JP2001296077A - Compression type heat pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent compressor suction pressure from being abnormally lowered while effectively performing defrosting operation or deicing operation. SOLUTION: In a defrosting or deicing operation in which a heat exchanger 2 on which frosting or ice deposition happen in an operation as an evaporator E acts as a condenser C by switching of refrigerant circulation passage, there is provided a bypass passage 9 for short-circuitting a high pressure side liquid refrigerant passage a to a extending from an outlet of the beat exchanger up to expansion means vaporized refrigerant suction passage b to a compressor 4. A valve S3 is interposed on the bypass passage 9, and further control means 8 for controlling the valve 3 on the basis of detection information of suction pressure Pi such that the suction pressure Pi of the compressor 4 is kept at a proper value in defrosting or deicing operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compression heat pump, and more particularly, to the case where frost or icing occurs on a heat exchanger as an evaporator that absorbs heat from a heat source such as air or water.
The present invention relates to a compression heat pump for performing a defrosting or deicing operation in which the heat exchanger functions as a condenser by switching a refrigerant circulation path.

[0002]

2. Description of the Related Art In a compression heat pump of this type, during the above-mentioned defrosting or deicing operation, a cooling operation of frost or ice is performed on a heat exchanger to be defrosted or deiced which is switched from an evaporator to a condenser. However, if the amount of the refrigerant is large, the safety device is activated against the abnormal decrease of the suction pressure of the compressor due to the large amount of the refrigerant, and the operation of the heat pump is forcibly automatically stopped (so-called Low pressure cut).

Conventionally, in order to prevent such automatic stop from occurring frequently and to stabilize the defrosting or deicing operation, the defrosting or deicing operation is performed in comparison with other normal operations. The output of the compressor has been reduced, and the amount of refrigerant charged into the refrigerant circuit has been increased in advance.

[0004]

However, if the output of the compressor is reduced during the defrosting or deicing operation, the amount of heat generated per unit time in the heat exchanger to be defrosted or deiced (as a condenser). Of the heat pump), the time required for defrosting and deicing becomes longer, which limits the operation of the normal operation in which the heat exchanger functions as an evaporator, and lowers the effective operation rate of the heat pump. There was a problem.

On the other hand, when the amount of refrigerant charged into the refrigerant circuit is increased in advance, the automatic stop (so-called high-pressure cut) due to an abnormal rise in the compressor discharge pressure during normal operation is performed.
Liquid refrigerant is sucked into the compressor when the heat exchanger is switched to the evaporator because the amount of refrigerant accumulated in the heat exchanger to be defrosted or deiced becomes large. (So-called liquid back) is liable to occur.

In view of this situation, the main problems of the present invention are:
A reasonable improvement is to effectively prevent an abnormal decrease in compressor suction pressure during defrosting or deicing operation, while avoiding the above-mentioned secondary problems in the conventional type.

[0007]

Means for Solving the Problems [1] In the invention according to the first aspect, a heat exchanger in which frost or icing has occurred during operation as an evaporator is made to function as a condenser by switching a refrigerant circulation path. In the frost or deicing operation, a bypass path is provided to short-circuit the high-pressure side liquid refrigerant path from the outlet of the heat exchanger to the expansion means to the evaporative refrigerant suction path to the compressor, and a valve is provided in this bypass path. A control means is provided for controlling the valve based on the suction pressure detection information so as to maintain the suction pressure of the compressor at an appropriate value in the defrosting or deicing operation.

That is, according to this configuration, during the defrosting or deicing operation, the refrigerant stays in the heat exchanger to be defrosted or deiced switched from the evaporator to the condenser due to the frost or ice cooling action. And the suction pressure of the compressor tends to decrease due to this. On the other hand, the pressure of the high-pressure side liquid refrigerant path is increased through the bypass path, and the evaporative refrigerant suction path to the compressor (that is, By short-circuiting to the refrigerant path between the outlet of the evaporator and the suction port of the compressor, it is possible to prevent an abnormal decrease in the compressor suction pressure.

[0009] By controlling the valve interposed in the bypass passage by the control means based on the detection information of the suction pressure of the compressor, and controlling the short-circuit pressure induction through the bypass passage, excessive Prevents excessive increase in compressor suction pressure due to pressure induction, and prevents insufficient increase in compressor suction pressure due to insufficient pressure.This ensures accurate and stable compressor suction pressure during defrosting or deicing operation. Can be maintained.

[0010] Further, the above-described pressure guiding through the bypass passage is performed from the liquid refrigerant passage on the high pressure side between the outlet of the heat exchanger to be defrosted or deiced and the expansion means, so that the defrosting or deicing target is removed. The refrigerant flow in the heat exchanger can be effectively promoted by the compressor suction pressure applied in a short-circuit manner to the outlet of the heat exchanger through the bypass path, whereby the heat exchange in the heat exchanger to be defrosted or deiced is performed. A large heat value (heat value as a condenser) can be secured, and accumulation of refrigerant in the heat exchanger can be reduced.

From these facts, according to the above configuration, the problem in the above-mentioned conventional method, that is, the time required for defrosting and deicing due to a decrease in the amount of heat generated in the heat exchanger to be defrosted or deiced is reduced. Becomes longer, conversely, automatic stop due to abnormal rise in compressor discharge pressure is more likely to occur, the amount of refrigerant accumulated in the heat exchanger to be defrosted or deiced becomes larger, and the heat exchanger evaporates. While preventing the problem that the liquid back trouble easily occurs when switching to the compressor, it is possible to effectively prevent the abnormal reduction of the compressor suction pressure during the defrosting or the defrosting operation, and perform the defrosting or the defrosting operation. It can be implemented stably.

[2] In the invention according to the second aspect, the first aspect
In the implementation of the invention according to the above, in the defrosting or deicing operation, the valve is opened when the detected value of the compressor suction pressure is less than a set lower limit, and the detection of the compressor suction pressure When the value is equal to or greater than the set lower limit, the valve is closed.

In other words, in order to control the short-circuit pressure induced through the bypass as described above, one method is to proportionally adjust and control the opening of the valve in accordance with the detected value of the compressor suction pressure. Although the type can be considered, compared to this, with the above configuration, the valve can be simply opened and closed, so the valve interposed in the bypass path and the control means for that valve can be simplified, Thus, while obtaining the above-described effects of the first aspect of the present invention, the increase in apparatus cost due to the improvement can be reduced.

[3] According to the third aspect of the present invention, the first aspect
Or in the embodiment of the invention according to 2, in a different mode operation in which the heat exchanger is removed from the refrigerant circulation path, the heat exchanger is connected to the evaporative refrigerant suction path to the compressor through the bypass path. A bypass path is provided, and the control means controls the valve based on detection information of the degree of superheat so that the degree of superheat of the refrigerant sucked in the compressor is maintained at an appropriate value in the another mode operation.

That is, in another mode operation in which the heat exchanger is disconnected from the refrigerant circulation path (that is, an operation in which circulation of the circulating refrigerant to the heat exchanger is interrupted), the heat exchanger is operated by the previous operation mode. A state in which a large amount of the refrigerant is sealed may cause a situation in which the effective circulation amount of the refrigerant is greatly reduced.

On the other hand, with the above configuration, in another mode operation, the refrigerant sealed in the heat exchanger can be returned to the refrigerant circulation path by the suction pressure of the compressor through the bypass path. Effective circulation amount can be recovered.

In the other mode of operation, when the refrigerant sealed in the heat exchanger is returned to the evaporative refrigerant suction path to the compressor through the bypass path, the superheat degree of the compressor suction refrigerant is maintained at an appropriate value. Since the control means controls the valve interposed in the bypass passage based on the detection information of the degree of superheat, for example, a fixed throttle having a large resistance for safety is interposed in the refrigerant recovery passage corresponding to the bypass passage. As a result, the refrigerant in the compressor can be reliably prevented from being sucked in the liquid-phase refrigerant (liquid back) caused by the enclosed refrigerant being returned to the evaporative refrigerant suction passage at a stretch, while efficiently collecting the enclosed refrigerant.

In the defrosting or deicing operation, the bypass used for the short-circuit pressure introduction and the valve interposed in the bypass are provided as follows:
In the above-mentioned other mode operation, by using as a refrigerant path and a valve for collecting the enclosed refrigerant, a dedicated refrigerant for collecting the enclosed refrigerant which is different from the bypass path and the valve used for short-circuit pressure induction in the defrosting or deicing operation. The apparatus can be simplified and the apparatus cost can be reduced as compared with the case where a path or a dedicated valve is provided.

[4] In the invention according to claim 4, claim 3
In the implementation of the invention according to the, the control means, when performing an operation to function the heat exchanger as an evaporator after the defrosting or deicing operation, performing the separate mode operation prior to the operation, The operation mode is automatically switched so as to shift from the other mode operation to an operation in which the heat exchanger functions as an evaporator.

That is, in the defrosting or deicing operation, the suction pressure of the compressor is short-circuited to the outlet of the heat exchanger to be defrosted or deiced through the bypass path as described above, so that the refrigerant in the heat exchanger is removed. Even if the accumulation of water is reduced, the fact that the refrigerant tends to accumulate due to the cooling action of frost or ice in the heat exchanger to be defrosted or deiced cannot be avoided. After the operation (especially after the defrosting or deicing operation is stopped in the middle due to the low pressure cut or the like described above), if the operation is directly shifted to the operation in which the heat exchanger to be defrosted or deiced functions as an evaporator, the heat The accumulated refrigerant in the exchanger becomes a state where it is sucked into the compressor at a stretch,
There is a possibility that a trouble that the liquid-phase refrigerant is sucked into the compressor may occur.

On the other hand, when performing the operation for functioning the heat exchanger, which has been the object of defrosting or deicing, as an evaporator after the defrosting or deicing operation as described above, prior to the operation, the above-mentioned separate mode is used. If the operation is performed and the operation is shifted from the other mode operation to an operation in which the heat exchanger functions as an evaporator, the recovery of the enclosed refrigerant as described above in the other mode operation using the bypass path as the refrigerant recovery path. (That is, recovery of the refrigerant accumulated in the heat exchanger in the deicing or deicing operation)
In the subsequent operation in which the heat exchanger functions as an evaporator, it is possible to reliably avoid the liquid-phase refrigerant suction trouble of the compressor caused by the suction of the accumulated refrigerant.

In the embodiment of the invention according to the fourth aspect, either the case where the defrosting or deicing operation is normally completed or the case where the defrosting or deicing operation is automatically stopped (ie, abnormally stopped) during the operation. In the case of, also in the form of shifting to the operation in which the heat exchanger that was the object of defrosting or deicing functions as an evaporator after passing through another mode operation, or when the defrosting or deicing operation ends normally Moves to an operation in which the heat exchanger that was the object of defrosting or deicing functions as an evaporator without going through another mode operation because the risk of suction of liquid refrigerant from the compressor is low. Alternatively, only when the deicing operation is automatically stopped (abnormal stop) in the middle, the mode in which the heat exchanger that has been the object of defrosting or deicing is switched to the operation of functioning as an evaporator after another mode operation is performed. You may take it.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a two heat source heat pump device which generates heat using water W and air A as heat source heat medium.
Is a water heat exchanger for exchanging heat between water W as a heat source heat medium (for example, water circulated to an underground heat exchanger and subjected to ground heat exchange) and a refrigerant R, and 2 is the other heat source heat medium. An air heat exchanger for exchanging heat between the air A (generally atmospheric air) and the refrigerant R, and the heat exchanger 3 for heat exchange between the refrigerant R and the load-side heat medium L (for example, water or brine circulated through the heat exchanger for snow melting). This is the load side heat exchanger to be replaced.

Reference numeral 4 denotes a compressor, 5 denotes an expansion valve, 6 denotes a refrigerant guide circuit in which four check valves 6a to 6d are combined in a bridge circuit, 7 denotes a receiver, and these and the above three heat exchangers 1, A heat pump circuit is formed by using the components 2 and 3 as main components.

Reference numeral 8 denotes a control device for switching the refrigerant circulation path and adjusting the compressor 4. In this heat pump device, three four-way valves V1 to V3 and two on-off valves S1,
By switching the refrigerant circulation path with S2, the following first to eighth modes (A) to (H) can be selected and executed.

(A) First mode: water heat source mode In this mode, as shown in FIG. 2, a refrigerant R is supplied to a compressor 4-first four-way valve V1-load-side heat exchanger 3-refrigerant guide circuit 6-receiver 7- Expansion valve 5-refrigerant guide circuit 6-second four-way valve V2
-Circulating in the order of the water heat exchanger 1-the third four-way valve V3-the compressor 4;

That is, by this refrigerant circulation, the water heat exchanger 1 functions as the evaporator E and the load-side heat exchanger 3 functions as the condenser C, whereby heat is taken from the water W in a load corresponding operation. The heat medium L on the load side is heated in the form of (endothermic).

(B) Second mode: two heat source modes (air →
In this mode, as shown in FIG. 3, in this mode, the refrigerant R is supplied to the compressor 4-first four-way valve V1-load-side heat exchanger 3-refrigerant guide circuit 6-receiver 7-expansion valve 5-refrigerant guide circuit 6-second. Four-way valve V2
-Air heat exchanger 2-first on-off valve S1-water heat exchanger 1
-Circulate in the order of the third four-way valve V3-compressor 4.

In other words, the circulation of the refrigerant allows the air heat exchanger 2 and the water heat exchanger 1 to function as an evaporator E in a serial arrangement in that order, and the load side heat exchanger 3 functions as a condenser C. As a result, the load-side heat medium L is heated in the form of taking heat (absorbing heat) from the air A and the water W as a load-responsive operation.

(C) Third mode: air heat source mode In this mode, as shown in FIG. 4, the refrigerant R is supplied to the compressor 4-first four-way valve V1-load-side heat exchanger 3-refrigerant guide circuit 6-receiver 7- Expansion valve 5-refrigerant guide circuit 6-second four-way valve V2
-Air heat exchanger 2-first four-way valve V1-third four-way valve V3
Circulating in the order of the compressor 4;

In other words, the circulation of the refrigerant allows the air heat exchanger 2 to function as the evaporator E and the load side heat exchanger 3 to function as the condenser C. The heat medium L on the load side is heated in the form of (endothermic).

(D) Fourth mode: two heat source modes (water → air) In this mode, as shown in FIG. 5, refrigerant R is supplied to compressor 4-first four-way valve V1-load-side heat exchanger 3-refrigerant guide circuit. 6-Receiver 7-Expansion valve 5-Refrigerant guide circuit 6-Second four-way valve V2
-Water heat exchanger 1-Third four-way valve V3- Second four-way valve V2-
Heat exchanger against air 2-first four-way valve V1-third four-way valve V3-
Circulation is performed in the order of the compressor 4.

That is, this refrigerant circulation allows the heat exchanger for water 1 and the heat exchanger for air 2 to function as an evaporator E together in a serial arrangement in that order, while the load side heat exchanger 3 functions as a condenser C. As a result, the load-side heat medium L is heated in the form of taking heat (absorbing heat) from the water W and the air A as a load-responsive operation.

(E) Fifth mode: Defrosting / load handling mode In this mode, as shown in FIG. 6, the refrigerant R is supplied to the compressor 4-first four-way valve V1-air heat exchanger 2-second four-way valve V2. -The third four-way valve V3-the first four-way valve V1-the load side heat exchanger 3-the refrigerant guide circuit 6-the receiver 7-the expansion valve 5-the refrigerant guide circuit 6
-Second four-way valve V2- to water heat exchanger 1-third four-way valve V3-
Circulation is performed in the order of the compressor 4.

That is, by this refrigerant circulation, the water heat exchanger 1 functions as the evaporator E, and the air heat exchanger 2 and the load side heat exchanger 3 function as the condenser C in a serial arrangement in this order. As a result, the defrosting of the air heat exchanger 2 is performed while heating the load-side heat medium L in a mode of collecting heat (absorbing heat) from the water W as an operation that combines load handling and defrosting.

(F) Sixth mode: water heat source defrosting mode In this mode, as shown in FIG. 7, the refrigerant R is supplied to the compressor 4-first four-way valve V1-air heat exchanger 2-second on-off valve S2- Receiver 7-expansion valve 5-refrigerant guide circuit 6-second four-way valve V2
-Circulating in the order of the water heat exchanger 1-the third four-way valve V3-the compressor 4;

That is, by the circulation of the refrigerant, the water heat exchanger 1 functions as the evaporator E and the air heat exchanger 2 functions as the condenser C, thereby collecting heat from the water W as a defrosting operation. The defrosting of the air heat exchanger 2 is performed in a (heat absorbing) mode.

(G) Seventh mode: Two heat source defrosting mode In this mode, as shown in FIG. 8, the refrigerant R is supplied to the compressor 4-first four-way valve V1-air heat exchanger 2-second four-way valve V2- Refrigerant guide circuit 6-Receiver 7-Expansion valve 5-Refrigerant guide circuit 6
-Load side heat exchanger 3-First four-way valve V1-Third four-way valve V3
-Second four-way valve V2- to water heat exchanger 1-third four-way valve V3-
Circulation is performed in the order of the compressor 4.

That is, the refrigerant circulation allows the load side heat exchanger 3 and the water heat exchanger 1 to function as an evaporator E in a serial arrangement in that order, and the air heat exchanger 2 functions as a condenser C. Thereby, the defrosting of the air heat exchanger 2 is performed as a defrosting operation by collecting heat (absorbing heat) from the load-side heat medium L and the water W.

(H) Eighth mode: load side heat source defrosting mode In this mode, as shown in FIG. 9, the refrigerant R is supplied to the compressor 4-first four-way valve V1-air heat exchanger 2-second four-way valve V2. -Refrigerant guide circuit 6-receiver 7-expansion valve 5-refrigerant guide circuit 6
-Load side heat exchanger 3-First four-way valve V1-Third four-way valve V3
Circulating in the order of the compressor 4;

That is, by the circulation of the refrigerant, the load side heat exchanger 3 functions as the evaporator E and the air heat exchanger 2 functions as the condenser C. As a result, the load side heat medium L is used as a defrosting operation. The defrosting of the air heat exchanger 2 is performed in a mode of collecting heat (absorbing heat).

In order to form the refrigerant circuit, a circuit portion serving as a high-pressure side liquid refrigerant path in the fifth mode (see FIG. 6) (that is, a portion from the outlet of the air heat exchanger 2 to the expansion valve 5). Out of the second four-way valve V2 to the third four-way valve V3, and a circuit portion which also serves as a vapor refrigerant suction path to the compressor 4 in the fifth mode (that is, the compressor is connected to the outlet of the water heat exchanger 1 through the outlet). Of the fourth four-way valve V
A bypass path 9 for short-circuiting the two points a and b is provided between the point 3 and the point b extending from the suction port of the compressor 4 to the compressor b.
Further, a third on-off valve S3 is interposed in the bypass passage 9.

Then, with respect to the equipment of the bypass path 9,
In the case of the operation in the fifth mode, as shown in FIG. 10, when the suction pressure Pi of the compressor 4 detected by the pressure sensor 10 becomes less than the set lower limit value Px, the control device 8 operates the third on-off valve S.
3 and the detected suction pressure Pi is equal to the set lower limit P
When x or more, the valve control for closing the third on-off valve S3 is executed.

That is, in the fifth mode (see FIG. 6) in which the defrosting operation and the load corresponding operation are performed in parallel, the refrigerant R stays in the air heat exchanger 2 to be defrosted due to the frost cooling action. Further, making the load-side heat exchanger 3 function as a condenser is a contributing factor, and the suction pressure P of the compressor 4 is increased.
In response to the fact that i is greatly reduced, by controlling the opening and closing of the third on-off valve S3 based on the detection of the compressor suction pressure Pi as described above, the pressure of the high-pressure side liquid refrigerant passage is reduced by the compressor 4 through the bypass passage 9. In this manner, the compressor suction pressure Pi is kept at an appropriate value by short-circuiting to the evaporative refrigerant suction passage to the suction passage, thereby preventing a trouble of abnormal reduction of the suction pressure Pi.

Further, in the first mode (see FIG. 2) in which the air heat exchanger 2 is disconnected from the refrigerant circulation path, the bypass path 9 transfers the air heat exchanger 2 in the cutoff state of the circulating refrigerant to the compressor 4. In contrast, in the case of operation in the first mode, the control device 8 detects the superheat degree sensor 11 as shown in FIG. 11 when operating in the first mode. When the superheat degree SH of the compressor suction refrigerant R rises above the set high threshold value SHA, the third on-off valve S3 is opened, and when the detected superheat degree SH falls below the set low threshold value SHb, the third on-off valve S3 is closed. It performs a hysteresis type valve control.

In other words, in the first mode (see FIG. 2) in which the air heat exchanger 2 is disconnected from the refrigerant circulation path, a large amount of the refrigerant R is sealed in the air heat exchanger 2 by the previous operation mode. In some cases, the effective circulation amount of the refrigerant R is greatly reduced.
By performing the opening / closing control of the third opening / closing valve S3 based on the detection of H, the refrigerant refrigerant R ′ in the air heat exchanger 2 is returned to the refrigerant circulation path while reliably avoiding the liquid refrigerant suction trouble of the compressor 4. Thus, the effective circulation amount of the refrigerant R is restored to an appropriate amount.

The control device 8 operates in the fifth to eighth modes in which the air heat exchanger 2 functions as the condenser C to perform defrosting, and the compressor suction pressure P during the operation.
If there is an automatic operation stop (abnormal stop by the safety device) due to an abnormal decrease in x, etc., then, the load corresponding operation in the second to fourth modes (that is, the air heat exchanger 2 is set as the evaporator E) When resuming the operation to function, the operation in the first mode is first performed for a predetermined time, and then the operation mode is changed from the first mode to the desired operation in the second to fourth modes. It switches automatically.

In other words, when the load corresponding operation in the second to fourth modes is restarted, the first mode operation is performed and the above-described refrigerant recovery is performed by performing the first mode operation. A trouble that may occur when the load corresponding operation is suddenly performed in the second to fourth modes after the abnormal stop in the eight-mode defrost operation, that is, the air heat is stopped at the time of the abnormal stop in the previous defrost operation. The refrigerant R 'that has accumulated in the exchanger 2 is switched to the second to fourth modes in which the air heat exchanger 2 functions as the evaporator E, and the compressor 4
Thus, it is possible to reliably prevent the liquid refrigerant from being sucked into the compressor 1 due to the state of being sucked into the compressor.

When the defrosting operation in the fifth to eighth modes is completed normally, the second to second modes are not executed without passing through the first mode except when the first mode itself is the target mode.
The operation shifts to the load corresponding operation in the fourth mode.

The normal mode switching except for the automatic mode switching when the abnormal stop is performed in the defrosting operation of the fifth to eighth modes is performed by detecting the temperature of the heat source heat medium W, A or detecting the temperature of each part of the heat pump circuit. It is performed automatically (or according to an artificial command) based on temperature, pressure, etc.

As described above, in the heat pump apparatus according to the present embodiment, the heat exchanger
In the defrosting operation (operation in the fifth mode) in which the (air-to-air heat exchanger) functions as the condenser C by switching the refrigerant circulation path, the expansion means 5 is provided from the outlet of the heat exchanger 2.
A bypass passage 9 for short-circuiting the liquid refrigerant passage on the high pressure side to the (expansion valve) to the evaporative refrigerant suction passage to the compressor 4 is provided, and a valve V3 (third on-off valve) is interposed in the bypass passage 9. It is.

The bypass passage 9 allows the heat exchanger 2 to pass through the bypass passage 9 to the compressor 4 in another mode operation (operation in the first mode) in which the heat exchanger 2 is disconnected from the refrigerant circulation path. Are connected to the evaporative refrigerant suction passage of the first embodiment.

Then, in the defrosting operation (operation in the fifth mode), the valve V3 based on the detection information of the suction pressure Pi so as to maintain the suction pressure Pi of the compressor 4 at an appropriate value.
And controls the valve V3 based on the detection information of the superheat degree SH so as to keep the superheat degree SH of the compressor suction refrigerant R at an appropriate value in the other mode operation (operation in the first mode). Control means 8 (control device) for performing the control.

[Another Embodiment] Next, another embodiment of the present invention will be described. FIG. 12 shows an example in which the invention according to claim 1 is applied to a compression heat pump including two heat exchangers N1 and N2. In this heat pump, the first heat exchanger N1 functions as a condenser C, and An operation in which the second heat exchanger N2 functions as the evaporator E, and conversely, an operation in which the first heat exchanger N1
Is operated as an evaporator E, and the second heat exchanger N2 is operated as a condenser C. Defrosting or deicing operation is selectively performed by switching the four-way valve V.

In the above defrosting or deicing operation, the high-pressure side liquid refrigerant path from the outlet of the second heat exchanger N2 to the expansion means 5 such as an expansion valve or a capillary tube passes through the evaporative refrigerant to the compressor 4. A bypass path 9 that short-circuits the suction path is provided, and a valve S interposed in the bypass path 9 is controlled to a suction pressure Pi of the compressor 4 so that the suction pressure Pi of the compressor 4 is maintained at an appropriate value during defrosting or deicing operation. Control means 8 based on the detection information
Is controlled by

In addition, the present invention can be applied to compression heat pumps having various circuit structures.

In the heat pump device shown in the above-described embodiment, as shown in FIG.
b, thereby providing the suction pressure Pi of the compressor 4 for each of the defrosting operations in the fifth to eighth modes.
The third opening / closing valve S3 may be controlled by the control means 8 based on the detection information of the suction pressure Pi so as to keep the pressure at a proper value.

The target heat exchanger in which the bypass according to the first aspect of the present invention is located on the outlet side in the operation as a condenser is a device in which air is subjected to heat exchange (that is, defrosting is performed in the operation as an evaporator). However, the present invention is not limited to this, and may be one in which water or an aqueous solution is subjected to heat exchange (that is, deicing by operation as an evaporator).

In the defrosting operation or the deicing operation, the control of the valve interposed in the bypass passage based on the detection information of the compressor suction pressure Pi is performed in place of the control method shown in the above-described embodiment. When the pressure falls below the set low threshold, the valve is opened, and when the detected suction pressure Pi rises above the set high threshold, the valve is closed, so that a hysteresis control may be performed. Alternatively, the control for proportionally adjusting the opening of the valve may be performed.

In another mode operation in which the heat exchanger removed from the refrigerant circulation path is connected to the evaporative refrigerant suction path to the compressor through the bypass path, the valve interposed in the bypass path is used to overheat the refrigerant sucked in the compressor. In order to control based on the detection information of the degree SH, instead of the control method described in the above-described embodiment, control may be performed to proportionally adjust the opening degree of the valve according to the detected superheat degree SH. Further, control may be performed such that the valve is opened when the detected superheat degree SH is equal to or more than the set value, and the valve is closed when the detected superheat degree SH is less than the set value.

Further, a temperature-sensitive or electronic expansion valve unitized with control means is used as a valve for opening and closing control in accordance with the detected superheat degree SH in another mode operation by interposing the bypass passage. In some cases, a valve that controls opening and closing based on detection information of the compressor suction pressure Pi in defrosting or deicing operation, and a valve that controls opening and closing based on detection information of the degree of superheat SH in another mode operation. May be separately provided, and the valves may be interposed in the bypass passage.

The application of the compression heat pump to which the present invention is applied may be any application such as snow melting, air conditioning, or temperature control of articles.

[Brief description of the drawings]

FIG. 1 is a diagram showing a circuit structure of a heat pump.

FIG. 2 is a diagram showing a refrigerant path in a first mode.

FIG. 3 is a diagram showing a refrigerant path in a second mode.

FIG. 4 is a diagram showing a refrigerant path in a third mode.

FIG. 5 is a diagram showing a refrigerant path in a fourth mode.

FIG. 6 is a diagram showing a refrigerant path in a fifth mode.

FIG. 7 is a diagram showing a refrigerant path in a sixth mode.

FIG. 8 is a diagram showing a refrigerant path in a seventh mode.

FIG. 9 is a diagram showing a refrigerant path in an eighth mode.

FIG. 10 is a graph showing a control mode of a bypass passage interposed valve in a fifth mode.

FIG. 11 is a graph showing a control mode of the bypass passage interposed valve in the first mode.

FIG. 12 is a circuit diagram showing another embodiment.

FIG. 13 is a circuit diagram showing another embodiment.

[Explanation of symbols]

 2 Heat exchanger 4 Compressor 5 Expansion means 8 Control means 9 Bypass path C Condenser E Evaporator Pi Compressor suction pressure S3 Valve SH Compressor suction superheat degree a High pressure side liquid refrigerant path b Evaporation refrigerant suction path

Claims (4)

[Claims] 1. A defrosting or deicing operation in which a heat exchanger that has formed frost or icing during operation as an evaporator functions as a condenser by switching a refrigerant circulation path, and expands from an outlet of the heat exchanger. A bypass path for short-circuiting the high-pressure side liquid refrigerant path to the compressor to the evaporative refrigerant suction path to the compressor, a valve is interposed in the bypass path, and the compressor is used in the defrosting or deicing operation. A compression heat pump provided with control means for controlling the valve based on detection information of the suction pressure so as to maintain the suction pressure at an appropriate value. 2. The control device according to claim 1, wherein the valve is opened when the detected value of the compressor suction pressure is less than a set lower limit in the defrosting or deicing operation, and the detected value of the compressor suction pressure is reduced. 2. The compression heat pump according to claim 1, wherein the valve is closed when the value becomes equal to or more than a set lower limit. 3. In another mode operation in which the heat exchanger is disconnected from the refrigerant circulation path, the bypass path is arranged so that the heat exchanger is connected to the evaporative refrigerant suction path to the compressor through the bypass path. The control means is configured to control the valve based on detection information of the degree of superheat so that the degree of superheat of the refrigerant sucked in the compressor is maintained at an appropriate value in the another mode operation.
Or the compression heat pump according to 2. 4. When performing an operation of causing the heat exchanger to function as an evaporator after the defrosting or deicing operation, the control means performs the another mode operation prior to the operation, The compression heat pump according to claim 3, wherein an operation mode is automatically switched so as to shift from a mode operation to an operation in which the heat exchanger functions as an evaporator.