JP3265994B2 - Drive device for electric compressor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for an electric compressor, and more particularly, to a driving device for an electric compressor suitable for an electric vehicle or a hybrid electric vehicle, which enables stable driving of the electric compressor even with a power supply having a large voltage fluctuation. It is about.

[0002]

2. Description of the Related Art FIG. 8 shows an example of a block diagram of a conventional electric compressor driving device using a DC power supply. The drive device for the electric compressor includes a battery 11, a DC / AC conversion circuit 13, a voltage zone detection unit 15, a pulse width control unit 17, and an overcurrent protection circuit 20.
The DC / AC conversion circuit 13 includes a battery 11 that is a power supply voltage.
Is converted into a three-phase pseudo AC voltage composed of a rectangular pulse train and applied to the electric compressor 21. The voltage zone detection unit 15 sets a plurality of voltage detection ranges at the time of voltage detection, and the input DC voltage falls within any of a predetermined voltage range (hereinafter, referred to as a “voltage zone”). Detect if there is. The overcurrent protection circuit 21 limits the maximum value of the current flowing through the DC / AC conversion circuit 13.
The average value and the effective value of the AC voltage applied to the electric compressor 21 are controlled by changing the pulse width of each pulse of a pulse train constituting the three-phase pseudo AC voltage applied to the electric compressor 21. Pulse width control unit 17
Outputs a control signal for controlling the pulse width of the pseudo AC voltage to the DC / AC conversion circuit 13 in accordance with the fluctuation of the power supply voltage based on the detection result from the voltage zone detection unit 15.

In an electric vehicle or a hybrid electric vehicle using such an electric compressor driving device as an air conditioner, the power supply voltage fluctuates much more than that of a commercial power supply for home use. Since a large load current flows, the power supply voltage decreases, and when the vehicle decelerates, the power supply voltage increases due to a regenerative current from the traveling motor. Further, since the electric compressor shares the power supply with the traveling motor, the voltage applied to the motor of the electric compressor also fluctuates greatly depending on the traveling state of the vehicle. As a result, when the motor of the electric compressor is a DC brushless sensorless motor, there is a problem that the rotation speed decreases when the power supply voltage decreases and the rotation speed increases when the power supply voltage increases, due to fluctuations in the power supply voltage during steady operation. In addition, at the time of startup, there is a problem that an over-excitation (when a voltage rises) or an overload (when a voltage falls) occurs and the overcurrent protection is activated. Similarly, when the motor of the electric compressor is an induction motor, there is a problem that the overcurrent protection circuit is activated due to overexcitation (when the voltage rises) or overload (when the voltage falls).

In order to solve such a problem, in a conventional driving device, a voltage zone detecting section 15 detects a voltage zone of an input voltage, and a pulse width control section 17 performs a pseudo AC switching according to the voltage zone. By changing the pulse width of the rectangular pulse of the voltage, the electric compressor 21
Is controlled so that the average voltage of the voltages applied to the first and second terminals is constant.

[0005]

FIG. 10 (a) shows that in the conventional driving device, the power supply voltage output from the battery 11 fluctuates from a high voltage zone to a low voltage zone, and the pulse width rapidly changes accordingly. The change of the electric current of the electric compressor 21 at the time of being performed is shown. FIG. 10B shows the time change of the torque of the electric compressor 21 at that time.
In the drive device of the conventional electric compressor 21, when the voltage zone of the power supply voltage is changed, if the pulse width is changed rapidly, the current of the electric compressor 21 transiently increases and decreases as shown in FIG. As a result, the overcurrent protection circuit 20 operates, the electric compressor 21 stops, or the motor torque suddenly increases or decreases as shown in FIG. There is a problem that the durability of the mechanical part is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and an object of the present invention is to provide an electric compressor driving device which operates an electric compressor stably with respect to a large fluctuation of a power supply voltage. It is in.

[0007]

A drive device for an electric compressor according to the present invention comprises an electric compressor, a voltage power supply for generating a DC voltage, and the DC compressor for converting the DC voltage into a pseudo AC voltage comprising rectangular pulses. DC-to-AC converter means, a voltage detection means for detecting which of the predetermined voltage ranges the DC voltage belongs to and outputting a detection signal, and an average value or an effective value of the pseudo AC voltage. A pulse width control unit that controls a pulse width of the pulse to change a value, wherein the pulse width control unit detects the pulse width of the pulse based on the detection signal. A pulse width correction delay unit that performs a step-by-step correction at predetermined correction times so as to have a predetermined value corresponding to the voltage range.

Preferably, in the electric compressor driving device, the pulse width correction delay means increases the correction time when correcting in a direction to increase the average value or the effective value of the pseudo AC voltage, and increases the pseudo time. The correction time is shortened when correcting in a direction in which the average value or the effective value of the AC voltage is decreased.

In the driving device for an electric compressor according to the present invention, the voltage of the DC voltage power supply is detected by the voltage detecting means for each predetermined voltage range. The pulse width is corrected by the pulse width correction delay means so that the pulse width becomes a predetermined value corresponding to the detected voltage range. At this time, the pulse width is corrected stepwise so that the pulse width becomes a predetermined value after a predetermined time has elapsed. Thereby, the voltage applied to the electric compressor is gradually corrected.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an electric compressor driving device according to the present invention will be described below with reference to the accompanying drawings. The drive device of the electric compressor according to the present embodiment has a function of gradually correcting the applied voltage when the voltage applied to the electric compressor fluctuates due to the fluctuation of the power supply voltage.

FIG. 1 shows a block diagram of a driving device for an electric compressor according to this embodiment. The drive device according to the present embodiment includes a battery 11, a DC / AC converter 13, a voltage zone detector 16, and a pulse width controller 18.
The pulse width control section 18 includes a pulse width correction delay section 19.

The voltage zone detecting section 16 detects the voltage of the battery 11 for each predetermined voltage zone (voltage range), and sends a detection result for specifying which zone the voltage of the battery 11 is in to the pulse width control section 18. Output. Pulse width control unit 1
8 outputs a signal for controlling the pulse width of the voltage applied to the electric compressor 21 to the DC / AC conversion circuit 13 based on the detection result from the voltage zone detection unit. The DC / AC converter 13 converts the DC voltage from the battery 11
Based on a control signal from the pulse width control unit 18, the voltage is converted into a three-phase pseudo AC voltage composed of a rectangular pulse train whose pulse width is controlled and applied to the electric compressor 21.

FIG. 2 shows a voltage zone detector 1 according to the present embodiment.
6 is a circuit diagram. The voltage zone detector 16 includes a window comparator 25 and an insulating circuit 27 for insulating the output of the window comparator 25 from the voltage of the battery 11, that is, the power supply voltage. The insulation circuit 27 includes photocouplers 40 and 41. The window comparator 25 includes comparators 30 and 31 and resistors 33 to 37.
And the connection relationship as shown in FIG. Voltages divided by the resistors 33 to 35 are input to the + input terminals of the comparators 30 and 31 as reference voltages, and the voltage from the battery 11 is input to the − input terminals. The values of the resistors 33 to 35 are determined by the voltage ranges detected by the window comparator 25, respectively. Outputs of the comparators 30 and 31 are input to photocouplers 40 and 41, respectively. In the present embodiment, voltage detection is performed in three voltage zones as described later.
FIG. 3 shows the output of the voltage zone detector 16 for each voltage zone. As shown in FIG.
The output 2 determines which voltage zone the power supply voltage is in.

In this embodiment, the voltage is detected by dividing the voltage into three voltage zones. The range of each zone is set to be within ± 10% from the center value of each zone. In the present embodiment, since the center voltage value of the zone B is 300 V, the voltage range of the zone B is 270 V to 330 V. Therefore, when the center voltage value is determined so that the value of + 10% from the center voltage value of zone A becomes 270 V, it becomes 245 V, which is the center voltage value of zone A. Similarly, the center voltage value of zone C is 367V. In the present embodiment, the input voltage is detected for three voltage zones for convenience of description, but more voltage zones may be set and the voltage may be detected more finely. .

If the power supply voltage fluctuates from one voltage zone to another voltage zone, the peak value of the pulse applied to the electric compressor 21 immediately after the fluctuation will be higher in proportion to the center voltage of each zone. Higher when moving to a zone, lower when moving to a lower voltage zone. Therefore, in order to equalize the average value of the voltage applied to the electric compressor 21, as shown in FIG. 4, individual pulses of the pulse train of the pseudo AC voltage output from the DC / AC conversion circuit 13 to the electric compressor 21. It is necessary to change the width in inverse proportion to the center voltage value of the zone. That is, assuming that the pulse width of zone B is 100, the pulse width of zone A is 122 (= 367/300 × 100), and the pulse width of zone C is 82 (= 245/300 × 1).
00). In this embodiment, this value is used as the “target pulse width” of each zone. FIG. 3 shows the target pulse width for each zone determined in this manner.

The pulse width correction delay unit 19 determines the pulse width of the output pulse of the DC / AC converter 13 for the electric compressor 21 so as to have a predetermined pulse width at predetermined time intervals based on the voltage zone of the power supply voltage. Is controlled step by step. Hereinafter, the operation of the pulse width correction delay unit 19 will be described with reference to the flowchart of FIG. The pulse width correction delay unit 19 repeats the operation shown in the flowchart of FIG. 5 every predetermined correction time.

The pulse width correction delay unit 19 determines which zone the value of the power supply voltage is in from the detection result from the voltage zone detection unit 16. First, it is determined whether or not the value of the power supply voltage is in the zone A (S1). If the value of the power supply voltage is in the zone A, the target pulse width is set to 122 according to FIG. 3 (S4), and step S6 is performed. Proceed to. If the value of the power supply voltage is not in the zone A, it is determined whether or not the value of the power supply voltage is in the zone B (S2). If the value is in the zone B, the target pulse width is set to 100 (S5). Proceed to S6.
When the value of the power supply voltage is neither zone A nor zone B, that is, when it is zone C, the target pulse width is set to 82 (S3).

In step S6, the target pulse width is compared with the current pulse width. Here, the current pulse width is set to 100 before the electric compressor 21 is started, and the value set as needed by the pulse width control unit is held during the start. When the target pulse width is equal to the current pulse width, the processing ends. If the target pulse width is not equal to the current pulse width, the process proceeds to step S7, and it is determined whether the target pulse width is larger than the current pulse width. If the target pulse width is larger than the current pulse width, the correction time is set to 10 ms (S8), the current pulse width is increased by 1 (S9), and the process proceeds to step S12. If the target pulse width is smaller than the current pulse width, the correction time is set to 1 ms (S10), the current pulse width is reduced by 1 (S11), and the process proceeds to step S12. As described above, in the electric compressor driving device of the present embodiment, the interval of the voltage correction time is changed according to the correction direction of the output voltage of the DC / AC conversion circuit 13. That is, when the power supply voltage fluctuates to a lower side, the power supply voltage changes gradually, and when the power supply voltage fluctuates to a higher side, the power supply voltage changes more quickly than when the power supply voltage fluctuates to a lower side.
This means that in the case of voltage fluctuation in the direction of increasing voltage,
This is because the voltage needs to be corrected more quickly than the fluctuation in the voltage decreasing direction because the fluctuation speed is high.

In step S12, the electric compressor 2
The pulse width of the output voltage of the DC / AC conversion circuit 13 with respect to 1 is calculated from the current pulse width and a predetermined basic pulse width by the following equation, and the process ends. Output pulse width = Basic pulse width × Current pulse width / 100 (1)

The pulse width control section 18 controls the pulse width so that the pulse width of the pseudo AC voltage becomes the voltage of the output pulse width calculated by the pulse width delay correction section 19. The operation shown in the flowchart of FIG. 5 is repeated at intervals of the correction time set in step S8 or step S10. In this way, by changing the pulse width stepwise by the pulse width correction delay unit 19, the AC voltage applied to the electric compressor 21 is corrected with a delay of a predetermined time from the time of the fluctuation of the power supply voltage.

In the driving device for an electric compressor according to the present embodiment, the voltage zone detector 16 detects the power supply voltage for each voltage zone, and the pulse width controller 18 controls the pulse width so that the target pulse width corresponds to the voltage zone. Control the width.
At this time, the pulse width correction delay unit 19 corrects the pulse width by a predetermined amount at predetermined time intervals. Accordingly, even if the applied voltage to the electric compressor 21 fluctuates due to the fluctuation of the power supply voltage, the value of the applied voltage is gradually corrected, so that a sudden change in current or torque in the electric compressor 21 can be prevented. . Further, when the power supply voltage fluctuates to a higher voltage, the voltage is corrected more quickly than when the power supply voltage fluctuates to a lower voltage.

FIG. 6 shows how the pulse width is corrected when the power supply voltage changes from zone B to zone C when the basic pulse width is 1, that is, when the power supply voltage changes to the higher side. FIG. 6A shows a pulse immediately after the change from the voltage zone B to the voltage zone C. FIG. 6B shows 9 ms after the change.
A later pulse is shown. FIG. 6 (c) shows 18 m after the change.
The pulse after s is shown. As shown in FIG. 6, in the pulse width control unit 18 of the present embodiment, when the voltage fluctuates to the higher side, the pulse width is reduced every 1 ms and is applied to the electric compressor 21 by approaching the target value. Voltage is gradually corrected.

FIG. 7 shows how the pulse width is corrected when the power supply voltage changes from zone B to zone A when the basic pulse width is 1, that is, when the power supply voltage changes to the lower side. FIG. 7A shows a pulse immediately after the change from the voltage zone B to the voltage zone A. FIG. 7B shows the state after the change.
The pulse after ms is shown. FIG. 7 (c) shows that after the change,
The pulse after 20 ms is shown. As shown in FIG. 7, in the pulse width control unit 18 of the present embodiment, when the voltage fluctuates to the lower side, the pulse width is increased every 10 ms to approach the target value, thereby applying the voltage to the electric compressor 21. The voltage to be changed is corrected more slowly by further delaying the voltage when the voltage fluctuates to a higher value.

FIG. 9A shows a change in current flowing through the electric compressor 21 due to a voltage change by the drive device of the present embodiment. FIG. 9B shows a time change of the torque of the electric compressor 21 due to the voltage fluctuation at that time. As shown in the figure, in the drive device of the present embodiment, a sudden change in the current and torque of the electric compressor 21 is prevented by gradually correcting the pulse width in accordance with the voltage fluctuation.

In this embodiment, the method of stabilizing the average value of the voltage applied to the electric compressor has been described. However, the same effect can be obtained by the method of stabilizing the effective value. Further, in the present embodiment, the case where the motor is a DC brushless motor has been described. However, the present invention can be applied to a case where the motor is an induction motor, and similar effects can be obtained.

[0026]

According to the electric compressor driving apparatus of the present invention, in an electric compressor using a DC brushless motor or an induction motor as a motor, a power supply voltage is detected in a predetermined voltage range, and at every predetermined correction time interval. ,
By changing the current correction amount by a predetermined amount in a direction approaching the target correction value corresponding to the detection range, gradually recovering the average value and the effective value of the voltage to the electric compressor with respect to the fluctuation of the power supply voltage. Can be. As a result, it is possible to prevent a sudden increase or decrease in the current due to the transient current and a sudden change in the motor torque.

According to the electric compressor driving apparatus of the present invention having a preferable configuration, the correction time interval differs depending on the direction of the fluctuation of the power supply voltage. For this reason, when the fluctuation speed changes in the rising direction, the voltage applied to the electric compressor can be quickly recovered within a range where there is no influence of a transient current or the like.

[Brief description of the drawings]

FIG. 1 is a block diagram of a driving device for an electric compressor according to an embodiment.

FIG. 2 is a circuit diagram of a voltage zone detection unit.

FIG. 3 is a table showing voltage zones and target correction values.

FIG. 4 is a diagram showing a pulse width and a peak value of a pulse.

FIG. 5 is a flowchart of a pulse width correction delay unit.

FIG. 6 is a diagram showing a state of correction of a pulse width when a power supply voltage changes to a higher side.

FIG. 7 is a view showing a state of correction of a pulse width when a power supply voltage fluctuates to a lower side.

FIG. 8 is a block diagram of a conventional electric compressor driving device.

FIG. 9 is a diagram showing a time change of a current and a torque flowing through a motor of an electric compressor according to a change of an input power supply voltage in the embodiment.

FIG. 10 is a diagram showing a time change of a current and a torque flowing through a motor of an electric compressor according to a change of an input power supply voltage in the related art.

[Explanation of symbols]

11: battery, 13: DC / AC converter circuit, 15, 16
... Voltage zone detector, 17, 18 ... Pulse width controller, 1
9: pulse width correction delay unit, 20: overcurrent protection circuit, 21
... electric compressor, 25 ... window comparator, 2
7 ... Insulation circuit, 30, 31 ... Comparator, 33-39
... Resistance, 40, 41 ... Photocoupler.

Continuation of the front page (56) References JP-A-7-255178 (JP, A) JP-A-7-298628 (JP, A) JP-A-7-172155 (JP, A) JP-A-7-107749 (JP) , A) JP-A-6-284745 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02M 7/48 B60H 1/32 H02P 7/63

Claims (1)

(57) [Claims] 1. An electric compressor, a voltage power supply for generating a DC voltage, DC / AC converting means for converting the DC voltage into a pseudo AC voltage composed of rectangular pulses, and applying the pseudo AC voltage to the electric compressor; Voltage detecting means for detecting which voltage range belongs to the predetermined voltage range and outputting a detection signal; and a pulse for controlling a pulse width of the pulse to change an average value or an effective value of the pseudo AC voltage An electric compressor drive device having a width control means, wherein the pulse width control means corrects the pulse width of the pulse to a predetermined value corresponding to the voltage range detected based on the detection signal. includes a pulse width correction delay means for stepwise correction every time, the pulse width correction delay hand
When correcting in the direction in which the pulse width is increased,
The correction delay time is lengthened, and the pulse width is compensated for in the direction of narrowing.
An electric compressor driving device, wherein the correction delay time is shortened when correcting .