JP2004299000A - Joint driving device for industrial robot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a joint driving device for an industrial robot, realizing a high speed reducing ratio with a speed reduction gear easy in manufacturing, preventing the generation of resonance even in a high rotation speed area of a servomotor, and keeping backlash small for a long period. <P>SOLUTION: A speed reducer G1 has two-step speed reducing portions that are a front step speed reducing portion 100 of an internal gearing planetary gear structure, and a rear step speed reducing portion 200 of the internal gearing planetary gear structure. A front step casing 102 and a rear step casing 202 can be divided. The speed reducing ratio of the front step speed reducing portion is made to be not more than 1/20, and the speed reducing ratio of the rear step speed reducing portion is made to be not less than 1/25. Furthermore, the total speed reducing portion achieved by the front step speed reducing portion 100 and the rear step speed reducing portion 200 is made to be 1/150 to 1/400. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a joint driving device for an industrial robot.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a reducer having an internally meshing planetary gear structure including an external gear and an internal gear having a small difference in the number of teeth has been widely used as a joint drive device of an industrial robot.
[0003]
In this reduction gear, one of the external gears or the internal gear is eccentrically swung with respect to the other gear in a state where the rotation of one of the gears is restrained, and the rotation is restrained during the eccentric swing. The rotation component generated on the non-driven gear is taken out as an output, and a large reduction ratio can be obtained in one stage.
[0004]
Meanwhile, as a conventionally known problem in the joint driving device of an industrial robot, there is a “resonance phenomenon” generated by a reduction gear as a vibration source. When the reduction gear of the reduction gear is an internally meshing planetary gear structure, the external gear or the internal gear rotates in an oscillating manner, so that a radial load due to this oscillating is inevitably generated, and the direction is reduced. Such a resonance phenomenon is particularly likely to occur because of rotation around the axis of the machine.
[0005]
When the resonance phenomenon occurs, the position of the tip of the arm of the industrial robot cannot be determined, and the workability or accuracy of the robot is significantly reduced.
[0006]
As a technique for suppressing such a resonance phenomenon, in Japanese Patent No. 25626127 (Patent Document 1), the internal meshing planetary gear structure is provided in front of the reduction portion of the internal meshing planetary gear structure that easily becomes a vibration source. A "parallel shaft gear structure" having a structure different from that described above, in which a prior-stage reduction portion having a reduction ratio of 1/2 to 1/5 is disposed.
[0007]
In Japanese Patent Application Laid-Open No. 10-586 (Patent Document 2), in order to cope with a resonance that newly occurs with the speeding up of the servomotor, a case where a plurality of natural torsional frequencies are used is disclosed. It separately proposes the optimal range of the reduction ratio of each reduction section and the like.
[0008]
All of these technologies combine the former reduction unit of a parallel shaft gear structure having a structure that is less likely to be a vibration source with the reduction unit of an internally meshing planetary gear structure having a structure that easily becomes a vibration source. The technology bases on shifting the frequency of resonance generated due to the oscillating rotation of the reduction portion of the internal meshing planetary gear structure.
[0009]
[Patent Document 1]
Japanese Patent No. 25661227
[Patent Document 2]
JP-A-10-586
[0010]
[Problems to be solved by the invention]
However, in general, in the reduction unit of the “parallel shaft gear structure”, only one-fifth reduction ratio can be obtained in one stage, so in order to obtain the total reduction ratio required for the reduction gear of the recent industrial robot, It is necessary to take measures such as setting the rear reduction section to a high reduction ratio such as 1/80 or more, or setting the front reduction section itself of the parallel shaft gear structure to two stages.
[0011]
In the case of the internally meshing planetary gear structure, the reduction ratio in this region can be realized by itself. However, the range of the reduction ratio that is easiest to make is in the range of about 1/30 to 1/40, which is not so high. It is not preferable to set such a high reduction ratio in terms of easiness of manufacture, securing of transmission capacity, and, above all, processing and assembling of precision parts with small backlash.
[0012]
On the other hand, measures to reduce the speed of the parallel shaft gear structure to two are increased in weight and size.
[0013]
Further, as a practical problem, there is a problem that backlash increases due to a change with time. The reduction gear having the parallel shaft gear structure has relatively large wear over time due to a low engagement ratio. A reduction gear for driving a joint of an industrial robot is often operated continuously, and generally has a long operation time. Abrasion over time induces an increase in backlash and tends to cause a decrease in positional accuracy.
[0014]
Further, as another practical and serious problem, each of the above-mentioned prior arts has a casing structure in which a front reduction portion of a parallel shaft gear structure and a rear reduction portion of an internally meshing planetary gear structure are "integrally integrated". Therefore, there is a problem that the structure for realizing the purpose of avoiding resonance lacks flexibility.
[0015]
That is, even if the industrial robot is a robot having the same structure, the resonance point actually generated and its amplitude vary depending on the use of the customer or the installation environment (such as the rigidity of the installation base). There is a problem. In addition, since the movement of the robot differs depending on the application and the work content, for example, in the work at the customer A, the second arm could be rotated with the rigidity of the first arm being high. In such a case, since the second arm needs to rotate at the end where the first arm is fully extended, a situation may occur in which resonance tends to appear. To cope with all of the resonances that change variously due to such uncertain factors, preparing the reducer each time on the manufacturer side not only increases the inventory burden, but also results in delivery of the Since there is only one unit, the other preparations are burdened by the manufacturer in the form of "increase in delivery cost". As a result, the increase in the delivery cost also increases the product cost per reduction gear. This has become a new facet in the field of industrial robot joint drive devices in recent years as work by robots has become extremely precise.
[0016]
The present invention has been made in view of such various circumstances, and has reexamined the mechanism of the resonance phenomenon drastically, at a low cost, has a high resonance suppression effect, and has more freedom in design and handling. It is an object of the present invention to provide a joint driving device for an industrial robot with high reliability.
[0017]
[Means for Solving the Problems]
The present invention relates to a joint drive device for an industrial robot, comprising: a motor, a front-stage reduction unit of an internally meshing planetary gear structure having an external gear and an internal gear having a small difference in the number of teeth, and a small difference in the number of teeth. A reduction mechanism portion having a two-stage reduction portion of an internal meshing planetary gear structure that further includes an external gear and an internal gear having the following, and further reduces the speed by receiving the output of the previous reduction portion. The above problem is solved by a configuration in which the front-stage reduction unit and the rear-stage reduction unit are provided in independent front-stage casings and rear-stage casings, respectively, and the front-stage casing and the rear-stage casing are separable from each other. is there.
[0018]
Here, the "small difference in the number of teeth" means a difference in the number of teeth of about 1 to 6.
[0019]
In order to confirm the mechanism of the resonance phenomenon, the inventor prototyped reduction gears having various reduction ratios having various structures and performed a resonance test. As a result, a predetermined correlation is confirmed between the resonance performance of the single-stage reduction gear having the internal meshing planetary gear structure and the resonance performance of the two-stage reduction gear having the pre-reduction section at the preceding stage. I was able to. The present invention has been made by adding even more realistic and rational ideas based on the test results.
[0020]
In the present invention, as the structure of the pre-stage reduction unit (pre-reduction unit), the reduction unit itself of the internal meshing planetary gear structure, which is conventionally considered to be most likely to cause resonance, is dared to be employed. This is based on the result that the above test showed that "there is a sufficient effect of suppressing resonance even if an internal meshing planetary gear structure is adopted as the structure of the pre-stage reduction portion".
[0021]
Since this operation is an important base of the present invention, it will be described later in detail along with the explanation of test results and the like.
[0022]
As a result, the reduction ratio of the front reduction unit is set to 1/6 or more (it was difficult to achieve with the reduction unit having the single-stage parallel shaft gear structure). Has become extremely easy, and it has become easy to shift the resonance frequency to a frequency higher than the practical rotation speed of the servomotor. Therefore, it is possible to adequately cope with a resonance problem that is expected to newly occur with the further increase in the speed of the servomotor (described later).
[0023]
Further, since the internal meshing planetary gear structure having a high meshing rate and little wear over time can be employed, the problem of an increase in backlash over time can be avoided.
[0024]
In the present invention, the front-stage reduction unit and the rear-stage reduction unit are accommodated in independent front-stage casings and rear-stage casings, respectively, and the front-stage casing and the rear-stage casing can be divided from each other.
[0025]
As a result, the natural torsional frequency, its amplitude, etc., have changed due to differences in the effective arm length of the robot, the rotational speed of the motor, or the installation conditions that vary depending on the customer's application, or the required specifications and work content. However, it is possible to easily obtain an optimal combination of drive devices capable of effectively suppressing the resonance actually occurring, and to reduce the burden on inventory.
[0026]
This operation is achieved by, for example, providing that the motor is also housed in an independent motor casing, and that the front casing that houses the front speed reducer and the motor casing that houses the motor are also separable. It is also possible to exchange only one of them, so that a more effective form can be obtained. That is, with this configuration, high-precision machining and assembly is required, and therefore, the cost of the latter-stage deceleration portion, which tends to be high, is, for example, only one type of design (or stock). By connecting the front-stage deceleration unit, it is possible to obtain a joint drive device having many resonance-compatible variations at low cost as a result.
[0027]
Further, the position of the connection hole between the front casing and the rear casing matches the position of the mounting hole of the member to be mounted of the industrial robot, and the connection between the front casing and the rear casing, and the front casing and When the rear casing is mounted on the member to be mounted by using the same mounting bolts, replacement and mounting of each deceleration unit and the like are further facilitated.
[0028]
The reduction ratio of the preceding reduction unit is 1/20 or less (the denominator is small), the reduction ratio of the subsequent reduction unit is 1/25 or more (the denominator is large), and the former reduction unit and the latter reduction unit Is preferably set in the range of 1/150 or more and 1/500 or less.
[0029]
As a result, it is easy to manufacture the rear-stage reduction unit as the reduction unit of the internal meshing planetary gear structure while maintaining a high total reduction ratio that can sufficiently cope with the recent high rotation speed servomotor. The speed reduction ratio, in particular, a speed reduction ratio of about 1/30 to 1/40 can be obtained. Since the manufacturing accuracy of the latter reduction unit directly affects the determination of the final performance of the joint drive device of the industrial robot, the merit that this latter reduction unit can be manufactured with a reduction ratio that is easy to manufacture is actually extremely small. large.
[0030]
If the difference in the number of teeth between the external gear and the internal gear in the preceding reduction unit is set to two or more, the former reduction unit with a reduction ratio of 1/20 or less can be easily manufactured. Can be realized at low cost while maintaining a low level.
[0031]
Furthermore, when the backlash of the rear deceleration section is set to be smaller than the backlash of the front deceleration section below the value corresponding to the corresponding reduction ratio, particularly when the backlash is set to 1/10 or less, the efficiency is improved. In addition, it is possible to obtain a highly accurate joint driving device for the entire reduction gear.
[0032]
Details will be described later.
[0033]
As a result, the prior art having "a structure in which a reduction portion of an internally meshing planetary gear structure is arranged in front of a reduction portion of an internally meshing planetary gear structure", which is a part of the configuration of the present invention, is obtained. Is disclosed in Japanese Utility Model Publication No. 57-16714.
[0034]
However, in this conventional example, the front-stage deceleration unit and the rear-stage deceleration unit are integrated in a mixed manner, and the resonance point of the resonance generated in the rear-stage deceleration unit is set to “outside the practical range by providing the front-stage deceleration unit. It is not based on the idea of "shifting." Actually, the resonance phenomenon is not considered at all, and the reduction ratio is merely described as being able to realize a high reduction ratio of 1/2000 or more by using two reduction stages. Further, the two reduction gears are completely integrated and fused, and the great advantages of the present invention, such as flexibility in the field, are not obtained.
[0035]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0036]
FIG. 1 is a cross-sectional view showing a driving part (reduction gear) of a joint device of an industrial robot according to an embodiment of the present invention. FIGS. 2 and 3 are taken along lines II-II and III-III in FIG. 1, respectively. FIG. 4 is a cross-sectional view illustrating an example of a joint driving device for an industrial robot according to an embodiment of the present invention.
[0037]
The speed reducer G1 is connected to a motor (servo motor) M, and is mounted to rotate the second arm 14 with respect to the first arm 12 of the industrial robot 10 in a manner as shown in FIG.
[0038]
The speed reducer G <b> 1 includes a first-stage speed reduction unit 100 having an internal meshing planetary gear structure and a second-stage speed reduction unit 200 that receives an output of the first-stage speed reduction unit 100.
[0039]
Hereinafter, the first-stage reduction unit 100 and the second-stage reduction unit 200 will be described in detail in this order.
[0040]
In FIG. 1, the first-stage reduction unit 100 is housed in an independent first-stage casing 102. The front casing 102 includes a main casing 104 and first and second side covers 106 and 108 connected to both sides in the axial direction. A connecting portion 112 is integrally extended at one end of the input shaft 110 of the front reduced side portion 100. An insertion hole 114 is formed in the connection portion 112, and the motor shaft 30 of the motor M is inserted and connected to the insertion hole 114.
[0041]
The input shaft 110 is supported by a first side cover 106 of the front casing 102 and a flange body 172 of a front output shaft 170 (= the rear input shaft 210) described later via a pair of bearings 120 and 122. An eccentric body 124 is incorporated between the pair of bearings 120 and 122. Two external gears 130 and 132 are mounted on the outer periphery of the eccentric body 124 via roller bearings 126 and 128 so as to be swingably rotatable. The external gears 130 and 132 are internally meshed with an internal gear 140 integrated with the casing main body 104 of the front casing 102. The internal teeth of the internal gear 140 are formed by roller-shaped pins (external pins) 142.
[0042]
Internal pin holes 150 and 152 are formed through the two external gears 130 and 132, respectively, and the internal pin 160 is inserted therein. A pipe-shaped inner roller 162 is rotatably mounted on the inner pin 160. The inner pin 160 is fixed to a flange body 172 formed integrally with the previous output shaft 170, and is supported by the flange body 172 in a cantilever state.
[0043]
The front-stage output shaft 170 is directly used as the rear-stage input shaft 210 of the rear-stage reduction unit 200.
[0044]
The rear speed reducer 200 is also housed in the independent rear casing 202.
[0045]
The rear-stage input shaft 210 is supported by first and second output flanges 266 and 268, which will be described later, via a pair of tapered roller bearings 222 and 220, and a portion of the flange body 172 is connected to a front stage via a ball bearing 190. It is also supported by the second side cover 108 of the casing 102. An eccentric body 224 is incorporated between the pair of tapered roller bearings 220 and 222. Two external gears 230 and 232 are mounted on the outer periphery of the eccentric body 224 via roller bearings 228 and 226. The external gears 230 and 232 are internally meshed with an internal gear 240 integrated with the rear casing 202. The internal teeth of the internal gear 240 are formed by roller-shaped pins (outer pins) 242.
[0046]
Inner pin holes 250, 252 are formed through the two external gears 232, 230, respectively, and a highly accurate eccentric inner pin 260 is inserted therein. The eccentric inner pin 260 is different from the inner pin 160 of the preceding stage reduction portion 100 and is slidable on the entire outer circumference of the inner pin holes 250 and 252 via roller bearings 262 and 263 (corresponding to the eccentric amount). ) Eccentric projections 264 and 265 are provided, and there is no space corresponding to the amount of eccentricity between the inner pin holes 250 and 252.
[0047]
The eccentric inner pin 260 is supported at both ends by tapered roller bearings 270 and 272 on a pair of disk-shaped first and second output flanges 266 and 268 arranged on both sides of the external gears 232 and 230. ing.
[0048]
The first and second output flanges 266 and 268 are rotatably supported by the rear casing 202 via tapered roller bearings 274 and 276, respectively.
[0049]
The latter stage input shaft 210, the eccentric inner pin 260, and the first and second output flanges 266, 268 are supported by tapered roller bearings 220, 222, 270, 272, 274, 276. Is used for the purpose of driving the joints of the first arm 12 and the second arm 14 of the industrial robot 10, so that a load in the thrust direction is input from either of the first and second arms 12 and 14. This is because there is a possibility that
[0050]
Here, the connection mode of each member and the like will be described with reference to FIG.
[0051]
The first and second output flanges 266 and 268 of the rear reduction section 200 are firmly fixed by carrier pins 280. The first output flange 266 and the carrier pin 280 are fixed by bolts 282. On the other hand, the second output flange 268 and the carrier pin 280 are fixed by a bolt 286 inserted and screwed through the second arm 14.
[0052]
The casing 32 of the motor M and the first side cover 106 of the front reduction section 100 can be connected and separated by bolts 52 through spigots 50. Further, the second side cover 108 of the front reduction section 100 and the rear casing 202 of the rear reduction section 200 can also be connected and divided by bolts 55 through the spigot 54. Furthermore, the bolt position P1 of the second side cover 108 and the rear casing 202 matches the mounting hole position P2 of the first arm 12 of the industrial robot 10, and the connection of the second side cover 108 and the rear casing 202 Further, the cover 108 and the casing 202 are attached to the first arm 12 at the same time by the bolt 55.
[0053]
The outer diameter of the front deceleration section 100 is set smaller than the outer diameter of the rear deceleration section 200, and the space S1 secured thereby can accommodate accessories such as an encoder (not shown).
[0054]
As is clear from FIG. 2, the number of teeth of the external gears 130 and 132 of the pre-stage reduction unit 100 is “12”, the number of teeth of the internal gear 140 is “14”, and the difference in the number of teeth is “2”. The ratio is 2/12 = 1/6. As is clear from FIG. 3, the number of teeth of the external gears 230 and 232 of the rear-stage reduction unit 200 is “78”, the number of teeth of the internal gear 240 (the number of the outer pins 242) is “80”, and the number of teeth is The difference is “2”, and the reduction ratio is 2/78 = 1/39.
[0055]
In addition, since it is necessary to manufacture the post-stage deceleration unit 200 precisely including the management of the backlash, the deceleration ratio is in the range of 1/30 to 1/40, which is the easiest to manufacture, more specifically, 1/25 or more, / 50 or less. On the other hand, the speed reduction ratio of the pre-stage reduction unit 100 is set to 1/16 or less.
[0056]
In this embodiment, the backlash is set to be smaller than the backlash A1 of the rear deceleration section 100 to about 1/10 of the value corresponding to the corresponding deceleration ratio, in this embodiment. .
[0057]
Here, “backlash” refers to a range in which the output shaft moves (rotates) with the input shaft of the speed reduction unit stopped, and the unit is “degree” or “minute”.
[0058]
In general, when the reduction section is manufactured under the same level of manufacturing control, the backlash tends to decrease as the reduction ratio increases. For example, the backlash A2 of the latter reduction unit 200 at the reduction ratio of 1/39 is reduced to about 1/2 to 1/3 of the backlash A1 of the former reduction unit 100 having the reduction ratio of 1/6 if the processing accuracy is the same. . This is the “value corresponding to the corresponding reduction ratio” in this combination of reduction ratios. In the present embodiment, the backlash A2 is intentionally reduced to about 1/10 of the equivalent value. That is, as a result, the rear-stage backlash A2 is set to be 1/20 to 1/30 of the front-stage backlash A1.
[0059]
The effect of such a reduction ratio (a range in which the equivalent value varies) is at most about 1/8. In consideration of this, that is, when the back-stage backlash A2 is manufactured under the control of the same processing accuracy, the back-stage backlash A2 does not become 1/8 or less of the back-stage backlash A1 regardless of the reduction ratio and the frame number. In consideration of the above, if it can be intentionally maintained at a level of 1/10 or less (more preferably, 1/12 or less) of the preceding backlash A1 which clearly exceeds this, a corresponding effect can be obtained.
[0060]
As for the manufacturing technique itself for reducing the backlash, a known backlash reduction method can be adopted. For example, in the simplest case, several types of external gears having slightly different dimensions are prepared, and actually incorporated to determine the state of occurrence of backlash and the smoothness of rotation in the set of the external gear and the internal gear. A method of selecting an optimal external gear while confirming it may be used.
[0061]
Next, the operation of the speed reducer G1 according to this embodiment will be described.
[0062]
When the input shaft 110 of the pre-stage reduction unit 100 is rotated by the rotation of the motor M, the eccentric body 124 integrated with the input shaft 110 also rotates. When the eccentric body 124 rotates, the external gears 130 and 132 try to oscillate around the input shaft 110. However, since the internal gear 140 suppresses the rotation, the external gears 130 and 132 In this case, almost only swinging is performed while being in contact with the internal gear 140. However, since the number of teeth of the external gears 130 and 132 is set to 12 and the number of teeth of the internal gear 140 is set to 14, the external gears 130 and 132 become the internal gear 140 every one rotation of the input shaft 110. On the other hand, it shifts (rotates) by the difference in the number of teeth “2”. This means that one rotation of the input shaft 110 has been reduced to a rotation of −2/12 of the external gears 130 and 132, that is, a rotation of a reduction ratio of −1/6. A minus sign indicates that the rotation direction of the external gears 130 and 132 is opposite to the rotation direction of the input shaft 110. The rotation of the external gears 130, 132 is absorbed by the gap between the inner pin holes 150, 152 and the inner roller 162, and only the rotation component is passed through the inner pin 160 to the output shaft 170 (the input shaft 210). ).
[0063]
In the rear-stage deceleration unit 200, the same deceleration action as in the front-stage deceleration unit 100 is performed. That is, the external gears 230 and 232 are shifted (rotated) by the tooth number difference “2” with respect to the internal gear 240 every one rotation of the rear-stage input shaft 210. However, since the number of teeth of the external gears 230 and 232 of the rear-stage reduction unit 200 is set to 78 and the number of teeth of the internal gear 240 is set to 80, one rotation of the rear-stage input shaft 210 ends up being-of the external gear. The rotation is reduced to a rotation of 2/78, that is, a rotation of a reduction ratio of -1/39. Note that the rotation direction is once reversed in the first-stage reduction unit 100, but is reversed again in the second-stage reduction unit 200. Therefore, the external gears 230 and 232 of the second-stage reduction unit 200 are eventually rotated in the same direction as the rotation of the motor M. Will rotate.
[0064]
The rotation of the external gears 230 and 232 is absorbed by the presence of the eccentric projections 264 and 265 of the eccentric inner pin 260, and only the rotation component of the external gears 232 and 230 is The power is transmitted to the first and second output flanges 266 and 268 arranged on both sides. Since the first and second output flanges 266 and 268 are firmly connected via the carrier pin 280, the two output flanges 266 and 268 rotate integrally, and the rotation of the output flanges 266 and 268 is performed by the industrial robot 10 which is a counterpart machine. Power is transmitted to the second arm 14 via a bolt 286 and a bolt (not shown) connecting the second arm 14 and the output flange 268 (see FIG. 4).
[0065]
As a result, a deceleration corresponding to a reduction ratio of (−1/6) × (−1/39) = 1/234 is realized by multiplication with the preceding-stage reduction unit 100.
[0066]
Here, before describing the specific operation related to resonance cancellation, a resonance test on which the present invention is based will be briefly described. FIG. 5 shows an outline of the test apparatus.
[0067]
In the test apparatus T, the servo motor SM, the front reduction section PG, and the rear reduction section MG are connected by couplings C1 and C2. A flywheel FW is connected to the output side of the latter-stage reduction unit MG, and a piezoelectric pickup PU is built in an outer peripheral end of the flywheel FW. The pickup PU has a displacement (mm) and an acceleration (m / s) of the flywheel FW at a position of a radius r from the center of the flywheel FW. ² ) Is detected. The latter reduction unit MG has the same configuration as that of the latter reduction unit 200 described above. The reduction ratio is 1/39. The measurement range is 25 to 2000 rpm, the sampling width of the rotation speed is 25 rpm, and the inertia of the flywheel FW is 20 kgf · m · sec. ² The measurement position (radius r) is 850 mm. In this configuration, various configurations including the above-described pre-stage deceleration unit 100 as the pre-stage deceleration unit PG and reduction gears having reduction ratios were incorporated and vibration tests were performed.
[0068]
6 and 7 show test results. FIG. 6 shows a case where the preceding reduction unit 100 having the reduction ratio of 1/6 is combined (No. 1) and a case where the reduction unit of the parallel shaft gear structure having the reduction ratio of 1/5 is combined (No. 2). , And when there is no preceding-stage deceleration section (No. 0), the respective acceleration-motor rotation speed characteristics are shown. FIG. 7 shows the displacement-motor rotation speed characteristics.
[0069]
No. As is clear from the graph of 0, when only the rear deceleration unit 200 is used, that is, when the front deceleration unit 100 is not connected, peaks of the primary resonance and the secondary resonance are observed at around 500 rpm and 250 rpm, respectively. On the other hand, when the reduction portions of the parallel shaft gear structure having a reduction ratio of 1/5 are combined (No. 2), all of these peaks almost disappear, and instead, a new resonance occurs around 1300 rpm. I have. It can be understood that the rotation speed is about five times the secondary resonance frequency (250 rpm).
[0070]
On the other hand, when the pre-stage reduction unit 100 having a reduction ratio of 1/6 is combined (No. 1), the peaks of the original primary resonance and the secondary resonance also disappear, and a new resonance occurs instead at around 1500 rpm. are doing. It can be understood that the rotation speed is about six times the secondary resonance frequency (250 rpm).
[0071]
From these results, in the case of the conventional apparatus having the preceding stage reduction portion of the parallel shaft gear structure, when the practical rotation speed was up to about 1000 rpm, the peak certainly did not almost occur, and the effect of eliminating the resonance was obtained. It is recognized that there was. However, as described above, it can be confirmed from this test result that a new resonance is certainly generated when the practical rotation speed is increased to a region exceeding 1500 rpm.
[0072]
Tests were performed on the front reduction section of many types of internally meshing planetary gear structures, and various other types of front reduction sections. As a result, the configuration of the front reduction section mainly depends on the amplitude of vibration (resonance). Alternatively, it was confirmed that, although the width of the tail was affected, the qualitative tendency of the graph regarding the resonance frequency was not significantly affected. More specifically, in most tests, the new resonance is an integer multiple of the denominator of the deceleration ratio with respect to the resonance frequency generated when only the rear deceleration unit is used, regardless of the specific structure of the front deceleration unit. (5 times if the reduction ratio of the preceding reduction unit is 1/5).
[0073]
The description returns to the specific operation of this embodiment.
[0074]
In the present embodiment, the following advantages are obtained because the front reduction section 100 having the internal meshing planetary gear structure is adopted as the additional front reduction section PG.
[0075]
In other words, in the first-stage reduction unit 100, a predetermined reduction ratio (in this embodiment, 1/6) can be obtained, so that the reduction ratio of the second-stage reduction unit 200 is the easiest reduction ratio even if the required total reduction ratio increases. The area of 1/50 or less, particularly the area of 1/40 or less, can be easily selected. At the same time, the rotational speed at which a new resonance occurs (because the reduction ratio of the pre-stage reduction unit can be easily set to 1/6 or more) is shifted to a higher region than the practical rotational speed region of the increased servomotor. Thus, even when a high-speed servomotor is used, it is possible to prevent new resonance from occurring.
[0076]
On the other hand, even if the reduction ratio of the pre-stage reduction unit 100 is increased, it is preferable to suppress the reduction ratio to 1/20 or less. Thus, even if the required reduction ratio is relatively low, it is possible to easily select a region of 1/25 or more, particularly a region of 1/30 or more, which is the region of the reduction ratio in which the reduction ratio of the rear-stage reduction unit 200 is most easily created. . In addition, the reduction ratio of the former-stage reduction ratio of 1/20 or less can be manufactured by the design in which the difference in the number of teeth between the external gear and the internal gear is 1, but as in the above embodiment, for example, By setting the number difference to be 2 or more, it is possible to perform advantageous production in terms of securing transmission capacity and easiness of processing and assembling precision parts with small backlash.
[0077]
Further, in this embodiment, since both the first-stage reduction unit 100 and the second-stage reduction unit 200 have an internally meshing planetary gear structure, the engagement ratio is high (compared to the reduction unit of the parallel shaft gear structure), Low wear. Therefore, good backlash characteristics, that is, high positioning accuracy can be obtained over a long period of time.
[0078]
Further, in the present embodiment, the front deceleration unit 100 and the rear deceleration unit 200, and the front deceleration unit 100 and the motor M are housed separately in independent casings. Only the pre-stage deceleration section 100 between the steps can be changed. Of course, it is also possible to replace the motor M and the pre-stage reduction unit 100 individually. For this reason, only one type of rear-stage reduction unit, which is likely to be expensive due to its high accuracy, is designed with only one type, and a general-purpose internal-meshed planetary gear structure reduction device, which already has a wide variety of types, is prepared as the front-stage reduction unit. Is installed between the motor and the rear reduction unit, a reduction gear with a small backlash having various reduction ratios can be easily obtained, and the degree of freedom in design can be increased.
[0079]
In particular, in the present embodiment, the position (position of the bolt 55) P1 of the connection hole of the front casing 102 and the rear casing 202 is the position of the mounting hole of the member to be mounted of the industrial robot (the mounting hole position of the first arm 12). ) P2, the connection of the front casing 102 and the rear casing 202 and the attachment of the front casing 102 and the rear casing 202 to the member to be attached (attachment to the first arm 12) are simultaneously performed by the same bolt 55. Since the configuration is performed, the exchange itself is easy.
[0080]
The pre-stage reduction unit 100 in the present embodiment has a reduction ratio adjusting function of “performing pre-deceleration” and a resonance avoidance function of “changing the degree of movement of the resonance point by selecting the reduction ratio”. The easiness of the exchange is a great merit in any of the aspects.
[0081]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, resonance avoidance can be implement | achieved at low cost, and the joint drive device of the industrial robot with a higher degree of freedom of design can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a main part of a speed reducer of a joint drive device for an industrial robot according to an embodiment of the present invention.
FIG. 2 is a sectional view taken along the line II-II in FIG.
FIG. 3 is a sectional view taken along the line III-III in FIG. 1;
FIG. 4 is a cross-sectional view showing the overall configuration of the joint driving device for the industrial robot.
FIG. 5 is a schematic configuration diagram of a test apparatus used for confirming a resonance mechanism of the industrial robot.
FIG. 6 is a characteristic diagram of acceleration-motor rotation speed, showing a test result performed by the above test apparatus.
FIG. 7 is a characteristic diagram of displacement-motor rotation speed.
[Explanation of symbols]
10 ... Industrial robot
12 ... 1st arm
14 ... second arm
100: front deceleration section
102: Front casing
106 ... 1st side cover
108 ... second side cover
110 ... input shaft
124 ... eccentric body
130, 132 ... external gear
140 ... internal gear
160 ... inner pin
170: Output shaft at the previous stage
200: Rear-stage reduction unit
202: Rear casing
210: input shaft at the rear
230, 232 ... external gear
240 ... internal gear
260 ... eccentric inner pin
262, 264: First and second output flanges

Claims (8)

In the joint drive of industrial robots,
Motor and
A front reduction unit having an internal meshing planetary gear structure having an external gear and an internal gear having a small difference in the number of teeth, and the external reduction gear having an external gear and an internal gear having a small difference in the number of teeth; And a reduction mechanism portion having a two-stage reduction portion of an internally meshing planetary gear structure that further reduces the speed in response to the output of the output portion, and wherein the front reduction portion and the rear reduction portion are independent of each other. A joint driving device for an industrial robot, wherein the joint driving device is accommodated in a front casing and a rear casing, and the front casing and the rear casing are separable from each other. In claim 1, further,
The joint drive device for an industrial robot, wherein the motor is also housed in an independent motor casing, and the front casing housing the front speed reduction unit and the motor casing housing the motor are also separable. In claim 1 or 2,
The position of the connection hole between the front casing and the rear casing matches the position of the mounting hole of the member to be mounted of the industrial robot, and the connection between the front casing and the rear casing, and the connection between the front casing and the rear casing. A joint drive device for an industrial robot, wherein the casing is attached to the attachment member by the same attachment member. In any one of claims 1 to 3,
A joint driving device for an industrial robot, wherein accessories such as an encoder can be accommodated in a space formed by making the outer periphery of the first casing smaller than the outer periphery of the second casing. In any one of claims 1 to 4,
The speed reduction ratio of the preceding speed reduction unit is 1/20 or less;
The reduction ratio of the latter reduction unit is 1/25 or more, and
A joint drive device for an industrial robot, wherein a total reduction ratio achieved by the first-stage reduction unit and the second-stage reduction unit is set in a range of 1/150 or more and 1/500 or less. In claim 5,
3. The joint drive device for an industrial robot according to claim 1, wherein a difference in the number of teeth between the external gear and the internal gear of the front reduction unit is set to two or more. In any one of claims 1 to 6,
A joint drive device for an industrial robot, wherein the backlash of the rear speed reducer is set to be smaller than the value of the corresponding speed reduction ratio than the backlash of the front speed reducer. In claim 7,
The backlash of the rear deceleration unit is set to a value equal to or less than 1/10 of the backlash of the front deceleration unit.

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