Precession-type deceleration or acceleration device

Abstract

Provided is a precession-type deceleration or acceleration device with which it is possible to increase load capacity. Provided is a precession-type deceleration or acceleration device provided with a first face gear (1) and a second face gear (2) meshing with the first face gear (1) and configured to perform precession, wherein one of either a tooth surface (21a) of a tooth (21) of the first face gear (1) and a tooth surface (22a) of a tooth (22) of the second face gear (2) engaging with the first face gear (1) is formed as a concave surface, and the other is formed as a convex surface.

Description

Precession type speed reducer or speed increaser

[0001] The present invention relates to a precession speed reducer or speed increaser.

[0002] A known precession type reduction gear includes a first face gear and a second face gear that meshes with the first face gear and undergoes differential motion (see Patent Document 1). The precession is a motion in which the rotation axis of the second face gear describes a cone with the precession center at its apex, similar to the oscillating motion of a top.

[0003] As in the precession type reduction gear described in Patent Document 1, for example, when the first face gear is fixed and the input shaft is rotated to cause the second face gear to precess, the second face gear rotates at a reduced speed by the difference in the number of teeth between the first face gear and the second face gear. If the reduced rotation of the second face gear is output to the output shaft, it can be used as a reduction gear. If the output shaft is made the input side and the input shaft is made the output side, it can be used as a speed increaser.

[0004] In the reduction gear disclosed in Patent Document 1, the tooth tips of the first face gear and the second face gear are formed in the shape of a portion of a cone. The tooth roots of the first face gear are formed on an envelope curve when the tooth tips of the second face gear are precessed. The tooth roots of the second face gear are formed on an envelope curve when the tooth tips of the first face gear are precessed relative to each other.

[0005] Patent No. 6777404

[0006] However, in conventional reduction gears, the tips of the teeth of the first and second face gears are formed on a part of a cone with a small base radius, so contact occurs between an arc with a small radius of curvature and an envelope, which increases the contact stress of the teeth and poses a problem of being unable to increase the load capacity.

[0007] The present invention has been made in view of the above-mentioned problems, and has an object to provide a precession type speed reducer or speed increaser that can increase the load capacity.

[0008] In order to solve the above-described problems, one aspect of the present invention is a precession type speed reducer or speed accelerating device including a first face gear and a second face gear that meshes with the first face gear and precesses, wherein one of the tooth flanks of the teeth of the first face gear and the tooth flanks of the teeth of the second face gear that mesh with each other is formed as a concave surface, and the other is formed as a convex surface.

[0009] Another aspect of the present invention is a precession type speed reducer or speed increaser including a first face gear and a second face gear that meshes with the first face gear and precesses, wherein the cross-sectional shape of the tooth flanks of the first face gear is formed into an involute tooth profile, or a precession tooth profile based on a precession locus obtained by projecting onto a two-dimensional plane a three-dimensional locus of the teeth of a moving cone of the second face gear when the moving cone of the second face gear is precessed relative to the fixed cone of the first face gear, and the cross-sectional shape of the tooth flanks of the second face gear is formed into an involute tooth profile, or a precession tooth profile based on a precession locus obtained by projecting onto a two-dimensional plane a three-dimensional locus of the teeth of a fixed cone of the first face gear when the fixed cone of the first face gear is precessed relative to the moving cone of the second face gear.

[0010] In another aspect of the present invention, the tooth flanks of the teeth of both the first face gear and the second face gear may be formed into an involute tooth profile, or the tooth flanks of both the teeth may be formed into a precession tooth profile. Also, the tooth flanks of the teeth of either the first face gear or the second face gear may be formed into an involute tooth profile, and the tooth of the other may be formed into a precession tooth profile.

[0011] According to one aspect of the present invention, one of the tooth flanks of the teeth of the first face gear and the second face gear that mesh with each other is formed concave and the other is formed convex, thereby increasing the contact area of ​​these tooth flanks and reducing contact stress, thereby increasing the load capacity of the precession type speed reducer or speed increaser.

[0012] According to another aspect of the present invention, the cross-sectional shapes of the tooth flanks of the teeth of the first face gear and the second face gear are formed into an involute tooth profile or a precession tooth profile defined on a two-dimensional plane, so that the tooth flanks of the first face gear and the second face gear can be brought into contact with each other at arcs with large radii of curvature, thereby reducing the contact stress of these tooth flanks and increasing the load capacity of the precession type speed reducer or speed increaser.

[0013] 9(a) is a perspective view showing the meshing of the first face gear and the second face gear at the closest point, and FIG. 9(b) is a perspective view showing the taper of the first face gear and the second face gear. FIG. 9(b) is a perspective view showing the fixed cone of the first face gear and the dynamic cone of the second face gear. FIG. 9(c) is a perspective view showing the state where tooth profiles are formed on the fixed cone and the dynamic cone. FIG. 9(d) is a perspective view showing the state where teeth are arranged on the pitch circles of the fixed cone and the dynamic cone. Figure 13(a) is a top view of Figure 12, and Figure 13(b) is a diagram showing the positional relationship between the teeth of a fixed cone and the teeth of a moving cone projected onto a sketch plane. Figure 14(a) is a diagram showing the precession locus and precession tooth profile on the sketch plane, and Figure 14(b) is a diagram showing an involute tooth profile approximating the precession tooth profile. Figure 14(b) is a diagram showing an involute tooth profile on the sketch plane. Figure 14(a) is a diagram showing the involute tooth profile on the sketch plane with tooth tips and tooth roots added. Figure 17(a) is a perspective view of the first face gear and taper, and Figure 17(b) is a side view. Figure 18(a) is a perspective view of the second face gear and taper, and Figure 18(b) is a side view. Figure 20(a) is a conventional example showing the meshing length of a spur gear, and Figure 20(b) is an example of the present invention showing the meshing length of this embodiment. 1 is a cross-sectional view of an actuator to which a precession type reduction gear transmission according to an embodiment of the present invention is applied.

[0014] Hereinafter, a reduction gear according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. However, the reduction gear according to the present invention can be embodied in various forms and is not limited to the embodiments described in this specification. The present embodiment is provided with the intention that those skilled in the art will be able to fully understand the invention by fully disclosing the specification.

[0015] (Configuration of a precession type reduction gear according to an embodiment of the present invention) Figure 1 is a cross-sectional view of a precession type reduction gear 10 according to an embodiment of the present invention. In the following explanation, for convenience of explanation, the configuration of the precession type reduction gear 10 will be explained using the directions when the rotation axis A of the precession type reduction gear 10 is arranged vertically and the input unit 3 is arranged below and the output unit 4 is arranged above, that is, the up / down and left / right directions in Figure 1. Of course, the arrangement of the precession type reduction gear 10 is not limited to this.

[0016] 1, the precession type reduction gear 10 includes a first face gear 1 and a second face gear 2 that meshes with the first face gear 1 and precesses. The precession is a motion in which the rotation axis B of the second face gear 2 describes a conical surface with its vertex at point O (precession center O) on the rotation axis A of the precession type reduction gear 10, similar to the oscillating motion of a top.

[0017] Reference numeral 3 denotes an input section, 4 an output section, 5 a motion conversion section, and 6 a spherical spline. When the input section 3 is rotated around the rotation axis A, the inclined cam 12 of the motion conversion section 5 rotates together with the input section 3, causing the second face gear 2 to precess. The first face gear 1 is fixed to a housing 7. Therefore, when the second face gear 2 precesses, the second face gear 2 rotates at a reduced speed by the difference in the number of teeth between the first face gear 1 and the second face gear 2. The reduced rotation of the second face gear 2 is taken out to the output section 4 via the spherical spline 6.

[0018] Here, the number of teeth of the first face gear 1 is Z １ , the number of teeth of the second face gear 2 is Z ２ Then, the rotation ratio 1 / U between the input part 3 and the output part 4 is 1 / U=(Z １ -Z ２ ) / Z ２ It is expressed as:

[0019] The motion converting unit 5 includes an inclined cam 12, a plurality of first rolling elements 11 interposed between the inclined cam 12 and the second face gear 2, and a plurality of second rolling elements 13 interposed between the inclined cam 12 and the housing 7. The motion converting unit 5 presses the second face gear 2 against the first face gear 1. The inclined cam 12 is connected to the input unit 3. When the input unit 3 is rotated, the motion converting unit 5 causes the second face gear 2 to precess while pressing it against the first face gear 1.

[0020] The spherical spline 6 includes an inner ring 14, an outer ring (output portion 4), and a plurality of balls 15 between the inner ring 14 and the output portion 4. The reduced rotation of the second face gear 2 is transmitted to the output portion 4 via the spherical spline 6. The second face gear 2 is supported by the spherical spline 6 so as to be capable of precessing.

[0021] An inner ring 14 is formed integrally with the second face gear 2. A spline groove 14a is formed on the outer surface of the inner ring 14. A spline groove 4a opposing the spline groove 14a is formed on the inner surface of the output portion 4. The output portion 4 is rotatably supported by the housing 7 via a bearing 17.

[0022] 2, the first face gear 1 is annular. A plurality of teeth 21 are formed on the lower surface of the first face gear 1, i.e., the surface facing the second face gear 2. The outer surface 1a of the first face gear 1 is formed as part of a spherical surface centered on the precession center O.

[0023] The second face gear 2 includes an annular main body 16 and an inner ring 14 formed integrally with the main body 16. A plurality of teeth 22 are formed on the upper surface of the main body 16 of the second face gear 2, i.e., the surface facing the first face gear 1. The number of teeth of the second face gear 2 is different from the number of teeth of the first face gear 1. The outer surface 2a of the main body 16 is formed as part of a spherical surface centered on the precession center O.

[0024] In the present embodiment, an example of a precession type reduction gear 10 including a first face gear 1 and a second face gear 2 that meshes with the first face gear 1 and precesses is described, but the precession type reduction gear is not limited to one that includes only a first face gear and a second face gear. For example, a precession type reduction gear may be one that includes a first face gear, a second face gear that meshes with the first face gear and precesses, a third face gear that precesses together with the second face gear, and a fourth face gear that meshes with the third face gear.

[0025] (Tooth Flanks of First Face Gear and Second Face Gear) As shown in Fig. 3, the cross-sectional shape of the tooth flank 21a of the tooth 21 of the first face gear 1 is formed into an involute tooth profile or a precession tooth profile. The cross-sectional shape of the tooth flank 22a of the tooth 22 of the second face gear 2 is also formed into an involute tooth profile or a precession tooth profile. The involute tooth profile and the precession tooth profile will be described later.

[0026] As shown in Fig. 3, the tooth flanks 22a of the teeth 22 of the second face gear 2 are formed convexly, i.e., convexly, with an external tooth shape. On the other hand, the tooth flanks 21a of the teeth 21 of the first face gear 1 are formed concavely, i.e., concavely, with an internal tooth shape. In the first face gear 1, the tooth flanks 21a of the internal tooth shape are on the side opposite to the involute tooth profile or precession tooth profile of the external tooth shape. It is also possible to form the tooth flanks 21a of the teeth 21 of the first face gear 1 convexly, and the tooth flanks 22a of the teeth 22 of the second face gear 2 concavely.

[0027] 4 and 5, the teeth 21 of the first face gear 1 have similar shapes on the inner diameter side and the outer diameter side, and are tapered so that the teeth become larger from the inner diameter side to the outer diameter side. The taper converges at the precession center O. A crowning 21d is formed at the radial end of the first face gear 1, for example, at the end on the inner diameter side.

[0028] 6 and 7, the teeth 22 of the second face gear 2 are also similar in shape on the inner diameter side and the outer diameter side, and are tapered so that the teeth become larger from the inner diameter side to the outer diameter side. The taper converges at the precession center O. A crowning 22d is formed at the radial end of the second face gear 2, for example, at the end on the outer diameter side.

[0029] In the case of the precession type reduction gear 10, the difference in the number of teeth between the first face gear 1 and the second face gear 2 is small. For example, the number of teeth of the first face gear 1 is 101, and the number of teeth of the second face gear 2 is 100. Therefore, the teeth 21 of the first face gear 1 and the teeth 22 of the second face gear 2 are close to each other, making interference and edge loads likely to occur. For this reason, as shown in FIG. 3 , reliefs 23 are provided at the tip 21b and bottom 21c of the teeth 21 of the first face gear 1 to avoid interference and edge loads. Similarly, reliefs 23 are provided at the tip 22b and bottom 22c of the teeth 22 of the second face gear 2. The shape of the reliefs 23 is not particularly limited, and may be, for example, an arc shape.

[0030] 8 and 9 , the meshing of the plurality of teeth 21 of the first face gear 1 and the plurality of teeth 22 of the second face gear 2 will be described. As shown in FIG. 9 , at the point P1 where the base of the cone of the first face gear 1 and the base of the cone of the second face gear 2 are closest to each other, the teeth 21 of the first face gear 1 and the teeth 22 of the second face gear 2 do not mesh with each other, and a gap exists between them. The base of the cone of the first face gear 1 is a fixed cone 41, which will be described later, and the base of the cone of the second face gear 2 is a dynamic cone 42, which will be described later. In FIGS. 9( a) and 9(b), reference numeral 32 denotes the valley-shaped taper of the tooth 21 of the first face gear 1, and reference numeral 31 denotes the valley-shaped taper of the tooth 22 of the second face gear 2. As shown in FIG. 9(b), a gap g exists between them.

[0031] As shown in Figure 8, the first face gear 1 and the second face gear 2 are meshed at meshing positions 24, with multiple teeth 21 of the first face gear 1 and multiple teeth 22 of the second face gear 2, at positions circumferentially to the right and left of the closest point of approach P1. The meshing positions are symmetrical from the closest point of approach P1. When a clockwise (rightward) torque acts on the second face gear 2, multiple teeth 22 of the second face gear 2 and multiple teeth 21 of the first face gear 1 mesh at positions circumferentially to the right of the closest point of approach P1. The opposite is true when a counterclockwise (leftward) torque acts on the second face gear 2.

[0032] (Involute Tooth Profile and Precession Tooth Profile) The involute tooth profile and precession tooth profile of the first face gear 1 and the second face gear 2 are formed as follows. For ease of understanding, the number of teeth Z of the first face gear 1 is １ is 101 and the module is 1, and the number of teeth Z of the second face gear 2 is ２ Let's say the number of teeth is 100 and the module is 1. The number of teeth and module can be set arbitrarily.

[0033] FIG. 10 shows the fixed cone of the first face gear 1 and the dynamic cone of the second face gear 2. Reference numeral 41 denotes the fixed cone of the first face gear 1, and reference numeral 42 denotes the dynamic cone of the second face gear 2. Reference numeral θ denotes the precession angle. As shown in FIG. 11, the fixed cone 41 is equal to the cone on which the tooth trace of the first face gear 1 extends, i.e., its apex angle and pitch circle (base circle) are equal to those of the first face gear 1. The dynamic cone 42 is equal to the cone on which the tooth trace of the second face gear 2 extends, i.e., its apex angle and pitch circle (base circle) are equal to those of the second face gear 2. Note that the shapes of the fixed cone and dynamic cone in FIG. 10 are exaggerated vertically for clarity, but in reality they are flattened as shown in FIG. 9.

[0034] 10 , first, the fixed cone 41 and the moving cone 42 are arranged so that their generating line 43 is common. That is, the apex of the fixed cone 41 and the apex of the moving cone 42 are positioned at the precession center O, and the base circle 41 a of the fixed cone 41 and the base circle 42 a of the moving cone 42 are positioned on the surface of a sphere Q whose center is the precession center O. The base circle 42 a of the precessing moving cone 42 is always positioned on the surface of the sphere Q. The base circle 41 a of the fixed cone 41 is the pitch circle of the first face gear 1, and the base circle 42 a of the moving cone 42 is the pitch circle of the second face gear 2.

[0035] The tooth profile of the first face gear 1 can be formed by forming an involute tooth profile I or a precession tooth profile F (see FIG. 14(b)) of the constant cone 41 on a two-dimensional plane R (hereinafter referred to as sketch plane R) perpendicular to the generatrix 43 and converging this involute tooth profile I or precession tooth profile F to the precession center O. Similarly, the tooth profile of the second face gear 2 can be formed by forming an involute tooth profile or a precession tooth profile of the moving cone 42 on sketch plane R and converging this involute tooth profile or precession tooth profile to the precession center O.

[0036] The involute tooth profile I or precession tooth profile F of the fixed cone 41 is defined on a sketch plane R. The precession tooth profile F of the fixed cone 41 is obtained by projecting onto the sketch plane R the three-dimensional trajectory of the teeth of the moving cone 42 when the moving cone 42 precesses relative to the fixed cone 41, and adding a tooth space width W to the precession trajectory T (see FIG. 14(a)).

[0037] The precession locus T and precession tooth profile F of the fixed cone 41 will now be described. As shown in FIG. 10, the number of teeth Z of the first face gear 1 is １ If the number of teeth of the second face gear 2 is 101 and the module is 1, the constant cone 41 is set so that the diameter of the pitch circle 41a is 101. ２ When the modulus is 100 and the module is 1, the dynamic cone 42 is set so that the diameter of the pitch circle 42a is 100. In practice, to reduce the height of the first face gear 1 and the second face gear 2, the pitch circle 41a of the fixed cone 41 is shifted negatively (for example, the diameter of the pitch circle 41a of the fixed cone 41 is set to 100.8), and the pitch circle 42a of the dynamic cone 42 is shifted positively (for example, the diameter of the pitch circle 42a of the dynamic cone 42 is set to 100.2).

[0038] Next, a precession locus T is obtained by projecting onto the sketch plane R the three-dimensional locus of the teeth of the moving cone 42 when the moving cone 42 precesses relative to the fixed cone 41. Here, as shown in FIG. 12 , the teeth 51a to 51e (points) of the fixed cone 41 are arranged at a predetermined pitch on the pitch circle 41a of the fixed cone 41. The predetermined pitch is, for example, 100.8×π÷101=3.135. Similarly, the teeth 52a to 52e (points) of the moving cone 42 are arranged at a predetermined pitch on the pitch circle 42a of the moving cone 42. The predetermined pitch is, for example, 100.2×π÷100=3.148. The tooth 51a of the fixed cone 41 and the tooth 52a of the moving cone 42 overlap on the common generatrix 43, but the teeth 51b to 51e of the fixed cone 41 and the teeth 52b to 52e of the moving cone 42 are shifted horizontally by δ1 mainly due to the difference in pitch, and shifted vertically by δ2 mainly due to the precession angle θ. Also, as shown in the top view of Figure 13, the teeth 51b to 51d of the fixed cone 41 and the teeth 52b to 52d of the moving cone 42 are shifted radially by δ3 mainly due to the difference in pitch circle diameter.

[0039] 13(b) shows the positional relationship between the teeth 51a to 51d of the fixed cone 41 and the teeth 52a to 52d of the moving cone 42 projected onto a sketch plane R. Multiple sketch planes are also shown in FIG. 13(b). The symbol R indicates a sketch plane perpendicular to the common generating line 43, the symbol R1 indicates a sketch plane perpendicular to the generating line passing through the tooth 51b of the fixed cone 41, the symbol R2 indicates a sketch plane perpendicular to the generating line passing through the tooth 51c of the fixed cone 41, and the symbol R3 indicates a sketch plane perpendicular to the generating line passing through the tooth 51d of the fixed cone 41.

[0040] When the moving cone 42 is caused to precess, the teeth 52a to 52d of the moving cone 42 trace a three-dimensional trajectory along the surface of the sphere Q and overlap with the teeth 51a to 51d of the fixed cone 41. Therefore, by consolidating the positional relationships between the teeth 51a to 51d of the fixed cone 41 and the teeth 52a to 52d of the moving cone 42 projected onto multiple sketch planes R and R1 to R3 onto a single sketch plane R, it is possible to trace the precession trajectory T of the teeth 52a to 52d of the moving cone 42.

[0041] This precession locus T becomes the basis of the precession tooth profile F of the fixed cone 41. As shown in FIG. 14 , by drawing multiple circles C centered on the precession locus T and drawing lines tangent to the circles C, the precession tooth profile F of the fixed cone 41 can be formed. The radius of the circles C is set to have a predetermined tooth space width W on the pitch circle 41a of the fixed cone 41. For example, the predetermined tooth space width W is set to 100.8 × π ÷ 202 so that the tooth thickness and tooth space width are the same. By arranging the precession tooth profiles F symmetrically with respect to a common generatrix 43, a symmetric precession tooth profile F can be formed.

[0042] The precession tooth profile F of the constant cone 41 thus obtained may be used as the tooth profile of the first face gear 1, or as shown in Fig. 14(b) , an involute tooth profile I that is similar to the precession tooth profile F may be used as the tooth profile of the first face gear 1. As described above, the tooth flanks 21a of the teeth 21 of the first face gear 1 are formed into concave surfaces of an internal tooth shape. That is, in the first face gear 1, the side opposite to the involute tooth profile I or precession tooth profile F of the external tooth shape becomes the tooth flank 22a.

[0043] As shown in Figure 15, the involute tooth profile I is the path traced by the end of a thread 62 when a thread 62 is wound around a base circle 61 and then unwound while being pulled by holding the end of the thread 62. The involute tooth profile I is also defined on the sketch plane R. By setting the base circle 61 on the sketch plane R, the involute tooth profile I can be formed. The base circle 61 can be set from the diameter of the pitch circle 41a and the pressure angle (for example, 20°).

[0044] In this way, the involute tooth profile I or precession tooth profile F of the constant cone 41 can be determined, but the tooth tip and tooth root are not yet determined. For this reason, as shown in Fig. 16, the tooth root J and tooth tip K are added to the involute tooth profile I or precession tooth profile F. As shown in Fig. 8, the teeth 21 of the first face gear 1 and the teeth 22 of the second face gear 2 mesh only near the pitch circle PC (41a), so the tooth root J and tooth tip K can be set arbitrarily, and a relief can be provided.

[0045] As shown in FIG. 17 , if an involute tooth profile I or a precession tooth profile F of a fixed cone 41 drawn on a sketch plane R is formed into a taper 31 with the precession center O, the teeth 21 of the first face gear 1 can be formed.

[0046] On the other hand, when forming an involute tooth profile or a precession tooth profile for the second face gear 2, it is sufficient to find a precession locus by projecting onto the sketch plane R the three-dimensional locus of the teeth of the fixed cone 41 of the first face gear 1 when the fixed cone 41 is precessed relative to the dynamic cone 42 of the second face gear 2. Then, by providing a tooth space width to the precession locus of the fixed cone 41, it is possible to form the precession tooth profile F' of the dynamic cone 42, and to form an involute tooth profile I' that approximates the precession tooth profile F'. By adding a tooth bottom and a tooth tip to the involute tooth profile I' or the precession tooth profile F' and forming a taper 32 with the precession tooth profile F' or the involute tooth profile I' drawn on the sketch plane R as shown in FIG. 18 , the teeth 22 of the second face gear 2 can be formed.

[0047] (Tooth Profile Modification Using a Pseudo Number of Teeth) Reducing the difference in the number of teeth between the first face gear 1 and the second face gear 2 or shifting the teeth may reduce the precession angle θ to, for example, 1 to 3°. In this case, with a normal involute tooth profile, the teeth 21 of the first face gear 1 and the teeth 22 of the second face gear 2 interfere with each other and do not mesh. For this reason, as shown in FIG. 19 , the involute tooth profile of the first face gear 1 is modified using a pseudo number of teeth (e.g., 20) that is smaller than the actual number of teeth (e.g., 101). Reference numeral 64 denotes the involute tooth profile before the tooth profile modification, and reference numeral 65 denotes the involute tooth profile after the tooth profile modification. The involute tooth profile of the second face gear 2 is similarly modified using a pseudo number of teeth (e.g., 20) that is smaller than the actual number of teeth (e.g., 100). By modifying the tooth profile using the pseudo number of teeth, the radius of curvature of the involute tooth profile 65 becomes smaller, so that interference between the teeth 21 of the first face gear 1 and the teeth 22 of the second face gear 2 can be more effectively avoided.

[0048] Tooth profile modification using a pseudo number of teeth will now be described. As shown in Figure 19, for example, if the first face gear 1 has 101 teeth and a module of 1, an involute tooth profile 64 is formed on a pitch circle with 101 teeth (a pitch circle with a diameter of 101 mm). Also, an involute tooth profile 65 is formed on a pitch circle with a pseudo number of teeth of, for example, 20 (a pitch circle with a diameter of 20 mm), which is less than the actual number of teeth. If the involute tooth profile 65 formed with the pseudo number of teeth is arranged on the pitch circle with 101 teeth, tooth profile modification using the pseudo number of teeth becomes possible.

[0049] However, when the first face gear 1 is profile shifted, even if the involute tooth profile 65 formed on a pitch circle with 20 pseudo teeth is placed directly on a pitch circle with 101 teeth, it will not match the pitch after profile shifting. In this case, the involute tooth profile 65 after tooth profile modification can be divided into a right half and a left half, and the distance between the right half and the left half can be adjusted to match the pitch after profile shifting.

[0050] (Method of Manufacturing First Face Gear and Second Face Gear) There are no particular limitations on the method of manufacturing the first face gear 1 and the second face gear 2, but considering mass production, plastic processing by forging is preferable. If a die is machined with an end mill or the like to have a shape complementary to the teeth 21 of the first face gear 1 and the die is pressed against the base material of the first face gear 1, the shape of the die is transferred to the base material of the first face gear 1, and the first face gear 1 can be manufactured. The same applies to the manufacturing method of the second face gear 2.

[0051] (Actuator) Figure 21 shows a cross-sectional view of an actuator 80 to which the precession type reduction gear 10 according to this embodiment is applied. Reference numeral 81 denotes a motor, reference numeral 10 denotes a precession type reduction gear, reference numeral 1 denotes a first face gear, reference numeral 2 denotes a second face gear, reference numeral 3 denotes an input section, reference numeral 4 denotes an output section, reference numeral 5 denotes a motion converting section, and reference numeral 6 denotes a spherical spline. A motor shaft 81a of the motor 81 is connected to the input section 3. When the motor 81 rotates the input section 3, the second face gear 2 precesses due to the motion converting section 5, and the second face gear 2 rotates at a reduced speed by an amount corresponding to the difference in the number of teeth between the first face gear 1 and the second face gear 2. The reduced rotation of the second face gear 2 is output to the output section 4 via the spherical spline 6.

[0052] The above has described the configuration of the precession type reduction gear transmission 10 of this embodiment. The precession type reduction gear transmission 10 of this embodiment provides the following effects.

[0053] Since one of the tooth surfaces 21 a of the teeth 21 of the first face gear 1 and the tooth surfaces 22 a of the teeth 22 of the second face gear 2, which mesh with each other, is formed concave and the other is formed convex, the contact area between these tooth surfaces 21 a, 22 a can be increased, reducing contact stress and therefore the load capacity of the precession type reduction gear device 10 can be increased.

[0054] 10 , the tooth flanks 21 a of the first face gear 1 and the tooth flanks 22 a of the second face gear 2 are formed into an involute tooth profile I or a precession tooth profile F defined on a two-dimensional plane R, so that the tooth flanks 21 a of the first face gear 1 and the tooth flanks 22 a of the second face gear 2 can be brought into contact with each other on arcs with large radii of curvature. This reduces the contact stress of these tooth flanks 21 a, 22 a, and increases the load capacity of the precession type reduction gear device 10.

[0055] Since the teeth 21, 22 of the first face gear 1 and the second face gear 2 are formed with tapers 31, 32 that converge to the precession center O, the meshing length in the radial direction of the first face gear 1 and the second face gear 2 can be increased.

[0056] Since the involute tooth profile I of the first face gear 1 and / or the second face gear 2 is modified using a pseudo number of teeth smaller than the actual number of teeth, interference between the teeth 21 of the first face gear 1 and the teeth 22 of the second face gear 2 can be avoided.

[0057] Relief 23 is provided at the tooth tip 21b and tooth root 21c of the first face gear 1, and at the tooth tip 22b and tooth root 22c of the second face gear 2, thereby making it possible to avoid interference and edge load between the tooth 21 of the first face gear 1 and the tooth 22 of the second face gear 2. In addition, the teeth 21, 22 of the first face gear 1 and the second face gear 2 can be made similar to each other, preventing either the tooth 21 or 22 from becoming thin.

[0058] By forming the teeth 21 of the first face gear 1 and the teeth 22 of the second face gear 2 into an involute tooth profile I or a precession tooth profile F, a plurality of (e.g., 10) teeth 21 of the first face gear 1 and a plurality of (e.g., 10) teeth 22 of the second face gear 2 mesh only near the pitch circle PC, as shown in Fig. 8. For this reason, even if the first face gear 1 and the second face gear 2 are provided with a recess 23, this does not adversely affect the number of meshes and uniform velocity between the first face gear 1 and the second face gear 2.

[0059] The number of meshing teeth and uniform velocity will now be explained. As shown in Figure 20(a), in the case of conventional spur gears 71 and 72, the number of meshing teeth is about one, and it is necessary to use involute tooth profiles evenly, which results in a long meshing length L. Reference numeral 73 denotes the meshing position. The meshing position 73 moves above and below the pitch circles 74 and 75 as the spur gears 71 and 72 rotate. In the case of conventional spur gears 71 and 72, providing relief at the tooth tips and tooth roots reduces the meshing length L and the number of meshing teeth, resulting in a loss of uniform velocity.

[0060] As shown in Fig. 8, in the precession type reduction gear transmission 10 of this embodiment, the first face gear 1 and the second face gear 2 have a plurality of meshing teeth, for example, about 10 teeth, and the meshing positions 24 are only in the vicinity of the pitch circle PC. As shown in Fig. 20(b), the meshing length L is also short. For this reason, even if reliefs 23 are provided in the tooth tips and tooth roots, there is no adverse effect on the number of meshing teeth and uniform velocity.

[0061] At the closest point P1 between the base of the cone of the first face gear 1 and the base of the cone of the second face gear 2, the teeth 21 of the first face gear 1 and the teeth 22 of the second face gear 2 do not mesh with each other and a gap g exists between them, which makes it possible to avoid interference between the teeth 21 of the first face gear 1 and the teeth 22 of the second face gear 2. Furthermore, because the plurality of teeth 21 of the first face gear 1 and the plurality of teeth 22 of the second face gear 2 mesh with each other at a position circumferentially away from the closest point P1, it is possible to increase the load capacity.

[0062] Since the outer surfaces 1a, 2a of the first face gear 1 and the second face gear 2 are formed as part of a spherical surface centered on the precession center O, the strength of the first face gear 1 and the second face gear 2 can be improved.

[0063] This specification is based on Japanese Patent Application No. 2024-131812, filed on August 8, 2024, the entire contents of which are incorporated herein by reference.

[0064] REFERENCE SIGNS LIST 1...first face gear, 1a...outer surface of first face gear, 2...second face gear, 2a...outer surface of second face gear, 10...precession type reduction gear, 21...first face gear tooth, 21a...tooth flank of first face gear, 21b...tooth tip of first face gear, 21c...tooth root of first face gear, 22...second face gear tooth, 22a...tooth flank of second face gear, 22b...tooth tip of second face gear, 22c...tooth root of second face gear, 23...Relief, 31...Taper of tooth of first face gear, 32...Taper of tooth of second face gear, 41...Constant cone, 42...Dynamic cone, 51a to 51e...Teeth of fixed cone, 52a to 52e...Teeth of dynamic cone, 65...Involute tooth profile after tooth profile correction using pseudo number of teeth, g...Gap, T...Precession locus, F...Precession tooth profile, I...Involute tooth profile, R...Sketch plane (two-dimensional plane), O...Precession center, P1...Closest point of first face gear and second face gear

Claims

1. A precession type speed reducer or speed increaser comprising a first face gear and a second face gear that meshes with the first face gear and precesses, wherein one of the tooth surfaces of the teeth of the first face gear and the tooth surfaces of the teeth of the second face gear that mesh with each other is formed as a concave surface, and the other is formed as a convex surface.

2. A precession type speed reducer or speed increaser comprising: a first face gear; and a second face gear that meshes with the first face gear and precesses, wherein the cross-sectional shape of the tooth flanks of the first face gear is formed as an involute tooth profile, or a precession tooth profile based on a precession locus obtained by projecting onto a two-dimensional plane the three-dimensional locus of the teeth of the moving cone of the second face gear when the moving cone of the second face gear is precessed relative to the fixed cone of the first face gear; and the cross-sectional shape of the tooth flanks of the second face gear is formed as an involute tooth profile, or a precession tooth profile based on a precession locus obtained by projecting onto a two-dimensional plane the three-dimensional locus of the teeth of the fixed cone of the first face gear when the fixed cone of the first face gear is precessed relative to the moving cone of the second face gear.

3. A precession type speed reducing or increasing device according to claim 1 or 2, characterized in that the teeth of the first face gear and the teeth of the second face gear are formed to have a taper that converges to the center of precession.

4. A precession type speed reducing or increasing device as described in claim 2, characterized in that the cross-sectional shapes of the tooth flanks of the teeth of the first face gear and the tooth flanks of the teeth of the second face gear are formed into involute tooth profiles, and the involute tooth profiles of the teeth of the first face gear and the second face gear are modified using a pseudo number of teeth that is smaller than the actual number of teeth.

5. A precession type speed reducing or increasing device as described in claim 1 or 2, characterized in that reliefs are provided at the tip and bottom of the teeth of the first face gear and at the tip and bottom of the teeth of the second face gear.

6. A precession type speed reduction or speed increase device as described in claim 1 or 2, characterized in that at the closest point between the base of the cone of said first face gear and the base of the cone of said second face gear, the teeth of said first face gear and the teeth of said second face gear do not mesh with each other, leaving a gap between them, and multiple teeth of said first face gear and multiple teeth of said second face gear mesh with each other at a position circumferentially away from said closest point.

7. A precession type speed reducer or speed increaser according to claim 1 or 2, characterized in that the outer surfaces of the first face gear and the second face gear are formed as part of a sphere centered on the precession center.

8. An actuator comprising: a precession type speed reducing or speed increasing device according to claim 1 or 2; and a motor that causes the second face gear to precess.

Images