JPH0452465A - Refrigeration equipment operation control device - Google Patents

Abstract

PURPOSE:To prevent a wet refrigerant operation from occurring and contrive higher reliability by providing an air volume changing means for increasing the volume of air blown by a fan when the discharge pipe temperature of a compressor is lowered below a value obtained by adding a predetermined value to the condensation temperature of the refrigerant, during an operation of a refrigerator. CONSTITUTION:A means Th2 for detecting the discharge pipe temperature of a compressor 1 and means Thc or The for detecting the condensation temperature of a refrigerant in a condenser 3 or 6 are provided. During an operation of a refrigerator, when the discharge pipe temperature detected by the means Th2 is lowered below a value obtained by adding a predetermined value to the condensation temperature detected by the means Thc or The, an air volume changing means 51 increases the volume of air blown by a fan 6a or 3a provided for an evaporator 6 or 3. Where the predetermined value is set according to a desired dryness, the time when the refrigerant taken into the compressor l becomes wet is detected from the relationship between the detected discharge pipe temperature and the detected condensation temperature. Evaporating capacity is increased according to the detected time, whereby the condition of the intake refrigerant is shifted toward the dry side, to prevent a wet operation.

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 wet operation of a compressor.

(Prior Art) Conventionally, as disclosed in JP-A-63-32257, for example, an air conditioner equipped with a refrigerant circuit in which a compressor, a condenser, an electric expansion valve, and an evaporator are sequentially connected has been used. It is a known technique to control the opening degree of an electric expansion valve within a preset range to prevent the risk of liquid compression in the compressor due to the suction refrigerant becoming a bit wet.

(Problems to be Solved by the Invention) By the way, when restricting the opening degree of the electric expansion valve to a range that does not result in wet operation, as in the above-mentioned conventional system, it is necessary to control the opening degree of the electric expansion valve according to the suction superheat degree. This is generally done, and in order to detect the degree of suction superheat, it is necessary to detect the saturation temperature equivalent to the evaporation pressure, so there is a problem that an expensive pressure sensor must be installed.

The present invention has been made in view of the above points, and its purpose is to make it possible to estimate the dry state of suction refrigerant before compression with high accuracy, albeit approximately, from the relationship between the condensation temperature of the refrigerant and the discharge pipe temperature. The objective is to improve reliability at low cost by detecting the wet state of the refrigerant using a temperature sensor without arranging a pressure sensor and taking measures to prevent wet operation.

(Means for Solving the Problem) In order to achieve the above object, the first means for solving the problem is as shown in Fig. 1A. A refrigeration system is assumed to be provided with a refrigerant circuit (9) formed by sequentially connecting evaporators (6 or 3) equipped with fans (6a or 3a).

The compressor (
1) Discharge pipe temperature detection means (T
h2) and a condensing temperature detection means (Thc or The he
), and the discharge pipe temperature detection means (T
h2) and condensation temperature detection means (Thc or The he)
When the discharge pipe temperature drops to a value lower than the condensing temperature plus a predetermined value, the fan (6a
Alternatively, an air volume changing means (51) for changing the air volume of 3a) to increase the air volume is provided.

The second solution is a compressor (
1) A refrigeration system is assumed to be provided with a refrigerant circuit (9) formed by sequentially connecting a condenser (3 or 6), an electric expansion valve (5), and an evaporator (6 or 3).

The compressor (
1) Discharge pipe temperature detection means (T
h2), and a condensing temperature detection means (Thc or The
), and the discharge pipe temperature detection means (T
h2) and condensation temperature detection means (Thc or The he)
When the discharge pipe temperature decreases to a value lower than the condensing temperature plus a predetermined value, the electric expansion valve (5)
) opening control means (52
).

The third solution is a compressor (1
), condenser (3 or 6), pressure reducing valve (5) and evaporator (6)
or 3) is assumed to be a refrigeration system equipped with a refrigerant circuit (9) connected in sequence.

Furthermore, a bypass passage (11) connecting the discharge pipe and suction pipe of the refrigerant circuit (9) to enable refrigerant bypass, and an on-off valve (12) for opening and closing the bypass passage (11) are provided.

The compressor (
1) Discharge pipe temperature detection means (T
h2), and a condensing temperature detection means (Thc or The
), and the discharge pipe temperature detection means (T
h2) and condensation temperature detection means (Thc or The he)
When the discharge pipe temperature decreases to a value lower than the condensing temperature plus a predetermined value, the on-off valve (12)
The structure includes an opening/closing control means (53) for controlling the opening.

(Function) With the above configuration, in the invention of claim (1), the discharge pipe temperature detected by the discharge pipe temperature detection means (Th2) is the condensation temperature detected by the condensation temperature detection means (Thc or The he). When the air volume becomes lower than the value obtained by adding a predetermined value to
The air volume of a or 3a) is changed to increase.

In that case, by setting the above predetermined value according to the degree of dryness that you want to regulate, you can check the relationship between the discharge pipe temperature and condensing temperature detected by the temperature sensor without using an expensive pressure sensor. 1) It is detected when the suction refrigerant becomes wet. Then, since the evaporation capacity is changed to increase accordingly, the state of the suction refrigerant shifts to the dry side. Therefore, wet operation can be prevented at low cost.

In the invention of claim (2), by means similar to the invention of claim (1), when it is detected that the suction refrigerant becomes wet, the opening degree is changed without using an expensive pressure sensor. The means (52) reduces the opening degree of the electric expansion valve (5), so that the suction refrigerant moves to the dry side. therefore,
Wet operation is prevented at low cost.

In the invention of claim (3), when it is detected that the suction refrigerant becomes wet, the opening/closing control means is activated by means similar to the invention of claim (1) without using an expensive pressure sensor. As a result of (53), the on-off valve (12) of the bypass path (11) is opened, and the wet state of the suction refrigerant is alleviated.

Therefore, wet operation is avoided at low cost.

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

Figure 2 shows the refrigerant piping system of the air conditioner according to the first embodiment, where (1) is the scroll compressor, (2) is the solid line in the figure during cooling operation, and the broken line in the figure during heating operation. (3) is an outdoor heat exchanger which is a heat source side heat exchanger that functions as a condenser during cooling operation and as an evaporator during heating operation; (3a) is the outdoor heat exchanger (3); (4) is a receiver for storing liquid refrigerant; (5) is an electric expansion valve having a refrigerant pressure reduction function and a refrigerant flow rate adjustment function; (6) is installed indoors; An indoor heat exchanger that is a user-side heat exchanger that functions as an evaporator during cooling operation and as a condenser during heating operation, (6a) is an indoor fan attached to the indoor heat exchanger (6), and (7) is This is an accumulator that is installed in the suction pipe of the compressor (1) 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) in which heat transfer is caused by circulation of 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 as a bypass passage for returning the oil (0) together with the refrigerant 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. The refrigerant circuit (9) is opened at certain times 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). In the liquid pipe, the above-mentioned seater (4) and electric expansion valve (5) are arranged in series in a common path (8a) so that the electric expansion valve (5) communicates with the lower part of the receiver (4), that is, the liquid part. and the point (P) is the upper end of the receiver (4) of the common path (8a).
and the outdoor heat exchanger (3) are connected to the common path by the first inflow path (8b) via the first check valve (21) that allows refrigerant to flow only to the receiver (4) side. The point (8a) (
P) and the indoor heat exchanger (6) are connected by a second inflow path (8C) via a second check valve (22) that allows refrigerant to flow only to the receiver (4) side. On the other hand, a point (Q) which is the end of the common path (8a) on the electric expansion valve (5) side and a point (S) between the first check valve (21) and the outdoor heat exchanger (3) ) is the first capillary tube (C1
) via the first outflow channel (8d), the common channel (8a)
The above point (Q) and the point (R) between the second check valve (22) and the indoor heat exchanger (6) are the second capillary tube (C).
2) and are connected to each other by a second outflow path (8e).

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 (21), A third capillary tube (C3) for reducing the pressure of the refrigerant is interposed in the liquid seal prevention bypass path (8f).

In addition, sensors are installed in the air conditioner,
(T h2) is a discharge pipe sensor arranged 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 arranged in the outdoor heat exchanger (3). , an external heat exchange sensor (Th
a) is placed at the air intake port of the outdoor heat exchanger (3) and detects the outside air temperature; (The) is placed at the indoor heat exchanger (6) and detects the evaporation temperature Te during cooling operation.
, an internal heat exchange sensor that detects the condensation temperature T'c during heating operation; (Thr) is an indoor suction sensor that is disposed at the air suction port of the indoor heat exchanger (6) and detects the suction air temperature Tr; Each of the above sensors is connected to a controller (not shown) for controlling the operation of the air conditioner so that signals can be input, and the controller controls the operation of each device according to the sensor signals. is being done.

Here, to explain the control contents of the first embodiment according to the invention of claim (1) by the controller, during heating operation, in step S1, the discharge pipe sensor (T h2)
Input the value of the discharge pipe temperature T2 from the signal, and proceed to step S2.
Then, the value of the condensing temperature Tc is inputted from the signal of the internal heat exchange sensor (T he), and in step S3, T2 < Tc
+a (a is a constant of about 20°C, for example), and if T2<TC+α, the normal heating operation control is executed as is, but if T2<Tc+α, it is determined that the humid operation is in progress. Then, the process moves to step S4, and the air volume of the outdoor fan (3a) is increased.

In the above flow, the air volume changing means changes the air volume of the fan (3a) to increase when the discharge pipe temperature T2 decreases to a value lower than the value obtained by adding the predetermined value α to the condensation temperature Tc, by the control in step S4. (51) is configured.

Therefore, in the first embodiment, the air volume changing means (51
), the discharge pipe temperature T2 changes to the condensing temperature TC at a predetermined temperature α.
If the value becomes lower than the sum of
The air volume in a) is controlled to increase.

That is, as shown in the Mollier diagram of FIG. 4, suppose that the refrigerant is compressed from the state of the low-pressure side pressure line 11e to the state of the high-pressure side pressure line jlc, and the saturated vapor line g.

and the low-pressure side pressure line 1e are intersected at point (A), and the saturated steam line g
Let the intersection of o and the high-pressure side pressure line flc be a point (B). Here, the temperature of the refrigerant at point (B) is approximately equal to the condensation temperature Tc detected by the internal heat exchange sensor (The).

Next, the dryness of the suction refrigerant is 1°0 (that is,
Point (C ). If a point (D) is a point between points (B) and (C) on the high-pressure side pressure line Dc that is higher than the condensation temperature Tc by a predetermined temperature α, then the discharge pipe temperature Tc is the temperature above point (D). The condition of the suction refrigerant that becomes 1.0 is the iso-dryness line 1
1 (for example, dryness of about 0.98) and low pressure side pressure line 1
The state is represented by the intersection (E) with 1e.

Therefore, by setting α to a value corresponding to the humidity state (dryness) to be regulated (for example, 20°C
degree), as mentioned above, the discharge pipe temperature Tc and the condensation temperature Tc
From this relationship, it is possible to detect when the suction refrigerant becomes wet. As described above, the state of the suction refrigerant can be detected with high accuracy from the state of the refrigerant after being discharged by the compressor (1). When the wet state of the suction refrigerant is detected in this way, the air volume of the evaporator fan (3a) is changed to increase, so the refrigerant state shifts to the dry side due to the increase in evaporation capacity, and wet operation is started. can be effectively prevented.

At that time, the wet state of the refrigerant can be detected only with the temperature sensor (in the above embodiment, the discharge pipe sensor (Th2) and the internal heat exchanger sensor (Thc)) without using an expensive pressure sensor. Therefore, reliability can be improved at low cost.

Although the first embodiment described above describes the control contents during heating operation, the present invention can also be applied during cooling operation, and can be applied not only to air conditioners but also to container refrigerators, etc. can do.

Next, a second embodiment according to the invention of claim (2) will be described. In the second embodiment as well, the configuration of the refrigerant piping system of the air conditioner is the same as that in the first embodiment shown in FIG. 2 above.

FIG. 5 shows the control contents of the controller in the second embodiment, and in steps R and -R3, step 8 in FIG.
After performing the same control as Steps 1 to S3, only when T2<Tc+α is determined in Step R3, the process moves to Step R4, and the electric expansion valve (5) is controlled to reduce its opening degree.

In the above flow, in step R4, the opening degree changing means ( 52) is configured.

Therefore, in the second embodiment, similarly to the first embodiment, the discharge pipe temperature T detected by the discharge pipe sensor (T h2)
2 and the condensation temperature Tc detected by the internal heat exchanger sensor (Thc) (or the external heat exchanger sensor (Thc)), the wet state of the refrigerant is detected. When the refrigerant condition becomes a little damp, the degree of superheating of the refrigerant increases by reducing the degree of opening of the electric expansion valve (5) using the degree of opening change means (52), thereby effectively preventing wet operation. As a result, reliability can be improved at low cost.

Next, a third embodiment according to the invention of claim (3) will be described. In the third embodiment as well, the configuration of the refrigerant piping system of the air conditioner is the same as that in the first embodiment shown in FIG. 2 above.

The control contents of the controller in this embodiment will be explained based on FIG. 6, in steps Q1 to Q3.
Then, after performing the same control as steps 81 to S3 in FIG. 12) Control to open.

In the above flow, an opening/closing control means (53) is configured to control the opening/closing valve (12) to open when the discharge pipe temperature T2 becomes lower than a value obtained by adding a predetermined value α to the condensing temperature Tc by the control in step Q4. has been done.

Therefore, in the third embodiment, similarly to the first embodiment, the discharge pipe temperature T detected by the discharge pipe sensor (T h2)
2 and the internal heat exchanger sensor (Thc) (or the condensation temperature Tc detected by the heat exchanger sensor (Thehe)) as an indicator to detect the wet state of the refrigerant. Sometimes, by opening the on-off valve (12) of the oil return passage (11) by the on-off control means (53), hot gas is bypassed to the suction side of the compressor (1) to alleviate the wet state of the refrigerant. Therefore, reliability can be improved at low cost.

(Effect of the invention) As explained above, according to the invention of claim (1), in a refrigeration system, when the discharge pipe temperature becomes lower than the condensing temperature plus a predetermined value, the refrigerant is in a wet state. By determining that the refrigerant is wet, the wet state of the refrigerant can be detected from the relationship between the discharge pipe temperature and the condensing temperature without using an expensive pressure sensor, and the air volume of the evaporator fan can be adjusted based on the detected wet state of the refrigerant. By increasing the evaporation capacity, it is possible to eliminate the wet state of the refrigerant.
Therefore, reliability can be improved at low cost.

According to the invention of claim (2), in a refrigeration system in which an electric expansion valve is arranged as a pressure reducing valve, the wet state of the suction refrigerant is detected by means similar to the invention of claim (1), and the wet state is detected. Since the opening degree of the electric expansion valve is reduced according to the temperature, the wet state of the refrigerant can be eliminated by increasing the degree of superheating of the refrigerant, and therefore reliability can be improved at low cost.

According to the invention of claim (3), a bypass passage for bypassing hot gas is provided between the discharge pipe and the suction pipe, and an on-off valve is interposed in this bypass passage. The wet state of the refrigerant is detected by means similar to the invention, and the opening/closing valve is opened in response to the detection of the wet state, so that the wet state of the refrigerant can be alleviated by bypassing the hot gas to the suction side. Therefore, reliability can be improved at low cost.

[Brief explanation of the drawing]

Fig. 1 shows the structure of the invention, Fig. 1A shows the structure of the invention of claim (1), Fig. 1B shows the structure of the invention of claim (2), and Fig. 1C shows the structure of the invention of claim (3). 2 to 4 show the first embodiment, FIG. 2 is a refrigerant piping system diagram showing the configuration of the air conditioner, FIG. 3 is a flowchart showing the control contents of the controller, and FIG. The figure is a Mollier diagram for explaining the invention in detail, FIG. 5 is a flowchart showing the control content of the controller in the second embodiment, and FIG. 6 is a flowchart showing the control content of the controller in the third embodiment. Yes. 1 Compressor 3 Outdoor heat exchanger (condenser or evaporator) 5 Electric expansion valve (pressure reducing valve) 6 Indoor heat exchanger (evaporator or condenser) 11 Oil return passage (bypass passage) 12 Opening/closing valve 51 Air volume Changing means 52 Opening degree changing means 53 Opening/closing control means Th2 Discharge pipe sensor (discharge pipe temperature detecting means) The internal heat exchange sensor (condensing temperature detecting means) The external heat exchange sensor (condensing temperature detecting means) 1st enthalpy. Diagram

Claims (3)

[Claims] (1) Compressor (1), condenser (3 or 6), pressure reducing valve (5
) and an evaporator (6 or 3) equipped with a fan (6a or 3a) connected sequentially to a refrigerant circuit (9), in which a discharge pipe temperature of the compressor (1) is detected. A pipe temperature detection means (Th2), a condensation temperature detection means (Thc or The) that detects the condensation temperature of the refrigerant in the condenser (3 or 6), and a discharge pipe temperature detection means (Th2) that detects the condensation temperature of the refrigerant in the condenser (3 or 6). ) and condensation temperature detection means (Thc or Th
When the discharge pipe temperature drops to a value lower than the condensing temperature plus a predetermined value in response to the output of e), the fan (
6a or 3a); an air volume changing means (51) for changing the air volume to increase the air volume of the refrigeration system. (2) 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 Discharge pipe temperature detection means (Th2) for detecting the discharge pipe temperature of the compressor (1), condensation temperature detection means (Thc or The) for detecting the condensation temperature of the refrigerant in the condenser (3 or 6), During operation of the device, the discharge pipe temperature detection means (Th2) and the condensation temperature detection means (Thc or Th
Opening degree control means that receives the output of e) and controls the opening degree of the electric expansion valve (5) to be small when the discharge pipe temperature decreases to a value lower than a value obtained by adding a predetermined value to the condensing temperature. (
52) An operation control device for a refrigeration system, comprising: (3) Compressor (1), condenser (3 or 6), pressure reducing valve (5
) and an evaporator (6 or 3) connected in sequence, a bypass path connecting a discharge pipe and a suction pipe of the refrigerant circuit (9) so that the refrigerant can be bypassed. (11), an on-off valve (12) that opens and closes the bypass passage (11), and the compressor (11);
) Discharge pipe temperature detection means (Th2
), a condensation temperature detection means (Thc or The) for detecting the condensation temperature of the refrigerant in the condenser (3 or 6),
During operation of the refrigeration equipment, the discharge pipe temperature detection means (Th2)
and an opening/closing control for controlling the opening/closing valve (12) to open when the discharge pipe temperature decreases to a value lower than a value obtained by adding a predetermined value to the condensing temperature in response to the output of the condensing temperature detection means (Thc or The). An operation control device for a refrigeration system, comprising a control means (53).