JP2016196975A - Refrigeration cycle device and expansion valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refrigeration cycle device preventing failure, such as fault of a compressor, from occurring even when used in a refrigerant R410A.SOLUTION: A refrigerant used in a refrigeration cycle is R32. An outdoor expansion valve 13 makes a ratio of a flow rate of a refrigerant to opening change of the outdoor expansion valve 13 relatively small in a low-opening region part 42b whose opening is relatively low, and makes the ratio of the flow rate of the refrigerant to the opening change of the outdoor expansion valve 13 larger in a high-opening region part 42a, whose opening is larger than that of the low-opening region part 42b, than that of the low-opening region part 42b.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a refrigeration cycle apparatus and an expansion valve.

  As background art of this technical field, there is JP 2012-189238 A (Patent Document 1). According to this publication, the refrigerant R32 has different thermal properties than the refrigerant R410A, and therefore it is necessary to control the refrigeration cycle apparatus in accordance with the thermophysical properties. And in patent document 1, when it changes into refrigerant | coolant R32 from refrigerant | coolant R410A, the discharge temperature of a compressor will rise by the difference in the thermophysical property, and the phenomenon that the refrigeration oil of the compressor of a refrigerating cycle will generate | occur | produce will occur. It has been proposed to provide a bypass circuit connected from the expansion valve to the compressor heat chamber through the refrigerant heat exchanger to suppress an increase in the discharge temperature of the compressor.

JP 2012-189238 A

  Patent Document 1 proposes an apparatus configuration corresponding to the characteristics of the refrigerant R32 from the viewpoint of thermophysical properties. However, according to the knowledge of the present inventors, the following facts have been clarified by the difference in flow rate characteristics between the refrigerant R32 and the refrigerant R410A. That is, the amount of the refrigerant R32 that passes through the expansion valve of the outdoor unit (hereinafter referred to as the outdoor expansion valve) is more specific than the refrigerant R410A due to the difference in the flow rate characteristics of the refrigerant. Accordingly, it has been found that when the same outdoor expansion valve as the model using the refrigerant R410A is used, the temperature of the refrigerant greatly fluctuates.

Thereby, in particular, when the outdoor expansion valve used for the refrigerant R410A is used in the heating operation when the outside air temperature at which the circulation amount of the refrigerant R32 passing through the outdoor expansion valve is small is low, the opening degree change of the outdoor expansion valve is changed. The ratio of the change in the flow rate of the refrigerant with respect to the refrigerant changes greatly, and the temperature of the refrigerant R32 discharged from the outdoor expansion valve rises abnormally, which may cause a situation where the compressor breaks down due to deterioration of the refrigerating machine oil.
Then, this invention makes it a subject to provide the refrigerating-cycle apparatus which does not produce malfunctions, such as a failure of a compressor, even if it uses it for refrigerant | coolant R410A.

  In order to solve the above-described problem, according to one aspect of the present invention, the expansion valve has a relatively small ratio of the flow rate of the refrigerant to the change in the opening of the expansion valve in the low opening region where the opening is relatively low. However, in the high opening region higher than the low opening region, the ratio of the flow rate of the refrigerant to the change in the opening of the expansion valve is larger than that in the low opening region.

According to the present invention, it is possible to provide a refrigeration cycle apparatus that does not cause problems such as a compressor failure even when used for the refrigerant R410A.
Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

FIG. 1 is a system diagram of a refrigeration cycle apparatus that is Embodiment 1 of the present invention. FIG. 2 is a graph showing the flow rate-discharge temperature characteristics of the refrigerant R410A and the refrigerant R32 by the outdoor expansion valve. FIG. 3 is a graph for explaining the expansion valve opening degree-expansion valve flow rate characteristic of the outdoor expansion valve of the refrigeration cycle apparatus that is Embodiment 1 of the present invention. FIG. 4 is a longitudinal sectional view of an outdoor expansion valve of the refrigeration cycle apparatus that is Embodiment 1 of the present invention. FIG. 5 is a system diagram of a refrigeration cycle apparatus that is Embodiment 2 of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a system diagram of a refrigeration cycle apparatus that is Embodiment 1 of the present invention. The refrigeration cycle apparatus 1 according to the present embodiment includes an outdoor unit 2 and an indoor unit 3. The refrigeration cycle apparatus 1 includes a compressor 11, a four-way valve 12, an outdoor expansion valve 13, an outdoor heat exchanger 14, an indoor heat exchanger 21, an indoor expansion valve 22 (an expansion valve for the indoor unit 3) and the like through a refrigerant pipe 31. Connected to form a refrigeration cycle. In the present embodiment, the refrigerant R32 is used as the refrigerant.

In FIG. 1, the compressor 11 is connected to the four-way valve 12 via a refrigerant pipe 31. The four-way valve 12 has a function of switching the connection with the compressor 11 to the gas blocking valve 32 side or the outdoor heat exchanger 14 side. The outdoor heat exchanger 14 is provided with an outdoor fan 15 that exchanges heat between the refrigerant and the outside air, and discharges the heat of the refrigerant R32 to the outside air in the cooling operation, and the outside air in the heating operation. It has a function of pumping heat to the refrigerant R32.
An outdoor expansion valve 13 is connected to the outdoor heat exchanger 14 via a refrigerant pipe 31, and the outdoor expansion valve 13 is further connected to a liquid blocking valve 33. The gas blocking valve 32 and the liquid blocking valve 33 are connected to the indoor unit 3 side by the refrigerant pipe 31.

  The outdoor expansion valve 13 includes an expansion valve main body 41 (FIG. 4) reciprocated by the pulse motor 16, and the expansion valve main body 41 can continuously adjust the amount of the refrigerant R32. That is, the number of pulses of the pulse motor 16 and the movement amount (reciprocation amount) of the expansion valve main body 41 are determined in advance, and for example, the expansion valve main body 41 moves by 0.1 mm in one pulse. In this case, it is sufficient to give 10 pulses when moving 1 mm. Of course, the number of pulses and the amount of movement of the expansion valve body 41 can be arbitrarily set. Furthermore, the relationship between the amount of reciprocation of the expansion valve body 41 and the flow rate of the refrigerant R32 can be determined by the axial sectional shape of the expansion valve body 41, which will be described later. That is, in this embodiment, the cross-sectional shape is determined by the flow rate characteristic of the refrigerant R32. The relationship between the flow rate characteristics, the valve opening degree of the expansion valve body 41 and the cross-sectional shape will be described later with reference to FIGS.

A temperature sensor 17 serving as a discharge temperature detection unit is provided on the upper portion of the compressor 11 and indirectly detects the discharge temperature of the refrigerant.
A temperature sensor 18 serving as an outside air temperature detection unit is attached to the outdoor heat exchanger 14 and detects the outside air temperature.
A control device 19 serving as a control unit controls the pulse motor 16 based on detection values of the temperature sensors 17 and 18 and the like.

  In the present embodiment, during the heating operation, the high-temperature and high-pressure gas refrigerant discharged from the compressor 11 passes through the four-way valve 12, the gas blocking valve 32, and the refrigerant pipe 31, as indicated by solid arrows in FIG. 3 is condensed in the indoor heat exchanger 21 to become a liquid refrigerant. This liquid refrigerant normally passes through the indoor expansion valve 22 in a fully opened state, then reaches the outdoor expansion valve 13 through the refrigerant pipe 31 and the liquid blocking valve 33, and is decompressed by the outdoor expansion valve 13 to be a low-temperature and low-pressure gas liquid. It becomes a mixed refrigerant. The decompressed refrigerant is evaporated by the action of the outdoor heat exchanger 14 and the outdoor fan 15, becomes a gas refrigerant, and returns to the compressor 11 via the four-way valve 12 again. In addition, the flow of the refrigerant during the cooling operation is indicated by a broken line (detailed description is omitted because it is publicly known).

  During the heating operation, the refrigerant discharge temperature is indirectly detected by the temperature sensor 17 provided at the upper part of the compressor 11 so as not to deviate from the operable range of the compressor 11, and the refrigerant discharge temperature from the compressor 11 is detected. Is feedback controlled for the degree of opening of the outdoor expansion valve 13 so as to converge to a predetermined target temperature. That is, since the refrigerant discharge temperature can be adjusted by controlling the opening degree of the outdoor expansion valve 13, as a result, the refrigerant discharge temperature of the compressor 11 can be controlled. Such control is performed by the control device 19.

By the way, according to the knowledge of the present inventors, the following facts have been clarified by the difference in the flow rate characteristics between the refrigerant R32 and the refrigerant R410A. That is, the amount of the refrigerant R32 that passes through the outdoor expansion valve has a specific characteristic compared to the refrigerant R410A due to the difference in the flow rate characteristics of the refrigerant, and thus, a model using the refrigerant R410A as the outdoor expansion valve. It was found that the refrigerant temperature fluctuated greatly when the same outdoor expansion valve was used.
Refrigerant R32 has a characteristic that it is easier to flow than refrigerant R410A, and as a result, the ratio of the change in the flow rate of the refrigerant to the change in the degree of opening of the outdoor expansion valve that controls the temperature of refrigerant R32 increases, and compared with refrigerant R410A, Depending on this flow rate change, the temperature change of the refrigerant R32 tends to increase.

In particular, when the outdoor expansion valve of the model used for the refrigerant R410A is used in the heating operation when the outside air temperature at which the circulation amount of the refrigerant R32 passing through the outdoor expansion valve decreases is low, the change in the opening degree of the outdoor expansion valve can be prevented. The rate of change in the flow rate of the refrigerant R32 changes greatly, and the temperature of the refrigerant R32 discharged from the outdoor expansion valve rises abnormally, which may cause a situation where the compressor breaks down due to deterioration of the refrigerating machine oil.
In general, in the heating operation, the opening of the outdoor expansion valve is feedback controlled as in the above example so that the compressor temperature becomes a predetermined temperature. However, as described above, the opening of the outdoor expansion valve is not controlled. Since the rate of change in the flow rate of the refrigerant R32 is large with respect to the change in temperature, the temperature of the refrigerant R32 greatly fluctuates accordingly.

  Therefore, even if feedback control is performed so that the refrigerant discharge temperature of the compressor converges to a predetermined temperature, when the opening of the outdoor expansion valve is small, the change in the refrigerant flow rate (= temperature) Therefore, it is difficult for the refrigerant discharge temperature of the compressor to fluctuate correspondingly and converge to the target temperature. For this reason, when the heating operation is performed, the blowout temperature of the indoor unit rises and falls and the user's comfort is impaired.

Below, the means for eliminating these malfunctions in the refrigeration cycle apparatus 1 will be described.
FIG. 2 is a graph showing the flow rate-discharge temperature characteristics of the refrigerant R410A and the refrigerant R32 by the outdoor expansion valve. FIG. 2 shows the refrigerant flow rate (expansion valve flow rate) flowing through the outdoor expansion valve and the refrigerant discharge temperature (discharge temperature) when the refrigerant R410A and the refrigerant R32 are used using the outdoor expansion valve having the same flow rate characteristics. ), And the rotation speed of the compressor is the same for both refrigerant R410A and refrigerant R32.

  From FIG. 2, it can be seen that, in the low opening region of the outdoor expansion valve where the expansion valve flow rate is small, the rate of temperature change of the discharge temperature is large and the gradient is large with respect to the flow rate change of the expansion valve flow rate of the refrigerant R32. On the other hand, it can be seen that when the refrigerant R410A is used, the rate of change in the temperature of the discharge temperature with respect to the change in the flow rate of the expansion valve is small, and the inclination thereof is small. Therefore, in order to raise the temperature of the refrigerant from a certain discharge temperature T1 to a higher discharge temperature T2, the refrigerant R32 measures a small amount of refrigerant, whereas the refrigerant R410A measures a large amount of refrigerant. Will do.

Although the flow rate change of the expansion valve flow rate varies depending on the opening degree of the expansion valve, since the pulse motor 16 is used in this embodiment, the temperature of the refrigerant R32 for each pulse of the pulse motor 16 during the feedback control. It turns out that a change is large compared with refrigerant | coolant R410A. That is, it can be seen that the change in the refrigerant discharge temperature due to the change in the expansion valve flow rate or the expansion valve opening in the low opening region is large.
For example, as shown in FIG. 2, when the expansion valve flow rate of the refrigerant R410A is G1, the expansion valve flow rate of the refrigerant R32 is G2, and compared at the same discharge temperature (T1), the expansion valve of the refrigerant R32 is compared with the refrigerant R410A. It can be seen that the flow rate is lower. This indicates that the refrigerant R32 causes a large temperature change with a small flow rate change.

  FIG. 3 is a graph for explaining the expansion valve opening-expansion valve flow rate characteristics of the outdoor expansion valve 13 of the first embodiment. FIG. 3 shows the opening (expansion valve opening) and flow rate (expansion valve) of the existing outdoor expansion valve (a1) used for the refrigerant R410A and the outdoor expansion valve 13 (a2) of Example 1 used for the refrigerant R32. It is the characteristic view which showed the relationship with (flow rate). From the characteristics shown in FIG. 2, when the existing outdoor expansion valve used in the refrigerant R410A is used as it is in the refrigerant R32, the outdoor expansion valve used in the refrigerant R410A has a large flow rate change with respect to the discharge temperature. Even in the low opening region, the flow rate changes greatly, making it difficult to stabilize the discharge temperature.

Therefore, in this embodiment, the outdoor expansion valve 13 corresponding to the flow rate characteristic of the refrigerant R32 as shown in FIG. 3 (a2) is used. Specifically, the surface shape of the expansion valve main body 41 can be determined according to the required refrigerant flow rate with respect to the movement amount (opening change) of the expansion valve main body 41 (FIG. 4) in accordance with the characteristics of a2 in FIG. That's fine.
In this embodiment, the outdoor expansion valve 13 corresponding to the refrigerant R32 has a low opening range shown in FIG. 3, and the change in the discharge temperature is reduced by reducing the rate of change in the expansion valve flow rate relative to the change in the expansion valve opening. It can be made smaller.

  Further, in the high opening range, the expansion valve flow rate and the refrigerant circulation amount (in the refrigeration cycle apparatus 1) are large, so that the refrigerant discharge temperature tends to be low, but even when the expansion valve flow rate and the refrigerant circulation amount are large, the refrigerant Since the discharge temperature may increase, it is not a good idea to reduce the flow rate of the expansion valve. For this reason, it is good to make it the shape which enlarges the inclination of the flow volume change of the refrigerant | coolant with respect to the opening degree change of the outdoor expansion valve 13 in a high opening degree area | region.

Below, the concrete structure of the outdoor expansion valve 13 based on the above knowledge, its control, etc. are demonstrated.
FIG. 4 is a longitudinal sectional view of the outdoor expansion valve 13 of the first embodiment. The expansion valve main body 41 of the outdoor expansion valve 13 includes a valve portion 42 and an operating shaft 43 fixed to the valve portion 42. The valve portion 42 is disposed to face the wall surface 44 of the refrigerant passage, and the flow rate of the refrigerant R32 can be controlled by the opening area between the valve portion 42 and the wall surface 44.

  The other end of the operating shaft 43 is engaged with the rotor of the pulse motor 16 by a screw action, that is, a screw part that is engaged with the screw part formed inside the rotor by a screw action is formed. (Not shown). Therefore, the operating shaft 43 that is screw-engaged as the rotor rotates can reciprocate up and down in FIG. Then, the rotor rotates in accordance with the number of pulses applied to the pulse motor 16, and the operation shaft 43 is reciprocated by an operation amount corresponding to the rotation.

On the surface of the valve portion 42, at least two regions of a high opening region 42a and a low opening region 42b having different cross-sectional shapes are formed. The low opening region 42b realizes the opening-flow rate characteristic of the low opening region shown in FIG. 3, and the high opening region 42a has the opening-flow rate characteristic of the high opening region shown in FIG. Realize. The cross-sectional shape of the surface of the high opening area portion 42a and the low opening area portion 42b of the valve portion 42 shown in FIG. 4 can be formed as a curve or a straight line (in the example of FIG. The portion 42b is linear, and the high opening region 42a is curved). The variation of the cross-sectional shape of the surface of the valve portion 42 along the longitudinal direction of the operating shaft 43 is formed such that the high opening region portion 42a changes more sharply than the low opening region portion 42b. ing. If the cross-sectional shape of the surface of the high opening area portion 42a and the low opening area portion 42b is a shape as shown in FIG. It can be realized in various ways.
Here, in this embodiment, the outdoor expansion valve 13 is provided with a lower limit opening and a plurality of upper limit openings in advance, and the control device 19 determines the upper limit opening based on the outside air temperature detected by the temperature sensor 18, and the outdoor expansion is performed. The opening degree control of the valve 13 is performed.

  For example, the lower limit opening EVOmin shown in FIG. 3 is an existing refrigeration cycle that uses the refrigerant R410A in order to prevent liquid return to the compressor 11 at the next startup due to the movement of the refrigerant R32 immediately after the operation of the refrigeration cycle apparatus 1 is stopped. The refrigerant flow rate is set to be the same as the expansion valve flow rate of the apparatus (a1 and a2 match). Further, the upper limit opening EVOmax1 shown in FIG. 3 is set to the same expansion valve flow rate as that of the existing refrigeration cycle apparatus using the refrigerant R410A in order to prevent an abnormal increase in the refrigerant discharge temperature in the high opening range (a1 and a2 matches). The upper limit opening EVOmax1 may be equal to or lower than the expansion valve flow rate of R410A.

  In the normal outside air temperature detected by the temperature sensor 18, the upper limit opening is EVOmax1, which is the upper limit opening in the high opening region. However, if the outside air temperature falls below a preset temperature, the upper limit opening is The control device 19 performs control to change from EVOmax1 to the upper limit opening EVOmax2. Here, “the upper limit opening EVOmax1> the upper limit opening EVOmax2”, and the upper limit opening EVOmax2 is the upper limit value in the low opening range and the lower limit value in the high opening range in FIG.

  Control of the change from the upper limit opening EVOmax1 to the upper limit opening EVOmax2 is performed when the outside air temperature at which the circulation amount of the refrigerant R32 passing through the outdoor expansion valve 13 is reduced is low as described above. That is, when the opening degree of the outdoor expansion valve 13 is controlled in a high opening range where the fluctuation of the expansion valve flow rate is large, the change in the discharge temperature of the refrigerant from the compressor 11 becomes large, and the refrigerating machine oil due to the abnormal increase in the discharge temperature This is performed in order to prevent a user's comfort failure due to a large change in the air conditioning temperature based on the deterioration of the air conditioner or the opening degree change of the outdoor expansion valve 13.

When changing the upper limit opening to EVOmax2, the number of steps of the pulse motor 16 from the lower limit opening EVOmin to the upper limit opening EVOmax2 is stored in advance, and the opening control of the outdoor expansion valve 13 by the control device 19 is performed. Since the current opening degree of the outdoor expansion valve 13 can be roughly estimated by the number of accumulated steps after the start (adding when opening the outdoor expansion valve 13 and subtracting when closing the outdoor expansion valve 13), by comparing these accumulated step numbers The opening can be adjusted within a range not exceeding the upper limit opening EVOmax2.
Further, a position sensor for detecting the position of the operating shaft 43 of the outdoor expansion valve 13 may be provided, and the control device 19 may control the opening degree within a range not exceeding the upper limit opening degree EVOmax2 by a detection signal from the position sensor. .

  According to the refrigeration cycle apparatus 1 of the present embodiment described above, the outdoor expansion valve 13 is used in a low opening region when the outside air temperature is low so that the heating operation is performed, but the valve portion of the outdoor expansion valve 13 is used. The ratio of the change in the flow rate of the refrigerant with respect to the change in the opening degree (the amount of movement of the valve part 42) of the low opening degree region part 42b formed in 42 is set to be small. Therefore, even when the refrigerant R32 is used, the temperature change of the refrigerant R32 during the heating operation can be reduced, and the deterioration of the refrigerating machine oil due to the abnormal increase in the discharge temperature of the refrigerant R32 from the compressor 11 can be suppressed. it can.

  In the high opening range, the discharge temperature of the refrigerant R32 tends to be low, but even if the expansion valve flow rate and the refrigerant circulation amount are large, the discharge temperature of the refrigerant R32 may increase, so the expansion valve flow rate should be reduced. Is not a good idea. Therefore, in the high opening region, the ratio of the change in the refrigerant flow rate with respect to the opening change of the high opening region portion 42a (the amount of movement of the valve portion 42) is increased.

  Further, in this embodiment, when the outside air temperature at which the circulation amount of the refrigerant R32 passing through the outdoor expansion valve 13 decreases is low, the change from the upper limit opening EVOmax1 to the upper limit opening EVOmax2 is controlled (FIG. 3). That is, when the opening degree of the outdoor expansion valve 13 is controlled in a high opening degree region where the fluctuation of the expansion valve flow rate is large, a change in the discharge temperature of the refrigerant from the compressor 11 becomes large, or due to an abnormal increase in the discharge temperature. It is possible to prevent the deterioration of the refrigerating machine oil and the poor comfort of the user due to a large change in the air conditioning temperature based on the change in the opening degree of the outdoor expansion valve 13.

  The opening degree of the outdoor expansion valve 13 is feedback-controlled so that the discharge temperature of the refrigerant R32 of the compressor 11 becomes a predetermined temperature. And since the ratio of the flow volume change of refrigerant | coolant R32 can be made small with respect to the opening degree change of the outdoor expansion valve 13 as mentioned above, the temperature fluctuation of refrigerant | coolant R32 accompanying this also becomes small. Therefore, even when feedback control is performed so that the discharge temperature of R32 of the compressor 11 converges to a predetermined temperature, it is easy to converge to the target temperature. For this reason, when performing the heating operation, it is possible to maintain the comfort of the user without the temperature of the indoor unit 3 blowing up and down extremely.

FIG. 5 is a system diagram of a refrigeration cycle apparatus that is Embodiment 2 of the present invention. In FIG. 5, the same reference numerals as those in the first embodiment are the same members as those in the first embodiment, and detailed description thereof is omitted. In the second embodiment, the refrigerant R32 is also used.
In the refrigeration cycle apparatus 1 according to the first embodiment, the feedback control that converges the refrigerant discharge temperature of the compressor 11 to the target value as described above is slow in following the change in the refrigerant discharge temperature. It is assumed that.
For this reason, in the present embodiment, the change in the refrigerant discharge temperature can be further reduced by controlling the opening degree of the outdoor expansion valve 13 so that the suction dryness of the compressor 11 converges to the target value. To.

That is, the refrigeration cycle apparatus 100 of FIG. 5 differs from the refrigeration cycle apparatus 1 of the first embodiment in that the temperature sensor 51 that detects the refrigerant temperature on the suction side of the compressor 11 and the refrigerant pressure on the suction side of the compressor 11 are different. The pressure sensor 52 to detect and the pressure sensor 53 to detect the refrigerant pressure on the discharge side of the compressor 11 are provided. In addition, the control device 19 includes a suction dryness calculation unit 19a that calculates the suction dryness of the refrigerant sucked into the compressor 11 based on the detection values of these sensors.
In this embodiment, the control device 19 feedback-controls the opening degree of the outdoor expansion valve 13 so that the suction dryness calculated by the suction dryness calculation unit 19a becomes a preset target value.

Here, in the general refrigeration cycle apparatus using the existing refrigerant R410A, the target suction dryness is controlled to be a value close to 1 in order to avoid the liquid return of the refrigerant to the compressor. However, when the refrigerant R32 is used, the discharge temperature of the refrigerant R32 discharged from the compressor is likely to rise. Therefore, when control is performed so that the suction dryness target value is the same as when the refrigerant R410A is used, There is a risk of deterioration of the refrigeration oil due to an abnormal rise in the temperature of the refrigerant discharged from the compressor and a user's comfort failure due to a large temperature change based on a change in the degree of opening of the outdoor expansion valve. In order to prevent this point, if the suction dryness is set to a value sufficiently smaller than 1, there is a concern that the refrigerant returns to the compressor.
Therefore, it is desirable to perform the feedback control of the suction dryness so that the suction dryness becomes, for example, about 0.7 to 0.9. Thereby, the liquid return of the refrigerant | coolant to the compressor 11 and the raise of the discharge temperature of the refrigerant | coolant from the compressor 11 can be suppressed.

Therefore, in this embodiment, the outdoor expansion valve to be used is the above-described outdoor expansion valve 13 (FIGS. 3 and 4) corresponding to the characteristics of the refrigerant R32 as in the first embodiment, and the flow rate characteristics of the outdoor expansion valve 13 are the same. In the same manner as in the first embodiment, the flow rate change with respect to the change in the opening amount is reduced in the low opening range, and the flow rate change with respect to the change in the opening amount is increased in the high opening range.
When the suction dryness is relatively small, the opening degree of the outdoor expansion valve 13 is controlled to the closed side, and when the suction dryness degree is close to 1, the opening degree of the outdoor expansion valve 13 is controlled to the opening side. Thus, feedback control can be performed so as to converge to the target suction dryness.
Further, similarly to the first embodiment, the lower limit opening and the upper limit opening of the outdoor expansion valve 13 are provided in advance, and the upper limit opening is selected from EVOmax1 and EVOmax2 (FIG. 3) according to the degree of suction dryness. Control of the valve 13 can also be implemented.

  For example, similarly to the first embodiment, the lower limit opening EVOmin is equal to the expansion valve flow rate of the model using the existing refrigerant R410A in order to prevent the refrigerant from returning at the next activation due to the movement of the refrigerant R32 immediately after the operation is stopped. Set to the same flow rate. The upper limit opening EVOmax1 is set to the same expansion valve flow rate as that of a model using the existing refrigerant R410A in order to prevent an abnormal increase in the refrigerant discharge temperature from the compressor 11 in the high opening range.

  In a normal case, the upper limit opening when feedback control of the suction dryness is EVOmax1. However, when the suction dryness calculated by the suction dryness calculation unit 19a falls below a preset value, the control device 19 performs control to change the upper limit opening from EVOmax1 to the upper limit opening EVOmax2. Control for changing the upper limit opening to EVOmax2 can be realized by the same means as in the first embodiment.

According to the refrigeration cycle apparatus 100 of the present embodiment described above, the outdoor expansion valve 13 is used in the low opening region in a state where the outside air temperature is low so as to perform the heating operation. And in the low opening degree area | region part 42b formed in the valve part 42 of the outdoor expansion valve 13, the ratio of the flow volume change of the refrigerant | coolant with respect to opening degree change (movement amount of the valve part 42) is set small. Therefore, even when the refrigerant R32 is used, the temperature change of the refrigerant R32 during the heating operation can be reduced, and the deterioration of the refrigerating machine oil due to the abnormal increase in the refrigerant discharge temperature from the compressor 11 of the refrigerant R32 is suppressed. be able to.
In the high opening area of the outdoor expansion valve 13, since the discharge temperature of the refrigerant from the compressor 11 may increase even when the expansion valve flow rate is large, it is not a good idea to reduce the expansion valve flow rate. The shape of the gradient of the change in the flow rate of the refrigerant with respect to the change in the opening degree of the outdoor expansion valve 13 is increased.

Further, the opening degree of the outdoor expansion valve 13 is feedback-controlled so as to achieve the target suction dryness, but as described above, the rate of change in the flow rate of the refrigerant R32 is small with respect to the opening degree change of the outdoor expansion valve 13. Therefore, the temperature fluctuation of the refrigerant R32 accompanying this is also reduced. Accordingly, even when feedback control is performed on the suction dryness so as to converge to the target value, it becomes easy to converge to the target suction dryness with good followability.
Further, when the calculated suction dryness falls below a preset value, the control device 19 performs control to change the upper limit opening from EVOmax1 to the upper limit opening EVOmax2. Thereby, it can suppress that the suction dryness falls too much and the liquid return of the refrigerant | coolant to a compressor generate | occur | produces.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Moreover, it is also possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

DESCRIPTION OF SYMBOLS 1 Refrigeration cycle apparatus 11 Compressor 12 Four-way valve 13 Outdoor expansion valve (expansion valve)
14 Outdoor heat exchanger 17 Temperature sensor (discharge temperature detector)
18 Temperature sensor (outside temperature detector)
19 Control device (control unit)
19a Suction dryness calculation unit 21 Indoor heat exchanger 31 Refrigerant piping 42a High opening region (high opening region)
42b Low opening area (low opening area)
100 Refrigeration cycle equipment

Claims (6)

A compressor, a four-way valve, an expansion valve, an outdoor heat exchanger, and an indoor heat exchanger are connected to each other by a refrigerant pipe to constitute a refrigeration cycle,
The refrigerant used in the refrigeration cycle is R32,
The expansion valve has a relatively small ratio of the flow rate of the refrigerant to the change in the opening degree of the expansion valve in a low opening range where the opening degree is relatively low, and in a high opening range where the opening degree is higher than the low opening range. A refrigeration cycle apparatus having a shape in which a ratio of a flow rate of the refrigerant to a change in the opening degree of the expansion valve is larger than the low opening degree region. A discharge temperature detector for detecting a discharge temperature of the refrigerant of the compressor;
The refrigeration cycle apparatus according to claim 1, further comprising: a control unit that performs feedback control of an opening degree of the expansion valve so that the discharge temperature converges to a target temperature. A suction dryness calculating unit for calculating the suction dryness of the refrigerant sucked into the compressor;
2. The refrigeration cycle apparatus according to claim 1, further comprising: a control unit that feedback-controls an opening degree of the expansion valve so that the suction dryness converges to a target suction dryness. It has an outside air temperature detector that detects the temperature of outside air,
The control unit sets the upper limit opening of the expansion valve as the upper limit opening of the low opening range when the temperature of the outside air falls below a preset temperature, and sets the upper limit opening of the expansion valve otherwise. The refrigeration cycle apparatus according to claim 2, wherein an upper limit opening degree of the high opening degree region is set.   When the suction dryness calculated by the suction dryness calculation unit falls below a preset suction dryness, the control unit sets the upper limit opening of the expansion valve as the upper limit opening of the low opening range, and so on. If not, the upper limit opening of the expansion valve is set as the upper limit opening of the high opening region. An expansion valve used in a refrigeration cycle apparatus constituting a refrigeration cycle,
In the low opening range where the opening is relatively low, the ratio of the refrigerant flow rate to the change in opening of the expansion valve is relatively small, and in the high opening range where the opening is higher than the low opening range, the expansion valve is opened. An expansion valve characterized by having a shape in which the ratio of the flow rate of the refrigerant to the degree of change is larger than the low opening degree region.

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