Motor drive device, motor drive control method, and control program

Abstract

A motor drive device, a motor drive control method, and a control program are provided that can suppress vibration when a compressor stops driving. [Solution] The motor drive device comprises a brushless DC motor that drives a compressor, an inverter circuit that converts DC voltage to AC voltage and supplies power to the brushless DC motor, and a drive control unit that controls the drive of the brushless DC motor via the inverter circuit, and when the brushless DC motor stops driving the compressor, the drive control unit causes the inverter circuit to stop supplying power to the brushless DC motor at a timing when the compressor satisfies a predetermined condition that has been set in advance.

Description

[Technical Field]

[0001] The present disclosure relates to a motor drive device, a motor drive control method, and a control program. [Background technology]

[0002] Patent Document 1 discloses a refrigerator that reduces noise and vibration when the compressor stops driving by gradually reducing the rotation speed of the compressor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-233659 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a motor drive device, a motor drive control method, and a control program that can suppress vibration when a compressor stops driving. [Means for solving the problem]

[0005] The motor drive device of the present disclosure includes a brushless DC motor that drives a compressor, an inverter circuit that converts DC voltage to AC voltage and supplies power to the brushless DC motor, and a drive control unit that controls driving of the brushless DC motor via the inverter circuit, wherein when the brushless DC motor stops driving the compressor, the drive control unit causes the inverter circuit to stop supplying power to the brushless DC motor at a timing when the compressor satisfies a predetermined condition that has been set in advance.

[0006] The present disclosure also provides a motor drive control method for a motor drive device including a brushless DC motor that drives a compressor, an inverter circuit that converts DC voltage to AC voltage and supplies power to the brushless DC motor, and a drive control unit that controls driving of the brushless DC motor via the inverter circuit, wherein the drive control unit causes the inverter circuit to stop supplying power to the brushless DC motor at a timing when the brushless DC motor stops driving the compressor and the compressor satisfies a predetermined condition.

[0007] The control program disclosed herein is a control program for a motor drive device including a brushless DC motor that drives a compressor, an inverter circuit that converts DC voltage to AC voltage and supplies power to the brushless DC motor, and a drive control unit that controls the drive of the brushless DC motor via the inverter circuit, and the control program causes a processor constituting the drive control unit to execute processing for the inverter circuit to stop supplying power to the brushless DC motor from the inverter circuit when the brushless DC motor stops driving the compressor, at a timing when the compressor satisfies a predetermined condition that has been set in advance. [Effects of the Invention]

[0008] The motor drive device, motor drive control method, and control program disclosed herein cause the inverter circuit to stop supplying power to the brushless DC motor at a timing when the brushless DC motor stops driving the compressor and the compressor satisfies a predetermined condition that has been set in advance. Therefore, by setting the predetermined conditions to appropriate conditions, it is possible to suppress vibrations when the compressor is stopped. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a motor drive device according to an embodiment of the present invention; [Figure 2] 1 is a diagram showing an example of the configuration and operation of a compressor according to an embodiment of the present invention; [Figure 3] FIG. 10 is a diagram illustrating an example of an operation when the compressor according to the present embodiment is stopped. [Figure 4] 10 is a graph showing an example of a change in rotation speed of a motor when driving is stopped according to the present embodiment. [Figure 5] FIG. 2 is a diagram showing an example of the configuration of a drive control unit according to the present embodiment; [Figure 6] 1 is a flowchart showing an example of a mechanical angle calculation process according to an embodiment of the present invention; [Figure 7] 1 is a flowchart showing an example of a top dead center estimation process according to an embodiment of the present invention; [Figure 8] 10 is a flowchart showing a first example of a drive stop process according to the present embodiment. [Figure 9] 10 is a flowchart showing a second example of the drive stop process of the present embodiment. [Figure 10] 10 is a flowchart showing a third example of the drive stop process of the present embodiment. [Figure 11] Graph showing an example of a change in rotation speed of a motor when driving is stopped according to the related art DETAILED DESCRIPTION OF THE INVENTION

[0010] (Findings that formed the basis of this disclosure) At the time when the inventors came up with the present disclosure, refrigerators were known that reduce noise and vibration when the compressor is stopped by gradually reducing the rotation speed of the compressor, as described in Patent Document 1, for example. However, the inventors discovered a problem with the invention described in Patent Document 1 in that the position of the piston is unstable when the motor rotation speed becomes "zero," which can cause variations in vibration values ​​when the motor is stopped, resulting in increased vibration. In order to solve this problem, the inventors came up with the subject matter of the present disclosure. For example, when the drive is stopped, the motor, which rotates by inertia, decelerates mainly as it passes through the compression stroke, and there is a high possibility that the rotational speed will reach "zero" during the compression stroke, in the case of a reciprocating compressor. Furthermore, if the rotational speed is "zero" and there is compressed gas in the cylinder, the gas inside the cylinder expands due to the pressure difference with the outside of the cylinder, pushing the piston back. When this happens, the direction of rotation and the direction of piston movement suddenly change, causing vibration. The greater the load torque of the compressor, the greater the vibration, so large vibrations can occur under certain conditions. Therefore, the present disclosure provides a motor drive device, a motor drive control method, and a control program that can suppress vibrations when driving is stopped.

[0011] Hereinafter, embodiments will be described in detail with reference to the drawings. However, in some cases, more detailed explanation than necessary may be omitted. For example, detailed explanation of already well-known matters or redundant explanation of substantially the same configuration may be omitted. The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0012] [1. Configuration] [1-1. Motor drive device configuration] First, the configuration of a motor driving device 30 of this embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing the configuration of a motor driving device 30 of this embodiment. As shown in Fig. 1, motor drive device 30 of the present embodiment is connected to AC power supply 1 and drives brushless DC motor 5. Rotor 5a of brushless DC motor 5 drives reciprocating compressor 17. In the present embodiment, compressor 17 is mounted in refrigerator 100 and forms a part of refrigeration cycle 22. The configuration of the compressor 17 will be further described with reference to FIG.

[0013] The AC power supply 1 shown in FIG. 1 is a general commercial power supply, which in Japan is a power supply with an effective value of 100V at 50 Hz or 60 Hz. As shown in FIG. 1, the motor drive device 30 includes a rectifier circuit 2, a smoothing circuit 3, an inverter circuit 4, a voltage detection unit 6, a terminal voltage detection unit 7, a drive control unit 8, and a drive circuit 9.

[0014] The rectifier circuit 2 is a so-called "diode bridge" that full-wave rectifies the AC power input from the AC power supply 1. The rectifier circuit 2 is made up of four bridge-connected rectifier diodes, namely, rectifier diode 2a, rectifier diode 2b, rectifier diode 2c, and rectifier diode 2d.

[0015] The smoothing circuit 3 is connected to the output side of the rectifier circuit 2 and smoothes the output of the rectifier circuit 2. The smoothing circuit 3 includes a smoothing capacitor 3e and a smoothing reactor 3f. The output from the smoothing circuit 3 is input to the inverter circuit 4.

[0016] The inverter circuit 4 sequentially switches the DC power input from the smoothing circuit 3 to convert it into three-phase AC power. The inverter circuit 4 includes six switching elements, namely, switching element 4a, switching element 4b, switching element 4c, switching element 4d, switching element 4e, and switching element 4f. The inverter circuit 4 also includes six freewheeling diodes, namely, freewheeling diode 4g, freewheeling diode 4h, freewheeling diode 4i, freewheeling diode 4j, freewheeling diode 4k, and freewheeling diode 4l.

[0017] Freewheeling diode 4g, freewheeling diode 4h, freewheeling diode 4i, freewheeling diode 4j, freewheeling diode 4k, and freewheeling diode 4l are connected to switching element 4a, switching element 4b, switching element 4c, switching element 4d, switching element 4e, and switching element 4f, respectively. Freewheeling diode 4g, freewheeling diode 4h, freewheeling diode 4i, freewheeling diode 4j, freewheeling diode 4k, and freewheeling diode 4l are connected so that a current flows in the opposite direction to the current flowing through the switching element.

[0018] The drive circuit 9 controls the ON / OFF of the switching elements 4a, 4b, 4c, 4d, 4e, and 4f of the inverter circuit 4 in accordance with instructions from the drive control unit 8. By controlling the ON / OFF of the six switching elements of the inverter circuit 4, the drive circuit 9 causes the inverter circuit 4 to supply a three-phase AC voltage to the three-phase windings of the stator 5b.

[0019] Further, the drive circuit 9 outputs PWM (Pulse Width Modulation) signals to the six switching elements of the inverter circuit 4 in accordance with instructions from the drive control unit 8. That is, the drive circuit 9 controls the duty ratio of the PWM signals in accordance with instructions from the drive control unit 8, thereby controlling the three-phase AC power supplied from the inverter circuit 4 to the three-phase windings of the stator 5b.

[0020] The brushless DC motor 5 includes a rotor 5a having a permanent magnet and a stator 5b having three-phase windings. The three-phase AC voltage generated by the inverter circuit 4 is supplied to the three-phase windings of the stator 5b. This rotates and drives the rotor 5a of the brushless DC motor 5. The three-phase windings of the stator 5b are, for example, Y-connected.

[0021] The voltage detection unit 6 detects the voltage between the DC buses output from the smoothing circuit 3 to the inverter circuit 4. The voltage detection unit 6 outputs the detected voltage between the DC buses to the terminal voltage detection unit .

[0022] The terminal voltage detector 7 detects the terminal voltage VT of the three-phase winding of the stator 5b of the brushless DC motor 5. The terminal voltage detector 7 outputs the detected terminal voltage VT to the drive controller 8.

[0023] The drive control unit 8 instructs the drive circuit 9 of the target rotation speed RSA of the brushless DC motor 5. The drive circuit 9 controls the ON / OFF of the six switching elements of the inverter circuit 4 and also controls the duty ratio of the PWM signal so that the rotation speed RS of the brushless DC motor 5 becomes the target rotation speed RSA.

[0024] Furthermore, when stopping the driving of the brushless DC motor 5, the drive control unit 8 sets the target rotation speed RSA to "zero." When the brushless DC motor 5 stops driving the compressor 17, the drive control unit 8 causes the inverter circuit 4 to stop supplying power to the brushless DC motor 5 from the inverter circuit 4 at the timing when the compressor 17 satisfies a predetermined condition that has been set in advance. The "predetermined condition" will be further explained with reference to FIG. The configuration of the drive control unit 8 will be further described with reference to FIG.

[0025] Next, the configuration of the refrigeration cycle 22 of the refrigerator 100 will be described with reference to FIG. The refrigerant compressed by the compressor 17 flows through a refrigeration cycle 22, passing through a condenser 19, a two-way valve 18, a pressure reducer 20, and an evaporator 21 in this order, and then returning to the compressor 17. At this time, heat is released in the condenser 19, and heat is absorbed in the evaporator 21. This allows the interior of the refrigerator 100 to be cooled.

[0026] A solenoid valve or the like that can be opened and closed by energization is used as two-way valve 18. When compressor 17 is operating, two-way valve 18 is in an open state, connecting condenser 19 and pressure reducer 20 to allow refrigerant to flow. On the other hand, when compressor 17 is not operating, two-way valve 18 is in a closed state, blocking the space between condenser 19 and pressure reducer 20 to prevent refrigerant from flowing.

[0027] [1-2. Compressor configuration and operation] Next, the configuration and operation of the compressor 17 will be described with reference to FIG. FIG. 2 is a diagram showing an example of the configuration and operation of the compressor 17 of this embodiment. 2, the compressor 17 is of a reciprocating type and includes a crankshaft 17a, a piston 17b, a cylinder 17c, and a drive member 17d.

[0028] The driving member 17d is rotationally driven by the brushless DC motor 5. In this embodiment, the driving member 17d rotates integrally with the rotor 5a of the brushless DC motor 5. That is, the driving force output from the rotor 5a via a drive shaft (not shown) of the brushless DC motor 5 is transmitted to the driving member 17d via a transmission mechanism (not shown). The reduction ratio of the transmission mechanism is "1". The driving member 17d is formed, for example, in a disk shape.

[0029] One end of the crankshaft 17a, here the upper end, is rotatably fixed to the piston 17b, and the other end of the crankshaft 17a, here the lower end, is rotatably fixed to the outer periphery of the drive member 17d. In this way, the rotational motion of the rotor 5a of the brushless DC motor 5 is converted into reciprocating motion by the crankshaft 17a.

[0030] Piston 17b connected to crankshaft 17a reciprocates within cylinder 17c. Due to this reciprocating motion, refrigerant is sucked into cylinder 17c and compressed.

[0031] Next, with reference to Fig. 2, the operation of compressor 17 when brushless DC motor 5 drives compressor 17 to rotate will be described. Note that the description will be made for a case where brushless DC motor 5 drives compressor 17 to rotate at a constant target rotation speed RSA. In this case, the duty ratio of the PWM signal output from drive circuit 9 to inverter circuit 4 is constant. The first state ST1 indicates a state in which the piston 17b of the compressor 17 is located at top dead center TDC. In the first state ST1, the compressor 17 completes the discharge of the refrigerant.

[0032] The second state ST2 indicates a state in which the compressor 17 draws in the refrigerant. By transitioning from the first state ST1 to the second state ST2, the piston 17b of the compressor 17 descends from the top dead center TDC, and the refrigerant is drawn into the cylinder 17c.

[0033] The third state ST3 indicates a state in which the piston 17b of the compressor 17 is located at the bottom dead center BDC. In the third state ST3, the compressor 17 completes drawing the refrigerant into the cylinder 17c. Refrigerant is drawn into cylinder 17c from first state ST1 through second state ST2 to third state ST3. Because the load torque is very small while refrigerant is being drawn, if the duty ratio of the PWM signal is constant, the output torque of brushless DC motor 5 exceeds the load torque, and the rotation speed RS of brushless DC motor 5 accelerates.

[0034] The fourth state ST4 represents a state in which the compressor 17 compresses the refrigerant. By transitioning from the third state ST3 to the fourth state ST4, the piston 17b of the compressor 17 rises from the bottom dead center BDC, and the refrigerant in the cylinder 17c is compressed.

[0035] At a discharge start point DCD during the transition from the fourth state ST4 to the first state ST1, the compression of the refrigerant in the cylinder 17c is completed, and the discharge of the refrigerant in the cylinder 17c is started. Then, as shown in the first state ST1, the piston 17b of the compressor 17 reaches the top dead center TDC, and the discharge of the refrigerant is completed.

[0036] Since the refrigerant in the cylinder 17c is compressed when the piston 17b of the compressor 17 is between the bottom dead center BDC and the discharge start point DCD, the rotation speed RS of the brushless DC motor 5 is reduced by the pressure of the refrigerant. Therefore, the rotation speed RS of the brushless DC motor 5 is slowest near the discharge start point DCD, and is fastest near the bottom dead center BDC.

[0037] Next, with reference to Figures 2 and 3, an operation of compressor 17 when brushless DC motor 5 stops driving compressor 17 will be described. Figures 2 and 3 describe a case where rotor 5a and driving member 17d of brushless DC motor 5 are driven to rotate clockwise. FIG. 3 is a diagram showing an example of the operation when the compressor 17 of this embodiment is stopped from driving. 3 is a graph showing the relationship between the mechanical angle θM of the compressor 17 and the torque TR corresponding to the load of the compressor 17. The operation QP of the compressor 17 is shown in correspondence with the mechanical angle θM, which is the horizontal axis of this graph.

[0038] The horizontal axis of the graph shown in Fig. 3 is the mechanical angle θM of the compressor 17, and the vertical axis of the graph shown in Fig. 3 is the torque TR corresponding to the load on the compressor 17. Graph G1 shown in Fig. 3 shows the relationship between the mechanical angle θM and the torque TR.

[0039] When the mechanical angle θM of the compressor 17 is "zero degrees," the compressor 17 enters the first state ST1, and the piston 17b of the compressor 17 is positioned at top dead center TDC. In the first state ST1, the compressor 17 completes discharging the refrigerant.

[0040] When the mechanical angle θM of the compressor 17 is "90 degrees," the compressor 17 enters the second state ST2 and draws in the refrigerant. By transitioning from the first state ST1 to the second state ST2, the piston 17b of the compressor 17 descends from the top dead center TDC, and the refrigerant is drawn into the cylinder 17c.

[0041] When the mechanical angle θM of the compressor 17 is "180 degrees," the compressor 17 enters the third state ST3, and the piston 17b of the compressor 17 is positioned at the bottom dead center BDC. In the third state ST3, the compressor 17 completes the suction of the refrigerant into the cylinder 17c. During the period from the first state ST1 through the second state ST2 to the third state ST3, the load on the brushless DC motor 5 is substantially zero, and therefore the rotation speed RS of the brushless DC motor 5 is kept constant.

[0042] When the mechanical angle θM of the compressor 17 is 270 degrees, the compressor 17 enters the fourth state ST4 and compresses the refrigerant. By transitioning from the third state ST3 to the fourth state ST4, the piston 17b of the compressor 17 rises from the bottom dead center BDC, and the refrigerant in the cylinder 17c is compressed.

[0043] At a discharge start point DCD during the transition from the fourth state ST4 to the first state ST1, the compression of the refrigerant in the cylinder 17c is completed, and the discharge of the refrigerant in the cylinder 17c begins. The mechanical angle θM of the compressor 17 at the discharge start point DCD is, for example, 300 degrees. Then, as shown in the first state ST1, the piston 17b of the compressor 17 reaches the top dead center TDC, and the discharge of the refrigerant is completed.

[0044] The refrigerant in the cylinder 17c is compressed while the piston 17b of the compressor 17 is at bottom dead center BDC to the discharge start point DCD, and the torque TR of the compressor 17 increases due to the pressure of the refrigerant, and the rotation speed RS of the brushless DC motor 5 is reduced.

[0045] For example, if the torque TR when the compressor 17 stops rotating is equal to or less than 0.5 Nm, the compressor 17 stops without generating vibration. On the other hand, if the torque TR when the compressor 17 stops rotating is greater than 0.5 Nm, the compressor 17 generates vibration VB when it stops.

[0046] In other words, if the mechanical angle θM of the compressor 17 when the brushless DC motor 5 stops rotating is, for example, in the first range RD1 or the third range RD3, the compressor 17 stops without generating vibration. On the other hand, if the mechanical angle θM of the compressor 17 when the brushless DC motor 5 stops rotating is, for example, in the second range RD2, the compressor 17 generates vibration VB when it stops.

[0047] 3, the arrows indicate an example of the change in the mechanical angle θM of compressor 17 when vibration VB occurs. For example, if the mechanical angle θM of compressor 17 is 290 degrees when brushless DC motor 5 stops rotating, piston 17b is pressed downward by the pressure of the refrigerant in cylinder 17c when brushless DC motor 5 stops rotating. As a result, brushless DC motor 5 rotates in a direction that decreases the mechanical angle θM of compressor 17, i.e., counterclockwise, and vibration VB occurs.

[0048] Next, a change in rotation speed RS of brushless DC motor 5 when driving of brushless DC motor 5 by conventional motor drive device 30 is stopped will be described with reference to Fig. 11. Fig. 11 is a graph showing an example of change in rotation speed RS of brushless DC motor 5 when driving is stopped in the conventional manner. 11 represents time T, and the vertical axis of Fig. 11 represents rotation speed RS of brushless DC motor 5. Graph G3 shows the change in rotation speed RS of brushless DC motor 5 after driving of brushless DC motor 5 is stopped.

[0049] At time TS, that is, when time T is "zero," the driving of brushless DC motor 5 is stopped. At this time, the rotation speed RS of brushless DC motor 5 is, for example, 30 rpm. 2 and 3, when the mechanical angle θM of the compressor 17 is in the first range RD1, the load on the brushless DC motor 5 is substantially zero, and therefore the rotation speed RS of the brushless DC motor 5 is maintained constant. When the mechanical angle θM of the compressor 17 is in the second range RD2, the piston 17b is pressed by the pressure of the refrigerant, and therefore the rotation speed RS of the brushless DC motor 5 is decelerated. That is, in one rotation of the brushless DC motor 5, the rotation speed changes as shown in the first rotation period PR1 and the second rotation period PR2.

[0050] At time TVS, the rotation speed RS of the brushless DC motor 5 reaches "zero." However, at time TVS, the mechanical angle θM of the compressor 17 is in the second range RD2, so the brushless DC motor 5 rotates in the opposite direction, generating vibration VB. Then, at time TS, the rotation of the brushless DC motor 5 stops. Vibration VB occurs during the period from time TVS to time TE.

[0051] As described above, in the conventional motor drive device 30, when the drive of the brushless DC motor 5 is stopped and the rotation speed RS of the brushless DC motor 5 reaches "zero," the mechanical angle θM of the compressor 17 is in the second range RD2 shown in FIG. 3, and therefore vibration VB may occur.

[0052] For example, the motor drive device 30 of this embodiment controls the mechanical angle θM of the compressor 17 when the brushless DC motor 5 stops so that it is within a range of a predetermined mechanical angle θM, with the top dead center TDC of the compressor 17 as the starting point, i.e., "zero degrees." The predetermined mechanical angle θM is, for example, "270 degrees." In other words, the motor drive device 30 of this embodiment controls the mechanical angle θM of the compressor 17 when the brushless DC motor 5 stops so that it is within a range from "zero degrees" to "270 degrees."

[0053] Next, with reference to FIG. 4, a description will be given of changes in rotation speed RS of brushless DC motor 5 when driving of brushless DC motor 5 by motor driving device 30 of this embodiment is stopped. FIG. 4 is a graph showing an example of a change in rotation speed RS of brushless DC motor 5 when driving is stopped in this embodiment.

[0054] 4 represents time T, and the vertical axis of Fig. 4 represents rotation speed RS of brushless DC motor 5. Graph G2 shows the change in rotation speed RS of brushless DC motor 5 after driving of brushless DC motor 5 is stopped.

[0055] At time TS, that is, when time T is "zero," the driving of brushless DC motor 5 is stopped. At this time, the rotation speed RS of brushless DC motor 5 is, for example, 30 rpm. As shown in FIG. 4, during one rotation of the brushless DC motor 5, the rotation speed changes as shown in a first rotation period PR1, a second rotation period PR2, and a third rotation period PR3. Then, at time TE, the rotation speed RS of the brushless DC motor 5 reaches "zero." At this time, the mechanical angle θM of the compressor 17 is within the range of "zero degrees" to "270 degrees," so that the vibration VB does not occur and the rotation of the brushless DC motor 5 stops.

[0056] The motor drive device 30 of this embodiment sets the timing at which the brushless DC motor 5 stops driving the compressor 17 so that the mechanical angle θM of the compressor 17 when the brushless DC motor 5 stops is within a range of "zero degrees" to "270 degrees." The timing at which the brushless DC motor 5 stops driving the compressor 17 is determined, for example, by a stop command mechanical angle θMS, which is the mechanical angle θM of the brushless DC motor 5 set in accordance with the rotational speed RS of the brushless DC motor 5. The stop command mechanical angle θMS is determined by the drive control unit 8.

[0057] [1-3. Configuration of drive control unit] Next, the configuration of the drive control unit 8 will be described with reference to Fig. 5. Fig. 5 is a diagram showing an example of the configuration of the drive control unit 8 of this embodiment. As shown in FIG. 4, the drive control unit 8 includes a processor 81 and a memory 82.

[0058] The processor 81 is configured with a CPU (Central Processing Unit), an MPC (Micro Processing Unit), etc. The memory 82 is configured with a ROM (Read Only Memory), etc.

[0059] The processor 81 may be configured with multiple processors or may be configured with a single processor. The processor 81 may be hardware programmed to implement the functions of each unit described below. That is, the processor 81 may be configured to include the control program 821 as a hardware circuit. In this case, the processor 81 may be configured, for example, with an ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), or the like. In the following description, a case will be described in which the processor 81 executes the control program 821 to realize various functions of the drive control unit 8.

[0060] The memory 82 has a storage area for storing programs executed by the processor 81 and data processed by the processor 81. The memory 82 stores a control program 821 executed by the processor 81 and the like. The memory 82 has a nonvolatile storage area that stores programs and data in a nonvolatile manner. The memory 82 may include, for example, a ROM, a hard disk drive (HDD), or a solid state drive (SSD) as the nonvolatile storage area. The memory 82 may also include a volatile storage area that constitutes a work area that temporarily stores programs executed by the processor 81 and data to be processed. The memory 82 may also include, for example, a random access memory (RAM) as the volatile storage area.

[0061] The drive control unit 8 includes a position estimation unit 811, a speed estimation unit 812, a state estimation unit 813, a stop instruction unit 815, and a stop instruction mechanical angle storage unit 822. Specifically, the processor 81 executes the control program 821 to function as the position estimation unit 811, the speed estimation unit 812, the state estimation unit 813, and the stop instruction unit 815. Furthermore, the processor 81 executes the control program 821 to cause the memory 82 to function as the stop instruction mechanical angle storage unit 822.

[0062] The stop command mechanical angle storage unit 822 stores, based on experimental results, a stop command mechanical angle θMS of the brushless DC motor 5 in association with the rotation speed RS of the brushless DC motor 5 when driving of the compressor 17 is stopped. The stop command mechanical angle θMS is the mechanical angle θM of the compressor 17 when driving of the compressor 17 is stopped by the brushless DC motor 5. The time when brushless DC motor 5 stops driving compressor 17 is when stop instruction unit 815 instructs drive circuit 9 to stop the power supplied from inverter circuit 4 to brushless DC motor 5.

[0063] The position estimation unit 811 acquires the terminal voltage VT of the brushless DC motor 5 and detects the electrical angle θE, which is the relative position of the magnetic poles of the brushless DC motor 5. The position estimation unit 811 also estimates the mechanical angle θM of the compressor 17 based on the electrical angle θE.

[0064] The position estimation unit 811 compares the induced voltage VJ with a reference voltage and detects a zero-crossing point ZC of the induced voltage VJ. The position estimation unit 811 detects the electrical angle θE based on the zero-crossing point ZC of the induced voltage VJ. The zero-crossing point ZC of the induced voltage VJ indicates, for example, the timing at which the induced voltage VJ of any one of the three three-phase windings of the stator 5b becomes "zero." If the three-phase windings are configured, for example, with the motor coil 5U, the motor coil 5V, and the motor coil 5W, the zero-crossing point ZC of the induced voltage VJ indicates, for example, the timing at which the induced voltage VJ of the motor coil 5U, the induced voltage VJ of the motor coil 5W, or the induced voltage VJ of the motor coil 5W becomes "zero."

[0065] The position estimation unit 811 may obtain, for example, a DC bus voltage from the voltage detection unit 6 and use the DC bus voltage as a reference voltage for the zero-crossing points ZC of the induced voltage VJ. Alternatively, the position estimation unit 811 may generate a virtual midpoint voltage from the terminal voltage VT of the three-phase winding of the stator 5b and use the generated voltage as a reference voltage for the zero-crossing points ZC of the induced voltage VJ. The processing of the position estimation unit 811 will be described with reference to FIG.

[0066] The speed estimation unit 812 estimates the rotational speed RS of the brushless DC motor 5 from the electrical angle θ or the mechanical angle θ detected by the position estimation unit 811. For example, the speed estimation unit 812 measures the elapsed time from the detection of the zero-crossing point ZC of the induced voltage VJ, and estimates the rotational speed RS from the measured time and the electrical angle θ or the mechanical angle θ.

[0067] The state estimation unit 813 detects the compression state of the compressor 17. The position estimation unit 811 determines that the compression process has progressed every time it detects a zero cross point ZC of the induced voltage VJ. For example, when the piston 17b moves from bottom dead center (BDC) to top dead center (TDC), the piston 17b compresses and discharges the refrigerant. While the refrigerant is being compressed and discharged, the speed of the rotor 5a decreases. Therefore, the state estimation unit 813 determines that the piston 17b of the compressor 17 is located at top dead center (TDC) when the rotation speed RS is at its minimum. Then, the state of the compressor 17 is determined from the electrical angle θE detected by the position estimation unit 811, with top dead center (TDC) as the reference. The processing of the state estimation unit 813 will be described with reference to FIG.

[0068] Stop instruction unit 815 acquires an instruction rotation speed RSC that instructs the rotation speed RS of brushless DC motor 5 that drives compressor 17 from a control unit (not shown) of refrigerator 100. In refrigerator 100, the drive of compressor 17 is stopped when the temperature inside the refrigerator becomes a predetermined value (for example, 5°C) or less. Therefore, in refrigerator 100, the rotation speed RS, suction pressure, and discharge pressure of compressor 17 are likely to be constant values ​​at the timing when the drive of compressor 17 is stopped.

[0069] Then, when the command rotation speed RSC is "zero rps," the stop command unit 815 executes the following process. That is, the stop command unit 815 acquires the rotation speed RS from the speed estimation unit 812. Then, the stop command unit 815 reads out the stop command mechanical angle θMS corresponding to the acquired rotation speed RS from the stop command mechanical angle storage unit 822. Next, the stop command unit 815 acquires the mechanical angle θM from the position estimation unit 811. Then, the stop command unit 815 outputs an instruction to the inverter circuit 4 via the drive circuit 9 to stop driving of the brushless DC motor 5 at the timing when the acquired mechanical angle θM matches the stop command mechanical angle θMS. The processing of the stop instruction unit 815 will be described with reference to FIG.

[0070] [2. Processing of drive control unit] Next, the processing of the drive control unit 8 will be described with reference to FIGS. First, the "mechanical angle calculation process" executed by the position estimation unit 811 will be described with reference to Fig. 6. Fig. 6 is a flowchart showing an example of the "mechanical angle calculation process" of this embodiment. The "mechanical angle calculation process" is a process for estimating the mechanical angle θM from the induced voltage VJ, and is executed by the position estimation unit 811. The "mechanical angle calculation process" is repeatedly executed by the position estimation unit 811 when the brushless DC motor 5 drives the compressor 17 at a constant rotation speed. The "constant rotation speed" indicates that the command rotation speed RSC is a constant value. Before executing the "mechanical angle calculation process", the position estimation unit 811 initializes the electrical angle θE and the mechanical angle θM to "zero degrees". 7, when it is determined that the mechanical angle θM is initialized to "zero degrees" and the number of speed acquisition times NR is equal to or greater than (number of pole pairs N × 6), the position estimation unit 811 may start executing the "mechanical angle calculation process." Note that the number of pole pairs N is the number of north and south magnetic poles of the rotor 5a counted as one pair. The number of pole pairs N is, for example, "2."

[0071] First, in step S101, the position estimation unit 811 determines whether or not the induced voltage VJ has reached the zero cross point ZC. If the position estimation unit 811 determines that the induced voltage VJ has not reached the zero-cross point ZC (step S101; NO), the process goes to a standby state. If the position estimation unit 811 determines that the induced voltage VJ has reached the zero-cross point ZC (step S101; YES), the process proceeds to step S103.

[0072] Then, in step S103, the position estimation unit 811 adds "60 degrees" to the electrical angle θE. Next, in step S105, the position estimation unit 811 determines whether the electrical angle θ E is equal to or greater than “360 degrees”. If the position estimation unit 811 determines that the electrical angle θ is not equal to or greater than "360 degrees" (step S105; NO), the process proceeds to step S109. If the position estimation unit 811 determines that the electrical angle θ is equal to or greater than "360 degrees" (step S105; YES), the process proceeds to step S107.

[0073] Then, in step S107, the position estimation unit 811 subtracts "360 degrees" from the electrical angle θE. Next, in step S109, the position estimation unit 811 adds "60 / (number of pole pairs) degrees" to the mechanical angle θ. If the number of pole pairs N is "2", the position estimation unit 811 adds "30 (=60 / 2) degrees" to the mechanical angle θ. Next, in step S111, the position estimation unit 811 determines whether the mechanical angle θ M is equal to or greater than "360 degrees."

[0074] If the position estimation unit 811 determines that the mechanical angle θ M is equal to or greater than "360 degrees" (step S111; YES), the process proceeds to step S113. Then, in step S113, the position estimation unit 811 subtracts "360 degrees" from the mechanical angle θ M. Thereafter, the process returns to step S101. If the position estimation unit 811 determines that the electrical angle θ E is not equal to or greater than “360 degrees” (step S111; NO), then the process returns to step S101.

[0075] As described with reference to Fig. 6, when the brushless DC motor 5 drives the compressor 17 at a constant speed, the position estimation unit 811 executes the "mechanical angle calculation process" to estimate the mechanical angle θM. Note that, as described with reference to Fig. 6, the mechanical angle θM is calculated every "60 / (number of pole pairs) degrees".

[0076] Next, the "top dead center estimation process" will be described with reference to Fig. 7. Fig. 7 is a flowchart showing an example of the "top dead center estimation process" of this embodiment. The "top dead center estimation process" is a process for initializing the mechanical angle θM to "zero degrees" at the timing corresponding to the top dead center TDC, and is executed by the state estimation unit 813. The "top dead center estimation process" is repeatedly executed by the position estimation unit 811 when the brushless DC motor 5 drives the compressor 17 at a constant rotation speed. The "constant rotation speed" indicates that the command rotation speed RSC is a constant value.

[0077] First, in step S201, the state estimation unit 813 initializes the minimum rotation speed RSN to its maximum value. The maximum value is a value that is even greater than the maximum value expected for fluctuations in the rotation speed RS over one rotation relative to the command rotation speed RSC. The maximum value is, for example, 1.5 times the command rotation speed RSC. Next, in step S230, the state estimation unit 813 initializes the number of times speed acquisition has been performed NR to “zero.” The number of times speed acquisition has been performed NR indicates the number of times the state estimation unit 813 has acquired the rotation speed RS from the speed estimation unit 812.

[0078] Next, in step S205, the state estimation unit 813 determines whether the number of speed acquisition times NR is equal to or greater than "(number of pole pairs N)×6". If the state estimation unit 813 determines that the number of speed acquisition times NR is equal to or greater than "(number of pole pairs N) × 6" (step S205; YES), the process then returns to step S201. If the state estimation unit 813 determines that the number of speed acquisition times NR is not equal to or greater than "(number of pole pairs N) × 6" (step S205; NO), the process proceeds to step S207.

[0079] Then, in step S207, the state estimation unit 813 determines whether or not the induced voltage VJ has reached the zero cross point ZC. If the state estimation unit 813 determines that the induced voltage VJ has not reached the zero-cross point ZC (step S207; NO), the process goes to a standby state. If the position estimation unit 811 determines that the induced voltage VJ has reached the zero-cross point ZC (step S207; YES), the process proceeds to step S209.

[0080] Then, in step S209, the state estimation unit 813 acquires the rotation speed RS from the speed estimation unit 812. Next, in step S211, the state estimation unit 813 determines whether the rotation speed RS acquired from the speed estimation unit 812 is smaller than the minimum rotation speed RSN. If the state estimation unit 813 determines that the rotation speed RS is not lower than the minimum rotation speed RSN (step S211; NO), the process proceeds to step S217. If the state estimation unit 813 determines that the rotation speed RS is lower than the minimum rotation speed RSN (step S211; YES), the process proceeds to step S213.

[0081] Then, in step S213, the state estimation unit 813 updates the rotation speed RS to the minimum rotation speed RSN. Next, in step S215, the state estimation unit 813 initializes the mechanical angle θ M to “zero degrees”. Next, in step S217, the state estimation unit 813 adds "1" to the number of speed acquisition times NR. After that, the process returns to step S205.

[0082] As described with reference to Fig. 7, when the brushless DC motor 5 drives the compressor 17 at a constant speed, the state estimation unit 813 can estimate the mechanical angle θM corresponding to the top dead center TDC by executing the "top dead center estimation process." Note that, as described with reference to Fig. 6, the mechanical angle θM is calculated every "60 / (number of pole pairs) degrees."

[0083] Next, a first example of the "drive stop processing" executed by the stop instruction unit 815 will be described with reference to Fig. 8. Fig. 8 is a flowchart showing a first example of the "drive stop processing" of this embodiment. The "drive stop processing" is processing in which, when the command rotation speed RSC is "zero rps," the stop command unit 815 outputs a command to stop driving of the brushless DC motor 5 at the timing when the mechanical angle θM matches the stop command mechanical angle θMS corresponding to the rotation speed RS. The "drive stop processing" is executed by the stop command unit 815.

[0084] First, in step S301, the stop instruction unit 815 determines whether the instruction rotation speed RSC is "zero rps." The instruction rotation speed RSC is output from a control unit (not shown) of the refrigerator 100 to the drive control unit 8. The instruction rotation speed RSC indicates the rotation speed RS of the brushless DC motor 5 that drives the compressor 17. If the stop instruction unit 815 determines that the instruction rotation speed RSC is not "zero rps" (step S301; NO), the process proceeds to step S303. Then, in step S303, the stop instruction unit 815 instructs the drive circuit 9 to set the instructed rotation speed RSC as the target rotation speed RSA. In accordance with the instruction from the stop instruction unit 815, the drive circuit 9 controls the inverter circuit 4 so that the rotation speed RS of the brushless DC motor 5 becomes the target rotation speed RSA.

[0085] If the stop instruction unit 815 determines that the instruction rotation speed RSC is "zero rps" (step S301; YES), the process proceeds to step S305. Then, in step S305, the stop instruction unit 815 acquires the rotation speed RS from the speed estimation unit 812. Next, in step S207, the stop instruction unit 815 reads out from the stop instruction mechanical angle storage unit 822 the stop instruction mechanical angle θMS corresponding to the rotation speed RS acquired from the speed estimation unit 812.

[0086] Next, in step S309, the stop instruction unit 815 determines whether the mechanical angle θ M matches the stop instruction mechanical angle θ MS. Note that the mechanical angle θ M is estimated by the position estimation unit 811. If the stop instruction unit 815 determines that the mechanical angle θ does not match the stop instruction mechanical angle θ (step S309; ​​NO), the process enters a standby state. If the stop instruction unit 815 determines that the mechanical angle θ matches the stop instruction mechanical angle θ (step S309; ​​YES), the process proceeds to step S311. Then, in step S311, the stop instruction unit 815 outputs an instruction to the inverter circuit 4 to stop driving the brushless DC motor 5. Thereafter, the process returns to step S301.

[0087] 8, at the timing when the mechanical angle θM matches the stop command mechanical angle θMS corresponding to the rotation speed RS, the stop command unit 815 outputs to the inverter circuit 4 a command to stop driving the brushless DC motor 5. Therefore, by setting the stop command mechanical angle θMS to an appropriate value, it is possible to stop the rotation of the brushless DC motor 5 without generating vibrations VB, as described with reference to FIG.

[0088] As described with reference to Fig. 6, the mechanical angle θM is calculated for each "60 / (number of pole pairs) degrees." Therefore, the determination in step S309 of Fig. 8 as to whether the mechanical angle θM matches the stop command mechanical angle θMS is performed as follows. That is, if the difference between the mechanical angle θM and the stop command mechanical angle θMS is equal to or less than "30 / (number of pole pairs) degrees," the stop command unit 815 determines in step S309 that the mechanical angle θM matches the stop command mechanical angle θMS. If the difference between the mechanical angle θM and the stop command mechanical angle θMS is greater than "30 / (number of pole pairs) degrees," the stop command unit 815 determines in step S309 that the mechanical angle θM does not match the stop command mechanical angle θMS.

[0089] Alternatively, the stop command mechanical angle θ may be set to one angle that is a multiple of 60 / (number of pole pairs) degrees and is equal to or greater than zero degrees and less than 360 degrees. In this case, the determination in step S309 of FIG. 8 as to whether the mechanical angle θ matches the stop command mechanical angle θ may be performed as normal processing. In the following explanation, we will explain the case where the stop command mechanical angle θMS is set as one angle that is a multiple of “60 / (number of pole pairs) degrees” and is greater than or equal to “zero degrees” and less than 360 degrees.

[0090] Next, a second example of the "drive stop processing" executed by the stop instruction unit 815 will be described with reference to Fig. 9. Fig. 9 is a flowchart showing the second example of the "drive stop processing" of this embodiment. The second example of the "driving stop processing" differs from the first example of the "driving stop processing" shown in FIG. 8 in that the rotation speed RS of the brushless DC motor 5 is decelerated to a second rotation speed RS2 before an instruction to stop driving the brushless DC motor 5 is output to the inverter circuit 4.

[0091] In this case, it is sufficient to store only the stop command mechanical angle θMS corresponding to the second rotation speed RS2 in the stop command mechanical angle storage unit 822. This reduces the amount of experimentation required to determine the stop command mechanical angle θMS. The second rotation speed RS2 is, for example, "30 rps." In this embodiment, the second rotation speed RS2 is, for example, the minimum rotation speed of the command rotation speeds RSC that a control unit (not shown) of the refrigerator 100 outputs to the drive control unit 8.

[0092] First, in step S401, the stop instruction unit 815 determines whether the instruction rotation speed RSC is "zero rps." If the stop instruction unit 815 determines that the instruction rotation speed RSC is not "zero rps" (step S401; NO), the process proceeds to step S403. Then, in step S403, the stop instruction unit 815 instructs the drive circuit 9 to set the instructed rotation speed RSC as the target rotation speed RSA. In accordance with the instruction from the stop instruction unit 815, the drive circuit 9 controls the inverter circuit 4 so that the rotation speed RS of the brushless DC motor 5 becomes the target rotation speed RSA.

[0093] If the stop instruction unit 815 determines that the instruction rotation speed RSC is "zero rps" (step S401; YES), the process proceeds to step S405. Then, in step S405, the stop instruction unit 815 acquires the rotation speed RS from the speed estimation unit 812. Next, in step S407, the stop instruction unit 815 determines whether the rotation speed RS acquired from the speed estimation unit 812 is greater than the second rotation speed RS2. If stop instructing unit 815 determines that rotation speed RS acquired from speed estimating unit 812 is not greater than second rotation speed RS2 (step S407; NO), the process proceeds to step S411. If stop instructing unit 815 determines that rotation speed RS acquired from speed estimating unit 812 is greater than second rotation speed RS2 (step S407; YES), the process proceeds to step S409.

[0094] Then, in step S409, the stop instruction unit 815 reduces the rotation speed RS of the brushless DC motor 5 to a second rotation speed RS2. The second rotation speed RS2 is, for example, "30 rps." Next, in step S411, the stop instruction unit 815 reads out the stop instruction mechanical angle θMS corresponding to the second rotation speed RS2 from the stop instruction mechanical angle storage unit 822.

[0095] Next, in step S413, the stop instruction unit 815 determines whether the mechanical angle θ M matches the stop instruction mechanical angle θ MS. Note that the mechanical angle θ M is estimated by the position estimation unit 811. If the stop instruction unit 815 determines that the mechanical angle θ does not match the stop instruction mechanical angle θ (step S413; NO), the process enters a standby state. If the stop instruction unit 815 determines that the mechanical angle θ matches the stop instruction mechanical angle θ (step S413; YES), the process proceeds to step S415. Then, in step S415, the stop instruction unit 815 outputs an instruction to the inverter circuit 4 to stop driving the brushless DC motor 5. After that, the process returns to step S401.

[0096] 9, the rotation speed RS is decelerated to the second rotation speed RS2, and at the timing when the mechanical angle θM coincides with the stop command mechanical angle θMS corresponding to the second rotation speed RS, the stop command unit 815 outputs an instruction to the inverter circuit 4 to stop driving of the brushless DC motor 5. Therefore, by setting the stop command mechanical angle θMS corresponding to the second rotation speed RS2 to an appropriate value, it is possible to stop the rotation of the brushless DC motor 5 without generating vibrations VB, as described with reference to FIG.

[0097] Next, a third example of the "drive stop processing" executed by the stop instruction unit 815 will be described with reference to Fig. 10. Fig. 10 is a flowchart showing the third example of the "drive stop processing" of this embodiment. The third example of the "drive stop processing" differs from the first example of the "drive stop processing" shown in FIG. 8 in that the drive control unit 8 shown in FIG. 5 has a stop mechanical angle calculation unit 814 that calculates the stop command mechanical angle θMS instead of a stop command mechanical angle memory unit 822 that stores the stop command mechanical angle θMS.

[0098] The stop mechanical angle calculation unit 814 shown in FIG. 5 calculates the stop command mechanical angle θMS based on, for example, the moment of inertia of the compressor 17 driven by the brushless DC motor 5, the rotation speed RS of the brushless DC motor 5, and the suction pressure, discharge pressure, and suction gas temperature of the compressor 17.

[0099] The moment of inertia of the compressor 17 driven by the brushless DC motor 5 is stored in advance in, for example, the memory 82. When the stop mechanical angle calculation unit 814 calculates the stop command mechanical angle θMS, it reads out the moment of inertia of the compressor 17 driven by the brushless DC motor 5 from the memory 82. The stop mechanical angle calculation unit 814 acquires the suction pressure, discharge pressure, and suction gas temperature of the compressor 17 from sensors arranged in the compressor 17, for example.

[0100] First, in step S501, the stop instruction unit 815 determines whether the instruction rotation speed RSC is "zero rps." If the stop instruction unit 815 determines that the instruction rotation speed RSC is not "zero rps" (step S501; NO), the process proceeds to step S503. Then, in step S503, the stop instruction unit 815 instructs the drive circuit 9 to set the instructed rotation speed RSC as the target rotation speed RSA. In accordance with the instruction from the stop instruction unit 815, the drive circuit 9 controls the inverter circuit 4 so that the rotation speed RS of the brushless DC motor 5 becomes the target rotation speed RSA.

[0101] If the stop instruction unit 815 determines that the instruction rotation speed RSC is "zero rps" (step S501; YES), the process proceeds to step S505. Then, in step S505, the stop instruction unit 815 acquires the rotation speed RS from the speed estimation unit 812. Next, in step S507, the stop instruction unit 815 reads the moment of inertia of the compressor 17 from the memory .

[0102] Next, in step S509, the stop instruction unit 815 acquires the suction pressure from the sensor disposed in the compressor 17. Next, in step S511, the stop instruction unit 815 acquires the discharge pressure from the sensor disposed in the compressor 17. Next, in step S513, the stop instruction unit 815 acquires the intake gas temperature from the sensor disposed in the compressor 17.

[0103] Next, in step S515, the stop instruction unit 815 calculates a stop instruction mechanical angle θMS based on the moment of inertia of the compressor 17, the rotation speed RS of the brushless DC motor 5, and the suction pressure, discharge pressure, and suction gas temperature of the compressor 17. Note that the stop instruction unit 815 calculates, as the stop instruction mechanical angle θMS, one angle that is a multiple of "60 / (number of polar pairs) degrees" and is equal to or greater than "zero degrees" and less than 360 degrees. Next, in step S517, the stop instruction unit 815 determines whether the mechanical angle θ M matches the stop instruction mechanical angle θ MS. Note that the mechanical angle θ M is estimated by the position estimation unit 811.

[0104] If the stop instruction unit 815 determines that the mechanical angle θ does not match the stop instruction mechanical angle θ (step S517; NO), the process enters a standby state. If the stop instruction unit 815 determines that the mechanical angle θ matches the stop instruction mechanical angle θ (step S417; YES), the process proceeds to step S519. Then, in step S519, the stop instruction unit 815 outputs an instruction to the inverter circuit 4 to stop driving the brushless DC motor 5. Thereafter, the process returns to step S501.

[0105] 10, the stop instruction unit 815 calculates the stop instruction mechanical angle θ MS, and at the timing when the mechanical angle θ M matches the stop instruction mechanical angle θ MS, the stop instruction unit 815 outputs an instruction to the inverter circuit 4 to stop driving of the brushless DC motor 5. Therefore, by calculating the stop instruction mechanical angle θ MS to an appropriate value, it is possible to stop the rotation of the brushless DC motor 5 without generating vibrations VB, as described with reference to FIG.

[0106] [3. Composition and Effects] As described above, motor drive device 30 includes brushless DC motor 5 that drives compressor 17, inverter circuit 4 that converts DC voltage to AC voltage and supplies power to brushless DC motor 5, and drive control unit 8 that controls the drive of brushless DC motor 5 via inverter circuit 4. When brushless DC motor 5 stops driving compressor 17, drive control unit 8 causes inverter circuit 4 to stop supplying power from inverter circuit 4 to brushless DC motor 5 at a timing when compressor 17 satisfies a predetermined condition that has been set in advance.

[0107] According to this, by setting the predetermined conditions to appropriate conditions, it is possible to suppress vibrations when the compressor 17 is stopped from driving.

[0108] In the motor drive device 30, the predetermined condition is a condition defined by the stop command mechanical angle θMS, which is the mechanical angle θM of the compressor 17 set according to the rotational speed RS of the brushless DC motor 5 when driving of the compressor 17 is stopped.

[0109] According to this, by appropriately setting the stop command mechanical angle θMS in accordance with the rotation speed RS of the brushless DC motor 5, vibrations when the compressor 17 is stopped can be suppressed.

[0110] In the motor drive device 30, the predetermined condition is a condition defined by a stop command mechanical angle θMS, which is the mechanical angle θM of the compressor 17 set according to the pressure of the compressor 17 when the drive of the compressor 17 is stopped and the rotation speed RS of the brushless DC motor 5.

[0111] According to this, by appropriately setting the stop command mechanical angle θMS in accordance with the pressure of the compressor 17 and the rotation speed RS of the brushless DC motor 5, vibrations when the compressor 17 is stopped can be suppressed.

[0112] In the motor drive device 30, the compressor 17 is of a reciprocating type.

[0113] According to this, because compressor 17 is a reciprocating type, there is a high possibility that the rotation speed RS will become "zero" during the compression stroke. Therefore, vibrations are likely to occur when compressor 17 is stopped. According to the present disclosure, by setting the predetermined conditions to appropriate conditions, vibrations when compressor 17 is stopped can be suppressed.

[0114] In the motor drive device 30, the predetermined condition is set so that the mechanical angle θM of the compressor 17 when the brushless DC motor 5 stops is within a predetermined range of mechanical angle θM starting from the top dead center TDC of the compressor 17.

[0115] According to this, the predetermined conditions can be set to appropriate conditions, so that vibrations when the compressor 17 is stopped can be suppressed.

[0116] In the motor drive device 30, the predetermined mechanical angle θM is 270 degrees or less.

[0117] According to this, the predetermined conditions can be set to appropriate conditions, so that vibrations when the compressor 17 is stopped can be suppressed.

[0118] In the motor drive device 30, the predetermined condition is set based on experimental results so that the mechanical angle θM of the compressor 17 when the brushless DC motor 5 stops is within a predetermined range of mechanical angle θM starting from the top dead center TDC of the compressor 17.

[0119] According to this, the predetermined conditions can be set to appropriate conditions based on the experimental results, so that vibrations when the compressor 17 is stopped can be reliably suppressed.

[0120] In the motor drive device 30, the drive control unit 8 calculates the predetermined conditions based on the moment of inertia of the compressor 17 driven by the brushless DC motor 5, the rotation speed RS of the brushless DC motor 5, and the suction pressure, discharge pressure, and suction gas temperature of the compressor 17.

[0121] According to this, the predetermined conditions can be set to appropriate conditions, so that vibrations when the compressor 17 is stopped can be suppressed.

[0122] In the motor drive device 30, when the brushless DC motor 5 stops driving the compressor 17, if the rotational speed RS of the brushless DC motor 5 is a first rotational speed RS1 that is greater than the second rotational speed RS2, the drive control unit 8 causes the inverter circuit 4 to decelerate the rotational speed RS of the brushless DC motor 5 to the second rotational speed RS2, and after the rotational speed RS of the brushless DC motor 5 reaches the second rotational speed RS2, at the timing when the compressor 17 satisfies the predetermined condition, causes the inverter circuit 4 to stop supplying power from the inverter circuit 4 to the brushless DC motor 5.

[0123] According to this, by setting the predetermined condition to an appropriate condition corresponding to the second rotation speed RS2, it is possible to suppress vibration when the compressor 17 is stopped from driving.

[0124] In the motor drive device 30, the compressor 17 constitutes the refrigeration cycle 22 of the refrigerator 100.

[0125] According to this, when the compressor 17 constituting the refrigeration cycle 22 of the refrigerator 100 is stopped, vibration of the compressor 17 can be suppressed.

[0126] The motor drive control method is a motor drive control method for a motor drive device 30 including a brushless DC motor 5 that drives a compressor 17, an inverter circuit 4 that converts DC voltage to AC voltage and supplies power to the brushless DC motor 5, and a drive control unit 8 that controls the drive of the brushless DC motor 5 via the inverter circuit 4, wherein when the brushless DC motor 5 stops driving the compressor 17, the drive control unit 8 executes a process for causing the inverter circuit 4 to stop supplying power from the inverter circuit 4 to the brushless DC motor 5 at a timing when the compressor 17 satisfies a predetermined condition that has been set in advance.

[0127] According to this, the motor drive control method has the same effects as those of the motor drive device 30 described above.

[0128] The control program 821 is a control program 821 for a motor drive device 30 that includes a brushless DC motor 5 that drives a compressor 17, an inverter circuit 4 that converts DC voltage to AC voltage and supplies power to the brushless DC motor 5, and a drive control unit 8 that controls the drive of the brushless DC motor 5 via the inverter circuit 4, and causes a processor 81 that constitutes the drive control unit 8 to stop the power supplied from the inverter circuit 4 to the brushless DC motor 5 when the brushless DC motor 5 stops driving the compressor 17, at a timing when the compressor 17 satisfies a predetermined condition that has been set in advance.

[0129] According to this, the control program 821 has the same effect as that of the motor driving device 30 described above.

[0130] (Other embodiments) As described above, the present embodiment has been described as an example disclosed in the present application. However, the technology in the present disclosure is not limited to this, and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made. Furthermore, it is also possible to combine the components described in the present embodiment to create new embodiments. Therefore, other embodiments will be exemplified below.

[0131] In the above-described embodiment, the compressor 17 of the motor drive device 30 of the present disclosure configures the refrigeration cycle 22 of the refrigerator 100. The "compressor" of the motor drive device 30 of the present disclosure is not limited to the refrigeration cycle 22 of the refrigerator 100. The "compressor" of the motor drive device 30 of the present disclosure may configure the refrigeration cycle of a so-called "freezer," for example.

[0132] In the above-described embodiment, the compressor 17 is of a reciprocating type. However, the compressor 17 may be of a rotary type, that is, a so-called "rotary type."

[0133] In the above-described embodiment, the number of pole pairs N of the brushless DC motor 5 of the motor drive device 30 of the present disclosure is, for example, two. However, the number of pole pairs N of the brushless DC motor 5 of the motor drive device 30 of the present disclosure may be three or more. The larger the number of pole pairs N, the more accurately the mechanical angle θM can be estimated by the "mechanical angle calculation process" shown in FIG. 6. Furthermore, the larger the number of pole pairs N, the more accurately the mechanical angle θM corresponding to top dead center TDC can be estimated by the "top dead center estimation process" shown in FIG. 7. Furthermore, the larger the number of pole pairs N, the more reliably vibrations occurring when the motor is stopped can be suppressed in the "drive stop process." Furthermore, the larger the number of pole pairs N, the more accurately the stop command mechanical angle θMS can be set.

[0134] In the above-described embodiment, the position estimation unit 811 detects the electrical angle θ, which is the relative position of the magnetic poles of the stator 5b of the brushless DC motor 5, from the induced voltage V. The position estimation unit 811 may also detect the electrical angle θ, which is the relative position of the magnetic poles, from the current flowing through the three-phase windings of the stator 5b of the brushless DC motor 5, for example.

[0135] In the above-described embodiment, the state estimation unit 813 estimates that the mechanical angle θM is at top dead center TDC when the rotation speed RS is the minimum rotation speed in the "top dead center estimation process." The state estimation unit 813 may also estimate that the mechanical angle θM is at top dead center TDC when the rotation acceleration is the minimum rotation acceleration in the "top dead center estimation process."

[0136] In the above-described embodiment, the state estimation unit 813 has illustrated a case in which, in the "top dead center estimation process," the state estimation unit 813 estimates that the mechanical angle θM is at top dead center TDC when the rotational speed RS is the minimum rotational speed. Note that the slower the rotational speed RS, the larger the current flowing through the three-phase windings of the stator 5b of the brushless DC motor 5. Therefore, in the "top dead center estimation process," the state estimation unit 813 may estimate that the mechanical angle θM is at top dead center TDC when the current flowing through the three-phase windings is the maximum current.

[0137] In the above-described embodiment, the stop command mechanical angle θMS is set so that the mechanical angle θM of the compressor 17 when the brushless DC motor 5 stops is within the range of "zero degrees" to "270 degrees." The stop command mechanical angle θMS may be set so that the mechanical angle θM of the compressor 17 when the brushless DC motor 5 stops is included in the first range RD1 or the third range RD3 shown in FIG.

[0138] In the above-described embodiment, the second example of the "drive stop processing" shown in FIG. 9 illustrates a case where the rotation speed RS of the brushless DC motor 5 is decelerated to the second rotation speed RS2 before an instruction to stop driving the brushless DC motor 5 is output to the inverter circuit 4. In addition, the second rotation speed RS2 is 30 rps. The smaller the second rotation speed RS2, the shorter the time of inertial rotation, and therefore the smaller the variation. Therefore, the smaller the second rotation speed RS2, the more reliably the vibration when the compressor 17 is stopped can be suppressed. However, if the second rotation speed RS2 is equal to or lower than a predetermined rotation speed (for example, 5 rps), vibrations may occur while the brushless DC motor 5 is driving the compressor 17 at a constant speed. Therefore, the second rotation speed RS2 needs to be set to a rotation speed higher than the predetermined rotation speed.

[0139] The configuration of the drive control unit 8 shown in Figure 5 is one example, and the specific implementation form is not particularly limited. In other words, it is not necessarily necessary to implement hardware corresponding to each unit individually, and it is also possible to configure the functions of each unit to be realized by a single processor executing a program. Furthermore, some of the functions realized by software in the above-mentioned embodiment may be realized by hardware, or some of the functions realized by hardware may be realized by software.

[0140] The processing steps of the drive control unit 8 shown in each of the flowcharts in Figures 6 to 10 are divided according to the main processing content to make the processing easier to understand, and the processing is not limited by the way the processing units are divided or the names of the processing units. The processing may be divided into more step units depending on the processing content. Furthermore, one step unit may be divided so that it includes more processing. Furthermore, the order of the steps may be changed as appropriate within the scope of the present disclosure.

[0141] It should be noted that the above-described embodiments are intended to illustrate the technology of the present disclosure, and various modifications, substitutions, additions, omissions, etc. may be made within the scope of the claims or their equivalents.

[0142] (Addendum) The above description of the embodiments discloses the following techniques.

[0143] (Technology 1) A motor drive device comprising: a brushless DC motor that drives a compressor; an inverter circuit that converts DC voltage to AC voltage and supplies power to the brushless DC motor; and a drive control unit that controls driving of the brushless DC motor via the inverter circuit, wherein when the brushless DC motor stops driving the compressor, the drive control unit causes the inverter circuit to stop supplying power to the brushless DC motor from the inverter circuit at a timing when the compressor satisfies a predetermined condition that has been set in advance. According to this configuration, by setting the predetermined condition to an appropriate condition, it is possible to suppress vibration when the compressor is stopped.

[0144] (Technology 2) The motor drive control device according to Technology 1, wherein the predetermined condition is a condition defined by a stop command mechanical angle, which is a mechanical angle of the compressor set according to the rotational speed of the brushless DC motor when driving of the compressor is stopped. According to this configuration, by appropriately setting the stop command mechanical angle in accordance with the rotation speed of the brushless DC motor, it is possible to suppress vibrations when the compressor is stopped from driving.

[0145] (Technology 3) The motor drive control device according to Technology 1, wherein the predetermined condition is a condition defined by a stop command mechanical angle, which is a mechanical angle of the compressor set according to the pressure of the compressor when the drive of the compressor is stopped and the rotation speed of the brushless DC motor. According to this configuration, by appropriately setting the stop command mechanical angle in accordance with the pressure of the compressor and the rotation speed of the brushless DC motor, it is possible to suppress vibrations when the compressor is stopped from driving.

[0146] (Technology 4) The motor drive control device according to any one of Technologies 1 to 3, wherein the compressor is a reciprocating type. With this configuration, because the compressor is a reciprocating type, there is a high possibility that the rotational speed will become "zero" during the compression process. Therefore, vibrations are likely to occur when the compressor is stopped. According to the present disclosure, by setting the predetermined conditions to appropriate conditions, vibrations when the compressor is stopped can be suppressed.

[0147] (Technology 5) The motor drive control device according to Technology 4, wherein the predetermined condition is set so that the mechanical angle of the compressor when the brushless DC motor stops is within a predetermined range of mechanical angles starting from the top dead center of the compressor. According to this configuration, the predetermined conditions can be set to appropriate conditions, so that vibrations when the compressor is stopped can be suppressed.

[0148] (Technology 6) The motor drive control device according to Technology 5, wherein the predetermined mechanical angle is 270 degrees or less. According to this configuration, the predetermined conditions can be set to appropriate conditions, so that vibrations when the compressor is stopped can be suppressed.

[0149] (Technology 7) The motor drive control device according to Technology 5 or Technology 6, wherein the predetermined condition is set based on experimental results so that the mechanical angle of the compressor when the brushless DC motor stops is within a predetermined range of mechanical angles starting from the top dead center of the compressor. According to this configuration, the predetermined conditions can be set to appropriate conditions based on experimental results, so that vibrations when the compressor is stopped can be reliably suppressed.

[0150] (Technology 8) The motor drive control device according to any one of Technology 5 to Technology 7, wherein the drive control unit calculates the predetermined condition based on the moment of inertia of the compressor driven by the brushless DC motor, the rotation speed of the brushless DC motor, and the suction pressure, discharge pressure, and suction gas temperature of the compressor. According to this configuration, the predetermined conditions can be set to appropriate conditions, so that vibrations when the compressor is stopped can be suppressed.

[0151] (Technology 9) A motor drive control device according to any one of Technologies 5 to 8, wherein when the brushless DC motor stops driving the compressor, if the rotational speed of the brushless DC motor is a first rotational speed that is higher than a second rotational speed, the drive control unit causes the inverter circuit to decelerate the rotational speed of the brushless DC motor to the second rotational speed, and after the rotational speed of the brushless DC motor reaches the second rotational speed, causes the inverter circuit to stop supplying power from the inverter circuit to the brushless DC motor at a timing when the compressor satisfies the predetermined condition. According to this configuration, by setting the predetermined condition to an appropriate condition corresponding to the second rotation speed, it is possible to suppress vibration when the compressor is stopped from driving.

[0152] (Technical Aspect 10) The motor drive control device according to any one of Technical Aspects 1 to 9, wherein the compressor constitutes a refrigeration cycle of a refrigerator. According to this configuration, vibration of the compressor that constitutes the refrigeration cycle of the refrigerator can be suppressed when the compressor stops operating.

[0153] (Technology 11) A motor drive control method for a motor drive device comprising a brushless DC motor that drives a compressor, an inverter circuit that converts DC voltage to AC voltage and supplies power to the brushless DC motor, and a drive control unit that controls driving of the brushless DC motor via the inverter circuit, wherein when the brushless DC motor stops driving the compressor, the drive control unit executes processing on the inverter circuit to stop supplying power from the inverter circuit to the brushless DC motor at a timing when the compressor satisfies a predetermined condition. This configuration provides the same effects as the motor drive control device described in the first technique.

[0154] (Technology 12) A control program for a motor drive device comprising a brushless DC motor that drives a compressor, an inverter circuit that converts DC voltage to AC voltage and supplies power to the brushless DC motor, and a drive control unit that controls the drive of the brushless DC motor via the inverter circuit, wherein the control program causes a processor constituting the drive control unit to execute processing for stopping the power supplied from the inverter circuit to the brushless DC motor when the brushless DC motor stops driving the compressor, at a timing when the compressor satisfies a predetermined condition that has been set in advance. This configuration provides the same effects as the motor drive control device described in the first technique. [Industrial Applicability]

[0155] As described above, the motor drive control device, motor drive control method, and control program according to the present invention can be used to suppress vibration when the compressor is stopped. [Explanation of symbols]

[0156] 100 refrigerator 22 Refrigeration cycle 30 Motor drive control device 17 Compressor 4. Inverter circuit 5 Brushless DC motor 5a Rotor 5b Stator 6 Voltage detection section 7 Terminal voltage detection section 8 Drive control unit 81 processors 811 Position estimation part 812 Speed ​​estimation part 813 State Estimation Unit 814 Stop mechanical angle calculation section 815 Stop instruction section 42 memory 421 Control Program 422 Stop instruction mechanical angle storage unit BDC bottom dead center N number of pole pairs RD1 1st range RD2 Second Range RD3 3rd range RS rotation speed RS1 1st rotation speed RS2 Second rotation speed RSA target rotation speed RSC indicated rotation speed RSN minimum rotation speed ST1 First state ST2 Second state ST3 Third state ST4 Fourth state TDC top dead center VJ Induced voltage ZC Zero crossing point θE electrical angle θM mechanical angle θMS Stop instruction mechanical angle

Claims

1. a brushless DC motor that drives the compressor; an inverter circuit that converts a DC voltage into an AC voltage and supplies power to the brushless DC motor; a drive control unit that controls driving of the brushless DC motor via the inverter circuit, the drive control unit causes the inverter circuit to stop supplying power to the brushless DC motor at a timing when the brushless DC motor stops driving the compressor and the compressor satisfies a predetermined condition that has been set in advance. Motor drive device.

2. the predetermined condition is a condition defined by a stop command mechanical angle, which is a mechanical angle of the compressor set in accordance with the rotational speed of the brushless DC motor when driving of the compressor is stopped. The motor drive device according to claim 1 .

3. the predetermined condition is a condition defined by a stop command mechanical angle, which is a mechanical angle of the compressor set in accordance with the pressure of the compressor and the rotation speed of the brushless DC motor when driving of the compressor is stopped. The motor drive device according to claim 1 .

4. The compressor is a reciprocating type. The motor drive device according to any one of claims 1 to 3.

5. the predetermined condition is set so that a mechanical angle of the compressor when the brushless DC motor stops is within a predetermined range of mechanical angles starting from a top dead center of the compressor. The motor drive device according to claim 4.

6. The predetermined mechanical angle is 270 degrees or less. The motor drive device according to claim 5 .

7. the predetermined condition is set based on experimental results so that the mechanical angle of the compressor when the brushless DC motor stops is within a predetermined range of mechanical angles starting from a top dead center of the compressor. The motor drive device according to claim 5 .

8. the drive control unit calculates the predetermined condition based on a moment of inertia of the compressor driven by the brushless DC motor, a rotation speed of the brushless DC motor, and a suction pressure, a discharge pressure, and an intake gas temperature of the compressor. The motor drive device according to claim 5 .

9. When the brushless DC motor stops driving the compressor, if the rotation speed of the brushless DC motor is a first rotation speed that is higher than a second rotation speed, the drive control unit: causing the inverter circuit to reduce the rotational speed of the brushless DC motor to the second rotational speed; and stopping the inverter circuit from supplying power to the brushless DC motor at a timing when the compressor satisfies the predetermined condition after the rotation speed of the brushless DC motor reaches the second rotation speed. The motor drive device according to claim 5 .

10. The compressor constitutes a refrigeration cycle of a refrigerator. The motor drive device according to claim 4.

11. a brushless DC motor that drives the compressor; an inverter circuit that converts a DC voltage into an AC voltage and supplies power to the brushless DC motor; a drive control unit that controls driving of the brushless DC motor via the inverter circuit, When the brushless DC motor stops driving the compressor, the drive control unit executes a process for causing the inverter circuit to stop supplying power to the brushless DC motor at a timing when the compressor satisfies a predetermined condition. Motor drive control method.

12. a brushless DC motor that drives the compressor; an inverter circuit that converts a DC voltage into an AC voltage and supplies power to the brushless DC motor; a drive control unit that controls driving of the brushless DC motor via the inverter circuit, A processor constituting the drive control unit When the brushless DC motor stops driving the compressor, the inverter circuit is caused to execute a process of stopping the supply of power from the inverter circuit to the brushless DC motor at a timing when the compressor satisfies a predetermined condition that has been set in advance. Control program.

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