Grinding spindle

Abstract

To provide a grinding spindle capable of ensuring durability and stability of a grinding wheel. [Solution] The present disclosure provides a grinding spindle 10 comprising a plurality of linearly extending shafts 11, 12, 13 and a transmission mechanism 14, 15 for transmitting rotation of one side shaft of adjacent ones of the plurality of shafts 11, 12, 13 on the power source 1 side to the other side shaft on the grinding wheel 2 side, the transmission mechanism 14, 15 having a drive bevel gear 16, 18 fixedly provided on the one side shaft and a driven bevel gear 17, 19 fixedly provided on the other side shaft and arranged opposite the drive bevel gear 16, 18, the rotation axis of the one side shaft and the rotation axis of the other side shaft are inclined to each other, the inclination angle between the rotation axis of the one side shaft and the rotation axis of the other side shaft is greater than or equal to 150 degrees and less than 180 degrees, and the speed transmission ratio between the drive bevel gears 16, 18 and the driven bevel gears 17, 19 is 1.

Description

[Technical field]

[0001] The present disclosure relates to a grinding spindle. [Background technology]

[0002] Patent Document 1 relates to a grinding spindle of a thread grinding machine for grinding a thread groove on the inner peripheral surface of a workpiece, and in particular discloses a grinding spindle of a thread grinding machine in which the rotation axis of a grinding wheel arranged at the tip of a quill is inclined with respect to the axis of the quill according to the lead angle of the thread groove formed on the inner peripheral surface of the workpiece. This grinding spindle is divided into two in the axial direction into a fixed side unit attached to a spindle housing and a tip side unit detachably connected to the tip of the fixed side unit and made replaceable. The fixed side unit is mainly composed of a fixed side quill and a flexible first drive shaft rotatably supported therein. The axial middle part of the first drive shaft is accommodated inside a through hole inclined with respect to the axis of the fixed side quill. The tip side unit is mainly composed of a tip side quill connected to the tip of the fixed side quill, a flexible second drive shaft and a grinding wheel shaft rotatably supported therein, and a disk-shaped grinding wheel attached to the tip of the grinding wheel shaft. The axis of rotation of the grinding wheel is inclined at a predetermined angle to the axis of the quill, the angle being set equal to the lead angle of the thread groove of the workpiece to be machined. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-91171 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the grinding spindle described in Patent Document 1, the rotation axis of the grinding wheel shaft is inclined with respect to the axis of the quill, and flexible drive shafts (first drive shaft and second drive shaft) are used in both the fixed side unit and the tip side unit, and power is transmitted from the spindle housing side to the grinding wheel via these flexible drive shafts.

[0005] However, grinding spindles may require high power and high speed rotation (e.g., 3.7 kW, 6,000 rpm, etc.). In such cases, it is difficult to ensure the life of the drive shaft to meet the requirements with a flexible drive shaft (e.g., a flexible shaft, etc.) or a universal joint, such as the drive shaft of the grinding spindle described in Patent Document 1. In addition, vibration of the drive shaft may cause the rotation of the grinding wheel to become unstable, making it difficult to ensure the desired surface roughness on the inner peripheral surface of the workpiece.

[0006] Therefore, an object of the present disclosure is to provide a grinding spindle that can ensure durability and stability of the grinding wheel. [Means for solving the problem]

[0007] In order to solve the above problems, a first aspect of the present invention is a grinding spindle that transmits power from a power source to a grinding wheel at a tip to rotate the grinding wheel, the grinding spindle comprising: a plurality of linearly extending shafts; and a transmission mechanism that transmits rotation of one of the plurality of shafts, which is adjacent to each other and is located on the power source side, to the other shaft on the grinding wheel side. The transmission mechanism has a drive bevel gear fixedly provided on the one shaft, and a driven bevel gear fixedly provided on the other shaft, which is disposed opposite the drive bevel gear and meshes with the drive bevel gear. The rotation axis of the one shaft and the rotation axis of the other shaft are inclined to each other, the inclination angle between the rotation axis of the one shaft and the rotation axis of the other shaft is greater than or equal to 150 degrees and less than 180 degrees, and the speed transmission ratio between the drive bevel gear and the driven bevel gear is 1.

[0008] A second aspect of the present invention is the grinding spindle of the first aspect, wherein the driving bevel gear and the driven bevel gear are spiral bevel gears.

[0009] A third aspect of the present invention is a grinding spindle according to the first or second aspect, wherein the surface roughness Ra of the tooth surfaces of the driving bevel gear and the driven bevel gear is 0.32 μm or less.

[0010] A fourth aspect of the present invention is the grinding spindle of the first or second aspect, wherein the outer diameter of the driving bevel gear and the driven bevel gear is 30 mm or less. Effect of the Invention

[0011] According to the present disclosure, it is possible to provide a grinding spindle capable of ensuring durability and stability of the grinding wheel. [Brief description of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view of a grinding spindle according to an embodiment of the present invention; [Diagram 2] FIG. [Diagram 3] FIG. 2 is an external perspective view of a bevel gear. [Figure 4] FIG. 4 is an enlarged view of a portion IV in FIG. [Diagram 5] FIG. 2 is a schematic diagram of a cross section of a bevel gear tooth. [Figure 6] FIG. [Figure 7] FIG. 7 is a cross-sectional view taken along the line VII-VII of FIG. 6. [Figure 8] This is a simulation result regarding durability when the service factor of a bevel gear is 1.0. [Figure 9] This is a simulation result regarding durability of a bevel gear when the service factor is 1.1. [Figure 10] This is a simulation result regarding durability of a bevel gear when the service factor is 1.2. [Figure 11] 1 is a table showing usage coefficients of bevel gears. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] FIG. 1 is a cross-sectional view of a grinding spindle according to an embodiment of the present invention. FIG. 2 is an explanatory diagram of a transmission mechanism. FIG. 3 is an external perspective view of a bevel gear. FIG. 4 is an enlarged view of part IV in FIG. 3. FIG. 5 is a schematic diagram of a cross section of a tooth of a bevel gear. Note that the shaft is not shown in FIG. 2. In the following description, the term "rotation axis" refers to the center of rotation (axial center).

[0015] As shown in Fig. 1, a grinding spindle 10 according to this embodiment is used as a part of an internal thread groove grinding machine (not shown) that grinds the internal thread groove of a ball nut, for example. In this internal thread groove grinding machine, the grinding spindle 10 is used at high speed, high output, and high torque. Specifically, for example, the operating speed of the grinding spindle 10 in the internal thread groove grinding machine is 6000 rpm or more and 12000 rpm or less, the maximum output is 3.7 kW, and the torque is 2.9 N m or more and 5.9 N m or less.

[0016] 1, the grinding spindle 10 is a device that transmits power from a power source 1 to a grinding wheel 2 at the tip thereof to rotate the grinding wheel 2. The rotation axis of the grinding wheel 2 (rotation axis CL3 of a third shaft 13 described later in this embodiment) is inclined with respect to the rotation axis of the power source 1 (rotation axis CL1 of a first shaft 11 described later in this embodiment) so as to correspond to the lead angle of the internal thread groove of the ball nut.

[0017] 1, the grinding spindle 10 includes a plurality of linearly extending shafts and a transmission mechanism for transmitting rotation of one of the plurality of adjacent shafts, which is located on the power source 1 side, to the other shaft, which is located on the grinding wheel 2 side. In this embodiment, the grinding spindle 10 includes three shafts 11, 12, and 13, and two transmission mechanisms 14 and 15. In the following description, "one side" refers to the driving side (the power source 1 side) in the power transmission direction, and "the other side" refers to the driven side (the grinding wheel 2 side).

[0018] The three shafts 11, 12, and 13 are disposed in a cylindrical case 3 and rotatably supported by the case 3 etc. (including the support member 4). The three shafts 11, 12, and 13 are a first shaft (shaft) 11 located closest to the power source 1, a second shaft (shaft) 12 located in the middle, and a third shaft (shaft) 13 located closest to the grinding wheel 2. The three shafts 11, 12, and 13 are rotatable about rotation axes CL1, CL2, and CL3 respectively that extend in the direction of their extension.

[0019] The first shaft 11 is supported by the support member 4 so as to be rotatable about a rotation axis CL1. The second shaft 12 is disposed adjacent to the first shaft 11 on the other side of the first shaft 11, and is supported by the case 3 so as to be rotatable about a rotation axis CL2. The rotation axes CL1 and CL2 are inclined relative to each other. The inclination angle θ1 between the rotation axes CL1 and CL2 is set to be equal to or greater than 150 degrees and less than 180 degrees. The other end of the first shaft 11 is connected to one end of the second shaft 12 via a transmission mechanism 14 so as to be capable of transmitting power.

[0020] The third shaft 13 is disposed adjacent to the second shaft 12 on the other side of the second shaft 12, and is supported by the case 3 so as to be rotatable about the rotation axis CL3. The rotation axis CL2 and the rotation axis CL3 are inclined to each other. In this embodiment, the rotation axis CL3 is inclined to the rotation axis CL2 in the opposite direction to the rotation axis CL1. The inclination angle θ2 (see FIG. 2) between the rotation axis CL2 and the rotation axis CL3 is set to be equal to or greater than 150 degrees and less than 180 degrees (for example, 167 degrees in this embodiment). In this embodiment, as shown in FIG. 1, the rotation axis CL1 and the rotation axis CL2, and the rotation axis CL2 and the rotation axis CL3 are inclined at the inclination angles θ1 and θ2 in the same cross section. The other end of the second shaft 12 is connected to one end of the third shaft 13 via a transmission mechanism 15 so as to be capable of transmitting power.

[0021] The transmission mechanisms 14 and 15 are transmission mechanisms that transmit the rotation (power) of one side shaft on the power source 1 side to the other side shaft on the grinding wheel 2 side among the multiple shafts 11, 12, and 13 that are adjacent to each other. Specifically, one transmission mechanism 14 of the two transmission mechanisms 14 and 15 is a transmission mechanism that transmits the rotation of the first shaft (one side shaft) 11 to the second shaft (other side shaft) 12. The other transmission mechanism 15 of the two transmission mechanisms 14 and 15 is a transmission mechanism that transmits the rotation of the second shaft (one side shaft) 12 to the third shaft (other side shaft) 13. That is, the one side shaft and the other side shaft are different concepts depending on the combination of the shafts adjacent to each other, and the same shaft can be a one side shaft or an other side shaft in relation to the other shaft. For example, the second shaft 12 is the other side shaft in relation to the first shaft 11, and is a one side shaft in relation to the third shaft 13.

[0022] Each of the transmission mechanisms 14 and 15 is formed by a combination of a pair of constant speed transmission bevel gears (spiral bevel gears).

[0023] The transmission mechanism 14 has a drive bevel gear 16 fixedly provided at the other end of the first shaft (one-side shaft) 11, and a driven bevel gear 17 fixedly provided at one end of the second shaft (other-side shaft) 12. The drive bevel gear 16 and the driven bevel gear 17 are spiral bevel gears. The drive bevel gear 16 and the driven bevel gear 17 have teeth (gradient teeth) twisted in opposite directions, and are disposed opposite to each other to mesh with each other. The drive bevel gear 16 and the driven bevel gear 17 have the same diameter and the same number of teeth. That is, the speed transmission ratio between the drive bevel gear 16 and the driven bevel gear 17 is 1. The speed transmission ratio is expressed by the formula (number of teeth of driven bevel gear / number of teeth of drive bevel gear).

[0024] The transmission mechanism 15 has a drive bevel gear 18 fixedly provided at the other end of the second shaft (one-side shaft) 12, and a driven bevel gear 19 fixedly provided at one end of the third shaft (other-side shaft) 13. The drive bevel gear 18 and the driven bevel gear 19 are spiral bevel gears. The drive bevel gear 18 and the driven bevel gear 19 have teeth (gradient teeth) twisted in opposite directions, and are disposed opposite to each other to mesh with each other. The drive bevel gear 18 and the driven bevel gear 19 have the same diameter and the same number of teeth. That is, the speed transmission ratio between the drive bevel gear 18 and the driven bevel gear 19 is 1. In this embodiment, the drive bevel gear 18 and the driven bevel gear 19 of the transmission mechanism 15 are formed to have a smaller diameter than the drive bevel gear 16 and the driven bevel gear 17 of the transmission mechanism 14. Although the two transmission mechanisms 14, 15 have different bevel gear sizes, they have approximately the same configuration. Therefore, in the following, we will explain the transmission mechanism 15 between the second shaft 12 and the third shaft 13, and will omit a detailed explanation of the transmission mechanism 14.

[0025] As shown in Figs. 2 to 5, the drive bevel gear 18 and the driven bevel gear 19 of the transmission mechanism 15 have teeth (gradient teeth) with opposite twist directions, and are disposed opposite to each other to mesh with each other. The outer diameters of the drive bevel gear 18 and the driven bevel gear 19 are 30 mm or less. Generally, in bevel gears with such a small diameter, the tooth contact is concentrated on the radially outer side, making it difficult to properly mesh with each other, and the transmission error becomes large. In the drive bevel gear 18 and the driven bevel gear 19 of this embodiment, the radius of curvature of the tooth surface on one side of the tooth gap 21 between the teeth 20 and the radius of curvature of the tooth surface on the other side facing this are appropriately set, so that the tooth contact is concentrated in the center part of the tooth surface, thereby reducing the transmission error.

[0026] The tooth surfaces of the drive bevel gear 18 and the driven bevel gear 19 may be formed symmetrically to each other, or may be formed differently from each other. In this embodiment, from the viewpoint of cost reduction, processing (adjustment) for concentrating the tooth contact at the center part of the tooth surface is performed on one gear, and normal grinding processing described later is performed on the other gear, so that the tooth surfaces of the drive bevel gear 18 and the driven bevel gear 19 are formed differently from each other.

[0027] As shown in Figs. 3 to 5, in the driving bevel gear 18, the radius of curvature r1 in the tooth width direction of the convex tooth surface 22 located on one side of the tooth groove 21 is made larger than the radius of curvature r2 in the tooth width direction of the concave tooth surface 23 located on the other side of the tooth groove 21. The radius of curvature r1 of the convex tooth surface 22 is the radius of curvature r1 of the largest part of the curved surface constituting the convex tooth surface 22, and the radius of curvature r2 of the concave tooth surface 23 is the radius of curvature r2 of the smallest part of the curved surface constituting the concave tooth surface 23. This allows the tooth contact to be concentrated at the center part of the tooth surface, thereby reducing the transmission error. Note that Fig. 5 is a cross-sectional view of the middle part of the tooth 20 in the height direction. In Fig. 5, the tooth surface is illustrated as a complete arc for ease of understanding, but is not limited thereto.

[0028] In this embodiment, the radius of curvature in the tooth width direction of the convex tooth flank of the driven bevel gear 19 is smaller than the radius of curvature in the tooth width direction of the concave tooth flank. That is, the size relationship between the radius of curvature in the tooth width direction of the convex tooth flank and the radius of curvature in the tooth width direction of the concave tooth flank is different between the drive bevel gear 18 and the driven bevel gear 19. This is because one gear (drive bevel gear 18) is subjected to grinding using two grinding wheels, which will be described later, in order to concentrate the tooth contact at the center of the tooth flank, while the other gear (driven bevel gear 19) is subjected to normal grinding using one grinding wheel in order to reduce costs.

[0029] The surface roughness Ra of the tooth surfaces (convex tooth surface 22 and concave tooth surface 23; the same applies below) of the drive bevel gear 18 and the driven bevel gear 19 is preferably 0.32 μm or less. By making the surface roughness Ra of the tooth surfaces of the drive bevel gear 18 and the driven bevel gear 19 0.32 μm or less, the frictional resistance between the drive bevel gear 18 and the driven bevel gear 19 can be reduced, and the life (durability) of the drive bevel gear 18 and the driven bevel gear 19 can be improved. The surface roughness Ra of the tooth surfaces can be measured, for example, in accordance with JIS B0601:2001. The relationship between the surface roughness Ra of the tooth surfaces and the life (durability) will be described in detail later.

[0030] Next, a method for manufacturing the bevel gear used for the drive bevel gear 18 of the grinding spindle 10 according to the present disclosure will be described.

[0031] Fig. 6 is an external perspective view of the grindstone. Fig. 7 is a cross-sectional view taken along line VII-VII in Fig. 6. Figs. 6 and 7 are explanatory diagrams of the shapes of the first grindstone 30A and the second grindstone 30B. The first grindstone 30A and the second grindstone 30B are separate members with different diameters, but the following description will use the same figures (Figs. 6 and 7).

[0032] The manufacturing method of the bevel gear (drive bevel gears 16, 18; the same applies below) according to the present disclosure includes a convex tooth flank grinding step and a concave tooth flank grinding step. Note that the manufacturing method of the bevel gear may include various other steps (blank step, gear cutting step, hardening step, etc.) in addition to the two steps of grinding the tooth flank (convex tooth flank grinding step and concave tooth flank grinding step).

[0033] In the convex tooth flank grinding process and the concave tooth flank grinding process, the tooth flank of the bevel gear is ground using cylindrical grindstones 30 having different diameters. The grindstone 30 has an annular protrusion 31 on one end side in the axial direction (the upper side in the figure).

[0034] 6 and 7, the protrusion 31 has a mountain-like shape tapering toward the tip T in an axial cross section of the central axis 30CL of the grindstone 30. An inner peripheral surface 32 and an outer peripheral surface 33 of the protrusion 31 having a mountain-like cross section are inclined with respect to the axial direction of the central axis 30CL.

[0035] In the convex tooth flank grinding process, the convex tooth flank 22 located on one side of the tooth groove 21 of the bevel gear is ground by an inner circumferential surface 32A on one end side of a cylindrical first grinding wheel 30A. The radius RA of the inner circumferential surface 32A at the tip T of the first grinding wheel 30A is set to, for example, 20.38 mm. When grinding the convex tooth flank 22 of the bevel gear, the first grinding wheel 30A is rotated about the central axis 30CL with the convex portion 31A of the first grinding wheel 30A inserted into the tooth groove 21 of the bevel gear to grind the convex tooth flank 22 of the bevel gear.

[0036] In the concave tooth surface grinding process, the concave tooth surface 23 located on the other side of the tooth groove 21 of the bevel gear is ground by the outer peripheral surface 33B on one end side of the cylindrical second grinding wheel 30B. The second grinding wheel 30B has a smaller diameter than the first grinding wheel 30A. Specifically, the radius RB of the outer peripheral surface 33B at the tip T of the second grinding wheel 30B is set to, for example, 19.13 mm. When grinding the concave tooth surface 23 of the bevel gear, the second grinding wheel 30B is rotated about the central axis 30CL with the convex portion 31B of the second grinding wheel 30B inserted into the tooth groove 21 of the bevel gear to grind the concave tooth surface 23 of the bevel gear. In addition, since the first grinding wheel 30A and the second grinding wheel 30B are described using the same figures (FIGS. 6 and 7), in FIG. 7 the radius RB is larger than the radius RA, but in reality the radius RB of the outer peripheral surface 33B of the second grinding wheel 30B is smaller than the radius RA of the inner peripheral surface 32A of the first grinding wheel 30A. In addition, the concave tooth flank grinding step is preferably performed after the convex tooth flank grinding step, but may be performed before the convex tooth flank grinding step.

[0037] In this embodiment, the radius of curvature in the tooth width direction of the convex tooth flanks of the driven bevel gears 17, 19 is smaller than the radius of curvature in the tooth width direction of the concave tooth flanks, so the convex and concave tooth flanks of the driven bevel gears 17, 19 can be ground using one grindstone 30. This makes it possible to reduce costs, unlike the case where the tooth flanks of both the drive bevel gears 16, 18 and the driven bevel gears 17, 19 are ground using two grindstones (the first grindstone 30A and the second grindstone 30B).

[0038] The grinding spindle 10 configured as above includes a plurality of shafts 11, 12, 13 and transmission mechanisms 14, 15 connecting them. The transmission mechanisms 14, 15 include driving bevel gears 16, 18 and driven bevel gears 17, 19 arranged opposite to the driving bevel gears 16, 18 and meshing with the driving bevel gears 16, 18. In this manner, the grinding spindle 10 transmits power from the power source 1 to the grinding wheel 2 at the tip by the driving bevel gears 16, 18 and the driving bevel gears 16, 18 arranged opposite to each other. Therefore, the inclination angles θ1, θ2 between the rotation axes CL1, CL2, CL3 of the adjacent shafts are 150 degrees or more and less than 180 degrees, the speed transmission ratio is 1, and even with high output and high speed rotation (for example, 3.7 kW 6,000 rpm), the life can be secured and the stability of the grinding wheel 2 can be secured, unlike flexible shafts and universal joints.

[0039] In this way, according to this embodiment, it is possible to provide a grinding spindle 10 capable of ensuring the durability and stability of the grinding wheel 2.

[0040] Furthermore, in the manufacturing method of the bevel gear configured as above, by going through the above-mentioned convex tooth flank grinding process and concave tooth flank grinding process, it is possible to make the radius of curvature r1 in the tooth width direction of the convex tooth flank 22 of the bevel gear larger than the radius of curvature r2 in the tooth width direction of the concave tooth flank 23 located on the other side of the tooth groove 21. Therefore, by using the bevel gear manufactured by the above manufacturing method as one of the gears of the grinding spindle 10 (in this embodiment, the drive bevel gears 16, 18), it is possible to reduce costs and concentrate the tooth contact in the center part of the tooth flank to reduce the transmission error even in the case of a small-diameter bevel gear.

[0041] In addition, as in this embodiment, it is preferable that the grinding spindle 10 transmits all of the power from the shaft (first shaft 11) disposed closest to the power source 1 to the grinding wheel 2 by the shaft and transmission mechanism according to the present disclosure. This can reliably ensure the durability and stability of the grinding wheel 2.

[0042] In this embodiment, the radius of curvature r1 of the convex tooth surface 22 of one gear (the driving bevel gears 16, 18) is larger than the radius of curvature r2 of the concave tooth surface 23 (r1>r2), but this is not limited to this. For example, the radius of curvature of the convex tooth surface of both the driving bevel gear and the driven bevel gear may be smaller than the radius of curvature of the concave tooth surface. Even in this case, by making the difference d1 of the radius of curvature between the convex tooth surface and the concave tooth surface of one gear larger than the difference d2 of the radius of curvature between the convex tooth surface and the concave tooth surface of the other gear (d1>d2), the tooth contact can be concentrated at the center of the tooth surface, thereby reducing the transmission error. In this case, the convex tooth surface and the concave tooth surface of the other gear, which have a smaller difference in the radius of curvature, can be ground with one grinding wheel 30, as in the case of the driven bevel gears 17, 19 described above. On the other hand, when grinding the convex tooth surface and the concave tooth surface of one gear having a large difference in the radius of curvature, if one grinding wheel 30 is used, the thickness of the convex part 31 of the grinding wheel 30 becomes too large to be inserted into the tooth groove 21 due to the large difference in the radius of curvature. For this reason, when grinding the convex tooth surface and the concave tooth surface of one gear having a large difference in the radius of curvature, two grinding wheels 30 with different radii may be used. Note that if the difference d1 in the radius of curvature between the convex tooth surface and the concave tooth surface of one gear is made larger than the difference d2 in the radius of curvature between the convex tooth surface and the concave tooth surface of the other gear (d1>d2), the tooth contact tends to be extremely small or extremely large, so that it is necessary to set the tooth contact to an appropriate size, and it may take time to adjust the size of the tooth contact during processing. For this reason, from the viewpoint of ease of processing, it is preferable to make the radius of curvature r1 of the convex tooth flank 22 of one gear larger than the radius of curvature r2 of the concave tooth flank 23 (r1>r2) as in this embodiment.

[0043] Next, the relationship between the surface roughness Ra of the tooth surfaces of the drive bevel gear and the driven bevel gear and their life (durability) will be described.

[0044] FIG. 8 shows the results of a simulation of durability when the bevel gear service factor is 1.0. FIG. 9 shows the results of a simulation of durability when the bevel gear service factor is 1.1. FIG. 10 shows the results of a simulation of durability when the bevel gear service factor is 1.2. FIG. 11 is a table showing the service factors of bevel gears. In FIG. 8 to FIG. 11, the vertical axis on the left indicates the life (hours), the vertical axis on the right indicates the safety factor of the tooth root and tooth surface, and the horizontal axis indicates the gear accuracy grade (JIS B 1702-1:1998). The service factor (KA) of a gear is a factor that takes into account the influence of external dynamic loads, and is specified in ISO 6336 and JGMA 6101 / 6102. FIG. 11 shows ISO 6336.

[0045] As shown in Figures 8 to 11, a simulation was performed on the relationship between the surface roughness Ra of the tooth surface of the drive bevel gear and the driven bevel gear and their lifespan (durability) for three gear usage coefficients (1.0, 1.1, 1.2). This simulation was performed using KISSsoft and calculations in accordance with ISO10300. In this simulation, the diameter of both the drive bevel gear and the driven bevel gear (spiral bevel gear) was 30 mm, the number of teeth was 20, the pressure angle was 20 degrees, the inclination angle between both rotation axes was 167 degrees, the tooth twist angle was 28 degrees, the tooth width was 4 mm, the tooth depth was 3 mm, the material was 18CrNiMo7-6, carburized and hardened, the surface hardness was HRC61, and the deep hardness was HBW325, and the operating conditions were set to 3.7 kW, 6,000 rpm.

[0046] As shown in Figs. 8 to 11, it was confirmed that the life of the bevel gears is longer when the gear accuracy grade is "4" or higher (0 to 4) for the three service coefficients (1.0, 1.1, 1.2) of the bevel gears. In particular, it was confirmed that the life of the tooth flanks is significantly longer for the service coefficients (1.0, 1.1) for the gear accuracy grade of "4" or higher. Bevel gears with gear accuracy grades of "4" or higher are bevel gears whose tooth flanks are ground and finished, and whose surface roughness Ra of the tooth flanks is 0.32 μm or less. In other words, it was confirmed that by setting the surface roughness Ra of the tooth flanks of the drive bevel gear and the driven bevel gear to 0.32 μm or less, the frictional resistance between the drive bevel gear and the driven bevel gear can be reduced, and the life (durability) of the drive bevel gear and the driven bevel gear can be improved.

[0047] In this embodiment, the grinding spindle 10 includes three shafts 11, 12, and 13 and two transmission mechanisms 14 and 15, but the number of shafts and transmission mechanisms is not limited to this. The grinding spindle 10 may include at least two shafts and at least one transmission mechanism provided between the two shafts.

[0048] In addition, in this embodiment, the entire power transmission from the shaft (first shaft 11) of the grinding spindle 10 located closest to the power source 1 to the grinding wheel 2 is performed by the shaft and the transmission mechanism according to the present disclosure, but this is not limited to this. The shaft and the transmission mechanism according to the present disclosure may be applied to only a part of the power transmission from the shaft (first shaft 11) located closest to the power source 1 to the grinding wheel 2. For example, the grinding spindle 10 may apply the transmission mechanism 15 between the second shaft 12 and the third shaft 13, and apply another transmission mechanism different from that disclosed in the present disclosure between the first shaft 11 and the second shaft 12.

[0049] Although the present invention has been described based on the above embodiment, the present invention is not limited to the contents of the above embodiment, and can be modified as appropriate without departing from the scope of the present invention. In other words, all other embodiments, examples, and operational techniques made by those skilled in the art based on this embodiment are naturally included in the scope of the present invention. [Explanation of symbols]

[0050] 1: Power source 2: Grinding wheel 10: Grinding spindle 11: First shaft (shaft) 12: Second shaft (shaft) 13: 3rd shaft (shaft) 14, 15: Transmission mechanism 16,18: Drive bevel gear 17, 19: Driven bevel gear 20: Teeth 21:Tooth groove 22: Convex tooth surface 23: Concave tooth surface 30: Grindstone 30A: First whetstone 30B: Second whetstone 32A: Inner surface 33B: Outer surface

Claims

1. A grinding spindle that transmits power from a power source to a grinding wheel at a tip end to rotate the grinding wheel, A plurality of linearly extending shafts; a transmission mechanism for transmitting rotation of one of the shafts on the power source side of adjacent shafts of the plurality of shafts to the other shaft on the grinding wheel side, the transmission mechanism includes a drive bevel gear fixedly provided on the one-side shaft, and a driven bevel gear fixedly provided on the other-side shaft, disposed opposite the drive bevel gear, and meshing with the drive bevel gear; The rotation axis of the one-side shaft and the rotation axis of the other-side shaft are inclined to each other, The inclination angle between the rotation axis of the one side shaft and the rotation axis of the other side shaft is equal to or greater than 150 degrees and less than 180 degrees, The transmission ratio between the driving bevel gear and the driven bevel gear is 1.

1. A grinding spindle comprising:

2. The driving bevel gear and the driven bevel gear are spiral bevel gears.

2. The grinding spindle according to claim 1 .

3. The surface roughness Ra of the tooth surfaces of the driving bevel gear and the driven bevel gear is 0.32 μm or less.

3. A grinding spindle according to claim 1 or 2.

4. The outer diameter of the driving bevel gear and the driven bevel gear is 30 mm or less.

3. A grinding spindle according to claim 1 or 2.

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