JPH0814431B2 - Cooling device controller - Google Patents

Description

The present invention relates to a control device for a cooling device, and more particularly to a control device for variably controlling the rotation speed (operating frequency) of a motor of a compressor in a refrigeration cycle.

(B) Conventional technology In a conventional refrigerating device of this type, for example, a refrigerator, an electric motor driving a compressor of a refrigerating cycle is operated at an upper limit temperature set above and below a target temperature, and stopped at a lower limit temperature so that an average storage temperature is reduced. It was configured so that the inside would be the target temperature. However, such a so-called ON-OFF control system cannot reduce the temperature difference due to the durability problem of the compressor.
Therefore, the temperature fluctuation in the refrigerator is inevitably large, and there is a limit to the storage performance of stored foods.

Therefore, in recent years, for example, as disclosed in Japanese Patent Laid-Open No. 58-101281, an inverter circuit composed of power transistors is used, and by controlling this with a microcomputer, the rotation speed of the electric motor of the compressor is changed according to the temperature in the refrigerator. It is considered to control the temperature to a substantially constant temperature.

(C) Problems to be solved by the invention In this type of cooling device, if the electric motor of the compressor is started before pressure balance between the discharge side and the suction side of the compressor is not achieved, for example, immediately after a momentary power failure, a large start-up occurs. Since torque is required, the motor may be overloaded and the motor may be locked (hereinafter referred to as a lock), and a large amount of winding current may flow, resulting in burnout. In the past, as a measure against such a problem, for example, as in Japanese Utility Model Publication No. 59-7954, a thermal dynamic overload electric contact that operates by an excessive winding current flowing to break the circuit is connected in series to the motor winding. Then, the power supply to the electric motor is stopped when the lock occurs.

In order to solve such a problem, the present invention is a cooling device for controlling the temperature of a space to be cooled by changing the operating frequency of the electric motor of the compressor, without using the thermal overload relay as described above. It is an object of the present invention to provide a control device that prevents accidents due to accidents.

(D) Means for Solving the Problems The present invention is a control means for calculating an operating frequency of an electric motor of a compressor of a refrigeration cycle based on temperature information to generate an output, and a drive for driving the electric motor based on the output. Means and a power supply means connected to an AC power supply and supplying a predetermined voltage to the control means and the driving means, which constitute a control device of the cooling device, and the control means is a change amount of a current value flowing between the AC power supply and the power supply means. Based on the change amount of the operating frequency, the restraint state of the electric motor is detected and stopped when the current value does not change with respect to the change of the operating frequency.

(E) Function According to the present invention, when the operating frequency signal changes by a predetermined amount and the current value does not change, it can be detected as a lock, and the electric motor can be stopped and protected.

(F) Example Next, an example of the present invention will be described with reference to the drawings. FIG. 1 shows an electric circuit diagram of a refrigerator control device (1) (not shown) as a cooling device, and FIG. 2 shows a functional block diagram thereof. (2) is a first power supply board connected to a commercial AC power supply (AC) by a power supply line (L ₁ ) (L ₁ ), which is composed of a rectifier circuit, a filter circuit, etc., and is a power supply line (L ₂ ) (L ₂ ) and 100 V AC, and between the power lines (L ₃ ) and (L ₃ ) 300 V DC, for example. (3) is a control board connected to the power supply lines (L ₂ ) (L ₂ ), and (4) is a second power supply board connected to the power supply lines (L ₃ ) (L ₃ ). Further, (5) is a driver similarly connected to the power supply line (L ₃ ) (L ₃ ), and (6)
Is an inverter composed of 6 power transistors and is similarly connected to the power supply lines (L ₃ ) (L ₃ ). (CM)
Is a motor which is a three-phase synchronous electric motor for driving the compressor (C) of the refrigeration cycle described later, and is connected to the three-phase output of the inverter (6). Further, (CT) is a current transformer provided therein for detecting an alternating current flowing in the power supply line (L ₁ ), and its output is input to the A / D converter (7).

Next, the outline of the operation of the control device (1) of the present invention will be described with reference to the functional block diagram of FIG. The control board (3) is a control microcomputer (9) composed of a general-purpose microcomputer and a power supply line (L ₂ ) for powering the microcomputer.
It comprises a rectifying step-down means (10) connected to (L ₂ ). To the control microcomputer (9), the output of the temperature detecting means (11) for detecting the temperature (T _P ) in the refrigerator (not shown) and the output of the A / D converter (7) are input, and predetermined arithmetic processing is performed. To output the operating frequency signal (H) of the motor (CM) from the output terminal (OUT). Next, the second power supply board (4) is a power supply microcomputer (12) which is also a general-purpose microcomputer and a step-down means (14) connected to the power supply lines (L ₃ ) (L ₃ ) to serve as the power supply for the microcomputer. ) Consists of.
The power supply microcomputer (12) receives the operating frequency signal (H), executes arithmetic processing based on the input, and outputs a waveform shaping output (W) for driving the motor (CM) to the driver circuit (16). To do. The two microcomputers (9) and (12) form a control means. The driver (5) is composed of a driver circuit (16) including a plurality of switching means such as transistors, and a step-down means (17) connected to the power supply lines (L ₃ ) (L ₃ ) to serve as a power supply for the driver circuit. The driver circuit (16) triggers the bases of the six power transistors of the inverter (6) based on the waveform shaping output (W) to form a rotating magnetic field, and as a result, the rotation speed according to the operating frequency signal (H). To drive the motor (CM). The driver (5) and the inverter (6) constitute a driving means.

The motor (CM) drives the compressor (C), and as a result, as shown in the refrigerant circuit diagram of the refrigeration cycle in Fig. 5, the high-temperature and high-pressure gas refrigerant discharged from the compressor (C) is condensed in the condenser (2). Flow into the condenser to be radiated and liquefied, the pressure is reduced through the capillary tube (21), and then the refrigerant flows into a cooler (22) provided in a refrigerator (not shown) and evaporates there, and then the compressor (C).
Cycle to return to. When the number of rotations of the motor increases, the amount of refrigerant circulation increases and the amount of refrigerant that evaporates in the cooler (22) also increases, so the interior is cooled strongly, and when the number of rotations decreases, the amount of refrigerant that evaporates also decreases, so the cooling capacity is reduced. become weak. or,
(23) is a blower for circulating cold air in the refrigerator.

Next, the operation of the control device (1) will be described with reference to the flowcharts showing the software of the control microcomputer (9) in FIG. 3 and FIG. First power board (2)
Is connected to an AC power supply (AC), and after the power is supplied to the control microcomputer (9), everything is reset in step (S ₀ ), flag 4 is set in step (S ₁ ), and step (S ₁ ). _{In step 2} ), it is determined whether or not flag 1 is set. If not, it is determined in step (S ₃ ) whether or not flag 3 is set. Therefore, the process proceeds to step (S ₄ ). At step (S ₄ ) the current operating frequency signal (H)
Judges whether it is 60Hz or not, so proceeds to step (S ₇ ) and further
If it is 120 Hz, the process proceeds to step (S ₂₀ ) because it is not.
Step by (S ₂₀₎ In the temperature detection means (11) detects the refrigerator inside temperature (T _P), then set the step temperature (S ₂₁₎ (T _P) advance control microcomputer (9) It is judged whether the temperature is higher than the set temperature (T _S ) (eg, -20 ° C) by 4 ° C (T _S +4) or more, and if it is higher, the process proceeds to step (S ₂₂ ) and the inside of the control microcomputer (9) Set the decision frequency (H ₀ ) to 120Hz and step (S ₃₂ )
Proceed to. When (T _P ) is lower than (T _S +4) in step (S ₂₁ ), the process proceeds to step (S ₂₃ ). This time, it is judged whether or not (T _S +2) or more, and if it is, (T _S +2) ≦ (T _P ).
If <(T _S +4), the determined frequency (H ₀ ) described above in step (S ₂₄ ) is set to 90 Hz, and the flow advances to step (S ₃₂ ). When (T _P ) is lower than (T _S +2) in step (S ₂₃ ), the process proceeds to step (S ₂₅ ), and it is judged whether (T _P ) is (T _S ). _{If S} ) ≦ (T _P ) <(T _S +2), set the decision frequency (H ₀ ) to 60 Hz in step (S ₂₆ ), then reset flag 3 in step (S ₂₇ ), and then step (S ₃₂ ).
Proceed to. When (T _P ) is lower than (T _S ) in step (S ₂₅ ), the process proceeds to step (S ₂₈ ), it is determined whether (T _S -2) or more, and (T
_{If S−} 2) ≦ (T _P ) <(T _S ), proceed to step (S ₂₉ ). Set the decision frequency (H ₀ ) to 30 Hz and proceed to step (S ₃₂ ).

In step (S ₃₂ ), it is determined whether or not flag 1 is set. Since it is negative, it is determined in step (S ₃₃ ) whether or not flag 4 is set, and flag 4 is set in step (S ₁ ). reset the flag 4 proceeds to step (S ₃₄₎ from there, and sets a flag 2 in step operating frequency signal (S ₃₅₎ a (H) and 20Hz step by starting the motor (CM) (S _36). Next step (S ₃₇ )
It is determined whether or not the flag 2 is set. Since it is set, the process proceeds to step (S ₃₈ ), and the control microcomputer (9) counts, for example, the timer 2 for 2 seconds which has the function, and at step (S ₃₉ ). If it is determined whether or not the timer 2 has finished counting, the process returns to step (S ₂ ). The following steps (S ₃₃₎ until performs the same processing proceeds because now the flag 4 is reset from step (S ₃₃₎ to (S _37), from being further flag 2 also sets the step (S ₃₈ ) To (S ₃₉ ). If the timer 2 has finished counting here, the timer 2 is reset in step (S ₄₀ ), the current operating frequency signal (H) is increased by 4 Hz in step (S ₄₁ ), and the operating frequency is increased in step (S ₄₂ ). It is judged whether or not the signal (H) is equal to or higher than the previously determined frequency (H ₀ ) and if not, the process returns to step (S ₂ ). The same processing is repeated thereafter, and in step ( _S42 ), the operating frequency signal (H) determines the frequency (H).
₀ ) When it is above, proceed to step (S ₄₃ ) to reset flag 2, return to step (S ₂ ), perform the same processing to determine the determined frequency (H ₀ ), and then to step (S ₃₇ ). When the operation proceeds, the flag 2 is reset this time, so the operation proceeds to step ( _S44 ) to output the operating frequency signal (H) as the value of the determined frequency (H ₀ ). In this way, the controller (1) sets the operating frequency (rotation speed) of the motor (CM) to 20 Hz after turning on the power (AC), and then accelerates every 2 seconds to reach the current temperature (T _P ). Start the motor (CM) by accelerating to the optimum value. After that, as the internal temperature (T _P ) approaches the set temperature (T _S ), the rotation speed of the motor (CM) is decreased to decrease the cooling capacity of the cooler (22) and the set temperature (T _S). ) Maintaining the temperature (T _P ) at approximately the preset temperature (T _S ) by increasing the number of rotations and increasing the cooling capacity with increasing distance from the engine. That is, if (T _S +4) ≦ (T _P ), the operating frequency (rotation speed) of the motor (CM) is set to 120 Hz, and (T
_{If S} +2) ≤ (T _P ) <(T _S +4), 90 Hz, (T _S ) ≤
If (T _P ) <(T _S +2), 60 Hz, (T _S -2) ≦ (T _P ).
If <(T _S ), set to 30 Hz. Also, the temperature (T _P ) is (T _S −
When it becomes lower than 2), the process proceeds from step (S ₂₈ ) to (S ₃₀ ), the operating frequency signal (H) is set to 0 Hz, the motor (CM) is stopped, and the flag 4 is set at step (S ₃₁ ).
Also, when the motor (CM) is operating at 120Hz, the current that flows in the power supply line (L ₁ ) is usually about 5A, 90A is 4A, 60Hz
3A, 2A at 30Hz, and about 100mA because it is only supplied to both microcomputers (9) (12) while stopped.
It is a degree.

If the operating frequency (H) rises to 60 Hz during the above-mentioned start-up or in the temperature control state after that, the process proceeds from step (S ₄ ) to (S ₅ ) by the current transformer (CT) at this time to the power line ( The alternating current (I ₀ ) flowing in L ₁ ) is detected and stored in step (S ₆ ). If the operating frequency signal (H) further rises from this state to 120 Hz, the process proceeds from step (S ₇ ) to (S ₈ ) and the alternating current (I ₁ ) flowing in the power line (L ₁ ) at this time. Then, in step (S ₉ ), the difference (ΔI) between the current (I ₁ ) at 120 Hz and the current (I ₀ ) at 60 Hz stored previously is calculated, and then step At (S ₁₀ ), it is determined whether or not this difference (ΔI) is larger than 1 A, for example. The current (I ₀ ) when the motor (CM) is operating normally is 3 A as described above, and the current (I ₁ ) is 5 A, so the difference (ΔI) is usually 2 A or more. , Step (S ₁₀ ) to (S ₁₁ ) to set flag 3 to step (S ₂₀ ), and then step (S ₃ ) to (S ₃ ) until flag 3 is reset in step (S ₂ ). Current will not be detected because it will proceed to step ₂₀ ).
That is, the current is detected only when the operating frequency signal (H) rises to 60 Hz and 120 Hz. Further, the stored current (I ₀ ) is updated by the next detection of (I ₀ ).

The above is the situation when the motor (CM) of the compressor (C) is rotating normally. For example, the motor (CM) as described above
The motor (CM) is locked when an overload condition occurs at startup. That is, the control microcomputer (9) outputs a driving frequency signal (H) for driving the motor (CM) at any frequency, and the inverter (6) also generates a three-phase output. The motor (CM) is stopped in a restrained state. In such a locked state, a large current flows through the winding of the motor (CM), and this value is substantially constant at each operating frequency (H). Further, when such a large current flows for a long time, the winding is burned. Therefore, since the compressor (C) does not operate in the refrigerator, no cooling effect is exerted and the temperature (T _P ) rises at an accelerating rate.

On the other hand, the control microcomputer (9) still continues to calculate the operating frequency signal (H), and the temperature (T _P )
When the operating frequency signal (H) reaches 60 Hz due to the rise of the current, steps (S ₄ ) (S ₅ ) (S ₆ ) are executed and the current (I ₀ )
Is detected and stored, step (S ₇ ) (S ₈ ) is executed at the time when the frequency reaches 120 Hz, the current (I ₁ ) is detected, and then the difference (ΔI) is calculated in step (S ₉ ). To calculate. Here, as described above, in the locked state, the current flowing through the winding of the motor (CM) is substantially constant at each operating frequency signal (H), so the current flowing through the power supply line (L ₁ ) also has a substantially constant value of about 9A. is there. Therefore, the difference (ΔI) almost disappears, so it becomes negative in step (S ₁₀ ), and the operation frequency signal (H) is set to 0 Hz in step (S ₁₂ ), and the output from the inverter (6) is stopped. Release the locked state, motor (CM)
The burnout of the winding is prevented, flag 1 is set in step (S ₁₃ ), and flag 4 is set in step (S ₁₄ ). After that, the decision frequency (H ₀ ) is similarly determined, but since the operation returns from step (S ₃₂ ) to (S ₂ ), the operating frequency (H) remains 0 Hz.

Further, from step (S ₂ ) to (S ₁₅ ), the control microcomputer (9) counts, for example, the timer 1 for 3 minutes which its function has, and then at step (S ₁₆ ) the timer 1 counts. Judge whether it is finished,
If not, proceed to step (S ₁₉ ) and set the operating frequency signal (H) to 0 Hz. After that, in step (S ₁₆ ), until the timer 1 finishes counting, that is, 3 from the release of the locked state.
The operating frequency signal (H) is kept at 0 Hz until the time elapses, and the cause of the overload condition disappears. When these three minutes have passed, the process proceeds from step (S ₁₆ ) to (S ₁₇ ) and timer 1
Is reset, the flag 1 is reset in step (S ₁₈ ), the process proceeds to step (S ₂₀ ), and the motor (CM) is made ready for operation again.

In the embodiment, the lock is detected by the change of the operating frequency signal from 60 Hz to 120 Hz, but the lock is not limited to this and may be detected at another frequency.

(G) Effect of the Invention According to the present invention, the lock of the electric motor can be detected because the value of the current flowing in the circuit does not change even if the operating frequency of the electric motor changes, so that the conventional thermal overload relay or the like is unnecessary. The circuit configuration of the electric motor can be simplified. In particular, since the lock is detected by the alternating current between the alternating current power source and the power supply means, it is possible to detect the lock by using a normal alternating current device.

[Brief description of drawings]

Each drawing shows an embodiment of the present invention. FIG. 1 is an electric circuit diagram of a control device, FIG. 2 is a functional block diagram of FIG. 1, and FIG.
4 and 5 are flowcharts showing software of the control microcomputer, and FIG. 5 is a refrigerant circuit diagram of the refrigeration cycle. (1) ... Control device, (2) ... First power supply board, (6)
…… Inverter, (9) …… Control microcomputer, (12) …… Power supply microcomputer, (AC)…
… AC power supply, (CT) …… Current transformer, (CM) …… Motor,
(L ₁ ) …… Power line.

Claims (1)

[Claims] 1. A control means for calculating an operating frequency of an electric motor of a compressor included in a refrigeration cycle based on temperature information to generate an output, a driving means for driving the electric motor based on the output, and an AC power supply. The control means and the power supply means for supplying a predetermined voltage to the driving means are connected, and the control means is based on a change amount of a current value flowing between the AC power supply and the power supply means and a change amount of the operating frequency. A control device for a cooling device, which detects that the electric motor is in a restrained state and generates an output for stopping the electric motor when the current value does not change with respect to a change in an operating frequency.