JPS6229853A - Air conditioner - Google Patents

Abstract

PURPOSE:To enhance the heating efficiency by avoiding unnecessary operation stoppages and frequent repetition of turning ON and OFF by modulating the operation frequency of a variable capacity compressor to a value which is higher than the previous value by a certain amount and holding said value for a certain time if, during the heating operation, the temperature of the room unit heat exchanger became lower than the set value. CONSTITUTION:During the heating operation, the control section 10 detects the temperature of the condenser by a heat exchanging temperature sensor 13, and if said temperature is within the predetermined frequency setting conditions, the normal frequency control is performed. If the pressure on the high pressure side is not so high, the operation frequency is controlled relative to the difference between the set room temperature and the actual room temperature. As the load increases and the condenser temperature rises, the control section 10 sets the operation frequency at a value which is lower by a certain amount so as to prevent the pressure on the high pressure side from being increased. When the condenser temperature gets lowered, the control section 10 further reduces the operation frequency by a certain amount, and holds said operation frequency without allowing it to change for a certain time.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to an air conditioner equipped with a variable capacity heat pump type refrigeration cycle.

[Technical background of the invention and its problems]

In general, air conditioners are equipped with a heat pump refrigeration cycle that sequentially connects a variable capacity compressor, a four-way valve, an external heat exchanger, a pressure reducing device, an indoor heat exchanger, etc. By controlling the operating frequency according to the air conditioning load, that is, the difference between the indoor temperature setting and the indoor temperature,
Some are designed to improve comfort and energy saving effects.

However, in such air conditioners, when heating is overloaded, the operating frequency increases and the capacity of the compressor increases, which causes the pressure on the high pressure side to rise abnormally and activate the high pressure switch, causing unnecessary shutdowns. Sometimes.

Therefore, conventionally, the temperature TC of the indoor heat exchanger that acts as a condenser (hereinafter referred to as condenser temperature) is detected, that is, the pressure on the high pressure side is indirectly detected, and the condenser temperature Tc and the fifth
There is a system in which the control pattern of the operating frequency F is switched by comparison with operating frequency setting conditions as shown in the figure.

That is, as shown in FIGS. 5 and 6, during heating operation, when the condenser temperature Tc is in the O zone, normal frequency control is performed according to the difference between the indoor set temperature Ts and the indoor temperature [Ta. , when the condenser temperature Tc rises to the P zone due to heating overload, the operating frequency F is increased by Δ from the previous value.
The operating frequency F is set to a lower value by f1, so that when the condenser temperature Tc falls to the Q zone, the operating frequency F is maintained at the same value as before.

However, when the condenser temperature Tcff1 changes from the Q zone to the O zone, the operating frequency F suddenly increases due to heating overload, and even if the high pressure side pressure increases abnormally, the condenser temperature Tc cannot follow it. There are drawbacks. In this case, since frequency control cannot be performed in the P zone, the high pressure side pressure Pd reaches the operating point Pds of the high pressure switch, as shown in Figure 7, and the high pressure switch is eventually activated, resulting in a shutdown of the operation. . In particular, when the high pressure switch is of the self-reset type, the high pressure switch repeatedly activates and returns, causing the heating operation to turn on and off frequently, resulting in a significant drop in heating efficiency. Moreover, frequent on/off operation adversely affects the life of the compressor.

[Object of the invention] This invention was made in view of the above circumstances,
The aim is to create highly reliable air conditioners that can prevent unnecessary shutdowns and frequent turning on and off, thereby improving heating efficiency and extending the life of the compressor. Our goal is to provide the following.

[Summary of the invention]

This invention includes a control means that maintains the operating frequency of the variable capacity compressor at a value higher than the previous value by a predetermined value and for a predetermined period of time when the temperature of the indoor heat exchanger falls below a set value during heating operation. It was established.

[Embodiments of the invention]

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

As shown in FIG. 2, a variable capacity compressor 1, a four-way valve 2, an outdoor heat exchanger 3, a pressure reducing device such as an expansion valve 4, an indoor heat exchanger 5, etc. are connected in sequence to form a heat pump type refrigeration cycle. ing.

That is, during cooling operation, the refrigerant flows in the direction of the solid arrow in the figure to form a cooling cycle, and the outdoor heat exchanger 3 acts as a condenser, and the indoor heat exchanger 5 acts as an evaporator. In addition, during heating operation, the four-way valve 2 switches to cause the refrigerant to flow in the direction of the dashed arrow in the figure, forming a heating cycle, and the outdoor heat exchanger 3 acts as an evaporator, while the indoor heat exchanger 5 acts as an evaporator. Acts as a condenser.

An outdoor fan 6 is provided near the outdoor heat exchanger 3, and an indoor fan 7 is provided near the indoor heat exchanger 5. Further, a high pressure switch 8 is attached to the refrigerant discharge side piping of the compressor 1.

FIG. 1 shows the control circuit.

Reference numeral 10 denotes a control section, which includes a microcomputer and its peripheral circuits. The control unit 10 includes an operation operation unit 11, a blank temperature sensor 12, and the indoor heat exchanger 5.
A heat exchanger temperature sensor 13 that detects the temperature of the indoor fan, an indoor fan drive circuit 14, a relay driver 15, and the like are connected.

Here, the indoor fan drive circuit 14 drives the indoor fan motors 7 to 1 in accordance with commands from the control section 10.

The relay driver 15 drives the fan relay 16 and the four-way valve relay 17 in accordance with commands from the control unit 10. The fan relay 16 opens and closes a current supply path to the outdoor fan motor 6M. The four-way valve relay 17 opens and closes the current supply path to the four-way valve 2.

Further, an inverter drive circuit 18 is connected to the control section 10. This inverter drive circuit 18 includes a control unit 1
The switching element of the inverter circuit 19 is turned on and off in accordance with the command from the inverter circuit 19. The inverter circuit 19 once rectifies the output voltage of the commercial AC power supply 20,
a given frequency (and voltage) by switching it
This converts the AC power into AC power and supplies it to the compressor motor 1M.

Next, the operation of the above configuration will be explained with reference to FIGS. 3 and 4.

The heating operation is set using the operating unit 11, a desired indoor temperature TS is set, and the operation switch is turned on.

Then, the control unit 10 detects the indoor temperature Ta using the indoor temperature sensor 12, and if the indoor temperature Ta is lower than the set temperature Ts, switches the four-way valve 2, and
The inverter circuit 19 is driven to start the compressor motor 1M. That is, the compression e11 is turned on, a heating cycle is formed, and the heating operation is started.

During this heating operation, the control unit 10 detects the temperature Tc of the condenser, that is, the indoor heat exchanger 5, by the heat exchanger temperature sensor 13, and the condenser concentration C is the frequency setting condition (Fig. 5).
When the frequency is in the 0 zone, normal frequency control is performed.

That is, when the high pressure side pressure Pd is not so high, the operating frequency F (output frequency of the inverter circuit 19) is controlled according to the difference between the indoor temperature setting Ts and the indoor temperature Ta. Therefore, the capacity of the compressor 1 is set to an optimal value corresponding to the air conditioning load.

When the condenser temperature TC rises to the P zone due to a heating overload or the like, the Ill Ta section 10 sets the operating frequency F to a value lower than the previous value by a predetermined value Δfl. In other words, when the high pressure side pressure Pd increases, the compressor 1
This is to keep the capacity at a certain value and suppress any further increase in the high pressure side pressure Pd.

In this way, when the condenser temperature TC falls to the Q zone, the control unit 10 maintains the operating frequency F at the same value as before.

Then, when the condenser temperature Tc shifts from the Q zone to the O zone, the control unit 1o sets the operating frequency F to a value higher than the previous value by a predetermined value Δf2, and maintains the operating frequency F at a constant value based on the count of the internal timer. It is held for a time tO. In other words, the operating frequency F is not changed for a certain period of 1°, so even if there is a heating overload, the high pressure side pressure P
d does not rise, and the activation of the high pressure switch 8 can be avoided. Moreover, since the operating frequency F to be maintained is taken into account +Δf2, it becomes an appropriate value, and there will be no shortage or excess of heating capacity.

However, for a certain period of time 1. After that, perform the normal frequency control that is original to O Gene. In other words, after a certain period of time to, the condenser temperature Tc is in a state where it can sufficiently follow changes in the high pressure side pressure Pd, and the frequency control by the P zone is effective against subsequent heating overloads. become.

Therefore, unnecessary stoppage of operation and frequent turning on and off of operation can be prevented, thereby improving heating efficiency and extending the life of the compressor 1. In addition, the broken line in FIG. 4 shows the change in the high pressure side pressure Pd in the conventional case for comparison.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various modifications can be made without changing the gist.

(Effects of the Invention) As described above, according to the present invention, it is possible to prevent unnecessary operation stoppages and frequent turning on and off of operation, thereby making it possible to improve heating efficiency and extend the life of the compressor. We can provide air conditioners with excellent reliability.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the configuration of a control circuit in an embodiment of the present invention, Fig. 2 is a diagram showing the configuration of a refrigeration cycle in the embodiment, and Fig. 3 is a flowchart for explaining the operation of the embodiment. , FIG. 4 is a diagram showing the change in high pressure side pressure in the same embodiment, FIG. 5 is a diagram showing the operating frequency setting conditions in the same embodiment and the conventional air conditioner, and FIG. A flowchart to explain the operation,
FIG. 7 is a diagram showing changes in high pressure side pressure in the same conventional air conditioner. 1... Variable capacity compression tank, 2... Four-way valve, 3... Outdoor heat exchanger, 4... Expansion valve (pressure reducing device @), 5... Indoor heat exchanger, 8... High pressure switch, 13... Heat exchanger temperature sensor, 19... Inverter circuit.

Claims (1)

[Claims] A heat pump type refrigeration cycle is provided in which a variable capacity compressor, a four-way valve, an outdoor heat exchanger, a pressure reduction device, an indoor heat exchanger, etc. are connected in sequence, and the operating frequency of the variable capacity compressor is controlled according to the load. In an air conditioner, when the temperature of the indoor heat exchanger falls below a set value during heating operation,
An air conditioner comprising a control means for maintaining the operating frequency of the variable capacity compressor at a value higher than the previous value by a predetermined value and for a fixed period of time.