JPH068461Y2 - Refrigeration equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a refrigerating apparatus, and more particularly to a refrigerating and air-conditioning apparatus in which the amount of residual liquid refrigerant in an accumulator is controlled within a certain level.

<Prior Art and Its Problems> Conventionally, for example, an air conditioner for a vehicle is provided with a compressor 1, a condenser 5, and an evaporator 4 whose compression capacity changes continuously, as shown in FIG. An accumulator 3 is arranged between the evaporator 4 and the compressor 1, and a fixed throttle mechanism 2 such as a capillary tube is attached to the condenser 5 and the evaporator 4.
A cooling device arranged between and is used.

Therefore, in this device, the amount of the residual liquid refrigerant in the accumulator 3 is determined by the cooling load or the change in the rotational speed of the compressor, and the refrigerant liquid level is determined, but the volume of the accumulator 3 described above is constant, Depending on the conditions, the liquid refrigerant in the accumulator 3 may be in a full state or an empty state.

For example, in an air conditioner for a vehicle in which the compressor 1 is driven by an axle driving prime mover, when the rotation speed of the compressor 1 is low such as when the prime mover is idling, the evaporator 4
When the cooling load on the side is low and the capacity of the compressor 1 is controlled, the refrigerant liquid level in the accumulator 3 becomes full, and the refrigerant liquid flows into the compressor (liquid back), In some cases, the performance of the compressor 1 may deteriorate, or the compressor 1 may be damaged. On the contrary, when the capacity of the compressor 1 is not controlled and the load of the evaporator 4 is large, the refrigerant liquid level in the accumulator 3 decreases and becomes empty, so that the refrigerant in the evaporator 4 is overheated. It becomes a state. Therefore, there is a possibility that the cooling capacity of the evaporator 4 will decrease and the temperature of the refrigerant discharged from the compressor 1 will rise.

If the compressor 1 is started under such conditions, the pull-down performance deteriorates, and it takes a long time to reach a comfortable indoor temperature. In the conventional example, since the throttle mechanism having a fixed opening degree such as a capillary tube or an orifice is used as the throttle mechanism 2, the throttle mechanism 2 remains open immediately after the compressor 1 is started, so that the pressure is changed from the high pressure side to the low pressure side. Since the liquid refrigerant flows in, a large amount of liquid refrigerant may flow into the compressor 1. When the liquid refrigerant flows into the compressor 1, it becomes liquid compression, which is not preferable in terms of the durability performance of the compressor 1 and may cause the compressor 1 to be damaged.

Further, the liquid refrigerant existing in the accumulator and the evaporator evaporates as the pressure in the low-pressure side pipe decreases immediately after the compressor 1 starts up, but since the liquid refrigerant flows in from the high-pressure side, the cooling at the initial stage of start-up. It has the drawback of poor performance.

Further, as a refrigerating apparatus of this type, Japanese Patent Application Laid-Open No. 55-9956
Those described in JP-A No. 7, JP-A-57-127755 and JP-A-54-163458 are known.

However, since the refrigerating apparatus described in JP-A-55-99567 does not control the refrigerant flow rate at the time of startup, the liquid refrigerant may flow into the compressor at the time of startup.

Further, in the refrigerating apparatus described in Japanese Patent Laid-Open No. 57-127755, the control valve between the evaporator and the compressor is closed for a certain period of time at startup, so that the refrigerant pressure in the evaporator is unlikely to drop and the refrigerant cannot be discharged at the initial stage of startup. Poor cooling performance.

Further, the refrigerating apparatus described in Japanese Patent Laid-Open No. 54-163458 does not have a liquid reservoir, and the circulating refrigerant amount is controlled by an estimated value from the refrigerant temperature and the state quantity of compression, so the circulating refrigerant is Since the amount control is delayed or too fast, the liquid refrigerant may flow into the compressor at startup.

<Means for Solving Problems> The present invention is a refrigeration system in which the refrigerant liquid level in the accumulator does not become full or empty by controlling the refrigerant liquid level in the accumulator within a certain range. It is intended to provide.

A compressor, a condenser connected to the compressor, an evaporator connected to the condenser and connected to the compressor, and an accumulator provided between the evaporator and the compressor. In the refrigeration system including an externally controlled expansion valve provided between the condenser and the evaporator, and a refrigerant liquid level detector arranged in the accumulator, the refrigerant liquid level detector Is provided with an upper limit level sensor and a lower limit level sensor to detect whether the refrigerant liquid level is above the upper limit or below the lower limit or between the upper limit and the lower limit, and from the start of starting the compressor at the time of starting. The external control is performed when the refrigerant liquid level is below the lower limit when the external control type expansion valve is closed until the refrigerant liquid level is below the lower limit, and when the external control type expansion valve is subsequently opened. Swelling The valve opening of the valve is increased, the valve opening is reduced when the refrigerant liquid level is equal to or higher than the upper limit, and the valve is opened when the refrigerant liquid level is between the upper limit and the lower limit. The opening is kept constant.

<Operation of the device> When the compressor is started, the external control type expansion valve is closed until the refrigerant liquid level becomes equal to or lower than the lower limit from the start of starting, and then the external control type expansion valve is opened. When the refrigerant liquid level is equal to or lower than the lower limit, the valve opening of the external control type expansion valve is increased to increase the flow rate, and when the refrigerant liquid level is equal to or higher than the upper limit, the valve opening is adjusted. By making the flow rate smaller and reducing the flow rate, the refrigerant liquid in the accumulator can be maintained within a certain range, the cooling capacity of the evaporator can be improved, and the inflow (liquid back) of the refrigerant liquid to the compressor can be prevented. it can.

<Embodiment> An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 2 is a basic system diagram of the refrigerating and air-conditioning apparatus of the present invention.
The compressor 1 used in this apparatus uses the compressor 1 whose compression capacity varies continuously, but it is also possible to use a compressor whose compression capacity does not vary. An externally controlled expansion valve 6 is used as the throttle mechanism.

That is, the accumulator 3 arranged between the evaporator 4 and the compressor 1 is provided with the detector 8 including the level sensor 81 for the upper limit setting liquid level L ₁ and the level sensor 82 for the lower limit setting liquid level L _2. The two sensors 81 and 82 of the detector 8 detect the refrigerant liquid level in the accumulator 3 and transmit the detected signal to the controller 7 to control the valve opening degree of the external control type expansion valve 6. Have control.

First, when the refrigerant liquid level in the accumulator 3 is higher than the set liquid level L ₁ , the valve opening degree of the externally controlled expansion valve 6 is reduced to reduce the circulating amount of the refrigerant and set liquid levels L ₁ and L _{1.
When the} refrigerant liquid is between ₂ and, the valve opening is maintained the same, and when the set liquid level is L ₂ or less, the valve opening is increased,
The circulation amount of the refrigerant is increased.

Next, a specific embodiment of the present invention will be described with reference to FIG. That is, the device shown in FIG. 3 is used for refrigeration and air conditioning for vehicles, and the compressor 12 in this embodiment is used.
Uses a so-called variable capacity compressor whose capacity continuously changes from time to time so that the compressor suction pressure does not drop below a set value, and is driven by a vehicle drive prime mover 13.

An accumulator 3 is arranged between the compressor 12 driven by the prime mover 13 and the evaporator 4. A detector 8 having thermistors 10 and 11 is provided in the accumulator 3 to set the set liquid levels L ₁ and L ₂ , and the set liquid level L ₁ is set to the thermistor 10 to set the set liquid level L _2. It is detected by the thermistor 11. That is, the refrigerant liquid level in the accumulator 3 is detected from the resistance change of the thermistors 10 and 11. The controller 7 controls the valve opening degree of the external control type expansion valve 6 arranged between the condenser 5 and the evaporator 4 as described below according to the refrigerant liquid level in the accumulator 3 detected by the detector 8. To do.

That is, when the refrigerant liquid level in the accumulator 3 is higher than the set liquid level L ₁ , the valve opening degree of the external control type expansion valve 6 is decreased at a certain speed to reduce the refrigerant circulation amount, The refrigerant liquid level in the accumulator 3 is lowered to control the liquid level below the set liquid level L ₁ . Further, when the refrigerant liquid level in the accumulator 3 is in the middle of the set liquid levels L ₁ and L ₂ , the external control type expansion valve 6 described above is used.
The valve opening of is maintained at a constant opening. Therefore, in the process in which the refrigerant liquid level decreases from the level higher than the set liquid level L _{1 as} described above, the valve opening degree at the time when the refrigerant liquid level reaches the set liquid level L ₁ is maintained. If the above-mentioned valve opening is appropriate, the refrigerant liquid level is stationary between the set liquid levels L ₁ and L ₂ , and the circulation amount of the refrigerant is stable, but the maintained valve opening is the set liquid level. If it is unsuitable (too small) to stabilize within the range, the coolant liquid level will drop below the set liquid level L ₂ .

Further, when the refrigerant liquid level is equal to or lower than the set liquid level L ₂ , the valve opening degree of the external control type expansion valve 6 is increased at a certain constant speed to increase the refrigerant circulation amount, thereby increasing the refrigerant circulation amount. The refrigerant liquid level rises, and when the set liquid level L ₂ is reached, the valve opening is maintained at that opening. Then, if the maintained valve opening degree is appropriate, it becomes stable between the refrigerant liquid levels L ₁ and L ₂ in the accumulator 3.

On the other hand, when the valve opening degree is maintained inappropriate (too large) is refrigerant liquid level rises to set liquid level L ₁ or more, the refrigerant liquid level for as set liquid level L ₁ described above By controlling the valve opening of the externally controlled expansion valve 6 by the controller 7 so as to decrease, and repeating the operation by the control, the refrigerant liquid in the accumulator 3 is finally between the set liquid levels L ₁ and L _2. Stabilize the level.

4 and 5 show the operating characteristics of the present invention.
FIG. 4 shows the operation from the start of the compressor 12 to the capacity control of the compressor 12 when the rotation speed of the compressor 12 is constant and the heat load condition of the outside air is also constant [Fig. (E)] to a certain point. It shows the state. It should be noted that, unlike this embodiment, when a normal type compressor which is not a variable displacement compressor is used, the operating characteristics are close to this characteristic.

In FIG. 4, (a) is the relationship between the vapor inlet air temperature and time, (b) is the relationship between the refrigerant liquid level in the accumulator and time, and (c) is the expansion valve lift amount (valve opening). Time relationship, (d) shows the relationship between compressor suction pressure and time, and (e) shows the relationship between compressor capacity and time.

That is, immediately after the start of the compressor 12, the valve opening of the external control type expansion valve 6 is fully closed from the start of the start until the refrigerant liquid level becomes equal to or less than the set liquid level L ₂ , so that the compressor suction is performed. The pressure rapidly drops, and after a certain time elapses, the valve opening of the expansion valve 6 opens to a preset opening. At this time, the actual load on the evaporator 4 side, compression 12
There is a slight difference between the valve opening degree and the valve opening degree that matches the conditions such as the number of revolutions.

Therefore, the refrigerant liquid level (b) in the accumulator 3 deviates from the set liquid levels L ₁ and L ₂ and rises or falls, but as described above, the controller 7 causes the expansion valve 6 as shown in FIG. The valve opening (c) of is controlled, and the refrigerant liquid level stabilizes within the set range. However, since the inlet air temperature of the evaporator 4 gradually decreases immediately after the compressor 12 is started, and continues to [(b)], the refrigerant liquid level (b) in the accumulator 3 gradually increases, Finally, the upper limit value L ₁ of the set liquid level is exceeded. Also at this time, as described above, the valve opening degree of the expansion valve 6 is controlled as shown in FIG. 3C to stabilize the refrigerant liquid level within the set liquid levels L ₁ and L ₂ . This control of the valve opening is repeated according to the decrease of the inlet air temperature of the evaporator 4, and the valve opening decreases, and at the same time, the suction pressure (d) of the compressor 12 also decreases. The set suction pressure P ₁ is reached.

FIG. 5 shows a state after the suction pressure of the compressor 12 reaches the set suction pressure P ₁ , and the respective graph characteristics are as follows.
Follow Fig. 4.

That is, since the inlet air temperature of the evaporator 4 continues to decrease, the capacity of the compressor 12 decreases as shown in FIG. Therefore, the refrigerant liquid level (b) in the accumulator 3 rises,
When the set liquid level L ₁ is reached, the above-mentioned control of the valve opening degree (c) is performed at that time. This operation is repeated, but the valve opening degree (c) of the expansion valve 6 is closed each time,
At the same time, the compressor capacity (e) decreases and reaches a stable state.

<Effect of the Invention> Since the present invention has the above-mentioned configuration, the refrigerant liquid level in the accumulator is within a certain range even during a transient state such as pull-down after starting the compressor. It is possible to prevent the refrigerant liquid from flowing into the compressor (liquid back) and prevent the refrigerant from overheating at the evaporator outlet, which prevents the compression function power from decreasing and the efficiency of the evaporator to be improved. You can do it well, and you can expect improved pull-down performance.

Further, it is possible to always provide stable cooling performance against fluctuations in the number of revolutions of the compressor and heat load on the outside air, and there is also a risk of damage to the compressor due to inflow (liquid back) of the refrigerant liquid into the compressor. Little.

Furthermore, at the beginning of starting the compressor, the liquid refrigerant existing inside the evaporator and between the evaporator and the accumulator flows into the accumulator while evaporating, and the pressure in the low-pressure side pipe decreases and evaporates. Since the external control type expansion valve is kept closed until the liquid level of the refrigerant falls below the lower limit, the refrigerant does not flow from the high pressure side, so it is possible to reliably prevent a large amount of liquid refrigerant from flowing into the compressor. It has the effect that

Similarly, at the beginning of starting the compressor, the external control type expansion valve remains closed until the refrigerant liquid level of the accumulator becomes equal to or lower than the lower limit, so that the refrigerant flows from the high pressure side to the low pressure side. Since there is no pressure drop, the pressure on the low-pressure side drops quickly, so that the cooling performance in the initial stage at startup can be improved.

Further, since the refrigerant liquid level in the accumulator is detected by the detector, it is possible to easily obtain an appropriate amount of refrigerant enclosed by using this, and it is also possible to easily detect a shortage of refrigerant and the like.

[Brief description of drawings]

FIG. 1 is a system diagram of a conventional refrigeration / air-conditioning system, FIG. 2 is a system diagram showing an outline of the present invention, and FIG. 3 is a system diagram showing an example in which the present invention is applied to an axle refrigeration system. Fig. 4 is a graph showing the operation from the start of the present invention to the state where the compressor does not reach the capacity control, (a) is the relationship between the evaporator inlet temperature and time, and (b) is the refrigerant liquid level in the accumulator. With time, (c) shows the relationship between the valve opening of the expansion valve and time, (d) shows the relationship between compressor suction pressure and time, and (e) shows the relationship between compressor capacity and time. is there. FIG. 5 is a graph showing the operation in a state where the capacity of the compressor changes, where (a) is the relationship between the evaporator inlet air temperature and time, and (b) is the relationship between the refrigerant liquid level in the accumulator and time. , (C) shows the relationship between the valve opening of the expansion valve and time, (d) shows the relationship between compressor suction pressure and time, and (e) shows the relationship between compressor capacity and time. 1, 12 ... Compressor, 3 ... Accumulator, 4 ... Evaporator, 5 ... Condenser, 6 ... (External control type) expansion valve, 7
...... Controller, 8 …… Detection mechanism, 81,82 …… Liquid level sensor, 10,11 …… Thermistor.

Claims (1)

[Scope of utility model registration request] 1. A compressor, a condenser connected to the compressor, an evaporator connected to the condenser and connected to the compressor, and provided between the evaporator and the compressor. In the refrigerating apparatus, the accumulator, the externally controlled expansion valve provided between the condenser and the evaporator, and the refrigerant liquid level detector arranged in the accumulator, The liquid level detector includes an upper limit level sensor and a lower limit level sensor, which detect whether the refrigerant liquid level is above the upper limit, below the lower limit, or between the upper limit and the lower limit, and when starting the compressor. In the case of closing the external control type expansion valve from the start of startup until the refrigerant liquid level becomes equal to or lower than the lower limit, and thereafter opening the external control type expansion valve, the refrigerant liquid level is equal to or lower than the lower limit. When said The valve opening of the section-controlled expansion valve is increased, the valve opening is reduced when the refrigerant liquid level is equal to or higher than the upper limit, and the refrigerant liquid level is between the upper limit and the lower limit. A refrigeration system characterized in that the valve opening is kept constant at a certain time.