Air conditioner

Abstract

To provide an air conditioner capable of attaining both vibration suppression and high efficiency of a compressor.SOLUTION: An air conditioner 100 comprises a compressor 11 driven by a motor M1, and a control unit 52 that controls the motor M1, and as the suction pressure of the compressor 11 is lower, the control unit 52 increases the effect of speed fluctuation suppression control for suppressing fluctuation in the rotation speed of the motor M1. Also, the control unit 52 changes a compensation order in the speed fluctuation suppression control based on the suction pressure of the compressor 11.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an air conditioner.

Background Art

[0002] As a technique for suppressing vibration associated with torque pulsation (fluctuation of load torque) of a compressor, for example, the technique described in Patent Document 1 is known. That is, Patent Document 1 describes that a control unit adjusts an allowable range of fluctuation of the rotational speed of a motor based on at least one of the rotational speed of the motor connected to a load and the load torque.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the technique described in Patent Document 1, the vibration of the compressor is suppressed by adjusting the allowable range of fluctuation of the rotational speed of the motor, but there is still room for improvement.

[0005] Therefore, an object of the present invention is to provide an air conditioner capable of achieving both vibration suppression and high efficiency of a compressor.

Means for Solving the Problems

[0006] In order to solve the above-described problems, an air conditioner according to the present invention includes a compressor driven by a motor and a control unit that controls the motor. The control unit strengthens the effect of speed fluctuation suppression control for suppressing fluctuations in the rotational speed of the motor as the suction pressure of the compressor becomes lower. Then, based on the suction pressure of the compressor, the compensation order in the speed fluctuation suppression control is changed. The rotational n-th order component (n: natural number) as the compensation order is a component included in the fluctuation of the rotational speed of the motor and suppressed by the speed fluctuation suppression control, and is a component whose waveform exhibits n periods of sine wave shape during one rotation of the motor in mechanical angle. It was decided to do so. In addition, other matters will be described in the embodiments.

Effects of the Invention

[0007] According to the present invention, it is possible to provide an air conditioner capable of achieving both vibration suppression and high efficiency of a compressor.

Brief Description of the Drawings

[0008]

Figure 1

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Figure 22

Embodiments for Carrying Out the Invention

[0009] <<First Embodiment>> <Configuration of Air Conditioner> FIG. 1 is a configuration diagram of an air conditioner 100 according to the first embodiment. Note that the solid arrows in FIG. 1 indicate the flow of the refrigerant in the heating cycle. Also, the broken arrows in FIG. 1 indicate the flow of the refrigerant in the cooling cycle. The air conditioner 100 is a device that performs air conditioning such as cooling operation and heating operation. As shown in FIG. 1, the air conditioner 100 includes a compressor 11, an outdoor heat exchanger 12, an outdoor fan 13, and an expansion valve 14. Further, the air conditioner 100 includes an indoor heat exchanger 15, an indoor fan 16, and a four-way valve 17, and also includes a plurality of sensors such as an indoor temperature sensor 21. In addition, as a configuration used for driving the motor M1 of the compressor 11, the air conditioner 100 includes a converter 31, a smoothing capacitor 32, an inverter 33, a voltage detector 34, a current detector 35, and a motor drive device 50.

[0010] The compressor 11 is a device that compresses a low-temperature and low-pressure gas refrigerant and discharges it as a high-temperature and high-pressure gas refrigerant, and includes a motor M1 as a drive source. As such a motor M1, for example, a permanent magnet synchronous motor is used. Also, as the compressor 11 driven by the motor M1, for example, a rotary compressor or a scroll compressor is used. The compressor 11 has a characteristic that the load torque of the motor M1 periodically varies during the compression process of the refrigerant.

[0011] The outdoor heat exchanger 12 is a heat exchanger in which heat exchange is performed between the refrigerant flowing through its heat transfer tubes (not shown) and the outside air. The outdoor fan 13 is a fan that sends outside air into the outdoor heat exchanger 12. The outdoor fan 13 includes an outdoor fan motor 13a as a drive source and is installed near the outdoor heat exchanger 12. The expansion valve 14 is a valve that decompresses the refrigerant condensed in the "condenser" (either the outdoor heat exchanger 12 or the indoor heat exchanger 15). Note that the refrigerant decompressed by the expansion valve 14 is guided to the "evaporator" (the other of the outdoor heat exchanger 12 and the indoor heat exchanger 15).

[0012] The indoor heat exchanger 15 is a heat exchanger in which heat exchange is performed between the refrigerant flowing through its heat transfer tubes (not shown) and the indoor air (the air in the air-conditioned room). The indoor fan 16 is a fan that sends indoor air into the indoor heat exchanger 15. The indoor fan 16 includes an indoor fan motor 16a as a drive source and is installed near the indoor heat exchanger 15.

[0013] The four-way valve 17 is a valve that switches the refrigerant flow path according to the operating mode of the air conditioner 100. For example, during cooling operation (refer to the dashed arrow in FIG. 1), in the refrigerant circuit 10, the refrigerant circulates sequentially through the compressor 11, the outdoor heat exchanger 12 (condenser), the expansion valve 14, and the indoor heat exchanger 15 (evaporator). On the other hand, during heating operation (refer to the solid arrow in FIG. 1), in the refrigerant circuit 10, the refrigerant circulates sequentially through the compressor 11, the indoor heat exchanger 15 (condenser), the expansion valve 14, and the outdoor heat exchanger 12 (evaporator).

[0014] In the example of FIG. 1, the compressor 11, the outdoor heat exchanger 12, the outdoor fan 13, the expansion valve 14, and the four-way valve 17 are installed in the outdoor unit 30. Also, the indoor heat exchanger 15 and the indoor fan 16 are installed in the indoor unit 20.

[0015] The indoor temperature sensor 21 shown in FIG. 1 is a sensor that detects the temperature of the air-conditioned room and is installed in the indoor unit 20. The indoor heat exchanger temperature sensor 22 is a sensor that detects the temperature of the indoor heat exchanger 15 and is installed in the indoor heat exchanger 15 (or its connecting pipe). The discharge temperature sensor 23 is a sensor that detects the temperature (discharge temperature) of the refrigerant discharged from the compressor 11 and is installed on the discharge side of the compressor 11.

[0016] The outdoor temperature sensor 24 is a sensor that detects the temperature of the outside air and is installed in the outdoor unit 30. The outdoor heat exchanger temperature sensor 25 is a sensor that detects the temperature of the outdoor heat exchanger 12 and is installed in the outdoor heat exchanger 12 (or its connecting pipe). The detection values of these respective sensors are output to the load state determination unit 51 etc. of the motor drive device 50.

[0017] Converter 31 is a power converter that converts the AC voltage applied from the AC power supply E1 into a DC voltage. The smoothing capacitor 32 is a capacitor that smooths the DC voltage (DC voltage including pulsating current) on the output side of the converter 31. The inverter 33 is a power converter that converts the DC voltage smoothed by the smoothing capacitor 32 into an AC voltage and applies this AC voltage to the windings of the motor M1. As such an inverter 33, for example, a three-phase full-bridge inverter is used.

[0018] The voltage detector 34 detects the DC voltage across the smoothing capacitor 32. The current detector 35 is, for example, a shunt resistor and detects the current flowing from the converter 31 to the inverter 33. The detection values of the voltage detector 34 and the current detector 35 are output to the control unit 52 of the motor drive device 50.

[0019] The motor drive device 50 is a device that drives the motor M1 and, although not shown in the figure, is configured to include electronic circuits such as a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and various interfaces. Then, the program stored in the ROM is read out and expanded in the RAM, and the CPU executes various processes. As shown in FIG. 1, the motor drive device 50 includes a load state determination unit 51 and a control unit 52.

[0020] The load state determination unit 51 determines the load state of the compressor 11 based on the detection values of a plurality of sensors such as the room temperature sensor 21 and the rotation speed of the motor M1. In the first embodiment, the load state determination unit 51 calculates the suction pressure of the compressor 11 and outputs the comparison result between this suction pressure and a predetermined value to the control unit 52 as load determination information.

[0021] The control unit 52 performs a predetermined vector calculation based on the detection values of the voltage detector 34 and the current detector 35, as well as the load determination information input from the load state determination unit 51, etc., to control the motor M1. For example, the control unit 52 generates a predetermined PWM (Pulse Width Modulation) pulse and outputs this PWM pulse to a driver circuit (not shown). Then, a predetermined command signal is output from the driver circuit to each switching element (not shown) of the inverter 33, thereby driving the motor M1.

[0022] <Configuration of the control unit> FIG. 2 is a functional block diagram of the control unit 52 provided in the motor drive device of the air conditioner. As shown in FIG. 2, the control unit 52 includes a three-phase / two-axis conversion unit 52a, an axis error calculation unit 52b, a PLL circuit 52c (Phase Locked Loop), an integrator 52d, and a speed control unit 52e. In addition to the above-described configuration, the control unit 52 further includes subtractors 52f, 52g, a current control unit 52h, a voltage command calculation unit 52i, a two-axis / three-phase conversion unit 52j, and a PWM signal generation unit 52k.

[0023] Based on the current detection value of the current detector 35 (see FIG. 1), the currents (Iu, Iv, Iw) in the three-phase coordinate system are reproduced in the control unit 52, and the values of these currents (Iu, Iv, Iw) are output to the three-phase / two-axis conversion unit 52a.

[0024] The three-phase / two-axis conversion unit 52a converts the currents (Iu, Iv, Iw) in the three-phase coordinate system into the current detection values (Idc, Iqc) on the dc axis and the qc axis based on the phase θdc of the rotor of the motor M1 (see FIG. 1). Note that the direction of the actual magnet flux Φ in the motor M1 is defined as the d axis, and the axis orthogonal to this d axis is defined as the q axis. Also, the d axis assumed in the control unit 52 is defined as the dc axis (similarly for the qc axis). That is, the current detection values (Idc, Iqc) are the motor currents on the dc axis and the qc axis assumed in the control unit 52.

[0025] The axis error calculation unit 52b calculates the axis error Δθ between the phase of the actual magnet flux Φ in the motor M1 (see FIG. 1) and the phase θd that is the calculation result of the integrator 52d based on, for example, the following equation (1). Note that R shown in equation (1) is the winding resistance of the motor M1, and Lqc is the q-axis inductance of the motor M1. Also, the superscript "*" attached to the d-axis voltage command Vd * and the like indicates that it is a command value.

[0026]

Equation

[0027] The PLL circuit 52c calculates the actual rotational speed ωr of the motor M1 (see FIG. 1) based on PI control (Proportional Integral Control) so that the axis error Δθ calculated by the axis error calculation unit 52b becomes zero. As a result, since the assumed dc axis and qc axis in the control unit 52 coincide with the d axis and q axis corresponding to the actual magnet flux Φ of the motor M1, the motor M1 can be vector-controlled without a position sensor. The integrator 52d calculates the rotor phase θdc of the motor M1 by integrating the actual rotational speed ωr.

[0028] The speed control unit 52e calculates the torque current command Iq based on the load determination information input from the load state determination unit 51 (see FIG. 1), the predetermined rotational speed command ωr calculated in the control unit 52 * and the actual rotational speed ωr of the motor M1 (see FIG. 1) input from the PLL circuit 52c. The processing of this speed control unit 52e is one of the main features of the first embodiment, and the details will be described later. *

[0029] The subtractor 52f calculates the difference ΔId between the predetermined excitation current command Id * and the current detection value Idc that is the calculation result of the three-phase / two-axis conversion unit 52a. Note that when the motor M1 (see FIG. 1) is non-salient (Ld = Lq), the excitation current command Id * ​is set to zero. When the motor M1 is of the reverse salient pole type (Ld < Lq), a predetermined excitation current command Id * is set based on the torque current command Iq * . The subtractor 52g calculates the difference ΔIq between the torque current command Iq * which is the calculation result of the speed control unit 52e, and the current detection value Iqc which is the calculation result of the three-phase / two-axis conversion unit 52a.

[0030] The current control unit 52h calculates a second excitation current command Id ** and a second torque current command Iq ** so that the above-described differences ΔId and ΔIq become zero. The voltage command calculation unit 52i calculates voltage commands (Vd ** and Vq ** ) based on the second excitation current command Id * and the second torque current command Iq * which are the calculation results of the current control unit 52h, using a well-known voltage equation.

[0031] The two-axis / three-phase conversion unit 52j converts the d-axis and q-axis voltage commands (Vd * and Vq * ) which are the calculation results of the voltage command calculation unit 52i, into three-phase voltage commands (Vu * , Vv * , Vw * ) based on the phase θdc which is the calculation result of the integrator 52d.

[0032] The PWM signal generation unit 52k generates a predetermined PWM pulse) based on the three-phase voltage commands (Vu * , Vv * , Vw * ) which are the calculation results of the two-axis / three-phase conversion unit 52j. Based on this PWM pulse, the on / off of each switching element (not shown) of the inverter 33 is switched so that a three-phase alternating current flows through the windings of the motor M1 (see FIG. 1).

[0033] <Regarding the torque pulsation of the compressor> In the compressor 11 of the air conditioner 100 (see Fig. 1), when the motor M1 is rotated once in mechanical angle, the load torque fluctuates during the refrigerant compression process. Such a fluctuation in the load torque is referred to as "torque pulsation". Regarding the characteristics of this torque pulsation, the inventors obtained the following new findings. In the following descriptions of Figs. 16 to 22, the components such as the compressor and the motor are not particularly labeled with reference signs.

[0034] Fig. 16 shows the simulation results of torque pulsation when the motor of the drive source is rotated once in mechanical angle in a single-cylinder rotary compressor. Note that the horizontal axis in Fig. 16 is the crank angle of the compressor. Also, the vertical axis in Fig. 16 is the load torque of the compressor. The simulation results in Fig. 16 explain the characteristics of the load torque of the compressor, and the motor control of the first embodiment is not particularly performed (the same applies to Figs. 17 to 22).

[0035] The single-cylinder rotary compressor that is the subject of the simulation in Fig. 16 is a device that compresses the refrigerant in the compression chamber between the cylinder (not shown) and the roller (not shown) as the roller (not shown) revolves in the cylinder (not shown) with the drive of the motor. Such a single-cylinder rotary compressor includes a pair of cylinders (not shown) and rollers (not shown). Also, in a single-cylinder rotary compressor, one torque pulsation occurs during the process of the motor of the drive source rotating once in mechanical angle.

[0036] Fig. 16 shows not only the case where the suction pressure Ps of the compressor is low (solid line graph), but also the case where the suction pressure Ps is medium (dashed-dotted line graph) and the case where the suction pressure Ps is high (dashed line graph). Regarding these three patterns, the average value of the load torque (about 1.9 [N·m] shown by the dashed line in Fig. 16) is the same when the motor of the drive source rotates once in mechanical angle. Incidentally, in the three patterns with different suction pressures Ps, the lower the suction pressure Ps, the greater the differential pressure between the discharge pressure (not shown) and the suction pressure Ps.

[0037] As shown in Fig. 16, even when the average value of the load torque is the same, the lower the suction pressure Ps, the greater the torque pulsation of the compressor (i.e., a single-cylinder rotary compressor). This is presumably because the lower the suction pressure Ps, the longer the compression period of the refrigerant until the discharge valve (not shown) of the compressor opens (i.e., until the pressure of the refrigerant overcomes the elastic force of the discharge valve). Thus, the fact that the lower the suction pressure Ps, the greater the torque pulsation of the compressor is a newly obtained finding by the inventors.

[0038] Fig. 17 shows the simulation results of frequency analysis of torque pulsation in a single-cylinder rotary compressor under multiple patterns with different suction pressures. Note that the horizontal axis in Fig. 17 is the suction pressure Ps of the compressor. Also, the vertical axis in Fig. 17 is the torque pulsation when the average value of the load torque is set to 100%. For example, when the suction pressure Ps is 0.5 [Mpa], the first-order rotational component of the torque pulsation (shown as "1st" in Fig. 17) is 144 [%], and the second-order rotational component ("2nd") is 66 [%]. In addition, Fig. 17 also shows the third-order rotational component ("3rd") and the fourth-order rotational component ("4th") of the torque pulsation.

[0039] Here, the first-order rotational component is one of the components included in the torque pulsation of the compressor, and the waveform during one rotation of the motor of the compressor in mechanical angle exhibits a sine wave shape for one cycle. Similarly, the nth-order rotational component (n: natural number) is one of the components included in the torque pulsation of the compressor, and the waveform during one rotation of the motor of the compressor in mechanical angle exhibits a sine wave shape for n cycles. As shown by the white arrows in Fig. 17, the lower the suction pressure Ps of the compressor, the greater not only the first-order rotational component of the torque pulsation but also the second-order rotational component. Also, for example, when the suction pressure Ps is as low as 0.5 [Mpa], the third-order rotational component of the torque pulsation is also relatively large.

[0040] Fig. 18 shows the simulation results of the torque pulsation when the motor of the drive source is rotated once in mechanical angle in a two-cylinder rotary compressor. Note that the horizontal axis of FIG. 18 represents the crank angle of the compressor. Also, the vertical axis of FIG. 18 represents the load torque of the compressor. As shown in FIG. 18, in addition to the case where the suction pressure Ps of the compressor is low (solid line graph), for the case where the suction pressure Ps is medium (dashed-dotted line graph) and the case where the suction pressure Ps is high (dashed line graph), the average value of the load torque (about 3.0 [N·m] shown by the dashed line in FIG. 18) is the same.

[0041] The two-cylinder rotary compressor, which is the object of the simulation in FIG. 18, is a device that compresses refrigerant in a compression chamber between a cylinder (not shown) and a roller (not shown) as the roller (not shown) revolves in the cylinder (not shown) with the drive of a motor. Such a two-cylinder rotary compressor is provided with two pairs of cylinders (not shown) and rollers (not shown). Also, in a two-cylinder rotary compressor, two torque pulsations occur in the process of one rotation of the drive source motor at a mechanical angle. As shown in FIG. 18, even when the average value of the load torque is the same, the lower the suction pressure Ps of the compressor (that is, the two-cylinder rotary compressor), the greater the torque pulsation.

[0042] FIG. 19 shows the simulation results when frequency analysis of torque pulsation is performed for a plurality of patterns with different suction pressures in a two-cylinder rotary compressor. Note that the horizontal axis of FIG. 19 represents the suction pressure Ps of the compressor. Also, the vertical axis of FIG. 19 represents the torque pulsation when the average value of the load torque is set to 100%. As shown by the white arrows in FIG. 19, the lower the suction pressure Ps of the compressor, the greater the second-order rotational component and the greater the fourth-order rotational component. Note that the torque pulsation of a two-cylinder rotary compressor hardly includes the first-order rotational component and the third-order rotational component.

[0043] FIG. 20 shows the simulation results showing the torque pulsation when the drive source motor of a scroll compressor is rotated once at a mechanical angle. Note that the horizontal axis of FIG. 20 represents the crank angle of the compressor, and the vertical axis of FIG. 20 represents the load torque of the compressor. As shown in FIG. 20, in addition to the case where the suction pressure Ps of the compressor is low (solid line graph), for the case where the suction pressure Ps is medium (dashed-dotted line graph) and the case where the suction pressure Ps is high (dashed line graph), the average value of the load torque (about 20 [N·m] shown by the dashed line in FIG. 20) is the same.

[0044] The scroll compressor, which is the object of the simulation in FIG. 20, is a device that compresses the refrigerant in the compression chamber between the fixed scroll (not shown) in a spiral shape and the orbiting scroll (not shown) in a spiral shape by orbiting while meshing with each other. As shown in FIG. 20, even if the average value of the load torque is the same, the lower the suction pressure Ps, the greater the torque pulsation of the compressor (that is, the scroll compressor).

[0045] FIG. 21 shows the simulation results when frequency analysis of torque pulsation is performed in a plurality of patterns with different suction pressures in the scroll compressor. Note that the horizontal axis of FIG. 21 represents the suction pressure Ps of the compressor, and the vertical axis of FIG. 21 represents the torque pulsation when the average value of the load torque is set to 100%. In the case of a scroll compressor, compared with a rotary compressor (refer to FIG. 17 for the single-cylinder type and FIG. 19 for the two-cylinder type), the torque pulsation is smaller. However, as shown by the white arrow in FIG. 21, the lower the suction pressure Ps of the compressor, the greater the first-order rotational component and the second-order rotational component of the torque pulsation. Therefore, under operating conditions where the suction pressure Ps is low, there is a possibility that noise may be generated due to vibration associated with the torque pulsation of the motor.

[0046] Thus, in any of the single-cylinder rotary compressor (see FIGS. 16 and 17), two-cylinder rotary compressor (see FIGS. 18 and 19), and scroll compressor (see FIGS. 20 and 21), the lower the suction pressure Ps, the greater the torque pulsation of the compressor. More specifically, even under the condition that the average value of the load torque is the same, the lower the suction pressure Ps, the higher-order components such as the second-order rotational component and the third-order rotational component, in addition to the first-order rotational component of the torque pulsation, tend to be larger. These are newly obtained findings by the inventors.

[0047] <Influence of Torque Pulsation on Motor Rotation Speed> As described above, in a compressor, the load torque periodically varies during the refrigerant compression process. The influence of such a variation in the load torque (torque pulsation) on the variation in the motor rotation speed will be described. First, based on the equation of motion of a rotating body, the motor torque T is given by the following equation (2). Note that J shown in equation (2) is the inertia of the motor, and ω is the angular velocity of the motor.

[0048]

Equation

[0049] Furthermore, differentiating both sides of equation (1) with respect to time t gives the following equation (3).

[0050]

Equation

[0051] FIG. 22 is an explanatory diagram showing the relationship between the maximum value Tpeak of the load torque, the average value Tave of the load torque, and the torque pulsation when the motor makes one revolution in mechanical angle in a compressor. Note that the horizontal axis of FIG. 22 is the crank angle of the compressor. Also, the vertical axis of FIG. 22 is the load torque of the compressor. In the example of FIG. 22, a scroll compressor is used as the type of compressor. Tpeak shown in FIG. 22 is the maximum value of the load torque of the compressor. Also, Tave is the average value of the load torque. Also, dT indicates the torque pulsation of the motor of the compressor.

[0052] As shown in FIG. 22, the torque pulsation dT is the difference between the maximum value Tpeak of the load torque and the average value Tave of the load torque. Here, when the torque pulsation dT is approximated by a sine wave of the first-order component of the motor rotation, it is expressed by the following equation (4). Note that ΔTamp is the amplitude of the torque pulsation, ω is the angular frequency, and t is the time.

[0053]

Equation

[0054] Furthermore, using equations (3) and (4), the rotational speed fluctuation dω of the motor of the compressor is expressed by the following equation (5).

[0055]

Equation

[0056] As shown in equation (5), the rotational speed fluctuation dω of the motor of the compressor is proportional to the amplitude ΔTamp of the torque pulsation. Note that equation (5) relates to the first-order component of the rotation of the torque pulsation dT of the compressor and the first-order component of the rotation of the rotational speed fluctuation dω of the motor, but the same can be said for higher-order components of the second-order component of rotation and above. That is, the order of the components included in the torque pulsation of the compressor and the order of the components included in the rotational speed fluctuation of the motor correspond.

[0057] Further, as the suction pressure Ps of the compressor decreases and the torque pulsation increases, the rotational speed fluctuation of each component of the torque pulsation also increases. However, if all components (rotational fundamental component, rotational second harmonic component, ···, rotational n-th harmonic component) included in the rotational speed fluctuation of the motor are uniformly reduced, the peak value of the motor current fluctuates greatly, and the loss (copper loss) of the motor may rather increase.

[0058] Therefore, in the first embodiment, based on the comparison result between the suction pressure of the compressor 11 (see FIG. 1) and a predetermined value, the speed control unit 52e (see FIG. 3) described below selects which component among the rotational fundamental component, rotational second harmonic component, ···, rotational n-th harmonic component of the rotational speed fluctuation of the motor M1 (see FIG. 1) to reduce.

[0059] <Configuration of speed control unit> FIG. 3 is a functional block diagram of a speed control unit 52e provided in the air conditioner according to the first embodiment. The speed control unit 52e shown in FIG. 3 is included in the control unit 52 (see FIGS. 1 and 2) of the motor drive device 50 (see FIG. 1). As described above, the speed control unit 52e is based on the load determination information, the rotational speed command ωr * and the actual rotational speed ωr of the motor M1, and generates a torque current command Iq * As shown in FIG. 3, the speed control unit 52e includes a subtractor 521e, a speed controller 522e, a speed fluctuation suppression control unit 523e, and an adder 524e.

[0060] The subtractor 521e calculates a rotational speed deviation Δω by subtracting the actual rotational speed ωr of the motor M1 from the rotational speed command ωr * The speed controller 522e calculates a torque current command Iq0 * corresponding to the average torque current command value of the motor M1 so as to bring the rotational speed deviation Δω close to zero, for example, based on PI control. The speed fluctuation suppression control unit 523e is based on the load determination information and the rotational speed command ωr * ​Based on the rotation speed deviation Δω and others, a torque ripple suppression q-axis current command Iq*_trq is calculated. Details of the processing of the torque ripple suppression control unit 523e will be described later. The adder 524e adds the torque ripple suppression q-axis current command Iq*_trq to the above-described torque current command Iq0 * to calculate a torque current command Iq * This torque current command Iq * is output to the subtractor 52g (see FIG. 2) of the control unit 52 (see FIG. 2) as described above.

[0061] <Configuration of Torque Ripple Suppression Control Unit> FIG. 4 is a functional block diagram of a torque ripple suppression control unit 523e provided in the air conditioner according to the first embodiment. The torque ripple suppression control unit 523e shown in FIG. 4 has a function of selectively suppressing one or more of the rotational primary component, rotational secondary component, ···, rotational n-th component of the speed fluctuation accompanying the torque ripple of the motor M1 (see FIG. 1). When suppressing the speed fluctuation of the motor M1 in this way, the transfer function shown in the following equation (6) is used. Note that s included in equation (6) is a Laplace operator, K1, K2, and K3 are control coefficients, and ω0 is a predetermined center frequency.

[0062]

Equation

[0063] FIG. 5 is an explanatory diagram showing the gain characteristics of the transfer function used in the torque ripple suppression control unit. Note that the horizontal axis in FIG. 5 is the angular frequency of the motor M1 (see FIG. 1), and the vertical axis is the gain (amplification factor) of the above-described equation (6). As shown in FIG. 5, the transfer function of Equation (6) has the characteristic of having a large sensitivity at a predetermined center frequency ω0 and almost no sensitivity at other frequencies. Therefore, by setting this center frequency ω0 to a predetermined frequency, it is possible to achieve high sensitivity (high gain) at the predetermined frequency without substantially increasing the sensitivity at other frequencies. Further, the gain of this transfer function can be adjusted by appropriately changing the magnitudes of the control coefficients K1, K2, and K3 included in the transfer function of Equation (6).

[0064] As shown in FIG. 4, the speed fluctuation suppression control unit 523e includes a gain command calculation unit 61, a speed fluctuation suppression q-axis current command generation unit 62, and an adder 63. The gain command calculation unit 61 receives load determination information, a rotational speed command ωr * and a rotational speed deviation Δω. Then, the gain command calculation unit 61 calculates the control coefficients K1 and K2 included in Equation (6) for each of the first-order rotational component (denoted as "1" in FIG. 4), second-order rotational component (denoted as "2"), third-order rotational component (denoted as "3"),..., nth-order rotational component (denoted as "n") of the speed fluctuation of the motor M1 (see FIG. 1). The setting of such control coefficients K1 and K2 is performed based on the load determination information. st "), second-order rotational component ("2 nd "), third-order rotational component ("3 rd "),..., nth-order rotational component ("n th "). The setting of such control coefficients K1 and K2 is performed based on the load determination information.

[0065] As described above, the load determination information is information indicating the comparison result between the suction pressure Ps of the compressor 11 (see FIG. 1) and a predetermined value, and is output from the load state determination unit 51 (see FIG. 1) to the control unit 52 (see FIG. 1). For example, when the suction pressure Ps of the compressor 11 is relatively low, as described above, since the torque pulsation is large, the speed fluctuation of the motor M1 is likely to increase. In such a case, in order to suppress the speed fluctuation of the motor M1, the speed fluctuation suppression control unit 523e increases the control coefficients K1 and K2 corresponding to a predetermined order such as the rotational primary component and the rotational secondary component. As a result, since the gain of the transfer function in Equation (6) increases, the effectiveness of the control for suppressing the speed fluctuation of the motor M1 becomes stronger. Note that the remaining control coefficient K3 (damping constant) included in Equation (6) is preset based on stability discrimination based on the Bode diagram, prior experiments, etc.

[0066] Also, among the rotational primary component, rotational secondary component, rotational tertiary component, ···, rotational nth component of the speed fluctuation of the motor M1, at which order the control effectiveness based on Equation (6) is to be strengthened (or weakened) is determined by the gain command calculation unit 61 based on, in addition to the load determination information, the type of the compressor 11, the operation mode, etc. The gain command calculation unit 61 outputs information including the rotational speed command ωr * and the rotational speed deviation Δω, associated with each order, to the speed fluctuation suppression q-axis current command generation unit 62.

[0067] The speed fluctuation suppression q-axis current command generation unit 62 generates a q-axis current command for each order to suppress the rotational speed fluctuation associated with the torque pulsation of the motor M1 (see FIG. 1). As shown in FIG. 4, the speed fluctuation suppression q-axis current command generation unit 62 includes a primary component calculation unit 62a, a secondary component calculation unit 62b, a tertiary component calculation unit 62c, and also includes an nth component calculation unit 62n, etc.

[0068] For example, the primary component calculation unit 62a generates a q-axis current command Iq*_trq_1 st to cancel (suppress) the rotational primary component of the speed fluctuation associated with the torque pulsation of the motor M1 (see FIG. 1). Specifically, the primary component calculation unit 62a substitutes the control coefficients K1 and K2_1 st set by the gain command calculation unit 61 into Equation (6), and further substitutes the rotational speed command ωr of the motor M1 *By substituting (or the actual rotational speed ωr), the q-axis current command Iq*_trq_1 is obtained. st This q-axis current command Iq*_trq_1 st is a control command value for suppressing the first-order rotational component of the speed fluctuation of the motor M1.

[0069] Note that the processing performed by the second-order component calculation unit 62b, the third-order component calculation unit 62c, etc. is the same. However, in the second-order component calculation unit 62b, a value twice that of the rotational speed command ωr of the motor M1 (2·ωr * ) is substituted into the center frequency ω0 of Equation (6). Also, in the third-order component calculation unit 62c, a value three times that of the rotational speed command ωr of the motor M1 (3·ωr * ) is substituted into the center frequency ω0 of Equation (6). In this way, the speed fluctuation of the motor M1 is suppressed for each order. Such control is called "speed fluctuation suppression control". * * * ) is substituted. In this way, the speed fluctuation of the motor M1 is suppressed for each order. Such control is called "speed fluctuation suppression control".

[0070] The adder 63 shown in FIG. 4 sums the respective calculation results of the first-order component calculation unit 62a, the second-order component calculation unit 62b, the third-order component calculation unit 62c,..., the nth-order component calculation unit 62n, and calculates the speed fluctuation suppression q-axis current command Iq*_trq. This speed fluctuation suppression q-axis current command Iq*_trq is output to the adder 524e (see FIG. 3) of the speed control unit 52e (see FIG. 3).

[0071] <Processing of the motor drive device> FIG. 6 is a flowchart of the processing executed by the motor drive device of the air conditioner (refer to FIGS. 1 and 4 as appropriate). Note that the compressor targeted by the series of processes shown in FIG. 6 is, for example, a single-cylinder rotary compressor. Also, at the time of "START" in FIG. 6, it is assumed that a predetermined air conditioning operation such as a cooling operation or a heating operation is being performed. In step S101, the motor drive device 50 calculates the suction pressure Ps of the compressor 11 by the load state determination unit 51. For example, the load state determination unit 51 calculates the rotational speed of the motor M1 (rotational speed command ωr *Based on the actual rotational speed ωr), the indoor temperature (the temperature of the air-conditioned room), and the outdoor temperature, the suction pressure Ps of the compressor 11 is calculated. Thus, in the first embodiment, the load state determination unit 51 calculates the suction pressure Ps of the compressor 11. Therefore, since it is not necessary to particularly provide a suction pressure sensor (not shown) in the air conditioner 100 (see FIG. 1), the manufacturing cost can be reduced.

[0072] In step S102, the motor drive device 50 determines, by the load state determination unit 51, whether or not the suction pressure Ps of the compressor 11 is equal to or greater than a predetermined value. This predetermined value is a threshold value that serves as a criterion for determining whether to strengthen (corresponding to S104) or weaken (corresponding to S103) the effectiveness of the above-described speed fluctuation suppression control, and is set in advance.

[0073] In step S102, when the suction pressure Ps of the compressor 11 is equal to or greater than the predetermined value (S102: Yes), the process of the motor drive device 50 proceeds to step S103. When the suction pressure Ps is relatively high in this way, as described above, the torque pulsation of the compressor 11 is not so large (see the broken-line graph in FIG. 16). In step S103, the control unit 52 of the motor drive device 50 compensates for the rotational first-order component of the speed fluctuation of the motor M1 by the speed fluctuation suppression control unit 523e (see FIG. 4). That is, when the suction pressure Ps of the compressor 11 is equal to or greater than the predetermined value (S102: Yes), the control unit 52 sets the compensation order in the speed fluctuation suppression control to the rotational first-order component of the speed fluctuation of the motor M1 (S103).

[0074] Note that "compensating" the rotational primary component means that the speed fluctuation suppression control unit 523e (see FIG. 4) outputs a predetermined speed fluctuation suppression q-axis current command Iq*_trq (see FIG. 4) so as to cancel (suppress) the rotational primary component of the speed fluctuation of the motor M1. Also, the rotational nth component (n: natural number) as the compensation order is a component included in the fluctuation of the rotational speed of the motor M1 that is suppressed by the speed fluctuation suppression control and has a sinusoidal waveform for n cycles during one rotation of the motor M1 in mechanical angle. In short, among the components included in the speed fluctuation of the motor M1, the order of the components that are the target of the speed fluctuation suppression control is the compensation order.

[0075] To give a specific example of the process of step S103, the speed fluctuation suppression control unit 523e (see FIG. 4) sets control coefficients K1, K2_1 st (see FIG. 4) corresponding to the rotational primary component of the speed fluctuation of the motor M1 to a predetermined value by the gain command calculation unit 61 (see FIG. 4). Also, the speed fluctuation suppression control unit 523e sets the center frequency ω0 of the above-described formula (6) to the rotational speed command ωr of the motor M1 * by the primary component calculation unit 62a (see FIG. 4). Note that among the components included in the speed fluctuation of the motor M1, for the higher-order components of the rotational second component and above, the respective control coefficients K1, K2 are set to zero. As a result, the speed fluctuation suppression q-axis current command Iq*_trq that cancels the rotational primary component of the speed fluctuation of the motor M1 is output from the adder 63 (see FIG. 4).

[0076] As shown in FIG. 17, in a single-cylinder rotary compressor, when the suction pressure Ps is high (for example, when the suction pressure is 2 [Mpa] or more), the rotational primary component of the torque pulsation is relatively large, but the higher-order components such as the rotational second component, rotational third component, and rotational fourth component are not so large. Therefore, for the higher-order components of the rotational second component and above, they are deliberately excluded from the target of the speed fluctuation suppression control. As a result, the fluctuation of the peak value of the motor current can be suppressed, and the motor M1 can be driven with high efficiency.

[0077] Also, in step S102 of FIG. 6, when the suction pressure Ps of the compressor 11 is less than a predetermined value (S102: No), the process of the motor drive device 50 proceeds to step S104. When the suction pressure Ps is low like this, as described above, the torque pulsation of the compressor 11 tends to increase (refer to the solid line graph in FIG. 16). In step S104, the control unit 52 of the motor drive device 50 compensates for the rotational primary component and rotational secondary component of the speed fluctuation of the motor M1 by the speed fluctuation suppression control unit 523e (refer to FIG. 4). That is, when the suction pressure Ps of the compressor 11 is less than a predetermined value (S102: No), the control unit 52 includes the rotational primary component and rotational secondary component of the speed fluctuation of the motor M1 as the compensation order in the speed fluctuation suppression control (S104).

[0078] To give a specific example of the process of step S104, the speed fluctuation suppression control unit 523e (refer to FIG. 4) has control coefficients K1, K2_1 corresponding to the rotational primary component of the speed fluctuation by the gain command calculation unit 61 (refer to FIG. 4). st In addition to that, control coefficients K1, K2_2 corresponding to the rotational secondary component nd are set to a predetermined value. Note that the speed fluctuation suppression control unit 523e may make the control coefficients K1, K2_1 corresponding to the rotational primary component st larger than in the case of step S103. As a result, since the gain in the transfer function of the above-described formula (6) becomes larger, the effect of the speed fluctuation suppression control can be strengthened with respect to the rotational primary component of the speed fluctuation of the motor M1.

[0079] Also, the speed fluctuation suppression control unit 523e sets the center frequency ω0 of the above-described formula (6) to the rotational speed command ωr of the motor M1 by the primary component calculation unit 62a (refer to FIG. 4). * Similarly, the speed fluctuation suppression control unit 523e sets the center frequency ω0 of the above-described formula (6) to the rotational speed command ωr of the motor M1 by the secondary component calculation unit 62b (refer to FIG. 4). *Set it to twice that value. As a result, the adder 63 (see Fig. 4) outputs a torque ripple suppression q-axis current command Iq*_trq that cancels out the first-order and second-order rotational components of the speed fluctuation of the motor M1.

[0080] In this way, the control unit 52 (see Fig. 1) strengthens the effectiveness of the speed fluctuation suppression control for suppressing the speed fluctuation of the motor M1 as the suction pressure Ps of the compressor 11 (see Fig. 1) becomes lower. For example, when suppressing a predetermined component (order) included in the speed fluctuation of the motor M1, the process of increasing the gain of the control transfer function (see Equation (6)) is included in the matter of "strengthening the effectiveness" of the speed fluctuation suppression control. Also, the process of including the order of speed fluctuation that was not targeted when the suction pressure Ps was high in the target of the speed fluctuation suppression control is also included in the matter of "strengthening the effectiveness" of the speed fluctuation suppression control.

[0081] In short, "strengthening the effectiveness" of the speed fluctuation suppression control means that at least one of the q-axis current commands Iq*_trq_1 st , Iq*_trq_2 nd , Iq*_trq_3 rd , ···, and Iq*_trq_n th (see Fig. 4) is made larger compared to the case where the suction pressure Ps is high. When strengthening the effectiveness of the speed fluctuation suppression control, the control unit 52 (see Fig. 1) increases the compensation amount of the torque current (q-axis current) corresponding to at least one of the above-mentioned compensation orders (for example, the q-axis current command Iq*_trq_1 st ). In this way, by increasing the compensation amount of the torque current, the vibration associated with the torque pulsation of the compressor 11 (see Fig. 1) can be appropriately suppressed.

[0082] As shown in Fig. 17, in a single-cylinder rotary compressor, when the suction pressure Ps is low (for example, when the suction pressure is less than 2 [Mpa]), in addition to the rotational primary component of the torque pulsation, the rotational secondary component also becomes relatively large. As described above, the speed fluctuation suppression control unit 523e generates a speed fluctuation suppression q-axis current command Iq*_trq (see Fig. 4) so as to cancel out the rotational primary component and rotational secondary component of the speed fluctuation of the motor M1, thereby suppressing vibrations and noises associated with the torque pulsation of the compressor 11. After the process of step S103 or S104 in Fig. 6 is performed, the process of the motor drive device 50 returns to "START" ("RETURN"). In this way, the motor drive device 50 repeatedly performs a series of processes shown in Fig. 6 as specified.

[0083] As described with reference to Fig. 6, it is preferable that the control unit 52 (see Fig. 1) changes the compensation order in the speed fluctuation suppression control based on the suction pressure Ps of the compressor 11. Thereby, while suppressing the vibration of the compressor 11, the motor M1 can be driven with high efficiency.

[0084] Further, it is preferable that the control unit 52 (see Fig. 1) increases the upper limit value of the compensation order in the speed fluctuation suppression control as the suction pressure Ps of the compressor 11 becomes lower. Thereby, when the suction pressure Ps of the compressor 11 is low, by including higher-order components (rotational secondary component and above) of the speed fluctuation of the motor M1 as the target of the speed fluctuation suppression control, vibrations associated with torque pulsation can be appropriately suppressed.

[0085] <Simulation Results> Fig. 7 shows the simulation results regarding the speed fluctuation of the motor of a single-cylinder rotary compressor. Note that the horizontal axis in Fig. 7 represents the order of the speed fluctuation of the motor M1 (see Fig. 1). Also, the vertical axis in Fig. 7 represents the speed fluctuation of the motor M1. The simulation in Fig. 7 was performed using the motor M1 having the characteristics shown in Table 1 below. The commanded rotational speed of the motor M1 is 2000 [rpm] (=[min -1 ) and was performed under the conditions that the suction pressure of the compressor 11 is 1.0 [Mpa] and the discharge pressure is 3.5 [MPa].

[0086]

Table 1

[0087] In FIG. 7, simulations were performed for each of three patterns: when the speed fluctuation suppression control is not performed, when the rotational primary component of the speed fluctuation of the motor M1 is suppressed, and when the rotational primary component and the rotational secondary component are suppressed. As shown in FIG. 7, in a single-cylinder rotary compressor, when the rotational speed fluctuation suppression control is not performed, a large speed fluctuation occurs in the rotational primary component (「1 st 」), and a speed fluctuation about 1 / 5 the size of the rotational primary component occurs in the rotational secondary component (「2 nd 」).

[0088] Also, compared with the case where the speed fluctuation suppression control is not performed, when the rotational primary component is suppressed (i.e., sensitivity is given to the transfer function), the speed fluctuation of the rotational primary component is significantly reduced. Also, compared with the case where the speed fluctuation suppression control is not performed, when the rotational primary component and the rotational secondary component are suppressed (i.e., sensitivity is given to the transfer function), not only is the speed fluctuation of the rotational primary component significantly reduced, but the speed fluctuation of the rotational secondary component is also reduced.

[0089] FIG. 8 shows the simulation results of Comparative Example 1, which shows the waveform of the rotational speed of the motor when the speed fluctuation suppression control is not performed in a single-cylinder rotary compressor. Note that the horizontal axis in FIG. 8 is time, and the vertical axis is the rotational speed of the motor M1. Also, the unit of the rotational speed on the vertical axis [rpm] is the number of rotations of the motor M1 per minute, which is synonymous with [min -1 (the same applies to FIGS. 9 and 10 below). Also, the characteristics of the motor M1 and the operating conditions of the compressor 11 used in FIG. 8 are the same as those in the simulation results of FIG. 7 (the same applies to FIGS. 9 and 10 below). As shown in FIG. 8, when the speed fluctuation suppression control is not performed, the fluctuation of the rotational speed of the motor M1 is relatively large.

[0090] FIG. 9 shows the simulation results of Comparative Example 2 showing the waveform of the rotational speed of the motor when the rotational primary component is suppressed in a single-cylinder rotary compressor. As shown in FIG. 9, when the rotational primary component is suppressed, the speed fluctuation of the motor M1 is significantly smaller than when the speed fluctuation suppression control is not performed (see FIG. 8).

[0091] FIG. 10 shows the simulation results of the first embodiment showing the waveform of the rotational speed of the motor when the rotational primary component and the rotational secondary component are suppressed in a single-cylinder rotary compressor. As shown in FIG. 10, when the rotational primary component and the rotational secondary component are suppressed, the amplitude of the waveform of the rotational speed (the pulsation width of the speed fluctuation) is further smaller than when only the rotational primary component is suppressed (see FIG. 9). That is, the speed fluctuation of the motor M1 is suppressed.

[0092] FIG. 11 shows the simulation results of Comparative Example 1 showing the waveforms of the motor torque and the load torque when the speed fluctuation suppression control is not performed in a single-cylinder rotary compressor. Note that the horizontal axis in FIG. 11 is time, and the vertical axis is the torque of the motor M1. Also, the characteristics of the motor M1 and the operating conditions of the compressor 11 used in FIG. 11 are the same as those in the simulation results of FIG. 7 (the same applies to FIGS. 12 and 13 below). As shown in FIG. 11, when the speed fluctuation suppression control is not performed, the amplitudes and phases of the motor torque and the load torque are greatly deviated. As a result, large speed fluctuations as shown in FIG. 8 occur in the motor M1.

[0093] FIG. 12 shows the simulation results of Comparative Example 2 showing the waveforms of the motor torque and the load torque when the rotational primary component is suppressed in a single-cylinder rotary compressor. As shown in FIG. 12, when the rotational primary component is suppressed, the deviation of the amplitudes and phases of the motor torque and the load torque is smaller than when the speed fluctuation suppression control is not performed (see FIG. 11). As a result, as shown in FIG. 9, the fluctuation of the rotational speed of the motor M1 is relatively small.

[0094] Figure 13 shows the simulation results of the first embodiment, which illustrate the waveforms of the motor torque and the load torque when the rotational primary component and the rotational secondary component are suppressed in a single-cylinder rotary compressor. As shown in Figure 13, when the rotational primary component and the rotational secondary component are suppressed, the amplitude and phase deviation between the motor torque and the load torque are further reduced compared to the case where the rotational primary component is suppressed (see Figure 12). As a result, as shown in Figure 10, the fluctuation of the rotational speed of the motor M1 is sufficiently suppressed.

[0095] In the case of a two-cylinder rotary compressor or a scroll compressor as well, when suppressing the speed fluctuation of the motor M1 caused by torque pulsation, the vibration of the compressor 11 can be reduced by performing speed fluctuation suppression control for a predetermined compensation order.

[0096] For example, when a two-cylinder rotary compressor is used as the compressor 11, it is preferable for the control unit 52 (see Figure 1) to perform the following processing. That is, when the suction pressure Ps of the compressor 11 is equal to or higher than a predetermined value, the control unit 52 sets the compensation order in the speed fluctuation suppression control to the rotational secondary component of the speed fluctuation of the motor M1. Thereby, while suppressing the vibration of the compressor 11, the fluctuation of the peak value of the motor current is also suppressed, and the motor M1 can be driven with high efficiency. Also, when the suction pressure Ps of the compressor 11 is less than the predetermined value, the control unit 52 includes the rotational secondary component and the rotational fourth component of the speed fluctuation of the motor M1 as the compensation order in the speed fluctuation suppression control. Thereby, even when the suction pressure Ps is less than the predetermined value, the vibration associated with the torque pulsation of the compressor 11 can be appropriately suppressed.

[0097] Also, when a scroll compressor is used as the compressor 11, the control unit 52 (see FIG. 1) preferably switches the execution of the speed fluctuation suppression control based on the suction pressure Ps of the compressor 11. Specifically, when the suction pressure Ps is equal to or higher than a first predetermined value, the control unit 52 does not particularly perform the speed fluctuation suppression control. This is because in a scroll compressor, when the suction pressure Ps is relatively high, the torque pulsation of the compressor 11 is relatively small (see the broken line graph in FIG. 20). On the other hand, when the suction pressure Ps is less than the first predetermined value, the control unit 52 executes the speed fluctuation suppression control. Thereby, the vibration associated with the torque pulsation of the compressor 11 (see the solid line graph in FIG. 20) can be suppressed.

[0098] Also, in a scroll compressor, when the suction pressure of the compressor 11 is equal to or higher than a predetermined value (a second predetermined value lower than the above-mentioned "first predetermined value"), the control unit 52 sets the compensation order in the speed fluctuation suppression control to the rotational primary component of the speed fluctuation of the motor M1. On the other hand, when the suction pressure Ps of the compressor 11 is less than the predetermined value, the control unit 52 includes the rotational primary component and the rotational secondary component of the speed fluctuation of the motor M1 as the compensation order in the speed fluctuation suppression control. Thereby, the vibration associated with the torque pulsation of the compressor 11 can be appropriately suppressed.

[0099] <Effect> According to the first embodiment, the lower the suction pressure Ps of the compressor 11, the stronger the control unit 52 makes the effect of the speed fluctuation suppression control. Also, based on the height of the suction pressure Ps of the compressor 11, the control unit 52 selects the compensation order to be targeted by the speed fluctuation suppression control. Thereby, when the control unit 52 performs the speed fluctuation suppression control, there is almost no need to take the compensation order overly wide, so that the fluctuation of the peak value of the motor current can be suppressed and the motor M1 can be driven with high efficiency.

[0100] In addition, if all of the nth-order speed fluctuation suppression control is operated, there is a risk of malfunctioning even in a load state (suction pressure Ps) where speed fluctuation suppression control is not originally desired to operate due to effects such as misdetection of current, and unnecessary current may increase. As a result, there may be problems such as an increase in the loss of the motor M1 and destabilization of the control.

[0101] On the other hand, in the first embodiment, based on the suction pressure Ps of the compressor 11, the frequency components (orders) for which it is desired to suppress the speed fluctuation of the motor M1 are narrowed down. By switching such a selection based on the suction pressure Ps at each moment, it is possible to suppress the fluctuation of the rotational speed associated with torque pulsation without generating wasteful current and loss in the motor M1. Thus, according to the first embodiment, it is possible to provide the air conditioner 100 (see FIG. 1) capable of achieving both vibration suppression and high efficiency of the compressor 11.

[0102] ≪Second Embodiment≫ The second embodiment is different from the first embodiment in that the speed control unit 52Ae (see FIG. 14) includes the first gain command calculation unit 525e. Further, in the second embodiment, in the speed fluctuation suppression control unit 523Ae (see FIG. 15), in addition to the control coefficients K1 and K2 of the above-described formula (6), the magnitude of the control coefficient K3 is also adjusted, which is different from the first embodiment. Note that the other aspects are the same as those of the first embodiment. Therefore, the parts different from the first embodiment will be described, and the description of the overlapping parts will be omitted.

[0103] FIG. 14 is a functional block diagram of the speed control unit 52Ae provided in the air conditioner according to the second embodiment. The speed control unit 52Ae shown in FIG. 14 includes the first gain command calculation unit 525e in addition to the configuration of the first embodiment (see FIG. 3). The first gain command calculation unit 525e uses load determination information (that is, the suction pressure Ps) and speed fluctuation information Δω *Based on this, the control coefficient K3 in the transfer function of the above formula (6) is calculated for each order. Then, the first gain command calculation unit 525e outputs the calculation result of the control coefficient K3 to the speed fluctuation suppression control unit 523Ae in association with each order. Note that the speed fluctuation information Δω * is information indicating the fluctuation of the rotational speed of the motor M1 (for example, the difference from the average value of the rotational speed), and is generated by the control unit 52 (see FIG. 1).

[0104] For example, the lower the suction pressure Ps of the compressor 11, the smaller the first gain command calculation unit 525e makes the value of the control coefficient K3 in the above formula (6). In formula (6), since the control coefficient K3 is included in the denominator, the smaller the value of the control coefficient K3, the larger the gain of the transfer function, and as a result, the effect of the speed fluctuation suppression control becomes stronger.

[0105] More specifically, when strengthening the effect of the speed fluctuation suppression control in the first-order component of the rotation of the motor M1, the first gain command calculation unit 525e sets the control coefficient K3_1 st of the first-order component of the rotation to a smaller value. Also, when almost eliminating the effect of the speed fluctuation suppression control in the third-order component of the rotation of the motor M1, the first gain command calculation unit 525e sets the control coefficient K3_3 rd of the third-order component of the rotation to as large a value as possible. In this way, the first gain command calculation unit 525e associates the control coefficients K3_1 st , K3_2 nd , K3_3 rd , ···, K3_n th with each order of the speed fluctuation of the motor M1 and outputs them to the speed fluctuation suppression control unit 523Ae. Note that which order is to be compensated preferentially in each order (frequency component) included in the speed fluctuation of the motor M1 is determined based on load determination information and the like.

[0106] FIG. 15 is a functional block diagram of the speed fluctuation suppression control unit 523Ae provided in the air conditioner according to the second embodiment. As shown in FIG. 15, the speed fluctuation suppression control unit 523Ae includes a second gain command calculation unit 61A, a speed fluctuation suppression q-axis current command generation unit 62A, and an adder 63. Similar to the gain command calculation unit 61 described in the first embodiment (see FIG. 4), the second gain command calculation unit 61A calculates control coefficients K1 and K2 of each order included in the speed fluctuation of the motor M1 based on load determination information and the like. Then, the second gain command calculation unit 61A associates the calculation results of the control coefficients K1 and K2 with each order one-to-one and outputs them to the speed fluctuation suppression q-axis current command generation unit 62A.

[0107] For each order included in the speed fluctuation of the motor M1, the speed fluctuation suppression q-axis current command generation unit 62A calculates the q-axis current command Iq*_trq_k th (k = 1, 2, 3, ···, n) based on the control coefficient K3 input from the first gain command calculation unit 525e (see FIG. 14) and the control coefficients K1 and K2 input from the second gain command calculation unit 61A.

[0108] Specifically, the control coefficients K1, K2, and K3 of each order are set so that the effect of the speed fluctuation suppression control becomes stronger as the suction pressure Ps of the compressor 11 becomes lower. The adder 63 obtains the sum of the calculation results of the first-order component calculation unit 62a, the second-order component calculation unit 62b, the third-order component calculation unit 62c, ···, and the nth-order component calculation unit 62n to generate the speed fluctuation suppression q-axis current command Iq*_trq. Thereby, the vibration associated with the torque pulsation of the compressor 11 can be appropriately suppressed.

[0109] When strengthening the effect of the speed fluctuation suppression control, the control coefficient K3 may be decreased by the first gain command calculation unit 525e (see FIG. 14), or the control coefficients K1 and K2 may be increased by the second gain command calculation unit 61A (see FIG. 15). On the other hand, when weakening the effect of the speed fluctuation suppression control, the control coefficient K3 may be increased by the first gain command calculation unit 525e (see FIG. 14), or the control coefficients K1 and K2 may be decreased by the second gain command calculation unit 61A (see FIG. 15).

[0110] <Effect> According to the second embodiment, in addition to adjusting the magnitudes of the control coefficients K1 and K2, the magnitude of the control coefficient K3 by the first gain command calculation unit 525e (see FIG. 14) can also set the strength of the speed fluctuation suppression control for each order (frequency component). Further, based on the suction pressure Ps of the compressor 11, by selecting the compensation order so as to narrow down the components for which the fluctuation of the rotational speed of the motor M1 is to be suppressed, both vibration suppression and high efficiency of the compressor 11 can be achieved simultaneously.

[0111] <<Modification Example>> As described above, the air conditioner 100 and the like according to the present invention have been described according to each embodiment, but the present invention is not limited to these descriptions, and various modifications can be made. For example, in each embodiment, the load state determination unit 51 (see FIG. 1) has been described for the process of calculating the suction pressure Ps of the compressor 11 based on information including the rotational speed of the motor M1, the indoor temperature (temperature of the air-conditioned room), and the outdoor temperature, but it is not limited thereto. That is, the load state determination unit 51 may include at least one of the temperature of the outdoor heat exchanger 12 (detection value of the outdoor heat exchanger temperature sensor 25: see FIG. 1), the temperature of the indoor heat exchanger 15 (detection value of the indoor heat exchanger temperature sensor 22), and the discharge temperature of the compressor 11 (detection value of the discharge temperature sensor 23) in the above-described information. For example, in addition to the suction pressure Ps of the compressor 11, the designers or the like may previously acquire the correlation data of the above-described respective temperatures and the rotational speed of the motor M1, and based on the detection values of the respective temperatures, the actual rotational speed of the motor M1, and the above-described correlation data, the load state determination unit 51 may calculate (estimate) the suction pressure Ps of the compressor 11. Such correlation data may be acquired in advance for each operation mode such as cooling operation and heating operation and stored in the motor drive device 50. Note that the speed fluctuation suppression control based on the suction pressure Ps is the same as in each embodiment. As a result, the suction pressure Ps of the compressor 11 can be calculated with high accuracy, and the vibration accompanying the torque pulsation of the compressor 11 can be appropriately suppressed. Note that a suction pressure sensor (not shown) may be provided on the suction side of the compressor 11, and the suction pressure Ps may be directly detected by this suction pressure sensor.

[0112] Also, in each embodiment, it has been described that the lower the suction pressure Ps of the compressor 11 (see FIG. 1), the stronger the control unit 52 makes the effect of the speed fluctuation suppression control, but it is not limited to this. For example, the greater the differential pressure (Pd - Ps) between the suction pressure Ps and the discharge pressure Pd of the compressor 11, the control unit 52 may strengthen the effect of the speed fluctuation suppression control. Even with such processing, the same effects as those of each embodiment are achieved.

[0113] Also, in each embodiment, it has been described that the motor drive device 50 (see FIG. 1) includes the load state determination unit 51 and the control unit 52, but it is not limited to this. For example, the control unit 52 may also perform the function of the load state determination unit 51. Even with such a configuration, the same effects as those of each embodiment are achieved.

[0114] Also, in each embodiment, the case where a rotary compressor or a scroll compressor is used as the compressor 11 (see FIG. 1) has been described, but it is not limited to this. That is, each embodiment can also be applied to other types of compressors such as reciprocating compressors.

[0115] Also, in each embodiment, the control of the compressor 11 of the air conditioner 100 has been described, but it is not limited to this. That is, each embodiment can also be applied to other types of refrigeration cycle devices such as water heaters and refrigerators as long as the configuration is such that a compressor that can generate periodic torque pulsation is driven by a motor.

[0116] Also, in each embodiment, the configuration of the control unit 52 included in the motor drive device 50 has been illustrated by the configuration of FIG. 2, but it is not limited to this. That is, as the configuration of the control unit 52, other well-known configurations related to sensorless vector control may be used. Also, the transfer function described in the first embodiment is not limited to the formula (6). That is, other transfer functions may be used as long as they have high sensitivity at a specific frequency.

[0117] Note that each embodiment is described in detail for the purpose of clearly explaining the present invention, and is not necessarily limited to the one having all the configurations described. Also, it is possible to add, delete, or replace a part of the configuration of each embodiment with other configurations. In addition, some or all of the above-described configurations, functions, processing units, processing means, etc. may be realized by hardware, for example, by designing them with an integrated circuit or the like. Also, the mechanisms and configurations shown are those considered necessary for explanation, and not all mechanisms and configurations are necessarily shown in the product.

Description of Reference Numerals

[0118] 11 Compressor 12 Outdoor heat exchanger 13 Outdoor fan 14 Expansion valve 15 Indoor heat exchanger 16 Indoor fan 17 Four-way valve 20 Indoor unit 30 Outdoor unit 31 Converter 32 Smoothing capacitor 33 Inverter 34 Voltage detector 35 Current detector 50 Motor drive device 51 Load state determination unit 52 Control unit 100 Air conditioner M1 Motor

Claims

1. A compressor driven by a motor, and a control unit that controls the motor, and the control unit strengthens the effect of speed fluctuation suppression control for suppressing fluctuations in the rotational speed of the motor as the suction pressure of the compressor decreases, and changes the compensation order in the speed fluctuation suppression control based on the suction pressure of the compressor, wherein the rotational n-th order component (n: natural number) as the compensation order is a component among the components included in the fluctuation of the rotational speed of the motor that is suppressed by the speed fluctuation suppression control, and is a component having a sine wave shape for n periods during one rotation of the motor in mechanical angle, an air conditioner.

2. A compressor which is a scroll compressor driven by a motor, and a control unit that controls the motor, and the control unit strengthens the effect of speed fluctuation suppression control for suppressing fluctuations in the rotational speed of the motor as the suction pressure of the compressor decreases, and switches the execution of the speed fluctuation suppression control based on the suction pressure of the compressor, an air conditioner.

3. When the control unit strengthens the effect of the speed fluctuation suppression control, the control unit increases the compensation amount of the torque current corresponding to at least one of the compensation orders The air conditioner according to claim 1, characterized in that.

4. The control unit increases the upper limit value of the compensation order in the speed fluctuation suppression control as the suction pressure of the compressor decreases The air conditioner according to claim 1, characterized in that.

5. The compressor is a single-cylinder rotary compressor, when the suction pressure of the compressor is equal to or higher than a predetermined value, the control unit sets the compensation order in the speed fluctuation suppression control as the rotational first-order component of the speed fluctuation of the motor, when the suction pressure of the compressor is less than the predetermined value, the control unit includes the rotational first-order component and the rotational second-order component of the speed fluctuation of the motor as the compensation order in the speed fluctuation suppression control The air conditioner according to claim 4, characterized in that.

6. The compressor is a two-cylinder rotary compressor, when the suction pressure of the compressor is equal to or higher than a predetermined value, the control unit sets the compensation order in the speed fluctuation suppression control as the rotational second-order component of the speed fluctuation of the motor, when the suction pressure of the compressor is less than the predetermined value, the control unit includes the rotational second-order component and the rotational fourth-order component of the speed fluctuation of the motor as the compensation order in the speed fluctuation suppression control The air conditioner according to claim 4, characterized in that.

7. The compressor is a scroll compressor, when the suction pressure of the compressor is equal to or higher than a predetermined value, the control unit sets the compensation order in the speed fluctuation suppression control as the rotational primary component of the speed fluctuation of the motor, when the suction pressure of the compressor is lower than the predetermined value, the control unit includes the rotational primary component and the rotational secondary component of the speed fluctuation of the motor as the compensation order in the speed fluctuation suppression control The air conditioner according to claim 4, characterized in that.

8. Comprising a load state determination unit that calculates the suction pressure of the compressor based on information including the rotational speed of the motor, the temperature of the air-conditioned room, and the outdoor temperature The air conditioner according to any one of claims 1 to 7, characterized in that.

9. Comprising an outdoor heat exchanger provided in the outdoor unit and an indoor heat exchanger provided in the indoor unit, the load state determination unit includes at least one of the temperature of the outdoor heat exchanger, the temperature of the indoor heat exchanger, and the discharge temperature of the compressor in the information The air conditioner according to claim 8, characterized in that.

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