JPH02114875A - Controller for air conditioner - Google Patents

Abstract

PURPOSE:To enable a vibration of an induction motor to be reduced when it is stopped, by outputting a sampling signal in accordance with a current value of the induction motor and giving an off-control signal to a switching means in a current period for the sampling signal to obtain a predetermined specified value when a stop command is issued. CONSTITUTION:An induction motor 2 drives a compressor for circulating a refrigerant to a refrigerating cycle, being connected with a running capacitor 3 correcting a power factor, and the induction motor 2 is connected to an AC power source 4 of fixed frequency. A sample generator 13 detects a current value with voltage, applied to the induction motor 2, serving as the reference, outputting a sampling signal in accordance with a level of this current value. A control signal generator 16, when this sampling signal obtains a predetermined specified value, gives an off-control signal to a switching means 5 opening the AC power source 4 and stopping the induction motor 2. In this way, a vibration can be decreased of an air conditioner when it is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a control device for an air conditioner driven by a fixed frequency AC power source.

(Prior Art) Conventionally, in an air conditioner, an AC motor connected to a compressor is driven by a fixed frequency power source in order to circulate refrigerant in a refrigeration cycle. This AC motor is operated intermittently so that the deviation between the indoor temperature and the set temperature becomes zero.

When the above-mentioned fixed frequency electric motor is stopped, it is stopped from a relatively high constant rotation speed corresponding to a fixed frequency, that is, 50 Hz or 60 Hz.

(Problem to be Solved by the Invention) However, in the air conditioner configured as described above, the load on the electric motor connected to the compressor is the maximum torque immediately before discharge of the compressor during one revolution, and the maximum torque when the compressor starts suction. There is a large change between the minimum torque and the minimum torque. Therefore, when the compressor stops, large vibrations may occur depending on the position of the rotating shaft of the compressor. In particular, when the frequency fixed window air conditioner is turned off, it may stop rapidly and produce large vibrations.

Therefore, the same applicant has already filed a patent application filed in 1983-18.
In order to reduce compressor vibration, No. 6368 detects the phase difference between the voltage zero-crossing point and the current zero-crossing point of the AC power waveform, and outputs a signal to turn off the switching means at the current zero-crossing point. but,
In this case, the turning off of the switching means will be shifted by half a cycle. As a result of the half-cycle shift, if the induction motor is not constantly slipping, there may be a slight shift in the compressor shaft position when the motor is stopped.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an air conditioner control device that reduces vibration when stopping the air conditioner.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an induction motor that is supplied with power from a fixed frequency AC power source and drives a compressor for circulating refrigerant in a refrigeration cycle, and an induction motor that drives a compressor for circulating refrigerant in a refrigeration cycle. A switching means inserted between the AC power source and the AC power source detects the current value of the induction motor based on the phase timing of the AC power voltage applied to the induction motor, and sequentially outputs a sampling signal corresponding to this current value for each cycle of the power source voltage. An output sample generator and an off control for opening the AC power supply to the switching means when the sampling signal output from the sample generator reaches a predetermined specific value when a command to stop the induction motor is issued. The control signal generator is equipped with a control signal generator that outputs a signal.

(Function) In the air conditioner control device configured as described above, since the induction motor is directly connected to the compressor, the induction motor is operated during one rotation between the maximum torque immediately before discharge and the minimum torque at the start of suction. The compressor pulsates loudly. Also, due to the directly connected compressor, slippage occurs in the induction motor, and due to this slippage, the above-mentioned pulsation does not match the sine wave of the power supply voltage, even if the relative phase matches at a certain point. , From that point on, the pulsation and sine wave gradually deviate, becoming larger and then smaller.

Then, the pulsation and the sine wave match again, and this change is repeated periodically. For example, if an induction motor is operated with 5% slip, the power supply voltage is 20
The relative relationship between the sine wave and pulsation of the power supply voltage becomes the same once every cycle. Further, the primary current of the induction motor causes a change in phase difference with the voltage phase of the power supply depending on the magnitude of the instantaneous torque. That is, when the torque is large, the phase difference becomes large, and when the torque is small, the phase difference becomes small. In addition to being able to estimate the shaft angle at each cycle of the power supply waveform from the trends of maximum, minimum, increase, and decrease of this phase difference, by detecting the current value at the zero crossing point of the voltage waveform, the current value can be detected before the current reaches zero. Outputs a signal to stop the compressor.

In the present invention, the sample generator detects a current value based on the voltage applied to the induction motor, and outputs a sampling signal according to the magnitude of this current value. When the sampling signal output from the sample detector reaches a predetermined specific value, the control signal generator applies an off control signal to the switching means to open the AC power supply and stop the induction motor. I.
to stop at a specific position.

(Example) A control device for an air conditioner according to the present invention will be described below based on the drawings. FIG. 1 shows an embodiment of an air conditioner control device (hereinafter referred to as a control device). This control device 1
An induction motor 2 that drives a compressor for circulating refrigerant in the refrigeration cycle is connected to the refrigeration system along with a running capacitor 3 that corrects the power factor. The induction motor 2 is connected to a fixed frequency AC power source 4, for example a 50 Hz commercial power source, and driving power is supplied via a triac 5 used as a switching means. A voltage sensor 6 and a current sensor 7 are attached to the AC power supply 4.
The current sensor 7 detects the voltage Vs and the current ll11 which are out of phase as shown in FIG. The voltage Vs detected by the voltage sensor 6 is applied to a zero-cross detection circuit 8, and the current 1m detected by the current sensor 7 is applied to a current detection circuit 9. The voltage sensor 6 and the zero-cross detection circuit 8 are coupled by a photocoupler (not shown), and the light-emitting portion of the voltage sensor 6 emits light as a current flows in the negative half cycle of the AC voltage waveform, and provides this optical signal to the zero-cross detection circuit 8.

The zero-crossing detection circuit 8 detects a zero-crossing point at the start or end of the optical signal, and outputs a zero-crossing signal Vo corresponding to this zero-crossing point. On the other hand, the current detection circuit 9 converts the current 1 m into a corresponding voltage signal Vi,
This voltage signal V1 is output. The voltage signal Vj and the zero-crossing signal Vo are given to a sample-and-hold circuit 10, and the sample-and-holding circuit 10 receives the voltage signal from the current detection circuit 9 at the time when it receives the zero-crossing signal VO, that is, when the AC power supply waveform changes from negative to positive. the magnitude of the voltage signal,
1', the current value is obtained, and a sample-and-hold signal Vt+ is formed according to the magnitude of this voltage signal. This sample hold signal Vh has a waveform shown in FIG. 3(a) in contrast to the power AC waveform shown in FIG. 3(c), and becomes a signal corresponding to the current Im. The waveform shown in FIG. 3(b) is formed by the sample and hold circuit]0, and is the delay to the current zero-crossing point when the sample bold signal Vl+ is obtained, that is, when the current value is detected at the voltage zero-crossing point. It shows the time. Figure 3(a) and Figure 3(
The relationship between the waveforms shown in C) will be explained in detail later. In this way, the zero cross detection circuit 8, the current detection circuit 9, and the sample hold circuit 10 constitute the sample generator 13.

Now, to explain the sample hold signal Vh,
The output of this sample and hold signal vh is repeated for each cycle of the power AC waveform. However, normally there is slippage in the induction motor 2, and if the induction motor 2 or two poles are rotating with a slippage of 5%, the number of shaft rotations per cycle of the voltage waveform will be 0.95 rotations. . On the other hand, the current waveform corresponding to one cycle of the voltage waveform becomes a waveform influenced by the load torque which is shifted by 5% from the period of the voltage waveform.

Since this deviation accumulates by 5% for each cycle of the voltage waveform, the
As shown in Figure (a), a sampling signal vh is obtained in which one cycle is 20 cycles of the AC power supply 4. This 2
The states of the voltage and current waveforms that change during the 0 cycle correspond to the rotational position of the shaft.

The sample-and-hold signal Vh formed by the sample-and-hold circuit 10 is held by the sample-and-hold circuit 10, and is also provided to a maximum value holding circuit 11 and a minimum value holding circuit 12, and also to a comparison circuit 14, which will be described later.

The maximum value holding circuit 1] and the minimum value holding circuit 12 store the maximum value VX and minimum value Vn of the received sample and hold signal vh.
At the same time, the maximum value VX is applied to one input terminal of the voltage dividing circuit 15, and the minimum value Vn is applied to the other input terminal of the voltage dividing circuit 15. The maximum value holding circuit 11 detects a signal corresponding to the maximum torque at voltage zero crossing, and the minimum value holding circuit 12 detects a signal corresponding to the minimum torque of the voltage phase value. The voltage dividing circuit 15 consists of a resistance element, and this resistance element is configured to obtain a comparison reference voltage signal Va corresponding to an intermediate value between the maximum value Vx and the minimum value Vn. The comparison reference voltage signal Va corresponds to the shaft position without being influenced by the compressor load since it divides the maximum value VX and the minimum value Vn. This comparison reference voltage signal Va
is applied to one input terminal of the comparison circuit 14, and the sample hold signal VI+ is applied to the other input terminal of the comparison circuit 14, as described above. Comparison circuit ] 4 compares the sample hold signal Vh with the comparison reference voltage signal Va, and when the sample hold signal Vh is larger than the comparison reference voltage signal Va, outputs the position indication signal Sa in the H state and samples and holds the sample hold signal Vh. When the signal Vh is smaller than the comparison reference voltage signal Va, an L-state position indication signal +3' S +1 is output. This position indication signal Sa is a signal based on the current value detected at the voltage cellocross point, and the time when this position indication signal Sa is obtained is the time when the current value gradually increases, and this IK purchase induction The load torque of the motor 2 is determined to be the maximum, and the position of the shaft of the compressor directly connected to the induction motor 2 at this time is determined as the position of the maximum torque of the compressor immediately before discharge. In this way, the maximum value holding circuit 11, the minimum value holding circuit 2, the voltage dividing circuit 15, and the comparison circuit 14 constitute the control signal generator 16.

The position indication signal Sa is applied to the edge detection circuit 17. This edge detection circuit 17 is designed to receive a compressor on/off command So.
When the compressor on/off command is issued,
Edge detection 111 circuit] 7 detects the front edge or the rear edge of the rectangular wave position indication signal Sa, and generates an off control signal Sc to turn off the induction motor 2 at the timing of either the front edge or the rear edge. Output.

The compressor on/off command SO is a command signal for turning off the combu I nozzer generated by the thermo-off due to the room temperature or by the stop signal from the manual switch.

This off control (ri signal Sc) is applied to a triac 5 connected in series to the conductor of the AC power source 4. This triac 5 and the edge detection circuit 17 are coupled by a photocoupler (not shown).

Therefore, the off control signal S (↓ is the edge detection circuit 17
The light is output as an optical signal from the light emitting section of the triac 5, and is applied to the light receiving section of the triac 5, thereby turning off the induction motor 2.

Next, the operation of the control device 1 shown in FIG. 1 will be explained based on FIG. 4. Note that the sample hold signal Vh is as shown in Figure 3 (a
) is simplified to a sine wave.

As already mentioned, the comparison circuit 14 compares the sample hold signal Vh and the comparison reference voltage signal Va, and outputs the position indication signal Sa when the sample hold signal Vh is larger than the comparison reference voltage signal Va. If the compressor on/off command So is in the H state at the time when the position instruction signal Sa changes from the L state to the H state, the induction motor 2 continues to rotate, that is, the compressor continues to operate. If the compressor on/off command So is in the L state at the time when the position instruction signal Sa changes from the L state to the H state, the off control signal Sc in the L state is generated at either the front edge or the rear edge of the position instruction signal Sa. , this off control signal Sc is applied to the triac 5. This causes the triac 5 to cut off power to the induction motor 2.

This power cutoff is performed at the voltage zero-crossing point of the power supply voltage waveform. That is, the sample hold circuit 10 detects the magnitude of the current 1 m at the voltage cross point of the voltage Vs, and based on the sample hold signal Vh corresponding to the magnitude of the current 1 m, the position indication signal S a % and Since the off control signal Sc is formed, power to the induction motor 2 is cut off during the phase delay time of the current from the voltage zero cross point.

In experiments, it was found that when one cycle of torque pulsation is divided into eight stages and stopped at each point, the minimum point of vibration acceleration is found near the minimum point of phase difference. In this case, there was a difference in vibration acceleration of about 12 between the minimum point and the maximum point. In addition,
The shaft position that minimizes vibration may be determined through experiments based on the size of the compressor, etc., and the voltage dividing circuit 15 may be adjusted based on the results to determine the comparison reference voltage signal Va. As described above, according to the present invention, it is possible to make the air conditioner with small vibrations i+ when the compressor is stopped.

FIG. 5 shows another embodiment of the control device 1 of the present invention. In this embodiment, the valves are switched when the air conditioner is operated for cooling, heating, defrosting, etc., and the aim is to reduce the noise generated at that time. That is, if the valve is switched at a specific point in time at the shaft position of the compressor directly connected to the induction motor 2]3, the pressure difference between the refrigerant inlet and outlet sides of the valve will be minimal, so the noise caused by the valve switching will be reduced. can be minimized.

To explain the control device 1 shown in FIG. 5, this control device 1 has the same configuration as that already explained based on FIG. The configuration of this control device 1 that differs from the above embodiment is that one input terminal of a sequential control circuit 18 is connected to the output terminal of the edge detection circuit 7, and a valve switching circuit is connected to the output terminal of the sequential control circuit 18. The other input terminal of the sequential control circuit 18 receives the valve switching signal Ba from another circuit.Therefore, in this case, the control device 1 receives the AC power waveform. The current value is detected at the voltage zero cross point of the current value, and based on the sample hold signal vh corresponding to this current value, the valve switching instruction signal Bi is generated so that the shaft position of the compressor minimizes the pressure on the discharge side of the compressor. A plurality of sets of the sequential control circuit 18 and one valve switching circuit are provided for each valve, and the above-mentioned valve switching instruction signal B1 is transmitted to the plurality of sequential control circuits]8
given every time. The valve switching circuit 19 turns on and off energization to the operating coil of the valve when opening and closing the valve or switching from one side to the other.

When energizing the valve's operating coil is turned on, a valve switching signal Ba in an H state is first applied to the C terminal. H to C terminal
While the valve switching signal Ba in the state is being applied, the edge detection circuit 17 outputs the valve switching instruction signal Bj, and when this is passed to the D terminal of the sequential control circuit 18, the Q terminal becomes the H state. . This H signal is applied to the valve switching circuit 19 to energize the actuating coil of the valve. At this time, the valve switching instruction signal Bi is the shaft position (No. The noise during switching is reduced.

On the other hand, when turning off the power to the valve's operating coil, C
The valve switching signal Ba in the L state is applied to the terminal, and the L state is applied to the C terminal.
While state valve switching No. 15 B +1 is given, D
When the valve switching instruction signal Bj is given to the terminal, the Q terminal becomes L.
state. This L signal is given to the valve switching circuit ]9,
De-energize the valve's operating coil. At this time, as in the case described above, the pressure difference between the refrigerant inflow side and the outflow side of the valve is minimized, and the switching noise is reduced.

Although the triac 5 is used as the switching means in the above embodiment, an element capable of turn-off control may also be used.

〔Effect of the invention〕

As described above, the air conditioner control device of the present invention detects the current value based on the phase of the voltage applied to the induction motor, outputs a sampling signal according to this current value, and issues a stop command to the induction motor. When the induction machine is stopped, an off control signal is given to the switching means at a sampling signal or a current cycle that reaches a predetermined specific value. It is possible to generate an off control signal between the phase delay time of the current and stop the induction machine at the current zero cross point, and the compressor shaft can be stopped at the optimal position without slipping. can.

[Brief explanation of the drawing]

Fig. 1 is a circuit configuration diagram showing a control device for an air conditioner according to the present invention, Fig. 2 is a waveform diagram showing voltage and current waveforms of an AC power supply, and Fig. 3 is a sample and hold signal, current delay time, and A waveform diagram showing the relationship with the waveform of AC power supply,
FIG. 4 is a waveform diagram showing the operation of the control device, and FIG. 5 is a circuit configuration diagram showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Control device, 2... Induction motor, 4... AC power supply, 5... Switching means (TRIAC), 6
... Voltage sensor, 7... Current sensor, 1B... Sample generator, 16... Control (K generator, 17...
・Edge detection circuit, Vll...sampling signal (sample hold signal), Sa...position instruction signal, So
...stop command (compressor on/off signal), Sc.
...Off control signal.

Claims (1)

[Scope of Claims] An induction motor that is supplied with power from a fixed frequency AC power source and drives a compressor for circulating refrigerant in a refrigeration cycle; a switching means inserted between the induction motor and the AC power source; a sample generator that detects a current value of the induction motor at a specific phase timing of an AC power supply voltage applied to the induction motor and sequentially outputs a sampling signal corresponding to the current value for each cycle of the power supply voltage; and the induction motor. control for outputting an off control signal to the switching means to open the AC power supply when the sampling signal output from the sample generator reaches a predetermined specific value when a stop command is issued; A control device for an air conditioner, comprising: a signal generator.