JP2007127259A - Gear and gear drive unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gear and gear drive unit which sufficiently prepares a oil film between teeth surfaces of the gears rotating at high speed, prevents generation of pitching, abrasion, scoring, and improves its durability by preventing a temperature rise and wear. <P>SOLUTION: A large number of fine concave dents are arranged on the tooth surface at random, an average area of the dents on the tooth surface having the dents is set up to be within a range of 30 to 100 μm<SP>2</SP>, and a Rymax is set to be within a range of 0.4 to 1.0. Accordingly, highly effective oil film forming capability is prepared on the tooth surface, and the tapered roller bearing acquires a longer life under conditions that an extremely thin oil film is prepared under a low-viscosity, thin lubricating condition. Further, a nitrogen-enriched layer is prepared on the tooth surface, and a grain number of austenite crystal grains on the nitrogen enriched layer is in a range exceeding No.10. thus, a fatigue life of the gear is considerably improved. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a gear and a gear driving device, and can be applied to, for example, a gear and a gear driving device used in a power transmission unit of a transmission of an automobile or a gear pump.

For example, Patent Document 1 discloses a gear in which countless dents are randomly provided on a tooth surface. The average area of the micro-indentation is 35 to 150 μm ² , the ratio of the micro-indentation to the surface is 10 to 40%, the surface roughness provided with the micro-indentation is Rmax 0.6 to 2.5 μm on average, and the micro-indentation The parameter Sk value of the surface roughness of the tooth surface provided with is set so that Sk ≦ −1.6. As a result, the oil film forming ability on the surface is improved and the oil film between the gear tooth surfaces is sufficiently formed to prevent damage caused by poor lubrication such as peeling from the surface of the gear and improve durability. Yes.
Japanese Utility Model Publication No. 4-56254

  In recent years, gear transmissions and other parts where gears are used are becoming smaller and more powerful, and there is a tendency for the usage environment, such as lower viscosity of the lubricating oil, to increase in load and temperature. For this reason, gears are changing to a more severe lubrication environment than ever, and wear due to poor lubrication, surface-origin separation, reduced fatigue life due to high surface pressure, and delamination in a foreign environment are increasingly occurring. It's getting easier. That is, with the multi-stage transmission, the torque and load acting on the gears used therein and the rotation speed tend to increase, and the gears are required to have functions such as downsizing and high-speed response. As a result, the lubrication conditions of gears become increasingly severe, and wear and damage due to poor lubrication are likely to occur. For this reason, even if the conditions of the tooth surface of the gear are set as described in Patent Document 1, the effect may not be sufficiently exhibited.

  An object of the present invention is to provide a gear that can sufficiently form an oil film between tooth surfaces of a gear that rotates at high speed, prevents occurrence of pitching, abrasion, and scoring, prevents temperature rise and wear, and improves durability. Another object of the present invention is to provide a gear driving device using such a gear.

In order to solve the above-mentioned problems, the gear of the present invention is a gear in which a number of minute concave recesses are randomly provided on the tooth surface, and the average area of the recesses on the surface provided with the recesses is 30 to 100 μm ² . Within the range, the surface roughness parameter Rymax of the surface provided with the recess is in the range of 0.4 to 1.0 μm, the gear has a nitrogen-enriched layer on the surface layer, and the nitrogen The grain size number of the austenite crystal grains in the enriched layer is in the range exceeding 10th. The parameter Rymax is the maximum value of the maximum height for each reference length (ISO 4287: 1997).

The gear driving device of the present invention is a gear driving device having a driving gear driven by a driving force and a driven gear driven by meshing with the driving gear, wherein the driving gear and the driven An infinite number of minute concave recesses are provided on both tooth surfaces of the gear, and the average surface area of the recesses in the range where the recesses are provided is in the range of 30 to 100 μm ² , and the surface of the surface provided with the recesses The roughness parameter Rymax is in the range of 0.4 to 1.0 μm, the gear has a nitrogen-enriched layer on the surface layer, and the austenite grain size number in the nitrogen-enriched layer is No. 10. It is characterized by being in the range exceeding.

As described above, in the gear and the gear driving device of the present invention, the average area of the recesses in the surface provided with the tooth surface recesses is defined within a range of 30 to 100 μm ² , and the surface roughness of the surface provided with the recesses is set. By setting the thickness parameter Rymax within the range of 0.4 to 1.0 μm, the oil film forming ability can be improved, so a long life is obtained even under extremely thin oil film conditions under dilute lubrication. Can do.

  The nitrogen-enriched layer is a layer having an increased nitrogen content formed on the tooth surface, and can be formed by a process such as carbonitriding, nitriding, or nitriding. After the formation of the nitrogen-enriched layer, the fatigue life can be greatly improved because the austenite grain size is finer as the grain size number of the austenite crystal grains in the nitrogen-enriched layer exceeds 10. When the austenite grain size number is 10 or less, the fatigue life is not greatly improved, so the range exceeds 10 and is usually 11 or more. Although it is desirable that the austenite particle size is finer, it is usually difficult to obtain a particle size number exceeding # 13. In addition, austenite crystal grains appear when heated to a temperature above the transformation point in the heat treatment, and when cooled, the austenite crystal grains transform to another structure, but after the transformation, traces of austenite grain boundaries remain, and crystals based on the traces It shall refer to a grain.

  In this gear and the gear driving device, when the surface roughness of the surface provided with the recess is represented by the parameter Rqni, the ratio of the axial surface roughness Rqni (L) to the circumferential surface roughness Rqni (C) When the value Rqni (L) / Rqni (C) is set to 1.5 or less, the oil film forming ability of the tooth surface can be further improved. The parameter Rqni is the square root of the value obtained by integrating the square of the height deviation from the roughness center line to the roughness curve in the section of the measurement length and averaging it, and is also called the root mean square roughness. . Rqni is obtained by numerical calculation from the cross-sectional curve and roughness curve recorded in an enlarged manner, and is measured by moving the stylus of the roughness meter in the width direction and the circumferential direction.

The nitrogen content in the nitrogen-enriched layer is preferably in the range of 0.1% to 0.7%. On the other hand, if the nitrogen content is less than 0.1%, the effect cannot be obtained, and the fatigue life particularly under the foreign matter mixing condition is reduced. When the nitrogen content is more than 0.7%, voids called voids are formed, or the retained austenite increases so much that the hardness does not come out, resulting in a short life. For the nitrogen-enriched layer formed on the tooth surface, the nitrogen content is a value at a surface layer of 50 μm on the tooth surface, and can be measured by, for example, EPMA (wavelength dispersive X-ray microanalyzer).

  As described above, according to the present invention, by providing an infinite number of minute concave concaves, the tooth surface becomes a minute rough surface and an oil film is easily formed. In addition, since this dent becomes an oil reservoir, an oil film can be reliably formed on the sliding surface. As a result, the temperature rise can be reduced, and the metal contact between the tooth surfaces of the meshing gears can be alleviated. Pitting, abrasion, and scoring occur even in the high-speed rotation region. Can be prevented. Therefore, even if the oil film thickness is extremely thin under low viscosity and dilute lubrication, a long life of the gear and the gear driving device can be obtained. Furthermore, by improving the fatigue life of the surface layer of the gear, it is possible to obtain excellent crack resistance and aging resistance.

  Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of a transmission used in an automobile. An input shaft 2, a drive pinion 3 and an output shaft 4 are arranged in series in a case 1, and a counter shaft 5 and a reverse shaft are parallel to the output shaft 4. 6 is arranged, and a gear 7 group is attached to the drive pinion 3 and the shafts 2, 4, 5. By changing the meshing of each gear 7 group by an operation from the outside of the case 1, The insertion is taken out of the output shaft 4 while being shifted or reversed. In this transmission, as the input shaft 2 rotates, oil accumulated in an oil pan (not shown) is splashed onto the gear 7, lubricates the gear 7 group, the bearings 8, 9 and the like, and returns to the oil pan. In other words, this transmission includes a gear drive device having a drive gear driven by a driving force and a driven gear driven by meshing with the drive gear.

FIG. 2 shows a gear 7 constituting a part of the gear driving device. The tooth surface 7a of the gear 7 is a minute rough surface in which numerous independent minute depressions are randomly formed. The minute rough surface has an indentation average area in the range of 30 to 100 μm ² and a surface roughness parameter Rymax in the range of 0.4 to 1.0 μm. Further, when the surface roughness is obtained in the axial direction and the circumferential direction of each surface and displayed by the parameter Rqni, the ratio of the axial surface roughness Rqni (L) to the circumferential surface roughness Rqni (C) The value Rqni (L) / Rqni (C) is 1.5 or less. As the surface processing for obtaining such a fine rough surface, a desired finished surface can be obtained by special barrel polishing, but not limited thereto, for example, a shot or the like may be used.

  The surface layer of the tooth surface 7a of the gear wheel 7 is formed with a nitrogen-enriched layer by a treatment such as carbonitriding, nitriding, or nitriding, and the austenite grain size number in the nitrogen-enriched layer is in a range exceeding 10 For example, No. 12 is set. Further, the nitrogen content in the surface layer 50 μm of the tooth surface 4a is set within a range of 0.1 to 0.7%.

  FIG. 3 is a view showing the microstructure of the tooth surface of the gear, particularly austenite grains. FIG. 3A shows a gear having an austenite grain size of No. 12 according to JIS standard (Example of the present invention), and FIG. 3B shows a gear having a No. 10 grain size (Comparative Example). FIGS. 4A and 4B show the austenite grain sizes illustrated in FIGS. 3A and 3B. The average particle diameter of FIG. 3 (A) was 5.6 μm as a result of measurement by the intercept method.

As described above, the gear of the gear driving device according to the present invention is provided with an infinite number of minute concave recesses, whereby the tooth surface becomes a minute rough surface and an oil film is easily formed. In addition, since this dent becomes an oil reservoir, an oil film can be reliably formed on the sliding surface. As a result, the temperature rise can be reduced and the metal contact between the tooth surfaces 7a of the meshing gear 7 can be relaxed, and the occurrence of pitching, abrasion and scoring can be prevented even in the high-speed rotation region, and the life can be extended. Can be planned. In particular, the oil film forming ability is improved by setting the average area of the recesses within the range of 30 to 100 μm ² and the surface roughness parameter Rymax of the surface provided with the recesses within the range of 0.4 to 1.0 μm. Therefore, a long life can be obtained even under conditions where the oil film thickness is extremely thin under dilute lubrication.

  Since the surface layer has a nitrogen-enriched layer and the grain size number of the austenite crystal grains in the nitrogen-enriched layer exceeds 10, the austenite grain size becomes fine, and the fatigue life can be greatly improved.

  Also, by setting the value Rqni (L) / Rqni (C) of the ratio of the axial surface roughness Rqni (L) and the circumferential surface roughness Rqni (C) to 1.5 or less, the oil film forming ability is increased. Can be improved.

  If the nitrogen content in the nitrogen-enriched layer is less than 0.1%, the fatigue life under the contamination condition decreases, and conversely, if more than 0.7%, voids called voids are formed or residual austenite is generated. Too much and harder, resulting in short life. For this reason, by setting the nitrogen content in the range of 0.1% to 0.7%, the life of the gear can be extended.

  Therefore, the gear of the present invention can obtain a long life even under conditions of low viscosity and dilute lubrication and the oil film thickness is extremely thin, and the gear driving device of the present invention using such a gear has a long life. Can be obtained. Furthermore, by improving the fatigue life of the surface layer, it is possible to obtain excellent cracking resistance and aging resistance.

  As described above, the gear of the present invention is excellent in pitching resistance, abrasion resistance, and scoring resistance, and is therefore optimal as a gear 7 for an automobile transmission as shown in FIG. In addition, an automatic transmission (AT) for automobiles normally uses two to three sets of planetary gear mechanisms, and has a structure in which the reduction ratio varies by fastening the carrier and ring gear of these planetary gear mechanisms with a clutch. . For this reason, it is preferable to apply the surface properties of the present invention to the sun gear, planetary pinion, ring gear, and the like in such a planetary gear mechanism.

  By the way, in a pair of gears engaged with each other, even if a surface treatment satisfying the surface properties according to the present invention is applied only to the tooth surface of one gear, an effect such as a long life can be sufficiently obtained. It is more effective to subject the surface to surface treatment that satisfies the surface properties according to the present invention.

  Of course, the gear of the present invention can be used in various gear drive devices other than the transmission for automobiles.

In order to show the usefulness of the present invention, the life of gears was evaluated. As will be described later, the measurement methods and conditions of the parameters Ryni, Rymax, Sk, and Rqni measured in this example are as follows. The parameter Ryni is the average value of the maximum height for each reference length, that is, the reference curve is extracted from the roughness curve in the direction of the average line, and the distance between the peak line and the valley line of this extracted part is rough. It is a value measured in the direction of the vertical magnification of the curve (ISO 4287: 1997). The parameter Sk indicates the degree of distortion (skewness) of the roughness curve (ISO 4287: 1997), and is a standard statistic for knowing the asymmetry of the uneven distribution. In a symmetric distribution such as a Gaussian distribution, the Sk value is close to 0, and takes a negative value when the concave and convex portions are deleted, and takes a positive value in the opposite case. When measuring the surface properties represented by these parameters, a single measured value can be relied on as a representative value, but it is preferable to measure, for example, two locations facing each other in the diameter direction.
Parameter calculation standard: JIS B 0601: 1994 (Surfcom JIS 1994)
Cut-off type: Gaussian Measurement length: 5λ
Cut-off wavelength: 0.25mm
Measurement magnification: × 10000
Measurement speed: 0.30 mm / s
Measurement location: Number of measurements in the center: 2
Measuring device: Surface roughness measuring device Surfcom 1400A (Tokyo Seimitsu Co., Ltd.)

Moreover, in order to carry out quantitative measurement of a hollow, it can expand and can quantify from the image by the image analysis system marketed. Furthermore, if the surface texture inspection method and the surface texture inspection apparatus disclosed in Japanese Patent Laid-Open No. 2001-183124 are used, stable and accurate measurement can be performed. This method irradiates the inspection surface having a curvature with light, images the inspection surface with a camera, measures the luminance of the image of the inspection surface imaged with the camera, and measures the bright and dark portions of the measured luminance. A surface texture inspection method for inspecting the surface texture of a surface to be inspected with a light-dark pattern formed with a contrast of light, and irradiating light with matching the optical axis direction of the camera, and the luminance distribution of the measured image has a peak value By positioning the inspection surface so that the position indicating the position coincides with the optical axis of the camera, shading (luminance distribution) due to the curvature of the inspection surface is suppressed. Also, the light is irradiated so as to coincide with the optical axis direction of the camera, and the luminance distribution of the image to be measured is based on the part of the inspection surface corresponding to the position where this luminance distribution shows the peak value, and the symmetry axis of curvature is In the orthogonal two-dimensional coordinates as one axis, approximate the one-dimensional luminance distribution along each orthogonal coordinate axis with an approximate function, and use these approximate functions to remove the luminance distribution of the image. By correcting the brightness of the measured image corresponding to each coordinate position with the peak value of the reference value as the reference value, and inspecting the surface properties of the inspection surface with the brightness pattern of the corrected brightness, it is possible to obtain a light and dark pattern without shading. Surface properties can be inspected. The measurement conditions are as follows, for example. Further, when measuring the area ratio and the average area of the indentation, like the above parameters, even one measured value can be relied on as a representative value, but for example, it is better to measure two locations facing each other in the diameter direction.
Area ratio: Percentage of pixels (black) smaller than the binarization threshold ((bright area brightness + dark area brightness) / 2) in the observation visual field range Average area: total black area / total number Observation visual field: 826 μm × 620 μm
Measurement location: Number of measurements in the center: 2

FIG. 5 shows an example of a test rolling bearing. The rolling bearing 10 is a needle roller bearing in which a needle roller 12 is incorporated in an outer ring 13 as a rolling element, and the counterpart shaft 14 is supported by the needle roller 12. It is like that. A description will be given of the results of manufacturing a plurality of types of needle roller bearings having surface treatments with different finishing surfaces on the surface of the needle rollers and performing a life test. As shown in FIG. 6, the needle roller bearing used in the life test has 15 outer diameters Dr = 33 mm, an inner diameter dr = 25 mm, a diameter D = 4 mm of the needle roller 12, and a length L = 25.8 mm. This is a bearing with a cage 15 using needle rollers. Three types of test roller bearings with different surface roughness finishes were produced. That is, bearing A (comparative example) subjected to superfinish after grinding, bearing B (comparative example), bearing C (comparative example), and bearing D (reference example) in which numerous indentations having a small concave shape are randomly formed. It is. 7 to 9 show the finished surface conditions of the needle rollers of each test bearing. Specifically, FIG. 7 shows the surface roughness of the bearing A, FIG. 8 shows the surface roughness of the bearing B, and FIG. 9 shows the surface roughness of the bearing C and the bearing D, respectively. Table 1 shows a list of characteristic value parameters of the surface finish of each test bearing. In addition, about Rqni (L / C), the bearings B, C, and D are 1.5 or less, and the bearing A is a value around 1.5. The crystal grain size was measured based on the JIS G 0551 steel austenite grain size test method.

The test apparatus used is a radial load tester 16 as schematically shown in FIG. 10, and the test bearings 10 are attached to both sides of the rotating shaft 17 and the test is performed by applying rotation and load. The finish of the inner race (mating shaft) used for the test is Ra 0.10 to 0.16 μm of the polished finish. The outer race (outer ring) is also common. The test conditions are as follows.
Bearing radial load: 2000kgf
Rotation speed: 4000rpm
Lubricant: Crisecoil H8 (2 cst under test conditions)

  FIG. 11 shows the life test results under the oil film parameter Λ = 0.13. The vertical axis of the figure represents the lifetime (h). As shown in the figure, the bearing A was 78h, the bearing B was 82h, the bearing C was 105h, and the bearing D was 121h. As is apparent from this data, the bearing D that has been surface-treated so that the surface of the needle roller satisfies the surface shape according to the present invention has a low viscosity, lean and extremely severe lubricating condition with an oil film parameter Λ = 0.13. Long life effect can be obtained even under. Therefore, the gear according to the present invention in which the tooth surface is set in the above numerical range can obtain a high long-life effect.

  Next, a gear pitching test was performed using a spur gear fatigue tester shown in FIG. 12, and the pitching strength was evaluated. In FIG. 12, a drive side gear 31 (29 teeth) and a driven side gear 32 (30 teeth) are attached to one side of each rotary shaft 33, 34, and the drive side shaft 33 is a motor (not shown). It is driven by. Further, a torque is applied by a load lever 35 and a weight 36 attached to the drive-side shaft 33. Two types of drive-side gear 31 were prepared depending on whether or not the surface treatment according to the present invention was performed. Details of test conditions and the like are as shown in Table 2.

  The data of the gear pitching test are shown in Table 3, Table 4, and Table 5. Table 3 shows the result (comparative example) in the case where neither the drive-side gear nor the driven-side gear is subjected to surface treatment, and Table 4 shows the surface properties according to the present invention on the tooth surface of the drive-side gear. Table 5 shows the results (Examples) of the case (b) in which the surface treatment was performed so as to satisfy the conditions, and Table 5 shows that the tooth surface of the drive side gear and the driven side gear satisfy the surface properties according to the present invention. (C) results (Examples) are shown in the case of using a surface-treated material. From these, it can be confirmed that the pitching life is improved by 2 times or more in the case of (b) and 3 times or more in the case of (c) compared with the case of (a).

Next, the implementation products 1 to 5 and the comparison products 1 to 3 were manufactured, and the relationship between the nitrogen content and the life of the test piece under the contamination condition was tested. The results are shown in Table 6. In this test, the needle-shaped roller bearings shown in FIGS. 5 and 6 are used as the implementation product and the comparison product, and innumerable indentations having a small concave shape as shown in Table 1 are randomly formed on the surface of the roller. . The test conditions are as follows.
Radial load: 17.64kN
Axial load: 1.47kN
Rotation speed: 2000rpm
Hard foreign matter contamination: 1g / L

  From Table 6, it can be seen that with respect to Examples 1 to 5, the nitrogen content and the foreign substance lifetime are in a substantially proportional relationship. However, the comparative product 3 having a nitrogen content of 0.72 should have an upper limit of 0.7 for the nitrogen content in light of the extremely short life of foreign matter. Further, it can be seen from the product 1 and the comparative product 1 that the lower limit of the nitrogen content should be 0.1.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

Partial sectional view of an automobile transmission The principal part expansion perspective view of the gearwheel 4 It is a figure which shows the microstructure of a gearwheel, especially an austenite grain, Comprising: (A) is a gearwheel of the example of this invention, (B) is a conventional gearwheel. (A) shows the austenite grain boundary illustrated in FIG. 3 (A), and (B) shows the austenite grain boundary illustrated in FIG. 3 (B). Cross section of needle roller bearing Cross section of needle roller bearing used for life test Roughness curve diagram showing the condition of the finished surface of test bearing A Roughness curve diagram showing the condition of the finished surface of test bearing B Roughness curve diagram showing the finished surface condition in test bearings C and D Partial sectional view of test equipment Graph showing life test results Partial perspective view of spur gear testing machine

Explanation of symbols

2 Input shaft 4 Output shaft 5 Counter shaft 7 Gear 10 Rolling bearing 12 Needle roller

Claims (8)

In a gear with a myriad of indentations of minute concave shape randomly formed on the tooth surface,
The average area of the depressions on the surface provided with the depressions is in the range of 30 to 100 μm ² , and the surface roughness parameter Rymax of the surface provided with the depressions is in the range of 0.4 to 1.0 μm,
The gear has a nitrogen-enriched layer on a surface layer, and the austenite crystal grain size number in the nitrogen-enriched layer is in a range exceeding 10th.   When the surface roughness of the surface provided with the depression is represented by the parameter Rqni, the ratio value Rqni (L) / Rqni (C) of the axial surface roughness Rqni (L) to Rqni (C) is 1.5. The gear according to claim 1, wherein:   The gear according to claim 1, wherein the nitrogen content in the nitrogen-enriched layer is in the range of 0.1% to 0.7%.   The gear according to claim 3, wherein the nitrogen content is a value at a surface layer of a tooth surface of 50 μm. In a gear driving device having a driving gear driven by a driving force and a driven gear driven by meshing with the driving gear,
An infinite number of minute concave depressions are randomly provided on the tooth surfaces of both the drive gear and the driven gear, the average area of the depressions on the surface where the depressions are provided is in the range of 30 to 100 μm ² , and The surface roughness parameter Rymax of the surface provided with the depression is in the range of 0.4 to 1.0 μm,
The gear drive device according to claim 1, wherein the gear has a nitrogen-enriched layer on a surface layer, and the austenite crystal grain size number in the nitrogen-enriched layer is in a range exceeding # 10.   When the surface roughness of the surface provided with the depression is represented by the parameter Rqni, the ratio value Rqni (L) / Rqni (C) of the axial surface roughness Rqni (L) to Rqni (C) is 1.5. The gear driving device according to claim 5, wherein:   6. The gear drive according to claim 5, wherein the nitrogen content in the nitrogen-enriched layer is in the range of 0.1% to 0.7%.   The gear driving device according to claim 7, wherein the nitrogen content is a value at a surface layer of a tooth surface of 50 μm.

Images