CN111664605A

CN111664605A - Air conditioner

Info

Publication number: CN111664605A
Application number: CN202010090255.7A
Authority: CN
Inventors: 黑崎真由; 高野玲央; 小仓洋寿; 上田和弘; 尾花紫织
Original assignee: Hitachi Johnson Controls Air Conditioning Inc
Current assignee: Hitachi Johnson Controls Air Conditioning Inc
Priority date: 2019-03-08
Filing date: 2020-02-13
Publication date: 2020-09-15
Anticipated expiration: 2040-02-13
Also published as: JP2020143871A; CN111664605B

Abstract

The invention provides an air conditioner, which is a four-way valve capable of driving the air conditioner with a low-cost structure. An air conditioner is provided with: a charge storage unit (50) having first and second capacitors (52, 54) connected in series via one end (58) of an excitation coil (10) of a four-way valve (8); a rectifier circuit (40) that rectifies an alternating-current voltage and charges the charge storage unit (50); a switch unit (70) which is connected in parallel with the charge accumulation unit (50) and has first and second switching elements (72, 74) connected in series via the other end (78) of the excitation coil (10); and a control unit (24) that drives the first switching element (72) by means of a first PWM signal (S10) when the excitation coil (10) is energized in the first direction (Dr), and drives the second switching element (74) by means of a second PWM signal (S12) when the excitation coil (10) is energized in the second direction (Da).

Description

Air conditioner

Technical Field

The present invention relates to an air conditioner.

Background

As background art in this field, claim 1 of the following patent document 1 describes that "a refrigerant control valve is characterized by comprising: a coil wound into a cylinder; a plunger guided in a predetermined direction in a magnetic field generated by excitation of the coil; a spring that guides the plunger in a direction opposite to the predetermined direction; a permanent magnet that is excited by the coil and holds the plunger at a position in a predetermined direction against a force of the spring when the plunger is guided in the predetermined direction by a predetermined amount or more; a member that switches a flow of refrigerant based on a position of the plunger; an energization switching unit that cuts an energization direction of the dc power to the coil in a forward direction or a reverse direction; and an intermittent control unit that intermittently supplies the coil with the forward or reverse direct-current power, wherein the refrigerant control valve is configured to move the plunger by a magnetic field generated by a permanent magnet and a magnetic field generated by the forward or reverse direct-current power intermittently supplied to the coil. ".

Patent document 2 describes "a free-cooling/heating air conditioner including a four-way valve 3 that switches an operation mode by reversing by supplying a switching direct current in a predetermined direction to an exciting coil 3a for a predetermined supply time, at least one of a compressor inverter (inverter)12 and an outdoor fan inverter 14 that control the rotation speeds of a compressor 2 and an outdoor fan 7, respectively. The air conditioner includes an external temperature sensor 20 for detecting an external temperature, and a four-way valve driving device 21 for supplying a direct current for switching a four-way valve to an excitation coil 3a of the four-way valve by using switching elements TR1 to TR6 of an inverter 14 for an outdoor fan, and changing a time period for which the excitation coil is energized in accordance with the external temperature detected by the external temperature sensor. ".

Patent documents 1 and 2 describe a drive circuit for driving a four-way valve. These drive circuits include a power relay that turns on/off a current supplied to the four-way valve. However, since the power relay is expensive, there is a problem that the cost increases when the power relay is used.

Patent document 1: japanese patent No. 3369808

Patent document 2: japanese laid-open patent publication No. 2002-372322

Disclosure of Invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide an air conditioner capable of driving a four-way valve with a low-cost configuration.

In order to solve the above problem, an air conditioner according to the present invention includes: a charge accumulation unit having first and second capacitors connected in series via one end of an excitation coil of a four-way valve; a rectifier circuit that rectifies an alternating-current voltage and charges the charge storage unit; a switch unit connected in parallel to the charge accumulation unit and having first and second switching elements connected in series via the other end of the excitation coil; and a control unit that drives the first switching element by a first PWM signal when the exciting coil is driven in a first direction, and drives the second switching element by a second PWM signal when the exciting coil is driven in a second direction.

According to the present invention, the four-way valve can be driven by a low-cost structure.

Drawings

Fig. 1 is a diagram of a refrigerant cycle system of an air conditioner according to a first embodiment of the present invention.

Fig. 2 is a block diagram showing a configuration of a power supply unit according to the first embodiment.

Fig. 3 is a circuit diagram of the predriver in the first embodiment.

Fig. 4 is a waveform diagram of a voltage applied to the exciting coil.

Fig. 5 is a block diagram showing the configuration of a power supply unit in the first comparative example.

Fig. 6 is a block diagram showing a configuration of a power supply unit in a second comparative example.

Fig. 7 is a block diagram showing a configuration of a power supply unit according to the second embodiment.

Description of the reference numerals

A 8-four-way valve; 10-a field coil; 24-a control section; a 40-voltage doubler rectifier circuit (rectifier circuit); 50-a charge accumulation unit; 52-electrolytic capacitor (first capacitor); 54-electrolytic capacitor (second capacitor); 58-connection point (one end); 60-voltage sensor (voltage measuring part); 70-a switching section; 72-switching element (first switching element); 74-switching element (second switching element); 78-connection point (other end); 82-inverter (compressor inverter); 84-inverter (fan inverter); 92-a permanent magnet; 94-a plunger; 96-force application (safety) means; 102-photocoupler (drive); 114-electrolytic capacitor (third capacitor); 900-air conditioner; 961-a compressor; 965-outdoor fan; -a direction of departure (first direction); da-adsorption direction (second direction); s10 — drive signal (first PWM signal); s12 — drive signal (second PWM signal); vc-dc voltage (output voltage).

Detailed Description

[ Structure of self-holding four-way valve ]

As a premise of each embodiment described later, a self-holding four-way valve applied to each embodiment will be described. In a refrigeration cycle of an air conditioner, the flow direction of a refrigerant is largely divided into two systems of a refrigeration/dehumidification/defrost cycle and a heating cycle. As a means for realizing this, for example, a solenoid valve called a four-way valve as shown in patent document 1 is generally used.

Such a four-way valve includes, for example: a cylinder connected to 4 pipes, a valve body provided inside the cylinder and switching a coupling relationship between the pipes, a pilot valve for moving the valve body by a differential pressure, an iron core called a plunger for generating the differential pressure inside the pilot valve, an excitation coil for exciting the plunger, a permanent magnet for biasing the plunger in a direction of adsorbing or separating the plunger according to an excitation direction of the plunger, a biasing member (for example, a coil spring) for biasing the plunger in a direction of separating the permanent magnet, and 3 capillaries for transmitting the differential pressure generated by the pilot valve to the cylinder.

In the four-way valve described above, the position of the plunger is moved by changing the direction of the current flowing through the exciting coil, and the pressure of 1 of the 3 capillaries is changed according to the position. The valve body in the cylinder is configured to be operated by the pressure difference between the 3 capillaries. As described above, the refrigerant control valve (four-way valve) of patent document 1 includes the "intermittent control unit that intermittently energizes the coil with the dc power in the forward direction or the reverse direction", but due to recent improvement in energy saving awareness, a self-holding type four-way valve that can hold the plunger position at a constant position without intermittently energizing the exciting coil is often used. It is assumed that such a self-holding four-way valve is applied to each embodiment described later.

In the self-holding four-way valve, a current in a predetermined direction (hereinafter referred to as a "attracting direction") is applied to the exciting coil so that the plunger is attracted to the permanent magnet. In this way, the plunger is attracted to the permanent magnet by the electromagnetic force generated by the magnetic fields of the exciting coil and the permanent magnet being superposed against the biasing member and the frictional force, and the plunger is thereby made stationary. This state is hereinafter referred to as "adsorption state". After the plunger is attracted, the exciting coil is powered off. Thus, even if the coil magnetic field disappears, the attractive state of the plunger can be maintained against the reaction force of the urging member by the resultant force of the magnetic force of the permanent magnet and the frictional force.

On the other hand, when the plunger is separated from the permanent magnet, a current in a direction opposite to the attracting direction (hereinafter, referred to as a separating direction) is caused to flow through the exciting coil. In this way, the direction of the magnetic field generated by the exciting coil and the direction of the magnetic field generated by the permanent magnet are opposite, and the plunger is separated from the permanent magnet by the force generated by the biasing member, so that the plunger is stationary. This state is hereinafter referred to as "leaving state".

However, in such a self-holding four-way valve, a residual magnetic field may be generated in a member around the plunger. When a residual magnetic field is generated, the plunger may be attracted by the residual magnetic field to adversely affect the operation of the four-way valve, and therefore, the smaller the residual magnetic field, the better. In order to suppress the residual magnetic field, it is preferable to make the current flowing in the separating direction of the exciting coil smaller than the current flowing in the attracting direction. More specifically, it is considered that a predetermined voltage source is maintained and connected to the exciting coil when a current flows in the attracting direction, and a resistor is connected in series to the exciting coil and the voltage source is connected to the series circuit when a current flows in the separating direction.

[ first embodiment ]

Structure of the first embodiment

(integral Structure of air conditioner)

Fig. 1 is a diagram of a refrigerant cycle system of an air conditioner 900 according to a first embodiment of the present invention. As shown in fig. 1, the air conditioner 900 of the present embodiment includes an outdoor unit 960 and an indoor unit 970, and further includes a gas pipe 982 and a liquid pipe 984 for connecting the both.

The outdoor unit 960 includes: a compressor 961, a four-way valve 8, an outdoor heat exchanger 963, and an outdoor expansion valve 964. These are connected in sequence by piping (no reference numeral). The outdoor unit 960 includes an outdoor fan 965 and an outdoor fan motor 16. The outdoor fan 965 is rotationally driven by the outdoor fan motor 16 to cool the outdoor heat exchanger 963.

In addition, indoor unit 970 includes: an indoor heat exchanger 973, and an indoor expansion valve 974. Both are connected to each other by piping (no reference numeral). Indoor unit 970 includes an indoor fan 975 and an indoor fan motor 976. The indoor fan 975 is rotationally driven by an indoor fan motor 976 to blow air to the indoor heat exchanger 973. The four-way valve 8 provided in the outdoor unit 960 switches between a cooling operation and a heating operation. The outdoor expansion valve 964 and the indoor expansion valve 974 reduce the pressure of the refrigerant to a low temperature and a low pressure.

In fig. 1, arrows along solid lines shown in pipes such as the gas pipe 982 and the liquid pipe 984 indicate the flow of the refrigerant during the cooling operation of the air conditioner 900.

In the cooling operation, as shown by a solid line, the four-way valve 8 communicates the discharge side of the compressor 961 with the outdoor heat exchanger 963, and communicates the suction side of the compressor 961 with the gas pipe 982. The refrigerant discharged from the compressor 961 is in a high-temperature high-pressure gas state, passes through the four-way valve 8, and flows to the outdoor heat exchanger 963. The gaseous refrigerant flowing into the outdoor heat exchanger 963 exchanges heat with outdoor air supplied by the outdoor fan 965, is condensed, and becomes a liquid refrigerant. The liquid refrigerant passes through the outdoor expansion valve 964 and the liquid pipe 984 in the fully opened state, and flows into the indoor unit 970.

The liquid refrigerant flowing into indoor unit 970 is decompressed by indoor expansion valve 974, and becomes a low-temperature low-pressure gas-liquid mixture refrigerant. The low-temperature and low-pressure gas-liquid mixed refrigerant flows into the indoor heat exchanger 973, exchanges heat with indoor air supplied by the indoor fan 975, evaporates, and turns into a gaseous refrigerant. At this time, the indoor air is cooled by latent heat of evaporation of the gas-liquid mixed refrigerant, and cool air is sent indoors. Thereafter, the gaseous refrigerant flowing out of the indoor unit 120 passes through the gas pipe 982 and returns to the outdoor unit 960. The gaseous refrigerant returned to the outdoor unit 960 passes through the four-way valve 8, is sucked into the compressor 961, and is compressed again therein, thereby forming a series of refrigeration cycles.

The four-way valve 8 is the above-described self-holding four-way valve, and includes: an exciting coil 10, a permanent magnet 92, a plunger 94, an urging member 96, and a valve body 98. The exciting coil 10 excites the plunger 94 according to the direction of the supplied current. The permanent magnet 92 attracts or separates the plunger 94 according to the excitation direction of the plunger 94. The biasing member 96 is, for example, a coil spring, and biases the plunger 94 in a direction away from the permanent magnet 92. The valve body 98 switches the connection relationship of the pipes during the cooling operation and the heating operation.

The four-way valve 8, which is a self-holding four-way valve, has two states, i.e., an "adsorption state" and a "separation state" depending on the positional relationship between the plunger 94 and the permanent magnet 92, one of which corresponds to a cooling operation and the other of which corresponds to a heating operation. The compressor 961 includes: a compression mechanism 14 for compressing the refrigerant, and a compressor motor 12 for rotationally driving the compression mechanism 14. The power supply unit 20 receives ac power from an ac power supply 22 such as a commercial power supply, and drives the excitation coil 10, the compressor motor 12, the outdoor fan motor 16, and the like. The control unit 24 controls the power supply unit 20 and the like.

(Power supply section 20)

Fig. 2 is a block diagram showing the configuration of the power supply unit 20, and as shown in the drawing, the power supply unit 20 includes: a noise filter 30, a reactor 32, a voltage doubler rectifier circuit 40 (rectifier circuit), a charge storage unit 50, a voltage sensor 60, a predriver 62, a switch unit 70, a current detection unit 80, an inverter 82 (compressor inverter), and an inverter 84 (fan inverter).

The noise filter 30 suppresses leakage of noise to the ac power supply 22. The voltage doubler rectifier circuit 40 includes a diode 42 and a diode 44 connected in series thereto. The charge storage unit 50 includes an electrolytic capacitor 52 (first capacitor) and an electrolytic capacitor 54 (second capacitor) connected in series thereto, and the charge storage unit 50 is connected in parallel to the voltage doubler rectifier circuit 40. The connection point of the

diodes

42 and 44 is connected to the output terminal 30b of the noise filter 30. One end of the reactor 32 is connected to the other output terminal 30a of the noise filter 30, and a connection point 58 (one end) between the other end of the reactor 32 and the

electrolytic capacitors

52 and 54.

The voltage sensor 60 (voltage measuring unit) measures the dc voltage Vc, which is the terminal voltage of the charge accumulation unit 50, and outputs the measurement result to the control unit 24. The switch unit 70 includes a switching element 72 (first switching element), a switching element 74 (second switching element) connected in series with the switching element via a connection point 78 (the other end), and

reflux diodes

73 and 75 connected in anti-parallel with the switching elements 72 and 74, respectively. The switch unit 70 is connected in parallel to the charge accumulation unit 50. In the illustrated example, the switching elements 72 and 74 are n-channel MOSFETs (Metal-Oxide-Semiconductor Field-Effect transistors). However, other switching elements may be used as the switching elements 72, 74.

The excitation coil 10 is connected between the connection point 58 of the charge accumulation unit 50 and the connection point 78 of the switch unit 70. The switch unit 70 PWM modulates (Pulse Width Modulation) the dc voltage output from the charge accumulation unit 50, and applies the modulated voltage to the excitation coil 10. The control unit 24 outputs drive signals S10, S12 for driving the switching elements 72, 74 to the pre-driver 62.

The predriver 62 buffers and applies the driving signals S10 and S12 between the gates and the sources of the switching elements 72 and 74. Here, the switching element 72 is driven when the four-way valve 8 is driven in the separating direction. At this time, in the exciting coil 10, a current flows in the illustrated separating direction Dr. On the other hand, the switching element 74 is driven when the four-way valve 8 is driven in the adsorption direction. At this time, in the exciting coil 10, a current flows in the drawing attraction direction Da.

The compressor motor 12 and the outdoor fan motor 16 are both three-phase motors, and the inverter 82 PWM-modulates the dc voltage Vc output from the charge storage unit 50 to generate a three-phase ac voltage, which is applied to the compressor motor 12. Similarly, the inverter 84 PWM-modulates the dc voltage Vc to generate a three-phase ac voltage, and applies the three-phase ac voltage to the outdoor fan motor 16. The control section 24 supplies a drive signal for PWM modulation to the

inverters

82, 84.

(predriver 62)

Fig. 3 is a circuit diagram of the predriver 62. As shown, the predriver 62 includes: a photocoupler 102 (driving part);

resistors

104, 112, 116, 118, 120, 124, 126, 134, 136;

diodes

106, 110;

capacitors

108, 122, 132; an electrolytic capacitor 114 (third capacitor); and a transistor 128. The photocoupler 102 includes an LED102a and a phototransistor 102 b.

The power supply voltage VCC shown in the figure is, for example, a DC voltage of about 12 to 24[ V ]. The drive signals S10 and S12 are, for example, digital signals of about 2 to 5[ Vp-p ]. The

resistors

124, 126, 134, 136 and the capacitor 132 and the transistor 128 constitute an amplifying circuit 130. That is, the amplitude of the driving signal S12 is amplified to about 12 to 24[ Vp-p ] through the transistor 128. The amplified signal is applied between the gate and the source of the switching element 74, and thereby the switching element 74 is controlled to be turned on and off based on the drive signal S12.

When the switching element 74 is turned on, the voltage at the connection point 78 is about 0V, which is lower than the power supply voltage VCC. Thus, the electrolytic capacitor 114 is charged via the resistor 104 and the diode 106. The terminal voltage of the electrolytic capacitor 114 is charged to substantially coincide with the power supply voltage VCC. When the switching element 74 is turned off, the voltage at the connection point 78 becomes higher than the power supply voltage VCC. At this time, the terminal voltage of the electrolytic capacitor 114 is substantially equal to the power supply voltage VCC, and thus the voltage is continuously applied to the phototransistor 102 b.

When the driving signal S10 goes high, the LED102a is turned on, and the phototransistor 102b is turned on. As such, current flows from the electrolytic capacitor 114 to the phototransistor 102b, the

resistors

116, 118. Therefore, the voltage divided by the

resistors

116 and 118 is applied between the gate and the source of the switching element 72, and the switching element 72 is turned on. On the other hand, when the drive signal S10 goes low, the phototransistor 102b is turned off, and thus the gate-source voltage of the switching element 72 becomes a value in the vicinity of 0V, and the switching element 72 becomes off.

Action of the first embodiment

(case of driving the four-way valve 8 in the adsorption direction)

In fig. 3, when the four-way valve 8 is driven in the adsorption direction, the control unit 24 maintains the drive signal S10 at the low level and outputs the drive signal S12 which is a PWM modulation wave. The drive signal S12 is amplified by the amplifier circuit 130, and the switching element 74 is controlled to be turned on/off in synchronization with the drive signal S12. As a result, a current flows in the attraction direction Da through the exciting coil 10 of the four-way valve 8, and the plunger 94 (see fig. 1) of the four-way valve 8 is attracted to the permanent magnet 92.

Fig. 4 is a waveform diagram of the voltage V applied to the exciting coil 10. The voltage V changes to a pulsating state in which the ac component is superimposed on the dc component, and the period T thereof is, for example, 0.01 second. Specifically, the voltage V is changed to a full-wave rectification waveform obtained by full-wave rectifying a sine wave, and more specifically, the voltage V is changed to a step waveform approximating the full-wave rectification waveform. When the period T is set to 10msec, the waveform of the voltage V is similar to a waveform obtained by full-wave rectifying an ac voltage of 50 Hz. In addition, when the voltage V changes to a step wave, the step period Ts of the amplitude change thereof is 500 μ sec in the illustrated example. When the switching frequency of the voltage V is set to 10kHz, the step period Ts is 5 times the switching period (100 μ sec).

In the present embodiment, the reason why the voltage V is changed as described above is that the four-way valve 8 is originally designed in consideration of driving with a full-wave rectification wave. Here, the four-way valve 8 can be driven by a dc voltage having a level close to the effective value of the expected full-wave rectification wave. However, when the voltage V is a dc voltage, the current is not suppressed by the inductance component of the exciting coil 10, and thus the current flowing to the exciting coil 10 may increase, and the residual magnetic field generated around the plunger 94 of the four-way valve 8 may increase. On the other hand, if the voltage V is changed completely in accordance with the full-wave rectification wave, the control in the control unit 24 becomes complicated. Therefore, in the present embodiment, the step period of the step wave is made longer than the switching period, and the voltage V is changed to a step wave shape that approximates the full-wave rectification wave with the step wave.

(case of driving the four-way valve 8 in the direction away from it)

In fig. 3, when the four-way valve 8 is driven in the separating direction Dr, first, the control unit 24 maintains the driving signal S12 at a high level for a predetermined time. That is, before the four-way valve 8 is driven in the separating direction Dr, a square-wave pulse current is caused to flow in the adsorbing direction Da via the switching element 74. This is to charge the electrolytic capacitor 114. The time for causing the current to flow in the adsorption direction Da may be a time to the extent that the four-way valve 8 is brought into the adsorption state, or may be a time to the extent that the adsorption state is not reached.

When electrolytic capacitor 114 is charged in this manner, controller 24 maintains drive signal S12 at the low level and outputs drive signal S10 which is a PWM modulated wave. The output current from the electrolytic capacitor 114 is turned on/off in accordance with the drive signal S10, whereby the drive signal S10 is amplified, and the switching element 72 is on/off controlled in synchronization with the drive signal S10.

Thereby, in the exciting coil 10 of the four-way valve 8, the current flows in the separating direction Dr, and the plunger 94 of the four-way valve 8 is separated from the permanent magnet 92. While the drive signal S10, which is a PWM modulated wave, is at a low level, the switching element 72 is turned off. During this period, since a forward current flows through the free wheeling diode 75, the voltage at the connection point 78 becomes equal to the forward voltage drop of the free wheeling diode 75, and the electrolytic capacitor 114 is charged. Therefore, the electrolytic capacitor 114 is also intermittently continuously charged while the four-way valve 8 is driven in the separating direction.

The polarity of the waveform of the voltage V applied to the exciting coil 10 by the drive signal S10 is opposite to the waveform shown in fig. 4, and the amplitude value becomes small. That is, the duty ratio of the driving signal S10 is lower than the duty ratio of the driving signal S12. This is because, when the plunger 94 of the four-way valve 8 is driven in the separating direction, the required energy is smaller than the adsorbing direction, and the residual magnetic field generated around the plunger 94 of the four-way valve 8 can be suppressed. In this way, by controlling the switching element 72 of the upper arm with the drive signal S10 having a low duty ratio, the charging time of the electrolytic capacitor 114 can be ensured to be long, and the switching element 72 can be driven stably. When the four-way valve 8 is not driven, the drive signals S10 and S12 may be set to low level at the same time.

(operation corresponding to fluctuation of DC voltage Vc)

As described above, in fig. 2, dc power is supplied to the

inverters

82 and 84 in addition to the switch unit 70, the voltage doubler rectifier circuit 40, and the charge storage unit 50. Therefore, when the load of the

inverters

82 and 84 increases, the dc voltage Vc output from the charge storage unit 50 decreases, and this can be detected by the voltage sensor 60. In the present embodiment, the control unit 24 collectively increases the duty ratio of the drive signals S10 and S12 as the dc voltage Vc decreases. This greatly changes the current flowing through the exciting coil 10, and the four-way valve 8 can be stably driven.

Comparative example

(first comparative example)

Next, before the effects of the present embodiment are explained, the configurations of various comparative examples will be explained. In the following description, the same reference numerals are given to portions corresponding to those of the first embodiment, and the description thereof may be omitted.

Fig. 5 is a block diagram showing the configuration of the power supply unit 300 in the first comparative example. In the first comparative example, the power supply unit 300 is used instead of the power supply unit 20 (see fig. 2), but the other configuration is the same as that of the first embodiment.

The power supply unit 300 is not provided with the switch unit 70 and the pre-driver 62 provided in the power supply unit 20 of the first embodiment. On the other hand, the power supply unit 300 includes: a relay driver 302; power relays 304, 306; a diode bridge circuit 308; and a resistor 310. The power relay 304 includes: relay coil 304a, and contact portion 304 b. The power relay 306 includes: the relay coil 306a and the

contact portions

306b and 306c of the system 2.

The relay driver 302 drives the power relays 304 and 306 based on a control signal from the control unit 24. The power relay 304 switches an on/off state of energization to the exciting coil 10. The power relay 306 switches the driving direction of the four-way valve 8, i.e., the adsorption direction and the separation direction. The switching state of the

contact portions

306b and 306c shown in the figure is a state in which the four-way valve 8 is driven in the separating direction. That is, in the illustrated state, when the power relay 304 is in the on state, the ac voltage output from the noise filter 30 is full-wave rectified by the diode bridge circuit 308.

The full-wave rectified voltage is applied to the series circuit of the excitation coil 10 and the resistor 310, in both of which current flows in the leaving direction Dr. In this way, when the current is caused to flow in the separation direction Dr to the exciting coil 10, the resistor 310 suppresses the current. When the switching state of the

contact portions

306b and 306c is opposite to the illustrated state, the four-way valve 8 is driven in the suction direction. That is, a full-wave rectified voltage is applied to the exciting coil 10, and a current flows in the exciting coil 10 in the attracting direction Da.

According to the configuration of the first comparative example, a plurality of power relays 304 and 306 are required as shown in the drawing, which causes a problem of cost increase. In addition, since the diode bridge circuit 308 needs to use a circuit having a high withstand voltage, the cost is also increased. In the diode bridge circuit 308, the loss increases due to the forward voltage drop of the built-in diode. Further, since the current is limited by using the resistor 310 when the four-way valve 8 is separated, there is a problem that the loss in the resistor 310 also increases.

(second comparative example)

Fig. 6 is a block diagram showing the configuration of the power supply unit 320 in the second comparative example. The second comparative example uses the power supply unit 320 instead of the power supply unit 20 (see fig. 2), but the other configuration is the same as that of the first embodiment.

The switch unit 70 and the pre-driver 62 provided in the power supply unit 20 of the first embodiment are not provided in the power supply unit 320. On the other hand, the power supply unit 320 includes: a diode bridge circuit 308; a resistor 310; a relay driver 322; a pre-driver 324; a power relay 326; and switching

elements

330 and 332 and

reflux diodes

331 and 333 connected in antiparallel therewith, respectively.

The power relay 326 includes a relay coil 326a and a contact 326 b. The relay driver 322 drives the power relay 326 based on a control signal from the control unit 24. The power relay 326 switches the driving direction of the four-way valve 8, i.e., the adsorption direction/separation direction. The predriver 324 controls the on/off states of the switching

elements

330 and 332 based on a control signal from the control unit 24.

When the four-way valve 8 is driven in the separating direction, the control unit 24 sets the switching state of the contact portion 326b to the illustrated state, turns the switching element 330 to the on state, and turns the switching element 332 to the off state. Thus, the full-wave rectified voltage output from the diode bridge circuit 308 is applied to the series circuit of the excitation coil 10 and the resistor 310, and the current flows in the separation direction Dr in both. When the four-way valve 8 is driven in the suction direction, the control unit 24 sets the switching state of the contact 326b to a state opposite to the illustrated state, turns off the switching element 330, and turns on the switching element 332. Thus, the full-wave rectified voltage output from the diode bridge circuit 308 is applied to the excitation coil 10, and a current flows in the attraction direction Da in the excitation coil 10.

When the exciting coil 10 is not energized, the control unit 24 sets the switching

elements

330 and 332 in the off state. According to the configuration of the second comparative example, the number of power relays is reduced as compared with the first comparative example, and the power relay 326 and the diode bridge circuit 308 are still required, thereby there is a problem of an increase in cost. Further, the diode bridge circuit 308 and the resistor 310 have a problem of loss generation as in the first comparative example.

Effects of the first embodiment

As described above, the air conditioner 900 of the present embodiment includes: a charge storage unit 50 having first and

second capacitors

52 and 54 connected in series via one end 58 of the excitation coil 10 of the four-way valve 8; a rectifier circuit 40 that rectifies the ac voltage and charges the charge storage unit 50; a switch unit 70 connected in parallel with the charge accumulation unit 50 and having first and second switching elements 72 and 74 connected in series via the other end 78 of the excitation coil 10; and a controller 24 that drives the first switching element 72 with a first PWM signal S10 when the exciting coil 10 is energized in the first direction Dr, and drives the second switching element 74 with a second PWM signal S12 when the exciting coil 10 is energized in the second direction Da.

According to the present embodiment, when the first and second switching elements 72 and 74 are collectively turned off, the energization to the exciting coil 10 can be cut off, and when one of the first and second switching elements 72 and 74 is driven, the four-way valve 8 can be driven in the first direction Dr or the second direction Da. Therefore, it is not necessary to use a power relay as in the configuration of patent document 2 or the first and second comparative examples described above, and the four-way valve 8 can be driven at low cost with a simple circuit configuration.

Further, the air conditioner 900 includes: a compressor inverter 82 connected to the charge storage unit 50 to drive the compressor 961; and a fan inverter 84 connected to the charge storage unit 50 and driving the outdoor fan 965, wherein the switching unit 70, the compressor inverter 82, and the fan inverter 84 are configured to be capable of operating simultaneously.

This enables the compressor 961, the outdoor fan 965, and the four-way valve 8 to be driven simultaneously.

The air conditioner 900 further includes a voltage measuring unit 60 that measures the output voltage Vc of the charge storage unit 50, and the control unit 24 has a function of increasing the duty ratio of the first PWM signal S10 and the second PWM signal S12 as the output voltage Vc becomes lower.

Thus, even when the output voltage Vc of the charge storage unit 50 varies, the four-way valve 8 can be stably driven.

The four-way valve 8 includes a permanent magnet 92, a plunger 94 attracted to the permanent magnet 92, and an urging member 96 that urges the plunger 94 in a direction away from the permanent magnet 92, and when the plunger 94 is driven in a direction away from the permanent magnet 92, that is, in a direction away from the permanent magnet Dr, the control unit 24 drives the first switching element 72 with the first PWM signal S10, and when the plunger 94 is driven in an attraction direction, that is, in a direction toward the permanent magnet 92, that is, in a direction toward the second direction Da, the control unit 24 drives the second switching element 74 with the second PWM signal S12, and the control unit 24 makes the duty ratio of the second PWM signal S12 higher than the duty ratio of the first PWM signal S10.

Accordingly, when the plunger 94 is driven in the separating direction, the current flowing through the exciting coil 10 can be suppressed, and the residual magnetic field generated around the plunger 94 can be suppressed.

The air conditioner 900 further includes: a third capacitor 114 that is charged when the second switching element 74 is turned on; and a driving unit 102 that operates the third capacitor 114 as a power source when the second switching element 74 is in the off state, drives the first switching element 72 based on the first PWM signal S10, and when driving the plunger 94 in the separating direction, which is the direction in which the plunger separates from the permanent magnet 92, the control unit 24 charges the third capacitor 114 by turning the second switching element 74 into the on state, and supplies the first PWM signal S10 to the driving unit 102 after charging the third capacitor 114.

Thus, the third capacitor 114 can constitute a power source for driving the driving unit 102 at low cost. Further, since the first switching element 72 is driven by the first PWM signal S10 having a lower duty ratio than the second PWM signal S12, the burden on the third capacitor 114 can be reduced.

The controller 24 outputs the first PWM signal S10 and the second PWM signal S12 so that the voltage waveform applied to the exciting coil 10 is a waveform that approximates the full-wave rectified wave to a staircase shape.

This allows the reactance of the exciting coil 10 to suppress the current flowing through the exciting coil 10.

[ second embodiment ]

Next, the structure of an air conditioner according to a second embodiment of the present invention will be described. In the following description, the same reference numerals are given to portions corresponding to those of the first embodiment, and the description thereof may be omitted.

Fig. 7 is a block diagram showing the configuration of the power supply unit 220 in the second embodiment. The second embodiment uses a power supply unit 220 instead of the power supply unit 20 (see fig. 2) of the first embodiment, but the other configuration is the same as that of the first embodiment.

The power supply unit 220 includes all the components of the power supply unit 20 of the first embodiment, and further includes an active converter 230 and a pre-driver 236. The active converter 230 includes: a diode bridge circuit 232, and a switching element 234. In the illustrated example, the switching element 234 is an IGBT (Insulated Gate Bipolar Transistor), but other switching elements may be applied.

One input terminal of the diode bridge circuit 232 is connected to the output terminal 30b of the noise filter 30, and the other input terminal is connected to the connection point 58 of the charge storage unit 50. A pair of output terminals of the diode bridge circuit 232 are connected to the collector terminal and the emitter terminal of the switching element 234. The predriver 236 intermittently turns on/off the switching element 234 based on a control signal supplied from the control section 24.

When the switching element 234 is turned on, the reactor 32 is directly connected to the

output terminals

30a and 30b of the noise filter 30, and energy can be stored in the reactor 32 as magnetic flux. When the switching element 234 is turned off, the energy stored in the reactor 32 is discharged as a current. Therefore, by repeating on/off of the switching element 234, the power factor of the power supply unit 220 can be brought close to 1.0, and harmonic components flowing from the power supply unit 220 to the ac power supply 22 can be suppressed.

When the active converter 230 is in an operating state, the switching element 234 is intermittently turned on and off in order to efficiently drive the

motors

12 and 16 with reduced copper loss. In the operating state of the active converter 230, the controller 24 observes the voltage measured by the voltage sensor 60 and controls the dc voltage Vc of the charge storage unit 50, thereby boosting the dc voltage Vc to an arbitrary voltage value. That is, in the operating state of the active converter 230, the dc voltage Vc can be set higher than in the stopped state. At this time, the duty ratio of the drive signals S10 and S12 is reduced as the dc voltage Vc becomes higher by the operation corresponding to the fluctuation of the dc voltage Vc. This allows

motors

12 and 16 to be efficiently driven, and also allows four-way valve 8 to be stably driven with a small change in current flowing through field coil 10. The operation of the present embodiment when the active converter 230 is in the stopped state is the same as that of the first embodiment.

[ modified examples ]

The present invention is not limited to the above-described embodiments, and various modifications can be made. The above-described embodiments are illustrative for easy understanding of the present invention, and are not limited to having all the configurations described. Further, a part of the structure of one embodiment may be replaced with the structure of another embodiment, and the structure of another embodiment may be added to the structure of one embodiment. Further, a part of the configurations of the embodiments may be deleted, or other configurations may be added or replaced. The control lines and information lines shown in the drawings are considered to be necessary for the description, and do not necessarily represent all the control lines and information lines necessary for the product. In practice, it is also possible to consider almost all structures connected to one another.

(1) In the above embodiments, the example in which the four-way valve having the permanent magnet 92, the plunger 94 attracted to the permanent magnet 92, and the urging member 96 for urging the plunger 94 in the direction of separating from the permanent magnet is applied has been described, but the configuration of the four-way valve is not limited to the above, and four-way valves having various configurations can be applied.

Claims

1. An air conditioner is characterized by comprising:

a charge accumulation unit having a first capacitor and a second capacitor connected in series via one end of an excitation coil of a four-way valve;

a rectifier circuit that rectifies an alternating-current voltage and charges the charge storage unit;

a switch unit that is connected in parallel to the charge accumulation unit and has a first switching element and a second switching element that are connected in series via the other end of the excitation coil; and

and a control unit that drives the first switching element by a first PWM signal when the exciting coil is energized in a first direction, and drives the second switching element by a second PWM signal when the exciting coil is energized in a second direction.

2. The air conditioner according to claim 1,

the air conditioner further includes:

a compressor inverter connected to the charge accumulation unit to drive the compressor; and

a fan inverter connected to the charge accumulation unit to drive an outdoor fan,

the switching unit, the compressor inverter, and the fan inverter are configured to be capable of operating simultaneously.

3. The air conditioner according to claim 2,

the air conditioner further comprises a voltage measuring unit for measuring the output voltage of the charge accumulating unit,

the control unit has a function of increasing the duty ratio of the first PWM signal and the second PWM signal as the output voltage decreases.

4. An air conditioner according to claim 3,

the four-way valve has a permanent magnet, a plunger attracted to the permanent magnet, and a force application member for applying a force in a direction in which the plunger is separated from the permanent magnet,

the control unit drives the first switching element by the first PWM signal when the plunger is driven in a separating direction corresponding to the first direction, which is a direction in which the plunger is separated from the permanent magnet, and drives the second switching element by the second PWM signal when the plunger is driven in an attracting direction corresponding to the second direction, which is a direction in which the plunger is attracted to the permanent magnet,

the control unit makes the duty ratio of the second PWM signal higher than the duty ratio of the first PWM signal.

5. The air conditioner according to claim 4,

the air conditioner further includes:

a third capacitor that is charged when the second switching element is turned on; and

a driving unit that operates the third capacitor as a power source when the second switching element is in an off state, and drives the first switching element based on the first PWM signal,

when the plunger is driven in a direction in which the plunger is separated from the permanent magnet, that is, in a separating direction, the control unit charges the third capacitor by bringing the second switching element into an on state, and supplies the first PWM signal to the drive unit after the third capacitor is charged.

6. The air conditioner according to claim 5,

the control unit outputs the first PWM signal and the second PWM signal so that a voltage waveform applied to the exciting coil is a waveform that approximates a full-wave rectification wave to a staircase shape.

7. The air conditioner according to claim 4,

the air conditioner further includes an active converter for boosting the output voltage in comparison with a case of a stop state when the active converter is in an operating state,

the control unit has a function of making the duty ratio of the first PWM signal and the second PWM signal lower than that in a stop state when the active converter is in an operating state.