Reduction gear and geared motor

Abstract

A reduction gear (3) is provided with a sun gear (11), a fixed internal gear (12), a movable internal gear (13) having a different number of teeth than the fixed internal gear (12), and planetary gears (14) provided between the sun gear (11) and the fixed internal gear (12) and the movable internal gear (13). The planetary gears (14) are each provided with a fixed-side planetary meshing part (14a) that meshes with both the sun gear (11) and the fixed internal gear (12) and a movable-side planetary meshing part (14b) that meshes with the movable internal gear (13) and that has the same number of teeth and the same module as the fixed-side planetary meshing part (14a). The sun gear (11) is provided with a fixed-side sun meshing part (11a) that meshes with the fixed-side planetary meshing part (14a) and a movable-side sun meshing part (11b) that meshes with the movable-side planetary meshing part (14b) and that has the same number of teeth and the same module as the fixed-side sun meshing part (11a). The movable-side planetary meshing part (14b) has a different tooth profile than the fixed-side planetary meshing part (14a).

Description

Gear reducers and geared motors

[0001] This matter concerns speed reducers and geared motors.

[0002] Conventionally, a type of gear reducer known as the 3K type planetary gear reducer is known, which comprises a coaxially arranged sun gear and two internal gears, and a planetary gear interposed between the sun gear and the two internal gears. In the 3K type planetary gear reducer, one of the two internal gears (the fixed internal gear) is fixed so as to be immobile, while the other internal gear (the movable internal gear) is supported so as to be able to rotate relative to the sun gear and the fixed internal gear. Furthermore, the fixed internal gear and the movable internal gear have different numbers of teeth. The planetary gear meshes with the sun gear, and a part of it meshes with the fixed internal gear, while the other part meshes with the movable internal gear. In the 3K type planetary gear reducer, the rotation of the sun gear, which rotates integrally with the input shaft, causes the planetary gears to revolve around the sun gear while rotating on their own axes, and the movable internal gear rotates according to the difference in the number of teeth between it and the fixed internal gear, thereby reducing the rotational power of the input shaft to a large reduction ratio and outputting it as output.

[0003] Furthermore, a type of 3K planetary gear reducer called a "mysterious planetary gear reducer" is known in which the planetary gears are configured such that the portion that meshes with the fixed internal gear and the portion that meshes with the movable internal gear have the same number of teeth, module, and tooth profile (for example, Patent Document 1).

[0004] Japanese Patent Publication No. 2021-131160

[0005] Incidentally, in the aforementioned unusual planetary gear reducer, the planetary gears are configured such that the portion that meshes with the fixed internal gear and the portion that meshes with the movable internal gear have the same number of teeth, module, and tooth profile. Therefore, the constraints for achieving meshing between the planetary gears and two internal gears with different numbers of teeth are strict, which can reduce the degree of design freedom. In other words, there is room for improvement in conventional unusual planetary gear reducers in terms of increasing the degree of design freedom.

[0006] Furthermore, in 3K-type planetary gear reducers other than the unusual planetary gear reducer (hereinafter referred to as "general 3K-type planetary gear reducer"), the number of teeth, module, and tooth profile can be set separately for the part of the planetary gear that meshes with the fixed internal gear and the part that meshes with the movable internal gear, thus increasing the degree of design freedom. However, in the general 3K-type planetary gear reducer, the sun gear meshes with only one of the parts of the planetary gear that meshes with the fixed internal gear or the part that meshes with the movable internal gear. As a result, force is applied unevenly to the planetary gear, and from the viewpoint of improving efficiency, durability, and noise reduction, it is desirable to support the planetary gear with shaft members or bearings so that it does not tilt in the axial direction. However, there are concerns that this will lead to increased structural complexity and worsen ease of assembly due to an increase in the number of parts.

[0007] This invention was devised in light of these challenges, and one of its objectives is to provide a reducer and geared motor that can suppress the tilt of planetary gears in the axial direction with a higher degree of design freedom than conventional mysterious planetary gear reducers and with a simpler configuration than conventional general 3K type planetary gear reducers. In addition to this objective, another objective of this invention is to achieve effects and advantages that cannot be obtained by conventional technology, which are derived from the various configurations shown in the embodiments for carrying out the invention described later.

[0008] The disclosed speed reducer and geared motor can be realized in the embodiments (application examples) disclosed below, and solve at least some of the above problems.

[0009] The disclosed reduction gear comprises a sun gear that rotates integrally with the input shaft; a fixed internal gear that is coaxial with the sun gear and fixed non-rotatably around the sun gear; a movable internal gear that is coaxial with the sun gear and rotatable relative to it, and has a different number of teeth than the fixed internal gear; and a planetary gear provided between the sun gear, the fixed internal gear and the movable internal gear, which revolves around the sun gear while rotating on its own axis. The planetary gear is provided with a fixed-side planetary meshing portion that meshes with both the sun gear and the fixed internal gear, and a movable-side planetary meshing portion that meshes with the movable internal gear and has the same number of teeth and module as the fixed-side planetary meshing portion. The sun gear is provided with a fixed-side sun meshing portion that meshes with the fixed-side planetary meshing portion, and a movable-side sun meshing portion that meshes with the movable-side planetary meshing portion and has the same number of teeth and module as the fixed-side sun meshing portion, and the movable-side planetary meshing portion has a different tooth profile from the fixed-side planetary meshing portion.

[0010] The disclosed geared motor comprises a reduction gear including the above-described embodiment, and a motor having the input shaft which rotates integrally with the sun gear of the reduction gear.

[0011] According to the disclosed invention, it is possible to provide a gear reducer and a geared motor that offer greater design freedom than conventional mysterious planetary gear reducers and have a simpler configuration than conventional general 3K type planetary gear reducers, while suppressing the tilt of the planetary gears in the axial direction.

[0012] This is a side view showing a geared motor equipped with a reduction gear according to an embodiment. This is an axial cross-sectional view of the reduction gear of Figure 1, showing the sun gear and input shaft of the reduction gear in an axial half-cross-section. This is a perspective view of the part of the reduction gear of Figure 1 excluding the case, output plate, and output shaft, viewed from a first direction. This is a partial enlarged view of a planetary gear as an example provided in the reduction gear of Figure 1, showing a part of the planetary gear (corresponding to part X in Figure 3) viewed from a second direction. This is a partial enlarged view of a sun gear that meshes with the planetary gear of Figure 4, showing a part of the sun gear (corresponding to part Y in Figure 3) viewed from a first direction.

[0013] The following embodiments of a speed reducer and geared motor will be described with reference to the drawings. The embodiments shown below are merely illustrative, and there is no intention to exclude various modifications and applications of technologies not explicitly shown in the embodiments below. Each component of these embodiments can be modified in various ways without departing from their spirit.

[0014] [1. Overall Configuration] As shown in Figure 1, the geared motor 1 according to this embodiment comprises a motor 2 and a reduction gear 3. The reduction gear 3 is attached to the motor 2 on one side of the axial direction of the motor 2's shaft 4 (input shaft).

[0015] Hereinafter, the direction in which the shaft 4 extends (the direction of the axis C of the shaft 4) will be referred to as the axial direction. Of the axial directions, the direction in which the reduction gear 3 is attached to the motor 2 (one of the above axial directions) will be referred to as the first direction C1, and the direction opposite to the first direction C1 will be referred to as the second direction C2. Furthermore, the direction perpendicular to the axial direction and away from the axis C of the shaft 4 will be referred to as the radially outward direction, and the direction in the same direction and toward the axis C will be referred to as the radially inward direction. When there is no distinction between inside and outside, it will simply be referred to as the radial direction. The direction perpendicular to the axial direction and revolving around the axis C will be referred to as the circumferential direction.

[0016] Motor 2 is, for example, a permanent magnet field type brushed DC motor, and has a stator and rotor (not shown) built into a bottomed cylindrical housing 5. The shaft 4, which rotates integrally with the rotor of motor 2, is rotatably supported by a bearing (not shown) and protrudes outward from the housing 5 in a first direction C1.

[0017] As shown in Figure 2, the reduction gear 3 is a so-called "mysterious planetary gear reduction gear" comprising a sun gear 11 and two internal gears 12 and 13 arranged coaxially with the shaft 4, and a planetary gear 14 provided between the sun gear 11 and the two internal gears 12 and 13. The reduction gear 3 may be provided with a bottomed cylindrical case 20 that houses these gears 11 to 14 and a cover 24 that closes the opening of the case 20.

[0018] As shown in Figure 3, the sun gear 11 is an external gear having external teeth that mesh with the planetary gear 14 located radially outward, and rotates integrally with the shaft 4. The sun gear 11 is, for example, cylindrical, and the shaft 4 is inserted into the inner bore of the cylindrical sun gear 11 and fastened, thereby rotating integrally with the shaft 4. Fastening may be by press-fitting or by using a fastening member (e.g., a key).

[0019] The two internal gears 12 and 13 each have internal teeth that mesh with the planetary gear 14, and are mounted coaxially with the sun gear 11 around the sun gear 11, and are arranged side by side in the axial direction. Of the two internal gears 12 and 13, one internal gear 12 or 13 is fixed so as to be immobile, while the other internal gear 13 or 12 is supported so as to be rotatable relative to the sun gear 11, the other internal gear 12 or 13, and the planetary gear 14.

[0020] In this embodiment, of the two internal gears 12 and 13, the internal gear 12 located on the second direction C2 side is fixed so as to be immobile, while the internal gear 13 located on the first direction C1 side is supported so as to be rotatable relative to it. Hereinafter, the internal gear 12 located on the second direction C2 side will be referred to as the "fixed internal gear 12," and the internal gear 13 located on the first direction C1 side will be referred to as the "movable internal gear 13." The fixed internal gear 12 and the movable internal gear 13 have the same module as each other, but have different numbers of teeth, and the displacement coefficient of at least one of the two internal gears 12 and 13 is adjusted so that their center distances from the planetary gear 14 coincide.

[0021] The planetary gear 14 is an external gear having external teeth that mesh with the sun gear 11. The portion of the planetary gear 14 on the second direction C2 side meshes with the sun gear 11 and the fixed internal gear 12, and the portion of the planetary gear 14 on the first direction C1 side meshes with the movable internal gear 13. Hereinafter, the portion of the planetary gear 14 that meshes with both the sun gear 11 and the fixed internal gear 12 will be referred to as the "fixed side planetary meshing portion 14a," and the portion that meshes with the movable internal gear 13 will be referred to as the "movable side planetary meshing portion 14b."

[0022] The fixed planetary meshing portion 14a and the movable planetary meshing portion 14b are integrally formed from, for example, resin. This eliminates the need for fastening members to securely fasten the fixed planetary meshing portion 14a and the movable planetary meshing portion 14b so that they can rotate together. The fixed planetary meshing portion 14a and the movable planetary meshing portion 14b may also be integrally formed from a material other than resin.

[0023] In this case, the movable planetary meshing portion 14b of the planetary gear 14 meshes not only with the movable internal gear 13 but also with the sun gear 11. That is, the sun gear 11 extends axially so that, when viewed radially, it overlaps not only with the fixed internal gear 12 but also with the movable internal gear 13. By providing the sun gear 11 not only on one side of the planetary gear 14 in the axial direction but on both sides of the planetary gear 14 in the axial direction, the tilting of the planetary gear 14 with respect to the axial direction is suppressed. As a result, the shaft members (shafts) and bearings that suppress the tilting of the planetary gear 14 can be omitted, and the reducer 3 can be made simpler in configuration than conventional general 3K type planetary gear reducers that require these components. Hereinafter, the portion of the sun gear 11 that meshes with the fixed planetary meshing portion 14a will be referred to as the "fixed sun meshing portion 11a," and the portion that meshes with the movable planetary meshing portion 14b will be referred to as the "movable sun meshing portion 11b."

[0024] Furthermore, in this embodiment, as shown in Figure 3, the planetary gear 14 does not have a shaft to support it, but is sandwiched between the fixed sun gear 11a and the movable sun gear 11b and the fixed internal gear 12 and the movable internal gear 13. In other words, the planetary gear 14 is not simply provided between the sun gear 11 and the two internal gears 12 and 13, but is sandwiched between the sun gear 11 and the two internal gears 12 and 13 in such a way that its radial movement is restricted.

[0025] Since the planetary gear 14 is sandwiched between the sun gear 11, which has a fixed sun meshing portion 11a and a movable sun meshing portion 11b, and the two internal gears 12 and 13, without depending on the shaft, the tilt of the planetary gear 14 with respect to the axial direction is further suppressed. Furthermore, since the planetary gear 14 does not have a shaft, and consequently does not have bearings, the reduction gear 3 can be made smaller and its cost reduced, and the reduction in the durability of the reduction gear 3 itself that may occur if bearings are provided is suppressed.

[0026] Note that multiple planetary gears 14 may be provided, as shown in Figure 3. Here, five planetary gears 14 are provided. Each planetary gear 14 is provided independently without being connected to any other planetary gears 14. In other words, each planetary gear 14 does not have a pin (shaft) to support it, nor is there a carrier that rotates (revolves) each planetary gear 14 around axis C via these pins. Instead, it is provided sandwiched between the sun gear 11 and the two internal gears 12 and 13.

[0027] The five planetary gears 14 may all have the same shape and be arranged around the sun gear 11 at equal intervals and spaced apart from each other in the circumferential direction. As shown in Figures 2 and 3, the planetary gears 14 may be cylindrical with through holes penetrating in the axial direction, or they may be solid cylinders.

[0028] In the reduction gear 3, the sun gear 11 rotates integrally with the shaft 4, causing the planetary gear 14 to rotate on its own axis and revolve around the sun gear 11. The rotation and revolve of the planetary gear 14 causes the movable internal gear 13 to rotate. The reduction gear 3 then outputs the rotational power of the shaft 4 as the rotational power of the movable internal gear 13. The gears 11 to 14 may be spur gears as shown in Figure 3, or helical gears.

[0029] As shown in Figure 2, an output plate 15 and an output shaft 16 for extracting the rotational power of the reduced-speed shaft 4 may be connected in this order on the first direction C1 side of the movable internal gear 13, which serves as the output gear. The movable internal gear 13, output plate 15, and output shaft 16 may be formed as a single unit. The output shaft 16 is a shaft portion provided coaxially with the shaft 4 radially inward from the movable internal gear 13, and is, for example, cylindrical in shape.

[0030] The output plate 15 is the part that connects the movable internal gear 13 and the output shaft 16, and is, for example, a disc shape that covers the sun gear 11, the movable internal gear 13, and the planetary gear 14 from the first direction C1 side. The output plate 15 may be a flat plate with a uniform thickness in the axial direction, or a part of it on the second direction C2 side and radially inward may be recessed as shown in the figure. Preferably, the output plate 15 is provided such that the surface 15f facing the second direction C2, which is radially inward from the tooth roots of the movable internal gear 13, is located slightly toward the first direction C1 side than the planetary gear 14. This restricts the movement of the planetary gear 14 toward the first direction C1 side. The output shaft 16 is connected to the radially inward side and first direction C1 side of the output plate 15 and extends toward the first direction C1.

[0031] The case 20 has a bottomed cylindrical shape, with a cylindrical side wall portion 21 having an inner diameter larger than the outer diameter of the fixed internal gear 12 and the movable internal gear 13, and a bottom portion 22 that closes the side wall portion 21 from a first direction C1. A cylindrical tube portion 23 may be provided radially inside the bottom portion 22 of the case 20, forming a through hole through which the output shaft 16 is inserted. The cover 24 is a member that closes the side wall portion 21 of the case 20 from a second direction C2, and has an annular shape that forms a through hole radially inside through which the shaft 4 is inserted.

[0032] In this embodiment, the fixed internal gear 12 is provided on the first direction C1 side of the cover 24 and is formed integrally with the cover 24. The fixed internal gear 12 is thus fixed so as not to rotate. The movable internal gear 13 is, for example, positioned radially inward of the side wall portion 21 and, together with the output plate 15, positioned between the fixed internal gear 12 and the bottom portion 22, thereby restricting its radial and axial movement and supporting it so as to be rotatable relative to the output plate 15. The planetary gear 14 is positioned between the output plate 15 and the cover 24, thereby restricting its axial movement.

[0033] In conventional planetary gear reducers, the planetary gears are configured such that the portion that meshes with the fixed internal gear and the portion that meshes with the movable internal gear have the same number of teeth, module, and tooth profile. In contrast, the reducer 3 of this invention is provided with a configuration in the planetary gear 14 that improves the design freedom of the reducer 3. Specifically, the planetary gear 14 is configured such that the movable planetary meshing portion 14b and the fixed planetary meshing portion 14a have the same number of teeth and module, while the movable planetary meshing portion 14b has a different tooth profile from the fixed planetary meshing portion 14a.

[0034] Furthermore, the fact that the movable planetary meshing portion 14b has a different tooth profile from the fixed planetary meshing portion 14a means that, for at least one of the parameters defining the tooth profiles of each meshing portion 14a, 14b, there is a difference between the fixed planetary meshing portion 14a and the movable planetary meshing portion 14b that is greater than the dimensional error. The above parameters include, for example, pressure angle, displacement coefficient, tip circle diameter, tip R (radius of curvature of the tooth tip), root circle diameter, root R (radius of curvature of the tooth root), tooth thickness, etc. If gears 11 to 14 are helical gears, the parameters may also include the helix angle.

[0035] That is, regarding the above-described parameters, a difference in shape on the order of dimensional error between the fixed-side planetary meshing portion 14a and the movable-side planetary meshing portion 14b is not included in the case of different tooth profiles, and the fixed-side planetary meshing portion 14a and the movable-side planetary meshing portion 14b are regarded as having equivalent tooth profiles. Also, a difference in shape that does not depend on the above-described parameters (for example, a difference in the degree of chipping during manufacturing) between the fixed-side planetary meshing portion 14a and the movable-side planetary meshing portion 14b is not included in the case of different tooth profiles.

[0036] FIG. 4 is a partially enlarged view of the planetary gear 14 as an example, and corresponds to a view of the X portion in FIG. 3 as seen from the second direction C2. In FIG. 4, for convenience, the movable-side planetary meshing portion 14b located on the first direction C1 side of the planetary gear 14 is shown by dot painting. In FIG. 4, the pitch circles (reference pitch circles) of the fixed-side planetary meshing portion 14a and the movable-side planetary meshing portion 14b are shown by a two-dot chain line, the root circle of the fixed-side planetary meshing portion 14a is shown by a short broken line, and the root circle of the movable-side planetary meshing portion 14b is shown by a long broken line.

[0037] As described above, the movable-side planetary meshing portion 14b and the fixed-side planetary meshing portion 14a have the same number of teeth and module as each other. For this reason, the pitch circle of the movable-side planetary meshing portion 14b and the pitch circle of the fixed-side planetary meshing portion 14a coincide with each other (have the same diameter) when viewed from the axial direction. On the other hand, the tooth profile of the fixed-side planetary meshing portion 14a and the tooth profile of the movable-side planetary meshing portion 14b have different shapes from each other.

[0038] Specifically, the pressure angle α2 of the movable-side planetary meshing portion 14b is different from the pressure angle α1 of the fixed-side planetary meshing portion 14a (α2≠α1). Also, the root circle diameter d f2 of the movable-side planetary meshing portion 14b is different from the root circle diameter d f1 of the fixed-side planetary meshing portion 14a (d f2 ≠d f1 ). Further, the tooth thickness s2 of the movable-side planetary meshing portion 14b is different from the tooth thickness s1 of the fixed-side planetary meshing portion 14a (s2≠s1).

[0039] In order to establish meshing with the planetary gear 14 described above, the sun gear 11 is configured such that the fixed sun meshing portion 11a and the movable sun meshing portion 11b have the same number of teeth and module. Similar to the planetary gear 14, the movable sun meshing portion 11b of the sun gear 11 may have a different tooth profile from the fixed sun meshing portion 11a. It is more preferable that the tooth profile of the movable sun meshing portion 11b has a difference from the tooth profile of the fixed sun meshing portion 11a, corresponding to the difference between the tooth profile of the movable planetary meshing portion 14b and the tooth profile of the fixed planetary meshing portion 14a.

[0040] Figure 5 is a magnified view of a portion of the sun gear 11 that meshes with the planetary gear 14 as an example in Figure 4, and corresponds to a view of section Y in Figure 3 from the first direction C1. For convenience, in Figure 5, the movable sun gear meshing portion 11b located on the first direction C1 side of the sun gear 11 is shown with dots. In Figure 5, the pitch circles (reference pitch circles) of the fixed sun gear meshing portion 11a and the movable sun gear meshing portion 11b are shown with dashed lines. The tip circle of the fixed sun gear meshing portion 11a is shown with a short dashed line, and the tip circle of the movable sun gear meshing portion 11b is shown with a long dashed line.

[0041] As described above, the fixed-side sun meshing portion 11a and the movable-side sun meshing portion 11b have the same number of teeth and module. Therefore, the pitch circle of the fixed-side sun meshing portion 11a and the pitch circle of the movable-side sun meshing portion 11b coincide (have the same diameter) when viewed from the axial direction. On the other hand, the tooth profile of the fixed-side sun meshing portion 11a and the tooth profile of the movable-side sun meshing portion 11b have a difference corresponding to the difference in the tooth profile of the movable-side planetary meshing portion 14b compared to the tooth profile of the fixed-side planetary meshing portion 14a.

[0042] Specifically, corresponding to the difference between the pressure angle α2 of the movable planetary meshing portion 14b and the pressure angle α1 of the fixed planetary meshing portion 14a, the pressure angle α4 of the movable sun meshing portion 11b is different from the pressure angle α3 of the fixed sun meshing portion 11a (α4 ≠ α3). Also, the root circle diameter d of the movable planetary meshing portion 14b f2 and the root circle diameter d of the fixed planetary meshing portion 14a f1 Corresponding to the difference between the two, the tooth tip diameter d of the movable sun meshing portion 11b a4 However, the tip diameter d of the fixed side sun meshing portion 11a a3 (da4 ≠d a3 ). Corresponding to the difference between the tooth thickness s2 of the movable-side planetary meshing portion 14b and the tooth thickness s1 of the fixed-side planetary meshing portion 14a, the tooth thickness s4 of the movable-side sun meshing portion 11b is different from the tooth thickness s3 of the fixed-side sun meshing portion 11a (s3≠s4).

[0043] As a result, the fixed-side planetary meshing portion 14a and the fixed-side sun meshing portion 11a, and the movable-side planetary meshing portion 14b and the movable-side sun meshing portion 11b mesh better, so that the rotation and revolution of the planetary gear 14 by the sun gear 11 are suppressed from being inhibited. In addition, the tooth profile of the movable-side sun meshing portion 11b may have a difference that does not correspond to the difference between the tooth profiles of the fixed-side planetary meshing portion 14a and the movable-side planetary meshing portion 14b with respect to the tooth profile of the fixed-side sun meshing portion 11a.

[0044] [2. Action, Effect] (1) In the speed reducer 3 and the geared motor 1 described above, unlike the conventional mysterious planetary gear speed reducer, the movable-side planetary meshing portion 14b of the planetary gear 14 has a tooth profile different from that of the fixed-side planetary meshing portion 14a. As a result, the constraint conditions for establishing the meshing of the planetary gear 14 with the two internal gears 12 and 13 having different numbers of teeth can be relaxed, so that the design freedom of the speed reducer 3 is increased.

[0045] Further, in the speed reducer 3 and the geared motor 1 described above, the sun gear 11 is provided with a fixed-side sun meshing portion 11a that meshes with the fixed-side planetary meshing portion 14a and a movable-side sun meshing portion 11b that meshes with the movable-side planetary meshing portion 14b. With such a sun gear 11, the planetary gear 14 is supported from the radially inner side over the entire axial direction, so that the inclination of the planetary gear 14 toward the radially inner side can be suppressed. Therefore, the inclination of the planetary gear 14 in the axial direction can be suppressed with a simpler configuration than that of the conventional general 3K-type planetary gear speed reducer that requires a configuration (such as a shaft or a bearing) for suppressing the inclination of the planetary gear. In addition, by suppressing the inclination of the planetary gear 14 in the axial direction, the efficiency, durability, and noise of the speed reducer 3 can be improved.

[0046] (2) When the planetary gear 14 is sandwiched between the fixed sun gear 11a and the movable sun gear 11b and the fixed internal gear 12 and the movable internal gear 13, the tilt of the planetary gear 14 can be further suppressed without relying on the shaft that supports the planetary gear 14. Also, if the planetary gear 14 is not provided with a shaft or bearing that supports the planetary gear 14, the reduction gear 3 can be made smaller and its cost can be reduced, and the reduction in the durability of the reduction gear 3 itself that may occur due to the provision of bearings can be suppressed.

[0047] (3) In the reduction gear 3 and geared motor 1 described above, the movable sun gear meshing portion 11b of the sun gear 11 has a different tooth profile from the fixed sun gear meshing portion 11a. This makes it possible to relax the constraints on achieving meshing between the planetary gear 14 having a fixed planetary meshing portion 14a and a movable planetary meshing portion 14b, and the sun gear 11 having a fixed sun gear meshing portion 11a and a movable sun gear meshing portion 11b. Therefore, it is possible to construct a reduction gear 3 with a high degree of design freedom while suppressing tilting of the planetary gear 14, miniaturizing the reduction gear 3, reducing costs, and improving durability.

[0048] (4) If the tooth profile of the movable sun mesh portion 11b has a difference from the tooth profile of the fixed sun mesh portion 11a that corresponds to the difference between the tooth profile of the movable planetary mesh portion 14b and the tooth profile of the fixed planetary mesh portion 14a, the meshing between the movable planetary mesh portion 14b and the movable sun mesh portion 11b can be improved. This contributes to improving the transmission efficiency of the reducer 3.

[0049] (5) When the fixed planetary meshing portion 14a and the movable planetary meshing portion 14b are formed integrally, the fastening member for fastening the fixed planetary meshing portion 14a and the movable planetary meshing portion 14b so that they can rotate together can be omitted. Therefore, the reduction gear 3 can be made smaller and costs can be reduced.

[0050] [3. Others] The configuration of the reduction gear 3 and geared motor 1 described above is just one example and is not limited to the above configuration. In the planetary gear 14 described above, between the fixed planetary meshing portion 14a and the movable planetary meshing portion 14b, the pressure angles α1 and α2 and the root circle diameter d are among the parameters described above. f1 ,d f2Although examples have been given where the tooth thicknesses s1 and s2 are different, the examples of differentiating the tooth profiles of the fixed planetary meshing portion 14a and the movable planetary meshing portion 14b are not limited to these. Similarly, the examples of differentiating the tooth profiles of the fixed sun meshing portion 11a and the movable sun meshing portion 11b of the sun gear 11 are not limited to the example shown in Figure 5. The movable sun meshing portion 11b of the sun gear 11 may have the same tooth profile as the fixed sun meshing portion 11a.

[0051] The planetary gear 14 may have a fixed planetary meshing portion 14a and a movable planetary meshing portion 14b provided separately. The reduction gear 3 may be provided with a shaft (carrier pin or carrier) to support the planetary gear 14. The geared motor 1 may have an input shaft that rotates integrally with the rotor, and may be a brushless motor or an AC motor. The gears 11 to 14 provided in the reduction gear 3 may be built into the housing 5 of the motor 2. In this case, the case 20 and cover 24 may be omitted.

[0052] 1 Geared motor 2 Motor 3 Reducer 4 Shaft (input shaft) 11 Sun gear 11a Fixed sun gear meshing part 11b Movable sun gear meshing part 12 Fixed internal gear 13 Movable internal gear 14 Planetary gear 14a Fixed planetary gear meshing part 14b Movable planetary gear meshing part

Claims

1. A sun gear that rotates integrally with the input shaft; a fixed internal gear that is fixed coaxially with the sun gear and immobilely around it; a movable internal gear that is provided coaxially with the sun gear and rotatable relative to it, and has a different number of teeth from the fixed internal gear; a planetary gear provided between the sun gear, the fixed internal gear and the movable internal gear, which revolves around the sun gear while rotating on its own axis; the planetary gear is provided with a fixed-side planetary meshing portion that meshes with both the sun gear and the fixed internal gear, and a movable-side planetary meshing portion that meshes with the movable internal gear and has the same number of teeth and module as the fixed-side planetary meshing portion; the sun gear is provided with a fixed-side sun meshing portion that meshes with the fixed-side planetary meshing portion, and a movable-side sun meshing portion that meshes with the movable-side planetary meshing portion and has the same number of teeth and module as the fixed-side sun meshing portion. A gearbox characterized in that the movable planetary meshing portion has a tooth profile different from that of the fixed planetary meshing portion.

2. The gearbox according to claim 1, characterized in that the movable sun mesh portion has a tooth profile different from that of the fixed sun mesh portion.

3. The gearbox according to claim 2, characterized in that the tooth profile of the movable solar mesh portion has a difference corresponding to the difference in the tooth profile of the movable planetary mesh portion with respect to the tooth profile of the fixed planetary mesh portion.

4. The reduction gear according to claim 1, characterized in that the planetary gear does not have a shaft that supports the planetary gear, and is provided sandwiched between the fixed-side sun meshing portion and the movable-side sun meshing portion and the fixed internal gear and the movable internal gear.

5. The gearbox according to claim 1, characterized in that the fixed planetary meshing portion and the movable planetary meshing portion are integrally formed.

6. A geared motor comprising a reduction gear according to any one of claims 1 to 5, and a motor having the input shaft that rotates integrally with the sun gear of the reduction gear.

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