JP2638366B2 - Operation control device for refrigeration equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operation control device for a refrigeration system, and more particularly to an improvement in an operation control device for controlling an opening of an electric expansion valve so that a discharge pipe temperature is adjusted to an optimum temperature.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Publication No. 59-1294
As disclosed in Japanese Unexamined Patent Publication No. 2 (1995), as an operation control device of a refrigeration system including a refrigerant circuit in which a compressor, a condenser, an electric expansion valve, and an evaporator are sequentially connected, based on a refrigerant evaporation temperature and a condensation temperature. Calculates the optimum temperature of the discharged refrigerant that provides the optimum refrigeration effect, and controls the opening of the electric expansion valve so that the discharged refrigerant temperature converges to the optimum temperature. It is a known technique that attempts to perform efficient operation with a simple configuration.

[0003]

By the way, as for the refrigerating apparatus provided with the scroll type compressor whose operating frequency is variably adjusted by the inverter, if the above-mentioned publication is applied,
The following problems occur.

That is, in a scroll compressor, unlike a rotary compressor in which a rotor is pressed against the inner wall of a cylinder by a spring, a seal between a pair of scrolls is made by utilizing centrifugal force due to rotation. Therefore, when the rotation speed is low, that is, when the inverter frequency is low, the sealing function is weak, and the refrigerant may leak. For this reason, the temperature of the discharge pipe increases, and the refrigerating effect is deteriorated. In addition, a load is applied to the compressor, and there is a possibility that the reliability may be impaired.

SUMMARY OF THE INVENTION The present invention has been made in view of the foregoing, and an object of the present invention is to reduce the flow rate of a refrigerant by adopting a means for correcting the opening of an electric expansion valve to an open side in a region where an inverter frequency is low. Therefore, it is possible to effectively prevent the refrigeration effect and the reliability from deteriorating.

[0006]

Means for Solving the Problems To achieve the above object, a solution of the present invention is to control the discharge pipe temperature at an optimum temperature in a region where the inverter frequency is low.
The correction is performed so as to lower the calculated value of the optimum temperature.

Specifically, as shown in FIG. 1, the means adopted in the first aspect of the invention is a scroll compressor (1) whose frequency is variably adjusted by an inverter (13), and a condenser (3). Or 6), the electric expansion valve (5), and the evaporator (6).
Or 3) with a refrigeration apparatus provided with a refrigerant circuit (9) sequentially connected.

[0008] As an operation control device of the refrigeration system,
Evaporating temperature detecting means (Th or Thc) for detecting the evaporating temperature of the refrigerant; condensing temperature detecting means (Thc or Th) for detecting the condensing temperature of the refrigerant; and detecting the temperature of the refrigerant discharged from the compressor (1). The optimum temperature for receiving the output of the discharge temperature detecting means (Th2), the evaporating temperature detecting means (Th or Thc) and the condensing temperature detecting means (Thc or Th), and calculating the optimum temperature of the discharged refrigerant giving the optimum refrigerating effect. Arithmetic means (5
1) receiving the output of the discharge temperature detecting means (Th2);
An opening control means (53) for controlling the opening of the electric expansion valve (5) so that the discharged refrigerant temperature becomes the optimum temperature calculated by the optimum temperature calculating means (51) is provided.

Further, when the output frequency of the inverter (13) is lower than a predetermined value, a correction means (52) for correcting the lower the frequency value, the lower the optimum temperature calculated by the optimum temperature calculation means (51). Is provided.

The means adopted in the invention of claim 2 is the invention according to claim 1, wherein the correction means (53) determines a difference between a predetermined value of the inverter frequency as a reference for correction judgment and the current inverter frequency value. On the other hand, the temperature is corrected so as to linearly reduce the optimum temperature.

[0011]

With the above arrangement, in the first aspect of the present invention, the optimum temperature calculating means (51) calculates the optimum temperature of the discharge pipe temperature which gives the optimum refrigeration effect based on the evaporation temperature and the condensation temperature of the refrigerant. The opening of the electric expansion valve (5) is controlled by the opening control means (53) so that the discharge pipe temperature converges to this optimum temperature.

In this case, in the scroll compressor (1) whose operating frequency is variably adjusted by the inverter (13),
When the operating frequency is reduced, the leakage of the refrigerant between the scrolls increases and the discharge amount of the refrigerant decreases, so that the discharge pipe temperature increases, and there is a possibility that the refrigeration effect and reliability may deteriorate, but in the present invention, The correction means (52) corrects the optimum temperature lower as the inverter frequency is lower, that is, the calculated value of the optimum temperature approaches the optimum temperature in consideration of the leakage of the refrigerant. , And the deterioration of the refrigeration effect and reliability is prevented.

According to a second aspect of the present invention, in the operation of the correcting means (52) according to the first aspect of the present invention, the difference between the predetermined value of the inverter frequency and the current inverter frequency value, which is a reference for the correction judgment of the optimum temperature, is obtained. As a result, the optimum temperature is linearly reduced, so that the correction calculation is simplified, and the inverter frequency is quickly reduced.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows a refrigerant piping system of an air conditioner to which the present invention is applied, which is a so-called separate type in which one outdoor unit (A) is connected to one indoor heat exchanger (B). Things. The outdoor unit (A) includes a scroll-type compressor (1) whose operating frequency Ft is variably adjusted by an inverter (13), as shown by the solid line in the cooling operation, and as shown by the broken line in the heating operation in the heating operation. A four-way switching valve (2) for switching, an outdoor heat exchanger (3) functioning as a condenser during a cooling operation and as an evaporator during a heating operation, and a decompression unit (2) for decompressing the refrigerant.
0) and an accumulator (7) interposed in the suction pipe of the compressor (1) for removing the liquid refrigerant in the suction refrigerant are arranged as main equipment. The indoor unit (B) is provided with an indoor heat exchanger (6) that functions as an evaporator during the cooling operation and as a condenser during the heating operation. The above devices are sequentially connected by a refrigerant pipe (8), and a refrigerant circuit (9) is configured to generate heat transfer by circulation of the refrigerant.

The pressure reducing section (20) includes a receiver (4) for storing the liquid refrigerant, and an electric expansion valve (5) having a function of reducing the liquid refrigerant and a function of adjusting the flow rate. The receiver (4) and the electric expansion valve (5) are arranged so that the electric expansion valve (5) communicates with the lower part of the receiver (4), that is, the liquid part. ) Auxiliary heat exchanger (3a)
Are arranged in series on the common path (8a) via And, between the outdoor heat exchanger (3) and the end (P) on the upstream side of the receiver (4) of the common path (8a), from the outdoor heat exchanger (3) to the receiver (4). Between the point (P) of the common path (8a) and the indoor heat exchanger (6) by a first inflow path (8b1) via a first check valve (D1) that permits only the flow of the refrigerant. Is the receiver (4) from the indoor heat exchanger (6)
Connected via a second check valve (D2) allowing only the flow of refrigerant to the second inflow path (8b2), while being connected to the electric expansion valve (5) and the like in the common path (8a). Between the end (Q) on the end side and a point (R) between the second check valve (D2) and the indoor heat exchanger (6), the electric expansion valve (5) to the indoor heat exchanger (6). The point (Q) of the common path (8a) and the first check valve (D1) through the first outflow path (8c1) via the third check valve (D3) that permits only the flow of refrigerant to the first check valve (D1). A fourth check valve (D4) that allows only refrigerant to flow from the electric expansion valve (5) to the outdoor heat exchanger (3) between the point (S) between the outdoor heat exchangers (3); Via the second outflow channel (8c2)
Are connected to each other.

Further, between the point (P) on the upstream side of the receiver (4) and the point (Q) on the outflow side, there is provided a capillary tube (C) for preventing liquid sealing. Bypass road (8f)
The liquid seal prevention bypass passage (8f) prevents liquid seal when the compressor (1) is stopped, and allows the gas refrigerant to flow from the upper part of the receiver (4) to the first outflow passage (8c1). ) Side. The degree of pressure reduction of the capillary tube (C) is set to be sufficiently larger than that of the electric expansion valve (5), so that the function of adjusting the refrigerant flow rate by the electric expansion valve (5) during normal operation can be improved. It is made so that it can be maintained.

Note that (F1) to (F4) are filters for removing dust in the refrigerant, and (ER) is a muffler for reducing the operation noise of the compressor (1).

Further, sensors are provided in the air conditioner, (Th2) is disposed in the discharge pipe, a discharge pipe sensor as discharge temperature detecting means for detecting the discharge pipe temperature T2, and (Tha) is an outdoor An outdoor suction sensor that is disposed at an air suction port of the unit (A) and detects an intake air temperature Ta, which is an outside air temperature, and (Thc) is disposed at an outdoor heat exchanger (3). An external heat exchange sensor that detects an external heat exchange temperature Tc that is sometimes an evaporation temperature;
(Thr) is disposed at the air suction port of the indoor unit (B), detects an indoor air temperature Tr, which is an indoor air suction sensor, and (The) is disposed at the indoor heat exchanger (6).
An internal heat exchange sensor for detecting an internal heat exchange temperature Te which becomes an evaporating temperature during a cooling operation and becomes a condensing temperature during a heating operation, (HP
S) is a high-pressure switch which is turned on by an excessive rise of the high-pressure side pressure and activates a protection device (11) described later, (LP
S) is a low-pressure switch that is turned on when the low-pressure side pressure is excessively low to activate the protection device (11). The signals from the sensors are inputably connected to a controller (10) that controls the operation of the air conditioner, and the controller (10) responds to the signals from the sensors to control the operation of the air conditioner. Driving is controlled.

Further, in the controller (10),
During operation of the air conditioner, a protection device (1) that is activated when an abnormality occurs to stop the air conditioner abnormally.
1), a timer (12) and the like are built in. Although not shown, the protection device (11) has a discharge pipe sensor (T2) in addition to the high / low pressure switches (HPS) and (LPS).
When the discharge pipe temperature T2 exceeds a predetermined temperature, the protection device (11) is activated to stop the air conditioner abnormally and prevent accidents such as burnout of the compressor (1). Has been made.

In the refrigerant circuit (9), during the cooling operation, the liquid refrigerant condensed and liquefied in the outdoor heat exchanger (3) flows in from the first inflow path (8b1) and passes through the first check valve (D1). After being stored in the receiver (4) and decompressed by the electric expansion valve (5), it is evaporated in the indoor heat exchanger (6) through the first outflow passage (8c1) and returns to the compressor (1). While circulating,
During the heating operation, the liquid refrigerant condensed and liquefied in the indoor heat exchanger (6) flows in from the second inflow path (8b2) and is stored in the receiver (4) through the second check valve (D2). After the pressure is reduced by the electric expansion valve (5), the refrigerant evaporates in the outdoor heat exchanger (3) via the second outflow passage (8c2) and returns to the compressor (1).

Here, the control contents of the controller (10) will be described. FIG. 3 shows the controller (1).
0) shows the control contents during the cooling operation in step S).
At T1, the evaporation temperature Te detected by the internal heat exchange sensor (The) and the condensation temperature T detected by the external heat exchange sensor (Thc)
c, discharge pipe temperature T detected by discharge pipe sensor (Th2)
2 and the current inverter frequency Ft, respectively, and in step ST2, it is determined whether or not the inverter frequency Ft is equal to or lower than a predetermined value of 60 Hz. If Ft ≦ 60 (Hz), an optimum temperature Tk described later is calculated. It is determined that there is no problem in performing the above by using an ordinary arithmetic expression. In step ST3, while the correction term Tdx is set to “0”, if Ft ≦ 60 (Hz), the rotation speed of the compressor (1) is low. It is determined that it is necessary to prevent an abnormal rise in the discharge pipe temperature due to refrigerant leakage, and in step ST4, the correction term Tdx is calculated based on the following equation (1) Tdx = A × (60−Ft) + B (1) After performing the calculation, step ST
Go to 5.

Next, in step ST5, based on the following equation (2), Tk = C + D × Te + E × Tc−Tdx (2) (where A, B, C, D, and E are constants) The optimum temperature Tk, which is the discharge pipe temperature that gives the refrigeration effect EER, is calculated. Here, each coefficient of the above equation (2) is obtained by an experiment, for example, A = 0.5, B = 0, C
= 4, D = -1.13, and E = 1.72.

For example, if the inverter frequency Ft is 30 (H
In the case of z), Tdx = 0.5 × (60−30) = 15
(° C.), and the optimum temperature Tk is corrected to be lower by 15 ° C.

Then, in step ST6, the equation ΔT2 =
After calculating the temperature difference ΔT2 between the discharge pipe temperature T2 and the optimum temperature Tk based on T2−Tk, in step ST7, | ΔT
2 | ≦ 5, that is, the discharge pipe temperature T2 is the optimum temperature Tk
It is determined whether or not convergence has occurred within the upper and lower fixed ranges. Until convergence, the process proceeds to step ST8 to determine whether or not ΔT2 is positive.
That is, it is determined whether or not the discharge pipe temperature T2 is higher than the optimum temperature Tk.
At T9, while the electric expansion valve (5) is controlled to open to the middle level, if the discharge pipe temperature T2 is lower, the control proceeds to step ST1.
At 0, control is performed to close the opening of the electric expansion valve (5) to an intermediate level.

On the other hand, in step ST7, | Δ
When T2 | ≦ 5, and the discharge pipe temperature T2 converges within a certain range above and below the optimum temperature Tk, the process proceeds to step ST11, and although not described in detail, the opening degree of the electric expansion valve (5) is finely adjusted. Execute fuzzy control.

In the above flow, step STST
2. The control from step 2 to step ST5 through step ST3.
The optimum temperature calculating means (51) according to the present invention is constituted, and the control means (52) is constituted by the control from step ST2 to step ST5 through step ST4.
The control of T11 constitutes an opening control means (53).

Although the description is omitted, even during the heating operation, the calculation of the optimum temperature Tk accompanied by the correction by the inverter frequency Ft is performed similarly to the above-described control, and the electric expansion valve is operated in accordance with the calculated value. The opening degree of (5) is controlled.

Therefore, in the above embodiment, the optimum temperature calculating means (51) is based on the evaporating temperature Te and the condensing temperature Tc of the refrigerant, and the discharge pipe temperature T2 which gives the optimum refrigerating effect.
Is calculated. However, in the scroll compressor (1) in which the operating frequency Ft is variably adjusted by the inverter (13), as described above, the operating frequency Ft
Lower, the leakage of the refrigerant may increase. When the refrigerant leaks, the discharge pipe temperature T2 rises due to the decrease in the refrigerant flow rate, and the refrigeration effect deteriorates.
In extreme cases, the reliability may be degraded due to an excessive rise in the discharge pipe temperature T2.

Here, in the above embodiment, the correction means (5
According to 2), the lower the inverter frequency Ft is, the lower the optimum temperature Tk is, that is, the optimum temperature Tk is corrected to an optimum value in consideration of the leakage of the refrigerant, so that the electric power controlled by the opening control means (53). The opening degree of the expansion valve (5) is corrected to the increasing side, and the flow rate of the refrigerant is secured. Therefore, a good refrigeration effect is maintained, and an excessive rise in the discharge pipe temperature T2 is effectively prevented.

In particular, as in the above embodiment, the correction operation is simplified by linearly reducing the optimum temperature Tk according to the difference between the predetermined value (60 Hz in the above embodiment) of the inverter frequency Ft and the current value. Therefore, it is possible to quickly respond to a decrease in the inverter frequency Ft.

[0032]

As described above, according to the first aspect of the present invention, the scroll type compressor whose frequency is variably adjusted by the inverter is provided, and the optimum refrigerating effect is provided based on the condensation temperature and the evaporation temperature of the refrigerant. The operation control device of the refrigeration system that calculates the optimum temperature of the discharge pipe temperature to give the discharge pipe temperature and controls the opening degree of the electric expansion valve so that the discharge pipe temperature becomes the optimum temperature. At times, the calculated value of the optimum temperature is corrected to be lower as the inverter frequency is lower, so that it is possible to prevent the discharge pipe temperature from abnormally rising due to the leakage of the refrigerant between the scrolls of the compressor, and thus the refrigeration effect can be prevented. And deterioration of reliability can be effectively prevented.

According to a second aspect of the present invention, in the first aspect of the present invention, the correction is performed so as to linearly reduce the optimum temperature with respect to a difference between a predetermined value serving as a reference for correction judgment and the current inverter frequency value. Therefore, by simplifying the control, it is possible to quickly respond to the reduction of the inverter frequency.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a refrigerant piping system diagram of the air-conditioning apparatus according to the embodiment.

FIG. 3 is a flowchart showing the control contents of a controller.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Compressor 3 Outdoor heat exchanger (condenser or evaporator) 5 Electric expansion valve 6 Indoor heat exchanger (evaporator or condenser) 9 Refrigerant circuit 13 Inverter 51 Optimal temperature calculation means 52 Correction means 53 Opening control means Th2 Discharge pipe sensor (discharge temperature detection means) The inside heat exchange sensor (evaporation temperature detection means or condensation temperature detection means) Thc outside heat exchange sensor (condensation temperature detection means or evaporation temperature detection means)

Claims (2)

(57) [Claims] A scroll compressor (1) whose frequency is variably adjusted by an inverter (13), and a condenser (3).
Or 6), an electric expansion valve (5), and an evaporator (6 or 3)
And a refrigerant circuit (9) comprising a refrigerant circuit (9) and a refrigerant temperature detector (Thc or Thc) for detecting the vaporization temperature of the refrigerant, and a condenser temperature detector (Thc) for detecting the refrigerant condensation temperature. Or Th), discharge temperature detecting means (Th2) for detecting the temperature of the refrigerant discharged from the compressor (1), and evaporating temperature detecting means (The or Thc) and condensing temperature detecting means (Thc or Th). The optimum temperature calculating means (5) which receives the output and calculates the optimum temperature of the discharged refrigerant which gives the optimum refrigerating effect.
1) receiving the output of the discharge temperature detecting means (Th2);
Opening degree control means (53) for controlling the opening degree of the electric expansion valve (5) so that the discharged refrigerant temperature becomes the optimum temperature calculated by the optimum temperature calculating means (51); If the output frequency is lower than the predetermined value, the optimum temperature calculating means (51) becomes lower as the frequency value becomes lower.
An operation control device for a refrigeration system, comprising: a correction means (52) for correcting the optimum temperature calculated by (1) to be lower. 2. The operation control device for a refrigeration system according to claim 1, wherein the correction means (53) linearly adjusts a difference between a predetermined value of the inverter frequency and a current inverter frequency value as a reference for the correction judgment. An operation control device for a refrigerating device, wherein the operation control device performs correction so as to reduce an optimum temperature.