JPS59170578A - Control method of reversible proportionate expansion valve - Google Patents

Abstract

PURPOSE:To accurately control the valve opening by controlling a reversible proportionate expansion valve at every timing pulse, and controlling in the reverse direction at more than the maximum value of dispersion of hysteresis of the valve in a case when driven in a direction opposite to a previous direction of the valve operation. CONSTITUTION:In a case where a power source 4 of a reversible proportionate expansion valve disposed in a freezing cycle, respective outputs from a temperature sensor 6 and a pressure sensor 7 which detect the temperature and pressure on the outlet side of an evaporator are inputted to a controller 16 via temperature-voltage signal and pressure-voltage signal transducers 13, 14 and an A/D transformer 15. Here, the difference between a temperature TE of refrigerant and a pressure equivalent temperature TP of the refrigerant is computed to obtain the degree of super-heating SH, and have it memorized. When the direction of operation of the valve is same between the previous and the following valve operation, a power source 4 is controlled relative to the deviation of said degree of superheating SH, while in a case the directions are opposite, control is made by adding a signal of more than the maximum value of the dispersion of hysteresis to an electrical signal which corresponds to said deviation.

Description

Detailed Description of the Invention The present invention provides control of a reversible proportional expansion valve that is installed in a refrigerant flow path of a refrigeration system and uses electromagnetic force to adjust the refrigerant flow rate or the rotational force of a motor. The method attempts to compensate for the effects of hysteresis due to friction in mechanical sliding parts.

The refrigeration system in the refrigeration equipment has a configuration as shown in Figure 1, where 1 is a compressor and 2 is an outdoor heat exchanger (condenser).
, 3 is a reversible proportional expansion valve; 4 is a drive source such as an electromagnet or motor that adjusts the opening degree of the expansion valve 3 according to an input signal; 5
is an indoor heat exchanger (evaporator L6.7 is a temperature sensor and a pressure sensor that detect the temperature and pressure on the outlet side of the evaporator 5.

Further, 8 is a temperature detection circuit that converts the temperature detected by the temperature sensor 6 into an electrical signal, 9 is a pressure detection circuit that converts the pressure detected by the pressure sensor 7 into an electrical signal, and 10 is a pressure signal from the pressure detection circuit 9. 11 is a subtraction path (b) for subtracting the signal from the function generation circuit 10 from the signal from the temperature detection circuit 8 to obtain the degree of superheat (superheat); 12 is the subtraction circuit 11
A controller for controlling the drive source 3 is used to maintain the degree of superheating within a neutral zone with a preset width.
It is la.

Next, to explain the operation, a drive source 4 (for example, a pulse motor) that controls the opening degree of the expansion valve 3 is connected to a controller 1.
It is controlled by the output from 2.

That is, as shown in FIG. 2, since the controller 12 outputs the operation pulse P at every preset sampling time tS, the operation pulse P causes the pulse motor 4 to
is controlled. By the way, as shown in FIG.
The output is proportional to the degree of

,, Δ8H-8H-8H6 From the combination of FIG. 2 and FIG. 3 described above, it can be seen that there are three states of deafness of the operation pulse P.

(1) When the deviation ΔSH is on the + side, a pulse is output in the direction of opening the valve.

(It) When deviation Δ19)t is within the dead zone,
No pulse is output even when the output timing comes (dashed line in Figure 2).

(When the ID deviation ΔSM is on one side, a pulse is output in the direction of closing the valve 3.

Incidentally, the opening versus flow rate characteristic of the motor-driven WBM expansion valve 3 is linear as shown in FIG. 4, and the pulse number versus opening f''W characteristic of the valve is also linear as shown in FIG. .4th above
, 5 shows ideal valve characteristics, but in reality, the flow characteristics in the opening and closing directions are the same and have hysteresis. This is illustrated in terms of pulse number convection healing characteristics as shown in FIG. 6.

Now, if the number of pulses in the opening direction required to obtain an arbitrary flow iQM is PM and the number of pulses in the closing direction is PM', the hysteresis Ph of the valve 3 can be expressed by the following equation.

ph=pM-PM' Therefore, when operating the valve 3, the reversal of the operation, such as opening operation → closing operation or six, closing operation → opening operation, requires the pulse number Pα such that Pα>Pb. Valve 3 does not reverse.

By the way, when the ninth valve for the same application was manufactured, there were variations in the hysteresis, so the value of the pulse number Pα had to be determined for each product by making a one-to-one correspondence between the valve 3 and the control device. There was poor productivity.

Alternatively, instead of making a one-to-one correspondence, it is possible to take the average value of the variations and determine the number of pulses Pα from that value, but according to this method, t! This means that valves with large hysteresis cannot be corrected by one-time control, and must be operated several times at each sampling time before the valve moves for the first time.On the other hand, for valves with small hysteresis,
Problems such as excessive correction caused by one-time control may occur, such as inducing hunting.

This invention has been developed by focusing on the points mentioned above, and its purpose is to provide a reversible system that can quickly and accurately control the opening and closing of the valve according to the calculation result, regardless of the variation in the hysteresis of the valve. This invention provides a method for controlling a proportional type expansion valve.

An embodiment of the present invention will be described below.

In FIG. 7, 13 receives the signal from the temperature sensor 6, and
a temperature-voltage signal converter 14 that performs calculations and amplification to obtain a signal level suitable for input to the subsequent Mu/D converter 15;
15 is a pressure car pressure signal converter that receives the signal from the pressure sensor 7 and calculates and amplifies it to a signal level suitable for input to the MU/D converter 150; 15 is controlled by a controller 16, and input data is A MU/D converter that performs selection, conversion from analog data to digital data, output of digital data, etc., 16 is ROMX! (It is a 1-chip microcomputer with built-in AM, I10 ports, etc., and according to a pre-stored program, the MU/D converter 15
, inputs the digital data, performs calculations based on the program, and outputs the results to the motor drive section 17 .

Reference numeral 17 denotes a motor drive unit that sends a pulse signal to the motor 4 of the motor-driven expansion valve 3 to rotate it based on the output signal from the controller 16.

Next, to explain the operation based on the above selection, the flow rate of the refrigerant is controlled by increasing or decreasing the number of pulses. The operating pulse ΔpM at a certain temperature can be calculated as necessary. In this case, it is necessary to detect the reference position. Therefore, the valve 3 is brought into a fully closed or fully open state before starting the control, and this is used as a reference position to start the control.

In other words, the number of pulses required from fully closed to fully open is PIT
)O, when the power to the controller 16 is established, P'> P son ! is always in the direction of closing the valve. The number of pulses P' is given. As a result, regardless of the previous opening degree of the valve 3, the valve 3 becomes fully closed. Note that valve 3 was not fully open last time, and P
l. . When the fully closed state is achieved with the number of pulses P',
Although the pulse p'-p' is extra, this pulse is consumed in the motor 4 as magnetic loss. Through the above operations, the fully closed position Lo can be set as the reference position.

After performing the above operations in the controller 16, actual control begins. The operation will be explained below.

The temperature TE of the refrigerant at the outlet of the evaporator 5 is converted into a digital signal by the M/D converter 13, and the controller 16 reads and stores this digital data.

Moreover, the pressure PE of the refrigerant at the outlet of the evaporator 5 is
The data is converted into a digital signal by the D converter 14, and the controller 16 reads and stores this digital data.

Then, within the controller 16, the refrigerant temperature TE
The difference between the temperature and the refrigerant pressure equivalent temperature TP is obtained to obtain the superheat degree SR, and the value of this superheat degree 8H is stored.

In the above, the pressure equivalent temperature TP can be obtained from the pressure P= from the saturated vapor pressure diagram of the refrigerant used. That is, since the pressure equivalent temperature TP is a function of the pressure PE, this can be expressed as follows: Tp=f(PK).

Since pE is digital data, pressure→temperature conversion can be easily performed by the controller 16 by programming the value of TP corresponding to each 7′-ta.

Next, the controller 16 calculates the superheat degree deviation ΔSH, and sets the superheat degree SR at the center of the dead zone shown in FIG.
8, the deviation ΔSH is calculated from the formula below and this value is stored.

Δ5H-8H-, 8H0 Also, from the value of this deviation value ΔSH of the degree of superheating, the number of operation pulses ΔPM per sampling time is calculated from the formula below,
Remember this value.

ΔP M −K*ΔSM Here, K is a unique constant determined by the characteristics of the refrigeration system and is stored in advance in the controller 16, so that the number of operating pulses ΔPM can be easily determined.

Then, the controller 16 outputs the operation pulse ΔpM at every sampling time ts shown in FIG. 1, and the motor driving section 17 controls the motor 4.

There are three output states of the operation pulse ΔpM when .

That is, Medium: When the deviation ΔSH is on the + side, ΔPM=ni・ΔSH Open the valve 3 by the number of pulses ΔpM calculated by .

(11) When the deviation ΔSI( is within the dead zone, ΔpM−
.

However, even if the sampling pulse is output, the operation pulse is not output.

G11l When the deviation ΔSH is on one side, close the valve 3 by the number of pulses ΔpM calculated by ΔfsH at ΔPM=.

At this time, generally Ph>ΔpM, so if the previous operation was closing, it will operate without any problem, but when the operation is reversed from opening to closing, even if a pulse is output due to hysteresis. The flow rate does not change.

Therefore, in order to eliminate the above problem, the valve 3 is closed by the number of operation pulses ΔpM calculated above → then Pα> Ph
The pulse 'ePα is further closed → then Pα>Ph
It is opened by the number of pulses Pα.

By the above operation, the valve 3 is closed by 72M in terms of opening direction characteristics.

That is, as shown in FIG. 6, if the current number is pM, the number of pulses after the output timing is as described above (I, (II), corresponding to OI+, (I) PM
= PM + ΔPM (II) PM = PM 1ri PH - PM + ΔpM - pα + Pα.

FIG. 8 shows a flowchart of the above-described operation of the controller 16.

In the above embodiment, the opening operation is performed at the previous timing pulse and the closing operation is performed at the next timing pulse, but this is the opposite. Then, the number of pulses PMld in the case where the closing operation was performed at the time of the previous timing pulse and the opening operation was performed at the time of the next timing pulse, In the case of (1), PM''PM + ΔpM - pα + Pα ( 11
), in the case of pM-pM Olo, it becomes PM-PM+ΔPM.

Furthermore, in the above embodiment, a motor is used as the drive source for the valve 3, and the control is controlled by the number of pulses. However, it is also possible to use an electromagnet as the drive source, and in this case, the drive current is controlled by the number of pulses instead of the number of pulses. Just do it.

The method of the present invention can be applied not only to refrigeration systems but also to controlling the flow rate of refrigerant in air-conditioning systems in general.

As described above, the present invention controls a reversible proportional type It tension valve using a motor or an electromagnet as a driving source for each timing pulse and drives the valve in the same direction as the opening/closing direction of the valve at the previous timing. is controlled according to the calculation result, and when driving in the opposite direction, it is controlled in the opposite direction beyond the maximum value of the hysteresis variation of the valve, and then controlled in the opposite direction by that value and only by the calculation result. Since the valve is controlled, the opening degree of the valve can be accurately controlled regardless of variations in the hysteresis of the valve, the connection between the valve and the control device is compatible, and the time required for adjusting the valve is short. This has effects such as improved controllability and energy savings.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an example of a conventional reversible proportional expansion valve control device, Fig. 2 is a waveform chart showing the control timing of the expansion valve, and Fig. 3 is a graph showing the relationship between the number of operating pulses and the deviation in degree of superheat. Figure 4 is a diagram showing the relationship between the valve opening/closing degree and flow rate, Figure 5 is a diagram showing the relationship between the number of operating pulses and the valve opening degree, and Figure 6 is a diagram showing the relationship between the valve opening degree and the valve hysteresis. FIG. 7 is a block diagram used in the method of the present invention, and FIG. 8 is a flowchart of the controller in the same. 3P

Claims (1)

[Claims] The degree of superheating of the refrigerant at the outlet of the evaporator of a refrigeration system, etc.
A control method for an expansion valve in which the opening degree is adjusted by being driven by an electric signal output at each timing pulse so that the expansion valve exists within a preset dead zone, and the flow rate of the refrigerant is controlled according to the opening degree. When the valve opening/closing direction during the previous timing pulse control and the next valve opening/closing direction are the same, control is performed using an electric signal according to the deviation in heating degree, and when driving in the opposite direction, the valve is controlled using an electric signal that corresponds to the variation in hysteresis of the valve. A reversible proportional expansion valve characterized in that an electrical signal greater than the maximum value is controlled by adding it to the electrical signal corresponding to the deviation, and then controlled in the opposite direction by an amount of the electrical signal greater than the maximum value. control method.