JPH0646206Y2 - Small motor with positive temperature coefficient thermistor - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention provides a small motor equipped with a positive temperature coefficient thermistor, especially by detecting the motor temperature to control overcurrent.
In a small motor equipped with a positive temperature coefficient thermistor designed to prevent overheating of a small motor, by mounting the above positive temperature coefficient thermistor inside the motor cover plate, the response of the positive temperature coefficient thermistor is improved, and the overheat prevention function of the small motor is prevented. The present invention relates to a small motor equipped with a positive temperature coefficient thermistor, which is capable of improving the performance of the small motor and improving the productivity of the small motor.

[Conventional technology]

FIG. 3 is a block diagram of a well-known general small motor which is a premise of the present invention. The small motor shown in FIG. 3 has a commutator fixed to a motor shaft 14 supported by a terminal 11 whose current is held by a motor cover plate 10, a brush 12 in contact with the commutator 4, and a bearing 13. By being supplied to the rotor winding 5 wound around the rotor core 15 fixed to the motor shaft 14 via 4, the permanent magnet 17 fixed to the inner peripheral surface of the motor case 16 The rotor 18 present in the field being formed is configured to rotate.

Small motors such as those shown in FIG. 3 can be used for automobile electrical equipment (eg electric mirrors, power windows, etc.),
It has a wide range of applications as a drive source for electric toys and tape recorders. However, as a matter of course, the small motor has a low output, so even if the driven part has a minor malfunction (for example, rust, dust intrusion, etc.), an overload condition (generally unrotatable condition) will occur. As a result, an undesired state in which the rotor winding 5 is overheated and eventually burned out may occur.

As a measure to prevent overheating of the rotor winding 5, bimetal,
A method of cutting off the current when an overload is used by using a fuse or a thermal element relay is considered. However, the bimetal method has poor operating characteristics at low voltage, the fuse method requires replacement of the fuse after the fuse has blown, and the thermal element relay method has a large circuit device.
There is a drawback that.

As a measure against overheating for solving the above-mentioned drawbacks, a method of supplying power from a power source 21 to a small motor 20 via a positive temperature coefficient thermistor 19 is well known as shown in FIG. The positive temperature coefficient thermistor 19 is arranged so as to be in close contact with the inside of the small motor 20 or the surface of the motor case in order to effectively detect the temperature of the small motor 20.

The PTC thermistor 19 has a certain temperature (for example, 100 ° C)
When it exceeds, the internal resistance value is rapidly increased. Accordingly, if the temperature of the small motor 20 rises due to overcurrent that flows when the small motor 20 is continuously overloaded or the rotation of the small motor 20 is forcibly locked, the positive temperature coefficient thermistor 19 Since the internal resistance value rapidly increases, it is possible to prevent the current supplied to the small motor 20 from rapidly decreasing and the small motor 20 from overheating.

[Problems to be solved by the device]

In a conventional small motor with a positive temperature coefficient thermistor, the positive temperature coefficient thermistor was mounted on the outside or inside of the motor so as to be in close contact with the motor case.

A small motor that mounts the PTC thermistor outside the motor requires an independent device that houses the PTC thermistor and has a connection terminal, etc., which not only increases the number of parts but also increases the number of mounting steps. Also increases and costs increase. Further, since it is attached to the outside of the motor, there is an undesired problem that an extra protruding portion is formed in terms of shape.

On the other hand, a small motor in which the PTC thermistor is mounted inside the motor requires a space for housing the PTC thermistor. Therefore, for example, an electric device having an overheat prevention function proposed in Japanese Utility Model Laid-Open No. Sho 61-120226 has a structure in which a housing for the positive temperature coefficient thermistor is formed by expanding a motor case. However, in the case of this configuration, not only is it troublesome to process the motor case, but there is an undesired problem that an extra protruding portion is formed in terms of shape.

[Means for Solving the Problems]

The present invention is intended to solve the above problems, and therefore, a small motor having a positive temperature coefficient thermistor according to the present invention has a plurality of stator and rotor cores having permanent magnets for forming a field. A rotor in which individual rotor windings are wound, and a current is supplied to the rotor windings via a commutator slidingly contacting a brush for power supply supported by a motor cover plate. In addition, in a small motor having a positive temperature coefficient thermistor for controlling the current to the rotor winding, a pair of brush arms made of a conductive elastic material in the motor cover plate and integrally formed with a brush for power feeding. And a pair of terminals made of a conductive elastic material and electrically connected to the brush arm and having a free end projecting outward of the motor cover plate. And a brush arm comprising at least said is one of the brush arms and electrically connected,
At least one terminal is provided so as to face each other, and a sandwiching contact portion formed in a tongue shape is provided at at least one of the facing portions of the brush arm base and the terminal, and the positive temperature coefficient thermistor is provided through this sandwiching contact portion. We adopted a technical means of forming so that it can selectively hold and hold or directly contact the brush arm base and the terminal.

〔Example〕

FIG. 1 is a perspective view of an essential part showing an embodiment of the present invention, and the same parts are designated by the same reference numerals as in FIG. In FIG. 1, reference numeral 22 is a terminal, which is formed by processing a strip-shaped member made of a conductive elastic material such as copper or copper alloy into a substantially rectangular shape. Next, 23 is a positive temperature coefficient thermistor, which is formed in a substantially rectangular plate shape and has electrodes (not shown) made of a conductive elastic material deposited on the front and back surfaces. Reference numeral 24 denotes a brush arm base, which is formed by processing and forming it into a substantially rectangular shape with the same material as that of the terminal 22, and also has a brush 12 for power supply.
Is fixed to the free end and is connected integrally with the brush arm 25 made of a conductive elastic material or so as to ensure an electrically conductive state. Next, on the motor cover plate 10, the terminal 22,
Grooves 22a, 23a, 24a corresponding to the cross-sectional shape dimensions of the positive temperature coefficient thermistor 23 and the brush arm base 24 are provided adjacent to each other and formed substantially in parallel. The groove 22a is provided so as to penetrate the motor cover plate 10, but the other grooves 23a and 24a are provided so as to open only on the inner side surface of the motor cover plate 10. Further, at the portions of the terminal 22 and the brush arm base 24 facing the positive temperature coefficient thermistor 23, the tongue pieces 22b,
Project 24b. Next, the terminal 22, thermistor 23, and the brush arm base 24 having the above-described configurations are inserted and fixed in the grooves 22a, 23a, 24a provided in the motor cover plate 10 as shown by arrows A, B, C. To do. Although not shown, another brush arm and another terminal electrically connected to the brush arm are fixed to the motor cover plate 10 so as to form a pair with the terminal 22 and the brush arm.

2 (a) and 2 (b) are enlarged cross-sectional views of the main part of the motor cover plate in the embodiment of the present invention, and the same parts are designated by the same reference numerals as in FIG. First, in FIG. 2 (a), since the positive temperature coefficient thermistor 23 is sandwiched and held by the tongues 22b and 24b provided on the terminal 22 and the brush arm base 24, it is assembled as a small motor as shown in FIG. A small motor can be driven by supplying power to the terminal 22. When the small motor is continuously overloaded or the rotation of the small motor is forcibly locked, the positive characteristics of the terminals 22 and 24b of the brush arm base 24 sandwiched and held by the tongues 22b and 24b, respectively. Since the internal resistance value of the thermistor 23 rapidly increases, the current value supplied to the small motor is rapidly reduced to prevent overheating of the small motor.

Next, FIG. 2B shows a state in which the positive temperature coefficient thermistor 23 in FIG. 2A is omitted. That is, depending on the usage mode of the small motor, there is a case where the value of the supplied current hardly changes or changes little and it is not necessary to adopt the overheat prevention measure. In such a case, the PTC thermistor 23 is removed and used. However, as shown in FIG. 2B, the tongues 22b and 24b provided on the terminal 22 and the brush arm base 24 have elasticity. At the same time, since the elastic displacement is set to be large, when the positive temperature coefficient thermistor 23 does not exist, the positive characteristic thermistor 23 is directly contacted to secure the electrical conduction state.
Therefore, there is no problem in driving the small motor.

FIG. 2 (c) is a motor cover plate in another embodiment of the present invention.
FIG. 11 is an enlarged cross-sectional view of the main part of 10, corresponding to FIGS. 2 (a) and 2 (b). In FIG. 2 (c), the groove 22a is the motor cover plate 10.
The structure is the same as that shown in FIGS. 2 (a) and 2 (b) except that the opening is provided only on the outer side surface.

With the above configuration, even if the PTC thermistor 23 and the brush arm base 24 are assembled in advance, the PTC thermistor 23 can be held at a predetermined position even if the PTC thermistor 23 is transported or otherwise handled. Then, in actual use, the terminal 22 is inserted and fitted in the groove 22a from the outer side surface of the motor cover plate 10 in the arrow direction.

Although the terminal and the brush arm base are formed in a substantially rectangular shape and the positive temperature coefficient thermistor is formed in a rectangular plate shape in the present embodiment, the present invention is not limited to these, and the shape and dimensions of a small motor are taken into consideration. Can be selected as appropriate. In addition, an example is shown in which both terminals of the terminal and the brush arm base are provided with tongue-shaped sandwiching contact portions. However, even if these sandwiching contact portions are provided on either side, the positive temperature coefficient thermistor The operation is the same as long as it is a structure capable of selectively performing the sandwiching support and the direct contact between the both.

[Effect of device]

Since the present invention has the structure and operation as described above,
An overheat prevention function can be added without increasing the number of parts and without requiring an independent device that houses the positive temperature coefficient thermistor, and the productivity of small motors can be greatly improved. Further, the positive temperature coefficient thermistor can be housed and held in the motor cover plate, there is no need to bulge the motor case, and the shape and size of the small motor can be made compact and compact.

[Brief description of drawings]

FIG. 1 is a perspective view of an essential part showing an embodiment of the present invention, FIGS. 2 (a) and 2 (b) are enlarged sectional views of an essential part of a motor cover plate in the embodiment of the present invention, and FIG. FIG. 4 is an enlarged sectional view of an essential part of a motor cover plate according to another embodiment of the present invention, FIG.
The figure is an explanatory view for explaining the overheat prevention function of the positive temperature coefficient thermistor. 10: Motor cover plate, 22: Terminal, 22b, 24b: Tongue piece, 23: Positive characteristic thermistor, 24: Brush arm base, 25: Brush arm.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yutaka Nishida, 430 Matsuhidai, Matsudo City, Chiba Prefecture, Mabuchi Motor Co., Ltd. Ki-Tochigi Prefecture Utsunomiya-shi Shimodo Matsuri 1-12-7 Sunlights Obuchi 2-505 (56) Reference JP-A-53-91358 (JP, A) Actual Kaihei 1-146763 (JP, U) Actual Kai Sho 51- 117108 (JP, U) Actually open 61-120226 (JP, U)

Claims (1)

[Scope of utility model registration request] 1. A brush for power supply, which is provided with a stator having a permanent magnet for forming a field and a rotor having a plurality of rotor windings wound around a rotor core and supported by a motor cover plate. In a small motor equipped with a positive temperature coefficient thermistor that controls the current to the rotor winding, the motor is configured to supply the current to the rotor winding through a commutator that is in sliding contact with A pair of brush arms made of a conductive elastic material and integrally formed with a power feeding brush, and a pair of brush arms made of a conductive elastic material, electrically connected to the brush arms, and having a free end protruding outside the motor cover plate. A pair of terminals formed as described above, a brush arm made of a conductive elastic material and electrically connected to at least the one brush arm, and at least one of the tar arms. And a pinch contact portion formed in a tongue shape on at least one of the opposing portions of the brush arm base and the terminal. The positive characteristic thermistor is pinched and held via the pinch contact portion. Alternatively, a small motor having a positive temperature coefficient thermistor, which is formed so that direct contact between the brush arm base and the terminal can be selectively made.