JPH0225103Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to improvement of an air conditioner using an electric expansion valve.

[Technical background of the invention and its problems] Air conditioners using electric expansion valves detect the temperature, pressure, etc. of the refrigeration cycle in order to maintain good cooling and heating operations. The degree of superheat is calculated from this detected information, and the opening degree of the electric expansion valve is controlled so that the calculated value becomes a preset degree of superheat of the refrigeration cycle.

By the way, in a heat pump type air conditioner, during heating operation, the frost on the outdoor heat exchanger that occurs due to a drop in outside temperature is defrosted using condensed heat generated when switching to cooling operation. , so-called defrosting operation is being performed. Of course, it goes without saying that the same applies to air conditioners using electric expansion valves.

However, in systems that perform defrosting by simply switching from heating operation to cooling operation based on the state of the refrigeration cycle, the opening degree of the electric expansion valve is controlled based on the degree of superheating, which is based on the state of the refrigeration cycle. However, there was a problem in that the amount of condensation heat obtained was small, which required a long time for defrosting, and the heating effect was inevitably reduced.

[Purpose of the invention] This invention was made with attention to the above-mentioned circumstances, and its purpose is to provide an air conditioner that can shorten the defrosting time.

[Summary of the invention] In other words, this invention uses the degree of superheating during defrosting operation as the degree of superheating determined by the value at which the load on the compressor is maximum, in addition to the degree of superheating during air-conditioning operation, and uses this degree of superheating and the sensor as the degree of superheating during defrosting operation. During defrosting operation, the opening degree of the electric expansion valve is controlled in accordance with the difference in the degree of superheat obtained from the defrosting operation, thereby increasing the amount of heat of condensation.

[Embodiment of the invention] This invention will be described below based on an embodiment shown in FIGS. 1 to 5. Figure 1 shows an air conditioner, in which 1 is a variable capacity compressor, 2
is a four-way valve, 3 is an outdoor heat exchanger, 4 is an electric expansion valve, and 5 is an indoor heat exchanger. Each of these devices is sequentially connected by a refrigerant pipe 6, and is used for cooling (defrosting).
and a heat pump type refrigeration cycle 7 capable of heating operation. Further, on the suction side of the compressor 1, as shown in FIG. 5, a suction gas temperature sensor 9 and a suction gas pressure sensor 10 are provided, respectively, which are connected to a calculation section 11 of a control circuit 8 composed of a microcomputer. Thus, the value of the degree of superheat can be calculated from the information on the refrigeration cycle state (suction temperature, suction pressure) output from each sensor 9, 10.

In addition, the control circuit 8 includes a first superheat degree setting section 12 in which the degree of superheat during cooling/heating operation is set, as shown in FIG.
A second degree of superheat setting section 13 is provided, in which the degree of superheat during defrosting operation is set to a value that maximizes the load. Furthermore, the control circuit 8 includes a first control section 14 connected to the first superheat degree setting section 12 and a second control section 15 connected to the second superheat degree setting section 13.
(all consisting of microcomputers) are installed. The first control section 14 and the second control section 15 are both connected to the calculation section 11 and the electric expansion valve 4, and the degree of superheat obtained from the sensors 9 and 10 during cooling/heating operation. He is trying to control the opening degree of the electric expansion valve 4 according to the difference with the superheat degree set by the 1st superheat degree setting part 12. Further, during defrosting operation, the opening degree of the electric expansion valve 4 is controlled according to the difference between the degree of superheat obtained from the sensors 9 and 10 and the degree of superheat set by the second degree of superheat setting section 13. That's what I do. In other words, the defrosting operation is performed independently of the heating and cooling operation.

When performing heating using the air conditioner configured as described above, if the four-way valve 2 is set to the heating side and the compressor 1 is operated, the compressor 1,
four-way valve 2, indoor heat exchanger 5, electric expansion valve 4,
A heating cycle is formed in which the refrigerant sequentially flows through the indoor heat exchanger 3 to heat the room.

Here, the operating state of the electric expansion valve 4 during heating operation is as follows.

That is, the suction temperature and suction pressure of the compressor 1 are outputted to the control circuit 8 through each suction gas temperature sensor 9 and suction gas pressure sensor 10, and a calculation section 11 calculates the degree of superheat. and,
The opening degree of the electric expansion valve 4 is controlled by the first control section 14 so that this calculated value becomes the set superheat degree set by the first superheat degree setting section 12. Here, if the set superheat degree value SH ₁ is set, for example, to the point P ₁ of "6deg" shown in Fig. 3, it will always be "6deg".
The opening degree of the electric expansion valve 4 is controlled so that the heating operation is performed according to the set superheat degree as in the conventional case.

If frost forms on the outdoor heat exchanger 3 during such a heating operation, the four-way valve 2 is switched to the cooling side and a defrosting operation is performed. Here, to explain the flowchart shown in FIG. 2 regarding this defrosting operation, at the same time as the heating operation is switched to the defrosting operation, the control of the electric expansion valve 4 that has been set from the refrigeration cycle state is changed. From the related setting superheat degree "6deg", the superheat degree set by the second superheat degree setting unit 13 at which the load of the compressor 1 is maximum, for example, the value of "0deg" where the power consumption is maximum as shown in FIG.
SH ₂ changes to point P ₂ . When the operation is switched, first, SH ₂ and the degree of superheat of the refrigeration cycle are compared. In other words, the degree of superheating of the refrigeration cycle is
SH is the degree of superheat (deg), TS is the suction gas temperature of compressor 1 (℃), and Ps is the suction gas pressure of compressor 1 (Kg/
cm ²・G), and K is a coefficient (℃ ・cm ² /Kg). In the arithmetic circuit 11, SH=Ts−K・Ps is calculated, and the superheat degree (SH) at that time is set in advance. The degree of superheat (SH ₂ ) is compared. When the degree of superheat (SH) is larger than the set degree of superheat (SH ₂ ), the second control section 15 controls the electric expansion valve 4 to open, and conversely, when the degree of superheat (SH) is smaller than the set degree of superheat (SH 2 ), the electric expansion valve 4 is opened. 4 to the closed side, and the opening degree of the electric expansion valve 4 is controlled so that the degree of superheat (SH) becomes a preset degree of superheat (SH ₂ ).

In this way, a defrosting operation is performed in which the maximum load is applied to the compressor 1, that is, the power consumption is maximized, and the amount of heat of condensation can be maximized. Therefore, the frost on the outdoor heat exchanger 3 can be defrosted in a short time. In other words, the defrosting time Δt (h) is determined by the formula for calculating the amount of condensation heat ΔQc (Kcal) during defrosting; ΔQc=t×Qe′+Δt×860×W From Δt=ΔQc/Qe′+860×W However, Qe′ is the amount of heat of evaporation during defrosting (Kcal), W is the power consumption of the compressor during defrosting (kw), and 860 is the coefficient (Kcal/kw・h), where the power consumption of compressor 1 reaches its maximum. Since the opening degree of the electric expansion valve 4 is controlled so as to increase the opening degree, it is obvious that the defrosting time Δt can be shortened.

Then, when the degree of superheat (SH) and the set degree of superheat (SH ₂ ) are stably almost the same, that is: SHn+α≧SH≧SHn−α, where α: stable range (deg) Defrosting is completed and heating operation resumes. In other words, the heating superheat degree (SH ₁ ) to be set
Based on the comparison with the degree of superheat (SH) of the refrigeration cycle, the control circuit 8 controls the opening of the electric expansion valve 4 to the open side or the closed side so as to reach the set degree of superheat (SH ₁ ). Return to heating operation. In addition,
It goes without saying that the four-way valve 2 is set to the heating side.

In FIG. 2, solid line arrows indicate the flow of refrigerant during defrosting, and broken line arrows indicate the flow of refrigerant during heating.

In addition, in the above-mentioned embodiment, this idea was applied to a device in which the frost formed during the heating cycle was defrosted in the cooling cycle; It can also be applied to things.

[Effects of the invention] As explained above, according to this invention, defrosting operation can be performed with a large amount of condensing heat, and the defrosting time can be shortened.

Therefore, the reduction in the heating effect can be reduced. It is especially effective in areas with a large amount of frost.

Moreover, since the output of the same sensor used during cooling/heating operation is used during defrosting operation, the control system is correspondingly simpler. Furthermore, since a single sensor output is used, reliability is high.

[Brief explanation of drawings]

Figures 1 to 5 show one embodiment of this invention, Figure 1 is a schematic configuration diagram showing an air conditioner, and Figure 2 is a flowchart showing opening/closing control of an electric expansion valve during defrosting operation. 3 is a diagram showing the degree of superheating set during heating operation, FIG. 4 is a diagram showing the degree of superheating set during defrosting operation, and FIG. 5 is a block diagram showing the control system. 4...Electric expansion valve, 7...Heat pump type refrigeration cycle, 8...Control circuit, 9...Suction gas temperature sensor, 10...Suction gas pressure sensor, 1
2...First superheat degree setting section, 13...Second superheat degree setting section, 14...First control section, 15...Second
control section.

Claims (1)

[Scope of utility model registration request] A refrigeration cycle consisting of a variable-capacity compressor, a four-way valve, an outdoor heat exchanger, an electric expansion valve, and an indoor heat exchanger connected in sequence; a suction gas temperature sensor and a suction gas pressure sensor that detect temperature;
a first degree of superheat setting section that sets the degree of superheat during cooling/heating operation; and an opening degree of the electric expansion valve according to the difference between the set degree of superheat and the degree of superheat obtained by the sensor during heating/cooling operation; a second superheat degree setting part that sets a degree of superheat during defrosting operation determined at a value that maximizes the load on the compressor; and a second control section that controls the opening degree of the electric expansion valve according to the difference between the degree of superheat set in the degree of superheat setting section and the degree of superheat obtained from the sensor. air conditioner.