JP2003047210A - Motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To absorb a spark in a DC commutator motor. SOLUTION: Counter electromotive force, which is generated at the winding of a rotating rotor, is absorbed by connecting a spark absorbing circuit structured by connecting a constant voltage diode 71 and a capacitor 72 in series to the terminal of a winding L of the DC commutator motor.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC commutator motor. 2. Description of the Related Art Conventionally, each winding of a DC commutator motor is connected to a delta connection type as shown in FIG.
There is a star connection type as shown in FIG. The delta connection type shown in FIG. 10 has three windings L1, L2, L
3 are connected to each other, and the connection point is connected to each of the commutators P1, P2, and P3.
Since the windings L1, L2, and L3 are triangular (Δ: delta) as shown in the figure, a delta connection type is often used. In the star connection type shown in FIG. 11, one end of each of the three windings L1, L2, and L3 is connected to one point, and the other end is connected to each commutator P.
1, P2, and P3. Since the windings L1, L2, and L3 are formed in a star shape as shown in the figure in the case of a diagram, a star connection type is often referred to. However, the conventional DC commutator motor as described above has a large back electromotive force because the current instantaneously changes greatly at the moment when the commutator contacts or separates from the brush during rotation. Occurs. Since the spark generated by the back electromotive force damages the brush and the commutator, there is a problem that the demand for the motor is remarkably shortened and a problem that pulse noise is generated by the spark. In order to solve such a problem, conventionally, a varistor 701 is connected between the terminals of each winding as shown in FIG. 12 or as shown in FIG. Connect the capacitor 702 between the terminals of each winding,
Connecting resistors was done. And, since the spark absorbing element connected to each winding in this way needs to be fixed to the rotor of the motor, the size restriction is large, so that only a small element can be adopted. Are not easy to procure in general commercial products,
From the viewpoint of cost, the selection of parts was greatly restricted. For example, when the rated voltage of the motor is 100 V, it is necessary to use an electrolytic capacitor having an operating voltage of about 150 WV or more. However, since the electrolytic capacitor having such an operating voltage is not small, It was difficult to push it into the gap between the rotors. For this reason, in many cases, an electrolytic capacitor having a small capacity has to be used while recognizing that the effect is low. As described above, in addition to the problem of the life of the motor, a large amount of pulse noise that adversely affects the outside is generated. Therefore, a circuit configuration for suppressing such noise is required. There is also a problem. For example, a case where the present invention is applied to a small hand-held router using a commercial power supply shown in FIG. 14 will be described. In FIG. 14, a power supply of AC 100 V of a commercial power supply has a resistance 90 of several tens ohms.
The current is supplied to a bridge rectifier circuit 92 via a switch 91 and is rectified to a direct current. The ripple is removed by a capacitor 93 to be stabilized and supplied to a motor 94. In order to remove a large amount of pass noise generated by sparks generated in the motor 94, a noise removing circuit having a choke coil 95 of several μH and a capacitor 96 is required. However, although a small and inexpensive ceramic capacitor can be used as the capacitor 96, the choke coil 95 is neither inexpensive nor small, which has been a bottleneck for cost reduction and miniaturization of a product such as a router using the motor 94. . SUMMARY OF THE INVENTION The present invention has been made in order to provide a technique for realizing a sufficient spark absorbing ability by combining a general commercially available product having a small size in place of a special spark absorbing element. [0008] In the motor according to the present invention, a spark absorbing circuit comprising a constant voltage diode and a capacitor connected in series is connected to a terminal of a winding of the DC commutator motor. Accordingly, a measure is taken to absorb the back electromotive force generated in the winding of the rotating rotor. The connection type between the winding and the spark absorbing circuit may be a delta connection type or a star connection type. As shown in FIG. 9, the characteristics of the constant voltage diode are such that, when the applied voltage in the forward direction is equal to or higher than a predetermined voltage determined by the junction, the resistance is extremely low. When the voltage exceeds a predetermined Zener voltage, the voltage is suddenly turned on and a breakdown occurs. The back electromotive force generated in the rotating winding is several times the supplied operating voltage. Therefore, if the constant voltage diode is connected in parallel to both ends of the winding, both the back electromotive force in the forward direction and the back electromotive force in the reverse direction are short-circuited by the extremely low resistance of the winding, so that spark spark is generated. Can be suppressed. If a constant-voltage diode is directly connected to the winding directly, the operating voltage to the winding will also be short-circuited.By using a capacitor, the operating voltage, which is a DC voltage, will not Only the back electromotive force is short-circuited. In this way, the back electromotive force generated in the winding is absorbed by the spark absorbing circuit of the present invention, so that the generation of spark spark is suppressed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a motor according to the present invention will be described in detail with reference to the drawings showing an embodiment. FIG. 1 is an exploded perspective view of one embodiment of a motor according to the present invention. In FIG. 1, reference numeral 1 denotes a motor, and a pair of permanent magnets 3
Is arranged, and a bearing is arranged at the back. Reference numeral 4 denotes a support having a front bearing and a power supply brush. A power supply terminal 5 electrically connected to the power supply brush is provided on an outer surface of the support 4. Reference numeral 6 denotes a rotor mounted inside the casing 2, which includes a bearing at the back of the casing and a support 4
And is rotatably supported by a near-side bearing formed at the front side. As shown in FIG. 2, a shaft 61 of the rotor 6 has three poles of magnetic cores 62, 62, 62, windings L 1, L 2, L 3 wound around the respective magnetic cores, The two commutators P1, P2, P3 are fixed. One terminal of each of the windings L1, L2, L3 is connected to the terminal 63 of each of the three commutators P1, P2, P3. Reference numeral 7 denotes a spark absorbing circuit which is a main part of the present invention, and is inserted and fixed in a gap between three magnetic cores.
As shown in FIG. 3, the spark absorbing circuit 7 includes a constant voltage diode 71 and a capacitor 72 connected in series and covered with an insulating coating material. When the rated voltage of the motor 1 is 100V, the zener voltage of the constant voltage diode 71 is preferably set to about 150V. Generally, the Zener voltage is 1.5 times or more of the rated voltage.
The operating voltage of the capacitor 72 is 50 W lower than the rated voltage.
V, a small capacitor of about 3.3 μF can be used. Reference numeral 8 denotes a connection ring, which is a spark absorbing circuit 7.
Is a star connection type connection, each winding L1, L
2 and L3 are connected to each other. In FIG. 2, the connection ring 8 is not shown. The connection diagram of FIG. 4 is a connection diagram in the case where the winding is a delta connection type and the connection of the spark absorbing circuit is a star connection. In FIG. 4, three connection points of three windings L1, L2, L3 connected in a delta connection type are soldered to terminals of the commutators P1, P2, P3.
The three spark absorbing circuits 7, 7, 7 are connected by a star connection. That is, one terminal of each spark absorbing circuit 7 is soldered to the terminal of each commutator similarly to the winding, and the other terminal of each of the three spark absorbing circuits 7 is connected to the connection ring 8 shown in FIG. Soldered. As described above, since each spark absorbing circuit 7 is connected to each winding, the back electromotive force generated at both ends of the rotating winding is absorbed by the spark absorbing circuit 7. Therefore, the generation of sparks and sparks due to the back electromotive force is suppressed. There are two types of connection types for the three windings, a delta connection type and a star connection type, and there are two types of connection types for the three spark absorbing circuits, the delta connection type and the star connection type. As a motor,
Four combinations are possible. Therefore, other three combinations except for the combination of FIG.
As shown in FIG. Also in these figures, three windings L
1, L2, L3 and three commutators P1, P2, P3,
Three spark absorbing circuits 7, 7, 7 are shown, and the configuration of the spark absorbing circuit 7 is the same. Next, as an application form of the motor 1, a configuration example including a power supply circuit when used in a small hand-held router using a commercial power supply is shown in FIG. In FIG. 8, a power supply of AC 100 V, which is a commercial power supply, is rectified by a bridge rectifier circuit 13 through a resistor 11 and a switch 12 of several tens of ohms and supplied to the motor 1. Since the motor 1 is provided with the spark absorbing circuit 7, pulse noise is hardly generated, but the generated slight pulse noise is removed by the two ceramic capacitors 14.
The middle point of the two ceramic capacitors 14 is soldered to the metal casing 2 of the motor 1. As described above, when the motor 1 having the spark absorbing circuit 7 of the present invention is used, the spark generated in the winding can be suppressed, and the life of the motor can be extended. Also,
Since components such as a choke coil are not required, a power tool such as a hand-held router can be made sufficiently small and the cost can be reduced. It is needless to say that the present invention can be applied not only to a motor having a three-pole structure but also to various motors using a commutator. As described above, according to the motor of the present invention, the back electromotive force generated in the winding is absorbed, so that the generation of sparks can be suppressed and the life of the motor can be extended. be able to. In addition, since the generation of sparks can be suppressed, the generation of pulse noise that adversely affects the outside can be suppressed, and the noise removal circuit and the like in a power tool or the like incorporating the motor can be simplified with a simple circuit configuration. This has the effect that the size and cost can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspective view of an embodiment of a motor according to the present invention. FIG. 2 is a side view of a rotor of the motor. FIG. 3 is a side view of the spark absorbing circuit. FIG. 4 is an example of a connection diagram of windings. FIG. 5 is another example of a winding connection diagram. FIG. 6 is still another example of the connection diagram of the windings. FIG. 7 is still another example of a winding connection diagram. FIG. 8 is an example of a motor drive circuit. FIG. 9 is an example of a characteristic diagram of a low-voltage diode. FIG. 10 is an example (delta connection type) of a connection diagram of a conventional winding. FIG. 11 is another example (star connection type) of a connection diagram of a conventional winding. FIG. 12 is another example of a connection diagram of a conventional winding. FIG. 13 is another example of a connection diagram of a conventional winding. FIG. 14 is an example of a conventional motor drive circuit. [Description of Signs] 1 Motor 2 Casing 3 Permanent magnet 4 Support 5 Power supply terminal 6 Rotors L1, L2, L3 Windings P1, P2, P3 Commutator 7 Spark absorption circuit 71 Constant voltage diode 72 Capacitor

Claims (1)

Claims: 1. A winding of a rotating rotor by connecting a spark absorbing circuit formed by connecting a constant voltage diode and a capacitor in series to a terminal of a winding of a DC commutator motor. A motor configured to absorb back electromotive force generated in the motor.