JP2013090406A - Electric vehicle drive motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric vehicle drive motor with a simple configuration capable of securing a predetermined torque in a low-speed rotation region and reducing generation of a counter-electromotive force in a high-speed rotation region, and of properly setting current flowing timings in the low-speed and high-speed rotation regions.SOLUTION: An electric vehicle drive motor includes a rotor having a magnet with 2n magnetic poles, a stator core 24 opposed to respective magnetic poles of the rotor and having 6m projection parts on a peripheral surface, a rotation detector, a current controller, and a drive circuit. The stator core 24 includes 3m first projection part groups and 3m second projection part groups formed at regular intervals in a circumferential direction. First projection parts 36 constituting the first projection part groups and second projection parts 38 constituting the second projection part groups are alternately arranged. First coils are wound around the first projection parts 36, and second coils are wound around the second projection parts 38. The second projection part groups and the first projection part groups are arranged so that the second projection parts 38 are arranged closer to one of the two first projection parts 36 sandwiching the second projection parts 38.

Description

  The present invention relates to a technique for an electric vehicle drive motor, and more particularly to an electric vehicle drive motor applicable to a wide range of rotation speeds.

  In recent years, electric motors are increasingly used as a drive source for vehicles from the viewpoint of ecology. In the case of a vehicle, it is desired to start from a stopped state and smoothly accelerate to realize high-speed running. On the other hand, in the case of an electric motor, the ratio of the magnitude of the counter electromotive force generated per unit rotational speed of the motor (back electromotive force constant), for example, when the number of turns of the motor coil is increased in order to secure the low-speed torque necessary for starting. Becomes larger. When the back electromotive force constant increases, the upper limit of the rotational speed decreases and high speed rotation cannot be performed. That is, when the number of turns of the motor coil is increased, the upper limit rotational speed at which the motor can be operated is limited to be low. On the other hand, in order to suppress the occurrence of counter electromotive force at high speed rotation, if the number of turns of the motor coil is reduced and importance is attached to the rotational drive performance in the high speed region, it becomes difficult to secure low speed torque and The low speed characteristics are impaired. Therefore, in other fields, for example, in the field of elevators and machine tools, an electric motor drive device that includes a low-speed winding and a high-speed winding and can be used at low speed and high speed by switching the winding has been proposed (for example, Patent Document 1).

JP 2003-33067 A

  However, even in the case of control by switching windings as in Patent Document 1, the timing of current flow (phase) of the motor drive current is relatively delayed in the high-speed rotation region because the timing of energization is delayed due to the inductance of the coil. Therefore, there is a tendency that the generated torque is reduced. Further, in order to improve the decrease in torque, it is not preferable to advance the current so as to compensate for a delay in the current application timing in the high-speed rotation region because efficiency loss occurs in the low-speed rotation region.

  The present invention has been made in view of such a situation, and an object thereof is to secure a predetermined torque in a low-speed rotation region and reduce the occurrence of back electromotive force in a high-speed rotation region, and to achieve a low-speed rotation region and a simple configuration. An object of the present invention is to provide an electric vehicle drive motor capable of appropriately switching the current application timing in a high-speed rotation range.

  In order to solve the above-described problems, a drive motor for an electric vehicle according to an aspect of the present invention includes a rotatable rotor including a magnet that arranges 2n (n is a natural number) magnetic poles in the circumferential direction, and each magnetic pole of the rotor. The stator core is arranged so as to be opposed to each other and 6 m (m is a natural number) protrusions are arranged on the peripheral surface, and 3 m first protrusions are formed at equal intervals in the circumferential direction as the protrusions. A second projecting group that includes the first projecting part group and the second projecting part group that includes the first projecting part group and the 3m second projecting part group formed at equal intervals in the circumferential direction as the projecting part. Detecting the rotation state of the rotor, the stator core formed by alternately arranging the protrusions, the first coil wound around the first protrusion, the second coil wound around the second protrusion, respectively. According to the rotation detection means and the result detected by the rotation detection means Comprising a current control means for controlling the amount of current flowing through the first coil and the second coil. The second protruding portion group and the first protruding portion group are formed such that the second protruding portion is arranged to be biased to one of the two first protruding portions sandwiching the second protruding portion.

  According to this aspect, the rotational drive can be controlled by separately controlling the current flowing through the first coil wound around the first protrusion group and the current flowing through the second coil wound around the second protrusion group. For example, if a current is passed through both the first coil and the second coil, a driving torque corresponding to the number of turns of both coils can be obtained. That is, it becomes a mode in which high torque is generated in the low speed rotation region. In addition, if a current is passed through one of the first coil and the second coil, the current is substantially the same as when a current is passed through a coil having a small number of turns compared to a mode in which high torque is generated. As a result, even if the number of rotations increases, the generation of the back electromotive force associated therewith is reduced, and driving with less influence of the back electromotive force in the high speed rotation region becomes possible. Further, the second protrusion group and the first protrusion group are arranged such that the second protrusion is biased to one of the two first protrusions sandwiching the second protrusion, so that one coil has a current. It is possible to switch the current application timing simply by preventing the current from flowing. In other words, it is possible to correct the deviation of the energization timing and suppress the decrease in the torque in the high-speed rotation area only by setting the bias amount of the second protrusion group according to the energization timing of the current desired to be set in the high-speed rotation area. it can.

  According to the present invention, a predetermined torque is ensured in the low-speed rotation region, the generation of back electromotive force is reduced in the high-speed rotation region, and the current application timing is appropriately set in the low-speed rotation region and the high-speed rotation region with a simple configuration. An electric vehicle drive motor that can be switched can be provided.

It is a block diagram explaining the system configuration | structure of the drive motor for electric vehicles of this embodiment. It is explanatory drawing explaining the example of arrangement | positioning of the 1st projection part group of the stator core of this embodiment, and a 2nd projection part group. It is explanatory drawing explaining the example which wound the 1st coil and the 2nd coil to the stator core of FIG. 2, and has arrange | positioned the rotor around the stator core. FIG. 4A is an explanatory diagram for explaining a connection state using the first coil and the second coil for the low-speed rotation region, and FIG. 4B shows only the first coil for the high-speed rotation region. It is explanatory drawing explaining the connection state using this. It is a circuit diagram explaining the circuit structure containing the electric current control part for switching the electricity supply state of a 1st coil and a 2nd coil. It is explanatory drawing explaining the relationship between the magnetic flux change rate at the time of low speed rotation in this embodiment, and the torque which arises at that time. FIG. 7A is an explanatory diagram for explaining the deviation of the magnetic flux change rate and the current during low-speed rotation. FIG. 7B is an explanatory diagram for explaining the deviation of the magnetic flux change rate and the current during high-speed rotation. It is explanatory drawing explaining the relationship between the value which converted the time constant of the electric current into the electrical angle, and average torque. It is a table | surface explaining the relationship between the magnetic pole number of this embodiment, the number of protrusion parts, an electrical angle, and a mechanical angle.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings. The same or equivalent components and members shown in the drawings are denoted by the same reference numerals, and repeated descriptions are appropriately omitted. In addition, the dimensions of the members in each drawing are appropriately enlarged or reduced for easy understanding. In addition, in the drawings, some of the members that are not important for describing the embodiment are omitted.

  In the following description, an angle not particularly specified is described as a mechanical angle in which one rotation of the motor is 360 °. In the following description, the electrical angle refers to an angle expressed by 2π (rad) as an angle (fan angle) formed by a pair of N poles and S poles (one pole pair) of the magnetic poles of the magnet. Accordingly, in the case of having 2n magnetic poles, a mechanical angle of 360 ° may be expressed as an electrical angle of 2π · n (rad). For example, when the number of magnetic poles of the magnet is 2n = 8 (n = 4, that is, four pole pairs), one rotation of the rotor is expressed as 360 ° in mechanical angle and 2π · 4 = 8π (rad) in electrical angle. . Further, in the following description, the term “current” unless otherwise specified is described as indicating a drive current flowing in the first coil or the second coil.

  FIG. 1 is a block diagram illustrating a system configuration of an electric vehicle drive motor 10 according to the present embodiment. In the present embodiment, the electric vehicle drive motor 10 refers to the entire system including the motor body 12, the drive circuit 14, the rotation detection sensor 16, the position detection unit 18, the speed detection unit 20, the current control unit 22, and the like. It will be explained as a thing. Moreover, each structure mentioned above may be included in the housing containing a motor main body, and the whole may be called the drive motor 10 for electric vehicles.

  Although details of the motor body 12 will be described later, in a three-phase brushless motor, for example, in the case of an outer rotor type, a ring-shaped magnet having a plurality of magnetic poles arranged in the circumferential direction on the inner peripheral surface is a freely rotatable ring shape. With a rotor. In addition, a stator core in which a coil is wound around a plurality of projecting portions (saliency poles) disposed to face the magnetic poles of the magnet is disposed on the inner periphery of the rotor. When a drive current is sequentially switched and applied to the coils wound around the protrusions by the drive circuit 14 according to a known three-phase brushless motor drive sequence, the coils generate a rotating magnetic field at the protrusions of the stator core. A rotational driving force, that is, torque is generated by the interaction between the driving magnetic pole of the rotor magnet and the rotating magnetic field. Then, the rotor can be rotated at a torque and a rotational speed (rotational speed) according to the drive current and the power supply voltage. The rotation state of the motor body 12 is detected by a rotation detection sensor 16 configured by a Hall IC or the like disposed between protrusions formed on the starter core, and the rotation detection sensor 16 determines the state of the rotor based on the detection result. That is, the rotational position of the rotor with respect to a predetermined reference position is detected. Further, the speed detector 20 detects the rotational speed of the rotor based on the change in the rotational position detected by the position detector 18. Note that, as will be described later, the current control unit 22 determines whether or not to supply current to a coil wound around which protrusion group (saliency pole group) for rotational driving based on the rotational speed of the rotor. It has a function as a means.

  FIG. 2 is an explanatory diagram for explaining the shape of the stator core 24 included in the motor body 12 of the present embodiment. FIG. 3 shows a state in which the coil 28 is wound around the protrusion 26 of the stator core 24 included in the motor body 12 of the present embodiment, and the rotor 32 having the annular magnet 30 is arranged on the outer peripheral side thereof. Show. In the present embodiment, an outer rotor type motor structure in which the rotor 32 is disposed on the outer peripheral side of the stator core 24 will be described as a configuration example of the motor body 12.

  The rotor 32 includes an annular housing 34 and a magnet 30, and a power transmission member (not shown) that outputs the rotational force of the rotor 32 to the outside is fixed to a part of the housing 34. For example, a part of the output shaft may be fixed to the housing 34, or a drive gear that meshes with a driven gear provided on the output shaft may be fixed. The annular magnet 30 has 2n (n is a natural number) magnetic poles arranged in the circumferential direction. FIG. 3 shows an example in which S poles and N poles are alternately arranged and a total of eight magnetic poles (four pole pairs) are arranged.

  As shown in FIG. 3, the stator core 24 of the present embodiment is arranged on the inner peripheral side so as to face each magnetic pole of the magnet 30 of the rotor 32. As shown in FIG. 2, 6 m (m is a natural number) protrusions are arranged on the peripheral surface of the stator core 24. Each of these protrusions becomes a salient pole. As shown in FIGS. 2 and 3, in the case of the present embodiment, an example is shown in which 12 (m = 2) protrusions are formed for 8 (n = 4) magnetic poles. As shown in detail in FIG. 2, the stator core 24 of the present embodiment is formed with 3 m first protrusions formed as protrusions at equal intervals in the circumferential direction, and as protrusions at equal intervals in the circumferential direction. And 3m second protrusion group. The 1st projection part 36 which comprises a 1st projection part group, and the 2nd projection part 38 which comprises a 2nd projection part group are arrange | positioned alternately. The second projecting portion group and the first projecting portion group are arranged such that a certain second projecting portion 38 is biased to one of the two first projecting portions 36 sandwiching the second projecting portion 38.

  Further, the first protrusion 36 is wound with a first coil 40 that is used as a coil 28 during low-speed rotation and high-speed rotation. The second protrusion 38 is only used as a coil 28 at low-speed rotation. The 2nd coil 42 used for is wound. In the present embodiment, since it is a three-phase motor, there are U-phase, V-phase, and W-phase, and U1-1 and U1-2 are present as the U-phase of the first coil 40. Further, V1-1 and V1-2 exist as the V phase of the first coil 40, and W1-1 and W1-2 exist as the W phase of the first coil 40. Similarly, U2-1 and U2-2 exist as the U phase of the second coil. Further, V2-1 and V2-2 exist as the V phase of the second coil 42, and W2-1 and W2-2 exist as the W phase of the second coil 42.

  As described above, the first protrusions 36 of the first protrusion group are disposed at equal intervals of, for example, 60 ° in mechanical angle. Similarly, each 2nd projection part 38 of the 2nd projection part group is arrange | positioned at equal intervals of 60 degrees by a mechanical angle, for example. As shown in FIG. 2, a certain second protrusion 38 a is disposed so as to be biased to one of the two first protrusions 36 a and 36 b sandwiching the second protrusion 38 a. In the case of FIG. 2, the second protrusion 38 a is arranged so as to be biased toward the first protrusion 36 a from the first protrusion 36 b. Therefore, the first fan angle θ1 is formed by the first protrusion 36a and the second protrusion 38a, and the second fan angle θ2 is formed by the second protrusion 38a and the first protrusion 36b. That is, the first coil 40 and the second coil 42 are arranged in a relationship between the first sector angle θ1 and the second sector angle θ2. In addition, it can be said that the 2nd projection part group has arrange | positioned by the shift | offset | difference method which rotates the rotor 32 in the normal rotation direction, for example, the direction opposite to the clockwise direction with respect to the 1st projection part group.

  FIG. 4A is an explanatory diagram illustrating a connection state for energizing the first coil 40 and the second coil 42 for the low-speed rotation region. In the case of FIG. 4A, the U-phase first coil U1 and the U-phase second coil U2 are connected in series, the V-phase first coil V1 and the V-phase second coil V2 are connected in series, and the W-phase first Coil W1 and W-phase second coil W2 are connected in series to form a Y connection. On the other hand, FIG.4 (b) is explanatory drawing explaining the connection state for energizing only a 1st coil for a high-speed rotation area. In the case of FIG. 4B, the U-phase second coil U2, the V-phase second coil V2, and the W-phase second coil W2 are separated on the circuit, and the U-phase first coil U1, the V-phase first coil V1, and W The phase first coil W1 constitutes a Y connection.

  FIG. 5 is a diagram illustrating a circuit configuration including the current control unit 22 for switching the energization state of the first coil 40 and the second coil 42. The current control unit 22 shown in FIG. 5 includes two types of switches SW1 and SW2. When the electric vehicle drive motor 10 is used in the high speed mode, the switch SW1 is turned on and the switch SW2 is turned off. When the electric vehicle drive motor 10 is used in the low speed mode, the switch SW1 is turned off and the switch SW2 is turned on. Note that the switch SW1 and the switch SW2 are not particularly limited as long as they are devices capable of controlling the conduction state and the non-conduction state. As an example, the switch SW1 and the switch SW2 can be configured using a relay having a mechanical contact. As another example, the switches SW1 and SW2 can be formed using semiconductor elements.

  The drive circuit 44 forms a totem pole type output circuit in which the transistors Tr1 to Tr6 are three pairs. Each output terminal of the totem pole type output circuit is connected to the first coil 40 and the second coil 42 and outputs a drive current to the coil. The transistors Tr1 to Tr6 have their gates supplied with a gate drive signal from the drive timing generation circuit and controlled in conduction. The transistors Tr1 to Tr6 perform PWM driving based on a known principle.

  When the electric vehicle drive motor 10 is used in the high speed mode, the switch SW1 is turned on and the switch SW2 is turned off. In this state, the transistors Tr1 to Tr6 of the drive circuit 44 are sequentially switched to a conductive state by a known three-phase brushless motor drive sequence. The conduction state of the transistors Tr1 to Tr6 is a state in which the duty ratio of PWM drive is other than 0% and is larger than that. For example, the transistor Tr1 and the transistor Tr4 are in a conductive state so that current flows from the U-phase first coil U1 to the V-phase first coil V1 at a certain timing, and the protruding portion around which the U-phase first coil U1 is wound and the V-phase A magnetic field is generated on the protrusion around which the first coil V1 is wound. Next, the transistor Tr1 and the transistor Tr6 are turned on so that current flows from the U-phase first coil U1 to the W-phase first coil W1, and the protrusion around which the U-phase first coil U1 is wound and the W-phase first A magnetic field is generated on the protrusion around which the coil W1 is wound. By performing similar switching, a rotating magnetic field is generated on the stator core 24, and the rotor 32 including the magnet 30 disposed on the outer peripheral side of the stator core 24 rotates.

  Similarly, when the electric vehicle drive motor 10 is used in the low speed mode, the switch SW1 is turned off and the switch SW2 is turned on. In this state, the conduction state is controlled by sequentially switching the transistors Tr1 to Tr6 of the drive circuit 44 by a known three-phase brushless motor drive sequence. By the above-described operation, an alternating current is passed through the first coil 40 and the second coil 42 as a drive current by the transistors Tr1 to Tr6.

  Here, if the magnitude of the change in the magnetic flux linked to the coil with respect to the change in the angle of the rotor is referred to as the magnetic flux change rate, the torque generated by each coil is proportional to the product of the magnetic flux change rate and the drive current flowing in the coil. . In other words, the torque generated when the drive current is passed at a timing when the flux change rate is relatively large as compared to the magnitude of the torque generated when the drive current is passed at a timing when the flux change rate is relatively small, It's a big relationship. In this embodiment, at the rotor position where the center of the protrusion coincides with the center of the magnetic pole, the rate of change of magnetic flux becomes zero, and the center of the protrusion coincides with the boundary between the N pole and the S pole of the magnetic pole. At the position, the rate of change of magnetic flux is maximized. In the present embodiment, the magnetic poles are configured so that the rate of change of magnetic flux is a sine function with the electrical angle of the rotational position of the rotor as a variable.

  Further, the counter electromotive force induced in the coil is proportional to the magnitude of the change in magnetic flux interlinking with the coil with respect to the time change. Therefore, the rate of change in magnetic flux and the counter electromotive force are common in that they are proportional to the magnitude of the change in magnetic flux interlinking with the coil, and when the rotational speed and drive current are constant, the change in magnetic flux with respect to the rotor angle. The rate and back electromotive force waveforms are similar. For this reason, the magnetic flux change rate can be indirectly confirmed as a similar waveform by observing the counter electromotive force induced in the coil.

  When the electric vehicle drive motor 10 is used in the low speed mode, the first coil 40 and the second coil 42 contribute to the generation of the magnetic field at the same time, so that the magnetic field is generated only by the first coil 40 when used in the high speed mode. A larger torque can be generated as compared with the case of making it. Here, the magnitude of the back electromotive force is proportional to the rotational speed of the motor body 12. Therefore, in this case, since the motor main body 12 rotates at a low speed, the back electromotive force generated is low and does not hinder the increase in the rotation speed of the motor main body 12. On the other hand, when the electric vehicle drive motor 10 is used in the high speed mode, the magnetic field is generated only by the first coil 40. Therefore, when the first coil 40 and the second coil 42 simultaneously generate the magnetic field in the low speed mode. Compared with this, the number of turns of the coil that is actually operated is reduced. As a result, the generated back electromotive force is reduced, and the increase in the rotational speed of the motor body 12 is not hindered.

  As described above, in the case of the present embodiment, the winding state effective at low speed rotation by using the first coil 40 and the second coil 42 and the winding state effective at high speed rotation by using only the first coil 40 are used. And switching. FIG. 6 shows the relationship between the magnetic flux change rate of the first coil 40 and the magnetic flux change rate of the second coil 42, the relationship between the magnetic flux change rate resulting from the combination and the torque generated at that time, and the first coil 40 and the second coil 42. It is explanatory drawing which showed the example of a relationship of the electric current which flows, while driving. The abscissa indicates the rotation position (angle) of the rotor 32 in terms of electrical angle of 4π (rad), that is, the amount of rotation of the rotor half a circle when the rotor 32 is constituted by the four counter magnets 30. Note that the remaining half-turn rotation repeats the same change, and is not shown.

  Curve A is the rate of change of magnetic flux for one phase by the first coil 40, and curve B is the rate of change of magnetic flux for one phase by the second coil 42. Then, the curve C represents the change rate of the magnetic flux for one phase generated by the first coil 40 and the second coil 42 that are generated when both the first coil 40 and the second coil 42 which are referred to as the low speed mode in the present embodiment are used. This is the combined magnetic flux change rate in a state where the magnetic flux change rates for one phase are combined. In addition, the current is flowing when the waveform D is in the low speed mode. Further, a curve E is a combined torque obtained by synthesizing the torque generated by the coils of each phase for three phases. Note that the rate of change in magnetic flux when referred to as the high-speed mode in the present embodiment has only to take into account the counter electromotive force of only the first coil 40, and therefore the curve corresponding to the counter electromotive force induced in the first coil 40. Indicated by A.

  By the way, when an alternating current flows through a coil of each phase of a three-phase motor, the current does not flow instantaneously, but there is a delay time for rising due to the inductance of the coil. That is, a delay in the alternating current of the coil occurs. This delay time is substantially constant regardless of the rotational speed of the rotor. When the rotational speed of the rotor is low, the alternation period of the alternation current is long, so the rise delay time is relatively negligible. On the other hand, when the rotational speed increases, the frequency of the alternating current increases and the alternating cycle becomes shorter, the delay time of the current rise also becomes relatively large and cannot be ignored. That is, as the rotational speed increases, the influence of the delay in the timing of current flow becomes significant. 7 (a) and 7 (b) show that the current flow timing in the high speed mode is different from the counter electromotive force generated in the high speed mode when the rotational speed of the rotor is in the low speed mode and in the high speed mode. It is explanatory drawing explaining delaying later.

  FIG. 7A and FIG. 7B show the generated torque waveform with respect to the rotation angle of the rotor 32 by simulation. FIG. 7A shows a case where the deviation in the lag direction is relatively small with respect to the coil current, and FIG. 7B shows a case where the deviation in the lag direction is relatively large with respect to the coil current. As described above, since the torque is proportional to the product of the magnetic flux change rate and the current, a large torque is generated by passing the current at a timing when the magnetic flux change rate is relatively large. Conversely, when a current is passed at a timing at which the rate of change of magnetic flux is relatively small, the generated torque is small. Furthermore, if current is passed at a timing when the rate of change in magnetic flux is negative, torque in the negative direction, that is, in the reverse direction is generated. When the deviation of the coil current in the delay direction is small, the current flows at a timing at which the rate of change of the magnetic flux is relatively large, so that the average value of the generated torque is also large (FIG. 7A). On the other hand, when there is a large delay in the coil current, the current flows even when the rate of change of the magnetic flux is relatively small, so the average value of the generated torque is small (FIG. 7B). Further, when the coil current has a larger deviation in the delay direction, the current flows even when the rate of change in magnetic flux is negative, so that the average value of the generated torque is further reduced by generating the negative direction torque. On the other hand, the average value of generated torque is the same when there is a deviation in the advance direction at the coil current timing. As described above, the delay time of the coil current can be expressed by the time constant τ from the current application start timing shown by line a in FIG. 7B to the timing of line b corresponding to 63% of the current peak. it can. The time constant τ is constant regardless of the rotational speed, but the value converted into an electrical angle with an alternating period of 2π increases in proportion to the rotational speed. Therefore, the value obtained by converting the time constant τ into an electrical angle increases as the rotational speed increases and the alternating period becomes shorter, and the influence of current delay increases.

  FIG. 8 shows the time constant τ of the current due to the coil inductance and the average magnitude of the generated torque obtained by simulation. The horizontal axis is a value obtained by converting the time constant τ into an electrical angle. The vertical axis represents the average magnitude (hereinafter referred to as “average torque”) during one rotation of the combined torque obtained by synthesizing three phases of the torque generated in the coils of each phase. For example, in FIG. 8, when the value obtained by converting the current time constant τ into an electrical angle is π / 6, the average torque is 79. with respect to the average torque when the electrical angle without current delay is 0 (rad). 3%. That is, the average torque is reduced by 20.7% compared to the case where there is no current delay. That is, in FIG. 6, when the current to the second coil 42 is interrupted for switching to the high speed mode, the phase change amount of the magnetic flux change rate (curve A) of only the first coil 40 in FIG. If the current delays are made uniform, the reduction in average torque is improved. In this case, the phase of the magnetic flux change rate can be changed by rotating the second protrusion 38 in the circumferential direction with respect to the first protrusion 36, that is, by advancing the angle. As described above, when the rotation speed (rotation speed) increases, the value obtained by converting the time constant τ in the current delay direction into an electrical angle increases, and the average torque decreases. That is, if the arrangement relationship between the first protrusions 36 and the second protrusions 38 is set corresponding to the number of rotations (rotational speed) required for the electric vehicle drive motor 10, the average torque can be obtained when switching to the high speed mode. Adjustments that improve are possible.

  The inventors' experiments have found that when the average torque drop exceeds 5%, it is necessary to improve practically. Further, as a result of the simulation, as shown in FIG. 8, it was found that the average torque decreases within 5% when the value obtained by converting the current time constant τ to the electrical angle is π / 18 or less. Therefore, until the value obtained by converting the time constant τ by the first coil 40 during high-speed rotation into an electrical angle becomes π / 18, torque-oriented driving is performed in the low-speed mode using the first coil 40 and the second coil 42. It was confirmed that this is preferable. In addition, when the value obtained by converting the time constant τ of the current during high-speed rotation into an electrical angle is π / 18 or more, the first coil 40 and the second coil 42 are arranged so that the low-speed mode can be switched to the high-speed mode. It has been thought that the relationship, that is, the arrangement relationship between the first protrusion 36 and the second protrusion 38 may be set.

  When the current time constant τ can be substantially ignored in the low-speed mode, the curve C indicating the magnetic flux change rate and the curve D indicating the current in FIG. Accordingly, when the value obtained by converting the time constant τ of the current into the electrical angle becomes π / 18 when the rotation speed is high, the phase of the magnetic flux change rate is adjusted to the value according to this value. By shifting by π / 18 as indicated by curve A, the decrease in average torque can be suppressed to 5% or less. That is, the curve A indicating the rate of change of magnetic flux due to the first coil 40 is delayed by π / 18 with respect to the curve C indicating the rate of change of magnetic flux due to the first coil 40 and the second coil 42. What is necessary is just to set the arrangement | positioning relationship of the projection part 38. FIG. Since the curve C is a combination of the curve A and the curve B, the curve B indicating the rate of change of magnetic flux by the second coil 42 can be described above if the curve A indicating the rate of change of magnetic flux by the first coil 40 is advanced by π / 9. You can set as follows.

  Therefore, the difference in electrical angle between the first fan angle θ1 indicated by the first protrusion 36a and the second protrusion 38a and the second fan angle θ2 indicated by the second protrusion 38a and the first protrusion 36b in FIG. If the first protrusion group and the second protrusion group are arranged so that becomes π / 9, the phase of the magnetic flux change rate when switching to the high-speed mode becomes a value obtained by converting the time constant τ of the current into an electrical angle. Adjustments can be made to match. In this case, the larger the difference between the electrical angles of the first fan angle θ1 and the second fan angle θ2, the more the first and second protrusion groups suitable for high-speed rotation can be arranged. However, since the electric vehicle drive motor 10 of the present embodiment is a three-phase coil, if the difference in electrical angle becomes π / 3 or more, torque is applied to reverse rotation. Therefore, the first fan angle θ1 and the second fan angle θ2 are set to π / 3 as a difference in electrical angle. The first fan angle θ1 and the second fan angle θ2 are angles formed by lines connecting the rotation center of the rotating body (rotor) and the magnetic center generated from the tip of the protrusion.

  FIG. 9 shows the number of magnetic poles of the rotor 32 and the number of protrusions (number of slots) in the case where the difference between the electrical angles of the first fan angle θ1 and the second fan angle θ2 is π / 9 and 2π / 3. , The first fan angle θ1 and the second fan angle θ2 corresponding to the combination of the number of teeth and the number of salient poles) are illustrated as mechanical angles. When configuring a motor, there are various combinations of the number of magnetic poles and the number of protrusions. The number of magnetic poles may be an even number (2n: n is a natural number). If the number of magnetic poles is small, the number of coil turns may be limited. In this embodiment, the minimum number of magnetic poles is set to four, and “n” is a multiple of two. The number of protrusions is a multiple of 6 (6 m: m is a natural number) with the unit having two protrusions in each of the three phases. In the case of the present embodiment, since there are the first protrusion group and the second protrusion group in the present embodiment, the total number of the protrusions is indicated by 6 m indicating a multiple of 3, and the number of protrusions of the first protrusion group is shown. The number of protrusions in the second protrusion group is 3 m, and “m” is a natural number starting from 1. For example, when the number of magnetic poles is 4, the number of protrusions is 6. At this time, there are three first protrusions 36 and three second protrusions 38.

  As described above, when the phase difference of the magnetic flux change rate during low-speed rotation and high-speed rotation is π / 18 in electrical angle, the first fan angle θ1 indicated by the first protrusion 36a and the second protrusion 38a is The difference in electrical angle between the second fan angle θ2 indicated by the second protrusion 38a and the first protrusion 36b is π / 9.

  When the number of magnetic poles is 2n, there is a relationship of electrical angle = mechanical angle × π / 180 × n. Therefore, if the difference in electrical angle between the first fan angle θ1 and the second fan angle θ2 is θd and the difference in mechanical angle is θk, both have the relationship of Equation 1.

θk = θd × 180 / π / n (Formula 1)
If the mechanical angles of θ1 and θ2 are θ1k and θ2k, respectively, they are expressed as follows.

θk = θ2k−θ1k (Formula 2)
The average angular interval θa of the protrusions is expressed as follows assuming that the number of protrusions is 6 m.

θa = 360 / (6 m) = 60 / m (Expression 3)
Since θa is also an average of θ1k and θ2k, it is expressed as follows.

θa = (θ1k + θ2k) / 2 (Formula 4)
From Equations 2 and 4, θ1k and θ2k are expressed as follows.

θ2k = θa + θk / 2
θ1k = θa−θk / 2
Substituting Equations 1 and 3 into these, θ1k and θ2k are expressed as follows.

θ2k = 60 / m + θd × 90 / (πn) (Formula 5)
θ1k = 60 / m−θd × 90 / (πn) (Formula 6)
For example, when the difference in phase of the magnetic flux change rate during low-speed rotation and high-speed rotation is π / 18 in electrical angle, the difference in electrical angle between the first sector angle θ1 and the second sector angle θ2 is θd = π / 9 is enough. If the number of magnetic poles is 4 (n = 2) and the number of protrusions (slots) is 6 (m = 1), θ1k and θ2k can be obtained from Equations 5 and 6 as follows.

θ2k = 60/1 + π / 9 × 90 / (2π) = 60 + 5 = 65 °
θ1k = 60 / 1−π / 9 × 90 / (2π) = 60−5 = 55 °
Therefore, the first fan angle θ1k = 55 ° and the second fan angle θ2k = 65 °.

Similarly, the difference in electrical angle between the first fan angle θ1 and the second fan angle θ2 is θd = π / 9, the number of magnetic poles is 8 (n = 4), and the number of protrusions (slots) is 12 (m = If 2), θ1k and θ2k are obtained as follows.

θ2k = 60/2 + π / 9 × 90 / (4π) = 30 + 2.5 = 32.5 °
θ1k = 60 / 2−π / 9 × 90 / (4π) = 30−2.5 = 27.5 °
Therefore, the first fan angle θ1k = 27.5 ° and the second fan angle θ2k = 32.5 °. The same calculation can be performed for other combinations of the number of magnetic poles and the number of protrusions.

  Further, when the phase difference of the magnetic flux change rate at the low speed rotation and the high speed rotation is π / 3 in electrical angle, the electrical angle difference between the first sector angle θ1 and the second sector angle θ2 is θd = 2π / 3 may be used. If the number of magnetic poles is 4 (n = 2) and the number of protrusions (slots) is 6 (m = 1), θ1k and θ2k can be obtained from Equations 5 and 6 as follows.

θ2k = 60/1 + 2π / 3 × 90 / (2π) = 60 + 30 = 90 °
θ1k = 60 / 1-2π / 3 × 90 / (2π) = 60-30 = 30 °
Therefore, the first fan angle θ1k = 30 ° and the second fan angle θ2k = 90 °.

Similarly, the difference in electrical angle between the first fan angle θ1 and the second fan angle θ2 is θd = 2π / 3, the number of magnetic poles is 8 (n = 4), and the number of protrusions (slots) is 12 (m = If 2), θ1k and θ2k are obtained as follows.

θ2k = 60/2 + 2π / 3 × 90 / (4π) = 30 + 15 = 45 °
θ1k = 60 / 2-2π / 3 × 90 / (4π) = 30−15 = 15 °
Therefore, the first fan angle θ1k = 15 ° and the second fan angle θ2k = 45 °. The same calculation can be performed for other combinations of the number of magnetic poles and the number of protrusions.

  In this way, the difference between the mechanical angles of the first fan angle θ1 and the second fan angle θ2 formed by dividing the fan angle formed by the two adjacent first protrusions 36 into two by the second protrusion 38 is determined in advance. It is determined corresponding to the required maximum rotational speed determined as the specification of the electric vehicle drive motor 10. That is, the difference between the phase of the magnetic flux change rate by the first coil 40 and the second coil 42 and the electrical angle of the magnetic flux change rate phase by only the first coil 40 is determined to be in the range of π / 18 to π / 3. . Specifically, even if the combination of the number of magnetic poles and the number of protrusions changes by setting the difference between the mechanical angles of the first fan angle θ1 and the second fan angle θ2 to an angle as illustrated in FIG. It is possible to switch from the low speed mode to the high speed mode with simple control by simply detaching the second coil 42 from the connection. A low speed mode in which the rotor 32 can be rotationally driven with high torque by the rotating magnetic field generated by the first coil 40 and the second coil 42 can be realized. In addition, a high-speed mode that enables high-speed rotation by cutting off current supply to the second coil 42 and generating a rotating magnetic field only by the first coil 40 to suppress generation of a large counter electromotive force during high-speed rotation. Can be realized. In the high speed mode, the phase of the rate of change of magnetic flux by the first coil 40 corresponds to the value obtained by converting the time constant τ of the current into an electrical angle only by the control for cutting off the current supply to the second coil 42. Since the adjustment is made, the decrease in average torque can be reduced. As a result, it is possible to realize driving of the electric vehicle drive motor 10 that suppresses variation in average torque when switching from low-speed rotation drive to high-speed rotation drive. It is also possible to perform control in combination with current phase adjustment or the like.

  By the way, the 1st coil 40 and the 2nd coil 42 may use the same thing. However, when switching from the low speed mode to the high speed mode, the counter electromotive force induced in the coil is reduced and the coil resistance is also reduced, so that the current value of the coil is increased. In this case, when switching from the low speed mode using the first coil 40 and the second coil 42 to the high speed mode using only the first coil 40, the current value may increase and exceed the allowable current of the circuit and damage the circuit. is there. In response to this problem, the ratio of the number of turns of the first coil 40 and the second coil 42 is such that the maximum current supplied to the first coil 40 when the rotational speed of the rotor exceeds a predetermined value is the rotational speed of the rotor. May be determined so as not to exceed the maximum current supplied to the first coil 40 and the second coil 42 when the value is equal to or less than a predetermined value. In general, the maximum current in the low-speed mode using the first coil 40 and the second coil 42 is the starting current. In this case, the maximum current in the high-speed mode using only the first coil 40 is in the low-speed mode. It can be configured not to exceed the starting current.

  By increasing the number of turns of the first coil 40, the back electromotive force increases in the high speed mode using only the first coil 40, so that the current decreases. Further, by increasing the resistance value of the first coil 40, the resistance value increases in the high speed mode using only the first coil 40, so that the current decreases. Therefore, the condition that the maximum current supplied to the first coil 40 when switching from the low speed mode to the high speed mode does not exceed the maximum current supplied to the first coil 40 and the second coil 42 in the low speed mode is that the first coil 40 The number of turns of the second coil 42, the resistance value, and the switching rotational speed for switching from the low speed mode to the high speed mode can be determined by experiments. In the present embodiment, the number of turns of the first coil 40 is 150% to 180% of the number of turns of the second coil 42, and the resistance value of the first coil 40 is 150% of the resistance value of the second coil 42. The switching rotational speed is set to 75% to 85% of the maximum rotational speed in the low speed mode. It was confirmed that this configuration smoothly switched from the low speed mode to the high speed mode without being affected by individual differences in coil characteristics, signal processing time, and the like. In addition, with this configuration, it is possible to ensure a sufficient torque at the time of low-speed rotation and a sufficient rotation speed at the time of high-speed rotation while preventing an excessive current of the circuit when switching from the low-speed mode to the high-speed mode.

  As described above, the first coil 40 is used in both the low speed mode and the high speed mode. On the other hand, the second coil 42 is not used in the high speed mode. In other words, when it is desired to reduce the amount of heat generated by the coil, it is efficient to take measures with the first coil 40. Therefore, in the present embodiment, the wire diameter of the first coil 40 is made larger than the wire diameter of the second coil 42. By setting the wire diameter of the coil in this way, the resistance of the first coil 40 that constantly supplies current is reduced, the amount of heat generation can be reduced, and heat countermeasures for the electric vehicle drive motor 10 can be facilitated.

  In this embodiment, in order to detect the rotation speed of the rotor 32, the rotation detection sensor 16 is used as a rotation detection means, and the two fan angles formed by the two first protrusions 36 adjacent to each other and the second protrusion 38 sandwiched therebetween. Of these, the rotor 32 is disposed close to the first protrusion 36 and the second protrusion 38 forming the wider fan angle. That is, it arrange | positions in any position among 2nd fan angle (theta) 2 in FIG. In this case, the rotation detection sensor 16 can be moved away from each protrusion, and the influence of noise due to the magnetic flux emitted from the tip of the protrusion can be minimized, and a reliable output signal can be transmitted from the rotation detection sensor 16. Can output. The rotation detection of the rotor 32 can be detected using, for example, an encoder, or can be calculated based on the state of occurrence of the counter electromotive force.

  In the above-described embodiment, the example in which the current supply to the second coil 42 is interrupted and the current is supplied to the first coil 40 when the rotational speed of the rotor exceeds a predetermined value has been described, but the present invention is not limited thereto. . For example, when the rotational speed of the rotor exceeds a predetermined value, a current may be supplied to the first coil 40 and a current may be supplied to the second coil 42 in parallel with the first coil 40.

  In the embodiment described above, the case where the speed detection unit 20 detects the rotational speed of the rotor based on the change in the rotational position detected by the position detection unit 18 has been described, but the present invention is not limited thereto. For example, the speed detection unit 20 may be configured to detect the rotation speed of the rotor based on the detection result of the rotation detection sensor 16.

  In the above-described embodiment, as shown in FIG. 3, in the outer rotor type motor structure, the first protrusion group and the second protrusion group include two first protrusions sandwiching the second protrusion. An example in which the protrusions are formed so as to be biased toward one side has been described. Such a configuration of the first protruding portion group and the second protruding portion group can be applied to an inner rotor type motor structure, and the same effect can be obtained. Further, the above-described embodiment is an exemplification, and it is needless to say that the principle and application of the present invention are merely shown. It is understood by those skilled in the art that many modifications and arrangements can be made to the embodiments without departing from the spirit of the present invention defined in the claims, and that such modifications are also within the scope of the present invention. Is understood.

  θ1 first fan angle, θ2 second fan angle, 10 drive motor for electric vehicle, 24 stator core, 28 coils, 30 magnets, 32 rotor, 36 first protrusion, 38 second protrusion, 40 first coil, 42 first 2 coils.

Claims (8)

A rotatable rotor including a magnet that arranges 2n (n is a natural number) magnetic poles in the circumferential direction;
The stator core is arranged to face each magnetic pole of the rotor and has 6 m (m is a natural number) protrusions arranged on the circumferential surface, and the protrusions are 3 m formed at equal intervals in the circumferential direction. Each of the first protrusions and the 3 m second protrusions formed at equal intervals in the circumferential direction as the protrusions, the first protrusions constituting the first protrusions and the first A stator core in which the second protrusions constituting the two protrusion group are alternately arranged;
A first coil wound around each of the first protrusions;
A second coil wound around each of the second protrusions;
Rotation detection means for detecting the rotation state of the rotor;
Current control means for controlling the amount of current flowing through the first coil and the second coil according to the result detected by the rotation detection means;
Including
The second projecting portion group and the first projecting portion group are formed such that the second projecting portion is arranged to be biased to one of the two first projecting portions sandwiching the second projecting portion. An electric vehicle drive motor characterized by comprising:   The difference between the mechanical angle of the first fan angle and the second fan angle formed by dividing the fan angle formed by the two adjacent first protrusions into two by the second protrusion is equal to the change in the angle of the rotor. When the magnitude of change in the magnetic flux interlinking with each coil is defined as a magnetic flux change rate, the phase of the magnetic flux change rate by the first coil and the second coil corresponding to a predetermined required maximum rotational speed, and the 2. The drive motor for an electric vehicle according to claim 1, wherein the difference in electrical angle of the phase of the magnetic flux change rate due to only the first coil is determined to be within a range of [pi] / 18 to [pi] / 3. .   The current control means supplies current to the first coil and the second coil when the rotational speed of the rotor is equal to or less than a predetermined value, and when the rotational speed of the rotor exceeds the predetermined value, 3. The electric vehicle drive motor according to claim 1, wherein supply of current to the two coils is interrupted and current is supplied to the first coil. 4.   4. The electric vehicle drive motor according to claim 3, wherein the current control means determines a practical maximum switching rotational speed obtained by subtracting a switching margin value from a maximum allowable rotational speed at low speed of the rotor as the predetermined value.   The drive motor for an electric vehicle according to any one of claims 1 to 4, wherein the number of turns of the first coil and the second coil is different.   The winding ratio between the first coil and the second coil is such that the maximum current supplied to the first coil when the rotational speed of the rotor exceeds the predetermined value is less than the predetermined value. 6. The drive motor for an electric vehicle according to claim 5, wherein the motor is determined so as not to exceed a maximum current supplied to the first coil and the second coil.   The rotation detection means includes: the first protrusion that forms a wider one of two fan angles formed by two adjacent first protrusions and the second protrusion sandwiched between the first protrusions; The drive motor for an electric vehicle according to any one of claims 1 to 6, wherein the drive motor for an electric vehicle according to any one of claims 1 to 6, wherein the drive motor is disposed close to the rotor at a position between the second protrusions.   The drive motor for an electric vehicle according to any one of claims 1 to 7, wherein a wire diameter of the first coil is larger than a wire diameter of the second coil.

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