JP2007113701A - Reduction gear for joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reduction gear for a joint suitably applied to the joint of an artificial limb or a prosthesis and having a thin thickness with a high reduction ratio using a gear with no dislocation. <P>SOLUTION: Using a 3S type planetary mechanism, a first planetary gear 2 meshed with a sun gear 1 is meshed with a first internal tooth gear 5 on the fixed side, and a second planetary gear 3 is fixed to the first planetary gear 2 so as to be integrally rotated. The second planetary gear 3 is meshed with a second internal tooth gear 4 on the driven side and rotationally driven. The difference ΔZ between the number of teeth of the first internal tooth gear 5 and that of the second internal tooth gear 4 and the difference ΔZ between the number of teeth of the first planetary gear 2 and that of the second planetary gear 3 are made equal and set to 1. Further, a train of the driven side gears 3, 4 is held by a train of the fixed side gears 1, 2, 5 from the lateral side to form a sandwich structure, thus withstanding high load torque. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a reduction gear for an electric joint used for an orthosis, a prosthetic limb, a prosthetic leg, a prosthetic hand, a knee joint, a hip joint, an elbow joint, and the like, and also relates to a reduction gear applicable to a robot joint.

  FIG. 1 is a side view showing an example to which a reduction gear according to the present invention is applied. A joint constituted by a reduction gear driven by a motor is used in various fields. FIG. 1A generally shows a case where the present invention is applied to a joint, and a fixed side of a reduction gear 101 that is rotationally driven by a motor is coupled to one skeleton holding unit 102, and a driven side is coupled to the other skeleton holding unit 103. Here, the fixed side and the driven side are relative concepts, and the same is true regardless of which is defined as the fixed side or the driven side. FIG. 1B shows a case where it is applied to a prosthetic limb. The hip joint 106 connects the body 104 and the femur 105, the knee joint 108 connects the femur 105 and the crus 107, the crus 107 and the foot 109. Are applied to the ankle joint 110. FIG. 1C shows a case where the present invention is applied to a brace that assists a patient whose muscles are paralyzed, and includes a hip joint 113, a thigh holder 112, and a crus holder 114 that connect the body corset 111 and the thigh holder 112. It is applied to the knee joint 115 that joins the leg joint 117 and the leg joint 117 that joins the lower leg holder 114 and the foot holder 116. Although not shown in the drawings, the present invention can also be applied to the shoulder joint, elbow joint, etc. of the upper limb.

  As a speed reducer used for such a joint, a weight reducer that can rotate against a large torque, that is, a speed reducer with a large reduction ratio, is particularly desired because the joints of the lower limbs are heavy. Furthermore, a thin one with a small diameter is desired because of the limitation of the mounting location. The first thing that comes to mind is a harmonic drive that has a large reduction ratio. However, the harmonic drive processes teeth on the outer circumference of the flexible cylinder and engages them at the two elliptical long-diameter ends. The slight deflection of the minor axis at the open end of the cylinder, that is, the curvature is reduced, and one tooth is released. Since a total of 2 teeth are used for deceleration, a cylinder with a short axial length increases the bending force of the harmonic mechanism itself, and even if it can be realized, the concentrated stress increases and the fatigue limit decreases. There is a risk of inviting. Therefore, the planetary gear mechanism is adopted. Japanese Patent Application Laid-Open No. 2004-01990 (Patent Document 1) proposes a 3K type (3S type) that achieves a reduction ratio of 1/217. Here, the same gear is adopted as the fixed planetary gear PG1 and the driven planetary gear PG2, and the tooth number difference ΔZ between the fixed internal gear RG1 and the driven internal gear RG2 is 1. The driven internal gear RG2 is shifted by +0.5 in order to enable engagement between two internal gears GR1 and GR2 having a different number of teeth and one planetary gear (Patent Document 1, paragraph 0030). ). Since this speed reducer is thick and can be accommodated in the joint, it is estimated that this speed reducer is a speed reducer for the knee joint of the robot.

  Japanese Unexamined Patent Publication No. 2001-90792 (Patent Document 2) proposes a 3K type (3S type) that realizes a reduction ratio of 1/224. Here, one planetary gear has a large diameter so as to mesh only with the sun gear, and a small-diameter planetary gear that rotates integrally with the large-diameter planetary gear meshes with the fixed side and driven-side internal gears. The number of teeth difference ΔZ between the fixed-side internal gear C and the driven-side internal gear D is set to 3. Then, in order to allow the internal gears C and D having a difference in the number of teeth to mesh with the one planetary gear B2, the driven-side internal gear D is shifted by +0.9 (Patent Document 2, Paragraph 0012). . The tooth number difference ΔZ between the fixed side internal gear RG1 and the driven side internal gear RG2 was set to 1. A predetermined condition is provided between the dislocation coefficient and the tooth number difference ΔZ (Patent Document 2, paragraph number 0004).

  The 3K type (3S type) planetary gear mechanism is shown in FIG. 11 on page B1-177 of “Mechanical Engineering Handbook 1989 edition of the Japan Society of Mechanical Engineers” and FIG. 389. The ones that rotate integrally and mesh with the fixed-side internal gear S2 and the driven-side internal gear S3 are substantially disclosed.

JP 2004-01990 A JP 2004-01990 A "Mechanical Engineering Handbook, 1989 Edition, Japan Society of Mechanical Engineers", page B1-177, Fig. 389

  In the planetary gear mechanism of Patent Document 1, the driven-side internal gear RG2 is shifted in order to allow the internal gears GR1 and GR2 having a difference in the number of teeth to mesh with one planetary gear. For this reason, there is a problem that the meshing rate of the gears is deteriorated, and that it is disadvantageous in terms of strength as a speed reducer for a knee joint in which a large torque is applied. Further, the reduction ratio is stopped at 1/217 (Patent Document 1, paragraph number 0031). Furthermore, in order to arrange the four planetary gears at equal intervals, the fixed planetary gear PG1 and the driven planetary gear PG2 must be incorporated with a predetermined phase difference for each of the four sets (Patent Document 1, paragraph). Number 0035, FIG. 8). For this reason, there is a problem that the structure is complicated, the cost is increased, and the strength is weakened. Further, many gears that are not standard gears are used, and these have to be combined, resulting in an increase in cost.

  In the planetary gear mechanism of Patent Document 2, the driven-side internal gear D is displaced in order to allow the internal gears C and D having a difference in the number of teeth to mesh with the one planetary gear B2. Then, a delicate relationship is provided between the shift amount and the tooth number difference rate to ensure that the internal gears C and D having different number of teeth and the planetary gear B2 can be engaged in practice. For this reason, there are the same problems as the planetary gear mechanism of the above-mentioned Patent Document 1, and there is a problem that the degree of freedom of design is narrowed. Moreover, the reduction ratio is also stopped at 1/119 (Patent Document 2, paragraph number 0011).

  The present invention has been made to solve the above-described problems, and achieves a higher reduction ratio than conventional with a standard gear without using a dislocation gear, and has a thin axial thickness and assists patient's joint movement. It aims at providing the reduction gear for joints suitable for applying to a brace. It is another object of the present invention to provide a joint reducer that operates stably without generating an axial bending moment even when a large torque is applied between the fixed side and the driven side of the joint reducer.

  In order to solve the above problems, a reduction gear for joint according to the present invention includes a sun gear integrated with an input shaft, a plurality of first planetary gears meshed with the sun gear, and the first planetary gears. A plurality of second planetary gears that are integrally rotated with each other and do not mesh with the sun gear, a plurality of first internal gears that mesh with the plurality of first planetary gears, and the plurality of planetary gears. A second internal gear meshing with the second planetary gear, a difference ΔZ between the number of teeth of the first internal gear and the number of teeth of the second internal gear, and the first planetary gear The difference ΔZ between the number of teeth and the number of teeth of the second planetary gear is equal, one of the first or second internal gear is a fixed side, and the other is a driven side, It is characterized by providing. Here, the difference ΔZ in the number of teeth may be 1.

  When configured in this way and the difference ΔZ in the number of teeth is set to a small value, a large reduction ratio can be obtained between the sun gear and the driven-side internal gear. When the difference ΔZ in the number of teeth is 1, the reduction ratio is the largest. Here, each gear need not be a shift gear. This is because planetary gears having different diameters (number of teeth) mesh with internal gears having different diameters (number of teeth). The difference ΔZ between the number of teeth of the first internal gear and the number of teeth of the second internal gear, and the difference ΔZ of the number of teeth of the first planetary gear and the number of teeth of the second planetary gear. Are equal to each other, the phase difference between the first planetary gear and the second planetary gear when the first planetary gear and the second planetary gear are fixed can be made the same in all the groups. There is no need to change the phase difference for each gear. Since the difference ΔZ in the number of teeth of the two is the same, the phase of the teeth of the planetary gear and the two internal gears on the entire circumference is considered when the planetary gear is revolved while revolving without rotating. The relationship is consistent. Therefore, if a plurality of planetary gear sets assembled with the same phase difference are arranged and assembled in the same direction on the revolution trajectory, they can be arranged in phase with the two internal gears.

  In addition, a second gear comprising the first gear train comprising the sun gear, the first planetary gear, and the first internal gear, and the second planetary gear and the second internal gear. There is a plurality of sets of one of the two gear series with the gear series, and a sandwich structure in which one of the plurality of sets is incorporated so as to sandwich the other gear series in the axial direction. Can be a feature. With this configuration, even if a large torque is applied between the fixed side and the driven side, one gear train is sandwiched and incorporated in the other gear train, so the axial bending moment is canceled. It does not occur outside and operates stably. In other words, the shaft support of the integral planetary gear group in the sandwich structure is not cantilevered, but the both ends support is automatically aligned, and the generation of bending load on the planetary gear shaft is small, so that the whole can be thinned and the joint speed reducer can be thinned. In other words, it can withstand high load torque.

  FIG. 2 is a schematic diagram showing the basic concept of the present invention. A large-diameter gear 201 composed of 45 teeth and a small-diameter gear 202 composed of 44 teeth are integrated with each other so as to rotate together. The large diameter gear 201 meshes with the driven side rack 204, and the small diameter gear 202 meshes with the fixed side rack 203. Here, the difference in the number of teeth ΔZ between the large-diameter gear 201 and the small-diameter gear 202 is 1. The gap d between the pitch circles of both gears 201 and 202 is ½ teeth × module, and the diameter of the pitch circle of the large-diameter gear 202 is 45 teeth × module. Therefore, the amount of movement of the driven rack 204 when the large-diameter gear 201 is rotated is considered based on the lever principle, and is 1/45 / 0.5 = 1/90 of the movement amount F of the large-diameter gear 201. Become. Thus, a large reduction gear ratio of 1/90 can be realized by combining the gears 201 and 202 having a small number of teeth difference Δ together and engaging the fixed side rack 203 and the driven side rack 204. In order to realize this principle as a speed reducer, the finite racks 203 and 204 are wound in a circular shape to make them infinite, and the internal gear has a large number of teeth, and the fixed side is realized as a planetary gear mechanism. Further, a larger reduction ratio can be obtained by the product of the reduction ratio by the rack and the reduction ratio by the planetary gear, and space saving can be achieved by a linear axis that is not an orthogonal axis like a worm reduction gear.

  FIG. 3 is a perspective view showing the concept of the joint speed reducer according to the present invention. A joint 115 composed of a planetary gear mechanism is formed between the fixed side skeleton holding unit 102 and the driven side skeleton holding unit 103. The motor 120 is fixed to the fixed side skeleton holding unit 102. The sun gear 1 is rotationally driven by the input shaft 121 that is rotationally driven by the motor 120. The sun gear 1 meshes with the three first planetary gears 2 arranged every 120 °. A second planetary gear 3 is concentrically fixed to each first planetary gear 2 and rotates integrally therewith. The diameter of the second planetary gear 3 is smaller than the diameter of the first planetary gear 2. The three first planetary gears 2 mesh with the fixed-side first internal gear 5 integrated with the fixed-side skeleton holding unit 102. The three second planetary gears 3 mesh with the driven second internal gear 4 integrated with the driven skeleton holding portion 103. The diameter of the first internal gear 5 is larger than the diameter of the second internal gear 4. The carrier (arm) that holds the three sets of planetary gears 2 and 3 is not shown. When the sun gear 1 is rotationally driven, the first planetary gear 2 is rotationally driven, and the first planetary gear revolves while rotating with the first internal gear 5 on the fixed side. Due to the movement of the second planetary gear 3 that moves exactly the same as the first planetary gear 2, the second internal gear 4 on the driven side slightly rotates and the driven-side skeleton holding portion 103 is driven to rotate.

  FIG. 4 is a configuration diagram showing a planetary gear mechanism of the joint speed reducer. The first planetary gear 2 that is rotationally driven by the sun gear 1 meshes with the first internal gear 5 on the fixed side. The second planetary gear 3 that rotates integrally with the first planetary gear 2 meshes with the second internal gear 4 on the driven side. Three sets of planetary gears 2 and 3 are held by a carrier (arm) 6. Here, the number of teeth of the first internal gear 5 on the fixed side is increased by ΔZ, specifically by 1, from the number of teeth of the second internal gear 4 on the driven side. Similarly, the number of teeth of the first planetary gear 2 is made larger than the number of teeth of the second planetary gear 3 by the same ΔZ as described above, specifically by one.

FIG. 5 is an exploded view showing the planetary gear mechanism. The module is 0.5. The number of teeth of the sun gear 1 is Z ₁ = 18. The number of teeth is set to 18 teeth with a margin because the limit of gear cutting at a pressure angle of 20 ° is 14 teeth. The number of teeth of the first planetary gear 2 meshing with the sun gear 1 is Z ₂ = 45, and the number of teeth of the second planetary gear 3 is Z ₃ = 44. The difference ΔZ in the number of teeth is 1. The number of teeth of the first internal gear 5 on the fixed side was Z ₅ = 108. This is because Z ₅ = 18 + 45 + 45. The number of teeth of the second internal gear 4 on the driven side is Z ₄ = 107. This is because Z ₄ = 18 + 45 + 44. The difference ΔZ in the number of teeth is 1. The carrier (arm) 6 holds three sets of planetary gears 2 and 3.

  FIG. 6 is a table in which the reduction ratio of the planetary gear mechanism is calculated by the “glue method”. First, it is assumed that the first internal gear 5 can also freely rotate. The carrier (arm) 6 is fixed and the sun gear 1 is rotated once to the right to rotate the gears 1, 2, 3, 4, and 5. Check out. That is the first column in the table of FIG. Next, the whole mechanism is fixed to each other (glued) and rotated one time to the right. That is the second column in the table of FIG. Next, the carrier (arm) 6 is fixed, and the first internal gear 5 is rotated once in the left direction. That is the third column in the table of FIG. The fourth column is the algebraic sum of the second and third columns. The rotation of the first internal gear 5 is 0, indicating a fixed state. The 5th column of the table | surface of FIG. 5 is arranged, and it turns out that the 2nd internal gear 4 rotates 1/535 with respect to 1 rotation of the sun gear 1. FIG. That is, a high reduction ratio of 1/535 could be achieved using a standard gear without dislocation.

  FIG. 7 is an explanatory diagram for explaining that the phase difference between the integrated first planetary gear 2 and the second planetary gear 3 may be the same for a plurality of sets (three sets) of planetary gears. Here, for simplicity of explanation, the number of teeth of the sun gear 51 is 6, the number of teeth of the large-diameter planetary gear 52 is 6, the number of teeth of the small-diameter planetary gear 53 is 5, and the number of teeth of the small-diameter driven-side internal gear 54 is 17 and the number of teeth of the large-diameter fixed-side internal gear 55 is 18. The large-diameter planetary gear 52 having 6 teeth and the small-diameter planetary gear 53 having 5 teeth are coupled and fixed together and rotate as a set of planetary gears. The planetary gears 53 and 52 having 5 teeth and 6 teeth are coupled and fixed so that the tooth profile symmetry lines of one tooth coincide with each other. The direction in which the phases coincide is indicated by an arrow X. In the position of A in the figure, the internal gears 54 and 55 are also set to Y so that the symmetry lines of the bottom shape coincide with each other, and the phase of one tooth of the planetary gears 53 and 52 is made to coincide with this. When meshed with 55 and 54 so as to coincide with the direction of X, the planetary gears 52 and 53 mesh with the internal gears 55 and 54 without difficulty.

  Next, another set of planetary gears is moved while keeping the same direction X as the planetary gear in the position A in parallel with the direction Y, and brought to a position B shifted by 120 °. Here, on the planetary gear, the phase difference of the large-diameter planetary gear 52 with respect to the small-diameter planetary gear 53 is 2/6 = 1/3 of one tooth. Even in the driven-side internal gear 54, the phase difference of the driven-side internal gear 54 with respect to the fixed-side internal gear 55 is also 6/18 = 1/3 of one tooth. It becomes possible. Since the position C is deviated by −120 ° from the position A, if the X direction of the planetary gear is parallel to the Y direction, the same phase shift as described above occurs in the reverse direction. Therefore, meshing is possible. That is, with respect to the large-diameter planetary gear 52 that meshes with the large-diameter internal gear 55 in the gear train having the sun gear 51, there are three ways to give the phase difference of the small-diameter planetary gear 53 that does not mesh with the sun gear 51. All that is the same. In addition, the planetary gears of each set may be meshed with the phase matching direction X in parallel. In this way, if the planetary gear device is assembled with the phase difference of the three sets of planetary gears being the same and the phase coincidence direction X being parallel, the internal gears 55 and 54 that are the counterparts of the planetary gears 52 and 53, respectively. Is also completed at the same time. That is, there is an advantage that the assembling of the planetary gear device becomes very simple. This means that the first and second internal gears are not 108 and 107 in the same reduction mechanism combination, that is, when the difference in the number of teeth is not 1, or are arranged for each unequal arc while satisfying the constraint conditions. The same holds true when the number of planetary gear pairs is different.

  Referring to FIG. 4, when a large moment is applied between the fixed-side internal gear 5 and the driven-side internal gear 4, the carrier (arm) is determined from the existence of the distance between the first planetary gear 2 and the second planetary gear. ) A bending moment in the axial direction is generated at 6. The carrier (arm) 6 must withstand this. The bending moment increases as the speed reduction ratio increases, and the carrier (arm) 6 must be thickened to obtain a large sticking moment, which is a factor that the axial distance cannot be shortened. To solve this problem, if the planetary mechanism has a sandwich structure, the shaft is supported at both ends, and a thin joint speed reducer that cancels the cantilever moment can be proposed.

  FIG. 8 is a perspective view showing the concept of a joint speed reducer having a sandwich structure. Here, two sets of fixed-side gear trains comprising a sun gear, a first planetary gear, and a fixed-side first internal gear are prepared, and a second planetary gear and a driven-side second internal gear are prepared. A set of driven side gear series consisting of And it is set as a sandwich structure so that two sets of fixed side gear series may sandwich one set of driven side gear series. The fixed-side skeleton holding portion 102 is divided into two forks at the planetary gear mechanism, and the fixed-side first internal gears 15 and 25 having a large diameter are integrally formed. The driven-side skeleton holding portion 103 is rotatably supported by being sandwiched between the first internal gears 15 and 25 of the fixed-side skeleton holding portion 102 and has a small-diameter driven-side second internal gear 14.

  The motor 120 is fixed to the fixed side skeleton holding unit 102. The two sun gears 11 and 21 are rotationally driven by an input shaft 121 that is rotationally driven by a motor 120. Each sun gear 11, 21 meshes with two series of first planetary gears 12, 22. The large-diameter first planetary gears 12 and 22 mesh with the large-diameter fixed-side first internal gears 15 and 25. A second planetary gear 13 having a small diameter is fixed concentrically between the first planetary gears 12 and 22. The second planetary gear 13 meshes with the small-diameter driven second planetary gear 14. The carrier (arm) that holds the planetary gears 12, 13, and 22 is not shown.

The number of teeth of each gear is the same as that shown in FIG. 5, the number of teeth of the sun gears 11, 21 is Z ₁ = 18, and the number of teeth of the first planetary gears 12, 22 meshing with the sun gears 11, 21 is The number of teeth was Z ₂ = 45, and the number of teeth of the second planetary gear 13 was Z ₃ = 44. The difference ΔZ in the number of teeth is 1. The number of teeth of the large-diameter fixed-side first internal gears 15 and 25 is Z ₅ = 108, and the number of teeth of the small-diameter driven-side second internal gear 14 is Z ₄ = 107. The difference ΔZ in the number of teeth is 1. The module is 0.5.

  FIG. 9 is a cross-sectional view of a joint speed reducer having a sandwich structure. Two fixed side plates 31, 31 are fixed to the fixed side skeleton holding portion 102, and the motor 120 is fixed to one of the fixed plates 31 with screws. Also, substantially disk-shaped fixed casings 32, 32 are respectively arranged on the left and right sides of the two fixed-side plates 31, 31 and fixed with screws. In the left and right fixed casings 32, 32, annular first internal gears 15, 25 are fixed to the left and right by screws. The two large-diameter fixed-side first internal gears 15 and 25 are depicted at the top and bottom of the drawing. The tooth surfaces of the fixed-side first internal gears 15 and 25 are shown as 15A and 25A in the drawing.

  The driven side skeleton holding part 103 is rotatably supported by four bearings 33, 33, 33, 33 installed at the circumferential end of the fixed casing 32. An annular driven second internal gear 14 is formed at a portion extending to the center of the driven skeleton holding portion 103. The driven-side second internal gear 14 has a slightly smaller diameter than the fixed-side first internal gears 15, 25. The tooth surface of the driven-side second internal gear 14 is shown as 14A in the drawing.

  Two carriers (arms) 16, 16 are rotatably supported by four bearings 34, 34, 34, 34 installed near the center of the fixed casings 32, 32. Between the two carriers (arms) 16, three planet shafts 35 (only two are shown in the drawing) are passed and integrated. Three planetary gears are rotatably supported on the planetary shafts 35 by bearings. That is, the second planetary gear 13 with a small diameter at the center and the first planetary gears 12 and 22 with a large diameter on the left and right. The three planetary gears 12, 13, and 22 are integrated by a pin so as to rotate integrally.

  The sun gears 11 and 21 are rotatably supported by bearings installed at the center of the fixed casings 32 and 32. The tooth surfaces of the sun gears 11 and 21 are indicated by 11A and 21A. The input shaft 121 passes through the center of the sun gears 11 and 21 and rotates together with the rotation of the motor 120. The tooth surfaces 11A and 21A of the sun gears 11 and 21 mesh with the first planetary gears 12 and 22 having large left and right diameters. The first planetary gears 12 and 22 mesh with the tooth surfaces 15A and 25A of the fixed-side first internal gears 15 and 25 having large diameters, respectively. The small-diameter second planetary gear 13 that moves and rotates integrally with the first planetary gears 12 and 22 meshes with the tooth surface 14A of the small-diameter driven second internal gear 14.

  FIG. 10 is a table showing specifications of used gears of the joint reduction gear. The sun gears 11 and 21 used the gears shown in the bottom column among the four gears shown in the first column. The gears shown in the second column were used for the large-diameter first planetary gears 12 and 22. The small diameter second planetary gear 13 used was the one shown in the third column. The small-diameter driven second internal gear 14 shown in the fourth column was used. As the large-diameter fixed-side first internal gears 15 and 25, those shown in the fifth column were used. Here, the driven-side second internal gear 14 shown in the fourth column is a gear having a prime number and must be made specially. However, since the other gears 11, 21, 12, 22, and 15 are standard gears, not shift gears, they can be selected from off-the-shelf products and can be procured at low cost.

  The operation will be described based on the above configuration. The function as the planetary gear mechanism is exactly the same as that described in FIGS. 2 to 5, and a high reduction ratio of 1/535 is realized between the input shaft 121 and the driven side skeleton holding unit 103. Since the sandwiched structure in which the driven side gear series 13 and 14 are sandwiched between the fixed side gear series 11, 12, 15, 20, 22, and 25 is adopted, the driven side second internal gear is referred to with reference to FIG. 14 and the fixed-side first internal gears 15 and 25 are supported at both ends of the shafts 35 of the planetary gears 13, 12, and 22 supported by the sandwich structure even if a large torque is generated between the planetary shafts 35 and 15. The inside is not cantilevered, the bending moment in the direction perpendicular to the axis is canceled, and no bending moment is generated when the planet shaft 35 is fixedly supported on the carriers (arms) 16 and 16. Moreover, there is an advantage of preventing the uneven contact between the gear meshing tooth surfaces at the same time. Therefore, the carriers (arms) 16 and 16 may be thin, and as a result, the joint speed reducer becomes thin and can be easily applied to a brace that assists the patient's muscle strength.

  The main point of this configuration is a sandwich structure of a complete planetary gear mechanism that is provisionally fixed and an incomplete planetary gear mechanism that is provisionally driven and has no sun gear. The parts that are connected together and rotate integrally are fixed and matched with the phase of the position of one tooth of each planetary gear meshing with each internal gear. There are as many planetary gear pairs fixed in this way as the number of arms of the carrier. Moreover, the direction in which the teeth coincide is always kept parallel and rotates. This planetary gear pair has a lever relationship. In other words, the meshing point with the sun gear is used as a power point, and the meshing point with the driven-side internal gear is set as the working point with the meshing point with the fixed-side internal gear as a fulcrum. In this case, the fulcrum, force point, and action point are not on one straight line. The sandwich structure offsets this eccentricity. Further, it is assumed that the meshing constraint condition of the planetary gear arrangement on the complete planetary gear mechanism side is satisfied. The incomplete planetary gear may have a ring-shaped internal gear or a planetary gear side sandwiched between the complete planetary gear side, or may have a tooth number difference of the same sign. It is the same category whether the difference in the number of teeth is + or? When the difference in the number of teeth is the smallest integer 1, the reduction ratio of the relationship between the rack and the lever, which is not the reduction ratio by the planetary gear, becomes the largest. There is an advantage that only one sun gear is required when sandwiching with the complete side in. If the incomplete side is used as a sandwich, two sun gears are required. If a slight phase difference in the circumferential direction is added between the two with a spring or the like, there is an advantage that a backlash removal effect can be realized.

The side view which shows the usage example of the reduction gear for joints. It is a schematic diagram which shows the basic concept of this invention. The perspective view which shows the concept of the reduction gear for joints. The block diagram which shows the planetary gear mechanism of the reduction gear for joints. The block diagram which decomposes | disassembles and shows the planetary gear mechanism of the reduction gear for joints. The table which calculated the reduction ratio of the planetary gear mechanism of the reduction gear for joints by the "gluing method". Explanatory drawing explaining that the phase difference of the 1st planetary gear 2 and the 2nd planetary gear 3 which were united may be the same with multiple sets (3 sets) of planetary gears. The perspective view which shows the concept of the reduction gear for joints which has a sandwich structure. Sectional drawing of the reduction gear for joints which has a sandwich structure. The table | surface which shows the specification of the use gearwheel of the reduction gear for joints. The block diagram of the 3S type planetary gear mechanism described in the mechanical engineering handbook.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sun gear 2 Large diameter fixed side first planetary gear 3 Small diameter driven side second planetary gear 4 Small diameter driven side second internal gear 5 Large diameter fixed side first internal gear 6 Carrier ( arm)
32 fixed casing 33 bearing 35 planetary shaft

Claims (3)

A sun gear integrated with the input shaft;
A plurality of first planetary gears meshing with the sun gear;
A plurality of second planetary gears that are integrated with each of the first planetary gears and rotate integrally and do not mesh with the sun gear;
A first internal gear that meshes with the plurality of first planetary gears;
A second internal gear that meshes with the plurality of second planetary gears;
The difference ΔZ between the number of teeth of the first internal gear and the number of teeth of the second internal gear is equal to the difference ΔZ of the number of teeth of the first planetary gear and the number of teeth of the second planetary gear. And
Either one of the first or second internal gear is a fixed side, and the other is a driven side;
A reduction gear for joints, comprising:   The joint reduction gear according to claim 1, wherein the difference ΔZ in the number of teeth is one.   A first gear series comprising the sun gear, the first planetary gear, and the first internal gear; and a second gear series comprising the second planetary gear and the second internal gear. And the two gear trains have a sandwich structure in which there are a plurality of gear trains, and one gear train of the plurality of gears is incorporated so as to sandwich the other gear train in the axial direction. The joint speed reducer according to claim 1 or 2.

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