Compressor drive arrangement
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- PANASONIC ENTERTAINMENT INTERACTIVE CO LTD
- Filing Date
- 2024-11-11
- Publication Date
- 2026-06-09
Smart Images
Figure CN122181102A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to compressor drive devices used in various refrigeration and freezing equipment. Background Technology
[0002] Patent Document 1 discloses an inverter control device that can start even under relatively large starting load conditions. The inverter control device is configured such that the carrier frequency of the PWM signal during the start-up control period from the start of motor startup until a predetermined time has elapsed is set higher than the carrier frequency in the steady-state control state after the aforementioned period.
[0003] Existing technical documents
[0004] Patent documents
[0005] Patent Document 1: Japanese Patent Application Publication No. 2005-168196 Summary of the Invention
[0006] The technical problem that the invention aims to solve
[0007] According to the inventor's in-depth research, it has been clarified that: since the reference point for switching the carrier frequency from high frequency to low frequency during the compressor's driving process is time, when the switching position is near the top dead center where the load torque fluctuates greatly, overcurrent may sometimes cause the compressor to vibrate or generate noise.
[0008] This invention was made to solve such a technical problem, and its purpose is to provide a compressor drive device that can effectively suppress the generation of overcurrent when switching carrier frequencies.
[0009] Technical means for solving technical problems
[0010] To solve the above-mentioned technical problems, the compressor drive device of the present invention is configured to include: an inverter device including an inverter circuit for converting DC to AC and a control unit; and a compressor including a motor connected to the inverter circuit and a piston that reciprocates (reciprocating motion) in a cylinder under the action of the motor. The control unit includes: a multi-phase PWM signal generation unit capable of setting multiple carrier frequencies for driving the compressor; and a bottom dead center detection unit that detects the bottom dead center of the piston in the compressor, wherein when the carrier frequency is switched from a high frequency to a low frequency during the rotation of the compressor, the timing of the switching is set to the bottom dead center of the compressor.
[0011] Based on the above structure, when multiple carrier frequencies driving the compressor are controlled, the carrier frequency can be switched from a high frequency to a low frequency when the load torque variation is small. Therefore, the carrier frequency can be switched smoothly without compromising controllability, thus suppressing the generation of overcurrent during switching.
[0012] The above-mentioned objects, other objects, features and advantages of the present invention will become clear from the following detailed description of preferred embodiments with reference to the accompanying drawings.
[0013] Invention Effects
[0014] In this invention, by adopting the above structure, the following effect can be achieved: a compressor drive device that can effectively suppress the generation of overcurrent when switching carrier frequencies can be provided. Attached Figure Description
[0015] Figure 1 This is a block diagram illustrating a representative structural example of a compressor drive device according to an embodiment of the present invention.
[0016] Figure 2 It means Figure 1 The diagram shows a schematic representation of the rotational position of the compressor driven by the compressor drive unit.
[0017] Figure 3 It means by Figure 1 The flowchart shows an example of the control performed by the compressor drive device.
[0018] Figure 4 It means Figure 1 The timing diagram shows an example of carrier frequency switching for a compressor drive unit.
[0019] Figure 5 This is a timing diagram illustrating an example of carrier frequency switching in a compressor drive device according to a conventional embodiment. Detailed Implementation
[0020] (Insights, etc., that form the basis of this invention)
[0021] When the inventors conceived of the subject matter of this invention, they knew that, from the perspective of reducing power losses in the inverter circuit, a low carrier frequency of the PWM signal driving the compressor significantly reduces power losses when driving the compressor. Furthermore, it is also known that, from the perspective of increasing the control correction frequency and ensuring control stability during compressor start-up acceleration, a high carrier frequency of the PWM signal makes it easier to ensure control stability.
[0022] Typically, the sampling interval for acquiring the drive state used to control the compressor is synchronized with the carrier frequency of the PWM signal. Therefore, during compressor operation, when the carrier frequency is switched from a high frequency to a low frequency, the sampling interval, which could originally be performed with a short period, becomes a long period, resulting in a correction delay.
[0023] When switching occurs near the top dead center or other locations with large load torque fluctuations, the lag correction may not provide sufficient feedback control to respond to load changes, resulting in failure to follow the drive. In particular, when the required torque is insufficient, an overcurrent proportional to the shortfall can occur, leading to compressor vibration and noise.
[0024] The inventors of this invention independently discovered this technical problem, and in order to solve it, the subject of this invention was ultimately formed. Specifically, the compressor drive device of this invention, while taking into account both control stability during compressor startup and acceleration, and reduced power loss during steady-state drive, is able to suppress the generation of overcurrent when switching the carrier frequency from a high frequency to a low frequency.
[0025] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, sometimes unnecessary detailed descriptions will be omitted. For example, detailed descriptions of well-known matters or repeated descriptions of substantially the same structures will sometimes be omitted. This is to avoid unnecessary verbosity in the following description and to make it easier for those skilled in the art to understand. Furthermore, in the following description, the same or corresponding elements will be labeled with the same reference numerals in all the drawings, and repeated descriptions will be omitted.
[0026] Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the invention, and are not intended to limit the subject matter described in the claims.
[0027] [1. Example of the structure of a compressor drive unit]
[0028] Reference Figure 1 A structural example of a representative compressor drive device of the present invention will be described. For example, such as... Figure 1 As shown, the compressor drive device of this embodiment includes an inverter device 1 and a compressor 30. In this embodiment, the inverter device 1 includes an inverter circuit 10, a drive circuit 11, a current detection circuit 12, and a control unit 20. Furthermore, in this embodiment, the control unit 20 includes an arithmetic unit 21, a carrier frequency setting unit 22, a PWM signal generation unit 23, and a bottom dead center detection unit 24.
[0029] The inverter circuit 10 outputs a signal to drive the brushless DC motor 31 included in the compressor 30. The inverter circuit 10 is a circuit that includes driving elements such as IGBTs (Insulated Gate Bipolar Transistors) or FETs (Field Effect Transistors). In this embodiment, for example... Figure 1 As shown schematically, temperature sensors 13 include NTC (Negative Temperature Coefficient) thermistors.
[0030] The drive circuit 11 converts the signal output from the control unit 20 into a signal that matches the inverter circuit 10. Additionally, the drive circuit 11 may incorporate protection circuits such as overcurrent protection. The current detection circuit 12 periodically obtains the current value (circuit current) from the inverter circuit 10 and outputs it to the lower dead center detection unit 24 of the control unit 20.
[0031] The control unit 20 controls the drive of the compressor 30 via the inverter circuit 10. Furthermore, the control unit 20 may also be configured to perform various controls in addition to driving the compressor 30, depending on the specific structure of the compressor drive unit.
[0032] The arithmetic unit 21 performs various arithmetic operations that accompany the control unit 20. Specific arithmetic operations, such as those described later, include calculations of voltage command values used to drive the compressor 30.
[0033] The carrier frequency setting unit 22 sets multiple carrier frequencies for driving the compressor 30. The PWM signal generation unit 23 converts the voltage command value calculated by the calculation unit 21 into a PWM signal. The bottom dead center detection unit 24 calculates the rotation phase of the brushless DC motor 31 and the position of the bottom dead center based on the circuit current detected by the current detection circuit 12.
[0034] Here, the specific structure of the control unit 20, as well as the structures of the arithmetic unit 21, carrier frequency setting unit 22, PWM signal generation unit 23, and lower dead point detection unit 24 included in the control unit 20, are not particularly limited. For example, the control unit 20 described in this embodiment can be composed of a microcomputer or microcontroller's arithmetic unit and storage unit, etc.
[0035] The storage device constituting the control unit 20 can be configured as the internal memory of a microcomputer or microcontroller, or as a separate memory or storage device. Furthermore, the storage device does not have to be a single device; it can also be configured as multiple storage devices (e.g., internal memory and external hard disk drives or SSDs).
[0036] The computing device constituting the control unit 20 can be any structure as follows: it can be composed of a general-purpose processor, a special-purpose processor, an integrated circuit, an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuits), a GPU, or a combination of two or more of these, and it can operate according to the program stored in the storage device to realize the function of the control unit 20.
[0037] A processor, as a computing device, is a hardware circuit (or processing circuit) because it contains circuits composed of a large number of transistors, memory, etc. Integrated circuits or ASICs also contain processors or processing modules such as CPUs, and are therefore also hardware circuits. FPGAs contain a large number of integrated logic circuits (functional blocks), and are therefore hardware circuits. GPUs contain a large number of parallel computing circuits (cores), and are therefore hardware circuits. Software, such as programs, stored in storage devices, is used in the structure of hardware circuits (processors, integrated circuits, FPGAs, ASICs, GPUs, etc.). Alternatively, a computing device can also be configured as a logic circuit composed of known switching elements, subtractors, comparators, etc.
[0038] Furthermore, the specific structures of the inverter circuit 10, drive circuit 11, current detection circuit 12, etc., described in this embodiment are not particularly limited, and known structures can be used appropriately. For example, as described above, the inverter circuit 10 can be any circuit that includes IGBTs or FETs as switching elements (drive elements).
[0039] The inverter device 1 with this structure is connected to the compressor 30 via multiple interconnecting wires. The inverter device 1 is supplied with voltage by a DC voltage source 32. The compressor 30 includes a brushless DC motor 31. The brushless DC motor 31 is driven by a voltage signal output from the inverter circuit 10 of the inverter device 1. Specific driving methods include, for example, two-phase modulation control, three-phase modulation control, or rectangular wave control, which is controlled by energizing a sine wave.
[0040] Next, refer to Figure 2The structure of key components of compressor 30 is described below. For example... Figure 2 As schematically shown, a crank mechanism 33 is provided in the brushless DC motor 31, and a piston 34 is connected to the crank mechanism 33. The piston 34 reciprocates within the cylinder 35. The space within the cylinder 35, divided by the piston 34, is a compression chamber.
[0041] The specific structure of the compressor 30 is not particularly limited, as long as it includes an electric motor such as a brushless DC motor 31, a piston 34, and a cylinder 35. As a representative example of the structure of the compressor 30, for example, a crank mechanism 33 includes a crankshaft having a main shaft and an eccentric shaft, the main shaft being fixed to the brushless DC motor 31, and the eccentric shaft being connected to the piston 34 through a connecting mechanism (such as a connecting rod).
[0042] When the crankshaft rotates due to the rotation of the brushless DC motor 31, the piston 34, connected to the eccentric shaft, reciprocates within the cylinder 35. Additionally, in Figure 2 In the schematic representation of the crank mechanism 33, the rotational phases of the piston 34 at top dead center and bottom dead center are indicated by blackened circles.
[0043] [2. Example of compressor drive unit operation]
[0044] The operation of the compressor drive unit configured as described above will be explained below.
[0045] [2-1. Compressor startup actions 1 (immediately after startup)]
[0046] based on Figure 1 This explains the basic operation of the inverter device 1. During the start-up and acceleration of the brushless DC motor 31, the arithmetic unit 21 within the control unit 20 calculates the appropriate voltage command value for startup.
[0047] Assuming the compressor 30 is in a balanced pressure state, since no preparatory actions are performed before startup, sufficient back electromotive force information from the brushless DC motor 31 cannot be obtained in the low rotational region at the start of startup. Therefore, it is difficult to calculate the rotor position of the brushless DC motor 31. Consequently, after startup, it becomes a forced commutation drive (i.e., a forced commutation drive) that does not perform rotor position calculation.
[0048] On the other hand, for example, in a system equipped with compressor 30, in order to reduce power loss and maintain the pressure state just before stopping, the pressure state at startup will become unbalanced, so sometimes it is difficult to start with forced commutation drive.
[0049] As a countermeasure, one could include: calculating the rotor position in advance based on preparatory actions such as reversing motion before starting, or implementing control methods such as stopping at a position far from the top dead center where a large load torque is required before the process.
[0050] After startup, the voltage command value calculated by the arithmetic unit 21 is converted into a PWM signal by the PWM signal generation unit 23. At this time, the carrier frequency is the frequency set by the carrier frequency setting unit 22. This frequency is determined by the setting from the arithmetic unit 21.
[0051] To generate a PWM signal, the current detection circuit 12 periodically obtains the current value from the compressor 30. The sampling interval for obtaining this current value is synchronized with the carrier frequency. Based on the sampled value, the arithmetic unit 21 calculates the next voltage command value, and the PWM signal generation unit 23 converts it into a PWM signal.
[0052] During startup, the pressure state of compressor 30 changes as it accelerates from a standstill to a specified speed. Therefore, control is required using short-cycle sampling intervals. Thus, in addition to the speed changes caused by acceleration, a sampling interval sufficient to adequately track load changes caused by pressure variations is also needed. Therefore, the carrier frequency is set here to, for example, 6kHz or higher.
[0053] As described above, the signal used to drive the brushless DC motor 31 is output from the inverter circuit 10. Representative driving methods for the brushless DC motor 31, as described above, include, for example, sinusoidal wave control (2-phase modulation control, 3-phase modulation control) or rectangular wave control. In such control, the control voltage primarily used in the inverter circuit 10 is 15V, not the 3.3V or 5V used in the control unit 20. Furthermore, voltage conversion is required to drive the high-side components via a bootstrap circuit or the like. Therefore, a drive circuit 11 is provided between the control unit 20 and the inverter circuit 10, and the drive circuit 11 performs signal conversion.
[0054] [2-2. Compressor Start-up Actions 2 (Acceleration)]
[0055] When the brushless DC motor 31 starts to rotate, it generates a back electromotive force caused by the rotation. Based on this back electromotive force, the control unit 20 calculates the rotor position of the brushless DC motor 31, and further, the control unit 20 outputs a voltage command value corresponding to the rotor position.
[0056] Specifically, based on the circuit current value of the inverter circuit 10 obtained by the current detection circuit 12, the calculation unit 21 of the control unit 20 performs a calculation to estimate the rotor position. Then, the calculation unit 21 continuously calculates an appropriate voltage command value corresponding to the rotational phase obtained from the rotor position calculation. As a result, the calculation unit 21 (control unit 20) continuously outputs this voltage command value. Consequently, the brushless DC motor 31 continues to rotate.
[0057] [2-3. The transition action of the compressor to steady-state drive]
[0058] When the speed of the brushless DC motor 31 reaches the target value and stabilizes, the control unit 20 begins to change the carrier frequency. The steps are explained.
[0059] In the bottom dead center detection unit 24 included in the control unit 20, the rotation phase of the brushless DC motor 31 is calculated based on the circuit current of the inverter circuit 10 detected by the current detection circuit 12, and the position of the bottom dead center of the piston 34 is also calculated. Here, in the control of the compressor 30, although it is difficult to directly detect the bottom dead center or to calculate the point where the load torque variation is small, ... Figure 2 As shown, the bottom dead center and top dead center of piston 34 are mechanically opposite positions. The load torque of piston 34 at top dead center varies greatly.
[0060] Therefore, in this embodiment, the bottom dead center detection unit 24 detects the top dead center of the piston 34 and indirectly calculates the bottom dead center of the piston 34 by adding the top dead center to the machine angle 180°. That is, in this embodiment, the position calculation of the bottom dead center of the piston 34 is essentially synonymous with the direct detection of the bottom dead center during the control of the control unit 20.
[0061] The position of the bottom dead center of the piston 34, detected (calculated) by the bottom dead center detection unit 24, is output to the arithmetic unit 21. The arithmetic unit 21 sends a command to the carrier frequency setting unit 22 to switch the carrier frequency at the calculated bottom dead center position. At this time, the carrier frequency is set to a frequency lower than the carrier frequency at startup, for example, 1.5kHz. Upon receiving the carrier frequency switching command, the carrier frequency setting unit 22 switches the carrier frequency accordingly and sends a command to the PWM signal generation unit 23.
[0062] In the PWM signal generation unit 23, the voltage command value output by the arithmetic unit 21 is converted into a PWM signal at the switched carrier frequency. The drive circuit 11 converts this PWM signal into a signal suitable for the input of the inverter circuit 10. The inverter circuit 10 outputs a voltage signal at the set carrier frequency to drive the brushless DC motor 31.
[0063] Such a change in carrier frequency is executed as control by the control unit 20. (Except for reference...) Figure 1In addition to the block diagram, it also refers to Figure 3 The flowchart illustrates an example of the control performed by the control unit 20.
[0064] First, the control unit 20 detects the circuit current of the inverter circuit 10 through the current detection circuit 12 (step S1). Next, the bottom dead center detection unit 24 of the control unit 20 detects (calculates) the position of the bottom dead center of the piston 34 based on the circuit current obtained from the current detection (step S2). The bottom dead center detection unit 24 determines whether the piston 34 is at the bottom dead center based on the circuit current (step S3).
[0065] When the piston 34 is detected to be at the bottom dead center by the bottom dead center detection unit 24 (YES in step S3), the arithmetic unit 21 of the control unit 20 outputs a command to the carrier frequency setting unit 22 of the control unit 20 to switch the carrier frequency from a high carrier frequency to a low carrier frequency, that is, a switching command to switch from a high carrier frequency to a low carrier frequency (step S4). The carrier frequency setting unit 22 receives the command and switches the high carrier frequency to a low carrier frequency (step S5).
[0066] In the PWM signal generation unit 23 of the control unit 20, a PWM signal is generated based on the voltage command value from the calculation unit 21 at a low carrier frequency switched by the carrier frequency setting unit 22 (step S6). On the other hand, if the bottom dead center detection unit 24 fails to detect that the piston 34 is at the bottom dead center (No in step S3), the PWM signal generation unit 23 generates a PWM signal based on the voltage command value from the calculation unit 21 at the high carrier frequency before the switch (step S6).
[0067] Control unit 20 Figure 1 As shown, the PWM signal generated by the PWM signal generation unit 23 is input to the inverter circuit 10 via the drive circuit 11. Thus, the inverter circuit 10 drives the brushless DC motor 31 using either the switched low carrier frequency voltage signal or the original high carrier frequency voltage signal.
[0068] Here, refer to Figure 4 and Figure 5 The timing of switching carrier frequencies is explained. Figure 4 or Figure 5 The upper section (upper part) represents the change in load torque of the brushless DC motor 31 (compressor 30), with the vertical axis representing the magnitude of the load torque and the horizontal axis representing the rotation phase of the rotor of the brushless DC motor 31. The black dots on the load torque change curve are points sampled for the control unit 20 to execute the control. Figure 4 or Figure 5 The lower segment (lower part) is a carrier waveform corresponding to the change in load torque of the brushless DC motor 31. Figure 4 The compressor drive device corresponding to the embodiments of the present invention, Figure 5 This corresponds to the compressor drive device in the conventional implementation.
[0069] like Figure 4 As shown, when the rotor's rotational phase approaches the top dead center of piston 34, the load torque gradually increases, reaches a maximum value, and then gradually decreases. When it reaches the top dead center, the load torque decreases sufficiently, reaches a minimum value shortly after exceeding the top dead center, and then temporarily increases before remaining in a stable state with small fluctuations. This stable state continues until the bottom dead center of piston 34 is reached. After exceeding the bottom dead center, the load torque gradually increases.
[0070] Thus, the area near the bottom dead center of piston 34, compared to the area near the top dead center, is a stable region where the load torque variation of brushless DC motor 31 is smaller. Therefore, as... Figure 4 As shown, even if the carrier frequency switches from a high carrier frequency to a low carrier frequency, causing the sampling interval to widen, it is still near the lower dead center. Compared with the area near the upper dead center, the region where the sampling interval widening is less affected by changes in load torque is the region where the sampling interval widening is less affected by changes in load torque.
[0071] Moreover, in Figure 5 In the conventional embodiments shown, since the timing of carrier frequency switching is not specified, carrier frequency switching sometimes occurs in the region near the top dead center, i.e., the region where the load torque fluctuates significantly. In this case, because the area where the sampling interval widens overlaps with the region where the load torque fluctuates significantly, control can sometimes become unstable. In the compressor drive device of this embodiment, this can be avoided. Figure 5 The unstable situation is shown.
[0072] [3. Effects, etc.]
[0073] As described above, the compressor drive device of this embodiment includes an inverter device 1 and a compressor 30. The inverter device 1 includes an inverter circuit 10, a drive circuit 11, a current detection circuit 12, and a control unit 20. The control unit 20 includes an arithmetic unit 21, a carrier frequency setting unit 22, a PWM signal generation unit 23, and a bottom dead center detection unit 24. The compressor 30 includes a brushless DC motor 31. The inverter device 1 is connected to the compressor 30 via a multi-connection wiring. A DC voltage source 32 supplies voltage to the inverter device 1. In this configuration, when the carrier frequency switches from a high frequency to a low frequency during the rotation of the brushless DC motor 31, the timing is set to the bottom dead center of the compressor 30.
[0074] Therefore, the carrier frequency can be switched when the load torque of the brushless DC motor 31 is stable. As a result, the overcurrent or vibration of the compressor 30 caused by the switching of the carrier frequency can be effectively suppressed.
[0075] Furthermore, in the compressor drive device of this embodiment, as in this embodiment, the carrier frequency can be set high during the start-up acceleration of the brushless DC motor 31, and then set lower than the carrier frequency during start-up acceleration after the compressor 30 transitions to steady-state rotation. In other words, the compressor drive device can also have the following structure: the control unit 20 sets the carrier frequency of the compressor 30 during start-up acceleration to be higher than the carrier frequency during steady-state rotation after acceleration.
[0076] During the start-up acceleration of compressor 30, it is difficult to determine the regularity of control due to factors such as pressure conditions or load variations. In this embodiment, the compressor drive device, through the structure described above, sets a high carrier frequency during start-up acceleration. Therefore, even when the regularity of control is difficult to determine, high-frequency sampling corresponding to the high carrier frequency can be performed. Thus, highly reliable start-up can be achieved even during the start-up acceleration of compressor 30.
[0077] Furthermore, in the above structure, the carrier frequency is set lower during the steady-state rotation of the compressor 30 than during startup acceleration. Therefore, since the carrier frequency switches from high to low at the bottom dead center of the compressor 30, the switching of the carrier frequency can be performed while effectively suppressing overcurrent or compressor 30 vibration. Thus, both high-reliability startup and reduced power loss during steady-state rotation can be achieved.
[0078] Furthermore, in the compressor drive device of this embodiment, when the speed of the motor such as the brushless DC motor 31 reaches a specified speed (speed threshold) or higher, or when the input power value input to the inverter device 1 reaches a specified value (input power threshold) or higher, the control unit 20 may set the carrier frequency to be higher than the carrier frequency during steady-state rotation.
[0079] Thus, in the compressor drive device of this embodiment, the control unit 20 can also have the following structure: after the compressor 30 is started, it switches at least two carrier frequencies to control the rotational speed. In the above example, when the carrier frequency during steady-state rotation is set as the first carrier frequency, the carrier frequency when the speed threshold or input power threshold is reached or exceeded can be set as the second carrier frequency. Furthermore, based on the setting of the speed threshold or input power threshold, three or more frequencies can be preset, such as a third carrier frequency.
[0080] Furthermore, in structures that switch between two or more carrier frequencies, the control unit 20 only needs to determine the switching between the two or more carrier frequencies based on at least one of the actual rotational speed of the compressor 30 (motor) and the input electrical power input to the inverter device 1. A representative example of such a switching structure is one in which the carrier frequency set by the control unit 20 increases as the actual rotational speed or the input electrical power increases.
[0081] In this way, by setting multiple carrier frequencies and switching between them based on rotational speed or input power, or both, the compressor 30 (motor) can be driven in steady-state operation and at higher speeds by switching these carrier frequencies. Furthermore, even with carrier frequency switching, the generation of noise or vibration from the compressor 30, or overcurrent flowing to the compressor drive unit (inverter unit 1), can be effectively avoided or suppressed. Therefore, a good balance can be struck between reducing power loss during steady-state operation and maintaining control stability during higher speeds.
[0082] Furthermore, in the compressor drive device of this embodiment, such as Figure 1 As shown, the inverter circuit 10 can have a structure that includes a temperature sensor 13. In this structure, when the temperature of the drive element included in the inverter circuit 10 reaches or exceeds a set temperature according to the temperature sensor 13, the control unit 20 performs control to ensure that the set carrier frequency does not exceed the current value.
[0083] Therefore, for example, when the set temperature is set to the temperature rating of the drive element, the temperature rise of the drive element caused by increasing the carrier frequency can be suppressed within the temperature rating of the drive element. Thus, performance degradation and damage of the drive element in the inverter circuit 10 can be effectively suppressed.
[0084] (Other implementation methods or variations)
[0085] As described above, the aforementioned embodiments have been presented as examples of the technology disclosed in this application. However, the technology of the present invention is not limited to these embodiments and can be applied to other embodiments that have been modified, substituted, added, or omitted. In other words, the present invention also includes variations of the aforementioned embodiments. Furthermore, the technology of the present invention can also combine the constituent elements described in the above embodiments to form new embodiments.
[0086] Specifically, for example, in the aforementioned embodiment, the circuit current detected by the current detection circuit 12 is used to calculate the position of the bottom dead center of the piston 34. However, the calculation of the bottom dead center position is not limited to the detection of the circuit current by the current detection circuit 12. For example, a sensor such as a Hall element built into the brushless DC motor 31 can be used to calculate the bottom dead center of the piston 34, or the position of the bottom dead center or top dead center of the piston 34 can be calculated based on the rotational speed of the rotor of the brushless DC motor 31.
[0087] Alternatively, in the aforementioned embodiments, the structure is as follows: to generate a PWM signal, the current detection circuit 12 needs to periodically acquire current values from the compressor 30, and the sampling interval for acquiring these current values is synchronized with the carrier frequency. However, the number of times the current values are acquired is not limited to once when synchronized with the carrier frequency; multiple acquisitions are also possible. Furthermore, an asynchronous structure where the sampling interval is not synchronized with the PWM signal is also possible.
[0088] Alternatively, in the aforementioned embodiments, the current detection circuit 12 is a single-shunt structure that detects the circuit current from the DC section of the inverter circuit 10, but the detection of the circuit current is not limited to this. For example, a circuit that detects the current of each of the three phases from the inverter circuit 10 in a three-shunt manner can also be used.
[0089] Alternatively, in the aforementioned embodiments, the timing for switching the carrier frequency is set at the bottom dead center of piston 34. However, the position of the bottom dead center is a target value and may deviate due to factors such as control accuracy and various tolerances. Therefore, the timing for switching the carrier frequency is not limited to the bottom dead center of piston 34. For example, the bottom dead center can also be used as a reference, and the switching timing can be set at a position where the change in load torque is smaller than that at the top dead center (estimated position).
[0090] (Postscript)
[0091] Based on the descriptions of the above embodiments, the following techniques are disclosed in this specification.
[0092] (Technology 1)
[0093] A compressor drive device includes: an inverter device including an inverter circuit for converting DC to AC and a control unit; and a compressor including a motor connected to the inverter circuit and a piston reciprocating within a cylinder via the motor. The control unit includes: a multi-phase PWM signal generation unit capable of setting multiple carrier frequencies for driving the compressor; and a bottom dead center detection unit that detects the bottom dead center of the piston in the compressor, wherein the switching timing is the bottom dead center of the compressor when the carrier frequency is switched from a high frequency to a low frequency during the rotation of the compressor.
[0094] (Technology 2)
[0095] In the compressor drive device as described in Technology 1, the control unit sets the carrier frequency during acceleration to be higher than the carrier frequency during steady-state drive after acceleration ends when starting the compressor.
[0096] (Technology 3)
[0097] In the compressor drive device as described in Technology 1 or Technology 2, the control unit switches at least two carrier frequencies to control the rotational speed after the compressor is started.
[0098] (Technology 4)
[0099] The compressor drive device as described in any one of the technologies 1 to 3, wherein the control unit determines the switching of two or more carrier frequencies based on at least one of the actual rotational speed of the compressor and the input electrical power input to the inverter device.
[0100] (Technology 5)
[0101] In the compressor drive device as described in Technology 4, the control unit also increases the set carrier frequency as the actual rotational speed or the input electrical power input to the inverter device increases.
[0102] (Technology 6)
[0103] The compressor drive device according to any one of the technologies 1 to 5, wherein: the inverter circuit has a temperature sensor, and when the temperature of the drive element included in the inverter circuit reaches or exceeds a set temperature according to the temperature sensor, the control unit does not set the carrier frequency to a value higher than the current value.
[0104] Furthermore, the present invention is not limited to the embodiments described above. Various modifications can be made to the present invention within the scope of the claims. Embodiments obtained by appropriately combining the technical means described in different embodiments and variations are also included within the technical scope of the present invention.
[0105] Furthermore, based on the foregoing description, many modifications or other embodiments of the present invention will be apparent to those skilled in the art. Therefore, the foregoing description should be interpreted as merely illustrative, provided to demonstrate to those skilled in the art the best mode for carrying out the invention. Details that can substantially change its construction and / or function without departing from the spirit of the invention are included.
[0106] Industrial availability
[0107] This invention can be widely and appropriately applied to the field of driving compressors used in various refrigeration and freezing equipment. In particular, it can be appropriately applied to the field of compressor drive devices included in refrigeration and freezing equipment such as refrigerators and air conditioners.
[0108] Explanation of reference numerals in the attached figures
[0109] 1: Inverter device
[0110] 10: Inverter Circuit
[0111] 11: Drive circuit
[0112] 12: Current detection circuit
[0113] 13: Temperature sensor
[0114] 20: Control Department
[0115] 21: Arithmetic Department
[0116] 22: Carrier frequency setting unit
[0117] 23: PWM signal generation section
[0118] 24: Bottom dead center detection unit
[0119] 30: Compressor
[0120] 31: Brushless DC motor (electric motor)
[0121] 32: DC voltage source
[0122] 33: Crank mechanism
[0123] 34: Piston
[0124] 35: Cylinder.
Claims
1. A compressor drive device, characterized in that, include: An inverter device, comprising an inverter circuit for converting direct current to alternating current and a control unit; and The compressor includes an electric motor connected to the inverter circuit and a piston that reciprocates within a cylinder under the action of the electric motor. The control unit includes: A multi-phase PWM signal generation unit capable of setting multiple carrier frequencies for driving the compressor; and A bottom dead center detection unit that detects the bottom dead center of the piston in the compressor. When the carrier frequency is switched from a high frequency to a low frequency during the rotation of the compressor, the switching occurs at the bottom dead center of the compressor.
2. The compressor drive device as described in claim 1, characterized in that: When the compressor is started, the control unit sets the carrier frequency during acceleration to be higher than the carrier frequency during steady-state drive after acceleration.
3. The compressor drive device as described in claim 1, characterized in that: After the compressor is started, the control unit switches between at least two carrier frequencies to control the rotational speed.
4. The compressor drive device as described in claim 1, characterized in that: The control unit determines the switching of two or more carrier frequencies based on at least one of the actual speed of the compressor and the input electrical power input to the inverter device.
5. The compressor drive device as described in claim 4, characterized in that: The control unit increases the set carrier frequency as the actual rotational speed or the input electrical power to the inverter increases.
6. The compressor drive device according to any one of claims 1 to 5, characterized in that: The inverter circuit has a temperature sensor. If the temperature of the drive element included in the inverter circuit according to the temperature sensor reaches a temperature higher than the set temperature, the control unit will not set the carrier frequency to a value higher than the current value.