JP3358215B2 - Motor control device for electric vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electric vehicle,
The present invention relates to a technique for reducing noise called so-called switching noise or chopper noise.

[0002]

2. Description of the Related Art In an electric vehicle at present, it is usual to control electric power supplied to a motor by intermitting DC power stored in a battery by a switching circuit. Further, for example, in order to eliminate a differential gear and to provide a motor for each drive wheel, it is common to have a plurality of motors. In a conventional electric vehicle, the control switching frequencies of a plurality of motors as described above are configured to be operated completely independently of each other. Therefore, as the number of driven motors increases, switching noise or chopper noise increases. There is a problem that the noise called the noise increases. In order to improve the efficiency, it is desirable to lower the switching frequency in order to reduce the switching loss generated in the switching power element. However, in order to reduce noise as described above, the upper limit of the audible range is reduced. There is a problem that the frequency cannot be lowered to 20 kHz or less. As an apparatus for solving the above problem, there is an apparatus described in JP-A-61-109495. This device attempts to reduce noise by using interference between a plurality of motors by controlling the rotation speeds of a plurality of motors to be equal and controlling the phases to be opposite.

[0003]

In the above-described conventional apparatus, the operation is performed while the rotational speeds of the plurality of motors are made to coincide with each other. However, the number of rotations of a motor in an electric vehicle is determined according to the configuration and operating state of the system, and the number of rotations of a plurality of motors may not always be the same. For example, when a motor is mounted on each of the left and right driving wheels, when traveling on a curved road, the left and right rotation speeds change according to the turning radius, and the two cannot be the same. As described above, the conventional noise reduction method may not be applicable to ordinary electric vehicles.

The present invention has been made to solve the problems of the prior art as described above, and provides a motor control device for an electric vehicle that can effectively reduce switching noise in a normal electric vehicle. The purpose is to do.

[0005]

Means for Solving the Problems In order to achieve the above object, the present invention is configured as described in the claims. That is, according to the first aspect of the present invention, each of the motors includes
Generates an AC command value for instructing AC to drive the motor.
Means for comparing the AC command value with the carrier carrier.
And a comparator for generating a PWM signal by
AC by intermittent DC power according to PWM signal
Switching means for converting the power into electric power and supplying the electric power to the motor;
And dividing the plurality of motors into two sets.
In each group, the above comparator of each motor
The carrier carrier having the same frequency and a predetermined phase difference
Is provided. Further, the invention according to claim 2 includes a microphone for measuring noise, and means for controlling a phase difference of the carrier carrier so that a noise value measured by the microphone becomes a minimum value. Things.

[0006]

According to the first aspect of the present invention, the switching frequencies of the respective switching means are all the same, a plurality of motors are divided into two sets, and one switching means and the other switching means in each set. Since the switching phase is set to have a difference by a predetermined value, the noise generated by the switching is canceled by the phase difference in each group, and the noise as a whole can be reduced. Further, in the invention according to claim 2, by controlling the switching phase difference so that the noise value measured by the microphone becomes the minimum value,
Since the phase difference can be controlled to the optimum, the noise can be further reduced.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.
FIG. 1 is a circuit diagram of one embodiment of the present invention, and illustrates the case of an induction motor system. In FIG. 1, reference numeral 1 denotes an accelerator opening sensor for detecting the opening of an accelerator pedal, 2 denotes a torque command calculator for a plurality of motors, 3 denotes an AC current command generation calculator for the first motor 11, and 4 denotes a second motor. Motor 12
The AC current command generators 5, 5 and 6 are respectively comparators for comparing the AC current command values output from the AC current command generators 3 and 4 with the carrier carrier and converting them into PWM pulses. An inverter bridge including a power element such as an IGBT element; 9, an oscillator for a carrier carrier; 10, a delay device for outputting a signal with the phase of the output of the oscillator 9 delayed; The rotation speed detector 15 is a battery. FIG. 2 is a block diagram showing the details of the AC current command generation arithmetic units 3 and 4, and FIG. 3 is a cross-sectional view of an example of a multiple motor power unit constituted by the motors 11 and 12.

Next, the operation will be described. First, when an accelerator command signal corresponding to the accelerator pedal opening is input from the accelerator opening sensor 1, a torque command signal T ₁ of the first motor 11 and a second motor 1
The second torque command signal T ₂ is calculated. For example, in a partial load state between the accelerator command signal from 0 to a certain predetermined value, only the T ₁ is T _1> 0 becomes, T ₂ becomes T ₂ = 0. That is, only one motor is driven and one motor is stopped. When the accelerator command signal exceeds a certain predetermined value, T ₂ also becomes T ₂ > 0, and both the first motor 11 and the second motor 12 are driven. In general, the control is performed as in the former when the load is light such as constant speed operation, and the control is performed as in the latter when the load is high such as acceleration operation. In some cases, the first motor 11 and the second motor 12 are operated with the same torque command signal.

As described above, torque command signals T ₁ and T ₂ are output from torque command calculator 2 and input to AC current command generators 3 and 4, respectively.

In the AC current command generation arithmetic units 3 and 4, FIG.
As shown in (1), first, in the arithmetic unit 16, the rotational speed information ω _i (i = 1, 2,..., N and the same hereinafter) of each motor detected by the rotor rotational speed detectors 13 and 14 and the torque command Based on the signal T _i , a current amplitude value I _i and a slip frequency value ω _Si for realizing T _i are determined based on a map prepared in advance. The resulting slip frequency is added to the current frequency obtained in rotor rotation speed detector 13, the applied frequency command value omega _i is determined. next,
In 3-phase AC command unit 17 to 19, three-phase AC command value and a current amplitude value I _i obtained in the calculating unit 16 and the applied frequency command value _{ω i (I ui, I vi} , I wi) and is obtained Is output. That is, the three-phase AC command values (I _u1 , I _v1 , I _w1 ) for the first motor 11 are output from the AC current command generator 3, and the second motor The 12-phase three-phase AC command values (I _u2 , I _v2 , I _w2 ) are output. The above command values are analog signals, which are input to the comparators 5 and 6, respectively. On the other hand, the comparator 5 is supplied with a carrier 9 and the comparator 6 is supplied with a carrier obtained by delaying the phase of the carrier 9 by a delay unit 10. Then, the above command value and the carrier carrier are compared by a comparator, and the PWM
It is output as a signal train. The outputs of the comparators 5 and 6 are applied to input terminals of inverter bridges 7 and 8, respectively, and drive the inverters. As a result, the DC power of the battery 15 becomes three-phase AC power,
12 and the motors 11 and 12 are driven with a desired torque.

In the above operation, the comparators 5 and 6
Are the same in frequency and the phases are shifted by a predetermined value. Therefore, the PWM signals output from the comparators 5 and 6 also have the same frequency and the phase is shifted by a predetermined value, and the switching phase of the inverter is also shifted by the predetermined value. Therefore, the first motor 11
And the phase of the switching noise generated by the second motor 12 is also shifted by a predetermined value, and the noise is canceled and reduced by the phase difference.

The above point will be further described. FIG.
, 20 is a rotor of the first motor 11, 21 is its coil, 22 is a rotor of the second motor 12, 23 is a coil, and 24 is a case. As shown in FIG. 3, assuming a case where the first motor 11 and the second motor 12 are packaged in one case, two sound sources are present close to each other and in a form very close to a point sound source. It is considered something. Therefore, as shown in FIG. 3, the noise from the two motors is canceled by the phase shift, and the sound generated from the two sound sources is reduced in a wide range in the vehicle interior.

Further, as shown in FIG.
If the interval between 1 and 12 is large and deviates from the point sound source,
When the switching frequency is several kHz, there are places where two sounds are canceled at intervals of several tens of centimeters, so it is difficult to reduce the noise of the entire cabin. However, if the switching frequency is several hundred Hz, several m Since the places where two sounds can be canceled at intervals are widened, it is possible to reduce noise in the entire vehicle interior. If the switching frequency is set to several hundred Hz, switching loss can be reduced, which is advantageous from the viewpoint of improving efficiency.

FIG. 5 is a circuit diagram of a second embodiment of the present invention, illustrating the case of a DC motor system. In FIG. 5, 25 and 26 are motors, 27 and 28 are power switches for performing chopper control, 29 is a battery, 30
Is an accelerator opening sensor, 31 is a microphone that measures noise, 32 is a torque command converter that determines the flow rate to the DC motor, 33 is a carrier oscillator, and 34 is an oscillator 33
The delay devices 35 and 36 are capable of delaying the phase of the carrier and varying the delay amount, and are comparators.

Next, the operation will be described. First, the torque command converter 32 determines the amount of current to be applied to the motors 25 and 26 in accordance with the signal of the accelerator opening sensor 30, and controls the power switches 27 and 28 based on the signal. Thus, the motors 25 and 26 are driven. This method is so-called DC motor chopper control. In the above control, the on / off pulses of the power switches 27 and 28 have the same frequency and are out of phase by the value set by the delay unit 34. The phase difference in the delay unit 34 is controlled so as to minimize the room noise level detected by the microphone 31.
If the cycle of the chopper is set to several hundred Hz, the wavelength of the noise will be several meters. Therefore, as shown in FIG. Becomes possible.

[0016]

As described above, according to the present invention, the switching frequencies of the respective switching means are all the same, a plurality of motors are divided into two sets, and one switching means and the other are included in each set. Since the configuration is such that the switching phase of the switching means is provided with a difference by a predetermined value, the noise generated by the switching is canceled by the phase difference in each group, and the noise as a whole can be reduced. According to the second aspect of the present invention, since the switching phase difference is controlled so that the noise value measured by the microphone becomes the minimum value, the noise can be controlled to the optimum phase difference. Can be further reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

FIG. 2 is a block diagram showing details of AC current command generation arithmetic units 3 and 4;

FIG. 3 is a cross-sectional view of an example of a multiple-motor power unit constituted by motors 11 and 12;

FIG. 4 is a diagram showing a sound field when two motors (sound sources) are installed separately.

FIG. 5 is a circuit diagram of a second embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Accelerator opening sensor 2 ... Torque command calculator 3 ... AC current command generation calculator of the first motor 11 4 ... AC current command generation calculator of the second motor 12 5, 6 ... Comparator 7, 8 ... Inverter Bridge 9 Oscillator 24 Case 10 Delayer 25, 26
... Motors 13, 14 ... Rotor rotation speed detectors 27, 28
... Power switch 15 ... Battery 29 ... Battery 16 ... Calculation unit 30 ... Accelerator opening sensor 17, 18, 19 ... 3-phase AC command unit 31 ... Microphone 20 ... Rotor of the first motor 11 32 ... Torque command converter 21 ... Coil 33 of first motor 11 ... Oscillator 22 ... Rotor of second motor 12 34 ... Delay device 23 ... Coil 35 of second motor 12
…comparator

Claims (2)

(57) [Claims] 1. A vehicle comprising a plurality of motors, wherein the electric power is stored in a battery.
DC power intermittent with switching means provided for each motor
Supply to each motor
Motors for electric vehicles that independently control power
In the control device, a motor consisting of multiples of 2 and each motorTo instruct the AC to drive the motor
AC command value generating means, the AC command value and carrier carrier
Which generates a PWM signal by comparing
And intermittent DC power according to the PWM signal
Switch to convert it to AC power and supply it to the motor.
And a chining means, And dividing the plurality of motors into two sets,
The same frequency to the above comparator of each motor.
To give the carrier carrier having a predetermined phase difference
Step Motor control device for an electric vehicle, comprising:
Place. 2. The motor control device for an electric vehicle according to claim 1, wherein a microphone for measuring noise and a phase difference between the carrier carriers are controlled so that the noise value measured by the microphone becomes a minimum value. A motor control device for an electric vehicle, comprising: