JPS6367452A - Speed reduction mechanism vibration isolator - Google Patents

Abstract

PURPOSE:To negate the torque fluctuations and reduce the resonance vibration by setting the gear ratio between a motor shaft pulley and the input shaft pulley of a harmonic driven speed reducer to 1:2 and making the motor shaft pulley eccentric. CONSTITUTION:The gear ratio between a motor shaft pulley 3 and the input shaft pulley 4 of a harmonic drive speed reducer 2 is set to 1:2, and both pulleys 3, 4 are connected by a timing belt 5. The motor shaft pulley 3 is formed in an eccentric pulley. Accordingly, two torque fluctuations generated due to the harmonic driven speed reducer 2 for each rotation of the speed reducer input shaft are negated, and the resonance vibration of a robot arm or the like can be reduced.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a reduction mechanism vibration isolator for suppressing vibrations of a robot arm, for example, caused by a harmonic drive reduction gear. .

(Prior Art) In a harmonic drive speed reducer, torque fluctuations occur twice per rotation of the speed reducer input shaft, and these torque fluctuations can become a source of vibration, for example, causing the arm of a robot to vibrate. In particular, when the frequency of torque fluctuation matches the robot's natural frequency, the robot arm causes resonant vibration.

A common method for dealing with vibration is to mechanically add a dynamic vibration absorber, but when considering application to robots, adding a new dynamic vibration absorber is cost-effective. It is also difficult in terms of space. Furthermore, since the natural frequency changes depending on the posture and load of the robot, it is not practical to add a dynamic vibration absorber that can cope with such changes in the natural frequency.

FIG. 3 shows a sectional view of a conventional robot joint drive unit. In particular, no mechanical dynamic vibration reducer is added, and resonance vibration caused by the harmonic reduction gear is unavoidable in such a joint drive mechanism.

In addition, there is a method of controlling vibrations by absorbing torque fluctuations caused by a harmonic drive reducer rather than mechanically adding a dynamic vibration absorber, such as the one described in the Proceedings of the Japan Society of Mechanical Engineers () 11860-I P21 Robots. Research on anti-vibration control (resonant vibration caused by torque unevenness in harmonic drives) is described. However, this method has a problem in terms of cost because it requires a new circuit for creating a correction signal to be constructed in the control system in order to absorb vibrations in a controlled manner.

(Problems to be Solved by the Invention) As described above, mechanically adding a dynamic vibration absorber is difficult in terms of cost and space.

Furthermore, vibration cannot be sufficiently prevented. Furthermore, in the method of absorbing vibrations in a controlled manner, a new circuit for creating a correction signal is required, which poses a problem in terms of cost.

Therefore, it is an object of the present invention to provide a reduction mechanism vibration isolator that can reduce the resonance vibration of a robot arm caused by a harmonic drive reduction gear without adding a new vibration prevention device mechanically or controllingly. It is an object.

[Structure of the invention]

(Means for Solving the Problem) The robot vibration isolator of the present invention is composed of a motor shaft eccentric pulley having an appropriate eccentricity, a reducer input shaft pulley with a tooth ratio of twice the motor shaft eccentric pulley, and a timing belt. has been done.

(Operation) Torque fluctuations are generated in the following manner to cancel out the torque fluctuations that occur twice per rotation of the reducer input shaft due to the harmonic drive reduction gear. In other words, the tooth ratio between the motor shaft pulley and the reducer input shaft pulley is 1:2.
Furthermore, by giving the motor shaft pulley an appropriate eccentricity, torque fluctuations of once per revolution of the motor shaft, that is, twice per revolution of the reducer input shaft, can be controlled by the eccentric pulley of the motor shaft, the input shaft pulley of the reducer, and the timing bell. can be generated. The amount of torque fluctuation caused by the motor shaft eccentric pulley, reducer input shaft pulley, and timing belt is adjusted to the same level as the torque fluctuation caused by the harmonic drive by the eccentricity of the motor shaft eccentric pulley and the initial tension of the timing belt. The torque caused by the harmonic drive reducer can be reduced by incorporating it into the robot joint drive unit so that the phases of both torque fluctuations are opposite, or when the motor shaft is rotated in forward and reverse directions, both are close to opposite phases. The fluctuations and the torque fluctuations caused by the motor shaft eccentric pulley, reducer input shaft pulley, and timing belt cancel each other out, and as a result, the resonant vibration of the robot arm caused by the harmonic drive reducer is reduced.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 shows an embodiment of a robot vibration isolator according to the present invention, and is a sectional view of a joint drive section of a robot. In the figure, (1) is a servo motor for driving the joint, and (2) is a harmonic drive speed reducer.

The motor shaft of the servo motor (1) is provided with a motor shaft eccentric pulley (3) having a suitable eccentricity with the number of teeth n (an integer).

The input shaft of the harmonic drive reducer (2) has 2 teeth.
0 reducer input shaft pulley (4) is attached, and both pulleys are connected by a timing belt. The difference from the conventional example shown in Figure 3 is that the ratio of the number of teeth between the motor shaft pulley and the reducer input shaft pulley is 1:2.

The point is that the motor shaft pulley has an appropriate eccentricity. In addition, as shown in Fig. 2, this motor shaft eccentric pulley (3) has the geometric center of the pulley at O in order to make the pulley eccentric, whereas the motor shaft center, that is, the rotation center O1
is located at a position shifted by X. A balancing hole (9) is provided to prevent imbalance of the motor shaft eccentric pulley caused by this eccentricity.

〔Effect of the invention〕

As described in detail above, according to the present invention, the teeth of the motor shaft eccentric pulley and the motor shaft eccentric pulley with appropriate eccentricity can be adjusted without adding any new vibration isolating device mechanically or in terms of control. As a result, the torque fluctuations caused by the harmonic drive reducer are canceled out by the torque fluctuations generated by the reducer input shaft pulley and the timing belt, which have a double numerical ratio.
For example, resonance vibrations caused by harmonic drive of a robot arm can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a robot joint drive unit showing the configuration of an embodiment of a speed reduction mechanism vibration isolator according to the present invention, Fig. 2 is a plan view of a motor shaft eccentric pulley, and Fig. 3 is a conventional robot joint. It is a sectional view of a drive part. 1... Servo motor 2... Harmonic drive reducer 3... Motor shaft eccentric pulley 4... Reducer input shaft pulley 5... Timing belt 6... Cross roller bearing 7... Tension adjustment Bolt 8...Motor shaft hole 9...Balancing hole 10...Motor shaft pulley

Claims (1)

[Claims] In a robot joint drive unit including a servo motor, a harmonic drive reducer, a motor shaft pulley, a reducer input shaft pulley, and a timing belt connecting the two pulleys, the motor shaft pulley and the reducer input shaft pulley are connected to each other. A vibration isolating device for a reduction gear mechanism, characterized in that the ratio of the number of teeth is 1:2, and the motor shaft pulley has an appropriate eccentricity.