JPH0784954B2 - Refrigerant retention device for air conditioner - Google Patents

Description

TECHNICAL FIELD The present invention relates to a multi-type air conditioner having a plurality of indoor units and capable of performing heating operation for each indoor unit. The present invention relates to an improvement of a refrigerant accumulation suppressing device for an air conditioner that limits and suppresses refrigerant accumulated in other stopped indoor units during operation.

(Prior Art) As disclosed in Japanese Patent Application Laid-Open No. 62-258968, the applicant of the present invention, as a refrigerant retention suppressing device for an air conditioner of this type, stops the operation in a multi-type air conditioner. The temperature difference between the inlet side refrigerant (superheated gas refrigerant) and the outlet side refrigerant (supercooled liquid refrigerant) of the condenser built in the inside indoor unit is detected, and when this temperature difference is a large value, the By enlarging the passage area on the refrigerant outlet side of the condenser with a motor-operated valve, the amount of passing refrigerant is increased to reduce the temperature difference, while in the situation where the temperature difference is a small value, the passage area is reduced to pass. Repeatedly increasing the temperature difference by reducing the amount of refrigerant, hold the temperature difference at the set value, and thus limit the refrigerant flow rate to the stopped condenser to the amount of refrigerant commensurate with the amount of condensation by natural heat dissipation. , So that the amount of accumulated refrigerant is kept constant or suppressed Have proposed a thing was.

(Problems to be Solved by the Invention) However, in the above proposal, it is premised that the state of the refrigerant on the inlet side of the condenser when stopped is the normal time when the refrigerant is the superheated gas refrigerant. Therefore, in a special case where the refrigerant on the inlet side of the condenser becomes supercooled liquid refrigerant, for example, at the time of thermo-OFF (when the heating operation is stopped when the room temperature converges to an appropriate temperature), the entire condenser that has already stopped Between the inlet and outlet of the condenser when the liquid refrigerant is stagnant (up to the refrigerant inlet side) or when the liquid refrigerant is too stagnant due to a rapid temperature change during heating operation. Both refrigerants become supercooled refrigerants, and the temperature difference between the refrigerants becomes small. As a result, the passage area of the refrigerant outlet passage is controlled to be reduced, and the refrigerant continues to accumulate.

The present invention has been made in view of such a point, and an object thereof is to stay in the stopped condenser both when the refrigerant state on the condenser inlet side is a superheated gas refrigerant or a supercooled liquid refrigerant. This is to appropriately collect the liquid refrigerant that has been formed.

(Means for Solving the Problem) In order to achieve the object, in the invention according to claim (1) of the present application, the superheat degree of the refrigerant at the inlet side of the condenser which is stopped is detected, and this superheat degree is set. If it is less than the value, it is judged that the liquid refrigerant is staying in the stopped condenser. Even in a special case of a supercooled state, it is necessary to reliably collect the stagnant refrigerant.

In that case, when the superheat degree of the refrigerant at the condenser inlet side is stopped, the supercooling degree of the refrigerant at the condenser outlet side also changes, and when the superheat degree decreases, the supercooling degree increases conversely. Therefore, in the invention according to claim (2) of the present application, instead of detecting the degree of superheat, the degree of supercooling of the refrigerant at the outlet side of the stopped condenser is detected, and ) To achieve the same object as that of the invention.

That is, in the specific configuration of the invention according to claim (1), a single outdoor unit (A) and a plurality of indoor units (B) to (F) form a refrigerant circulation system (14), Each indoor unit (B)-(F)
Separately, it is premised on a refrigerant retention suppressing device for an air conditioner capable of heating operation. And each indoor unit (B)-
A control valve (11) arranged on the refrigerant outlet side of the condenser (10) built in (F) and closed when the corresponding indoor unit is requested to stop to prevent the flow of the refrigerant to the built-in condenser (10). A superheat degree detecting means (40) for detecting a superheat degree which is a difference between the temperature of the refrigerant on the refrigerant inlet side of each of the condensers (10) and the saturation temperature corresponding to the condensation pressure of the refrigerant, and the superheat degree detecting means ( 40), the refrigerant in the stopped condenser (10) is cooled according to the magnitude relationship with the set value of the superheat degree on the refrigerant inlet side of the stopped condenser (10) (when the value is less than the set value). Refrigerant returning means (41) is provided for returning the accumulated refrigerant by opening the passage on the outlet side to the refrigerant circulation system (14).

In the invention according to claim (2), the above claim (2)
In place of the superheat detection means (40) of the invention according to the invention, supercooling for detecting the degree of supercooling, which is the difference between the temperature of the refrigerant on the refrigerant outlet side of each condenser (10) and the saturation temperature equivalent to the condensation pressure of the refrigerant. The degree detecting means (42) is provided.

(Operation) With the above configuration, in the inventions according to claims (1) and (2), the corresponding control valve (11) is applied to each of the indoor units (B) to (F) during heating operation, for example, when the thermostat is turned off. Is closed and the passage on the refrigerant outlet side of the condenser (10) is closed. For this reason, the refrigerant flows into the condenser (10) but does not flow out from the refrigerant outlet side, and easily accumulates in the condenser (10).

When the amount of accumulated refrigerant in the stopped condenser (10) increases, the degree of superheat on the refrigerant inlet side of the condenser (10) becomes small and the outlet of the stopped condenser (10) also decreases. When the supercooling degree of the refrigerant on the side becomes a large value and the superheat degree falls below the set value or the supercooling degree rises above the set value, in this situation, the condenser (10) inlet that is stopped Since the refrigerant on the side is a normal time when it is a superheated gas refrigerant or a special time when it is a supercooled liquid refrigerant, the refrigerant return means (41) operates and the passage on the refrigerant outlet side of the stopped condenser (10). Is opened. As a result, the refrigerant circulates in the stopped condenser (10), and the refrigerant that has accumulated inside is returned to the refrigerant circulation system (14) together with the circulating refrigerant and is collected. At this time, the circulation amount of the refrigerant to the stopped condenser (10) increases due to the circulation of the refrigerant,
Since the heat loss of the refrigerant to the condenser (10) is reduced, the superheat degree on the inlet side of the condenser (10) returns to a large value and the supercooling degree on the outlet side also returns to a small value. Returns to the value.

(Effects of the Invention) As described above, the claims (1) and (2) of the present application
According to the invention of claim 1, in the multi-type air conditioner, during the heating operation of some indoor units, the amount of liquid refrigerant accumulated in the remaining stopped condensers of the indoor units increases, and The superheat degree of the refrigerant on the inlet side and the supercooling degree of the refrigerant on the outlet side change,
When the degree of superheat is equal to or lower than the set value, or the degree of supercooling is equal to or higher than the set value, the passage on the outlet side of the stopped condenser is opened to allow the refrigerant to flow, so that the refrigerant on the inlet side of the stopped condenser is overheated. Regardless of the normal time, which is a gas refrigerant, or the special time, which is a supercooled liquid refrigerant, the accumulated liquid refrigerant can be returned to the refrigerant circulation system and recovered to ensure reduction of the amount of accumulated liquid refrigerant. .

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings starting from FIG.

In FIG. 2, (A) is a single outdoor unit (outdoor unit), and (B) to (F) are multiple units (5 units) having the same internal configuration.
The indoor unit (indoor unit) of, wherein the outdoor unit (A) includes a first compressor (1) and a second compressor (2) connected in parallel with each other, and a four-way switching. Valve (3)
And an outdoor heat exchanger (4) having an outdoor blower fan (4a)
And an expansion valve (5), and each of the devices (1) to
Each of (5) is connected to a refrigerant pipe (6) so that the refrigerant can flow therethrough. In addition, the above indoor units (B) to (F)
Each include an indoor heat exchanger (10) having an indoor blower fan (10a) and an expansion valve (control valve) (11), and each of the devices (10) and (11) is a refrigerant pipe (12). Is connected so that the refrigerant can flow. The expansion valve (11) is composed of an indoor electric expansion valve for adjusting the air conditioning capacity whose valve opening degree can be electrically increased or decreased.

The five indoor units (B) to (F) are connected in parallel to each other by refrigerant pipes (13) ... And are connected to the outdoor unit (A) so that the refrigerant can circulate. 14) is formed, and during the cooling operation, the four-way switching valve (3) is switched as shown by the broken line in the drawing to circulate the refrigerant as shown by the broken line arrow in the drawing, whereby each indoor heat exchanger (10) is
The indoor heat exchanger (4) repeatedly radiates the amount of heat absorbed from the room to the outside air to cool each room, while switching the four-way selector valve (3) as shown by the solid line during heating operation. By circulating the refrigerant as shown by the solid line arrow in the figure, the heat quantity is exchanged in the opposite manner to heat the room. Thus, each indoor electric expansion valve (control valve) (11)
Is disposed on the refrigerant outlet side during heating operation, and each indoor unit (B) is controlled by closing control of each electric expansion valve (11).
(F) can be individually cooled and heated.

An inverter (15) is connected to the first compressor (1), and 30% to 100% of the inverter (15) is connected.
The operating frequency of the first compressor (1) is adjusted in eight steps by the output of the frequency setting signal in 10% steps, and the capacity is adjusted in multiple steps (9 steps including the stop). I am trying.

Further, the second compressor (2) has a pilot solenoid valve (17).
Depending on the opening and closing of, the capacity is adjusted in two stages: full load (100%) and unload state of 50%.

Further, in FIG. 2, (20) is a pressure equalizing hot gas bypass circuit that connects the refrigerant pipes (6), (6) (the discharge pipe and the suction pipe) before and after the four-way switching valve (3), The bypass circuit (20) is provided with a hot gas solenoid valve (21) which is opened during a low load in a cooling operation state, a defrosting operation of the outdoor heat exchanger (4), and the like.

Further, (22) is a heating overload bypass circuit connected to the refrigerant pipe (6) serving as a discharge pipe during the heating operation, and the bypass circuit (22) includes an auxiliary capacitor (23).
Further, a high pressure control valve (24) which is opened when the pressure of the refrigerant is high is interposed, and the refrigerant from the compressors (1) and (2) is exchanged with the heat of each room through the bypass circuit (22) at the time of heating overload. Bowl (1
0) are bypassed, and each indoor heat exchanger (10) is bypassed to the refrigerant pipe (6) on the downstream side.

In addition, (25) is the heating overload bypass circuit (22).
Is a liquid injection bypass circuit that connects the downstream side of the auxiliary condenser (23) to the refrigerant pipe (6) (suction pipe) on the downstream side of the four-way switching valve (3), and the liquid injection bypass circuit (25) includes Compressor (1),
An injection solenoid valve (26) that opens and closes in conjunction with the operation of (2) and an expansion valve (27) are interposed.

Also, (30) is the receiver, (31) is the accumulator,
(32) is a supercooling coil, (33) is an oil separator, and the lubricating oil separated by the oil separator (33) passes through an oil passage (34) to both compressors (1), (2 ).

Furthermore, in each indoor unit (B) to (F), (TH
1) is a room temperature sensor that detects the temperature of the corresponding indoor air (intake air temperature), and (TH2) and (TH3) are indoor heat exchangers that act as condensers (and evaporators during cooling operation), respectively. (10) ... A temperature sensor that detects the temperature of the refrigerant before and after. In the outdoor unit (A), (TH
4) is a temperature sensor that detects the refrigerant discharge temperature of the first and second compressors (1) and (12), and (TH5) is evaporation that detects the refrigerant evaporation temperature in the outdoor heat exchanger (4) during heating operation. Temperature sensor, (TH6) is the first and second compressor (1), (2)
Is a suction gas temperature sensor for detecting the temperature of the suction gas. Also, (P1) is a pressure sensor that detects the discharge gas pressure during heating operation and the suction gas pressure during cooling operation,
(HPS) is a high pressure switch for compressor protection.

Next, the operation control of the electric expansion valves (11) of the indoor units (B) to (F) during the heating operation will be described based on the control flow of FIG.

First, the thermo-OF of the corresponding indoor units (B) to (F)
Start at F (when requesting operation stop), and then step S ₁
Reads the refrigerant inlet temperature T ₁ of the indoor heat exchanger (condenser) (10) based on the output of the temperature sensor (TH3), and condenses the refrigerant based on the discharge gas pressure detected by the pressure sensor (P1). calculates a pressure corresponding saturation temperature Tc, then, the degree of superheat of refrigerant at the inlet of the condenser based on the both temperatures in the step S ₂ (10)
To calculate the SH (= T ₁ -Tc).

Thereafter, the superheat degree SH is compared with a set value of Todokotamari easy availability of the refrigerant alpha (e.g. 5 ° C.) in step S _3, during normal SH> alpha, in step S ₄ the electric expansion valve (11) The opening degree is controlled to a zero value or a minute opening degree to close the passage on the refrigerant outlet side of the corresponding condenser (10), thereby preventing the refrigerant from flowing to the corresponding indoor units (B) to (F). , Return to step S ₁ .

On the other hand, in the situation where the refrigerant is liable to accumulate in SH ≤ α, in order to recover the accumulated refrigerant, the termination condition for refrigerant recovery (discussed later) is determined in step S ₅ , and it is initially not established. In S ₆ , the opening of the electric expansion valve (11) is controlled to a set opening (for example, a half-open value), the refrigerant outlet side passage of the corresponding condenser (10) is opened, and the refrigerant is supplied to the condenser (10). The refrigerant that circulates and accumulates is collected in the refrigerant circulation system (14).

After that, in step S ₇ , the refrigerant inlet temperature T ₁ of the condenser (10) is read again, and the saturation temperature Tc equivalent to the condensation pressure of the refrigerant is calculated, and in step S ₈ , the refrigerant at the inlet of the condenser (10) is calculated. The superheat degree SH (= T ₁ −T _C ) of the refrigerant is calculated, and then, in step S ₅ , the refrigerant recovery end condition is set as the refrigerant superheat degree SH at the inlet side of the condenser (10) and after refrigerant recovery (electric When SH> α + β (β is a differential value of 5 ° C, for example) or when the set time (for example, 5 minutes) has elapsed, the accumulated refrigerant is recovered after the expansion valve (11) is opened halfway. When it is determined that the process has been completed, the process returns to step S ₄ , the opening of the electric expansion valve (11) is set to a zero value or a minute opening, the normal condition is restored, and the process returns to step S ₁ .

Therefore, in the control flow of FIG. 3 above, step S ₁
And S ₂ constitute a superheat degree detecting means (40) for detecting the superheat degree SH on the refrigerant inlet side of the indoor heat exchanger (condenser) (10). Further, in step S ₃ and S _6, the refrigerant outlet of the stopped when the refrigerant inlet side of the superheat degree SH of the condenser of the (thermo OFF) (10) is equal to or less than the set value alpha, a condenser in said stop (10) Side passage to the corresponding electric expansion valve (1
The refrigerant is circulated by the open control of (1) to allow the refrigerant to flow through the stopped condenser (10), and the stopped condenser (1
Refrigerant returning means (41) is configured to return the refrigerant accumulated in (0) to the refrigerant circulation system (14).

Therefore, in the above embodiment, when a predetermined indoor unit (for example, (B)) is stopped by the thermostat during the heating operation (the indoor blower fan (10a) continues to operate at low speed), The corresponding electric expansion valve (11) is closed, the passage on the refrigerant outlet side of the condenser (10) is closed, and the flow of the refrigerant to the condenser (10) is stopped.

In that state, as shown in FIG. 5, when the refrigerant on the inlet side of the condenser (10) is superheated gas and the refrigerant on the outlet side is cedar cooling liquid, on the Mollier diagram shown in FIG. , Inlet temperature T ₁
Is the superheated gas temperature value that is lower than the discharge gas temperature T ₀ of the refrigerant by the heat loss amount _TL in the refrigerant pipe, and the outlet temperature T ₂ is the supercooled liquid that is lower than the condensation pressure equivalent saturation temperature T _C by the supercooling degree SC amount. There is a temperature value.

Now, when the amount of liquid refrigerant accumulated in the stopped condenser (10) increases, the inlet temperature T ₁ decreases, the superheat SH at the inlet side of the condenser (10) decreases, and the refrigerant increases as it approaches the saturated vapor line. Has a large fluid density and easily accumulates in the condenser (10) as a liquid refrigerant. However, when the superheat degree SH at the inlet becomes SH ≤ α (SH = 0 at the time when it coincides with the saturated vapor line, and when it reaches the refrigerant inlet of the condenser (10) as shown in Fig. 6, it is in a supercooled state. And decreases to the temperature value T ₁ ′ (T ₁ ′ <0) in the figure),
Regardless of whether the refrigerant state at the inlet of the condenser (10) is superheated gas or supercooled liquid, the electric expansion valve (11) is controlled to open and the refrigerant circulates in the stopped condenser (10). The liquid refrigerant accumulated inside is returned to the refrigerant circulation system (14) and recovered. In this case, as the circulation amount of the refrigerant increases, the heat loss amount T _{L in} the refrigerant pipe per unit amount decreases, the refrigerant temperature T ₁ at the inlet of the condenser (10) rises, and the superheat degree of the refrigerant at the inlet is increased. SH becomes a large value, SH
At the time of> α + β, the electric expansion valve (11) is closed and the return collection of the accumulated refrigerant is stopped.

Then, when the refrigerant stays again and the superheat degree becomes SH <α, the operation similar to the above is repeated to return and collect the staying refrigerant, and in the long term, the quantity of the staying refrigerant reaches a predetermined amount. It will be limited or suppressed to a very small amount.

Also, when the above thermo is off (when heating operation is unnecessary),
The indoor blower fan (10a) of the indoor unit (for example, B) that is stopped continues to operate at low rotation speed, and the expansion valve (1
Due to the half-open operation of 1), the refrigerant flows and the heating capacity is exhibited, but since the circulation of this refrigerant is limited to the time of returning and collecting the stagnant refrigerant, the opening of the expansion valve (11) is always set to the opening. Compared with the case where the opening control is performed in the above, the unnecessary heating capacity can be suppressed to a small extent.

As described above, the superheat degree SH on the inlet side of the stopped condenser (10) is SH ≤
The case of returning and collecting the accumulated refrigerant in the situation of α has been explained.
When the superheat degree SH ≦ α, the supercooling degree SC of the refrigerant at the outlet side of the stopped condenser (10) becomes equal to or greater than the set value γ (SC ≧ γ). Therefore, the means for detecting the supercooling degree SC (42) The condenser (10)
Temperature signal T2 detected by the temperature sensor (TH2) on the outlet side
And the condensing pressure equivalent saturation temperature T _C calculated based on the output of the pressure sensor (P1), the difference (T2-T _C ) which is the supercooling degree SC is detected, and The accumulated refrigerant may be recovered.

In the above description, the superheat degree S on the inlet side of the condenser (10) is
At the time of detecting H and the degree of supercooling on the outlet side of the condenser (10), a pressure sensor (P1) for detecting the discharge pressure on the downstream side of the four-way switching valve (3) is used for calculating the condensation temperature equivalent saturation temperature T _C. Although the pressure sensor (P1) is provided, a temperature sensor that detects the discharge gas temperature of the compressors (1) and (2) may be provided instead of the pressure sensor (P1).

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention. 2 to 6 show an embodiment of the present invention, FIG. 2 is a refrigerant piping system diagram showing the overall configuration, FIG. 3 is a flow chart diagram showing the opening control of the electric expansion valve during heating operation, FIG. FIG. 4 is a Mollier diagram, and FIGS. 5 and 6 are explanatory views of the state of the refrigerant accumulated in the stopped condenser. (A) ... Outdoor unit (outdoor unit), (B) to (F) ...
… Indoor unit (indoor unit), (11) …… Indoor electric expansion valve ((control valve), (14) …… Refrigerant circulation system, (TH2), (T
H3) ... Temperature sensor, (P1) ... Pressure sensor, (40) ...
… Superheat detection means (41)… Refrigerant return means (42)…
... Supercooling degree detection means.

Claims (2)

[Claims] 1. A single outdoor unit (A) and a plurality of indoor units (B) to (F) form a refrigerant circulation system (14), and each indoor unit (B) to (F) is heated. A refrigerant retention suppressing device of an air conditioner which is operable, wherein each of the indoor units (B) to
A control valve (11) arranged on the refrigerant outlet side of the condenser (10) built in (F) and closed when the corresponding indoor unit is requested to stop to prevent the flow of the refrigerant to the built-in condenser (10). A superheat degree detecting means (40) for detecting a superheat degree which is a difference between the temperature of the refrigerant on the refrigerant inlet side of each of the condensers (10) and the saturation temperature corresponding to the condensation pressure of the refrigerant, and the superheat degree detecting means ( 40), the passage on the refrigerant outlet side of the stopped condenser (10) is opened according to the magnitude relationship with the set value of the superheat degree on the refrigerant inlet side of the stopped condenser (10), and the passage is accumulated. And a refrigerant return means (41) for returning the refrigerant to the refrigerant circulation system (14). 2. The refrigerant retention suppressing device for an air conditioner according to claim 1, wherein the superheat detection means (40) is replaced by
Air comprising a supercooling degree detecting means (42) for detecting a supercooling degree which is a difference between a temperature of the refrigerant on the refrigerant outlet side of each condenser (10) and a saturation temperature corresponding to the condensation pressure of the refrigerant. Refrigerant stagnation suppression device for air conditioner.