JP4512194B2 - Robot arm - Google Patents

Description

  The present invention relates to a robot arm provided with a joint mechanism that bends so that a link member is folded, for example, used in a humanoid robot.

  As an example of the bending joint mechanism that operates to fold the link members that are freely connected to each other, there is a robot joint structure disclosed in Patent Document 1, for example. Here, a bent joint structure using a link member of a nut and a screw is shown.

JP 2002-113681 A

  The robot arm has a structure in which a plurality of link members and a movable part are connected in series. For this reason, an actuator that drives a certain movable part has a structure that includes the movable part and the actuator on the adjacent tip side. Therefore, an actuator having a driving force that is progressively larger is required as it approaches the root from the tip. On the other hand, the backlash at the movable part increases cumulatively on the tip side as it passes through each movable part. In addition, mechanical parts for operation are concentrated on the movable part, but it is necessary to pay attention to accidents such as the human body being caught in these parts.

  In order to solve the above problems, in a robot arm including a structure that bends with a link member connected by a freely rotatable joint, a drive motor and a driven joint are arranged with the joint interposed therebetween, and the drive motor And the driven joint portion are connected by a wire, and include two wire guide pulleys for guiding the wire to the bending axis of the joint portion, and the wire is divided into a bent inner side and an outer side and wound as a joint portion, The inertia weight on the tip side was reduced.

  In addition, the joint portion is rotated and bent by two bending shafts that are rotationally constrained by a gear, the two bending shafts are connected by a plate, and the center of one bending shaft of the plate is fixed, and the other A joint that is a plate that has a slit on the opposite side of the one bending axis in a hole that penetrates the bending axis and closes the other bending axis to the one bending axis by closing the slit. As part, backlash was reduced.

  Furthermore, a cover sheet is provided inside and outside the bent portion of the joint, and the cover sheet is a cover sheet in which one end is fixed to the link member and the other end is connected to each other. Prevent accidents.

  According to the present invention, the weight on the tip side of the robot arm can be reduced, and the actuator can be downsized. In addition, the driving load and backlash angle of the joint mechanism can be optimized. Further, by covering the mechanism with a cover, it is possible to prevent a human body from entering the joint mechanism.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 schematically shows a front view of a robot arm 1 according to the present invention. From the base side of the arm toward the distal end side, the shoulder portion 2, the shoulder joint 3, the upper arm portion 4, the elbow joint 5, the forearm portion 6, the wrist joint 7 and the hand portion 8 are formed.

  The shoulder 2 is driven by the shoulder turning motor 21 and turns around the axis c as indicated by the arrow a. The shoulder joint 3 is driven by two shoulder joint motors 31 and performs a bending operation indicated by an arrow B and a turning operation indicated by an arrow C. The elbow joint 5 is driven by an elbow joint motor 51 and performs a bending motion indicated by an arrow 2. The wrist joint 7 is driven by two wrist joint motors 71 and performs a bending operation indicated by an arrow e and a turning operation indicated by an arrow. The elbow joint motor 51 and the wrist joint motor 71 are built in the upper arm portion 4.

  A specific example of the elbow joint 5 of the robot arm 1 will be described with reference to FIGS. The elbow joint 5 shown in this example has a double-joint structure that bends at two locations, a first bending shaft 56 and a second bending shaft 57. The advantage of the double joint structure is that mechanical interference between the upper arm portion 4 and the forearm portion 6 is difficult to occur when the elbow joint 5 bends over 90 degrees.

  An elbow joint motor 51 and a wrist joint motor 71 are fixed to the upper arm frame 41. The first bending shaft 56 is fixed to the elbow frame 55 and is rotatably connected to the upper arm frame 41 via a bearing or the like. The second bending shaft 57 is rotatably connected to the elbow frame 55 via a bearing or the like and fixedly connected to the forearm frame 61. On the other hand, the elbow joint motor 51 drives the first gear 53 via the drive gear 52. The first gear 53 is fixed to the first bending shaft 56. The first gear 53 meshes with the second gear 54 to transmit a driving force. The second gear 54 is fixed to the second bending shaft 57. When the elbow joint motor 51 is rotated in such a structure, as shown in FIG. 4, when the first bending shaft 56 is driven to rotate by the angle α, the second bending shaft is also moved relative to the forearm frame 61. Angle α bends. Further, the elbow stopper 58 abuts against the upper arm frame 41 and the forearm frame 61 and restricts the operation at a position where the both are in a substantially linear relationship.

In the above elbow joint 5, a rotatable wire guide pulley 59 is provided on the first bending shaft 56 and the second bending shaft 57. And it was set as the structure which transmits the driving force of the wrist joint motor 71 installed in the upper arm part 4 to the wrist joint 7 through the elbow joint 5 via the wire 72. That is, as shown in FIG. 4, when the first bending shaft 56 and the second bending shaft 57 are each bent at an angle α, the wire 72 is wound around the wire guide pulley 59a provided on the first bending shaft 56. When the diameter of the wire guide pulley 59 is D, the length is
Lw = π × D × α / 360 (Formula 1)
Decrease. On the other hand, the winding length of the wire guide pulley 59b provided on the second bending shaft 57 increases by the length L. Accordingly, the wire 72 is not pulled or loosened due to the bending of the elbow joint 5. Therefore, the driving force of the wrist joint motor 71 can be transmitted to the wrist joint 7 through the elbow joint 5.

  As a result, the wrist joint motor 71 can be arranged on the base side of the robot arm 1, the inertia weight of the robot arm 1 can be reduced, and a small and inexpensive motor with a small driving force can be used.

  Further, the backlash can be adjusted with the first gear 53 and the second gear 54. In general, when the backlash of the gear is small, the driving load is increased. In order to perform this adjustment precisely and inexpensively, the structure shown in FIG. 3 was used. That is, in the part where the first bending shaft 56 and the elbow frame 55 are in contact, the first bending shaft 56 is a prism and the elbow frame 55 is a square hole. The elbow frame 55 is provided with a slit S on the side opposite to the second bending shaft 57 and a screw 102 for reducing the slit interval. In addition, an adjustment member 101 is provided between the square hole of the elbow frame 55 and the prism of the first bending shaft 56.

  Here, when the screw 102 is tightened to contract the slit S, a force is generated in the direction indicated by the arrow G, and the first bending shaft 56 is pressed in the direction of the second bending shaft 57. On the other hand, since the minimum distance between the first bending shaft 56 and the second bending shaft 57 is regulated by the adjustment member 101, the center distance between both the shafts can be set accurately. The backlash amount of the second gear 54 can be appropriately given.

  Thereby, the driving load does not increase, and the elbow joint 5 with an appropriate backlash angle can be configured. Furthermore, it is important to protect these mechanical components from being caught in a human body such as a finger. Therefore, a slide cover is provided to cover the inside and outside of the bend. In FIG. 2, the mechanism structure is shown by dotted lines.

  A flexible sheet 91 made of plastic or the like is provided inside and outside the bend of the elbow joint 5 to cover the mechanical parts. The flexible sheet 91 is fixed to the forearm frame 61 by a fixing member 93. On the other hand, the upper arm frame 41 is smoothly guided by the sliding member 92 and one end thereof is pulled by the wire 94. The inner flexible sheet 91 a and the outer flexible sheet 91 b are connected via a wire 94. The direction of the wire 94 is smoothly changed by a seat wire pulley 95 provided on the upper arm frame 41.

Here, as shown in FIG. 4, when the first bending shaft 56 and the second bending shaft 57 are bent at an angle α, the inner flexible sheet 91 a
Ls = W × tan α (Formula 2)
It is necessary to shorten the length. On the other hand, the outer flexible sheet 91b needs to be longer by the length Ls. As described above, since the inner flexible sheet 91a and the outer flexible sheet 91b are connected by the wire 95, the shortened length of the inner flexible sheet 91a is the same as that of the outer flexible sheet 91b. Supplied to the stretched length, the flexible sheet 91 can continue to cover the elbow joint 5. Further, by inserting an elastic body 96 such as a spring in the middle of the wire 94, the flexible sheet 91 can be kept in a moderately stretched state.

  In the above embodiment, the elbow joint 5 has been described as a double joint structure. However, the present invention is not limited thereto, and the elbow joint 5 can be applied to a joint portion that performs a bending operation.

The front view of one Example of a robot arm. The front view of the elbow joint used for the robot arm shown in FIG. The top view of the elbow joint used for the robot arm shown in FIG. The figure explaining the operation | movement of the elbow joint used for the robot arm shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Robot arm, 2 ... Shoulder part, 3 ... Shoulder joint, 4 ... Upper arm part, 5 ... Elbow joint, 6 ... Forearm part, 7 ... Wrist joint, 8 ... Hand part, 21 ... Shoulder turning motor, 31 ... Shoulder joint Motor, 41 ... upper arm frame, 51 ... elbow joint motor, 52 ... drive gear, 53 ... first gear, 54 ... second gear, 55 ... elbow frame, 56 ... first bending axis, 57 ... second Bending shaft, 58 ... elbow stopper, 59 ... wire guide pulley, 61 ... forearm frame, 71 ... wrist joint motor, 72 ... wire, 91 ... flexible sheet, 92 ... sliding member, 93 ... fixing member, 94 ... sheet Wire 95, sheet wire pulley, 96, elastic body, 101, adjusting member, 102, screw.

Claims (2)

In a robot arm including a structure that bends by a link member connected by a freely rotatable joint, the joint is rotated and bent by two bending axes that are rotationally constrained by gears, and the two bending axes are plates. in coupled, the plate is centered fixation of one of said bending axis, the holes and the other of said bending axis passes, provided with a slit to the opposite side of the one bending axis, closed to close the slit Thus, the robot arm is characterized in that the other bending axis is brought close to the one bending axis.   2. The robot arm according to claim 1, wherein the robot arm further has a structure simulating a human arm, the joint is an elbow joint corresponding to an elbow, and an inner side of the elbow joint is bent. A cover sheet is provided on each outer side, one end of the inner and outer cover sheets is fixed to a forearm frame corresponding to a human forearm, and the other ends of the inner and outer cover sheets are connected to each other with wires. Robot arm.

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