JPH0378551B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a failure detection device for an electric expansion valve in an air conditioner incorporating a compressor driven by an inverter that makes frequency variable. (Prior Art) Conventionally, a compressor 1 and an inverter 1a that varies the operating frequency of the compressor 1 to adjust its capacity are known.
An air conditioner is known in which the capacity is controlled by including an electric expansion valve 5 whose opening degree changes according to the capacity of the compressor 1 (Japanese Patent Laid-Open No. 58-205057).
(see publication). (Problems to be solved by the invention) By the way, in such an air conditioner,
If an abnormality occurs in the control of the electric expansion valve due to a failure in the drive electronic circuit of the electric expansion valve or a failure in the electric line, the abnormality can be detected, but the abnormality can be detected if the electric expansion valve itself is defective or foreign matter has been mixed in. No suitable method has been found to reliably detect malfunction of the electric expansion valve itself. For example, if the electric expansion valve stops working at a small opening due to chips mixed in during machining, foreign objects mixed in during assembly, or foreign objects mixed in the lubricant, there may be a lack of air conditioning capacity, or especially when indoors when cooling. It is relatively easy to detect because frost forms on the coil, but
If the compressor stops working with a large opening, there is a risk that the refrigerant liquid will flow around the compressor before the abnormality is noticed and the compressor will be damaged due to liquid compression. The present invention has been made in view of the above, and its purpose is to solve the problem that when the electric expansion valve is throttled during high-capacity operation of the compressor, the state quantity of the refrigerant changes before and after that change. The purpose of this invention is to reliably detect failure of the electric expansion valve from the value of the change in the state quantity and prevent damage to the compressor. (Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention is as shown in FIG. The present invention is directed to an air conditioner equipped with an inverter 1a and an electric expansion valve 5. As a failure detection device for the electric expansion valve of such an air conditioner, a high capacity detection means 11 detects when the capacity of the compressor 1 is operating at a set value or more, and a system detects the failure detected by the high capacity detection means 11. A control means 12 for controlling the capacity adjustment of the compressor 1 by the inverter 1a to be fixed and greatly reducing the opening degree of the electric expansion valve 5 during high capacity operation of the compressor 1; and an output of the control means 12. state quantity detection means TH2 that detects the state quantity of the refrigerant before and after the change in the opening degree of the electric expansion valve 5 in response to the change in the opening degree of the electric expansion valve 5;
and a determining means 13 which outputs a failure signal when the change in the state quantity detected by the state quantity detection means TH2 is less than a set value. (Function) With the above configuration, in the present invention, when the high capacity detection means 11 detects the operating period when the capacity of the compressor 1 becomes higher than the set value, the signal of the high capacity detection means 11 is By the received control means, the capacity of the compressor 1 is fixed in that state, and the opening degree of the electric expansion valve 5 is greatly reduced. At this time, when the operation of the electric expansion valve 5 is normally throttled, the state amount of the refrigerant changes by more than the set value before and after the change in the electric expansion valve 5, and this is determined to be normal by the determining means 13. Ru. On the other hand, when the opening degree is not throttled due to a failure in the electric expansion valve 5 and the state quantity does not change by more than the set value, the determining means 13 determines that the electric expansion valve 5 is malfunctioning, so that the failure of the electric expansion valve 5 is detected. This effectively prevents malfunction and damage to the compressor 1, especially when the opening degree is large. (Example) Hereinafter, an example of the present invention will be described in detail based on the drawings from FIG. 2 onwards. Fig. 2 shows a refrigerant piping system of an air conditioner to which the present invention is applied, where A is an outdoor unit and B is an indoor unit. a four-way switching valve 2 that switches as shown by the solid line in Figure 2 during heating operation and as shown by the broken line during cooling operation, and an accumulator 3.
, an outdoor heat exchanger 4, and an electric expansion valve 5 for adjusting the refrigerant flow rate are installed as main equipment, and the indoor unit B is provided with an indoor heat exchanger 6 as the main equipment, and each of the above-mentioned main The devices are connected to each other by refrigerant pipes 8. In addition, TH1 includes a room temperature thermostat 10 disposed in the main body casing of the indoor unit B.
is a control unit for an air conditioner. During heating operation, the flow of refrigerant is as shown by the solid arrow, and the refrigerant discharged from the compressor 1 undergoes heat exchange in the indoor heat exchanger 6, and then is subjected to a throttling action by the electric expansion valve 5. It is vaporized in the outdoor heat exchanger 4, passed through the accumulator 3, and then refluxed to the compressor 1 again. In the above refrigerant flow, the control unit 10 controls the room temperature thermostat.
A frequency signal for adjusting the frequency of the inverter 1a is output according to the deviation signal between the room temperature and the set temperature inputted from the TH1, and the opening degree of the electric expansion valve 5 is adjusted according to the value f of the frequency signal. Outputs a pulse signal to adjust the Table 1 below shows the relationship between the frequency signal value f and the pulse signal value N. The upper row shows the frequency signal value f of the inverter 1a, and the middle row shows the output corresponding to the frequency signal value f during heating operation. The pulse signal value N shown in the lower row is the pulse signal value N output during cooling operation, both of which increase as the frequency signal value f increases.

[Table] Next, the capacity of the compressor 1 is controlled by the inverter 1a which varies the output frequency according to the frequency signal, while the electric expansion valve 5 is operated by the third electric expansion valve 5 in response to the pulse signal. Change the opening degree as shown in the graph in the figure. In the graph of FIG. 3, the horizontal axis is the pulse signal value N input to the electric expansion valve 5, and the vertical axis is the opening degree of the electric expansion valve 5. As the pulse signal value N increases, the opening degree increases. It increases almost linearly, and the refrigerant evaporation temperature in the outdoor heat exchanger 4 is adjusted to an appropriate range by the opening degree of the electric expansion valve 5. Through the above procedure, the capacity of the compressor 1 is appropriately controlled in accordance with the increase or decrease in the load on the outdoor unit B detected by the room temperature thermostat TH1. The above explanation is about heating operation, but during cooling operation, the flow of refrigerant is as shown by the broken line arrow in Figure 2, and as above, the capacity of compressor 1 is adjusted appropriately according to the load of indoor unit B. It is designed to be controlled. Furthermore, in FIG. 2, TH2 is a temperature sensor which is a means for detecting the state quantity of the refrigerant and is disposed on the suction pipe side of the compressor 1, and the temperature sensor detects the temperature Te of the refrigerant to obtain a refrigerant temperature value. It outputs a signal. The graphs in FIGS. 4A and 4B show that during heating operation, when the frequency of the inverter 1a is fixed and the opening degree of the electric expansion valve 5 is changed by changing the pulse signal value, the temperature sensor
Figure 4A shows the value of the temperature Te of the refrigerant detected by TH2, and Figure 4A shows the value when the frequency is 90Hz, and Figure 4B shows the value when the frequency is 30Hz. As shown in Fig. 4 A and B, when the frequency f is large, that is, the operating capacity of the compressor 1 is large, the refrigerant temperature rises significantly when the opening degree of the electric expansion valve 5 is throttled (refrigerant overheating). ), the frequency f is small, i.e. the compressor 1
When the operating capacity of the refrigerant is small, the refrigerant temperature hardly changes even if the opening degree of the electric expansion valve 5 is reduced. Therefore, when the frequency f is large to some extent,
By outputting a pulse signal to reduce the opening degree of the electric expansion valve 5 and detecting the change value of the refrigerant temperature at that time, it can be determined whether the electric expansion valve 5 has operated normally. Although the explanation has been given above regarding the heating operation, the same applies to the cooling operation. Figure 5 shows the above room temperature thermostat during normal operation.
An example of a change in the frequency f of the inverter 1a that is controlled according to the load signal of the indoor unit B from TH1 is shown. The broken line f=A shown in FIG. 5 indicates the lower limit of the frequency f at which the above check operation should be performed,
In this embodiment, f=70Hz is set, and when f>70 for two consecutive minutes, it is determined that the indoor load is sufficiently large and a check operation is started. Furthermore, the broken line at time t=B indicates the initial setting time until the compressor 1 is continuously operated and stabilized, and is set to 30 minutes in this embodiment. Based on the above considerations, a check operation procedure for detecting failure of the electric expansion valve 5 will be explained with reference to the flowchart of FIG. In the flowchart of FIG. 6, first in step _S1 it is determined whether the compressor 1 is started for the first time,
If NO, the check operation has already been completed, and the process proceeds to step _S2 , normal operation; if YES, the process proceeds to step _S3 . In step _S3 , it is determined whether or not the above-mentioned initial setting time t=30 (minutes) shown in FIG. 5 has elapsed, and when the answer is YES that 30 minutes have elapsed, the process moves to step _S4 . Next, in step _S4 , the frequency f is set to the set value f=70 as shown in the graph of FIG.
(Hz) for 2 consecutive minutes,
When the indoor load is determined to be sufficiently large and the result is YES, the process moves to step _S5 and the abnormality determination procedure begins. In this abnormality determination procedure, first, in step _S5 , from time to, the load signal of indoor unit B input from room temperature thermostat TH1 is ignored, and the frequency f is set to the value at that time, as shown in the graph of Fig. 7A. Then, in step _S6 , the temperature Te of the refrigerant detected by the above temperature sensor TH2 at this time is set.
Set to Te ₁ . Further, immediately in step _S7 , the pulse signal value N is changed as shown in FIG. 7B.
is forcibly set to "0" and the opening degree of the electric expansion valve 5 is commanded to be narrowed down to "0". Next, step S ₈
After measuring the refrigerant temperature Te again in step _S9 , it is determined whether the change value from _Te1 to Te (Te- _Te1 ) is smaller than the abnormality judgment value Δt of the electric expansion valve 5. Here, as shown in FIG. 7C, the judgment value Δt is the electric expansion valve 5 with respect to the refrigerant temperature Te ₁ at time t ₁ when the pulse signal value N is changed to "0". This is the lower limit of the change value of the refrigerant temperature Te that would naturally occur if the opening is narrowed to 0 when operating normally, and is determined by the capacity of the air conditioner, the installation condition, etc. In step _S9 , the above change value (Te-Te ₁ ) is determined as the judgment value △t
If the result is NO, it is determined that the electric expansion valve 5 is normal, and the process moves to step _S2 , whereupon normal operation begins. On the other hand, if the change value (Te-Te ₁ ) is smaller than the determination value Δt, the process moves to step _S10 . In step _S10 , as shown in Fig. 7A, the time to maintain the frequency f at a constant value is set to 3 minutes, which does not have an adverse effect on the room temperature or the air conditioner, and the frequency f is maintained at a constant value. After repeating the steps S ₈ and S ₉ for 3 minutes from the held time to, if the determination at step S ₉ is still YES after 3 minutes, the process moves to step S ₁₁ . In step _S11 , it is determined whether or not the abnormality determination procedure for the electric expansion valve 5 has been performed three times in succession according to the steps _S4 to _S10 , and if NO, the process moves to step _S12 . Pulse signal value N that commands to temporarily fix the frequency f and throttle the opening degree of the electric expansion valve 5
Release the fixation of =0 and set the room temperature thermostat TH1.
After returning to the release operation in which the capacity _{of the} compressor ₁ is controlled according to the load signal of Execute. Even if the above abnormality determination procedure of steps S ₄ to _{S 10} is executed three times, the change value (Te − Te ₁ ) of the refrigerant temperature Te is still smaller than the determination value Δt, and the determination in step S ₁₀ is YES. Sometimes, a failure signal is output to determine that the electric expansion valve 5 is abnormal, and the air conditioner is stopped. As described above, in this embodiment, the high capacity detection means 11 for detecting the high capacity operation of the compressor 1 is configured in step _S4 , and the high capacity state of the compressor 1 is configured in steps _S5 and _S6 . control means 1 for controlling to fix the electric expansion valve 5 and to narrow the opening degree of the electric expansion valve 5;
2 are configured. Further, in steps S ₉ , S ₁₀ , and S ₁₁ , the magnitude of the change value (Te − Te ₁ ) of the evaporation temperature before and after the opening degree of the electric expansion valve 5 is throttled, which is detected by the state quantity detection means TH2, is determined. A determining means 13 is configured to determine whether or not the electric expansion valve 5 is malfunctioning. Therefore, in the above embodiment, the compressor 1
After the operation of the compressor 1 becomes stable, when the load on the indoor unit B increases and the compressor 1 starts to maintain high capacity operation, the opening degree of the electric expansion valve 5 usually increases as the capacity of the compressor 1 increases. The pulse signal value N
Since we force the increase of N to 0,
If the electric expansion valve 5 operates normally, failure of the electric expansion valve 5 can be determined based on the presence or absence of an increase in the refrigerant temperature Te due to a change in the pulse signal value N as shown in FIG. 4A, which is observed. . That is, the refrigerant temperature
When the change value of Te is smaller than △t, whether the electric expansion valve 5 has stopped closing due to its large opening, or
Or, there are two possibilities: either the opening degree is small and it is becoming unable to open, so in either case, a failure state has been detected in which the electric expansion valve 5 is no longer operating due to a foreign object, etc. This effectively prevents the compressor 1 from being damaged if it continues to operate when the temperature is too high. In addition, in step _S11 , the abnormality determination procedure is repeated three times, so when no rise in the refrigerant temperature Te is observed due to some other incidental cause other than a failure in the electric expansion valve 5, the electric expansion valve 5 is Misjudgment as failure is effectively prevented. It is known from experience that malfunctions of the electric expansion valve 5 due to foreign objects, etc. almost always occur immediately after the start of operation. It is effective to perform this once a day when the operation of the compressor 1 becomes stable after startup, but the number of times and timing can be arbitrarily determined depending on the capacity of the air conditioner, the installation state, etc. Further, in the above embodiment, an example in which a single indoor unit B is connected to an outdoor unit A has been described, but the same applies to a multi-type air conditioner in which a plurality of indoor units are connected. Furthermore, in this embodiment, a temperature sensor as a means for detecting the state quantity of the refrigerant is attached to the suction pipe of the compressor to detect changes in the temperature of the suction gas, but instead of the temperature sensor, a pressure sensor is used.
A change in pressure (a change in temperature when a change in pressure is converted into a change in temperature) may be detected. In addition, the temperature sensor may be installed not only in the suction pipe but also in the indoor heat exchanger or outdoor heat exchanger. It's good. In addition to setting the opening degree for each frequency as in this embodiment, the electric expansion valve 5 detects the degree of superheat at the outlet of the heat exchanger that serves as the evaporator, and is configured to keep this degree of superheat constant. An electric expansion valve whose opening degree is controlled may also be used. (Effects of the Invention) As explained above, according to the present invention, when the compressor is operating at high capacity, the opening degree of the electric expansion valve is reduced while maintaining the high capacity operation state, and the change in the opening degree is suppressed. Since the abnormality of the electric expansion valve is determined based on the magnitude of the change in the refrigerant temperature Te before and after, it is possible to detect failures of the electric expansion valve, especially when the opening is large. Malfunction can be detected reliably, and damage to the compressor due to malfunction of the electric expansion valve can be effectively prevented.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention. 2 to 7 show examples of the present invention, FIG. 2 is a refrigerant piping system diagram, FIG. 3 is a graph showing the relationship between the opening degree of the electric expansion valve 5 and the pulse signal value N, and FIG. In Figure 4 A and B, the frequency f is 90Hz.
and a graph showing changes in refrigerant temperature Te with respect to pulse signal value N during heating when fixed at 30Hz,
Figure 5 shows the frequency f versus the change in time t during operation.
FIG. 6 is a flowchart showing the check operation procedure for detecting failure of the electric expansion valve 5, and FIG. It is a graph showing changes in f, pulse signal value N, and refrigerant temperature Te. DESCRIPTION OF SYMBOLS 1... Compressor, 1a... Inverter, 5... Electric expansion valve, 11... High capacity detection means, 12... Control means, 1
3...Discrimination means, TH2...Temperature sensor (state quantity detection means).

Claims (1)

[Claims] 1. In an air conditioner equipped with a compressor 1, an inverter 1a that adjusts the capacity by varying the operating frequency of the compressor 1, and an electric expansion valve 5, when the capacity of the compressor 1 is operated at a set value or more. When the compressor 1 is operating at a high capacity detected by the high capacity detection means 11, the capacity adjustment of the compressor 1 by the inverter 1a is fixed and the electric expansion valve 5 is opened. a control means 12 for controlling the opening degree of the electric expansion valve 5 to a large extent; a state quantity detection means TH2 for detecting the state quantity of the refrigerant before and after the change in the opening degree of the electric expansion valve 5 by the control means 12; Discrimination means 13 that outputs a failure signal when the detected change in state quantity is less than a set value
A failure detection device for an electric expansion valve of an air conditioner, characterized by comprising: