INDUSTRIAL ROBOT

Abstract: An industrial robot which is so constructed that opera­ tions of robot moving portions (16, 18, 20) are controlled by drive motors (Mϑ, Mw, Mu) that have absolute position detecting encoders (ECϑ, ECw, ECu, ECα, ECβ, ECγ). The drive motor (Mϑ) for controlling the operation of the robot moving portion is mounted on a turning body (16) that is installed on a fixed base (12) of a robot frame (10). There is further mounted a storage battery (46) that supplies a back-­ up voltage to the encoders of the drive motors (Mw, Mu, Mα, Mβ, Mγ) for the robot moving portions (18, 20). The storage battery is wired to each of the encoders (ECϑ to ECγ) via cables (48, 49).

Description: The present invention relates to an industrial robot in general, see e.g. US-A-4 356 554 and, more particularly, to a backup voltage supply battery mounting construction for an industrial robot equipped with a driving motor provided with an absolute position detecting encoder for controlling the respective actions of the movable robot components. An absolute position detecting encoder capable of detecting and storing the present angular position of a rotary shaft through the calculation and storage of the direction of rotation, the number of rotation, and angular position in one cycle of rotation of the rotary shaft is proposed in Japanese Unexamined Patent Publication No. 60-218,029, corresponding to EP-A-0 158 781, which however was published after the priority date of the present application and therefore is prior art only in the meaning of Article 54(3) EPC, and a driving motor incorporating such an absolute position detecting encoder and capable of detecting the present angular position of the output shaft thereof has been provided. The application of a driving motor provided with such an absolute position detecting encoder to control the actions of the movable robot components of an industrial robot enables the detection of the respective present position of the movable robot components interlocked with the output shaft of the driving motor, and storing the data of the present respective positions of the movable robot components. Accordingly, the robot control operation of a robot controller can be started quickly according to teaching data and can be very accurately carried out by reading the data of the present positions of the movable robot components. When, however, the driving motor provided with the above-mentioned absolute position detecting encoder is applied to an industrial robot, it is necessary to provide the industrial robot with a battery for supplying a backup voltage to prevent the extinguishment of the data stored in the absolute position detecting encoder, so that a backup voltage is applied to the absolute position detecting encoder when a feeder line for supplying an excitation voltage from the robot controller to the absolute position detecting encoder in the normal state is disconnected from the absolute position detecting encoder for robot maintenance work or when the absolute position detecting encoder is accidentally disconnected from the robot controller. Accordingly, the battery must be always provided on the robot unit. But, since most recent industrial robots have a swivel body mounted on a fixed base disposed at the lowermost position of the robot unit, electric cables and pipes of the industrial robot are twisted as the swivel body is driven for swivel motion, which is liable to cause breakage of the electric cables and the pipes. In view of such an inconvenience, it is necessary to arrange the cable extending between the backup voltage supplying battery and each driving motor in such a way that the cable will not be twisted and accidentally broken by the swivel motion of the swivel body. According to the present invention, an industrial robot having a robot unit comprises a fixed base and movable robot components, the movable robot components being at least a swivel body mounted on the fixed base so as to swivel about a longitudinal axis, a first robot arm pivotally joined to the swivel body, and a second robot arm pivotally joined to one end of the first robot arm and provided with a robot wrist unit, and is characterised in that driving motors for operatively controlling the movable robot components are equipped with absolute position detecting encoders, respectively, the driving motor for driving the swivel body mounted on the fixed base of the robot unit is mounted on the swivel body, and a battery for supplying backup voltage to the encoders of the driving motors for driving the movable robot components other than the swivel body is mounted on the outside of the swivel body. Other objects and features of the present invention will be apparent from the following description of an embodiment of the invention illustrated in the accompanying drawing, in which the single figure is a partially sectional front elevation of an industrial robot, in a preferred embodiment, according to the present invention, showing the constitution thereof. The single figure is a partially sectional front elevation of an industrial robot, more specifically, a six-axis type industrial robot by way of example, embodying the present invention. In the drawing, the robot unit 10 of the industrial robot has a hollow cylindrical fixed base 12, and a swivel body 16 is mounted for swivel motion about a longitudinal axis (axis ϑ) on a bearing 14 on the fixed base 12. The swivel body 16 has a rotary base 16a, as illustrated in section. A first arm 18 is joined pivotally at the lower end thereof to an upper end 16b of the swivel body 16 so as to be swingable about a horizontal axis (axis W). A second arm 20 is joined pivotally to the upper end of the first arm 18 so as to be swingable in a vertical plane about a horizontal axis (axis U). An inner shaft 22, an intermediate shaft 24, and an outer shaft 26 are extended coaxially and rotatably within the second arm 20 to apply a wrist unit, not shown, attached to the free end of the second arm 20 for motions of three degrees of freedom of motion, namely, motions about an axis α, an axis β, and an axis γ. The respective basic constructions of the movable robot components of the robot unit 10 of the industrial robot, namely, the swivel body 16, the first arm 18, the second arm 20, the inner shaft 22, the intermediate shaft 24 and the outer shaft 26, movable about the six axes, namely, the axes ϑ, W, U, α, β and γ, are substantially the same as those of the conventional six-axis cylindrical coordinates type robot. A balancing link 28 has one end pivotally joined to the first arm 18, and the other end pivotally joined to the second arm 20. A driving motor Mϑ for driving the swivel body 16 is attached to the rotary base 16a of the swivel body 16 with the axis of the output shaft thereof in alignment with the axis ϑ. The output shaft of the driving motor Mϑ is interlocked with the fixed base 12 by a reduction gear 30, and thereby the swivel body 16 is driven for rotation on the bearing 14 about the axis ϑ by the counter action of the fixed base 12 when the driving motor Mϑ is actuated. Accordingly to the construction of the conventional robot unit, generally, the driving motor Mϑ is held at a fixed position on the fixed base 12 and the output shaft of the driving motor Mϑ is interlocked with the swivel body 16 by the reduction gear 30; consequently, the cable is twisted disadvantageously. The driving motor Mϑ is provided with an absolute position detecting encoder ECϑ. A pair of two driving motors MW and MU for driving the first arm 18 and the second arm 20, respectively, are pivotally supported, one on the right-hand side and the other on the left-hand side, on an arm 32 projecting from the swivel body 16. The driving motors MW and MU are provided also with absolute position detecting encoders ECW and ECU, respectively. Similar to the conventional robot unit, a transmission mechanism for transmitting the rotative outputs of the driving motors MW and MU to drive the first arm 18 for swing motion about the axis W and to drive the second arm 20 for swing motion about the axis U is accommodated in a shaft tube 34, the first arm 18, and the second arm 20. Driving motors Mα, Mβ, and Mγ for respectively driving the inner shaft 22, the intermediate shaft 24, and the outer shaft 26, are held on the second arm 20. The driving motor Mα drives the inner shaft 22 rotatively through a belt-pulley mechanism 36; the driving motor Mβ drives the intermediate shaft 24 rotatively through a belt-pulley mechanism 38; and the driving motor Mγ drives the outer shaft 26 rotatively through a reduction gear 40 and a gear train 42. Naturally, the driving motors Mα, Mβ, and Mγ are provided with absolute position detecting encoders ECα, ECβ, and ECγ, respectively, to detect and store the respective present positions of the inner shaft 22, the intermediate shaft 24, and the outer shaft 26 through the detection and storage of the respective present positions of the output shafts of the driving motors Mα, Mβ, and Mγ, respectively. Electric power and excitation voltage are always supplied to the driving motors Mϑ, MW, MU, Mα, Mβ, and M γ, and the encoders ECϑ, ECW, ECU, ECα, ECβ, and ECγ of the same, through an electric cable 44 electrically interconnecting a robot controller, not shown, and the robot unit 10. Although the cable 44 has a sufficient length in reserve within the fixed base 12, the cable 44 is twisted around the axis ϑ as the swivel body 16 is driven for swivel motion relative to the fixed base 12, and hence it is impossible to avoid the breakage of the cable 44 during the operation of the industrial robot for an extended period of time. Accordingly, cables for supplying the backup voltage to those encoders including the encoder ECϑ should not be included in the cable 44. A backup voltage supply battery 46 is mounted on the rotary base 16a of the swivel body 16. Accordingly, the battery 46 is not rotated relative to the movable robot components including the swivel body 16, the first arm 18, and the second arm 20, when the swivel body 16 swivels about the axis ϑ. Accordingly, the breakage of the backup voltage supply cables 48 and 49 extended from the battery 46 to the respective encoders ECϑ, ECW, ECU, ECα, ECβ, and ECγ of the driving motors Mϑ, MW, MU, Mα, Mβ, and Mγ attributable to the twist of the same is surely obviated. Since the extension and contraction of the cables 48 and 49 resulting from the swing motion of the first arm 18 and the swing motion of the second arm 20 in a vertical plane are avoidable by extending the cables 48 and 49 beforehand to a sufficient length, the breakage of the cables 48 and 49 attributable to the extension and contraction of the same is prevented. The battery 46 is a dry element battery available in the market, and is contained in a battery box. The battery 46 is replaceable. Backup voltage supply cables are extended from terminals provided on the battery case to the encoders ECϑ, ECW, ECU, ECα, ECβ, and ECγ. As apparent from the above description, the industrial robot having the driving motors equipped with the absolute position detecting encoders, respectively, for operatively controlling the movable robot components thereof, is provided, on the swivel body thereof, with the backup voltage supply battery for preventing the extinguishment of the data stored in the encoders, and the driving motor for driving the swivel body, and hence the battery swivels together with the swivel body about the axis of swivel motion of the swivel body to avoid rotation relative to the other movable robot components. Accordingly, breakage of the cables for supplying the backup voltage from the battery to the encoders, attributable to the twist of the sane is avoided, and hence the respective present positions of the movable robot components can be safely detected by and stored in the absolute position detecting encoders. The foregoing advantages are remarkably effective in securing safety, because it is possible for the cables to be twisted and broken at some part when the battery is mounted on the robot unit in the conventional robot mechanism, in which the driving motors are attached to and held on the fixed base. LIST OF REFERENCE CHARACTERS 10 Robot unit 12 Fixed base 14 Bearing 16 Swivel body 16a Rotary base 16b Upper end 18 First arm 20 Second arm 22 Inner shaft 24 Intermediate shaft 26 Outer shaft 28 Balancing link 30 Reduction gear 32 Arm 34 Shaft tube 36 Belt-pulley mechanism 38 Belt-pulley mechanism 40 Reduction gear 42 Gear train 44 Electric cable 46 Battery 48 Cable 49 Cable M0, MW, MU, Mα, Mβ, Mγ Driving motors ECϑ, ECW, ECU, ECα, ECβ, ECγ Absolute position detecting encoders

Claims: An industrial robot having a robot unit (10), the robot comprising a fixed base (12) and movable robot components, the movable robot components being at least a swivel body (16) mounted on the fixed base (12) so as to swivel about a longitudinal axis, a first robot arm (18) pivotally joined to the swivel body (16), and a second robot arm (20) pivotally joined to one end of the first robot arm (18) and provided with a robot wrist unit, wherein driving motors (MΘ,Mu,Mw) for operatively controlling the movable robot components are equipped with absolute position detecting encoders (ECΘ,ECu,ECw), respectively, the driving motor (MΘ) for driving the swivel body (16) mounted on the fixed base (12) of the robot unit is mounted on the swivel body, and a battery (46) for supplying backup voltage to the encoders (ECΘ,ECu,ECw) of the driving motors (MΘ,Mu,Mw) for driving the movable robot components (18,20) other than the swivel body is mounted on the outside of the swivel body (16). An industrial robot according to claim 1, wherein the driving motor (MΘ) for operatively controlling the swivel body (16) is mounted with the axis of the output shaft thereof in alignment with the axis of a swivel motion of the swivel body, and the battery (46) for supplying backup voltage is disposed beside the driving motor (MΘ). An industrial robot according to claim 1 or claim 2, wherein the battery (46) is replaceably contained in a battery case.

Inventors: NAKASHIMA, SEIICHIRO, TORII, NOBUTOSHI, TOYODA, KENICHI
Applicants: FANUC LTD.
Application year: 1986
Main classification: B25J19
IPC codes: B25J19, B25J9, G05B19