JPH0527019B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a refrigeration system, and more particularly to a refrigeration system having a function of determining whether the amount of circulating refrigerant is depleted of gas.

(Prior Art) As a conventional example of determining whether the amount of circulating refrigerant is out of gas, for example, the applicant's earlier application (Japanese Patent Application No. 1983)
-40741). This device will be explained based on FIG. 2 in the embodiment of the present invention. As shown in the figure, this device has a configuration in which one outdoor unit X is connected to a plurality of indoor units A to D. Each indoor heat exchanger 18 is connected between the liquid side branch pipes 15...15 and the gas side branch pipes 17...17. Also, the first liquid pipe 10 and the second liquid pipe 12
A liquid receiver 11 is interposed between the two, and the liquid receiver 11 is connected to the suction pipe 4 of the compressor 1 via a capillary reach tube 21 and a pipe 20. Note that a first electric expansion valve 13 is installed in the first liquid pipe 10, and a second electric expansion valve 13 is installed in each liquid side branch pipe 15...15.
Electric expansion valves 16...16 are provided respectively. Also, a first temperature sensor 31 is attached to the pipe 20.
However, a second temperature sensor 32 is attached to the suction pipe 4 of the compressor 1, and a fourth temperature sensor 34 is attached to the gas side branch pipe 17, respectively. The first temperature sensor 31 is for detecting the pressure-equivalent saturation temperature T1 of the low-pressure gas refrigerant.

In the above-described apparatus, during cooling operation, the temperature of the evaporative refrigerant at the outlet of the indoor heat exchangers 18...18 serving as evaporators is measured by the fourth temperature sensor 34.
At the same time, the degree of superheat of the evaporative refrigerant is determined from this detected temperature T4 and the detected temperature T1 of the first temperature sensor 31, and each of the second electric expansion valves 16... 16 opening degree controls are performed. On the other hand, during heating operation, the degree of superheat is determined from the temperature T2 detected by the second temperature sensor 32 and the temperature T1 detected by the first temperature sensor 31, and the opening degree of the first electric expansion valve 13 is controlled in the same manner as above. Do this. When the detected degree of superheat is greater than the reference degree of superheat, each electric expansion valve 16, 13 is operated to the open side in order to increase the amount of flowing refrigerant; If the degree of superheat that is detected does not continue to decrease and each electric expansion valve 16, 13 remains at or above the set upper limit opening for a certain period of time, an abnormal dryness determination is made.
Furthermore, it is determined that the gas is out of gas and outputs an abnormal signal.

(Problems to be Solved by the Invention) By the way, in the above device, each electric expansion valve 16, 13 is initially set to an initial opening degree and starts operation, and then the degree of superheat is sequentially determined and the electric expansion valve 16 is , 13, there is a limit to the additional opening per time, so for example, leakage from refrigerant piping occurs while the equipment is stopped, which can cause a large amount of gas to run out. If the gas is running low, it will take a long time to reach the set upper limit opening corresponding to the gas shortage condition, and in addition, the gas shortage will be determined after the condition has passed for a certain period of time.
During this period, problems such as burnout of the compressor coils occurred. Furthermore, liquid pipe 10,
In the case where the refrigerant in the refrigerant 12 is not liquefied or there is a large gas shortage where liquefaction is insufficient, the first temperature sensor 31 cannot detect the temperature as the pressure equivalent saturation temperature.
Since the above-mentioned opening degree control based on the detection of the degree of superheating cannot be performed, there is a problem that it becomes impossible to detect an abnormal state of gas shortage. Additionally, the temperature sensor 30, which is generally attached to the discharge piping of the compressor, is provided for the purpose of preventing abnormal temperature rise inside the compressor in such a gas starvation state. This is based on the premise that there is a temperature correlation between the inside of the compressor and the discharge piping due to heat transfer from the refrigerant, such as the amount of heat generated within the compressor being transferred to the discharge piping by the refrigerant circulating internally. Therefore, the amount of circulating refrigerant is significantly reduced,
There has been a problem in that it is not possible to automatically detect a situation in which there is a large gas shortage such that the above-mentioned temperature correlation cannot be obtained, particularly in a case where the gas shortage is greater than at the time of startup.

This invention was made in order to solve the above-mentioned conventional problems, and even when a large gas shortage occurs, it can be accurately determined and prevent troubles such as burnout of the compressor coil. An object of the present invention is to provide a refrigeration system that can prevent the occurrence of such occurrence.

(Means for Solving the Problems) Therefore, as shown in FIG. 1, the refrigeration system of the present invention includes a compressor 1 whose capacity is controlled by the compression capacity according to the required load on the user side heat exchanger 18 side. The refrigeration system includes an input amount detection means 48 for detecting the amount of electrical input to the compressor 1, and a storage means 52 for storing in advance a reference input amount for determining gas shortage determined according to the compression capacity. In the operating range above the specific compression capacity, where there is a stably detectable difference between the detected input amount during normal operation and the above reference input amount,
A determining means 50 determines that the amount of circulating refrigerant is out of gas when the detected input amount is less than or equal to the reference input amount corresponding to the compression capacity for a predetermined period of time; Abnormal signal output means 51 for outputting a signal is provided.

(Function) In the above device, in the compressor 1 which is driven to provide the required compression capacity, the input amount corresponding to the required compression work is applied to the circulating refrigerant during normal operation. A reference input amount set based on the total input amount is stored in advance in the storage means 52. On the other hand, when there is a gas shortage, in the compressor 1 that is driven to provide the same compression capacity as described above, the amount of input required for compression work for a smaller amount of circulating refrigerant than in normal times becomes smaller than in normal times. Therefore, by comparing the input amount during actual operation with the reference input amount, it is possible to determine whether the gas is out of gas. In particular, in the above case, the larger the out-of-gas condition, the larger the difference between the normal input amount and the input amount at the time of out-of-gas. belongs to. Therefore, by providing an input amount detection means 48, a determination means 50 for comparing and determining the detected input amount and a reference input amount, and an abnormality signal output means 51, automatic detection becomes possible even in a particularly excessive gas shortage state. , the occurrence of troubles such as burnout of the coils of the compressor 1 can be prevented.

Furthermore, the reason why the gas shortage determination is performed in the operating region where the compression capacity is equal to or higher than the specific capacity is as follows. That is, when the compression capacity is low, the reference input amount and the detected input amount during normal operation are very close to each other, and there is a risk of erroneous determination. On the other hand, as the compression capacity increases, the proportion of the amount of work required to compress the refrigerant in the total power consumption of the compressor 1 increases, and therefore gas shortage can be clearly determined based on the difference in input values. Since the capacity of the compressor 1 is controlled in accordance with the requested load from the user side heat exchanger 18, even if the operation is started with a low capacity as the initial value, when the user side heat exchanger 18 runs out of gas, the user side heat exchanger 18 Therefore, the compression capacity is controlled in the direction of increasing the compression capacity. This means that even if you do not make a judgment on the low capacity side, which is likely to cause false judgments, the compression capacity will inevitably increase when you run out of gas. This makes it possible to make reliable judgments.

(Example) Next, a refrigeration system of the present invention will be described in detail using an air conditioner as an example with reference to the drawings.

First, Figure 2 shows a refrigerant circuit diagram of a multi-model air conditioner equipped with four indoor units.
In the figure, X indicates the outdoor unit, and A to D indicate the first unit.
~The fourth indoor unit is shown, respectively. The above-mentioned outdoor unit 5. A first gas pipe 6 and a second gas pipe 7 are connected to the four-way switching valve 5, respectively, and an outdoor heat exchanger 8 is connected to the second gas pipe 7. Note that an outdoor fan 9 is attached to the outdoor heat exchanger 8. Further, a first liquid pipe 10, a liquid receiver 11, and a second liquid pipe 12 are sequentially connected to the outdoor heat exchanger 8, and a first electric expansion valve 13 is interposed in the first liquid pipe 10. has been done.
The second liquid pipe 12 is connected to a header 14, and a plurality of liquid side branch pipes 15, four in the case of the figure, branch from the header 14.
A second electric expansion valve 16...16 is provided in each liquid side branch pipe 15...15, respectively. On the other hand, from the first gas pipe 6, there are also four gas side branch pipes 1 corresponding to the above.
7...17 is branched, and each of the above branch pipes 15, 17
In between, the indoor heat exchanger 18 which becomes the user side heat exchanger
...18 are connected. In addition, each indoor heat exchanger 1
8 is equipped with an indoor fan 19, and both 18 and 1
9 constitute indoor units A to D. Further, the liquid receiver 11 and the suction pipe 4 of the compressor 1 are connected by a pipe 20, and a capillary reach tube 21 is interposed in the pipe 20. In the figure, 22 is a gas shutoff valve, 23 is a liquid shutoff valve, 24 and 25 are mufflers, and 2
6 indicates an accumulator. In the above air conditioner, as shown by the solid arrow in the figure, the refrigerant discharged from the compressor 1 is recirculated from the outdoor heat exchanger 8, which serves as a condenser, to the indoor heat exchangers 18, which serve as evaporators. In contrast, the refrigerant discharged from the compressor 1 is circulated from the indoor heat exchanger 18, which serves as a condenser, to the outdoor heat exchanger 8, which serves as an evaporator. Therefore, heating operation is performed (dashed line arrow in the figure).

In the refrigerant circuit, a first temperature sensor 31 is attached to a position on the exit side of the capillary reach tube 21. The purpose is to detect Further, a second temperature sensor 32 is installed in the suction pipe 4 of the compressor 1.
On the other hand, each of the liquid side branch pipes 15...15 is provided with a third temperature sensor 33...33, and each of the gas side branch pipes 16 is further provided with a third temperature sensor 33...33.
...16 has a fourth temperature sensor 34...34, and the discharge pipe 3 of the compressor 1 has a fifth temperature sensor 30.
The functions of each of these temperature sensors will be described later.

FIG. 3 shows a block diagram of the control system of the air conditioner. As shown in the figure, the outdoor unit X has an outdoor control device 35, and each of the indoor units A to D has an indoor control device 36. The indoor control device 36 includes an operation switch 37 and an indoor thermostat 3.
8 are connected to each other, and the indoor control device 3
6, the following three signals to the outdoor control device 35, that is, the operation switch 37 are ON,
In addition, an operation command signal issued when the room temperature has not reached the set temperature, a ΔT signal corresponding to the temperature difference between the detected room temperature and the set temperature, and a model code signal are output.

On the other hand, the outdoor control device 35 has a load capacity value grasping section 39 that grasps the total load capacity value ΣS of the indoor units A to D that have the operation command, and integrates the ΔT signals of the indoor units A to D that have the operation command. teΣΔT
and a temperature difference detection unit 40 that calculates the temperature difference. A frequency control section 41 that issues an operating frequency command signal based on the above ΣS and ΣΔT, and an inverter control section 43 that receives this command signal and controls the inverter 2 to which the drive motor 1a of the compressor 1 is connected. have.
Further, the outdoor control device 35 further includes the first to
It has a valve control section 42 that controls the opening degrees of the first and second electric expansion valves 13, 16, . . . , 16 based on the temperatures detected by the fourth temperature sensors 31 to 34. Furthermore, the outdoor control device 35, as described later,
A circulating refrigerant state determining unit 46 and a discharge pipe temperature monitoring unit 47 having a function of determining whether the amount of circulating refrigerant is out of gas.
and a determination section 50.

In the control circuit with the above configuration, first the compressor 1
The compression capacity of the inverter, that is, the control of the inverter frequency, will be explained.

In the outdoor control device 35, as described above, based on the model code signal output from each indoor control device 36...36, the load capacity grasping section 39 determines the total load capacity of the indoor units A to D for which the operation command is given. Efforts have been made to understand ΣS, and this is done through the following steps. First, the model code signal output from the indoor control devices 36...36 is determined according to the capacity of each indoor heat exchanger 18, and is, for example, 2240kcal/
For the capacity of h, the code “000” is
2800kcal/h is defined as "001", 3550kcal/h as "010", 4500kcal/h as "011", and these codes are stored in each indoor unit A to D. has been done. In addition, in the load capacity grasping section 39, the storage section 44 has the following information:
A load capacity value S corresponding to the above model code is stored. This load capacity value S is 2240kcal/
h (model code “000”) is the standard value “1”,
2800kcal/h (model code "001") to "1.25",
3550kcal/h (model code "010") to "1.5",
4500kcal/h (model code "011") is set as "2", and the load capacity grasping circuit 45 reads out the load capacity value S for each indoor unit A to D for which an operation command is given. With,
The sum of these ΣS is calculated.

In the outdoor control device 35, the total load capacity value ΣS of the indoor units A to D for which the operation command is given as described above is grasped, and the difference between this and the room temperature set by the indoor thermometer 38 is determined. The frequency of the compressor 1 is controlled by the frequency control section 41 based on the corresponding signal ΣΔT. That is, the initial setting frequency corresponding to the above ΣS and ΣΔT is memorized, and the operation is performed at the above initial setting frequency at the start of operation and when the number of operating rooms is increased, and after a predetermined time has passed, P is set based on ΣΔT. The frequency is changed by control, PID control, etc. Therefore, for example, indoor unit A with an operation command
When the number of units ~D is large, the total load capacity value ΣS generally becomes large, and in this case, the compressor 1 is driven at a high frequency, thereby increasing the air conditioning capacity and providing each room with the capacity that meets the demand. At the same time, it is air conditioned.

Next, the first and second valves are controlled by the valve controller 42.
A method of controlling the electric expansion valves 13, 16, . . . 16 will be explained. First, during cooling operation, the first electric expansion valve 1
3 fully open, and each second electric expansion valve 1
6...16 opening control is performed, and each indoor heat exchanger 1
Control is performed so that the degree of superheating of the gas refrigerant that evaporates within 8...18 is approximately constant. In this case, the low pressure equivalent saturation temperature T1 detected by the first temperature sensor 31
and the evaporative refrigerant temperature T4...T4 detected by the fourth temperature sensor 34, that is, the detected superheat degree (T4-
T1) and the standard superheat degree SHO: deviation E = (T4-
T1) - Increase or decrease the opening degree of each second electric expansion valve 16...16 by the opening degree P=C・E (C is a positive constant) proportional to SHO (P>0 is open, P<0 is closed) , so-called P control is performed.

On the other hand, during heating operation, the degree of superheat of the refrigerant evaporated in the outdoor heat exchanger 8 is controlled by the first electric expansion valve 13.
PID control is performed, and in each of the second electric expansion valves 16...16, control (referred to as FD control) is performed to equalize the condensed refrigerant temperature at the outlet of each indoor heat exchanger 18...18 during operation. The former is the first
The difference between the low pressure equivalent saturation temperature T1 detected by the temperature sensor 31 and the evaporative refrigerant temperature T2 detected by the second temperature sensor 32, that is, the detected superheat degree (T2-
T1) and this detected superheat degree (T2-
Deviation E between T1) and standard superheat degree SHO = (T2-T
1) Find -SHO at each predetermined sampling time,
Deviation for each sampling E0, E1, E2,...
This method controls the opening degree of the first electric expansion valve 13 based on the following equation.

P=K0・E0+K1・(E0−E1) +K2・(E0−2E1−E2) (However, K0, K1, and K2 are constants) In other words, if P>0, the first electric expansion valve 13 is opened only by P pulse. , on the other hand, if P<0, then P (absolute value)
Control is performed to close the valve only during pulses.

Further, the FD control by each of the second electric expansion valves 16...16 is performed by detecting the condensed refrigerant temperature T3...T3 at the outlet of the indoor heat exchanger 18...18 in operation with each third temperature sensor 33...33, and The average temperature Tm of these detected temperatures T3...T3 is determined, and the opening degree of each of the second electric expansion valves 16...16 is determined by the average temperature Tm.
and detected temperature T3...Temperature difference between T3 (Tm-T3)
Quantity proportional to P=D・(Tm−T3) (however, D
is a positive constant) (P>0 is open, P<0 is closed).

The opening control signals for the electric expansion valves 13 and 16 as described above are also input to the circulating refrigerant state determination unit 46 that determines abnormally wet operation or abnormally dry operation. For example, if the opening degree of the first electric expansion valve 13 remains abnormal at its set upper limit during heating for 20 minutes or more, the opening degree of each second electric expansion valve 16 in the driver's cab during cooling will similarly change. If the condition at or above the set upper limit continues for 20 minutes or more, this is determined to be a gas shortage condition, and an abnormality signal is input from the circulating refrigerant condition determination section 46 to the frequency control section 41, and the frequency control section 41 , a signal to stop the compressor 1 is output.

Furthermore, the temperature signal detected by the fifth temperature sensor 30 attached to the discharge pipe 3 of the compressor 1 is
If the detected temperature exceeds, for example, 120°C, an abnormal signal is output from the discharge pipe temperature monitoring section 47, and this abnormal signal causes the frequency control section 41 to forcibly lower the frequency. If the abnormality signal is not canceled by the command signal or this process, a compressor 1 stop signal is output.

The circulating refrigerant state determination unit 46 determines that the circulating refrigerant in the liquid pipes 10 and 12 is in a liquid state and is therefore in a low gas depletion state within a range where the pressure equivalent saturation temperature can be detected through the pipe 20. It is possible to determine the Furthermore, due to the refrigerant flowing inside the compressor 1,
The temperature inside the compressor 1 and the temperature detected by the fifth temperature sensor 30 attached to the discharge pipe are
Moderate gas starvation conditions within a range having a substantially proportional relationship can be automatically detected by the discharge pipe temperature monitoring section 47. However, there is an even more severe gas shortage, in which the circulating refrigerant in the liquid pipes 10 and 12 is no longer liquid, making it impossible to detect the pressure-equivalent saturation temperature and depriving the compressor 1 of the heat generated. This is transmitted to the discharge pipe 3, and in a gas-deficient state where the amount of circulating refrigerant is less than that which can maintain the temperature correlation between the two, the circulating refrigerant state determination section 46 and the discharge pipe temperature monitoring section 47 It becomes impossible to determine this. Therefore, in this air conditioner, in order to automatically detect the above excessive gas shortage state, a power supply line for driving the compressor 1 to the inverter 2 is provided to detect the supplied current value Ii. a determination unit (i.e., determination means) 50 that converts the detected value of a certain current transformer (i.e., input amount detection means) 48 into a digital signal via an A/D converter 49, and determines a gas shortage state based on this signal; , an abnormal signal output section (i.e.,
An abnormality signal output means) 51 and a storage section (that is, storage means) 52 in which a reference current value corresponding to the compression capacity of the compressor 1 is stored in advance are provided, and control as shown in the flowchart of FIG. 4 is provided. is being carried out.

First, after the start of operation, as will be described later, a timer T that counts the duration of time during which the input current value Ii to the inverter 2 is less than or equal to the set value is reset (step
S1), execute the following gas shortage determination step. That is, in step S2, the input current value Ii is detected, and then the command frequency output from the frequency control section 41 to the inverter control section 43 at this time is read. Then, in step S4, the storage section 44
The reference input current value Il for the above-mentioned command frequency is then read out. The storage unit 44 stores the frequency and lower limit current value Il based on the graph shown in FIG.
The relationship data is entered as a data table. In FIG. 5, the horizontal axis is the compressor drive frequency, and the vertical axis is the inverter input current value.
In the same figure, the shaded area is the normal operating range that takes into account the fluctuation range during normal operation, and its center reference line is 0.1F+
0.6(A) (F is frequency). As shown in the figure, the higher the frequency, the higher the compression capacity, and therefore the higher the input current. Here, if there is a gas shortage, the compression work of the compressor will decrease, and as a result, the power consumption, that is, the input current value during constant voltage drive will become smaller than in the normal state, and so on. , a gas shortage determination line Il is provided on the lower current side than the normal operating range. This determination line Il has a lower limit determination frequency of 55 Hz, and is intended to perform determination at 55 Hz or higher. This is because the Il line approaches the normal operating range at low frequencies, which may lead to erroneous determination. On the other hand, as the frequency increases, the proportion of work required to compress the liquid refrigerant increases in the total power consumption of the compressor, and therefore it becomes difficult to clearly determine gas shortage based on the difference in input current values. Become so. Since the compressor's frequency is controlled to match the load required from the heat exchanger on the user side, even if operation is started with a low frequency as the initial value, if there is a gas shortage, the heat exchanger on the user side will This requirement is not satisfied, and therefore frequency control is performed in the direction of increasing the frequency. From this, even if the judgment line Il on the low frequency side, which tends to cause false judgments, is cut, the control frequency will inevitably increase when the gas runs out, so it is necessary to set the judgment range as shown in the figure. This enables reliable determination without causing erroneous determination.

Based on the determination line Il as described above, in step S4 in FIG. 4, the reference current value Il corresponding to the current command frequency detected in step S3 is read out from the storage section 52.
Then, the input current value Ii to inverter 2 at that time
and the above-mentioned Il (step S5), and if Ii exceeds Il, it is judged as normal, and the process returns to step S1, and the above-mentioned monitoring steps S2 to S5 are continued. and,
If Ii is less than Il in step S5, the process moves to step S6, and the timer T starts counting.
This timer T is provided to determine whether the low current input state corresponding to the gas shortage continues for a certain period of time Tc. This is provided to prevent the phenomenon from being judged as a gas shortage. In the above embodiment, Tc is set to a value of 24 minutes based on the time required for the coil of the compressor 1 to burn out when the compressor 1 is completely out of gas. Therefore, in step S7, the process returns to step S2 until the count value of T exceeds Tc, and steps S2 to S5 are repeated.
The state determination of Ii and Il is repeated. If the measured value of the timer T exceeds Tc in step S7, the process moves to step S8, and the error signal output section 5
1 outputs an abnormal signal to the frequency control section 41,
This signal causes the compressor 1 to be stopped. If Ii exceeds Il during the above-mentioned low current input state continuation determination step, it is determined that the decrease in the input current value Ii is the above-mentioned temporary transient phenomenon, and the process moves from step S5 to step S1. Then, the time value of the timer T up to that point is reset, and the gas shortage monitoring step is executed again.

As mentioned above, the gas shortage state is determined by monitoring the input current value to the inverter 2 as shown in FIG. 4 in parallel with the frequency control operation of the compressor 1. Therefore, it is possible to prevent troubles such as coil burnout of the compressor 1 from occurring.

Note that although the above example shows an example of implementation in an inverter-type multi-type air conditioner, it can also be applied to an air conditioner with only one indoor unit or a refrigeration system with other configurations of compression capacity control methods. It is possible to implement. Further, in the above embodiment, the amount of input to the compressor 1 is the input current value, and the detection means is configured with a current transformer. It is also possible to configure a variable capacity compressor with a voltage control configuration to detect the input voltage value, etc. In these cases, it is possible to detect the input voltage value, etc. What is necessary is just to adopt the structure which provides a detection means.

(Effects of the Invention) As explained above, in the refrigeration system of the present invention, when there is a flow rate of refrigerant during normal operation, the amount of input required to provide the required compression capacity is By comparing the reference input amount and the actually detected input amount, if the detected input amount continues to be smaller than the reference input amount, a determination means is provided to determine that the gas is out of gas. In particular, even when an excessive gas shortage occurs, this can be automatically detected, and troubles such as compressor coil burnout can be prevented.

Furthermore, since the gas shortage determination is performed on the high-capacity side, which is easier to perform the determination, it is possible to perform the gas shortage determination reliably with fewer false determinations.

[Brief explanation of the drawing]

The figures show an embodiment of the refrigeration system of the present invention, in which Fig. 1 is a functional system diagram, Fig. 2 is a refrigerant circuit diagram,
FIG. 3 is a block diagram of the operation control system, FIG. 4 is a flowchart for determining gas shortage, and FIG. 5 is a graph showing the relationship between inverter frequency and input current value. DESCRIPTION OF SYMBOLS 1... Compressor, 18... Indoor heat exchanger (utilization side heat exchanger), 48... Current transformer (input amount detection means), 50... Judgment part (judgment means), 51...
...Abnormal signal output section (abnormal signal output means), 52...
...Storage unit (storage means).

Claims (1)

[Claims] 1 A refrigeration system having a compressor 1 whose capacity is controlled by the compression capacity according to the required load on the user side heat exchanger 18 side, and an input amount detection means 48 for detecting the amount of electrical input to the compressor 1. and a storage means 52 that stores in advance a reference input amount for determining gas shortage determined according to the compression capacity, and a stable detectable difference between the detected input amount during normal operation and the reference input amount. determining means 50 for determining the amount of circulating refrigerant to be in a gas-deficient state when a state in which the detected input amount is equal to or less than a reference input amount corresponding to the compression capacity continues for a predetermined time in an operating region exceeding a specific compression capacity; A refrigeration system characterized in that it is provided with an abnormality signal output means 51 which outputs an abnormality signal in response to the output of the determination means 50.