JPH0251117B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a defrosting control device for a heat pump type air conditioner.

Conventional configuration and its problems During heating operation of a heat pump type air conditioner, under low outside temperatures, frost forms on the surface of the outdoor heat exchanger as the operating time passes, and the heating capacity decreases significantly. To prevent this, it is necessary to defrost the outdoor heat exchanger at an appropriate time by, for example, reversing the flow of the refrigerant.

Traditionally, most defrosting control devices for heat pump type air conditioners have detected outdoor heat exchanger temperature or outside air temperature as frost detection means, and depending on the installation location, these may be affected by strong winds or gusts. There was a problem in that the temperature was easily detected and malfunctions were easily caused, such as starting defrosting when it was not necessary.

Purpose of the Invention The present invention solves the above-mentioned problems by detecting the frosting state of the outdoor heat exchanger based on changes in the refrigerant flow rate, thereby eliminating the need for conventional temperature detection, which is susceptible to the effects of strong winds and gusts. It is an object of the present invention to provide a defrosting control device for a heat pump type air conditioner that can start defrosting more reliably and at a more accurate time than the other methods.

Structure of the Invention In order to achieve this object, the defrosting control device for a heat pump type air conditioner of the present invention has a flow rate detection means for detecting a refrigerant flow rate Gr, and a differential value dGr/dτ of the refrigerant flow rate Gr with respect to time τ. a comparator circuit that compares the differential value dGr/dτ with a negative set value K, and a state in which the differential value dGr/dτ remains equal to or less than the negative set value K for a predetermined time L. and an output circuit that outputs a signal to start defrosting the outdoor heat exchanger when

In the defrosting control device of the present invention, as frost forms on the outdoor heat exchanger during heating operation and the heat transfer performance decreases, the suction pressure of the compressor gradually decreases and the flow rate of refrigerant circulating through the refrigeration cycle decreases. This study focuses on the fact that the refrigerant flow rate gradually decreases, and as the amount of frost increases, the decreasing tendency of the refrigerant flow rate becomes more rapid.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an example of a heat pump type air conditioner equipped with a defrosting control device of the present invention.

Reference numeral 1 denotes a heat pump type air conditioner, in which a compressor 2, an indoor heat exchanger 3, a throttle device 4, an outdoor heat exchanger 5, a four-way valve 6, and a flow rate sensor 7 are connected in sequence to constitute a refrigeration cycle, and also performs defrosting control. It includes a device 8, an indoor fan 9, and an outdoor fan 10. The flow rate sensor 7 used as a refrigerant flow rate detection means is provided on the discharge side of the compressor 2 in this case, and is a multi-blade turbine type flow sensor.

The solid arrow direction shown in the figure indicates the flow direction of the refrigerant during heating operation, and the outdoor heat exchanger 5 acts as an evaporator and absorbs heat from the outside air. When frost forms and grows on the outdoor heat exchanger 5 as the heating operation time elapses, the defrost control device 8, which receives the refrigerant flow rate signal from the flow rate sensor 7 as an input signal, determines whether or not defrosting has started. When starting defrosting, the four-way valve 6 is switched to set the flow direction of the refrigerant in the direction of the broken line arrow in the figure, and defrosting of the outdoor heat exchanger 5 is started.

FIG. 2 shows a block diagram of a defrosting control device for a heat pump type air conditioner, which is an embodiment of the present invention.

11 is an arithmetic circuit, 12 is a comparison circuit, and 13 is an output circuit.

FIG. 3 is a flowchart illustrating the operation of the defrosting control device shown in FIG. 2 in more detail. Fourth
The figure shows an example of a time change in the refrigerant flow rate Gr during heating operation.

As shown in Figure 4, under low outside temperatures, the refrigerant flow rate G increases as the heating operation time τ elapses.
The refrigerant flow rate gradually decreases from a stable state except immediately after startup, and after this stable state passes, the refrigerant flow rate decreases.
The decreasing trend of Gr becomes rapid. This appears to be the time when the amount of frost on the outdoor heat exchanger began to have a significant effect on heat transfer performance, and the continuous operation of the heat pump air conditioner during heating began to show its limits.

As shown in FIG. 2, such a refrigerant flow rate Gr is detected by a flow rate sensor 7, and this refrigerant flow rate signal is inputted to a defrosting control device 8. In the defrosting control device 8, a calculation circuit 11 calculates a differential value dGr/dτ of the refrigerant flow rate Gr with respect to time τ. For example, if the refrigerant flow rate signal acquisition time interval is Δτ, this calculation is calculated as the amount of change in Gr during the time Δτ. Next, the comparison circuit 12 compares the differential value dGr/dτ and the negative set value K. As shown in Figure 3, this differential value
If dGr/dτ is larger than K, it is determined that there is not much frost on the outdoor heat exchanger 5, and the heating operation is continued and the refrigerant flow rate is increased again after a time Δτ.
Detect Gr. On the other hand, when this differential value dGr/dτ becomes equal to or smaller than K (when τ=τf in FIG. 4), it is determined that a considerable amount of frost has formed on the outdoor heat exchanger 5, and the output circuit 13 The timer function operates. In other words, if I is the number of times that the state dGr/dτ≦K occurs continuously in FIG. 3, then the time during which this state continues can be expressed as Δτf=I·Δτ. If this duration Δτf is smaller than the predetermined time L, the heating operation continues and the refrigerant flow rate Gr is detected again.

On the other hand, when this duration Δτf exceeds the predetermined time L, it is determined that the amount of frost on the outdoor heat exchanger 5 is extremely large and that continuous operation is at its limit, and the output circuit 13 shown in FIG. 2 sends a signal to start defrosting. emits.

As described above, upon receiving the defrost start signal issued by the defrost control device 8, the four-way valve 6 is switched to start defrosting operation of the outdoor heat exchanger 5 in a reverse cycle. Fourth
As shown in the figure, the defrosting start time is expressed as τd=τf+Δτf when totaled from the start of heating operation. Thereafter, for example, the defrosting operation is continued for a predetermined time or until the temperature of the outdoor heat exchanger 5 reaches a predetermined temperature, and then the heating operation is resumed, and the series of operations described above is repeated again.
In the above embodiment, a case has been described in which a turbine type flow rate sensor is provided on the discharge side of the compressor as the flow rate detection means, but it is clear that the type of flow rate sensor and its installation position are not limited.

Further, in the above embodiment, a case has been described in which a flow rate sensor is used as the flow rate detection means for detecting the refrigerant flow rate Gr, but the flow rate sensor does not necessarily need to be provided. In other words, it is possible to know the refrigerant flow rate by using the flow rate characteristics of a pressure reducing device such as an expansion valve or a capillary, or the flow rate characteristics of a compressor. Figure 5 shows an example of the flow rate characteristics of a pressure reducing device, where the horizontal axis is the pressure reducing device inlet pressure: P, the vertical axis is the logarithm of the refrigerant flow rate Gr, and the pressure reducing device inlet subcool SC is taken as a parameter. be. Therefore, although not shown, if the pressure and temperature (or subcool) at the inlet of the pressure reducing device are detected using a flow rate detection means, the refrigerant flow rate Gr can be determined from FIG.

Figure 6 shows an example of the flow rate characteristics of the compressor, where the horizontal axis shows the suction pressure Ps, the vertical axis shows the refrigerant flow rate Gr*, and the discharge pressure Pd is the parameter when the suction superheat degree SH = 11 degC. That is.

FIG. 7 shows an example of the suction refrigerant density ratio with respect to the suction superheat degree SH.

Therefore, although not shown, if the suction pressure, suction temperature, and discharge pressure of the compressor are detected as a flow rate detection means, the refrigerant flow rate Gr* at SH=11 degC can be determined from FIG. 6. Furthermore, the suction superheat degree SH is determined from the detected suction temperature, and the suction refrigerant density ratio at that time can be determined from FIG.
Therefore, the actual refrigerant flow rate can be known as Gr=・Gr*.

In addition, in the above embodiment, the defrosting of the outdoor heat exchanger was explained using a reverse cycle method by switching a four-way valve.
It goes without saying that a hot gas bypass system in which the discharge gas from the compressor is directly guided to the outdoor heat exchanger without switching the four-way valve has the same effect.

Effects of the Invention As described above, the defrosting control device for a heat pump air conditioner of the present invention has a flow rate detection means for detecting the refrigerant flow rate Gr, and calculates the differential value dGr/dτ of the refrigerant flow rate Gr with respect to time τ. an arithmetic circuit that performs calculations; a comparison circuit that compares the differential value dGr/dτ with a negative set value K; The output circuit also includes an output circuit that outputs a signal to start defrosting the outdoor heat exchanger at the same time, so defrosting control can be performed by detecting the outdoor heat exchanger temperature or outside air temperature, which is more widely used than before. This is a highly effective method that can almost completely eliminate malfunctions of the temperature detection method in starting defrosting due to gusts or strong winds, and can also start defrosting reliably and at an appropriate time.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a heat pump air conditioner equipped with a defrosting control device of the present invention, and FIG. 2 is a block diagram of a defrosting control device for a heat pump air conditioner that is an embodiment of the present invention. Figure 3 is a flowchart for explaining the action of Figure 2 in detail, Figure 4 is a diagram showing time changes in refrigerant flow rate Gr during heating operation, and Figure 5
The figure shows the flow rate characteristics of the pressure reducing device, Figure 6 shows the flow rate characteristics of the compressor, and Figure 7 shows the suction superheat degree SH.
FIG. 3 is a diagram showing the relationship of the suction refrigerant density ratio to DESCRIPTION OF SYMBOLS 1...Heat pump type air conditioner, 7...Flow rate sensor (flow rate detection means), 8...Defrosting control device for heat pump type air conditioner, 11...Arithmetic circuit, 12...
Comparison circuit, 13...output circuit.

Claims (1)

[Claims] 1. A flow rate detection means for detecting a refrigerant flow rate Gr,
an arithmetic circuit that calculates a differential value dGr/dτ of the refrigerant flow rate Gr with respect to time τ; a comparison circuit that compares the differential value dGr/dτ with a negative set value K;
A defrosting control device for a heat pump air conditioner comprising an output circuit that outputs a signal to start defrosting an outdoor heat exchanger when dGr/dτ remains below this negative set value K for a predetermined time L. .