JP2001194035A - Compression heat pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a compression heat pump which can be protected effectively against damage due to abrupt inner temperature rise. SOLUTION: Means 9, 10 for detecting the degree of superheat Si of refrigerant R sucked into a compressor 1 and the degree of superheat So of refrigerant R delivered from the compressor 1 are provided. Based on the information detected by the detecting means 9, 10, a protective control means 11 executes a specified protective control, e.g. stopping of the compressor, if the degree of superheat Si of refrigerant R sucked into a compressor 1 is higher than the degree of superheat So of refrigerant R delivered from the compressor 1 and the difference exceeds a set allowance a (Si>So+α).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a compressor-condenser-
The present invention relates to a compression heat pump that circulates refrigerant in the order of an expansion valve and an evaporator, and more particularly, to protection of a compressor.

[0002]

2. Description of the Related Art Conventionally, a compression heat pump employs one or more of the following methods (a) to (c) to prevent damage to a compressor due to abnormal operation of the compressor. Was.

(A) The temperature of the compressor body is detected, and the compressor is automatically stopped when the temperature of the compressor body becomes higher than a set value based on the detected information.

(B) The temperature of the refrigerant discharged from the compressor is detected, and based on the detected information, when the temperature of the refrigerant discharged from the compressor becomes higher than a set value, the compressor is automatically stopped.

(C) The pressure of the refrigerant sucked into the compressor and the pressure of the refrigerant discharged from the compressor are detected, and based on the detected information, when the pressure of the refrigerant sucked into the compressor becomes lower than a set value or when the pressure of the compressed refrigerant is reduced. When the pressure of the refrigerant becomes higher than the set value, the compressor is automatically stopped.

[0006]

However, in the compression heat pump, when the expansion valve is adjusted to the throttle side by adjusting the operation state or the like, the degree of superheat of the refrigerant sucked into the compressor increases, and the cooling factor of the compressor is reduced. As the suction refrigerant decreases, the internal temperature of the compressor also tends to increase.However, if this change is rapid and the internal temperature of the compressor rises rapidly, the operating part inside the compressor becomes larger rapidly than the outer part. Thermal expansion may occur, and due to the difference in thermal expansion, the operating part inside the compressor may come into contact with the outer part, causing damage to the compressor.

The temperature of the compressor body, the temperature of the refrigerant discharged from the compressor, or the pressure of the refrigerant sucked into the compressor or the pressure of the refrigerant discharged from the compressor are detected, and the detected temperatures and detected pressures simply exceed the set values. According to the protection methods (a) to (c), the presence or absence of an abnormality is determined only by determining whether the internal temperature of the compressor suddenly increases, as described above. At this stage, it is not possible to accurately detect the temperature difference, unlike the case where only a slow internal temperature rise occurs, which does not lead to compressor damage due to the difference in thermal expansion. There was a problem that damage to the compressor could not be effectively prevented.

In view of this situation, the main problems of the present invention are:
The reason is that it is possible to effectively prevent damage to the compressor caused by the rapid rise in the internal temperature of the compressor by the rational abnormality detection.

[0009]

According to a first aspect of the present invention, there is provided a compression heat pump for circulating a refrigerant in the order of a compressor, a condenser, an expansion valve, and an evaporator. Detecting means for detecting the degree of superheating and the degree of superheating of the refrigerant discharged from the compressor is provided.Based on the detection information of the detecting means, the degree of superheating of the suction refrigerant is larger than the degree of superheating of the discharged refrigerant. Protection control means for executing a predetermined protection control when is larger than the set tolerance.

That is, when the expansion valve is adjusted to the throttle side by adjusting the operating state or the like, the degree of superheat of the compressor suction refrigerant increases and the internal temperature of the compressor tends to increase. In such a case, as a phenomenon, first, the superheat degree of the compressor suction refrigerant rapidly rises, causing a large difference between the superheat degree of the compressor suction refrigerant and the superheat degree of the compressor discharge refrigerant, and the compression is slightly delayed. Experiments have confirmed that a sudden rise in the internal temperature of the compressor and an increase in the degree of superheating of the refrigerant discharged from the compressor occur.

From the above, as described above, when the detected superheat degree of the compressor suction refrigerant is larger than the detected superheat degree of the compressor discharge refrigerant, and the difference becomes larger than the set tolerance,
If it is determined that a sudden increase in the internal temperature of the compressor occurs and the predetermined protection control is executed, a situation in which the internal temperature of the compressor suddenly increases will be regarded as a state in which the internal temperature increase does not occur. In the initial stage or the initial stage, there is also a situation where only a slow internal temperature rise that does not lead to compressor damage due to the difference in thermal expansion occurs (that is, the superheat degree of the refrigerant suctioned by the compressor is slowly increased, which is a large difference from that. In which the degree of superheat of the refrigerant discharged from the compressor rises without causing any
In the state where it is accurately detected in distinction from the above, it is possible to appropriately perform predetermined protection control for the abnormal situation.
Effective against damage to the compressor caused by a sudden rise in the internal temperature of the compressor (that is, damage to the compressor due to the fact that the operating part inside the compressor thermally expands more rapidly than the outer part and contacts the outer part) Can be prevented.

Incidentally, in order to prevent the compressor from being damaged due to a rapid rise in the internal temperature of the compressor, the superheat degree of the refrigerant sucked into the compressor slightly precedes the increase in the internal temperature of the compressor as described above. Although it is conceivable to execute a predetermined protection control when the superheat degree of the compressor suction refrigerant becomes larger than the set value, it is possible to determine whether the detected superheat degree of the compressor suction refrigerant simply exceeds the set value. If only the determination condition is used, the protection control may be unnecessarily executed even for a gradual increase in the degree of superheat, which involves only a gradual increase in the internal temperature that does not lead to compressor damage due to the difference in thermal expansion. However, there is a problem that the stability of the heat pump operation is impaired.

In this respect, with the above configuration, the situation in which the internal temperature of the compressor suddenly rises is referred to as the situation in which the internal temperature of the compressor is only slowly increased without causing damage to the compressor due to the difference in thermal expansion as described above. Since the detection can be accurately performed separately, the unnecessary execution of the protection control can be avoided, and the stability of the heat pump operation can be kept high.

[2] In the invention according to the second aspect, the first aspect
In the embodiment of the present invention, the protection control means is configured to stop the operation of the compressor as the protection control.

That is, as the protection control for preventing the compressor from being damaged due to a rapid rise in the internal temperature of the compressor, the resistance of the expansion valve circuit portion is forcibly reduced so that the suction of the compressor which becomes a cooling factor of the compressor is performed. Although it is conceivable to increase the refrigerant rapidly, the amount of time required from the sudden increase in the degree of superheat of the refrigerant sucked into the compressor to the sudden increase in the internal temperature of the compressor is extremely short. In the case of protection control while continuing compressor operation, such as cooling the inside of the compressor, the effectiveness of the protection control tends to be delayed as the compressor internal temperature rises. In some cases, there may not be.

On the other hand, if the operation of the compressor itself is stopped as the protection control as described above, if the internal temperature of the compressor suddenly rises and the operating part inside the compressor is thermally expanded, it becomes an outer part. Even if it comes into contact, the operation of the operating part inside the compressor is stopped by stopping the operation of the compressor, so that only static contact is required between the operating part and the outer part, The compressor can be more reliably prevented from being damaged due to a rapid rise in the internal temperature of the compressor.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an apparatus configuration of a compression heat pump. H denotes a heat pump circuit (refrigeration circuit) for circulating a refrigerant R in the order of a compressor, a condenser, an expansion valve, and an evaporator. It is.

Reference numeral 5 denotes a first opening / closing valve for blocking the passage of the refrigerant R to the expansion valve 3, and reference numeral 6 denotes a bypass for a series connection circuit of the expansion valve 3 and the first opening / closing valve 5.
Has a capillary tube 7 functioning as a simple expansion valve.
And a second on-off valve 8 for blocking passage of the refrigerant R to the bypass passage 6 in series.

The expansion valve 3 employs a mechanical automatic temperature expansion valve, and sends out refrigerant from the evaporator 4 according to the temperature of the refrigerant sensed by the temperature-sensitive cylinder 3a attached to the outlet-side refrigerant passage of the evaporator 4. The degree of opening of the expansion valve 3 is adjusted and the refrigerant flow rate is adjusted such that the superheat degree R of R (the superheat degree of the compressor suction refrigerant R) becomes a set value.

9 is a superheat degree Si of the refrigerant R sucked into the compressor 1.
Is a discharge side superheat sensor that detects the superheat So of the refrigerant R discharged from the compressor 1, and 11 is a first superheat sensor based on detection information of both superheat sensors 9 and 10. The controller controls the second on-off valves 5 and 8 and the compressor 1.

It should be noted that, in detail, each of the superheat sensors 9 and 1
0 is constituted by a sensor for detecting the temperature and pressure of the refrigerant R,
Refrigerant superheat degrees Si and So of the respective parts are calculated by the controller 11 based on the detected temperatures and detected pressures of the sensors.

The controller 11 performs normal operation control as shown in FIG.
As shown in the figure, when the degree of superheat So of the refrigerant R discharged from the compressor is smaller than the first set value So1, the first and second on-off valves 5, 8
Are closed, but when the superheat degree So of the compressor discharge refrigerant R becomes larger than the first set value So1 (specifically, So1 + e) from this state, only the first opening / closing valve 5 is opened, Further, when the superheat degree So of the compressor discharge refrigerant R becomes larger than the second set value So2 (specifically, So2 + e) from that state, the second on-off valve 8 is opened.

On the contrary, the degree of superheat So of the refrigerant R discharged from the compressor is So
Is larger than the second set value So2, the first and second on-off valves 5 and 8 are both opened. On the other hand, the superheat degree So of the refrigerant R discharged from the compressor is changed from the second set value So2.
(Specifically, So2-e), only the second on-off valve 8 is closed, and from that state, the superheat degree So of the refrigerant R discharged from the compressor is reduced to the first set value So1 (specifically, So1).
When it becomes smaller than 1-e), the first on-off valve 5 is closed.

In other words, by controlling the opening and closing of the first and second on-off valves 5 and 8 in this manner, the adjustable range of the refrigerant flow rate can be secured by opening and closing the bypass passage 6, but the large adjustable range of the flow rate can be obtained. The adjustment of the refrigerant flow rate by the expansion valve 3 can be accurately performed over the entirety of the above.

Note that e is a set value for providing a hysteresis to the operation history of the first and second on-off valves 5 and 8 to stabilize the operation of each of the valves 5 and 8.

The controller 11 includes a heat pump circuit H
When the operation of the compressor 1 is started, the compressor 1 is started with the first and second on-off valves 5 and 8 closed, but after the start of the compressor 1, the superheat degree Si of the compressor suction refrigerant R is set. Value (for example, 1
2 ° deg) (that is, when the suction side superheat increases to a certain degree due to the suction of the compressor with the refrigerant circulation shut off), the first on-off valve 5 is opened as shown by the broken line in FIG. To start the compressor 1
The transition to the normal operation state is performed smoothly in a state where the suction of the liquid refrigerant to the air is prevented.

Further, the controller 11 may cause damage to the compressor 1 due to a rapid rise in the internal temperature of the compressor which may occur when the expansion valve 3 is adjusted to the throttle side (refrigerant flow reduction side). On the other hand, as shown in FIG.
Is greater than the superheat degree So of the compressor discharge refrigerant R by more than the set tolerance α (for example, α = 15 ° deg) (Si> So + α), the compressor 1 is used as protection control.
Emergency stop of the operation.

That is, if the superheat degree Si of the compressor suction refrigerant R becomes lower than the set value due to the return of the confined refrigerant R in the refrigerant confinement section existing in the circuit H to the circulation system or a decrease in load, the expansion valve 3 Is adjusted to the throttle side. At this time, the degree of superheat Si of the compressor suction refrigerant R increases, and the internal temperature of the compressor 1 also increases due to the decrease of the suction refrigerant R which is a cooling factor of the compressor 1. Becomes

When this change is rapid and the temperature inside the compressor rises rapidly, the operating part inside the compressor expands more rapidly than the outer part, and the difference in thermal expansion causes the internal part of the compressor to expand. Of the compressor 1 may be damaged due to the contact of the working part with the outer shell part, whereas the comparison between the suction side superheat degree Si and the discharge side superheat degree So (Si> So + α?) By accurately judging a situation in which a rapid rise in the internal temperature of the compressor occurs, and stopping the operation of the compressor 1 in response to the abnormal situation, damage to the compressor 1 due to a rapid rise in the internal temperature of the compressor can be prevented. This is effectively prevented.

As described above, in the present embodiment, the superheat degree sensors 9 and 10 on the suction side and the discharge side detect the superheat degree Si of the refrigerant R sucked into the compressor 1 and the superheat degree So of the refrigerant R discharged from the compressor 1. A detecting means for detecting the signal;
Is determined when the superheat degree Si of the compressor suction refrigerant R is larger than the superheat degree So of the compressor discharge refrigerant R based on the detection information of the detection means, and the difference becomes larger than the set tolerance α. Construct protection control means for executing protection control.

[Another Embodiment] Next, another embodiment will be described. The specific circuit structure of the heat pump circuit H is not limited to the structure as shown in FIG. 1 and can be variously changed. For example, a plurality of evaporators or a plurality of condensers connected in series or in parallel are connected. A structure including a four-way valve or the like may be used to switch between a state in which the heat exchanger functions as an evaporator and a state in which the heat exchanger functions as a condenser.

The expansion valve 3 is not limited to a mechanical automatic expansion valve. For example, an electronically controlled expansion valve may be used.
Various types of expansion valves can be used.

Whether or not the superheat degree Si of the compressor suction refrigerant R is larger than the superheat degree So of the compressor discharge refrigerant R by the set tolerance α or more (Si> So + α), the sudden rise in the internal temperature of the compressor is determined. In order to determine whether or not a situation occurs, an appropriate value of the set tolerance α may be determined according to the heat pump circuit structure, operating conditions, and the like.

In the above-described embodiment, the operation of the compressor 1 is stopped as the protection control. However, in a case where the internal temperature of the compressor is relatively unlikely to rise, the expansion control may be used as the protection control in some cases. Control such as rapidly increasing the suction refrigerant amount of the compressor 1 by forcibly reducing the resistance of the valve circuit portion may be employed.

Further, when the superheat degree Si of the compressor suction refrigerant R becomes larger than the superheat degree So of the compressor discharge refrigerant R by more than the set tolerance α (Si> So + α), predetermined protection control such as compressor stop is performed. In addition to the above, the protection methods described in (a) to (c) above may be used in combination for the purpose of protecting the compressor against other abnormal situations.

The compression heat pump according to the present invention may be any one such as one using the heat generated in the condenser for heating, heating various objects or melting snow, and one using the cold generated in the evaporator for cooling or cooling various objects. Such applications may be used.

[Brief description of the drawings]

FIG. 1 is a diagram showing a device configuration.

FIG. 2 is a diagram showing a control mode of an on-off valve;

FIG. 3 is a diagram showing a control flow.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor 2 Condenser 3 Expansion valve 4 Evaporator 9,10 Detecting means 11 Protection control means R Refrigerant Si Superheat degree of compressor suction refrigerant So Superheat degree of compressor discharge refrigerant α Setting tolerance

Claims (2)

[Claims] 1. A compression heat pump that circulates refrigerant in the order of a compressor, a condenser, an expansion valve, and an evaporator, wherein a degree of superheat of refrigerant sucked into the compressor and a degree of superheat of refrigerant discharged from the compressor are provided. Detecting means for detecting the detected refrigerant, based on the detection information of the detecting means, when the degree of superheat of the suction refrigerant is larger than the degree of superheat of the discharge refrigerant and the difference is larger than a set tolerance, a predetermined protection. A compression heat pump provided with protection control means for performing control. 2. The protection control means according to claim 1, wherein the operation of the compressor is stopped as the protection control.
A compression heat pump as described.