Eccentric Oscillation Type Gear Device

Abstract

To provide an eccentric rocking type gear device having a hollow part that can be enlarged.SOLUTION: An eccentric rocking type gear device 100 includes: an internal gear 16; an external gear 14; an eccentric body to oscillate the external gear 14; a carrier arranged on a side in an axial direction of the external gear 14; and plural inner pins 32 connected to the carrier at a position offset from the center of the carrier and passing through the external gear. A ratio between a pitch circle diameter Dp of the inner pins 32 and a tooth tip diameter De of the external gear 14 (pitch circle diameter Dp / tooth tip diameter De) is 0.77 to 0.85, a ratio between a diameter Dq of the inner pin 32 and the tooth tip diameter De of the external gear 14 (inner pin diameter Dq / tooth tip diameter De) is 0.06 to 0.10, and an inner pin occupancy that is a ratio of the inner pin 32 in a pitch circle of the inner pin 32 is at or larger than 0.25.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an eccentric swing type gear device.

Background Art

[0002] An eccentric swing type speed reducer that decelerates the rotation input to the input shaft is known. The applicant has disclosed, in Patent Document 1, an eccentric swing type speed reducer including an external gear that swings as the input shaft rotates and an internal gear that meshes internally with the external gear. This input shaft is a hollow shaft having a large-diameter hollow portion.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a speed reducer, wiring such as an electric cable or a pipe for sending air (hereinafter referred to as "wiring") is passed through the hollow portion. In order to allow the wiring to pass through with a margin, it is desirable that the hollow portion be large. However, if the hollow portion is enlarged under the condition that the outer diameter of the speed reducer is constant, the strength of the speed reducer may decrease.

[0005] The present invention has been made in view of such problems, and an object thereof is to provide an eccentric swing type gear device capable of expanding the hollow portion.

Means for Solving the Problems

[0006] In order to solve the above problems, an eccentric swing type gear device according to an aspect of the present invention includes an internal gear, an external gear, an eccentric body that swings the external gear, a carrier disposed on an axial side portion of the external gear, and a plurality of internal pins that are connected to the carrier at a position offset from the center of the carrier and penetrate the external gear. The eccentric swing type gear device is characterized in that the ratio (pitch circle diameter / tooth tip diameter) of the pitch circle diameter of the internal pin to the tooth tip diameter of the external gear is 0.77 to 0.85, the ratio (internal pin diameter / tooth tip diameter) of the diameter of the internal pin to the tooth tip diameter of the external gear is 0.06 to 0.10, and the internal pin occupancy rate, which is the ratio of the internal pins in the pitch circle circumference of the internal pins, is 0.25 or more.

[0007] In addition, any combination of the above components, or those obtained by mutually replacing the components and expressions of the present invention among methods, systems, etc., are also effective as aspects of the present invention.

Effects of the Invention

[0008] According to the present invention, an eccentric swing type gear device capable of expanding the hollow portion can be provided.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0010] Hereinafter, the present invention will be described with reference to the drawings based on preferred embodiments. In the embodiments and modifications, the same or equivalent components and members are denoted by the same reference numerals, and redundant descriptions will be omitted as appropriate. Also, the dimensions of the members in each drawing are appropriately enlarged or reduced for easy understanding. Further, some members that are not important for explaining the embodiments in each drawing are omitted from the display.

[0011] Also, terms including ordinal numbers such as first and second are used to describe various components, but this term is used only for the purpose of distinguishing one component from another, and the components are not limited by this term.

[0012] [Embodiment] Hereinafter, with reference to the drawings, the configuration of the eccentric swing type gear device 100 according to the embodiment of the present disclosure will be described. FIG. 1 is a side cross-sectional view schematically showing the eccentric swing type gear device 100 of the present embodiment. FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1. Although there is no limitation on the use of the eccentric swing type gear device 100, the eccentric swing type gear device 100 in this example can be used for the joints of a multi-joint robot.

[0013] The overall configuration of the eccentric swing type gear device 100 will be described. The eccentric swing type gear device 100 mainly includes an input shaft 12, an external gear 14, an internal gear 16, carriers 18 and 20, a casing 22, main bearings 24 and 26, an eccentric bearing 30, an inner pin 32, and input shaft bearings 33 and 34.

[0014] Hereinafter, the direction along the central axis La of the internal gear 16 is referred to as the "axial direction", and the circumferential direction and the radial direction of the circle centered on the central axis La are referred to as the "circumferential direction" and the "radial direction", respectively. Also, hereinafter, for convenience, one side in the axial direction (the right side in the figure) is referred to as the input side, and the other side (the left side in the figure) is referred to as the anti-input side. Such a notation of directions does not limit the use posture of the eccentric swing type gear device 100, and the eccentric swing type gear device 100 can be used in any posture.

[0015] The carriers 18 and 20 include a first carrier 18 disposed on the anti-input side of the external gear 14 and a second carrier 20 disposed on the input side of the external gear 14. The main bearings 24 and 26 include a first main bearing 24 disposed on the anti-input side of the external gear 14 and a second main bearing 26 disposed on the input side of the external gear 14. The input shaft bearings 33 and 34 include a first input shaft bearing 33 disposed on the anti-input side of the external gear 14 and a second input shaft bearing 34 disposed on the input side of the external gear 14.

[0016] The eccentric swing type gear device 100 of the present embodiment is of a center crank type in which the input shaft (eccentric body shaft) 12 is provided on the same axis as the central axis La of the internal gear 16. The eccentric swing type gear device 100 has a hollow portion H that penetrates axially in the central portion. The hollow portion H is provided on the input shaft 12.

[0017] The casing 22 constitutes the outer shell of the eccentric swing type gear device 100. The carriers 18 and 20 are disposed inside the casing 22 and rotate relative to the casing 22. The input shaft 12 has a hollow cylindrical shape with a hollow portion H at the center. For example, a power transmission member such as a gear or a pulley is connected to the input side end of the input shaft 12 by a connector such as a bolt, and the rotation of a motor disposed offset from the hollow portion H is transmitted.

[0018] The input shaft 12 has a plurality of eccentric portions 12a and functions as an eccentric body that swings the external gear 14. In this example, the input shaft 12 has two eccentric portions 12a with a 180° phase shift. Both ends of the input shaft 12 are supported by the carriers 18 and 20 via the input shaft bearings 33 and 34. Note that the number of the eccentric portions 12a is not limited to two and may be one or three or more.

[0019] There is no limitation on the configuration of the input shaft bearings 33 and 34. However, in this example, the rolling elements of the first input shaft bearing 33 are balls (spherical bodies), and the rolling elements of the second input shaft bearing 34 are rollers (cylindrical bodies).

[0020] The external gear 14 is rotatably supported by the corresponding eccentric portion 12a via an eccentric bearing 30. The external gear 14 is formed with a central hole 14c and a plurality of inner pin holes 14h. The central hole 14c is a through hole provided at the center of the external gear 14. The plurality of inner pin holes 14h are through holes provided on the same circumference (pitch circle) at positions offset from the center of the external gear 14. In the example of FIG. 2, ten inner pin holes 14h are arranged at intervals of 36° in the circumferential direction. Inner pins 32 are inserted into the inner pin holes 14h. The teeth formed on the outer periphery of the external gear 14 rotate while meshing with the teeth of the internal gear 16, causing the external gear 14 to swing.

[0021] The internal gear 16 meshes with the external gear 14. The internal gear 16 of the present embodiment is composed of an internal gear main body integrated with the casing 22 and an external pin 16p (pin member) rotatably supported by the internal gear main body. The external pin 16p constitutes the internal teeth of the internal gear 16. The number of internal teeth of the internal gear 16 (the number of external pins 16p) is slightly (by 1 in this example) more than the number of external teeth of the external gear 14.

[0022] The first carrier 18 and the second carrier 20 are rotatably supported by the casing 22 via main bearings 24 and 26. The first carrier 18 supports the input shaft 12 via a first input shaft bearing 33. The second carrier 20 supports the input shaft 12 via a second input shaft bearing 34.

[0023] The first carrier 18 and the second carrier 20 are connected via an inner pin 32. The inner pin 32 axially penetrates the inner pin hole 14h of the external gear 14 at a position radially offset from the axis of the external gear 14.

[0024] One of the carriers 18, 20 and the casing 22 functions as an output member that outputs rotational power to the device to be decelerated, and the other functions as a fixed member fixed to an external member for supporting the eccentric swing type gear device 100. In the present embodiment, the output members are the first carrier 18 and the second carrier 20, and the fixed member is the casing 22.

[0025] In this example, ten inner pins 32 are circumferentially arranged at 36° intervals on the same circumference (pitch circle) offset from the center (axis) of the first carrier 18. In FIG. 1, one inner pin 32 is shown. The anti-input side of the inner pin 32 is fixed (connected) to the first carrier 18, and the input side is fixed (connected) to the second carrier 20. The inner pin 32 connects the first carrier 18 and the second carrier 20. In the example of FIG. 2, the inner pin 32 is integrally formed with the first carrier 18, and the input side is fixed to the second carrier 20 by bolts B2. A sleeve 32s is provided on the outer circumference of the inner pin 32. The inner pin 32 is inserted through the inner pin hole 14h with a gap. The inner pin 32 is in contact with a part of the inner pin hole 14h via the sleeve 32s. The inner pin 32 restrains the rotation of the external gear 14 and only allows its oscillation.

[0026] The main bearings 24 and 26 are arranged between the first carrier 18 and the casing 22 and between the second carrier 20 and the casing 22. There is no limitation on the configuration of the main bearings 24 and 26, but in this example, the main bearings 24 and 26 are angular ball bearings with spherical rolling elements. The outer rings of the main bearings 24 and 26 are supported by the casing 22. The inner ring of the first main bearing 24 is integrally formed with the carrier 18. The inner ring of the second main bearing 26 is integrally formed with the carrier 20.

[0027] The casing 22 is a hollow cylindrical member that surrounds the carriers 18 and 20. The casing 22 has a large-diameter portion 22f that protrudes radially outward. A bolt hole 22h that penetrates axially is provided in the large-diameter portion 22f. The large-diameter portion 22f is connected to an external mating member 50.

[0028] An oil seal 28 for sealing the lubricant from the main bearing 24 is provided between the casing 22 and the first carrier 18.

[0029] Hereinafter, the characteristic configurations of this embodiment will be described.

[0030] The inventor has conducted research on an eccentric swing type gear device and obtained the following findings. The eccentric swing type gear device is used in various applications such as industrial robots and machine tools. Wires such as electric cables are passed through the hollow portion of the eccentric swing type gear device. If the gap between this wiring and the hollow portion is small, there is a risk that they will interfere with each other, stress will be applied to the wiring, and damage will occur. Therefore, from the viewpoint of allowing the wiring to pass through with a margin, it is desirable that the diameter of the hollow portion be large.

[0031] The load applied to the gear device is large in a large gear device and small in a small gear device. For this reason, the diameter of the hollow portion can be generalized in relation to the size of the gear device. From the viewpoint of reducing the influence of variations in the casing shape, in this specification, the diameter of the hollow portion is generalized by the ratio (hollow portion diameter / tooth tip diameter) to the diameter of the circle passing through each tooth tip of the external gear (hereinafter referred to as the "tooth tip diameter"). Hereinafter, this diameter ratio may be referred to as the hollow portion diameter ratio.

[0032] With reference to FIGS. 3 and 4, the stress of each part of the eccentric swing type gear device 100 with respect to the load will be described. FIG. 3 is an enlarged view of a part of the external gear 14. FIG. 4 is an explanatory diagram for explaining the dimensions of each part. In FIG. 4, the hollow portion diameter Dh, the tooth tip diameter De, and the pitch circle diameter Dp are shown. The tooth tip diameter De is the diameter of the circle passing through each tooth tip 14e. The pitch circle diameter Dp is the diameter of the pitch circle 32d passing through the centers of the respective inner pins 32 (pitch circle diameter: PCD).

[0033] The inventor repeatedly conducted experiments and simulations from the viewpoint of expanding the hollow portion diameter Dh for the eccentric swing type gear device 100 of the present embodiment, and examined the influence when the dimensions of each part were changed. As a result, it was found that the stress of the inner pin 32, the portion 14j between the tooth bottom 14b of the external gear 14 and the inner pin hole 14h, and the portion 14k between the center hole 14c and the inner pin hole 14h is important. That is, it was found that by satisfying the stress standard determined from the market requirements in the normal use of an eccentric swing type gear device such as an industrial robot or a machine tool for the stress of these parts, a service life strength that can withstand practical use can be realized.

[0034] First, the influence when changing the dimensions of each part will be described. When the diameter Dh of the hollow part is enlarged, the thickness of the portion 14k between the center hole 14c and the inner pin hole 14h of the external gear 14 becomes thinner. Therefore, it is advantageous for the pitch circle diameter Dp of the inner pin 32 (which can also be referred to as the pitch circle diameter of the inner pin hole 14h) to be larger. On the other hand, if the pitch circle diameter Dp is too large, the thickness of the portion 14j between the tooth root 14b of the external gear 14 and the inner pin hole 14h becomes thinner, and there is a possibility that the desired strength cannot be satisfied.

[0035] Also, in order to increase the diameter Dh of the hollow part while ensuring the thickness of the portion 14k and the thickness of the portion 14j, it is advantageous for the inner pin hole diameter Dr to be smaller. On the other hand, when the inner pin hole diameter Dr is reduced, the inner pin diameter Dq will also be reduced. In this case, there is a possibility that the strength of the inner pin cannot be satisfied.

[0036] Also, in order to satisfy the strength while making the inner pin diameter Dq as small as possible, it is conceivable to increase the number of inner pins to disperse the load borne by each inner pin. The inner pin occupancy ratio Eq may be increased to enhance the strength of the entire plurality of inner pins. However, if the inner pin occupancy ratio Eq is increased too much, the interval between the inner pins becomes small, making forging difficult, or there may be manufacturing problems such as the tool interfering with the inner pins during processing. Note that the inner pin occupancy ratio Eq is the ratio of the inner pins 32 occupying the circumference of the pitch circle 14d of the inner pins 32.

[0037] The inventor conceived that it is important to find an appropriate range for the pitch circle diameter Dp, the inner pin diameter Dq, and the inner pin occupancy ratio Eq of the inner pin 32 in order to enlarge the diameter Dh of the hollow part while satisfying the stress criterion. In the present invention, it can be said that the very fact of arriving at this conception is extremely important.

[0038] Referring to FIGS. 5 to 7, the relationships between the pitch circle diameter Dp, the inner pin diameter Dq, and the inner pin occupancy Eq of the inner pin 32 and the stresses of each part will be described. The pitch circle diameter Dp and the inner pin diameter Dq can be generalized in relation to the size of the gear device. Hereinafter, the pitch circle diameter Dp and the inner pin diameter Dq are treated as ratios to the addendum diameter De of the external gear 14.

[0039] In FIGS. 5 to 7, the vertical axis represents the stress of each part. In these figures, (a) shows the stress of the inner pin 32, (b) shows the stress of the portion 14j between the root 14b of the external gear 14 and the inner pin hole 14h, and (c) shows the characteristic line of the stress of the portion 14k between the central hole 14c and the inner pin hole 14h. These stresses are the stresses generated in each part when a predetermined test load is applied to the gear device. The predetermined test load is a load set by simulating the load capacity required in the market for the gear device. Also, the "standard" indicates the standard level (upper limit level) of the stress determined from market requirements. In these figures, the value on the horizontal axis at the intersection of the stress characteristic line and the standard line is the lower limit or upper limit of the stress standard range (hereinafter simply referred to as the "lower limit" or "upper limit"). That is, when the value on the horizontal axis is within the range from the lower limit to the upper limit, it can be said that the stress is within the standard.

[0040] FIG. 5 shows the changes in the stresses of the inner pin 32, the portion 14j, and the portion 14k when the ratio of the pitch circle diameter Dp to the addendum diameter De (pitch circle diameter Dp / addendum diameter De) is changed. The horizontal axis of this figure is the ratio of the pitch circle diameter Dp to the addendum diameter De.

[0041] As shown in FIG. 5, as the pitch circle diameter Dp increases, the stresses of the inner pin 32 and the portion 14k decrease, and the stress of the portion 14j increases. From this figure, when the ratio of the pitch circle diameter Dp to the addendum diameter De is in the range of 0.77 to 0.85, the stresses of the inner pin 32, the portion 14j, and the portion 14k are all within the standard. The lower limit of the portion 14k is 0.77, which is larger than the lower limit of the inner pin 32 and has a larger slope of the stress characteristic line, so it is the lower limit of the entire range. The upper limit of the portion 14j is 0.85, which is the upper limit of the entire range.

[0042] FIG. 6 shows the changes in the stresses of the inner pin 32, the portion 14j, and the portion 14k when the ratio of the inner pin diameter Dq to the tip diameter De (inner pin diameter Dq / tip diameter De) is changed. As shown in FIG. 6, as the inner pin diameter Dq increases, the stress of the inner pin 32 decreases, and the stresses of the portion 14j and the portion 14k increase. From this figure, when the ratio of the inner pin diameter Dq to the tip diameter De is in the range of 0.06 to 0.10, the stresses of the inner pin 32, the portion 14j, and the portion 14k are all within the standard. The lower limit of the inner pin 32 is 0.06, which becomes the lower limit of the entire range. The upper limit of the portion 14j is 0.10, which is smaller than the upper limit of the portion 14k and has a larger slope of the stress characteristic line, so it becomes the upper limit of the entire range.

[0043] FIG. 7 shows the changes in the stresses of the inner pin 32, the portion 14j, and the portion 14k when the inner pin occupancy ratio Eq is changed. As shown in FIG. 6, as the inner pin occupancy ratio Eq increases, the stresses of the inner pin 32, the portion 14j, and the portion 14k decrease. From this figure, when the inner pin occupancy ratio Eq is in the range of 0.25 or more, the stresses of the inner pin 32, the portion 14j, and the portion 14k are all within the standard. The lower limit of the inner pin 32 is 0.25, which is larger than the lower limits of the portion 14j and the portion 14k and has a larger slope of the stress characteristic line, so it becomes the lower limit of the entire range. Note that the upper limits of the inner pin 32, the portion 14j, and the portion 14k are limited by the processing limit, and if the processing technology improves and the processing limit increases, the upper limit will increase.

[0044] From these, it can be said that when all of the following conditions (1) to (3) are satisfied, the eccentric swing type gear device 100 satisfies the stress standard determined from the market requirements in normal applications. (1) The ratio of the pitch circle diameter Dp of the inner pin 32 to the tip diameter De of the external gear 14 (pitch circle diameter Dp / tip diameter De) is 0.77 to 0.85. (2) The ratio of the diameter Dq of the inner pin 32 to the tip diameter De of the external gear 14 (diameter Dq of the inner pin 32 / tip diameter De) is 0.06 to 0.10. (3) The inner pin occupancy ratio Eq, which is the ratio of the inner pin 32 in the pitch circle circumference of the inner pin 32, is 0.25 or more.

[0045] If the inner pin occupancy ratio Eq is too large, the distance between adjacent inner pin holes 14h becomes small, the rigidity during hole machining is insufficient, and the machining accuracy may decrease. Therefore, the inner pin occupancy ratio Eq of this embodiment is set to less than 0.4. In this case, a decrease in machining accuracy can be suppressed.

[0046] The market demands that the gear device has a hollow portion large enough to allow wiring such as electric cables to pass through with a margin. In the eccentric swing type gear device 100 of this embodiment, the input shaft 12 having the eccentric portion 12a has a hollow structure having a hollow portion H. By adopting the above-described configuration, a large-diameter hollow portion H in which the ratio of the diameter Dh of the hollow portion H to the tooth tip diameter De (hollow portion diameter Dh / tooth tip diameter De) is 0.4 or more is realized. In this case, the wiring can pass through the hollow portion H with a margin and meet the market requirements.

[0047] In the eccentric swing type gear device, as the reduction ratio becomes smaller, the eccentricity of the eccentric portion 12a becomes larger, and the diameter Dr of the inner pin hole 14h also becomes larger. Therefore, it has been difficult to increase the diameter of the hollow portion H as the reduction ratio becomes smaller. However, in the eccentric swing type gear device 100 of this embodiment adopting the above-described configuration, even when the reduction ratio is 30 or less, a large-diameter hollow portion H (a large-diameter hollow portion H in which the ratio of the diameter Dh of the hollow portion H to the tooth tip diameter De (hollow portion diameter Dh / tooth tip diameter De) is 0.4 or more) can be realized.

[0048] As described above, according to the present disclosure, if the three indexes of the pitch circle diameter Dp, the inner pin diameter Dq, and the inner pin occupancy ratio Eq are optimized, it is shown that the inner pin stress standard and the external gear (14j portion, 14k portion) stress standard determined from the market requirements in the normal use of the eccentric swing type gear device 100 can be satisfied. Further, the present disclosure has reached the optimal ranges of the three indexes of the pitch circle diameter Dp, the inner pin diameter Dq, and the inner pin occupancy ratio Eq and shown the results.

[0049] The operation of the eccentric swing type gear device 100 configured as described above will be described. When rotation is transmitted from the motor to the input shaft 12, the eccentric portion 12a of the input shaft 12 rotates around the rotation center line passing through the input shaft 12, and the external gear 14 swings via the eccentric bearing 30. When the external gear 14 swings, the meshing position between the external gear 14 and the internal gear 16 is sequentially shifted. As a result, every time the input shaft 12 makes one rotation, rotation of one of the external gear 14 and the internal gear 16 corresponding to the difference in the number of teeth between the external gear 14 and the internal gear 16 occurs. In the present embodiment, the external gear 14 rotates, and decelerated rotation is output from the first carrier 18 and the second carrier 20 via the inner pin 32.

[0050] The features of the eccentric swing type gear device 100 configured as described above will be described. By satisfying the optimal ranges of the above three indicators, an eccentric swing type gear device capable of expanding the diameter Dh of the hollow portion H can be provided. The above is the description of the embodiment.

[0051] The examples of the embodiments of the present invention have been described in detail above. The above-described embodiments are merely specific examples for implementing the present invention. The content of the embodiments does not limit the technical scope of the present invention, and many design changes such as changes, additions, and deletions of components are possible without departing from the idea of the invention defined in the claims. In the above-described embodiments, regarding the content in which such design changes are possible, descriptions have been given with notations such as "in the embodiment" and "in the embodiment", but design changes are not necessarily not allowed for the content without such notations. Also, the hatching attached to the cross-section of the drawing does not limit the material of the object to which the hatching is attached.

[0052] Hereinafter, a modification will be described. In the drawings and description of the modification, the same or equivalent components and members as those in the embodiment are denoted by the same reference numerals. Descriptions overlapping with those of the embodiment will be omitted as appropriate, and the configurations different from those of the embodiment will be mainly described.

[0053] [Modification] In the description of the embodiment, an example in which the casing 22 is formed of an integral member has been shown, but the casing may be formed of a plurality of members.

[0054] In the description of the embodiment, an example in which the number of external gear wheels 14 is 2 has been shown, but the number of external gear wheels may be 1 or 3 or more.

[0055] In the description of the embodiment, an example in which an inner pin 32 that contributes to the transmission of the driving force of the external gear wheel 14 is provided as a pin member for connecting the carriers 18 and 20 has been shown. A carrier pin that does not contribute to the transmission of the driving force may be provided separately from the inner pin 32 as a pin member for connecting the carriers 18 and 20.

[0056] In the description of the embodiment, an example in which the inner pin 32 is integrally formed with the first carrier 18 has been shown, but the inner pin 32 may be formed separately from the first carrier 18 and connected by a fixture such as a bolt.

[0057] In the description of the embodiment, an example in which the number of inner pins 32 and the number of inner pin holes 14h are 10 has been shown, but these numbers may be 9 or less or 11 or more. Also, the number of inner pins 32 may be less than the number of inner pin holes 14h.

[0058] In the description of the embodiment, an example in which the inner rings of the main bearings 24 and 26 are integrally formed with the carriers 18 and 20 has been shown, but the inner rings of the main bearings may be separate from the carriers. Further, the present invention is particularly effective for an eccentric swing type gear device having a hollow portion H, but is not limited thereto, and can also be applied to an eccentric swing type gear device provided with an input shaft 12 that does not have a hollow portion H.

[0059] Each of the above-described modification examples has the same operations and effects as the embodiment.

[0060] Any combination of the components of the above-described embodiment and the modification examples is also useful as an embodiment of the present invention. The new embodiment generated by the combination has the effects of the combined embodiment and modification example.

Description of Signs

[0061] 12 Input shaft, 12a Eccentric portion, 14 External gear, 14b Tooth bottom, 14c Central hole, 14d Pitch circle, 14e Tooth tip, 14h Inner pin hole, 16 Internal gear, 18 Carrier, 18 First carrier, 20 Second carrier, 22 Casing, 24 First main bearing, 26 Second main bearing, 32 Inner pin, 32d Pitch circle, 100 Eccentric swing type gear device.

Claims

1. An eccentric swing type gear device comprising an internal gear, an external gear, an eccentric body for swinging the external gear, a carrier disposed on an axial side portion of the external gear, and a plurality of internal pins connected to the carrier at a position offset from the center of the carrier and penetrating the external gear, wherein: The ratio (pitch circle diameter / tooth tip diameter) of the pitch circle diameter of the internal pin to the tooth tip diameter of the external gear is 0.77 to 0.85; The ratio (internal pin diameter / tooth tip diameter) of the diameter of the internal pin to the tooth tip diameter of the external gear is 0.06 to 0.10; The internal pin occupancy rate, which is the ratio of the internal pins occupying the pitch circle circumference of the internal pins, is in the range of 0.25 or more and less than 0.4; The eccentric body shaft having the eccentric body has a hollow structure, and the ratio (hollow portion diameter / tooth tip diameter) of the hollow portion diameter to the tooth tip diameter is 0.4 or more. The eccentric swing type gear device is characterized by this.

2. The eccentric swing type gear device according to claim 1, wherein the reduction ratio is 30 or less.

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