JPH0772648B2 - Refrigerant flow control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a refrigerant flow rate control device in a refrigeration cycle, and in particular, presets a throttle amount of a pulse motor driven expansion valve used in all refrigeration air conditioners. The present invention relates to a refrigerant flow rate control device in a refrigeration cycle, which is suitable for controlling according to a control procedure.

[Conventional technology]

In a refrigerating and air-conditioning apparatus that constitutes a refrigeration cycle by connecting a compressor, a condenser, an expansion means, and an evaporator with a refrigerant flow path,
In the case of using an electric expansion valve whose throttle amount can be adjusted by an electric signal as the expansion means, the refrigerant temperature at the evaporator outlet or the compressor inlet, that is, the refrigerant superheat is detected by a temperature sensor such as a thermistor. The throttle amount of the electric expansion valve is adjusted so that the degree of superheat is constant.

Examples of control of such a refrigerating apparatus are described in JP-A-55-116068 and JP-A-55-152360. Also,
Another method of controlling an expansion valve for a transient state is disclosed in Japanese Patent Laid-Open No. 56-
It is disclosed in Japanese Patent No. 44566. In this conventional example, a temperature sensor is also provided at the inlet or intermediate part of the condenser to detect the condensing temperature, and the expansion valve opening is fully opened from the start of the compressor until the condensing temperature reaches a predetermined value, and then overheating is performed. Degree control.

[Problems to be Solved by the Invention]

In the above conventional device, good control can be performed during steady operation, but for rapid transient conditions such as when the compressor starts, the control of the electric expansion valve changes the refrigeration cycle due to the detection delay of the temperature sensor. However, the refrigerant superheat at the evaporator outlet or the compressor inlet was too large, and the rise time of the refrigeration cycle was long. Further, in the above-mentioned JP-A-55-116068 and JP-A-55-152360, although it is taken into consideration that the load of the evaporator fluctuates significantly, it is not always within a satisfactory time. It was not possible to achieve the desired operating conditions.

Further, the one described in JP-A-56-44566 has an excellent effect that the transition from the transient state at the time of starting the compressor to the steady state is smoothly performed, but it is possible to change the control stage. Since the condensing temperature is used for the timing, the degree of superheat at the evaporator outlet may be excessive, which may cause a liquid return condition.

Further, in general, when the maximum opening degree of the expansion valve and the optimum opening degree in the steady state are significantly different, there is a problem that it takes a lot of time until the set superheat degree is reached after switching to the steady control.

The present invention has been made to solve the above-mentioned problems of the conventional technology, and when a pulse motor drive type expansion valve with good controllability is used, the compressor is caused by insufficient response of the sensor. The purpose is to improve the problems of the start-up characteristics of the refrigeration cycle immediately after the start of the. Specifically, the amount of refrigerant flowing into the evaporator is increased immediately after the compressor is started, and the function of the evaporator is effectively utilized to realize a refrigerant flow rate control method having a good start-up characteristic.

[Means for Solving the Problems]

To achieve the above object, a refrigeration cycle formed by sequentially connecting a compressor, a condenser, a pulse motor drive type expansion valve whose throttle amount can be adjusted by an electric signal, and an evaporator with a refrigerant pipe. A method of controlling a refrigerant flow rate for controlling the amount of refrigerant flowing through, having a transient operation mode after the start of the compressor and a steady operation mode after this transient operation mode has elapsed, wherein the transient operation mode is the A predetermined amount of time (τ _s1 ) after the start of the compressor minimizes the expansion amount of the expansion valve, and thereafter, during a preset time, the refrigerant evaporation temperature (Te) of the evaporator detected by the first temperature sensor The detected temperature difference with the refrigerant temperature (Ts) at the evaporator outlet or the compressor inlet detected by the second temperature sensor is obtained, and the expansion is performed so that the detected temperature difference approaches the set temperature difference (SHa). Adjust the valve throttle amount for a predetermined time ( τ _s2 ) The superheat degree of the evaporator is gradually increased by monotonically increasing to a predetermined preset throttle amount every interval, and the transient operation mode is set when the preset time elapses. From the normal operation mode.

It should be noted that the present invention controls the expansion amount of the expansion valve so that the refrigerant superheat degree at the evaporator outlet portion or the compressor inlet portion becomes constant during steady operation.

[Action]

In the present invention, when a pulse motor drive type expansion valve is used as the expansion valve, in order to eliminate the instability of the refrigeration cycle at the time of starting the compressor due to insufficient response of the sensor, the compressor is By increasing the amount of refrigerant flowing through the expansion valve and minimizing the amount of expansion of the expansion valve as the engine starts, the rate of decrease in the evaporation temperature Te immediately after startup is small, and the temperature difference from the intake refrigerant temperature Ts (Ts-Te) Is small. As a result, the time from the start to the steady state is shortened, and the rise time is significantly shortened.

In addition, since the expansion amount is adjusted stepwise according to the temperature difference (Ts-Te) from the state where the expansion valve is at the minimum throttle amount to the control for steady operation, the steady operation control Switching is smoothly performed. That is, if the expansion valve is throttled early in an attempt to match only the opening degree of the expansion valve, the degree of superheat changes beyond the target degree of superheat, and the process of opening the expansion valve to bring it closer to the target degree of superheat is repeated. On the other hand, in the present invention, since the throttle amount is changed stepwise, the target superheat degree is asymptotically reached. Further, when the aperture is changed uniformly, the actual opening is always delayed with respect to the opening target, so that the change is asymptotic but slow, and in the present invention, it is a stepwise change, so Each (τ _s2 ) can shorten the time to reach the target value of superheat.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 4. First, FIG. 1 is a configuration diagram of a refrigerant flow rate control device in a refrigeration cycle according to an embodiment of the present invention, and FIG.
The figure is a control flowchart of the electric expansion valve of the apparatus of FIG. 1, and (a) shows the flow at the time of starting the compressor, and (b) shows the flow at the time of steady operation.

In FIG. 1, 1 is a compressor, 2 is a condenser, 3 is an electric expansion valve whose throttle amount can be adjusted by an electric signal, and 4 is an evaporator. It is configured.

5 is a first temperature sensor such as a thermistor for detecting the refrigerant evaporation temperature of the evaporator, 6 is a second temperature sensor such as a thermistor for detecting the refrigerant temperature at the evaporator outlet or the compressor inlet, that is, the degree of refrigerant superheat, 7 is The arithmetic control device is related to a control device for controlling the refrigerant throttle amount of the electrically driven expansion valve 3, and is, for example, a microcomputer that performs information input, storage, comparison / judgment, calculation, electric signal output transmission, and the like.

The flow of the refrigerant in the refrigeration cycle circulates in the order of compressor 1 → condenser 2 → motorized expansion valve 3 → evaporator 4 → compressor 1.

For example, in such a refrigeration air-conditioning apparatus of a refrigeration cycle, the high-temperature and high-pressure refrigerant gas discharged from the compressor 1 exchanges heat with external air and the like in the condenser and radiates heat to condense from the refrigerant itself. The condensed and liquefied refrigerant is expanded and decompressed through the electric expansion valve 3 and enters the evaporator 4. Here, the refrigerant removes heat of vaporization from room air or the like to enhance the cooling effect, evaporates from the refrigerant itself and becomes low-temperature low-pressure refrigerant gas, and returns to the compressor 1.
The same cycle is repeated thereafter.

Next, the refrigerant flow rate control of the electric expansion valve 3 will be described.

First, the control procedure during steady operation shown in FIG. 2 (b) will be described.

The arithmetic and control unit 7 shown in FIG. 1 detects the evaporation temperature Te and the suction refrigerant temperature (superheat degree) Ts at the inlet of the compressor at a preset time interval τa by using the first and second temperature sensors 5 , 6
To detect. When the detected temperature difference (Ts-Te) is smaller than the preset temperature difference value SHa,
The arithmetic and control unit 7 emits an electric signal to that effect to increase the throttle amount of the electric expansion valve 3. If the throttle amount is increased, the flow rate of the refrigerant decreases and Ts-Te increases.

Conversely, when the detected temperature difference (Ts-Te) is larger than the preset temperature difference value SHa, an electric signal to that effect is issued to reduce the throttle amount of the electrically driven expansion valve 3. If the throttle amount is reduced, the refrigerant flow rate increases (Ts-Te).

The throttle amount of the electrically driven expansion valve 3 is adjusted so that the temperature difference (Ts-Te) thus detected becomes the set temperature difference value, that is, the set temperature SHa.

Next, a control procedure at the time of starting the compressor shown in FIG. 2 (a) will be described.

A preset control procedure described below is input to the arithmetic and control unit 7, and an electric signal for adjusting the throttle amount of the electric expansion valve 3 is output according to the control procedure.

When the compressor 1 is started, the throttle amount of the electric expansion valve 3 is minimized and the state is maintained for a preset constant time τs ₁ .

After τs _{1 has} elapsed, at a preset time interval τs ₂ ,
The evaporation temperature Te and the suction refrigerant temperature Ts at the compressor inlet are detected by the temperature sensors 5 and 6, and when the detected temperature difference (Ts−Te) is smaller than the set temperature SHa, the electric expansion valve 3 Increase the aperture. By performing this operation at every time interval τ s ₂ , the throttle amount of the electric expansion valve 3 is increased stepwise.

When the throttle amount reaches a preset predetermined throttle amount, the expansion valve opening is not changed, and when the preset time elapses, the control during the steady operation described above with reference to FIG. 2 (b). Move to.

An example of operation when the above-described control is performed is shown in FIG.

FIG. 3 is a diagram showing changes in the expansion valve throttle amount and the refrigerant temperature from the start of the compressor to the steady operation. The horizontal axis indicates time, the vertical axis indicates the expansion valve throttle amount, and the refrigerant temperature, that is, the refrigerant temperature. The evaporation temperature Te and the suction refrigerant temperature Ts at the compressor inlet are taken.
The solid line shows an operation example according to one embodiment of the present invention, and the broken line shows an operation example of the related art in which the control at the time of starting is not performed for comparison.

Here, an example in which a pulse motor driven expansion valve is used as the electric expansion valve is shown, and the expansion valve throttle amount before starting is the throttle amount before stopping the compressor. As is clear from the figure, in the present embodiment, in order to minimize the expansion amount of the expansion valve with the start of the compressor, the amount of refrigerant flowing through the expansion valve increases, and the decrease rate of the evaporation temperature Te immediately after the start is small. Also, the temperature difference (Ts-Te) from the suction refrigerant temperature Ts is small.

Further, in the operation of this embodiment shown by the solid line, the time from the start to the steady state is shorter, and it can be seen that the rising time is significantly shortened by this embodiment.

In addition, since the expansion amount is adjusted stepwise according to the temperature difference (Ts-Te) from the state where the expansion valve is at the minimum throttle amount to the control for steady operation, the steady operation control Switching is smoothly performed.

In the above-described embodiment, the increase of the throttle amount from the time when the throttle amount of the electric expansion valve is minimum to the time of shifting to the control of the steady operation is controlled according to the degree of refrigerant superheat at the inlet of the compressor. However, as shown in FIG. 4, control may be performed by a preset control pattern by temporal change of the aperture amount according to the starting characteristics of the device.

FIG. 4 is a diagram showing a control pattern of a refrigerant flow rate control device in a refrigerant cycle according to another embodiment of the present invention, in which the abscissa axis indicates time passage and the ordinate axis indicates expansion valve throttle amount. FIG. 4 is a diagram corresponding to the diagram of changes in expansion valve throttle amount shown in FIG. 3.

As described above, in the example of FIG. 4, the control pattern that minimizes the expansion amount of the expansion valve at the time of starting the compressor and then gradually increases the expansion amount is set as the refrigerant at the evaporator outlet or the compressor inlet. Rather than controlling according to the degree of superheat, the time variation of the throttle amount according to the starting characteristics of the device is set in advance, stored in the arithmetic and control unit, and operated according to the control pattern of the stored control procedure. Thus, the same effect as that of the previous embodiment can be obtained.

According to each of the above-described embodiments, the rate of decrease in the evaporation temperature after starting can be reduced, and the evaporator can be effectively used, so that effective operation can be performed.

Further, since the start-up time at the time of starting can be shortened, the comfort is remarkably improved when applied to an air conditioner.

〔The invention's effect〕

As described above, according to the present invention, immediately after starting the compressor, the amount of refrigerant flowing into the evaporator is increased, and then the amount of refrigerant is decreased stepwise, so that refrigeration by utilizing the function of the evaporator is performed. This has the effect of reducing the cycle rise time and preventing the failure of the compressor due to liquid return to the compressor. Further, when the expansion valve opening reaches a predetermined value during the set time at the time of starting the compressor, the expansion valve opening is not changed until the set time elapses, so it is possible to prevent an unstable phenomenon due to a time delay of the temperature sensor. Another advantage is that the cycle can be stabilized early.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a refrigerant flow rate control device in a refrigeration cycle according to an embodiment of the present invention, FIG. 2 is a control flowchart of an electric expansion valve of the device of FIG. 1, and (a) is a compressor At the time of start-up, (b) shows the flow during steady operation, FIG. 3 is a diagram showing changes in expansion valve throttle amount and refrigerant temperature from the start of the compressor to steady operation, and FIG. FIG. 6 is a diagram showing a control pattern of a refrigerant flow rate control device in a refrigeration cycle according to another embodiment. 1 ... Compressor, 2 ... Condenser, 3 ... Motorized expansion valve, 4
...... Evaporator, 5 ...... First temperature sensor, 6 ...... Second temperature sensor, 7 ...... Computational control device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masakatsu Hayashi, 390 Muramatsu, Shimizu City, Shizuoka Prefecture, Hitachi, Ltd., Mechanical Research Laboratory (72) Inventor, Shiro Asai, 390, Muramatsu, Shimizu City, Shizuoka, Hitachi, Ltd., Shimizu Plant, Hitachi, Ltd. (72) The inventor, May woman, 390 Muramatsu, Shimizu city, Shizuoka prefecture, Shimizu factory, Hitachi, Ltd. (56) References JP 55-116068 (JP, A) JP 55-152360 (JP, A)

Claims (1)

[Claims] 1. A refrigeration cycle formed by sequentially connecting a compressor, a condenser, a pulse motor drive type expansion valve whose throttle amount can be adjusted by an electric signal, and an evaporator with a refrigerant pipe. A method of controlling a refrigerant flow rate for controlling the amount of refrigerant to be used, which has a transient operation mode after the compressor is started, and a steady operation mode after the transient operation mode has elapsed, and the transient operation mode is the compressor. For a predetermined time (τ _s1 ) after the start, the expansion amount of the expansion valve is minimized, and thereafter, during a preset time, the refrigerant evaporation temperature (Te) of the evaporator detected by the first temperature sensor and the second Obtain the temperature difference detected with the refrigerant temperature (Ts) at the evaporator outlet or compressor inlet detected by a temperature sensor, and adjust the expansion valve throttle so that the detected temperature difference approaches the set temperature difference (SHa). Quantity at predetermined time intervals (τ _s2 ) The heating degree of the evaporator is gradually increased by monotonically increasing to a predetermined throttle amount set stepwise, and when the preset time elapses, the transient operation mode is changed to the steady operation mode. A method for controlling a refrigerant flow rate, which is characterized in that: