Robot

Abstract

The object of the present invention is to provide a manipulator capable of reducing the influence of reverse drive. The manipulator (100) has a joint (40) assembled with a motor (38) and a reducer (6), and the manipulator has: an acquisition mechanism for acquiring information related to the rotation of the motor (38); and a control mechanism for detecting the application of external force based on the information acquired by the acquisition mechanism and performing a retreat action. The reducer (6) has a parallel shaft gear mechanism (8) and an eccentric swing type gear mechanism (10), and the output rotation of the parallel shaft gear mechanism (8) is input to the eccentric swing type gear mechanism (10). The eccentric swing type gear mechanism (10) is a center crank type in which the eccentric body shaft (12) is arranged on the axis of the internal gear (16), and its reduction ratio is less than 35.

Description

[0001] This application claims priority based on Japanese Patent Application No. 2019-151531 filed on August 21, 2019. The entire contents of the Japanese patent application are incorporated herein by reference. Technical Field

[0002] The invention relates to a manipulator. Background Art

[0003] A robot with multiple joints is known. Patent document 1 describes a robot that performs a retreat action based on an external force. The robot described in patent document 1 detects an external force acting on the robot, and when the detected external force is greater than a first threshold, the robot performs a retreat action, and when the change in the detected external force after the retreat action is less than a second threshold, the retreat action is stopped.

[0004] Patent Document 1: Japanese Patent No. 6034895

[0005] When an external force sensor is provided on the output side of the speed reducer as in Patent Document 1, the external force sensor is expensive, which is disadvantageous in terms of cost. Summary of the invention

[0006] The present invention has been made in view of such a problem, and an object of the present invention is to provide a robot that can cope with external force without relying on an external force sensor on the output side of a speed reducer.

[0007] In order to solve the above-mentioned problems, a manipulator according to one embodiment of the present invention has a joint assembled with a motor and a reducer, and the manipulator has: an acquisition mechanism for acquiring information related to the rotation of the motor; and a control mechanism for detecting the situation where an external force is applied and performing a retreat action based on the information acquired by the acquisition mechanism. The reducer has a parallel shaft gear mechanism and an eccentric swing type gear mechanism, and the output rotation of the parallel shaft gear mechanism is input to the eccentric swing type gear mechanism. The eccentric swing type gear mechanism is a center crank type in which the eccentric body shaft is arranged on the axis of the internal gear, and its reduction ratio is 35 or less.

[0008] In addition, any combination of the above-mentioned constituent elements or any mode in which constituent elements or expressions of the present invention are replaced with each other in methods, systems, etc. may also be practiced as additional modes of the present invention.

[0009] According to the present invention, it is possible to provide a robot that can cope with external force without relying on an external force sensor on the output side of a speed reducer. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a side view schematically showing the robot hand involved in the embodiment.

[0011] Figure 2 Yes means Figure 1 Side sectional view of the reducer of the robot.

[0012] Figure 3 It roughly indicates Figure 1 Block diagram of the robot.

[0013] Figure 4 This is a graph showing the relationship between the reduction ratio and efficiency of an eccentric oscillating gear mechanism.

[0014] In the figure: 6-reducer, 8-parallel shaft gear mechanism, 10-eccentric swing gear mechanism, 12-eccentric body shaft, 14-external gear, 14a-external teeth, 16-internal gear, 16a-internal teeth, 38-motor, 40-joint, 42-arm, 52-acquisition unit, 54-control unit, 54c-external force detection unit, 100-manipulator. DETAILED DESCRIPTION

[0015] The present inventors have studied a robot having a joint in which a motor and a speed reducer are incorporated, and have obtained the following findings.

[0016] In the joint of the manipulator, if the rotational driving force of the motor is input to the input shaft of the reducer, the output component of the reducer rotates at a reduced speed at a specified reduction ratio, so that the arm connected to the output component rotates around the axis of the joint. If an external force is applied from the arm to the joint through direct teaching, the reducer of the joint is driven in reverse. If it is driven in reverse, the reverse drive torque is transmitted from the output side of the reducer to the input side. This reverse drive torque applies excessive stress (load) to the internal mechanism of the reducer, sometimes damaging its internal mechanism. The research results found that if the transmission efficiency of the reducer is high, the stress (load) applied to the internal mechanism of the reducer is small, and reverse drive is not easy to cause damage.

[0017] As a result of studying reducers of various structures from the perspective of improving transmission efficiency, it was found that the transmission efficiency can be particularly improved by sequentially arranging a parallel shaft gear mechanism and a center crank type eccentric oscillating gear mechanism (hereinafter sometimes referred to as a "oscillating gear mechanism") and appropriately selecting the reduction ratio of the eccentric oscillating gear mechanism. Figure 4 Graph g1 shows the relationship between the reduction ratio Rg (the speed ratio obtained by dividing the input speed by the output speed) and the transmission efficiency Eg of the swing type gear mechanism. From the data, it can be seen that when the reduction ratio Rg is 35 or less, the transmission efficiency is high, and when the reduction ratio Rg exceeds 35, the transmission efficiency will drop significantly. In addition, it is also found that the transmission efficiency is further improved when the reduction ratio Rg is 17 or less. In addition, in this reducer, the reduction ratio of the parallel shaft gear mechanism has little effect on the transmission efficiency. Here, the transmission efficiency refers to the ratio of the output torque to the input torque, which is obtained by (output torque) ÷ (input torque × reduction ratio) × 100%.

[0018] Moreover, in this manipulator, from the viewpoint of preventing damage caused by reverse drive, a structure for causing the motor to perform a retreat action according to an external force has been studied. For example, it is conceivable to set a torque sensor on the output side of the reducer, and cause the motor to perform a retreat action according to its detection result. However, in this structure, there is a possibility that the torque sensor may be damaged by external force, and an additional space is required for setting the torque sensor and its wiring, which is disadvantageous in terms of cost. Therefore, a structure for identifying the state of external force based on information related to the rotation of the motor, such as the motor current, without using a torque sensor has been studied. As a result, it was found that the retreat action can be performed without using the above-mentioned torque sensor.

[0019] In summary, it can be considered that by combining a parallel shaft gear mechanism and a center crank type eccentric swing type gear mechanism, and using a reducer with a reduction ratio Rg of 35 or less for the eccentric swing type gear mechanism, and making the motor perform a retreat action based on information related to the rotation of the motor, a manipulator capable of coping with external force (reverse drive) at low cost can be provided. Hereinafter, a manipulator based on these insights will be described according to an embodiment.

[0020] Hereinafter, the preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the embodiments and the modified examples, the same or equivalent components and parts are marked with the same symbols, and repeated descriptions are appropriately omitted. In addition, in each of the drawings, the size of the components is appropriately enlarged or reduced for ease of understanding. In addition, in each of the drawings, a part of the components that are not important for the description of the embodiments is omitted.

[0021] Furthermore, terms including numbers 1, 2, etc. are used to describe various constituent elements. Such terms are only used to distinguish one constituent element from other constituent elements, and the constituent elements are not limited by such terms.

[0022] [Implementation Method]

[0023] Hereinafter, the structure of the robot 100 according to the embodiment will be described with reference to the drawings. Figure 1 1 is a side view schematically showing the manipulator 100 involved in the present embodiment. The manipulator 100 is a multi-joint manipulator having a plurality of arms connected together via a plurality of joints from the front end side to the base end side. The manipulator 100 of the present embodiment has a joint 40 and an arm 42. In addition, the manipulator 100 has an acquisition unit 52 for acquiring information related to the rotation of the motor in order to perform an evacuation action according to an external force, and a control unit 54 for detecting the application of an external force based on the information and performing an evacuation action. First, the joint 40 and the arm 42 are described, and the acquisition unit 52 and the control unit 54 will be described later.

[0024] The joint 40 includes the first joint 40a, the second joint 40b, the third joint 40c, the fourth joint 40d, the fifth joint 40e and the sixth joint 40f in order from the front end side. The arm 42 includes the first arm 42a, the second arm 42b, the third arm 42c, the fourth arm 42d, the fifth arm 42e and the sixth arm 42f. The first arm 42a is connected to the front end side (output side) of the first joint 40a. The second arm 42b to the sixth arm 42f are connected between the first joint 40a to the sixth joint 40f. The base end side of the sixth joint 40f is connected to the base 42g, and the base 42g is fixedly connected to the setting surface Gf.

[0025] The motor 38 and the reducer 6 are assembled in the joint 40. If the rotational driving force is input from the motor 38 to the reducer 6, the output component of the reducer 6 performs a reduced rotation so that the arm 42 rotates around the axis of the joint 40. In the manipulator 100, the rotation of each motor 38 is controlled in such a manner that the tool 42h installed on the output side of the first arm 42a moves along a prescribed trajectory. In the case of having a plurality of joints 40 as in the manipulator 100 of the present embodiment, it is not necessary to assemble the object of the present invention (i.e., the reducer) to all the joints, and it is sufficient to assemble the object of the present invention (i.e., the reducer) to at least one joint. In particular, it is preferred to assemble the object of the present invention (i.e., the reducer) in the joint on the front end side.

[0026] The motor 38 may be any motor based on various principles as long as it can input a rotational driving force to the speed reducer 6. The motor 38 of this embodiment is a servo motor. In this case, it has the advantages of being small and having a large output, having a long life, and requiring almost no maintenance.

[0027] Next, the speed reducer 6 will be described. Figure 2 1 is a side sectional view showing the reducer 6. The reducer 6 has a parallel shaft gear mechanism 8 and an eccentric oscillating gear mechanism 10, and the output rotation of the parallel shaft gear mechanism 8 is input to the eccentric oscillating gear mechanism 10. The eccentric oscillating gear mechanism 10 is a center crank type gear mechanism in which an eccentric body shaft 12 described later is arranged on the axis of an internal gear. In the present embodiment, the parallel shaft gear mechanism 8 and the eccentric oscillating gear mechanism 10 are accommodated in a housing 20 described later.

[0028] Hereinafter, the direction along the central axis La of the internal gear 16 (described later) of the eccentric oscillating gear mechanism 10 is referred to as the "axial direction", and the circumferential direction and the radial direction of a circle centered on the central axis La are referred to as the "circumferential direction" and the "radial direction", respectively. Also, hereinafter, for the sake of convenience, one side in the axial direction (the right side in the figure) is referred to as the input side, and the other side (the left side in the figure) is referred to as the opposite input side.

[0029] The parallel axis gear mechanism 8 has a driving shaft 8a, a driving gear 8b and a driven gear 8c. In this example, the driving shaft 8a is the output shaft of the motor 38. The driving shaft 8a extends parallel to the center axis La at a position deviated from the center axis La. The driving shaft 8a enters the housing 20 from the motor mounting hole 20h provided on the input side side portion 20c of the housing 20 toward the opposite side of the input together with the motor 38. The driving gear 8b is fixed to the outer periphery of the driving shaft 8a. The driven gear 8c is fixed to the outer periphery of the eccentric body shaft 12 extending parallel to the driving shaft 8a, and meshes with the driving gear 8b. The driving gear 8b and the driven gear 8c can be spur gears or other types of gears such as helical gears.

[0030] The eccentric oscillating gear mechanism 10 is an eccentric oscillating gear device that causes an external gear meshing with an internal gear to oscillate so that one of the internal gear and the external gear rotates and the generated motion component is output from an output member to a driving member. In the eccentric oscillating gear mechanism 10 of this example, the rotation of the external gear is restricted so that the internal gear rotates, thereby outputting rotation from the internal gear.

[0031] The eccentric oscillating gear mechanism 10 of the present embodiment includes an eccentric body shaft 12, an external gear 14, an internal gear 16, a transmission member 18, a housing 20, a bearing support portion 22, an eccentric body shaft bearing 24, a center bearing 26, an eccentric bearing 28, an inner pin 30, a flange member 32, an output member 34 and a main bearing 36.

[0032] (shell)

[0033] The housing 20 has a cylindrical portion 20b surrounding the internal gear 16 and an input side side portion 20c provided on the side portion of the input side of the internal gear 16. The bearing support portion 22 is a portion extending from the central portion of the input side side portion 20c toward the opposite side of the input. In this example, the bearing support portion 22 and the input side side portion 20c are formed integrally from a single material. The bearing support portion 22 has a hollow cylindrical shape surrounding the central axis La. The flange member 32 is a hollow circular member, which is fixed to the opposite side end of the input of the cylindrical portion 20b of the housing 20 by bolts B4. The inner circumference of the flange member 32 extends radially inwardly further than the cylindrical portion 20b, and covers a portion of the opposite side of the input of the main bearing 36. The flange member 32 protrudes radially outward further than the cylindrical portion 20b. The flange member 32 is fixed to the frame (not shown) of the joint 40, etc.

[0034] The internal gear 16 meshes with the external gear 14. The output member 34 rotates synchronously with the internal gear 16. The housing 20 rotates synchronously with the external gear 14. The main bearing 36 is arranged between the output member 34 and the cylinder 20b. An eccentric shaft bearing 24 that supports the eccentric shaft 12 is arranged on the outer periphery of the bearing support portion 22.

[0035] (Eccentric body shaft)

[0036] The eccentric shaft 12 rotates about the rotation center line by the rotation power input from the driven gear 8c of the parallel shaft gear mechanism 8. The eccentric shaft 12 is supported by the bearing support portion 22 of the housing 20 via the eccentric shaft bearing 24 and is rotatably supported by the housing 20.

[0037] like Figure 2 As shown, the input side end of the eccentric body shaft 12 is located closer to the input side than the input opposite side end of the drive shaft 8a. That is, when viewed from the radial direction, the eccentric body shaft 12 partially overlaps with the drive shaft 8a. The parallel shaft gear mechanism 8 is included in the axial range of the eccentric swing type gear mechanism 10. And, when viewed from the axial direction, the drive shaft 8a overlaps with the external gear 14. And, the input opposite side end of the drive shaft 8a is opposite to the external gear 14 in the axial direction.

[0038] The eccentric swing type gear mechanism 10 is a center crank type eccentric swing type gear device in which the eccentric body shaft 12 is arranged on the central axis La of the internal gear 16. The eccentric body shaft 12 has a plurality of eccentric parts 12a for swinging the external gear 14. The axis of the eccentric part 12a is eccentric with respect to the rotation center line of the eccentric body shaft 12. In the present embodiment, two eccentric parts 12a are provided, and the eccentric phases of adjacent eccentric parts 12a are offset from each other by 180°.

[0039] (External gear)

[0040] The external gear 14 is provided individually corresponding to the plurality of eccentric portions 12a, and swings and rotates according to the rotation of the eccentric body shaft 12. The external gear 14 is rotatably supported by the corresponding eccentric portion 12a via the eccentric bearing 28. External teeth 14a are formed on the outer periphery of the external gear 14. The external gear 14 moves while meshing with the internal teeth of the internal gear 16, thereby swinging.

[0041] A plurality of inner pin holes 14h are provided at positions offset from the axis of the external gear 14. An inner pin 30 is inserted through each inner pin hole 14h. A clearance (i.e., gap) is provided between the inner pin 30 and the inner pin hole 14h to absorb the swing component of the external gear 14. The inner pin 30 is partially in contact with the inner wall surface of the inner pin hole 14h.

[0042] (Internal gear)

[0043] The internal gear 16 is a hollow cylindrical member having internal teeth 16a on its inner circumference that mesh with the external gear 14. In the present embodiment, the number of internal teeth 16a of the internal gear 16 is one more than the number of external teeth of the external gear 14. The internal gear 16 rotates relative to the external gear 14 in accordance with the swinging rotation of the external gear 14.

[0044] (Transfer parts)

[0045] The transmission member 18 is a hollow circular member disposed between the internal gear 16 and the output member 34. The transmission member 18 in this example is disposed on the side opposite to the input side of the external gear 14. The transmission member 18 transmits the power from the internal gear 16 to the output member 34. The transmission member 18 is fixed to the side opposite to the input side of the internal gear 16 by bolts B1. A central bearing 26 is provided between the inner peripheral surface of the transmission member 18 and the outer peripheral surface of the bearing support portion 22. The transmission member 18 is rotatably supported by the bearing support portion 22 via the central bearing 26.

[0046] The eccentric body shaft bearing 24 is arranged between the eccentric body shaft 12 and the bearing support portion 22 to support the eccentric body shaft 12. The eccentric bearing 28 is arranged between the eccentric portion 12a and the external gear 14 to transmit the eccentric motion to the external gear 14. The central bearing 26 is arranged between the transmission member 18 and the bearing support portion 22 to support the transmission member 18. The central bearing 26 is arranged adjacent to the side portion of the eccentric body shaft bearing 24 on the opposite side to the input.

[0047] The main bearing 36 is disposed between the output member 34 and the cylindrical portion 20b of the housing 20 to support the output member 34. In the present embodiment, the eccentric shaft bearing 24, the central bearing 26 and the eccentric bearing 28 are ball bearings having spherical rolling elements, and the main bearing 36 is a cross roller bearing using cylindrical rollers as rolling elements. These bearings may also be other types of bearings.

[0048] (Domestic Sales)

[0049] The inner pin 30 is a rod-shaped member that transmits power between the external gear 14 and the output member 34, and a plurality of inner pins 30 are provided at intervals in the circumferential direction. The inner pin 30 of this example is pressed into and fixed to the input side side portion 20c, and extends from the input side side portion 20c through the inner pin hole 14h of the external gear 14 toward the opposite side of the input. The inner pin 30 abuts against a portion of the inner pin hole 14h to restrict the rotation of the external gear 14, and only allows it to swing.

[0050] (Output component)

[0051] The output member 34 is a circular member, and the power from the internal gear 16 is transmitted to the output member 34 via the transmission member 18. The output member 34 rotates integrally with the internal gear 16 and the transmission member 18. The output member 34 is arranged on the side opposite to the input in the axial direction of the external gear 14, and is provided on the radial inner side of the main bearing 36. The output member 34 is fixed to the side opposite to the input of the transmission member 18 by a bolt B2. The output member 34 is rotatably supported by the cylinder portion 20b of the housing 20 via the main bearing 36. The driven member 46 is fixed to the side opposite to the input of the output member 34 by a bolt B5. The output member 34 outputs the rotational driving force to the driven member 46. The driven member 46 is connected to the arm 42 supported by the joint 40.

[0052] Next, the operation of the speed reducer 6 of the above structure is described. If the motor 38 rotates, the driving gear 8b, the driven gear 8c meshing therewith, and the eccentric body shaft 12 rotate integrally. If the eccentric body shaft 12 rotates, the eccentric portion 12a of the eccentric body shaft 12 rotates eccentrically. If the eccentric portion 12a rotates eccentrically, it causes the external gear 14 to swing via the eccentric bearing 28. At this time, the external gear 14 swings in a manner that its own axis rotates around the rotation center line of the eccentric body shaft 12.

[0053] If the external gear 14 oscillates, the meshing positions of the external gear 14 and the internal gear 16 gradually deviate. As a result, each time the eccentric body shaft 12 rotates once, one of the external gear 14 and the internal gear 16 rotates by an amount corresponding to the difference in the number of teeth between the external gear 14 and the internal gear 16. In the present embodiment, the internal gear 16 rotates, and the reduced rotation is output from the output member 34 via the transmission member 18. If the output member 34 rotates, the driven member 46 fixed to the output member 34 rotates. If the driven member 46 rotates, the arm 42 connected to the driven member 46 rotates.

[0054] Next, the acquisition unit 52 and the control unit 54 will be described. Figure 3 It is a block diagram schematically showing the robot 100 . Figure 3 The functional blocks shown are implemented in hardware by components or mechanical devices headed by a computer CPU (Central Processing Unit) and in software by computer programs, etc., but here, the functional blocks implemented by their cooperation are drawn. Therefore, it can be understood by those skilled in the art who have access to this specification that these functional blocks can be implemented in various ways by combining hardware and software.

[0055] The acquisition unit 52 and the control unit 54 control the motor 38 to perform a retreat action according to the external force in order to prevent the speed reducer 6 from being damaged by the reverse drive (hereinafter referred to as "retreat control"). As described above, the acquisition unit 52 functions as an acquisition mechanism for acquiring information related to the rotation of the motor 38. The control unit 54 functions as a control mechanism for detecting the external force and performing the retreat action according to the acquisition result of the acquisition unit 52.

[0056] As information related to the rotation of the motor 38, the torque of the output shaft of the motor, the rotation speed of the motor, the driving voltage of the motor (the duty cycle of the PWM driving signal), and the current of the motor can be cited. In the present embodiment, the information related to the rotation of the motor 38 is the driving current Im of the motor 38, and the acquisition unit 52 includes a current sensor 52s for detecting the driving current Im. The current sensor 52s of the present embodiment is a series resistor with a small resistance value connected in series with the motor 38. The acquisition unit 52 can detect the driving current Im as a voltage drop of the series resistor.

[0057] The control unit 54 of this embodiment mainly includes a first receiving unit 54a, a second receiving unit 54b, an external force detection unit 54c, a motor driving unit 54d, and a retreat control unit 54e. The first receiving unit 54a receives information about the difference between the position command information from the upper control system 4 and the position information of each arm 42 from the position sensor 4s. The upper control system 4 may be, for example, a main system that controls the movement of each joint 40 of the manipulator 100. The first receiving unit 54a generates a position command signal Ps based on the reception result.

[0058] The second receiving unit 54b receives the drive current Im from the current sensor 52s of the acquisition unit 52. For example, the second receiving unit 54b may be configured to include a DA converter that converts the drive current Im into a digital signal.

[0059] The external force detection unit 54c detects the external force acting on the joint 40 based on the acquisition result of the acquisition unit 52. For example, the external force detection unit 54c can detect the external force based on the drive voltage Vd and the drive current Im of the drive motor 38. As an example, the external force detection unit 54c can pre-store information about the relationship between the drive voltage Vd and the drive current Im when there is no external force, and infer the external force based on the newly detected drive voltage Vd and the drive current Im and the stored information. For example, a regression line (including linear regression and polynomial regression) can be obtained from the stored information, and the external force can be inferred from the size of the deviation from the regression line.

[0060] The evacuation control unit 54e determines the evacuation operation according to the external force estimated by the external force detection unit 54c. As an example, the evacuation control unit 54e may generate evacuation information Pc such as non-evacuation, deceleration, stop, and reverse according to the magnitude of the external force.

[0061] The motor drive unit 54d supplies a driving voltage Vd whose size is determined according to the position command signal Ps and the back-off information Pc to the motor 38. The motor drive unit 54d can be configured to include a PWM inverter. The size of the driving voltage Vd depends on the duty cycle of the PWM driving signal. When the back-off information Pc is "no back-off", the motor drive unit 54d supplies a driving voltage Vd corresponding to the position command signal Ps. When the back-off information Pc is "slow down", the motor drive unit 54d supplies a driving voltage Vd with a reduced duty cycle. When the back-off information Pc is "stop", the motor drive unit 54d sets the duty cycle of the driving voltage Vd to zero%. When the back-off information Pc is "reverse", the motor drive unit 54d supplies a driving voltage Vd for reversal.

[0062] According to the acquisition unit 52 and the control unit 54 configured in this way, the motor 38 can be controlled to retreat according to the external force, thereby preventing the speed reducer 6 from being damaged by reverse driving and alleviating the impact when the person and the robot come into contact. In addition, compared with the structure in which the torque sensor is arranged on the output side of the speed reducer, the possibility of the torque sensor being damaged by the external force can be reduced, which is advantageous in terms of the space and cost for arranging the torque sensor.

[0063] Next, the reduction ratio Rs of the reduction gear 6 will be described. The reduction ratio Rs is the product of the reduction ratio Rg of the eccentric oscillating gear mechanism 10 and the reduction ratio Rp of the parallel shaft gear mechanism 8 . Figure 4 The graph g1 shows the relationship between the reduction ratio Rg and the transmission efficiency Eg of the eccentric oscillating gear mechanism 10. As shown in the graph g1, when the reduction ratio Rg is 35 or less, the transmission efficiency Eg is high, and when the reduction ratio Rg exceeds 35, the transmission efficiency Eg decreases rapidly. Furthermore, when the reduction ratio Rg is 17 or less, the transmission efficiency Eg is further improved. From the viewpoint of improving the transmission efficiency Eg, the reduction ratio Rg can be set to 35 or less.

[0064] When manufacturing the eccentric oscillating gear mechanism 10, manufacturing errors will inevitably occur in the tooth shapes of the internal teeth 16a and the external teeth 14a. This manufacturing error will cause the gap between the teeth to change and the contact time to change, which may have a negative impact on the transmission efficiency of the eccentric oscillating gear mechanism 10. In order to ensure a margin for this manufacturing error, the reduction ratio Rg is preferably less than 17. It can be seen that if it is set within this range, the impact of the manufacturing error on the transmission efficiency can be ensured to a level that does not cause practical problems. The reduction ratio Rg of this embodiment is set to 15, and the transmission efficiency of the eccentric oscillating gear mechanism 10 is 95%.

[0065] The reduction ratio Rp of the parallel shaft gear mechanism 8 can be set to the result of dividing the desired reduction ratio Rs of the reducer 6 by the reduction ratio Rg of the eccentric swing type gear mechanism 10. If the reduction ratio Rp is too large, the diameter ratio of the driving gear 8b and the driven gear 8c becomes larger, the backlash increases, and the transmission accuracy decreases. In order to ensure the transmission accuracy, the reduction ratio Rp is preferably less than 5. It can be seen that if it is set within this range, the transmission accuracy can be ensured at a level that is not a problem in practical use. The reduction ratio Rp of this embodiment is set to 5.

[0066] In order to enable accurate retreat control, the reduction ratio Rs of the reducer 6 is preferably less than 175, and more preferably less than 85. Furthermore, if the reduction ratio Rs of the reducer 6 is too small, the driving force of the arm 42 will become smaller. In order to ensure the driving force of the arm 42, the reduction ratio Rs of the reducer 6 is preferably greater than 50. It can be seen that if the reduction ratio Rs of the reducer 6 is in the range of 50 to 175 (more preferably in the range of 50 to 85), the accuracy of the retreat control and the driving force of the arm 42 can be ensured at a level that is not a problem in practical use. The reduction ratio Rs of the present embodiment is set to 75.

[0067] If the efficiency of the reducer 6 is too low, the time lag until the external force is transmitted from the output side of the reducer to the motor side becomes large, and the reducer 6 may be damaged during the period from detecting the external force to performing the retreat control. In order to detect the external force on the motor side and perform the retreat control before the reducer 6 is damaged, the efficiency of the reducer 6 is preferably 80% or more. It is known that if it is set within this range, the retreat control can be implemented at a level that is not a problem in practical use. The transmission efficiency of the reducer 6 in this embodiment is 90%.

[0068] According to the robot 100 having the above-described structure, it is possible to provide a robot that can cope with external forces without providing a torque sensor on the output side of the speed reducer 6 .

[0069] The examples of the embodiments of the present invention are described in detail above. The above embodiments are only specific examples of implementing the present invention. The contents of the embodiments are not intended to limit the technical scope of the present invention. Various design changes such as changes, additions, and deletions of constituent elements can be made without departing from the scope of the idea of ​​the invention defined in the claims. In the above embodiments, the contents that can be subjected to such design changes are described by marking phrases such as "in the embodiment" and "in the implementation", but this does not mean that design changes are not allowed without such marked contents. In addition, the hatched lines marked in the accompanying drawings do not limit the material of the objects marked with hatched lines.

[0070] [Modifications]

[0071] In the following, a modification example is described. In the drawings and description of the modification example, the same reference numerals are given to the same or equivalent components and parts as those in the embodiment. The description repeated with the embodiment is appropriately omitted, and the structure different from the embodiment is described in detail.

[0072] In the description of the embodiment, the evacuation action is described as an example of decelerating, stopping, or reversing the motor, but the present invention is not limited thereto. For example, the evacuation action may be any one of decelerating, stopping, or reversing the motor, or other actions.

[0073] In the description of the embodiment, an example of inferring the external force from the driving voltage Vd and the driving current Im by regression analysis is shown, but the present invention is not limited to this. For example, the external force can also be inferred by using an external force inference model generated by known machine learning (including supervised learning) based on information related to the rotation of the motor such as the driving voltage Vd and the driving current Im and data on the external force. In this case, the control unit 54 can also include a storage unit for storing the external force inference model. In addition, the control unit 54 can also include a model generation unit that generates an external force inference model by machine learning.

[0074] In the description of the embodiment, the example in which the rotation is output from the internal gear 16 is shown for the eccentric oscillating gear mechanism 10, but the present invention is not limited thereto. The eccentric oscillating gear mechanism may also be configured such that the internal gear is fixed and the rotation is output from the external gear.

[0075] In the description of the embodiment, an example of a multi-joint manipulator with six joints is shown, but the present invention is not limited to this. For example, the manipulator may also be a horizontal multi-axis manipulator (SC ARA type manipulator). In addition, the number of joints is not limited. The manipulator of the present invention is well suited for collaborative robots, service robots, and robot carts that work near humans without being separated from humans, but is not limited to this.

[0076] In the description of the embodiment, an example is shown in which the cylindrical portion 20 b , the input-side side surface portion 20 c , and the bearing support portion 22 are integrally formed of a single material, but they may be formed separately and then combined together.

[0077] In the description of the embodiment, an example is shown in which two external gears 14 are provided, but the present invention is not limited to this. One or three or more external gears 14 may be provided.

[0078] In the description of the embodiment, an example is shown in which only the input side of the inner pin 30 is supported, but the present invention is not limited thereto. A carrier may be provided on the opposite side of the input of the external gear, and the opposite side of the input of the inner pin may be fixed to the carrier.

[0079] The above-mentioned modifications also achieve the same effects as those of the embodiment.

[0080] Any combination of the above-described embodiments and modifications is also effective as an embodiment of the present invention. A new embodiment generated by the combination has the effects of the combined embodiments and modifications.

Claims

1. A robot having a joint assembled with a motor and a reducer, wherein the robot has: An acquisition mechanism for acquiring information related to the rotation of the motor; and The control mechanism detects the application of external force based on the information obtained by the acquisition mechanism and performs a retreat action. The speed reducer comprises a parallel shaft gear mechanism and an eccentric oscillating gear mechanism, wherein the output rotation of the parallel shaft gear mechanism is input to the eccentric oscillating gear mechanism. The eccentric oscillating gear mechanism is a center crank gear mechanism in which the eccentric body shaft is arranged on the axis center of the internal gear, and its reduction ratio is less than 35. The parallel axis gear mechanism comprises: a driving gear that rotates integrally with the rotation of the motor and is offset from the eccentric body axis; and a driven gear that meshes with the driving gear and has a central axis that is offset from the central axis of the driving gear; A driven gear meshing with the driving gear rotates integrally with the eccentric body shaft.

2. The robot according to claim 1, characterized in that: The driven gear is fixed to the eccentric body shaft and rotates integrally with the eccentric body shaft.

3. The robot according to claim 1 or 2, characterized in that: The reduction ratio of the parallel shaft gear mechanism is 5 or less.

4. The robot according to claim 1 or 2, characterized in that: The eccentric body shaft is supported by an eccentric body shaft bearing arranged on the inner periphery of the eccentric body shaft.

5. The robot according to claim 1 or 2, characterized in that: Viewed from a radial direction, the driven gear overlaps with the eccentric body shaft bearing.

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