JPH0443173B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an air-source heat pump type air conditioner in which a compressor, a four-way valve, an outdoor heat exchanger, a throttle device, and an indoor heat exchanger are connected in sequence. This relates to a defrosting operation control device for a machine.

[Prior art and problems to be solved by the invention]

Conventionally, the refrigeration cycle of this type of air conditioner is
As shown in FIG. 6, during heating operation, the refrigerant discharged from the compressor a passes through the four-way valve b as indicated by the solid arrow, is condensed in the indoor heat exchanger c, passes through capillary tubes d and e, It evaporates in the outdoor heat exchanger f, passes through the four-way valve b again, and returns to the compressor a.

In addition, when the outside temperature is low, the temperature of the outdoor heat exchanger f becomes low, and eventually frost begins to adhere to the surface of the outdoor heat exchanger f, which causes the heat transfer characteristics to deteriorate and the heat exchanger capacity to rapidly decrease. At first, the heating capacity also decreases.

Therefore, the pipe temperature of the outdoor heat exchanger f is detected by the heat exchanger temperature sensor g, and the outside air relative humidity is detected by the outside air humidity sensor h, and when the pipe temperature of the outdoor heat exchanger f is below a certain temperature, And when the relative humidity is above a certain value, as shown by the broken line in the figure, cooling operation is started, and high-temperature, high-pressure refrigerant is sent to the outdoor heat exchanger f to melt the frost attached to the outdoor heat exchanger f. , the capacity of the outdoor heat exchanger f is restored and the heating operation is resumed as indicated by the solid line in the figure.

However, in the conventional defrosting operation mode as described above, the judgment condition for starting the defrosting operation is only the outside air relative humidity at the temperature of the outdoor heat exchanger f. In the past, there were disadvantages in that the defrosting operation was not performed even if frost had formed, or the defrosting operation was performed even if no frost had formed.

In other words, relative humidity is the amount of water vapor actually contained in a certain volume of air and the maximum amount of water vapor that air can contain at that temperature (saturated water vapor amount).
It is expressed as a percentage. When this is expressed in terms of temperature vs. water vapor amount characteristics, as shown in Figure 7, the horizontal axis and the 100% (saturated water vapor amount) characteristic curve
It is shown by the curve between . No matter what the relative humidity is, frost will not form unless the temperature of the outdoor heat exchanger f is below zero degrees, and the temperature of the outdoor heat exchanger f is exposed to the outside air and is not relative to the outside temperature. It is designed to exhibit a substantially constant temperature difference ΔT.

Therefore, if the outside air temperature when the temperature of the outdoor heat exchanger f is 0 degrees is T ₁ and the amount of saturated water vapor is D ₁ when the temperature is 0 degrees, then a straight line Y ₁ passing through T ₁ and passing through D ₁ is parallel to the vertical axis. Frost will form at a relative humidity within the range surrounded by the straight line Z ₁ parallel to the horizontal axis and the above-mentioned curve X. The minimum relative humidity RH ₁ at which frost formation occurs is on the curve X ₁ , and this relative humidity RH ₁ is determined as the above-mentioned constant value. Also, as shown in the figure, if the outside air temperature drops to T ₂ and the temperature of the outdoor exchanger f also drops to T ₃ , then when the straight line Y ₂ passing through T ₂ and parallel to the vertical axis and the temperature T ₃ Frost formation occurs at the relative humidity surrounded by the straight line _{Z 2 passing} through _the saturated water vapor D ₂ of Therefore, when the relative humidity detected by the humidity sensor is RH ₁ , it is assumed that frost has formed and the defrosting operation is performed even if there is actually no frost.

This phenomenon is even more noticeable in a refrigeration cycle in which a variable capacity inverter type compressor is used and ΔT is varied.

Therefore, no matter how much defrosting operation is performed in such a case, the heating capacity cannot be improved, and conversely, during defrosting operation, heating operation is stopped, causing the room temperature to drop and comfort to be impaired. In addition, during defrosting operation, cooling operation is performed, so the condenser and evaporator are reversed, reducing operational efficiency.

In order to overcome the above drawbacks, the amount of moisture in the air flowing into the outdoor heat exchanger and the amount of moisture in the air flowing out of the outdoor heat exchanger can be obtained by using a humidity sensor and a temperature sensor installed at the inlet and outlet, respectively. A device has been proposed in which the amount of frost is determined by calculation based on the signals and the difference between them, but this device has the disadvantage that it requires a large number of sensors, is complex in structure, and is expensive.

Therefore, the present invention eliminates the above-mentioned drawbacks of the conventional system, and is configured to appropriately determine direct frost and measure the amount of frost with a simple configuration, and to start defrosting operation at the appropriate time. Therefore, it is an object of the present invention to provide a defrosting operation control device for an air conditioner that predicts frost formation and controls the defrosting operation to improve operational efficiency.

[Means for solving problems]

In order to achieve the above object, the defrosting operation control device for an air conditioner according to the present invention is an air conditioner in which a compressor, a four-way valve, an outdoor heat exchanger, a throttling device, and an indoor heat exchanger are connected in sequence. , an exchanger temperature sensor that detects the temperature of the outdoor heat exchanger, an outside air temperature sensor that detects the temperature of outside air, a humidity sensor that detects the humidity of outside air, and the temperature detected by the outside air temperature sensor and the humidity sensor. an absolute humidity calculation means for calculating the absolute humidity of the outside air based on the humidity detected by the exchanger temperature sensor; a comparison means for comparing the saturated water vapor amount with respect to the temperature detected by the exchanger temperature sensor and the calculated absolute humidity; The detected temperature is below zero,
determining means for determining frost formation based on the comparison result by the comparing means that the absolute humidity is greater than the saturated water vapor amount; and condensation, which is the difference between the calculated absolute humidity and the saturated water vapor amount when the determining means determines frost formation. means for calculating the amount of moisture; and means for calculating the time for the amount of frost to reach a predetermined amount based on the temperature detected by the exchanger temperature sensor and the amount of condensed moisture when frost formation is determined by the determining means. , the defrosting operation is started when the calculated time has elapsed after the determination of frost formation.

[Function] With the above configuration, the absolute humidity of the outside air is calculated from the temperature detected by the outside air temperature sensor and the humidity detected by the humidity sensor, and the temperature detected by the exchanger temperature sensor is below zero and the absolute humidity is saturated water vapor. The amount of condensed water is calculated as the difference between the absolute humidity at the time of frost determination and the saturated water vapor amount, and the temperature detected by the exchanger temperature sensor and the condensed moisture at the time of frost determination are calculated. The time required for the amount of frost to reach a predetermined amount is calculated based on the amount of frost formation, and the defrosting operation is started when the above calculated time has elapsed after frost formation is determined, so that the start of frost formation and subsequent frost formation It is possible to control the defrosting operation to start the defrosting operation in a timely manner by accurately grasping the amount.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 5.

First, conditions for frost formation on the outdoor heat exchanger will be explained.

Frost formation occurs when the temperature of the outdoor heat exchanger is below zero degrees and there is condensed water on the surface of the outdoor heat exchanger. In addition, condensed water on the surface of the outdoor heat exchanger is generated when the amount of water vapor contained in the outside air sent to the surface of the outdoor heat exchanger by a fan is greater than the saturated amount of water vapor at the temperature of the outdoor heat exchanger. .

From the above, by knowing the temperature and relative humidity of the outside air and the temperature of the outdoor heat exchanger, the frosting conditions can be determined as follows.

Since the saturated water vapor amount D _SA for each temperature is known as shown in Figure 3, the relative humidity
From RH and the outside air temperature T _A , the amount of water vapor in the outside air, that is, the absolute humidity D _A can be calculated by the calculation D _SA・RH/100, and the absolute humidity D _A and the temperature T of the outdoor heat exchanger can be calculated. By comparing the saturated water vapor amount D _SE at _E , it is possible to detect conditions where frost formation begins by detecting that T _E <0 and D _A >D _SE .
Of course, frost does not form when T _E >0 or when D _A <D _SE .

Generally, it is known that the performance of an outdoor heat exchanger does not decrease just when frost begins to form, but only when a certain amount of frost is exceeded. Therefore, it is completely wasteful to start the defrosting operation immediately upon detection of the frosting condition, and it is preferable not to start the defrosting operation until the amount of frosting reaches the predetermined value V.

By the way, when the above-mentioned frost formation conditions are met, the frost formation rate is approximately proportional to the condensed water content ΔD (=D _A −D _SE ) as shown in Figure 4, and as shown in Figure 5. If ΔT (=T _A −T _E ) is constant, it is approximately proportional to the temperature T _E (<0) of the outdoor heat exchanger.

Therefore, the amount of condensed water ΔD and the outdoor heat exchange temperature T _E with constant constants α and β, respectively, are expressed as time t.
When the sum of the integrated values becomes larger than a predetermined value V, that is, when ∫αΔDdt+∫βT _E dt>V, it is assumed that a predetermined amount of frost has formed and a defrost signal is generated to start defrosting operation. That's fine. Now, assuming that there is no change in ΔD and T _E after the start of frost formation, t can be determined as follows.

Solving the above equation for t yields t>V/αΔD+βT _E. Therefore, the actual defrost signal is generated by starting a timer upon detection of the frosting condition and waiting for a time t.
This can be done simply by counting.

Next, a defrosting operation control device according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

In the figure, 1 is a compressor, 2 is a four-way valve, 3 is an indoor heat exchanger, 4 and 5 are capillary tubes,
Reference numeral 6 denotes an outdoor heat exchanger, which constitutes a well-known refrigeration cycle by sequentially connecting these. The refrigerant flows as shown by the solid line during heating, and flows as shown by the broken line during defrosting and cooling operations. 7 is outdoor heat exchanger 6
8 is an outside air humidity sensor, and 9 is an outside air temperature sensor.

The start of frosting is determined by calculating the absolute humidity based on the saturated water vapor amount for the temperature measured by the outside air temperature sensor 9 and the relative humidity measured by the outside air humidity sensor 8, and when the temperature measured by the exchanger temperature sensor 7 is below zero degrees. , and by comparing the saturated water vapor amount at the temperature with the above-mentioned absolute humidity, this is determined on the condition that the absolute humidity is large. The generation of the defrost signal is calculated by calculating the amount of frost formed from the start of frost formation using the difference between the absolute humidity and the saturated water vapor amount with respect to the temperature of the outdoor heat exchanger, and the temperature of the outdoor heat exchanger. This is done in response to the amount of frost reaching a predetermined value or higher.

Next, the control circuit of the same embodiment will be explained with reference to FIG.

In the figure, an exchanger temperature sensor 7, an outside air humidity sensor 8, and an outside air temperature sensor 9 are connected to a control circuit 10. The control circuit 10 includes sense amplifiers 10a and 1 that amplify detection signals from each sensor.
0b and 10c, the output of the sense amplifier 10a is connected to one input of the absolute humidity calculation circuit 10d, and the output of the sense amplifier 10b is connected to the absolute humidity calculation circuit 1.
0d, the output of the sense amplifier 10c is connected to the input of the below-zero temperature detection circuit 10e and the input of the saturated water vapor amount determination circuit 10f, respectively.

The below-zero temperature detection circuit 10e detects that the exchanger temperature T _E applied to its input is below zero degrees and outputs a detection signal to its output, which is transmitted to the absolute humidity calculation circuit 10d and the saturated water vapor amount determination circuit. 1
It is applied to the control input c of 0f and one input of the AND circuit 10g.

The absolute humidity calculation circuit 10d has its control input c
When a signal is applied to the input, from the outside air temperature T _A and outside air relative humidity RH applied to the input, and the saturated water vapor amount D _SA for the known outside air temperature, the following formula D _A = D _SA・RH/100 is used. , calculate the absolute humidity D _A of the outside air.

The saturated water vapor amount determining circuit 10f determines the saturated water vapor amount D _SE for the exchanger temperature T _E applied to its input.

The output of the absolute humidity calculation circuit 10d and the output of the saturated water vapor amount determination circuit 10f are connected to both inputs of the comparison circuit 10h and the difference calculation circuit 10i, respectively, and in the comparison circuit 10h, the absolute humidity D _A and the saturated water vapor amount A comparison is made with D _SE , and when D _A > D _SE , a signal is output to the output and the AND circuit 10
is applied to the other input of g. AND circuit 10g
When a signal is applied to both of its inputs, it outputs a signal to the output, and this signal is applied to the start input T of the timer circuit 10j and the control input c of the difference calculation circuit 10i.
and apply it to.

When a signal is applied to its control input c, the difference calculation circuit 10i calculates the difference between the absolute humidity D _A applied to the input and the saturated water vapor amount D _SE , that is, the condensed water vapor amount ΔD using the following formula ΔD=D _A − Calculate by D _SE and send the calculation result to the time calculation circuit 10
k to one input. Time calculation circuit 10k
The exchanger temperature T _E is applied to the other input of
seek.

t=V/(αΔD+βT _E ) In the formula, V is a predetermined constant value and corresponds to the amount of frost on the outdoor heat exchanger that reduces the efficiency of the outdoor heat exchanger, and α and β are constants. .

The time t obtained by the time calculation circuit 10k is calculated by the timer circuit 10j in the comparison circuit 10l.
The measured time after startup is compared with the measured time t.
When it becomes larger, a signal is outputted to the output of the comparator circuit 10l. This signal is used as a defrost signal to turn on a relay coil (not shown), switch the four-way valve, and set the defrosting operation mode.

〔Effect of the invention〕

As explained above, according to the present invention, frost formation is determined based on whether the temperature detected by the exchanger temperature sensor is below zero degrees and the absolute humidity is greater than the saturated water vapor amount. However, it is possible to appropriately determine the onset of frost formation.

In addition, the amount of condensed water, which is the difference between the absolute humidity and the saturated water vapor amount at the time of frost determination, is calculated, and the amount of frost is determined based on this amount of condensed water and the temperature detected by the exchanger temperature sensor at the time of frost determination. The time required to reach a certain level is calculated, and the defrosting operation is started when the above calculated time has elapsed after frost formation judgment, so that the outdoor heat exchanger's capacity can be utilized to its maximum even when the defrosting operation starts. Therefore, the operating efficiency can be further improved.

These are realized by processing signals from three sensors, and the configuration is relatively simple compared to conventional ones.

[Brief explanation of drawings]

FIG. 1 is a refrigeration cycle diagram of an air conditioner equipped with a defrosting operation control device according to an embodiment of the present invention;
Fig. 2 is a block diagram showing the electric circuit of the defrosting operation control device, Figs. 3 to 5 are graphs for explaining the principle of the present invention, Fig. 6 is a refrigeration cycle diagram showing a conventional example, FIG. 7 is a graph for explaining the drawbacks of the conventional example. 1... Compressor, 2... Four-way valve, 3... Indoor heat exchanger, 4, 5... Capillary tube, 6... Outdoor heat exchanger, 7... Exchanger temperature sensor, 8... Outside air humidity Sensor, 9... Outside temperature sensor, 10...
Control circuit, 10d...Absolute humidity calculation circuit, 10e
... Zero temperature detection circuit, 10f ... Saturated water vapor amount determination circuit, 10g ... AND circuit, 10h ... Comparison circuit, 10i ... Difference calculation circuit, 10j ... Timer, 10k ... Time calculation circuit, 10l ... Comparison circuit.

Claims (1)

[Scope of Claims] 1. An air conditioner in which a compressor, a four-way valve, an outdoor heat exchanger, a throttle device, and an indoor heat exchanger are connected in sequence, comprising: an exchanger temperature sensor that detects the temperature of the outdoor heat exchanger; , an outside air temperature sensor that detects the temperature of the outside air, a humidity sensor that detects the humidity of the outside air, and an absolute humidity calculation means that calculates the absolute humidity of the outside air based on the temperature detected by the outside air temperature sensor and the humidity detected by the humidity sensor. and a comparison means for comparing the saturated water vapor amount with respect to the temperature detected by the exchanger temperature sensor and the calculated absolute humidity; and that the temperature detected by the exchanger temperature sensor is below zero degrees, and a comparison by the comparison means. determining means for determining frost formation based on the result that the absolute humidity is greater than the saturated water vapor amount; and calculating the condensed water amount that is the difference between the calculated absolute humidity and the saturated water vapor amount when frost formation is determined by the determining means. and a means for calculating a time period in which the amount of frosting reaches a predetermined amount based on the temperature detected by the exchanger temperature sensor and the amount of condensed water when the frosting is determined by the determining means, after the frosting is determined. A defrosting operation control device characterized in that the defrosting operation is started when the calculated time has elapsed.