JPS58205064A - Controller for heat pump type air conditioner - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a control device for a heat pump type air conditioner,
In particular, the present invention relates to improvements in defrosting control circuits for outdoor heat exchangers.

[Technical background of the invention]

Generally, during heating operation of a heat pump type air conditioner, there are cases where the outdoor heat exchanger is used at a surface temperature below the freezing point. For this reason, frost forms on the surface of the outdoor heat exchanger, inhibiting heat exchange. To remove this frost, the air conditioner is temporarily switched to the cooling cycle, and the outdoor heat exchanger is used as a condenser and heat is applied to it to melt it away. As a matter of course, a control circuit is formed to stop the outdoor air blower during defrosting so that the heat effectively acts on defrosting.

Conventional control circuits that perform such defrosting control determine the amount of frost on the outdoor heat exchanger based on detection signals from a temperature sensor that detects room temperature and a temperature sensor that detects the temperature of the indoor heat exchanger, and then performs heat exchange. In addition to starting defrosting in a state where the defrosting process was greatly inhibited, defrosting was also stopped when the timer that was set for the time required for defrosting expired.

In this case, the amount of frost formed is normally determined by the central processing unit that constitutes the control circuit, but if this central processing unit can accurately judge the actual amount of frost formed on the outdoor heat exchanger, a timer is used. There is no problem with defrosting for the time set by the indoor unit, and by determining whether or not frost is formed on the indoor unit side, it is possible to reduce the so-called crossover wire that connects the indoor unit and outdoor unit, and to control the outdoor unit. There are advantages such as being able to reduce the number of parts.

However, the amount of frost formation varies greatly depending on the length of the piping that circulates the refrigerant or the environment or region where the air conditioner is installed, and there is a natural limit to how indoor units can judge this.

Here, for example, when the central processing unit determines that defrosting is necessary, the actual amount of frost formed is extremely different.

The outline of the conventional control device will be explained with reference to FIG. 2 as well as the phenomena that occur in the air conditioner when defrosting is performed in this state.

Figure 1 (a), (b) H ((j) is the indoor heat exchanger temperature after starting defrosting, and the refrigerant pressure on the high pressure side of the outdoor heat exchanger (hereinafter referred to as outdoor heat exchanger pressure) and the change in the current of the electric motor that drives the compressor for refrigerant circulation (hereinafter referred to as compressor current).The curve ∆ shown by the broken line is for the case of no frost, and the curve 0 shown by the solid line is for the normal case. In the case of frost, the curve θ shown by a dashed-dotted line indicates the case of excessive frost formation.

Here, when defrosting is started at time to, the indoor heat exchanger temperature T initially decreases gradually regardless of the amount of frost, but after a certain period of time, the temperature decreases to the rate of falling dust and temperature. A big difference appears. In other words, in the case of no frost as shown by the curve ■, the temperature is maintained higher than the constant temperature TL at which it is determined that frost removal has been completed, and in the case of normal frost as shown by the curve 0, the temperature is rapidly increased. and is maintained at a value lower than the constant temperature TL, and further 1. ,,,,,,,. 8111
In the case of excessive frosting indicated by the line θ, although the temperature drops more slowly than in normal frosting, it is still maintained at a value lower than the constant temperature TL.

On the other hand, at the beginning of defrosting, the outdoor heat exchanger pressure p rises rapidly regardless of the amount of frosting, and then remains at a constant pressure, but after that, it changes greatly depending on the amount of frosting. It comes out. That is, during normal frosting and excessive M1 as shown by curves 0 and θ, the pressure p remains approximately constant, but during no frosting as shown by curve (■), this pressure p gradually increases.
This will exceed the allowable pressure P peak 1, which is generally specified for outdoor heat exchangers, etc.

In addition, the compressor current also drops slightly at the beginning of defrosting, regardless of the amount of frost, and then remains at a constant value, but after that it follows changes in the outdoor heat exchanger pressure p. In particular, when there is no frost as shown in curve (2), the allowable current H corresponding to the allowable pressure "dh" will be exceeded.

Note that the allowable pressure Pdh of the outdoor heat exchanger may be determined based on the allowable electric current H of the compressor.

Therefore, if the above-mentioned timer is set for 12 hours and defrosting is stopped when this timer times up, that is, at time t2, defrosting can be performed without any problems at least during normal frosting and excessive frosting. be.

By the way, if the central processing unit determines that defrosting is required even though there is no frost on the outdoor heat exchanger, and switches the refrigerant cycle and stops the outdoor fan, as described above, , before the time T2 set in the tie dimension elapses, the outdoor heat exchanger pressure p and the compressor mine flow exceed allowable values, creating an extremely dangerous situation.

As a countermeasure against this, for example, by predicting the outdoor heat exchanger pressure p1 or the rising curve of the compressor electric current when there is no frost, and setting up another timer that times out before this exceeds the allowable range, that is, at time T1, If the indoor heat exchanger temperature T exceeds a constant temperature TL at time t1 when this timer times up, a gap stop signal is output to prevent the outdoor heat exchanger pressure p from exceeding the allowable pressure Pc1h.

[Problems with background technology]

In such a conventional heat pump type air conditioner control device, defrosting is stopped when the indoor heat exchanger temperature T at time t1 is above the constant temperature TJ, L, and the outdoor Although the heat exchanger pressure p is prevented from increasing, the first
As is clear from Figure (a), the same effect will occur even in the case of excessive frost formation. This means that even though the defrosting operation must be continued, the defrosting operation must be stopped midway through, and as a result, sufficient defrosting cannot be achieved.

In addition, considering the difference in the amount of frost, the timer setting time T,
A constant temperature TL, which is a uniform standard for determining whether defrosting has been achieved or not, is determined, but there is a drawback in that it is quite difficult to optimally select these temperatures.

[Purpose of the invention]

The present invention has been made to eliminate the above-mentioned drawbacks.
To provide a control device for a heat pump type air-conditioning machine that can perform reliable defrosting while maintaining outdoor heat exchanger pressure within an allowable range even when frost formation 1: is significantly different.

[Summary of the invention]

In order to achieve the above object, a control device for a heat pump type air conditioner according to the present invention includes a current detection circuit that detects a compressor current for refrigerant circulation and generates a signal according to this current value, and a defrosting circuit. A level setting circuit capable of outputting a signal corresponding to the compressor current at the time when the pressure of the outdoor heat exchanger exceeds an allowable range, and the output signal levels of the current detection circuit and the level setting circuit are compared with each other; The present invention is configured to include a comparison circuit that outputs a defrosting stop signal when the output signal level of the current detection circuit becomes higher than the output signal level of the level setting circuit.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 2 is a block diagram showing the configuration of a control device for a heat pump type air conditioner according to the present invention.
11 output signals are taken into the central processing unit 3 via the A-D converter. This central processing unit 3 also has the function of a timer having the above-mentioned set time T2, and determines the amount of frost on the outdoor heat exchanger and determines that defrosting is required.
, a defrost start signal is applied to the four-way valve relay S and an outdoor fan relay B via the relay driver adapter, respectively. Here, the four-way valve relay S operates a four-way valve (not shown) that switches the refrigerant cycle, and the outdoor fan relay 6 operates an outdoor blower (not shown) that ventilates the outdoor heat exchanger.

Conventionally, almost all of these factors were used, and in addition, the setting time T1
Defrosting control was performed by providing the central processing unit 3 with a timer function that has a timer function, but here, a new current detection function is added to detect the compressor current ■ and generate a clear stream voltage signal according to this current value. circuit 10, a level setting circuit UO that generates a DC voltage signal corresponding to the compressor current when the outdoor heat exchanger pressure exceeds the allowable range, and a current detection circuit that compares these DC voltage signals with each other. A comparison circuit 30 is added that outputs a defrosting stop signal when the signal level of No. 10 becomes higher than the signal level of the level setting circuit SO.

Among these, the current detection circuit 10 includes a current transformer // capable of extracting a current proportional to the compressor current, a rectifier circuit /, 2 that performs full-wave rectification of the current of this current transformer, and this rectifier circuit /2. It is formed by a capacitor /+, 15 and a resistor 13 that smooths the output of the current transformer l/, a resistor /6 that stabilizes the output voltage of the current transformer l/, and a resistor 17 that stabilizes the output voltage of the rectifier circuit /:l. There is.

In addition, the level setting circuit U0 connects resistors 2/ and n in series, and by applying a DC voltage from a power supply (not shown) between both ends of this series circuit, the imaginary aK DC voltage of the connection between the resistors 2/ and n is determined. Measures are being taken to ensure that this occurs.

Next, the comparison circuit 30 includes an operational amplifier 3/, a resistor 32 connected between the output terminal and the non-inverting input terminal (+) of the operational amplifier 31, and one end connected to the non-inverting input terminal (+) of the operational amplifier 3/. ), the other end is formed by the negative terminal of the current detection circuit 10 and the level setting circuit 20, and a variable resistor 3 unit which is commonly grounded, and the inverting input terminal of the operational amplifier 3/ (→ is the resistor unit / and connected to the connection point of n.

The operation of the control circuit for the heat pump type air conditioner of the present invention configured as described above will be explained below.

First, the central processing unit 3 calculates the amount of frost based on the output signal of the temperature sensor 1, and when it becomes necessary to defrost, it activates the four-way valve relay! Then, the outdoor fan relay 6 is activated to start defrosting, and when 72 hours have elapsed (FIG. 1), the four-way valve relator and the outdoor fan relay 6 are restored and defrosted to stop the defrosting.

Next, the current detection circuit 10 detects the compressor current (Fig. 1) during defrosting using a current transformer //, full-wave rectifies this detection signal using a rectifier circuit /2, and then performs full-wave rectification using a rectifier circuit /2. 3 and capacitor /I/-, 15, a DC voltage signal corresponding to the compressor current is generated at the connection point between resistor /3 and capacitor 15, and this DC voltage signal is calculated. Add to the non-inverting input terminal (+) of amplifier 3/.

Also, level setting circuit: 1. O generates a DC voltage doubler signal corresponding to the compressor mine flow H when the outdoor exchanger pressure p exceeds the permissible pressure Pa at the connection point a of the resistor 2/ and 2, and also outputs this DC voltage signal. Add to the inverting input terminal (-) of operational amplifier 3/.

Further, in the comparison circuit 30, the voltage signal at the connection point a is used as a reference signal, and the variable resistor 32 is set so that the circuit state of the operational amplifier 3/ is inverted when the voltage signal level at the connection point A exceeds this reference signal level. is adjusted, and this inversion causes the output signal level of operational amplifier 3 to change from rLJ to rH.
Changes to J.

When the output of the operational amplifier 3/, that is, the output of the comparison circuit 30 changes from rLJ to "H", the central processing unit 3 receives this as a defrost stop signal, and sends this defrost stop signal to the four-way valve relay! and outdoor fan relay B.

Therefore, during defrosting, the outdoor heat exchanger pressure p changes to the allowable pressure P
If dh is exceeded, the defrosting operation is canceled at that moment, and if the outdoor heat exchanger pressure p remains at a value lower than the allowable pressure Pdh,
The defrosting operation is canceled after 12 hours set in the timer.

On the other hand, even if the external heat exchanger is excessively frosted, as long as the outdoor heat exchanger pressure does not increase significantly, the defrosting operation is continued until 72 hours have elapsed, so that reliable defrosting is possible.

In the above embodiment, the current detection circuit IQ and the level setting circuit J each output a DC voltage signal, and
The comparison circuit qo compares the levels of these voltage signals, but when using a comparison circuit that obtains the current value from comparison 1 to 1, the current detection circuit IO and level setting circuit each have
It is also possible to use devices that each output a direct current signal.

Further, in the above embodiment, the central processing unit 3 has a timer function, but even if a timer or a timer circuit having a similar function is provided outside the central processing unit 3, the same effect as described above can be obtained. It can be made to perform an action.

〔Effect of the invention〕

As is clear from the above explanation, according to the control device for a heat pump air conditioner of the present invention, even when the amount of frost formation varies greatly, the outdoor heat exchanger pressure can be maintained within an allowable range and can be reliably maintained. Can be defrosted.

In addition, with conventional equipment, taking into account the difference in the amount of frost,
The time T1 shown in FIG. 1 and the constant temperature TI, which is a uniform guide to whether or not defrosting has been performed, were determined, but in the present invention, the time T2 and the outdoor heat exchange assuming the case of overloaded boxes were determined. Simply set the compressor current corresponding to the allowable pressure of the air conditioner (this greatly simplifies the adjustment when installing the air conditioner.

[Brief explanation of the drawing]

Figure 7 is a time chart for explaining the outline and operation of a conventional heat pump air conditioner control device;
The figure is a block diagram showing the configuration of an embodiment of a control device for a heat pump type air conditioner according to the present invention. /...Temperature sensor, Co...A-D converter, 3...
Central processing unit, l...Relay driver, 3...Four-way valve relay, 6...Outdoor fan relay, 10...' current detection circuit, l/...Current transformer, /2... rectifier circuit,
/3. /A, /”1,2/,22゜33...resistance,
J...Level setting circuit, 3o...Comparison circuit, 3/...
...Operation amplifier, 3 units...variable resistor. Applicant's agent Kiyoshi Inomata (15) 1 6 Rokuken□

Claims (1)

[Claims] In a control device for a heat pump air conditioner that temporarily switches the refrigerant cycle to defrost when an outdoor heat exchanger is frosted, it detects the current during defrosting of the electric motor that drives the compressor for refrigerant circulation, and A current detection circuit generates a signal corresponding to this current value, and a signal corresponding to the current of the motor at the time when the refrigerant pressure on the high pressure side of the outdoor heat exchanger during defrosting exceeds an allowable range is output by setting. The output signal level of the current detection circuit and the level setting circuit are compared with each other, and when the output signal level of the current detection circuit becomes larger than the output signal level of the level setting circuit, defrosting is performed. 1. A control device for a heat pump air conditioner, comprising a comparison circuit that outputs a stop signal.