tool 30 may include a downstream edge 45 connected to the downstream face 42 and identical to the ridge 123 of the second tooth 12 and / or an upstream edge 44 connected to the upstream face 41 and identical to the ridge 113 of the first tooth 11.

[0076] According to another aspect, the body 40 comprises a material from the silicone group.

[0077] Furthermore, the tool 30 includes an abrasive 50 cooperating with the body 40.

[0078] According to the example in [Fig. 2], the abrasive 50 is integrated into the body 40. This abrasive 50 includes grains attached to body 40 and protruding outside of this body 40.

[0079] Alternatively, the abrasive 50 can be an abrasive paste disposed on the body 40 or the tooth to be retouched. For example, an abrasive paste is disposed on the body 40.

[0080] Figures 3 to 5 illustrate manufacturing processes for such a tool 30.

[0081] Regardless of the variant, this manufacturing process involves STPF manufacturing of a body 40 of the tool by conforming the body 40 to the objective inter-tooth volume 13 and an STPA design of an abrasive 50 independently of said manufacture of the body or during said manufacture.

[0082] According to [Fig.3], this STPF fabrication can include an STPM molding of the body 40 by disposing during an STPR filling step of a material of the body 40 in an inter-tooth volume 65 present between two teeth 71, 72 conforming to the theoretical definition.

[0083] For example, plates 66, 67, 68, 69 are arranged to create a casing around this inter-tooth volume 65. An operator then places one or more materials of the tool 30, and in particular the body 40, into the casing. For example, the operator places silicone, possibly abrasive grains 50, and a catalyst in the volume delimited by the casing and the teeth. Alternatively, an abrasive paste is prepared separately in the usual manner during an STPA manufacturing operation.

[0084] According to variations of this alternative, the teeth 71, 72 can be teeth of a reference part 75 or of the mechanical transmission part 20 to be modified as such. When the mechanical transmission part 20 to be modified is used, the process first involves checking the conformity of the teeth of this mechanical transmission part 20 to be modified with a conventional checking machine in order to identify two adjacent teeth conforming to the theoretical definition, the STPM molding being carried out between these two teeth.

[0085] According to the alternative in [Fig. 4], this STPF fabrication includes a modeling STPSCAN of the objective interdental volume with an 80 scanner to define a three-dimensional model of the objective interdental volume. As before, the volume inter-teeth objective can be a volume of a reference part 75 or of the mechanical transmission part to be reworked 20 as such.

[0086] Therefore, this STPF manufacturing step includes an STPFAB1 fabrication of the body 40 using STPSCAN modeling. The model obtained during STPSCAN modeling can be transmitted to a 3D printer 81 which fabricates the body 40 in the usual way. Alternatively, a mold can be made from this STPSCAN model, the STPFAB1 fabrication then comprising a molding of the body 40 in this mold as explained previously. An abrasive paste can be produced separately in the usual way during an STPA fabrication operation.

[0087] According to the alternative in [Fig. 5], this STPF manufacturing process involves creating a definition plane 83 of the objective interdental volume using, for example, a computer-aided design system 99. Therefore, this STPF manufacturing step includes an STPFAB2 fabrication of the body using the definition plane.

[0088] The body 40 can then be produced in various ways, via a mold conforming to the definition plan or by three-dimensional printing for example with a three-dimensional printer 82. An abrasive paste can be produced separately in the usual way during an STPA manufacturing operation.

[0089] Regardless of how a morphological abrasive tool according to the invention is made, [Fig.6] illustrates a retouching process for retouching a mechanical transmission part to be retouched 20. The mechanical transmission part to be retouched 20 comprises a plurality of teeth 21, each of which must comply with a theoretical definition, each tooth 21 having an upstream flank 211 and a downstream flank 212 connected by a ridge 213.

[0090] However, at least one tooth 21, referred to as "tooth to be retouched 56", does not conform to the theoretical definition.

[0091] Therefore, after the manufacture of the tool 30 on the mechanical transmission part to be retouched or not, the retouching process includes a sliding STPC of the tool 30 in the non-conforming inter-tooth volume 55 present between the tooth to be retouched 56 and an adjacent tooth 57.

[0092] An operator moves the tool 30 once or several times, possibly back and forth in a first direction Fl then a second direction F2 opposite, in order to remove material from the tooth to be retouched 56, and where appropriate from the adjacent tooth 57.

[0093] Following this STPC sliding step, the retouching process includes an STPV verification of the conformity of the tooth to be retouched 56 with the theoretical definition. This step can be carried out using a standard inspection machine 60.

[0094] If necessary, the STPC sliding and STPV verification steps are carried out several times successively, as long as the tooth to be retouched 56 does not conform to the theoretical definition.

[0095] Naturally, the present invention is subject to numerous variations in its implementation. Although several embodiments have been described, it is understood that it is not conceivable to exhaustively identify all possible embodiments. It is, of course, conceivable to replace a described means with an equivalent means without departing from the scope of the present invention and the claims.

Claims

Demands

1. Method of manufacturing a tool for retouching a mechanical transmission part to be retouched (20), the mechanical transmission part to be retouched (20) comprising a plurality of teeth (21), each of which must comply with a theoretical definition, each tooth (21) having an upstream flank (211) and a downstream flank (212) connected by a ridge (213), a first tooth (11) and a second tooth (12) adjacent which conform to said theoretical definition delimiting an objective inter-tooth volume (13) between them, the objective inter-tooth volume (13) being delimited by the downstream flank (112) of the first tooth (11) as well as the upstream flank (121) of the second tooth (12) and a tooth root (131) connecting the downstream flank (112) of the first tooth (11) to the upstream flank (121) of the second tooth (12),characterized in that the manufacturing process comprises a fabrication (STPF) of a body (40) shaped to the objective inter-tooth volume (13) so as to be able to be self-centered and moved within an inter-tooth volume of the mechanical transmission part to be reworked (20) delimited by a tooth to be reworked, said fabrication (STPF) comprising a modeling (STPSACN) of the objective inter-tooth volume with a scanner (80) on a reference part (75) or on the mechanical transmission part to be reworked (20), and a fabrication (STPFAB1) of said body using said modeling.

2. A manufacturing process according to claim 1 characterized in that said manufacturing process comprises the making of an abrasive, said making of an abrasive being carried out independently of said body making or during said body making.