JPH0578745B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an air conditioner, and more particularly to an air conditioner designed to protect a compressor from damage due to refrigerant overfilling.

[Conventional technology]

Fig. 12 is a refrigerant circuit diagram of a conventional device shown in, for example, Japanese Utility Model Application Publication No. 13377/1983, which is widely used in small split-type air conditioners. , 2 is a four-way valve, 3
4 is an outdoor heat exchanger, 4 is a throttle device, and 5 is an accumulator connected to the suction side of the compressor 1, which are housed in an outdoor unit 6. Also, 7
is an indoor heat exchanger housed in the indoor unit 8,
The outdoor unit 6 and the indoor unit 8 constitute a refrigerant circuit connected by a refrigerant pipe 9.

The refrigerant circuit configured in this manner is generally well known, and during cooling operation, the refrigerant is supplied to the compressor 1, four-way valve 2, outdoor heat exchanger 3, throttle device 4,
Indoor heat exchanger 7, four-way valve 2, accumulator 5,
flows in this order. At this time, the outdoor heat exchanger 3 acts as a condenser, and the indoor heat exchanger acts as an evaporator, respectively, to perform a predetermined cooling effect. During heating operation, the refrigerant flows through the compressor 1, the four-way valve 2, the indoor heat exchanger 7, the expansion device 4, the outdoor heat exchanger 3, the four-way valve 2, and the accumulator 5 in this order. At this time, the indoor heat exchanger 7 serves as a condenser, and the indoor heat exchanger 3
Each acts as an evaporator and performs a predetermined heating effect. Also, the accumulator 5
is for storing surplus refrigerant in the refrigerant circuit. That is, the refrigerant pipe 9 connecting the outdoor unit
is determined by the installation conditions of the air conditioner, and its length varies, and the amount of refrigerant required for the system differs depending on the length.

In Fig. 13, the refrigerant pipe length L is shown in the horizontal axis direction.
(m), and the vertical axis shows the amount of refrigerant LQ required for the system.
This is a characteristic diagram showing the change in the amount of refrigerant required for the system due to the change in refrigerant pipe length, expressed in kg.
indicates heating characteristics, and C indicates cooling characteristics. As is clear from Figure 7,
Whether surplus refrigerant is generated during cooling operation or heating operation depends on the installation conditions of the air conditioner. It is necessary to absorb it.

[Problem to be solved by the invention]

Since the conventional air conditioner is configured as described above, when installing the air conditioner, it is necessary to adjust the amount of refrigerant to an appropriate amount according to the length of the refrigerant piping. However, when adding refrigerant, there is no particular problem if the additional refrigerant is measured and charged, but measurement is not often done at the installation site, and even if it is measured, there may be a large error and overfilling may occur. There are many. Another method is to operate the air conditioner and determine the appropriate amount by checking the compressor's superheat (SH), but if there is excess refrigerant in the accumulator, SH will always be 0. , which can only be determined in the operating state that requires the most refrigerant,
As explained above, the appropriate amount of refrigerant often differs depending on whether the temperature is cool or hot, and the amount of refrigerant also differs depending on the air condition, so there are actually very few opportunities to make a determination using this method. Therefore, in most cases, it is filled a little more. Continuing to operate under these conditions will cause an increase in condensing pressure, increasing the load on the compressor, and, especially if too much refrigerant is added, excess refrigerant may exceed the accumulator volume and overflow the accumulator. There was a problem in that there was always a risk that liquid refrigerant would be sucked into the compressor and damage the compressor due to liquid compression.

This invention was made to solve the above-mentioned problems, and an object of the present invention is to provide an air conditioner that can protect the compressor by outputting an abnormal signal in the case of refrigerant overfilling.

[Means to solve the problem]

An air conditioner according to the present invention includes a refrigerant circuit having a compressor, a four-way valve, an outdoor heat exchanger, a pressure reducing device, an indoor heat exchanger, and an accumulator, and a saturation temperature that detects the saturation temperature of the low pressure of the refrigerant circuit. means, a bypass circuit provided between the accumulator and the compressor and having a refrigerant heating means and a refrigerant temperature detection means for the refrigerant heated by the refrigerant heating means; A liquid level determination means is provided for determining the liquid level in the accumulator by comparing the saturation temperature with the temperature of the refrigerant detected by the refrigerant temperature detection means of the bypass circuit.

[Effect]

In the air conditioner of this invention, the liquid level determination means determines the liquid level of the accumulator by comparing the temperatures obtained from the saturation temperature means and the refrigerant temperature detector of the bypass circuit, thereby preventing troubles due to refrigerant overfilling. do.

[Embodiments of the invention]

FIG. 1 is a refrigerant circuit diagram of an air conditioner according to the present invention. In the same figure, reference numerals 1 and 2 are the same components as those of the conventional device shown in FIG. 12, and the explanation thereof will be omitted. Further, 10 and 11 are capillary tubes, one end of which is connected before and after the throttle device 4, and the other end merges and is connected to the inlet pipe of the accumulator 5. A temperature detector 15 is disposed to constitute the saturation temperature detection means 12. Reference numeral 13 is also a capillary tube, one end of which is connected to a specific height position of the accumulator 5 (a level at which surplus refrigerant does not overflow the accumulator), and the other end is connected to the suction pipe of the compressor 1, and the bypass circuit is connected to the suction pipe of the compressor 1. A PTC heater 18, which is a refrigerant heating means, is provided upstream of the refrigerant 14, and a temperature detector 16, which is a second refrigerant temperature detection means, is provided downstream. Reference numeral 17 denotes a liquid level determining means for determining the liquid level of the accumulator 5 from the temperatures detected by the first and second temperature detectors 15 and 16.

FIG. 2 is a circuit diagram showing an embodiment of the liquid level determination means 17, and 15 is a first temperature sensor using, for example, a thermistor, which is connected in series with a resistor 21 and connected between the Vcc power supply and ground. The divided voltage (V+) from both is input to the non-inverting input 24 of the voltage comparator 23. In addition, 16 is a second temperature sensor that also uses a thermistor, and has a resistor of 2
2 in series and between the Vcc power supply and ground, and the divided voltage (V-) from both is applied to the inverting input 25 of the voltage comparator 23. 18 is
It is a PTC heater and is connected between the Vcc power supply and ground. Further, an indicator light 28 made of an LED or the like is connected via a resistor 27 between the output terminal 26 of the voltage comparator and the Vcc power supply.

The operation of the refrigerant circuit configured as above will be explained. The cooling and heating effects of the components 1 to 9 are completely the same as those of the conventional device, so a description of the operations will be omitted.

The saturation temperature detection means 12 is a circuit for detecting the saturation temperature with respect to the low pressure. During cooling, the high pressure liquid refrigerant condensed in the outdoor heat exchanger 7 is throttled and depressurized by the capillary tube 10 to detect the saturation temperature at the low pressure. The refrigerant flows in a two-phase state, and the outlet of the saturation temperature detection means 12 is brought to a saturation temperature at a low pressure, and this temperature is detected by the first temperature detector 15.In addition, during heating, the indoor heat exchanger The saturation temperature is detected in the same manner as during cooling by reducing the pressure of the high-pressure liquid refrigerant condensed in the vessel 7 through the capillary tube 11. To explain the operation at this time using the Mollier diagram shown in FIG. By detecting the outlet temperature corresponding to 52, it becomes possible to measure the saturation temperature.

On the other hand, the refrigerant in the accumulator passes through the bypass circuit 14, and a very small amount flows toward the suction pipe of the compressor. The capillary tube 13 is for restricting the flow rate of the refrigerant. The refrigerant in the accumulator 5 is divided into a liquid part and a gas part, and corresponds to the liquid part 53 and the gas part to 54 on the Mollier diagram of FIG. Here, if the amount of refrigerant in the accumulator 5 is low and the inlet of the bypass circuit 14 is gas refrigerant, gas refrigerant will flow into the bypass circuit 14, and a large amount of refrigerant will accumulate in the bypass circuit 14. If the inlet portion of the refrigerant is a liquid refrigerant, the liquid refrigerant will flow into the bypass circuit 14. In the bypass circuit 14, the internal refrigerant and the bypass circuit 1
Heat exchange is performed with the PTC heater 18 provided upstream of the refrigerant 4, but if the refrigerant flowing inside at this time is liquid, there is no temperature rise in the bypass circuit.
The temperature of the piping in the bypass circuit is almost equal to the saturation temperature of the low pressure, and if the internal refrigerant is gas, some superheating occurs and the temperature of the piping in the bypass circuit increases somewhat. In other words, the refrigerant and
If there is a heat exchange of Δi between the PTC heaters,
The state of the refrigerant in the middle of the bypass circuit corresponds to 55 in the case of liquid refrigerant and 56 in the case of gas refrigerant on the Mollier diagram in Figure 3, and the respective temperatures are
t ₁ and t ₂ , and the temperature increases by Δ _t = t ₂ − t ₁ .

Therefore, the temperature in the middle of the bypass circuit is detected by the second temperature sensor 16, and the temperature in the middle of the bypass circuit is detected by the second temperature sensor 16.
By comparing the saturation temperature of the low pressure detected in step 5, it is possible to determine whether liquid refrigerant or gas refrigerant is flowing through the bypass circuit 14. That is, it is possible to determine whether or not the refrigerant has accumulated up to the bypass circuit inlet installed at a specific height position of the accumulator 5.

The amount of refrigerant flowing into the bypass circuit 14 is determined by the pressure difference before and after the bypass circuit 14 caused by the head of the liquid refrigerant in the accumulator and the pressure loss in the piping from the accumulator to the compressor.

Since the piping pressure loss is determined by the amount of refrigerant circulated, the amount of refrigerant flowing through the bypass circuit 14 is influenced by the operating state of the air conditioner. Here, if the refrigerant flow rate of the bypass 14 is low and the heating amount of the heater is too large, the temperature of even the liquid refrigerant will rise and it will be mistakenly determined to be a gas refrigerant.If the refrigerant flow rate is high and the heating amount of the heater is too small, the temperature of the gas refrigerant will also rise. Although the amount is extremely small and there is a risk of misidentifying it as liquid refrigerant, heating
Misjudgment can be prevented by using the PTC heater 18. In other words, as shown in Fig. 4, the resistance value of the PTC heater decreases as the temperature increases and exceeds the Curie temperature (Tc). Because the resistance value increases rapidly
When the PTC heater 18 is operated at a constant voltage, in the region of low resistance, the electric power is large and the heating amount is high, and the temperature rises instantaneously.When the resistance exceeds the Curie temperature (Tc), the resistance increases, so the electric power decreases and the heating amount also decreases. For example, T ₁
It becomes stable between ~T ₂ . When the amount of heat dissipation increases, the temperature decreases and resistance decreases, so the amount of heating increases, and conversely, when the amount of heat dissipation decreases, the temperature rises, and as the resistance increases, the amount of heating decreases, and as a result, the temperature is always kept constant. Since it has a self-control property, when a large amount of refrigerant is flowing through the bypass circuit 14, if the amount of heating is too small, the temperature will tend to drop.
The self-controllability of the PTC heater 18 increases the amount of heating, and when the refrigerant flow rate is low, if the amount of heating is too large, the temperature tends to rise, but the self-controllability of the PTC heater 18 automatically increases the amount of heating. This has the effect of always obtaining an appropriate amount of heating and preventing erroneous judgments. Furthermore, due to the difference in ambient temperature between cooling and heating, heat exchange with the ambient temperature in the bypass circuit 14 is also suppressed by the PTC heater 18, allowing stable liquid level detection.

Next, the operation of the liquid level determining means shown in FIG. 2 will be explained. The resistance value of a thermistor increases as the detected temperature decreases, so each divided voltage (V+), (V
-) increases as the temperature decreases. Therefore, as shown in FIG. 5, when the liquid level in the accumulator 5 is low and the gas refrigerant is flowing through the bypass circuit 14, the temperature detected by the second temperature sensor 16 is high, and therefore,
The divided voltage (V-) is becoming lower. Further, as the liquid level rises and the liquid refrigerant gradually begins to flow, the detected temperature decreases and the partial voltage (V-) gradually increases. On the other hand, since the temperature detected by the first temperature detector 15 is always a substantially constant value, its divided voltage (V+) is also substantially constant. Therefore, when the liquid refrigerant starts flowing into the bypass circuit 14, that is,
If the resistors 21 and 22 are selected in advance so that when the liquid level height of the accumulator 5 reaches a certain height H, the two divided voltages are the same, then the liquid level height becomes H. At this point, the output of the voltage comparator is inverted (from H level to L level), and as a result, a current flows through the indicator light 28 connected to the output, causing it to emit light.
The liquid level can be determined.

Therefore, if the mounting position of the bypass circuit 14 to the accumulator is set slightly lower than the position where the accumulator overflows,
By lighting the indicator light 28, it can be determined that the amount of refrigerant has reached a dangerous amount.

FIG. 6 is a circuit diagram showing another embodiment of the liquid level detection means of the present invention. In the same figure, 15,1
6, 18, and 21-26 are the same components as in the control circuit diagram shown in FIG. 29 is a voltage comparator 23
An electromagnetic relay coil 29 connected to the output end 26 of
_a is its normally closed contact, 31 is a power supply terminal, 32 is an electromagnetic contactor coil, 32 _a is its contact, and a compressor motor 33 is connected to the secondary side of the electromagnetic contactor contact 32 _a .
and an outdoor blower electric motor 34 are connected in parallel.

35 and 36 are operating capacitors for the compressor motor 33 and the outdoor blower motor 34. Reference numeral 37 denotes a control input terminal to which a compressor activation signal is input from an indoor unit (not shown). 38 is an auxiliary relay coil for starting the compressor, 3
8 _a is its normally open contact, is the self-holding relay coil,
_39a is its normally closed contact. In the above configuration, when a compressor start signal is input to the control input terminal 37, the auxiliary relay coil 38 for starting the compressor
is energized, its normally open contact _38a is closed, and the self-holding relay coil 39 and electromagnetic contactor coil 32
A voltage is applied to the series circuit of Here, in normal times, the self-holding relay coil 39 has a normally closed contact 39 _a of the self-holding relay and a normally closed contact 3 of the electromagnetic relay.
_9a , all the applied voltage is applied to the electromagnetic contactor coil 32, the electromagnetic contactor contact _32a is closed, the compressor motor 33 and the outdoor blower motor 34 are started, and the specified cooling or Perform heating operation. In this state, when the liquid level in the accumulator rises and the liquid reaches a specific height position or higher, the output of the voltage comparator 23 is reversed from H level to L level as described above, and the voltage comparator 23
The electromagnetic relay coil 29 connected to the output of is excited. Then, since the normally closed contact _29a of the electromagnetic relay is opened, the voltage that was previously applied to the electromagnetic contactor coil 32 is reduced to the self-holding relay coil 3.
9 and the electromagnetic contactor coil 32 in proportion to their respective impedances. Since the impedance of the self-holding relay coil 39 is sufficiently larger than the impedance of the electromagnetic contactor coil, most of the voltage is applied to the self-holding relay coil 39, and the self-holding relay coil 39 is excited. Conversely, the electromagnetic contactor coil 32 is demagnetized and the electromagnetic contactor contact _32a is opened, so the compressor motor 33 and the outdoor blower motor 34 are stopped. Furthermore, once the self-holding relay coil 39 is energized, the normally closed contact _39a of the self-holding relay is opened. Even if the electromagnetic relay 29 is demagnetized, this state can be maintained. As mentioned above,
When the liquid level in the accumulator 5 reaches a preset dangerous level, the compressor can be stopped and protected.

FIG. 7 is a refrigerant circuit diagram of another embodiment of the air conditioner according to the present invention. In the same figure, 1 to 17
are the same components as those in FIG. 1, and their explanation will be omitted. 41 is a capillary tube, one end of which is connected to a specific height position of the accumulator 5 (at a level where only gas refrigerant can flow out), the other end is connected to the suction pipe of the compressor 1, and the second bypass circuit 4
2. 45 is also a capillary tube, one end of which is connected to a position below the installation height of the second bypass circuit 42 of the accumulator 5 (a level at which surplus refrigerant does not overflow the accumulator), and the other end is connected to the suction of the compressor 1. It is connected to piping and constitutes a third bypass circuit 46. In the middle of the second bypass circuit 42 and the third bypass circuit 46
In the middle, there are the second and third temperature detectors 4 and 4, respectively.
3,47 are provided. Further, first and second heaters 44 and 48 are provided between one end of the accumulator 5 of the second and third bypass circuits 42 and 46 and the temperature sensor, respectively. 17 is the first, second and third temperature sensor 15, 43, 4;
7 is a liquid level determination means for determining the liquid level of the accumulator 5 from the detected temperature.

FIG. 9 is a circuit diagram showing an embodiment of the liquid level determination means 17, and 15 is a first temperature sensor using, for example, a thermocouple, which is connected to the input terminal 61 of the CPU for input. A second temperature sensor 43 also uses a thermocouple and is connected to the input terminal 62 of the CPU for input. Also, 47 is a third temperature sensor using a thermocouple, which is connected to the input terminal 63 of the CPU for input. Also, the output terminals 64, 6 of the CPU
5 is connected to first and second heaters 44 and 48. Also, Vcc is connected between the output terminals 66 and 67 of the CPU.
An indicator light 69 made of an LED or the like is connected via a power source and a resistor 86.

The refrigerant in the accumulator 5 passes through the third bypass circuit 16, and a very small amount flows toward the suction pipe of the compressor 1. The capillary tube 45 is for restricting the flow rate of the refrigerant. The refrigerant in the accumulator 5 is divided into a liquid part and a gas part, and the liquid part corresponds to 53 and the gas part corresponds to 54 on the Mollier diagram of FIG. Here, if the amount of refrigerant in the accumulator 5 is small and the inlet portion of the third bypass circuit 46 is gas refrigerant, the third bypass circuit 46
If a gas refrigerant flows and a large amount of refrigerant is accumulated in the third bypass circuit 46, and if the inlet portion of the third bypass circuit 46 is a liquid refrigerant, the liquid refrigerant will flow into the third bypass circuit 46. Since the temperature of the refrigerant in the accumulator 5 is naturally lower than the ambient temperature, in the third bypass circuit 46,
Heat exchange occurs between the internal refrigerant and the ambient temperature, but if the refrigerant flowing inside at this time is liquid,
There is no temperature rise in the bypass circuit, and the bypass circuit piping temperature is almost equal to the low pressure saturation temperature. Also, if the internal refrigerant is gas, there will be some superheating and the bypass circuit piping temperature will rise somewhat. . In other words, assuming that there is a heat exchange of Δi ₁ between the refrigerant and the ambient temperature, the state of the refrigerant in the middle of the bypass circuit corresponds to 55 on the Mollier diagram in Figure 8 for liquid refrigerant, and for gas 5 for refrigerant
This is because it corresponds to 6.

Therefore, the temperature in the middle of the bypass circuit is detected by the third temperature detector 47, and the temperature in the middle of the bypass circuit is detected by the third temperature detector 47.
By comparing the saturation temperature of the low pressure detected in step 5, it is possible to determine whether liquid refrigerant or gas refrigerant is flowing through the third bypass circuit 46. With only the heat exchange of Δi ₁ , the temperature difference between when the liquid refrigerant flows and when the gas refrigerant flows becomes very small due to the flow rate of the refrigerant flowing into the third bypass circuit 46. It becomes difficult to determine whether the refrigerant flowing in the refrigerant is a liquid refrigerant or a gas refrigerant. Therefore, by providing the second heater 48 between the third bypass circuit 46 and the accumulator 5, the amount of heat exchange Δi ₁ performed during this time increases to Δi ₂ , and the liquid refrigerant flows into the third bypass circuit 46. The accuracy of the determination increases because the temperature difference between when the gas refrigerant flows and when the gas refrigerant flows increases. This is because the state of the refrigerant at this time corresponds to 57 in the case of liquid refrigerant and 58 in the case of gas refrigerant on the Mollier diagram.

Here, the reason why the second bypass circuit 42 is provided at a specific height position of the accumulator 5 above the third bypass circuit 46 is to adjust the heating amount of the second heater 48. If the heating amount of the second heater 48 is constant, the third bypass circuit 46
Even if the refrigerant flowing through the refrigerant is a liquid refrigerant, if the refrigerant flow rate is small, the temperature of the liquid refrigerant will abnormally rise due to heat exchange with the second heater 48, and it will be gasified, resulting in an erroneous determination that this refrigerant is a gas refrigerant. There is a fear. Also,
Even if the refrigerant flowing into the third bypass circuit 46 is a gas refrigerant, if the refrigerant flow rate is large, the heating amount of the second heater 48 cannot keep up, and the third temperature sensor 47 This is because when the refrigerant passes through the refrigerant, there is a risk that the refrigerant may be mistakenly determined to be a liquid refrigerant. In addition, the reason why the third temperature sensor 47 is installed in the middle of the third bypass circuit 46 is that the part near the accumulator 5 is easily affected by the heat capacity of the outer shell of the accumulator 5. Furthermore, if the refrigerant is located at the outlet of the third bypass circuit 46, the flow rate of the refrigerant is extremely small, so even if it is a liquid refrigerant, the temperature will rise to some extent. Next, the 9th
The operation of the liquid level determination means shown in the figure will be explained with reference to the flowchart of FIG. In step (1), the temperature of the first temperature detector 15, that is, the saturation temperature of the low pressure (hereinafter referred to as T15) is detected. (2) In the step, the temperature of the second temperature detector 43, that is, the temperature of the gas refrigerant heated by the first heater 44 (hereinafter T
43) is detected. In step (3), T43 is compared to see if it is equal to T15 plus a predetermined temperature (hereinafter referred to as ΔT). If they are not equal, it means that the values of T43 and T15 do not have a predetermined temperature difference, and the process proceeds to step (4). If they are equal, there is a predetermined temperature difference, and the process proceeds to step (9).In step (4), ΔT is applied to T43 and T15.
If T43 is larger, proceed to step (5); if T43 is smaller, proceed to step (6). In step (5), reduce the heating amount of the first heater 44 (hereinafter referred to as H44) and return to step (2). Next, in step (6), increase H44 and proceed to step (7).In step (7), compare whether H44 is greater than or equal to the preset maximum value, and if not, proceed to step (2). Return to the step, and if it has changed, H44 has reached the maximum value or a larger value in step (8), so H4
Reassume that the value of 4 is the maximum value, and proceed to step (9). In step (9), H48 (heating amount of the second heater 48, hereinafter referred to as H48) is set to H44. In short, the operation from step (1) to step (9) is T4.
This is to adjust the heating amount of the heater to an appropriate value while performing feedback so that the temperature difference between T3 and T15 becomes a predetermined temperature. Next, in step (10), the temperature of the third temperature detector 47 (hereinafter referred to as T47) is
Detect. (11) At step T47 is compared to see if it is equal to T15, that is, third bypass circuit 4
6, it is determined whether the refrigerant flowing is a liquid refrigerant or a gas refrigerant. If T47 is larger than T15, it means that the refrigerant is gas, and the process returns to step (1) to continue the operating state. Also, if T47 is equal to T15, it is liquid refrigerant, so proceed to step (12), and in step (12), the output terminal 67 of the CPU is reversed (from H level to L level), and as a result, it is connected to the output. Since current flows through the indicator lamp 69 and it emits light, the liquid level in the accumulator 5 can be determined by lighting the indicator lamp 69.

Therefore, if the mounting position of the third bypass circuit 46 to the accumulator 5 is set to be a little lower than the position where the accumulator 5 overflows, the amount of refrigerant will become dangerous when the indicator light 69 lights up. It can be determined that

FIG. 11 is a circuit diagram of another embodiment of the liquid level detection means according to another embodiment of the present invention. In the same figure,
The same reference numerals as in the control circuit diagram shown in FIG. 9 indicate the same components. 70 is an electromagnetic relay coil connected to the output terminal 67 of the CPU, 70 _a is its normally closed contact, 7
1 is a power terminal, 72 is an electromagnetic contactor coil, 72 _a
is the contact point, and a compressor motor 73 and an outdoor blower motor 74 are connected in parallel to the secondary side of the electromagnetic contactor contact _72a . 75 and 76 are operating capacitors for the compressor motor 73 and the outdoor blower motor 74. Reference numeral 77 is a control input terminal to which a compressor activation signal is input from an indoor unit (not shown). 78 is an auxiliary relay coil for starting the compressor, 78 _a is its normally open contact,
79 is a self-holding relay coil, and 79 _a is its normally closed contact.

In the above configuration, when a compressor start signal is input to the control input terminal 77, the auxiliary relay coil 78 for starting the compressor is excited, its normally open contact _78a is closed, and the self-holding relay coil 79
A voltage is applied to the series circuit of the magnetic contactor coil 72 and the electromagnetic contactor coil 72. Here, in normal times, the self-holding relay coil 79 is a normally closed contact 79 _a of the self-holding relay.
Since it is short-circuited by the normally closed contact _70a of the electromagnetic relay, all the applied voltage is applied to the electromagnetic contactor coil 72, and the electromagnetic contactor contact _72a is closed.
Compressor motor 73 and outdoor blower motor) 7
4 starts and performs a predetermined cooling or heating operation. In this state, when the liquid level inside the accumulator rises and the liquid reaches a certain height position or higher, the output of the CPU output end 67 changes from the H level to the L level, as described above.
The electromagnetic relay coil 70 connected to the output of the CPU output terminal 67 is energized. Then, since the normally closed contact _70a of the electromagnetic relay is opened,
The voltage that was previously applied to the electromagnetic contactor coil 72 is divided in proportion to the impedances of the self-holding relay coil 79 and the electromagnetic contactor coil 72. Since the impedance of the self-holding relay coil 79 is sufficiently larger than the impedance of the electromagnetic contactor coil, most of the voltage is applied to the self-holding relay coil 79.
The self-holding relay coil 79 is energized, the electromagnetic contactor coil 72 is demagnetized, and the electromagnetic contactor contact _72a is opened, so the compressor motor 73 and the outdoor blower motor 74 are stopped. Once again,
The normally closed contact _79a of the self-holding relay is opened.
This state can be maintained even if the electromagnetic relay 70 is demagnetized. As described above, when the liquid level in the accumulator 5 reaches a preset dangerous level, the compressor can be stopped and protected.

〔Effect of the invention〕

According to the present invention, there is provided a refrigerant circuit having a compressor, a four-way valve, an outdoor heat exchanger, a pressure reducing device, an indoor heat exchanger, and an accumulator, a saturation temperature detection means for detecting the saturation temperature of the low pressure of the refrigerant circuit; A bypass circuit provided between the accumulator and the compressor and having a refrigerant temperature detection means for the refrigerant heated by the refrigerant heating means, and a saturation temperature of the low pressure detected by the saturation temperature detection means and the refrigerant in the bypass circuit. Since the structure includes a liquid level determining means for determining the liquid level in the accumulator by comparing the temperature of the refrigerant detected by the temperature detecting means, the amount of refrigerant in the accumulator can be accurately determined. This has the effect of preventing damage to the compressor due to liquid compression, etc., when the refrigerant is overfilled.

[Brief explanation of drawings]

Fig. 1 is a refrigerant circuit diagram showing an embodiment of the air conditioner of the present invention, Fig. 2 is an electric circuit diagram showing an embodiment of the liquid level determining means of the same, and Fig. 3 is the operation of the circuit shown in Fig. 1. The Mollier diagram that explains Figure 4 is the same as above.
A characteristic diagram of the PTC heater, FIG. 5 is an explanatory diagram of the operation of the electric circuit shown in FIG. 2, FIG. 6 is an electric circuit diagram showing another embodiment of the liquid level determination means same as above, and FIG. A refrigerant circuit diagram showing another embodiment of the harmonizer, FIG. 8 is a Mollier diagram explaining the operation of the circuit in FIG. 7, and FIG. 9 is an electric circuit diagram showing an embodiment of the liquid level determining means. FIG. 10 is a flowchart of the circuit shown in FIG. 9, FIG. 11 is an electric circuit diagram showing another embodiment of the liquid level determining means, FIG. 12 is a refrigerant circuit diagram of a conventional air conditioner, and FIG. The figure is a characteristic diagram showing changes in the amount of refrigerant in the system with respect to the length of the refrigerant piping. In the figure, 1 is a compressor, 3 is an outdoor heat exchanger, 5 is an accumulator, 7 is an indoor heat exchanger, 12 is a saturation temperature detection means, 14 is a bypass circuit, and 16 is a second temperature detector. , 17 is a liquid level determination device, 18 is a PCT heater, 42 is a second bypass circuit, 43 is a second temperature sensor, 44 is a first heater, 46 is a third bypass circuit, and 47 is a third bypass circuit. Temperature sensor 48 is a second heater. In addition,
In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A refrigerant circuit having a compressor, a four-way valve, an outdoor heat exchanger, a pressure reducing device, an indoor heat exchanger, and an accumulator, a saturation temperature detection means for detecting the saturation temperature of the low pressure of this refrigerant circuit, and the accumulator and A bypass circuit provided between the compressor and having a refrigerant heating means and a refrigerant temperature detection means for the refrigerant heated by the refrigerant heating means; An air conditioner comprising a liquid level determining means for determining a liquid level in the accumulator by comparing the temperature of the refrigerant detected by the refrigerant temperature detecting means.