JP6652006B2 - DC motor protection circuit device - Google Patents

Description

  The present invention relates to a DC motor protection circuit device provided with a thermal fuse in a current path of a DC motor.

2. Description of the Related Art Conventionally, when a key switch or the like fails for some reason and abnormal continuous energization in which current is continuously applied to a motor unit of a starter occurs, the motor unit may generate heat and may be damaged. On the other hand, as a protection circuit device for preventing damage to the motor unit, it is common to provide a fuse in the motor circuit that blows and shuts off the motor circuit when abnormal continuous energization of the motor unit occurs.
Patent Literature 1 describes an example in which a motor lead wire and a brush lead wire (or a field coil) wired from the outside of the motor to the inside of the motor via a grommet are joined by a low melting point brazing material.

  A preload is applied to the grommet to separate the motor lead wire and the brush lead wire when the brazing material is melted. The brazing material functions as a fuse that melts at 400 to 700 degrees. For example, when continuous energization to the motor unit or intermittent energization for a short cycle is performed, it melts before dielectric breakdown or the like occurs in the motor unit. . When the brazing material is melted and the motor lead wire and the brush lead wire are separated by pressurization of the grommet, current to the motor unit is forcibly cut off, so that damage to the motor unit due to overheating can be prevented.

Japanese Patent No. 4117234

By the way, if the fuse functions unintentionally and early so as to correspond to the cranking load at the time of normal engine start and the motor circuit is cut off, engine start failure occurs. Therefore, for the purpose of preventing engine start failure, a thermal fuse that operates by accurately detecting a high ambient temperature inside the motor, which is one of the causes of damage to motor components, is required.
However, the fuse (blow material) disclosed in Patent Document 1 is affected by heat transfer from the brush, which becomes high in temperature during energization to the motor unit, through the brush lead wire, and is in a temperature region where there is no problem in damage to the motor unit. However, there is a problem that the motor circuit is cut off at an early stage and the motor circuit is cut off.
SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a DC motor protection circuit device having a temperature fuse that can be blown depending on the ambient temperature inside the motor. .

The present invention is applied to a DC motor in which a brush slides on a commutator provided on an armature, and when a region surrounded by a motor frame forming an outer shell of the DC motor is referred to as a motor inside, the motor is used. A DC motor protection circuit device provided with a thermal fuse in an energization path of the armature formed therein, wherein the brush is disposed between a brush lead wire connected to the brush and the thermal fuse. A heat conduction buffering member for buffering heat conduction to the thermal fuse through the brush lead wire, wherein the thermal fuse is made of a material having a lower melting point than a metal material used for the current path inside the motor. Further, it is characterized by having a resistivity that does not reach the melting point by self-resistance heat generation during energization.
According to the first aspect of the present invention, the heat conduction buffer member has a lower thermal conductivity than the brush lead, and according to the second aspect, the heat conduction buffer member has a larger heat capacity than the brush lead. .
According to the third aspect, a conductive member is provided from the outside of the motor frame to the inside of the motor to constitute a part of the power supply path, and the thermal fuse is provided on the ground side of the conductive member. A thermal conduction buffer member is arranged between the brush lead wire connected to the brush on the side and the thermal fuse, the thermal conductive buffer member is joined to the ground side of the conductive member by the thermal fuse, and the conductive member is electrically connected by the insulating member. Fixed to
According to the fourth aspect, there is provided a conductive brush plate to which a brush holder for storing a brush is attached, the brush plate is arranged in contact with the motor frame, and the thermal fuse is located on the minus side of the armature. It is provided in the power supply path and is arranged on the brush plate.
Further, according to the fifth aspect, the temperature fuse is bypassed between a portion upstream of the thermal fuse and a portion downstream thereof in the energization path inside the motor, and the thermal fuse upstream of the thermal fuse is disposed. An elastic body is provided which is electrically insulated from at least one of the part and the part on the downstream side and stores elasticity in a direction separating the part on the upstream side and the part on the downstream side from the thermal fuse.

  In the above configuration, since the heat conduction buffer member is arranged between the brush lead wire and the thermal fuse, the effect of direct heat transfer from the brush to the thermal fuse can be suppressed. Further, the thermal fuse is provided in an energizing path inside the motor, is made of a material having a lower melting point than a metal material used for the energizing path, and has a resistivity that does not reach the melting point by self-resistance heating when energized. have. As a result, it is possible to prevent the thermal fuse from being blown out early due to the effect of heat transfer from the brush, which becomes hot when energized, and to blow the thermal fuse depending on the ambient temperature inside the motor.

FIG. 2 is a sectional view of the DC motor according to the first embodiment. FIG. 2 is a configuration diagram of a DC motor protection circuit device according to the first embodiment. FIG. 4 is a configuration diagram of another DC motor protection circuit device according to the first embodiment. FIG. 8 is a cross-sectional view of a DC motor according to a second embodiment. FIG. 9 is a configuration diagram of a DC motor protection circuit device according to a second embodiment. It is VI-VI sectional drawing of FIG. FIG. 9 is a configuration diagram of another DC motor protection circuit device according to the second embodiment. 9 is a drawing showing a shape of a heat conduction buffer member according to a third embodiment. FIG. 9 is a configuration diagram of a DC motor protection circuit device using the heat conduction buffer member of FIG. 8. 13 is a view showing another shape of the heat conduction buffer member according to the third embodiment. FIG. 11 is a configuration diagram of a DC motor protection circuit device using the heat conduction buffer member of FIG. 10. FIG. 13 is a configuration diagram of a DC motor protection circuit device according to a fourth embodiment. FIG. 13 is a configuration diagram of another DC motor protection circuit device according to the fourth embodiment. FIG. 14 is a configuration diagram of a DC motor protection circuit device according to a fifth embodiment. FIG. 14 is a cross-sectional view of a starter to which the DC motor protection circuit device according to the seventh embodiment is applied. FIG. 14 is a cross-sectional view of a starter to which the DC motor protection circuit device according to the seventh embodiment is applied.

  Embodiments for carrying out the present invention will be described in detail with reference to the following examples.

[Example 1]
Before describing the DC motor protection circuit device according to the present invention, the configuration of the DC motor will be briefly described. As shown in FIG. 1, the DC motor 1 includes motor frames 2 and 3, and a field element 4, an armature 5, a commutator 6, and a brush 7 housed inside the motor frames 2 and 3. It consists of.
The motor frames 2 and 3 each include a cylindrical yoke 2 also serving as a magnetic circuit, and an end frame 3 that closes a right opening of the yoke 2 in the drawing. Hereinafter, the area enclosed by the yoke 2 and the end frame 3 is referred to as the inside of the motor.
The field element 4 is configured by, for example, arranging a plurality of permanent magnets at equal intervals in the circumferential direction on the inner periphery of the yoke 2. The armature 5 has an armature shaft 9 whose right end in the figure is rotatably supported by the end frame 3 via a bearing 8, and is fitted to the armature shaft 9 to rotate integrally with the armature shaft 9. And an armature coil 11 wound around the armature core 10.

The commutator 6 has a commutator base 6a formed of, for example, a resin material, and a plurality of commutator pieces 6b held by the commutator base 6a. The commutator base 6a is fitted and fixed to the outer periphery of the armature shaft 9 by press fitting or the like. The commutator pieces 6b are arranged in a cylindrical shape with a certain gap in the circumferential direction of the commutator base 6a, and each of the commutator pieces 6b is connected to the armature coil 11.
The brush 7 has a positive brush 7 a arranged on the plus side of the armature 5 and a negative brush 7 b (see FIG. 4) arranged on the minus side of the armature 5. And is pressed against the commutator piece 6b by a brush spring (not shown). The brush holder 12 is attached to, for example, a brush plate 13 made of iron, and the brush plate 13 is fixed to the end frame 3 with screws or the like.

As shown in FIG. 2, the DC motor protection circuit device according to the first embodiment includes a temperature fuse 15 provided in an energization path upstream of a brush lead wire 14 connected to the positive brush 7a inside the motor, and a brush lead wire. A thermal conduction buffer member disposed between the thermal fuse and the thermal fuse; The energization path is a path configured to flow a current from a battery (not shown) to the armature 5. The brush lead wire 14 is made of, for example, a stranded copper wire, and is attached to the regular brush 7a with one end embedded in the side surface of the regular brush 7a. Connected.
The thermal fuse 15 has a function of fusing depending on the ambient temperature inside the motor. The thermal fuse 15 is made of a low melting point member (for example, a solder material or a brazing material) having a melting point of 200 ° C. to 600 ° C., and has the lowest melting point among metal materials used for a current supply path inside the motor. In addition, it has a resistivity that does not reach the melting point by self-resistance heat generation during energization.

  The heat conduction buffer member 16 is formed of a metal material (for example, iron) having a lower thermal conductivity than the brush lead wire 14 and is provided in a long plate shape having a larger heat capacity than the brush lead wire 14. The heat conduction buffering member 16 has, for example, a tongue piece 16a provided at an end of a long plate, and the tongue piece 16a is folded back to sandwich the other end of the brush lead wire 14 so that the brush lead wire 14 is electrically and mechanically connected. The configuration in which the tongue piece portion 16a is folded back to sandwich the other end of the brush lead wire 14 is one specific example of connecting the heat conduction buffering member 16 and the brush lead wire 14, and this configuration has It is not limited.

The ground end of the M lead member 17 formed by, for example, a stranded wire is joined (soldered or brazed) to the heat conduction buffer member 16 by the thermal fuse 15. Note that the ground side of the M lead member 17 indicates a low potential side opposite to the battery side which is a high potential side.
The M lead member 17 constitutes a part of a current supply path to the armature 5, is held by a rubber grommet 18 (see FIG. 1) attached to the yoke 2, and is wired from outside the yoke 2 to the inside of the motor. . As shown in FIG. 3, the M lead member 17 is connected to a plate-like lead portion 17a held by a grommet 18 and inserted from outside the yoke 2 into the motor, and to the lead portion 17a outside the yoke 2. A configuration may be used in which the stranded wire 17b is combined with a stranded lead wire 17b.

[Operation and Effect of First Embodiment]
In the DC motor protection circuit device according to the first embodiment, a thermal fuse 15 is provided in an energizing path inside the motor, and a thermal conduction buffer member 16 is arranged between the thermal fuse 15 and the brush lead wire 14. The heat conduction buffering member 16 is formed of a material having a lower thermal conductivity than the brush lead wire 14 and has a larger heat capacity than the brush lead wire 14. The effect of the heat transfer can be suppressed. Further, since the M lead member 17 provided with the thermal fuse 15 contacts the outside air outside the yoke 2 and heats well, the effect of suppressing the influence of heat transfer from the positive brush 7a is improved.

  Further, the thermal fuse 15 has the lowest melting point among the metal materials used for the energizing path inside the motor, and has a resistivity that does not reach the melting point by self-resistance heat generation during energization. According to these configurations, the thermal fuse 15 does not melt under the influence of the heat transfer from the positive brush 7a that becomes high temperature when energized, and the thermal fuse 15 can function depending on the ambient temperature inside the motor. . That is, in a temperature region where there is no problem in the damage of the motor section including the armature 5, the thermal fuse 15 is not blown early due to the influence of the heat transfer from the positive brush 7a. it can.

  On the other hand, when the ambient temperature inside the motor rises to the melting point of the thermal fuse 15 (200 ° C. to 600 ° C. in the first embodiment), the metal material (metal material excluding the thermal fuse 15) used for the current supply path inside the motor is blown. In this state, the thermal fuse 15 is quickly blown to cut off the current supply path to the armature 5, so that damage to the motor unit due to overheating of the armature 5 can be prevented. In other words, the thermal fuse 15 can be blown before the ambient temperature reaches a level at which the motor unit is damaged, and the energization path to the armature 5 can be cut off, so that a highly reliable DC motor protection circuit device can be provided. If the current supply path to the armature 5 is cut off, the function of the motor itself is lost, but it is possible to prevent damage to the motor from developing into damage to the vehicle.

Hereinafter, another embodiment according to the present invention will be described.
Components and configurations that are common to the first embodiment are denoted by the same reference numerals as in the first embodiment, and detailed description thereof is omitted (see the first embodiment).
[Example 2]
In the second embodiment, as shown in FIG. 4, a DC motor protection circuit device is installed in a current path on the minus side of the armature 5.
As shown in FIGS. 5 and 6, the heat conduction buffering member 16 is electrically and mechanically connected to an end opposite to the brush side of the brush lead wire 14 connected to the negative brush 7 b, and is connected to the thermal fuse 15. It is joined to the brush plate 13. In the example shown in FIG. 5, the entire area in the width direction (the left-right direction in the drawing) of the heat-conducting buffer member 16 having a plate shape is joined to the brush plate 13 by the thermal fuse 15. In other words, the thermal fuse 15 is provided over the entire area in the width direction of the thermal conduction buffer member 16, but the thermal fuse 15 is provided at a plurality of locations around the thermal conduction buffer member 16 as shown in FIG. 7. You can also.

Also in the DC motor protection circuit device according to the second embodiment, since the heat conduction buffer member 16 is disposed between the brush lead wire 14 connected to the negative brush 7b and the thermal fuse 15, the temperature becomes high when the power is supplied. The effect of direct heat transfer from the negative brush 7b to the thermal fuse 15 can be suppressed.
The heat conduction buffering member 16 is joined to the brush plate 13 by the thermal fuse 15, and the brush plate 13 is fixed to the end frame 3. Since the end frame 3 is exposed to the outside air and has good heat dissipation, providing the thermal fuse 15 on the brush plate 13 in contact with the end frame 3 improves the effect of suppressing the influence of heat transfer from the negative brush 7b. . As a result, as in the first embodiment, the thermal fuse 15 can function depending on the ambient temperature inside the motor, and when the ambient temperature reaches the melting point of the thermal fuse 15, the thermal fuse 15 is blown and energized. By blocking the path, thermal damage to the motor unit can be prevented.

[Example 3]
In the third embodiment, for example, in a configuration in which the DC motor protection circuit device is installed in the current path on the minus side of the armature 5 described in the second embodiment, the heat conduction buffer joined to the brush plate 13 by the thermal fuse 15 is used. This is a case where the joining area of the member 16 is expanded.
As shown in FIGS. 8 and 9, the heat conduction buffering member 16 has a plate-like end connected to the brush lead wire 14 and a flat end 16b provided at the other end. The periphery of the flat portion 16 b is joined to the brush plate 13 by the thermal fuse 15 in a state of contact with the surface of the brush 13.

Alternatively, as shown in FIGS. 10 and 11, the entire heat conduction buffering member 16 is formed as a flat portion 16 b, and the flat portion 16 b is brought into contact with the surface of the brush plate 13 so as to surround the flat portion 16 b. May be joined to the brush plate 13 by the thermal fuse 15. In this case, as shown in FIG. 11, the brush lead wire 14 is connected to the heat conduction buffer member 16 by being sandwiched by the tongue piece 16a on the back side (the back side in the thickness direction) of the flat portion 16b.
In the configuration of the third embodiment, compared to the case described in the second embodiment, the joining area of the heat conduction buffering member 16 joined to the brush plate 13 by the thermal fuse 15 is enlarged, so that external force other than heat is applied. (For example, bending or shearing force due to vibration) is improved.

[Example 4]
In the fourth embodiment, for example, in the configuration in which the DC motor protection circuit device is installed in the current path on the minus side of the armature 5 described in the second embodiment, the heat conduction buffer member 16 is attached to the brush plate 13 by the insulating member 19. This is an example of fixing.
The heat conduction buffering member 16 is joined to the brush plate 13 by a thermal fuse 15 and fixed to the brush plate 13 by an insulating member 19, as shown in FIG. In this configuration, even when a large joining area of the heat conduction buffering member 16 joined to the brush plate 13 by the thermal fuse 15 cannot be secured, the heat conduction buffering member 16 is fixed to the brush plate 13 by the insulating member 19. Strength against external forces other than the above (for example, bending or shearing force due to vibration) can be improved.
The fourth embodiment can also be applied to a configuration in which a DC motor protection circuit device is installed in a current path on the plus side of the armature 5. Specifically, a configuration is also conceivable in which the thermal conduction buffer member 16 joined to the ground-side end of the M lead member 17 by the thermal fuse 15 is fixed to the M lead member 17 by the insulating member 19.

[Example 5]
In the fifth embodiment, for example, in the configuration in which the DC motor protection circuit device is installed in the current path on the minus side of the armature 5 described in the second embodiment, the temperature between the heat conduction buffer member 16 and the brush plate 13 is reduced. This is an example in which the elastic body 20 is arranged bypassing the fuse 15.
The elastic body 20 is, for example, a leaf spring made of metal, and stores elasticity in a direction in which the heat conductive buffer member 16 and the brush plate 13 are separated from each other, as shown in FIG. The elastic body 20 is electrically insulated from at least one of the heat conduction buffering member 16 and the brush plate 13. In the example of FIG. 14, an insulating material 21 is interposed between the elastic body 20 and the brush plate 13. However, the elastic body 20 may be made of a rubber material instead of a metal leaf spring. In this case, needless to say, the insulating material 21 as shown in FIG. 14 is unnecessary.

  According to the configuration of the fifth embodiment, when the thermal fuse 15 is blown depending on the ambient temperature inside the motor, the elasticity stored in the elastic body 20 separates the heat conduction buffer member 16 and the brush plate 13 apart. be able to. That is, it is possible to avoid a situation in which the heat conduction buffering member 16 and the brush plate 13 are in electrical contact with each other and the current path is not interrupted even though the thermal fuse 15 is blown. As a result, the current path of the armature 5 can be reliably cut off by blowing the thermal fuse 15, so that the reliability of the DC motor protection circuit device is improved.

[Example 6]
The DC motor protection circuit device according to the sixth embodiment is an example in which a temperature fuse 15 and a resistance fuse (not shown) are used in combination.
The resistance fuse is a fuse that is blown when the melting point is reached due to self-resistance heating during energization, and is installed in an energization path other than the brush lead wire 14 connected to the positive brush 7a on the plus side of the armature 5. Specifically, a resistance fuse can be provided between the M lead member 17 and the brush lead wire 14 inside the motor. On the other hand, the thermal fuse 15 can be installed, for example, in the current path on the minus side of the armature 5 described in the second to fifth embodiments.

For example, when abnormal continuous energization is performed on the armature 5 due to a failure such as a key switch failure for some reason, the insulating coating of the armature coil 11 is damaged (melted by heat) and the armature coil 11 is damaged. When the strands of the wires reach a short circuit, a larger current is supplied to the armature 5 than at the time of normal motor startup. In such a case, the temperature of the members (the M lead member 17, the brush lead wire 14, etc.) in the current path increases instantaneously due to the resistance heating without waiting for the rise in the ambient temperature inside the motor. In response to such an event, with the configuration of the sixth embodiment, the resistance fuse instantaneously reaches its melting point due to self-resistive heat generation and is blown, so that the energization path is quickly cut off and damage to the motor unit can be prevented. Thus, by using the thermal fuse 15 and the resistance fuse together, a highly reliable DC motor protection circuit device can be provided.
Note that the resistance fuse does not necessarily need to be provided in the energization path inside the motor, and may be provided, for example, between the plate-shaped lead portion 17a illustrated in FIG. 3 and the lead wire 17b.

[Example 7]
The seventh embodiment is an example in which the DC motor protection circuit device is applied to the DC motor 1 of the starter 21.
FIG. 15 shows a specific example in which the DC motor protection circuit device is installed in the current path on the plus side of the armature 5. For example, the case described in the first embodiment can be applied. FIG. 16 shows a specific example in which the DC motor protection circuit device is installed in the current path on the minus side of the armature 5. For example, any of the cases described in the second to sixth embodiments can be applied.

  Since the DC motor 1 used in the starter 21 is generally used at a low voltage and a high current, a state in which the pinion 22 is restrained due to some trouble from a normal engine start, or a battery that supplies power to the starter 21 Various currents are supplied to the starter 21 from the large current region to the small current region depending on the state of the above. On the other hand, in the DC motor protection circuit device of the present invention, the temperature fuse 15 functions at the target ambient temperature inside the motor regardless of the magnitude of the current. Are suitable.

(Modification)
In the first embodiment, the case where the thermal fuse 15 is formed of a solder material or a brazing material having a melting point of 200 ° C. to 600 ° C. (that is, a metal material) is described. A resin material at 200 ° C to 600 ° C can also be used. However, when a resin material is used for the thermal fuse 15, the components joined by the thermal fuse 15 (the M lead member 17 and the thermal conductive buffer member 16 in the first embodiment, the brush plate 13 and the thermal conductive buffer member in the second embodiment) 16), it is necessary to secure a state of electrical contact, that is, a conduction path.

1 DC motor 2 Yoke (motor frame)
3 End frame (motor frame)
5 Armature 6 Commutator 7 Brush 12 Brush holder 13 Brush plate 14 Brush lead wire 15 Thermal fuse (DC motor protection circuit device)
16 Heat conduction buffer member (DC motor protection circuit device)
17 M lead member (conductive member)
19 Insulating member 20 Elastic body 21 Starter

Claims (18)

Applied to a DC motor (1) in which a brush slides on a commutator (6) provided on an armature (5),
When an area surrounded by the motor frames (2, 3) forming the outer shell of the DC motor is called an inside of the motor, a thermal fuse (15) is provided in a current supply path of the armature formed inside the motor. The provided DC motor protection circuit device,
A heat conduction buffer member (16) disposed between the brush lead wire (14) connected to the brush and the thermal fuse and configured to buffer heat conduction from the brush to the thermal fuse through the brush lead wire; Have
The temperature fuse, the consists of the current path is lower material melting point than the metallic material used for the internal motor, and, have a resistivity which does not reach a melting point in the self-resistance heating during energization,
The heat conduction buffering member has a lower thermal conductivity than the brush lead wire . Applied to a DC motor in which a brush slides on a commutator provided on an armature,
When an area surrounded by a motor frame forming an outer shell of the DC motor is called an inside of the motor, a DC motor protection circuit device provided with a thermal fuse in an energization path of the armature formed inside the motor. So,
A heat conduction buffer member disposed between a brush lead wire connected to the brush and the thermal fuse, for buffering heat conduction from the brush to the thermal fuse through the brush lead wire;
The thermal fuse is made of a material having a lower melting point than a metal material used for the energization path inside the motor, and has a resistivity that does not reach the melting point by self-resistance heating when energized,
The heat conduction buffering member has a larger heat capacity than the brush lead wire . The DC motor protection circuit device according to claim 1 ,
The heat conduction buffering member has a larger heat capacity than the brush lead wire. The DC motor protection circuit device according to any one of claims 1 to 3 ,
A conductive member (17) that constitutes a part of the energization path and is disposed from the outside of the motor frame to the inside of the motor, and the thermal fuse is provided on a ground side of the conductive member;
A DC motor protection circuit device, wherein the heat conduction buffer member is disposed between the brush lead wire connected to the brush (7a) on the plus side and the thermal fuse. The DC motor protection circuit device according to claim 4,
The DC motor protection circuit device, wherein the heat conduction buffer member is joined to a ground side of the conductive member by the thermal fuse. Applied to a DC motor in which a brush slides on a commutator provided on an armature,
When an area surrounded by a motor frame forming an outer shell of the DC motor is called an inside of the motor, a DC motor protection circuit device provided with a thermal fuse in an energization path of the armature formed inside the motor. So,
A heat conduction buffer member disposed between a brush lead wire connected to the brush and the thermal fuse, for buffering heat conduction from the brush to the thermal fuse through the brush lead wire;
The thermal fuse is made of a material having a lower melting point than a metal material used for the energization path inside the motor, and has a resistivity that does not reach the melting point by self-resistance heating when energized,
A conductive member that constitutes a part of the energization path and is disposed from the outside of the motor frame to the inside of the motor, and the thermal fuse is provided on a ground side of the conductive member;
The heat conduction buffering member is arranged between the brush lead wire connected to the brush on the plus side and the thermal fuse,
The DC motor protection circuit device, wherein the heat conduction buffer member is joined to the ground side of the conductive member by the thermal fuse, and is fixed to the conductive member by an insulating member (19). The DC motor protection circuit device according to claim 4 ,
The DC motor protection circuit device, wherein the heat conduction buffer member is joined to the ground side of the conductive member by the thermal fuse, and is fixed to the conductive member by an insulating member . Applied to a DC motor in which a brush slides on a commutator provided on an armature,
When an area surrounded by a motor frame forming an outer shell of the DC motor is called an inside of the motor, a DC motor protection circuit device provided with a thermal fuse in an energization path of the armature formed inside the motor. So,
A heat conduction buffer member disposed between a brush lead wire connected to the brush and the thermal fuse, for buffering heat conduction from the brush to the thermal fuse through the brush lead wire;
The thermal fuse is made of a material having a lower melting point than a metal material used for the energization path inside the motor, and has a resistivity that does not reach the melting point by self-resistance heating when energized,
A conductive brush plate (13) to which a brush holder (12) for storing the brush is attached, wherein the brush plate is disposed in contact with the motor frame;
The DC motor protection circuit device , wherein the thermal fuse is provided in the current path on the minus side of the armature, and is disposed on the brush plate . The DC motor protection circuit device according to any one of claims 1 to 3 ,
A conductive brush plate to which a brush holder for storing the brush is attached, the brush plate being arranged in contact with the motor frame;
The DC motor protection circuit device , wherein the thermal fuse is provided in the current path on the minus side of the armature, and is disposed on the brush plate . The DC motor protection circuit device according to claim 8 or 9 ,
The heat conduction buffer member is arranged between the brush lead wire connected to the brush (7b) on the minus side and the thermal fuse, is joined to the brush plate by the thermal fuse, and is an insulating member. A DC motor protection circuit device fixed to the brush plate by (19) . The DC motor protection circuit device according to claim 8 or 9 ,
The DC motor protection circuit device, wherein the heat conduction buffer member is fixed to the brush plate by an insulating member (19) . Applied to a DC motor in which a brush slides on a commutator provided on an armature,
When an area surrounded by a motor frame forming an outer shell of the DC motor is called an inside of the motor, a DC motor protection circuit device provided with a thermal fuse in an energization path of the armature formed inside the motor. So,
A heat conduction buffer member disposed between a brush lead wire connected to the brush and the thermal fuse, for buffering heat conduction from the brush to the thermal fuse through the brush lead wire;
The thermal fuse is made of a material having a lower melting point than a metal material used for the energization path inside the motor, and has a resistivity that does not reach the melting point by self-resistance heating when energized,
In the energization path inside the motor, the thermal fuse is bypassed between a portion on the upstream side of the thermal fuse and a portion on the downstream side of the thermal fuse. A DC motor protection circuit electrically insulated from at least one of the parts and having an elastic body (20) for storing elasticity in a direction separating the part on the upstream side and the part on the downstream side from the thermal fuse; apparatus. The DC motor protection circuit device according to claim 12 ,
A conductive member that constitutes a part of the energization path and is disposed from the outside of the motor frame to the inside of the motor, and the thermal fuse is provided on a ground side of the conductive member;
A DC motor protection circuit device , wherein the heat conduction buffer member is disposed between the brush lead wire connected to the brush on the plus side and the thermal fuse . The DC motor protection circuit device according to any one of claims 1 to 11 ,
In the energization path inside the motor, the thermal fuse is bypassed between a portion on the upstream side of the thermal fuse and a portion on the downstream side of the thermal fuse. A DC motor protection circuit device, comprising: an elastic body that is electrically insulated from at least one of the parts and stores elasticity in a direction separating the part on the upstream side and the part on the downstream side from the thermal fuse . The DC motor protection circuit device according to any one of claims 1 to 14,
A DC motor protection circuit device according to claim 1, wherein the thermal fuse is made of a solder material or a brazing material having a melting point of 200C to 600C. The DC motor protection circuit device according to any one of claims 1 to 14,
A DC motor protection circuit device, wherein the thermal fuse is made of a resin material having a melting point of 200C to 600C. The DC motor protection circuit device according to any one of claims 1 to 16,
A direct current, comprising: a resistance fuse provided in the current path upstream of the brush lead wire connected to the brush on the positive side, and blown when the melting point is reached due to self-resistance heat generated when current is applied. Motor protection circuit device. A DC motor protection circuit device according to any one of claims 1 to 17, wherein the DC motor protection circuit device is applied to a DC motor for a starter (21) for starting an internal combustion engine. apparatus.

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