JP2006022894A - Highly strong gear and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly strong gear having a highly tenacious diamond-like carbon film not peeled off even on the tooth faces of a gear used at a high speed reduction ratio and capable of realizing a reduction in friction on the tooth faces. <P>SOLUTION: In the tooth faces of a metal gear base material 1, an infinite number of recessed parts 2 with an averaged diameter of 0.1 to 10 μm and an averaged depth of 0.1 to 10 μm are formed in the area A of at least 0.3 to 0.7L from the addendum thereof where an entire engagement length is L. The diamond-like carbon film 3 with a thickness of 1 to 5 μm is formed on the surfaces of the recessed parts, and a carbon layer 4 with a thickness of 10 to 500 nm and containing hydrogen by an amount of 4×10<SP>22</SP>atms/cm<SP>3</SP>or more in density of atom number is formed on the diamond-like carbon film 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a high-strength gear having a hard coating formed on a tooth surface and a manufacturing method thereof, and more particularly to a high-strength gear suitable for use in a reduction gear having a high reduction ratio and a manufacturing method thereof.

  In recent years, it is expected that the number of automobiles driven by motors will increase in order to deal with environmental problems and the like. In such motor-driven automobiles, motors of several tens of thousands of rpm are used in reduction gears. It is necessary to decelerate the rotation with a compact size. There is a compound planetary gear mechanism that can obtain a high reduction ratio in a compact size. Among these mechanisms, there is a so-called 3K type (K is an element having the same rotation axis as the center line of the device). is there. This 3K type planetary gear mechanism has an advantage that the diameter of the reduction gear system hardly changes with respect to an input of several tens of thousands of revolutions, but has a disadvantage that the efficiency decreases as the reduction ratio becomes higher.

  In addition, as a measure for eliminating the above-mentioned drawbacks, it is conceivable to form a hard coating that is hard and provides low friction properties on the tooth surface, and the hard coating is particularly excellent in sliding with steel. In addition, there is a diamond-like carbon film (hereinafter abbreviated as “DLC film”) that exhibits low friction performance. The DLC film has already been applied to sliding parts of automobile engines, but when applied to gears for reduction gears, the DLC film is caused by sliding heat generated by high surface pressure and high rotation that are dynamically applied. Since the film may be lost, it is important to ensure the toughness of the DLC film.

Therefore, conventionally, as a method for improving the peel resistance of the DLC film to the base material, mechanical roughness is formed by forming irregularities of 10 to 100 nm on the surface of the base material by ion bombardment and then forming the DLC film. After forming a DLC film on the surface of the base material by the anchor effect and performing a microblast treatment on the surface using particles having a particle diameter of 1 to 50 μm and sharp edges, A method of smoothing the surface has been proposed. It was also considered effective in terms of peel resistance to ensure the toughness of the DLC film by projecting microblasts onto the surface of the substrate and making the surface rough.
JP-A-10-130817 JP 2001-304275 A Special table 2003-500231 gazette

  However, although the method of forming a DLC film after forming irregularities by ion bombardment is effective in improving the adhesion at the interface between the substrate and the DLC film, it cannot improve the toughness of the DLC film itself. There was a problem.

  In addition, the method of performing microblasting after film formation has difficulty in maintaining and managing the size and shape of the blast particles. Above all, at the tooth tip or tooth base where the oil film is thin, the level is several μm by microblasting. The reduction in surface roughness causes a metal contact due to local oil film breakage, which significantly degrades friction and, in turn, reduces the reduction gear efficiency, and further exceeds the above values. There is a problem that it is difficult to obtain a dense surface using small blast particles.

  The present invention has been made in view of the above-described conventional situation, and can be provided with a diamond-like carbon film that does not peel even on the surface of a gear used at a high reduction ratio, and has a low tooth surface. An object of the present invention is to provide a high-strength gear capable of realizing friction and a manufacturing method thereof.

The high-strength gear of the present invention has an average diameter of 0.1 to 10 μm in the tooth surface of the metal gear base material in the range of at least 0.3 L to 0.7 L from the tooth tip with respect to the total meshing length L. And many recessed parts with an average depth of 0.1-10 micrometers are formed. Then, a diamond-like carbon film having a thickness of 1 to 5 μm is formed on the tooth surface on which the concave portion is formed. Further, on the diamond-like carbon film, the thickness is 10 to 500 nm and hydrogen has an atomic density of 4 The carbon layer containing × 10 ²² atms / cm ³ or more is provided. Further, as a more preferred embodiment, the concave portion of the tooth surface is formed by irradiation with a laser pulse.

  In the method for producing a high-strength gear according to the present invention, a laser pulse is applied to a tooth surface of a metal gear base material in a range of at least 0.3 L to 0.7 L from the tooth tip with respect to the total meshing length L. Thus, a large number of recesses having an average diameter of 0.1 to 10 μm and an average depth of 0.1 to 10 μm are formed. Thereafter, a diamond-like carbon film is formed on the tooth surface by the PVD method in the PVD processing chamber, and subsequently, a hydrocarbon gas is introduced into the PVD processing chamber to form a carbon layer containing hydrogen on the diamond-like carbon film. Thus, a high-strength gear having a recess, a diamond-like carbon film, and a carbon layer on the tooth surface is obtained.

  According to the high-strength gear of the present invention, it is possible to provide a diamond-like carbon film that does not peel even on the surface of the gear used at a high reduction ratio, and to achieve low friction of the tooth surface. Can do.

  According to the method for producing a high-strength gear of the present invention, a diamond-like carbon film that does not peel even on the surface of a gear used at a high reduction ratio can be formed, and the friction of the tooth surface can be reduced. A strength gear can be provided.

  As shown in FIG. 1, the high-strength gear according to the present invention has a total meshing length (a length from the tooth tip to the tooth root) on the tooth surface of the metal gear material 1 made of iron, copper, aluminum, an alloy thereof, or the like. ) A large number of recesses 2 having an average diameter of 0.1 to 10 μm and an average depth of 0.1 to 10 μm are formed in a range A from 0.3 L to 0.7 L at least from the tooth tip with respect to L. .

In addition, a diamond-like carbon film 3 having a thickness of 1 to 5 μm is formed on the entire surface of the tooth surface where the concave portion 2 is formed in the above range. Further, a thickness of 10 to 10 μm is formed on the entire surface of the DLC film 3. A carbon layer 4 having 500 nm and containing hydrogen with an atomic number density of 4 × 10 ²² atms / cm ³ or more is formed.

  In order to manufacture the high-strength gear, a laser pulse is applied to the tooth surface of the gear base 1 in a range A of 0.3 L to 0.7 L at least from the tooth tip with respect to the total meshing length L. Thus, a large number of recesses 2 of the size described above are formed. Thus, by using the laser pulse for forming the concave portion 2, it is possible to easily control the formation and formation range of the fine concave portion, which has been difficult by the method of projecting particles as in the blasting process, and Stable quality can be obtained.

  Thereafter, in the PVD (physical vapor phase synthesis) processing chamber, the DLC film 3 is formed on the tooth surface by the PVD method. As this PVC treatment, an arc ion plating method, a sputtering method, or the like is preferable from the viewpoint of the adhesion strength of the film to the substrate.

  Then, following the formation of the DLC film 3, in a PVD process in which hydrogen does not naturally enter the DLC film 3, a hydrocarbon gas such as methane gas is introduced into the PVD process chamber to introduce hydrogen into the DLC film 3. The carbon layer 4 containing is formed. As a result, a high-strength gear having a predetermined range of recesses 2, DLC film 3, and carbon layer 4 on the tooth surface is obtained.

  In the high-strength gear described above, the gear material 1 is made of metal, and therefore has high heat conduction, and easily transmits and releases heat generated on the sliding surface during power transmission. In addition, in the tooth surface, a range A of at least 0.3 L to 0.7 L from the tooth tip with respect to the total meshing length L is a portion where the surface pressure is particularly high and high toughness is required. The tooth root is a part where sliding becomes particularly severe.

  Therefore, in the high-strength gear, by forming a large number of recesses 2 by laser pulses in the above-described range A where the surface pressure becomes high, the DLC film 3 is formed on the entire tooth surface, so that the above-described range A, that is, the surface pressure. In the portion around the pitch point of the tooth surface that requires high toughness, the DLC film 3 is formed after forming the concave portion 2 without deteriorating the surface roughness as in the blasting process. In the formed area A, the DLC film 3 is in a fine block shape, and becomes a high toughness film in which local defects and scratches are not propagated throughout.

  Further, since the high-strength gear does not form the concave portion 2 at the tooth tip and the tooth base where sliding becomes particularly severe, the surface of these portions is denser than the above-mentioned range A, and the metal contact is not made. This is advantageous in that it is less likely to occur, friction can be reduced, and manufacturing costs can be reduced.

  Here, the average diameter of the recesses 2 is set to 0.1 to 10 μm and the average depth is set to 0.1 to 10 μm. When the average diameter is set to less than 0.1 μm and the average depth is set to less than 0.1 μm, This is because it becomes difficult to obtain the block-shaped DLC film 3 because it is substantially equal to the state in which there is no recess 2. On the other hand, if the average diameter exceeds 10 μm and the average depth exceeds 10 μm, the DLC film 3 This is because it becomes difficult to maintain the high toughness due to the loss of the block-like fineness.

  The thickness of the DLC film 3 is set to 1 to 5 μm because if the thickness is less than 1 μm, it is difficult to obtain sufficient wear resistance because it is too thin. This is because if the thickness exceeds 5 μm, the DLC film 3 is too thick and easily peels off.

  Further, the carbon layer 4 has a property of being polished by a certain amount of sliding and becoming familiar with the counterpart material. Such a familiar layer is formed evenly from the tooth tip to the tooth base, and after the familiarity, the original DLC layer is formed. Works to expose. For this reason, the thickness of the carbon layer 4 is set to 10 to 500 nm, and if the thickness is less than 10 nm, it is difficult to obtain sufficient conformability because it is too thin. If the thickness exceeds 500 nm, it is too thick and it becomes difficult to expose the DLC layer after accustoming.

Further, the reason why the hydrogen content of the carbon layer 4 is set to an atomic number density of 4 × 10 ²² atms / cm ³ or more is that the carbon film has a high hardness when the atomic density is less than 4 × 10 ²² atms / cm ³ This is because the aggressive opponent (abrasion due to foreign matter) causes aggression against the other party and becomes inadequate as the conforming layer as described above.

  Therefore, in the high-strength gear of the present invention and the manufacturing method thereof, the laser is applied to the tooth surface of the metal gear base 1 at least in a range A of 0.3 L to 0.7 L from the tooth tip with respect to the total mesh length L. A number of recesses 2 having an average diameter of 0.1 to 10 μm and an average depth of 0.1 to 10 μm are formed with high precision by pulses, and then a DLC film 3 having a thickness of 1 to 5 μm is formed on the entire tooth surface. By forming the DLC film 3, a high-toughness DLC film 3 free from strength reduction and wear at the tooth tip due to the thickening of the DLC film 3 is obtained in the entire meshing range of the tooth surface.

Further, by providing the carbon layer 4 having a thickness of 10 to 500 nm and containing hydrogen at an atom number density of 4 × 10 ²² atms / cm ³ or more on the DLC film 3, the carbon layer 4 is formed of a carbon film. The hardness of the material is abruptly lost, which reduces the aggressiveness of the opponent against abrasive wear. It is soft and has no diamond structure characteristics, but it is excellent as a mating layer that has excellent polishing action on the mating surface and is lost immediately after sliding. As a result, a further low friction performance is obtained. As a result, the sliding heat generation is reduced and the DLC film 3 is not easily worn.

  Thus, according to the high-strength gear and the manufacturing method thereof, it is possible to provide the DLC film 3 that does not peel off even on the gear surface used at a high reduction ratio, and the tooth surface has a sufficient surface. Low friction can be realized.

In order to investigate the effect of the high-strength gear according to the present invention, a compound planetary gear having the following specifications was experimentally produced as Examples A and B and Comparative Examples A to G. The material of the pinion gear (large pinion gear, small pinion gear) and the counter gear (sun gear, internal gear), which are the gears according to the present invention, is JIS-SCM420H. After teeth are formed by hobbing, carburizing and quenching The surface hardness was set to Hv730 and the effective hardened layer depth was set to 0.6 mm. In addition, each gear was trimmed by tooth surface grinding.
<Gear shape test piece>
Sungear module: 0.87
Number of teeth of test gear: 24
Pressure angle: 17.5 °
Twist angle: 25 °
Large pinion gear Number of test gear teeth: 60
Small pinion gear module: 1.19
Number of teeth of test gear: 20
Pressure angle: 21 °
Twist angle: 11 °
Internal gear Number of test gear teeth: 87

Thereafter, a laser pulse was applied to the tooth surfaces of each test gear except Comparative Example F under the following conditions to form a large number of recesses in a predetermined range of the tooth surfaces. The principle of this recess forming method is to irradiate the tooth surface of the gear in water with a laser pulse to locally generate plasma and dissolve the pole surface. At this time, each concave portion of the tooth surface is obtained by forming a large number of extremely minute irregularities within the area irradiated with one pulse, and does not correspond to the size of one irradiated laser pulse. . In Comparative Example E, a recess was formed on the entire tooth surface.
<Laser pulse irradiation conditions>
Beam diameter: φ0.2mm
Pulse density: 80000 pulses / m ²

  In addition, when forming recesses by laser pulses, water containing a rust preventive agent was used as a medium, but this medium only needs to be able to transmit the laser. good. Furthermore, in order to confirm the effect of the size of the recesses, each comparative example except each example and comparative example F was manufactured by changing the irradiation pulse energy.

  Thereafter, a diamond-like carbon film was formed on the tooth surfaces of each test gear except Comparative Example F by non-equilibrium magnetron sputtering. This is because, after the tooth surface of the gear is sputtered with argon (Ar) ions, a Cr layer is formed as an intermediate layer so that the pitch point is 0.5 μm, and then a WC (tungsten carbide) / C layer is formed. Formed. At this time, in order to confirm the influence of the thickness of the DLC film, the film formation time was changed to change the film thickness.

At the end of film formation, 30% methane gas (CH ₄ ) was introduced as a hydrocarbon gas with respect to the total flow rate of Ar gas to form a carbon layer. The hydrogen content of this carbon layer was measured with a secondary ion mass spectrometer, and the atomic number density of the carbon layer was determined as 1 × 10 ²³ atms / cm ³ . In Comparative Example B, no carbon layer was formed.
<DLC deposition conditions>
Degree of vacuum before introducing Ar gas: 1 × 10 ⁻⁴ Torr
Sputtering pressure: Ar 0.3 Pa
Pressure after introducing nitrogen gas: 30 mTorr
Pre-filming temperature: 130 ° C

Then, for each of Examples and Comparative Examples, performs gear unit test under the following conditions, was examined for change and peeling of the surface roughness of the mating gear after ¹⁰⁷ rotation. Also, the efficiency was calculated from the torque and compared. After the test, the film thickness and the surface shape were observed with an SEM (scanning electron microscope), and the roughness of the mating surface was measured.
<Gear test conditions>
Lubricating oil: Nissan genuine ATF Matic D
Test oil temperature: 90 ° C
Input rotation speed: 15000rpm
Torque: 15Nm
Table 1 summarizes the results.

  In Examples A and B of the present invention, the mating surface roughness was clearly improved with respect to Comparative Examples A to F, and the high peeling limit and high efficiency of the DLC film were confirmed.

  On the other hand, in Comparative Example A, the recess was deep and too large, and the DLC film was peeled off. Further, in Comparative Example B in which the carbon layer was not formed, and in Comparative Examples D and E in which the thickness of the carbon layer was reduced, the contact surface roughness and the contact state between the gear surfaces were not improved. The concave portion was too deep and too large to lose the DLC film. In Comparative Example D, the DLC film was too thin and the tooth base film was lost due to wear. On the contrary, in Comparative Example C, the DLC film was too thick and peeling occurred from the tooth tip side.

Furthermore, in Comparative Example E, the DLC film was not peeled because the concave portions were formed on the entire surface. However, the efficiency was low, and Comparative Examples A to D in which peeling occurred similarly did not improve the efficiency. Further, in Comparative Example G, the hydrogen content of the outermost carbon layer was less than 4 × 10 ²² atms / cm ³ , so the hardness was high and it did not function as a conforming layer.

It is sectional drawing explaining the tooth surface in the high strength gear of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gear base material 2 Concave part 3 Diamond-like carbon film 4 Carbon layer A Concave formation range (the range of 0.3L-0.7L with respect to L)

Claims (3)

In the tooth surface of the metal gear base, the average diameter is 0.1 to 10 μm and the average depth is 0.1 to at least 0.3 L to 0.7 L from the tooth tip with respect to the total mesh length L. A large number of recesses of 10 to 10 μm are formed, a diamond-like carbon film having a thickness of 1 to 5 μm is formed on the surface thereof, and the thickness of the diamond-like carbon film is 10 to 500 nm and hydrogen has an atomic number density. A high-strength gear comprising a carbon layer containing 4 × 10 ²² atms / cm ³ or more.   2. The high-strength gear according to claim 1, wherein the concave portion of the tooth surface is formed by laser pulse irradiation.   With respect to the tooth surface of the metal gear base material, a laser pulse is irradiated in a range of at least 0.3 L to 0.7 L from the tooth tip with respect to the total meshing length L, and the average diameter is 0.1 to 10 μm. After forming a large number of recesses with an average depth of 0.1 to 10 μm, a diamond-like carbon film is formed on the tooth surface by the PVD method in the PVD processing chamber, and then hydrocarbon gas is introduced into the PVD processing chamber. And forming a carbon layer containing hydrogen on the diamond-like carbon film.

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