JPH0481707B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method for controlling the opening of an expansion valve in an air conditioner using an expansion valve as a pressure reducer.

<Prior Art> FIG. 3 is a diagram of a refrigeration cycle used in a general air conditioner. In FIG. 3, 1 is a compressor whose operation is controlled by an inverter circuit 4 connected to an AC power source 2 via a converter 3. 5 is a four-way switching valve that switches the direction of refrigerant discharged from the compressor 1. 6 is an indoor heat exchanger, 7 is an outdoor heat exchanger, and 8 is an expansion valve as a pressure reducer.

Figure 4 shows a control circuit for a general air conditioner. (The parts common to those in Figure 3 are given the same symbols.)
In this FIG. 4, 9 is an indoor control circuit, 10
is an outdoor control circuit, and both control circuits 9 and 10
are connected by power lines 11 and 12 so that they are both supplied with power by the AC power source 2. Reference numeral 13 denotes a relay switch interposed by the power line 12, and the outdoor control circuit 10 is turned on and off by turning on and off the relay switch 13. Reference numeral 14 denotes a microcomputer on the indoor side. This microcomputer 14 is connected to the power supply 2 via a transformer 15 and a diode bridge 16. The diode bridge 16 generates a DC voltage, and this DC voltage is applied to the microcomputer 14. is applied to. Reference numeral 17 denotes a remote controller placed indoors, and this remote controller 17 is connected to the microcomputer 14 so that information such as air conditioning mode, temperature setting, etc. is input to the microcomputer 14. 18 is a temperature sensor such as a thermistor, which inputs room temperature information to the microcomputer 14.

Next, regarding the outdoor side control circuit 10, 3 is the above-mentioned converter, which constitutes a diode bridge. 4 is the inverter circuit section, and 6
This inverter circuit 4 has power transistors, and by switching these transistors,
The operation of the compressor 1 connected to the compressor 1 is controlled. 19 is a microcomputer on the outdoor side, which connects the power line 1 via a transformer 20 and a diode bridge 21.
Power is supplied from 1 and 12. This microcomputer 19 controls the transistor bases B _u , B _v , B _w ,
In addition to outputting signals to B _x , B _y , and B _z via the driver 22, the four-phase coil φ ₁ of the expansion valve 8,
A signal is output to φ ₂ , φ ₃ , and φ ₄ via the driver 23 .

In such a heat pump cycle, the operation of the compressor 1 is controlled according to the air conditioning load by controlling the power frequency by the inverter circuit 4, and the opening degree of the expansion valve 8 is appropriately controlled according to the amount of refrigerant circulation. As shown in FIG. 5, the refrigerant flow rate is proportionally controlled according to the valve opening degree.

The structure of this expansion valve 8 will be explained. In FIG. 6, 24 is a case, and a refrigerant discharge port 25 is provided on the lower surface of the case, and the periphery of the discharge port 25 is formed as a valve seat. 26 is this discharge port 2
A needle for controlling the amount of refrigerant discharged from the motor shaft 2 supported by the case 24.
6 to move upward and downward,
The refrigerant flow rate is adjusted by the distance Δt from the periphery serving as the valve seat.

Reference numeral 27 denotes a step motor for rotating the motor shaft 26, and the rotation of the motor 27 is controlled by instructions from the microcomputer 19. The timing chart of the signals applied to the four phases of this step motor 27 is as shown in FIG.

Reference numeral 29 denotes a stopper pin provided on the motor shaft 26, and when the motor shaft 26 rotates to a predetermined position and descends, it comes into contact with a stopper 28 provided on the upper surface of the case 24, and prevents the motor shaft 26 from rotating any further. ing. In addition, the stopper pin 29 is the stopper pin 28.
At the time of contact, Δt is not 0 and there is a slight gap, allowing a small amount of refrigerant to flow. This takes into account variations in the dimensions of the mechanism.

Now, such an expansion valve 8 has an opening degree adjustment range of N steps (for example, 240 steps) from fully closed to fully open, but when restarting operation after stopping, the valve 8 itself has an opening adjustment range of N steps (for example, 240 steps). Since the opening degree is unknown, initialize the valve opening degree. That is, as shown in FIG. 8, after the valve 8, which is at a predetermined opening degree, is once fully closed a, the operating opening degree b is adjusted based on this fully closed state.

On the other hand, when the operation is stopped, in order to prevent the compressor from overloading when the operation is restarted, the
Low pressure needs to be balanced. For this reason, the power to the outdoor unit is turned off after the expansion valve 8 is fully opened. In this case, if you open the expansion valve 8 too suddenly, the high and low pressures will become unbalanced all at once, making a loud noise. To avoid this, open the expansion valve 8 by a few steps c from the opening level just before stopping operation. was.

However, when the operation is stopped, the opening is opened by a few steps c from the opening just before the end of operation, and then when the operation is started, it is always fully closed. It is outputted to the step motor 27 to ensure that it is fully closed.

However, since the stopper pin 29 and the stopper 28 are provided to prevent the needle 26 from getting stuck in the discharge port 25 and becoming unable to drive, it is possible to prevent the needle 26 from being in a fully closed state (for example, N ₁ (N>N ₁ )).
(assumed to be a step state) to fully closed (N
+α) steps in the closing direction, the stopper pin 29 comes into contact with the stopper 28 after driving up to _N1 steps, and the remaining (N+
α) −N ₁ minute is a blank firing state. In other words, even if the rotation is stopped by the stopper 28, the motor 27 tries to rotate, so the stopper pin 29 rotates slightly in reverse due to the reaction of contacting the stopper 28, and then contacts the stopper 28 again and rotates in the reverse direction, which is repeated. Since the stopper pin 29 and the stopper 28 are both made of metal, they produce a clicking sound due to the above-mentioned blank firing, which is unpleasant to the user's ears and has a negative effect on the expansion valve itself.

<Means for solving conventional problems> When the operation is stopped, the expansion valve is further opened for a predetermined amount and for a predetermined time from the opening degree immediately before the operation is stopped, and is then fully opened.

<Function> When the operation is stopped, the expansion valve is further opened for a predetermined amount and for a predetermined time from the opening immediately before the operation is stopped, and then the expansion valve is fully opened, so that the pressure balance in the refrigeration cycle is balanced. Since this is not done all at once, no loud noise is generated.

In addition, at the start of operation, in order to change the expansion valve from the fully open state at the time of stopping the operation to the fully closed state for initial setting, even if a fully closed command is issued by adding an extra α to the opening adjustment width N, it will not be possible to open the expansion valve. The only thing left to hit is the extra α, and this α is usually a very small step width, so there are almost no empty hits.

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

FIG. 1 is a diagram showing the opening degree of the expansion valve over time. FIG. 2 is a flowchart of the same example.

The control method according to the embodiment of the present invention will be explained based on FIGS. 1 and 2.

First, it is determined whether the operation is ON or OFF. When the operation is turned on by operating the operation switch or the like, the microcomputer 19 on the outdoor side outputs a closing command for 250 steps, which is an opening width of 240 steps plus an extra 10 steps, through the microcomputer 14 on the indoor side. This fully closing initializes the expansion valve opening,
Initial setting c of the expansion valve is performed based on this fully closed state. After the initial setting is made, the opening degree control of the expansion valve will continue depending on the air conditioning condition until the operation is turned off.

At this point, operation can be started by operating the operation switch, etc.
When it turns OFF, first the expansion valve 8 is turned off for 50 steps.
A command to open the flow path is output from the outdoor microcomputer 19 to the step motor 27, and this command causes the step motor 27 to move up the needle 26 and slightly open the flow path. This state of opening for 50 steps continues for 30 seconds, during which time the high and low pressures in the cycle are balanced to some extent. After 30 seconds have elapsed, a drive command is output to the step motor 27 until it is fully open. After performing this full opening operation, the power to the outdoor unit is turned off.

In this OFF state, ON and OFF operations are monitored. When the operation is turned on here, the expansion valve 8 is fully closed by performing the closing drive for 250 steps (opening width 240 steps + extra 10 steps) as described above. After being fully closed, the initial settings are again made and the opening degree of the expansion valve 8 is controlled.

Therefore, even if the fully closed operation is performed for 250 steps at the start of operation, the expansion valve is fully opened before the start of operation, so the expansion valve is only operated for an extra 10 steps, which is different from the conventional one. Compared to , there is almost no blank firing.

Further, when the operation is stopped, the valve is first opened for 50 steps and then fully opened, so that the high and low pressures are balanced to some extent when the 50 steps are opened, and no noise is generated due to the balance between high and low pressure during the fully opened operation.

<Effects> As described above, according to the present invention, it is possible to prevent the generation of noise accompanying the pressure balance adjustment of the refrigeration cycle when the operation is stopped, and furthermore, it is possible to suppress the dry firing caused by the fully closing operation of the expansion valve at the start of operation.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the valve opening degree of an embodiment of the present invention, Fig. 2 is a flowchart of the same example, Fig. 3 is a general heat pump cycle diagram, Fig. 4 is an electric circuit diagram used in an air conditioner, Fig. 5 is a characteristic diagram of valve opening and flow rate, Fig. 6 is a sectional view of the expansion valve, Fig. 7 is an input timing chart for each phase of the expansion valve, and Fig. 8 is an explanation of the valve opening of the conventional control method. figure. 8: Expansion valve, 27...Step motor.

Claims (1)

[Claims] 1. In a refrigeration cycle equipped with an electric compressor, a condenser, an expansion valve and an evaporator whose opening degree is adjusted by a step motor, when the compressor starts operating, The expansion valve is once fully closed, then adjusted to the desired opening and operated, and when the operation is stopped, the expansion valve is further opened by a predetermined amount and for a predetermined time from the opening of the expansion valve immediately before the operation is stopped, and then fully opened. 1. A method for controlling an expansion valve in an air conditioner, characterized in that: