Power transmission mechanism and gear manufacturing method

Abstract

The power transmission mechanism (3) has a drive gear (10) fixed to the drive shaft (1) and a driven gear (20) fixed to the driven shaft (2) and meshing with the drive gear (10), and outputs power input to the drive shaft (1) to the driven shaft (2), in which a tooth group of the drive gear (10) and / or the driven gear (20) changes the torsion angle and / or the pressure angle of the teeth in the circumferential direction. A change in the torsion angle and / or pressure angle of the teeth in the circumferential direction is shaped, for example, to correspond to a waveform of a sine wave in the circumferential direction.

Description

Technical Field

[0001] This disclosure relates to a power transmission mechanism and a method for manufacturing a gear that can maintain the original power transmission performance and durability required by the gear and suppress gear noise. Background Technology

[0002] With the electrification of vehicles in recent years, the use of engines is being phased out and engine start-up time is being reduced. As a result, engine noise, which hides gear noise, is disappearing. Therefore, from a quietness point of view, it is desirable to further reduce gear noise compared to the past.

[0003] Patent document 1 discloses a technique for suppressing gear noise by having periodically varying teeth that cause the tooth width to change periodically along the circumferential direction.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2012-122504 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] In Patent Document 1, gear noise caused by meshing transmission error is suppressed by periodically changing the tooth width and making the meshing transmission error irregular, i.e. randomized.

[0009] However, if the tooth width is varied periodically, the mass in the circumferential direction will become unbalanced, and the gear may become eccentric. Eccentricity will generate vibration and accompanying noise. Furthermore, the machining process for periodically varying the tooth width requires machining the portion that reduces the tooth width. Moreover, periodically changing the tooth width significantly alters the width of the tooth contact, thus greatly increasing the meshing transmission error and requiring improved power transmission performance.

[0010] The present invention was made to solve the above-mentioned problems, and its purpose is to provide a power transmission mechanism and a method for manufacturing gears that can maintain the original power transmission performance and durability required by gears and suppress gear noise.

[0011] Methods for solving problems

[0012] To solve the above problems and achieve the objective, the power transmission mechanism of the present invention has a drive gear fixed to a drive shaft and a driven gear fixed to a driven shaft and meshing with the drive gear, outputting power input to the drive shaft to the driven shaft. The mechanism is characterized in that at least one of the drive gear and the driven gear has a tooth set that causes the torsional angle and / or pressure angle of the teeth to vary along the circumferential direction.

[0013] Furthermore, based on the above technical solution, in the power transmission mechanism of the present invention, the change of the torsion angle and / or pressure angle of the teeth along the circumferential direction is shaped to correspond to the waveform of a sine wave along the circumferential direction.

[0014] Furthermore, based on the above technical solution, in the power transmission mechanism of the present invention, the characteristic is that the change of the torsion angle and / or pressure angle of the teeth along the circumferential direction is shaped to correspond to a predetermined randomly changing waveform along the circumferential direction.

[0015] Furthermore, based on the above technical solution, in the power transmission mechanism of the present invention, the change of the torsion angle and / or pressure angle of the teeth along the circumferential direction is shaped to correspond to a monotonically increasing and / or monotonically decreasing waveform along the circumferential direction.

[0016] Furthermore, based on the above technical solution, in the power transmission mechanism of the present invention, the characteristic is that the torsion angle and / or pressure angle of the teeth along the circumferential direction cause the waveform to change periodically within one revolution of the circumference.

[0017] Furthermore, based on the above technical solution, in the power transmission mechanism of the present invention, the driving gear and the driven gear are helical gears.

[0018] Furthermore, the gear manufacturing method of the present invention causes the torsion angle and / or pressure angle of the teeth to vary along the circumferential direction. The method is characterized by comprising: a tooth cutting process, in which a set of teeth whose torsion angle and / or pressure angle vary along the circumferential direction of the gear being processed is formed; and a tooth surface machining process, in which the tooth set formed by the tooth cutting process is ground to form the tooth surface.

[0019] Furthermore, the gear manufacturing method of the present invention causes the torsion angle and / or pressure angle of the teeth to vary along the circumferential direction. The method is characterized by comprising: a tooth cutting process, in which a set of teeth having a uniform torsion angle and / or pressure angle along the circumferential direction of the gear being processed is formed; and a tooth surface machining process, in which tooth surface machining is performed on each tooth formed by the tooth cutting process to cause the torsion angle and / or pressure angle to vary along the circumferential direction.

[0020] Furthermore, based on the above technical solution, the gear manufacturing method of the present invention is characterized in that, in the gear cutting process, gear cutting is performed by any one of gear hobbing, gear scraping, milling, end milling, and gear shaping; and in the gear surface processing process, gear surface processing is performed by any one of grinding, gear scraping, honing, gear shaving, milling, end milling, and gear shaping.

[0021] Invention Effects

[0022] According to the present invention, the original power transmission performance and durability required by the gear can be maintained, and gear noise can be suppressed. Attached Figure Description

[0023] Figure 1 This is a perspective view showing the overall structure of the power transmission mechanism of this embodiment.

[0024] Figure 2 It is a diagram illustrating the change in the torsion angle of the driven gear.

[0025] Figure 3 This diagram illustrates an example of machining a tooth with only one tooth surface affected by a change in the torsion angle.

[0026] Figure 4 It is a diagram illustrating the shape of the tooth surface on the meshing side of the tooth.

[0027] Figure 5 It is a diagram illustrating the inherent meshing transmission error that occurs when the teeth of manufactured gears mesh.

[0028] Figure 6 This is a graph showing the time variation of the inherent meshing transmission error generated during gear meshing.

[0029] Figure 7 This is a graph showing the time waveform and spectrum of the sound pressure when the torsion angle of the tooth remains unchanged and when it changes.

[0030] Figure 8 This is a graph showing the time waveform and spectrum of the sound pressure in Modified Example 1.

[0031] Figure 9 This is a graph showing the time waveform and spectrum of the sound pressure in Modified Example 2.

[0032] Figure 10 This diagram illustrates the machining process of forming a gear set with a uniform torsion angle using a threaded cutting tool.

[0033] Figure 11 This is a diagram illustrating the machining of the tooth surface to make the uniform torsion angle vary along the circumference of the gear (one of the diagrams).

[0034] Figure 12 This is a diagram illustrating the machining of the tooth surface to make the uniform torsion angle vary along the circumference of the gear (Part Two).

[0035] Figure 13 This is a diagram illustrating the machining of the tooth surface to make the uniform torsion angle vary along the circumference of the gear (Part Three).

[0036] Figure 14 This is a diagram illustrating the machining of the tooth surface to make the uniform torsion angle vary along the circumference of the gear (Figure 4).

[0037] Figure 15 This is a diagram illustrating an example of tooth surface machining based on honing.

[0038] Figure 16 This is a diagram illustrating an example of tooth surface machining based on profile grinding.

[0039] Figure 17 It is a diagram illustrating the torsion angle and pressure angle.

[0040] Figure 18 It is a graph showing the relationship between the torsional angle dispersion, pressure angle dispersion, and the rate of change of the gear when the tooth surface meshes during slow acceleration, with the optimal sound pressure point set to 100%.

[0041] Figure 19 It is a graph showing the relationship between the gear's torsional angle dispersion, pressure angle dispersion, and the rate of change when the optimal sound pressure point is set to 100% at the system's maximum torque.

[0042] Figure 20 Is with Figure 18 Correspondingly, a graph is shown showing the relationship between the rate of change of the sound pressure during tooth meshing under slow acceleration, with the optimal point of sound pressure set to 100%, and the torsional angle dispersion with pressure dispersion as a parameter.

[0043] Figure 21 Is with Figure 18Correspondingly, a graph is shown showing the relationship between the rate of change of the sound pressure at the optimal point of 100% during tooth meshing under slow acceleration and the pressure angle dispersion with the torsional angle dispersion as a parameter. Detailed Implementation

[0044] Hereinafter, with reference to the accompanying drawings, the manufacturing method of the power transmission mechanism and gear of this embodiment will be described.

[0045] <Overall Structure of Power Transmission Mechanism>

[0046] Figure 1 This is a perspective view showing the overall structure of the power transmission mechanism 3 according to this embodiment. The power transmission mechanism 3 has a drive gear 10 and a driven gear 20, and transmits the power input to the drive gear 10 to the driven gear 20. The drive gear 10 is fixed to a drive shaft 1 that rotates about a shaft C1, and the driven gear 20 is fixed to a driven shaft 2 that rotates about a shaft C2.

[0047] The drive gear 10 with teeth 11 and the driven gear 20 with teeth 12 are helical gears. Teeth 11 are formed with a uniform torsion angle, and teeth 21 are formed with a torsion angle that varies circumferentially along the same uniform torsion angle as teeth 11. Furthermore, the gear having the torsion angle varying circumferentially may be on the drive gear 10 side rather than the driven gear 20 side. Alternatively, the torsion angle varying circumferentially may be formed for both the drive gear 10 and the driven gear 20.

[0048] For the metal materials used in the drive gear 10 and the driven gear 20, examples of materials with high mechanical strength include carbon steel (S45C), chromium-molybdenum alloy steel (SCM440, SCM415), and stainless steel (SUS303). The drive gear 10 and the driven gear 20 can also be formed from materials other than metals. For example, they can be formed from resin, ceramics, etc. The drive gear 10 and the driven gear 20 can also be formed from different materials.

[0049] <Changes in the angle of twist>

[0050] Figure 2 This is a diagram illustrating the change in the torsion angle of the driven gear 20. For ease of explanation, Figure 2 The upper part of the diagram shows the arrangement of teeth 21 along the rotation direction AR (circumferential direction) of the driven gear 20, unfolded as a straight line according to the circumference DR. The tooth width d, which is the thickness of the driven gear 20, is set accordingly to the tooth width of the driving gear 10. The torsion angle of the tooth set 21 varies along the circumferential direction based on a torsion angle θ, which is the same as the uniform torsion angle θ of the teeth 11 of the driving gear 10. Figure 2As shown in the lower part of the diagram, the vibration amplitude of the change in the torsion angle θ is ±θa. The change in the torsion angle θ relative to the reference, i.e., the torsion variation angle, varies along the circumferential direction corresponding to the waveform of a sine wave with a vibration amplitude of θa. The torsion variation angle is small, and with a constant tooth width d, it can be approximately represented in machining by the amount of torsion vibration at the tooth tip. For example, the torsion variation angle θa is approximately 0.05°, in which case the amount of torsion vibration is ±10 μm, resulting in a vibration amplitude of 20 μm.

[0051] Since the teeth of tooth 21 are discretely arranged at a specified interval along the circumferential direction, the torsion angle of tooth 21 relative to the reference torsion angle θ causes the torsion change angle shown by the waveform of the sine wave corresponding to the arrangement position of tooth 21 to increase or decrease. Figure 2 In the diagram, the starting position in the circumferential direction represents the maximum negative torsion angle obtained by subtracting the vibration amplitude (torsion variation angle θa) from the reference torsion angle θ, while the center position in the circumferential direction represents the maximum positive torsion angle obtained by adding the vibration amplitude (torsion variation angle θa) to the reference torsion angle θ. The midpoints between the starting and center positions in the circumferential direction, and the midpoints between the center and ending positions in the circumferential direction, represent the same torsion angle θ as the reference without applied vibration amplitude. Corresponding to the waveform of a sine wave, each tooth 21 increases the torsion angle from the starting position to the midpoint in the circumferential direction, and decreases the torsion angle from the midpoint to the ending position in the circumferential direction. Furthermore, line L0 is perpendicular to the circumferential direction, and line L1 is a line indicating the reference torsion angle θ.

[0052] exist Figure 2 In the upper part of the diagram, the thickness of each tooth 21 in the torsion angle direction is made uniform, but... Figure 1 In the helical gears shown, only the torsion angle of the meshing tooth surfaces needs to be changed. For example, as... Figure 3 As shown, it is sufficient to perform machining that only changes the torsion angle on the SA side of the tooth surface where the teeth 11 mesh in tooth 21. Figure 3 The dashed line shows the tooth surface of tooth 21 shaped with respect to the reference torsion angle θ. Figure 3 In (a), thickening the tooth surface SA on the end face 22 side of tooth 21 increases the twist angle. Conversely, thinning the tooth surface SA on the end face 22 side decreases the twist angle. Figure 3 In (b), the tooth surface SA on the opposite side of the end face 22 of tooth 21 is made thinner, thereby increasing the torsion angle. Alternatively, if the tooth surface SA on the opposite side of the end face 22 of tooth 21 is made thicker, the torsion angle can be reduced.

[0053] For machining processes that change the torsion angle, using the central side in the tooth width direction as the reference for torsion allows for either thickening of the tooth surface SA on the end face 22 side of tooth 21 and thinning of the tooth surface SA on the opposite side of end face 22, or thinning of the tooth surface SA on the end face 22 side of tooth 21 and thickening of the tooth surface SA on the opposite side of end face 22. Figure 2 In the tooth 21 shown, the torsion angle is shaped in such a way that the thickness in the torsion angle direction is uniform. However, in this case, the end face 22 side can be used as the reference for torsion, the opposite side of the end face 22 can be used as the reference for torsion, or the central side in the tooth width direction can be used as the reference for torsion.

[0054] In the case of a power transmission mechanism such as a spur gear that rotates in opposite directions, the shape is designed to account for the change in the torsion angle between the meshing tooth surfaces during forward rotation and the meshing tooth surfaces during reverse rotation. In this case, such as Figure 3 As shown, when only the meshing tooth surfaces are processed to change the torsion angle, both the driving gear 10 and the driven gear 20 will have changes in the torsion angle.

[0055] <Meshing transmission error>

[0056] Figure 4 It is a diagram illustrating the shape of the tooth surface on the meshing side of the tooth. Figure 5 This diagram illustrates the inherent meshing transmission error that occurs during the meshing of manufactured gears. The manufactured gears have a uniform torsion angle. Gear noise is generated due to and is correlated with this meshing transmission error. As the meshing transmission error increases, the gear noise also increases. Figure 5 For ease of explanation, spur gears 10a and 20a are used in the illustration, but if... Figure 4 As shown in the enlarged view of part A of the meshing of teeth 11a and 21a, by making the meshing tooth surfaces of teeth 11a and 21a into the involute tooth surfaces SB shown by the dashed lines, the meshing transmission error can be made zero, and gear noise can be eliminated.

[0057] However, in actual manufacturing, it is difficult to make the tooth surface match the involute. Even if the tooth surface can be made close to the involute like tooth surface SA, it is impossible to make it completely consistent, which will produce inherent meshing transmission errors.

[0058] Because the tooth surfaces of each tooth are machined with high precision, the inherent meshing transmission error exhibits a periodic, continuous, and similar waveform throughout the entire rotation. That is, as... Figure 4 As shown, when the tooth surface shape is involute, the meshing position becomes Figure 5 The action line LW is shown, but the actual meshing position of the tooth surface SA will be the position indicated by the circular mark offset from the action line LW, resulting in meshing transmission error. For example... Figure 6As shown, the meshing transmission error changes as the meshing time elapses.

[0059] That is, such as Figure 6 As shown in (a), when the tooth surface shape is involute, as indicated by the straight line L10, the meshing transmission error is always zero. However, with the actual tooth surface shape SA, as indicated by the curve L11, the meshing transmission error changes over time. Furthermore, as... Figure 6 As shown in (b), whenever the teeth mesh, Figure 6 The curve L11 of the meshing transmission error shown in (a) appears periodically and continuously. As mentioned above, gear noise is generated due to and correlated with the meshing transmission error; as the meshing transmission error increases, the gear noise increases. This is because the periodic and continuous meshing transmission error generates continuous air vibrations. These air vibrations are also periodic and are perceived as sounds of specific frequencies. As a result, sound pressure (gear noise) is generated due to the meshing transmission error.

[0060] <Changes in the angle of twist>

[0061] Figure 7 This is a graph showing the time waveform and spectrum of the sound pressure when the tooth twist angle remains unchanged and when it changes. Figure 7 In this context, one cycle is the time it takes for the gear to rotate once.

[0062] like Figure 7 As shown in (a), when the torsion angle of the teeth remains unchanged, the sound pressure changes periodically and continuously in the time waveform whenever the teeth mesh. Therefore, a sharp, large peak waveform forms in the sound pressure spectrum near a specific frequency, such as 1000 Hz. This sound pressure becomes gear noise. Furthermore, as mentioned above, the change in sound pressure corresponds to an inherent meshing transmission error.

[0063] In contrast, such as Figure 7 As shown in (b), if the torsion angle of the tooth is as follows: Figure 2 As shown, when varying along the circumferential direction, the time waveform of the sound pressure becomes a waveform modulated according to the vibration amplitude of the torsion angle. Furthermore, when the torsion angle is varied, the tooth contact area on the tooth surface at the reference torsion angle θ during meshing will shift slightly to the left and right in the tooth width direction; this displacement is used to adjust the meshing transmission error. Figure 7 In (b), there are two cycles within one cycle of the gear. Figure 2 The torsional angle shown.

[0064] The result is, as Figure 7As shown in the sound pressure spectrum of (b), the sound pressure at a specific frequency (around 1000 Hz) decreases, and the frequency component corresponding to the period of the torsional angle appears dispersed before and after the specific frequency. That is, the specific frequency component corresponding to the periodic change of the inherent meshing transmission error is dispersed (spread) into the frequency component corresponding to the change of the torsional angle, which can reduce the specific frequency component with a large sound pressure and reduce the overall gear noise.

[0065] In this embodiment, for the tooth set of at least one of the driving gear 10 and the driven gear 20, only the torsion angle of the tooth changes in accordance with the waveform of the sine wave along the circumferential direction, without changing the tooth width, etc. Therefore, the original power transmission performance and durability required by the gear can be maintained, and gear noise can be suppressed.

[0066] <Variation Example 1>

[0067] In the above embodiments, the change in the torsion angle of the teeth along the circumferential direction of the gear corresponds to the waveform of a sine wave. However, in this modified example 1, the teeth of the gear are shaped such that the change in the torsion angle of the teeth along the circumferential direction corresponds to a predetermined randomly changing waveform along the circumferential direction.

[0068] Figure 8 This is a graph showing the time waveform and spectrum of the sound pressure in Modified Example 1. Figure 8 As shown, in Modification 1, since the torsional angle changes in accordance with the prescribed random waveform, the meshing transmission error also changes in accordance with the prescribed random change. As a result, the time waveform of the sound pressure also changes in accordance with the prescribed random change. Furthermore, since the random change includes a sharp change in the torsional angle, the sinusoidal wave components containing multiple frequencies can be efficiently dispersed to correspond to the reference torsional angle.

[0069] As a result, similar to the implementation method, the sound pressure component corresponding to the frequency of the specified random variation increases, the frequency component corresponding to the inherent meshing transmission error decreases, and the overall gear noise decreases.

[0070] <Variation Example 2>

[0071] In the above embodiments, the change in the torsion angle of the teeth along the circumferential direction of the gear corresponds to the waveform of the sine wave. However, in this modified example 2, the teeth of the gear are shaped such that the change in the torsion angle of the teeth along the circumferential direction corresponds to the waveform of monotonically increasing or monotonically decreasing along the circumferential direction.

[0072] Figure 9 This is a graph showing the time waveform and spectrum of the sound pressure in Modified Example 2. Figure 9As shown, in Modification 2, since the torsional angle changes in accordance with the monotonically decreasing waveform, the meshing transmission error also changes in accordance with the monotonically decreasing change. Consequently, the time waveform of the sound pressure level also changes in accordance with the monotonically decreasing change. Furthermore, since the monotonically decreasing waveform repeats according to each circumference, it includes abrupt changes in the torsional angle and contains sinusoidal components of multiple frequencies, allowing for efficient dispersion of the sinusoidal components corresponding to the reference torsional angle. Alternatively, a monotonically increasing waveform can be used instead of a monotonically decreasing one.

[0073] As a result, similar to the implementation method, the sound pressure component corresponding to the monotonically decreasing change increases, the frequency component corresponding to the inherent meshing transmission error decreases, and the overall gear noise decreases.

[0074] In the embodiments and variations 1 and 2, the change in the torsion angle of the teeth along the circumferential direction can also cause the waveforms (sine wave waveform, specified random waveform, monotonically decreasing and / or monotonically increasing waveform) to change periodically and repeatedly within one revolution of the circumference.

[0075] <Gear Manufacturing Methods>

[0076] The manufacturing method of a gear in which the torsion angle of the teeth varies along the circumferential direction is explained. Figure 10 This diagram illustrates the machining process of forming a set of teeth with a uniform torsion angle using one or more threaded cutting tools 40.

[0077] like Figure 10 As shown, a disc-shaped gear component 23 is fixed to a gear holding device 31. The gear component 23 is fixed with the rotation axis CL passing through its center and orthogonal to the rotation axis CL. The gear holding device 31 holding the gear component 23 rotates about the rotation axis CL.

[0078] Next, a threaded cutting tool 40, rotating around the rotation axis CN, is pressed against the outer circumference of the gear piece 23 being machined and tooth cutting is performed. This generates a gear 24 with a tooth set having a uniform torsion angle. Furthermore, if the rotation axis CN is arranged perpendicular to the rotation axis CL, a spur gear with a torsion angle of 0 degrees is generated. If the rotation axis CN is arranged at an angle from its perpendicular arrangement to the rotation axis CL, a helical gear with a uniform desired torsion angle is generated. In other words, a gear 24 with a uniform torsion angle is generated by generating grinding.

[0079] Then, the grinding threaded grinding wheel 50 corresponding to the threaded cutting tool 40 is rotated and pressed against the gear 24 which is held in the gear holding device 31 and rotates. The rotation axis CL of the rotating gear 24 is tilted about the rotation axis, and the tooth surface is machined for each tooth by means of this tilt, so that the uniform torsion angle varies along the circumferential direction.

[0080] Figures 11-14 This diagram illustrates the machining of the tooth surface to achieve a uniform torsion angle that varies along the circumference of the gear. For ease of explanation, gear 24 is depicted as a spur gear with 48 teeth and a uniform torsion angle of 0 degrees. Figure 11 (b) Figure 12 (b) Figure 13 (b) Figure 14 (b) shows the amount of torsional angular vibration that should be formed relative to the number of teeth (position of teeth in the circumferential direction) of gear 24. Figure 11 (a) Figure 12 (a) Figure 13 (a) Figure 14 (a) is shown with Figure 11 (b) Figure 12 (b) Figure 13 (b) Figure 14 (b) Three-view diagram showing the positional relationship between the grinding threaded grinding wheel 50, gear 24 and rotating shaft CL corresponding to the respective positions of 〇.

[0081] The rotary shaft CL completes tooth surface machining for all teeth with varying torsional angles by rotating once, but it can also be rotated repeatedly for grinding. During one rotation, the upper end P1 of the rotary shaft CL is tilted around the bearing P0, tracing a circular path. Therefore, the rotary shaft CL traces the lateral side of a cone with the bearing P0 as its vertex while rotating. The tilting amount of the rotary shaft CL corresponds to the amount of torsional angular vibration.

[0082] Figure 12 The diagram shows the case where the torsional angular vibration is at its maximum, with the rotating shaft CL tilted in the -X direction. Figure 14 The case where the torsional angular vibration is minimal is shown, with the rotation axis CL tilted in the +X direction. In this case, the rotation axis CN of the threaded grinding wheel 50 is parallel to the XZ plane containing the rotation axis CL.

[0083] Figure 11 The case where the torsional angular vibration is 0 is shown, with the rotating axis CL tilted in the +Y direction. Figure 13 The case where the torsional angular vibration is 0 is shown, with the rotating axis CL tilted in the -Y direction.

[0084] exist Figures 11-14 The tooth surface is machined at the middle position of the circular track at the upper end P1 of the rotating shaft CL, with the torsional angular vibration corresponding to the inclination amount of the ±X direction component of the rotating shaft CL.

[0085] In this gear manufacturing method, since the upper end P1 of the rotating shaft CL is drawn with a circular track, it is easy to shape the change in torsion angle corresponding to the waveform of a sine wave. Furthermore, the amount of torsion angle vibration can also be changed by making the rotating shaft CL move linearly only in the ±X direction. In this case, the change in torsion angle corresponding to modified examples 1 and 2 can be shaped.

[0086] In the aforementioned gear manufacturing method, after cutting (hobbing) the gear set with a uniform torsion angle, grinding (grinding with a threaded grinding wheel) is performed to change the torsion angle. However, the two-stage cutting and grinding processes can also be combined into a single stage performed by a threaded grinding tool, directly shaping the gear set whose torsion angle changes along the circumferential direction. In this case, the upper end P1 of the rotating shaft CL is cut at an angle corresponding to the change in torsion angle.

[0087] <Example 1 of a variation in the gear manufacturing method>

[0088] In a variation of the gear manufacturing method, a set of teeth whose torsion angle varies along the circumferential direction is formed by scraping with a rotary scraper. In this scraping process, a rotary scraper with a set of cutting inserts formed on its outer circumference for forming the set of teeth whose torsion angle varies along the circumferential direction is pressed against the circumferential surface of the gear piece 23 being processed, which forms a set of teeth that is an integer multiple of the set of cutting inserts. The rotary scraper and the gear piece being processed are rotated synchronously, and the set of teeth whose torsion angle varies along the circumferential direction is formed on the circumferential surface of the gear piece being processed. In this variation of the gear manufacturing method, a set of teeth whose torsion angle varies can be formed by a single stage of processing performed by a rotary scraper. Furthermore, the torsion angle can also vary by tilting the rotation axis of the rotary scraper in the same way as tilting the rotation axis CL.

[0089] Because the rotary scraper rotates at high speed, after shaping a tooth assembly with a uniform torsion angle using the rotary scraper, the tooth surface of the tooth assembly can be machined to change the torsion angle (grinding). This tooth surface machining can also be performed, for example, by honing.

[0090] like Figure 15 As shown, in honing, a gear 24 with a uniform torsion angle is meshed with the inner circumference of an annular grinding wheel 60, whose inner circumference has grinding teeth that vary in torsion angle along the circumferential direction. By rotating the annular grinding wheel 60, grinding is performed on the tooth surfaces of the gear 24, transferring the torsion angle to the tooth surfaces, and machining is performed on the tooth surfaces that vary in torsion angle along the circumferential direction. Furthermore, Figure 15 The number of grinding teeth is twice that of gear 24.

[0091] Gears with a uniform torsion angle that are the object of honing are not limited to generating grinding; they can also be gears with a uniform torsion angle that are shaped by any cutting process.

[0092] <Example 2 of a variation on a gear manufacturing method>

[0093] In the gear manufacturing method described above, after generating a gear 24 with a uniform torsion angle by generating grinding, tooth surface machining is performed to impart a change in the torsion angle. However, tooth surface machining can also be performed by milling as a form grinding process.

[0094] First, it is not limited to generating grinding; gear cutting with a uniform torsion angle can be achieved through any grinding process. For example, as... Figure 16 As shown, in milling, the disc-shaped cutting tool 70 mounted on the rotating shaft 71 is rotated around the shaft CL1 and ground to produce gear 24 with uniform torsion angle on the gear part 23 being machined.

[0095] Then, by tilting the rotation axis 71 of the disc-shaped grinding wheel corresponding to the disc-shaped cutting tool 70 and grinding, the teeth of the gear 24 are machined so that the torsion angle of the teeth changes along the circumferential direction.

[0096] The above-described gear cutting and tooth surface machining are examples. Gear cutting can also be performed using any of the following methods: hobbing, scraping, milling, end milling, and gear shaping. Tooth surface machining can also be performed using any of the following methods: grinding, scraping, honing, shaving, milling, end milling, and gear shaping. That is, gears can also be manufactured by appropriately combining various gear cutting and tooth surface machining methods.

[0097] <Variation Example 3>

[0098] In the above embodiments and variations 1 and 2, the torsion angle of the tooth is varied along the circumferential direction, but the pressure angle of the tooth can also be varied along the circumferential direction.

[0099] Figure 17 This is a diagram illustrating the torsion angle and pressure angle. For example... Figure 17 As shown in (a), in the embodiments and variations 1 and 2, by varying the torsion angle θ along the circumferential direction AR, the tooth contact position PP of the tooth surface SA varies left and right in the direction of the gear rotation axis GC (tooth width direction) of tooth 21. In this variation 3, as... Figure 17As shown in (b), by varying the pressure angle φ along the circumferential direction AR, the tooth contact position PP of the tooth surface SA varies along the radial direction of tooth 21. The pressure angle φ is the angle between the radius line RL passing through the tooth contact position PP from the gear rotation axis GC and the tangent direction of the tooth contact position PP, and is the inclination of the tooth surface SA. Just as the change in the torsional angle θ can be substantially represented by the change in the torsional angular vibration quantity wθ, the change in the pressure angle φ can be substantially represented by the change in the pressure angular vibration quantity wφ.

[0100] In this variation 3, the pressure angle of the tooth is varied along the circumferential direction. In this case, the time waveform of the sound pressure becomes a waveform modulated according to the vibration amplitude of the pressure angle. When the pressure angle is varied, the tooth contact area on the tooth surface SA at the reference pressure angle during meshing will shift slightly up and down in the radial direction, and this displacement is used to increase or decrease the meshing transmission error. The specific frequency component corresponding to the periodic change of the inherent meshing transmission error is dispersed (spread) into a frequency component corresponding to the change of the pressure angle, which can reduce the specific frequency component with a large sound pressure. Similar to the embodiment and variations 1 and 2, the overall gear noise is reduced.

[0101] In this variation 3, the change in the pressure angle of the teeth along the circumferential direction can also cause the waveforms (sine wave, specified random waveform, monotonically decreasing and / or monotonically increasing waveform) to change periodically and repeatedly within one revolution of the circumference. Changes in the torsional angle and the pressure angle can also occur simultaneously. In this case, the changes in the torsional angle and the pressure angle can be synchronous, asynchronous, or even different.

[0102] Here, Figure 18 This is a graph showing the relationship between the torsional angle dispersion, pressure angle dispersion, and the rate of change of tooth 21 during tooth surface meshing under slow acceleration, with the optimal sound pressure point set to 100%. Figure 19 This is a graph showing the relationship between the torsional angle dispersion, pressure angle dispersion, and rate of change of gear 21 when the system is at maximum torque, with the optimal sound pressure point set to 100%. Figure 18 and Figure 19 The figure shows three-dimensional data obtained by visualizing the rate of change of the sound pressure optimum with the two-dimensional data of torsional angular dispersion and pressure angular dispersion. Figure 18 and Figure 19 Sound pressure measurements were performed only in measurement areas E1 and E2.

[0103] The torsional angle dispersion is the amplitude of vibration from a reference torsional angle. The pressure angle dispersion is the amplitude of vibration from a reference pressure angle. The rate of change when the optimal sound pressure level is set to 100% is the ratio of the minimum measured sound pressure (the optimal sound pressure level) to the measured sound pressure, expressed as a percentage. Therefore, the value at the optimal measured sound pressure level is 100, and it decreases as the measured sound pressure increases. Furthermore, the changes in the torsional angle and pressure angle along the circumferential direction correspond to the waveform of a sine wave.

[0104] like Figure 18 and Figure 19 As shown, when the dispersion of torsional angle and pressure angle are varied, there are sound pressure optimal points PN1 and PN2 in each measurement area E1 and E2 with the largest rate of change and the smallest gear noise when the optimal sound pressure point is set to 100%. Figure 18 and Figure 19 The optimal sound pressure points PN1 and PN2 shown are minimized when the torsional angle dispersion is approximately 18 μm and when the pressure angle dispersion is approximately 2.5 μm, respectively.

[0105] For example, Figure 20 Is with Figure 18 Correspondingly, a graph is shown showing the relationship between the rate of change of the sound pressure during tooth meshing under slow acceleration, with the optimal point of sound pressure set to 100%, and the torsional angle dispersion with pressure dispersion as a parameter. Figure 20 The curves LA1, LA2, and LA3 shown are characteristic curves for pressure angular dispersion of 1.5 μm, approximately 2.5 μm, and 3.5 μm, respectively. Figure 20 As shown, regardless of the pressure dispersion, the rate of change is greatest and the gear noise is smallest when the torsional angle dispersion is about 18 μm and the optimal sound pressure is set to 100%.

[0106] Figure 21 Is with Figure 18 Correspondingly, a graph is shown showing the relationship between the rate of change of the sound pressure at the optimal point of 100% during tooth meshing under slow acceleration and the pressure angle dispersion with the torsional angle dispersion as a parameter. Figure 21 The curves LB1, LB2, and LB3 shown are characteristic curves for twist angle dispersions of 15 μm, 18 μm, and 25 μm, respectively. Figure 21 As shown, regardless of the torsional angle dispersion, the rate of change is greatest and the gear noise is smallest when the pressure angle dispersion is about 2.5 μm and the optimal sound pressure is set to 100%.

[0107] Therefore, based on the operating conditions of the system structure using gears, there exists a torsional angle dispersion and a pressure angle dispersion that are near the optimal sound pressure point. By setting these torsional angle dispersion and pressure angle dispersion, gear noise can be significantly suppressed. Furthermore, in the embodiments and variations 1 and 2, just as gear noise can be reduced by changing only the torsional angle, gear noise can also be reduced by changing only the pressure angle.

[0108] The gear manufacturing method that includes the change of pressure angle can be applied to the gear manufacturing method that changes the torsion angle mentioned above, as long as the shape of the machining tool, the machining conditions, and the pressure angle are adjusted.

[0109] The structures illustrated in the above embodiments and variations are functionally generalized structures and do not necessarily need to be physically formed as shown in the illustrations. That is, the form in which the devices are distributed or combined is not limited to the form shown in the illustrations, and they can be functionally or physically distributed or combined in any unit according to various loads, usage conditions, etc.

[0110] Industrial availability

[0111] The power transmission mechanism and gear manufacturing method of the present invention are useful in maintaining the original power transmission performance and durability required by the gear while suppressing gear noise.

[0112] Explanation of reference numerals in the attached figures

[0113] 1. Drive shaft

[0114] 2 Driven shaft

[0115] 3. Power transmission mechanism

[0116] 10 Drive Gear

[0117] 10a and 20a spur gears

[0118] Teeth 11, 11a, 21, 21a

[0119] 20 Driven gears

[0120] 22 End face

[0121] 23. Gear parts being machined

[0122] 24 Gears

[0123] 31 Gear retaining device

[0124] 40. Threaded cutting tools

[0125] 50. Threaded grinding wheel for grinding.

[0126] 60 ring grinding wheel

[0127] 70 Disc-shaped cutting tools

[0128] 71, CL, CN Rotating Axes

[0129] AR rotation direction

[0130] C1, C2, CL1 axes

[0131] d Tooth width

[0132] Measurement areas E1 and E2

[0133] DR perimeter

[0134] GC gear rotating shaft

[0135] L0, L1 lines

[0136] L10 Straight Line

[0137] L11, LA1~LA3, LB1~LB3 curves

[0138] LW line of action

[0139] P0 bearing

[0140] P1 upper end

[0141] Optimal sound pressure levels for PN1 and PN2

[0142] PP tooth contact position

[0143] RL radius line

[0144] SA, SB tooth surface

[0145] wθ Torsional angular vibration

[0146] wφ Pressure angular vibration

[0147] θ Twist angle

[0148] θa Twist angle

[0149] φ is the pressure angle.

Claims

1. A power transmission mechanism, comprising a drive gear fixed to a drive shaft and a driven gear fixed to and meshing with the drive gear on a driven shaft, wherein power input to the drive shaft is output to the driven shaft, characterized in that, The tooth set of at least one of the driving gear and the driven gear causes the torsion angle and / or pressure angle of the teeth to vary along the circumferential direction.

2. The power transmission mechanism according to claim 1, characterized in that, The changes in the torsion angle and / or pressure angle of the teeth along the circumferential direction are shaped to correspond to the waveform of a sine wave along the circumferential direction.

3. The power transmission mechanism according to claim 1, characterized in that, The variation of the torsion angle and / or pressure angle of the teeth along the circumferential direction is shaped to correspond to a waveform of a specified random variation along the circumferential direction.

4. The power transmission mechanism according to claim 1, characterized in that, The changes in the torsion angle and / or pressure angle of the teeth along the circumferential direction are shaped to correspond to a monotonically increasing and / or monotonically decreasing waveform along the circumferential direction.

5. The power transmission mechanism according to any one of claims 2 to 4, characterized in that, The twist angle and / or pressure angle of the teeth along the circumferential direction cause the waveform to change periodically within one revolution of the circumference.

6. The power transmission mechanism according to any one of claims 1 to 4, characterized in that, The driving gear and the driven gear are helical gears.

7. A method for manufacturing a gear, wherein the torsion angle and / or pressure angle of the teeth vary along the circumferential direction, characterized in that, The method for manufacturing the gear includes: A gear cutting process, wherein a gear assembly whose torsion angle and / or pressure angle vary along the circumferential direction of the gear being processed is shaped; and The tooth surface machining process involves grinding the tooth assembly formed by the cutting process to shape the tooth surface.

8. A method for manufacturing a gear, wherein the torsion angle and / or pressure angle of the teeth vary along the circumferential direction, characterized in that, The method for manufacturing the gear includes: The gear cutting process involves shaping a set of teeth that have a uniform torsion angle and / or pressure angle along the circumferential direction of the gear being processed; and The tooth surface machining process involves machining the tooth surfaces of each tooth after it has been formed by the cutting process, such that the torsion angle and / or pressure angle vary along the circumferential direction.

9. The method for manufacturing a gear according to claim 7 or 8, characterized in that, In the aforementioned gear cutting process, gear cutting is performed using any one of the following methods: gear hobbing, gear scraping, milling, end milling, or gear shaping. In the tooth surface machining process, the tooth surface is machined by any one of the following: grinding, scraping, honing, shaving, milling, end milling, and gear shaping.

Images