gear mechanism

Abstract

To realize a gear mechanism capable of exhibiting a speed variation suppression effect.SOLUTION: A gear mechanism having an externally toothed arc gear having M arc teeth and rotating around a first central axis, and an externally toothed non-arc gear having N non-arc teeth and rotating around a second central axis at a predetermined distance D from the first central axis. The shape of at least a part of the non-arc gear tooth side part is formed so that when a virtual circle of radius D×N / (M+N) centered on the second central axis is taken as a fixed circle, a virtual circle of radius D×M / (M+N) centered on the first central axis is taken as a moving circle, and the center of the arc gear tooth side part is taken as a drawing point, an epitrochoid curve drawn is an offset epitrochoid curve by a length r.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a gear mechanism. [Background technology]

[0002] BACKGROUND ART Gear mechanisms including an externally toothed gear that rotates about a first central axis and an externally toothed gear that rotates about a second central axis that is spaced a predetermined distance from the first central axis are already well known. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-82893 Summary of the Invention [Problem to be solved by the invention]

[0004] In the past, some of these gear mechanisms had a drawback in that while one externally toothed gear rotates at a constant speed, the other externally toothed gear would wobble, causing variations in speed (called speed variation). Therefore, there was a demand for a gear mechanism with a new tooth shape that does not have this drawback.

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a gear mechanism that exhibits the effect of appropriately suppressing speed variations. [Means for solving the problem]

[0006] The main invention to achieve the above object is: A gear mechanism having an externally toothed arc-shaped gear having M arc-shaped teeth and rotating around a first central axis, and an externally toothed non-circular gear having N non-circular teeth and rotating around a second central axis separated by a predetermined distance D from the first central axis, the arc-shaped teeth of the externally toothed arc-shaped gear have arc-shaped gear tooth tip portions and arc-shaped gear tooth side portions that are located on the sides of the arc-shaped gear tooth tip portions and have an arc shape with a radius r, a non-circular tooth of the externally toothed non-circular gear has a non-circular gear tooth tip portion and a non-circular gear tooth side portion located on a side of the non-circular gear tooth tip portion and in contact with the arc-circular gear tooth side portion, The non-circular gear tooth side portion is Among the portions that come into contact with the side portions of the arc-shaped gear teeth, At least some of the shape When a virtual circle of radius D×N / (M+N) centered on the second central axis is defined as a fixed circle, a virtual circle of radius D×M / (M+N) centered on the first central axis is defined as a moving circle, and the center of the circular-arc gear tooth side portion is defined as a drawing point, the drawn epitrochoid curve is an offset epitrochoid curve offset by a length r, The gear mechanism is characterized by being formed.

[0007] Other features of the present invention will become apparent from the description of this specification and the accompanying drawings. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is an explanatory diagram for explaining a gear mechanism 1 according to the present embodiment. [Figure 2] 2 is an explanatory diagram for explaining arc-shaped teeth 14 of the externally toothed arc-shaped gear 10 according to the present embodiment. FIG. [Figure 3] This is a diagram showing how to draw an epitrochoid curve EP. [Figure 4] This is a diagram showing another way to draw the epitrochoid curve EP. [Figure 5] 10 is an explanatory diagram for explaining the behavior of a cam mechanism including a cam 60 relating to an epitrochoid curve EP and a cam follower 62a with a radius of 0. FIG. [Figure 6] FIG. 10 is an explanatory diagram for explaining an offset epitrochoid curve OEP. [Figure 7] 10 is an explanatory diagram for explaining the behavior of a cam mechanism including a cam 60 relating to an offset epitrochoid curve OEP and a cam follower 62a relating to a circle of radius r. FIG. [Figure 8] 3 is an explanatory diagram for explaining non-circular teeth 34 of the externally toothed non-circular gear 30 according to the present embodiment. FIG. [Figure 9] FIG. 10 is a diagram showing the correspondence relationship between tooth sides. DETAILED DESCRIPTION OF THE INVENTION

[0009] At least the following matters will become clear from the description of this specification and the accompanying drawings.

[0010] A gear mechanism having an externally toothed arc-shaped gear having M arc-shaped teeth and rotating around a first central axis, and an externally toothed non-circular gear having N non-circular teeth and rotating around a second central axis separated by a predetermined distance D from the first central axis, the arc-shaped teeth of the externally toothed arc-shaped gear have arc-shaped gear tooth tip portions and arc-shaped gear tooth side portions that are located on the sides of the arc-shaped gear tooth tip portions and have an arc shape with a radius r, a non-circular tooth of the externally toothed non-circular gear has a non-circular gear tooth tip portion and a non-circular gear tooth side portion located on a side of the non-circular gear tooth tip portion and in contact with the arc-circular gear tooth side portion, The non-circular gear tooth side portion has a shape in which at least a part thereof is When a virtual circle of radius D×N / (M+N) centered on the second central axis is defined as a fixed circle, a virtual circle of radius D×M / (M+N) centered on the first central axis is defined as a moving circle, and the center of the circular-arc gear tooth side portion is defined as a drawing point, the drawn epitrochoid curve is an offset epitrochoid curve offset by a length r, A gear mechanism characterized in that it is formed.

[0011] According to such a gear mechanism, it is possible to realize a gear mechanism that exhibits the effect of suppressing speed variations.

[0012] In such a gear mechanism, The non-arcuate gear tooth side portion has a shape in which all of the portions that come into contact with the arcuate gear tooth side portion are When a virtual circle of radius D×N / (M+N) centered on the second central axis is defined as a fixed circle, a virtual circle of radius D×M / (M+N) centered on the first central axis is defined as a moving circle, and the center of the circular-arc gear tooth side portion is defined as a drawing point, the drawn epitrochoid curve is an offset epitrochoid curve offset by a length r, It may be formed.

[0013] According to such a gear mechanism, it is possible to realize a gear mechanism that more appropriately exerts the effect of suppressing speed variations.

[0014] In such a gear mechanism, the arc-shaped gear tooth side portion is a first arc-shaped gear tooth side portion, The arc-shaped teeth of the externally toothed arc-shaped gear are a second arc-shaped gear tooth side portion having a radius r, the second arc-shaped gear tooth side portion being located on a side of the arc-shaped gear tooth tip portion and on the opposite side of the arc-shaped gear tooth tip portion from the first arc-shaped gear tooth side portion, the second arc-shaped gear tooth side portion having a center different from the center of the first arc-shaped gear tooth side portion; the non-circular tooth is a first non-circular tooth; the externally toothed non-circular gear has second non-circular teeth different from the first non-circular teeth, the second non-circular tooth of the externally toothed non-circular gear has a non-circular gear tooth tip portion and a non-circular gear tooth side portion located on a side of the non-circular gear tooth tip portion and in contact with the second circular gear tooth side portion, The non-circular gear tooth side portion of the second non-circular tooth has a shape of at least a part thereof, When a virtual circle of radius D×N / (M+N) centered on the second central axis is defined as a fixed circle, a virtual circle of radius D×M / (M+N) centered on the first central axis is defined as a moving circle, and the center of the second circular arc gear tooth lateral portion is defined as a drawing point, the drawn epitrochoid curve is an offset epitrochoid curve offset by a length r, It may be formed.

[0015] According to such a gear mechanism, it is possible to realize a gear mechanism that more appropriately exerts the effect of suppressing speed variations.

[0016] In such a gear mechanism, The non-circular gear tooth side portion of the second non-circular tooth has a shape in which all of the portions that contact the second circular gear tooth side portion are When a virtual circle of radius D×N / (M+N) centered on the second central axis is defined as a fixed circle, a virtual circle of radius D×M / (M+N) centered on the first central axis is defined as a moving circle, and the center of the second circular arc gear tooth lateral portion is defined as a drawing point, the drawn epitrochoid curve is an offset epitrochoid curve offset by a length r, It may be formed.

[0017] According to such a gear mechanism, it is possible to realize a gear mechanism that more appropriately exerts the effect of suppressing speed variations.

[0018] ===Gear Mechanism 1 According to the Present Embodiment=== Next, a gear mechanism 1 according to this embodiment will be described with reference to Fig. 1. Fig. 1 is an explanatory diagram for explaining the gear mechanism 1 according to this embodiment.

[0019] The gear mechanism 1 includes two externally toothed gears (external gears) that mesh with each other. As will be described in detail later, the teeth of one gear are arc-shaped, while the teeth of the other gear are not. Therefore, for convenience, the former gear is referred to as the externally toothed arc gear 10, and the latter gear is referred to as the externally toothed non-circular gear 30.

[0020] The externally toothed arc gear 10 is a gear that rotates around a first central axis 12 and has M (eight in this embodiment) teeth (for convenience, referred to as arc teeth 14). In other words, the number of teeth M of the externally toothed arc gear 10 is eight.

[0021] The externally toothed non-circular gear 30 is a gear that rotates around a second central axis 32 that is a predetermined distance (i.e., axis distance D) away from the first central axis 12, and has N (16 in this embodiment) teeth (for convenience, referred to as non-circular teeth 34). In other words, the number of teeth N of the externally toothed arc gear 10 is 16.

[0022] The arc-shaped teeth 14 and the non-arc-shaped teeth 34 mesh with each other.

[0023] The number of teeth M and the number of teeth N are not limited to 8 and 16 (the number of teeth M and the number of teeth N may be the same number).

[0024] Furthermore, the externally toothed arc-circular gear 10 has M (8) arc-circular teeth 14, and the externally toothed non-circular gear 30 has N (16) arc-circular teeth 14, with the number of teeth of the externally toothed non-circular gear 30 being N / M (2) times the number of teeth of the externally toothed arc-circular gear 10. Based on this, the size of the externally toothed non-circular gear 30 is twice that of the externally toothed arc-circular gear 10. More specifically, the value M / (M+N) times (1 / 3) the center distance D is used as the pitch radius R1 of the pitch circle PC1 of the externally toothed arc-circular gear 10, and the value N / (M+N) times (2 / 3) the center distance D is used as the pitch radius R2 of the pitch circle PC2 of the externally toothed non-circular gear 30.

[0025] ===About Arc Tooth 14=== Next, the arc-shaped teeth 14 of the externally toothed arc-shaped gear 10 according to this embodiment will be described with reference to Figures 1 and 2. Figure 2 is an explanatory diagram for explaining the arc-shaped teeth 14 of the externally toothed arc-shaped gear 10 according to this embodiment. Note that in Figure 2, for the sake of clarity, only one arc-shaped tooth 14 is shown, and the other arc-shaped teeth 14 are omitted.

[0026] The arc-shaped tooth 14 has a tooth side portion with an arc curve that differs from the involute curve typically found in gears. That is, the arc-shaped tooth 14 has an arc-shaped gear tooth tip 16 and an arc-shaped gear tooth side portion 18 that is located on the side of the arc-shaped gear tooth tip 16 and has an arc shape with a radius r. Two arc-shaped gear tooth side portions 18 are provided (referred to as a first arc-shaped gear tooth side portion 18a and a second arc-shaped gear tooth side portion 18b, both of which have the same radius r).

[0027] The second arc-shaped gear tooth side portion 18b is located on the opposite side of the first arc-shaped gear tooth side portion 18a when viewed from the arc-shaped gear tooth tip 16. The center C2 of the second arc-shaped gear tooth side portion 18b is different from the center C1 of the first arc-shaped gear tooth side portion 18a. The distance L from the first central axis 12 to the center C1 is the same as the distance L from the first central axis 12 to the center C2 (this distance L can be set as desired). The radius r and the pitch angle α of the arc shown in FIG. 2 (the face width can be adjusted by adjusting this angle) can also be set as desired.

[0028] The tooth height can also be set arbitrarily, but in this embodiment, the module m (= pitch circle radius R1 × 2 / number of teeth M) is used, and the arc tooth 14 is formed by cutting an arc at a position −1.25 × m on the inside and a position + m on the outside based on the pitch circle PC1 of radius R1.

[0029] ===Non-circular tooth 34=== Next, we will explain the non-circular teeth 34 of the externally toothed non-circular gear 30 according to this embodiment. As will be explained below, the shape of the non-circular teeth 34 is an offset epitrochoid curve OEP, which is an offset from the epitrochoid curve EP.

[0030] <<<About the Epitrochoid Curve EP>>> A trochoid curve is defined as the curve described by a fixed point (also called a drawing point) inside or outside a circle when the circle is rolled along a curve (circle being a special case) without slipping. In particular, a curve composed of two circumscribed circles (i.e., the curve described by a drawing point inside or outside the moving circle when the moving circle is rolled along a fixed circle without slipping) is called an epitrochoid curve EP.

[0031] FIG. 3 shows how to draw an epitrochoid curve EP. In the upper left diagram, the fixed circle (second friction wheel 52) is located on the left, and the moving circle (first friction wheel 50) is located on the right. In this example, the radius of the fixed circle (second friction wheel 52) is twice the radius of the moving circle (first friction wheel 50), and the drawing point P is located within the moving circle (first friction wheel 50) and on the X-axis. From this state, the moving circle (first friction wheel 50) rotates and revolves around the fixed circle (second friction wheel 52) (upper left diagram → upper right diagram → lower left diagram → lower right diagram. θ1 represents the rotation angle, and θ2 represents the revolution angle). When the revolution angle reaches 360 degrees, the moving circle (first friction wheel 50) returns to its original position. The trajectory drawn by the drawing point P during this movement of the moving circle (first friction wheel 50) becomes the epitrochoid curve EP.

[0032] The method of drawing the epitrochoid curve EP shown in Figure 3 above follows the definition of the epitrochoid curve EP, but there are other ways to draw it. Figure 4 shows another way to draw the epitrochoid curve EP.

[0033] In the example of FIG. 3, the second friction wheel 52 is fixed, but in this example, the second friction wheel 52 rotates. Also, in the example of FIG. 3, the first friction wheel 50 revolves while rotating on its axis, but in this example, the first friction wheel 50 only rotates on its axis and does not revolve. That is, in this example, the first friction wheel 50 and the second friction wheel 52 rotate (spin) so as not to slip on each other, with the rotation centers of the first friction wheel 50 and the second friction wheel 52 fixed (upper left diagram → upper right diagram → lower left diagram → lower right diagram. θ1 represents the rotation angle of the first friction wheel 50, and θ2 represents the rotation angle of the second friction wheel 52). During this movement of the first friction wheel 50, the locus drawn by the drawing point P (the arrangement of the drawing point P is the same as in the example of FIG. 3) becomes an epitrochoid curve EP, but in this example, the XY coordinate system rotates together with the rotation of the second friction wheel 52 (therefore, the previously drawn locus moves along with the rotation of the XY coordinate system). In this way, in this example, the drawing is performed based on the locus drawn by the drawing point P when the first friction wheel 50 rolls without slipping when the second friction wheel 52 is rotated, and the locus drawn by the drawing point P is drawn as viewed from the XY coordinate system fixed to the second friction wheel 52. The lower right diagram in Figure 4 shows the state in which the first friction wheel 50 rotates two times (θ1 = 720 degrees) and the second friction wheel 52 rotates once (θ2 = 360 degrees), and the XY coordinate system returns to its original position, and an epitrochoid curve EP is drawn. As is clear from a comparison with the lower right diagram in Figure 3, the method of this example can also draw the same epitrochoid curve EP as shown in Figure 3.

[0034] Next, let us consider the behavior of the cam mechanism when we assume that the epitrochoid curve EP is a cam 60 and the drawing point P is a cam follower 62a with a radius of 0 (in other words, a diameter that is infinitely close to 0). Figure 5 is an explanatory diagram for explaining the behavior of a cam mechanism that includes a cam 60 relating to the epitrochoid curve EP and a cam follower 62a with a radius of 0.

[0035] Figure 5 is basically the same as Figure 4. However, in Figure 5, the epitrochoid curve EP depicted in Figure 4 is shown in its entirety in four complete views (the epitrochoid curve EP is depicted in its entirety not only in the lower right view but also in the upper left, upper right, and lower left views), and this is taken as the cam 60. In addition to this, the depicted point P in Figure 4 is taken as the cam follower 62a with a radius of 0 (in other words, a diameter that is infinitely close to 0), and the section from the depicted point P to the center of the first friction wheel 50 is taken as the arm 62b, and a follower 62 having the cam follower 62a and the arm 62b is assumed.

[0036] 5, when the epitrochoid curve EP rotates in accordance with the rotation of the second friction wheel 52 (upper left diagram → upper right diagram → lower left diagram → lower right diagram), the drawing point P, which moves in accordance with the rotation of the first friction wheel 50, moves on the epitrochoid curve EP. In other words, the cam 60 (epitrochoid curve EP) and the cam follower 62a (drawing point P) move in a state of engagement (contact) with each other.

[0037] Furthermore, because the first friction wheel 50 and the second friction wheel 52 rotate without slipping on each other, when the second friction wheel 52 rotates at a constant speed, the first friction wheel 50 also rotates at a constant speed. This relationship also applies to the cam 60 (epitrochoid curve EP) and the cam follower 62a (drawing point P). That is, when the second friction wheel 52 rotates at a constant speed, the cam 60 (epitrochoid curve EP), which rotates along with the second friction wheel 52, also rotates at a constant speed, and the cam follower 62a (drawing point P), which rotates along with the first friction wheel 50, which rotates at a constant speed, also rotates at a constant speed. In this way, the cam 60 (epitrochoid curve EP) and the cam follower 62a (drawing point P) rotate at a constant speed while engaged (contacting) with each other. That is, even though the cam 60 (epitrochoid curve EP) rotates at a constant speed, the cam follower 62a (drawing point P) is unstable and the speed varies (hereinafter referred to as speed variation). This is appropriately suppressed.

[0038] <<<About the Offset Epitrochoid Curve OEP>>> In the above, we have assumed (assumed) that the epitrochoid curve EP is the cam 60 and the drawing point P is the cam follower 62a with a radius of 0 (in other words, a diameter infinitely close to 0). However, here we will define an offset epitrochoid curve OEP associated with the epitrochoid curve EP, and consider the behavior of the cam mechanism when we assume that this offset epitrochoid curve OEP is the cam 60 and that a circle of radius r centered at the drawing point P on the epitrochoid curve EP is the cam follower 62a. Figure 6 is an explanatory diagram for explaining the offset epitrochoid curve OEP. Figure 7 is an explanatory diagram for explaining the behavior of a cam mechanism including a cam 60 associated with the offset epitrochoid curve OEP and a cam follower 62a associated with the circle of radius r.

[0039] A tangent line TA is drawn at each point on the epitrochoid curve, and a point is taken that is offset inward from each point in the normal direction to the tangent line TA by a certain distance. The curve connecting these points is defined as the offset epitrochoid curve OEP. In other words, as shown in Figure 6, when the bar 70 is moved so that the line LI perpendicular to the bar 70 at the outer end 70a of the bar 70 always becomes the tangent line TA to the epitrochoid curve EP, the locus of the inner end 70b of the bar becomes the offset epitrochoid curve OEP.

[0040] Then, an offset epitrochoid curve OEP with this fixed distance as length r (i.e., an offset epitrochoid curve OEP offset by the length r from the epitrochoid curve EP) is assumed to be the cam 60, and a circle of radius r centered at the drawing point P on the epitrochoid curve EP is assumed to be the cam follower 62a. That is, in FIG. 7, the offset epitrochoid curve OEP offset by the length r from the epitrochoid curve EP is shown in all four diagrams, and this is assumed to be the cam 60. In addition to this, a circle of radius r centered at the drawing point P is assumed to be the cam follower 62a, and the part from the drawing point P to the center of the first friction wheel 50 is assumed to be the arm 62b, and a follower 62 having the cam follower 62a and the arm 62b is assumed.

[0041] 7, when the offset epitrochoid curve OEP rotates in conjunction with the rotation of the second friction wheel 52 (epitrochoid curve EP) (upper left diagram → upper right diagram → lower left diagram → lower right diagram), the cam follower 62a, which moves in conjunction with the rotation of the first friction wheel 50 (drawing point P), operates while maintaining contact with the offset epitrochoid curve OEP. In other words, the cam 60 (offset epitrochoid curve OEP offset by a length r from the epitrochoid curve EP) and the cam follower 62a (circle of radius r) move in a state of engagement (contact) with each other.

[0042] Furthermore, because the first friction wheel 50 and the second friction wheel 52 rotate without slipping against each other, when the second friction wheel 52 rotates at a constant speed, the first friction wheel 50 also rotates at a constant speed. This relationship also applies to the cam 60 (an offset epitrochoid curve OEP obtained by offsetting the epitrochoid curve EP by a length r) and the cam follower 62a (a circle with a radius r). In other words, when the second friction wheel 52 rotates at a constant speed, the cam 60 (offset epitrochoid curve OEP) that rotates along with the second friction wheel 52 also rotates at a constant speed, and the cam follower 62a (a circle with a radius r) that rotates along with the first friction wheel 50 (revolving around the center of the first friction wheel 50) also rotates at a constant speed. In this way, the cam 60 (offset epitrochoid curve OEP) and the cam follower 62a (a circle with a radius r) engage (contact) with each other and perform uniform rotational motion together. That is, even though the cam 60 (offset epitrochoid curve OEP) rotates at a constant speed, the cam follower 62a (circle of radius r) is unstable and the speed varies (speed variations) and this is appropriately suppressed.

[0043] <<<Regarding the shape of the non-circular teeth 34>>> As described above, if we consider the cam 60 to be an offset epitrochoid curve OEP (which is obtained by offsetting the epitrochoid curve EP by a length r), and the cam follower 62a to be a circle of radius r centered at the drawing point P of the epitrochoid curve EP, then this cam mechanism will exhibit the effect of appropriately suppressing speed variations (hereinafter also referred to as the speed variation suppression effect). Therefore, this matter will be applied to the design of the teeth of the gear mechanism 1.

[0044] This point will be explained using Figures 1, 2, 7 to 9. Figure 8 is an explanatory diagram for explaining the non-circular teeth 34 of the externally toothed non-circular gear 30 according to this embodiment. Figure 9 will be described later.

[0045] As described above, the arc-shaped tooth 14 has arc-shaped gear tooth side portions 18 (first arc-shaped gear tooth side portion 18a and second arc-shaped gear tooth side portion 18b) with arc-shaped curves. Here, since the arc-shaped gear tooth side portions 18 are part of a circle with radius r, the first arc-shaped gear tooth side portion 18a of one arc-shaped tooth 14 (for example, the arc-shaped gear tooth side portion 18 indicated by reference symbol TC1) can correspond to the cam follower 62a (see the upper diagrams of FIGS. 7 and 8). In this case, when an imaginary circle of radius R2 (= center distance D × number of teeth N / (number of teeth M + number of teeth N)) centered on the second central axis 32 is defined as the fixed circle (second friction wheel 52), an imaginary circle of radius R1 (= center distance D × number of teeth M / (number of teeth M + number of teeth N)) centered on the first central axis 12 is defined as the dynamic circle (first friction wheel 50), and the center C1 of the first circular gear tooth side portion TC1 is defined as the drawing point P, the drawn epitrochoid curve EP is offset by a length r to form an offset epitrochoid curve OEP (see FIG. 7 ), which corresponds to the cam 60. Therefore, if the shape of the non-circular gear tooth side portion 38 that comes into contact with the circular gear tooth side portion 18 (first circular gear tooth side portion 18 a) is set to the offset epitrochoid curve OEP (see the upper diagram in FIG. 8 ), a gear mechanism 1 that suppresses speed variations can be realized.

[0046] As described above, the shape of at least a portion of the non-arcuate gear tooth side portion 38 according to this embodiment is formed so that, when a virtual circle of radius R2 (= axis distance D × number of teeth N / (number of teeth M + number of teeth N)) centered on the second central axis 32 is taken as the fixed circle (second friction wheel 52), a virtual circle of radius R1 (= axis distance D × number of teeth M / (number of teeth M + number of teeth N)) centered on the first central axis 12 is taken as the moving circle (first friction wheel 50), and the center C1 of the first arc-circular gear tooth side portion 18a is taken as the drawing point P, the drawn epitrochoid curve EP becomes an offset epitrochoid curve OEP (see FIG. 7 ) that is offset by the length r.

[0047] Like the arc-shaped tooth 14, the non-arc gear tooth 34 has a non-arc gear tooth tip 36 in addition to a non-arc gear tooth side 38. In other words, the non-arc gear tooth 34 has the non-arc gear tooth tip 36 and the non-arc gear tooth side 38 located on the side of the non-arc gear tooth tip 36.

[0048] A specific design example of the non-circular gear tooth 34 according to this embodiment is as follows. First, one first arc-shaped gear tooth side portion 18a (e.g., the arc-shaped gear tooth side portion 18 designated by reference symbol TC1) is selected, and the corresponding offset epitrochoid curve OEP is drawn. Then, as with the arc-shaped tooth 14, a portion of the offset epitrochoid curve OEP that may come into contact with the first arc-shaped gear tooth side portion TC1 is cut at a position −1.25×m inward and a position +m outward from the pitch circle PC2 of radius R2, resulting in the non-circular gear tooth side portion 38 (designated by reference symbol TN1a) of the non-circular gear 34 (however, the tooth height can be set arbitrarily, as with the arc-shaped tooth 14).

[0049] Furthermore, in this embodiment, the number of teeth of the externally toothed non-circular gear 30 is twice the number of teeth of the externally toothed arc-circular gear 10, so the externally toothed non-circular gear 30 rotates once while the externally toothed arc-circular gear 10 rotates twice. Therefore, there are two non-arc gear tooth side portions 38 that contact the first arc-circular gear tooth side portion TC1, and therefore the non-arc gear tooth side portion 38 (denoted by symbol TN1b) is also obtained by cutting the offset epitrochoid curve OEP, which is point-symmetrical to the non-arc gear tooth side portion TN1a when viewed from the second center axis 32. Due to the above-described design, the non-arc gear tooth side portions TN1a and TN1b in this embodiment have an overall shape that is the offset epitrochoid curve OEP. Therefore, the non-arc gear tooth side portions TN1a and TN1b are formed so that the shape of the entire portion that contacts the arc-gear tooth side portion 18 is the offset epitrochoid curve OEP.

[0050] Next, the above steps are repeated for the second arc-circular gear tooth side portion 18b (designated TC2), which is located on the opposite side of the first arc-circular gear tooth side portion TC1 as viewed from the arc-circular gear tooth tip 16 (see the lower diagram in Figure 8). That is, the offset epitrochoid curve OEP corresponding to the second arc-circular gear tooth side portion TC2 is drawn. Then, for the portion of the offset epitrochoid curve OEP that may come into contact with the second arc-circular gear tooth side portion TC2, the offset epitrochoid curve OEP is cut at a position −1.25×m inward and a position +m outward from the pitch circle PC2 of radius R2, which defines the non-arcuate gear tooth side portion 38 (designated TN2a) of the non-arcuate tooth 34. Furthermore, the offset epitrochoid curve OEP, which is point-symmetrical to the non-arcuate gear tooth side portion TN2a as viewed from the second center axis 32, is also cut and defined as the non-arcuate gear tooth side portion 38 (designated TN2b). The non-arc gear tooth side portion TN2a (non-arc gear tooth side portion TN2b) is a tooth side portion of another (adjacent) non-arc tooth 34 (also called second non-arc tooth 34b) that is different from the non-arc tooth 34 (also called first non-arc tooth 34a) that has the non-arc gear tooth side portion TN1a (non-arc gear tooth side portion TN1b).

[0051] Then, by carrying out the above steps (procedures) on the other seven arc-circular teeth 14, all of the non-arcuate teeth 34 can be obtained. Figure 9 is a diagram showing the correspondence of the tooth sides. Non-arcuate gear tooth side portions 38 obtained by carrying out the above steps on the first arc-circular gear tooth side portion TC1 (TC3, TC5, TC7, TC9, TC11, TC13, TC15) are designated by symbols TN1a and TN1b (TN3a and TN3b, TN5a and TN5b, TN7a and TN7b, TN9a and TN9b, TN11a and TN11b, TN13a and TN13b, TN15a and TN15b), and the second arc-circular gear tooth side portions 38 are designated by symbols TN1a and TN1b (TN3a and TN3b, TN5a and TN5b, TN7a and TN7b, TN9a and TN9b, TN11a and TN11b, TN13a and TN13b, TN15a and TN15b). The non-circular gear tooth side portions 38 obtained by subjecting the two-circular gear tooth side portions TC2 (TC4, TC6, TC8, TC10, TC12, TC14, TC16) to the above procedure are designated by the symbols TN2a and TN2b (TN4a and TN4b, TN6a and TN6b, TN8a and TN8b, TN10a and TN10b, TN12a and TN12b, TN14a and TN14b, TN16a and TN16b).

[0052] Like the arc-gear tooth side portion 18, the non-arc gear tooth 34 also has two tooth sides as the non-arc gear tooth side portion 38: a first non-arc gear tooth side portion 38a (for example, the non-arc gear tooth side portion 38 designated by the symbol TN3a) and a second non-arc gear tooth side portion 38b (for example, the non-arc gear tooth side portion 38 designated by the symbol TN2a) provided on the opposite side of the non-arc gear tooth tip 36 from the first non-arc gear tooth side portion 38a.

[0053] In the above description, the externally toothed non-circular gear 30 is formed by carrying out the above steps when the externally toothed arc-shaped gear 10 is positioned at the rotation position shown in Fig. 9, but this rotation position can be arbitrary. For example, a similar externally toothed non-circular gear 30 can be formed by carrying out the above steps when the externally toothed arc-shaped gear 10 is positioned slightly rotated from the rotation position shown in Fig. 9.

[0054] Effectiveness of the Gear Mechanism 1 According to the Present Embodiment As described above, the gear mechanism 1 according to this embodiment comprises the externally toothed arc-shaped gear 10, which has M arc-shaped teeth 14 and rotates around the first central axis 12, and the externally toothed non-arc-shaped gear 30, which has N non-arc-shaped teeth 34 and rotates around the second central axis 32 that is a predetermined distance D away from the first central axis 12. Each arc-shaped tooth 14 of the externally toothed arc-shaped gear 10 has an arc-shaped gear tooth tip portion 16 and an arc-shaped gear tooth side portion 18 (for example, a first arc-shaped gear tooth side portion 18a designated by the symbol TC1 in FIG. 8) that is located on the side of the arc-shaped gear tooth tip portion 16 and has an arc shape with a radius r.

[0055] The non-arc gear tooth 34 of the externally toothed non-circular gear 30 has a non-arc gear tooth tip 36 and a non-arc gear tooth side portion 38 (for example, the non-arc gear tooth side portion 38 indicated by reference numerals TN1a and TN1b in FIG. 8) located on the side of the non-arc gear tooth tip 36 and in contact with the arc-gear tooth side portion 18 (for example, the first arc-gear tooth side portion 18a indicated by reference numeral TC1 in FIG. 8), and the non-arc gear tooth side portion 38 (for example, the non-arc gear tooth side portion 38 indicated by reference numerals TN1a and TN1b in FIG. 8) is at least a part of The shape is formed so that when an imaginary circle of radius R2 (= axis distance D × number of teeth N / (number of teeth M + number of teeth N)) centered on the second central axis 32 is taken as the fixed circle (second friction wheel 52), an imaginary circle of radius R1 (= axis distance D × number of teeth M / (number of teeth M + number of teeth N)) centered on the first central axis 12 is taken as the moving circle (first friction wheel 50), and the center C1 of the first circular arc gear tooth side portion 18a is taken as the drawing point P, the drawn epitrochoid curve EP becomes an offset epitrochoid curve OEP (see Figure 7) offset by a length r.

[0056] Therefore, as described above, it is possible to realize the gear mechanism 1 that exhibits the effect of suppressing speed variations.

[0057] Furthermore, in this embodiment, the shapes of all parts of the non-arc gear tooth side portion 38 (for example, the non-arc gear tooth side portion 38 designated by the symbols TN1a and TN1b in FIG. 8) that come into contact with the arc-shaped gear tooth side portion 18 (for example, the first arc-shaped gear tooth side portion 18a designated by the symbol TC1 in FIG. 8) are formed so as to form an offset epitrochoid curve OEP (see FIG. 7) that is offset by a length r from the epitrochoid curve EP drawn when an imaginary circle of radius R2 (= center distance D × number of teeth N / (number of teeth M + number of teeth N)) centered on the second central axis 32 is defined as the fixed circle (second friction wheel 52), an imaginary circle of radius R1 (= center distance D × number of teeth M / (number of teeth M + number of teeth N)) centered on the first central axis 12 is defined as the moving circle (first friction wheel 50), and the center C1 of the first arc-shaped gear tooth side portion 18a is defined as the drawing point P.

[0058] Therefore, it is possible to realize a gear mechanism 1 that more appropriately exerts the effect of suppressing speed variations.

[0059] The arc-shaped gear tooth side portion 18 is a first arc-shaped gear tooth side portion 18a, and the arc-shaped tooth 14 of the externally toothed arc-shaped gear 10 is a second arc-shaped gear tooth side portion 18b that is located on the side of the arc-shaped gear tooth tip 16 and has an arc shape of radius r and is provided on the opposite side of the first arc-shaped gear tooth side portion 18a (for example, the first arc-shaped gear tooth side portion 18a indicated by reference symbol TC1 in FIG. 8) when viewed from the arc-shaped gear tooth tip 16, and the center of the second arc-shaped gear tooth side portion 18b is different from the center of the first arc-shaped gear tooth side portion 18a. The externally toothed non-circular gear 30 has a second arc-circular gear tooth side portion 18b (for example, the second arc-circular gear tooth side portion 18b indicated by the symbol TC2 in FIG. 8), the non-circular tooth 34 is a first non-circular tooth 34a (see the upper diagram in FIG. 8), the externally toothed non-circular gear 30 has a second non-circular tooth 34b (see the lower diagram in FIG. 8) different from the first non-circular tooth 34a, and the second non-circular tooth 34b of the externally toothed non-circular gear 30 has a non-circular gear tooth tip 36 and a second arc-circular tooth 34b located on the side of the non-circular gear tooth tip 36. and a non-circular gear tooth side portion 38 (for example, non-circular gear tooth side portion 38 indicated by reference symbols TN2a and TN2b in FIG. 8) that comes into contact with the wheel tooth side portion 18b (for example, second circular gear tooth side portion 18b indicated by reference symbol TC2 in FIG. 8), and the shape of at least a part of the non-circular gear tooth side portion 38 (for example, non-circular gear tooth side portion 38 indicated by reference symbols TN2a and TN2b in FIG. 8) of the second non-circular tooth 34b is such that the shape of the non-circular gear tooth side portion 38 of the second non-circular tooth 34b is a radius R2 When an imaginary circle of radius R1 (= center distance D × number of teeth M / (number of teeth M + number of teeth N)) is taken as the fixed circle (second friction wheel 52), an imaginary circle of radius R1 (= center distance D × number of teeth M / (number of teeth M + number of teeth N)) centered on the first central axis 12 is taken as the moving circle (first friction wheel 50), and the center C2 of the second circular arc gear tooth side portion is taken as the drawing point P, the drawn epitrochoid curve EP is offset by a length r to become an offset epitrochoid curve OEP (see Figure 7).

[0060] Therefore, it is possible to realize a gear mechanism 1 that more appropriately exerts the effect of suppressing speed variations.

[0061] Furthermore, in this embodiment, the non-arc gear tooth side portions 38 of the second non-arc gear tooth 34b (for example, the non-arc gear tooth side portions 38 designated by the symbols TN2a and TN2b in FIG. 8) and the second arc-circular gear tooth side portions 18b (for example, the second arc-circular gear tooth side portions 18b designated by the symbol TC2 in FIG. 8) are shaped so that the shape of the entire portion that comes into contact with the second arc-circular gear tooth side portion 18b is an offset epitrochoid curve OEP (see FIG. 7) that is offset by a length r from the epitrochoid curve EP drawn when an imaginary circle of radius R2 (= axis distance D × number of teeth N / (number of teeth M + number of teeth N)) centered on the second central axis 32 is defined as the fixed circle (second friction wheel 52), an imaginary circle of radius R1 (= axis distance D × number of teeth M / (number of teeth M + number of teeth N)) centered on the first central axis 12 is defined as the moving circle (first friction wheel 50), and the center C2 of the second arc-circular gear tooth side portion is defined as the drawing point P.

[0062] Therefore, it is possible to realize a gear mechanism 1 that more appropriately exerts the effect of suppressing speed variations.

[0063] ===Other embodiments=== While the gear mechanism according to the present invention has been described above based on the above-mentioned embodiment, the above-mentioned embodiment of the invention is intended to facilitate understanding of the present invention and does not limit the present invention. The present invention may be modified or improved without departing from the spirit and scope of the present invention, and of course, equivalents thereof are also included in the present invention. [Explanation of symbols]

[0064] 1 Gear mechanism 10 Externally Toothed Circular Arc Gear 12 First central axis 14 arc teeth 16 Circular gear tooth tip 18 Circular gear tooth side 18a First circular gear tooth side 18b Second circular arc gear tooth side 30 Externally toothed non-circular gear 32 Second central axis 34 Non-circular teeth 34a First non-circular tooth 34b Second non-circular tooth 36 Non-circular gear tooth tip 38 Non-circular gear tooth side 38a First non-circular gear tooth side 38b Second non-circular gear tooth side 50 First friction wheel 52 Second friction wheel 60 Cam 62 Followers 62a Cam follower 62b Arm 70 bars 70a outer edge 70b inner edge C1 center C2 center D Center distance EP Epitrochoid curve L distance LI Line OEP Offset Epitrochoid Curve P drawing point PC1 pitch circle PC2 pitch circle R1 Pitch circle radius R2 pitch circle radius TA tangent α Arc pitch angle TC1 First circular gear tooth side TC2 Second circular gear tooth side TC3 First circular gear tooth side TC4 Second circular gear tooth side TC5 First circular gear tooth side TC6 Second circular gear tooth side TC7 First circular gear tooth side TC8 Second circular gear tooth side TC9 First circular gear tooth side TC10 Second circular gear tooth side TC11 First circular gear tooth side TC12 Second circular gear tooth side TC13 First circular gear tooth side TC14 Second circular gear tooth side TC15 First circular gear tooth side TC16 Second circular gear tooth side TN1a, TN1b Non-circular gear tooth side TN2a, TN2b Non-circular gear tooth side TN3a, TN3b Non-circular gear tooth side TN4a, TN4b Non-circular gear tooth side TN5a, TN5b Non-circular gear tooth side TN6a, TN6b Non-circular gear tooth side TN7a, TN7b Non-circular gear tooth side TN8a, TN8b Non-circular gear tooth side TN9a, TN9b Non-circular gear tooth side TN10a, TN10b Non-circular gear tooth side TN11a, TN11b Non-circular gear tooth side TN12a, TN12b Non-circular gear tooth side TN13a, TN13b Non-circular gear tooth side TN14a, TN14b Non-circular gear tooth side TN15a, TN15b Non-circular gear tooth side TN16a, TN16b Non-circular gear tooth side

Claims

1. A gear mechanism having an externally toothed arc-shaped gear having M arc-shaped teeth and rotating around a first central axis, and an externally toothed non-circular gear having N non-circular teeth and rotating around a second central axis separated by a predetermined distance D from the first central axis, the arc-shaped teeth of the externally toothed arc-shaped gear have arc-shaped gear tooth tip portions and arc-shaped gear tooth side portions that are located on sides of the arc-shaped gear tooth tip portions and have an arc shape with a radius r, a non-circular tooth of the externally toothed non-circular gear has a non-circular gear tooth tip portion and a non-circular gear tooth side portion located on a side of the non-circular gear tooth tip portion and in contact with the arc-circular gear tooth side portion, The non-arcuate gear tooth side portion has a shape such that at least a part of the portion that contacts the arcuate gear tooth side portion is When a virtual circle of radius D×N / (M+N) centered on the second central axis is defined as a fixed circle, a virtual circle of radius D×M / (M+N) centered on the first central axis is defined as a moving circle, and the center of the circular-arc gear tooth side portion is defined as a drawing point, the drawn epitrochoid curve is an offset epitrochoid curve offset by a length r, A gear mechanism characterized in that it is formed.

2. 2. The gear mechanism according to claim 1, The non-arcuate gear tooth side portion has a shape in which all of the portions that come into contact with the arcuate gear tooth side portion are When a virtual circle of radius D×N / (M+N) centered on the second central axis is defined as a fixed circle, a virtual circle of radius D×M / (M+N) centered on the first central axis is defined as a moving circle, and the center of the circular-arc gear tooth side portion is defined as a drawing point, the drawn epitrochoid curve is an offset epitrochoid curve offset by a length r, A gear mechanism characterized in that it is formed.

3. 3. The gear mechanism according to claim 1 or 2, the arc-shaped gear tooth side portion is a first arc-shaped gear tooth side portion, The arc-shaped teeth of the externally toothed arc-shaped gear are a second arc-shaped gear tooth side portion having a radius r, the second arc-shaped gear tooth side portion being located on a side of the arc-shaped gear tooth tip portion and on the opposite side of the arc-shaped gear tooth tip portion from the first arc-shaped gear tooth side portion, the second arc-shaped gear tooth side portion having a center different from the center of the first arc-shaped gear tooth side portion; the non-circular tooth is a first non-circular tooth; the externally toothed non-circular gear has second non-circular teeth different from the first non-circular teeth, the second non-circular tooth of the externally toothed non-circular gear has a non-circular gear tooth tip portion and a non-circular gear tooth side portion located on a side of the non-circular gear tooth tip portion and in contact with the second circular gear tooth side portion, The non-circular gear tooth side portion of the second non-circular tooth has a shape of at least a part thereof, When a virtual circle of radius D×N / (M+N) centered on the second central axis is defined as a fixed circle, a virtual circle of radius D×M / (M+N) centered on the first central axis is defined as a moving circle, and the center of the second circular arc gear tooth lateral portion is defined as a drawing point, the drawn epitrochoid curve is an offset epitrochoid curve offset by a length r, A gear mechanism characterized in that it is formed.

4. 4. The gear mechanism according to claim 3, The non-circular gear tooth side portion of the second non-circular tooth has a shape in which all of the portions that contact the second circular gear tooth side portion are When a virtual circle of radius D×N / (M+N) centered on the second central axis is defined as a fixed circle, a virtual circle of radius D×M / (M+N) centered on the first central axis is defined as a moving circle, and the center of the second circular arc gear tooth lateral portion is defined as a drawing point, the drawn epitrochoid curve is an offset epitrochoid curve offset by a length r, A gear mechanism characterized in that it is formed.

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