KR101058867B1 - Driving system for electric vehicles utilizing two induction motors - Google Patents

Abstract

PURPOSE: A driving system for electric vehicles utilizing two induction motors is provided to reduce manufacturing costs of an inverter by driving two motor in parallel. CONSTITUTION: In a driving system for electric vehicles utilizing two induction motors, first and second induction motors(5a,5b) drive the both wheels of an electric vehicle respectively. A single inverter(3) supplies necessary power required for driving the first and second induction motors. An inductor(4) divides the power from the single inverter and connects the first and second induction motors in parallel to supply power them. The inductor is comprised of first inductor and second inductors which have different inductance in driving the electric vehicle.

Description

Driving system for electric vehicles utilizing two induction motors

The present invention relates to a drive system of an electric vehicle using two induction motors, and more particularly, two induction motors attached to both wheels of an electric or hybrid vehicle and connected to one inverter and driven in parallel. A drive system for an electric vehicle using two induction motors.

In addition, the present invention by installing a variable inductor that can vary the inductance in each of the two induction motors and moving the central core of the variable inductor in accordance with the rotation direction in conjunction with the direction of rotation of the car, there is a risk that the car suddenly rotates when the inverter breaks down It relates to a drive system of an electric vehicle using two induction motors which can reduce and equalize the torque of both motors by adjusting the voltage applied to both motors through the inductor during rotation.

In general, when two motors are installed on both shafts of the rear wheels of an electric vehicle, the speed can be changed without a differential gear, so that the rotation of the vehicle can be smoothed without skidding. However, a disadvantage of this case is that two inverters must be used, and a bigger problem is when one of the two inverters has failed. That is, if only one inverter breaks down while driving, there is a risk that a sudden rotational force may be generated in the vehicle and lead to a big accident.

The present invention was created in order to solve the above problems, in the method of driving two induction motors in parallel with one inverter, using two induction motors that can vary the speed of both induction motors when the vehicle rotates. The purpose is to provide a drive system of an electric vehicle.

That is, in the present invention, the wheel that rotates the inner circle is relatively slower than the wheel that rotates the outer circle when the vehicle rotates, but the electric angular velocity of the voltage applied to both motors is the same, so that the induction connected to the inner wheel The slippage of the motor is greater than the slippage of the induction motor connected to the outer wheel, resulting in greater torque. To overcome this torque imbalance, two inductions can be used to reduce the voltage applied to the inner motor by using a variable inductor. It is an object to provide a drive system for an electric vehicle using a motor.

In addition, the present invention can not only prevent the car from rotating rapidly because both motors are controlled identically in the conventional vehicle using two induction motors, and the operation of both motors is the same when the inverter fails. It is an object of the present invention to provide a driving system of an electric vehicle using two induction motors, which can provide the same effect as having a differential gear by changing the speed of both motors.

In order to achieve the above object, a drive system for an electric vehicle using two induction motors according to the present invention includes: first and second induction motors installed for individual driving of both wheels of the electric vehicle; A single inverter for supplying power for driving the first and second induction motors; And an inductor for connecting the first and second induction motors in parallel so as to separate the power supplied from the single inverter and to supply the first and second induction motors. The inductor may be formed of first and second inductors which form inductances having different values during rotational operation of the electric vehicle.

Advantageously, said first and second inductors comprise a first core and a second core and a central core movably interposed between said first and second cores.

Preferably, each of the first and second cores is formed to have an “E” shape so as to face each other with respect to the center core, and the center cores are formed such that both sides thereof correspond to the first and second cores, respectively. It is characterized by being formed in the E "shape.

Preferably, the apparatus further comprises a central core moving device for moving the central core on one axis.

Preferably, the central core moving device comprises a stepping motor and a control device for controlling the stepping motor.

 Preferably, the control device, the inner wheel connected to the first induction motor by controlling the stepping motor connected to the central core, so that the torque applied to the inner wheel and the outer wheel is the same when the electric vehicle rotates. The inductance of the first inductor corresponding to the first induction motor is increased to reduce the torque applied to the first induction motor, and the inductance of the second inductor corresponding to the second induction motor connected to the outer wheel is reduced.

According to the present invention, since one inverter drives two motors, each driving both wheels of the electric vehicle, in parallel, the inverter manufacturing cost can be reduced, and troubles and management factors can be reduced.

Further, according to the present invention, since two motors mounted on the electric vehicle have the same operating characteristics at normal times or in failure, it is possible to prevent the vehicle from rapidly rotating in the event of an inverter failure.

In addition, according to the present invention, the speed can be varied while generating the same torque in both wheels as if the differential gear is mounted during the rotation of the electric vehicle.

Furthermore, according to the present invention, since the variable inductor having a movable magnetic material is used for voltage control of both motors, manufacturing cost can be reduced and volume can be reduced.

1 is a conceptual diagram of a driving system of an electric vehicle using two induction motors according to the present invention.
2 is a conceptual diagram showing that the inner diameter of the inner wheel and the outer wheel is different when the electric vehicle rotates.
3 is a graph illustrating torque-speed characteristics of a general induction motor.
Figure 4 is a configuration diagram of the connection of the variable inductor, both induction motor and inverter according to the present invention.
5 is a circuit diagram of a variable inductor applied to the present invention.
6 is a view showing that the relative magnitude of the inductance changes in accordance with the change in the position of the center core according to the present invention.
7 is a view for explaining the setting of the position of the center core according to the rotation direction in the present invention.
8 is a per phase equivalent circuit diagram to which the variable inductor of the present invention is added.
9 is a flow control flow chart of a central core in the variable inductor of the present invention.
10 is a configuration diagram illustrating a center inductor of a variable inductor applied to the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, a driving system of an electric vehicle according to the present invention includes a battery 1 for generating a variable voltage / variable frequency voltage PWM (pulse width modulation) waveform, a boost converter (2), And an inverter 3: an inverter; Two first and second induction motors 5a and 5b which are connected to both wheels 7a and 7b of the electric vehicle to provide driving power, respectively, are separated from the motor driving power supplied from the inverter 3. Inductor 4 for connecting the first and second induction motors in parallel so as to be supplied to the first and second induction motors 5a and 5b, and shaft torque of the first and second induction motor shafts. Gears / chains 6a and 6b for conveying them.

2 is a conceptual diagram showing that the inner diameter of the inner wheel and the outer wheel is different when the electric vehicle rotates. 2, the radius of curvature of the inner circle is 8a and the radius of curvature of the outer circle is 8b. Since the inner wheel 7a rotates along a small circle and the outer wheel 7b rotates along a large circle, the rotation speed of the inner wheel is smaller than that of the outer wheel.

3 shows a typical torque-speed characteristic curve of an induction motor. Referring to FIG. 3, ω _e denotes the electric angular velocity, and ω _a and ω _b denote the rotor angular velocity of the first and second induction motors 5a and 5b, respectively. Since the speed of the inner wheel 7a is smaller than the speed of the outer wheel 7b, ω _b > ω _a . Therefore, the slip speeds of the first and second induction motors 5a and 5b are given by ω _e -ω _a and ω _e -ω _b , and ω _e -ω _a > ω _e -ω _b is satisfied. do. In Figure 3 the torque for each slip is denoted by Ta and Tb. It is necessary to note that Ta> Tb in FIG. 3. That is, the slip speed of the inner induction motor is larger than the slip speed of the outer induction motor so that the corresponding torque is relatively large. If the torque of the inner induction motor is large, the speed of the inner wheel is increased, which hinders the rotation. In order to solve such a problem, the present invention uses the variable inductor 4 as shown in Figs.

4 shows a connection circuit diagram from the variable inductor 4 to the inverter 3 and the first and second induction motors 5a and 5b according to the present invention, and FIG. 5 shows an equivalent circuit diagram of the variable inductor 4. FIG. 6 shows the cores 9, 10a and 10b of the variable inductor 4, moving two 'E' shaped first and second cores 10a and 10b and moving therebetween. It is composed of a magnetic center core 9.

Referring to FIG. 6A, the center core 9 is located at the lower side, and the second inductor core 10b on the right side is advantageous in forming a ruler. At the same time, in the case of the first inductor core 10a on the left side, the protruding portion of the core is shifted so that it is relatively difficult to form a ruler. Therefore, the inductance of the second inductors 9 and 10b located on the right side is larger than the inductance of the first inductors 9 and 10a located on the left side. That is, La <Lb. Referring to FIG. 6C, in this case, the inductance of the first inductors 9 and 10a located on the left side is on the right side because the center core 9 is located on the upper side as opposed to the case of FIG. 6A. It becomes larger than the inductance of the located second inductors 9 and 10b. That is, Lb <La. In addition, referring to FIG. 6 (b), the center core 9 is positioned in neutral so that both inductances are equal. That is, La = Lb. The voltage drop across the inductor is calculated as ω _e LI. Here, I means current flowing through the inductor.

FIG. 7 shows the position of the intermediate core 9 of the inductor when the electric vehicle turns left and when it turns right. Referring to FIG. 7A, when the left turn, the center core 9 moves upward to maximize the area of the flux linkage with the first E-core 10a located on the left side. However, the area of the flux linkage with the second E-core 10b located on the right side is minimized. Therefore, La> Lb. That is, since the impedance is given by ω _e La> ω _e Lb, the voltage drop by the first inductors 10a and 9 located on the left side is increased to prevent the current from increasing in the first induction motor 5a.

On the other hand, when the electric vehicle turns right as shown in FIG. 7B, the center core 9 moves downward to maximize the area of the flux linkage with the second E-core 10b located on the right side. However, the area of the flux linkage with the first E-core 10a located on the left side is minimized. Therefore, La <Lb. That is, since the impedance is given by ω _e La <ω _e Lb, the voltage drop by the second inductors 10b and 9 located on the right side is increased to prevent the current from increasing in the second induction motor 5b.

When the slip s is small, the torque is described by Equation 1 below. In Equation 1, P is the number of poles, V _s is the motor phase voltage, ω _r is the rotor speed, r _r is the rotor resistance of the motor. That is, the torque is proportional to the square of the phase voltage.

[Equation 1]

), 양 인덕턴스가 동일한 경우 (

), 좌측의 제1 유도 모터(5a)가 더 많은 토크를 발생시킨다. 이것은 상대적으로 낮은 속도를 유지해야만 하는 좌측 바퀴에 상반되는 결과를 가져온다. 이를 해결하는 방법으로 좌측 인덕턴스를 크게 하여

가 되도록 한다. 그러면, 좌측의 제1 유도 모터(5a)에 인가되는 전압이 상대적으로 작게 (

)가 되어 좌측의 제1 유도 모터(5a)의 슬립이 크다 하더라도 양쪽 모터의 토크가 거의 동일하게 (

)가 된다. 8 shows a per phase equivalent circuit of an induction motor according to the invention. In the equivalent circuit of FIG. 8, the AC voltage source 11 means an inverter. Two first and second induction motors 5a and 5b are connected in parallel via an inductor. When the left turn, the slip of the first induction motor 5a on the left side becomes larger and more current flows (

), If both inductances are equal (

), The first induction motor 5a on the left side generates more torque. This has the opposite effect to the left wheel, which must maintain a relatively low speed. The solution to this problem is to increase the left inductance

To be Then, the voltage applied to the first induction motor 5a on the left side is relatively small (

Even if the slip of the first induction motor 5a on the left side is large, the torques of both motors are almost equal (

)

Turning to the right is similar to turning to the left. In other words, the right inductance is increased to prevent the right wheel from slowing down and from slipping to increase torque.

The inductance can be easily changed by using a small motor (eg, stepping motor) 13 for moving the central core 9 shown in FIG. 10 and a control device 100 for controlling the small motor. It will be apparent to those skilled in the art.

9 shows a flowchart for determining the position of the inductor center core 9 according to the rotation direction of the electric vehicle. FIG. 10 shows a mechanism part configured to move the first and second cores 10a and 10b, the center core 9 and the center core 9 on one axis of the inductor of the present invention. The mechanism shown in FIG. 10 includes a small motor 13 such as a stepping motor and a lead screw 14 for transmitting the driving force of the small motor to the central core 9. It will be apparent to those skilled in the art that the mechanism shown in FIG. 10 can be constructed using solenoid drivers or springs instead of motors.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and those skilled in the art may realize other embodiments corresponding to various modifications and equivalents therefrom. Will understand. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

1: battery 2: boost converter
3: inverter 4: inductor
5: Rotor 5a 5b: Induction Motor
6a 6b: reduction gear 7a 7b: wheel
8a: inner turning radius 8b: outer turning radius
9: center core of inductor 10a: fixture (half) of inductor
10b: fixed part of inductor (half) 11: equivalent voltage source representing the inverter
13: small motor (stepping motor) 14: lead screw

Claims (6)

In the drive system of an electric vehicle,
First and second induction motors installed for individually driving both wheels of the electric vehicle;
A single inverter for supplying power for driving the first and second induction motors; And
An inductor for connecting the first and second induction motors in parallel so as to separate the power supplied from the single inverter and supply the first and second induction motors;
The inductor is a drive system of an electric vehicle using two induction motors, characterized in that the first and second inductor to form a different value inductance during rotational operation of the electric vehicle. The method of claim 1,
The first and second inductors may include a first core and a second core, and a central core movably interposed between the first and second cores. Driving system. The method of claim 2,
And a central core moving device for moving said central core on one axis. The method of claim 3,
The central core moving device includes a stepping motor and a control device for controlling the stepping motor. The method of claim 4, wherein
The control device controls the stepping motor connected to the central core so that the torque applied to the inner and outer wheels is the same when the electric vehicle rotates, so that the torque applied to the inner wheel connected to the first induction motor is controlled. Two inductions, characterized in that to increase the inductance of the first inductor corresponding to the first induction motor to reduce, and to reduce the inductance of the second inductor corresponding to the second induction motor connected to the outer wheels The drive system of an electric vehicle using a motor. The method of claim 2,
The first and second cores are each formed in an “E” shape so as to face each other with respect to the center core. The central core has an “E” shape so that both sides thereof correspond to the first and second cores, respectively. Drive system of an electric vehicle using two induction motors, characterized in that formed as.

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