JP2507369B2 - Air conditioner - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an air conditioner that constitutes a variable capacity refrigeration cycle having a control device equipped with change control of a compressor operating frequency, and particularly relates to a condensing temperature and The present invention relates to an air conditioner that employs a pressure ratio control method based on evaporation temperature.

[Conventional technology]

The conventional device, as described in JP-A-55-158457, adjusts the opening degree of the expansion valve by the temperature detector provided on the discharge side,
The rise in discharge gas temperature was prevented.

[Problems to be solved by the invention]

However, consideration is given to the excessive rise of the motor temperature under the condition that the compressor motor temperature rises without the rise of the discharge gas temperature, that is, the suction pressure is low and the discharge pressure is high (the pressure ratio is high). Therefore, there was a problem that the reliability of the compressor was not sufficiently satisfied.

The object of the present invention was devised in view of the above-mentioned drawbacks, and it is to prevent a rise in the motor temperature of the compressor by setting the pressure ratio, which is the ratio of the discharge pressure and the suction pressure, to a set value or less. .

[Means for solving problems]

The above purpose is the condensation temperature (TC) of high pressure at the compressor outlet.
The first detector for detecting the temperature and the evaporation temperature (T
The second detector that detects E ′) and the operating frequency of the compressor are detected, and the operating frequency and the evaporation temperature (TE ′) are used to correct the pressure loss between the expansion valve outlet and the compressor, and the suction of the compressor. A means for calculating an evaporation temperature (TE) corresponding to the pressure, a means for calculating a set condensing temperature (TCO) from a preset set pressure ratio with respect to the evaporating temperature (TE), and a set condensing temperature (TC
O) and the condensing temperature (TC) are compared in a predetermined time cycle, and when the condensing temperature (TC) is higher than the set condensing temperature (TCO) by a certain value or more, the pressure ratio during operation is within a certain range. And a control device for controlling the operating frequency by lowering the operating frequency so as to enter.

Further, the second detector for detecting the evaporation temperature (TE ') at the outlet of the expansion valve and the operating frequency of the compressor are detected, and the operating frequency and the evaporation temperature (TE') are used to detect the difference between the outlet of the expansion valve and the compressor. Instead of the means for calculating the evaporation temperature (TE) corresponding to the suction pressure of the compressor by correcting the pressure loss, the second detector directly detects the evaporation temperature (TE) corresponding to the suction pressure. Alternatively, the set condensing temperature (TCO) may be calculated from the directly detected evaporation temperature (TE) from a preset set pressure ratio.

[Operation] In the present invention, the set condensing temperature (TCO) is calculated from the evaporation temperature corresponding to the suction pressure based on the preset set pressure ratio, and this is used as the actually detected condensing temperature (TC) at the discharge outlet. To compare. When the condensing temperature (TC) is higher than the set condensing temperature (TCO) by a certain value or more, a control device is provided to reduce the operating frequency so that the pressure ratio during operation falls within a certain range. Since the pressure ratio (discharge pressure / suction pressure) can be controlled within the allowable value for the set pressure ratio, and the pressure ratio is controlled to a value close to or lower than the set pressure ratio during operation, the discharge gas temperature will not rise excessively. Not accompanied. Therefore, since the operating frequency of the compressor motor can be controlled while preventing the temperature rise of the compressor motor, the reliability of the compressor can be improved.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cycle system diagram of an embodiment of the present invention. The refrigeration cycle is formed by sequentially connecting the four-way switching valve 4, the outdoor heat exchanger 5, the forward / reverse flow expansion valve 6, and the indoor heat exchanger 7 to the compressor 3, and the condensing temperature on the discharge side of the compressor 3 The thermistor for detection (first detector) 1 is placed on the refrigerant pipe between the expansion valve 6 and the outdoor heat exchanger 5 to detect the evaporation temperature (second detector).
2, each of which is further provided with a control device 8 which drives the expansion valve 6 to detect the electric resistance values of the thermistors 1 and 2 and change the operating frequency of the motor (not shown) of the compressor 3. Is.

FIG. 5 shows each arithmetic circuit inside the control device 8. Reference numeral 11 is a temperature drop correction arithmetic circuit for a temperature difference ΔTE corresponding to the pressure loss of the piping system between the outlet of the expansion valve 6 and the compressor 3 corresponding to the operating frequency of the compressor 3, and 12 is the temperature drop value ( ΔTE) and the detected evaporation temperature (TE ') are corrected to a corrected evaporation temperature (TE) corresponding to the suction pressure, and 13 is a set condensation temperature (TE) corresponding to a predetermined pressure ratio with respect to the corrected evaporation temperature (TE). Tco) arithmetic circuit, 14 is the set condensing temperature (T
co) and a condensing temperature (TC) detected by the condensing temperature detecting thermistor 1 are compared, and 15 is a comparison arithmetic circuit.
It is an operating frequency detector of the compressor 3.

FIG. 6 shows an example in which the control device 8 and the compressor drive unit 19 are separated from each other, and a signal is sent from the compressor drive unit 19 to the operating frequency detector 151 of the compressor 3 via a signal line 191.

FIG. 7 shows another control device 81. The evaporation temperature detecting thermistor (second detector) 21 is mounted at a position near the suction side of the suction side pipe 20 of the compressor 3 as shown in FIG. It is an example. According to this, the arithmetic circuit for correcting the temperature drop of the piping system and changing the temperature drop amount to the corrected evaporation temperature corresponding to the suction pressure can be omitted.

The heating refrigerant is discharged to the indoor heat exchanger 7 and condensed there. On the other hand, it is evaporated in the expansion valve 6, cooled in the outdoor heat exchanger 5, and sucked into the compressor 3 via the four-way valve 4. Here, the condensing temperature TC is detected by the thermistor 1 as a saturation temperature of the discharge pressure by cooling the pipe branched from the discharge side pipe of the compressor 3 with the low pressure side pipe. The refrigerant at the outlet of the expansion valve 6 is a saturated two-phase refrigerant, which is detected by the thermistor 2 as the saturation temperature TE 'of the low pressure side pressure. However, for the suction pressure of the compressor 3, the outdoor heat exchanger 5
There is a temperature difference ΔTE due to the pressure loss that occurs inside. Therefore, a function for performing the processing flow shown in FIG. 4 is provided in the control device. That is, TE ′ corresponding to the operating frequency of the compressor 3
And ΔTE are calculated, and the evaporation temperature of the refrigerant corresponding to the suction pressure of the compressor 3 is calculated by the following formula.

TE = TE′−ΔTE The ΔTE with respect to TE ′ has a characteristic that the higher the TE ′, the larger the ΔTE, and the higher the frequency, the larger the ΔTE, and can be calculated. Further, when a set value is set for the pressure ratio, there is a fixed relationship between TE and the set condensing temperature Tco, as shown in FIG. FIG. 3 shows that the maximum allowable condensing temperature can be set to 50 ° C. if the calculated result TE is −20 ° C. when the set pressure ratio ε is 8. The maximum condensation temperature is set as the set condensation temperature Tco, and the detected TC is compared with the detected TC to determine whether the current pressure ratio is ε or less.

If the judged result is ε or more, the operating frequency of the compressor 3 is lowered by a predetermined value. If it is determined to be ε or less, the frequency is increased by a predetermined value. The frequency is raised and lowered from the above TE 'detection at predetermined time intervals.

According to the present embodiment, when the frequency decreases, the circulation amount of the refrigerant decreases, the suction pressure increases, and the discharge pressure decreases, so the pressure ratio becomes less than or equal to the set value, and the pressure ratio is set when the frequency increases. Greater than or equal to the value. Therefore, the pressure ratio can be controlled within a certain range with respect to the set value, and burnout due to overheating of the compressor motor can be prevented and reliability can be improved.

EFFECTS OF THE INVENTION As described above, according to the present invention, the compressor can be operated at the set pressure ratio, so that the frequency is controlled without excessively increasing the compression ratio and the motor temperature of the compressor. The reliability of the compressor can be improved.

[Brief description of drawings]

FIG. 1 is a refrigeration cycle diagram of an embodiment of the present invention, FIG. 2 is a temperature drop characteristic curve diagram with respect to a detected evaporation temperature, FIG. 3 is a set pressure ratio characteristic diagram, FIG. 4 is a control flow chart, and FIG. Is an arithmetic circuit diagram, FIG. 6 is a control device diagram of another embodiment, and FIG.
Still another control device diagram, FIG. 8 is a partial refrigeration cycle diagram of another embodiment. 1 ... Thermistor for detecting condensation temperature (first detector), 2,
21 ... Evaporation temperature detection thermistor (second detector), 3 ...
… Compressor, 4 …… four-way valve, 5 …… outdoor heat exchanger, 6 ……
Expansion valve, 7 ... Indoor heat exchanger, 8 ... Control device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noriaki Horiuchi 390 Muramatsu, Shimizu Ichi, Shimizu Plant, Hitachi, Ltd. (72) Inventor Hiroki Terada 390 Muramatsu, Shimizu Ichi, Shimizu, Hitachi (72) ) Inventor Naoki Suzuki, 390 Muramatsu, Shimizu City, Hitachi, Ltd., Shimizu Plant (72) Inventor, Kensaku Oguni, 502, Kamimachi, Tsuchiura City, Ltd. 390 Address, Shimizu Plant, Hitachi, Ltd. (56) References: 61-178159 (JP, U)

Claims (2)

(57) [Claims] 1. A refrigeration cycle equipped with a compressor having a motor driven with a variable frequency, for detecting a condensing temperature (TC) of high pressure at the compressor outlet.
A detector, a second detector for detecting the evaporation temperature (TE ') at the outlet of the expansion valve, and an operating frequency of the compressor, the operating frequency and the evaporation temperature (TE') detected by the second detector. ) From the expansion valve outlet to correct the pressure loss between the compressors to calculate the evaporation temperature (TE) corresponding to the suction pressure of the compressor, and the evaporation temperature (TE) preset Means for calculating a set condensing temperature (TCO) corresponding to a set pressure ratio, and comparing the set condensing temperature (TCO) and the condensing temperature (TC) detected by the first detector in a predetermined time period, When the condensing temperature (TC) is higher than the set condensing temperature (TCO) by a certain value or more, a control device that controls so as to reduce the operating frequency of the compressor so that the pressure ratio falls within a certain range. An air conditioner characterized by being equipped. 2. A refrigeration cycle equipped with a compressor having a motor driven with a variable frequency, for detecting a condensing temperature (TC) of high pressure at the compressor outlet.
A detector, a second detector for detecting the evaporation temperature (TE) corresponding to the suction pressure, and a means for calculating a set condensation temperature (TCO) from the evaporation temperature (TE) from a preset set pressure ratio And comparing the set condensing temperature (TCO) with the condensing temperature (TC) detected by the first detector in a predetermined time period, and the condensing temperature (TC) is a constant value from the set condensing temperature (TCO). And a control device for controlling so that the operating frequency of the compressor is lowered so that the pressure ratio falls within a certain range when the pressure is higher than the above.