JP2000152586A - Dc motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the maximum starting current of a DC motor which has four or more brushes around an armature substantially in comparison with the maximum starting current of a conventional constitution with simple structure. SOLUTION: A DC motor has four or more brushes B1, B2, B3 and B4 arranged around an armature 11 whose revolution is changed by changing the number of brushes B1, B2, B3 and/or B4 to which a current is applied. A relay 35 which is closed by an electromotive force generated by the rotation of the armature 11 is attached to at least one of the brushes B1, B2, B3 and B4 and a current is applied to that brush B1, B2, B3 or B4 through the closed relay 35.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC motor, and more particularly, to a DC motor having four or more brushes arranged around an armature.

[0002]

2. Description of the Related Art Conventionally, four brushes are arranged around an armature, and by changing the number of brushes to be energized,
2. Description of the Related Art DC motors that change the rotation speed of an armature are known.
FIG. 5 shows this type of DC motor. This DC motor is used for driving a radiator cooling fan or an air conditioning fan of an automobile.

In this DC motor, first to fourth four brushes B1, B2, B
3, B4 are arranged. A voltage of, for example, 12 V is applied to the first brush B1 via the start switch 2. Further, the second brush B2 is directly grounded, the third brush B3 is applied with a voltage of 12 V via the switch 3, and the fourth brush B4 is grounded via the switch 4.

[0004] In such a DC motor, the armature 1 is rotated at a low speed by turning on the start switch 2.
By turning on the start switch 2 and the switch 3, the armature 1 is rotated at a medium speed. Further, by turning on the start switch 2 and the switches 3 and 4, the armature 1 is rotated at a high speed.

That is, in such a DC motor, the rotational speed of the armature 1 is changed by changing the number of brushes B1, B2, B3, B4 to be energized.

[0006]

However, in such a conventional DC motor, when the start switch 2 and the switches 3 and 4 are simultaneously turned on to directly bring the armature 1 into a high-speed rotation state, the steady-state current becomes 3 to 3 times. There is a problem that a large starting current of about six times occurs.

When such a DC motor is used to drive a radiator cooling fan or an air-conditioning fan of an automobile, fuse jumps and headlights of the electric system of the automobile are momentarily darkened. There was a possibility that troubles such as becoming inconsistent would occur. The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide a DC motor capable of greatly reducing the maximum starting current generated by a very simple configuration as compared with the conventional motor. .

[0008]

According to a first aspect of the present invention, there is provided a DC motor in which four or more brushes are arranged around an armature and the number of brushes to be energized is changed to reduce the number of rotations of the armature. In the DC motor that changes, at least one of the brushes is provided with a relay that is turned on by a back electromotive force due to rotation of the armature and energizes the brushes.

In the DC motor according to the first aspect, when the start switch is turned on, a part or all of the brushes except for at least one brush is energized, and the armature is rotated. Then, after the back electromotive force generated by the rotation of the armature reaches a predetermined value, the relay is turned on, the one brush is energized, and the rotation speed of the armature is increased.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a first embodiment of a DC motor according to the present invention.
For example, it is used for driving a fan for cooling a radiator of an automobile or a fan for air conditioning.

In this DC motor, the armature 11
Around the first to fourth four brushes B1, B2, B
3, B4 are arranged. 1st to 4th brush B
1, B2, B3, and B4 have first to fourth wirings 21,
22, 23 and 24 are connected. First brush B1
The first wiring 21 is connected to, for example, a 12 V DC power supply 33 via a start switch 31.

Also, the second wiring 2 of the second brush B2
The second and fourth wirings 24 of the fourth brush B4 are directly grounded. Then, the third brush B3
Is connected to one end of the coil 37 and a contact 39 of a relay 35 having a coil 37 and a contact 39 that is turned on by energizing the coil 37.

The other end of the contact 39 is connected to a first wiring 21 via a fifth wiring 25,
The other end of 7 is connected to the second wiring 22. In the DC motor described above, when the start switch 31 is turned on,
First, the first brush B1, the second brush B2, and the fourth
, And the armature 11 is rotated in the medium-speed rotation state.

The rotation of the armature 11 causes the third
After the back electromotive force generated in the third brush B3 reaches a predetermined value, the contact 39 of the relay 35 is turned on, and the third brush B3 is turned on.
3, the rotation speed of the armature 11 is increased and the armature 11 enters a high-speed rotation state. As described above, by delaying the energization to the brush B3 with a very simple configuration, the generated maximum starting current can be significantly reduced as compared with the related art.

That is, FIG. 2 shows a starting current generated when the starting switch 31 of the DC motor is turned on. First, when the starting switch 31 is turned on, a first starting current A1 is generated. After the back electromotive force generated by the rotation of the armature 11 reaches a predetermined value, for example, 0.2
It can be seen that a second start-up current A2 smaller than the first start-up current A1 has occurred after a lapse of ０．５0.5 seconds.

The maximum starting current at this time is about 2
1.5A. Note that the curve shown by the two-dot chain line in FIG. 2 is the starting current A0 when the first to fourth brushes B1, B2, B3, and B4 are simultaneously energized by turning on the starting switch 31, and the maximum starting current is , About 34.5A. Therefore, in this embodiment, the maximum starting current can be reduced by about 13.0 A, that is, 38% from the conventional one.

FIG. 3 shows a second embodiment of the DC motor according to the present invention. In this embodiment, a second motor which is turned on by energizing the coil 37 to the relay 35 of the first embodiment is shown. 35A in which additional contacts 41 are arranged
And the fourth wiring 24 connected to the fourth brush B4
A is connected to one end of the contact 41 of the relay 35A.

The other end of the contact 41 is connected to a second wiring 22. In this embodiment, the contact 39 and the second contact 41 are excited by the coil 37 of the relay 35A.
Are turned on at the same time, and the third brush B3 and the fourth brush B4 are energized simultaneously.

Note that, in the second embodiment, the first
The same reference numerals are given to the same members as those of the embodiment, and the detailed description is omitted. In the above-described DC motor, when the start switch 31 is turned on, first, the first brush B1 and the second brush B2 are energized, and the armature 11 is rotated at a low speed.

After the back electromotive force generated by the rotation of the armature 11 reaches a predetermined value, the first contact 39 and the second contact 41 of the relay 35A are turned on, and the third brush B3 and the third The brush B4 of No. 4 is energized to increase the rotation speed of the armature 11 and enter a high-speed rotation state. As described above, with a very simple configuration, by delaying the energization of the brushes B3 and B4, the generated maximum starting current can be significantly reduced as compared with the related art.

FIG. 4 shows a third embodiment of a DC motor according to the present invention. In this embodiment, a fourth brush B is used.
The fourth switch 24 is connected to the second switch 43.
Is arranged. In the third embodiment, the same members as those in the first embodiment are denoted by the same reference numerals, and the detailed description is omitted.

In the above-described DC motor, when the start switch 31 is turned on with the second switch 43 turned off, first, the first brush B1 and the second brush B2 are energized, and the armature 11 is driven at a low speed. It is rotated in a rotating state. Then, after the back electromotive force generated by the rotation of the armature 11 reaches a predetermined value, the contact 39 of the relay 35 is turned on, and the third brush B3 is energized to increase the rotation speed of the armature 11. It becomes a state of high speed rotation.

Thereafter, the second switch 43 is turned on as necessary, whereby the rotation speed of the armature 11 is increased and the armature 11 enters a high-speed rotation state. As described above, with a very simple configuration, by delaying the energization of the brush B3,
The generated maximum starting current can be greatly reduced as compared with the related art. In the above-described embodiment, for example, when the coolant temperature of the radiator of the automobile is relatively low, only the start switch 31 is turned on, and when the coolant temperature becomes higher than the predetermined temperature, the second Switch 43 is turned on.

[0024]

As described above, in the DC motor according to the first aspect, after the back electromotive force generated by the rotation of the armature reaches a predetermined value, the relay is turned on and the brush connected to the relay is turned on. Since the energization increases the rotation speed of the armature, the generated maximum starting current can be significantly reduced with a very simple configuration.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a DC motor according to the present invention.

FIG. 2 is an explanatory diagram showing a starting current generated in the DC motor of FIG. 1;

FIG. 3 is a circuit diagram showing a second embodiment of the DC motor of the present invention.

FIG. 4 is a circuit diagram showing a third embodiment of the DC motor according to the present invention.

FIG. 5 is a circuit diagram showing a conventional DC motor.

[Explanation of symbols]

 11 Armature B1 First brush B2 Second brush B3 Third brush B4 Fourth brush 35, 35A Relay

Claims (1)

[Claims] 1. Arranging four or more brushes (B1, B2, B3, B4) around an armature (11), and changing the number of brushes (B1, B2, B3, B4) to be energized. In the DC motor that changes the rotation speed of the armature (11), at least one of the brushes (B1, B2, B3, B
4), the brush (B1, B2, B3, B4) is turned on by the back electromotive force due to the rotation of the armature (11).
A DC motor comprising a relay (35, 35A) for energizing a motor.