JPH01167556A - Refrigerator - Google Patents

Abstract

PURPOSE:To prevent damage of a compressor at the time of starting by provid ing a temperature detecting means for discharging temperature and a pressure detecting means between a compressor and a four-way valve, set upper limit operating frequencies of the compressor by discharge superheat obtained by both the means and operating the refrigerator at less than said frequency. CONSTITUTION:In a controller 12 the discharge superheat of a compressor 1 is detected by a temperature sensor 9 and a pressure sensor 10, upper limit value of frequencies of the compressor 1 is set and the compressor 1 is operated and controlled at operating frequencies less than the upper limit value. Thus, temperature difference between room temperature and room set temperature is large, and in the case where the discharge superheat is small even if a need for operating the compressor 1 at high operating frequencies is called for, the operating frequencies can be controlled up to the upper limit value and the failure of the compressor 1 based on lubrication failure can be prevented. Further, when discharge superheat gains gradually, the upper limit value of the operating frequencies also increases gradually, a time for operating the compressor 1 at low speed is short and startup is fast.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application J] The present invention relates to a refrigerant device equipped with a compressor whose operating frequency is varied by a frequency conversion device, and particularly relates to protection of the compressor.

[Conventional technology]

If an air conditioner is left in a stopped state for a long time, a large amount of refrigerant will accumulate in the cooler outdoor unit due to the difference in ambient temperature, and even if the ambient temperature rises, the compressor in particular will have a large heat capacity. The temperature does not rise easily and as a result, the temperature is the lowest, making it easy for refrigerant to accumulate. When the compressor is started in this state, the refrigerant in the compressor will form, and at this time, the refrigerating machine oil in the compressor will be taken out into the refrigerant circuit at the same time as the 7-ohm minced refrigerant, lowering the oil level in the compressor and causing poor lubrication. There were problems such as wake-up. One way to prevent this is to use a crankcase heater to keep the compressor warm and prevent refrigerant from accumulating.

If the user turns off the main power to the air conditioner,
You cannot expect the effectiveness of the crankcase heater.

Also, in order to prevent a large amount of refrigerant that has accumulated in various parts during startup from being returned to the compressor and compressing the liquid and damaging the compressor, it is common to install an accumulator on the low pressure side of the compressor. This is because there is a sudden pressure change inside the Akinimulator when it starts up.

? H% tends to cause foaming, and the gas-liquid separation performance of the accumulator is lower than that during normal operation, resulting in a liquid back state in which some liquid refrigerant returns to the compressor.

If the compressor is sufficiently warm, a slight liquid back-up is not a problem, but if a liquid back-up occurs when the compressor itself is completely cold, such as during startup, the discharged refrigerant will not become gas refrigerant, and the second Since compression is completed in the phase state, the load on the compressor bearings increases rapidly, and the liquid refrigerant accumulates inside the compressor shell, diluting the refrigerating machine oil, reducing the lubrication ability and causing bearing seizure. There is a problem.

On the other hand, in air conditioners whose capacity can be varied by changing the operating frequency of the compressor using a zero frequency conversion device, the air conditioning load is the heaviest at startup.

Attempts are made to operate at high speeds to increase capacity and speed up start-up, but high-speed operations encourage forming, take out a large amount of refrigerating machine oil, and cause severe liquid back-up, and the load on the crankshaft increases due to high-speed operations. This interaction can result in damage to the compressor. As a countermeasure to this problem, for example, as shown in Japanese Utility Model Application Laid-open No. 53-18849, a method has been proposed in which the compressor is operated at a low capacity for a certain period of time at startup, but this method does not.

Even if the amount of refrigerant stored in the compressor, amount of liquid back up, air conditions, etc. vary, the compressor will always operate at low capacity for a certain period of time, so it is necessary to set the time under the most severe conditions from the perspective of protecting the compressor. Of course, the time will be longer, and the start-up time at startup b'
This goes against the request to speed up the process.

Additionally, there is a problem with the restart feature, which causes the compressor to operate at a lower capacity even when it is sufficiently warm.

[Problem that the invention seeks to solve]

Conventional air conditioners with variable compressor capacity operate the compressor at low capacity for a certain period of time as a way to prevent damage to the compressor due to insufficient lubrication due to foaming or liquid backing during startup. In order to ensure the full protection performance of the compressor, it is necessary to operate at low capacity for a sufficiently long period of time, and even if the compressor is sufficiently warm and there is no need to operate at low capacity, it is necessary to operate at low capacity for a certain period of time. There was a problem that startup was slow.

This invention was made to overcome the above-mentioned problems, and aims to provide a refrigerant device that can prevent damage to the compressor during startup and that can be started up quickly.

[Means for solving problems]

The refrigerant device according to the present invention is provided with temperature detection means for detecting discharge temperature and pressure detection means between the compressor and the four-way valve, and υ compression by discharge superheat obtained by the temperature detection means and pressure detection means. The upper limit operating frequency of the compressor is set at all times, and the compressor is fully operated below the upper limit frequency.

[Effect]

In this invention, the discharge superheat of the compressor is detected by the temperature detection means and the pressure detection means.

The controller controls the discharge superheat of the compressor so that it does not exceed a set value.

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

In FIG. 1, (1) is a compressor driven by the output signal of a frequency converter (8), and (2) is a four-way valve that is a switching valve.

(3) is an outdoor heat exchanger that is a condenser for cooling and an evaporator for heating, (4) is a throttling device that is a pressure reduction device, and (5) is an evaporator for cooling and a condenser for heating. indoor heat exchanger,
(6) is an accumulator, which is successively connected by refrigerant piping (7) to constitute a refrigeration cycle of an air conditioner, which is a refrigerant device. (9) is a temperature sensor α1 which is a temperature detection means for detecting the temperature of the refrigerant discharged from the compressor (1).
is a pressure sensor which is a pressure detection means for detecting the discharge pressure of the compressor (1), aυ is a temperature sensor which is a degree detector which detects the room temperature, (I2 is the temperature and pressure signal 'fc This is a control device that controls all the operating frequencies of the compressor +11 using the 9 frequency converter (8).

FIG. 2 is a block diagram of the control device α2, in which an analog-to-digital converter (A/D converter) Gυ, an input circuit 6,
Central processing unit (CPU) (to), memory (b),
Consists of output circuit (to) and output buffer country.

The operating frequency signal of the compressor is outputted from the output buffer (to) and inputted to the first frequency conversion device (8). Note that only one example of the input section is displayed.

Next, the effect will be explained. Four-way valve (2) during cooling operation
is set to the solid line state, and the refrigerant gas discharged from the compressor (1) is sent to the four-way valve (2), the outdoor heat exchanger (3), the throttling device (4), the indoor heat exchanger (5), and the four-way valve. (2), the accumulator (6) is deposited and returned to the compressor 11+, the outdoor heat exchanger (3) serves as a condenser, and the indoor heat exchanger (5)
) acts as an evaporator to cool the room.

During cooling operation, a signal from the temperature sensor αυ that detects the indoor temperature is input to the control device (17J), and this control device a3 operates at a high operating frequency when the temperature difference between the indoor temperature and the indoor set temperature is large. On the other hand, when the temperature difference is small, an operating frequency signal is output to the frequency converter (8) so that the compressor is fully operated at a low operating frequency.The operating frequency of the compressor is, for example, in the range of 30 to 90 Hz. During heating operation, the four-way valve (2) is switched to the broken line state, and the refrigerant gas discharged from the compressor +1+ is controlled by the four-way valve (2).
), indoor heat exchanger (5).

Throttle device (4), outdoor heat exchanger (3), four-way valve (2),
The gold flows sequentially through the accumulator (6) and returns to the compressor (1), and the room is heated by the indoor heat exchanger (5) acting as a condenser and the outdoor heat exchanger (3) acting as an evaporator. . During such heating operation, the operating frequency is determined by the temperature difference between the indoor temperature and the indoor set temperature, just like during cooling operation.
Compressor +11 is operated in the range 30-90 Hz.

In steady operation, the operating frequency of the compressor (1) is controlled according to the indoor air conditioning load as explained above, but in transient conditions such as during startup, the upper limit of the operating frequency is controlled in order to protect the compressor Il+. It is driven with less

Figure 3 is a characteristic diagram showing the permissible operating range for stable operation of compressor +11 for a long time.
), and the vertical axis is the discharge superheat of the compressor tl+, that is, the difference in temperature between the saturation temperature and the discharged gas refrigerant with respect to the discharge pressure. As shown in the figure, it is necessary to operate with a discharge superheat of a certain value or more, and the higher the operating frequency, the higher the discharge superheat needs to be operated. In other words, if the discharge superheat is small, the temperature of the refrigerant discharged from the compressor is low, and the temperature of the refrigerating machine oil in the compressor +11 also decreases, and a large amount of refrigerant dissolves in the refrigerating machine oil, reducing the lubrication performance. In addition, if there is a sudden pressure change, foaming can easily occur inside the compressor (1), causing refrigerating machine oil to be carried out into the refrigerant circuit, lowering the oil level of the refrigerating machine oil, and causing poor lubrication. On the other hand, as the operating frequency increases, the bearing load on the compressor (1) increases, so it is necessary to ensure better lubrication performance than in low frequency operation, resulting in higher discharge superheat. In particular, if the start-up special compressor is started when it is cold, heat will be taken away by the compressor +11 and the discharge refrigerant temperature will rise, so if high frequency operation is performed in this state, the compressor +
This results in seizure of the bearing of No. 11.

In the control device α2 of the present invention, the discharge superheat of the compressor (11) is detected by a temperature sensor (9) and a pressure sensor aα.
The compressor (11
Set the upper limit value of the operating frequency, and at the operating frequency below the upper limit value, the pressure, JA? Control operation to J machine +11'.

FIG. 4 is a flowchart for explaining an example of controlling the operating frequency of the compressor (1) by the control device α2.

When the flow starts, in the compressor operating frequency determination routine 0, the operating frequency (FM) is determined based on the temperature difference between the indoor temperature and the indoor set temperature, as described above. Then, in step (42), the high pressure detected by the pressure sensor Q(l) is converted into a saturation temperature, and this saturation temperature (voltage 1) is input.

In step @j, the temperature sensor (9) detects and inputs the discharge refrigerant temperature (t2). In step C4, discharge superheat (SH) as the difference between these temperatures is calculated. From step θ to step @η, it is determined in which ik1 range the discharge superheat is located.

If there is no 10 deg groove, step (to 4I, 10 deg
If the value is greater than or equal to g and less than 15 deg, proceed to step (41, 1
If it is 5deg or more and less than 25deg, step (To)
If it is 25 degrees or more, proceed to step (51).

From step 0 keg to step (51), the upper limit value (maxHz) of the operating frequency of the compressor is set. and.

In step (52), the operating frequency (FW) determined in step ht+ is changed from step (4 barrels) to step (51).
), it is determined whether the frequency is higher than the upper limit frequency (maxHz) set in step (53).
At step (54), the operating frequency (FW) is corrected to the upper limit frequency, and at step (54), the operating frequency is output.

According to this flowchart, the upper limit of the operating frequency of the compressor (1) is set by the discharge superheat, so the temperature difference between the indoor temperature and the indoor set temperature is large, and the compressor fil is operated at a high operating frequency. Even if a request is made, if the discharge superheat is small, the operating frequency can be suppressed to the upper limit value, and failure of the compressor (1) due to poor lubrication can be prevented. In addition, as the discharge superheat gradually increases, the upper limit of the operating frequency also gradually increases, so the compressor (11
Considering the number of refrigerant accumulated in the tank, the amount of liquid back up, and the cold state of the compressor (1), if necessary, run the compressor (1+) at low speed until it warms up, and when restarting, etc. If the discharge temperature rises quickly when the engine is at rest or after starting operation when there is little accumulation of refrigerant, the time to high-speed operation will be quicker and the start-up can be made faster.

FIG. 5 is a refrigerant circuit diagram showing another embodiment of the present invention,
A saturation temperature detection circuit α3 is used for the pressure sensor αG, and the temperature sensor I, which is a saturation temperature detection means, directly detects the saturation temperature at the pressure sensor. This detection circuit 0 is heat exchanger 5 ilG and capillary f15
1, and the refrigerant at the outlet of the compressor is passed through a heat exchanger tte.
It becomes a two-phase refrigerant and is transferred to the compressor + in the capillary αS.
The pressure was reduced to 11 suction pressure.

The refrigerant becomes a low-temperature two-phase refrigerant, and by exchanging heat with the heat exchanger C18, a cycle is completed with a low-pressure refrigerant such as 2-phase refrigerant, which has approximately the same enthalpy as the refrigerant at the outlet of the compressor (1).

Figure 6 shows the behavior of this refrigerant on a Molinyl hetogram, where the solid line is the detection circuit (the state of the refrigerant in +31,
In Figure 7, where the broken line ABCD represents the state of the refrigerant in a normal refrigeration cycle, E is.

Indicates the capillary Q5 population status, and temperature sensor C1 is installed at this location.
By installing 41i, it becomes possible to detect the high pressure saturation temperature without using a pressure sensor.

[Effects of the Invention] As described above, according to the present invention, the upper limit of the operating frequency of the compressor is set by the discharge superheat of the compressor obtained by the temperature detecting means and the pressure detecting means, and the upper limit value of the operating frequency of the compressor is set lower than the upper limit frequency. Since the compressor is operated at a high frequency, the operating frequency can be suppressed when the discharge superheat is small, such as during start-up, and compressor failures due to poor lubrication can be prevented.
When the discharge superheat is applied, the upper limit of the frequency is increased, so the time during which the compressor is operated at low speed can be shortened, and a refrigerant device with a quick start-up can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a refrigerant circuit diagram of an air conditioner according to an embodiment of the present invention, FIG. 2 is a block diagram of the control device u, and FIG. 3 is a characteristic diagram showing the allowable operating range of the compressor. FIG. 4 is a flow chart diagram explaining the operation of the control device;
FIG. 5 is a refrigerant circuit diagram showing another embodiment, and FIG. 6 is a Mollier diagram showing the state of the refrigerant in the saturation temperature detection circuit. +11 is a compressor, (3) is an outdoor heat exchanger, and (4) is a throttling device. (5) is an indoor heat exchanger, (6) is an accumulator,
(91u temperature sensor, αl is pressure sensor, (I2
is a control device. 0 is a saturation temperature detection circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (2)

[Claims] (1) A refrigerant circuit including a compressor, a condenser, a pressure reducing device, and an evaporator, a temperature detection means for detecting the temperature of the refrigerant discharged from the compressor, a pressure detection means for detecting the discharge pressure, and the temperature detection means. and a control device that sets an upper limit of the operating frequency of the compressor based on the discharge superheat obtained by the pressure detection means, and operates the compressor at a frequency lower than this frequency. Device. (2) The refrigerant device according to claim 1, wherein the discharge superheat is performed by temperature detection means and high-pressure saturation temperature detection means.