JP5734944B2 - Composite metal powder variable boundary gear and method - Google Patents

Description

The present invention relates to a forged metal powder part, in particular a composite metal powder variable boundary part, and a method for manufacturing the same.

In producing parts, there has been a need for a manufacturing process that can reduce cost, time, and steps. The benefits brought about by the improved manufacturing process are sought by customer demand to first improve the product to have better dimensional, mechanical and / or performance characteristics. For example, the conventional differential side gear (differential sidegear)
May have any or all of the following performance requirements: dimensiona
splinearea that requires lprecision, high shear strength, and brinnelling resistance; dimensional accuracy, surface finish, and case suitability (c
hub and thrustface that require asecompatibility; gear geometry that requires dimensional accuracy, surface finish, and optimized profile; and impact resistance;
Abrasion resistance, peeling resistance, and different surface and core metallurgy (core)
Tooth and core strength that can require metallurgies). Different incompatible manufacturing methods, ie
Different performance requirements of the same part or otherwise are achieved by casting, steel forging, or metal powder forging.

According to FIG. 1, to meet these performance requirements, the gear 10 forges the metal powder 14 and then casecarburizes the gear to a substantially constant effective boundary depth (effect).
ivecasedepth) 16. For a constant case depth 16 for each (gear) tooth 12, see the partial cross-sectional view of FIG. However, case carburized gears provide improved performance characteristics for the gear body obtained when the parts are composed of composite materials, but improved toothwear and fatigue strength (fatiguestrength). ) And other desired mechanical properties are not necessarily obtained. It would be advantageous to better balance these performance requirements in the final product, which saves time, processing, or costs from not being adversely affected by the manufacturing process.

A manufacturing method for improving the performance requirements of metal powder parts is described in US Pat. No. 5,903,815 (Title: Composite metal powder parts). This method is compressed and sintered 2
Disclosed are parts made of these separate metal powders. US Pat. No. 6,148,68.
No. 5 (Title of Invention: Double Sprocket / Gear Structure and Manufacturing Method) describes a method of manufacturing a gear from two or more separate metal powders that are compressed and sintered to obtain the final part. .
These patent documents only describe composite metal powder parts obtained by sintering. Toothroot has impact resistance and bending fatigue resistance (bendingfa)
tigueresistance), composite variable boundary layer
Or fully dens sufficiently compacted by compaction forging
epart), but improved load resistance (toothflank)
There is no mention of applying a composite powder process that can improve performance features such as bearings.

Therefore, a need existed for a composite metal powder variable boundary part having improved impact resistance and bending fatigue resistance at the root of the tooth. It is advantageous to provide a composite variable boundary layer or (substantially) sufficiently dense part by compression forging. There has also been a need for a method of providing variable boundaries in composite metal powder parts.

US Pat. No. 5,903,815 US Pat. No. 6,148,685

The present invention is based on the aforementioned needs and has a surface with greater tooth wear resistance (toothwe
arresistance, and its core has greater impact resistance
variable boundary composite metal powder gear that provides resistance).

The forged composite gear of the present invention includes a plurality of teeth extending from a core portion, a first portion having a first metal powder material, a second portion having a second metal powder material, and a variable boundary. Profile and
including. Here, the variable boundary profile is provided between the first part and the second part to provide better tooth wear resistance for the teeth and better for the gear core. Provides impact resistance.

According to the present invention, a variable boundary composite metal powder gear having better tooth wear resistance on its surface and better impact resistance on its core can be obtained.

FIG. 1 is a partial cross-sectional view of a prior art case carburized gear. FIG. 2 is an isometric view of a composite preform made after compression and sintering required to obtain a product of the invention after forging, according to an embodiment of the invention. FIG. 3 is a partial cross-sectional view of the preform of FIG. 2 having a composite material. 4 is an isometric view of a differential side gear made from the composite preform of FIG. 2 in accordance with an embodiment of the present invention. FIG. 5 is a partial cross-sectional view of the differential side gear of FIG. FIG. 6 is a partial cross-sectional view of the differential side gear of FIG. FIG. 7 schematically shows a specific example of the method of the present invention for producing a composite metal powder boundary part.

For better understanding of the present invention, specific examples of the present invention will now be described with reference to the accompanying drawings.

In the drawings, the same reference numerals denote similar parts. Accordingly, the same reference numerals may be given in different drawings. In some examples, similar parts in different drawings may be numbered differently for reasons such as clarity.

FIG. 2 is an isometric view of a composite preform 84 obtained after compression and sintering required to obtain a product of the invention after forging, according to an embodiment of the invention.
view).

FIG. 3 is a partial cross-sectional view of the composite preform 84 of FIG. 2 having a composite material. The preform 84 includes a first metal powder material 55 and a second metal powder material 57 separated by a materialboundary 59. The material boundary 59 is a compression type of metal powder (compac
is a boundary between two or more materials obtained after compression. Although this material boundary 59 is shown as a precise boundary between the different materials 55, 57, the actual material boundary depends on the filling process used to produce the composite preform. Close to separation. Techniques for forming composite preforms by filling different metal powders in a compression mold are known to those skilled in the art, but will be briefly described for the understanding of the invention described herein. .

FIG. 4 is an isometric view of the differential side gear 50 manufactured from the composite preform 84 of FIG. 2 in accordance with an embodiment of the present invention. The differential side gear 50 includes a plurality of teeth 52 having a variable boundary profile 58 as shown in this specification and in FIG. Each tooth of the plurality of teeth 52 includes a first surface 54 and a tooth core or root 5.
6. The differential side gear 50 has a rotation shaft 60. Here, the teeth 52 extend radially outward in generally the same direction as the rotation axis of the gear, but are inclined with respect to the rotation axis. The differential side gear 50 includes an axially spline internal section 62 that is aligned with the rotary shaft 60 in the axial direction. The differential side gear 50 is manufactured by compression forging the composite preform 84.

FIG. 5 is a partial cross-sectional view of the differential side gear 40 of FIG. After forging, the differential side gear 50 has a first region 51 composed of the first metal powder material 55 and a second region 53 composed of the second metal powder material. The gear 50 includes the variable boundary profile 58 shown in FIG. The variable boundary profile 58 has the performance characteristics described above, but is not necessarily manufactured from the carburized portion, and can be manufactured from the material boundary 59 generated by forging the composite materials 55 and 57. The variable boundary profile 58 provides improved tooth wear or load resistance to the plurality of teeth 52, and improved impact and bending resistance to the gear core 56 (see FIG.
bendingresistance). Also, the second metal powder material 57 may be selected to obtain the advantageous performance characteristics of the spline 62 of the gear 50 while retaining the desired performance characteristics for the teeth 52.

Composite materials can be used strategically for each material region. Also, providing the preform with additional or multiple material regions can result in multiple composite variable boundary profiles in selected portions of the final forged part or gear, thereby achieving selective performance characteristics. .

FIG. 6 is a partial cross-sectional view of the differential side gear 50 of FIG. This differential side gear 50 is
A composite variable boundary profile 58 is included. The variable boundary profile 58 coincides with the material boundary 59 by chance in a specific sectional view as shown in FIG. 5, but the material boundary 59 does not determine the variable boundary profile 58 as shown in FIG. Absent.

The first surface 54 of the gear 50 includes a tip surface 64 and a pitch line surface (pit).
It includes a chlinesurface 66, a rootfillet surface 68, and a rootdiameter or landsurface 70. The variable boundary profile 58 has an effective boundary of 2.4 mm on the tip surface, 1.9 mm on the pitch line surface, 0.4 mm on the root fillet surface, and 0.8 mm on the root land surface.
iveboundary). Although a specific numerical value is shown in this specific example, the variable boundary profile may have an effective boundary profile that is not constant on a cross section of a specific surface, and is not limited to the specific profile shown here.

The variable boundary profile 58 can be represented by a boundary ratio. The effective boundary ratio is the boundary depth measured at the tip surface 64 (boundarydepth).
) To the boundary depth measured at the rootfillet surface 68,
Compare the boundary depth measured at the pitchline surface 66 to the boundary depth measured at the root fillet surface 66, or the boundary depth measured at the rootland surface 70 at the root fillet surface 68. It can be obtained by comparing with the measured boundary depth. For example, the variable boundary ratio of tip surface 64 to root fillet surface 68 is 6: 1, the variable boundary ratio of pitch line surface 66 to root fillet surface 68 is 19: 4, and root land surface 70 to root. The variable boundary ratio of the fillet surface 68 is 2: 1.

Boundary ratio (bounda in variable boundary profile 58 from maximum depth to shallower depth
Advantageously, the ryratio) is 6: 1. This is because it is possible to obtain a material excellent in predetermined mechanical properties such as tooth wear resistance and impact resistance.

It is also desirable to select the first metal powder material 55 as the first surface 54 of the tooth 52 to achieve a surface hardness of 58 HRC or higher in the forged gear. The gear core 56 having a hardness of less than 43 HC is preferably provided by the second metal powder material 57. In this regard, the second metal powder material is a non-hardened material such as low iron alloy steel having a carbon content of less than 2% (
The first metal powder material is selected to have a non-hardening material and is a hardening material made of different types of steel with a higher carbon content.

The variable boundary profile 58 provides better impact resistance to the first surface 54 while providing better impact resistance to the root 56 or better shear resistance to the spline 62 (see FIG.
A gear having toothwear resistance) can be provided. This variable boundary profile 58 may be an effective boundary profile obtained by strategically forging a preform. Therefore, the variable boundary profile 58 can be obtained by the forging process described in this specification.

Although the process will be described with respect to differential side gear 50, variable boundary boundary profile 58 may be used for various gears or parts including bevel gears, differential gears, or pinion gears (small gears). Can also be obtained.

One of the material portions of the differential side gear 50 may be composed of a low alloy, fully compacted iron metal powder material. However, the gear can be composed of various types of forged metal powder steel.

Returning to the manufacturing method of the variable boundary metal powder gear 50, FIG. 7 schematically shows an embodiment of the method of the present invention for obtaining a composite metal powder variable boundary part. This process begins with the mixing steps 219, 220. Here, each material is ready for filling into a compression form. Thereafter, filling steps 221, 22 for strategically placing each material in a compression mold.
Perform two steps. When the filling step is completed, the compression step 224, the sintering step 22
6. A forging step 232 and a cooling step 234 are performed. Postforging
operation) (not shown) is a process for further improving the gear. Because these process steps are well known to those skilled in the art (technical field for forging metal powders),
Only some features of the invention are described below. From this point of view, material selection, temperature treatment (temp
erature processing) and pressure during compression will be briefly mentioned.

In the mixing steps 219 and 220, a metal powder containing the required binder or lubricant (substantially homogeneous mixture obtained by mixing and suitable for filling into a compacting form in the filling step 22) is prepared. An optional separation step 223 may be included in the filling steps 221, 222 to facilitate placement of the material in the compression mold. Two mixing steps 2
Although 19 and 220 and two filling steps 221 and 222 are shown, further mixing or filling may be required for each additional desired material. Filling steps 221, 222 may be performed sequentially, for example, such that the first surface 54 is strategically placed on the preform prior to the material 57 for the second surface 56. However, even in this case, the filling steps 221 and 222 may be performed simultaneously or almost simultaneously.

The compression step 224 includes compressing two or more different metal powder materials into a compression mold to obtain a preform. Prior to compression, the first part of the compression mold is filled with the first metal powder material,
Thereafter, the second part of the compression mold is filled with the second metal powder material (using separator 223 if necessary). When the die cavity is filled, the composite metal powder is compressed in the mold cavity to form a preform. The preform includes one or more cross-sectional surfaces on which a variable boundary profile is formed (in the final forged part) as described herein. The process is then completed by a sintering, forging and cooling step, whereby a first part having a first metal powder material,
And the gearwheel provided with the 2nd part which has a 2nd metal powder material is obtained. The first and second parts in the filling step to form the preform are not necessarily the first and second parts of the final product.
It is not necessary to have the same boundary as this part.

The sintering step 226 can be performed by methods known to those skilled in the art. Since some of the composite material contributes to carburizing or “sinter-carbprocessing”, the material can be subjected to a carburizing step to provide further advantageous results prior to the forging process.

The variable forging or forging step 232 includes forging the preform at a forging temperature and forging pressure to obtain a substantially dense net shape part.
The variable boundary profile of the gear produces a substantially symmetrical profile for each tooth. It is due to the symmetrical nature of the forging process and the symmetrical nature of the preform. However, any carburization step or further forging step may be used to obtain multiple variable boundary profiles. A variable boundary profile can be obtained by variably improving the critical flow of different metal parts using a set of forging dies during forging. At this time, the defined boundary of the composite metal powder needs to be strategically compressed into the mold part. Here, a part of the preform is stretched and thinned during forging, and the other part of the preform is thickened and deepened. As a result, different metal powder regions are obtained from the composite preform.

In one example, the forging step used to obtain the composite variable boundary profile is by strategically forming a material boundary layer in the preform to improve the critical flow of the composite metal powder preform during forging, Further improvements are possible.

Cooling step 234 can provide the forging with specific metallurgy that produces a gear having the desired variable boundary profile. This forging part cooling step can be performed by quenching in oil, water, air, or other methods suitable for metal powder forging.

It may be possible to stabilize the material temperature of the forged part by dwelling the forged part for a predetermined time (dwell) before the cooling step, thereby improving the characteristics.

It is also conceivable to improve the desired metal flow during forging by preheating the preform to a pre-forge temperature before forging.

The post-forging operation (optional process) consists of product turning, facing and surface polishing based on final detailed requirements.
Rinding, splining, and broaching may be included. This makes it suitable for cleaning, packing, or shipping. Based on the multi-material workpiece, the finish class of these steps can be improved. For example, based on the non-hardened second material 57, the spline 62 of FIG. 4 can provide a higher spline rating. This is due to tool wear
to improve the overall machining system by improving the spline grade while reducing ar).

Metal powder, compaction form (compactionform), processing time, processing temperature, processing pressure, forging die,
And with the proper selection and combination of cooling methods, it is possible to obtain a near-net-shaped sufficiently dense (sufficiently dense) product with a variable boundary profile, whereby
Even if a machining process is required, the degree thereof is kept to a minimum, and cost reduction and performance improvement (performance improvement) can be promoted.

While the specification describes various process steps, they do not limit the scope of the invention as defined by the claims. Although the present invention has been described based on some specific examples, it should be understood that the present invention is not limited to these specific examples. Accordingly, the present invention includes modifications, variations, and equivalents included in the technical idea described in the following claims.

Claims (18)

Filling the first part of the compression mold corresponding to the shape of the preform with the first metal powder material;
Filling the second part of the compression mold with a second metal powder material;
Compressing the powder into the compression mold to form the preform, and a preforming step to preform two or more different metal powder materials into the preform,
Sintering the preform;
Forging the preform at a forging temperature and a forging pressure, a first portion having the first metal powder material, a second portion having the second metal powder material, and the first portion; Obtaining a substantially dense net-shaped forged part having a variable boundary profile formed between said second part;
Cooling the forged part;
In order, and
The initial boundary profile as a line separated between the first metal powder material and the second metal powder material in the sintered preform is altered or reformed by forging in the step of obtaining the forged part. A method of manufacturing a gear from two or more different metal powder materials, wherein the variable boundary profile is formed within a plurality of teeth of the gear.   The pre-forming step includes a separation step during filling by inserting the separator into the compression mold to fill any of the metal powder materials, and removing the separator from the compression mold before compression. The method of claim 1, comprising a removing step. A bevel gear manufactured by the method of claim 1, comprising a gear core, a rotating shaft, a plurality of radial tooth cores, and a plurality of radial teeth,
The radial teeth extend generally in the same direction as the rotational axis of the bevel gear and are inclined with respect to the rotational axis;
The first portion forms an outer surface of the plurality of radial teeth; and
A bevel gear having a core portion of the gear and the core portions of the plurality of radial teeth formed by the second portion. The plurality of teeth each have a first surface including a tip surface, a pitch line surface, a root fillet surface, and a root land surface; and
Of the boundary ratio of the root land surface to the root fillet surface of 2: 1, the boundary ratio of the tip surface to the root fillet surface of 6: 1, or the boundary ratio of the pitch line surface to the root fillet surface of 19: 4 The bevel gear according to claim 3 satisfying any one or more boundary ratios. The method of claim 1, wherein the first and second metal powder materials are different low carbon alloy iron materials. A gear core that forms a rotation axis; and
A plurality of radial teeth extending generally in the same direction as the rotational axis from the core of the gear and inclined with respect to the rotational axis;
A first metal powder material that at least partially forms the plurality of radial teeth;
A second metal powder material that forms a core of the gear and partially forms the core of the plurality of radial teeth;
A bevel gear manufactured by the method of claim 1, comprising:
A variable boundary profile is formed between the first metal powder material and the second metal powder material by sintering and forging the first and second metal powder materials having different hardness characteristics. A bevel gear characterized by that. The bevel gear according to claim 6 , wherein the bevel gear is a pinion gear having an axial inner region at a core portion of the gear. The bevel gear according to claim 6 , wherein the first metal powder material has a surface hardness of 58 HRC or more. The bevel gear according to claim 6 , wherein the second metal powder material has a hardness of less than 43 HRC. The bevel gear according to claim 6 , wherein the second metal powder material has a lower carbon content than the first metal powder material. A core containing a first metal powder material;
A plurality of teeth extending from the core and at least partially including a second metal powder material;
A variable boundary profile formed between the first metal powder material and the second metal powder material;
A forged compound gear manufactured by the method of claim 1, comprising:
The forged composite gear, wherein the first metal powder material and the second metal powder material have different hardness characteristics. The second metal powder material has a surface hardness of more than 58 HRC, forged composite gear of claim 1 1. The first metal powder material has a hardness of less than 43HRC, forged composite gear of claim 1 1. The variable boundary profile is one that is forged by the plurality of teeth, forged composite gear of claim 1 1. The first metal powder material has a carbon content lower than said second metal powder material, forged composite gear of claim 1 1. The gear is a bevel gear having a rotation axis; and
Wherein the plurality of teeth, said radially extending generally in the same direction as the rotation shaft of the bevel gear, and is inclined relative to the axis of rotation of the bevel gear, forged composite gear of claim 1 1. The forged composite gear according to claim 16 , wherein the bevel gear is a differential side gear having an axial spline inner region in the core portion. The plurality of teeth each have a first surface including a tip surface, a pitch line surface, a root fillet surface, and a root land surface, and the variable boundary profile is 2: 1 the root land surface The boundary ratio of the root fillet surface, the boundary ratio of the tip surface to the root fillet surface of 6: 1, or the boundary ratio of the pitch line surface to the root fillet surface of 19: 4 is selected. satisfied, forged composite gear of claim 1 1.

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