JP2945731B2 - Air conditioner - Google Patents

Description

The present invention relates to an air conditioner in which a compressor of a refrigeration cycle is variably controlled by an inverter, and particularly to high-pressure protection during heating.

(Prior art) Conventionally, high-pressure protection control during a heating operation of an air conditioner is applied to an inverter of a compressor when a condensing temperature Tc (heat exchange condensing temperature) of an indoor heat exchanger becomes higher than a certain temperature. High-temperature release control is performed by lowering the operating frequency Hz from the currently operating frequency by two steps from the approximately 15 command frequencies of the air conditioner.

(Problems to be Solved by the Invention) However, in the above-described high-temperature release control in which the frequency is reduced by two steps from the frequency during the current operation, the heat exchange condensation temperature Tc overshoots at a low air flow, so that a frequency hunting phenomenon occurs. . This is because the response of the temperature sensor is delayed due to the rapid rise of the heat exchange condensing temperature Tc, and the heat exchange condensing temperature Tc is too large, so that the release is applied too much.

On the other hand, in a set with a large horsepower, high-pressure protection cannot be provided with a margin when the power is lowered by two steps, and the design must be almost the limit.

The present invention has been made to solve the above problems, and has as its object to provide an air conditioner capable of performing high-pressure protection control without a hunting phenomenon.

[Means for Solving the Problems] In order to achieve the above object, the present invention detects the temperature of an indoor heat exchanger in an air conditioner in which a compressor of a refrigeration cycle is variably controlled by an inverter. An indoor heat exchange temperature sensor, a fan air volume setting device that sets the air flow of the indoor fan, and an overload transition temperature that is set slightly lower than the temperature at which the indoor air exchange temperature is overloaded with respect to the fan air volume during heating operation A maximum frequency determining means for monitoring whether or not the indoor heat exchange temperature has risen and for limiting the maximum frequency to be given to the inverter to a value lower than usual when the temperature has exceeded the overload transition temperature is provided.

In the air conditioner, further, the indoor heat exchange temperature is slightly lower than the overload temperature with respect to the fan air volume during the heating operation, and the indoor heat exchange temperature is set to a high temperature release temperature set higher than the overload transition temperature. An inverter frequency release means is provided for monitoring whether the heat exchange temperature has risen and for lowering the frequency of the inverter to a frequency lower than the current frequency by a predetermined step when the indoor heat exchange temperature exceeds the high temperature release temperature.

(Operation) The overload transition temperature related to the indoor heat exchange temperature (condensation temperature) Tc is set to, for example, 50 ° C. When the temperature is raised to zone A of 50 ° C. or more with this temperature of 50 ° C. as a boundary, the maximum frequency is determined. The means limits each maximum frequency according to the air volume set by the air volume setting device, for example, strong wind, medium wind, and weak wind. Specifically, when the normal frequency is 180 Hz to 30 Hz, the upper limit value of the operating frequency of the compressor is limited to, for example, 140 Hz, 80 Hz, and 70 Hz according to strong wind, medium wind, and weak wind. As a result, the heating capacity of the compressor is reduced, and even in the case of a breeze, the sudden increase in the indoor heat exchange temperature Tc is reduced.

In the conventional control, as shown in FIG. 6 (b), the operating frequency hunts, and the high pressure of the compressor moves closer to or away from the line just below the current value in the standard. As indicated by the allowance width W, even a model with high horsepower can provide high-pressure protection with a margin. Also,
Since the operating frequency is stabilized, noise and vibration are reduced. Further, since the blowing temperature is stabilized by stabilizing the operating frequency, comfort is also improved.

Further, the high temperature release temperature is lower than the overload temperature but higher than the overload transition temperature (50 ° C.), for example,
Zone C set at 55 ° C and above the zone A above 55 ° C
When the temperature rises, the frequency of the inverter is lowered to, for example, one step lower than the current frequency. As a result, the heating capacity of the compressor is further reduced, the rise in the indoor heat exchange temperature Tc is also moderated, and hunting of the operating frequency in the conventional control shown in FIG. You can do it.

Next, an embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows the basic configuration of the air conditioner of the present invention. The refrigeration cycle of the air conditioner is configured by sequentially connecting a compressor 1, a four-way valve 2, an outdoor heat exchanger 3, a pressure reducing device 4, and an indoor heat exchanger 5 by refrigerant piping. 6 is an outdoor fan and 7 is an indoor fan. Switching between cooling and heating is performed by the four-way valve 2, and the compressor 1
Is controlled by an inverter 9 which receives a command from the control unit 8.

As shown in FIG. 2, the control unit 8 is mainly composed of a microcomputer 10, and has switch inputs from a temperature setting device 14 and an air volume setting device 15 (FIG. 3) of a remote controller 11,
Based on the input from the indoor temperature sensor 12 and the input from the indoor heat exchange temperature sensor 13, the operation frequency control of the compressor 1 and the indoor fan 7
It has a motor rotation control function and an overall operation control function of the air conditioner. Here, the indoor temperature sensor 12 is a sensor that detects the suction port temperature of the indoor heat exchanger 5 as room temperature (indoor temperature) Ta, and the indoor heat exchange temperature sensor 13 is
Is a sensor for detecting the condensation temperature Tc.

Regarding the control of the operating frequency of the compressor 1, the control unit 8 is configured as software or hardware as shown in FIG. That is, in FIG. 3, an inverter output frequency determining means 16, a maximum frequency determining means 17, and an inverter output frequency limiting means 18 are provided. 19 is an inverter control circuit, and 20 is a fan drive circuit. Indoor fan motor 21, winds H, paralytic M ^+, paralytic M, weak wind L ^+, weak wind L, weak wind L ^-, a switching tap breeze UL, command the switching taps of the fan air volume setter 15 And the rotation frequency is adjusted within a predetermined range.

The inverter output frequency determining means 16 is an indoor temperature sensor.
The indoor temperature Ta detected by 12 is compared with the set temperature Ts specified by the temperature setting device 14 of the remote control 11, and the comparison result is the fourth
In accordance with which of the zones b to g in the drawing, the output frequency at which the inverter 9 should operate is, for example, f6 to f1 (= 30 to
180Hz).

At this time, the maximum frequency determining means 17 detects the air volume set by the fan air volume setting device 15 of the remote controller 11 at this time.
It is determined whether the indoor heat exchange temperature (condensation temperature) Tc detected in step 13 is appropriate. In other words, the set air volume (strong wind H, medium wind M ⁺ , medium wind M, light wind L ⁺ ,
Weak wind L, weak wind L ^-, to breeze UL), the temperature of the indoor heat exchanger 5 as it exceeds the pressure standard value temperature (overload temperature)
It is monitored whether the temperature is such that the temperature rises to be higher, more precisely, the temperature (overload transition temperature) Tx which is slightly earlier than the conventional high temperature release start temperature before reaching the overload temperature. Here, assuming that the conventional high-temperature release start temperature is 55 ° C., the overload transition temperature Tx is, for example, the temperature before reaching the temperature.
It is set to 50 ° C. Then, when the temperature reaches the overload transition temperature Tx, the maximum frequency determining means 17 sets the upper limit value of the variable output frequency range of the inverter 9 to a lower value so that the temperature of the indoor heat exchanger 5 does not suddenly increase. Set the upper limit.

FIG. 5 exemplifies how to recognize an overload transition. Here, the zone A has a temperature region after the indoor heat exchange temperature Tc further rises above the overload transition temperature Tx (50 ° C.) and a temperature region until the indoor heat exchange temperature Tc drops to 47 ° C. Is that the indoor heat exchange temperature Tc is the overload transition temperature Tx (50
° C) and the temperature range after the indoor heat exchange temperature Tc falls below 47 ° C below the overload transition temperature Tx.

Under a certain air flow, the indoor heat exchange temperature Tc is in the A zone (Tc ≧ 50).
℃), the indoor heat exchanger 5
, And the high pressure of the compressor rapidly rises to an overload temperature exceeding a specified value. Therefore, the maximum frequency determination means 17 determines whether or not the indoor heat exchange temperature Tc enters the A zone based on the overload transition temperature Tx before reaching the overload temperature, and enters the A zone. At this time, the output frequency at which the inverter 9 should operate is set to a lower value than usual.

Here, the frequency which is usually in the range of 180 Hz to 30 Hz (FIG. 4) is changed to 140 Hz in the case of strong wind H to medium wind M ⁺ as shown in FIG.
To paralysis M~ weak wind L ⁺ 80Hz in the case of, weak wind L~ weak wind L ^- in the case of and breeze UL to 70Hz, suppress, respectively. However, such a division can be arbitrarily performed, and for the sake of simplicity, the strong wind H, the medium wind M, and the weak wind L will be described below.
Limit to 140Hz, 80Hz, 70Hz respectively.

The inverter output frequency limiting means 18 actually operates the inverter 9 in response to the command from the inverter output frequency determining means 16, but at the time of the overload transition, the variable output of the inverter 9 in accordance with the command from the maximum frequency determining means 17. Limit the upper frequency limit. That is, the compressor 1 is operated at an output frequency of 30 to 180 Hz instructed by the inverter output frequency determining means 16 while in the normal B zone, but is instructed by the maximum frequency determining means 17 when entering the A zone. The upper limit value is limited to one of 140 Hz, 80 Hz, and 70 Hz according to the set air volume. As a result, the heating capacity of the compressor 1 decreases, and the rapid rise in the indoor heat exchange temperature Tc is reduced.

FIG. 6 (a) shows the indoor heat exchange temperature Tc in the case of a light wind.
This shows that the sudden rise in the frequency is reduced, and the hunting is performed once or twice in the initial stage, but thereafter the operating frequency becomes stable. In contrast to the conventional control, as shown in FIG. 6 (b), the operating frequency hunts, and the high pressure of the compressor approaches or leaves the line just below the upper limit of the specification. Therefore, according to the above embodiment, the sixth
As shown by the allowance width W in FIG. 7A, even a model with a high horsepower can perform high-pressure protection with a margin. Further, since the operating frequency is stabilized, noise and vibration are reduced. Further, since the blowing temperature is stabilized by stabilizing the operating frequency, comfort is also improved.

 Hereinafter, the details will be described in accordance with the flow of FIG.

In the flow of FIG.
First reads the room temperature Ta and the set temperature Ts, and
Is higher than the set temperature Ts of the remote controller 11 (step). Room temperature Ta is already set temperature Ts
When it is higher (zones h and i in FIG. 4), the compressor is stopped (step). When the room temperature Ta is still lower than the set temperature Ts (zones b to g in FIG. 4), the zones b to g in FIG. 4 correspond to heating in accordance with the difference (Ta−Ts). The output frequency at which the inverter 9 should operate is determined from the zone (step). Therefore, this step corresponds to the inverter output frequency determining means 16.

Next, the indoor heat exchange temperature Tc is read, and it is checked which of the zones A and B in FIG. 5 the indoor heat exchange temperature Tc is (step). While in the zone B, that is, until the indoor heat exchange temperature Tc rises to 50 ° C., the indoor heat exchanger 5 does not shift to overload, so there is no upper limit of the inverter drive frequency, and the inverter 9 is commanded. The maximum frequency remains at 180Hz (step). However, the indoor heat exchange temperature Tc
Rises above 50 ° C. and enters zone A, it is checked with the air volume setting device 15 whether the strong wind H, the medium wind M, or the weak wind L is set (steps-). The upper limit value of the maximum frequency to be commanded to the inverter 9 is limited as follows in accordance with the current air volume. That is, the operating frequency f of the compressor is limited to f = 140 Hz in the case of the strong wind H, f = 80 Hz in the case of the medium wind M, and f = 70 Hz in the case of the weak wind L (step to). Steps to here correspond to the maximum frequency determining means 16, and steps to correspond to the inverter output frequency limiting means 18.

In this way, at 50 ° C., which is slightly lower than the normal high-temperature release start temperature of 55 ° C., the maximum frequency of the compressor is already reduced to a value lower than the normal frequency in accordance with the set air volume,
As a result, the indoor heat exchange temperature Tc rises more slowly than before. Thereafter, the indoor heat exchange temperature Tc falls to 47 ° C., which is slightly lower than 50 ° C., and passes through the A zone without reaching the high pressure limit value of the compressor. Thus, the restriction on the maximum frequency is removed, and the control returns to the normal control of 180 Hz to 30 Hz.

With this control, even in the case of a slight wind, the frequency is limited to f = 70 Hz in the step, and as described with reference to FIG.
After that, the operation frequency becomes stable. In addition, even for models with high horsepower, there is room for high pressure protection. Since the operating frequency is stabilized, noise and vibration are reduced, and the blowing temperature is stabilized.

FIG. 8 shows an embodiment in which the above control is combined with the conventional high-temperature release control. This is a configuration in which a timer means 22, an inverter frequency release means 23, and an inverter output frequency selection means 24 are additionally provided.

As shown in FIG. 9, the control region is divided into three regions B, A, and C with the overload transition temperature of 50 ° C. and the temperature of 55 ° C. as boundaries in the process of increasing the indoor heat exchange temperature Tc. In addition, it is divided into four regions C, D, A, and B with the boundaries of 54 ° C., 53 ° C., and 49 ° C. in the process of decreasing the indoor heat exchange temperature Tc. 50 from zone B
In the control when the temperature is raised to the zone A of not less than ° C., the maximum frequency is limited according to the air volume, as already described with reference to FIGS. 3 to 5. Further, when the temperature rises from zone A to zone C of 55 ° C. or higher, the inverter frequency release means 23 operates for a certain period of time determined by the timer means 22 and sends a signal to the inverter output frequency selection means 24 preceding the inverter control circuit 19. the feed, the frequency of the inverter 4, current dropped 1 to step lower frequency f _n-1 than the frequency fn. As a result, the heating capacity of the compressor 1 is further reduced, the rise in the indoor heat exchange temperature Tc is also moderated, and hunting of the operating frequency in the conventional control shown in FIG. Can be done with

As will be described in detail, in the flow shown in FIGS. 10 and 11, steps to are the same as in the case of FIG. However, here, first, in step, the set air volume is read in addition to the indoor temperature Ta and the set temperature Ts, and the indoor fan 7 is operated at the set air volume. When the room temperature Ta is already higher than the set temperature Ts, the compressor is stopped (step). When the room temperature Ta is still lower than the set temperature Ts, the difference (Ta−
An output frequency for performing heating according to Ts) is determined (step).

Next, the indoor heat exchange temperature Tc is read, and it is checked which of the zones A, B, C and D in FIG. 5 the indoor heat exchange temperature Tc is (step).

While in zone B (<50 ° C), there is no upper limit on the inverter drive frequency, and the maximum frequency commanded to inverter 9
fn remains at fn = 180 Hz (step). However, when the indoor heat exchange temperature Tc rises to 50 ° C. or higher and enters the zone A, the strong wind H
The maximum frequency to be commanded to the inverter 9 is limited to fn = 140 Hz in the case of the strong wind H, fn = 80 Hz in the case of the medium wind M, and f = 70 Hz in the case of the weak wind L according to the M and the weak wind L (from step). Step ~). As a result, the heating capacity of the compressor 1 decreases, and the indoor heat exchange temperature Tc rises more slowly than in the past.

After that, the indoor heat exchange temperature Tc becomes 55 ° C, the high temperature release start temperature.
Increased to, upon entering the C zone, the frequency of the inverter 4, current dropped to 1 step lower frequency f _n-1 than the frequency fn (step). Then, the timer is started, the operation is performed at the frequency fn _-1 lower by one step for a fixed time (step), and the process returns to the step. Thereby, the heating capacity of the compressor 1 further decreases. Here, the steps correspond to the inverter frequency release means 23, the steps correspond to the inverter output frequency selection means 24, and the steps correspond to the timer means 22.

During this period, the indoor heat exchange temperature Tc falls to the D zone without reaching the high pressure limit value of the compressor after a slight delay due to inertia. When entering the D zone, it is checked whether the current frequency fn matches the normal maximum frequency f. If not, the current frequency fn is returned to the normal maximum frequency f and the above-mentioned maximum frequency constraint is set. Remove
Operate at the normal frequency of 180 to 30Hz.

In this way, by first preventing a sudden rise in the indoor heat exchanger at 50 ° C., and then performing the release control of the current frequency fn by one step down, the normal high-temperature release control alone or the above-mentioned 50 ° C. Compared with the case where only the sudden rise of the indoor heat exchanger is prevented, the operating frequency of the compressor can be stabilized by reducing the degree of hunting.

[Effects of the Invention] As described above, the present invention reduces the maximum value of the operating frequency of the compressor to a value lower than normal at a temperature lower than the high temperature release control temperature usually performed before reaching the overload temperature. Since the operation is performed with the restriction, the sudden rise of the indoor heat exchanger can be prevented, and the operation with a margin with respect to the high pressure limit value can be performed. In addition, since the operating frequency is stabilized, noise is eliminated, and the temperature of the discharged gas is also stabilized, so that a comfortable heating space can be created.

[Brief description of the drawings]

1 is a diagram showing a basic configuration of an air conditioner according to an embodiment of the present invention, FIG. 2 is a conceptual diagram of an input / output relationship of the control unit, FIG. 3 is a block diagram showing a circuit configuration of the control unit, FIG. 4 is a diagram showing a variable frequency control zone of an inverter in a normal case, FIG. 5 is a diagram showing a relationship between an overload transition temperature and a maximum frequency before and after the overload transition temperature, and FIG. FIG. 7 shows a comparison between the present invention and the prior art, FIG. 7 is a flowchart showing the operation of the control circuit of FIG. 3, and FIG. 8 is a control unit showing another embodiment of the present invention. FIG. 9 is a circuit diagram showing the relationship between the overload transition temperature and the high-humidity release temperature.
The figure is a flowchart showing the operation. In the figure, 1 is a compressor, 2 is a four-way valve, 3 is an outdoor heat exchanger, 4
Is a decompression device, 5 is an indoor heat exchanger, 6 is an outdoor fan, 7 is an indoor fan, 8 is an external heat exchange temperature sensor, 9 is an inverter,
11 is a remote controller, 12 is an indoor temperature sensor, 13 is an indoor heat exchange temperature sensor, 14 is a temperature setting device, 15 is an air volume setting device, 16 is an inverter output frequency determining means, 17 is a maximum frequency determining means, 18
Is an inverter output frequency limiting means, 19 is an inverter control circuit, 20 is a fan drive circuit, 21 is a fan motor, 22 is a timer means, 23 is an inverter frequency release means, and 24 is an inverter output frequency selection means.

Claims (1)

(57) [Claims] An air conditioner for variably controlling a compressor of a refrigeration cycle by an inverter, an indoor heat exchange temperature sensor for detecting a temperature of an indoor heat exchanger, a fan air volume setting device for setting an air volume of an indoor fan, Monitors whether the indoor heat exchange temperature has risen to the overload transition temperature set slightly lower than the overload temperature of the indoor heat exchange temperature with respect to the fan airflow during the heating operation, and if it rises above the overload transition temperature A maximum frequency determining means for limiting the maximum frequency given to the inverter to a value lower than usual; and a temperature slightly lower than the temperature at which the indoor heat exchange temperature is overloaded with respect to the fan air flow during the heating operation, and It monitors whether the indoor heat exchange temperature has risen to the high temperature release temperature set higher than the transition temperature, and if the indoor heat exchange temperature exceeds the high temperature An air conditioner characterized by comprising an inverter frequency release means lowering the frequency of the data in a predetermined step lower frequency than the current frequency.