Backlash adjustment gear

Abstract

The present invention provides a backlash adjustment gear that can suppress the progression of wear caused by the rotation of the external teeth of gears that mesh with each other. [Solution] This backlash adjustment gear 100 includes a gear body 1 which has a plurality of external teeth 11 and a central hole 14 that penetrates the central portion in the axial direction, and is provided with a slit 15 extending along the axial direction from the axial end face 11d (11e), and an adjustment member 2 (3) which includes an outer peripheral surface 21a (31) that abuts against the central hole 14 of the gear body 1, and adjusts the diameter D of the gear body 1 by changing the width We of the slit 15 when the outer peripheral surface 21a (31) abuts against the inner peripheral surface 14a of the central hole 14 of the gear body 1 and presses outward.

Description

Technical Field

[0005] , ,

[0001] The present invention relates to a backlash adjusting gear.

Background Art

[0002] Conventionally, a backlash adjusting gear has been known (see, for example, Patent Document 1).

[0003] In the above Patent Document 1, a Cizers gear for adjusting backlash is disclosed. This Cizers gear includes a main gear, a sub gear, and a coil spring. The main gear and the sub gear are axially overlapped. The coil spring is configured to bias the sub gear with respect to the main gear so that the phases of the outer teeth of the main gear and the outer teeth of the sub gear are shifted. Thereby, in a plurality of adjacent outer teeth of the gears meshing with the Cizers gear, one of the plurality of outer teeth and the outer teeth of the main gear abut against each other by the biasing force of the coil spring, and the other of the plurality of outer teeth and the outer teeth of the sub gear abut against each other by the biasing force of the coil spring. Thereby, the backlash between the Cizers gear and the gear meshing with the Cizers gear is adjusted.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the scissors gear described in Patent Document 1, the biasing force of the coil spring causes the scissors gear and the gear that meshes with the scissors gear to press against each other, resulting in zero backlash. When the backlash is reduced to zero by the biasing force of the coil spring, the external teeth of the scissors gear and the external teeth of the gear that meshes with the scissors gear come into closer contact with each other by the amount of the biasing force of the coil spring. As a result, when the scissors gear rotates, the external teeth of the gears, which are now in closer contact, mesh together as they rotate, which can lead to increased wear on the external teeth of the gears. Therefore, there is a need to realize a structure that can suppress the progression of wear on the gears that mesh with each other as the gears rotate.

[0006] This invention was made to solve the above-mentioned problems, and one of its objectives is to provide a backlash adjustment gear that can suppress the progression of wear between gears that mesh with each other as the gear rotates. [Means for solving the problem]

[0007] A backlash adjustment gear in one aspect of this invention comprises a gear body having a plurality of external teeth and a central hole that penetrates the central portion axially, and a slit extending axially from the axial end face, and an adjustment member having an outer peripheral surface that abuts the central hole of the gear body, and adjusting the diameter of the gear body by changing the width of the slit when the outer peripheral surface abuts against the inner peripheral surface of the central hole of the gear body and presses outward. [Effects of the Invention]

[0008] By adjusting the pressure exerted by the outer circumferential surface of the adjustment member on the outer circumferential surface of the central hole of the gear body, and by adjusting the change in the width of the slit, the diameter of the gear body is adjusted, thereby adjusting the radial position of the gear body's external teeth. This adjusts the insertion position of the gear body's external teeth in the space between the external teeth of the mating gear, allowing for appropriate adjustment of the amount of backlash between the gear body and the mating gear that meshes with it, according to the insertion position. As a result, the progression of wear on the meshing gears due to the rotation of the gears can be suppressed. Furthermore, since the amount of backlash between the gear body and the mating gear can be appropriately adjusted, an oil film of appropriate thickness can be secured between the external teeth of the gear body and the external teeth of the mating gear that meshes with it. As a result, reliable lubrication can be ensured between the external teeth of the gear body and the external teeth of the mating gear that meshes with it. Furthermore, since the amount of backlash between the gear body and the gear that meshes with it can be adjusted without using a spring, it is possible to avoid both a decrease in the power transmission efficiency of the gear body caused by the biasing force of the spring, and a decrease in the rotational position accuracy of the gear body caused by the expansion and contraction of the spring. [Brief explanation of the drawing]

[0009] [Figure 1] This is an exploded perspective view showing the overall configuration of the backlash adjustment gear according to the first embodiment. [Figure 2] This is a cross-sectional view along line II-II in Figure 1. [Figure 3] This is a front view of the gear body of the backlash adjustment gear in its non-expanded diameter state according to the first embodiment, viewed from the axial direction. [Figure 4] This is a magnified view of the Zm1 portion of Figure 3. [Figure 5] This is a cross-sectional view of the backlash adjustment gear according to the first embodiment, in the enlarged state where the gear body is enlarged by tapered bolts and tapered nuts. [Figure 6] This is a front view of the gear body of the backlash adjustment gear in the enlarged diameter state according to the first embodiment, viewed from the axial direction. [Figure 7]This is a magnified view of the Zm2 portion of Figure 6. [Figure 8] This is an exploded perspective view showing the overall configuration of the backlash adjustment gear according to the second embodiment. [Figure 9] This is a cross-sectional view showing the overall configuration of the backlash adjustment gear according to modifications of the first and second embodiments. [Modes for carrying out the invention]

[0010] The following describes embodiments of the present invention based on the drawings.

[0011] [First Embodiment] (Backlash adjustment gear) Referring to Figures 1 to 7, the configuration of the backlash adjustment gear 100 according to the first embodiment of the present invention will be described.

[0012] The backlash adjustment gear 100 is a gear capable of adjusting the amount of backlash Ma between the backlash adjustment gear 100 and the gear it meshes with. The backlash adjustment gear 100 is a gear configured to rotate by a shaft 200. The backlash adjustment gear 100 is used, for example, as a planetary gear and sun gear in a planetary gear mechanism of a reduction gear, as well as as one of two gears with different numbers of teeth. This allows for adjustment of the backlash Ma in the reduction gear, and adjustment of the backlash Ma of the idler gear. This adjustment of backlash Ma is performed with the backlash adjustment gear 100 and the gear it meshes with assembled. The configuration of such a backlash adjustment gear 100 is described below.

[0013] As shown in Fig. 1, the backlash adjusting gear 100 includes a gear body 1, a taper bolt 2, and a taper nut 3. Note that the combined structure of the taper bolt 2 and the taper nut 3 is an example of the "adjusting member" in the claims. Also, the taper bolt 2 is an example of the "bolt" in the claims. Further, the taper nut 3 is an example of the "nut" in the claims.

[0014] Here, the axial direction of the gear body 1 is defined as the Ax direction, the side of the taper bolt 2 in the Ax direction is defined as the Ax1 direction, and the side of the taper nut 3 in the Ax direction is defined as the Ax2 direction. Also, the radial direction of the gear body 1 is defined as the R direction, the outer side in the R direction is defined as the R1 direction, and the inner side in the R direction is defined as the R2 direction. Further, the circumferential direction of the gear body 1 is defined as the θ direction, one side in the θ direction is defined as the θ1 direction, and the other side in the θ direction is defined as the θ2 direction.

[0015] (Gear body) As shown in Fig. 1, the gear body 1 is a spur gear made of metal. The gear body 1 includes a plurality (16) of external teeth 11, a plurality (16) of tooth bottoms 12, a central portion 13, a central hole 14, and a plurality (32) of slits 15. Note that the plurality (16) of external teeth 11 may be other than 16. Also, the plurality (16) of tooth bottoms 12 may be other than 16. Further, the plurality (16) of slits 15 may be other than 16.

[0016] 〈External teeth〉 Each of the plurality of external teeth 11 protrudes radially outward (R1 direction) from the central portion 13. Each of the plurality of external teeth 11 has a tapered shape toward the radially outer side (R1 direction). Each of the plurality of external teeth 11 is arranged at equal angular intervals in the circumferential direction (θ direction). Each of the plurality of external teeth 11 extends along the axial direction (Ax direction).

[0017] Each of the plurality of external teeth 11 has a top surface 11a, a tooth surface 11b, a tooth surface 11c, an end surface 11d, and an end surface 11e. The top surface 11a is the radially outer (R1 direction) surface of each of the plurality of external teeth 11. The tooth surface 11b and the tooth surface 11c are the tooth surfaces on the θ1 direction side and the tooth surfaces on the θ2 direction side of each of the plurality of external teeth 11, respectively. The tooth surface 11b on the θ1 direction side is inclined from the top surface 11a toward the θ1 direction side with respect to the radial direction (R direction). The tooth surface 11c on the θ2 direction side is inclined from the top surface 11a toward the θ2 direction side with respect to the radial direction (R direction). The end surface 11d and the end surface 11e are the end surfaces on the Ax1 direction side and the end surfaces on the Ax2 direction side of each of the plurality of external teeth 11, respectively. The end surface 11d on the Ax1 direction side extends along the radially inner side (R1 direction) from the Ax1 direction side end of the top surface 11a. The end surface 11e on the Ax2 direction side extends along the radially inner side (R1 direction) from the Ax2 direction side end of the top surface 11a.

[0018] 〈Tooth bottom〉 Each of the plurality of tooth bottoms 12 is provided between adjacent external teeth 11 among the plurality of external teeth 11. Each of the plurality of tooth bottoms 12 is recessed radially inward (R2 direction) from the portion between adjacent external teeth 11. Each of the plurality of tooth bottoms 12 has a tapered arc shape toward the radially inner side (R2 direction). Each of the plurality of tooth bottoms 12 is arranged at equal angular intervals in the circumferential direction (θ direction). Each of the plurality of tooth bottoms 12 extends along the axial direction (Ax direction).

[0019] Each of the plurality of tooth bottoms 12 has a tooth bottom surface 12a. The tooth bottom surface 12a is the radially outer (R1 direction) surface of each of the plurality of tooth bottoms 12. The tooth bottom surface 12a has an arc shape when viewed from one side (Ax1 direction side) in the axial direction.

[0020] 〈Central side portion and central hole〉 The central portion 13 is the portion between the multiple tooth roots 12 and the central hole 14 in the radial direction (R direction). The central hole 14 penetrates the central portion of the central portion 13 of the gear body 1 in the axial direction (Ax direction). The central hole 14 has an inner circumferential surface 14a. The inner circumferential surface 14a has a circular shape when viewed from the axial direction (Ax direction). The inner circumferential surface 14a extends along the axial direction (Ax direction).

[0021] <slit> As shown in Figure 1, each of the multiple slits 15 is formed to extend radially (R direction) so as to connect the tooth root 12 and the central hole 14 of the gear body 1. The multiple slits 15 have one side slit 15a and the other side slit 15b.

[0022] One side slit 15a extends from the end face 11d on the Ax1 direction side along the Ax2 direction. The one side slit 15a extends from the end face 11d on the Ax1 direction side to a position closer to the Ax1 direction than the end face 11e on the Ax2 direction side. That is, the one side slit 15a extends from the end face 11d on the Ax1 direction side to a position between the end face 11d and the end face 11e.

[0023] The other slit 15b extends from the end face 11e on the Ax2 direction side along the Ax1 direction. The other slit 15b extends from the end face 11e on the Ax2 direction side to a position closer to the Ax2 direction than the end face 11d on the Ax1 direction side. That is, the other slit 15b extends from the end face 11e on the Ax2 direction side to a position between the end face 11d and the end face 11e.

[0024] Each of the slits 15a on one side and 15b on the other side extends to a position where they overlap each other in the axial direction (Ax direction). That is, the tip position of the slit 15a on the Ax2 direction side is located further to the Ax2 direction than the tip position of the slit 15b on the Ax1 direction side. Also, the tip position of the slit 15b on the Ax1 direction side is located further to the Ax1 direction than the tip position of the slit 15a on the Ax2 direction side.

[0025] (Tapered bolts and tapered nuts) As shown in Figure 2, the tapered bolt 2 and tapered nut 3 are components inserted into the central hole 14 of the gear body 1. Both the tapered bolt 2 and tapered nut 3 are made of metal. A shaft 200 for rotating the gear body 1 passes through each of the tapered bolt 2 and tapered nut 3.

[0026] <Tapered bolt> The tapered bolt 2 has a head 21, a male threaded portion 22, and a tightening groove 23.

[0027] The head 21 has a larger diameter than the male threaded portion 22. The head 21 has an outer circumferential surface 21a on the bolt head side. The outer circumferential surface 21a on the bolt head side is the radially outer (R1 direction) side of the head 21. The outer circumferential surface 21a on the bolt head side extends along the circumferential direction (θ direction). In a cross-section along the axial direction (Ax direction), the outer circumferential surface 21a on the bolt head side has a tapered shape in which the diameter increases from the central Gc side of the gear body 1 toward the end face 11d (towards the Ax1 direction). That is, the outer circumferential surface 21a on the bolt head side is a frustoconical surface. Thus, the outer circumferential surface 21a on the bolt head side has an inclined surface that extends in a direction intersecting the axial direction (Ax direction). This outer circumferential surface 21a on the bolt head side abuts against the inner circumferential surface 14a of the central hole 14 of the gear body 1. Note that the outer circumferential surface 21a on the bolt head side is an example of the "outer circumferential surface" in the claims.

[0028] The male threaded portion 22 is configured to screw into the female threaded portion 32 of the tapered nut 3, which will be described later. The male threaded portion 22 extends in the Ax2 direction from the end face of the head 21 on the Ax2 direction side. The tightening groove 23 is a groove into which a hex wrench is inserted for tightening the tapered bolt 2 into the tapered nut 3. The tightening groove 23 is formed as a recess in the Ax2 direction from the end face of the head 21 on the Ax1 direction side.

[0029] <Tapered nut> As shown in Figure 2, the tapered nut 3 has a nut-side outer circumferential surface 31, a female thread portion 32, and a pair of tightening surfaces 33. Note that the nut-side outer circumferential surface 31 is an example of the "outer circumferential surface" in the claims.

[0030] The nut-side outer circumferential surface 31 is the radially outer (R1 direction) circumferential surface of the tapered nut 3. The nut-side outer circumferential surface 31 extends along the circumferential direction (θ direction). In a cross-section along the axial direction (Ax direction), the nut-side outer circumferential surface 31 has a tapered shape in which the diameter increases from the central Gc side of the gear body 1 toward the end face 11e (towards the Ax2 direction). In other words, the nut-side outer circumferential surface 31 is a frustoconical surface. Thus, the nut-side outer circumferential surface 31 has an inclined surface that extends in a direction intersecting the axial direction (Ax direction). This nut-side outer circumferential surface 31 abuts against the inner circumferential surface 14a of the central hole 14 of the gear body 1.

[0031] The female thread portion 32 is configured to screw onto the male thread portion 22 of the tapered bolt 2. The female thread portion 32 is formed from the end face on the Ax1 direction side to the end face on the Ax2 direction side of the tapered nut 3. The pair of tightening surfaces 33 are surfaces that are gripped by a wrench used to tighten the tapered bolt 2 into the tapered nut 3. The pair of tightening surfaces 33 are formed by cutting out the end of the tapered bolt 2 on the Ax2 direction side.

[0032] (Regarding backlash adjustment) As shown in Figures 2 to 7, the backlash adjustment gear 100 of this embodiment is configured such that the width We of the slits 15 (one-sided slit 15a and the other-sided slit 15b) changes, thereby adjusting the diameter D of the gear body 1, when the outer circumferential surface 21a on the bolt head side and the outer circumferential surface 31 on the nut side come into contact with the inner circumferential surface 14a of the central hole 14 of the gear body 1 and press radially outward (towards the R1 direction).

[0033] In other words, even if the backlash adjustment gear 100 is designed so that the backlash between the gear body 1 and the mating gear 300 that meshes with the gear body 1 is zero, the tolerances of the gear body 1 and the gear 300 will cause them to press against each other. In this state, the resistance between the gear body 1 and the gear 300 will prevent either the gear body 1 or the gear 300 from rotating. For this reason, the backlash adjustment gear 100 has a structure that adjusts the backlash between the gear body 1 and the gear 300.

[0034] In the backlash adjustment gear 100, the diameter D of the gear body 1 (see Figure 3) is adjusted to increase to the diameter D of the gear body 1 (see Figure 6). Conversely, the diameter D of the gear body 1 (see Figure 6) is adjusted to decrease to the diameter D of the gear body 1 (see Figure 3). The following will be explained in detail with reference to Figures 2 to 7.

[0035] As shown in Figure 2, when the tapered bolt 2 and tapered nut 3 are not inserted into the central hole 14 of the gear body 1, the diameter of the gear body 1 is not adjusted. That is, as shown in Figure 3, the diameter of the gear body 1 is diameter D. Diameter D is the minimum diameter of the gear body 1. In this state, as shown in Figure 4, the backlash Ma between the external teeth 11 of the gear body 1 and the external teeth 301 of the mating gear 300 is relatively large, which may result in a deterioration of rotational accuracy and the generation of impact noise.

[0036] Therefore, as shown in Figures 5 and 6, the diameter D of the gear body 1 is adjusted by inserting the tapered bolt 2 and tapered nut 3 into the central hole 14 of the gear body 1 and then tightening the tapered bolt 2 into the tapered nut 3. In Figure 6, the central hole 14 of the gear body 1 in the state shown in Figure 3 is shown by a thick dotted line, and the central hole 14 of the gear body 1 after adjustment is shown by a solid line. Also in Figure 6, the one-sided slit 15a and the other-sided slit 15b of the gear body 1 in the state shown in Figure 3 are each shown by a thick dotted line.

[0037] As described above, the tapered bolt 2 and the tapered nut 3 each have an outer peripheral surface 21a on the bolt head side and an outer peripheral surface 31 on the nut side, respectively.

[0038] The outer circumferential surface 21a on the bolt head side and the outer circumferential surface 31 on the nut side are configured to increase the diameter D of the gear body 1 by increasing the width We of the slit 15 of the gear body 1, depending on the degree of insertion of the outer circumferential surface 21a on the bolt head side and the outer circumferential surface 31 on the nut side into the inner circumferential surface 14a of the central hole 14 of the gear body 1 in the Ax direction.

[0039] In other words, the outer circumferential surface 21a on the bolt head side is configured to increase the diameter D of the gear body 1 by increasing the width We of the slit 15a on one side of the gear body 1, depending on the degree of insertion of the outer circumferential surface 21a on the bolt head side relative to the inner circumferential surface 14a of the central hole 14 of the gear body 1 in the Ax2 direction. Similarly, the outer circumferential surface 31 on the nut side is configured to increase the diameter D of the gear body 1 by increasing the width We of the slit 15b on the other side of the gear body 1, depending on the degree of insertion of the outer circumferential surface 31 on the nut side relative to the inner circumferential surface 14a of the central hole 14 of the gear body 1 in the Ax1 direction.

[0040] Specifically, the tapered bolt 2 and tapered nut 3 are configured such that, with the outer peripheral surface 21a on the bolt head side and the outer peripheral surface 31 on the nut side in contact with the inner peripheral surface 14a of the central hole 14 of the gear body 1, the width We of the slit 15 of the gear body 1 changes, thereby adjusting the diameter D of the gear body 1. This is achieved by adjusting the amount of tightening of the tapered nut 3 by the tapered bolt 2 while the outer peripheral surface 21a on the bolt head side and the outer peripheral surface 31 on the nut side are in contact with the inner peripheral surface 14a of the central hole 14 of the gear body 1.

[0041] Here, by increasing the amount of tightening of the tapered nut 3 by the tapered bolt 2, the diameter D of the gear body 1 is adjusted to increase by a length Re (see Figure 5). Length Re is the length obtained by multiplying the rotational speed of the tapered bolt 2, the pitch of the male thread portion 22 of the tapered bolt 2, and the cosine of the taper angle θt1. Length Re is also the length obtained by multiplying the rotational speed of the tapered bolt 2, the pitch of the female thread portion 32 of the tapered nut 3, and the cosine of the taper angle θt2.

[0042] In other words, as shown in Figures 5 and 6, when the tapered bolt 2 is tightened onto the tapered nut 3, moving the tapered bolt 2 and tapered nut 3 closer together, the larger diameter surface on the outer circumferential surface 21a on the bolt head side and the outer circumferential surface 31 on the nut side presses the inner circumferential surface 14a of the central hole 14 of the gear body 1 radially outward (towards the R1 direction). As a result, the diameter D of the gear body 1 increases, and the external teeth 11 of the gear body 1 are positioned radially outward (towards the R1 direction). Here, although the external teeth 11 of the gear body 1 move radially outward (towards the R1 direction), the rotation center position of the gear body 1 remains unchanged. Also, because the diameter D of the gear body 1 increases, the width We of the slits 15 (one-sided slit 15a and the other-sided slit 15b) increases in order to release the stress generated inside the gear body 1.

[0043] In this way, each of the tapered external teeth 11 is adjusted to a radially outward position (towards the R1 direction) by adjusting the diameter D of the gear body 1 with the tapered bolt 2 and tapered nut 3 so that it increases.

[0044] Furthermore, by increasing the width We of the slit 15 in the gear body 1 and then loosening the tightening amount of the tapered nut 3 by the tapered bolt 2, the tapered bolt 2 and the tapered nut 3 are moved away from each other. As a result, the smaller diameter surfaces on the outer circumferential surface 21a on the bolt head side and the outer circumferential surface 31 on the nut side press the inner circumferential surface 14a of the central hole 14 of the gear body 1 radially outward (towards the R1 direction). This reduces the diameter D of the gear body 1, and the external teeth 11 of the gear body 1 are positioned radially inward (towards the R2 direction). Here, although the external teeth 11 of the gear body 1 move radially inward (towards the R2 direction), the rotation center position of the gear body 1 remains unchanged. Also, although the diameter D of the gear body 1 decreases, the stress generated inside the gear body 1 decreases, so the width We of the slit 15 (one-sided slit 15a and the other-sided slit 15b) decreases.

[0045] In this way, the radial position of each of the multiple tapered external teeth 11 is adjusted to an inward position in the radial direction (R direction) by adjusting the diameter D of the gear body 1 using the tapered bolt 2 and tapered nut 3 so that it becomes smaller.

[0046] As shown in Figure 7, by adjusting each of the tapered external teeth 11 to a radially outward position (towards the R1 direction), the insertion position between adjacent external teeth 301 of the mating gear 300 becomes deeper than the insertion position in Figure 3. As a result, the backlash Ma in Figure 7 is smaller than the backlash Ma in Figure 3. Also, by adjusting each of the tapered external teeth 11 to a radially inward position (towards the R2 direction), the insertion position between adjacent external teeth 301 of the mating gear 300 becomes closer to the insertion position in Figure 3. As a result, the backlash Ma in Figure 3 becomes larger than the backlash Ma in Figure 7.

[0047] Therefore, the backlash Ma is adjusted by first tightening the tapered nut 3 with the tapered bolt 2 and checking the rotation of the gear body 1 and the mating gear 300 while rotating the gear body 1. That is, if the rotational resistance of the gear body 1 and the mating gear 300 is large when the gear body 1 is rotated, the amount of tightening of the tapered nut 3 with the tapered bolt 2 is reduced, and if the rotational resistance of the gear body 1 and the mating gear 300 is small when the gear body 1 is rotated, the amount of tightening of the tapered nut 3 with the tapered bolt 2 is increased. This adjusts the backlash Ma to an appropriate level.

[0048] [Second Embodiment] Referring to Figure 8, the configuration of the backlash adjustment gear 400 according to the second embodiment will be described. In the second embodiment, the backlash adjustment gear 400 has a helical gear as the gear body 401. In the second embodiment, detailed explanations of the same configuration as in the first embodiment will be omitted.

[0049] (Backlash adjustment gear) Referring to Figure 6, the configuration of the backlash adjustment gear 400 according to the second embodiment of the present invention will be described.

[0050] The backlash adjustment gear 400 is a gear that allows adjustment of the amount of backlash Ma between the backlash adjustment gear 400 and the mating gear 300 that meshes with it.

[0051] As shown in Figure 6, the backlash adjustment gear 100 comprises a gear body 401, a tapered bolt 2, and a tapered nut 3. The combined configuration of the tapered bolt 2 and the tapered nut 3 is an example of the "adjustment member" in the claims. The tapered bolt 2 is an example of the "bolt" in the claims. The tapered nut 3 is an example of the "nut" in the claims.

[0052] Here, the axial direction of the gear body 1 is defined as the Ax direction, the side of the Ax direction that is on the tapered bolt 2 side is defined as the Ax1 direction, and the side of the Ax direction that is on the tapered nut 3 side is defined as the Ax2 direction. The radial direction of the gear body 1 is defined as the R direction, the outer side of the R direction is defined as the R1 direction, and the inner side of the R direction is defined as the R2 direction. The circumferential direction of the gear body 1 is defined as the θ direction, one side of the θ direction is defined as the θ1 direction, and the other side of the θ direction is defined as the θ2 direction.

[0053] (Gear body) As shown in Figure 6, the gear body 401 is a metal helical gear. The gear body 401 includes a plurality (16) of external teeth 411, a plurality (16) of tooth roots 12, a central portion 13, a central hole 14, and a plurality (32) of slits 15. The plurality (16) of external teeth 411 may be between 1 and 15, or 17 or more. The plurality (16) of tooth roots 12 may be between 1 and 15, or 17 or more. The plurality (32) of slits 15 may be between 1 and 31, or 33 or more.

[0054] The other configurations of the second embodiment are the same as those of the first embodiment, so their explanation will be omitted.

[0055] [Differentiation] It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims rather than by the description of the embodiments above, and further includes all modifications (exceptions) within the meaning and scope equivalent to the claims.

[0056] For example, the "adjustment member" in the patent claims may be a member that is press-fitted into the central hole of the gear body, rather than a bolt and a nut. Furthermore, the outer circumferential surfaces on the bolt head side and the nut side may not be frustoconical tapered shapes, but rather polygonal surfaces with multiple inclined surfaces arranged in the circumferential direction. Furthermore, the slit may include only a plurality of slits on one side, or it may include only a plurality of slits on the other side. Furthermore, neither the slit on one side nor the slit on the other side necessarily extends to a position where they overlap each other in the axial direction. Furthermore, each of the multiple slits may be formed to extend radially so as to connect the top surface of the external teeth with the central hole of the gear body. Furthermore, the inner circumferential surface of the central hole of the gear body may include an inclined surface. Specifically, as shown in the modified example in Figure 9, the inner circumferential surface 514a of the central hole 514 of the gear body 501 may include an inclined surface. In the modified example shown in Figure 9, the outer circumferential surface 521a of the head 521 of the bolt 502 does not have an inclined surface, and the outer circumferential surface 531 of the nut 503 does not have an inclined surface. Also, both the inner circumferential surface of the central hole of the gear body and the outer circumferential surface of the adjustment member may include an inclined surface. Furthermore, the gear body may be a spur gear or helical gear made of resin. Furthermore, the bolts and nuts may be made of resin.

[0057] [Aspect] Those skilled in the art will understand that the exemplary embodiments described above are specific examples of the following embodiments.

[0058] (Item 1) A gear body comprising multiple external teeth and a central hole penetrating the central portion in the axial direction, and having a slit extending along the axial direction from the axial end face, A backlash adjustment gear comprising an adjustment member that includes an outer circumferential surface that abuts the central hole of the gear body, and which adjusts the diameter of the gear body by changing the width of the slit when the outer circumferential surface abuts against the inner circumferential surface of the central hole of the gear body and presses outward. By adjusting the pressure exerted by the outer circumferential surface of the adjustment member on the outer circumferential surface of the central hole of the gear body, and by adjusting the change in the width of the slit, the diameter of the gear body is adjusted, thereby adjusting the radial position of the gear body's external teeth. This adjusts the insertion position of the gear body's external teeth between the external teeth of the mating gear, allowing for appropriate adjustment of the amount of backlash between the gear body and the mating gear that meshes with it, according to the insertion position. As a result, wear on the meshing gears due to the rotation of the gear body can be suppressed. Furthermore, since the amount of backlash between the gear body and the mating gear can be adjusted, an oil film of appropriate thickness can be secured between the external teeth of the gear body and the external teeth of the mating gear that meshes with it. As a result, reliable lubrication of the gear body and the mating gear that meshes with it can be ensured. Furthermore, since the amount of backlash between the gear body and the mating gear can be adjusted without using a spring, it is possible to avoid both a decrease in the power transmission efficiency of the gear body caused by the biasing force of the spring, and a decrease in the rotational position accuracy of the gear body caused by the expansion and contraction of the spring. (Item 2) The backlash adjustment gear according to item 1, wherein at least one of the inner circumferential surface of the central hole of the gear body and the outer circumferential surface of the adjustment member includes an inclined surface extending in a direction intersecting the axial direction such that the diameter of the gear body increases as the width of the slit of the gear body increases in accordance with the degree of axial insertion of the outer circumferential surface of the adjustment member into the inner circumferential surface of the central hole of the gear body. The outermost radial surface of the inclined surface contacts the inner circumferential surface of the gear body's central hole, thereby maximizing the outward pressing force against the inner circumferential surface of the gear body's central hole. Similarly, the innermost radial surface of the inclined surface contacts the inner circumferential surface of the gear body's central hole, thereby maximizing the outward pressing force against the inner circumferential surface of the gear body's central hole. In this way, the force pressing the gear body's central hole against the inner circumferential surface by the inclined surface can be changed according to the degree of insertion of the inclined surface, making it easy to adjust the adjustment member to increase the diameter of the gear body. (Item 3) The aforementioned adjustment member is A bolt including a head on which the outer circumferential surface on the bolt head side is provided as the inclined surface, The nut includes the nut side outer circumferential surface which serves as the inclined surface, and is fastened by the bolt, The backlash adjustment gear described in item 2 is configured such that the width of the slit in the gear body changes and the diameter of the gear body is adjusted by adjusting the amount of tightening of the nut by the bolt while the outer peripheral surface on the bolt head side and the outer peripheral surface on the nut side are in contact with the inner peripheral surface of the central hole of the gear body, thereby adjusting the degree of insertion of the outer peripheral surface on the bolt head side and the outer peripheral surface on the nut side into the inner peripheral surface of the central hole of the gear body. By implementing the adjustment member using a bolt and nut, the bolt head and nut can be moved closer together or further apart depending on the amount the bolt tightens the nut. As a result, the diameter of the gear body can be adjusted from both sides in the axial direction of the gear body to the axial center of the gear body simply by tightening the bolt to the nut, making it easy to adjust the diameter of the gear body along its entire axial direction. (Item 4) The outer circumferential surface on the bolt head side has a tapered shape that extends in a direction intersecting the axial direction, with the diameter increasing from the central side of the gear body toward the end face on one side in the axial direction. The backlash adjustment gear according to item 3, wherein the outer circumferential surface on the nut side has a tapered shape in which the diameter increases from the central side of the gear body toward the other end face in the axial direction, extending in a direction intersecting the axial direction. By tapering the outer circumferential surface of the bolt head on the bolt head side and the outer circumferential surface of the nut on the nut side, the diameter of the gear body can be gradually increased or decreased depending on the amount the bolt tightens the nut. This allows the diameter of the gear body to be easily adjusted to a size that suits the operator's intentions. (Item 5) The backlash adjustment gear according to items 1 to 4, wherein the slit is formed extending radially from the gear body so as to connect the tooth roots provided between adjacent external teeth among the plurality of external teeth with the central hole of the gear body. Since the tooth roots are not used to transmit driving force to the mating gear that meshes with the gear body, it is possible to realize a backlash-adjustable gear that can adjust the backlash between the gear body and the mating gear to an appropriate amount while suppressing the reduction in driving force from the gear body to the mating gear that meshes with the gear body. (Item 6) The aforementioned slit is A one-sided slit extending from one end face in the axial direction of the gear body to a position on the one side beyond the other end face in the axial direction, The backlash adjustment gear according to items 1 to 4, comprising a other-side slit provided in the circumferential direction of the gear body alongside the one-side slit, and extending from the other end face of the gear body in the axial direction to a position further to the other than the one-side end face in the axial direction. The pressing force of the adjustment member adjusts the diameter of one side of the gear body in the axial direction, and the width of the slit on that side changes by the amount of the diameter adjustment, thereby releasing the stress generated within the gear body due to the pressing force. Furthermore, the pressing force of the adjustment member adjusts the diameter of the other side of the gear body in the axial direction, and the width of the slit on the other side changes by the amount of the diameter adjustment, thereby releasing the stress generated within the gear body due to the pressing force. In this way, the axial diameter of the gear body can be smoothly changed. (Item 7) The backlash adjustment gear according to item 6, wherein each of the one-sided slit and the other-sided slit extends to a position where they overlap each other in the axial direction. In gear bodies located at positions where they overlap in the axial direction, the width of one slit widens, and the width of the other slit widens, allowing the diameter of the gear body to be changed even with a smaller pressing force of the adjustment member than in the non-overlapping portions. (Item 8) Each of the aforementioned multiple external teeth has a tapered shape toward the radially outward direction of the gear body, The backlash adjustment gear described in items 1 to 4, wherein each of the tapered external teeth is adjusted to an outer position in the radial direction by adjusting the gear body diameter to be larger by the adjustment member, and is adjusted to an inner position in the radial direction by adjusting the gear body diameter to be smaller by the adjustment member. The tapered shape of the external teeth allows for adjustment of the backlash between the gear body and the mating gear by increasing or decreasing the diameter of the gear body and moving the external teeth radially. [Explanation of Symbols]

[0059] 1.401 Gear body 2. Tapered bolt (adjustment member, bolt) 3. Tapered nut (adjustment component, nut) 11, 411 External teeth 11d, 11e end face 12 Root 13 Center side part (center part) 14 Center hole 14a Inner surface 15 slits 15a One-sided slit 15b Other side slit 21 Head 21a Bolt head side outer surface (outer surface, inclined surface) 31 Nut-side outer surface (outer surface, inclined surface) 100, 400 Backlash Adjustment Gear Gc central Ma Backlash

Claims

1. A gear body comprising multiple external teeth and a central hole penetrating the central portion in the axial direction, and having a slit extending along the axial direction from the axial end face, A backlash adjustment gear comprising an adjustment member that includes an outer circumferential surface that abuts the central hole of the gear body, and which adjusts the diameter of the gear body by changing the width of the slit when the outer circumferential surface abuts against the inner circumferential surface of the central hole of the gear body and presses outward.

2. The backlash adjustment gear according to claim 1, wherein at least one of the inner circumferential surface of the central hole of the gear body and the outer circumferential surface of the adjustment member includes an inclined surface extending in a direction intersecting the axial direction such that the diameter of the gear body increases as the width of the slit of the gear body increases in accordance with the degree of axial insertion of the outer circumferential surface of the adjustment member into the inner circumferential surface of the central hole of the gear body.

3. The aforementioned adjustment member is A bolt including a head on which the outer circumferential surface on the bolt head side is provided as the inclined surface, The nut includes the nut side outer circumferential surface which serves as the inclined surface, and is fastened by the bolt, The backlash adjustment gear according to claim 2, wherein the adjustment member is configured to adjust the diameter of the gear body by adjusting the amount of tightening of the nut by the bolt while the outer peripheral surface on the bolt head side and the outer peripheral surface on the nut side are in contact with the inner peripheral surface of the central hole of the gear body, thereby adjusting the degree of insertion of the outer peripheral surface on the bolt head side and the outer peripheral surface on the nut side into the inner peripheral surface of the central hole of the gear body, thereby changing the width of the slit of the gear body.

4. The outer circumferential surface on the bolt head side has a tapered shape that extends in a direction intersecting the axial direction, with the diameter increasing from the central side of the gear body toward the end face on one side in the axial direction. The backlash adjustment gear according to claim 3, wherein the outer circumferential surface on the nut side has a tapered shape in which the diameter increases from the central side of the gear body toward the other end face in the axial direction, extending in a direction intersecting the axial direction.

5. The backlash adjustment gear according to claim 1, wherein the slit is formed to extend radially in the gear body so as to connect the tooth roots provided between adjacent external teeth among the plurality of external teeth with the central hole of the gear body.

6. The aforementioned slit is A one-sided slit extending from one end face in the axial direction of the gear body to a position on the one side beyond the other end face in the axial direction, The backlash adjustment gear according to claim 1, further comprising a other-side slit provided in the circumferential direction of the gear body alongside the one-side slit, and extending from the other end face of the gear body in the axial direction to a position further to the other than the end face of the one-side end face in the axial direction.

7. The backlash adjustment gear according to claim 6, wherein each of the one-sided slit and the other-sided slit extends to a position where they overlap each other in the axial direction.

8. Each of the aforementioned multiple external teeth has a tapered shape toward the radially outward direction of the gear body, The backlash adjustment gear according to claim 1, wherein each of the tapered external teeth is adjusted by the adjustment member to increase the diameter of the gear body, thereby adjusting it to an outer position in the radial direction, and by the adjustment member to decrease the diameter of the gear body, thereby adjusting it to an inner position in the radial direction.

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