JP5063656B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner that has an electric motor for an outdoor fan that exchanges heat by blowing air to an outdoor heat exchanger, and controls the rotation speed of the electric motor for the outdoor fan according to the load state of the electric motor for the outdoor fan. is there.

In the conventional air conditioner, at least a DC voltage is switched by the inverter means and applied to the motor of the outdoor fan, and the rotational speed of the motor of the outdoor fan is controlled to become the target rotational speed, while the input current of the inverter means In some cases, the target rotational speed is varied by a predetermined value in accordance with (see, for example, Patent Document 1).
Also, when frost formation on the outdoor heat exchanger is detected or estimated during heating operation, fan control during frost formation to reduce the rotation speed of the outdoor fan is performed before the defrost operation, and heating operation is continued. Some of them (for example, refer to Patent Document 2).

JP-A-11-51454 (first page, third page to fourth page, FIGS. 1 to 2) Japanese Unexamined Patent Publication No. 2009-58222 (first page, sixth page, FIGS. 1 to 2, FIGS. 4 to 5)

However, in the technique described in Patent Document 1, the input current of the inverter means pulsates at a frequency that is six times the frequency of the output voltage of the inverter. When this current is detected and controlled, the control is stabilized. However, there is a problem that the rotational speed becomes unstable and noise is generated.
In addition, when the output voltage reaches a value corresponding to the overcurrent value, the performance deterioration due to the operation stop of the motor of the outdoor fan is a problem.

  Further, in the technique described in Patent Document 2, the frosting speed changes depending on the outside air temperature, the outside air humidity, and the rotation speed of the motor of the outdoor fan, and thus it is difficult to accurately detect and estimate the amount of frosting. For this reason, the rotational speed of the motor of the outdoor fan cannot be reduced against the increase in the ventilation resistance of the heat exchanger due to frost formation, so the current of the motor of the outdoor fan increases, and the operation is stopped due to demagnetization or overcurrent interruption of the motor. Performance degradation due to is a problem.

  In addition, because the motor speed of the outdoor fan cannot be controlled in response to an increase in the motor load of the outdoor fan due to external factors such as strong winds, the motor current of the outdoor fan increases, causing the motor to demagnetize or stop operation due to overcurrent interruption. Performance degradation due to is a problem.

  The present invention has been made to solve the above-described problems, and optimally and stably drives an electric motor of an outdoor fan against the influence of frost formation and outdoor wind of an outdoor heat exchanger during heating operation. Therefore, an object is to obtain an air conditioner having a high heating capacity.

An air conditioner according to the present invention includes an outdoor heat exchanger, an outdoor fan that blows air to the outdoor heat exchanger, an electric motor that drives the outdoor fan, an inverter that applies a voltage to the electric motor using a DC power supply as a power source, and An inverter control means for controlling the voltage output from the inverter; a shunt resistor connected between the DC power supply and the inverter; a charging means connected to the voltage across the shunt resistor via a backflow prevention means; the voltage charged in the charging unit, and a discharging means for discharging at a first time constant is at least 1/6 times the period of the voltage output of the inverter, the inverter control unit, the charge Current detecting means for detecting a current flowing through the shunt resistor based on a voltage charged in the means, and the inverter according to the output of the current detecting means And a frequency control means for controlling the frequency of the voltage output by chromatography, wherein the frequency control means, said inverter on the basis of the deviation between the output and the current control value is less than the overcurrent interrupting value of said current detecting means comprising a frequency correction means for correcting the frequency of the voltage output by said frequency control means, when the output of said current detecting means exceeds the current control value, decrease the frequency of the voltage output by the pre-Symbol inverter When the current control value falls below the current control value , the frequency of the voltage output by the inverter is increased, and the inverter control means keeps the current value constant within a range not reaching the overcurrent cutoff value. The rotational speed of the electric motor is controlled .

  The air conditioner of the present invention detects an electric current of an electric motor that drives an outdoor fan, and controls the electric motor at an optimum number of rotations according to the electric current value, thereby allowing outdoor air or outdoor heat exchangers to form frost. In addition to ensuring strong controllability that allows operation to continue with respect to fan motor load fluctuations, heat exchange can be efficiently performed by rotating the motor of the outdoor fan at the maximum rotation speed that can be operated during heating operation. Since it is performed, the heating capacity can be improved.

It is a block diagram of the air conditioner which shows Embodiment 1-4 of this invention. It is a block diagram of the voltage holding means 15 which shows Embodiment 1-4 of this invention. It is a figure which shows operation | movement of the voltage holding means 15 in Embodiment 1-4 of this invention. It is a figure which shows the structure of the inverter control means 11 in Embodiment 1-3 of this invention. It is a figure which shows operation | movement of the position and speed estimation means 19 in Embodiment 1-4 of this invention. It is a block diagram which shows the structure of the electric current detection means 20 in Embodiment 1 of this invention. It is a block diagram which shows the structure of the frequency command calculating means 21 in Embodiment 1-4 of this invention. It is a block diagram which shows the structure of the voltage control means 22 in Embodiment 1-4 of this invention. It is a figure which shows operation | movement of the voltage control means 22 in Embodiment 1-4 of this invention. It is explanatory drawing which compares and compares conventional rotation speed control and electric current control, and rotation speed control and current control of this invention. It is a block diagram which shows the structure of the electric current detection means 20 in Embodiment 2 of this invention. It is a figure which shows the output of the electric current detection means 20 of FIG. It is a block diagram which shows the structure of the electric current detection means 20 in Embodiment 3 of this invention. It is a flowchart which shows the operation | movement of the peak hold means 31 in the electric current detection means 20 of FIG. It is a figure which shows the output of the current detection means 20 of FIG. It is a graph showing the relationship between the pulse duty of shunt voltage in Embodiment 4 of this invention, and a current detection error. It is a figure showing the relationship between a voltage and an electric current vector. It is a figure showing the operation | movement at the time of the electric current detection error generation | occurrence | production of this invention. It is a block diagram which shows the structure of the inverter control means 11 in Embodiment 4 of this invention. It is a block diagram which shows the structure of the electric current detection means 20 in Embodiment 4 of this invention. It is a block diagram which shows the Example of frequency control. It is a block diagram which shows an example of the calculation method of a frequency correction calculating means. It is a figure which shows the voltage command waveform at the time of three-phase modulation, and the both-ends voltage waveform of shunt resistance. It is a figure which shows the voltage command waveform at the time of two-phase modulation, and the both-ends voltage waveform of shunt resistance.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of an air conditioner showing Embodiment 1 of the present invention. Here, a separate type air conditioner will be described as an example.
In FIG. 1, a compressor 1, a four-way valve 2, an outdoor heat exchanger 3, an expansion valve 4 and an indoor heat exchanger 5 are attached via a refrigerant pipe 6. In addition, a blower fan (hereinafter sometimes referred to as an outdoor fan) 7 for sending air to the outdoor heat exchanger 3 to perform heat exchange and an electric motor 8 for operating the fan are provided. An inverter 9 that drives the motor 8 by applying a voltage is operated by supplying power from a DC power source 10 and is electrically connected to the motor 8. The control input terminal of the inverter 9 is connected to the inverter control means 11. In addition, DC voltage detecting means 12 for detecting the DC voltage value Vdc by the DC power supply 10, magnetic pole position detecting means 13 for detecting the magnetic pole position (Hu, Hv, Hw) of the electric motor 8, between the inverter 9 and the DC power supply 10. Voltage holding means 15 for holding the terminal voltage of the shunt resistor 14 provided is provided. The inverter control means 11 generates PWM signals (UP, VP, WP, UN, VN, WN) based on the outputs of the DC voltage detection means 12, the magnetic pole position detection means 13, and the voltage holding means 15, and bridges them to the inverter 9. The connected switching elements 16a to 16f are driven to control the voltage applied to the electric motor 8.

  The voltage Vsh across the shunt resistor 14 (hereinafter sometimes referred to as a shunt voltage) is intermittently generated in accordance with the switching timing of the inverter 9 and the current flowing through the motor 8, so that it is detected by a microcomputer or the like. Since it is necessary to detect in synchronization with the switching timing, the detection method becomes complicated, and an expensive microcomputer having a high processing speed is required.

Therefore, the voltage holding means 15 charges the charging means 17 with the voltage Vsh of the shunt resistor 14 via the backflow prevention means 33 as shown in FIG. 2A, thereby intermittently changing the peak of the shunt voltage Vsh. It is possible to store the value voltage Vc. Further, the backflow preventing means 33 can improve the reliability without causing the voltage Vc having the peak value of the shunt voltage Vsh to flow back to the input side. However, the charging means 17 remains charged unless discharged. Therefore, even when the electric motor 8 is lightly loaded and the voltage value decreases, the motor 8 is kept at a high voltage, which may cause erroneous control. In addition, even when noise is generated, there is a possibility that this high noise voltage may continue to be maintained, so that there is a large deviation from the voltage when there is no noise, which may lead to erroneous control. Therefore, by providing the discharging means 18 in parallel with the charging means 17, it is possible to improve the reliability by eliminating the influence. As shown in FIG. 3, the peak voltage Vc of the shunt voltage Vsh can be detected at all times, and the current can be detected without any problem regardless of the performance of the microcomputer. It can be used and cost reduction can be achieved.
Furthermore, depending on the element used for the backflow prevention means 33, there is a possibility that the detection accuracy of the peak value of the shunt voltage Vsh is lowered due to the voltage drop of the element. Therefore, by using the voltage drop compensation means 34 as shown in FIG. 2B, the voltage charged in the charging means 17 is set to the same potential as the shunt voltage Vsh applied as the input voltage of the voltage drop compensation means 34. It becomes possible to. As a result, the shunt voltage Vsh can be detected in consideration of the voltage drop of the element used for the backflow prevention means 33, and the reliability can be improved.

  Here, the backflow prevention means 33 can be realized by a diode, and the charging means 17 can be realized by a capacitor. As for the discharging means 18, the voltage stored in the charging means 17 can be discharged by connecting a discharging resistor in parallel with the charging means 17 or by providing a short circuit means such as a switch or a relay in parallel with the charging means 17. Is possible. Although representative means have been described this time, it goes without saying that there are no problems as long as they have other similar functions.

  When the charging means 17 is constituted by a capacitor and the discharging means 18 is constituted by a resistor, the voltage stored in the capacitor is discharged at the first time constant of the product of the capacitance C of the capacitor and the resistance value R. For this reason, if the first time constant is too small, the voltage of the capacitor is immediately discharged, and the peak value cannot be detected accurately. In addition, as shown in FIG. 3, the envelope of the shunt voltage Vsh pulsates at a frequency six times the frequency of the output voltage of the inverter, and if the first time constant is small, the pulsation may be detected. The first time constant is set to 1/6 or more of the operation cycle of 8.

  Next, as shown in FIG. 4, the inverter control means 11 includes a position / speed estimation means 19, a current detection means 20, a frequency command calculation means 21, a voltage control means 22, an output Vdc of the DC voltage detection means 12, a magnetic pole The PWM signal (UP, VP, WP, UN, VN, WN) based on the output (Hu, Hv, Hw) of the position detection means 13 and the voltage Vc of the peak value of the shunt voltage Vsh that is the output of the voltage holding means 15. Is output.

  The operation of the position / velocity detecting means 19 will be described with reference to FIG. 5 when the magnetic pole position detecting means 13 is a Hall sensor. As for the output of the Hall sensor, HIGH (= 1) and LOW (= 0) are repeated approximately every 180 [deg] in accordance with the magnetic pole position of the rotor of the electric motor 8, and signals different in phase by 120 degrees in the UVW phase are output. Is done. The period from the rising edge of the U phase to the next rising edge is one period of electricity, and the control of the period Ts occurs n times during that period. Then, one cycle of electricity can be expressed by n × Ts, and by taking this reciprocal, the electrical frequency can be obtained, and by multiplying by 2π, the rotational electrical angular frequency ωe of the motor 8 which is the electrical angular frequency is obtained. Furthermore, it is also possible to obtain the mechanical rotational speed by multiplying the number of pole pairs of the electric motor 8.

  Next, how to determine the magnetic pole position θ when the rise of the U-phase Hall sensor output Hu is set to 0 degrees will be described. When the rise of the U-phase Hall sensor output Hu is set to 0 degree, the case of (Hu, Hv, Hw) = (1, 0, 1) is 0 to 60 [deg], (1, 0, 0). 60 to 120 [deg]... (0, 0, 1) is set to 300 to 360 [deg] to detect θh. Since θh is stepped, an angle to be added for each control period Ts is obtained based on the obtained electrical angular frequency ω, and is added to θh, so that 0 [deg] to 360 as shown in FIG. It is possible to obtain the magnetic pole position θ that changes almost linearly up to [deg].

  Next, the operation of the current detection means 20 will be described. FIG. 6 is a block diagram showing a configuration of the current detection means 20 according to the first embodiment of the present invention, and includes a voltage / current conversion means 23 and a restriction means 24. Based on the voltage Vc at the peak value of the shunt voltage Vsh that is the output of the voltage holding means 15 and the resistance value Rsh of the shunt resistor 14, the voltage-current converter 23 converts the current I flowing through the shunt resistor 14 to I = Vc according to Ohm's law. / Rsh. Next, since the obtained current I may be an unexpected current exceeding the overcurrent cutoff value due to the influence of noise or the like, the current exceeding the overcurrent cutoff value is limited by the limiting means 24. , Current I is detected.

  In this time, the current is obtained by the voltage / current conversion means 23 and then the current is restricted by the restriction means 24. However, the current value is obtained by the voltage / current conversion means 23 after being restricted by the voltage means by the restriction means 24. Needless to say, there is no problem.

  Next, the frequency command calculation means 21 will be described. FIG. 7 is a block diagram showing the configuration of the frequency command calculating means 21 in the first embodiment of the present invention, which includes a frequency correction calculating means 25 and a frequency command limiting means 26. The frequency correction calculation means 25 performs frequency command correction value Δω by proportional-integral control as shown in FIG. 22B based on the deviation between the current value I output from the current detection means 20 and a preset current control value I *. By obtaining *, a frequency command with a constant current can be obtained. However, the frequency command limit means 26 can limit the frequency range so as not to operate in a frequency band outside the required range so as not to operate at a frequency at which noise or a decrease in driving performance is a concern. It is possible to operate with *, and stable operation is possible without causing an operation stop due to overcurrent interruption even under conditions where the load of the electric motor 8 such as outside wind or frost increases.

  Actually, how to combine the motor model and the frequency correction calculation means 25 will be described in detail with reference to FIG. FIG. 21A shows a block diagram of general frequency control, in which a voltage command calculation unit obtains a voltage command based on the deviation between the frequency command and the actual frequency fed back and applies it to the motor 8.

  In this embodiment, as shown in FIG. 21 (b), the frequency correction calculation means 25 based on the deviation between the current command and the actual current performs the frequency command by proportional-integral control as shown in FIG. 22 (b). A corrected frequency command is obtained by correcting. Next, after the frequency range is limited by the frequency command limiting means 26 so as not to operate in a frequency band outside the required range, the voltage command calculation unit obtains a voltage command based on the deviation from the actual frequency fed back, and the motor 8 is applied.

  As a result, the frequency can be controlled so as not to exceed the current command, and stable operation can be performed without occurrence of stoppage due to overcurrent interruption even under conditions where the load of the electric motor 8 such as outside wind and frost increases. Is possible. In addition, since the heat exchange is efficiently performed by rotating the electric motor 8 of the outdoor fan 7 at the maximum rotation speed that can be operated during the heating operation, the heating capacity can be improved.

  This time, the method of obtaining the frequency command and the correction frequency command by the proportional integral control has been described. However, if the current value can be kept constant, the proportional control of FIG. 22 (a), FIG. 22 (c). It goes without saying that there is no problem even if the proportional integral derivative control or other control method is used. For example, when proportional integral control is used assuming frost formation, optimal frequency correction is possible by setting a gain that can follow the load fluctuation of the electric motor 8 during frost formation.

  It should be noted that I * needs to be set to an overcurrent cutoff value or less so as not to fall into an overcurrent cutoff.

  Next, the voltage control means 22 will be described. FIG. 8 is a block diagram showing the configuration of the voltage control means 22 in Embodiment 1 of the present invention, which includes a voltage command amplitude calculation means 27, a three-phase voltage command calculation means 28, and a PWM generation means 29. The voltage command calculation means 27 obtains the voltage command amplitude V * by proportional integral control based on the deviation between the rotating electrical angular frequency ω and the rotating electrical angular frequency command ω *, thereby rotating in accordance with the rotating electrical angular frequency command ω *. Operation at an electrical angular frequency ω is possible.

  The three-phase voltage command calculation means 28 converts the three-phase voltage commands Vu *, Vv *, and Vw * into the following equations (1) to (3) based on the voltage command amplitude V *, the DC voltage value Vdc, and the magnetic pole position θ. Ask.

  Here, θv represents the applied voltage phase, and is represented by the sum of the magnetic pole position θ and the leading phase angle θf with respect to the magnetic pole position θ. By setting the lead phase angle θf optimally, it is possible to apply a voltage with an optimal phase, which can contribute to an improvement in the operation efficiency of the electric motor 8.

  Although the expressions (1) to (3) have been described as very basic voltage command generation methods, any voltage command generation means such as third-order harmonic superposition modulation, space vector modulation, three-phase modulation, and two-phase modulation can be used. Needless to say, there is no problem even if it is used.

For example, when a voltage command is generated by three-phase modulation, the result is as shown in FIG. In this case, the voltage waveform applied to both ends of the shunt resistor is as shown in FIG. 23B, and is not continuous, but a thin rectangular waveform. For this reason, in order to take in the peak value of the voltage across the shunt resistor, the voltage holding means 15, the peak holding means 31, and the like are required.
If the duty of the rectangular wave of the voltage across the shunt resistor is small, the error between the voltage detected by the voltage holding means 15, the peak holding means 31, and the actual voltage becomes large.

  Therefore, for example, when a voltage command is generated by two-phase modulation, it becomes as shown in FIG. 24A, and the voltage waveform applied to both ends of the shunt resistor is as shown in FIG. 24B, which is rectangular compared to three-phase modulation. Wave duty increases. That is, the error between the voltage detected by the voltage holding means 15 and the peak hold means 31 and the actual voltage is reduced.

  In this way, by using the voltage command generation method that reduces the error, the detection accuracy of the current value converted from the voltage across the shunt resistor is improved, and a highly reliable value can be obtained, and overcurrent cutoff is achieved. Since the predetermined value can be set as close as possible to the value, for example, it becomes possible to improve the heating capacity by increasing the corresponding number of rotations at the time of light load of the electric motor 8 where frosting does not proceed during heating operation. .

  The PWM generation means 29 is shown in FIG. 9 based on the magnitude relationship between the three-phase voltage command values Vu *, Vv *, Vw * obtained by the equations (1) to (3) and the triangular wave carrier having an amplitude of 1. Thus, PWM signals (UP, VP, WP, UN, VN, WN) are generated. A voltage based on the voltage command value can be applied to the electric motor 8 by switching the switching elements 16a to 16f of the inverter 9 by the PWM signal.

  During the heating operation of the air conditioner, the ambient temperature of the outdoor unit is generally low and the air density is high. Therefore, the output torque of the electric motor 8 necessary for the operation of the blower fan 7 is increased, and the flowing current is increased. In addition, frost is generated in the outdoor heat exchanger, and the torque required to drive the blower fan 7 to block the heat exchanger increases with the passage of time of operation.

  In the conventional control, since the motor 8 is controlled at a constant rotation speed, the current value increases from I0 to I1 according to the amount of frost that progresses with time as shown in FIG. 10B. Therefore, it is necessary to set the rotation speed of the electric motor 8 to N0 as shown in FIG. 10A so that the overcurrent cutoff value is not reached even if frost formation occurs, and the heating capacity cannot be improved by increasing the rotation speed.

  Therefore, it is considered to improve the heating capacity by using the current up to I1 at the time of light load of the electric motor 8 where frosting has not progressed and increasing the number of rotations accordingly. By using the air conditioner of the first embodiment, control is performed so that the current value is constant (for example, I1 is constant) as shown in FIG. 10 (d) within a range where the overcurrent cutoff value is not reached. As shown in (c), it is possible to increase the number of rotations of the electric motor 8 in which frost formation has not progressed at a light load from N0 to the maximum N1, and it is possible to efficiently exchange heat with the outdoor heat exchanger. Thus, it is possible to obtain an air conditioner that can improve the heating capacity.

  Moreover, when the wind of the reverse direction to a ventilation direction blows on the ventilation fan 7, the load of the electric motor 8 will increase and an electric current value may increase. In the case of the conventional control, since it is difficult to control the current value, the motor 8 stops due to an overcurrent interruption due to the increase in the current value, and heat exchange cannot be performed efficiently. However, since the current value is controlled to be constant in the first embodiment of the present invention, the rotational speed is decreased even when a reverse wind is generated, and the rotational speed is increased when the wind stops. Thus, it is possible to continue the heating operation, and it is possible to obtain an air conditioner with high reliability and capable of improving the heating capacity.

  Furthermore, even when the outdoor heat exchanger becomes blocked due to aging and accumulation of dust and the torque required to drive the blower fan 7 increases, the outdoor heat exchanger can be operated at an optimum rotational speed at which the current value is constant. Therefore, it is possible to obtain an air conditioner that is highly reliable and capable of improving the heating capacity.

Embodiment 2. FIG.
In the air conditioner of the first embodiment, when the voltage holding means 15 detects the voltage Vc of the peak value Vsh of the shunt resistor 14, the first required is due to restrictions on the selection of the capacitor capacity and the resistance value. It may be difficult to obtain a time constant of In that case, a pulsation having a frequency 6 times the output frequency of the inverter appears significantly in the voltage Vc of the peak value of the shunt voltage Vsh, the detected current value I also pulsates, and the frequency calculated based on the pulsating current value I The command ω * also pulsates, and there is concern about deterioration of controllability and noise.

  The purpose of the second embodiment is to solve the above problems, and the contents will be described below. 1 to 5 and FIGS. 7 to 10 are also used in the second embodiment. FIG. 11 is a block diagram showing the configuration of the current detection means 20 according to Embodiment 2 of the present invention. As shown in FIG. 11, except that a low-pass filter unit 30 is added to the current detection unit 20, there is no difference from the first embodiment. .

  In the first embodiment, the voltage Vc having the peak value of the shunt voltage Vsh, which is the output of the voltage holding means 15, is detected and converted to the current value I by the voltage / current conversion means 23 of the current detection means 20, and the limiting means 24 Had been restricted. On the other hand, in the second embodiment, the current value of the voltage-current converter 23 is removed by the second time constant low-pass filter 30 to remove pulsations having a frequency six times the output frequency of the inverter. Suppresses pulsation of value I. As a result, the stability of the control can be ensured, and the noise can be improved.

  Here, since it is necessary to remove the pulsating component that could not be removed by the first time constant, the second time constant is set to a time constant higher than the first time constant, as shown in FIG. In addition, the pulsation component can be removed by the low-pass filter means 30 to obtain a highly stable air conditioner.

  However, as can be seen from FIG. 12, the low-pass filter means 30 generates a difference ΔI from the current peak value due to the output of the voltage holding means 15. With respect to ΔI, it is possible to reduce the detection error of the current value I by previously adding and considering the average ΔI obtained experimentally.

  According to the second embodiment, the number of revolutions at the time of light load of the motor 8 where frosting has not progressed is increased by performing control so that the current value is accurately constant within a range that does not reach the overcurrent cutoff value. This makes it possible not only to obtain an air conditioner that can improve the heating capacity, but also to pulsate the detected current. By suppressing it, stable control becomes possible, and an air conditioner with less noise can be obtained.

  Moreover, when the wind of the reverse direction to a ventilation direction blows on the ventilation fan 7, the load of the electric motor 8 will increase and an electric current value may increase. In the case of the conventional control, since it is difficult to control the current value, the motor 8 stops due to an overcurrent interruption due to the increase in the current value, and heat exchange cannot be performed efficiently. However, since the current value is controlled to be constant in the first embodiment of the present invention, the rotational speed is decreased even when a reverse wind is generated, and the rotational speed is increased when the wind stops. Thus, it is possible to continue the heating operation, and it is possible to obtain an air conditioner with high reliability and capable of improving the heating capacity.

  Furthermore, even when the outdoor heat exchanger becomes blocked due to aging and accumulation of dust and the torque required to drive the blower fan 7 increases, the outdoor heat exchanger can be operated at an optimum rotational speed at which the current value is constant. Therefore, it is possible to obtain an air conditioner that is highly reliable and capable of improving the heating capacity.

Embodiment 3 FIG.
In the air conditioner of the second embodiment, when the voltage holding means 15 detects the peak value of the voltage of the shunt resistor 14, the necessary first time constant is obtained due to restrictions on the selection of the capacitor capacity and the resistance value. The low-pass filter means 30 has been used as an improvement in control stability when this is difficult.
In the third embodiment, a mode in which the voltage peak value of the shunt resistor is detected more accurately than in the above embodiment will be described.

  1 to 5 and FIGS. 7 to 10 are also used in the third embodiment. FIG. 13 is a block diagram showing the configuration of the current detection means 20 according to Embodiment 3 of the present invention. As shown in FIG. 13, except that a peak hold unit 31 is added to the current detection unit 20, there is no difference from the first embodiment. .

  In the first embodiment, the voltage Vc having the peak value of the shunt voltage Vsh, which is the output of the voltage holding means 15, is detected and converted to the current value I by the voltage / current conversion means 23 of the current detection means 20, and the limiting means 24 Had been restricted. On the other hand, in the third embodiment, only the peak value of the current value flowing through the shunt resistor 14 is extracted from the current value of the voltage / current conversion means 23 by the peak hold means 31, and the peak value of this current value and the current command value are extracted. As in the first embodiment, the frequency command is corrected based on the above, and the frequency of the electric motor 8 is controlled based on the corrected frequency command, so that there is no current detection error and the operation is not stopped due to overcurrent interruption. A high air conditioner can be obtained.

  FIG. 14 is a flowchart showing the operation of the peak hold means 31 in the current detection means 20 of FIG. Next, the operation of the peak hold means 31 will be described with reference to FIG. The peak hold means 31 sets the output of the voltage-current conversion means 23 to Ibuf (step S1401), compares it with the current value I set to, for example, the initial value 0 (step S1402), and if Ibuf is larger, I = Ibuf Thus, the peak value is held (step S1403). However, a current that is considerably higher than normal may be detected instantaneously due to the influence of noise, etc., and if the current due to the noise is kept as it is, the reliability of the control will decrease, so it will be attenuated with the third time constant. Thus, a countermeasure is taken (step S1404). The above operation is repeated.

  In step S1404, if I is larger than Ibuf, an arithmetic means such as a microcomputer such as I × exp (−t / τ) is used to attenuate with time constant τ with the elapse of time t, with I as an initial value. It is possible to attenuate the peak value erroneously detected due to noise or the like.

  Further, the third time constant needs to remove a frequency component that is six times the frequency of the output voltage of the inverter 9 that could not be removed by the first time constant, so the third time constant is larger. It is necessary to set, and by appropriately setting, the peak value of the current flowing through the shunt resistor 14 can be detected as shown in FIG.

  According to the third embodiment, by controlling so that the current value is accurately constant within a range that does not reach the overcurrent cutoff value, the number of revolutions at the time of light load of the motor 8 where frosting has not progressed is increased. This makes it possible not only to obtain an air conditioner that can improve the heating capacity, but also to pulsate the detected current. By suppressing it, stable control becomes possible, and an air conditioner with less noise can be obtained.

  Moreover, when the wind of the reverse direction to a ventilation direction blows on the ventilation fan 7, the load of the electric motor 8 will increase and an electric current value may increase. In the case of the conventional control, since it is difficult to control the current value, the motor 8 stops due to an overcurrent interruption due to the increase in the current value, and heat exchange cannot be performed efficiently. However, since the current value is controlled to be constant in the third embodiment of the present invention, the rotational speed is decreased even when a reverse wind is generated, and the rotational speed is increased when the wind stops. Thus, it is possible to continue the heating operation, and it is possible to obtain an air conditioner with high reliability and capable of improving the heating capacity.

  Furthermore, even when the outdoor heat exchanger becomes blocked due to aging and accumulation of dust and the torque required to drive the blower fan 7 increases, the outdoor heat exchanger can be operated at an optimum rotational speed at which the current value is constant. Therefore, it is possible to obtain an air conditioner that is highly reliable and capable of improving the heating capacity.

Embodiment 4 FIG.
In the air conditioners of the first to third embodiments, the method for accurately detecting the current value from the voltage pulsating at the frequency six times the frequency of the output voltage of the inverter 9 generated in the voltage holding means 15 has been described.
The voltage Vc held by the voltage holding means 15 is stabilized at a place where the charging speed to the charging means 17 and the discharging speed of the discharging means 18 are balanced. In this case, if the ratio of the voltage zero interval (Duty) becomes smaller than the pulse voltage generation time of the chargeable shunt voltage, the discharge time becomes longer than the charge time, and a voltage error occurs as shown in FIG. To do.

  In particular, as shown in FIG. 17, for example, when a current vector exists on the U phase where the U phase current is maximum, a switching pattern (UP, VN, WN = ON) by the U phase PWM signal is entered. , A U-phase current flows through the shunt resistor 14. However, when the phase difference φ of the voltage vector is significantly different from the current vector (poor power factor), the U-phase current is caused to flow through the shunt resistor 14 as shown in FIG. Since the vector is small, the switching time for flowing the U-phase current on the shunt resistor 14 is shortened, the pulse width is narrowed, the error of the voltage holding means 15 is increased, and it is difficult to detect the peak value. Become.

  Further, during heating operation, the load on the motor 8 increases with time due to the influence of frost formation, and the power factor during operation decreases as shown in FIG. For this reason, as described above, a current detection error occurs with the deterioration of the power factor, making it difficult to keep the current value constant, and depending on the operating condition, there is a possibility that the overcurrent is interrupted and the heating operation cannot be continued.

  The purpose of the fourth embodiment is to solve the above problems, and the contents will be described below. 1 to 3, 5 and 7 to 10 are also used in the fourth embodiment. FIG. 19 is a block diagram showing the configuration of the inverter control means 11 in Embodiment 4 of the present invention. As shown in FIG. 19, an electrical angular frequency ω is added as an input to the current detection means 20, and the current detection means 20 is added with a current detection value correction means 32 that receives each electrical angular frequency ω as shown in FIG. Except for this, there is no difference from the other embodiments, so that the same reference numerals are assigned and description thereof is omitted, and only the changes are described.

  As shown in FIG. 18, when the control according to the fourth embodiment is used, the electrical angular frequency ω increases or decreases according to the load status of the electric motor 8. That is, when the electrical angular frequency ω is lowered, the load on the motor 8 is heavy and the power factor is poor. Therefore, the current detection value correction unit 32 stores the relationship between the electrical angular frequency ω and the current detection error in a storage unit (not shown) in advance, and reads out the corresponding current error in accordance with the electrical angular frequency ω from the storage unit. The current value detected using the current error as a correction value is corrected. Thereby, it is possible to correct the current value with a simple operation.

Although the method for correcting the current detection error with the electrical angular frequency ω has been described, it goes without saying that there is no problem even if the current detection error is corrected using information such as the power factor and the pulse width.
For example, in the case of the power factor, the current detection value correction means 32 stores the relationship between the power factor and the current detection error in a storage means (not shown) in advance, and the U-phase current vector flowing through the shunt resistor 14 and the shunt The power factor is calculated based on the voltage across the resistor 14, the current error corresponding to the obtained power factor is read from the storage means, and the current value detected using the current error as a correction value is calculated. to correct. Thereby, it is possible to correct the current value with a simple operation.
In the case of the pulse width, the current detection value correction unit 32 stores the relationship between the duty of the voltage applied to the shunt resistor 14 shown in FIG. 16 and the current detection error in a storage unit (not shown) in advance. A current error corresponding to the duty of the voltage applied to the resistor 14 is read from the storage means, and the current value detected using the current error as a correction value is corrected. Thereby, it is possible to correct the current value with a simple operation.

  According to the fourth embodiment, by performing control so that the current value is accurately constant within a range that does not reach the overcurrent cutoff value, the number of revolutions at the time of light load of the motor 8 where frosting has not progressed is increased. This makes it possible not only to obtain an air conditioner that can improve the heating capacity, but also to pulsate the detected current. By suppressing it, stable control becomes possible, and an air conditioner with less noise can be obtained.

  Moreover, when the wind of the reverse direction to a ventilation direction blows on the ventilation fan 7, the load of the electric motor 8 will increase and an electric current value may increase. In the case of the conventional control, since it is difficult to control the current value, the motor 8 stops due to an overcurrent interruption due to the increase in the current value, and heat exchange cannot be performed efficiently. However, since the current value is controlled to be constant in the fourth embodiment of the present invention, the rotational speed is decreased even when a reverse wind is generated, and the rotational speed is increased when the wind stops. Thus, it is possible to continue the heating operation, and it is possible to obtain an air conditioner with high reliability and capable of improving the heating capacity.

  Furthermore, even when the outdoor heat exchanger becomes blocked due to aging and accumulation of dust and the torque required to drive the blower fan 7 increases, the outdoor heat exchanger can be operated at an optimum rotational speed at which the current value is constant. Therefore, it is possible to obtain an air conditioner that is highly reliable and capable of improving the heating capacity.

  In the first to fourth embodiments of the present invention, the electric motor 8 is controlled based on the output of the magnetic pole position sensor. However, even if this control is performed using the magnetic pole position sensorless control based on the phase current detection of the electric motor 8, no matter what. It goes without saying that there is no problem.

  As an application example of the present invention, not only an air conditioner but also an apparatus using a blower fan such as a heat pump water heater or a vacuum cleaner can be applied.

  DESCRIPTION OF SYMBOLS 1 Compressor, 2 Four way valve, 3 Outdoor heat exchanger, 4 Expansion valve, 5 Indoor heat exchanger, 6 Refrigerant piping, 7 Blower fan, 8 Electric motor, 9 Inverter, 10 DC power supply, 11 Inverter control means, 12 DC voltage Detection means, 13 Magnetic pole position detection means, 14 Shunt resistance, 15 Voltage holding means, 16a to 16f Switching element, 17 Charging means, 18 Discharge means, 19 Position / speed estimation means, 20 Current detection means, 21 Frequency command calculation means, 22 Voltage control means, 23 Voltage current conversion means, 24 Limiting means, 25 Frequency correction calculating means, 26 Speed command limiting means, 27 Voltage command amplitude calculating means, 28 Three-phase voltage command calculating means, 29 PWM generating means, 30 Low pass Filter means, 31 Peak hold means, 32 Current detection value correction means, 33 Backflow prevention Stage, 34 the voltage drop compensation means.

Claims (11)

An outdoor heat exchanger,
An outdoor fan that blows air to the outdoor heat exchanger;
An electric motor that drives the outdoor fan;
An inverter that applies a voltage to the motor using a DC power source as a power source;
Inverter control means for controlling the voltage output from the inverter;
A shunt resistor connected between the DC power source and the inverter;
Charging means connected to the voltage across the shunt resistor via backflow prevention means;
Discharging means for discharging the voltage charged in the charging means with a first time constant that is 1/6 times or more of the cycle of the voltage output from the inverter ,
The inverter control means,
Current detecting means for detecting a current flowing through the shunt resistor based on a voltage charged in the charging means;
Frequency control means for controlling the frequency of the voltage output by the inverter according to the output of the current detection means,
The frequency control means includes frequency correction means for correcting the frequency of the voltage output by the inverter based on the deviation between the output of the current detection means and a current control value that is equal to or less than the overcurrent cutoff value,
The frequency control means includes
When the output of said current detecting means exceeds the current control value, lowers the frequency of the voltage output by the pre-Symbol inverter, if it falls below the current control value, the frequency of the voltage output by the inverter increase,
The inverter control means includes
The number of revolutions of the motor is controlled in a state where the current value is kept constant within a range not reaching the overcurrent cutoff value.
Air conditioner, wherein a call. The charging means is constituted by a capacitor,
The air conditioner according to claim 1, wherein the current detection unit obtains a current value based on a voltage charged in the capacitor and a resistance value of the shunt resistor. The air conditioner according to claim 1 or 2, wherein the current detection means includes low-pass filter means for smoothing the detected current value with a low-pass filter having a second time constant. The air conditioner according to claim 3 , wherein the second time constant is larger than the first time constant. The air conditioner according to claim 3 or 4 , wherein the current detection unit includes a low-pass filter output correction unit that corrects an output of the low-pass filter unit. It said current detecting means, according to claim 1, characterized in that it comprises a damping means for attenuating the output of maximum value detecting means and the maximum value detecting means for detecting a maximum value of the detected current value at a third time constant or The air conditioner according to claim 2 . The air conditioner according to claim 6 , wherein the third time constant is larger than the first time constant. The air conditioner according to any one of claims 1 to 7 , wherein the current detection unit includes a current detection value correction unit that corrects a detection value of a current according to an operation state of the electric motor. The current detection value correction means includes storage means for storing a relationship between an electrical angular frequency and a current detection error,
The current value detected by using the current error as a correction value is corrected after reading out the current error corresponding to the electrical angular frequency of the voltage output by the inverter from the storage means. 8. The air conditioner according to 8 . The current detection value correction means includes storage means for storing a relationship between a power factor and a current detection error,
The current error corresponding to the power factor obtained based on the U-phase current vector flowing through the shunt resistor and the voltage applied to the shunt resistor is read from the storage means, and the current error is calculated. The air conditioner according to claim 8 , wherein the detected current value is corrected. The current detection value correction means includes storage means for storing a relationship between a duty of a voltage applied to the shunt resistor and a current detection error,
In terms of the error of the current corresponding according to Duty of the voltage applied to the shunt resistor is read from the storage means, according to claim 8, characterized in that to correct the current value detected as a correction value to the error of the current Air conditioner as described in.

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