Differential reducer

Abstract

To suppress the lowering of the stiffness of an input shaft even if a key groove is formed at an input shaft.SOLUTION: A different gear 1 includes: an internal gear 3; an input shaft 12 coaxially penetrating the internal gear 3, having an eccentric part 15 which is decentered from its own center axis O1, and having a hollow part 13 which is opened at an end part in an axial direction; an external gear 17 externally fit to the eccentric parts 15, inscription-engaged with the inner gear 3, and planetary-moving accompanied by the rotation of the input shaft 12; and a carrier 4 for taking out rotational movement relatively moving with the inner gear 3 from the planetary movement of the external gear 17. A key groove 16 for allowing the insertion-coupling of an outside drive shaft therewith is formed in parallel with the center axis O1 in the hollow part 13. Then, the key groove 16 is arranged in a position different from an eccentric direction of the eccentric part 15 in a direction around the center axis O1.SELECTED DRAWING: Figure 2

Description

【Technical Field】 【0001】 The present disclosure relates to an internal meshing swing type differential reducer including an internal gear and an external gear that meshes with the internal gear in an inscribed manner. 【Background Art】 【0002】 A differential reducer includes an internal gear, an input shaft that penetrates the internal gear coaxially and has an eccentric portion that is eccentric with respect to its central axis, an external gear that is externally mounted on the eccentric portion, meshes with the internal gear in an inscribed manner, and performs a planetary motion as the input shaft rotates, and a carrier that extracts a rotational motion that rotates relative to the internal gear from the planetary motion of the external gear. That is, the external gear performs a planetary motion (eccentric motion) within the internal gear due to the rotational input from the input shaft, causing relative rotation between the two gears, and outputting rotation at a reduction ratio based on the rotational speed difference between the eccentric motion and the relative rotation. The input shaft is hollow cylindrical in order to connect to an external drive shaft (for example, Patent Document 1). 【Prior Art Documents】 【Patent Documents】 【0003】 【Patent Document 1】 Japanese Patent Application Laid-Open No. 2021-139466 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0004】 In the above conventional differential reducer, when the drive shaft has a key, it is necessary to form a key groove on the inner peripheral surface of the hollow portion of the input shaft. However, since a force due to the meshing between the internal gear and the external gear is applied from the radially outer side to the eccentric portion of the input shaft, the rigidity of the input shaft may decrease depending on the position where the key groove is provided. 【0005】 Therefore, an object of the present disclosure is to provide a differential reducer capable of suppressing a decrease in the rigidity of the input shaft even when a key groove is provided in the hollow portion for connecting the drive shaft. 【Means for Solving the Problems】 【0006】 To achieve the above objectives, this disclosure is intended to It is integrally provided on the inner circumferential surface of the cylindrical casing. An internal gear, an input shaft that passes through the internal gear coaxially and has an eccentric portion that is eccentric with respect to its own central axis, and has a hollow portion that opens at its axial end, An external gear, which is mounted on the eccentric portion, meshes with the internal gear in contact with it, and performs planetary motion in conjunction with the rotation of the input shaft, The input shaft is rotatably held within the casing and coaxially supported. The system includes a carrier that extracts rotational motion relative to the internal gear from the planetary motion of the external gear, A differential reducer having a keyway formed in the hollow portion parallel to the central axis for inserting and connecting an external drive shaft, The input shaft is rotatably supported inside the carrier via a pair of identical bearings arranged front to back in the axial direction of the central shaft, with the eccentric portion provided between the pair of bearings, The end of the hollow portion opposite to the opening at the end is located radially inward of the eccentric portion closest to the opening. The keyway is in the direction of the axial direction of the central axis and the direction of the eccentricity of the eccentric portion. The opposite side It is characterized by being arranged in a certain position. Furthermore, "opposite side of the eccentricity direction" refers to a predetermined angular range around the axis of the input shaft, including the direction opposite to the eccentricity direction. Another aspect of the present disclosure is characterized in that, in the above configuration, the side opposite to the eccentric direction is within a range of ±135° in the direction around the axis centered on the direction opposite to the eccentric direction. [Effects of the Invention] 【0007】 According to this disclosure, since the keyway is positioned at a location different from the eccentric direction of the eccentric portion, even if a keyway is provided in the hollow portion connecting the drive shaft, a decrease in the rigidity of the input shaft can be suppressed. especially By positioning the keyway on the opposite side of the eccentricity of the eccentric portion, the reduction in rigidity can be effectively suppressed. According to another aspect of this disclosure, in addition to the above effects, by arranging the keyway within a range of ±135° on the opposite side of the eccentricity direction of the eccentric portion, it becomes possible to arrange the keyway within a range that suppresses a decrease in rigidity while ensuring design flexibility. [Brief explanation of the drawing] 【0008】 [Figure 1] It is a front view of the differential reduction gear of Form 1 as seen from the input side. [Figure 2] It is an enlarged sectional view taken along line A-A of FIG. 1. [Figure 3] It is an enlarged sectional view taken along line B-B of FIG. 2. [Figure 4] It is an explanatory view showing the installable range of the key groove. [Figure 5] It is a graph showing the relationship between the key groove angle and the stress. [Figure 6] It is an enlarged sectional view corresponding to the sectional view taken along line A-A of FIG. 1 showing a modified example of Form 1. [Figure 7] It is a front view of the differential reduction gear of Form 2 as seen from the input side. [[ID=2...]] [Figure 8] It is an enlarged sectional view taken along line C-C of FIG. 7. [Figure 9] It is an enlarged sectional view taken along line D-D of FIG. 8. [Figure 10] It is an explanatory view showing the installable range of the key groove. [Figure 11] It is an enlarged sectional view corresponding to the sectional view taken along line C-C of FIG. 7 showing a modified example of Form 2. [Figure 12] It is an enlarged sectional view corresponding to the sectional view taken along line A-A of FIG. 1 of the differential reduction gear of Form 3. [Figure 13] It is an enlarged sectional view taken along line E-E of FIG. 12. 【Embodiments for Carrying Out the Invention】 【0009】 Hereinafter, embodiments of the present disclosure will be described based on the drawings. [Form 1] FIG. 1 is a front view showing an example of the differential reduction gear 1. FIG. 2 is a sectional view taken along line A-A of FIG. 1. In the differential reduction gear 1, the casing 2 is cylindrical, and an internal gear 3 is integrally provided on the inner peripheral surface. Inside the casing 2, the carrier 4 is coaxially and rotatably supported via a pair of angular ball bearings 5, 5 arranged axially front and rear. The carrier 4 includes an input carrier 6, an output carrier 7, and carrier pins 8, 8... The input carrier 6 is disc-shaped and arranged on the input side (the right side in FIG. 2). The output carrier 7 is disc-shaped and arranged on the output side (the left side in FIG. 2). Ten carrier pins 8, 8... are arranged at equal intervals on concentric circles with the input carrier 6 and the output carrier 7. Each carrier pin 8 is connected to the input carrier 6 and the output carrier 7 respectively by bolts 9, 9... with its end inserted into the opposing surfaces of the input carrier 6 and the output carrier 7. Sleeve-shaped metals 10 are respectively externally fitted on each carrier pin 8 between the input carrier 6 and the output carrier 7. 【0010】 Inside the carrier 4, the input shaft 12 is coaxially and rotatably supported via a pair of ball bearings 11, 11 arranged axially front and rear. The input shaft 12 is cylindrical with a hollow portion 13 inside. At both axial ends of the input shaft 12 supported by the ball bearings 11, 11, the shaft support portions 14, 14 have the same diameter. A pair of eccentric portions 15, 15 are formed between the shaft support portions 14, 14. The eccentric portions 15, 15 are formed with the same outer diameter around an eccentric axis O2 offset by an eccentricity δ from the central axis O1 of the input shaft 12. The eccentric portions 15, 15 are arranged such that the maximum eccentric sides are 180 degrees different in phase from each other across the central axis O1. A key groove 16 is formed on the inner peripheral surface of the hollow portion 13 of the input shaft 12. The key groove 16 is formed to penetrate the entire axial length of the input shaft 12. Here, as shown in FIG. 3, the key groove 16 is provided in a direction orthogonal to the eccentric direction of the eccentric portions 15, 15. That is, the key groove 16 is arranged at a position different from the eccentric direction of the eccentric portions 15, 15 in the circumferential direction around the central axis O1. Due to the position of this key groove 16, in the eccentric portions 15, 15, it is possible to ensure the radial wall thickness in the eccentric direction. 【0011】 Each of the eccentric sections 15, 15 is fitted with a pair of external gears 17, 17, each having the same external shape. Each external gear 17 has fewer teeth than the internal gear 3. Each external gear 17 has 10 circular through holes 18, 18·· formed concentrically around an eccentric axis O2, at equal intervals in the circumferential direction. Each carrier pin 8 passes through the through holes 18, 18 of the external gears 17, 17, respectively, and the outer circumference of the metal 10 is inscribed within the inner circumference of the through holes 18, 18, with each pin 180 degrees apart in phase. Between each eccentric portion 15 and each external gear 17, a needle bearing 19 is provided, consisting of multiple needles 20, 20... with a circular cross-section, arranged around the entire circumference. The external gears 17, 17 are supported via the needle bearing 19 so as to be rotatable coaxially with the eccentric portions 15, 15, and mesh with the internal gear 3 in contact with it. Between each shaft support 14 and the eccentric portion 15, and between the eccentric portions 15, 15, a disc-shaped shoulder portion 21 is provided around the entire circumference, protruding higher radially outward than the eccentric portion 15. This shoulder portion 21 restricts the axial outward movement of the needle 20 and the axial inward movement of the ball bearings 11, 11 around the entire circumference. 【0012】 In the differential reducer 1 configured as described above, an external drive shaft (not shown) is inserted and coupled to the hollow portion 13 of the input shaft 12. The drive shaft is provided with a key that fits into a keyway 16. When the drive shaft is inserted into the hollow portion 13 from the input side with the phases of the key and the keyway 16 aligned, the input shaft 12 is integrally coupled with the drive shaft in the rotational direction. Therefore, when the drive shaft rotates and the input shaft 12 rotates as a whole, the front and rear eccentric parts 15, 15 each perform symmetrical eccentric motion, causing each external gear 17, 17 to perform eccentric and rotational motion while being inscribed within the internal gear 3. As a result, each through hole 18 also performs eccentric and rotational motion, but since each through hole 18 is formed to be larger in diameter than the carrier pin 8 containing the metal 10, each metal 10 performs relative eccentric motion while being inscribed within the through hole 18, absorbing the eccentric component, and only the rotational component is extracted from each carrier pin 8. Thus, the carrier 4 rotates synchronously, and the output carrier 7 rotates at a predetermined reduction ratio. At this time, the eccentric portions 15, 15 are subjected to forces F (Figure 3) from the radially outer direction due to the meshing of the internal gear 3 and the external gears 17, 17. However, since the keyway 16 is not provided in the eccentric direction of the eccentric portions 15, 15, deformation due to a decrease in rigidity is less likely to occur, and durability can be maintained. 【0013】 As described above, the differential reducer 1 of the first embodiment includes an internal gear 3, an input shaft 12 that passes coaxially through the internal gear 3 and has an eccentric portion 15 that is eccentric with respect to its own central axis O1, and has a hollow portion 13 that opens at its axial end, an external gear 17 that is externally mounted on the eccentric portion 15, meshes with the internal gear 3 in contact with it, and performs planetary motion as the input shaft 12 rotates, and a carrier 4 that extracts rotational motion relative to the internal gear 3 from the planetary motion of the external gear 17, and a keyway 16 for inserting and connecting an external drive shaft is formed in the hollow portion 13 parallel to the central axis O1. The keyway 16 is positioned in the direction of the central axis O1, but at a position different from the eccentric direction of the eccentric portion 15. With this configuration, even if a keyway 16 is provided in the hollow section 13 connecting the drive shafts, a decrease in the rigidity of the input shaft 12 can be suppressed. In particular, since the keyway 16 is positioned perpendicular to the eccentric direction of the eccentric portion 15, it is possible to suppress a decrease in rigidity for each of the pair of eccentric portions 15, 15 whose eccentric directions are on opposite sides of each other. 【0014】 In the above embodiment 1, the keyway may be provided in the orthogonal direction opposite to the left and right sides in Figure 3. Furthermore, the keyway is not limited to a structure in which it is positioned in a direction strictly perpendicular to the eccentricity direction of the eccentric portion. For example, as shown in Figure 4, it may be positioned within a range of ±45° around the axis of the central axis O1, which is centered on the direction perpendicular to the eccentricity direction of the eccentric portion 15. This ±45° range setting is based on the analysis results obtained showing that when the keyway angle with respect to the eccentric direction is 45° or less, the stress applied to the keyway increases (i.e., the rigidity decreases), as shown in Figure 5, which illustrates the relationship between the keyway angle and stress when the eccentric direction is set to 0°. By positioning the keyway 16 on the side perpendicular to the eccentricity direction of the eccentric portion 15 (within a range of ±45°), it becomes possible to position the keyway 16 within a range that suppresses a decrease in rigidity while ensuring design flexibility. 【0015】 Furthermore, the hollow section is not limited to a structure that extends through the entire length in the axial direction of the input shaft. For example, as shown in Figure 6, even if the end of the hollow section 13 remains beyond the eccentric section 15 on the output side (hereinafter, when distinguishing between the eccentric sections 15, the eccentric section on the input side will be referred to as "15A" and the eccentric section on the output side as "15B"), the keyway 16 can be positioned perpendicular to the eccentric direction of the eccentric sections 15A and 15B. In this case as well, the keyway 16 may be positioned within a range of ±45° around the axis of the central axis O1, with the center being either the left or right direction perpendicular to the eccentric direction of the eccentric sections 15A and 15B, as shown in Figure 5. Note that the angle perpendicular to the eccentric direction is not limited to the ±45° range in the example above. This angle can be increased or decreased as appropriate, as long as it is at a different position from the eccentric direction. 【0016】 Next, other forms of the present disclosure will be described. However, the same reference numerals will be used for the same components as in Form 1, and redundant descriptions will be omitted. [Form 2] In the differential reducer 1A shown in Figures 7 and 8, the hollow section 13 to which the drive shaft is coupled does not penetrate the input shaft 12, but extends to approximately half the total length of the input shaft 12. Therefore, the keyway 16 also extends to approximately half the total length of the input shaft 12. The ends of this hollow section 13 and the keyway 16 are located radially inward of the eccentric section 15A on the input side. That is, the hollow section 13 radially overlaps with the eccentric section 15A, but does not radially overlap with the eccentric section 15B on the output side. Furthermore, as shown in Figure 9, the keyway 16 is positioned in the opposite direction to the eccentricity of the eccentric portion 15A, and is located at a position different from the eccentricity of the eccentric portion 15A in the direction of the axis of the central axis O1. This position of the keyway 16 ensures that the radial wall thickness in the eccentric direction is maintained in the eccentric portion 15A. 【0017】 In the differential reducer 1A of the above-described form 2, when the drive shaft is operated, a force F due to the meshing of the internal gear 3 and the external gears 17, 17 is applied to the eccentric portions 15A and 15B from the radially outward direction. However, since there is no keyway 16 in the eccentric direction of the eccentric portions 15A and 15B, deformation due to a decrease in rigidity is less likely to occur, and durability can be maintained. Thus, in the differential reducer 1A of the above-described embodiment 2, the keyway 16 is positioned in a direction different from the eccentric direction of the eccentric portion 15A in the direction of the axis of the central axis O1. With this configuration, even if a keyway 16 is provided in the hollow section 13, a decrease in the rigidity of the input shaft 12 can be suppressed. In particular, since the keyway 16 is positioned on the opposite side of the eccentricity direction of the eccentric portion 15A, a reduction in rigidity with respect to the eccentric portion 15A can be effectively suppressed. 【0018】 In the above embodiment 2, the keyway is not limited to a structure in which it is positioned in the opposite direction to the eccentricity of the eccentric portion. For example, as shown in Figure 10, the keyway 16 may be positioned within a range of ±135° around the axis of the central axis O1, which is centered in the direction opposite to the eccentricity of the eccentric portion 15A. This ±135° range setting is also based on the relationship between the keyway angle and stress shown in Figure 5. By positioning the keyway 16 on the opposite side of the eccentricity direction of the eccentric portion 15A (within a range of ±135°), it becomes possible to position the keyway 16 within a range that suppresses a decrease in rigidity while ensuring design flexibility. Furthermore, as shown in Figure 11, even when the end of the hollow portion 13 penetrates the eccentric portion 15A and radially overlaps a part of the eccentric portion 15B, the keyway 16 can be positioned in the opposite direction to the eccentric direction of the eccentric portion 15A, in the direction of the axis of the central axis O1. In this case as well, the keyway 16 can be positioned within a range of ±135° in the direction of the axis of the central axis O1, centered on the direction opposite to the eccentric direction of the eccentric portion 15A, as shown in Figure 10. Note that the angle on the opposite side of the eccentricity is not limited to the ±135° range in the example above. This angle can be increased or decreased as appropriate, as long as it is at a different position from the eccentricity. In the above embodiment 2, a pair of external gears is provided, but there may be only one external gear. In this case as well, the reduction in rigidity can be suppressed by providing a keyway in the direction opposite to the eccentric direction, or in a predetermined area other than the eccentric side. 【0019】 [Form 3] The drive shaft may also be key-coupled to the output side of the differential reducer. Figure 12 shows an example of such a differential reducer 1B. Here, a hollow section 13 and a keyway 16 are formed at the end of the input shaft 12 on the output carrier 7 side. This hollow section 13 and keyway 16 do not penetrate the input shaft 12, but are formed to a position approximately half the axial length of the eccentric section 15B, with their ends overlapping the eccentric section 15B. In this case as well, as shown in Figure 13, the keyway 16 is positioned in the opposite direction to the eccentricity of the eccentric portion 15B, and is located at a position different from the eccentricity of the eccentric portion 15B in the direction of the axis of the central axis O1. This position of the keyway 16 ensures that the radial wall thickness in the eccentric direction is maintained in the eccentric portion 15B. 【0020】 In the above embodiment 3, the keyway 16 may also be positioned within a range of ±135° around the central axis O1, centered in the direction opposite to the eccentricity direction of the eccentric portion 15B. Other angles can also be used. Furthermore, even if the hollow portion 13 formed from the output side penetrates the eccentric portion 15B and overlaps with a part of the eccentric portion 15A, the keyway 16 may be positioned within a range of ±135° around the axis of the central axis O1, which is centered in the direction opposite to the eccentric direction of the eccentric portion 15B. Other angles can also be used. Furthermore, if the hollow portion 13 formed from the output side penetrates the eccentric portion 15B and also penetrates the eccentric portion 15A, the keyway 16 can be provided in a direction perpendicular to the eccentric direction or within a range of ±45° centered on the perpendicular direction, as in Embodiment 1. Other angles can also be used. 【0021】 The following describes examples of changes common to each form. The casing structure is not limited to a single cylindrical body as described above; it may be formed by combining multiple parts. The internal gear may also be formed separately from the casing and fixed to the casing. Furthermore, the carrier's bearings are not limited to angular contact ball bearings; other types of bearings such as cross roller bearings and ball bearings can also be used, and the number of bearings can be increased. [Explanation of symbols] 【0022】 1, 1A, 1B... Differential reducer, 2... Casing, 3... Internal gear, 7... Output carrier, 8... Carrier pin, 12... Input shaft, 13... Hollow section, 14... Shaft support, 15 (15A, 15B)... Eccentric section, 16... Keyway, 17... External gear, 18... Through hole, 19... Needle bearing, O1... Central shaft, O2... Eccentric shaft, δ... Amount of eccentricity.

Claims

[Claim 1] An internal gear integrally provided on the inner circumferential surface of a cylindrical casing, The input shaft has an eccentric portion that passes through the aforementioned internal gear coaxially and is eccentric with respect to its own central axis, and has a hollow portion that opens at its axial end, An external gear, which is mounted on the eccentric portion, meshes with the internal gear in contact with it, and performs planetary motion in conjunction with the rotation of the input shaft, The system includes a carrier that is rotatably held within the casing and coaxially supports the input shaft, and extracts rotational motion relative to the internal gear from the planetary motion of the external gear, A differential reducer having a keyway formed in the hollow portion parallel to the central axis for inserting and connecting an external drive shaft, The input shaft is rotatably supported inside the carrier via a pair of identical bearings arranged front to back in the axial direction of the central shaft, with the eccentric portion provided between the pair of bearings, A differential speed reducer characterized in that the end of the hollow portion opposite to the opening at the end is located radially inward of the eccentric portion closest to the opening, and the keyway is located on the opposite side of the eccentric direction of the eccentric portion in the direction of the axis of the central shaft. [Claim 2] The differential reducer according to claim 1, characterized in that the side opposite to the eccentric direction is within a range of ±135° in the direction around the axis centered on the direction opposite to the eccentric direction.

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