JP7755536B2 - power transmission device - Google Patents

Description

This disclosure relates to a power transmission device.

Patent Document 1 discloses a power transmission device comprising a triangular first moving member and a second moving member that contacts the first moving member. These first and second moving members convert rotational motion input to the first moving member into reciprocating motion, which is then output from the second moving member.

Japanese Patent Application Publication No. 07-112082

The first and second moving members can be used to perform high-speed and low-speed rotational motion around different centers of rotation, and when one of these rotational motions is input, it can be converted into the other rotational motion and output. The inventors of this application have newly discovered that in such cases, depending on the shape of the first and second moving members, large speed variations can occur in the rotational speed of the output rotational motion, even when rotational motion is input at a constant rotational speed.

One of the objectives of the present disclosure is to provide a power transmission device that can suppress speed variations in the rotational motion output from either the first moving member or the second moving member.

The power transmission device disclosed herein comprises a first moving member having N first contact surfaces forming an N-gon on its outer periphery, where N is a natural number greater than or equal to 3, and a second moving member having multiple second contact surfaces in contact with the first contact surfaces. When the first moving member and the second moving member receive input of one of high-speed rotational motion and low-speed rotational motion around different centers of rotation, the first moving member and the second moving member can convert this input into the other of high-speed rotational motion and low-speed rotational motion through contact between the first contact surfaces and the second contact surfaces. The first contact surfaces are arc-shaped and convex radially outward relative to a line connecting adjacent vertices of the N-gon. The second contact surfaces are linear. When the contact position with the center of the first contact surface is defined as the center of the second contact surface, at least one of the first contact surface and the second contact surface has a convex portion that is offset from its center.

Another power transmission device disclosed herein is a power transmission device comprising: a first moving member having N first contact surfaces forming an N-gon on its outer periphery, where N is a natural number greater than or equal to 3; and a second moving member having multiple second contact portions in contact with the first contact surfaces; when the first moving member and the second moving member receive input of one of high-speed rotational motion and low-speed rotational motion around different centers of rotation, the first moving member and the second moving member are capable of converting this into the other of these through contact between the first contact surfaces and the second contact surfaces and outputting it; the first contact surfaces are arc-shaped and convex radially outward relative to a line connecting adjacent vertices of the N-gon; the second contact portions have multiple roller surfaces in rolling contact with the first contact surfaces; and the first contact surfaces have multiple recesses with which the roller surfaces make rolling contact.

This disclosure provides a power transmission device that can suppress speed variations in the rotational motion output from either the first moving member or the second moving member.

1 is a schematic side cross-sectional view of a power transmission device according to a first embodiment. 3 is a schematic cross-sectional view of a first moving member and a second moving member of the first embodiment as viewed from the axial direction. FIG. FIG. 10 is a view of the first and second moving members in their reference shapes as viewed from the axial direction. 5 is a motion diagram showing the motion trajectories of the first and second motion members; FIG. FIG. 10 is an explanatory diagram of a locus traced by a second rotation center. 10A and 10B are diagrams showing the first and second motion members in reference shapes in the middle of their movements; 10A and 10B are diagrams showing a convex portion of a second motion member in the first embodiment. 5A and 5B are explanatory diagrams relating to a convex portion of a second moving member in the first embodiment. 10A and 10B are diagrams showing a convex portion of a first moving member of the second embodiment. FIG. 10 is another view showing the convex portion of the first moving member of the second embodiment. 10 is an explanatory diagram of a convex portion of a first moving member of the second embodiment. FIG. FIG. 10 is a diagram schematically illustrating a convex portion of a first moving member according to a third embodiment. FIG. 10 is a schematic cross-sectional view of a first moving member and a second moving member of the fourth embodiment as viewed from the axial direction. FIG. 14 is an enlarged view of the first motion member of FIG. 13. 10 is a motion diagram showing the overall motion trajectory of the first motion member of the fourth embodiment. FIG. 10 is a motion diagram showing a motion locus of a part of the first motion member of the fourth embodiment. FIG.

The following describes the embodiments. Identical components are given the same reference numerals, and redundant explanations will be omitted. In each drawing, components are omitted, enlarged, or reduced as appropriate for the sake of clarity. The drawings should be viewed according to the orientation of the reference numerals. Unless otherwise specified, "input" and "output" in this specification include cases where the conditions mentioned are directly satisfied by two elements, as well as cases where the conditions are indirectly satisfied via other elements.

(First embodiment) Refer to Figure 1. The power transmission device 10 comprises a high-speed shaft 12 and a low-speed shaft 14, a first moving member 16 and a second moving member 18 that change the speed of rotational motion input from one of the high-speed shaft 12 and the low-speed shaft 14 and output it to the other, and a casing 20 that houses the first moving member 16 and the second moving member 18. In addition, the power transmission device 10 comprises a moving unit 22 having the first moving member 16, a carrier 24 arranged axially to the side of the moving unit 22, and a pin member 26 inserted through the moving unit 22 and the carrier 24. In this specification, the direction along the center of rotation C12 of the high-speed shaft 12 (first center of rotation Ca, described below) is referred to as the axial direction X.

The high-speed shaft 12 is an input member that receives rotational power from a drive source (not shown), while the low-speed shaft 14 is an output member that outputs power to a driven device. Examples of drive sources include a motor, gear motor, and engine. The high-speed shaft 12 is rotatably supported on the casing 20 by a first high-speed shaft bearing 28A, and is rotatably supported on the low-speed shaft 14 by a second high-speed shaft bearing 28B. The low-speed shaft 14 is rotatably supported on the casing 20 by a low-speed shaft bearing 30. In this embodiment, the high-speed shaft 12 is rotatably mounted integrally with an eccentric body 32. The center C32 of the eccentric body 32 is eccentric from the rotation center C12 of the high-speed shaft 12 by an eccentricity amount e1. The eccentric body 32 has a circular shape with the center C32 as its center. An eccentric bearing 34 is disposed between the first moving member 16 and the eccentric body 32, allowing relative rotation between the two. As a result, the center C32 of the eccentric body 32 rotates together with the high-speed shaft 12, causing the first moving member 16 (movement unit 22) to perform an oscillating motion together with the eccentric body 32.

The movement unit 22 includes a flange member 36 that is provided axially to the side of the first movement member 16 and is integrated with the first movement member 16. The flange member 36 is arranged to protrude radially outward from the first movement member 16 when viewed from the axial direction X.

In this embodiment, the carrier 24 is integrated with the low-speed shaft 14. The carrier 24 is rotatably supported in the casing 20 via a carrier bearing 38.

The pin member 26 comprises a carrier pin portion 26a rotatably supported on the carrier 24 via bearing 40A, and a unit pin portion 26b rotatably mounted on the flange member 36 of the motion unit 22 via bearing 40B. The unit pin portion 26b is eccentric with respect to the carrier pin portion 26a in the same eccentric direction and by the same eccentricity amount e2 as the eccentric body 32 that oscillates the motion unit 22 through which it is inserted. This allows the pin member 26 to rotate around the axis C26a of the carrier pin portion 26a in response to the oscillating motion of the motion unit 22, thereby allowing for the oscillating motion of the motion unit 22. This pin member 26 connects the first motion member 16 and the carrier 24 in a manner that is synchronized with the rotational component of the first motion member 16 while allowing for the oscillating motion of the first motion member 16. Here, "synchronized with the rotational component" refers to maintaining the same magnitude of the referenced rotational component within a numerical range that includes zero.

Refer to Figure 2. We will now move on to explaining the first moving member 16 and the second moving member 18. Below, when describing these, unless otherwise specified, we will explain their relationship as viewed from the axial direction X. Furthermore, hatching will be omitted in subsequent figures.

The first moving member 16 has N first contact surfaces 42 that form an N-sided polygon on the periphery, where N is a natural number greater than or equal to 3. In this specification, unless otherwise specified, "shape" does not only refer to a shape that geometrically closely matches the referenced shape, but also includes a shape similar to the referenced shape. In this embodiment, N is 3. The N (three) first contact surfaces 42 as a whole form an N-sided Reuleaux polygon on the periphery (here, a Reuleaux triangle).

The N-sided polygon formed by the N first contact surfaces 42 has N vertices 44. The N vertices 44 are located at equal distances from the center C16 of the first moving member 16 and are offset in central angle by 360°/N (here, 120°). The center C16 of the first moving member 16 here is concentric with the second rotation center Cb, which will be described later.

Each of the N first contact surfaces 42 forms an arc shape that is convex radially outward from the first moving member 16 with respect to a line La connecting adjacent vertices 44 of the N-gon. To satisfy this condition, the outer peripheral shape of the first contact surface 42 may be a single curve, a combination of multiple curves with different curvatures, or a combination of curves and straight lines. Here, "as a whole" refers to the object being referred to (here, the first contact surface 42) viewed as a whole. In other words, the first contact surface 42, when viewed as a whole, forms an arc shape that is convex radially outward from line La. Even if the first contact surface 42 is provided with a convex portion 80 (described below), the first contact surface 42 will also form an arc shape that is convex radially outward from line La.

The second moving member 18 is integrated with the casing 20. The second moving member 18 has a plurality of second contact surfaces 46 that contact the first contact surfaces 42 of the first moving member 16. The plurality of second contact surfaces 46 includes at least one pair of second contact surfaces 46 that face each other across the first center of rotation Ca, which will be described later. The centers C46 (described later) of the pair of second contact surfaces 46 are positioned so that the line Lb connecting them passes through the first center of rotation Ca. In this embodiment, the number of the plurality of second contact surfaces 46 is the same as the number of corners of the N+1 polygon, i.e., four. The plurality of second contact surfaces 46 includes two pairs of second contact surfaces 46.

The second contact surfaces 46 are linear as a whole. The second contact surfaces 46 are linear, intersecting at right angles to a line Lb passing through the center C46 of the pair of second contact surfaces 46. The multiple second contact surfaces 46, the number of which is the same as the number of corners of the N+1 polygon, are linear along the individual sides of the regular polygon with N+1 corners. In addition to the N+1 sides, this N+1 polygon has N+1 vertices 48. The N+1 vertices 48 are equidistant from the center 50 of the N+1 polygon and are located at positions offset by 360°/(N+1) (here, 90°). The center 50 of the N+1 polygon here is concentric with the first rotation center Ca, which will be described later.

In this embodiment, the first moving member 16 functions as an external gear, and the second moving member 18 functions as an internal gear that meshes with the first moving member 16 (external gear). The N first contact surfaces 42 of the first moving member 16 function as individual external teeth, and the N+1 second contact surfaces 46 of the second moving member 18 function as individual internal teeth.

Refer to Figure 3. In this specification, the center C42 of the first contact surface 42 and the center C46 of the second contact surface 46 are defined as follows. When a line Lc is assumed to pass through the vertex 44 constituting the farthest diagonal of the sides of the N-gon formed by the first contact surface 42 and the member center (second rotation center Cb) of the first moving member 16, the center C42 of the first contact surface 42 refers to the intersection of the line Lc and the first contact surface 42. In this embodiment, the center C42 of the first contact surface 42 is also the midpoint of the first contact surface 42. Furthermore, the center C46 of the second contact surface 46 refers to the position on the second contact surface 46 opposite the first contact surface 42 where the line Lc passes when the center C42 of the first contact surface 42 is positioned on the same line Lc as the first rotation center Ca and second rotation center Cb described below. In this embodiment, when this positional relationship is established, the center C46 of the second contact surface 46 is in contact with the center C42 of the first contact surface 42.

In addition, this specification assumes a reference shape for each of the first contact surface 42 of the first moving member 16 and the second contact surface 46 of the second moving member 18. The reference shape of each first contact surface 42 is a Reuleaux N-gon Sa (hereinafter referred to as a Reuleaux shape Sa) with the same number of sides as the N-gon formed by the first moving member 16. The reference shape, the Reuleaux shape Sa, is a geometrically strict Reuleaux N-gon. Each side of this reference shape, the Reuleaux shape Sa, is an arc with a constant distance L1 from the farthest diagonal. As a result, the Reuleaux shape is a constant-width figure with a constant across width L1. Here, the across width L1 refers to the distance between a pair of parallel lines circumscribing the reference shape (here, the Reuleaux shape) when viewed from the axial direction X. A constant across width L1 means that the distance between the pair of parallel lines is constant regardless of the circumscribing position of one of the parallel lines. The width L1 across can also be said to be the vertical height when the referenced shape is rolled on a horizontal plane. When the width L1 across is always constant, it can also be said that the vertical height when the referenced shape is rolled on a horizontal plane is always constant. In this reference shape, the Reuleaux shape Sa, the center C42 of each of the N first contact surfaces 42 of the first moving member 16 coincides with the center (midpoint) of each of its sides.

Imagine a line segment Ld with both ends Lda at the center C46 of a pair of opposing second contact surfaces 46 and a length equal to the across width L1. The reference shape of each second contact surface 46 is a straight line Sb extending perpendicularly from both ends Lda of this line segment Ld to the line segment Ld. The straight line Sb serving as the reference shape is a geometrically strict straight line. In the present embodiment, when there are N+1 second contact surfaces 46, the straight line Sb formed by the reference shape of the N+1 second contact surfaces 46 is a regular polygon (here, a square) with N+1 sides and L1. Hereinafter, the direction along the line segment Ld connecting the centers C46 of the opposing second contact surfaces 46 is referred to as the facing direction Da of the second contact surfaces 46.

Please refer to Figure 4. Below, only the contact surfaces 42, 46 of each moving member 16, 18 are shown schematically. Here, the movement trajectory of the moving members 16, 18 in their reference shape is illustrated, and the movement of the moving members 16, 18 in this embodiment is explained.

When either high-speed rotational motion or low-speed rotational motion about different rotation centers Ca and Cb is input to either the first moving member 16 or the second moving member 18, the high-speed rotational motion can be converted into the other by contact between the first contact surface 42 and the second contact surface 46 and output from either one. High-speed rotational motion is motion around the first rotation center Ca, and low-speed rotational motion is motion around the second rotation center Cb. High-speed rotational motion can be either swinging motion or rotational motion. Swinging motion refers to motion in which the second rotation center Cb swings (revolves) relative to the first rotation center Ca. In the following embodiments, swinging motion is performed by the second rotation center Cb swinging (revolving) around the first rotation center Ca while the first rotation center Ca remains stationary. Alternatively, swinging motion may be performed by the first rotation center Ca swinging (revolving) around the second rotation center Cb while the second rotation center Cb remains stationary. Rotation as high-speed rotational motion refers to motion in which a moving member performing high-speed rotational motion rotates around a first rotation center Ca that is concentric with the center of the member. Low-speed rotational motion refers to motion in which a moving member performing low-speed rotational motion rotates around a second rotation center Cb that is concentric with the center of the member. When high-speed rotational motion becomes rotational motion, the rotational directions (rotational directions) of the high-speed rotational motion and the low-speed rotational motion are the same.

In this embodiment, an example is described in which an oscillating motion (high-speed rotational motion) is input to the first moving member 16, and this oscillating motion is converted into rotational motion (low-speed rotational motion) of the first moving member 16 before being output from the first moving member 16. A power transmission device 10 that operates in this manner functions as an externally oscillating type eccentric oscillating gear device in which the first moving member 16, which functions as an external gear, performs an oscillating motion. In this way, it is sufficient for at least one of the first moving member 16 and the second moving member 18 to be moving; it is not essential that the other be moving.

To cause the first moving member 16 to perform an oscillating motion, the rotation of the high-speed shaft 12 rotates the center C32 of the eccentric body 32, which is concentric with the second center of rotation Cb, around the center of rotation C12 of the high-speed shaft 12, causing the first moving member 16 to perform an oscillating motion together with the eccentric body 32. To input an oscillating motion to the first moving member 16, the high-speed shaft 12 is rotated, and the oscillating motion is input from the high-speed shaft 12 to the first moving member 16 via the eccentric body 32.

When rotating on its own axis using the first moving member 16 that performs an oscillating motion, the casing 20 integrated with the second moving member 18 is fixed to an external support member to restrain the rotation of the second moving member 18. At the same time, the carrier 24 integrated with the low-speed shaft 14 and the first moving member 16 (movement unit 22) are connected by a pin member 26 that can synchronize with the rotational component while allowing the oscillating motion of the first moving member 16. This allows the low-speed shaft 14 to rotate at the same rotational speed as the rotational component of the first moving member 16 that performs an oscillating motion. This means that the low-speed shaft 14 can be rotated at the same rotational speed as the rotational motion output from the first moving member 16.

The first moving member 16 and the second moving member 18 convert the input rotational motion into the other rotational motion at a predetermined speed ratio and then output it. The predetermined speed ratio is determined based on the motion mode of each moving member 16, 18 and the magnitude of N. When high-speed rotational motion becomes oscillating motion, this speed ratio is determined based on the moving member performing rotational motion (low-speed rotational motion) and the magnitude of N. This speed ratio assumes a reduction ratio n of high-speed rotational motion relative to low-speed rotational motion. In this case, when the first moving member 16 performs rotational motion, the reduction ratio n is N (here, 3), and when the second moving member 18 performs rotational motion, the reduction ratio is N+1. In addition, when high-speed rotational motion becomes rotational motion, the reduction ratio n is (N+1)/N.

During the process of performing one of the input rotational motions, the first moving member 16 and the second moving member 18 can convert one rotational motion into the other by a force acting on a contact point 60 formed at the contact position between the first contact surface 42 and the second contact surface 46. This contact point 60 moves in the direction of travel Db within a second contact range R46 of the first contact surface 42 relative to the second contact surface 46 as the rotational motion of each moving member 16, 18 progresses. This second contact range R46 extends from an end position R46a on the counter-traveling direction, where contact begins during the process of contact between the first contact surface 42 and the second contact surface 46, to an end position R46b on the counter-traveling direction, where contact ends. Here, "counter-traveling direction" refers to the direction opposite to the direction of travel Db. The contact point 60 progresses in the direction of travel Db as the first contact surface 42 and the second contact surface 46 continuously or intermittently contact each other within this second contact range R46. The direction of travel Db of this contact point 60 varies depending on the mode of motion of each moving member 16, 18. When the high-speed rotational motion is a swinging motion, as in this embodiment, the direction of travel Db is the same as the direction of rotation Dc of the swinging motion around the first center of rotation Ca. Additionally, when the high-speed rotational motion is a rotational motion, the direction of travel Db is opposite to the direction of rotation Dc of the rotational motion.

When the contact points 60 of the preceding contact surfaces 42, 46 advance in the direction of travel Db, a contact initiation operation is performed in which the other contact surfaces 42, 46 adjacent to the preceding contact surfaces 42, 46 in the direction of travel begin to come into contact with the preceding contact surfaces 42, 46 while maintaining their contact state. Furthermore, when the contact points 60 of the preceding contact surfaces 42, 46 advance to the end position R46b of the second contact range R46 on the direction of travel, a contact release operation is performed in which the preceding contact surfaces 42, 46 release their contact while maintaining their contact state with the subsequent contact surfaces 42, 46. High-speed and low-speed rotational motions of the first moving member 16 and the second moving member 18 progress while the contact initiation operation between the subsequent contact surfaces 42, 46 and the contact release operation between the preceding contact surfaces 42, 46 are repeated.

Here, we will explain the problems that arise when using the first moving member 16 and the second moving member 18. Figure 5 shows the first and second loci 70A and 70B traced by the second center of rotation Cb when performing high-speed rotation (oscillating motion) and low-speed rotation (rotational motion) at constant rotational speeds w1 and w2. The first locus 70A is traced when the first moving member 16 is rotated such that the first contact surface 42 is always in contact with the second contact surface 46 within the second contact range R46 of each second contact surface 46, without constraining the relative positions of the first and second centers of rotation Ca and Cb of the first moving member 16. The second locus 70B is traced when the relative positions of the first and second centers of rotation Ca and Cb of the first moving member 16 are constrained. Both cases assume the use of moving members 16 and 18 in their reference shapes. The rotational speed w2 is calculated as the rotational speed w1 × (1/reduction ratio n). A portion of the first trajectory 70A and the second trajectory 70B are also shown in Figure 4 for reference.

As the high-speed rotational motion progresses for one revolution, circular first and second loci 70A and 70B are traced out, with the second center of rotation Cb rotating relatively around the first center of rotation Ca. When the second center of rotation Cb rotates relative to the first center of rotation Ca according to this first locus 70A, this means that high-speed and low-speed rotational motion can be performed at constant rotational speeds w1 and w2 while maintaining continuous contact of the contact points 60 within the second contact range R46 of each second contact surface 46. The first locus 70A that satisfies this condition traces out a circular shape that is different from a perfect circle centered on the first center of rotation Ca.

Regarding the rotation angle of the high-speed rotational motion around the first center of rotation Ca, the rotation angle at which the contact point 60 between the center C42 of the first contact surface 42 and the center C46 of the second contact surface 46 is located on a line passing through the first center of rotation Ca and the second center of rotation Cb is called the contact rotation angle θa. For example, Figure 3 shows a state in which the rotation angle of the high-speed rotational motion is at the contact rotation angle θa. The first locus 70A of the second center of rotation Cb narrows its distance from the first center of rotation Ca when the rotation angle of the high-speed rotational motion is the contact rotation angle θa. Contact rotation angles θa that satisfy this condition appear every N+1 equal angles of 360° (i.e., every 90° in this case). The rotation angle that bisects the rotation angle of adjacent contact rotation angles θa is called the intermediate rotation angle θb. At this time, the first trajectory 70A describes a circular shape in which the distance from the first center of rotation Ca increases as the rotation angle of the high-speed rotational motion approaches the intermediate rotation angle θb from the contact rotation angle θa.

In reality, because the relative positions of the first rotation center Ca and the second rotation center Cb are constrained during use, the second rotation center Cb traces the second circular locus 70B and cannot trace the first circular locus 70A, which is different from a perfect circle. As a result, when the first moving member 16 and the second moving member 18 of the reference shape simultaneously perform high-speed and low-speed rotational motions, continuous contact at the contact point 60 within the second contact range R46 cannot be maintained, and the first contact surface 42 and the second contact surface 46 separate.

Refer to Figure 6. When the first contact surface 42 and the second contact surface 46 separate while moving through the second contact range R46, a minute gap 72 momentarily forms between the first contact surface 42 and the second contact surface 46. Due to this gap 72, the first moving member 16 performs a low-speed rotational motion (here, rotational motion) that momentarily fluctuates in rotational speed while maintaining the rotation angle of the input high-speed rotational motion (here, swinging motion) until the first contact surface 42 and the second contact surface 46 come into contact, and then the contact point 60 attempts to move forward from the position where they made contact again. In other words, if the first contact surface 42 and the second contact surface 46 separate while moving through the second contact range R46, this causes speed unevenness in the rotational motion (here, rotational motion) output from the first moving member 16.

Here, when the center C42 of the first contact surface 42 of the first moving member 16 and the center C46 of the second contact surface 46 of the second moving member 18 come into contact, as described above, the second center of rotation Cb is located at the same position regardless of whether the first trajectory 70A or the second trajectory 70B is traced. Consider the positions of the first and second moving members 18 in this case as the reference rotation position, with high-speed rotation proceeding from there by a rotation angle θ1 and low-speed rotation proceeding by a rotation angle θ2 (= θ1 × (1/reduction ratio n)) (see Figure 6). At this time, the first contact surface 42 is closest to the second contact surface 46 on a straight line Le extending from the farthest diagonal Sa1 of the side of the Reuleaux shape Sa facing the second contact surface 46 in the facing direction Da of the second contact surface 46. The distance at the closest position when in the reference shape at these rotation angles θ1 and θ2 is referred to as the reference distance Ls.

The inventors of the present application have newly discovered that, as a countermeasure to the aforementioned speed unevenness, narrowing the distance between the first contact surface 42 and the second contact surface 46 at the closest positions when the rotation angles are θ1 and θ2 is more effective than the reference distance Ls. The narrower this distance, the smaller the gap 72 that allows for speed fluctuations in the rotational motion output from either moving member 16, 18 can be, even if the contact surfaces 42, 46 separate as the contact point 60 moves through the second contact range R46. The smaller this gap 72, the smaller the speed difference can be, even if speed fluctuations occur in the rotational motion output due to the gap 72. Ultimately, when a constant rotational speed is input to either moving member 16, 18, significant speed unevenness in the rotational motion output from either moving member 16, 18 due to the separation between the first contact surface 42 and the second contact surface 46 can be suppressed. This effect can be achieved regardless of whether the high-speed rotational motion is oscillating or rotating, and regardless of the combination of moving members 16, 18 that perform high-speed and low-speed rotational motion. To achieve this, it is effective to provide the first moving member 16 and the second moving member 18 with a convex portion 80, described below. Details of this convex portion 80 are explained below.

Refer to Figure 7. This figure shows the reference rotation position where the center C42 of the first contact surface 42 and the center C46 of the second contact surface 46 are in contact. For ease of explanation, this figure also shows the linear shape Sb, which is the reference shape of the second contact surface 46. At least one of the first contact surface 42 and the second contact surface 46 has a convex portion 80 that is positioned offset from its center C42, C46. In this embodiment, only the second contact surface 46 has the convex portion 80. Although not shown, in this embodiment, all second contact surfaces 46 of the second movement member 18 are provided with convex portions 80. In this embodiment, the convex portions 80 are individually provided on both sides of the center C46 of the second contact surface 46 on the second contact surface 46. The convex portions 80 are provided so as to be convex toward the opposing second contact surface 46 (the first movement member 16 side) relative to the linear shape Sb, which is the reference shape.

Refer to Figures 7 and 8. As mentioned above, the reference rotation position is the position of the first moving member 16 and the second moving member 18 when the center C42 of the first contact surface 42 and the center C46 of the second contact surface 46 are in contact. As mentioned above, when the high-speed rotational motion advances by a rotation angle θ1 from this reference rotation position and the low-speed rotational motion advances by a rotation angle θ2, a straight line Le is assumed extending from the diagonal angle Sa1 of the side of the Reuleaux shape Sa facing the second contact surface 46 in the facing direction Da of the second contact surface 46. As mentioned above, the first contact surface 42 is closest to the second contact surface 46 on this straight line Le. The first rotation angle θ1 is in the range of less than ±90°. The convex portion 80 is arranged so that the distance between the first contact surface 42 and the second contact surface 46 on this straight line Le is narrower than the reference distance Ls when they are in the reference shape. In this embodiment, the distance on this straight line Le is zero. In other words, the protrusions 80 are provided so that the contact point 60 between the first contact surface 42 and the second contact surface 46 is on this straight line Le. Alternatively, there may be a gap between the first contact surface 42 and the second contact surface 46 on this straight line Le. The protrusions 80 that satisfy this condition only need to be provided in a portion of the second contact range R46 that continues from the center C46 of the second contact surface 46. In this embodiment, the protrusions 80 that satisfy this condition are provided throughout the entire range from the center C46 of the second contact surface 46 to the end positions R46a and R46b of the second contact range R46.

The convex portion 80 has an increasing convex amount region 82 in which the amount of convexity gradually increases with increasing distance from the center C46 of the second contact surface 46. The "amount of convexity" here refers to the distance in the opposing direction Da from the linear shape Sb in the reference shape described above to the surface of the convex portion 80 when the convex portion 80 is provided on the second contact surface 46. In addition, the convex portion 80 has a decreasing convex amount region 84 that is continuous with the end opposite the center of the increasing convex amount region 82 and whose amount of convexity gradually decreases with increasing distance from the center C46.

(A) By providing such a convex portion 80, even if the first contact surface 42 and the second contact surface 46 separate while the contact point 60 moves within the second contact range R46, a large gap 72 that allows fluctuations in the rotational motion output from either of the moving members 16, 18 is less likely to occur. Consequently, when a rotational motion at a constant rotational speed is input to either of the moving members 16, 18, large speed variations in the rotational motion output from either of the moving members 16, 18 can be suppressed.

(B) Furthermore, the convex portions 80 are provided individually on both sides of the center C46 of the second contact surface 46. This has the effect of suppressing large speed variations in the rotational motion output from either of the moving members 16, 18 over a wider second contact range R46 compared to when the convex portions 80 are provided only on one side of the center C46 of the second contact surface 46.

In addition, an interference avoidance portion 88 is provided at the corner 86 including the vertex 44 of the first moving member 16 to avoid interference with the second moving member 18. The interference avoidance portion 88 is provided by positioning the actual corner 86 of the first moving member 16 more inward than the corner 86 of the first moving member 16 in its reference shape (the corner of the Reuleaux shape Sa). In this embodiment, the interference avoidance portion 88 is curved. In this embodiment, the first contact surface 42 of the first moving member 16 has a shape that matches the Reuleaux shape Sa except for the position where the interference avoidance portion 88 is located. In addition, the second contact surface 46 of the second moving member 18 in this embodiment is provided to extend outside the second contact range R46, but may be provided only within the second contact range R46.

(Second embodiment) See Figures 9 and 10. In the following embodiments, the same content as in the first embodiment applies unless otherwise specified. Here, an example will be described in which the aforementioned convex portions 80 are provided on the second contact surfaces 46 instead of the first contact surfaces 42. In this embodiment, convex portions 80 are provided on all first contact surfaces 42 of the first moving member 16. In this embodiment, the convex portions 80 on the first contact surfaces 42 are provided individually on both sides of the center C42 of the first contact surfaces 42. The convex portions 80 are provided so as to be convex radially outward of the first moving member 16 relative to the sides of the Reuleaux shape Sa, which is the reference shape. The convex portions 80 on the first contact surfaces 42 have a radius of curvature that is smaller than the radius of curvature of the sides of the Reuleaux shape Sa. The convex portions 80 in this embodiment are composed of multiple arc shapes that satisfy this condition.

Refer to Figures 9 to 11. Figure 11 shows the moving members 16, 18 of the second embodiment, viewed from the same viewpoint as part B in Figure 8, when the rotational movement has progressed from the reference rotation position by the same rotation angles θ1 and θ2 as in Figure 8. As in the first embodiment, when the rotational movement has progressed from the reference rotation position by the rotation angles θ1 and θ2, a straight line Le is assumed to extend from the farthest diagonal Sa1 of the side of the Reuleaux shape Sa that faces the second contact surface 46 in the facing direction Da of the second contact surface 46. As in the first embodiment, the convex portion 80 of this embodiment is also arranged so that the distance between the first contact surface 42 and the second contact surface 46 on this straight line Le is narrower than the reference distance Ls when they are in the reference shape. In this embodiment, the distance on this straight line Le is arranged to be zero. In other words, the convex portion 80 is arranged so that the contact point 60 between the first contact surface 42 and the second contact surface 46 is located on this straight line Le.

The contact range of the second contact surface 46 with the first contact surface 42 is referred to as the first contact range R42. The first contact range R42 ranges from the end position R42a on the counter-traveling direction side, where contact begins during the process of contact between the second contact surface 46 and the first contact surface 42, to the end position R42b on the traveling direction side, where contact ends. In this case, the convex portion 80 only needs to be provided in a portion of the first contact range R42 that continues from the center C42 of the first contact surface 42. In this embodiment, the convex portion 80 that satisfies this condition is provided in the entire range from the center C42 of the first contact surface 42 to the end positions R42a, R42b of the first contact range R42.

The convex portion 80 has an increasing convex amount region 82 in which the convex amount gradually increases with increasing distance from the center C42 of the first contact surface 42. The convex amount here refers to the radial distance from the diagonal corner of the Reuleaux shape Sa that is the farthest from the edge that overlaps with the first contact surface 42 when the convex portion 80 is provided on the first contact surface 42, and is the distance from the Reuleaux shape Sa to the surface of the convex portion 80. In addition, the convex portion 80 has a decreasing convex amount region 84 that is continuous with the anti-center end of the increasing convex amount region 82 and whose convex amount gradually decreases with increasing distance from the center position.

As a result, in this embodiment, the same effect as in (A) above can be achieved. Furthermore, the protrusions 80 are provided individually on both sides of the center C42 of the first contact surface 42 on the first contact surface 42. Therefore, as in (B) above, the effect of suppressing large speed variations can be achieved over a wider first contact range R42 compared to when the protrusions 80 are provided only on one side of the center C42 of the first contact surface 42.

In this embodiment, too, an interference avoidance portion 88 is provided at the corner 86 of the first moving member 16. In this embodiment, the convex portion 80 of the first moving member 16 is provided at a location on the first contact surface 42 other than the interference avoidance portion 88 and the center C42. In addition, in this embodiment, the second contact surface 46 of the second moving member 18 has a shape that matches the linear shape Sb, which is the reference shape.

(Third embodiment) Refer to Figure 12. The preferred conditions to be met when providing a convex portion 80 will be explained. When high-speed rotational motion and low-speed rotational motion are performed, the contact point 60 rotates around the instantaneous center 90. Assume a distance e from the first rotational center Ca to the second rotational center Cb. This distance e is also the eccentricity amount from the rotational center C12 of the high-speed shaft 12, which is concentric with the first rotational center Ca, to the center C32 of the eccentric body 32, which is concentric with the second rotational center Cb. In this case, if the high-speed rotational motion progresses by a first rotational angle θ1 from the reference rotational position and the low-speed rotational motion progresses by a second rotational angle θ2 (= θ1 × (1/n)), the instantaneous center 90 of the contact point 60 will exist on the straight line Lf passing through the first rotational center Ca and the second rotational center Cb, according to the three-instantaneous center theorem. Furthermore, in this case, the instantaneous center 90 of the contact point 60 is geometrically always located on this straight line Lf at a distance e×N from the second center of rotation Cb (here, a position e×3) on the opposite side of the second center of rotation Cb from the first center of rotation Ca.

Now, consider a case where, within a certain rotational angle range (0≦|θ1|<90°) where high-speed rotational motion occurs, there is a contact point 60 between the first contact surface 42 and the second contact surface 46 on a line Lg extending from the instantaneous center 90 along the opposing direction Da. In this case, within the rotational angle range where the conditions for that contact point 60 are satisfied, it is possible to satisfy what are generally called the mechanical requirements of gears. Furthermore, within the rotational angle range where the conditions for that contact point 60 are satisfied, it is possible to maintain a constant ratio of the angular velocity of high-speed rotational motion to the angular velocity of low-speed rotational motion.

It is preferable that the convex portions 80 of the first contact surface 42 are arranged so that the contact points 60 are on the straight line Lg passing through this instantaneous center 90. As described above, convex portions 80 that satisfy this condition need only be arranged in at least a portion of the first contact range R42 that continues from the center C42 of the first contact surface 42. In this embodiment, convex portions 80 that satisfy this condition are arranged throughout the entire first contact range R42 (the range excluding the center C42). This condition is satisfied for each of the multiple first contact surfaces 42. As a result, the ratio of the angular velocity of the high-speed rotational movement to the angular velocity of the low-speed rotational movement can be kept constant within the rotational angle range that satisfies this condition (here, the entire rotational angle range regardless of the rotational angle).

When both the first moving member 16 and the second moving member 18 are in their reference shapes, a gap 72 is formed between the first contact surface 42 and the second contact surface 46 on a straight line Lg extending from the instantaneous center 90 along the opposing direction Da of the second contact surface 46. Depending on the magnitude of the first rotation angle θ1, this straight line Lg passes through a position slightly different from the straight line Le in FIG. 8 described above. The convex portion 80 of this embodiment can be said to be arranged so as to eliminate the gap 72 on the straight line Lg that passes through a position different from the straight line Le.

(Fourth embodiment) Refer to Figure 13. The power transmission device 10 of this embodiment differs in the configuration of the first moving member 16 and the second moving member 18. The first moving member 16 and the second moving member 18 of this embodiment do not have the convex portion 80 described above. The second moving member 18 of this embodiment comprises a main body member 100 that is integrated with the casing 20, and a plurality of contact members 102 that are detachably attached to the main body member 100. Each of the plurality of contact members 102 is provided with an individual second contact surface 46.

The second contact surface 46 of the second moving member has multiple roller surfaces 103 that are in rolling contact with the first contact surface 42 of the first moving member 16. The roller surfaces 103 are made up of the outer peripheral surfaces of rollers 104 that are rotatably supported on the contact member 102. The second contact surface 46 is arranged so that the inner peripheral surface 102a of the contact member 102 and the roller surfaces 103 are arranged alternately. The rollers 104 are rotatably supported by being fitted into grooves 102b provided in the contact member 102. Alternatively, the rollers 104 may be rotatably supported via pins provided on the contact member 102. The multiple rollers 104 are arranged in a row perpendicular to a straight line Lb that connects the centers C46 of opposing pairs of second contact surfaces 46. In this embodiment, ten roller surfaces 103 are provided on each individual second contact surface 46.

Refer to Figures 13 and 14. The first contact surface 42 of the first motion member 16 has a plurality of recesses 106 with which the roller surfaces 103 make rolling contact. The plurality of recesses 106 on one first contact surface 42 correspond one-to-one with at least some of the roller surfaces 103 on one second contact surface 46. In this embodiment, six recesses 106 are provided on one first contact surface 42, and six of the ten roller surfaces 103 on one second contact surface 46 correspond one-to-one with the six recesses 106.

Consider the case where one or both of the moving members 16, 18 perform high-speed rotational motion at a constant first rotational speed w1 and low-speed rotational motion at a constant second rotational speed w2 (= first rotational speed w1 × (1/reduction ratio n)). In this case, the recesses 106 are formed so that they come into rolling contact with the corresponding roller surface 103. This can be achieved by positioning a rotary blade capable of cutting with the same diameter as the roller surface 103 at a position on the roller surface 103 during molding of the first moving member 16, while performing high-speed rotational motion at the first rotational speed w1 and low-speed rotational motion at the second rotational speed w2.

The recess amounts d1 to d3 of the multiple protrusions 80 on one first contact surface 42 decrease as the distance from the center C42 of the first contact surface 42 increases. The recess amount here refers to the maximum length from the line segment Lh connecting both ends of the recess 106 on the first contact surface 42 to the bottom of the recess 106 in a direction perpendicular to the line segment Lh. When the recess amounts of the three recesses 106 on either side of the center C42 of the first contact surface 42 are d1 to d3, in order from the center C42 side, the recess amounts decrease in the order d1, d2, and d3.

The widths w1 to w3 of the multiple recesses 106 on one first contact surface 42 increase with increasing distance from the center C42 of the first contact surface 42. Here, the widths w1 to w3 of the recesses 106 refer to the length of the line segment Lh connecting both ends of the recess 106. When the widths of the three recesses 106 on either side of the center C42 of the first contact surface 42 are designated w1 to w3, in order from the center C42 side, the widths increase in the order w1, w2, and w3.

To satisfy these conditions, the recesses 106 on one first contact surface 42 are arc-shaped, with the radius of curvature of the recess 106 closest to the center C42 of the first contact surface 42 being smallest, and the radius of curvature gradually increasing as the distance from that point increases. To satisfy these conditions, each recess 106 is arc-shaped, combining a single or multiple arcs.

See FIG. 15. Similarly to the first embodiment, when either high-speed or low-speed rotational motion is input, each of the moving members 16, 18 can convert one of the input rotational motions into the other through contact between the first contact surface 42 and the second contact surface 46 and then output the other rotational motion. Also, similar to the first embodiment, each moving member 16, 18 converts one rotational motion into the other rotational motion at a predetermined gear ratio and then outputs the other rotational motion. Similarly to the first embodiment, the contact point 60 (not shown) of the first contact surface 42 with the second contact surface 46 moves in the direction of travel Db within the second contact range R46 of the first contact surface 42 with the second contact surface 46 during the movement of each moving member 16, 18. Also, similar to the first embodiment, the high-speed and low-speed rotational motions of the first moving member 16 and the second moving member 18 progress by repeatedly initiating contact between the trailing contact surfaces 42, 46 and releasing contact between the leading contact surfaces 42, 46. Below, we will explain an example in which, as in the first embodiment, oscillating motion (high-speed rotational motion) is input from the high-speed shaft 12 to the first moving member 16, and this oscillating motion is converted into rotational motion (low-speed rotational motion) and then output from the first moving member 16 to the low-speed shaft 14.

Refer to Figure 16. Here, an example is shown in which the motion members 16, 18 operate in the order of Figure 16(A) → Figure 16(B) → Figure 16(C) → Figure 16(D). Each figure also shows the movement trajectory of the contact point 60 between the first contact surface 42 and the second contact surface 46. For ease of explanation, each roller surface 103 and roller 104 is distinguished by assigning an ordinal number that gradually increases in the direction of travel Db. In other words, the roller surfaces 103 are distinguished in the order of the first roller surface 103, the second roller surface 103, ... the ninth roller surface 103, and the tenth roller surface 103 in the direction of travel. In the figures, these ordinal numbers 1 to 10 are assigned to the rollers 104.

According to this embodiment, as the contact point 60 moves through the second contact range R46, the roller surface 103 of the second contact surface 46 that is in contact with the first contact surface 42 changes direction in the direction of travel Db, allowing the contact point 60 to move in a discontinuous manner within the second contact range R46 in the direction of travel Db. The roller surface 103 that is in contact with the first contact surface 42 within the second contact range R46 is referred to as the contact roller surface. Figure 16(A) shows an example in which the fifth roller surface 103 to the eighth roller surface 103 are the contact roller surfaces. Similarly, Figure 16(B) shows an example in which the sixth roller surface 103 to the ninth roller surface 103, Figure 16(C) shows an example in which the seventh roller surface 103 to the ninth roller surface 103, and Figure 16(D) shows an example in which the ninth roller surface 103 to the tenth roller surface 103 are the contact roller surfaces.

As the contact point 60 progresses, a contact initiation operation is performed in which the contact roller surface 103 and the roller surface 103 adjacent to it in the direction of travel Db begin contact with the first contact surface 42 while maintaining contact between the contact roller surface 103 and the first contact surface 42. Figure 16(A) shows an example in which the contact initiation operation is performed by the eighth roller surface 103, Figure 16(B) shows the ninth roller surface 103, and Figure 16(D) shows the tenth roller surface 103.

Furthermore, as the contact point 60 moves, the contact roller surface 103 in the opposite direction of travel and the first contact surface 42 move away from each other while maintaining contact with the contact roller surface 103 in the direction of travel Db, thereby performing a contact release operation that releases the contact between the two. Figure 16(A) shows an example of the contact release operation being performed by the fourth roller surface 103, Figure 16(B) shows the fifth roller surface 103, Figure 16(C) shows the sixth roller surface 103, and Figure 16(D) shows the seventh roller surface 103. While repeating this contact initiation and contact release operation between the roller surface 103 and the first contact surface 42, the contact point 60 on the second contact surface 46 moves discontinuously in the direction of travel Db.

When a contact point 60 exists on a roller surface 103 that corresponds one-to-one with a recess 106, that roller surface 103 comes into rolling contact with the inner surface of the recess 106. Figure 16 (A) shows an example in which the fifth to seventh roller surfaces 103 to 103 come into rolling contact with the inner surfaces of the recesses 106 that correspond one-to-one. The presence of the recesses 106 in this way allows the contact point 60 to move forward while avoiding interference between the recess 106 and the roller surface 103 that corresponds one-to-one.

As described above, the power transmission device 10 of this embodiment has a roller surface 103 on the second contact surface 46 of the second moving member 18 and a recess 106 on the first contact surface 42 of the first moving member 16. As a result, when the roller surface 103 and the first contact surface 42 are in contact, the rolling contact of the roller surface 103 allows the contact point 60 between the second contact surface 46 and the first contact surface 42 to advance without separating the roller surface 103 from the first contact surface 42. Furthermore, the contact point 60 can advance in a discontinuous manner while maintaining contact between any of the roller surfaces 103 of the second contact surface 46 and the first contact surface 42. Consequently, the second contact surface 46 and the first contact surface 42 are less likely to separate as the contact point 60 advances within the second contact range R46. As a result, large speed variations in the rotational motion output from either of the moving members 16, 18 caused by separation between the first contact surface 42 and the second contact surface 46 can be suppressed.

Next, we will explain variations of each of the components described above.

There is no particular limitation on the combination of the first moving member 16 and the second moving member 18 that perform high-speed rotational motion and low-speed rotational motion. Examples of such combinations include the following (1) to (3).
(1) The first moving member 16 performs a high-speed rotational motion (oscillating motion), and the second moving member 18 performs a low-speed rotational motion (spinning motion).
(2) The second moving member 18 performs high-speed rotational motion (swinging motion), and the first moving member 16 performs low-speed rotational motion (spinning motion).
(3) The first moving member 16 performs high-speed rotation (spinning), and the second moving member 18 performs low-speed rotation (spinning).

The power transmission device 10 of (1) is intended to function, for example, as an externally oscillating eccentric oscillating gear device in which the first moving member 16, functioning as an external gear, performs oscillating motion. In this case, to perform oscillating motion using the first moving member 16, the rotation of the high-speed shaft 12 is simply caused to cause the first moving member 16 to perform oscillating motion together with the eccentric body 32, as described above. Furthermore, to perform rotational motion using the second moving member 18, the carrier 24 is fixed to an external support member to constrain the rotation of the first moving member 16, while the casing 20 is integrated with the low-speed shaft 14. This allows the low-speed shaft 14 to rotate at the same rotational speed as the rotational component of the second moving member 18, which performs axial rotation. In this case, the number of second contact surfaces 46 (number of teeth) of the second moving member 18 may be N+1.

The power transmission device 10 (2) is assumed to function, for example, as an internally oscillating eccentric oscillating gear device in which the second moving member 18, functioning as an internal gear, oscillates. In this case, the second moving member 18 oscillates together with the eccentric body 32 due to the rotation of the high-speed shaft 12. In this case, an eccentric bearing 34 is disposed between the second moving member 18 and the eccentric body 32, which oscillates, allowing relative rotation between them. Furthermore, in this case, the first moving member 16 is rotated about its axis by the first moving member 16 being arranged so that it can rotate integrally with the low-speed shaft 14. This allows the low-speed shaft 14 to rotate at the same rotational speed as the rotational component of the first moving member 16. In this case, the first center of rotation Ca oscillates (revolves) around the second center of rotation Cb, which serves as the center of rotation for the rotation, while the second center of rotation Cb remains stationary, resulting in oscillating motion. In this case, the number of second contact surfaces 46 (number of teeth) of the second moving member 18 may be N+1.

In the case of (3), the first moving member 16 that performs high-speed rotational motion can be arranged to rotate integrally with the high-speed shaft 12, and the second moving member 18 that performs low-speed rotational motion can be arranged to rotate integrally with the low-speed shaft 14. In this case, when either high-speed or low-speed rotational motion is input to each moving member 16, 18, it can convert one into the other and output the other rotational motion. In this case, the reduction ratio n is (N+1)/N, as described above. In this case, the number of second contact surfaces 46 (number of teeth) of the second moving member 18 may be N+1.

So far, we have explained an example in which high-speed rotational motion is input from the high-speed shaft 12 to either the first moving member 16 or the second moving member 18, and the motion is converted into low-speed rotational motion before being output from either the first moving member 16 or the second moving member 18 to the low-speed shaft 14. Alternatively, when low-speed rotational motion is input from the low-speed shaft 14 to either the first moving member 16 or the second moving member 18, the motion may be converted into high-speed rotational motion before being output from either the first moving member 16 or the second moving member 18 to the high-speed shaft 12. In other words, the first moving member 16 and the second moving member 18 may decelerate the rotational motion input from the high-speed shaft 12 and output it to the low-speed shaft 14, or may accelerate the rotational motion input from the low-speed shaft 14 and output it to the high-speed shaft 12.

Alternatively, the first moving member 16 and the second moving member 18 may convert one of the high-speed and low-speed rotational motions into the other, and then output the converted motion rather than outputting it as is. For example, when oscillating motion (high-speed rotational motion) is input from the high-speed shaft 12 to the first moving member 16 via the eccentric body 32, that input may be converted into rotational motion (low-speed rotational motion) of the first moving member 16, and also into linear motion of the second moving member 18, which may then be output to the low-speed shaft 14 via the casing 20. This is intended for cases where the distance from the first center of rotation Ca to the second center of rotation Cb of the first moving member 16 (the eccentricity of the eccentric body 32) is increased, and the first moving member 16 is used as a cam. In this case, the second moving member 18 may only have a pair of second contact surfaces 46.

The number of first motion members 16 and second motion members 18 is not particularly limited. For example, multiple first motion members 16 may be connected so that they can rotate together, or multiple first motion members 16 may be connected via a pin member so that their rotational components can be synchronized. In this case, the multiple first motion members 16 are arranged at positions offset in the axial direction. In this case, the phases around the center of the multiple first motion members 16 that are connected to each other may be offset from each other. In this case, individual second motion members 18 corresponding to each of the multiple first motion members 16 may be used.

When the N first contact surfaces 42 of the first moving member 16 form an odd-numbered polygonal shape, N is not limited to 3 and may be an odd number greater than or equal to 5. When the second moving member 18 has N+1 second contact surfaces 46, it can also be said that the N+1 second contact surfaces 46 may form an even-numbered polygonal shape. Furthermore, the N first contact surfaces 42 of the first moving member 16 may also form an even-numbered polygonal shape, in which case N may be an even number greater than or equal to 4.

The protrusions 80 may be provided on both the first contact surface 42 and the second contact surface 46. In this case, too, the protrusions 80 need only be provided so as to narrow the distance on the aforementioned straight line Le below the reference distance Ls when the high-speed rotational movement and the low-speed rotational movement progress from the reference rotational position by rotation angles θ1 and θ2, respectively, as described above.

When the protrusion 80 is provided on the first contact surface 42, it may be provided on only one side of the center C42 of the first contact surface 42. When the protrusion 80 is provided on the first moving member 16, it may not be provided on all of the first contact surfaces 42, but may be provided on only some of the first contact surfaces 42.

When the protrusion 80 is provided on the second contact surface 46, it may be provided on only one side of the center C46 of the second contact surface 46. When the protrusion 80 is provided on the second moving member 18, it may not be provided on all of the second contact surfaces 46, but may be provided on only some of the second contact surfaces 46.

The pin member 26 need only connect the first moving member 16 and the carrier 24 in synchronization with the rotational component of the first moving member 16 while allowing the first moving member 16 to oscillate, and the specific configuration for this is not particularly limited. For example, the pin member 26 may be provided integrally with the carrier 24, and the insertion hole of the pin member 26 provided in the movement unit 22 may be eccentric with respect to the center of the pin member 26, with the direction and amount of eccentricity being the same as that of the eccentric body 32 that oscillates the movement unit 22 into which it is inserted. When connecting the first moving member 16 and the carrier 24 with the pin member 26, the two may be connected without using the flange member 36 that is integral with the first moving member 16.

The above embodiments and variations are merely examples. The abstract technical concepts behind them should not be interpreted as being limited to the content of the embodiments and variations. Many design changes are possible within the contents of the embodiments and variations, such as changing, adding, or deleting components. In the above embodiments, the terms "embodiment" are used to emphasize content that allows for such design changes. However, design changes are also permitted even in content that does not have such a notation. Hatching on cross sections in the drawings does not limit the material of the hatched objects. The structures/values referred to in the embodiments and variations naturally include those that can be considered identical when taking into account manufacturing errors such as dimensional errors.

Any combination of the above components is also valid. For example, an embodiment may be combined with any of the descriptions of other embodiments, or a variant may be combined with any of the descriptions of an embodiment and another variant. A component made up of a single member in an embodiment may be made up of multiple members. Similarly, a component made up of multiple members in an embodiment may be made up of a single member.

10...power transmission device, 16...first moving member, 18...second moving member, 42...first contact surface, C42...center, 44...vertex, 46...second contact surface, C46...center, 48...vertex, 60...contact point, 80...convex portion, 82...region of increased convexity, 88...interference avoidance portion, 104...roller, 106...recess.

Claims (9)

a first moving member having N first contact surfaces, the outer periphery of which has an N-sided polygonal shape, where N is a natural number of 3 or more;
a second moving member having a plurality of second contact surfaces that contact the first contact surface,
when one of high-speed rotational motion and low-speed rotational motion around different rotation centers is input to either of the first and second moving members, the first and second moving members can convert the input into the other of the high-speed rotational motion and the low-speed rotational motion and output the other of the input through contact between the first contact surface and the second contact surface,
the first contact surface has an arc shape that is convex radially outward with respect to a line connecting adjacent vertices of the N-gon,
the second contact surface is generally linear;
A power transmission device in which, when the contact position with the center of the first contact surface is the center of the second contact surface, at least one of the first contact surface and the second contact surface has a convex portion that is located at a position offset from its center. When a Reuleaux N-gon shape having the same number of angles as the N-gon and midpoints of each side coinciding with the centers of the N first contact surfaces and a linear shape extending perpendicularly from both ends of a line segment having both ends at the centers of the opposing pairs of second contact surfaces and a length equal to the across width of the Reuleaux N-gon shape are used as reference shapes, and a reduction ratio n of the high-speed rotational motion relative to the low-speed rotational motion determined based on the motion modes of the low-speed rotational motion and the high-speed rotational motion and N is assumed,
2. The power transmission device of claim 1, wherein when the high-speed rotational motion progresses by a first rotational angle θ1 and the low-speed rotational motion progresses by a second rotational angle θ2 (= θ1 × (1/n)) from a reference rotational position where the center of the first contact surface and the center of the second contact surface are in contact, the convex portion is arranged so that the distance in the direction along the line segment at the closest position between the first contact surface and the second contact surface is narrower than the distance when they are in the reference shape. When a distance e from a first center of rotation of the high-speed rotational motion to a second center of rotation of the low-speed rotational motion, an opposing direction along a line segment connecting centers of the opposing pairs of second contact surfaces, and a reduction ratio n of the high-speed rotational motion relative to the low-speed rotational motion determined based on the motion modes of the low-speed rotational motion and the high-speed rotational motion and N are assumed,
3. The power transmission device of claim 1, wherein the convex portion is arranged so that when the high-speed rotational motion progresses by a first rotational angle θ1 and the low-speed rotational motion progresses by a second rotational angle θ2 (= θ1 × (1/n)) from a reference rotational position where the center of the first contact surface and the center of the second contact surface are in contact, the contact point between the first contact surface and the second contact surface is on a line extending in the opposing direction from a position that is a distance e × N from the second rotational center on a line passing through the first rotational center and the second rotational center. A power transmission device according to any one of claims 1 to 3, wherein the protrusions are individually provided on both sides of the center of the first contact surface on the first contact surface, or on both sides of the center of the second contact surface on the second contact surface. When an N-gon Reuleaux shape is assumed, which has the same number of sides as the N-gon and the midpoints of the sides coincide with the centers of the N first contact surfaces,
The power transmission device according to claim 1 , wherein the convex portion of the first contact surface has a radius of curvature smaller than the radius of curvature of a side of the Reuleaux N-sided polygon. A power transmission device according to any one of claims 1 to 5, wherein the convex portion has an increasing convexity region in which the convexity gradually increases with increasing distance from the center of either the first contact surface or the second contact surface. a first moving member having N first contact surfaces, the outer periphery of which has an N-sided polygonal shape, where N is a natural number of 3 or more;
a second moving member having a plurality of second contact surfaces that contact the first contact surface,
when one of high-speed rotational motion and low-speed rotational motion around different rotation centers is input, the first moving member and the second moving member can convert the input into the other of the high-speed rotational motion and low-speed rotational motion and output the other of the high-speed rotational motion and low-speed rotational motion by contact between the first contact surface and the second contact surface,
the first contact surface has an arc shape that is convex radially outward with respect to a line connecting adjacent vertices of the N-gon,
the second contact surface comprises a plurality of roller surfaces in rolling contact with the first contact surface;
The first contact surface has a plurality of recesses with which the roller surface makes rolling contact. The power transmission device described in claim 7, wherein the recesses decrease in depth as they move away from the center of the first contact surface. A power transmission device as described in claim 7 or 8, wherein the width of the recesses decreases with increasing distance from the center of the first contact surface.