Gear grinding device and gear grinding method using said device

Abstract

[Problem] To provide a grinding device capable of reducing periodicity of a cumulative pitch error waveform of a gear being ground, and a grinding method using said grinding device. [Solution] A grinding device 100 for grinding a workpiece 90 comprises a main spindle 10 capable of holding the workpiece 90 and a sub spindle 20 disposed parallel to the main spindle 10. Two gears are provided to each of the spindles, and rotational force is transmitted to the workpiece 90 through the four gears. The workpiece 90 rotates together with the main spindle 10, and is ground by a grinding wheel. At the time of the grinding, at least one of the four gears serves as a correction gear, and a variation is imposed on a cumulative pitch error waveform in the workpiece 90. As a result, the periodicity of the cumulative pitch error waveform in the workpiece 90 is weakened, thereby reducing the meshing vibration at a time when the workpiece 90 is mounted. [Selected figure] FIG.1

Description

Gear grinding device and gear grinding method using the same

[0001] The present invention relates to a gear grinding device and a grinding method using the device, and particularly to a gear grinding device for finishing a tooth surface and a grinding method using the device.

[0002] Conventionally, gears are used in various devices such as speed change devices. After processing the material, the gear undergoes pre-processes such as a gear cutting process, heat treatment, and further a grinding process of a reference surface, and then honing, which is a finishing process using a grinding wheel, is performed to precisely finish the tooth surface. The finishing process is performed, for example, by holding a gear as a workpiece at one end of a rotating shaft and bringing the tooth surface of the workpiece into contact with a grinding wheel, and rotating the rotating shaft by a rotation driving means.

[0003] In the pre-process of the finishing process as described above, in the process of performing various grindings on the workpiece, due to the mounting error of the workpiece to the processing equipment, there may be a state where the center hole of the gear as the workpiece is displaced from the processing center, that is, a so-called center deviation state.

[0004] Fig. 16 shows such a center deviation state. The magnitude of the deviation is shown exaggerated from the actual scale. The original center of the workpiece 90 is the intersection portion C1 of the line L1 indicated by the dashed-dotted line, but in the mounted state, the intersection portion C2 of the line L2 indicated by the broken line is the center. When the workpiece clamped to the processing machine in such a state is rotated and processed with C2 as the center, that is, processed in a center deviation state, a pitch error occurs in the tooth surface of the processed gear. This pitch error appears as a cumulative pitch error of a sine wave having periodicity during the rotation of the gear, and the waveform showing the cumulative pitch error in the entire circumferential tooth surface region (hereinafter simply referred to as "cumulative pitch error waveform") has periodicity.

[0005] Furthermore, gears can also experience distortion in their shape due to processes other than grinding, such as the holding method during the heat treatment process, which is a pre-finishing step. For example, if a gear is suspended and held by passing a support rod through the central hole of the workpiece, the outer circumference of the workpiece may become slightly elliptical rather than perfectly circular. Moreover, if the inner circumference of the workpiece is supported from below and the workpiece is placed horizontally, the outer circumference may sag, causing the workpiece to become curved rather than flat.

[0006] Furthermore, if multiple cavities are provided on the inner circumference of the workpiece to remove material, the outer circumference of each cavity will contract towards the center of the workpiece compared to the areas without cavities, resulting in a circular shape that is not a perfect circle but a periodically undulating circle. Such distortion of the workpiece shape manifests as a cumulative pitch error of a sine wave with n periods (where n is a natural number), such as 1 period, 2 periods, etc., around the entire circumference.

[0007] As described above, misalignment due to mounting errors of workpieces to processing equipment, and shape distortion related to the heat treatment process of the gears, ultimately remain as a periodic cumulative pitch error waveform of the gear, causing phenomena such as deterioration of meshing vibration.

[0008] Patent Document 1 discloses a technique for reducing noise when gears mesh with each other. In a gear having multiple teeth, a set of continuously arranged teeth is shown, and such a set has differences in the shape and / or pitch of adjacent teeth, and one or more such sets are repeated. With this configuration, when the gears mesh with each other and rotate, non-uniformity occurs in the time difference in which each tooth meshes in sequence, resulting in increased non-integer noise and a smaller noise gap. As a result, the meshing sound generated when gears rotate while meshing with each other is less likely to be perceived as noise by the human ear, as it was in the past.

[0009] Japanese Patent Publication No. 2023-95160

[0010] However, the technology described in Patent Document 1 concerns adjustment techniques for when completed gears are actually assembled and mesh together. In other words, while the technology in that document aims to solve the problem of noise during the rotation of the finally installed gears, it does not attempt to make any corrections to tooth shape problems that occur during the finishing process of the gears. Therefore, it does not help to solve problems based on pitch errors in the processed gears caused by misalignment or distortion during manufacturing in finishing processes such as honing of gears, and the challenge of reducing the periodic cumulative pitch error waveform of the workpiece during the above-mentioned finishing process remains.

[0011] The present invention has been made in view of the above problems, and its purpose is to provide a gear grinding apparatus and a gear grinding method using the apparatus that can reduce the periodicity of the cumulative pitch error waveform of gears, which is the cause of meshing vibration when gears are mounted together due to the tooth profile shape accuracy of the gears, at the finishing stage.

[0012] One embodiment of the present invention is a gear grinding apparatus that rotatably holds a workpiece which is a gear and grinds the surface of the workpiece by engaging it with a grinding wheel, comprising: a main shaft to which rotational driving force is input at one end and capable of holding the workpiece at the other end; and at least one sub-shaft arranged parallel to the main shaft, wherein the main shaft has a first clutch for switching the one end side and the other end side between a connected state and a disconnected state, a first gear fixedly attached to the one end side with the first clutch in between, and a second gear fixedly attached to the other end side, wherein the sub-shaft has a second clutch for switching the one end side and the other end side between a connected state and a disconnected state, a third gear fixedly attached to the one end side with the second clutch in between and engaging with the first gear, and a fourth gear fixedly attached to the other end side and engaging with the second gear, At least one of the first to fourth gears is a correction gear for correcting the cumulative pitch error waveform, which is a waveform showing the cumulative pitch error in the entire circumferential tooth surface region of the held and rotating workpiece. The cumulative pitch error waveform of the correction gear mounted on the main spindle or sub-spindle is a sine wave that has the same number of periods per revolution as the cumulative pitch error waveform of the workpiece held on the main spindle, and is set up with a phase shift of approximately 1 / 2 period relative to the cumulative pitch error waveform of the workpiece.

[0013] This configuration effectively reduces the periodicity of the cumulative pitch error of the workpiece during the finish grinding stage. Specifically, one of the first to fourth gears that transmit rotational motion between the two axes is designated as a correction gear. The cumulative pitch error waveform of this correction gear is a sine wave whose number of periods per revolution is equal to the number of periods of the cumulative pitch error waveform of the workpiece, and its phase is set to be shifted by approximately 1 / 2 period, and the rotational motion in this state is transmitted to the workpiece.

[0014] In other words, the rotational motion of the workpiece held on the spindle is varied by the correcting gear, and the parts of the workpiece's cumulative pitch error waveform with large amplitudes are actively pressed against the grinding wheel, and finishing is performed in such a way that the cumulative pitch error waveform of the workpiece is actively corrected, and by canceling out the amplitude of the cumulative pitch error waveform, the periodicity can be effectively reduced, and the meshing vibration of the teeth when the gear, which is the workpiece, is mounted is reduced.

[0015] According to the present invention, in the finishing process of a gear workpiece using a grinding wheel, the periodicity of the cumulative pitch error waveform can be effectively reduced by introducing fluctuations in the rotational motion of the workpiece, thereby reducing meshing vibrations when the gear is mounted.

[0016] This is a schematic diagram showing a grinding apparatus according to an embodiment of the present invention. This is an explanatory diagram of a gear correction holder. This is a waveform diagram showing an example of the cumulative pitch error waveform of a workpiece before finishing. This is a waveform diagram showing an example of the cumulative pitch waveform of a gear correction. This is a waveform diagram showing an example of the cumulative pitch error waveform of a workpiece after finishing by the grinding apparatus of Figure 1. This is a chart diagram showing each step of the grinding method according to an embodiment of the present invention. This is a waveform diagram showing another example of the cumulative pitch error waveform of a workpiece before finishing that is the subject of other embodiments. This is a waveform diagram explaining the cumulative pitch error waveform of a gear correction equipped in a grinding apparatus according to another embodiment. This is a waveform diagram showing the cumulative pitch error waveform of a workpiece after finishing by the grinding apparatus according to another embodiment. This is a waveform diagram showing another example of the cumulative pitch error waveform of another workpiece before finishing that is the subject of other embodiments. This is a waveform diagram explaining the cumulative pitch error waveform of another gear correction equipped in a grinding apparatus according to another embodiment. This is a waveform diagram showing the cumulative pitch error waveform of another workpiece after finishing by the grinding apparatus according to another embodiment. This is a waveform diagram showing another example of the cumulative pitch error waveform of yet another workpiece before finishing that is the subject of other embodiments. This waveform diagram illustrates the cumulative pitch error waveform of an additional modified gear provided by a grinding apparatus according to another embodiment. This waveform diagram shows the cumulative pitch error waveform of an additional workpiece after finishing by a grinding apparatus according to another embodiment. This diagram illustrates the misalignment state that occurs when a gear workpiece is mounted on a grinding apparatus.

[0017] Hereinafter, with reference to Figure 1, the grinding apparatus 100 according to Embodiment 1 of the present invention will be described in detail. In Figure 1, the grinding apparatus 100 is an apparatus for machining the tooth surface of a workpiece 90, and is, for example, an apparatus for performing honing as a finishing process.

[0018] The grinding apparatus 100 includes a main shaft 10, which is a rotating shaft having a first clutch 16, and a sub-shaft 20, which is a rotating shaft arranged parallel to the main shaft 10 and having a second clutch 26. The main shaft 10 and the sub-shaft 20 are rotatably held by a bearing device (not shown). It is also possible to provide a control unit for controlling the entire apparatus, such as controlling the operation of the first clutch 16 and the second clutch 26 and the rotational driving force.

[0019] The spindle 10 has a rotational force input section 12 and a first gear 40 on one side relative to the first clutch 16, and a second gear 50 and a workpiece holding section 14 on the other side. The rotational force input section 12 is a part on one side of the spindle 10 to which rotational force is input. A motor 92 is connected to the rotational force input section 12. Between the rotational force input section 12 and the first clutch 16, the first gear 40 is fixed to the spindle 10 and rotates together with the spindle 10. The workpiece holding section 14 is provided on the other side of the spindle 10, and the workpiece 90 is fixed to the workpiece holding section 14.

[0020] A second gear 50 is fixedly mounted to the spindle 10 between the workpiece holding section 14 and the first clutch 16, and rotates together with the mounting section of the spindle 10. The first gear 40 and the second gear 50 are external gears. The first clutch 16 can selectively connect or disconnect one side of the spindle 10 from the other side, and this selection operation may be controlled by a control unit (not shown) or by the operator manually. The rotational force input section 12 may be provided between the first gear 40 and the first clutch 16, and may be a gear attached to the spindle 10 and driven by a motor 92, for example.

[0021] The workpiece 90 is held by the workpiece holder 14 and finished by the grinding wheel 94. The rotation axis of the grinding wheel 94, which is formed on the internal gear, is positioned to have a predetermined axial intersection angle with respect to the main spindle 10. In this state, the grinding wheel 94, which is in contact with each tooth surface of the workpiece 90 on the external gear, grinds the workpiece 90. Note that the workpiece 90 may be an internal gear and the grinding wheel 94 may be an external gear.

[0022] The sub-shaft 20 has a third gear 60 on one side that meshes with the first gear 40 relative to the second clutch 26, and a fourth gear 70 on the other side that meshes with the second gear 50. Each gear is fixed to the sub-shaft 20 and rotates together with the mounting portion of the sub-shaft 20. The third gear 60 and the fourth gear 70 are formed as external gears. The second clutch 26 can selectively connect or disconnect one side of the sub-shaft 20 from the other side, and this selection operation is performed by a control unit (not shown) or manually.

[0023] In this embodiment, the sub-shaft 20 is shown to have additional third gears 62 and 64 in addition to the corrective gear 60. One corrective gear is sufficient to achieve the function of the present invention, and it is permissible for at least one of the gears provided on the main shaft 10 or the sub-shaft 20 to be a corrective gear. The function and effects of the additional third gears 62 and 64 will be described later.

[0024] Furthermore, the first gear 40 and the third gear 60, which mesh with each other, and the second gear 50 and the fourth gear 70, which mesh with each other, are all formed to have the same pitch circle diameter and the same number of teeth.

[0025] Here, the basic processing operation and functions of the grinding device 100 shown in Figure 1 above will be explained. In this embodiment, the configuration will be described as having only one corrective gear, the third gear 60. Configurations with multiple corrective gears will be described later as other embodiments.

[0026] The third gear 60 is installed such that the cumulative pitch error waveform of its tooth surface is different from the cumulative pitch error waveform of the workpiece 90 held on the spindle 10. Specifically, the number of periods per revolution of the third gear 60 is the same as the number of periods per revolution of the cumulative pitch error waveform of the workpiece 90, which is a sine wave, but the phase of the cumulative pitch error waveform is shifted by approximately 1 / 2 period. In other words, the cumulative pitch error waveforms of the third gear 60 and the workpiece 90 are sine waves with the same period, but they are installed with a phase shift so that the peaks and troughs are opposite.

[0027] The above-mentioned modified gear 60 can be manufactured by using a dressing gear for pre-grinding the gear, and grinding it so that it has the same cumulative pitch error waveform with the same period as the gear with the same number of teeth as the workpiece 90. Other modified gears used in the embodiments of the present invention can be manufactured by a similar process.

[0028] Figures 3 to 5 show the cumulative pitch error waveforms of a workpiece 90 and a corrective gear, the third gear 60, installed in the grinding device 100 described in Figure 1. Figure 3 shows the cumulative pitch error waveform of the workpiece 90 before finish grinding, held in the workpiece holder 14. Figure 4 shows the cumulative pitch error waveform of the corrective gear, the third gear 60, and Figure 5 shows the cumulative pitch error waveform of the corrected workpiece 90 after finish grinding. In Figures 3 to 5, the horizontal axis represents the rotational angle position of each gear from 0° to 360°, and the vertical axis represents the cumulative pitch error from 0° at each rotational angle position.

[0029] The processing flow of the grinding apparatus 100 having the above configuration will be explained based on the chart in Figure 6.

[0030] As shown in the figure, first, in step 1, the workpiece 90 to be machined is attached to the workpiece holding part 14 of the spindle 10.

[0031] Next, in step 2, the clutch switching operation is performed, and only the first clutch 16 is engaged. That is, the second clutch 26 is disengaged, and in this state, the rotational force from the motor 42 is transmitted only through the transmission path shown as A in the diagram.

[0032] Next, in step 3, the cumulative pitch error measurement process of the workpiece 90 is performed. With the clutch engaged as in step 2, the operator rotates the spindle 10 and meshes a master gear (not shown) with the mounted workpiece 90 to perform the measurement. This measurement detects the runout of the tooth grooves on each tooth surface of the workpiece 90, and from this, the pitch error with respect to the rotational angle position of the workpiece 90 and a numerical value corresponding to the cumulative pitch error waveform can be calculated, and the cumulative pitch error waveform can be obtained. Workpieces 90 whose cumulative pitch error is larger than a predetermined standard value and cannot be adjusted by meshing with a corrective gear are excluded as NG products, and the subsequent processes are not performed.

[0033] Next, in the correction gear selection step of step 4, since only one correction gear (third gear 60) is installed in this embodiment, the correction gear is not switched by sliding movement as described later. Instead, a gear with a common period and number of teeth is selected and installed as the third gear 60, corresponding to the cumulative pitch error waveform of the workpiece 90 detected above.

[0034] Next, in step 5, the clutch switching operation is performed again, and the engagement state of the second clutch 26 is released. That is, both the first clutch 16 and the second clutch are left unengaged. In this state, the phase alignment process of step 6 is performed, and the phase alignment of the workpiece 90 and the third gear 60 is performed. For example, the phase alignment of the two is performed by adjusting and matching the rotation reference position of the workpiece 90 detected by an encoder (not shown) and the rotation reference position of the third gear 60.

[0035] Specifically, the phase of the cumulative pitch error waveform of the workpiece 90 and the phase of the cumulative pitch waveform of the third gear 60 are adjusted to be approximately 1 / 2 cycle out of phase. That is, the peaks and troughs of the cumulative pitch error waveform of the workpiece 90 are in phase with the troughs and peaks of the cumulative pitch waveform of the third gear 60, and the workpiece 90 is prepared for machining with the pitch of the cumulative pitch error waveform of the workpiece 90 canceled out. The grinding device 100 can perform phase matching and grinding for any number of cumulative pitch waveform periods per revolution of 1 cycle or more.

[0036] During this phase alignment process, the first clutch 16 and the second clutch 26 are appropriately disengaged by the control unit or by the operator, and the third gear 60 and the workpiece 90 are rotated appropriately to perform the phase alignment.

[0037] Next, in step 7, the clutch is switched so that the first clutch 16 is disconnected and only the second clutch 26 is engaged. This creates a rotational force transmission path consisting only of the transmission path shown as B in the diagram. Although the present invention can be achieved even if machining is performed with both the first and second clutches 16 and 26 engaged, using only the transmission path B allows for the exclusion of the rotational movement of the spindle 10 itself, thereby making the operation of the correcting gear more precise.

[0038] In this state, by performing finishing machining with a grinding wheel as step 8, the amplitude of the cumulative pitch error waveform of the workpiece 90 can be canceled out by the opposite phase of the correcting gear, thereby reducing the amplitude of the cumulative pitch error waveform of the workpiece 90. Then, in step 9, the workpiece 90 is removed and a new workpiece is attached, allowing the work to continue.

[0039] Next, we will explain in detail the change in the sine wave of the workpiece 90, which has one period per revolution, as shown in Figures 3 to 5. The cumulative pitch error of the workpiece 90 is measured, as is well known, by mounting the workpiece 90 on the spindle 10 and meshing it with a master gear (not shown). For example, if a mounting error occurs due to misalignment during the pre-processing stage of the workpiece 90, the cumulative pitch error waveform will be a sine wave with one period per revolution, as shown in the figure. In the example of Figure 3, the maximum amplitude a of the cumulative pitch error waveform of the workpiece 90 is, for example, about 40 μm.

[0040] Figure 4 shows an example of the cumulative pitch error waveform of the third gear 60, which is a corrective gear. The gear used here has a cumulative pitch error waveform with the same number of periods per revolution as the cumulative pitch error waveform of the workpiece 90. In this embodiment, the waveform has an amplitude that is slightly smaller than the cumulative pitch error waveform of the workpiece 90.

[0041] And importantly, the cumulative pitch error waveform of the third gear 60 is set such that its phase is shifted by 1 / 2 with respect to the cumulative pitch error waveform of the workpiece 90 by the phase alignment in the above step 6. That is, the starting point of the peak of the cumulative pitch error waveform of the workpiece 90 coincides with the starting point of the valley of the third gear 60.

[0042] FIG. 5 shows the cumulative pitch error waveform of the workpiece 90 after grinding, which is corrected by meshing the third gear 60 of the waveform shown in FIG. 4 with the cumulative pitch error waveform of the workpiece 90 shown in FIG. 3. As shown in the figure, the cumulative pitch error waveform of the workpiece 90 after this correction has a sine wave waveform, but its amplitude is small. By this correction, the periodicity of the cumulative pitch error waveform of the workpiece 90 is weakened, and the occurrence of vibrations during meshing when the finished gear is used is reduced.

[0043] Next, another embodiment of the grinding apparatus 100 will be described. In the grinding apparatus 100 shown in FIG. 1, three third gears 60, 62, and 64 are provided as correction gears, and an example of selectively using these multiple correction gears will be described as another embodiment. That is, in the present embodiment, in the correction gear selection step of the above step 4, one of the three third gears 60, 62, and 64 is selected.

[0044] FIG. 2 is an enlarged partial explanatory view of a gear holding mechanism 86 that holds the third gears 60, 62, and 64 provided on the subshaft 20. The gear holding mechanism 86 has a mechanism that holds the three third gears 60, 62, 64 and can slide and select a gear that meshes with the first gear 40 from among these three correction gears. The third gears 60, 62, 64 rotate together with the mounting portion of the subshaft 20 on one side of the subshaft 20, and are all formed with the same pitch circle diameter and the same number of teeth, but their cumulative pitch error waveforms are different from each other, and any one of them can be meshed with the corresponding first gear 40 by sliding. For example, the three third gears 60, 62, 64 are each prepared with different pitches, amplitudes, and number of cycles of the cumulative pitch error waveform.

[0045] Further, the third gears 60, 62, 64 are fitted to a key 82 provided on the countershaft 20, held firmly on the countershaft 20 without play, and held slidably along the key 82 on the countershaft 20.

[0046] At a position facing the first gear 40 of the countershaft 20, serrations 84 are provided on the entire circumference. The third gears 60, 62, 64 can be respectively fitted to the serrations 84 by being slid, and various detections by the encoder 96-3 are possible in the fitted state. Thus, the gear holding mechanism 86 is constituted by the countershaft 20, the key 82, and the serrations 84.

[0047] In the grinding device 100, it is possible to select an optimal gear from the third gears 60, 62, 64 to reduce the amplitude of the cumulative pitch error waveform of the workpiece 90 and mesh it with the first gear 40.

[0048] Note that the gear holding mechanism that enables the plurality of correction gears to be selectively meshed on the countershaft 20 only needs to be a mechanism that can exchange the plurality of correction gears by some means and attach them to the countershaft 20 in a state of meshing with the first gear 40. That is, it is not limited to the above-described slide mechanism, and various mechanisms can be adopted, and the operator of the grinding device may manually replace and mount them.

[0049] In the present embodiment, the third gear 60 is a correction gear having a cumulative pitch error waveform of a sine waveform of two cycles. The third gear 62 is a correction gear having a cumulative pitch error waveform of a waveform that repeats valleys periodically although it is not a sine waveform of six cycles. And the third gear 64 is a correction gear having a cumulative pitch error waveform of a composite waveform in which a large one-cycle waveform is combined with a random waveform including irregular amplitudes. Hereinafter, the operation and function of the grinding device 100 provided with the three third gears 60, 62, 64 having the above configuration will be described.

[0050] First, Figure 7 shows the cumulative pitch error waveform of the workpiece 90 detected based on the cumulative pitch error measured in step 3 above. As shown in the figure, the workpiece 90 has two peaks, L1 and L2, and two troughs, M1 and M2, per rotation, and has a two-period sine wave. This two-period cumulative pitch error waveform is caused by distortion of the workpiece 90 itself. In the figure, the actual magnitude of the amplitude a of the cumulative pitch error waveform of the workpiece 90 is, for example, about 40 μm. Here, using the gear holding mechanism 86 shown in Figure 2 above, a third gear 60 having a waveform that matches the cumulative pitch error waveform of the workpiece 90 is selected and meshed with the first gear 40.

[0051] Figure 8 shows the cumulative pitch error waveform of the third gear 60. As shown in the figure, the number of periods per revolution is the same as the sine wave of the cumulative pitch error waveform of the workpiece 90. In this embodiment, the maximum value of the amplitude a of the cumulative pitch is approximately 20 μm. The phases of these cumulative pitch error waveforms of the workpiece 90 and the third gear 60 are shifted by 1 / 2 through the phase alignment in step 5 described above. That is, the starting point of the peak of the cumulative pitch error waveform of the workpiece 90 and the starting point of the trough of the third gear 60 are aligned.

[0052] Figure 9 shows the cumulative pitch error waveform applied to the workpiece 90 when the cutting process of step 7 is performed in this state. As shown in the figure, the amplitude of the two-period sine wave is approximately halved. In this way, the periodicity of the workpiece 90 is weakened, and the workpiece 90 finished in this manner exhibits low vibration when meshing with other gears in the mounted state.

[0053] Next, Figure 10 shows the cumulative pitch error waveform of the other workpiece 90 measured in step 3 above.

[0054] As shown in the figure, the cumulative pitch error waveform of this workpiece 90 is a sine wave with six periods, consisting of six peaks L1 to L6 and six troughs M1 to M6, due to causes related to the heat treatment process, etc. This is due to distortion that occurs during the manufacturing of the workpiece 90 itself, for example. In the figure, the actual magnitude of the amplitude a of the cumulative pitch error waveform of the workpiece 90 is, for example, about 40 μm. Here, using the gear holding mechanism 86 shown in Figure 2, the third gear 62 having a waveform that matches the cumulative pitch error waveform of the workpiece 90 is selected and meshed with the first gear 40.

[0055] Figure 11 shows the cumulative pitch error waveform of the selected third gear 62. As shown in the figure, it has the same 6 cycles as the sine wave of the cumulative pitch error waveform of the workpiece 90, and in this embodiment, the maximum amplitude of the cumulative pitch is about 20 μm. The phases of these cumulative pitch error waveforms of the workpiece 90 and the third gear 62 are set with a 1 / 2 phase shift by the phase alignment in step 5 described above. That is, the starting point of the peak of the cumulative pitch error waveform of the workpiece 90 and the starting point of the trough of the third gear 62 are aligned.

[0056] Figure 12 shows the cumulative pitch error waveform applied to the workpiece 90 when the cutting process of step 7 is performed in this state. As shown in the figure, the approximate sine wave with 6 periods has an amplitude of almost half. In this way, the periodicity of the workpiece 90 is weakened, and the workpiece 90 finished in this way will have low vibration when meshing with other gears in the mounted state. At the same time, vibration during the finishing process is also reduced.

[0057] Next, Figure 13 shows the cumulative pitch error waveform of yet another workpiece 90 measured in step 3 above. As shown in the figure, this workpiece 90 has a cumulative pitch error waveform which is a sine wave of one period, due to the state of misalignment that occurs, for example, when the workpiece 90 is mounted to the device. In the figure, the actual magnitude of the amplitude a of the cumulative pitch error waveform of the workpiece 90 is, for example, about 40 μm. Here, using the gear holding mechanism 86 shown in Figure 2 above, a third gear 64 having a waveform that matches the cumulative pitch error waveform of the workpiece 90 is selected and meshed with the first gear 40.

[0058] Figure 14 shows the cumulative pitch error waveform of the selected third gear 64. As shown in the figure, the cumulative pitch error waveform is a composite waveform that combines a large, one-period, out-of-phase fundamental waveform with a random waveform containing irregular amplitudes. The phases of these cumulative pitch error waveforms of the workpiece 90 and the third gear 64 are set with an approximate 1 / 2 phase shift by the phase alignment in step 5 described above.

[0059] Figure 15 shows the cumulative pitch error waveform applied to the workpiece 90 when the cutting process of step 7 is performed in this state. As shown in the figure, the cumulative pitch error waveform of the workpiece 90 is not only weakened in amplitude due to the composite wave of random waveforms, but also becomes a turbulent waveform with many dips and ridges. In this way, the periodicity of the workpiece 90 is further weakened, and the workpiece 90 finished in this way exhibits low vibration when meshing with other gears in the mounted state.

[0060] The following describes some modifications of the embodiments of the present invention described above.

[0061] The corrective gears in the grinding device 100 do not have to be the third gears 60, 62, and 64; the effects of the present invention can also be achieved by configuring the first gear 40, the second gear 50, and the fourth gear 70 as corrective gears.

[0062] Furthermore, the installation of the gear holding mechanism 86, in which multiple corrective gears are slidably held on the rotation axis, can be appropriately modified depending on which gear is to be used as the corrective gear.

[0063] There may be more than one correcting gear engaged in the transmission path B, and it is permissible for any multiple gears of the first gear 40, second gear 50, third gear 60, and fourth gear 70 to each be correcting gears having a cumulative pitch error waveform for grinding the workpiece 90. In that case, the cumulative pitch error waveforms of the multiple correcting gears are combined and transmitted to the workpiece 90 as a rotational force. The multiple correcting gears may include gears having random waveforms, which are aperiodic waveforms in which the pitches are formed irregularly, and correcting gears having sine waveforms.

[0064] It should be noted that the present invention is not limited to the embodiments and modifications described above, and various modifications are possible without departing from the spirit of the invention.

[0065] 10 Main spindle 12 Rotational force input section 14 Workpiece holding section 16 First clutch 20 Sub-spindle 26 Second clutch 40 First gear 50 Second gear 60, 62, 64 Third gear 70 Fourth gear 82 Key 84 Serration 86 Gear holding mechanism 90 Workpiece 92 Motor 94 Grinding wheel 96-1, 96-2, 96-3 Encoder 100 Grinding device

Claims

1. A gear grinding apparatus that rotatably holds a workpiece, which is a gear, and grinds the surface of the workpiece by engaging it with a grinding wheel, comprising: a main shaft to which rotational driving force is input at one end and which is capable of holding the workpiece at the other end; and at least one sub-shaft arranged parallel to the main shaft, wherein the main shaft has a first clutch for switching the one end side and the other end side between a connected state and a disconnected state, a first gear fixedly attached to the one end side with the first clutch in between, and a second gear fixedly attached to the other end side, wherein the sub-shaft has a second clutch for switching the one end side and the other end side between a connected state and a disconnected state, a third gear fixedly attached to the one end side with the second clutch in between and which engages with the first gear, and a fourth gear fixedly attached to the other end side and which engages with the second gear, A gear grinding apparatus characterized in that at least one of the first to fourth gears is a correction gear for correcting a cumulative pitch error waveform, which is a waveform showing the cumulative pitch error in the entire circumferential tooth surface region of the held and rotating workpiece, and the cumulative pitch error waveform of the correction gear mounted on the main spindle or sub-spindle is a sine wave with the same number of periods per revolution as the cumulative pitch error waveform of the workpiece held on the main spindle, and is installed with a phase shift of approximately 1 / 2 period relative to the cumulative pitch error waveform of the workpiece.

2. The gear grinding apparatus according to claim 1, characterized in that the cumulative pitch error waveform of the corrected gear is a waveform obtained by combining both a sine wave and a non-periodic waveform in which the pitch is formed unevenly.

3. The gear grinding apparatus according to claim 1 or 2, characterized in that a plurality of gears are prepared as the correcting gears, the main shaft and / or sub-shaft are provided with a gear holding mechanism that allows the plurality of correcting gears to be selectively meshed on the shafts, and the plurality of correcting gears are installed such that each has a different cumulative pitch error waveform.

4. A method for grinding gears using the gear grinding apparatus described in claim 1, characterized in that the connection of the first clutch is released and only the second clutch is connected, the rotational driving force is input to the main shaft to rotate it, and the rotational force is transmitted to the first gear, the third gear, the fourth gear, and the second gear in that order to rotate the workpiece and perform the grinding process.

5. A method for grinding a gear using the gear grinding apparatus described in claim 1, characterized in that, before the grinding operation, the connection of the second clutch is released, and only the first clutch is connected, and the spindle is rotated to detect the cumulative pitch error and the phase of the cumulative pitch error waveform of the workpiece.

6. A gear grinding method using the gear grinding apparatus described in claim 1, characterized in that, before the grinding operation, the connection of both the first and second clutches is released, and the relative angular position of the correcting gear with respect to the rotational angular position of the workpiece is made adjustable, as described in claim 3.

7. A gear grinding method using the gear grinding apparatus described in claim 1, comprising: a cumulative pitch error waveform detection step of rotating the spindle with only the first clutch of the first and second clutches engaged, measuring the cumulative pitch error of the workpiece, and detecting the cumulative pitch error waveform of the workpiece based on the measurement; a phase matching step of setting the phase of the sine wave of the cumulative pitch error waveform of the corrected gear and the cumulative pitch error waveform of the workpiece held on the spindle to a state where they are shifted by approximately 1 / 2 period; and a gear grinding method using the gear grinding apparatus, characterized in that at least the second clutch is engaged and the workpiece is ground using the grinding wheel.

8. A gear grinding method using the gear grinding apparatus described in claim 1, wherein a plurality of corrective gears are installed, and each has a different cumulative pitch error waveform; the main shaft and / or sub-shaft are provided with a gear holding mechanism that allows the plurality of corrective gears to be selectively meshed on the shafts; and the method further comprises a corrective gear selection step of selecting the corrective gear according to the cumulative pitch error of the workpiece.

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