JPS5847628B2 - Refrigerant flow control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a refrigerant flow rate control device used in a refrigeration cycle 6, and particularly relates to a refrigerant flow rate control device using an expansion valve having a mechanism whose opening degree can be adjusted by an electric signal. Regarding a control device.

A refrigeration cycle is usually constructed as shown in FIG. 1, for example.

1 is a compressor, 2 is a condenser, 3 is an expansion valve, and 4 is an evaporator.

The expansion valve 3 has an inlet and an outlet of the evaporator 4.
, is controlled by a control circuit 5 that controls the valve opening degree of the expansion valve 3 according to the difference in refrigerant temperature detected by the second temperature sensor, so as to keep the temperature difference between the intake ports of the evaporator 4 constant. It has become.

Temperature sensors include those that convert temperature into resistance value and those that convert temperature into voltage, but regardless of which,
Any material that can be converted into an electrical signal is sufficient.

As the expansion valve 3, for example, there is one having a structure shown in FIG.

The valve frame 3A has a valve 3B, a valve seat 3C, an inflow port 3D, and an outflow port 3E, and the refrigerant flows from the inflow pipe 3F through the inflow port 3D, the gap between the valve seat 3C and the valve 3B, and the outflow port 3E. Then, it flows out through the outflow pipe 3G.

The valve drive unit is housed in the case 3H and is made of bimetal 31.
, an electric heater 3j1 for displacing the bimetal 31
Consists of 3k springs.

The power supply line of the electric heater 3j is drawn out to the outside via the connection terminal 3Lt3M.

With this configuration, while the compressor 1 is in operation, the difference (T2 - T1) between the temperature T1 detected by the first temperature sensor and the temperature T2 detected by the second temperature sensor must be lower than a predetermined temperature. For example, the control circuit 5 outputs a signal to reduce the amount of current supplied to the electric heater 3j, thereby reducing the valve opening of the expansion valve 3, thereby reducing the refrigerant flow rate, and thereby (T2 - T1
) increases.

Conversely, if (T2-T,) is higher than the predetermined temperature, the control circuit 5 controls the opening of the expansion valve 3 to increase, the refrigerant flow rate increases, and (T2-T,) decreases.

This operation keeps (T2-T1) at constant values, thereby keeping the degree of superheat at the outlet of the evaporator approximately constant.

However, when the refrigeration cycle is stopped, the electricity to the electric heater 3j of the expansion valve 3 is cut off, so that the valve is fully closed.

If the expansion valve 3 is closed when the compressor 1 is stopped, it will take a long time for the high and low pressures in the refrigeration cycle to balance to a level that does not interfere with the next start of the compressor 1. This poses a practical problem in, for example, a room air conditioner that requires on/off within a short period of time.

In order to solve the above-mentioned problem, a device as shown in FIG. 3, for example, can be considered.

Figure 3 also shows an electric circuit when the refrigeration cycle is applied to a room air conditioner.

I is a commercial power supply, 8 is an on/off switch for power supply to the following circuits, 9 is a usage-side ventilation fan motor, 10 is a room thermostat, 11 is a mork for the compressor 1, and 12 is a heat source-side ventilation fan mork.

When the switch 8 is closed, the user-side ventilation fan motor 9 operates, and if the room temperature is higher than the set temperature, the room thermostat 10 is turned on, the compressor motor 11 is started, and the heat source-side ventilation fan motor 12 is started. , cooling operation starts.

When the room thermostat 10 is turned off, the compressor moke 11 and the heat source side ventilation fan moke 12 are stopped, and the cooling operation is stopped.

The control circuit 6 is configured as follows.

60 is a DC power supply circuit, which is composed of an l-lance, a diode, and a capacitor.
It is cc.

5A and 5B are thermistors as first and second temperature sensors, which have the same characteristics in this embodiment.

A resistor 61 provides a predetermined temperature ΔT of the difference (T2-T1) between the evaporator inlet temperature T1 and outlet temperature T2.

If (T2-T1) - ΔT, the sum of the resistance value of the thermistor 5B and the resistance value of the resistor 61 becomes equal to the resistance value of the thermistor 5A, and the voltage ■A at point A becomes 0 DV.

If (T2-T1)>ΔT, the sum of the resistance value of the thermistor 5B and the resistance value of the resistor 61 becomes smaller than the resistance value of the thermistor 5B, and the voltage VA at point A becomes a positive voltage.

Conversely, if (T2-T1)<ΔT, the voltage vA at point A becomes a negative voltage.

That is, the temperature difference between the inlet and outlet temperatures T1 and T2 of the evaporator 4 is converted into a voltage vA as an electrical signal.

62 is an amplifier that proportionally multiplies the voltage vA at point A.

The amplifier 62 consists of a resistor and an operational amplifier.

A buffer 63 is composed of an operational amplifier, a resistor, and a transistor, and its output voltage is equal to the input voltage.

Therefore, if the human power voltage is viB, the voltage ■H applied to the heater 3j is (VOO-viB).

Reference numeral 64 denotes a stop control circuit, which is comprised of a relay 64A interlocked with the room thermostat 64, resistors 64D, 64E, 64F, a capacitor 64B, a diode, and a comparator 64C with an open collector output, the output of which is applied to a buffer 636.

Next, the operation of the circuit shown in FIG. 3 will be explained with reference to the timing chart shown in FIG. 4.

A is the voltage vA at point A, port is the output voltage of the amplifier 62, C is the applied voltage vH of the electric heater 3j, and second is the inverting input Vi (solid line) and non-inverting input vN (broken line) of the comparator of the stop control circuit. show.

First, switch 8 is closed at time tφ.

At this point, the room thermostat 10 is not turned on.

The inlet and outlet temperatures of the evaporator 4 are approximately equal, and the voltage at point A is vA.
becomes negative.

The output of amplifier 62 will be positive.

Relay 64A is off and Vi is connected to capacitor 64B6
Since this is not charged, vi<vN, and the comparator 64C output transistor is off, the buffer 636 +VOO is applied.

Therefore, the buffer 63 output becomes +VCC, VH becomes zero, and the expansion valve 3 becomes fully closed.

When the room thermostat 10 is turned on at time t1, the relay 64
A is turned on, the capacitor 64B starts to be charged, and Vi increases by G as time passes.

On the other hand, vN becomes +VOO.

Since vi<vN, the comparator 64C output transistor remains off.

When (T2-T1) is no longer zero due to the operation of the compressor 1, vA is generated accordingly, and the heat applied voltage VH
changes, and at a certain point, (T2-T, ) becomes equal to ΔT, and a stable state is entered.

The vibration shown in the intermediate diagram is a transient phenomenon seen in general control systems.

When the room thermostat 10 is turned off at time t2 due to a decrease in room temperature due to the cooling operation, the relay 64A is turned off and +VCC is applied to the buffer 63 via the resistor 62AK.

However, the charge on the capacitor 64B is the resistor 64D.
As a result, Vi decreases as shown by the solid line in FIG. 4 (2).

On the other hand, vN decreases to a voltage obtained by dividing the power supply voltage by resistors 64E and 64F.

During the period Vi>VN, the output transistor of the comparator 64C is turned on, so that the output voltage of the buffer 63 becomes -
VOO, the applied heat voltage becomes vH=:=2cc, and a fully open signal is output to the expansion valve 3.

At time t3, Vi<VN, the comparator 64C output transistor is turned off, and the buffer 63 has a resistor 62.
+VOO is applied through A, the heater applied voltage vH becomes zero, and the expansion valve 3 operates in the fully closed direction.

Through this operation, after the room thermostat 10 is turned off and the refrigeration cycle reaches the stopped state 6, the high and low pressures in the refrigeration cycle are quickly balanced by the fully open operation of the expansion valve 3 for a certain period of time, and the compression It is possible to restore the balance in which the machine 1 can be started, and the practical problems encountered in the past are eliminated.

However, even if there are 6 such devices, the compressor 11
If the compressor 1 is restarted in a state where the high and low pressures are not yet balanced, as is the case immediately after the compressor is stopped, the same problem as in the conventional case will occur.

The present invention provides a refrigerant flow rate control device that eliminates the drawbacks seen in the above-mentioned conventional examples.

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

In FIG. 5, a resistor 66A is provided in series with the relay contact of the stop control circuit 64 in FIG.
Diodes 66B, 66C, 66 are connected in parallel to the 4C output side.
This is a stop control circuit in which a relay coil 66E having a normally closed contact in series with a diode 66B is added.

When thermostat 10 turns off, comparator 64C
The output is LO for a certain period of time, and during this period the diode 66
Relay 66E is energized via B, and its contacts are turned off.

On the other hand, even if the thermostat 10 is turned on during this period, the common terminal of the relay 64A is almost negative via the diode 66D.
It is clamped to VOO, the capacitor 64B is not charged, and the output of the comparator 64C remains LO.

Therefore, during this period, regardless of whether the thermostat 10 is on or off, the normally closed contact of the relay 66E is open, and the compressor 1
1, restart is prohibited.

According to the circuit of the timer 66, when restarting the compressor 11 when the high and low pressures are not yet balanced due to a delay in the operation of the expansion valve, such as immediately after the compressor 11 has stopped, the discharge of the capacitor 64B causes Compressor 1 that can prohibit restarting for a certain period of time and maintains stability with the balance between high and low pressures always restored.
When a predetermined time period for restarting the engine has passed, the output of the comparator 64C becomes Hi, the prohibition is canceled, and the compressor 11 starts operating when the thermostat 10 is turned on.

According to the circuit of the timer 66, a restart prevention timer can be easily obtained by increasing the number of parts with a small number, and the restart prevention timer operates effectively even in the event of a power outage.

In this way, fully opening the expansion valve 3,
The refrigeration cycle and the compressor 11 can be effectively protected from both sides of preventing restart of the compressor 11.

In addition, if the resistor 64D is removed in the circuit of FIG. 3, the above-mentioned fixed time becomes substantially infinite, and the opening degree of the expansion valve becomes fully open when the freezing and no-cycle operation is stopped.

As described in detail above, according to the present invention, the control circuit outputs a signal to fully open the expansion valve after the refrigeration cycle is stopped, and the valve opening becomes fully open. The high and low pressure balance can be quickly restored, and restarting the compressor is prohibited during a certain period of darkness when a signal indicating the valve opening is fully open is output, so the high and low pressure can be unbalanced. This has the effect that the compressor does not start up in the wrong condition and can always restart the compressor stably.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a refrigeration cycle, FIG. 2 is a sectional view of an example of an expansion valve, FIG. 3 is a control circuit diagram of a refrigerant flow rate control device according to the present invention, and FIG. 4 is the circuit of FIG. 3. FIG. 5 is a circuit diagram showing a start control timer according to an embodiment of the present invention. 1... Compressor, 3... Expansion valve, 4...
...Evaporator, 5A...First depth sensor,
5B...Second temperature sensor, 6...Control circuit, 66...Stop control circuit.

Claims (1)

[Claims] 1. An expansion valve equipped with a mechanism whose valve opening degree can be adjusted by an electric signal, a first temperature sensor installed at the inlet or middle part of the evaporator and converting the refrigerant temperature into an electric signal, and an outlet part of the evaporator. outputting an electric signal for controlling the valve opening degree of the expansion valve according to the difference between the electric signals of the second temperature sensor provided in the first temperature sensor and the second temperature sensor; It consists of a control circuit that maintains a constant difference in electrical signals, outputs an electrical signal to fully open the expansion valve for a certain period of time after the compressor is stopped, and prohibits the restart of the compressor during the certain period of time. Refrigerant flow control device.