JPH09241736A - Method for highly strengthening gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high strength gear having sufficient compressive residual stress and smooth surface from face of tooth to root of tooth. SOLUTION: An apparatus for highly strengthening the gear is provided with a gear holding mechanism 16 for supporting the gear 12 so as to be freely rotated and advanced/retreated in a chamber 14a, an injection mechanism 24 for injecting jet flow 22 of water 18 and glass beads 20 toward the gear 12, a water supplying mechanism 26 for press-feeding the water 18 into the injection mechanism 24 and a glass bead supplying mechanism 28 for supplying the glass beads 20 into the injection mechanism 24 in each prescribed quantity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for increasing the strength of a gear for increasing the strength of the gear surface.

[0002]

2. Description of the Related Art Generally, a gear is subjected to repeated loads during use, and therefore it is necessary to increase the fatigue strength of its surface. Therefore, hitherto, shot peening has been widely performed in which a steel ball or the like is made to collide with the gear surface after heat treatment to give a compressive residual stress.

For example, in Japanese Unexamined Patent Publication No. 5-33407, the projection angle of the shot grain with respect to the tooth surface on which the shot grain is projected, the projection direction of the shot grain is orthogonal to the axis of the gear component in the gear component. There is disclosed a shot peening method in which the shot peening is made larger than that in the case of This is intended to improve the compressive residual stress and the like on the tooth surface.

[0004]

However, in the above-mentioned conventional technique, although the compression residual stress of the tooth surface is improved, the shot angle is large and therefore the shot particles cannot be sufficiently projected onto the tooth root. However, it has been pointed out that the desired compressive residual stress cannot be applied to the tooth root. Further, since the projection angle to the tooth surface is large, it is difficult to remove the oxide layer generated on the gear surface by heat treatment, and there is a problem that a step remains from the tooth surface to the tooth root. .

The present invention solves this kind of problem, and provides a method for increasing the strength of a gear capable of giving a sufficient compressive residual stress and obtaining a smooth surface from the tooth surface to the tooth root. The purpose is to provide.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is directed to jetting glass beads and a liquid jet from a nozzle toward a gear surface after heat treatment, thereby It is possible to impart a desired compressive residual stress with directivity. At that time, the glass beads are crushed on the surface of the gear, the oxide layer on the surface of the gear is removed, and a smooth surface is obtained at least from the portion corresponding to the reference pitch circle on the tooth surface to the tooth root.

Here, the jet stream is projected at an acute angle, particularly within an angle range of 10 ° to 30 °, with respect to the portion corresponding to the reference pitch circle of the tooth surface. As a result, the oxide layer can be reliably removed from the tooth surface without impairing the surface roughness, and a sufficient compressive residual stress can be applied from the tooth surface to the tooth root.

Further, the nozzle is offset from a straight line connecting the axis of the nozzle and the center of the gear, or tilted from the straight line. Therefore, it becomes possible to easily deal with various gears having different pressure angles and the like.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a partial cross-sectional front view of a strength-enhancing device 10 according to a first embodiment for carrying out a method for strengthening a gear according to the present invention, and FIG. It is a partial cross-sectional side view of the said strengthening apparatus 10.

The strengthening apparatus 10 includes a gear holding mechanism 16 for holding a gear 12 as an object to be processed and positioning and holding the gear 12 in a chamber 14a in a casing 14, a liquid such as water 18 and glass beads. 20 and a jet mechanism 24 for projecting a jet flow 22 toward the gear 12, and a water supply mechanism 26 for pumping the water 18 to the projection mechanism 24.
And a glass bead supply mechanism 28 for feeding the glass beads 20 to the projection mechanism 24 by a predetermined amount.

The gear holding mechanism 16 is, as shown in FIG.
An X-axis slide unit 30 and a spindle unit 32 mounted on the base 29 are provided. The X-axis motor 34 constituting the X-axis slide unit 30 is attached to the ball screw 36.
And the pair of guide bars 3 are connected to the ball screw 36.
8 are arranged in parallel, and a spindle motor 40 is supported by the ball screw 36 and the guide bar 38 so as to be movable back and forth in the arrow X direction.

The spindle unit 32 has a spindle 42 connected to a spindle motor 40, and the gear 12 is mounted on the tip of the spindle 42. The tip end side of the spindle unit 32 can be inserted into the casing 14 through an opening 44 formed in the side wall of the casing 14.

As shown in FIG. 2, the projection mechanism 24 comprises a Y-axis slide unit 46 and a Z-axis slide unit 48. The Y-axis slide unit 46 has a Y-axis motor 50 oriented in the horizontal direction, and via a ball screw 52 connected to the Y-axis motor 50 and a pair of guide bars 54 parallel to the ball screw 52, The Z-axis slide unit 48 can move back and forth in the arrow Y direction. The moving body 62 is moved in the arrow Z direction via a ball screw 58 extending vertically downward from the Z-axis motor 56 forming the Z-axis slide unit 48 and a pair of guide bars 60 parallel to the ball screw 58. You can move back and forth freely.

A tube body 66 is attached to the tips of a pair of support rods 64 extending from the moving body 62 in the arrow Y direction and oriented in the arrow Z direction. An opening / closing valve 68 for turning on / off the introduction of the water 18 is provided at an upper portion of the pipe body 66, and a mixing chamber for mixing the glass beads 20 with the water 18 is provided at a lower portion of the pipe body 66. 70 is connected to the bottom of the mixing chamber 70.
2 are provided.

The water supply mechanism 26 has a water pipe line 74 connected to the inlet side of the opening / closing valve 68. The water pipe line 74 is spirally wound inside the casing 14 and then is provided outside the casing 14. It is connected via a joint 76 (see FIG. 1). A high pressure pump (not shown) is connected to the joint 76, and the high pressure pump is set to project the jet flow 22 toward the gear 12 at a predetermined injection pressure.

The glass bead supply mechanism 28 includes a hopper 80 which is held on the upper surface of the casing 14 via a mounting base 78. A load cell 82 for detecting the remaining amount of the glass beads 20 in the hopper 80 is arranged below the hopper 80. As shown in FIG. 1, on the outlet side of the hopper 80, a metering valve 84, a negative pressure meter 86, and a laser flow meter 88 are connected in a vertically downward direction. One end of the conduit 90 is connected to the laser flow meter 88, and the other end is inserted into the chamber 14 a in the casing 14 and connected to the mixing chamber 70. The diameter of the glass beads 20 filled in the hopper 80 is set to 0.05 mm to 0.3 mm.

A mist collecting mechanism 92 is placed on the base 29. The tip ends of the pair of ducts 94 and 96 that form the mist collecting mechanism 92 are inserted into the chamber 14a from the side of the casing 14 and are arranged between the gear 12 and the nozzle 72 and close to the gear 12. ing.

On the lower side of the casing 14, there is integrally provided a conical portion 98 which is directed downward and has a reduced diameter. Below the lower opening of the conical portion 98, a drainage conveyor 100 is provided. It is arranged.

The operation of the strength-enhancing device 10 according to the first embodiment configured as described above will be described in relation to the strength-enhancing method of the present invention.

First, the gear 12 which has been subjected to gear cutting by cutting is carburized and quenched. And
The gear 12 after the carburizing and quenching treatment is set on the spindle 42 that constitutes the gear holding mechanism 16, while the projection mechanism 24
The nozzle 72 constituting the above is selectively position-adjusted in the arrow Y direction and the arrow Z direction via the Y-axis slide unit 46 and the Z-axis slide unit 48, and is arranged corresponding to the gear 12.

Therefore, the gear 12 rotates in a predetermined direction integrally with the spindle 42 via the spindle motor 40, and the gear 12 is rotated by the spindle unit 32 via the X-axis motor 34 constituting the X-axis slide unit 30. And moves in the direction of arrow X1 integrally with (see FIG. 1).

At this time, the projection mechanism 24 is driven, and the water 18 is pressure-fed from the pipe 66 to the mixing chamber 70 via the water pipe 74 under the action of a high-pressure pump (not shown). On the other hand, the metering valve 84 which constitutes the glass supply mechanism 28 is driven, and a predetermined amount of glass beads 20 are fed to the mixing chamber 70 from the conduit 90. Therefore, when the water 18 is jetted from the nozzle 72, a negative pressure is generated in the mixing chamber 70, and the glass beads 20 in the conduit 90 are generated.
Is mixed with this water 18 to form a jet 22 and the nozzle 7
2 is projected onto the gear 12.

Therefore, the jet flow 22 of the water 18 and the glass beads 20 has directivity, and the tooth tip 102 of the gear 12 and the tooth surface 1 are directed.
04 and the desired position of the root 106 are accurately collided (see FIGS. 3A to 3C).

Here, the module is 1.5 and the twist angle is 3
The jet 12 is projected at 18 ° to the portion corresponding to the reference pitch circle (PCD) of the tooth surface 104 by using the gear 12 set at 6 °, the pressure angle of 17.5 °, and the number of teeth of 52. As a result, the jet flow 22 can be reliably projected onto the tooth flank 104 and the tooth root 106 of the gear 12, and the tooth flank 10
4 and the tooth base 106 can be given a sufficient compressive residual stress.

Further, as shown in FIG. 4, when the glass beads 20 collide with the tooth surface 104 of the gear 12, the tooth surface 1
The surface of No. 04 is given a compressive residual stress via the glass beads 20 and is polished, and the glass beads 20 are crushed. At that time, the crushed pieces 20a are
The water 18 jetted toward the tooth surface 104 presses the surface of the tooth surface 104 at an acute angle. Therefore, the gear 12 has an effect that at least the portion corresponding to the reference pitch circle of the tooth surface 104 is subjected to the polishing process from the tooth root 106 to be surely processed into a smooth surface.

FIG. 5A shows an enlarged view of the tooth flank 104 after carburizing and quenching the gear 12, and FIG. 5B shows
An enlarged view of the tooth flank 104 after the gear 12 has been strengthened by the strengthening device 10 is shown. FIG. 6A is an enlarged view of the tooth root after the carburizing and quenching treatment.
B shows an enlarged view of the tooth bottom subjected to the strengthening treatment by the strengthening device 10. As a result, it was found that the surface of the tooth surface 104 and the tooth bottom were smoothed while the oxide layer was effectively removed by the strengthening treatment.

By the way, when the jet flow 22 is projected from the nozzle 72 to strengthen the gear 12, the chamber 14a
The crushed fine glass bead dust floats on the surface. Therefore, by driving the mist collecting mechanism 92, the fine glass bead waste floating in the chamber 14a can be sucked from the pair of ducts 94 and 96 and reliably collected. Further, the fragments of the water 18 and the glass beads 20 jetted into the chamber 14 a are discharged from the conical portion 98 provided in the lower portion of the casing 14 to the drainage conveyor 100.
It is discharged inside and collected outside via the drainage conveyor 100.

Next, after variously changing the angle (projection angle) projected on the portion corresponding to the reference pitch circle of the tooth surface 104 of the jet flow 22 to strengthen each gear 12, the respective gears 12 are treated. An experiment was conducted to measure the compressive residual stress and surface roughness of the. The result is shown in FIG.

As a result, the projection angle on the tooth surface 104 is 30.
If the angle is more than 0 °, the surface of the tooth surface 104 becomes rough, while if the projection angle is less than 10 °, sufficient compressive residual stress cannot be applied. Therefore, it was found that it is desirable to set the projection angle of the jet flow 22 in the angle range of 10 ° to 30 °.

By the way, as shown in FIG.
When the strength-enhancing process is performed on the gear 12a having a small pressure angle of a, it is possible to easily cope with it by moving the nozzle 72 in parallel (offset). That is,
A straight line L connecting the axis of the nozzle 72 and the center O of the gear 12a
When the projection angle of the jet flow 22 is 10 ° or less in the portion corresponding to the reference pitch circle with the nozzle 72 arranged above,
If it is used as it is, there occurs a problem that sufficient compressive residual stress cannot be applied as described above.

Therefore, as shown in FIG. 2, under the driving action of the Y-axis motor 50 constituting the Y-axis slide unit 46, the movable table 62 is moved in the direction of the arrow Y1 by a predetermined amount (corresponding to the pressure angle of the gear 12a). Translated distance). Then, the jet 2 to the tooth surface 104a of the gear 12a
The nozzle 72 may be positioned at a position where the projection angle of 2 is within the range of 10 ° to 30 °, and in this state, the strengthening process may be performed on the gear 12a. As a result, it is possible to easily deal with various different gears 12, 12a, etc., and it is possible to obtain the advantage of being extremely versatile.

Further, the nozzle 72 has a gear 12a (12).
It can be offset symmetrically with respect to a straight line L connecting the center of the nozzle and the center of the nozzle. Therefore, the gear 12a (12)
By rotating the gear 12a (12) in the reverse direction, both tooth flanks 10 of the gear 12a (12) are not replaced.
The jet 22 is projected onto the 4a (104) to efficiently perform the strengthening process.

Next, the gear 12 having the specifications shown in Table 1 and made of a material of JIS standard SCM420.
b and 12c were prepared, and the gears 12b and 12c were carburized and quenched. Furthermore, the rotation speed of the gear 12b is set to 28
Rotation, the number of rotations of the gear 12c was set to 23 rotations, and under the conditions shown in Table 2, the strengthening treatment was performed by the strengthening device 10. In this case, the projection angle with respect to the tooth surface of the gear 12b is 18 °, the projection angle with respect to the tooth surface of the gear 12c is 19 °,
The projection angles of the gears 12b and 12c with respect to the tooth bottoms were set to 45 ° and 40 °, respectively.

The composition of the glass beads 20 is SiO.
₂ is 72 wt%, AlO ₃ is 2 wt%, Na ₂ O and K ₂
The sum of O was 13.5 wt%, MgO was 3.5 wt%, and CaO was 9 wt%.

[0035]

[Table 1]

[0036]

[Table 2]

Therefore, the gears 12b and 12c that have been subjected to the above-mentioned strengthening treatment and the gears 12b 'and 12c' that have been subjected to only the carburizing and quenching treatment are respectively combined and rotated so that a predetermined torque is applied, An experiment was conducted to confirm the root strength and the tooth surface strength. The results are shown in Table 3 and FIG.

[0038]

[Table 3]

As a result, the gears 12b, 1 which have been strengthened by the glass beads 20 and the jet 22 of the water 18 are provided.
Reference numeral 2c designates gears 12b 'and 12c' which are only carburized and quenched.
The tooth root strength was improved by about 28%, and the tooth surface strength was also improved by about 31%.

Further, in FIG. 10, a gear 12d made of chrome steel (JIS standard SCr) is subjected to a strengthening treatment by a jet flow 22, and a gear made of the same material as the gear 12d and not subjected to the strengthening treatment. 12d 'and the results of measuring the root stress of each tooth are shown. This allows
By performing the strengthening process by the jet flow 22, the gear 12d has a tooth root stress of 5% as compared with the untreated gear 12d '.
It improved by 0%.

Next, FIGS. 11 and 12 show a projection mechanism 120 constituting a high strength device according to a second embodiment of the present invention. The same components as those of the projection mechanism 24 according to the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

The projection mechanism 120 is provided with a support plate 122 fixed to the tips of the pair of support rods 64, and a turning motor 124 is fixed to the support plate 122. The tubular body 66 is attached to the rotary drive shaft 126 of the turning motor 124 via a rotary member 128.

In the projection mechanism 120 thus constructed, as shown in FIG. 13, the tooth surface 104a having a small pressure angle is formed.
When the gear 12a having the
Under the driving action of the rotary member 12 through the rotary drive shaft 126.
The tube body 66 is tilted integrally with 8 by a predetermined angle. Therefore, the nozzle 72 is directed to the tooth surface 104a of the gear 12a in a posture tilted by a predetermined angle α ° from the posture toward the center O of the gear 12a (see the chain double-dashed line in FIG. 13). Therefore, the projection angle of the jet flow 22 projected from the nozzle 72 is set and changed within the angle range of 10 ° to 30 °.

As described above, by simply tilting the nozzle 72, various gears 12 and 12a having different pressure angles can be easily dealt with, and by changing the angle of the nozzle 72, the gears 12 and 12a can be easily changed. 12a tooth surface 104, 104
It is possible to project the jet flow 22 within an angle range of 10 ° to 30 ° on both sides of a.

That is, conventionally, after strengthening treatment on one side of the tooth flanks 104, 104a, the gears 12, 12a are detached from the spindle 42 and attached to the spindle 42 in the inverted state. Strengthening treatment was performed on the opposite side of 104 and 104a. On the other hand, in the second embodiment, the work of replacing the gears 12 and 12a is unnecessary, and the strength is increased on both sides of the tooth surfaces 104 and 104a with the gears 12 and 12a once attached to the spindle 42. The effect that the processing is performed and the efficiency of the strengthening processing is easily achieved is obtained.

[0046]

As described above, in the method for strengthening the strength of the gear according to the present invention, the jetting of the glass beads and the liquid is projected on the surface of the gear after the heat treatment to impart the compressive residual stress and the glass beads. The oxide layer is removed and the surface of the gear is smoothed by pulverizing.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional front view of a strengthening device according to a first embodiment.

FIG. 2 is a partial cross-sectional side view diagram of the strengthening device.

FIG. 3 is a diagram illustrating a method for strengthening strength according to the present invention, FIG. 3A is an explanatory diagram of a tooth tip processing state, and FIG.
FIG. 3A is an explanatory diagram of a tooth surface processing state, and FIG. 3C is an explanatory diagram of a tooth root processing state.

FIG. 4 is an explanatory view of a state where glass beads collide with a tooth surface.

FIG. 5 is an explanatory view of the method for strengthening, and FIG.
FIG. 5B is an enlarged view of a portion corresponding to the reference pitch circle after the carburizing and quenching treatment, and FIG. 5B is an enlarged view of the portion corresponding to the reference pitch circle subjected to the strengthening treatment.

FIG. 6 is an explanatory diagram of the strengthening processing, and FIG.
FIG. 6B is an enlarged view of the tooth root after the carburizing and quenching treatment, and FIG. 6B is an enlarged view of the tooth root after the strengthening treatment.

FIG. 7 is a relationship diagram of a projection angle, residual stress, and surface roughness.

FIG. 8 is an explanatory diagram showing a state in which nozzles are offset.

FIG. 9 is an explanatory diagram of respective load torques of a gear subjected to a strengthening treatment and a gear not subjected to the treatment.

FIG. 10 is an explanatory diagram of respective tooth root stresses of the gear subjected to the strength-enhancing treatment and the gear not subjected to the treatment.

FIG. 11 is a perspective explanatory view of a projection mechanism that constitutes the high strength device according to the second embodiment.

12 is a front explanatory view of the projection mechanism of FIG.

FIG. 13 is an explanatory diagram of an angle adjustment work by the projection mechanism of FIG.

[Explanation of symbols]

10 ... Strengthening device 12, 12a ... Gear 14 ... Casing 16 ... Gear holding mechanism 18 ... Water 20 ... Glass beads 22 ... Jet 24, 120 ... Projection mechanism 26 ... Water supply mechanism 28 ... Glass bead supply mechanism 30 ... X-axis Slide unit 32 ... Spindle unit 42 ... Spindle 46 ... Y-axis slide unit 48 ... Z-axis slide unit 66 ... Pipe 70 ... Mixing chamber 72 ... Nozzle 74 ... Water pipe 80 ... Hopper 90 ... Pipe 92 ... Mist collecting mechanism 102 ... Tooth tip 104, 104a
... Tooth surface 106 ... Root 124 ... Swing motor 128 ... Rotating member

Claims (5)

[Claims] 1. A method for increasing the strength of a gear for increasing the strength of the gear surface, which comprises jetting a jet of glass beads and a liquid from a nozzle toward a surface of the gear after heat treatment to reduce a compressive residual stress. By imparting, by crushing the glass beads on the gear surface,
A method for increasing the strength of a gear, characterized in that the oxide layer on the surface of the gear is removed and a smooth surface is formed at least from a portion corresponding to a reference pitch circle on the tooth surface to a root. 2. The method for strengthening a gear according to claim 1, wherein the jet flow is projected at an acute angle with respect to a portion of the tooth surface corresponding to a reference pitch circle. 3. The method for strengthening a gear according to claim 2, wherein the acute angle is within an angle range of 10 ° to 30 °. 4. The method according to claim 1, wherein the nozzle is provided with the gear from a position parallel to a straight line connecting an axis of the nozzle and a center of the gear and separated from the straight line by a predetermined distance. A method for strengthening a gear, comprising projecting the jet flow toward a surface. 5. The method according to claim 1, wherein the nozzle projects the jet flow toward the gear surface in a posture in which the nozzle is tilted by a predetermined angle from a posture toward the center of the gear. Method for strengthening gears.