JPH0473566A - Refrigeration equipment operation control device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an operation control device for a refrigeration system, and particularly to measures to prevent failures due to lack of refrigerant.

(Prior Art) Conventionally, for example, as disclosed in Japanese Patent Application Laid-open No. 56-71775, a pressure sensor for detecting low pressure side pressure is arranged in a refrigeration system, and the low pressure side pressure detected by the pressure sensor is By setting the compressor to stop when the amount of refrigerant drops below a predetermined value, and determining that the amount of refrigerant is insufficient when the number of times the compressor starts and stops increases beyond the preset value. An operation control device for a refrigeration system that attempts to detect leakage is a well-known technology.

(Problem to be solved by the invention) By the way, as shown in FIG. 4, when the refrigerant amount changes from 1°0% to 0%, the low pressure side pressure Lp is normally r3.
(kg/cd) It changes from about J to a value close to "0" (see the lower figure of the same figure). Therefore, as in the conventional system described above, it is possible to detect a shortage of refrigerant by using changes in the low-pressure side pressure LP.

However, regardless of when the amount of refrigerant changes drastically, if the amount of refrigerant changes slightly due to leakage, the change in the pressure on the low pressure side will be small, and the conventional method described above can accurately detect the shortage of refrigerant amount. There is a possibility that it cannot be detected well. That is, this is because the range of change in the low pressure side pressure LP is narrow with respect to a change in the amount of refrigerant.

Moreover, in order to detect the low-pressure side pressure LP, it is necessary to arrange an expensive pressure sensor, and there is a problem that an effect commensurate with the cost cannot be obtained.

On the other hand, looking at the change in the discharge pipe temperature T2 with respect to the change in the amount of refrigerant, as shown in the upper part of FIG. 4, when the amount of refrigerant is insufficient, the discharge pipe temperature T2 shows a rapid temperature rise.

The present invention has been made in view of the above, and its purpose is to focus on the characteristic that the temperature of the discharge pipe changes rapidly according to changes in the amount of refrigerant, and to utilize an existing temperature sensor. The object of the present invention is to detect a refrigerant deficiency state at low cost and with high precision, thereby improving reliability.

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention is as shown in FIG. A refrigeration system is assumed to be provided with a refrigerant circuit (9) formed by sequentially connecting an evaporator (6 or 3) and an evaporator (6 or 3).

As an operation control device for the air conditioner, there is a discharge pipe temperature detection means (T h2) for detecting the temperature of the discharge pipe of the compressor (1), and a discharge pipe temperature detection means (T h2) that receives the output of the discharge pipe temperature detection means (T h2). , signal output means for outputting a refrigerant starvation signal when the discharge pipe temperature remains at a predetermined value or higher for a predetermined time or longer and when the electric expansion valve (5) is opened at a predetermined opening close to full open or higher; (51).

(Function) With the above configuration, in the present invention, when the discharge pipe temperature becomes equal to or higher than a predetermined value during operation of the refrigeration system, the discharge pipe temperature detection means (
It is detected by T h2).

In other words, the amount of refrigerant in the refrigerant circuit (9) may be less than the required amount due to leakage of refrigerant from refrigerant piping, insufficient amount of refrigerant charged, or the opening degree may be fixed small due to a failure of the electric expansion valve (5). If the amount of refrigerant circulation is reduced, etc., the compressor (1
) is subjected to excessive stress and the temperature of the discharge pipe increases.

In that case, if the operation continues as it is, it may cause the compressor (1) to seize or otherwise malfunction. However, in the present invention, the discharge pipe temperature remains at a predetermined value or higher for more than a predetermined time, and the electric expansion valve (1) When the opening degree of 5) is equal to or higher than a predetermined opening degree close to fully open, the signal output means (51) outputs a refrigerant shortage signal. Therefore, a refrigerant deficiency state caused by insufficient charging fAjt or leakage can be detected with high accuracy based on the discharge pipe temperature, which changes greatly with respect to changes in the amount of refrigerant. That is,
By utilizing existing temperature sensors, reliability will be improved without increasing costs.

(Example) Hereinafter, an example of the present invention will be described based on the drawings from FIG. 2 onwards.

Fig. 2 shows the refrigerant piping system of an air conditioner to which the present invention is applied, in which (1) is the compressor, (2) is the four pipes that switch during cooling operation as shown by the solid line in the figure, and during heating operation as shown by the broken line in the figure. The road switching valve (3) functions as a condenser during cooling operation.
The outdoor heat exchanger is a heat source side heat exchanger that functions as an evaporator during heating operation, (4) is a receiver that stores liquid refrigerant, and (5) has a refrigerant pressure reduction function and a refrigerant flow rate adjustment function. The electric expansion valve (6) is an indoor heat exchanger that is installed indoors and functions as an evaporator during cooling operation and as a condenser during heating operation, and (7) is an indoor heat exchanger for the compressor (1). This is an accumulator installed in the suction pipe to remove liquid refrigerant from the suction refrigerant.

The above-mentioned devices (1) to (7) are sequentially connected by refrigerant piping (8) to form a refrigerant circuit (9) that improves heat transfer by circulating the refrigerant.

Here, an oil recovery device (10) for recovering oil in the discharged refrigerant is interposed on the discharge side of the compressor (1) of the refrigerant circuit (9), and the oil recovery device (10) From compressor (1)
- Oil skimmer (1) up to the suction pipe between the accumulator (7)
An oil return passage (11) is provided for returning the oil from the compressor (1) to the suction side of the compressor (1). The oil return passage (11) is provided with an on-off valve (12) that opens and closes the passage, and while the on-off valve (12) is normally closed, the oil return passage (11) is closed when the compressor (1) is started. At certain times, it is opened under predetermined control to return part of the oil and discharged refrigerant from the oil recovery device (10) to the suction side of the compressor (1).

Further, in the liquid pipe of the refrigerant circuit (9), the receiver (
4) and the electric expansion valve (5) are connected to a common path (8) so that the electric expansion valve (5) communicates with the lower part of the receiver (4), that is, the liquid part.
a), and the point (P) which is the upper end of the receiver (4) of the common path (8a) and the outdoor heat exchanger (
3) is connected to the first inflow path (8b
), there is a second check valve (22) between the point (P) of the common path (8a) and the indoor heat exchanger (6) that allows the refrigerant to flow only to the receiver (4) side. and the second inflow path (8
C), while the common path (8a
) between a point (Q) that is the end of the electric expansion valve (5) side of the electric expansion valve (5) and a point (S) between the first check valve (21) and the outdoor heat exchanger (3).
The first outflow path (8d) via the first capillary tube (C1) connects the point (Q) of the common path (8a) and the second check valve (22) to the indoor heat exchanger (6). ) between the points (R
) are connected to each other by a second outflow path (8e) via a second capillary tube (C2).

That is, during cooling operation, the liquid refrigerant condensed and liquefied in the outdoor heat exchanger (3) passes through the first check valve (21) and is stored in the receiver (4), and then flows through the electric expansion valve (5) and the second capillary. After being depressurized in the tube (C2), the indoor heat exchanger (6
) and return to the compressor (1), while during heating operation, the liquid refrigerant condensed and liquefied in the indoor heat exchanger (6) passes through the second check valve (22) and returns to the receiver (4). is stored in the electric expansion valve (5) and the first capillary tube (C
After being depressurized in step 1), the air is evaporated in an outdoor heat exchanger (3) and then returned to the compressor (1) for circulation.

Note that (8f) is a liquid seal prevention bypass path provided in the first inflow path (8b) between point (P) and point (S) by bypassing the first check valve (2]). A third capillary tube (C3) for reducing the pressure of the refrigerant is interposed in the liquid seal prevention bypass path (8f).

In addition, the air conditioner is equipped with sensors,
(T h2) is a discharge pipe sensor disposed in the discharge pipe of the compressor (1) and serves as a discharge pipe temperature detection means for detecting the discharge pipe temperature T2, and (T he) is a liquid pipe of the outdoor heat exchanger (3). The outdoor liquid pipe sensor (T ha) is placed at the air inlet of the outdoor heat exchanger (3) and detects the condensation temperature Tc of the refrigerant during cooling operation and the evaporation temperature Te of the refrigerant during heating operation. Outside temperature sensor that detects temperature, (The)
is an indoor liquid pipe sensor placed in the liquid pipe of the indoor heat exchanger (6) and detects the evaporation temperature Te during cooling operation and the condensation temperature Tc during heating operation; (T hr) is the indoor liquid pipe sensor of the indoor heat exchanger (6).
An indoor suction sensor is arranged at the air suction port of the air conditioner and detects the suction air temperature Tr, and each of the above-mentioned sensors is connected to a controller (not shown) for controlling the operation of the air conditioner so as to be able to input signals. The controller controls the operation of each device according to the sensor signals.

Next, the details of the overheating control performed by the controller will be explained.

FIG. 3 shows a part of the flow of superheating control, in which step S1
Then, it is determined whether the value of the discharge pipe temperature T2 detected by the discharge pipe sensor (T h2) is equal to or higher than a predetermined value of 125°C, and T
2≧]25, in step S2, the discharge pipe temperature T2
A timer counter (not shown) is used to count the elapsed time since the temperature exceeded 125°C as an integrated value Fgke every 20 seconds of sampling time, while T2≧125
Otherwise, proceed to step S3 and check whether the timer's integrated value Fgke is 19'' or higher, that is, the set time (3 minutes) after the discharge pipe i degree T2 reaches 125°C or higher.
When the set time (3 minutes) has elapsed, the process moves to step S4, and it is determined whether the total opening degree ΣP of the electric expansion valve (5) is 1800 (pulses) or more. However, if the total opening degree ΣP is 1800 pulses or more, a refrigerant shortage signal is output in step S5.

In addition, after that, the air conditioner is kept in the thermo-off state for a certain period of time (for example, about 3 minutes) at step 17, and if the condition changes to the thermo-on condition thereafter, so-called retry control is performed to automatically return the air conditioner to the thermo-on condition. By doing so,
The system is designed to avoid abnormal shutdowns as much as possible while protecting the air conditioner.

In the above flow, by the control in step S5, the discharge pipe temperature T2 is maintained at a predetermined value (125° C.) or more for more than a set time (3 minutes), and the electric expansion valve (5
) opening ΣP or a predetermined opening close to fully open (1800 pulses)
In the above case, a signal output means (51) is configured to output a refrigerant shortage signal.

Therefore, in the present invention, during installation of the refrigeration system, when the refrigerant is insufficient due to insufficient filling amount, the compressor (1)
A lack of refrigerant sucked into the compressor (1) causes problems such as excessive stress on the compressor (1).

On the other hand, in the above embodiment, the discharge pipe sensor (T h2
) The discharge pipe temperature T2 detected by
) If the above condition continues for more than the set time (3 minutes), check the opening degree (ΣP) of the electric expansion valve (5) and open the electric expansion valve (5).
) is greater than or equal to the predetermined opening (1800 pulses), the signal output means (51) issues a refrigerant shortage signal, indicating that there is no shortage of refrigerant circulation due to a failure of the electric expansion valve (5). Output.

Here, as shown in Fig. 4, when the refrigerant circulation rate changes from 100% to 0%, the change in the low pressure side pressure LP usually ranges from about 3 (kg/cn!) to nearly rOJ. , the range of change is relatively small (see the bottom of the same figure)
However, the discharge pipe temperature T2 changes over a very wide range (see the upper diagram in the same figure).

Therefore, it is possible to accurately detect a refrigerant deficiency state from a change in the discharge pipe temperature T2. Furthermore, since it is possible to detect a refrigerant shortage state while distinguishing between a reduction in the amount of refrigerant circulation due to a failure of the electric expansion valve (5) and a lack of refrigerant due to insufficient filling or leakage, a failure of the compressor (1) can be detected. etc. can be effectively prevented. Moreover, there is an advantage that accurate detection can be performed by using a temperature sensor without using an expensive pressure sensor.

Note that, as is not limited to the above embodiments, the present invention can be applied to both cooling and heating operations, and can also be applied to refrigeration-only equipment such as container refrigerators.

(Effects of the Invention) As described above, according to the present invention, the temperature of the discharge pipe of a refrigeration system is detected, and the state in which the temperature of the discharge pipe is equal to or higher than a predetermined value continues for a set time or longer, and the opening of the electric expansion valve is A refrigerant shortage signal is output when the opening is above a predetermined opening, so
By using an existing inexpensive temperature sensor, it is possible to accurately detect a refrigerant deficiency state based on the discharge pipe temperature, which changes over a wide range in response to changes in the amount of refrigerant circulated, thereby increasing costs. Reliability can be improved without any problems.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention. Figure 2 and the following diagrams show embodiments of the present invention. Figure 2 is a refrigerant piping system diagram showing the configuration of an air conditioner, Figure 3 is a flowchart showing the control details of the controller, and Figure 4 is a diagram showing the amount of refrigerant circulation. FIG. 3 is a characteristic diagram showing changes in discharge pipe temperature and low-pressure side pressure with respect to changes. ] Compressor 2 Outdoor heat exchanger (condenser or evaporator) 5 Electric expansion valve 6 Indoor heat exchanger (evaporator or condenser) 9 Refrigerant circuit 51 Signal output means Th2 Discharge pipe sensor (discharge pipe temperature detection means) Th2 Signal output means discharge pipe sensor (discharge pipe temperature detection means) Fig.

Claims (1)

[Claims] (1) In a refrigeration system equipped with a refrigerant circuit (9) formed by sequentially connecting a compressor (1), a condenser (3 or 6), an electric expansion valve (5), and an evaporator (6 or 3), the above-mentioned a discharge pipe temperature detection means (Th2) for detecting the temperature of the discharge pipe of the compressor (1);
), when the discharge pipe temperature remains above a predetermined value for a predetermined time or longer and the opening degree of the electric expansion valve (5) is at least a predetermined opening degree close to fully open, a refrigerant shortage signal is sent. An operation control device for a refrigeration system, comprising: a signal output means (51) for outputting a signal.