JPH06159823A - Air conditioner - Google Patents

Abstract

PURPOSE:To decrease the number of times by which the compressor stops due to high temperature release control so as to prevent impairment of the comfortableness due to the stopping of the compressor. CONSTITUTION:A high temperature release-controlling means 10 is provided with a time-extending means 10a: the high temperature release-controlling means 10, when the temperature of the condenser has exceeded a prescribed value, decreases the operating frequency of the compressor by a certain value at intervals of a specified time period so as to prevent an excess in pressure on the high pressure side in the refrigeration cycle; when the temperature of the condenser is judged to be falling while the operating frequency of the compressor 1 is decreased by the control of the high temperature release-controlling means 10, the time-extending means 10a extends the time period from the decrease of the operating frequency to the minimum value to the stopping of the compressor over a prescribed period of time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner for controlling the number of revolutions of a compressor by means of an inverter, and more particularly to improving a high temperature release control means for preventing an overpressure on the high pressure side of a refrigeration cycle based on a condenser temperature. Regarding the air conditioner.

[0002]

2. Description of the Related Art Generally, this type of air conditioner is provided with a high temperature release control means in order to prevent pressurization on the high pressure side. This conventional high temperature release control means detects the temperature of the indoor heat exchanger acting as a condenser as the condenser temperature Tc by the temperature sensor during the heating operation of the refrigerating cycle, and the condenser temperature Tc becomes the first limit value. When it exceeds, the operation frequency of the compressor is reduced stepwise over a predetermined time (t1 to t4) by a predetermined frequency S4 to S1 at every predetermined time t as shown in FIG. During this time (t1 to t4), when the condenser temperature does not drop below the second limit value lower than the first limit value, the operation of the compressor is forcibly stopped.

[0003]

However, in such a conventional high temperature release control means, when the temperature of the condenser does not drop below the second limit value during the control for reducing the operating frequency of the compressor, the compressor is controlled. Forcibly stop the operation of. Moreover, once the compressor stops operating, restarting is prohibited for a few minutes in order to protect the compressor, so the air conditioning operation is stopped during that time, and comfort and air conditioning efficiency are reduced.

Therefore, the present invention has been made in consideration of the above circumstances, and an object thereof is to suppress the operation stop of the compressor and improve the comfort and the air conditioning efficiency.

[0005]

According to the present invention, in high temperature release control, the operation of the compressor is avoided as much as possible, and it is constructed as follows.

That is, according to the present invention, a refrigeration cycle in which a compressor, a four-way valve, an outdoor heat exchanger, an expansion valve, an indoor heat exchanger, etc. are sequentially connected by a refrigerant pipe, and an operating frequency of the compressor is controlled. An inverter that controls the number of rotations, a temperature sensor that detects the temperature when one of the indoor and outdoor heat exchangers acts as a condenser as a condenser temperature, and the condenser temperature detected by this temperature sensor has a predetermined value. High temperature release control means for preventing the overpressure on the high-pressure side of the refrigeration cycle by reducing the operating frequency to a predetermined value at predetermined time intervals when the temperature exceeds the high-temperature release control means, When it is determined that the condenser temperature is decreasing during the control to reduce the operating frequency, the compressor operation is stopped from the lowest value of this operating frequency. The time until it is characterized in that a time extension unit for extending than the predetermined time,

[0007]

When the high temperature release control means determines that the condenser temperature is decreasing during the control for reducing the operating frequency of the compressor in steps, the operation from the lowest operating frequency of the compressor to the stop of operation is performed. The time is extended by the time extension means.

Therefore, since the time until the operation of the compressor is stopped is extended, the number of times the compressor is stopped can be reduced accordingly.

Further, during the extension time, the temperature of the condenser which is already falling may fall below the normal value, so that the number of times the compressor is stopped can be further reduced.

Therefore, according to the present invention, it is possible to prevent the deterioration of comfort due to the stoppage of the operation of the compressor and to improve the air conditioning efficiency.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a refrigeration cycle diagram of an air conditioner to which the present invention is applied. In the figure, the air conditioner includes a compressor 1, a four-way valve 2, an outdoor heat exchanger 4 having an outdoor fan 3, and an expansion. Indoor heat exchanger 7 having valve 5 and indoor fan 6
Are connected in this order sequentially and annularly by a refrigerant pipe 8 to form a closed refrigeration cycle for reversibly circulating the refrigerant.

In this refrigeration cycle, the refrigerant is circulated in the direction of the solid line arrow in the figure by switching the four-way valve 2 to perform the cooling operation, and in the direction of the broken line arrow in the figure to perform the heating operation.

Further, the air conditioner controls the operating frequency of the compressor 1 to control the rotational speed of the compressor 9, and the operating command frequency of the inverter 9 to further control the rotational frequency of the compressor 1. By controlling, the high temperature release control means 10 that prevents overpressure on the high pressure side of the refrigeration cycle, the indoor heat exchange temperature sensor 11 that detects the temperature of the indoor heat exchanger 7, and the temperature of the outdoor heat exchanger 4 are controlled. And an outdoor heat exchange temperature sensor 12 for detecting.

The high temperature release control means 10 operates when the indoor and outdoor heat exchangers 7 and 4 function as capacitors.
The temperatures of the indoor and outdoor heat exchangers 7 and 4 are read from the indoor and outdoor heat exchange temperature sensors 11 and 12 as the condenser temperature Tc.

That is, the high temperature release control means 10 reads, for example, the temperature of the indoor heat exchanger 7 acting as a condenser during heating operation from the indoor heat exchange temperature sensor 11 as a condenser temperature, and the outdoor side acting as a condenser during cooling operation. The temperature of the heat exchanger 4 is read as the condenser temperature Tc from the outdoor heat exchange temperature sensor 11.

Since the condenser temperature Tc is substantially proportional to the pressure on the high pressure side of the refrigeration cycle, the high temperature release control means 10 controls the condenser temperature Tc as shown in FIG. 3 in order to prevent the overpressure. For example, first to third limit values Tc1, Tc2, Tc3 (Tc1>Tc2> Tc3) are set.

The first limit value Tc1 is the operating frequency reduction control start temperature, and the capacitor temperature Tc is the first limit value Tc1.
When the above is reached, the operating frequency of the compressor 1 (Hz)
As shown in FIG. 4, the frequency is reduced by a predetermined frequency (S1 to S4) every predetermined time t seconds over a plurality of times t1 to t3, and the operation of the compressor 1 is forcibly stopped at the final time t4. Start control.

The second limit value Tc2 releases the operating frequency reduction control and keeps the operating frequency (keep).
Then, it is the temperature at which the control for suppressing the frequency increase is started.

The third limit value Tc3 is the temperature at which the control for releasing the holding of the operating frequency is started.

FIG. 1 shows a processing program of the high temperature release control means 10, and ST1 to ST4 in the figure show respective steps of the flowchart.

This high temperature release control 10 repeats the reduction of the operating frequency until the capacitor temperature Tc reaches the second and third limit values Tc2, Tc3, and the reduction of the operating frequency causes the capacitor temperature Tc to reach the second limit value Tc2. If it decreases, the operating frequency is maintained, and if it decreases to the third limit value Tc3, the high temperature release control 10 is released and control is resumed to normal operation.

For example, the indoor heat exchange temperature sensor 1 during heating operation
The detected temperature from 1 is read as the capacitor temperature Tc, and if the capacitor temperature Tc is the first limit value Tc1 or more, in ST1, the operating frequency (Hz) every t seconds.
The high temperature release control for reducing the noise is started.

In ST2, it is judged whether or not the operating frequency after the Hz reduction is the lowest frequency S1, and in the case of NO, the process returns to ST1 again to repeat the reduction of the operating frequency, while YES is determined. In case of, proceed to ST3,
It is determined whether the condenser temperature Tc is rising or falling, and when it is rising, the compressor 1 is controlled for a predetermined time t after the start time t3 at which the operating frequency of the compressor 1 is controlled to the lowest frequency S1. Forcibly stop the operation (ST
4).

Further, when the vehicle is descending, the time from the start t3 at which the operating frequency of the compressor 1 is controlled to the lowest frequency S1 until the control for forcibly stopping the operation of the compressor 1 is started, that is, (t4 -T3) is extended by .DELTA.t seconds from the predetermined time t (ST5).

Therefore, according to this embodiment, the time (t4 -t3) until the compressor 1 is forcibly stopped from the lowest operating frequency S1 is more than the predetermined time t of the frequency reduction interval by Δ.
Since the time is extended by t seconds, the temperature Tc of the condenser that is already falling may further drop during that time and fall below the second limit value T2. In this case, the operating frequency of the compressor 1 is the frequency. The operation stop of the compressor 1 is avoided.

Therefore, since the number of times the compressor 1 is stopped is reduced, the operating rate of the compressor 1 is improved. Therefore, it is possible to prevent a reduction in comfort caused by the operation stop of the compressor 1 and improve the air conditioning efficiency.

[0028]

As described above, according to the present invention, when the condenser temperature rises above a predetermined value, the operating frequency of the compressor is reduced stepwise according to the condenser temperature. At this time, when the condenser temperature is decreasing, the time from the lowest operating frequency to the compressor stoppage is extended by the time extension means, so the condenser temperature that is already decreasing falls to the normal value during that time. In some cases, the operation of the compressor is avoided. For this reason, the number of times the compressor is stopped is reduced, so that it is possible to prevent a decrease in comfort due to the stop of the compressor, and it is possible to improve the air conditioning efficiency.

[Brief description of drawings]

FIG. 1 is a flowchart showing a processing program of a main part of a high temperature release control means shown in FIG.

FIG. 2 is a configuration diagram of an embodiment of an air conditioner according to the present invention.

FIG. 3 is a diagram showing a limit value for a capacitor temperature set by a high temperature release control means shown in FIG.

FIG. 4 is a diagram showing a state in which the operating frequency of the compressor is reduced stepwise by the high temperature release control means shown in FIG.

FIG. 5 is a diagram showing a control method for reducing the operating frequency of the compressor stepwise by a conventional high temperature release control means.

[Explanation of symbols]

 1 Compressor 2 Four-way valve 3 Outdoor fan 4 Outdoor heat exchanger 5 Expansion valve 6 Indoor fan 7 Indoor heat exchanger 8 Refrigerant piping 9 Inverter 10 High temperature release control means 10a Time extension means

Claims (1)

[Claims] 1. A refrigeration cycle in which a compressor, a four-way valve, an outdoor heat exchanger, an expansion valve, an indoor heat exchanger and the like are sequentially connected by a refrigerant pipe, and an operating frequency of the compressor is controlled to control the number of revolutions thereof. And a temperature sensor that detects the temperature when one of the indoor and outdoor heat exchangers acts as a condenser as a capacitor temperature, and the capacitor temperature detected by this temperature sensor exceeds a predetermined value. In the air conditioner having a high temperature release control means for reducing the operating frequency to a predetermined value every predetermined time to prevent overpressure on the high pressure side of the refrigeration cycle,
The high temperature release control means, during the control for reducing the operating frequency, when it is determined that the condenser temperature is decreasing, the time from the lowest value of the operating frequency until the operation of the compressor is stopped. An air conditioner comprising a time extension means for extending the predetermined time.