JP2014161952A - Eccentric oscillation type reduction gear for driving joint of robot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an eccentric oscillation type reduction gear for driving a joint of a robot capable of more effectively relaxing the problem of exothermic heat while suppressing deterioration of operating accuracy of the robot.SOLUTION: An eccentric oscillation type reduction gear G4 for driving a joint of a robot includes an internal gear 22 and an external gear 20 that has a slight difference in the number of teeth from the internal gear and is to be oscillatingly internally engaged with the internal gear. In the reduction gear G4, a rotational speed of a first carrier (output shaft) 34 is 50 rpm or more, an operation rate is 20% ED or more, and lost motion is in a range of greater than 1 min and not more than 3 min.

Description

  The present invention relates to an eccentric oscillating speed reducer for joint drive of a robot.

  Patent Document 1 discloses an eccentric rocking type speed reducer used for driving a joint of a robot. This reduction device includes an internal gear and an external gear that has a slight difference in the number of teeth (for example, about 1 to 5) from the internal gear and that meshes with the internal gear while swinging. . The rotation of one of the internal gear and the external gear is restricted, and the relative rotation between the internal gear and the external gear is taken out as an output from the other side, and the joint of the robot is driven.

  The eccentric oscillating type speed reducer includes a type in which an eccentric body for oscillating the external gear is provided in an eccentric body shaft that penetrates the axial position of the external gear, and the eccentric body is connected to the shaft of the external gear. A type provided with a plurality of eccentric body shafts provided at positions offset from the center position is known.

  Eccentric oscillation type reduction gears are widely used for driving joints of robots that require compactness because a high reduction ratio can be obtained in one stage.

JP 2006-263878 A

  In order to increase the productivity of the robot, it is necessary to further increase the work speed (rotation speed of the output shaft) of the robot and to further increase the work time (operation rate). On the other hand, in order to perform a positioning operation with higher accuracy, it is necessary to set the backlash and lost motion of the reduction gear smaller.

  All of these tendencies are more severe in terms of heat generation for the speed reducer, and in recent years, countermeasures against the heat generated by the speed reducer that drives the joint of the robot have become a major problem.

  The present invention was made to alleviate such problems related to heat generation in an eccentric oscillating speed reducer for joint drive of a robot, and while suppressing a reduction in work accuracy of the speed reducer, An object of the present invention is to provide an eccentric oscillating type speed reducer for joint drive of a robot that can more effectively alleviate the problem of heat generation.

  The present invention includes an internal gear and an external gear that has a slight difference in the number of teeth from the internal gear and swings in the internal gear and meshes with the internal gear, and drives a robot joint. An eccentric oscillating type speed reducer for driving a joint, wherein the speed reducer has an output shaft rotation speed of 50 rpm or more, an operation rate of 20% ED or more, a lost motion larger than 1 min, 3 min. The above object is solved by adopting a configuration within the following range.

  The inventors conducted a detailed test on the relationship between the heat generation state and various conditions of the speed reducer for the eccentric rocking type speed reducer for driving the joint of the robot.

  As a result, as described later in detail, in order to maintain the working accuracy (robot positioning accuracy), with regard to the lost motion that has been conventionally reduced to a small value, the reduction of the lost motion and the increase in heat generation are as follows: Depending on the conditions, there is not always a simple “trade-off” relationship (only a simple relationship such that heat generation increases when lost motion decreases and heat generation decreases when lost motion increases) is always established. Not that).

  The present invention has been made on the basis of this finding, and proposes a configuration that can more effectively alleviate the problem of heat generation while suppressing a decrease in the work accuracy of the robot.

  ADVANTAGE OF THE INVENTION According to this invention, the eccentric rocking | fluctuation type reduction gear for the joint drive of the robot which can reduce the problem of heat_generation | fever more effectively can be obtained, suppressing the fall of the working precision of a robot.

Sectional drawing of the wrist part of the industrial robot incorporating the eccentric rocking | swiveling type reduction gear which concerns on embodiment of this invention FIG. 1 is an overall view of an eccentric oscillating speed reducer incorporated in the wrist portion of FIG. The schematic diagram which shows the general outline of the industrial robot provided with the wrist part of FIG. Graph showing an example of the test result of lost motion-no-load torque Graph showing another example of test result of lost motion-no-load torque Explanatory diagram for explaining lost motion

  Hereinafter, an example of an embodiment of the present invention will be described in detail based on the drawings.

  FIG. 1 is a cross-sectional view of a wrist portion of an industrial robot in which an eccentric oscillating speed reducer according to an example of the embodiment of the present invention is incorporated, and FIG. 2 is the eccentric portion incorporated in the wrist portion of FIG. FIG. 3 is a schematic diagram showing an overall outline of the industrial robot. FIG.

  First, the overall outline of the industrial robot R1 will be described.

  This industrial robot R1 has a base 10 on a floor surface 19, from which the first to sixth joints J1 to J6 and the first to sixth arms 11 to 16 are alternately connected. . The first to sixth arms 11 to 16 are driven by a drive motor and a speed reducer (not shown in FIG. 3) via the first to sixth joints J1 to J6.

  That is, the first arm 11 of the industrial robot R1 of the present embodiment can rotate around the vertical axis CL1 on the base 10 via the first joint J1, and the axis of the industrial robot R1 as a whole. It is responsible for turning around CL1. The second arm 12 can swing through the second joint J2 in a plane (in the vertical plane) including the axis CL1 of the first arm 11 with the second joint J2 as a fulcrum. It is responsible for the longitudinal movement of the arm 16 with respect to the workpiece. The third arm 13 can swing in a plane (in the vertical plane) including the axis CL2 of the second arm 12 with the third joint J3 as a fulcrum through the third joint J3. Responsible for vertical movement of the arm 16.

  On the other hand, the fourth arm 14 can rotate around the axis CL4 coaxial with the axis CL3 of the third arm 13 via the fourth joint J4. The fifth arm 15 can swing in a plane including the axis CL4 of the fourth arm 14 with the fifth joint J5 as a fulcrum through the fifth joint J5. The sixth arm 16 can rotate around the axis CL6 coaxial with the axis CL5 of the fifth arm 15 via the sixth joint J6.

  Various tools 18 such as a welding tool, a holding tool, and a painting tool for performing a predetermined work are attached to the tip of the sixth arm 16. From the above configuration, the sixth arm 16 to which the tool 18 is attached has six degrees of freedom, and moves and moves freely in the three-dimensional direction while contacting and attracting the work piece at an arbitrary position and posture. Or, such as spraying can be performed.

  Generally, the first to third arms 11 to 13 are referred to as basic three axes, and the fourth to sixth arms 14 to 16 are referred to as wrist three axes. The first to third arms 11 to 13 constituting the basic three axes mainly perform spatial positioning of the fourth to sixth arms 14 to 16 constituting the wrist three axes, and constitute the wrist three axes. More specifically, the fourth to sixth arms 14 to 16 determine the position and angle of the sixth arm 16 with respect to the work piece.

  The basic three axes (first to third arms 11 to 13) require a larger driving torque than the wrist three axes (fourth to sixth arms 14 to 16). Therefore, in general, the speed reducer incorporated in the first to third joints J1 to J3 of the basic three axes (first to third arms 11 to 13) is the wrist three axes (fourth to sixth arms 14 to 16). ) Is larger than the speed reducer incorporated in the fourth to sixth joints J4 to J6. Further, since the basic three axes move more slowly, the rotation speed of the output shaft of the speed reducer is slower than the wrist three axes. In addition, since the basic three axes often move once and stop, for example, the operating rate of the reducer is not so high, but the wrist three axes often move more frequently than the basic three axes. Therefore, the operating rate of the reducer is high.

  Here, the operating rate of the speed reducer is calculated for each speed reducer of each joint. Specifically, it is the ratio of the operating time TJ of the reduction gear to be calculated for the operating rate to the operating time TR of the robot itself, and (operating rate) = (TJ / TR) × 100 (% ED) Calculated. The operation time TR of the robot itself can be defined as the time when the power of the robot is turned on or the time when the power of the drive source (servo motor) that drives each joint is turned on. Therefore, the waiting time for waiting for the robot to work on a certain workpiece and setting the next workpiece is also included in the operation time TR of the robot itself. The operating time TJ of the speed reducer is the time during which the speed reducer for which the operating rate is to be calculated is driven, or the drive source (servo motor) that drives the speed reducer is rotating (the rotation is controlled). ) Can be defined as time. The higher the operating rate, the shorter the heat radiation time compared to the heat generation time, and therefore the speed reducer tends to be in a thermally severe situation.

  FIG. 1 is a cross-sectional view of the wrist (3-axis) portion of the industrial robot R1 of FIG. 3, and FIG. 2 is an eccentric oscillating type speed reducer incorporated in the wrist portion (according to an example of this embodiment). FIG.

  As described above with reference to FIG. 1, the fourth to sixth arms 14 to 16 constituting the wrist are connected via the fourth to sixth joints J4 to J6. In the present embodiment, the wrist has three joints. However, the present invention is not limited to this, and the wrist may be composed of four or more or two or less joints. These fourth to sixth joints J4 to J6 are equipped with reduction gears G4 to G6, respectively. The fourth joint J4 is provided with a reduction gear G4, the fifth joint J5 is provided with a reduction gear G5 (only the appearance is shown), and the sixth joint J6 is provided with a reduction gear G6.

  The other speed reducers G5 and G6 of the wrist and the speed reducers G1 to G3 of the first to third joints J1 to J3 not shown in FIG. 1 have basically the same configuration although the details are different. . Therefore, the reduction gear G4 will be described as a representative example, and the other reduction gears G1 to G3, G5, and G6 are given the same reference numerals for substantially the same or functionally similar main members, A duplicate description is omitted.

  A drive shaft 21 connected to a motor shaft (not shown) is disposed in the fourth arm 14, and an input ring 21A welded to the drive shaft 21 is connected to the reduction gear G4 via a spline 17A. It is connected to the input shaft 17.

  With reference to FIG. 2, the speed reducer G4 is a speed reducer called an eccentric swing type. The input shaft 17 of the reduction gear G4 is disposed coaxially with the axis of the internal gear 22 (= the axes CL3 and CL4 of the third and fourth arms 13 and 14). Three eccentric bodies 26 are integrally formed on the input shaft 17. Three external gears 20 are incorporated in the outer periphery of the eccentric body 26 via rollers 28, respectively. The eccentric phase difference of the three external gears 20 is 12 degrees. Each external gear 20 is in mesh with the internal gear 22. The internal gear 22 is integrated with the casing 24. The number of teeth of the external gear 20 is slightly smaller than the number of teeth of the internal gear 22 (a slight difference in the number of teeth). In this example, the difference in the number of teeth is set to 1.

  The casing 24 of the speed reducer G4 is connected to the fourth arm 14 through a joint cover 23 and a bolt 25. In this embodiment, the internal gear 22 is an internal gear main body 22A integrated with the casing 24, and a circle that is rotatably incorporated in the internal gear main body 22A and constitutes internal teeth of the internal gear 22. It consists of a columnar outer pin 22B. In this embodiment, the pitch circle diameter (PCD) d1 of the inner teeth (outer pins 22B), more specifically, the diameter d1 of the circle connecting the centers (axis centers) of the outer pins 22B It is called the inner diameter.

  A pin-shaped member 32 and an inner roller 33 as a sliding acceleration member pass through each external gear 20. A pair of first and second carriers 34 and 36 are rotatably supported on the casing 24 via bearings 38 and 40 on both axial sides of the external gear 20. The pin-shaped member 32 is integrated with the first carrier 34, and the first and second carriers 34, 36 are connected via the pin-shaped member 32 and the bolt 42. The fifth arm 15 is connected to the first carrier 34 via a bolt 44 (see FIG. 1).

  The operation of the power transmission system of the reduction gear G4 will be briefly described.

  When the input shaft 17 rotates, the three eccentric bodies 26 integrated with the input shaft 17 rotate, and the three external gears 20 swing through the rollers 28. As a result, a phenomenon occurs in which the meshing position of the external gear 20 with respect to the internal gear 22 is sequentially shifted. Since the number of teeth of the external gear 20 is one less than the number of teeth of the internal gear 22, the external gear 20 is one tooth apart from the internal gear 22 every time the input shaft 17 rotates once. The phases in the circumferential direction are shifted and rotate relative to the internal gear 22 (rotate). The rotation component is transmitted to the first and second carriers 34 and 36 via the pin-shaped member 32 and the inner roller 33, and the fifth arm 15 connected to the first carrier 34 via the bolt 44 includes: It rotates relative to the casing 24 (fourth arm 14).

  As described above, the eccentric oscillating speed reducer G4 has a structure in which power is transmitted while the external gear 20 oscillates every rotation of the input shaft 17, so that a pair of ordinary gears mesh with each other. In comparison, heat is easily generated. In particular, heat is likely to be generated in the vicinity of the roller 28 between the eccentric body 26 and the external gear 20, the sliding portion between the external gear 20, the pin-shaped member 32, and the inner roller 33. For example, the smaller the backlash in the meshing of the internal gear 22 and the external gear 20, the more likely it is to occur. If the heat increase of the reduction gear G4 is excessive, it is difficult to form an oil film on the tooth surface, the sliding surface, and the rolling surface, and the durability is remarkably reduced.

  FIG. 4 and FIG. 5 show the results of tests conducted by the inventors on the relationship between lost motion and no-load running torque. FIG. 4 shows a test result regarding a reduction gear having an inner diameter d1 of the internal gear 22 of 95 mm or more and 250 mm or less, and FIG. 5 shows a test result of a reduction gear having an inner diameter d1 of the internal gear 22 of 50 mm or more and less than 95 mm. 4 and 5, the horizontal axis represents lost motion and the vertical axis represents no-load running torque.

  First, lost motion and no-load running torque will be described. Measure the load and the displacement (twist angle) of the low-speed shaft by fixing the high-speed shaft (input shaft 17) to the rated torque from the low-speed shaft (first carrier 34) side until the load is slowly applied and unloaded, If the relationship is shown, the hysteresis curve of rigidity as shown in FIG. 6 is obtained. The torsion angle at the ± 3% point of the rated torque is called lost motion.

  On the other hand, the no-load running torque refers to the torque on the input shaft side necessary for rotating the reduction gear G4 in an unloaded state. Specifically, the casing 24 is fixed, the first carrier 34 is free, the input shaft 17 is rotated by a motor or the like, and the torque of the input shaft 17 at this time is measured. Since the no-load running torque is a torque generated by friction in the speed reducer G4, it can be regarded as a concept corresponding to the “heat generation amount” of the speed reducer G4.

  In a specific test, a large number of reduction gears are prepared, and the external gears 20 incorporated in the reduction gears have different tooth surface outer diameters by several μm. Then, the lost motion and no-load running torque are measured and plotted for each reduction gear as shown in FIGS. In this test, a reduction gear having a reduction ratio of 41 was used. In addition, instead of using a large number of reduction gears, a single reduction gear and a large number of external gears 20 having different tooth surface outer diameters are prepared, and the external gears are sequentially replaced for testing. Good.

  As shown in FIG. 4, when the internal gear 22 has a reduction gear with an inner diameter d1 of 95 mm or more and 250 mm or less, in a region where the lost motion is 1 min or less, the no-load running torque increases as the lost motion decreases. Correlation is seen. On the other hand, in the region where the lost motion is greater than 1 min, the no-load running torque is within a substantially constant range regardless of the magnitude of the lost motion. That is, there is no correlation between the magnitude of the lost motion and the no-load running torque. From the above, in the region where the lost motion is 1 min or less, the calorific value increases as the lost motion becomes smaller. However, in the region where the lost motion is greater than 1 min, the calorific value is almost equal regardless of the magnitude of the lost motion. It is constant. Moreover, in the area | region more than 1.2 minutes of lost motion, the width | variety in which a no-load running torque is settled becomes narrower, and it is seen that dispersion | variation decreases.

  As shown in FIG. 5, in the case of a reduction gear having an internal gear 22 with an inner diameter d1 of 50 mm or more and less than 95 mm, the no-load running torque increases as the lost motion decreases in the region where the lost motion is 1.5 min or less. Correlation is seen. On the other hand, in the region where the lost motion is greater than 1.5 min, the no-load running torque is within a substantially constant range regardless of the magnitude of the lost motion. That is, there is no correlation between the magnitude of the lost motion and the no-load running torque. From the above, in the region where the lost motion is 1.5 min or less, the calorific value increases as the lost motion decreases, but in the region where the lost motion is greater than 1.5 min, regardless of the magnitude of the lost motion. The calorific value is almost constant. Moreover, in the area | region more than 1.7 minutes of lost motion, the width | variety in which a no-load running torque is settled becomes narrower, and it is seen that dispersion | variation decreases.

  Usually, in the reduction gear used for the wrist three axes, the inner gear 22 has an inner diameter of about 50 mm to 250 mm, and the inner gear has a smaller inner diameter than the reduction gear used for the basic three axes. Therefore, the amount of lubricant enclosed in the speed reducer is small, and the heat radiation surface area is small, so that the temperature is likely to rise. However, in the conventional robot, even if the rotation speed of the output shaft is fast, it is not so fast as about 30 to 40 rpm, and the operation rate of each reduction gear is low enough to be less than 15% ED. Therefore, heat generation does not become a big problem, and it was common sense to place importance on controllability and to set the lost motion small (1 min or less).

  However, in recent years, there has been a demand for an increase in the working speed (rotation speed of the output shaft) of the industrial robot and an improvement in the operating rate. Specifically, there is a request of 50 rpm or more at the rotational speed of the output shaft. In many cases, the request is about 60 to 120 rpm, but there is a request up to about 200 rpm. In addition, there is a demand for an operating rate of 20% ED or more and a maximum of about 60% ED. The inventors have conceived that heat generation of the reduction gear becomes a big problem when responding to such a request, and pay attention to the relationship between the lost motion and the no-load running torque, as shown in FIG. 4 and FIG. Test results were obtained.

  And even if the rotation speed of the output shaft is high (50 rpm or more) and the operation rate is high (20% ED or more), in the reduction gear with the inner diameter d1 of the internal gear 22 of 95 mm or more and 250 mm or less, the lost motion It was found that heat generation can be suppressed by setting the value to be greater than 1 min, and more preferably 1.2 min or more. Further, according to the verification by the inventors, if the lost motion is set to 3 min or less, there is no major problem in positioning accuracy.

  Further, even when the output shaft has a high rotation speed (50 rpm or more) and a high operating rate (20% ED or more), the lost gear has a lost motion of 1 in the reduction gear whose inner diameter d1 of the internal gear 22 is less than 95 mm. It has been found that heat generation can be suppressed by setting it to more than 0.5 min, and more preferably 1.7 min or more. In this case as well, if the lost motion is set to 3 min or less, there is no major problem in positioning accuracy.

  As described above, according to the present invention, the lost motion, which has conventionally been set to be as small as possible (less than 1 min), is intentionally set large (greater than 1 min) (that is, the design in the opposite direction to the prior art). Thus, even if the rotation speed of the output shaft is fast and the operation rate is high, heat generation is suppressed while ensuring the necessary positioning accuracy.

  In the above embodiment, an eccentric oscillating type speed reducer of the type provided with an eccentric body shaft that penetrates the axial center position of the external gear as an eccentric body for oscillating the external gear has been shown. As an eccentric oscillating type speed reducer, there is also known a type of speed reducer provided with a plurality of eccentric body shafts at positions offset from the axial center position of the external gear, and has a similar qualitative tendency. Has been confirmed to have. Therefore, the present invention can be applied to this type of eccentric oscillating speed reducer, and a corresponding effect can be obtained.

  In the present embodiment, the speed reducer used for the wrist axis joint of the industrial robot has been described as an example. The speed reducer used for the wrist axis joint is particularly suitable for the present invention because the influence on positioning accuracy when the lost motion is increased is smaller than that of the speed reducer used for the basic 3-axis joint. However, the present invention is also applicable to a reduction gear used for a basic three-axis joint.

R1 ... industrial robot G1-G6 ... first-sixth reduction gears J1-J6 ... first-sixth joints 11-16 ... first-sixth arms 17 ... input shaft (input side)
DESCRIPTION OF SYMBOLS 20 ... External gear 22 ... Internal gear 24 ... Casing 26 ... Eccentric body 32 ... Pin-shaped member 34 ... 1st carrier (output side)

Claims (5)

For joint drive of a robot that includes an internal gear and an external gear that has a slight difference in the number of teeth from the internal gear and that meshes internally with the internal gear while swinging. An eccentric oscillating speed reducer,
The speed reducer
The rotation speed of the output shaft is 50 rpm or more,
Occupancy rate is 20% ED or more,
An eccentric oscillating speed reducer for joint drive of a robot, characterized in that the lost motion is larger than 1 min and within 3 min. In claim 1,
The speed reducer is used for a wrist joint of a robot. An eccentric rocking type speed reducer for driving a joint of a robot. In claim 1 or 2,
The rotational speed of the output shaft is 200 rpm or less. An eccentric oscillating speed reducer for driving a joint of a robot. In any one of Claims 1-3,
An eccentric oscillating speed reducer for driving a joint of a robot, wherein a pitch circle diameter of internal teeth of the internal gear is 95 mm or more. In any one of Claims 1-3,
An eccentric oscillating speed reducer for joint drive of a robot, wherein a pitch circle diameter of internal teeth of the internal gear is less than 95 mm, and a lost motion is greater than 1.5 min and 3 min or less.

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