Refrigeration cycle apparatus and control method of refrigeration cycle apparatus

Patent metadata

Field	Value
Publication number	US-10465964-B2
Application number	US-201214653295-A
Country	US
Kind code	B2
Filing date	Dec 26, 2012
Priority date	Dec 26, 2012
Publication date	Nov 5, 2019
Grant date	Nov 5, 2019

Abstract

A refrigeration cycle apparatus includes a discharge temperature sensor that detects a discharge temperature of refrigerant discharged from a compressor, and a controller that controls the opening degree of an expansion valve. The controller computes an amount of variation of the discharge temperature resulting from varying the opening degree of the expansion valve, computes a ratio of the amount of variation of the discharge temperature to an amount of variation of the opening degree of the expansion valve, and determines the opening degree to be set to the expansion valve on the basis of the opening degree of the expansion valve that causes a change of the ratio.

First claim

The invention claimed is:

1. A refrigeration cycle apparatus including a compressor, a condenser, an expansion valve having variable opening degree, and an evaporator which are connected in a loop via pipes so as to allow refrigerant to circulate therein, the apparatus comprising:
a temperature sensor to detect a discharge temperature of the refrigerant discharged from the compressor; and
a controller configured to control the opening degree of the expansion valve,
wherein the controller obtains an amount of variation (ΔTd) of the discharge temperature resulting from varying the opening degree of the expansion valve,
obtains a ratio of the amount of variation (ΔTd) of the discharge temperature to an amount of variation (ΔLP) of the opening degree of the expansion valve, and
determines an opening degree to be set to the expansion valve based on a value of the opening degree, at which the ratio changes, of the expansion valve.

2. A refrigeration cycle apparatus including a compressor, a condenser, an expansion valve having variable opening degree, and an evaporator which are connected in a loop via pipes so as to allow refrigerant to circulate therein, the apparatus comprising:
a temperature sensor to detect a discharge temperature of the refrigerant discharged from the compressor; and
a controller configured to increase the opening degree of the expansion valve by an amount of variation (ΔLP), and change the opening degree of the expansion valve to a predetermined opening degree after a ratio of an amount of variation (ΔTd) of the discharge temperature to the amount of variation (ΔLP) reaches a predetermined value,
wherein the controller obtains, based on the change of the ratio, the opening degree (LPs) of the expansion valve that turns a state of the refrigerant at an outlet of the evaporator into a saturated gas state, and determines an opening degree to be set to the expansion valve based on the opening degree (LPs) of the expansion valve.

3. The refrigeration cycle apparatus of claim 1 ,
wherein the controller changes the opening degree of the expansion valve a plurality of times, acquires information of the opening degree of the expansion valve and the discharge temperature before the change and information of the opening degree of the expansion valve and the discharge temperature after the change, computes the ratio of the amount of variation (ΔTd) of the discharge temperature to the amount of variation (ΔLP) of the opening degree of the expansion valve for each time of changing the opening degree,
classifies the acquired information into information of a first region and information of a second region based on magnitude of the ratio,
obtains a first relational expression expressed by a first straight line, the first straight line expressing a relation between the opening degree of the expansion valve and the discharge temperature based on the information classified in the first region,
obtains a second relational expression expressed by a second straight line, the second straight line expressing a relation between the opening degree of the expansion valve and the discharge temperature based on the information classified in the second region, and
obtains the opening degree of the expansion valve at an intersection between the first straight line and the second straight line as the opening degree (LPs) of the expansion valve that turns a state of the refrigerant at an outlet of the evaporator into a saturated gas state, and determines the opening degree to be set to the expansion valve based on the opening degree (LPs) of the expansion valve.

4. The refrigeration cycle apparatus of claim 1 ,
wherein the controller obtains a predicted value of the discharge temperature resultant from varying the opening degree of the expansion valve by a predetermined amount, utilizing information of the opening degree of the expansion valve and the discharge temperature at current time, and an equation prepared in advance,
changes the opening degree of the expansion valve a plurality of times, acquires information of the opening degree of the expansion valve and of the discharge temperature before the change and information of the opening degree of the expansion valve and a measured value of the discharge temperature after the change,
classifies the acquired information into information of a first region and information of a second region based on magnitude of difference between the measured value and the predicted value of the discharge temperature,
obtains a first relational expression expressed by a first straight line, the first straight line expressing a relation between the opening degree of the expansion valve and the discharge temperature based on the information classified in the first region,
obtains a second relational expression expressed by a first straight line, the first straight line expressing a relation between the opening degree of the expansion valve and the discharge temperature based on the information classified in the second region, and
obtains the opening degree of the expansion valve at an intersection between the first straight line and the second straight line as the opening degree (LPs) of the expansion valve that turns a state of the refrigerant at an outlet of the evaporator into a saturated gas state, and determines the opening degree to be set to the expansion valve based on the opening degree (LPs) of the expansion valve.

5. The refrigeration cycle apparatus of claim 1 ,
wherein the controller sets the expansion valve to an opening degree determined by subtracting a predetermined correction value of opening degree from the opening degree (LPs) of the expansion valve that turns a state of the refrigerant at the outlet of the evaporator into a saturated gas state.

6. The refrigeration cycle apparatus of claim 3 ,
wherein the controller determines as target discharge temperature a temperature obtained by adding a predetermined correction value of temperature to the discharge temperature at an intersection between the first approximation and the second approximation, and
sets the opening degree of the expansion valve so that the discharge temperature agrees with the target discharge temperature.

7. The refrigeration cycle apparatus of claim 3 ,
wherein the controller obtains the first approximation based on the information classified in the first region and indicating the opening degree of the expansion valve larger than a minimum value of the opening degree of the expansion valve classified in the second region.

8. The refrigeration cycle apparatus of claim 3 ,
wherein the controller obtains the second approximation based on the information classified in the second region and indicating the opening degree of the expansion valve larger than a maximum value of the opening degree of the expansion valve classified in the first region.

9. The refrigeration cycle apparatus of claim 1 ,
wherein the controller starts a control operation for determining an opening degree to be set to the expansion valve when a predetermined first time has elapsed after the compressor is activated, and the amount of variation (ΔTd) of the discharge temperature is stabilized within a predetermined range or a rotation speed of the compressor is fixed.

10. A control method of a refrigeration cycle apparatus including a compressor, a condenser, an expansion valve with variable opening degree, and an evaporator which are connected in a loop via a pipe so as to allow refrigerant to circulate therein, the method comprising:
obtaining the amount of variation (ΔTd) of the discharge temperature resulting from varying an opening degree of the expansion valve,
obtaining a ratio of the amount of variation (ΔTd)

Assignees

• Kato Yohei
• Yoshimura Kiyoshi
• Mitsubishi Electric Corp

Inventors

• Kato Yohei
• Yoshimura Kiyoshi

Classifications

• F25B2400/053

  between the storage receiver and another part of the system · CPC title

• F25B2313/0315

  Temperature sensors near the outdoor heat exchanger · CPC title

• F25B2600/2513

  Expansion valves · CPC title

• F25B2400/054

  between the suction tube of the compressor and another part of the cycle · CPC title

• F25B13/00 Primary

  Compression machines, plants or systems, with reversible cycle (defrosting cycles F25B47/02) · CPC title