JP2005006400A - Motor drive mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor drive mechanism capable of varying the number of poles or phases of a motor easily. <P>SOLUTION: The motor drive mechanism excites the coil of each phase of a motor by supplying a specified current in response to an AC polyphase signal. The coil of each phase is divided into a plurality of coil sections each of which is connected with at least one switch element. The switch elements function to switch connection state of the coil sections freely. Number of poles or phases of the motor can be varied easily by switching connection state of the coil sections. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a motor drive mechanism. In particular, the present invention relates to a motor drive mechanism capable of operating a motor by changing the number of poles and phases of the motor.
[0002]
[Prior art]
Development of electric vehicles using a motor for driving a vehicle, such as an electric vehicle and a hybrid car, is progressing. In such an electric vehicle, direct current power from the battery is converted into alternating current through an inverter, and predetermined electric power is supplied to the motor to perform drive control of the motor.
[0003]
In general, an inverter in which a bridge circuit is configured by a switching element such as an FET (field effect transistor) is used (for example, Non-Patent Document 1). In current motors, the number of motor poles and the number of phases of a driving voltage are usually determined at the beginning of the motor design, and a coil design and a drive circuit (inverter) design corresponding to the number are often performed. For example, when determining the number of phases and the number of poles of the motor, the number of rotations and the number of poles are determined from the relational expression (Formula 1) with the frequency of the sine wave that drives the motor.
[0004]
f = n · k / 2
[0005]
f is the frequency of the sine wave, n is the number of revolutions of the motor, and k is the number of poles.
Further, the number of poles of the motor is determined depending on how the electric wire is wound when winding a coil for generating a rotating magnetic field.
[0007]
[Non-Patent Document 1]
October 1997 Toyota Motor Corporation: Prius “New Car Guide” on page 1-13 [0008]
[Problems to be solved by the invention]
However, the conventional motor drive mechanism has the following problems.
(1) The cost of the switch element tends to increase as the output capacity of the inverter increases.
In recent years, the output capacity of inverters has increased with the increase in motor output. A switching element having a large output capacity also has a large current flowing through the element, and the element area itself increases in size, leading to an increase in cost due to a decrease in yield. In particular, in the conventional motor drive mechanism, since the switch elements are connected so as to supply the current collectively to the coils for each phase, the current flowing through one switch element must be increased. In addition, if the current flowing through the element is large, the amount of heat generated locally in the vicinity of the element is large, and the scale of the cooling mechanism is increased, leading to an increase in the cost of the entire motor driving mechanism.
[0009]
(2) The number of poles and phases of the motor cannot be easily changed.
In actual driving of an electric vehicle, a motor capable of obtaining a large torque at a low speed is required at the time of starting and the like, and a motor having a high speed and a low torque is required at a high speed. In general, when the number of poles of the motor is increased, the rotation angle is reduced by one cycle of electric power supplied from the drive circuit, so that the torque can be increased although the rotation speed is decreased. However, the frequency of the sine wave that drives the motor increases. Therefore, the number of poles is limited by the switching speed of the drive circuit. On the other hand, there is a demand for realizing high-speed rotation without increasing the frequency of the sine wave applied to the motor by reducing the number of poles as much as possible during high-speed running. However, the number of phases and the number of poles of the motor are determined at the beginning of the motor design, and the number of phases and the number of poles of the motor are varied according to the running characteristics in order to design the coil and drive circuit (inverter) accordingly. I can't. Conventionally, there is a technique for converting the number of poles by devising the coil connection, but this technique has the disadvantage of requiring two types of windings and increasing the size of the motor.
[0010]
Therefore, a main object of the present invention is to provide a motor drive mechanism that can easily vary the number of poles or phases of a motor.
[0011]
[Means for Solving the Problems]
The motor drive mechanism of the present invention is a motor drive mechanism that supplies a predetermined current to a coil of each phase of a motor and excites it by a multiphase AC signal. Each phase coil is divided into a plurality of divided coils, and at least one switch element is connected to each divided coil. In addition, the connection state of the divided coils can be switched by the operation of the switch element.
[0012]
Conventionally, the unit of the coil that has been fed together for each phase is further divided into a plurality of divided coils, and the connection state of the divided coils can be switched by the operation of the switch element provided in the divided coils. By switching the connection state of the divided coils, the number of poles and the number of phases of the motor can be easily realized.
[0013]
Further, since each switch element supplies power in divided coil units, the energization amount per element is also small, and the capacity of each element may be small. Therefore, a small element can be used, and the drive mechanism can be reduced in size and cost.
[0014]
Hereinafter, the configuration of the present invention will be described in more detail.
(1) By switching the connection state of each divided coil, the following motor characteristics can be varied.
[0015]
<Variable number of poles>
Switching the switching element to switch the connection state of the divided coils and changing the direction of the current flowing in some of the divided coils, that is, the total number of N poles and S poles formed in the motor field Can be varied. The number of poles before and after switching is not particularly limited. For example, it is possible to switch between 2 poles and 8 poles. By switching the number of poles, it can be operated as a motor with a low rotation and high torque with 8 poles at the time of starting and the like, and can be operated as a motor with a high rotation and low torque with 2 poles during high speed running.
[0016]
<Variable number of phases>
By switching the switching element to switch the connection state of the split coils, by changing the number of split coils to which current is supplied by providing a time difference, the number of phases of the motor, that is, the winding group that passes currents that differ in time in the motor The number can be made variable. By changing the number of phases, the motor can be driven so that both high torque and high speed rotation can be achieved. That is, by increasing the number of phases, it is possible to drive a motor with low rotation and high torque, and by reducing the number of phases, it is possible to drive a motor with high rotation and low torque.
[0017]
<Variable number of poles and number of phases>
By combining the above variable number of poles and variable number of phases, both the number of poles and the number of phases can be made variable. With this configuration, the motor can be driven so that both high torque and high speed rotation can be achieved.
[0018]
<Variable between concentrated winding and distributed winding>
When the coil is composed of concentrated windings, a switch is set so that a current is supplied to a part of the split coil by an AC signal of a certain phase and a current is supplied to the remaining part of the split coil by an AC signal of a different phase. By switching the elements, the concentrated winding coil can be operated in the same manner as the distributed winding coil. For example, each pole can be used as a field weakening, and reluctance torque can be easily obtained. Further, by using the concentrated winding coil, the manufacturing process of the motor can be simplified and the manufacturing efficiency can be improved. Therefore, the drive mechanism of the present invention is suitable for driving a motor for an electric vehicle / hybrid car, which is an application in which a fluctuation of a load is large and a field weakening region exists while a coil is formed by concentrated winding.
[0019]
(2) In order to change the motor characteristics, it is preferable to feed back the rotation state of the motor.
That is, a motor output state detection means is provided. The output state detection means detects the physical quantity having a correlation with the rotational speed of the motor or the rotational speed. Based on the detection result, the switching of the switch element is controlled by the determination means. For example, the number of rotations of the motor is detected, and when the number of rotations is less than a threshold value, a state that requires low-speed rotation such as at the time of starting is determined and the motor is operated with eight poles. On the other hand, when the rotation speed of the motor exceeds the threshold value, it is determined that high speed rotation such as high speed running is necessary, and the motor is operated with two poles. Therefore, it is possible to perform an operation suitable for the rotational characteristics required for the motor.
[0020]
(3) Characteristics of the switch element and arrangement location The switch element connected to each divided coil may have a lower capacity than the conventional one. Conventionally, since current is collectively supplied to a coil for one phase, it is necessary to increase the current capacity of the element. In the present invention, since it is sufficient to supply a current flowing through one split coil, the current capacity per element may be smaller than that of the conventional one, and an element with a high yield can be used.
[0021]
The switch element is preferably built in the motor. In order to divide the motor coil and connect the switch element to each divided coil, the switch element is preferably installed inside the motor. Usually, the inside of the motor becomes a high temperature of 150 ° C. or more. For this reason, a switching element using a wide-gap semiconductor capable of operating at a high temperature and having a low loss is preferable. More specifically, a switch element using SiC is suitable. Further, since the current capacity of the switch element may be small, a small switch element can be used, and accordingly, the switch element can be easily incorporated in the motor. And by incorporating this switch element, the motor drive mechanism itself can be miniaturized.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
(Example 1)
FIG. 1 is an explanatory diagram showing before and after the change when the number of poles is changed with the same number of coils in the embodiment of the present invention. FIG. 2 is an explanatory diagram showing a change in the connection state of the split coils in the case of FIG. FIG. 3 is a circuit diagram of the drive mechanism of the present invention that realizes the switching of the connection state of FIG.
[0023]
As shown in FIG. 1, by dividing one coil into four divided coils and switching the connection state of each divided coil, the eight poles shown in FIG. 1 (A) and the two poles shown in FIG. 1 (B) Can be switched.
[0024]
An electrical connection method for realizing the change in the number of poles is shown in FIG. As shown in this figure, in the case of 8 poles, the divided coils are connected so as to be connected to the adjacent divided coils sequentially. In the case of two poles, the direction of current flow to the second and fourth (upper and lower in the figure) split coils is opposite to that in the case of eight poles.
[0025]
An example of a circuit for realizing this change in the number of poles is shown in FIG. As shown in this figure, each split coil is connected to a switching element such as an FET. Both switch elements are installed in the motor. That is, the switch elements Q5 and Q7 are connected to the terminal 2 side of the split coils L2 and L4, and Q2 and Q3 are connected to the terminal 1 side of the split coils L3 and L1. Further, the switch elements Q4 and Q6 are connected to the terminal 2 side of the split coils L1 and L2, and the switch elements Q8 and Q6 are connected to the terminal 2 side of the split coils L3 and L4. These switch elements are composed of wide gap semiconductors made of SiC. The operation control of these switch elements is performed by a switching signal.
[0026]
In such a circuit configuration, when the switching signal between the 8-pole and 2-pole is set to H, the switching elements Q2, Q3, Q5, and Q7 are turned on, resulting in the connection shown in FIG. Drive. When this switching signal is set to L, the switching elements Q1, Q4, Q6, and Q8 are turned on, resulting in the connection shown in FIG. 1B and driving the motor as two poles. In a three-phase AC motor, by applying the configuration shown in FIG. 2 to each phase for three phases, it is possible to generate both three-phase eight-pole and three-phase two-pole rotating magnetic fields.
[0027]
In particular, switching of the split coil by the switch element is performed by detecting the motor output (rotation speed) and checking whether this rotation speed exceeds a certain threshold, thereby realizing a large torque at low rotation speed and High speed rotation is also possible without increasing the frequency of the applied sine wave.
[0028]
(Example 2)
Next, the motor drive mechanism of the present invention will be described for changing the number of phases of the motor. FIG. 4 is an explanatory diagram showing the basic principle when changing the number of phases in the motor drive mechanism of the present invention.
[0029]
Here, switch elements Q9, Q10 and Q11, Q12 are connected to both ends of each of the divided coils L5, L7. In this configuration, the coils L5 and L7 are in phase by simultaneously turning on and off the switching elements Q9 to Q12. Further, by turning on switching elements Q9, Q10 and Q11, Q12 alternately, the generated magnetic field is out of phase. Accordingly, it is possible to switch the number of phases of signals to be driven by arranging the coils L5 and L7 at appropriate positions.
[0030]
Example 3
Next, the same effect as that of the distributed winding coil can be obtained by using a concentrated winding coil motor.
[0031]
Here, a coil normally wound as one coil is wound as four divided coils on the stator core having slots (iron core grooves). FIG. 5 shows a schematic diagram of a state where each divided coil is wound. Then, switch elements are respectively connected to both sides of each divided coil as shown in FIG.
[0032]
Here, the switching elements Q1, Q5, Q2, Q6, Q3, and Q7 are turned on at a timing synchronized with one of the other phase signals that drive the motor, and the switching elements Q4 and Q8 are one of the other multiphase signals. Turns on when synchronized. Thereby, the effect equivalent to distributed winding can be acquired. Therefore, concentrated winding with excellent manufacturability may be used when the motor is manufactured, and operation equivalent to distributed winding can be performed when the motor is driven.
[0033]
【The invention's effect】
As described above, according to the motor drive mechanism of the present invention, conventionally, the switching elements are connected so as to supply current for each phase collectively, but the coils for each phase are divided into a plurality of divided coils. The connection state of the divided coils can be changed by installing a switch element that allows a current to flow for each divided coil. Therefore, the number of poles and phases of the motor can be changed, and the motor can be driven with both high torque and high rotation.
[0034]
Although concentrated winding, the same effect as distributed winding can be obtained, and the manufacturing process of the motor can be simplified.
[0035]
Since current is supplied to each divided coil, the current flowing through the switch element can be reduced, and the cost of the switch element can be reduced.
[0036]
By using a wide band gap semiconductor as the switch element connected to the split coil, the inverter can be operated at a high temperature with lower loss.
[0037]
Therefore, the motor drive mechanism of the present invention can be suitably used for driving a motor in a vehicle that uses the power of the motor for traveling, such as an electric vehicle or a hybrid car.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing before and after a change when the number of poles is changed with the same number of coils in the embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a change in the connection state of the split coils in the case of FIG. 1;
FIG. 3 is a circuit diagram of the drive mechanism of the present invention that realizes switching of the connection state of FIG. 2;
FIG. 4 is an explanatory diagram showing the basic principle when changing the number of phases in the motor drive mechanism of the present invention.
FIG. 5 is a schematic diagram showing a state in which each divided coil is wound.
FIG. 6 is a circuit diagram showing a connection state of switch elements when the concentrated motor is switched to distributed winding in the motor driving mechanism of the present invention.
[Explanation of symbols]
L1-L4 Split coil Q1-Q12 Switch element

Claims (7)

A motor drive mechanism for supplying a predetermined current to a coil of each phase of a motor by a multiphase AC signal and exciting the coil,
The coil of each phase is divided into a plurality of divided coils,
At least one switch element is connected to each divided coil,
A motor drive mechanism characterized in that the connection state of the split coils can be switched by the operation of the switch element. 2. The motor according to claim 1, wherein the number of poles of the motor is variably configured by switching the switch element to switch a connection state of the divided coils and changing a direction of a current flowing in a part of the divided coils. Drive mechanism. The number of phases of the motor is variably configured by switching the switching element to switch the connection state of the divided coils and changing the number of divided coils to which a current is supplied with a time difference. The motor drive mechanism according to 2. It has a motor output state detection means,
The motor drive mechanism according to claim 2 or 3, wherein the switch element is switched to switch the connection state of the divided coils based on the detection result of the detection means. The coil is composed of concentrated winding,
A part of the split coil is configured to switch the switching element so that a current is supplied by an AC signal having a certain phase, and a remaining part of the split coil is supplied by an AC signal having a different phase. The motor drive mechanism according to claim 1. 6. The motor drive mechanism according to claim 1, wherein the switch element is made of a wide gap semiconductor. The motor drive mechanism according to claim 1, wherein the switch element is built in the motor.

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