JP2024121966A - Compressor, air conditioner, and heating method - Google Patents

Abstract

To provide a compressor, an air conditioning device, and a warming method that can obtain a desired warming effect regardless of the position of a magnet at the time of stopping the compressor.SOLUTION: A compressor 21 includes a motor 30 comprising a plurality of coils and a magnet, a rotating shaft to be rotated by the motor 30, a compression mechanism for compressing fluid by using the rotation of the rotating shaft, lubricating oil to be supplied to a sliding part comprised in the compressor 21 through the inside of the rotating shaft, and a control unit 50 for generating rectangular wave signals for passing currents through the coils of the motor 30. The control unit 50 generates a rectangular wave signal for a predetermined coil so that a positional relation between the plurality of coils and the permanent magnet becomes a predetermined positional relation, and generating the rectangular wave signals for the respective coils in order to warm the lubricating oil via the rotating shaft after adjusting the position of the permanent magnet.SELECTED DRAWING: Figure 5

Description

The present invention relates to a compressor, an air conditioner, and a method for heating lubricating oil.

Compressors used in air conditioners use a refrigerant as a fluid, and lubricating oil flows through the system mixed with the refrigerant, lubricating various parts of the system, and is returned to the compressor. When the outside air temperature drops when the air conditioner is stopped, the refrigerant condenses, and since the liquid refrigerant is heavier than the lubricating oil, it accumulates at the bottom and forms a linear layer.

When the compressor is started in this state, the refrigerant in the lubricating oil, which has become low pressure due to the suction of the refrigerant, suddenly boils, causing the lubricating oil to foam and be discharged outside the compressor along with the refrigerant, lowering the lubricating oil level (oil foaming). This causes insufficient oil to be supplied to the sliding parts, resulting in poor lubrication. To prevent this from occurring, the lubricating oil is heated using a method that uses a heater or a method that utilizes the principles of electromagnetic induction heating.

Methods that use the principles of electromagnetic induction heating are less expensive than methods that use heaters, but to achieve the desired heating using the characteristics of permanent magnets and motor windings, it is necessary to pass a high-frequency alternating current through the motor's windings (coils) that is too high for the motor to keep up with in terms of rotational motion, and it is also necessary to adjust the amount of current.

The amount of current can be adjusted by changing the percentage of time that the current is on during one cycle of the PWM (Pulse Width Modulation) signal (DUTY). If the cycle of this PWM signal is made faster to create a high-frequency alternating current, the switching loss of the inverter elements increases, and it becomes necessary to take measures that increase costs, such as expanding the heat dissipation fins to dissipate heat.

Therefore, in order to reduce switching losses, a technology has been proposed that uses the current delay caused by the inductance of the motor windings to artificially shape the AC current (see, for example, Patent Document 1).

Chinese Patent Publication No. 107218711

However, in the above conventional technology, the heating effect differs depending on the position of the magnet in the electric motor, and there was a problem that the desired heating effect could not be obtained depending on the position of the magnet when the compressor was stopped.

In view of the above problems, the present invention provides an electric motor including a plurality of windings and magnets,
A rotating shaft rotated by an electric motor;
a compression mechanism that compresses a fluid by rotation of a rotating shaft;
Lubricating oil is supplied to a sliding part of the compressor through the rotating shaft;
and control means for generating a square wave signal for causing a current to flow through each winding of the motor;
A compressor is provided in which a control means generates a square wave signal for a predetermined winding so that the positional relationship between the multiple windings and the magnet is a predetermined positional relationship, adjusts the position of the magnet, and then generates a square wave signal for each winding to heat the lubricating oil via the rotating shaft.

According to the present invention, the desired heating effect can be obtained regardless of the position of the magnet when the compressor is stopped.

FIG. 1 is a diagram showing an example of the configuration of an air conditioning apparatus according to an embodiment of the present invention. FIG. 1 is a diagram showing an example of the configuration of a compressor used in an air conditioning apparatus. FIG. 1 shows an example of the configuration of an outdoor unit that utilizes the principle of electromagnetic induction heating. FIG. 4 is a diagram for explaining a PWM signal. FIG. 2 is a diagram showing an example of the configuration of a control unit included in the compressor. FIG. 1 is a diagram illustrating conventional heating control. FIG. 4 is a diagram for explaining an outline of the heating control. 6A and 6B are diagrams for explaining currents flowing in each phase in a preparation operation before a heating operation. 5A and 5B are diagrams for explaining PWM signals and currents flowing in each phase during a heating operation. 4 is a flowchart showing an example of the flow of the heating control. 13A and 13B are diagrams illustrating another example of currents flowing in each phase in the preparation operation before the heating operation.

Figure 1 shows an example of the configuration of an air conditioning device according to this embodiment. The air conditioning device 10 includes an indoor unit 11 that is installed in the space (indoors) where air conditioning is performed, and an outdoor unit 20 that is installed outdoors, and performs air conditioning by circulating a refrigerant as a fluid between the indoor unit 11 and the outdoor unit 20 and exchanging heat with the air in the room.

The indoor unit 11 and the outdoor unit 20 may each be configured with two or more units, and two or more indoor units 11 may be connected to one outdoor unit 20. The refrigerant may be a hydrofluorocarbon (HFC) or a hydrofluoroolefin (HFO). As the HFC, R32 (CH ₂ F ₂ ), R410A (CH ₂ F ₂ +C ₂ HF ₃ ), etc. may be used, and as the HFO, R1234yf (CF ₃ CF=CH ₂ ) etc. may be used.

The indoor unit 11 includes an indoor heat exchanger 12, an indoor fan 13, and an indoor fan drive motor 14. The indoor fan 13 is driven by the indoor fan drive motor 14, takes in indoor air, and sends it to the indoor heat exchanger 12. The indoor heat exchanger 12 has multiple heat transfer tubes through which a refrigerant flows, and is configured so that the sent-in air comes into contact with the surfaces of the multiple heat transfer tubes and exchanges heat with the refrigerant. The air that has been heat exchanged by the indoor heat exchanger 12 is sent out into the room.

The indoor unit 11 can also be equipped with various sensors for measuring the indoor temperature, an indoor expansion valve that reduces the pressure of the refrigerant and expands it, and can control the flow rate of the refrigerant.

The outdoor unit 20 includes a compressor 21, a four-way valve 22, an outdoor expansion valve 23, an outdoor heat exchanger 24, an outdoor fan 25, and an outdoor fan drive motor 26. The compressor 21 includes an accumulator 27 and is driven by a compressor drive motor to draw in low-pressure gas refrigerant from the accumulator 27, increase the pressure, and discharge it as high-pressure gas refrigerant. The accumulator 27 is a container for preventing liquid return to the compressor 21 during transients and for separating the liquid, and adjusts the refrigerant to an appropriate dryness. The dryness is the proportion of steam in wet steam, which indicates the mixed state of steam and microdroplets.

The four-way valve 22 is a valve that switches the direction of refrigerant flow depending on the operating state (operating mode) of the air conditioning device 10. The operating modes are cooling mode, heating mode, ventilation mode, etc. The outdoor expansion valve 23 is a valve that reduces the pressure of the high-pressure refrigerant and expands it, and is a valve that can control the flow rate of the refrigerant. The outdoor fan 25 is driven by the outdoor fan drive motor 26, takes in outdoor air, and sends it to the outdoor heat exchanger 24. Like the indoor heat exchanger 12, the outdoor heat exchanger 24 also has multiple heat transfer tubes through which the refrigerant flows, and is configured so that the sent-in air comes into contact with the surfaces of the multiple heat transfer tubes and exchanges heat with the refrigerant. The air that has been heat exchanged by the outdoor heat exchanger 24 is sent outside.

The outdoor unit 20 further includes a control device 28. The control device 28 is connected to the compressor 21, the four-way valve 22, the outdoor expansion valve 23, the indoor fan drive motor 14, and the outdoor fan drive motor 26, and controls these. The control device 28 controls the rotation speed of the compressor 21, the opening degree of the outdoor expansion valve 23, the rotation speed of the indoor fan drive motor 14, the rotation speed of the outdoor fan drive motor 26, etc. The control device 28 can perform these controls based on information detected by various sensors.

In cooling mode, the indoor heat exchanger 12 is used as an evaporator, and the outdoor heat exchanger 24 is used as a condenser, and the refrigerant sealed in the system is circulated in the order of the compressor 21, four-way valve 22, outdoor heat exchanger 24, outdoor expansion valve 23, indoor heat exchanger 12, four-way valve 22, accumulator 27, and compressor 21. In heating mode, on the other hand, the indoor heat exchanger 12 is used as a condenser, and the outdoor heat exchanger 24 is used as an evaporator, and the refrigerant sealed in the system is circulated in the order of the compressor 21, four-way valve 22, indoor heat exchanger 12, outdoor expansion valve 23, outdoor heat exchanger 24, four-way valve 22, accumulator 27, and compressor 21.

Here, the air conditioner 10 is given as an example of a device equipped with a compressor 21, but this is not limited, and a refrigerator, chiller unit, etc. may also be used. Furthermore, the control device 28 is not limited to the outdoor unit 20, and may be equipped in the indoor unit 11, or in both the indoor unit 11 and the outdoor unit 20. Furthermore, it may be provided as a central control panel, etc., separate from the indoor unit 11 and the outdoor unit 20.

Figure 2 shows an example of the configuration of the compressor 21 used in the air conditioning device 10. The compressor 21 includes a motor 30 having multiple coils and magnets as an electric motor, a rotating shaft (shaft) 31 rotated by the motor 30, a compression mechanism 32 that compresses the refrigerant by the rotation of the shaft 31, lubricating oil 33 supplied to the sliding parts of the compressor 21 through the shaft 31, and a control means that generates each square wave signal for passing a current through each coil of the motor 30. The compressor 21 stores the motor 30, the shaft 31, the compression mechanism 32, and the lubricating oil 33 in a sealed container 34.

The motor 30 is a three-phase motor that operates using three alternating currents with different phases, and includes a hollow cylindrical stator 30a having three coils as the multiple coils, and a rotor 30b that is rotatably arranged within the stator 30a and has a permanent magnet as the magnet. The shaft 31 is arranged at the center of the rotor 30b and rotates with the rotation of the rotor 30b. The coils of the three-phase motor are composed of three coils for the U phase, V phase, and W phase, and are arranged at positions shifted by 120° in a cross section centered on the shaft 31.

The compressor 21 includes a control unit that functions as a control means. The control unit may be implemented in the control device 28, or may be a device separate from the control device 28. The control unit receives a commercial power supply, converts AC current to DC current, generates a square wave signal, and generates a voltage (pulse wave) to be applied to the motor 30 based on the converted DC current and the generated square wave signal to pass a current through each coil of the motor 30.

The square wave signal is a PWM signal consisting of two levels, Hi and Low, such as an arbitrary positive voltage _Vcc and 0V, and is repeatedly turned on when Hi and off when Low. The PWM signal is a signal that applies a constant voltage when it is on (also called on time) and increases the current flowing through the coil, and stops applying the voltage when it is off (also called off time) and reduces the current flowing through the coil, controlling the average current to be constant. The control unit can adjust the amount of current flowing through the coil by changing the duty ratio of the PWM signal.

The three coils are positioned at positions offset by 120°, and the PWM signals are signals with a phase shift of 120°, so at any given time, a high voltage is applied to the coil of one of the three phases, generating an N pole, and the coils of the remaining two phases are at low voltage, generating an S pole, and the poles generated in each coil change over time. If the U phase, V phase, and W phase are positioned with a 120° offset in this order, the coil generating an N pole will change in the order U phase, V phase, W phase, U phase, and so on. The rotor 30b has a permanent magnet, and the S poles of the permanent magnets attract each other in the order of U phase, V phase, W phase, U phase, and so on, where the N poles are generated, to rotate in a certain direction.

The container 34 is a hollow container with a circular cross section and a long shape on one side, and the shaft 31 is disposed at the center of the cross section. The shaft 31 extends both upwards and downwards from the motor 30 along the longitudinal direction of the container 34, and is connected to the compression mechanism 32 disposed above the motor 30. The shaft 31 is hollow, and its lower end is immersed in the lubricating oil 33 stored at the bottom of the container 34 below the compression mechanism 32. The lubricating oil 33 is sucked up through the hollow interior by the rotation of the shaft 31, and is supplied from the upper end of the shaft 31 to the sliding parts of the compressor 21.

When the compressor 21 is a scroll compressor, the compression mechanism 32 compresses the refrigerant by fixing one of two spiral bodies, which are formed from two plate-shaped members into the same spiral shape, and moving the other in a circular motion, thereby changing the volume of the space partitioned by the two spiral bodies. Of the two spiral bodies, the one that is fixed is a fixed scroll, and the one that moves in a circular motion is an oscillating scroll. The refrigerant is sucked in through the suction port 35, compressed by the compression mechanism 32, and then discharged from the discharge port 36.

The sliding parts are the parts where the fixed scroll and the orbiting scroll come into contact, and the parts where the shaft 31 comes into contact with the bearings that rotatably support the shaft 31. The lubricating oil 33 is supplied to the sliding parts and lubricates the sliding parts. Excess lubricating oil 33 is returned to the bottom of the container 34 through holes provided in the bearings, etc.

The lubricating oil 33 is supplied between the fixed scroll and the oscillating scroll, and therefore functions as a medium to seal the gap between them so that the refrigerant does not leak out. It is also compatible with the refrigerant, and circulates through the system (refrigerant circuit) mixed with the refrigerant, returning to the compressor 21. While circulating through the system, the lubricating oil 33 lubricates parts with sliding parts such as the outdoor expansion valve 23, and seals gaps such as piping joints to eliminate them.

Here, the compressor 21 has been described as a scroll compressor, but the compressor 21 may also be a rotary compressor that contains a motor 30, a shaft 31, a compression mechanism 32, and lubricating oil 33 in a container 34.

However, when the above-mentioned oil foaming occurs, the oil supply to the sliding parts becomes insufficient, resulting in poor lubrication, so it is necessary to heat the lubricating oil 33 using a method that uses a heater or a method that utilizes the principle of electromagnetic induction heating.

Therefore, it is possible to use a method that uses a heater for heating, but this requires providing a heater around the container 34, which increases the number of parts and costs. In contrast, a method that uses the principle of electromagnetic induction heating can be provided at a lower cost than a method that uses a heater, since heating can be performed using parts currently included in the compressor 21. For this reason, a method that uses the principle of electromagnetic induction heating is more preferable.

Here, we will briefly explain the principle of electromagnetic induction heating. When high-frequency alternating current is passed through a coil, magnetic field lines are generated around it. When an electrically conductive metal is placed near the generated magnetic field lines, eddy currents flow within the metal in a direction that opposes changes in the magnetic flux. Because metals have electrical resistance, eddy currents flowing through the electrical resistance generate Joule heat, which heats the metal.

With reference to FIG. 3, an example of the configuration of an outdoor unit 20 that utilizes the principle of electromagnetic induction heating will be described. The outdoor unit 20 includes a compressor 21 and a control device 28. The outdoor unit 20 also includes an outdoor heat exchanger 24, etc., but the outdoor heat exchanger 24, etc. are omitted here. The control device 28 includes an ODU (Out Door Unit) 40 as an example of information processing means, and an INV (Inverter) 41 as an example of conversion means. A commercial power source 42 supplies AC power to the ODU 40 and the INV 41.

The ODU 40 starts up when it receives AC power from the commercial power source 42, generates a PWM signal, and outputs the PWM signal to the INV 41 via the transmission line 43. The INV 41 generates a pulse wave to be applied to the motor 30 of the compressor (CMP) 21 based on the AC power from the commercial power source 42 and the PWM signal output from the ODU 40.

The motor 30 includes coils 44-46 of phases U, V, and W. The pulse wave generated by the INV 41 is applied to each phase of the motor 30, and when current flows through the coils 44-46 of each phase, magnetic field lines are generated as described above, which generates eddy currents in the nearby rotor 30b made of a metal material, generating Joule heat and heating the rotor 30b.

The heat of the rotor 30b is transferred to the shaft 31, which is also made of a metal material and is in contact with the rotor 30b, and then transferred from the shaft 31 to the lubricating oil 33, heating the lubricating oil 33. The heating of the lubricating oil 33 reduces the amount of liquid refrigerant that condenses at the bottom of the lubricating oil 33, suppressing the occurrence of oil foaming.

Fig. 4 is a diagram for explaining a PWM signal. In Fig. 4, _Vu indicates a desired voltage waveform to be applied to the U phase, _Vv indicates a desired voltage waveform to be applied to the V phase, and _Vw indicates a desired voltage waveform to be applied to the W phase. These desired voltage waveforms are voltage waveforms given to achieve a predetermined duty ratio. _Vc indicates a voltage waveform of a carrier, which is a triangular wave.

FIG. 4 compares the voltage levels of _Vu , _Vv , and _Vw with the voltage level of _Vc . When the voltage levels of _Vu , Vv, and _Vw are higher than the voltage level of _Vc , U+, V ₊ , and W+ indicate Hi, and when they are lower than the voltage level of _Vc , U-, V-, and W- indicate Low.

Therefore, by setting a specific duty ratio, applying a desired voltage waveform, and comparing it with the carrier voltage waveform, it is possible to generate a PWM signal with a specific duty ratio in which high and low voltage levels are repeated.

Figure 5 is a diagram showing an example of the configuration of the control unit provided in the compressor 21. The control unit 50 includes a power supply circuit (also called a rectifier circuit) 51 as an example of a first conversion circuit included in the INV 41, an inverter bridge circuit 52 as an example of a second conversion circuit included in the INV 41, and a microcomputer 53 as an example of an ODU 40.

The rectifier circuit 51 is connected to the commercial power supply 42 and converts AC power from the commercial power supply 42 into DC power using a rectifier diode 54, a smoothing capacitor 55, etc. The rectifier diode 54 is an example of a rectifier means for converting AC power into DC power, and the smoothing capacitor 55 is an example of a smoothing means for smoothing the voltage of the converted DC power.

The inverter bridge circuit 52 includes switching elements 56 as an example of a switching means for switching between energized (ON) and de-energized (OFF), and operates the switching elements 56 based on the DC power from the rectifier circuit 51 and the PWM signal from the microcomputer 53 to generate voltages ( _Vu , _Vv , _Vw ) as three pulse waves to be applied to the motor 30. The switching elements 56 are, for example, field effect transistors (MOSFETs) or the like.

The microcomputer 53 includes a motor drive control unit 57, a heating control unit 58, a signal generation unit 59, and a control switching unit 60. The microcomputer 53 includes at least a processor and a memory, and the memory stores a control program. The processor reads and executes the control program from the memory to realize each of the functional units, such as the motor drive control unit 57. Note that all of these functional units may be realized by the control program, or some or all of them may be realized by hardware, such as an ASIC (Application Specific Integrated Circuit).

The motor drive control unit 57 is connected to the signal generation unit 59 by the control switching unit 60 while the motor 30 is driving, and calculates and outputs the on/off pulse width of the PWM signal to be applied to the switching element 56 that constitutes the inverter bridge circuit 52 based on the measurement results of various sensors that measure the discharge temperature of the compressor 21, the indoor temperature, etc., to control the driving of the motor 30. The motor drive control unit 57 can output a duty ratio as a calculation result.

The heating control unit 58 is connected to the signal generating unit 59 by the control switching unit 60 while the motor 30 is stopped, calculates the on/off pulse width of the PWM signal to be applied to the switching element 56, and outputs the duty ratio as the calculation result to perform heating control. The heating control unit 58 also adjusts the duty ratio of at least one of the three phases as necessary to adjust the amount of current flowing through the coil. The lubricating oil 33 is heated while the motor 30 is stopped in order to prevent oil foaming from occurring the next time the motor 30 is started.

The signal generating unit 59 is, for example, a PWM generating timer, and generates a PWM signal based on the duty ratio output from the motor drive control unit 57 and the heating control unit 58. When driving the motor 30, the control switching unit 60 switches the connection to connect to the motor drive control unit 57, and when stopping the drive, switches the connection to connect to the heating control unit 58.

A shunt resistor 61 is provided between the rectifier circuit 51 and the inverter bridge circuit 52 to measure the DC current input from the rectifier circuit 51 to the inverter bridge circuit 52. In addition, the DC voltage can be measured by measuring the voltage of the smoothing capacitor 55. The voltage and current of the U-phase, V-phase, and W-phase of the motor 30 can be calculated based on the above DC current and DC voltage and the PWM signal. The calculation method is already known, so details thereof will be omitted here.

To achieve the desired heating using a method that utilizes the principles of electromagnetic induction heating, it is necessary to pass a high-frequency alternating current, but as mentioned above, this increases the switching loss of the switching element 56, and requires cost-increasing measures such as expanding the heat dissipation fins.

To avoid this, the conventional technology mentioned above uses the current delay caused by the inductance of the motor coil to artificially shape the AC current and reduce switching losses.

A brief explanation of the conventional technology will be given with reference to FIG. 6. In this technology, one current cycle is divided into multiple sections, and when generating a PWM signal, half of the divided sections are turned on and the remaining half are turned off. In the example shown in FIG. 6, one current cycle is divided into six sections, three sections are turned on, and the remaining three sections are turned off. This generates a PWM signal with a 50% duty, and flows a positive AC current in the on section and a negative AC current in the off section.

Using this division into sections, PWM signals for each phase are generated with a phase shift of 120° (two sections) for the U, V, and W phases. This makes it possible to generate a three-phase AC current while reducing the switching period to the current period.

With this technology, the duty ratio of only one of the three phases, namely the U phase, can be adjusted from 50% to 33.3%. If the duty ratios of all three phases are 50%, when the asymmetric pulse waves of the U and V phases, the V and W phases, and the W and U phases are superimposed, there are three levels: high level, intermediate level, and low level, and the duration of the high level and the low level are the same. Therefore, no offset voltage is generated due to the difference between the duration of the high level and the duration of the low level.

On the other hand, if the duty ratio of the U phase is changed from 50%, an offset voltage is generated, which is applied as a DC amount. Therefore, if the amount of heating is insufficient, the duty ratio of the U phase can be changed to apply a DC amount, increasing the copper loss in the copper coil and ensuring the amount of heating. Copper loss is the loss that occurs due to the resistance component of the coil.

In this way, the duty ratio of the PWM signal can be adjusted to adjust the amount of current flowing through the coil.

The heating effect of the lubricating oil 33 varies depending on the characteristics of the permanent magnet and coil, and the position of the permanent magnet when the compressor is stopped. Under the Radio Law, approval from the Minister of Internal Affairs and Communications is required if the power exceeds 50 W. For this reason, to use it without approval, it is necessary to adjust the current while measuring the power as the permanent magnet position is changed. This means that when a motor with a wide range of characteristics is used, the power fluctuates greatly and it becomes difficult to adjust the current, making it difficult to obtain the desired heating.

In the compressor 21 according to this embodiment, the control device 28 generates a square wave signal for passing current through a specified phase so that the positional relationship between the three-phase coils and the permanent magnets is a specified positional relationship, adjusts the position of the permanent magnets, and then generates each PWM signal for passing current through each phase to heat the lubricating oil 33 via the shaft 31. As a result, when the motor 30 is driven, the permanent magnets are positioned to be in specified positions, so that even when motors with a wide range of characteristics are used, power fluctuations are small, current adjustments are easy, and the desired heating can be obtained.

The heating control by the control unit 50 will be described with reference to FIG. 7. The heating control unit 58 included in the control unit 50 performs heating control when the compressor is stopped. In the heating control, a PWM signal is generated for a specific coil and a current is passed through the specific coil before the start of a heating operation that warms the lubricating oil 33. The specific coil is a coil of a specific phase, for example, the U-phase coil. The coil of the specific phase is not limited to the U-phase, and may be a V-phase or W-phase coil. The current flowing through the specific coil is a direct current, and provides a torque sufficient to move the rotor of the motor 30.

In Figure 7, multiple rectangles are shown in an array, which indicate the on-time of the PWM signal, and the spaces between the rectangles indicate the off-time of the PWM signal. Before the heating operation begins, when a current is passed through the U-phase coil, the U-phase becomes an N pole, which attracts the S pole of the permanent magnet, and the rotor 30b rotates so that the S pole of the permanent magnet approaches the U-phase.

The rotor 30b will attempt to rotate past the U-phase due to its rotational momentum. For this reason, it is desirable to make the magnetic force of the north pole generated in the U-phase equal to the magnetic force of the south pole generated in the V-phase and W-phase, suppress the rotation, and fix the U-phase, which has become the north pole, at a predetermined position facing the south pole of the permanent magnet. Therefore, current is passed only through the U-phase coil, and the current flowing through the U-phase is split into half and half and flows through the V-phase and W-phase coils. In other words, as shown in Figure 8, the V-phase and W-phase are made to receive half of the current of the U-phase, with the opposite (negative) flow.

Specifically, of the upper and lower switching elements 56 used to apply voltage to the U phase, only the upper one is driven on/off by a PWM signal. For the V and W phases, only the lower switching element 56 is driven on/off by a PWM signal. By controlling in this way, the permanent magnet can be fixed in a specified position.

The position when the permanent magnet is fixed is set as the position at the start of the heating operation, and a three-phase PWM signal with AC output only is applied, current flows through the U-phase, V-phase, and W-phase coils, and the desired heating of the lubricating oil 33 can be achieved by electromagnetic induction heating. In this case, because of the AC output, both the upper and lower switching elements 56 for the U-phase coil are alternately turned on and off, and the V-phase and W-phase coils are operated in the same way.

As shown in FIG. 9, the heating control unit 58 generates one PWM signal for every three cycles of the carrier signal, and controls it to form one cycle of AC current to be passed through the coil of the motor 30. The carrier signal is divided into a first half and a second half into six sections, and each section is a fixed section for turning the PWM signal on and off.

All six sections of the U, V, and W phases may be fixed sections where the PWM signal is turned on/off, or one section of the U, V, or W phase may be a duty ratio adjustment section where the PWM signal is switched on/off at any timing, allowing the amount of current to be adjusted. Note that by changing the duty ratio in the duty ratio adjustment section, the amount of DC current can be added.

However, if a three-phase PWM signal with only AC output is applied, or if a DC amount is added to it, the balance of magnetic forces between the phase fixed in a specific position when positioned, for example the U phase, and the other two phases, the V phase and the W phase, will be lost, resulting in a magnitude relationship between the magnetic forces, causing the rotor 30b to rotate. Therefore, it is necessary to adjust the duty ratio so that the balance of magnetic forces is not lost.

Specifically, the duty ratio of the fixed phase is set to a value smaller than the duty ratios of the other two phases, and a DC current is applied to the fixed phase. If the fixed phase is the U phase, applying a DC current to the U phase generates a N pole in the U phase, and the S pole of the permanent magnet can be fixed in a position facing the U phase coil.

Figure 10 is a flow chart showing an example of the flow of this heating control. The heating of the lubricating oil 33 by this heating control can start when the motor 30 is stopped, but it may also start at any time while the motor 30 is stopped, or when the outside air temperature while the motor 30 is stopped falls below a first threshold value. If a sensor or the like is provided to measure the temperature of the lubricating oil 33, an example of an arbitrary time while the motor 30 is stopped is when the temperature of the lubricating oil 33 measured by the sensor or the like falls below a second threshold value.

Starting from step 100, in step 101, the heating control unit 58 sets the duty ratio of the PWM signal to be applied to the switching element 56 for a specified phase so that the positional relationship between the three-phase coils and the permanent magnet is a specified positional relationship, and the signal generating unit 59 generates a PWM signal for the specified phase based on the duty ratio.

In step 102, the inverter bridge circuit 52 generates a pulse wave of a specified phase based on the DC power from the rectifier circuit 51 and the PWM signal input from the signal generator 59, applies it to a specified phase of the motor 30, and positions the permanent magnet so that the three-phase coils and the rotor permanent magnet have a specified positional relationship. For example, the permanent magnet is positioned so that the S pole of the permanent magnet is positioned opposite the U-phase coil as the specified phase.

When the permanent magnet positioning is complete, the heating operation is started, and in step 103, the heating control unit 58 sets the duty ratio of the PWM signal to be applied to the three-phase switching element 56, and the signal generation unit 59 generates the PWM signal for the three phases based on the duty ratio.

In step 104, the inverter bridge circuit 52 generates a three-phase pulse wave based on the DC power from the rectifier circuit 51 and the PWM signal input from the signal generating unit 59, and inputs it to the three-phase coil. An AC current flows in the three-phase coil, and the lubricating oil 33 is heated via the shaft 31 by electromagnetic induction heating.

The control by the heating control unit 58 is performed until the control switching unit 60 switches the connection with the signal generating unit 59 from the heating control unit 58 to the motor drive control unit 57.

Figure 11 is a diagram explaining another example of the current flowing through each phase in the preparatory operation before the heating operation. Figure 11(a) shows a pattern similar to Figure 8 in which a positive current flows through the U phase, and a negative current that is half the current of the U phase flows through the V and W phases, with the flow direction reversed. Figure 11(b) shows a pattern in which a positive current flows through the U and V phases, and a negative current that is twice as large as the current of the U phase flows through the W phase.

Figure 11(c) shows a pattern in which a positive current is passed through the V phase, and a negative current that is half that of the V phase is passed through the U and W phases, while Figure 11(d) shows a pattern in which a negative current is passed through the U phase, and a positive current that is half that of the U phase is passed through the V and W phases. Figure 11(e) shows a pattern in which a positive current is passed through the W phase, and a negative current that is half that of the W phase is passed through the U and V phases, while Figure 11(f) shows a pattern in which a negative current is passed through the V phase, and a positive current that is half that of the V phase is passed through the U and W phases.

By passing a current in any of these patterns, the permanent magnet can be fixed in place.

As explained above, by providing the compressor, air conditioner, and heating method of the present invention, it is possible to use motors with a wide range of characteristics and provide them at low cost. In addition, there is little fluctuation in power during heating operation, and the amount of current can be easily adjusted, making it possible to achieve the desired heating.

Though the compressor, air conditioner, and heating method of the present invention have been described in detail using the above-mentioned embodiments, the present invention is not limited to the above-mentioned embodiments, and can be modified within the scope of what a person skilled in the art can imagine, such as other embodiments, additions, modifications, and deletions, and any aspect is within the scope of the present invention as long as it achieves the functions and effects of the present invention.

10...Air conditioning device 11...Indoor unit 12...Indoor heat exchanger 13...Indoor fan 14...Indoor fan drive motor 20...Outdoor unit 21...Compressor 22...Four-way valve 23...Outdoor expansion valve 24...Outdoor heat exchanger 25...Outdoor fan 26...Outdoor fan drive motor 27...Accumulator 28...Control device 30...Motor 30a...Stator 30b...Rotor 31...Shaft 32...Compression mechanism 33...Lubricant 34...Container 35...Suction port 36...Discharge port 40...ODU
41...INV
42... Commercial power supply 43... Transmission lines 44 to 46... Coil 50... Control unit 51... Rectifier circuit 52... Inverter bridge circuit 53... Microcomputer 54... Rectifier diode 55... Smoothing capacitor 56... Switching element 57... Motor drive control unit 58... Heating control unit 59... Signal generation unit 60... Control switching unit 61... Shunt resistor

Claims (8)

an electric motor having a plurality of windings and magnets;
A rotating shaft rotated by the electric motor;
a compression mechanism that compresses a fluid by rotation of the rotating shaft;
Lubricating oil is supplied to a sliding part of the compressor through the rotating shaft;
and control means for generating a square wave signal for applying a current to a winding of the motor;
The control means generates a square wave signal for a predetermined winding so that a positional relationship between the plurality of windings and the magnet becomes a predetermined positional relationship, and after adjusting the position of the magnet, generates a square wave signal for each winding to heat the lubricating oil via the rotating shaft. The compressor according to claim 1, wherein the control means includes a plurality of switching means for switching between energized and de-energized states, and when adjusting the position of the magnet, the control means switches which of the switching means to be operated based on the rectangular wave signal to change the amount of current flowing through the plurality of windings. The compressor according to claim 2, wherein the control means switches the switching means to be operated each time the compressor stops and a heating operation is performed to warm the lubricating oil. The compressor according to claim 1, wherein the control means generates each of the square wave signals so that the period of each of the square wave signals is equal to the period of the current flowing through each of the windings after adjusting the position of the magnet. The compressor according to claim 4, wherein the control means adjusts the duty ratio of at least one of the rectangular wave signals. The control means
A first conversion means for converting AC power from a commercial power source into DC power;
a second conversion means for generating a voltage to be applied to the electric motor so as to cause a current to flow through a winding of the electric motor, based on the DC power and the rectangular wave signal;
a signal generating means for generating a square wave signal for generating a voltage to be applied to the electric motor;
2. The compressor according to claim 1, further comprising a heating control means for setting a duty ratio for generating said square wave signal. An air conditioning apparatus including a compressor, the compressor comprising:
an electric motor having a plurality of windings and magnets;
A rotating shaft rotated by the electric motor;
a compression mechanism that compresses a fluid by rotation of the rotating shaft;
Lubricating oil is supplied to a sliding part of the compressor through the rotating shaft;
and control means for generating a square wave signal for applying a current to a winding of the motor;
The control means generates a rectangular wave signal for a specified winding so that the positional relationship between the multiple windings and the magnet is a specified positional relationship, adjusts the position of the magnet, and then generates a rectangular wave signal for each winding to heat the lubricating oil via the rotating shaft. A method for heating lubricating oil in a compressor including an electric motor having a winding and a magnet, a rotating shaft rotated by the electric motor, a compression mechanism that compresses a fluid by rotation of the rotating shaft, lubricating oil supplied to a sliding part of the compressor through the inside of the rotating shaft, and control means for generating a square wave signal for passing a current through a winding of the electric motor in order to heat the lubricating oil via the rotating shaft, the method comprising:
the control means generating a rectangular wave signal for a predetermined winding so that a positional relationship between the plurality of windings and a magnet is set to a predetermined positional relationship;
after adjusting the position of the magnet, the control means generates a square wave signal for each of the windings to heat the lubricating oil via the rotating shaft;
applying a voltage generated by a square wave signal to each of the windings to the electric motor, and heating the lubricating oil via the rotating shaft by electromagnetic induction heating.