Direct-current motor armature, direct-current motor, and method for winding coil around armature of direct-current motor

In a direct-current motor armature 3 corresponding to an 8-pole-10-slot-20-segment or 12-pole-15-slot-30-segment, a connection wire 25 for short-circuiting segments 14 having the same degree of electric potential is provided to a commutator, a coil 12 is connected electrically to the segments 14 having a potential difference that is equal to a potential difference between the adjacent segments 14, and the coil 12 is wound around teeth 9 to form armature coils 7. Accordingly, an armature for use in a direct-current motor, a direct-current motor, and a method for winding wires around the armature of the direct-current motor for enabling down-sized direct-current motors having extended product life and enhanced performance can be provided.

TECHNICAL FIELD

The present invention relates to the a direct-current motor armature mounted on vehicles etc., a direct-current motor, and a method for winding coils around the armature of a direct-current motor.

The present application claims priority from patent application No. 2006-293868 filed in Japan on Oct. 30, 2006, and patent application No. 2007-276373 filed in Japan on Oct. 24, 2007, the content of which are incorporated herein by reference.

DISCLOSURE OF INVENTION

Problems to be Solved by the Invention

Conventionally, direct-current brush motors mounted on vehicles or the like have been known. Direct-current motors of this type have a freely rotatable armature having armature coils wound therearound and disposed within a cylindrical yoke having an even number of magnets provided on an inner periphery of the direct-current motor. The armature has armature cores fitted and fixed onto the exterior of a rotation shaft. Each armature core has a tooth having a wire wound therearound and formed in a radial manner in the circumferential direction of the armature core, and slots elongated in the axial direction are formed among the teeth. Each tooth has a wire wound therearound to provide a three-phase coil structure. Each coil is electrically connected to a segment (commutator piece) attached to the rotation shaft. Each segment is capable of sliding on the brush. An electric current is supplied to each coil by charging a voltage to the terminals of the segments from the brush.

The shift of phase among electric currents flowing in the coils forms different magnetic fields among the coils, thereby driving the rotation shaft by means of a magnetic attracting or repulsive force produced between the yoke and the magnets.

In recent years, there has been an increased need for down-sized three-phase direct-current motors having extended product life and enhanced performance. A technical proposal for reducing the motor size aims to reduce cogging torque (vibration produced in a motor) or uneven motor torque by increasing the number of magnetic poles of the magnets and slots, and to enclose a part of the commutator within an enclosure hole formed on the armature cores.Patent Document 1: Japanese Unexamined Patent Application, First Publication No. 2006-204070

However, an attempt to produce a desirable attracting or repulsive magnetic force between each coil and magnet tends to increase voltage between segments since the number of poles and slots of a motor varies orderly based on the multiple of the number of pole pairs of a 2-pole-3-slot configuration in the aforementioned conventional technique. Therefore, a limit in an attempt to increase the durability of a brush results in a drawback that the attempt to produce a magnetic attracting or repulsive force cannot be an effective means of extending the product life of a motor.

In addition, a limit in an attempt to reduce the cogging torque or uneven motor torque also leads to a drawback that the motor performance cannot be enhanced.

To address this, an object of the present invention conceived in view of the aforementioned circumstances is to provide an armature for use in a direct-current motor, a direct-current motor, and a method for winding wires around the armature of the direct-current motor for enabling down-sized direct-current motors having extended product life and enhanced performance.

Means for Solving the Problems

In order to solve the aforementioned drawbacks, according to a first aspect of the present invention, there is a direct-current motor armature, wherein the direct-current motor is of 8-pole-10-slot-20-segment or 12-pole-15-slot-30-segment, the armature comprises: a rotation shaft supported by a yoke pivotably which has a plurality of magnetic poles; a plurality of teeth attached to the rotation shaft and extending radially in radial directions; armature cores formed between the teeth and having a plurality of slots extending in an axial direction; and a commutator provided on the rotation shaft adjacent to the armature cores and having a plurality of segments disposed in a circumferential direction. The armature is characterized in that a short-circuiting component for short-circuiting the segments having the same degree of electric potential is provided to the commutator, a coil is connected electrically to the segments having a potential difference that is equal to a potential difference between the adjacent segments, and the coil is wound around the teeth.

In this case, the coil may be wound continuously around the teeth that correspond to a same phase.

In addition, the coil may be connected to the adjacent segments electrically, and another coil may be wound around each tooth.

In this configuration, since the armature can be of a five-phase structure, an inter-segment voltage can be reduced more significantly than that of a three-phase structure.

Also, short-circuiting the segments having the same degree of electric potential by means of the short-circuiting component eliminates the need to dispose the same number of brushes as that of the segments, thereby, reducing the installed number of brushes.

In addition, since the segments having the same degree of electric potential are short-circuited, it is not necessary to connect the coil-starting end and the coil-finishing end of the coil to the adjacent segments; therefore, the coil-starting end and the coil-finishing end can be connected to the segments existing in the vicinity of the coil-starting end and the coil-finishing end respectively. Therefore, expansion in coil size can be prevented among the commutator and the armature cores.

Further, a direct-current motor may use the direct-current motor armature described above.

According to a second aspect of the present invention, there is a coil-winding method for a direct-current motor armature, wherein the direct-current motor is of 8-pole-10-slot-20-segment or 12-pole-15-slot-30-segment, the armature comprises: a rotation shaft supported by a yoke pivotably which has a plurality of magnetic poles; a plurality of teeth attached to the rotation shaft and extending radially in radial directions; armature cores formed between the teeth and having a plurality of slots extending in an axial direction; and a commutator provided on the rotation shaft adjacent to the armature cores and having a plurality of segments disposed in a circumferential direction, and the method comprises: short-circuiting the segments having the same degree of electric potential by means of the short-circuiting component; connecting a coil electrically to the segments having a potential difference that is equal to a potential difference between the adjacent segments, and winding the coil continuously around the teeth that correspond to the same phase.

According to a third aspect of the present invention, there is a coil-winding method for a direct-current motor armature, wherein the direct-current motor is of 8-pole-10-slot-20-segment or 12-pole-15-slot-30-segment, the armature comprises: a rotation shaft pivotably supported by a yoke which has a plurality of magnetic poles; a plurality of teeth attached to the rotation shaft and extending radially in radial directions; armature cores formed between the teeth and having a plurality of slots extending in an axial direction; and a commutator provided on the rotation shaft adjacent to the armature cores and having a plurality of segments disposed in a circumferential direction, and the method comprises: short-circuiting the segments having the same degree of electric potential; connecting a coil electrically to the adjacent segments, and winding another coil around each tooth.

Effects of the Invention

According to the present invention, since the armature can be of a five-phase structure, an inter-segment voltage can be reduced more significantly relative to that of a three-phase structure. Accordingly, the extended product life of brush results in extending the product life of the motor.

Also, since the five-phase structure motor having a less significant variance in electric current per rotation than that of a three-phase structure motor, the cogging torque or uneven torque of motor can be reduced more effectively than those of the three-phase structure motor. Accordingly, the performance of the direct-current motor can be enhanced.

In addition, short-circuiting the segments having the same degree of electric potential by means of the short-circuiting component eliminates the need to dispose the same number of brushes as that of the segments, thereby, reducing the installed number of brushes. Accordingly, the reduced number of parts enables a reduced production cost and down-sizing of a direct-current motor.

In addition, since the segments having the same degree of electric potential are short-circuited, it is not necessary to connect the coil-starting end and the coil-finishing end of the coil to the adjacent segments; therefore, the coil-starting end and the coil-finishing end can be connected to the segments existing in the vicinity of the coil-starting end and the coil-finishing end respectively. Therefore, expansion in coil size can be prevented among the commutator and the armature cores. Accordingly, the direct-current motor can be downsized.

Furthermore, according to the present invention, the use of the armature described above enables a direct-current motor having a more reduced size, longer product life, and a higher performance than those of the three-phase direct-current motor.

EXPLANATION OF REFERENCE NUMERALS AND SYMBOLS

BEST MODE FOR CARRYING OUT THE INVENTION

Referring now toFIGS. 1 to 6, a first embodiment of the present invention will be explained.

As shown inFIGS. 1 and 2, an electric motor1is a driving source for electrical equipment e.g. a radiator fan mounted on vehicles. The electric motor1has a cylindrical motor housing2having a bottom section in which a freely rotatable armature3is disposed. A plurality of permanent magnets4are disposed in the circumferential direction of the motor housing2and fixed on the inner periphery of the motor housing2. More specifically, the motor housing2has eight permanent magnets4, that is, including eight magnetic poles.

The armature3includes armature cores6fixed on a rotation shaft5; armature coils7wound around the armature cores6; and a commutator13disposed at one end of the armature core6. The armature core6includes a plurality of ring-shaped metal plates8laminated in the axial direction. A plurality of (ten pieces in the embodiment) evenly spaced teeth9(seeFIG. 2) each having a T-letter shape are formed radially on the outer periphery section of the metal plates8in the circumferential direction. Fitting the plurality of metal plates8onto the exterior of the rotation shaft5causes helical slots11to be formed among adjacent teeth9on the outer peripheries of the armature cores6. Each slot11extends in the axial direction. The plurality of equally spaced slots11(10 slots in the present embodiment) are formed in the circumferential direction. Enamel-coated coils12disposed among the slots11form the plurality of armature coils7each wound around the outer periphery of each armature core6.

The commutator13is fitted onto and fixed around the exterior of an end of the rotation shaft5. A plurality of segments14(twenty pieces in the embodiment) each made of a conductive member are attached on the outer periphery of the commutator13.

The equally spaced segments14made of metal plate pieces elongated in the axial direction are insulated from each other. The segments14are disposed and fixed side by side in the circumferential direction. A riser15bent outward radially is formed on and united with the end of each segment14in the vicinity of the armature cores6. The coil12having a coil-starting end section and a coil-finishing end section is wound around each riser15to form the armature coil7. The coil12is fixed to the riser15by means of fusing. This allows each segment14to be connected electrically with each corresponding armature coil7.

In addition, as shown inFIG. 2, a connection wire25is wound around the risers15that correspond to the segments14having the same degree of electric potential (in the embodiment, five segments14spaced by every four pieces). Each connection wire25is fixed to the risers15by means of fusing. The connection wire25serves for short-circuiting the segments14having the same degree of electric potential, and is wired between the commutator13and the armature cores6.

As shown inFIG. 1, the other end of the rotation shaft5is rotatably supported by a bearing16formed within an embossed part of the motor housing2. A cover17is provided on an opening end of the motor housing2. A holder stay18is attached on an inner periphery of the cover17. The holder stay18has two brush holders19separated by 45 degrees in the circumferential direction. Each brush holder19has a freely projecting brush21biased by a spring29and disposed thereinside. The tip sections of these brushes21biased by the springs29and slidably contacting the commutator13cause an external power source to be supplied via the brushes21to the commutator13.

In this configuration of the electric motor1having 8 poles, 10 slots, and 20 segments, the coil12is wound around the armature3in the following manner.

FIG. 3is a developed view showing the segments14(risers15) of the armature3, the teeth9, the permanent magnets4fixed in the vicinity of the motor housing2, and the connection wires25. Spaces among the adjacent teeth9correspond to the slots11. In the following, the segments14, the teeth9, and the wound coils12will be explained with reference to reference symbols allocated thereto.

As shown inFIG. 3, the segments14having the same degree of electric potential are short-circuited by the connection wire25. That is, the segments14every four pieces are short-circuited by the connection wire25.

In addition, each tooth9has a U, V, W, X, or Y phase allocated in the circumferential direction in this order. That is, the first and sixth teeth9correspond to the U phase, the second and seventh teeth9correspond to the V phase, the third and eighth teeth9correspond to the W phase, the fourth and ninth teeth9correspond to the X phase, and the fifth and tenth teeth9correspond to the Y phase.

For example, the coil-starting end30of the coil12is first wound around a first segment14a, and then wound around the riser15of the first segment14a. After that, the coil12is attracted into a slot11aprovided between the first and tenth teeth9existing in the vicinity of the first segment14a. Subsequently, the coil12is wound n times (n is an integer corresponding to 1 or greater) around the first tooth9to form a first coil7a.

Subsequently, the coil12is drawn from a slot11bprovided between the first and second teeth9, and then attracted into a slot11cprovided between the fifth and sixth teeth9. Subsequently, the coil12is wound n times around the sixth tooth9to form a second coil7b. The first tooth9and the sixth tooth9are positioned symmetrically with respect to the center of the rotation shaft5.

The coil12upon forming the second coil7bis drawn from a slot ld provided between the sixth and the seventh teeth9, and then wound around the riser15of a twelfth segment14bexisting in the vicinity of the sixth tooth9. Subsequently, a coil-finishing end40of the coil12is connected to the twelfth segment14b. Consequently, the armature coil7(U phase), wound around the first and sixth teeth9and provided with a pair of coils7aand7bconnected in series, is formed between the first and twelfth segments14aand14b. It should be noted that the connection wire25short-circuits the twelfth segment14bhaving the coil-finishing end40connected thereto and a second segment14eadjacent to the first segment14a. Therefore, the potential difference between the first segment14aand the twelfth segment14bis equal to the potential difference between the adjacent segments.

Similarly, for example, the coil-starting end30of the coil12is first wound around a third segment14cand then wound around the riser15of the third segment14c. After that, the coil12is attracted into a slot11bprovided between the first and second teeth9existing in the vicinity of the third segment14c. Subsequently, the coil12is wound n times around the second tooth9to form the first coil7a.

Subsequently, the coil12is drawn from a slot11eprovided between the second and third teeth9, and then attracted into the slot11dprovided between the sixth and the seventh teeth9. Subsequently, the coil12is wound n times around the seventh tooth9to form the second coil7b. The second tooth9and the seventh tooth9are positioned symmetrically with respect to the center of the rotation shaft5.

The coil12upon forming the second coil7bis drawn from a slot11fprovided between the seventh and the eighth teeth9, and then wound around the riser15of a fourteenth segment14dexisting in the vicinity of the seventh tooth9. Subsequently, a coil-finishing end40of the coil12is connected to the fourteenth segment14d. Consequently, the armature coil7(V phase), wound around the second and seventh teeth9and provided with the pair of coils7aand7bconnected in series, is formed between the second segment14cand the fourteenth segment14d.

Accordingly, armature coils7having five-phase-coil structure (including U, V, W, X, and Y phases) are formed on the armature cores6by making coils sequentially in this manner while forming two coils7aand7brepeatedly in between each pair of segments14.

Also, in the resultant structure, the armature coils7each corresponding to the U, X, V, Y, or W phase are sequentially connected in this order electrically between the adjacent segments14since the segments14having the same degree of electric potential are short-circuited by the connection wire25. That is, the first segment14aand the second segment14eare connected by the armature coil7corresponding to the U phase; the second segment14eand the third segment14care connected by the armature coil7corresponding to the X phase; and the subsequently adjacent segments14are connected by the armature coils7each corresponding to the X, Y, or W phase respectively.

Therefore, a five-phase motor structure such as the aforementioned first embodiment having the more significant number of variance in the electric current during the rotation than that of the three-phase motor structure can reduce the number of variance of the electric current per commutation, thereby, reducing uneven motor torque.

In addition, the 8-pole-and-10-slot configuration has a 40th order of harmonics. In contrast, an 8-pole-12-slot three-phase direct-current motor having the same number of magnetic poles has a 24th order of harmonics. That is, the direct-current motor having a 8-pole-and-10-slot five-phase structure enables an increased order of harmonics relative to the three-phase direct-current motor, thereby providing a more reduced degree of cogging torque than that of the three-phase direct-current motor.

As a general rule here, the degree is equal to the number of peaks of cogging torque in one rotation of an armature. Therefore, a greater degree can reduce the significance of the cogging torque indicated by the peaks in one rotation of the armature.

FIG. 4is a comparative graph showing variances of cogging torque curves with respect to the electric motor1(8 poles, 10 slots, 8P-10S) of the first embodiment and a conventional three-phase-structure electric motor (8 poles, 12 slots, 8P-12S) where the vertical axis indicates cogging torque and the horizontal axis indicates an arbitrary angle θ of the armature. This reveals that the cogging torque of the electric motor1is reduced to half the cogging torque of the conventional electric motor.

FIG. 5is a comparative graph showing unevenness of torque curves with respect to the electric motor1(8P-10S) of the first embodiment and the conventional electric motor (8P-12S) where the vertical axis indicates torque and the horizontal axis indicates an arbitrary angle θ of the armature. This reveals that the unevenness in torque of the electric motor1is reduced to approximately half the unevenness in that of the conventional electric motor.

In addition, the five-phase structure can provide a more reduced inter-segment voltage than that of the three-phase structure, thereby extending the product life of the brushes21.

FIG. 6is a comparative graph showing long-term durabilites of the brush21with respect to the electric motor1(8P-10S) of the first embodiment and the conventional electric motor (8P-12S). The drawing reveals that the product life of the brush21of the electric motor1is extended approximately twice as long as that of the conventional electric motor (8P-12S). In addition, the number of segments14installed which is twice as many as that of the slots11also reduces the voltage between the segments14; therefore, permitting farther extension of the product life of the brush21.

In addition, the number of brushes21installed in the aforementioned first embodiment can be reduced since the segments14having the same degree of electric potential are short-circuited by the connection wire25, and since not all the segments14must have brushes21corresponding to the same phase (U, V, W, X, or Y phase). Accordingly, the reduced number of parts enables a reduced production cost and down-sizing of a direct-current motor.

Furthermore, it is not necessary to connect the coil-starting end30and the coil-finishing end40of the coil12to the adjacent segments14while the coil-starting end30and the coil-finishing end40can be connected to the segments14existing in the vicinity of the coil-starting end30and the coil-finishing end40respectively. Therefore, expansion in coil size can be prevented among the commutator13and the armature cores6. Accordingly, the electric motor1can be downsized more significantly.

Although, the first embodiment has been explained referring to the structure in which the armature coil7is formed by connecting the pair of serial-connected coils7aand7beach formed on the tooth9having the same phase, the coil12may be connected to the adjacent segments14while each tooth9has the coil12wound therearound as shown inFIG. 7.

In this case, for example, the coil-starting end30of the coil12is first wound around the first segment14a, and then wound around the riser15of the first segment14a. After that, the coil12is attracted into the slot11aprovided between the first and the tenth teeth9existing in the vicinity of the first segment14a. Subsequently, the coil12is wound n times around the first tooth9.

Subsequently, the coil12is drawn from the slot11bprovided between the first and second teeth9, and then wound around the riser15of the second segment14eadjacent to the first segment14a. Subsequently, the coil-finishing end40is connected to the second segment14e. Accordingly, the armature coil7wound around the first tooth9corresponding to the U phase is formed between the first segment14aand the second segment14e. Accordingly, the armature coils7having five-phase-coil structure (including U, V, W, X, and Y phases) are formed on the armature cores6by making coils sequentially in this manner while forming the armature coils7each wound around the tooth9repeatedly between each pair of segments14.

Also, in the resultant structure, the armature coils7each corresponding to the U, X, V, Y, or W phase are sequentially connected in this order electrically between the adjacent segments14since the segments14having the same degree of electric potential are short-circuited by the connection wire25. Furthermore, in this configuration, an electric current is supplied to all the armature coils7having a corresponding phase with respect to the segments14making contact with the brush21in a case of charging a voltage from the brush21to the segments14via the connection wire25to supply the electric current to the armature coils7.

Accordingly, the armature coil7formed to each tooth9can increase the number of parallel circuits (the motor has four parallel circuits) relative to the number of parallel circuits (the motor has two parallel circuits) obtained by connecting the pair of serial-connected coils7aand7bformed for each tooth9having the same phase. Therefore, the diameter of coil12can be reduced.

Referring now toFIG. 1, a second embodiment of the present invention will be explained based onFIGS. 8 and 9.

An electric motor1explained according to the second embodiment is of 12-pole-15-slot-30-segment structure having twelve permanent magnets4(magnetic poles), fifteen slots11, and thirty segments14provided therein. It should be noted that two brush holders19are formed while being separated by 30 degrees in the circumferential direction in the second embodiment.

As shown inFIG. 8, for example, the coil-starting end30of the coil12is first wound around the first segment14a, and then wound around the riser15of the first segment14a. After that, the coil12is attracted into the slot11aprovided between the first and fifteenth teeth9existing in the vicinity of the first segment14a. Subsequently, the coil12is wound n times around the first tooth9to form the first coil7a.

Subsequently, the coil12is drawn from a slot11bprovided between the first and second teeth9, and then attracted into a slot11cprovided between the fifth and sixth teeth9. Subsequently, the coil12is wound n times around the sixth tooth9to form a second coil7b. Furthermore, the coil12is drawn from the slot11dprovided between the sixth and seventh teeth9, and then attracted into a slot11gprovided between the tenth and eleventh teeth9. Subsequently, the coil12is wound n times around eleventh tooth9to form a third coil7c. The first tooth9, the sixth tooth9, and the eleventh tooth9exist by an interval of 120 degrees respectively.

The coil12upon forming the third coil7cis drawn from a slot11hprovided between the eleventh and twelfth teeth9, and then wound around the riser15of a twenty-second segment14fexisting in the vicinity of the eleventh tooth9. Subsequently, the coil-finishing end40of the coil12is connected to the twenty-second segment14f. Accordingly, the armature coil7corresponding to the U phase and wound around the first tooth9, the sixth tooth9, and the eleventh tooth9and provided with the serial-connected coils7a,7b, and7c, is formed between the first and twenty-second segments14aand14f.

Accordingly, armature coils7having five-phase-coil structure (including U, V, W, X, and Y phases) are formed on the armature cores6by making coils sequentially in this manner while forming three coils7a,7b, and7crepeatedly between each pair of segments14.

Therefore, the 12-pole-15-slot-30-segment electric motor1according to the aforementioned second embodiment can provide the same effect as that of the first embodiment. In addition, increasing the number of poles of the permanent magnets4and the slots11can obtain a more reduced cogging torque or unevenness in the torque of the electric motor1than those of the first embodiment.

Although, the second embodiment has been explained referring to the structure in which the armature coil7is formed by serial-connecting the three coils7a,7b, and7ceach formed on the tooth9having the same phase, the coil12may be connected to the adjacent segments14while each tooth9has the coil12wound therearound as shown inFIG. 9.

In this case, the number of parallel circuits (the motor has six parallel circuits) can be increased relative to the number of parallel circuits (the motor has two parallel circuits) obtained by serial-connecting the three coils7a,7b, and7cformed for each tooth9having the same phase. Therefore, the diameter of coil12can be reduced.

It should be noted that the present invention not limited to the aforementioned embodiments includes various forms of modification added to the aforementioned embodiment without departing from the spirit and scope of the present invention.

Also, in the aforementioned embodiments, the segments14having the same degree of electric potential are short-circuited by the connection wire25, the holder stay18has two brush holders19formed thereon, and each brush holder19has a freely projecting brush21biased by a spring29and disposed thereinside. However, in the present invention, the number of locations for installing the brush holders19(brush21) is limited not to two even if the segments14having the same degree of electric potential are short-circuited by the connection wire25. The brush holders19(brush21) can be installed in extra locations depending on the significance of the current density supplied to each armature coil7.

In addition, the present invention is not limited to the case of the aforementioned embodiments in which the coil-starting end30and the coil-finishing end40of the coil12are located in the vicinity of the teeth9each having the coil12wound therearound and connected to the segments14corresponding to the phase (U, V, W, X, or Y phase) of the tooth9. The coil-starting end30and the coil-finishing end40may be connected to the segments14corresponding to the phase of the teeth9each having the coil12wound therearound.

In addition, although the aforementioned embodiments show the case in which the armature core6includes the plurality of ring-shaped metal plates8laminated in the axial direction; and the plurality of evenly spaced teeth9each having a T-letter shape viewed in cross section are formed radially on the outer periphery section of the metal plates8in the circumferential direction, the shape of the armature cores6not limited to this configuration may have a divided-core-structure which enables division in the circumferential direction, or may have a predetermined skew angle in which the armature cores6incline with respect to the axial direction while being twisted.