Industrial Robot

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 .theta.) 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 .alpha., an axis .beta., and an axis .gamma..

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 .theta., W, U, .alpha., .beta. and .gamma., 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 M.theta. 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. The output shaft of the driving motor M.theta. 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 .theta. by the counter action of the fixed base 12 when the driving motor M.theta. is actuated. Accordingly to the construction of the conventional robot unit, generally, the driving motor M.theta. is held at a fixed position on the fixed base 12 and the output shaft of the driving motor M.theta. is interlocked with the swivel body 16 by the reduction gear 30; consequently, the cable is twisted disadvantageously.

The driving motor M.theta. is provided with an absolute position detecting encoder EC.theta.. 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 M.alpha., M.beta., and M.gamma. 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 M.alpha. drives the inner shaft 22 rotatively through a belt-pulley mechanism 36; the driving motor M.beta. drives the intermediate shaft 24 rotatively through a belt-pulley mechanism 38; and the driving motor M.gamma. drives the outer shaft 26 rotatively through a reduction gear 40 and a gear train 42. Naturally, the driving motors M.alpha., M.beta., and M.gamma. are provided with absolute position detecting encoders EC.alpha., EC.beta., and EC.gamma., 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 M.alpha., M.beta., and M.gamma., respectively.

Electric power and excitation voltage are always supplied to the driving motors M.theta., MW, MU, M.alpha., M.beta., and M .gamma., and the encoders EC.theta., ECW, ECU, EC.alpha., EC.beta., and EC.gamma. 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 .theta. 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 EC.theta. should not be included in the cable 44. According to the present invention, 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 .theta.. Accordingly, the breakage of the backup voltage supply cables 48 and 49 extended from the battery 46 to the respective encoders EC.theta., ECW, ECU, EC.alpha., EC.beta., and EC.gamma. of the driving motors M.theta., MW, MU, M.alpha., M.beta., and M.gamma. 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 EC.theta., ECW, ECU, EC.alpha., EC.beta., and EC.gamma.. The encoder of U.S. Pat. No. 4,604,521, dated Aug. 5, 1986, discloses encoders suitable for such use.

As apparent from the above description, according to the present invention, 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 same 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.