JPH0799287B2 - Air conditioner - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement of an air conditioner including an inverter that controls the capacity of a compressor by changing an operating frequency.

(Prior Art) In an air conditioner in which the capacity of a compressor is controlled by an inverter with a variable frequency, the room temperature value and set temperature sent from a room temperature thermostat provided in an indoor unit have been conventionally used. It is known that the frequency of the inverter is controlled according to the deviation signal from the value.

However, in the above-mentioned method, it is necessary to connect the indoor unit and the outdoor unit for exchanging signals between them, which complicates the signal line. In particular, when there are a plurality of indoor units, a complicated circuit must be separately provided to process the signals sent from the plurality of indoor units, and the overall configuration becomes complicated.

In order to improve the above problems, for example, as disclosed in Japanese Utility Model Laid-Open No. Sho 58-69764, the temperature or pressure of the intake gas during cooling is detected between the indoor heat exchanger and the four-way switching valve. However, there is a method in which the frequency of the inverter is controlled so that the intake gas temperature has a constant target value, and a complicated signal line or a complicated circuit from the indoor unit to the outdoor unit is omitted. In this method, assuming that the temperature of the intake gas is an index indicating the saturated evaporation temperature in the indoor heat exchanger, if the temperature of the intake gas is maintained at an appropriate value, the saturated evaporation temperature in the indoor heat exchanger will also be maintained near the appropriate value. It is based on the idea of being done.

(Problems to be Solved by the Invention) However, in the above method, the temperature of the intake gas must be detected on the outdoor unit side in order to simplify the signal line. No pressure loss is expected in the refrigerant gas pipe between the unit and the outdoor unit. Especially when the load on the indoor unit is large, the pressure loss in the gas pipe also increases with the pressure loss of the refrigerant, and the saturated evaporation temperature in the indoor heat exchanger is actually higher than the temperature of the intake gas converted from the pressure. Since it has become high, if the temperature of the intake gas is controlled to be kept constant, the saturated evaporation temperature in the indoor heat exchanger will rise too much higher than the appropriate value, and the air conditioning capacity will not be fully exhibited. There's a problem. In addition, the above-mentioned thing causes the same problem in the case of controlling the high pressure or the saturation temperature corresponding to the pressure to be constant during heating.

The present invention has been made in view of such a point, and an object thereof is to correct the control target value for controlling the frequency of the inverter in consideration of the pressure loss of the refrigerant that occurs in the piping according to the refrigerant flow rate. , To make full use of the air conditioning capacity of the air conditioner.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the solution means of the present invention is, as shown in FIG. 1, a compressor (1), an outdoor heat exchanger (3), an expansion mechanism (6). Or 15) and the indoor heat exchanger (5) are connected by a refrigerant pipe, and an air conditioner equipped with an inverter (1a) that adjusts the capacity by changing the operating frequency of the compressor (1) is assumed. To do.

And a detection means (Pe) for detecting the refrigerant pressure or the refrigerant pressure equivalent saturation temperature in a portion of the refrigerant pipe between the compressor (1) and the indoor heat exchanger (6) near the compressor (1). And the output of the detection means (Pe), and controls the frequency of the inverter (1a) so as to maintain the refrigerant pressure at the outlet of the indoor heat exchanger (6) or the saturation temperature equivalent to the refrigerant pressure at a control target value. Depending on the operating frequency of the control means (31) and the compressor (1) controlled by the inverter (1a), a control target value corresponding to the pressure loss in the refrigerant pipe between the compressor and the indoor heat exchanger is set. A correction means (30) for correcting the control target value of the control means (31) is provided on the basis of a correction relational expression between the inverter frequency preset to be corrected and the correction amount of the control target value. It is a thing.

(Operation) With the above configuration, in the present invention, the frequency of the inverter (1a) is controlled by the control means (31) according to the temperature or pressure of the refrigerant, and the temperature or pressure of the refrigerant is held at the control target value. To do. At this time, the control target value corresponding to the frequency of the inverter (1a) corresponds to the pressure loss of the refrigerant in the pipe according to the refrigerant flow rate at that time, based on the preset correction formula by the correction means (30). Only the value to be corrected. Therefore, the difference caused by the pressure loss with the actual refrigerant pressure at the outlet of the indoor heat exchanger (5), such as the refrigerant pressure detected by the detection means (Pe) arranged near the compressor (1), is considered. The capacity can be controlled and the air conditioning capacity can be fully exerted.

(Embodiment) An embodiment of the present invention will be described below with reference to FIG.

FIG. 2 shows a refrigerant piping system of a multi-type air conditioner to which the present invention is applied, where (A) is an outdoor unit and (B)-
(E) is an indoor unit connected in parallel to the outdoor unit (A). Inside the outdoor unit (A),
A compressor (1) whose capacity is controlled by an inverter (1a) that makes the power supply frequency variable, and a four-way switching valve (2) that switches as shown by the solid line in the figure during cooling operation and switches as shown by the broken line in the figure during heating operation. An outdoor heat exchanger (3) that functions as a condenser during cooling operation and as an evaporator during heating operation is built in as a main device, and each of the devices (1) to (3) has a refrigerant communication pipe (8). ) Is connected so that the refrigerant can flow. Further, the indoor units (B) ... (E) have the same configuration, each of which is provided with an indoor heat exchanger (5) which functions as an evaporator during a refrigerant operation and as a condenser during a heating operation, and each indoor heat exchanger. In the liquid refrigerant pipe (8a) of (5), an electric expansion valve (6) for adjusting the flow rate of the refrigerant to reduce the pressure is provided.

Further, (7) is a room temperature thermostat that is installed near the air intake port of the main body casing of each of the indoor units (B) to (E) and detects the intake air temperature, and (Pe) is the suction pipe of the compressor (1). A pressure sensor arranged in (8b) as a detection means for detecting the suction gas temperature Te by the suction gas pressure,
(9) is an outdoor control unit for controlling the operation of the outdoor unit (A), (10) is connected in parallel to the outdoor control unit (9) by a signal line, and each indoor unit (B)-
It is an indoor control unit which controls the individual operation of (E).
Inside the outdoor control unit (9), a control circuit (20) for receiving the output signal of the suction gas temperature Te from the pressure sensor (Pe) and controlling the frequency f of the inverter (1a).
And a setting circuit (21) for setting the control target value Te ′ of the control circuit (20), and a storage circuit for storing a correction formula showing the relationship between the correction amount ΔTe of the control target value Te ′ and the frequency f ( 2
2) and a conversion circuit (23) for calculating the correction amount of the control target value Te 'based on the frequency signal of the inverter (1a) and the correction formula of the storage circuit (22).

In FIG. 2, during the cooling operation, the four-way switching valve (2) is connected as shown by the solid line, the flow of the refrigerant discharged from the compressor (1) is in the direction of the solid line arrow, and the refrigerant is condensed. After passing through the outdoor heat exchanger (3), which is a heat exchanger, the electric expansion valve (6), which is an expansion mechanism provided in the branch of each indoor unit (B) to (E), is subjected to a throttling action, and the room that is an evaporator It returns to the compressor (1) again via the pipe (8) vaporized by the heat exchanger (5).

In the flow of the refrigerant, each indoor unit (B)
(E) is a moderate refrigerant flow rate according to the output signal of the room temperature thermostat (7) that detects the condition in each room by the electric expansion valve (6) whose opening is controlled by the indoor control unit (10). The ability is controlled to receive the distribution of.

In order to keep the actual saturated evaporation temperature in the indoor heat exchanger (5) near the appropriate value Teo on the outdoor unit (A) side according to the operating states of the indoor units (B) to (E), The control circuit (2 arranged in the control unit (9)
0) is a control in which the setting circuit (21) sets the intake gas temperature Te as follows according to a signal converted from the pressure sensor (Pe) to the intake gas temperature Te that is the saturation temperature equivalent to the pressure. The frequency f of the inverter is controlled so as to be maintained at the target value Te '. The variation width of the frequency f is, for example,
It may be changed in steps of 1 Hz from 0 Hz to 120 Hz, may be changed stepwise every 5 Hz or 10 Hz, or the change width may be set to 20 Hz to 180 Hz or 30 Hz to 180 Hz.

Further, in the storage circuit (22) arranged in the outdoor control unit (9), as shown in the graph of FIG.
A correction formula indicating the relationship between Te and the frequency f of the inverter (1a) is stored. In the graph of FIG. 3, the solid line indicates the length of the connecting pipe (8) from the indoor units (B) to (E) to the outdoor unit (A) within the standard range, and the broken line indicates the length of the connecting pipe (8). Is longer than the standard range, the broken line corresponds to the case where the length of the connecting pipe (8) is shorter than the standard range. In both cases, when the frequency f becomes high, the indoor heat exchanger (B) increases with the refrigerant flow rate. Since the pressure loss in the pipe from (E) to the compressor (1) increases, the correction amount ΔTe is set to increase. However, if the frequency is 30Hz or less, there is almost no pressure loss, so it is not corrected. Further, if the length of the connecting pipe (8) is long, the pressure loss increases, so that the correction amount ΔTe becomes large for the same frequency f, and conversely, when the length of the connecting pipe (8) is short, A correction equation of, is set so that the correction amount ΔTe becomes small, and which equation is used is stored in advance so that it can be switched according to the state when the air conditioner is installed. Further, the conversion circuit (23) receives the signal of the frequency f of the inverter (1a), and determines the correction amount ΔTe based on the correction formula stored in the storage circuit (22) in advance. The setting circuit (21) has an appropriate value Te of the appropriate saturated evaporation temperature in advance.
The value of o is set as the control target value, the correction amount ΔTe input from the conversion circuit (23) is compared and calculated, and the corrected control target value Te ′ is calculated by the following equation.

Te ′ = Teo−ΔTe As shown in FIG. 4, at 30 Hz or higher, the appropriate value Teo is shown as a solid line or a broken line depending on the length of the connecting pipe.
The control target value Te ′ is changed based on the relational expression obtained by subtracting the correction amount ΔTe corresponding to the frequency from. In the graph of FIG. 4, and correspond to and of the graph of FIG. As described above, the control target value Te 'is set according to the frequency f at that time.

Then, the control circuit (20) sets a control target value in consideration of the pressure loss in the pipe set by the setting circuit (21).
The frequency f of the inverter (1a) is controlled so that the suction gas temperature Te is maintained at Te ′, and the capacity of the compressor (1) is controlled to set the saturated evaporation temperature of the indoor heat exchanger (5) to an appropriate value Teo. Keep near.

The memory circuit (22) and the conversion circuit (23) constitute a correction means (30) for correcting the control target value Te ', and the setting circuit (21) and the control circuit (20) configure the inverter (1a). A control means (31) for controlling the frequency f is configured.

With the configuration as shown in FIG. 2 above, for example, in an air conditioner having a connecting pipe length in the standard range, when the room temperature of each room rises and the loads on the indoor units (B) to (E) increase, In response to this, the intake gas temperature Te detected by the pressure sensor (Pe) increases, so that the control means (31) increases the frequency f of the inverter (1a) to increase the capacity of the compressor (1).

The changes in the control target value Te 'and the frequency of the inverter (1a) at this time are as follows. For example, initially the frequency f
Suppose you were driving at 30Hz. The control target value at this time is Te
o. Here, if the indoor load increases, the low pressure increases and Te> Teo. Therefore, Te is returned to Teo, and the frequency f increases. Therefore, the refrigerant circulation amount increases, and the suction gas temperature Te approaches Teo.

On the other hand, since the frequency f has increased, the control target value Te ′
Is lower than the correction value Teo by the correction amount ΔTe.

At this time, the intake gas temperature decreased due to the increase of the frequency f
Convergence control is performed as follows according to the magnitude relationship between Te and the control target value Te ′ changed by the increase of the frequency f.

(1) When the intake gas temperature Te is lower than the control target value Te 'In this case, the frequency f is decreased as the next control. In this case, the control target value Te ′ also increases by the correction amount ΔTe corresponding to the frequency decrease amount, and thus the control such as hunting is repeated, but the correction amount ΔTe is, for example, the frequency change range. Is 30Hz-12
At 0Hz, the correction amount ΔTe is 0 ° to 10 ° C (2kg / cm ^{2 at} pressure)
The frequency f is normally changed with respect to the change of the correction amount ΔTe.
Since the pressure fluctuation due to the change is designed to be larger, even if a little hunting is performed, the pressure eventually converges. Further, since the control target value Te 'is set so as to have a constant upper and lower optimum temperature range in actual control, even if the control target value Te' changes, the intake gas temperature Te
Since the frequency is controlled so as to enter, even if the hunting phenomenon occurs in the transient state, the hunting is finally suppressed.

(2) When the intake gas temperature Te is higher than the control target value Te 'In this case, as the next control, the frequency f is further increased so that the intake gas temperature Te approaches the control target value Te'. By continuing such control, the intake gas temperature
If Te is maintained at the control target value Te 'at that time, the operation is continued in that state, and if the intake gas temperature Te is below the control target value Te' at that time, the same as the control in (1) above. Controlled.

The control conditions (1) and (2) above are based on setting conditions for changing the frequency f (for example, stepwise change every 10 Hz or stepless change every 1 Hz, and frequency change time). As the interval, for example, sampling time of the intake gas temperature is performed every 10 seconds or 20 seconds, or is it always detected, whether the control target value Te ′ has an appropriate temperature range, etc.). .
Therefore, the actual saturated evaporation temperature of the indoor heat exchanger (5) is an appropriate value Teo (= Te ′) obtained by correcting the intake gas temperature Te with the pressure loss ΔTe of the communication pipe (8) by the correction means (30).
Since the deviation from + ΔTe) is kept in a very small range, the indoor units (B) to (E) can sufficiently exhibit the cooling capacity. In addition, the indoor unit (B) ... (E)
Even when the load is decreased, the saturated evaporation temperature of the indoor heat exchanger (5) can be controlled to be maintained near the appropriate value Teo by the same procedure.

On the other hand, without the above correction, the actual saturated evaporation temperature in the indoor heat exchanger (5) is the original control target value Teo.
(Teo + ΔTe), the load on the indoor units (B) to (E) becomes large and the frequency f of the inverter is increased to increase the capacity of the compressor (1). The deviation from the proper value Teo becomes large and the cooling capacity cannot be exhibited sufficiently.

Therefore, the present invention exerts a remarkable effect when the compressor (1) is operated at a high capacity.

Note that this example can be applied to the constant control of the condensing temperature (condensing pressure) as well as the control of the intake gas temperature. That is, in this case, the pressure sensor may be provided in a pipe that has a high pressure during heating (low pressure during cooling) as shown by the dotted line in FIG. 2 (see Pe ′), and the control target value. Is corrected by adding a correction amount to an appropriate value, which is the reverse of cooling.

As described above, the case where the length of the connecting pipe (8) is in the standard range has been described. When the length is longer than the standard range, Te ′ shown in the broken line of the graph of FIG. Based on the relationship of f, the control target value T
A similar effect can be obtained by correcting e '.

Further, in this example, since the saturated vaporization temperature of the refrigerant is kept constant, it is preferable to practically use the pressure sensor (Pe), but a temperature sensor that detects the intake gas temperature may be used. However, this temperature sensor is more inaccurate than the pressure sensor (Pe) due to the change in the degree of superheat of the refrigerant, but it can be sufficiently dealt with by correcting the change in the degree of superheat.

Further, when the length of the communication pipe (8) between the indoor unit (B) to (E) and the outdoor unit (A) is largely different, if the average value of them is selected, the saturated evaporation temperature of the refrigerant is selected. Compressor (1) so that is maintained near the proper value Teo
The capacity can be controlled.

Further, in the above-described embodiment, it is sufficient to detect the suction gas pressure of the compressor (1) of the outdoor unit (A) and the frequency of the inverter (1a), and many sensors are provided in the indoor units (B) to (E). Since there is no need for
The capacity of the compressor (1) can be controlled according to the actual situation of the indoor units (B) to (E).

In addition, for example, when there is only one indoor unit,
When the connection piping between the indoor unit and the outdoor unit can be regarded as substantially constant, the setting circuit (21) in the above embodiment does not need to be switchable in advance, and the compressor (1) can be easily controlled at a lower cost. be able to.

(Effect of the invention) As described above, according to the air conditioner of the present invention,
When changing the frequency of the inverter that changes the capacity of the compressor according to the fluctuation of the load, the value that is corrected by taking into account the pressure loss of the pipe according to the refrigerant flow rate is set as the control target value and held at this control target value. As described above, since the inverter is controlled, it is possible to provide an air conditioner capable of sufficiently exhibiting the capability of sky and the like. In particular, when applied to a separate type air conditioner, the number of sensors can be reduced and the signal line and circuit configuration can be simplified, and the air conditioner can be used at a lower cost than the method of detecting and controlling the degree of superheat. Can be configured.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention. 2 to 4 show an embodiment of the present invention, FIG. 2 is a block diagram showing the refrigerant piping system and control signal wiring, FIG. 3 is a graph showing the relationship between the correction amount and the inverter frequency, FIG. Four
The figure is a graph showing the relationship between the control target value and the inverter frequency. (1) …… Compressor, (1a) …… Inverter, (3) ……
Outdoor heat exchanger, (5) ... Indoor heat exchanger, (6) ... Electric expansion valve (expansion mechanism), (30) ... Correction means, (31) ...
... Control means (Pe) ... Pressure sensor (detection means).

Claims (1)

[Claims] 1. A compressor (1), an outdoor heat exchanger (3), an expansion mechanism (6 or 15) and an indoor heat exchanger (5) are connected by a refrigerant pipe, and the compressor (1) is operated. An air conditioner provided with an inverter (1a) for changing a frequency to adjust its capacity, wherein the compressor (1) of a refrigerant pipe between the compressor (1) and the indoor heat exchanger (6). Detection means (Pe) for detecting the refrigerant pressure or the saturation temperature equivalent to the refrigerant pressure in the vicinity
And the output of the detection means (Pe), and controls the frequency of the inverter (1a) so as to maintain the refrigerant pressure at the outlet of the indoor heat exchanger (6) or the saturation temperature equivalent to the refrigerant pressure at a control target value. Depending on the operating frequency of the control means (31) and the compressor (1) controlled by the inverter (1a), a control target value corresponding to the pressure loss in the refrigerant pipe between the compressor and the indoor heat exchanger is set. A correction means (30) for correcting the control target value of the control means (31) based on a correction relational expression between the inverter frequency preset to be corrected and the correction amount of the control target value. A characteristic air conditioner.