Gear grinding device and method for grinding gear using said device
The gear grinding apparatus addresses cumulative pitch error waveforms by using corrective gears to alter rotational motion, effectively reducing meshing vibrations and noise during gear assembly through precise tooth surface finishing.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- SUBARU CORP
- Filing Date
- 2024-12-06
- Publication Date
- 2026-06-11
Smart Images
Figure JP2024043308_11062026_PF_FP_ABST
Abstract
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 same, and more particularly to a gear grinding device for finishing a tooth surface and a grinding method using the same. 【0002】 Conventionally, gears are used in various devices such as transmission devices. In the manufacture of gears, after processing the material, a tooth cutting process and heat treatment are performed, and then processes such as grinding of a reference surface are performed, and finally honing, which is a finishing process using a grinding stone, is performed. As a result, precise finishing of the tooth surface is achieved. The finishing process is performed, for example, by holding a workpiece, which is a gear, at one end of a rotating shaft and bringing the tooth surface of the workpiece into contact with a grinding stone, and rotating the rotating shaft by a rotation driving means. 【0003】 As described above, in the process of performing various grindings on a workpiece during the manufacturing process of a gear, due to an attachment error of the workpiece to the processing equipment, a state may occur in which the center hole of the gear, which is the workpiece, is displaced from the processing center, that is, a state of so-called core deviation. The state of the core deviation is shown in FIG. 10. The size of the deviation is shown exaggeratedly compared to the actual scale. The original center of the workpiece 90 is the portion C1 where the line L1 indicated by the dashed-dotted line intersects, but in the attached 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 around the center C2, that is, when processed in a state of core deviation, 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 indicating the cumulative pitch error in the entire circumferential tooth surface region (hereinafter simply referred to as "cumulative pitch error waveform") has periodicity. 【0004】 In addition, the shape of the gear may be distorted for various reasons even outside the grinding process. For example, due to hanging and holding after heat treatment, the outer peripheral shape of the workpiece may become slightly elliptical instead of a perfect circle. Also, when the inner peripheral portion of the workpiece is supported from the lower surface side and the workpiece is placed horizontally, the outer peripheral side may sag and the workpiece may be curved instead of having a planar shape. 【0005】 As described above, misalignment due to mounting errors of workpieces to processing equipment, and shape distortion during the manufacturing stage of the gears, remain as cumulative pitch error waveforms, which can cause deterioration of meshing vibrations during mounting and vibrations during finishing processes. 【0006】 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. 【0007】 Japanese Patent Publication No. 2023-95160 【0008】 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. 【0009】 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, which causes the generation of meshing vibrations when gears are mounted together due to the tooth shape accuracy of the gears, at the finishing stage. 【0010】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 meshing it with a grinding wheel, comprising: a main shaft capable of holding the workpiece; and at least one sub-shaft arranged parallel to the main shaft, wherein one end of the main shaft is a rotational force input section into which rotational driving force is input, and has a first gear near the one end and a second gear near the other end, and the other end is a workpiece holding section, wherein the sub-shaft has a third gear that meshes with the first gear near the one end and a fourth gear that meshes with the second gear near the other end, and 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 workpiece, The correcting gear is characterized in that the cumulative pitch error waveform when mounted on the main shaft or sub-shaft is a waveform with a different number of periods per revolution or a non-periodic waveform with an uneven pitch compared to the cumulative pitch error waveform of the workpiece in the held state. 【0011】 This configuration makes it possible to mitigate the periodicity of the cumulative pitch error waveform caused by the pitch error present in a workpiece that is misaligned during the finish grinding stage of the workpiece. Specifically, at least one of the first to fourth gears that transmit rotational motion between the two axes is a corrective gear, and grinding by the grinding wheel is performed with the rotational motion of the workpiece held on the spindle fluctuating due to the influence of the corrective gear. 【0012】 More specifically, the cumulative pitch error waveform of the workpiece is combined with the cumulative pitch error waveform of a corrective gear having a different number of periods per revolution or a different phase, thereby disrupting the periodicity of the cumulative pitch error of the workpiece held on the spindle. For example, a waveform that is a smooth sine wave due to misalignment becomes a distorted waveform. As a result, the periodicity of the workpiece's cumulative pitch error waveform is reduced, and vibrations such as meshing vibrations in the mounted workpiece and vibrations during finishing processes by grinding wheels are reduced. Note that there is no limit to one corrective gear; multiple gears may be installed. 【0013】According to the gear grinding apparatus and gear grinding method using the apparatus 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 making it possible to reduce meshing vibrations when the gear is mounted. 【0014】 This is a schematic diagram showing a grinding apparatus according to a basic embodiment of the present invention. This is a schematic diagram showing a grinding apparatus according to another embodiment of the present invention. This is an enlarged explanatory diagram of the holding mechanism of the correction gear of the grinding apparatus of Figure 3. This is a diagram showing an example of the cumulative pitch error of a workpiece before finishing. This is a diagram showing an example of the cumulative pitch waveform of the correction gear of the grinding apparatus of Figure 3. This is a diagram showing an example of the cumulative pitch error of a workpiece after finishing by the grinding apparatus of Figure 3. This is a diagram showing the steps of the grinding method according to an embodiment of the present invention. This is a diagram illustrating an example of the cumulative pitch waveform of the correction gear of a grinding apparatus according to another embodiment of the present invention. This is a diagram showing an example of the cumulative pitch waveform of the correction gear of a grinding apparatus according to another embodiment of the present invention. This is an explanatory diagram showing the misalignment of the workpiece. 【0015】 Hereinafter, a grinding apparatus 100 according to an embodiment of the present invention will be described in detail based on the drawings. 【0016】 Figure 1 is a schematic diagram showing the basic configuration of a grinding apparatus 100 according to an embodiment of the present invention. In the figure, the grinding apparatus 100 is a device that performs honing on a workpiece 90, which is a gear to be manufactured. As will be described later, it performs grinding by reducing the periodicity of the cumulative pitch error waveform of the workpiece 90. 【0017】 The grinding device 100 includes a main spindle 10, which is a rotating shaft, and a secondary spindle 20, which is a rotating shaft arranged parallel to the main spindle 10. The main spindle 10 and the secondary spindle 20 are rotatably held by a bearing device (not shown). In this embodiment, the main spindle 10 is provided with a first clutch 16 at approximately the center position, and the secondary spindle 20 is provided with a second clutch 26 at approximately the center position. These clutches have the function of switching between a connected state and a disconnected state for the main spindle 10 and the secondary spindle 20 at their respective clutch positions. 【0018】 One end of the spindle 10 is a rotational force input section 12 to which rotational force is transmitted. It has a first gear 40 on one side of the first clutch 16 and a second gear 50 on the other side. The other end is a workpiece holding section 14 that holds the workpiece 90, and the workpiece holding section 14 holds the workpiece 90 so that it rotates together with the spindle 10. A spindle motor 92, which is a rotational force supply means provided on one side of the spindle 10, is connected to the rotational force input section 12. The first gear 40 is located between the rotational force input section 12 and the first clutch 16, is fixedly mounted to the spindle 10, and rotates together with the spindle 10. 【0019】 On the other hand, the second gear 50 is located between the workpiece holder 14 and the first clutch 16, is fixed to the spindle 10, and rotates together with the spindle 10. The first gear 40 and the second gear 50 are formed as external gears. The selective switching of connection and disconnection between one side and the other side of the spindle 10 by the first clutch 16 may be performed by a control unit (not shown) or manually. The rotational force input unit 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. 【0020】 The workpiece 90 is held in the workpiece holder 14 and ground by the grinding wheel 94. The grinding wheel 94, which is formed as an internal gear, is held so as to be rotatable with its rotation axis having a predetermined axial intersection angle with respect to the main spindle 10, and grinds each tooth surface of the workpiece 90 as it rotates on the main spindle 10, which is an external gear. It is also permissible for the workpiece 90 to be an internal gear and the grinding wheel 94 to be an external gear. 【0021】 The sub-shaft 20 has a third gear 60 on one side and a fourth gear 70 on the other side, flanking the second clutch 26. The third gear 60 and the fourth gear 70 are fixed to the sub-shaft 20 and rotate together with it. The first gear 40 and the third gear 60 mesh, and the second gear 50 and the fourth gear 70 mesh. The connection and disconnection of one side of the sub-shaft 20 by the second clutch 26 is performed by a control unit (not shown) or manually. 【0022】 The first gear 40 and the third gear 60, and the second gear 50 and the fourth gear 70, which mesh with each other, are all formed with the same pitch circle diameter and the same number of teeth. At least one of the first gear 40 to the fourth gear 70 is a corrective gear, which will be described later; for example, in this embodiment, the third gear 60 is the corrective gear. The grinding device 100 performs grinding by the grinding wheel by transmitting rotational motion via the corrective gear, thereby varying the rotational motion of the workpiece 90 held on the spindle. 【0023】 Furthermore, it is not limited to just one corrected gear; multiple gears can be used as corrected gears. Additionally, it is possible to prepare multiple corrected gears and install them in a selectable configuration. 【0024】 The operation and functions of the grinding apparatus 100, which is the basic configuration of the present invention as shown in Figure 1, will be described below. 【0025】 First, the present invention can perform its function even when both the first clutch 16 and the second clutch 26 are engaged. Therefore, in embodiments of the present invention, it is permissible to use a continuous, integrated shaft as the main shaft 10 and sub-shaft 20, without the first clutch 16 and the second clutch 26. The function when both clutches are provided will be described later. 【0026】 In this embodiment, the third gear 60 is a corrective gear, and when this third gear 60 rotates while installed on the sub-shaft 20, its cumulative pitch error waveform is set to have a different waveform from the cumulative pitch error waveform of the workpiece 90. In this embodiment, for example, a non-periodic gear with uneven tooth surface pitch is used. By performing finishing work with the grinding device 100 configured in this way, the periodicity of the cumulative pitch error waveform generated in the workpiece 90 due to misalignment of the workpiece 90 is reduced. 【0027】In this embodiment, the rotational movement of the workpiece 90 held on the spindle 10 is affected by the third gear 60, which has a non-periodic cumulative pitch error waveform. Specifically, the non-periodic cumulative pitch error waveform is combined with the cumulative pitch error waveform of the workpiece 90, thereby disrupting the periodicity of the cumulative pitch error waveform of the workpiece 90 held on the spindle 10. In other words, the smooth sine wave waveform becomes a distorted waveform. The periodicity of the cumulative pitch error waveform of the workpiece 90 is reduced, thereby reducing meshing vibrations in the mounted workpiece and vibrations during finishing with a grinding wheel. 【0028】 Furthermore, the installation of the third gear 60 is not limited to a setting that has a non-periodic cumulative pitch error waveform as described above. Even if the waveform is periodic, the function of the present invention can be achieved as long as it has a different number of periods per revolution than the cumulative pitch error waveform of the workpiece 90. Moreover, it may also be a waveform that is a combination of two or more of these waveforms. 【0029】 Next, the specific processing operation of the grinding device 100 described in Figure 1 will be explained based on Figures 4 to 7. Figure 4 shows an example of the cumulative pitch error waveform of the workpiece 90 before finish grinding. Figure 5 shows the cumulative pitch error waveform of the third gear 60, which is a corrected gear. Furthermore, Figure 6 shows the cumulative pitch error waveform of the workpiece 90 after grinding. In Figures 4 to 6, the horizontal axis represents the rotational angle position of each gear from 0° to 360°, and the vertical axis represents the cumulative pitch amount from 0° at each rotational angle position. 【0030】 The grinding operation of the grinding apparatus 100 having the above configuration will now be described in more detail. As shown in the chart in Figure 7, in step 1, the target workpiece 90 is mounted. Next, in step 2, the clutch switching operation is performed, and only the first clutch 16 is engaged. Then, in step 3, the workpiece 90 is rotated only through the transmission path shown as A in the figure, and the runout of the tooth grooves of the workpiece 90 is detected by engaging the workpiece 90 with a master gear (not shown), and numerical values corresponding to the pitch error and cumulative pitch error waveform are calculated from there. 【0031】If it is detected that the workpiece 90 has a pitch error that cannot be adjusted by meshing the corrective gears, grinding is not performed on that workpiece 90, and it is replaced with another workpiece. 【0032】 Next, in step 4, a corrective gear is selected. This is done by selecting an appropriate gear from a pre-prepared set of gears with different cumulative pitch error waveforms when mounted on the shaft. For example, multiple corrective gears with cumulative pitch error waveforms of varying amplitudes are prepared, and the one suitable for reducing the periodicity of the waveform corresponding to the cumulative pitch error waveform of the workpiece 90 detected in step 3 is selected. 【0033】 Although not an essential step in this invention, it is also possible to adjust the phase of the cumulative pitch error waveform of the workpiece 90 and the third gear 60. If it is deemed that adjusting the phase would be more effective when combining the two waveforms with respect to the cumulative pitch error waveform of the workpiece 90 detected in step 3, this may be done. 【0034】 Then, in step 5, the clutch is switched so that the first clutch 16 is disconnected and only the second clutch 26 is engaged. As a result, only the transmission path shown as B in the diagram is formed. As described above, the function of the present invention can also be achieved by performing machining with both the first and second clutches 16 and 26 engaged, but by using only the above transmission path B, the rotational movement of the spindle 10 itself can be excluded, and the operation of the corrective gear can be made more precise. 【0035】 In this state, machining is performed as step 6, which is the finishing process. Below, we will explain in more detail how this machining process reduces the periodicity of the cumulative pitch error waveform of the workpiece 90. 【0036】Figure 4 shows an example of the cumulative pitch error waveform of the workpiece 90 used in the above machining operation, and it can be seen that it is a periodic sine wave. In this example, there is a sine wave with one period per rotation, but in the case of misalignment due to errors in the mounting condition of the workpiece 90 or grinding wheel 94 on the device, the cumulative pitch error waveform of the workpiece 90 is usually a sine wave with one period as shown above. In addition, in this embodiment, the maximum value of the amplitude a of the cumulative pitch error is about 40 μm for the workpiece 90 and about 5 μm for the correcting gear. 【0037】 Furthermore, Figure 5 shows an example of the cumulative pitch error waveform of the third gear 60. The gear used here has a cumulative pitch error waveform that is at least different from the cumulative pitch error waveform of the workpiece 90. In this embodiment, a non-periodic gear with a non-uniform cumulative pitch error waveform is used. 【0038】 Figure 6 shows the cumulative pitch error waveform of the workpiece 90 after grinding, which has been corrected by meshing it with the third gear 60, which has the waveform shown in Figure 5, compared to the cumulative pitch error waveform of the workpiece 90 shown in Figure 4. As shown in the figure, the cumulative pitch error waveform of the corrected workpiece 90 is not a smooth sine wave, but a waveform with fine irregularities. This correction disrupts the periodicity and regularity of the cumulative pitch error waveform of the workpiece 90, reducing the occurrence of vibrations when the machined gear is mounted. 【0039】 Then, in step 8, which is the final step, the workpiece 90 is removed from the device. 【0040】 Next, with reference to Figure 2, a grinding apparatus 102 according to another embodiment will be described. Processes that perform the same functions as the grinding apparatus 100 shown in Figure 1 are denoted by the same reference numerals, and their descriptions are omitted. 【0041】 A unique feature of the grinding device 102 is that it has a mechanism for installing three corrective gears, which are located on the left side of the clutch 26 of the sub-shaft 20 in the diagram. As shown in the diagram, additional third gears 62 and 64 are provided on both sides of the aforementioned third gear 60. 【0042】Figures 8 and 9 show the cumulative pitch error waveforms of the additional third gears 62 and 64, respectively. These third gears 62 and 64, like the third gear 60, are manufactured under the same conditions in terms of pitch circle diameter, number of teeth, etc., but are set to aperiodic waveforms with different amplitudes of the cumulative pitch error waveform. 【0043】 These waveforms only need to meet the conditions such as having a different number of cycles per rotation and a different phase from the cumulative pitch error waveform of the workpiece 90, and being an aperiodic waveform. In this embodiment, however, aperiodic non-uniform waveforms are used. The waveform of the third gear 62 shown in FIG. 8 has a smaller amplitude than the waveform of the third gear 60, that is, a waveform with a smaller pitch error is used. Also, the waveform of the third gear 64 shown in FIG. 9 has a larger amplitude than the waveform of the third gear 60. 【0044】 Thus, by installing gears having different cumulative pitch error waveforms as the additional correction gears and selectively meshing them, it becomes possible to more effectively cause fluctuations in the rotational motion generated in the workpiece 90. 【0045】 Next, an example of a gear holding mechanism 86 for holding a plurality of third gears 60, 62, and 64 according to another embodiment of the present invention so that they can be selectively meshed with the first gear 40 will be described. 【0046】 As shown in FIG. 2, the gear holding mechanism 86 is provided on the left side in the drawing of the clutch 26 of the sub-shaft 20 of the grinding device 102. FIG. 3 is a schematic configuration diagram showing an example of the configuration of the gear holding mechanism 86, and any mechanism that can slide the gear to be meshed with the first gear 40 among the three third gears 60, 62, and 64 is sufficient. The third gears 60, 62, and 64 are fitted to a key 82 provided on the sub-shaft 20, held firmly on the sub-shaft 20 without play, and held slidably on the sub-shaft 20. The number of the third gears 60, 62, and 64 may be the number required for correcting the cumulative pitch error of the workpiece 90, and may be any of one, two, three, or four or more. 【0047】In the portion where the first gear 40 of the countershaft 20 faces, serrations 84 are provided over the entire circumference. The third gears 60, 62, 64 are fixed by fitting into the serrations 84 respectively, slide along the key 82 on the countershaft respectively, and selectively mesh with the first gear 40. 【0048】 The grinding device 102 can select any one of the third gears 60, 62, 64 that has an aperiodic waveform optimal for the waveform of each workpiece 90, and mesh it with the engaging first gear 40. 【0049】 For example, in the case of a workpiece 90 with a relatively small amplitude, it is preferable to select a correction gear with a cumulative pitch error waveform having a small amplitude as shown in FIG. 8. 【0050】 Conversely, in the case of a workpiece 90 with a relatively large amplitude, it is preferable to select a correction gear with a cumulative pitch error waveform having a larger amplitude as shown in FIG. 9. By selecting a correction gear according to the amplitude of the workpiece 90 in this way, it is possible to avoid over-cutting or under-cutting of the workpiece 90. Therefore, the cumulative pitch error correction of the workpiece 90 can be performed efficiently and effectively. 【0051】 Hereinafter, based on FIG. 7, the grinding procedure of the workpiece 90 by the grinding device 102 according to another embodiment will be described. The description of the operations similar to those of the grinding device 100 according to FIG. 1 will be omitted or simplified. 【0052】 Regarding the workpiece mounting process in step 1, the operation is the same as that of the grinding device 100, and the operator mounts the workpiece 90 on the workpiece holding portion 14 of the main shaft 10. 【0053】In the cumulative pitch error measurement step of step 2, the operator measures the cumulative pitch error of the workpiece 90 in the same manner as in the conventional method. The measurement is performed by engaging the first clutch 16 and disengaging the second clutch 26, rotating the workpiece 90, and engaging a master gear (not shown). The grinding device 102 is equipped with a control unit (not shown), which detects the pitch error of each tooth surface, the rotational angle position of the workpiece, and the cumulative pitch error waveform based on the above measurement. Workpieces 90 whose cumulative pitch error is greater than a predetermined value are excluded from the finishing process. 【0054】 In step 4, the gear selection process, a gear for grinding is selected according to the detected cumulative pitch error waveform of the workpiece 90. The operator selects a gear from the third gears 60, 62, and 64 that has a more appropriate cumulative pitch error amount and waveform, taking into account the cumulative pitch error waveform of the workpiece 90. The determination of the optimal gear can be achieved, for example, by a control unit (not shown) that reads the pitch error of the workpiece 90 and selects the optimal gear. Alternatively, the operator may select an appropriate gear. 【0055】 In this invention, the correcting gear is basically a gear with a waveform different from the cumulative pitch error waveform of the workpiece 90, and any gear capable of changing the cumulative pitch error waveform of the workpiece 90 can perform its function, so it is permissible to select one as appropriate. The operator slides one of the selected third gears 60, 62, or 64 into a predetermined position and engages it with the first gear 40. 【0056】 The clutch switching process in step 5, the grinding process in step 6, and the workpiece removal process in step 7 are the same as the operation of the grinding device 100 described above. After removing the workpiece 90, if the operator wishes to continue working on another workpiece 90, they attach the new workpiece 90 and repeat steps 1 through 8. In this way, grinding is performed on all workpieces 90. 【0057】 The following describes some modifications of the embodiments of the present invention described above. 【0058】The corrective gears in the grinding device 102 may be other than the third gears 60, 62, and 64; the first gear 40, the fourth gear 70, and the second gear 50 may also be set as corrective gears. 【0059】 There may be more than one corrective gear engaged in the transmission path B. That is, any multiple gears of the first gear 40, third gear 60, fourth gear 70, and second gear 50 may each be corrective gears having a cumulative pitch error waveform for correction. In that case, the cumulative pitch error waveforms of the multiple corrective gears are combined and transmitted to the workpiece 90 as a rotational force. 【0060】 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. 【0061】 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 Third gear 62, 64 Additional third gear 70 Fourth gear 82 Key 84 Serration 86 Gear holding mechanism 90 Workpiece 92 Motor 94 Grinding wheel 100 Grinding apparatus according to an embodiment 102 Grinding apparatus according to another embodiment
Claims
1. A gear grinding apparatus that rotatably holds a workpiece, which is a gear, and grinds the surface of the workpiece by meshing it with a grinding wheel, comprising: a main shaft capable of holding the workpiece; and at least one sub-shaft arranged parallel to the main shaft, wherein one end of the main shaft is a rotational force input section into which rotational driving force is input, and has a first gear near the one end and a second gear near the other end, and the other end is a workpiece holding section, wherein the sub-shaft has a third gear that meshes with the first gear near the one end and a fourth gear that meshes with the second gear near the other end, and 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 workpiece, The gear grinding apparatus is characterized in that the corrected gear, when mounted on the main shaft or sub-shaft, has a waveform with a different number of periods per revolution or a non-periodic waveform with an uneven pitch compared to the cumulative pitch error waveform of the workpiece in the held state.
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 the waveforms with different periods per revolution and the non-periodic waveform.
3. The gear grinding apparatus according to claim 1 or 2, characterized in that the main shaft has a first clutch between the first gear and the second gear that can be switched between connecting and disconnecting the first gear side and the second gear side, and the sub-shaft has a second clutch between the third gear and the fourth gear that can be switched between connecting and disconnecting the third gear side and the fourth gear side.
4. The gear grinding apparatus according to claim 1 or 2, characterized in that the correction gears include gears having a plurality of different cumulative pitch error waveforms, and the plurality of correction gears are provided in an interchangeable manner.
5. A method for grinding gears using the gear grinding apparatus described in claim 1, wherein the main shaft has a first clutch between the first gear and the second gear that can be switched between connecting and disconnecting the first gear side and the second gear side, the sub-shaft has a second clutch between the third gear and the fourth gear that can be switched between connecting and disconnecting the third gear side and the fourth gear side, the first clutch is released and the rotational driving force is transmitted to the main shaft with only the second clutch engaged, the rotational force is transmitted to the first gear, the third gear, the fourth gear and the second gear in that order, the workpiece is rotated and the workpiece is ground.
6. A method for grinding a gear using the gear grinding apparatus described in claim 1, characterized in that, before the grinding operation of the workpiece, the connection of the second clutch is released and only the first clutch is connected, the spindle is rotated to measure the cumulative pitch error of the tooth surface of the workpiece, and the cumulative error waveform of the workpiece is detected.
7. A gear grinding method using the gear grinding apparatus described in claim 1, wherein the correction gears consist of a plurality of gears each having a different cumulative pitch error waveform, which are interchangeable, and one correction gear is selected from the plurality of correction gears and installed before the grinding operation of the workpiece, as described in claim 5.