JPS6133343B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a step motor that performs stable stepwise rotation.

Figure 1a shows a conventional step motor, here 2
A diagram showing a polar single-phase step motor, and FIG. 1B is a cross-sectional view showing the rotor portion of the step motor. In FIGS. 1a and 1b, reference numeral 1 denotes a cylindrical rotor made of permanent magnets, and a stator 2 made of a magnetic material is arranged around the outer periphery of the rotor. In this case, in order to impart directionality to the rotation of the rotor 1, the stator 2 has an inner periphery at which the rotor 1 is inserted eccentrically relative to the outer periphery of the rotor 1 as shown. 3 is a coil wound around the stator 2, 4 is a transmission wheel, 5 is a tooth thereof, and 6 is a brake lever.

In other words, in such a step motor,
The rotor 1 rotates in steps of 180 degrees in the direction of the arrow in the figure each time the stator 2 is alternately excited with opposite polarity by the coil 3.

FIG. 2b is a diagram showing the operating characteristics of the conventional step motor mentioned above. The shaded area indicates the range in which the motor moves accurately for each step when a pulse voltage as shown in FIG. 2a is applied to the coil 3. The other parts show ranges in which they do not move or move too far and do not operate normally. Note that FIG. 2a shows the pulse voltage (peak value) on the vertical axis and the pulse width on the horizontal axis. In addition, Fig. 2c shows the current (curve i) of the coil 3 when a pulse voltage is applied.
) and the rotational movement of rotor 1 (shown by curve r)
This shows that.

In other words, this type of step motor performs jumping and oscillating movements, so as shown in Figure 2b, the range in which it can accurately step is extremely small, its stability is poor, and when it is incorporated into a device, it is difficult to transmit. There are problems such as a lot of wear on the gear train.

For this reason, conventional measures have been taken, such as increasing stability by engaging the brake lever with the teeth 5 of the transmission wheel 4 that transmits the rotation of the rotor 1 to the driven part, as shown in Figure 1a. Ta. That is, the impactful rotational force at the beginning of rotation is alleviated by the mechanical reaction force that is corrected when the teeth 5 of the transmission wheel 4 overcome the brake lever 6, and after the rotor 1 has rotated one step forward. , when the rotation is attempted to continue due to inertia, the next tooth 5 of the transmission wheel 4 is pressed against the brake lever 6.
The inertial force is canceled out by the reaction force generated when the robot tries to overcome the obstacle, preventing overshooting and providing stability in the walking motion.

However, in conventional step motors that apply braking by mechanical means, the brake lever 6
Advanced adjustment techniques are required, such as finely adjusting the meshing state between the teeth 5 of the transmission wheel 4 and adjusting the spring force of the brake lever 6, which not only makes it extremely difficult to mass-produce, but also makes the transmission wheel 4 There were drawbacks such as wear of the sliding portion of the brake lever 6, changes in the pressing force due to fatigue of the control lever 6, breakage, etc., and that stable operation could not be expected for a long period of time.

The present invention has been made to eliminate the above-mentioned drawbacks, and an object of the present invention is to provide a compact and inexpensive step motor that can provide stable stepping motion over a long period of time.

Embodiments of the present invention will be explained below with reference to FIGS. 3 to 5. FIG. 3a is a diagram showing an embodiment of a step motor according to the present invention, here a two-pole single-phase step motor, and FIG. 3b is a sectional view showing the rotor portion of the step motor. In these figures 3 a and b, 1, 2 and 3
1 shows a rotor, a stator, and a coil in the same way as in FIG. 1, but in this invention, the structure of the rotor 1 is different from the conventional one, as shown in detail in FIG. 3b. That is, in the figure, 11 is a cylindrical magnet made of a ferrite magnet, and 12 is a shaft that supports this cylindrical magnet 11. This shaft 12 is made of polyacetal resin or the like and is integrally formed with a hollow portion 13 located inside the cylindrical magnet 11 . Further, an appropriate amount of liquid 14 such as oil is sealed in the hollow portion 13 . Note that 15 indicates the inner wall surface of the hollow portion 13.

Next, the operation of the above-mentioned step motor of the present invention will be explained. That is, when an input pulse voltage as shown in FIG. 2a is applied to the coil 3, when the pulse voltage rises, braking is applied due to viscous friction generated between the liquid 14 and the inner wall surface 15. The impulsive magnetic power generated in the rotor 1 is suppressed. Therefore, the rotational force acting on the rotor 1 becomes gentle, the rotor 1 begins to rotate gently, and overrun is reduced. Also, when the rotor 1 steps from its initial resting position to a position rotated 180 degrees, damped vibrations occur around the normal position as shown in the last part of curve r in Figure 2c. However, in this case, each time the rotational direction of the rotor 1 is reversed, the direction of movement with the internal liquid 14 differs, so the effect of viscous friction becomes more pronounced, and an even greater braking force is applied to the rotor. 1
Acts on 1. Therefore, the vibration state of the rotor 1 is quickly damped, and the rotor 1 is quickly stopped at the normal position rotated by 180 degrees.

In the above-mentioned embodiment, a case has been described in which the hollow portion 13 is formed integrally with the shaft 12 during molding, but the present invention is not limited to this. For example, as shown in FIG. 4, a hollow portion 13 is formed by the inner wall of the cylindrical magnet 11 and lids 121 and 122 provided integrally with the shaft 12, or as shown in FIG.
Modifications such as incorporating a donut-shaped container 16 into the cylindrical magnet 11 to form the hollow portion 13 are possible.

As explained above, according to the present invention, the rotor 1 is provided with the hollow part 13, and the liquid 1 is filled in the hollow part 13.
4 is enclosed and the viscous friction of this liquid 14 is used to apply a braking force to the rotor 1, thereby suppressing the jumpy and vibratory movement of the rotor 1 and providing stable stepping motion. In addition, there is no wear and tear on the transmission wheel train, and stable operation can be expected over a long period of time.
In addition, as described above, the structure also includes liquid 1 in the rotor 1.
Since only 4 is sealed, it can be made compact without the need to add a separate braking member, etc., and there is no fear of deterioration, evaporation, or contamination of the liquid 14, and the overall cost is low. There is an effect.

[Brief explanation of the drawing]

Figures 1a and b are diagrams showing a conventional step motor and its rotor section, Figure 2a
Figures 3a to 3c are diagrams for explaining the characteristics of the step motor, Figures 3a and 3b are diagrams showing an embodiment of the stepper motor according to the present invention and its rotating parts, and Figures 4 and 5 are diagrams, respectively. It is a figure for explaining other examples of this invention. 1...Rotor, 13...Hollow part, 14...Liquid such as oil. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A step motor characterized in that a hollow portion is provided inside the rotor, a liquid is sealed in the hollow portion, and a braking force is generated on the rotor by the viscous friction of the liquid.