JP2006158032A - Dc motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inhibit a reduction in the motor efficiency due to an abrasion of a brush, and maintain the high efficiency. <P>SOLUTION: A DC motor is provided with a stator and a rotor. The rotor includes a shaft, a commutator and an armature provided on the shaft. The commutator includes a plurality of segments. The armature includes a coil. The coil and the commutator are delta-connected. The brush is provided in the commutator, contacts the commutator, and is formed from a single material as a block. A cross-section area of a contact with the commutator is the same as a cross-section area of a region from the contact to an opposite end. If a ratio of a resistance Rb of the brush to a resistance Rc of the coil is a resistance ratio Rb/Rc, there is a relationship for increasing/decreasing the motor efficiency so as to have one peak in response to an increase in the resistance ratio Rb/Rc. When the DC motor is new, the resistance ratio Rb/Rc is configured to a value within a predetermined range (35-45%) corresponding to a decrease in the motor efficiency from the peak in response to the increase in the resistance ratio Rb/Rc. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a DC motor including a commutator and a brush that contacts the commutator.

  Conventionally, as this type of DC motor, for example, there is an electric motor described in Patent Document 1 below. The brush of this electric motor is formed of two or more kinds of conductive materials having substantially the same total length of the portion that wears in contact with the commutator. That is, this brush is composed of a brush main portion formed of a conductive material having the highest resistivity among the conductive materials and a conductor formed of another conductive material having a lower resistivity than the conductive material of the brush main portion. Is done. Inside the brush main part, a plurality of conductors are dispersed and embedded along the longitudinal direction of the brush main part. The electric motor described in Patent Document 1 can reduce the resistance loss of the current in the brush by using the brush as described above, and can improve the operation efficiency.

JP-A-5-103447 (page 2-5, FIGS. 1 and 3)

  However, Patent Document 1 describes that the brush wears and the relationship between the brush wear powder and the substance that inhibits the flow of current, but the change in the resistance value of the brush due to the wear of the brush. Is not described or suggested. Here, since the DC motor is a device that converts electric power into power, its “efficiency” becomes a problem. The “efficiency” of a motor is the percentage of the mechanical output to electrical input expressed as a percentage. In general, resistance causes copper loss and reduces the efficiency of the motor. Therefore, as the material used for the brush, a material having a resistance value as small as possible within the allowable range of cost and reliability is selected. In addition, Patent Document 1 describes the relationship between the resistance value of a brush and the resistance value of a winding used in a DC motor, for example, the ratio of the resistance value of a brush to the resistance value of a winding used in a DC motor (hereinafter referred to as the resistance value of the brush). "Resistance ratio" is not described or suggested. Also, nothing is described in Patent Document 1 regarding the relationship between the “resistance value ratio” and the “efficiency” of the motor. Therefore, in the electric motor described in Patent Document 1, it cannot be said that the optimum value for the “efficiency” of the motor is used in relation to the above “resistance ratio”. Further, when the brush wears and the resistance value of the brush changes, the above-mentioned “resistance value ratio” changes, and there is a problem that the “efficiency” of the motor decreases.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a DC motor capable of maintaining high efficiency by suppressing reduction in efficiency of the motor due to brush wear.

  In order to achieve the above-mentioned object, the invention according to claim 1 includes a stator and a rotor, the rotor including a shaft, a commutator and an armature provided on the shaft, and a plurality of commutators. The armature includes a winding wound with a conductive wire, the winding and the commutator are delta-connected, and a brush provided in contact with the commutator is provided. In the motor, the brush is formed in a block shape from a single material, and the cross-sectional area of the contact portion with the commutator and the cross-sectional area of each part from the contact portion to the end opposite to the contact portion. And the ratio of the resistance value of the brush to the resistance value of the winding is the resistance value ratio, the motor efficiency increases or decreases so that it has a single peak with respect to the increase in the resistance value ratio. To have a new relationship During the resistance ratio, the efficiency of the motor and the spirit further comprising a setting to the value of the predetermined range corresponding to the side to decrease from the peak with an increase in the resistance ratio.

According to the configuration of the above invention, as the DC motor is used, the contact portion of the brush that contacts the commutator is worn and the brush is shortened. Here, the brush is formed in a block shape with a single material, and the cross-sectional area of the contact portion with the commutator and the cross-sectional area of each part from the contact portion to the end opposite to the contact portion. Are the same, the cross-sectional area of the contact portion that changes due to wear is always the same, and the resistance value of the brush is reduced by the amount that the brush becomes shorter due to wear.
Here, when the ratio of the resistance value of the brush to the resistance value of the winding is the resistance value ratio, the motor efficiency has a relationship to increase or decrease to have one peak with respect to the increase in the resistance value ratio. As the DC motor is used, the brush becomes shorter, so that the resistance value ratio decreases. In the above invention, when the DC motor is used, the resistance value ratio is set to a value within a predetermined range corresponding to the side where the efficiency of the motor decreases from the peak with respect to the increase in the resistance value ratio. The resistance ratio decreases from the predetermined range, and the motor efficiency increases toward the peak, and then decreases from the peak. The motor efficiency becomes a value including the peak.

  In order to achieve the above object, the invention according to claim 2 is characterized in that when the resistance value ratio corresponding to the peak is 25%, the resistance value ratio corresponding to the predetermined range is 35 to 45%. To do.

  According to the configuration of the invention described above, in the operation of the invention according to claim 1, when the resistance value ratio corresponding to the peak is 25%, the resistance value ratio at the time of a new article corresponds to the predetermined range described above. Since the resistance value ratio is 35 to 45%, when the resistance value of the brush decreases as the DC motor is used, the resistance value ratio decreases from 35 to 45% toward 25%, so that the motor efficiency is reduced. Increases toward the peak, and then the resistance ratio decreases from 25%, so that the motor efficiency decreases from the peak, and the motor efficiency becomes a value including the peak.

  In order to achieve the above object, a third aspect of the present invention includes a stator and a rotor, the rotor including a shaft, a commutator and an armature provided on the shaft, and a plurality of commutators. The armature includes a winding wound with a conductive wire, the winding and the commutator are delta-connected, and a brush provided in contact with the commutator is provided. In a motor, the brush is formed in a block shape from a single material, and the cross-sectional area of the contact portion with the commutator is maximized, and each part from the contact portion to the end opposite to the contact portion is formed. It is intended that the cross-sectional area is configured to decrease as the distance from the contact portion increases.

  According to the configuration of the above invention, as the DC motor is used, the contact portion of the brush that contacts the commutator is worn and the brush is shortened. On the other hand, the brush is formed in a block shape with a single material, and the cross-sectional area of the contact portion with the commutator is maximized, and each part from the contact portion to the end opposite to the contact portion. Since the cross-sectional area of the contact portion is configured to decrease as the distance from the contact portion increases, the cross-sectional area of the contact portion that changes due to wear gradually decreases. Therefore, since the cross-sectional area of the contact portion is reduced by the shorter brush, the change in the resistance value of the brush is generally reduced. Here, it is known that the efficiency of the motor changes according to the change in the resistance value of the brush. For this reason, even if the DC motor is used for a certain period of time and the brush wears, the change in the resistance value of the brush is small, so the change in the efficiency of the motor is also smaller than that when it is new.

  In order to achieve the above object, a fourth aspect of the present invention includes a stator and a rotor, the rotor including a shaft, a commutator and an armature provided on the shaft, and a plurality of commutators. The armature includes a winding wound with a conductive wire, the winding and the commutator are delta-connected, and a brush provided in contact with the commutator is provided. In the motor, the brush is formed in a block shape with a plurality of materials having different resistivity, and the cross-sectional area of the contact portion with the commutator and each part from the contact portion to the end opposite to the contact portion The ratio of the material with high resistivity in the cross section in each part from the contact portion with the commutator to the end opposite to the contact portion increases as the distance from the contact portion increases. Is configured to That the purpose of the.

  According to the configuration of the above invention, as the DC motor is used, the contact portion of the brush that contacts the commutator is worn and the brush is shortened. On the other hand, the brush is formed in a block shape by a plurality of materials having different resistivity, and the cross-sectional area of the contact portion with the commutator and each of the contact portion to the end opposite to the contact portion. The cross-sectional area of the part is configured to be the same. In addition, the ratio of the material having a high resistivity in the cross section in each part from the contact portion with the commutator to the end portion on the opposite side of the contact portion is configured to increase as the distance from the contact portion increases. For this reason, the cross-sectional area of the contact portion that changes due to wear is always the same, but the proportion of the material having high resistivity in the cross-section increases. Accordingly, since the resistance value of the contact portion increases as the brush becomes shorter, the change in the resistance value of the brush is generally reduced. Here, it is known that the efficiency of the motor changes according to the change in the resistance value of the brush. For this reason, even if the DC motor is used for a certain period of time and the brush wears, the change in the resistance value of the brush is small, so the change in the efficiency of the motor is also smaller than that when it is new.

  In order to achieve the above object, according to a fifth aspect of the present invention, there is provided a stator and a rotor, the rotor including a shaft, a commutator and an armature provided on the shaft, and a plurality of commutators. The armature includes a winding wound with a conductive wire, the winding and the commutator are delta-connected, and a brush provided in contact with the commutator is provided. In the motor, the brush is formed in a block shape by a plurality of materials having different resistivity, and the cross-sectional area of the contact portion with the commutator is maximized, and from the contact portion to the end opposite to the contact portion. The ratio of the material with high resistivity in the cross section in each part from the contact part with the commutator to the end on the opposite side of the contact part is configured so that the cross-sectional area of each part decreases as the distance from the contact part increases. But contact part And purpose to be configured to increase the farther al.

  According to the configuration of the above invention, as the DC motor is used, the contact portion of the brush that contacts the commutator is worn and the brush is shortened. On the other hand, the brush is formed in a block shape from a plurality of materials having different resistivity, and the cross-sectional area of the contact portion with the commutator is maximized, from the contact portion to the end opposite to the contact portion. It is comprised so that the cross-sectional area of each site | part may reduce, so that it leaves | separates from a contact part. In addition, the ratio of the material having a high resistivity in the cross section in each part from the contact portion with the commutator to the end portion on the opposite side of the contact portion is configured to increase as the distance from the contact portion increases. Accordingly, the cross-sectional area of the contact portion is reduced and the cross-sectional resistivity of the contact portion is increased as the brush is shortened, so that the change in the resistance value of the brush is generally reduced. Here, it is known that the efficiency of the motor changes according to the change in the resistance value of the brush. For this reason, even if the DC motor is used for a certain period of time and the brush wears, the change in the resistance value of the brush is small, so the change in the efficiency of the motor is also smaller than that when it is new.

  In order to achieve the above object, the invention according to claim 6 is the invention according to claim 3 or 5, wherein the brush is arranged such that the central axis of the brush is perpendicular to the axis of the shaft, It is intended that the cross-sectional area of the brush is reduced by decreasing the width of the brush in a direction parallel to the axis of the shaft as the distance from the contact portion increases.

  According to the configuration of the above invention, in the operation of the invention described in claim 3 or 5, the cross-sectional area of the brush is reduced by reducing the width of the brush in the direction parallel to the shaft axis by the amount that the brush becomes shorter due to wear. Becomes smaller. In this case, about the brush, the cross-sectional area of the contact part of a brush can be made small by changing the width | variety of the direction which does not change a brush width angle.

  In order to achieve the above object, the invention according to claim 7 is the invention according to claim 3 or 5, wherein the brush is arranged such that the central axis of the brush is parallel to the axis of the shaft, The point is that the cross-sectional area of the brush is reduced by decreasing the width of the brush in the direction perpendicular to the axis of the shaft as the distance from the contact portion increases.

  According to the configuration of the invention described above, in the operation of the invention according to claim 3 or 5, the cross-sectional area of the brush is reduced by reducing the width of the brush in the direction perpendicular to the axis of the shaft by the amount that the brush becomes shorter due to wear. Becomes smaller. In this case, about the brush, the cross-sectional area of the contact part of a brush can be made small by changing the width | variety of the direction which does not change a brush width angle.

  In order to achieve the above object, the invention according to claim 8 is the invention according to any one of claims 3 to 7, wherein the ratio of the resistance value of the brush to the resistance value of the winding is a resistance value ratio. The motor efficiency has a relationship to increase or decrease to have one peak with respect to the increase in resistance value ratio, and when new, the resistance value ratio is set to the value when the motor efficiency peaks. The purpose is to have

  According to the configuration of the invention, in the operation of the invention according to any one of claims 3 to 7, the resistance value ratio is set to a value when the motor efficiency reaches a peak, so that the DC motor has a certain period. Even if it is used, the efficiency of the motor is less changed with respect to the peak value.

  According to the first or second aspect of the invention, even if the brush is worn, the efficiency of the motor becomes a value including a peak. Therefore, a reduction in the efficiency of the motor due to the wear of the brush can be suppressed, and the efficiency of the motor can be reduced. A relatively high value can be maintained.

  According to the invention according to any one of claims 3 to 5, since the change in the resistance value of the brush is small and the change in the resistance value ratio is small even when the brush is worn, the motor efficiency is reduced due to the wear of the brush. And the motor efficiency can be maintained at a relatively high value.

  According to the invention described in claim 6 or 7, in addition to the effect of the invention described in claim 3 or 5, the change in the efficiency of the motor can be suppressed by the amount that the brush width angle does not change.

  According to the invention described in claim 8, compared with the invention described in any one of claims 3 to 7, even if the brush is worn, the change in the efficiency of the motor is small with respect to the peak value. Therefore, a reduction in motor efficiency due to brush wear can be suppressed, and the motor efficiency can be maintained at a value close to the maximum.

[First Embodiment]
Hereinafter, a first embodiment in which the DC motor of the present invention is embodied as a concentrated winding brushed DC motor will be described in detail with reference to the drawings.

  The basic structure of the concentrated winding brushed DC motor (hereinafter simply referred to as “DC motor”) of this embodiment is basically the same as that of a conventional general DC motor. FIG. 1 is a plan view showing a main internal configuration of a DC motor according to the present embodiment. FIG. 2 is a plan view showing the relationship between the commutator and the brush. This DC motor is mainly used for an electric fuel pump.

  This DC motor includes a stator 1 and a rotor 2. The stator 1 includes a housing 3 that also serves as a yoke, and an annular field magnet 4 that is disposed inside the housing 3. The field magnet 4 is composed of a plurality of pole pairs 5 each having an adjacent N pole and S pole as one pole pair.

  The rotor 2 includes a shaft 6 and a commutator 7 and an armature 8 provided on the shaft 6. The armature 8 is an iron core, and includes a plurality of slots (iron core grooves) 9. A conductive wire 10 is wound between adjacent slots 9, and a coil 11 as a concentrated winding is wound by the conductive wires 10. Composed.

  As shown in FIGS. 1 and 2, the commutator 7 is formed in a cylindrical shape by a plurality of fan-shaped segments 7 a. Each segment 7a is separated from each other through a slit 7b. A plurality of brushes 12 for energization are provided on the end face of the commutator 7 so as to be in contact with each other. These brushes 12 are supported by a bracket (not shown) that covers the end of the housing 3.

  As shown in FIG. 3, the connection method between each segment 7a of the commutator 7 and each conductor 10 is a delta connection. The number of pole pairs 5 of the field magnet 4 (hereinafter referred to as “pole pair number”) Np is “2”, and the number of slots 9 (hereinafter referred to as “slot number”) Ns is “6”. ing.

As shown in FIG. 2, when an angle formed by two tangents circumscribing from the axis L in the width direction of each brush 12 around the axis L of the shaft 6 is defined as a brush width angle A, in this embodiment, the brush The width angle A is an angle in the range of “10 to 15 °”. In general, the “motor efficiency” varies depending on the difference in the brush width angle A. Here, the efficiency of the motor means a ratio of output (torque × rotational speed) to input power of the motor. FIG. 4 is a graph showing the relationship between the brush width angle A and the motor efficiency. As is apparent from this graph, the motor efficiency is generally high in the range of the brush width angle A of “about 10 to 15 °”. Therefore, in this embodiment, the brush width angle A is set to an angle in the range of “10 to 15 °”.
The above is the basic structure of a concentrated winding brushed DC motor.

  Here, the DC motor of this embodiment is characterized by the following configuration. 5 is a front view of the brush 12, and FIG. 6 is a plan view of the brush 12. The brush 12 is formed in a rectangular parallelepiped block shape from a single conductive material. In FIG. 5, the lower surface of the brush 12 is a contact portion 12 a with the commutator 7. Further, in FIG. 5, electric wires 13 for electrical wiring are provided on the upper surface of the brush 12, that is, on an end portion (opposite end portion) 12 b opposite to the contact portion 12 a. Here, the brush 12 is configured such that the cross-sectional area of the contact portion 12a with the commutator 7 is the same as the cross-sectional area of each portion from the contact portion 12a to the opposite end portion 12b.

  Here, if the ratio of the resistance value Rb of the brush 12 to the resistance value Rc of the coil 11 is defined as a resistance value ratio Rb / Rc, as shown in FIG. 7, the DC motor of this embodiment has a resistance value ratio Rb / Rc. The motor efficiency is increased or decreased so that the motor efficiency has one peak. In the DC motor of this embodiment, the resistance value ratio Rb / Rc is reduced from the peak when the motor efficiency is increased with respect to the increase in the resistance value ratio Rb / Rc. Is set to a value in a predetermined range corresponding to. In this embodiment, when the resistance value ratio Rb / Rc corresponding to the peak is “25%”, the resistance value ratio Rb / Rc corresponding to the predetermined range is set to be “35 to 45%”.

  The characteristics of the motor efficiency with respect to the resistance value ratio Rb / Rc as shown in FIG. 7 are newly discovered by the applicant of the present application, and the reason for the characteristics will be described below. In a DC motor with a brush in which each coil and commutator are delta-connected, as shown in FIG. 8, when the brush is in a state of straddling the commutator segment, as shown in FIG. Will flow. This state is shown by an equivalent circuit diagram in FIG. In FIG. 9, “R1 and R2” indicate the resistance values of the brush. When the position of the brush on the commutator is changed and the brush is completely on one segment of the commutator, an equivalent circuit diagram is obtained. Is as shown in FIG. In FIG. 10, the resistance value of the brush is “R1 = R2 = Rb”. When the DC motor operates and the shaft rotates, the state of the equivalent circuit diagram of FIG. 9 and the state of the equivalent circuit diagram of FIG. 10 are alternately repeated. Therefore, according to a predetermined analysis, in the state of the equivalent circuit diagrams of FIGS. 9 and 10, the voltage value applied to the coil and the brush is the ratio of the resistance value Rb of the brush to the resistance value Rc of the coil, that is, the resistance value ratio Rb. It was found that it changed with / Rc.

  Here, in the conventional analysis, as shown in FIG. 10, the brush resistance value Rb is simply calculated as a resistance value Rb connected in series to the coil resistance value Rc. Therefore, the resistance of the brush is not only a loss, but has a characteristic indicated by a broken line in FIG. In other words, the efficiency of the motor decreases as the resistance value Rb of the brush increases and the resistance value ratio Rb / Rc increases. For this reason, conventionally, it has been considered that the smaller the brush resistance value Rb, the better the motor efficiency.

  However, as shown in FIG. 8, the DC motor of the present embodiment has a state in which the brush straddles the commutator segment, and therefore the state of the equivalent circuit diagram of FIG. 9 exists. At this time, a closed circuit is constituted by the resistance value Rc of the coil and the resistance values R1 and R2 divided by the brush, and a short-circuit current as shown in FIGS. Accordingly, the actual DC motor repeats the states of the equivalent circuit diagrams of FIGS. 9 and 10 alternately. Therefore, the present analysis was performed in consideration of this fact.

  If the closed circuit shown in FIG. 9 exists when the DC motor is operating, that is, the shaft is rotating, an induced electromotive force is generated due to a change in the magnetic field due to the rotation, and the circuits shown in FIGS. The short-circuit current shown flows. This short circuit current has the same property as the eddy current generated in the magnetic material of the DC motor, and the current flows in a direction that prevents the change of the magnetic field. For this reason, the torque of the DC motor is reduced, and the energy for generating the short-circuit current is obtained from the power supply power of the DC motor, so that an extra current flows as compared with the case where the short-circuit current does not occur. This causes a reduction in the efficiency of the motor.

  From the above, when paying attention only to the short-circuit current described above, the larger the brush resistance value Rb, the larger the divided resistance values R1 and R2, so that the short-circuit current can be reduced and the loss due to the short-circuit current can be reduced. Can be minimized. From this, when an analysis was performed in consideration of the short-circuit current, the characteristic shown by the solid line in FIG. 11 is obtained, and when the resistance value of the brush becomes a certain value, that is, the resistance value ratio Rb / Rc. When becomes a certain value, the efficiency of the motor shows a peak. As described above, the characteristics of the motor efficiency with respect to the resistance value ratio Rb / Rc are as shown by the solid lines in FIGS.

  According to the configuration of the DC motor of this embodiment described above, as the DC motor is used, the contact portion 12a of each brush 12 that contacts the commutator 7 is worn and each brush 12 is shortened. Here, each brush 12 is formed in a rectangular parallelepiped block shape with a single material, and the cross-sectional area of the contact portion 12a with the commutator 7 and each of the contact portion 12a to the opposite end portion 12b. Since the cross-sectional area of the part is configured to be the same, the cross-sectional area of the contact portion 12a that changes due to wear is always the same. For this reason, the resistance value Rb of the brush 12 is reduced by the amount that the brush 12 is shortened due to wear.

  Here, as shown in FIG. 7, the DC motor of this embodiment has a relationship in which the efficiency of the motor increases or decreases to have one peak with respect to the increase in the resistance value ratio Rb / Rc. As the brush 12 is shortened as the value is used, the resistance value ratio Rb / Rc decreases. In this embodiment, when new, the resistance value ratio Rb / Rc is set to a value in a predetermined range corresponding to the side where the motor efficiency decreases from the peak with respect to the increase in the resistance value ratio Rb / Rc. Therefore, as the DC motor is used, the resistance value ratio Rb / Rc decreases from the predetermined range, the motor efficiency increases toward the peak, and then decreases from the peak, and the motor efficiency reaches the peak. The value including Specifically, as shown in FIGS. 7 and 11, when the resistance value ratio Rb / Rc at the time of a new article is 25%, the above-mentioned predetermined range The resistance value ratio Rb / Rc corresponding to is “35 to 45%”. As a result, when the resistance value Rb of the brush 12 decreases as the DC motor is used, the resistance value ratio Rb / Rc decreases from “35 to 45%” to “25%”. Increases toward the peak, and then the resistance value ratio Rb / Rc decreases from “25%”, so that the motor efficiency decreases from the peak, and the motor efficiency becomes a value including the peak. For this reason, the reduction in the efficiency of the motor due to the wear of the brush 12 can be suppressed, and the efficiency of the motor can be maintained at a relatively high value.

  Here, with reference to FIG.7 and FIG.11, the efficiency of the motor before and after the use start of a DC motor is examined. According to the conventional characteristic indicated by the broken line in FIG. 11, the smaller the brush resistance value Rb, that is, the smaller the resistance value ratio Rb / Rc, the better the motor efficiency. However, in actuality, since it has the characteristics shown by the solid line in FIG. 11, the brush is assumed to be the same as the brush 12 of this embodiment, and the resistance ratio Rb / Rc is set to “25%” with the intention of having the conventional characteristics. When the DC motor is used, an efficiency of “about 58.7%” is obtained. However, if the DC motor is used until the brush reaches a length of “30%” when it is new, the resistance ratio Rb / Rc is “7.5%”, and the efficiency of the motor is “57”. .5% ".

  On the other hand, in the DC motor of this embodiment, the resistance value ratio Rb / Rc is set to “43%” in accordance with the characteristic indicated by the solid line in FIGS. If the DC motor is used until it reaches the length of “30%” of the length of the motor, the efficiency of the original motor is “58%”. After that, even if a DC motor is used until the resistance ratio Rb / Rc reaches “about 15%”, the motor efficiency can be maintained at a high efficiency of “58%”. It can be seen that the efficiency of the motor can be maintained at a higher level as a whole compared to the case where it is set.

[Second Embodiment]
Next, a second embodiment in which the DC motor of the present invention is embodied will be described in detail with reference to the drawings.

  In each of the embodiments described below (including this embodiment), the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted. Explained.

  In the DC motor of this embodiment, the configuration of the brush 21 is different from that of the first embodiment. That is, FIG. 12 shows a front view of the brush 21, and FIG. 13 shows a plan view of the brush 21. The brush 21 is formed in a block shape having a substantially quadrangular pyramid shape from a single conductive material. In FIG. 12, the lower surface of the brush 21 is a contact portion 21 a with the commutator 7. In FIG. 12, electric wires 13 for electrical wiring are provided on the upper surface of the brush 21, that is, on the end portion (opposite end portion) 21 b opposite to the contact portion 21 a. Here, the brush 21 has a maximum cross-sectional area of the contact portion 21a with the commutator 7, and the cross-sectional area of each part from the contact portion 21a to the opposite end portion 21b decreases as the distance from the contact portion 21a increases. Composed.

Here, the cross-sectional area of the contact portion 21a of the brush 21 is “S1”, the cross-sectional area of the opposite end 21b is “S2”, and the length in the longitudinal direction of the brush 21 shown in FIG. When the resistivity of the brush 21 is “ρ”, the resistance value Rb1 when the brush 21 is new is expressed by the following equation (1).
Rb1 = [ρ · L / (S2-S1)] loge (S2 / S1) (1)

  In this embodiment, as in the arrangement of the brushes 12 shown in FIGS. 1 and 2, the brushes 21 are arranged such that the central axes of the brushes 21 are parallel to the shaft 6. And the brush 21 is comprised so that the cross-sectional area of the brush 21 may reduce, so that the width W 1 of the brush 21 in the direction perpendicular | vertical to the shaft 6 reduces, so that it leaves | separates from the contact part 12a.

  In this embodiment, as shown in FIG. 7, on the assumption that the efficiency of the motor increases or decreases so as to have a single peak with respect to the increase in the resistance value ratio Rb / Rc, the resistance value at the time of a new product is obtained. The resistance value Rb of the brush 21 and the resistance value Rc of the coil 11 are set so that the ratio Rb / Rc becomes a value when the motor efficiency reaches a peak, specifically, “25%”.

  According to the configuration of the DC motor of this embodiment described above, as the DC motor is used, the contact portion 21a of each brush 21 that contacts the commutator 7 is worn and the brush 21 is shortened. On the other hand, the brush 21 is formed in a block shape from a single conductive material, and the cross-sectional area of the contact portion 21a with the commutator 7 is maximized, from the contact portion 21a to the opposite end portion 21b. Since the cross-sectional area of each part decreases as the distance from the contact portion 21a increases, the cross-sectional area of the contact portion 21a that changes due to wear gradually decreases. Therefore, since the cross-sectional area of the contact portion 21a is reduced by the amount of the brush 21 that is shortened, the change in the resistance value Rb of the brush 21 is generally reduced. Here, as shown in FIG. 7, it is known that the efficiency of the motor changes in accordance with the change in the resistance value Rb of the brush 21, that is, the change in the resistance value ratio Rb / Rc. Therefore, even if the DC motor is used for a period of time and the brush 21 is worn, the change in the resistance value Rb of the brush 21 is small, so the change in the resistance value ratio Rb / Rc is small, and the change in motor efficiency is also new. Smaller than that of time. As a result, a reduction in motor efficiency due to wear of the brush 21 can be suppressed, and the motor efficiency can be maintained at a high value. In particular, in this embodiment, even when the brush 21 is worn, the change in the motor efficiency due to the wear of the brush 21 can be suppressed because the change in the motor efficiency is small with respect to the peak value. The motor efficiency can be maintained at a value close to the maximum.

Here, if the length of the brush 21 is shortened to the length of “30%” of the new one as the DC motor is used, the resistance value Rb2 of the brush 21 at that time is expressed by the following formula ( 2).
Rb2 = {ρ · L / (S2-S1)] loge [10 · S2 / (3 · S1 + 7 · S2)] (2)

Here, when the ratio between the resistance value Rb1 and the resistance value Rb2 is obtained, it is expressed by the following equation (3).
Rb2 / Rb1 = loge {10 · S2 / (3 · S1 + 7 · S2)} / loge (S2 / S1) (3)

  According to the above equation (3), the smaller the cross-sectional area S2, the smaller the degree of change in the resistance value Rb1 and the resistance value Rb2. For example, if “S1 = 10 · S2” for the cross-sectional areas S1 and S2, the value of the above equation (3) is “0.568”, which is more than “0.3” when the cross-sectional areas are equal. The change in the resistance value Rb2 of the brush 21 becomes smaller. Therefore, by setting the resistance value ratio Rb / Rc at the time of a new product to “25%” when the motor efficiency reaches a peak, the motor efficiency is the highest value throughout the entire period of use of the DC motor. It can be maintained at a value close to “58.7%”.

[Third Embodiment]
Next, a third embodiment in which the DC motor of the present invention is embodied will be described in detail with reference to the drawings.

  In the DC motor of this embodiment, the configuration of the brush 22 is different from that of the above embodiments. 14 is a front view of the brush 22 and FIG. 15 is a plan view of the brush 22. The brush 22 is formed in a rectangular parallelepiped block shape by a plurality of conductive materials having different resistivity. In FIG. 14, the lower surface of the brush 22 is a contact portion 22 a with the commutator 7. Moreover, in FIG. 14, the electric wire 13 for electrical wiring is provided in the upper surface of the brush 22, ie, the edge part (opposite side edge part) 22b on the opposite side to the contact part 22a. Here, the brush 22 is configured so that the cross-sectional area of the contact portion 22a with the commutator 7 and the cross-sectional area of each portion from the contact portion 22a to the opposite end portion 22b are the same. Further, the brush 22 is configured such that the proportion of the material having high resistivity in the cross section in each part from the contact portion 22a to the opposite end portion 22b with the commutator 7 increases as the distance from the contact portion 22a increases. The Specifically, as shown by a two-dot chain line in FIG. 14, the brush 22 is configured such that a plurality of layers 23 are laminated along the longitudinal direction thereof. The ratio of the high resistivity material in each layer 23 is different, and the ratio of the high resistivity ratio of each layer 23 increases as the layer 23 is closer to the opposite end 22b.

  In this embodiment, as shown in FIG. 7, on the assumption that the efficiency of the motor increases or decreases so as to have a single peak with respect to the increase in the resistance value ratio Rb / Rc, the resistance value at the time of a new product is obtained. The resistance value Rb of the brush 22 and the resistance value Rc of the coil 11 are set so that the ratio Rb / Rc becomes a value when the motor efficiency reaches a peak, specifically, “25%”.

  According to the configuration of the DC motor of this embodiment described above, as the DC motor is used, the contact portion 22a of the brush 22 that contacts the commutator 7 is worn and the brush 22 is shortened. On the other hand, the brush 22 is formed in a rectangular parallelepiped block shape with a plurality of materials having different resistivity, and the cross-sectional area of the contact portion 22a with the commutator 7 and from the contact portion 22a to the opposite end portion 22b. The cross-sectional area of each part is configured to be the same. In addition, the ratio of the material having a high resistivity in the cross section in each part from the contact portion 22a to the opposite end portion 22b with the commutator 7 is configured to increase as the distance from the contact portion 22a increases. For this reason, the cross-sectional area of the contact portion 22a that changes due to wear is always the same, but the proportion of the high resistivity material in the cross-section increases. Therefore, since the resistance value of the contact portion 22a increases as the brush 22 is shortened, the change in the resistance value of the brush 22 is generally reduced. Here, as shown in FIG. 7, it is known that the efficiency of the motor changes in accordance with the change in the resistance value Rb of the brush. For this reason, even if the DC motor is used for a certain period of time and the brush 22 is worn, the change in the resistance value Rb of the brush 22 is small, so that the change in motor efficiency is also smaller than that in the new product. As a result, a reduction in motor efficiency due to wear of the brush 22 can be suppressed, and the motor efficiency can be maintained at a relatively high value.

[Fourth Embodiment]
Next, a fourth embodiment embodying the DC motor of the present invention will be described in detail with reference to the drawings.

  In the DC motor of this embodiment, the configuration of the brush 24 is different from that of each of the above embodiments. 16 is a front view of the brush 24, and FIG. 17 is a plan view of the brush 24. The brush 24 is formed in a substantially quadrangular pyramid block shape by a plurality of conductive materials having different resistivity. In FIG. 16, the lower surface of the brush 24 is a contact portion 24 a with the commutator 7. In FIG. 16, the upper surface of the brush 24, that is, the end portion (opposite end portion) 24b opposite to the contact portion 24a is provided with the electric wires 13 for electrical wiring. Here, in the brush 24, the cross-sectional area of the contact portion 24a with the commutator 7 is maximized, and the cross-sectional area of each part from the contact portion 24a to the opposite end portion 24b decreases as the distance from the contact portion 24a increases. Composed. Furthermore, the brush 24 is configured such that the proportion of the material having a high resistivity in the cross section at each portion from the contact portion 24a to the commutator 7 to the opposite end portion 24b increases as the distance from the contact portion 24a increases. The Specifically, as shown by a two-dot chain line in FIG. 16, the brush 24 is configured such that a plurality of layers 25 are stacked along the longitudinal direction thereof. The proportion of the high resistivity material in each layer 25 is different, and the proportion of the high resistivity in each layer 25 is increased as the layer 25 is closer to the opposite end 24b.

  In this embodiment, as shown in FIG. 7, on the assumption that the efficiency of the motor increases or decreases so as to have a single peak with respect to the increase in the resistance value ratio Rb / Rc, the resistance value at the time of a new product is obtained. The resistance value Rb of the brush 24 and the resistance value Rc of the coil 11 are set so that the ratio Rb / Rc becomes a value when the motor efficiency reaches a peak, specifically, “25%”.

  According to the configuration of the DC motor of this embodiment described above, as the DC motor is used, the contact portion 24a of the brush 24 that contacts the commutator 7 is worn and the brush 24 is shortened. On the other hand, the brush 24 is formed into a substantially quadrangular pyramid block shape with a plurality of materials having different resistivities, and the cross-sectional area of the contact portion 24a with the commutator 7 is maximized, and the opposite side from the contact portion 24a. The cross-sectional area of each part up to the end 24b is configured to decrease as the distance from the contact part 24a increases. In addition, the ratio of the high resistivity material in the cross section at each part from the contact portion 24a to the opposite end 24b with the commutator 7 is configured to increase as the distance from the contact portion 24a increases. Accordingly, the cross-sectional area of the contact portion 24a is reduced by the length of the brush 24, and the resistivity of the cross-section of the contact portion 24a is increased, so that the change in the resistance value Rb of the brush 24 is generally reduced. That is, in the second embodiment, the change in the resistance value Rb of the brush 21 is suppressed to be small by the change with time of the cross-sectional area of the brush 21, whereas in this embodiment, the change with time of the cross-sectional area of the brush 24 The change in the resistance value Rb of the brush 24 is kept small by combining with the change with time of the occupation ratio of the high resistivity material in the cross section. Here, as shown in FIG. 7, it is known that the efficiency of the motor changes in accordance with the change in the resistance value Rb of the brush. For this reason, even if the DC motor is used for a certain period of time and the brush 24 is worn, the change in the resistance value Rb of the brush 24 is small, so the change in the motor efficiency is also smaller than that in the new product. As a result, a decrease in motor efficiency due to wear of the brush 24 can be suppressed, and the motor efficiency can be maintained at a relatively high value.

[Fifth Embodiment]
Next, a fifth embodiment embodying the DC motor of the present invention will be described in detail with reference to the drawings.

  In this embodiment, the configuration is different from those of the above embodiments in terms of the arrangement of the commutator 17 and the brush 26. FIG. 18 is based on FIG. 1, and FIG. 19 is based on FIG. In this embodiment, the commutator 17 is formed in a cylindrical shape by a plurality of arc-shaped segments 17a. Each segment 17a is separated from each other through a slit 17b. A plurality of brushes 26 are provided in contact with the outer peripheral surface of the commutator 17. These brushes 26 are supported by brackets that cover the ends of the housing 3. In this configuration, the brush width angle A is defined as shown in FIG. The brush 26 of this embodiment has a configuration similar to the brush 22 of the third embodiment.

  Therefore, also in this embodiment, the resistance value of the contact portion 26a increases as the brush 26 is shortened, so that the change in the resistance value of the brush 26 is generally reduced. For this reason, even if the DC motor is used for a certain period of time and the brush 26 is worn, the change in the resistance value Rb of the brush 26 is small, so that the change in motor efficiency is also smaller than that in the new product. As a result, a reduction in motor efficiency due to wear of the brush 26 can be suppressed, and the motor efficiency can be maintained at a relatively high value.

[Sixth Embodiment]
Next, a sixth embodiment in which the DC motor of the present invention is embodied will be described in detail with reference to the drawings.

  In the DC motor of this embodiment, the configuration of the brush 27 is different from that of the above embodiments. 20 is a plan view of the brush 27, FIG. 21 is a side view of the brush 27, and FIG. 22 is a rear view of the brush 27. The DC motor of this embodiment is of the same type as the DC motor of the fifth embodiment, and the brush 27 of this embodiment is a modification of the brushes 21 and 24 of the second or fourth embodiment. Equivalent to. 20 and 21, the lower surface of the brush 27 serves as a contact portion 27 a with the commutator 17. In this embodiment, the brush 27 is arranged such that the central axis Lc of the brush 27 is perpendicular to the axis L of the shaft 6, and the brush 27 in a direction parallel to the axis L of the shaft 6 is further away from the contact portion 27 a. 27 is configured such that the cross-sectional area of the contact portion 27a of the brush 27 decreases as the width W2 of the brush 27 decreases.

  As shown in FIG. 4, the efficiency of the motor can also be changed by the brush width angle A shown in FIG. This is because the generation ratio of the two equivalent circuits shown in FIGS. 9 and 10 varies depending on the brush width angle A. That is, as the brush width angle A increases, the section in which the coil is short-circuited by the brush increases, so the generation ratio of the equivalent circuit shown in FIG. 9 increases and the energization state of the coil changes. For example, as shown in FIG. 4, when the brush width angle A is in the range of “about 10 to 15 °”, the motor efficiency is substantially maximum, and in other ranges, the motor efficiency is reduced. In this case, as in the second or fourth embodiment, when the cross-sectional area of the contact portions 21a and 24a becomes small due to wear of the brushes 21 and 24, the brush width angle A becomes small and the motor efficiency decreases. There is a case. Therefore, in this embodiment, the cross-sectional area of the contact portion 27a of the brush 27 is changed by changing the width W2 in the direction in which the brush width angle A is not changed by specifying the block shape of the brush 27 as described above. I try to change it.

  Therefore, according to the configuration of the DC motor of this embodiment, the width 27 of the brush 27 in the direction parallel to the axis L of the shaft 11 is reduced by the amount that the brush 27 is shortened due to wear, so that the contact portion 27a of the brush 27 is reduced. The cross-sectional area of becomes smaller. In this case, the cross-sectional area of the contact portion 27a of the brush 27 can be reduced by changing the width W2 of the brush 27 in the direction in which the brush width angle A is not changed. For this reason, also in this embodiment, since the resistance value of the contact portion 27a increases as the brush 27 is shortened, the change in the resistance value Rb of the brush 27 is generally reduced. In addition, even if the cross-sectional area of the contact portion 27a of the brush 27 is reduced, the brush width angle A does not change. For this reason, even if the DC motor is used for a certain period and the brush 27 is worn, the change in the resistance value Rb of the brush 27 is small, so the change in the motor efficiency is also smaller than that in the new product. As a result, a reduction in motor efficiency due to wear of the brush 27 can be suppressed, and the motor efficiency can be maintained at a relatively high value. In particular, in this embodiment, the change in the efficiency of the motor can be reliably suppressed by the amount that the brush width angle A does not change.

[Seventh Embodiment]
Next, a seventh embodiment in which the DC motor of the present invention is embodied will be described in detail with reference to the drawings.

  In the DC motor of this embodiment, the configuration of the brush 28 is different from that of each of the above embodiments. 23 is a plan view of the brush 28, FIG. 24 is a side view of the brush 28, and FIG. 25 is a rear view of the brush 28. The DC motor of this embodiment is the same type as the DC motor of the first embodiment, and the brush 27 of this embodiment is a modification of the brushes 21 and 24 of the second or fourth embodiment. Equivalent to. 24 and 25, the lower surface of the brush 28 serves as a contact portion 28 a with the commutator 7. In this embodiment, the brush 28 is arranged such that the central axis Lc of the brush 26 is parallel to the axis L of the shaft 6, and the brush 28 is in a direction perpendicular to the axis L of the shaft 6 as the distance from the contact portion 28 a increases. 28 is configured such that the cross-sectional area of the contact portion 28a of the brush 28 decreases as the width W3 of the 28 decreases. That is, also in this embodiment, the cross-sectional area of the contact portion 28a of the brush 28 is changed by specifying the block shape of the brush 28 as described above and changing the width W3 in the direction in which the brush width angle A is not changed. I try to change it.

  Therefore, according to the configuration of the DC motor of this embodiment, the width W3 of the brush 28 in the direction perpendicular to the axis L of the shaft 11 is reduced by the amount that the brush 28 is shortened due to wear, whereby the contact portion 28a of the brush 28 is obtained. The cross-sectional area of becomes smaller. In this case, the cross-sectional area of the contact portion 28a of the brush 28 can be reduced by changing the width W3 of the brush 28 in the direction in which the brush width angle A is not changed. For this reason, also in this embodiment, since the resistance value of the contact portion 28a increases as the brush 28 is shortened, the change in the resistance value Rb of the brush 28 is generally reduced. In addition, even if the cross-sectional area of the contact portion 28a of the brush 28 is reduced, the brush width angle A does not change. For this reason, even if the DC motor is used for a certain period of time and the brush 28 is worn, the change in the resistance value Rb of the brush 28 is small, so that the change in motor efficiency is also smaller than that in the new product. As a result, a reduction in motor efficiency due to wear of the brush 28 can be suppressed, and the motor efficiency can be maintained at a relatively high value. In particular, in this embodiment, the change in the efficiency of the motor can be reliably suppressed by the amount that the brush width angle A does not change.

  The present invention is not limited to the embodiments described above, and can be implemented as follows by appropriately changing a part of the configuration without departing from the spirit of the invention.

  For example, in the DC motor of each of the embodiments described above, the number of pole pairs Np is set to “2” and the number of slots Ns is set to “6”, but the number of pole pairs Np and the number of slots Ns are appropriately changed. By adopting the same configuration as that of each of the above embodiments, the same effect as that of each of the above embodiments can be obtained.

The top view which shows the main internal structures of a DC motor. The top view which shows the relationship between a commutator and a brush. The circuit diagram which shows a delta connection. The graph which shows the relationship between a brush width angle and the efficiency of a motor. The front view which shows a brush. The top view which shows a brush. The graph which shows the relationship between resistance value ratio and the efficiency of a motor. The conceptual diagram which shows the relationship between a brush, a commutator, and a coil. The equivalent circuit diagram which shows the relationship between a brush, a commutator, and a coil. The equivalent circuit diagram which shows the relationship between a brush, a commutator, and a coil. The graph which shows the relationship between resistance value ratio and the efficiency of a motor. The front view which shows a brush. The top view which shows a brush. The front view which shows a brush. The top view which shows a brush. The front view which shows a brush. The top view which shows a brush. The top view which shows the main internal structures of a DC motor. The top view which shows the relationship between a commutator and a brush. The top view which shows a brush. The side view which shows a brush. The rear view which shows a brush. The top view which shows a brush. The side view which shows a brush. The rear view which shows a brush.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stator 2 Rotor 6 Shaft 7 Commutator 7a Segment 10 Conductor 11 Coil (winding)
12 Brush 12a Contact part 12b Opposite end 17 Commutator 17a Segment 17b Slit 21 Brush 21a Contact part 21b Opposite end 22 Brush 22a Contact part 22b Opposite end 24 Brush 24a Contact part 24b Opposite end 26 Brush 26a Contact portion 26b Opposite end portion 27 Brush 27a Contact portion 27b Opposite end portion 28 Brush 28a Contact portion 28b Opposite end portion L Axis Lc Center axis Rc Coil resistance value Rb Brush resistance value Rb / Rc Resistance value ratio W1 Width W2 width W3 width

Claims (8)

A stator and a rotor;
The rotor includes a shaft, and a commutator and an armature provided on the shaft;
The commutator includes a plurality of segments;
The armature includes a winding wound with a conductive wire, and the winding and the commutator are delta-connected,
In a DC motor provided with a brush provided so as to be able to contact the commutator,
The brush is formed in a block shape from a single material, and has a cross-sectional area of a contact portion with the commutator and a cross-sectional area of each portion from the contact portion to an end opposite to the contact portion. Are configured the same,
When the ratio of the resistance value of the brush to the resistance value of the winding is a resistance value ratio, the motor efficiency has a relationship to increase or decrease to have one peak with respect to the increase of the resistance value ratio;
In a new article, the resistance value ratio is set to a value in a predetermined range corresponding to a side where the efficiency of the motor decreases from the peak with respect to the increase in the resistance value ratio. DC motor. The DC motor according to claim 1, wherein when the resistance value ratio corresponding to the peak is 25%, the resistance value ratio corresponding to the predetermined range is 35 to 45%. A stator and a rotor;
The rotor includes a shaft, and a commutator and an armature provided on the shaft;
The commutator includes a plurality of segments;
The armature includes a winding wound with a conductive wire, and the winding and the commutator are delta-connected,
In a DC motor provided with a brush provided so as to be able to contact the commutator,
The brush is formed in a block shape from a single material, and the cross-sectional area of the contact portion with the commutator is maximized, and each brush from the contact portion to the end on the opposite side of the contact portion. A DC motor, wherein the cross-sectional area is configured to decrease as the distance from the contact portion increases. A stator and a rotor;
The rotor includes a shaft, and a commutator and an armature provided on the shaft;
The commutator includes a plurality of segments;
The armature includes a winding wound with a conductive wire, and the winding and the commutator are delta-connected,
In a DC motor provided with a brush provided so as to be able to contact the commutator,
The brush is formed in a block shape from a plurality of materials having different resistivity, and a cross-sectional area of a contact portion with the commutator, and each portion from the contact portion to an end opposite to the contact portion. The cross-sectional area of the material is the same, and the ratio of the material having high resistivity in the cross section in each part from the contact portion with the commutator to the end opposite to the contact portion is separated from the contact portion. A DC motor configured to increase as much as possible. A stator and a rotor;
The rotor includes a shaft, and a commutator and an armature provided on the shaft;
The commutator includes a plurality of segments;
The armature includes a winding wound with a conductive wire, and the winding and the commutator are delta-connected,
In a DC motor provided with a brush provided so as to be able to contact the commutator,
The brush is formed in a block shape from a plurality of materials having different resistivity, and has a maximum cross-sectional area of a contact portion with the commutator, from the contact portion to an end portion on the opposite side of the contact portion. The cross-sectional area of each part is configured to decrease as the distance from the contact part increases, and a material having a high resistivity in a cross-section in each part from the contact part with the commutator to the end part opposite to the contact part is formed. The DC motor is configured to increase in proportion as it moves away from the contact portion. The brush is arranged such that the central axis of the brush is perpendicular to the axis of the shaft, and the width of the brush in a direction parallel to the axis of the shaft decreases as the distance from the contact portion increases. The DC motor according to claim 3, wherein the brush is configured so that a cross-sectional area of the brush decreases. The brush is disposed so that the central axis of the brush is parallel to the axis of the shaft, and the width of the brush in a direction perpendicular to the axis of the shaft decreases as the distance from the contact portion increases. The DC motor according to claim 3, wherein the brush is configured so that a cross-sectional area of the brush decreases. When the ratio of the resistance value of the brush to the resistance value of the winding is a resistance value ratio, the motor efficiency has a relationship to increase or decrease to have one peak with respect to the increase of the resistance value ratio;
The DC motor according to any one of claims 3 to 7, further comprising setting the resistance value ratio to a value at which the efficiency of the motor reaches the peak when new.

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