JPH08338664A - Freezing cycle device - Google Patents

Abstract

PURPOSE: To enable refrigerant of freezing cycle to reach rapidly is target value by a method wherein an operating amount in respect to a degree of opening of an electrical expansion valve at a present time is calculated in response to an amount of variation between a deviation between a degree of super-heating of refrigerant at the present time and the target value at an evaporator and a previous calculated deviation and then the operating amount is corrected in response to a gain. CONSTITUTION: During cooling operation or heating operation, control loops of specified time intervals are repeated so as to detect a degree of super-heating of refrigerant at an evaporator (during cooling operation, an indoor heat exchanger 6 and during heating operating, an outdoor heat exchanger 4). Then, a deviation E(t) between the degree of super-heating at the present time to be detected and a predetermined target value (a specified value) is calculated, and the amount of variation ΔE(t) between this deviation E(t) and the previous calculated deviation is calculated, an operating amount of the electrical control valve 5 in respect to its degree of opening at the present time is calculated under a feed-back control with the deviation E(t) and the amount of variation ΔE(t) being inputted, and its operating amount is corrected in response to a gain (the ratio between the total value of the operating variation corresponding to the operations and the total value of variation of control amount).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigeration cycle device used in an air conditioner or the like.

[0002]

2. Description of the Related Art In a refrigeration cycle of an air conditioner or the like, a compressor, a condenser, an expansion mechanism, and an evaporator are sequentially connected by piping to circulate a refrigerant, and in particular, an electric expansion valve is used as the expansion mechanism. In some cases, the operation is stabilized by controlling the opening degree of the electric expansion valve so that the degree of superheat of the refrigerant (controlled element) in the evaporator reaches a target value (constant value).

Feedback control is used for such superheat control. In feedback control,
In many cases, the tuning of control constants is performed in advance and then mounted.

[0004]

In the case of feedback control, it is considered preferable that the time interval of the control loop is short, but depending on the operating conditions, excessive control is repeated and it becomes difficult to properly detect the controlled element. However, there is a possibility that so-called hunting may occur in which the controlled element greatly changes. On the contrary, when the time interval of the control loop is long, excessive control is reduced and the dead time of the cycle can be dealt with, but since the number of operations is reduced, the advantage of feedback control of the strength against the influence of disturbance Will be damaged.

As an example of control that is considered to be effective in improving transient characteristics in feedback control, Japanese Patent Publication No. 63-53454
As shown in No. 2, some timers can use two types of time intervals for the control loop.

However, in this case, although the transient characteristic is improved, the manipulated variable is determined only in accordance with the deviation between the controlled element and the target value, and the temporal change amount of the controlled element, that is, the refrigeration No consideration is given to the dynamics of the cycle. Air conditioners often have a wide variety of operating conditions depending on the installation method and operating environment, and under each of these conditions, the dynamic characteristics of the refrigeration cycle, which greatly affects the control, will be quite different. Therefore, in the above control example in which the manipulated variable is uniform under any condition, it takes time for the controlled element to reach the target value, and there is a problem that the responsiveness is poor.

Regarding capture of the dynamic characteristics of the refrigeration cycle,
There is one disclosed in Japanese Patent Laid-Open No. 6-159819, but this is only for the purpose of estimating the pipe length, and similarly to the above, the problem of poor control response remains.

The present invention takes the above circumstances into consideration,
It is an object of the invention to provide a refrigeration cycle device having excellent responsiveness that allows controlled elements of the refrigeration cycle to quickly reach a target value.

[0009]

A refrigeration cycle apparatus of the first invention is a refrigeration cycle in which a compressor, a condenser, an expansion mechanism, and an evaporator are sequentially connected by piping to circulate a refrigerant, and a refrigeration cycle of the refrigeration cycle. The detecting means for detecting the control element, the operating means for operating the refrigeration cycle so that the controlled element detected by the detecting means is in a predetermined state, the changing direction of the operation amount of the operating means and the controlled element are When the number of operations of the operating means reaches a predetermined value without changing the direction of change of the received control amount, a detecting means for detecting a ratio between the total value of the changes in the operation amount and the total value of the changes in the control amount for the number of operations. And correction means for correcting the operation amount of the operation means according to the detection result of the detection means.

In the refrigeration cycle apparatus of the second invention, in the first invention, the expansion mechanism is an electric expansion valve, and the operation target of the operation means is the opening degree of the electric expansion valve. Is the degree of superheat of the refrigerant or the temperature of the refrigerant discharged from the compressor.

The refrigeration cycle apparatus of the third invention, in addition to the configuration of the first or second invention, estimates the pipe length of the refrigeration cycle by comparing the detection result of the detection means with a reference value stored in advance. The estimation means to do so is provided.

[0012]

In the refrigeration cycle apparatus of the first invention, the controlled element of the refrigeration cycle is detected, and the refrigerating cycle is operated so that the controlled element is in a predetermined state. When the number of operations of the operating means reaches a predetermined value without any change in the change direction of the operation amount and the change direction of the control amount received by the controlled element, the total value of the change in the operation amount and the change in the control amount for the operation number. The ratio with the total value of is detected. The manipulated variable for the refrigeration cycle is corrected according to the detection result.

In the refrigeration cycle apparatus of the second invention, the first
In the invention, the electric expansion valve is used as the expansion mechanism, and the opening degree of the electric expansion valve is the operation target. By this operation, the degree of superheat of the refrigerant that is the controlled element or the temperature of the refrigerant discharged from the compressor changes.

In the refrigeration cycle apparatus of the third invention, the first
Alternatively, in the second aspect of the invention, the pipe length of the refrigeration cycle is estimated by comparing the detected ratio with a reference value stored in advance.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Check valve 2 at the discharge port of variable capacity compressor 1
The outdoor heat exchanger 4 is pipe-connected via the four-way valve 3, and the indoor heat exchanger 6 is pipe-connected to the outdoor heat exchanger 4 via an expansion mechanism such as an electric expansion valve 5. And
The indoor heat exchanger 6 is pipe-connected to the suction port of the compressor 1 via the four-way valve 3.

The electric expansion valve 5 is a pulse motor valve (PMV) whose opening continuously changes according to the number of input drive pulses. During the cooling operation, a cooling cycle in which the refrigerant discharged from the compressor 1 flows in the direction indicated by the solid line arrow is formed, and the outdoor heat exchanger 4 functions as a condenser and the indoor heat exchanger 6 functions as an evaporator.

During the heating operation, the switching operation of the four-way valve 3 forms a heating cycle in which the refrigerant discharged from the compressor 1 flows in the direction of the dashed arrow in the figure, and the indoor heat exchanger 6 is the condenser and the outdoor heat exchanger 4 Functions as an evaporator.

One end of a bypass pipe 8 having a capillary tube 7 is connected to a pipe between the outdoor heat exchanger 4 and the electric expansion valve 5, and the other end of the bypass pipe 8 is connected to a suction port of the compressor 1. It

In the outdoor heat exchanger 4, a heat exchanger temperature sensor (Tc) 11 is attached to a portion on the refrigerant outlet side during cooling. A refrigerant temperature sensor (Tsu) 12 is attached to the refrigerant suction side pipe between the four-way valve 3 and the suction port of the compressor 1. In the bypass pipe 8, the capillary tube 7
A refrigerant temperature sensor (Tx) 13 is attached on the downstream side of.

On the other hand, an inverter circuit 21 and a control unit 30 are connected to the commercial AC power supply 20. Then, the control unit 30 includes the four-way valve 3, the electric expansion valve 5, the heat exchanger temperature sensor 11, the refrigerant temperature sensors 12 and 13, and the inverter circuit 2.
1, the operation unit 31, and the room temperature sensor 32 are connected.

The inverter circuit 21 rectifies the power supply voltage, converts it into an alternating current of a frequency (and voltage) according to a command from the control unit 30, and outputs it. This output is the compressor 1
Is supplied as driving power to the motor.

The control unit 30 controls the entire air conditioner, and as shown in FIG. 2, the SH calculation means, the stabilization control means, the dynamic characteristic detection means, and the opening degree are the main functional means. It has a control means, a dynamic characteristic comparison means, a dynamic characteristic reference value storage means, and a pipe length estimation means.

The SH calculation means is a detection means for detecting the superheat degree SH of the refrigerant as a controlled element of the refrigeration cycle,
During cooling, the difference between the temperature Su detected by the refrigerant temperature sensor 12 and the temperature detected by the refrigerant temperature sensor 13 (saturated refrigerant temperature) Tx is detected as the superheat degree SH of the refrigerant in the indoor heat exchanger 6, and during heating the refrigerant temperature. The difference between the detection temperature Tsu of the sensor 12 and the detection temperature (evaporator temperature) Te of the heat exchanger temperature sensor 11 is detected as the superheat degree SH of the refrigerant in the outdoor heat exchanger 4.

The stabilization control means, for each control loop of a constant time interval Δt, the deviation between the current superheat degree SH (t) detected by the SH calculation means and a predetermined target value (constant value) SHs. E (t) = SH (t) -SHs is calculated,
Moreover, the change amount ΔE (t) = E (t) -E (t-1) between this deviation E (t) and the previously obtained deviation E (t-1) is calculated, and these E
The manipulated variable ΔPLS with respect to the current opening degree of the electric expansion valve 5 is obtained by PID control (a type of feedback control) using (t) and ΔE (t) as inputs.

The dynamic characteristic detecting means detects the dynamic characteristic between the operation amount ΔPLS obtained by the stabilization control means and the control amount ΔSH which the superheat degree SH receives by adding the operation amount ΔPLS. Specifically, when the number of times of operation C for the electric expansion valve 5 reaches a predetermined value k without changing the direction of change of the operation amount ΔPLS and the direction of change of the control amount ΔSH received by the superheat degree SH, the number of times of the operation is reduced. The ratio of the total value of the manipulated variable changes and the total value of the controlled variable changes is detected as a gain γ.

The opening control means corrects the manipulated variable ΔPLS calculated by the stabilization control means according to the dynamic characteristic (gain γ) detected by the dynamic characteristic detecting means, and the correcting means. It has operation means for operating the opening degree of the electric expansion valve 5 by the operation amount ΔPLS ′.

The dynamic characteristic comparing means compares the dynamic characteristic (gain γ) detected by the dynamic characteristic detecting means with the dynamic characteristic reference value stored in advance in the dynamic characteristic reference value storage means. The pipe length estimation means estimates the pipe length of the refrigeration cycle according to the comparison result of the dynamic characteristic comparison means.

Next, the operation of the above configuration will be described with reference to the flowchart of FIG. During the cooling operation and the heating operation, the difference between the indoor temperature Ta detected by the indoor temperature sensor 32 and the set indoor temperature Ts set by the operation unit 31 is detected, and the compressor is determined according to the temperature difference (air conditioning load). The operating frequency F of 1 is controlled. By this operating frequency control, the indoor temperature Ta converges toward the set indoor temperature Ts.

During operation, the control loop of a constant time interval Δt is repeated, and the superheat degree SH of the refrigerant in the evaporator (indoor heat exchanger 6 during cooling, outdoor heat exchanger 4 during heating) is detected.
Then, the deviation E between the detected superheat degree SH (t) at the present time and a predetermined target value (constant value) SHs
(t) = SH (t) -SHs is obtained, and the amount of change ΔE (t) = between the deviation E (t) and the previously obtained deviation E (t-1).
E (t) -E (t-1) is obtained, and this E (t) and ΔE
The PID control (feedback control) with (t) as input controls the manipulated variable ΔPL with respect to the current opening of the electric expansion valve 5.
S is required.

When the manipulated variable ΔPLS is obtained, the manipulated variable ΔPLS is corrected according to a gain γ described later. Then, the opening degree of the electric expansion valve 5 is actually operated by the corrected operation amount ΔPLS ′.

When the opening degree of the electric expansion valve 5 is manipulated, the amount of refrigerant flowing into the evaporator changes, and the superheat degree SH changes. This change amount is the superheat S
It is the control amount ΔSH that H receives.

Each time the opening operation of the electric expansion valve 5 is repeated, it is determined whether or not there is a change in the direction of change of the manipulated variable ΔPLS and in the direction of change of the controlled variable ΔSH that the superheat degree SH receives. When there is no change in both changing directions, the count value C is incremented by "1". When there is a change in at least one of the two changing directions, the count value C is cleared.

When the count value C continues to increase without any change in both changing directions and the count value C reaches the predetermined value k, the total value of the manipulated variable changes and the total value of the controlled variable changes for the number k of operations are calculated by the following equation. Is detected as the gain γ.

[0034]

[Equation 1]

The manipulated variable ΔPLS is corrected according to the gain γ. For example, for the gain γ, three regions are defined: a region of less than 0.01, a region of 0.01 or more and less than 0.1, and a region of 0.1 or more. The correction amounts α ₁ , α ₂ , α ₂ , α ₂ , α ₃ is defined. If the gain γ is less than 0.01, the manipulated variable ΔPL
S is corrected by α ₁ .

Then, as described above, the opening degree of the electric expansion valve 5 is actually manipulated by the corrected manipulated variable ΔPLS '. At the start of operation, when the superheat degree SH deviates largely from the target value SHs and is in, for example, the liquid back region (the liquid refrigerant that has not been evaporated in the evaporator is sucked into the compressor), or when the electric expansion valve 5 is opened. If the degree of opening deviates greatly from the stable opening, even if the opening operation is repeated several times, the operation amount ΔP
Control amount ΔSH that changes direction of LS and superheat degree SH receives
Both change directions will keep one direction.

When the superheat degree SH is largely deviated from the target value SHs or the opening degree of the electric expansion valve 5 is largely deviated from the stable opening degree, the superheat degree S which is a controlled element is
When the time interval Δt of the control loop of the feedback control is lengthened for the purpose of preventing H hunting, it is necessary to continue normal stabilization control until the superheat degree SH reaches the target value SHs. It will cost you.

Therefore, the current dynamic characteristic of the refrigeration cycle, that is, the gain γ is captured, and the manipulated variable ΔPLS with respect to the opening degree of the electric expansion valve 5 is corrected based on the gain γ. By performing such correction, even if the dynamic characteristics of the refrigeration cycle change depending on the installation method of the air conditioner and the usage environment, the superheat degree SH is set to the target value SH regardless of the change.
s can be quickly reached, and control responsiveness can be improved.

An example of changes in the superheat degree SH and changes in the opening degree of the electric expansion valve 5 is shown in FIG. 4, and the responsiveness is remarkably improved as compared with the case of only the conventional stabilization control shown by the broken line. By the way, in consideration of the fact that the pipe length of the refrigeration cycle changes variously depending on the installation condition of the air conditioner, the detected gain γ is compared with the previously stored dynamic characteristic reference value.

In the case of an air conditioner in which the pipe length is variable in the range of 3 m to 30 m, the gain γ when the pipe length is 3 m
₁ and the gain γ ₂ when the pipe length is 30 m are confirmed by experiments, and they are stored as the dynamic characteristic reference value. Further, two types of gains γ ₁ and γ ₂ are prepared for cooling and for heating, respectively.

As shown in FIG. 5, there is a relationship between the gain γ and the pipe length that the longer the pipe length, the lower the gain γ. If the detected gain is γ ₂ , it is applied to the condition of the linear interpolation in FIG. 5, and the estimated value L of the pipe length is obtained.

The estimated value L is used as an adjustment value for automatically tuning the control constant of the feedback control in the stabilization control means. The pipe length of the refrigeration cycle changes in various ways depending on the installation situation.In such a situation, the pipe length can be estimated and the feedback control constant can be automatically tuned to affect the installation situation. Stable operation is possible.

In the above embodiment, the case where the controlled element is the superheat degree SH of the refrigerant has been described as an example, but the same can be applied to the case where the controlled element is the discharge refrigerant temperature Td of the compressor 1. Is. Further, it is also possible to implement the case where the controlled element has both the superheat degree SH and the discharge refrigerant temperature Td.

Although the application to the air conditioner has been described,
As long as it is equipped with a refrigeration cycle, it can be similarly applied to other devices. Besides, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.

[0045]

As described above, according to the present invention,
The controlled element of the refrigeration cycle is detected, the refrigeration cycle is operated so that the controlled element is in a predetermined state, and the direction of change of the manipulated variable and the direction of change of the controlled variable received by the controlled element remain unchanged. When the number of operations of the operating means reaches a predetermined value, the ratio between the total value of the operation amount changes and the total value of the control amount changes for the number of operations is detected, and the operation amount for the refrigeration cycle is determined according to the detection result. Since the correction is performed, it is possible to provide the refrigeration cycle device having excellent responsiveness that allows the controlled element of the refrigeration cycle to quickly reach the target value.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a refrigeration cycle and a control circuit according to an embodiment.

FIG. 2 is a block diagram showing main functional means of a control unit of the embodiment.

FIG. 3 is a flowchart for explaining the operation of the embodiment.

FIG. 4 is a diagram showing an example of a change in superheat and a change in opening of the electric expansion valve in the embodiment.

FIG. 5 is a diagram showing conditions for linear interpolation in the embodiment.

[Explanation of symbols]

1 ... Variable capacity compressor, 4 ... Outdoor heat exchanger, 5 ... Electric expansion valve (PMV), 6 ... Indoor heat exchanger, 8 ... Bypass pipe, 1
1 ... Heat exchanger temperature sensor, 12, 13 ... Refrigerant temperature sensor, 21 ... Inverter circuit, 30 ... Control part.

Claims (3)

[Claims] 1. A refrigeration cycle in which a compressor, a condenser, an expansion mechanism, and an evaporator are sequentially connected by piping to circulate a refrigerant, detection means for detecting a controlled element of the refrigeration cycle, and detection by this detection means. The controlled means for operating the refrigeration cycle so that the controlled element is brought into a predetermined state, and the changing direction of the operation amount of the operating means and the changing direction of the control amount received by the controlled element remain unchanged. When the number of operations of the operating means reaches a predetermined value, a detecting means for detecting a ratio between the total value of the change in the operation amount and the total value of the change in the control amount for the number of operations; A refrigeration cycle apparatus comprising: a correction unit that corrects an operation amount of the operation unit. 2. The refrigeration cycle apparatus according to claim 1, wherein the expansion mechanism is an electric expansion valve, the operation target of the operation means is an opening of the electric expansion valve, and the controlled element is a refrigerant. The refrigeration cycle device is characterized in that it is the degree of superheat of the refrigerant or the temperature of the refrigerant discharged from the compressor. 3. The refrigeration cycle apparatus according to claim 1, further comprising: an estimation unit that estimates a pipe length of the refrigeration cycle by comparing a detection result of the detection unit with a reference value stored in advance. A refrigeration cycle device characterized by being provided.