JPH09152200A - Controller of refrigerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to reduce the power consumption to a much lower level than conventionally in the use of a refrigerator in which the compressor is driven by an inverter so as to change the number of revolutions. SOLUTION: There are provided a compressor 1 having inside its shell a pressure which is about the same as that of the gas sucked in, a DC motor 3 for driving the compressor, an inverter 13 capable of variable speed control, a temperature difference detective circuit 29 for detecting the difference in temperature between the storage chamber temperature and a set point, and a revolution number-setting circuit 30 by which, when the difference in temperature has become smaller than a set value, the number of revolutions of the DC motor 3 is made smaller than the rotation under commercial power supply.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerator controller for controlling the rotation speed of a compressor equipped with a DC motor.

[0002]

2. Description of the Related Art There have been proposed many refrigerators aiming at energy saving and improvement of quick-freezing performance by making the rotation speed of a compressor variable.

As disclosed in, for example, Japanese Patent Laid-Open No. 2-140577, an attempt is made to find an effect by changing the number of revolutions of a compressor of a refrigerator with an inverter.

Further, as described in the above-mentioned prior art, a rotary type compressor is generally used as a compressor in which the number of revolutions is variable with an inverter. The reason is that it has excellent performance in that the refrigerating capacity changes almost linearly according to the change in the number of revolutions and that the refueling performance is relatively independent of the number of revolutions.

[0005]

However, the conventional configuration has the following problems when the rotary compressor is used. The rotary compressor generally had a high pressure inside the shell. That is, the low-pressure suction gas is directly sucked into the cylinder of the compression unit, is discharged into the shell after being compressed, and is then discharged into the cooling system through the discharge pipe.

Due to the high pressure inside the shell, high-pressure and high-temperature gas inside the shell leaks into the cylinder of the compression section and invades into the cylinder, which reduces the compression efficiency of the compressor (leakage). It is widely known that it is a heat loss factor.

However, this leakage heat loss is determined by the high pressure and the low pressure regardless of the rotation speed. That is, when the number of rotations becomes low and the refrigerating capacity itself of the compressor becomes small, the ratio of heat loss due to leakage increases,
As a result, there has been a phenomenon that the efficiency of the compressor is reduced.

As a result, particularly when the refrigerator internal temperature is stable and a large cooling capacity is no longer needed, the energy consumption is reduced by reducing the rotation speed by the inverter to reduce the cooling capacity, thereby reducing the efficiency of the compressor. There was a problem that energy saving could not be obtained.

Further, in the rotation speed control, voltage control is performed by PWM control, but precision can be improved by making the rotation speed control fine, but there is a problem that the circuit becomes complicated and the cost becomes high.

Further, there is a problem that large noise and vibration are generated when passing through the resonance point of the refrigerator when the number of revolutions changes.

The present invention solves the problems of the prior art, and prevents the efficiency of the compressor from being lowered due to heat loss due to leakage, and controls the refrigerator capable of achieving high efficiency even at a low rotation speed and drastically reducing power consumption. The purpose is to provide a device.

Another object of the present invention is to provide a control device for a refrigerator capable of realizing control of the number of revolutions with high accuracy.

Another object of the present invention is to provide a control device for a refrigerator capable of speeding up the change in the number of revolutions and preventing noise and vibration due to resonance of the compressor.

[0014]

In order to solve this problem, the present invention relates to a compressor in which the inside of the shell has almost the same pressure as the suction gas, and a DC motor for operating the compression section of the compressor. The counter electromotive voltage detection circuit that detects the rotational position of the rotor of the DC motor from the counter electromotive voltage generated in the stator winding and the output of the counter electromotive voltage detection circuit during normal operation performs commutation to enable the DC motor. The inverter for variable speed operation, the temperature difference detection circuit for detecting the temperature difference between the internal temperature and the set temperature, and the number of revolutions are set from the output of the temperature difference detection circuit. Especially, the temperature difference becomes smaller than the predetermined value. Occasionally, the rotation speed setting circuit that sets the rotation speed lower than the commercial power supply is compared with the target rotation speed by the rotation speed setting circuit and the actual rotation speed of the DC motor. PWM to increase or decrease the control of the duty width
It is composed of a control circuit.

Thus, it is possible to provide a control device for a refrigerator which can prevent the efficiency of the compressor from being lowered due to the heat loss due to leakage and can achieve a high efficiency even at a low rotational speed and a large reduction in power consumption.

In order to solve other problems, the present invention provides
Compressor and DC for operating the compression section of the compressor
The DC from the motor and the output from the back electromotive force detection circuit
A rotation speed detection circuit for detecting the rotation speed of the motor, a rotation speed setting circuit for setting a target rotation speed, a target rotation speed and an actual D
A PWM control circuit for comparing the number of revolutions of the C motor and increasing or decreasing the duty width of the PWM control of the inverter according to the result, and the PWM control circuit includes a main duty setting circuit and a complementary duty setting circuit, The basic duty of the PWM control pulse is determined by the duty setting circuit, and n times (n is 2
M times (m is 0 or more and n
Is set to a duty higher than the duty set by the main duty setting circuit.

Thus, the control of the rotation speed can be realized with high precision and with a simple circuit at a low cost.

In order to solve other problems, the present invention provides
Compressor and DC for operating the compression section of the compressor
The DC from the motor and the output from the back electromotive force detection circuit
A rotation speed detection circuit for detecting the rotation speed of the motor, a rotation speed setting circuit for setting a target rotation speed, a target rotation speed and an actual D
A PWM control circuit for comparing the number of revolutions of the C motor and increasing or decreasing the duty width of the PWM control of the inverter according to the result, and the PWM control circuit includes a main duty setting circuit and a complementary duty setting circuit, The basic duty of the PWM control pulse is determined by the duty setting circuit, and n times (n is 2
M times (m is 0 or more and n
The integer less than) should be set to a duty higher than the duty set by the main duty setting circuit,
The auxiliary duty setting circuit is operated only when the difference between the target rotation speed and the actual rotation speed of the DC motor is smaller than a predetermined value.

This makes it possible to speed up the change in the number of revolutions and prevent noise and vibration from occurring due to resonance of the compressor.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is a compressor in which the inside of the shell has almost the same pressure as the suction gas, a DC motor for operating the compression part of the compressor, and A counter electromotive voltage detection circuit that detects the rotational position of the rotor of the DC motor from the counter electromotive voltage that occurs in the stator windings, and during normal operation, commutation is performed by the output of the counter electromotive voltage detection circuit to make the DC motor a variable speed An inverter to be operated, an inside temperature detecting means for detecting the inside temperature of the refrigerator, an inside temperature setting means for setting inside temperature, and a temperature difference between the inside temperature detecting means and the inside temperature setting means. The temperature difference detection circuit for detecting the temperature difference and the number of rotations set from the output of the temperature difference detection circuit, and particularly when the temperature difference becomes smaller than a predetermined value, the number of rotations is set to a value below the commercial power supply. Circuit and the rotation Setting circuit compares the actual rotational speed of the DC motor and the target rotational speed according to increase or decrease the duty width of the inverter of the PWM control by a result P
A refrigerator control device having a WM control circuit, and when the inside of the refrigerator is stable and can be cooled with a small cooling capacity at the number of rotations of the compressor whose internal pressure is almost the same as the suction gas, By operating the rotation speed at a lower rotation speed than the normal commercial frequency rotation, it is possible to prevent the efficiency of the compressor from being reduced due to heat loss due to leakage, and to achieve high efficiency even at low rotation speeds, and to significantly reduce power consumption. It has the effect of being able to.

According to a second aspect of the present invention, the rotational position of the compressor, the DC motor for operating the compressor of the compressor, and the rotor of the DC motor is detected from the counter electromotive voltage generated in the stator winding. A counter electromotive voltage detection circuit, an inverter that performs commutation by the output of the counter electromotive voltage detection circuit during normal operation to operate the DC motor at a variable speed, and the DC motor based on the output from the counter electromotive voltage detection circuit. The rotation speed detection circuit for detecting the rotation speed of the DC motor, the rotation speed setting circuit for setting the target rotation speed, the target rotation speed by the rotation speed setting circuit and the actual rotation speed of the DC motor are compared, and the result is compared with the inverter. And a PWM control circuit for increasing / decreasing the duty width of the PWM control, wherein the PWM control circuit includes a main duty setting circuit and a complementary duty setting circuit. Define the basic duty of the PWM control pulse via road, n by the auxiliary duty setting circuit
For a PWM waveform of n times (n is an integer of 2 or more), m times (m
Is an integer greater than or equal to 0 and less than n) is a refrigerator control device that is set to a duty higher than the duty set by the main duty setting circuit. By setting a high duty m times every n times, it is possible to highly accurately adjust the voltage as the average voltage, so that the rotation speed can be accurately controlled.

The invention according to claim 3 is a compressor,
A DC motor for operating the compressor of the compressor,
The counter electromotive voltage detection circuit that detects the rotational position of the rotor of the DC motor from the counter electromotive voltage generated in the stator winding and the output of the counter electromotive voltage detection circuit during normal operation performs commutation to enable the DC motor. An inverter that performs variable speed operation, a rotation speed detection circuit that detects the rotation speed of the DC motor based on the output from the counter electromotive voltage detection circuit, a rotation speed setting circuit that sets a target rotation speed, and a target by the rotation speed setting circuit. And a PWM control circuit for comparing the rotation speed with the actual rotation speed of the DC motor and increasing or decreasing the duty width of the PWM control of the inverter according to the result. The PWM control circuit includes a main duty setting circuit and a supplementary duty setting circuit. Consists of
The basic duty of the PWM control pulse is determined by the main duty setting circuit, and m times (m is an integer of 0 or more and less than n) for the PWM waveform of n times (n is an integer of 2 or more) by the complementary duty setting circuit. Is set to a duty higher than the duty set by the main duty setting circuit, and the auxiliary duty setting circuit is operated only when the difference between the target rotation speed and the actual DC motor rotation speed is smaller than a predetermined value. It is a control device of the refrigerator consisting of the selection circuit so that, when the actual number of revolutions is far from the target number of revolutions, it approaches the target number of revolutions quickly by changing the main duty with rough accuracy, When the actual rotation speed approaches the target, by changing the supplement duty, highly accurate rotation speed control can be realized, and the change in rotation speed can be accelerated. An effect that can be made to the noise and vibration is not generated resonate like.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. (Embodiment 1) FIG. 1 is a block diagram of a control device for a refrigerator in an embodiment of the present invention.

In FIG. 1, reference numeral 1 is a compressor. Reference numeral 2 is a shell of the compressor 1. 3 is a DC motor, which is a rotor 3
a and a stator 3b. The rotor 3a has permanent magnets arranged around it (for example, in case of 4 poles, N is set every 90 degrees).
Place the SNS pole).

Reference numeral 4 denotes a shaft, which is fixed to the rotor 3a and rotates in the bearing 5 when the rotor 3a rotates. An eccentric portion 4a is provided at a lower portion of the shaft 4. Further, a refueling pump 6 is provided at a lower portion thereof.

Reference numeral 7 denotes a piston, and the rotational movement of the shaft 4 is converted into reciprocating movement by the eccentric portion 4a, and the piston 7
Reciprocates in the cylinder 8 to compress the refrigerant. The compressed refrigerant exits the discharge pipe 9, passes through the cooling system, and is discharged into the shell 2 of the compressor 1 through the suction pipe 10.

The cooling system referred to here is the condenser 1
1, a pressure reducer 12, an evaporator 13, and a cooling fan 14. The high-temperature, high-pressure refrigerant gas compressed by the compressor 1 is cooled by the condenser 11 and liquefied. After that, the decompressor 12
(Actually, a capillary tube is used) to reduce the pressure.

Then, by evaporating in the evaporator 13, heat is taken from the surroundings to perform cooling. At this time, the cooling fan 14 sends the cooled air to various places in the refrigerator to cool the entire refrigerator.

Reference numeral 20 is a commercial power source, for example, a 100V 60Hz AC power source in a general household. Reference numeral 21 is a rectifier circuit that rectifies the commercial power source 20, and here adopts a voltage doubler rectification method.
50V is output.

Reference numeral 22 is an inverter, which has a structure in which switching elements are connected in a three-phase bridge, converts the DC output of the rectifier circuit 21 into an output of an arbitrary voltage and an arbitrary frequency of three phases, and supplies electric power to the DC motor 3. .

Reference numeral 23 is a back electromotive force detection circuit, which is a DC motor 3
The relative position of rotation of the rotor 3a is detected from the counter electromotive voltage of the winding of the stator 3b. A drive circuit 24 turns on / off the switching element of the inverter 22.

A commutation circuit 25 generates a logic signal necessary for operating the DC motor from the rotor position detection signal from the counter electromotive voltage detection circuit 23. However, in this method, since the position detection signal is obtained from the counter electromotive voltage, the position signal cannot be detected during the stop.

Therefore, during the stop, the start-up circuit 26 is used to force the operation. This is to forcibly output a signal of a predetermined voltage and a predetermined frequency from the inverter 22 to activate the DC motor as a synchronous motor. After starting, the operation is based on the position signal as described above.

Reference numeral 27 is an inside temperature detecting means for detecting the temperature inside the refrigerator (for example, a freezer). Reference numeral 28 denotes an inside temperature setting means, which sets the temperature inside the refrigerator (for example, a freezer) manually (slide volume, slide switch, etc.) or automatically.

Reference numeral 29 denotes a temperature difference detection circuit, which is used to set the temperature inside the cold storage detected by the internal temperature detection means 27 and the internal temperature setting means 2
The temperature difference from the set temperature set in 8 is detected. A rotation speed setting circuit 30 sets a target rotation speed based on the output from the temperature difference detection circuit 29.

Reference numeral 31 is a rotation speed detection circuit, which detects the actual rotation speed from the output from the counter electromotive voltage detection circuit 31. D
In the case of the C motor, the actual rotation speed can be detected from the position detection signal from the back electromotive force.

An error detector 32 compares the set rotation speed of the rotation speed setting circuit 30 with the actual rotation speed detected by the rotation speed detection circuit 31, and sends the difference. 33 is PW
M control circuit, PWM by output from error detector
The control duty is increased, decreased, or stopped to adjust the rotation speed of the DC motor.

Reference numeral 34 denotes a synthesizing circuit, which synthesizes the commutation signal from the commutation circuit 25 and the duty signal from the PWM control circuit 33 and sends it to the drive circuit 24. Specifically, the PWM control in the DC motor is performed by the inverter 22-6.
Of the switching elements, 3 on the lower or upper arm side
It is already known that only the individual elements need to be PWM controlled. Therefore, in the present embodiment, description will be made by PWM-controlling the element of the lower arm, but it goes without saying that this may be the upper arm.

The control device for the refrigerator configured as described above will be described in more detail. FIG. 2 is a characteristic diagram of the rotation speed setting circuit 30 in this embodiment.

The rotation speed is set as shown in the figure by the difference from the set temperature output from the temperature difference detection circuit 29.

When the inside of the refrigerator is getting cold from the high temperature, if the temperature difference is 2K or more, it is 58r / se.
c, if the temperature difference is less than 2K and 0K or more, 48r / se
c, less than 0K -2K or more, 40r / sec, -2
If it is less than K, it is set to 0 r / sec.

At this time, the temperature inside the chamber once rises (door opening / closing,
Since food is being added), it is necessary to reach the set temperature as quickly as possible, so cooling is performed at a relatively high rotational speed (that is, a state with high cooling capacity). When the temperature is less than -2K, the cooling is no longer required and the rotation is stopped.

When the inside temperature rises from the state where the inside temperature is sufficiently cold, if the temperature difference is less than 0K, 0r
/ Sec, 40r / if the temperature difference is between 0K and less than 2K
sec, 2K or more and less than 4K, 48r / sec, 4
If it is K or more, it is set to 58 r / sec.

At this time, since the temperature inside the refrigerator is once stable, an increase in the number of revolutions is suppressed as much as possible and an efficient operation is performed. That is, when the temperature is stable in a normal refrigerator, the temperature does not fluctuate so much, so 40 r / sec (ON) and 0 r
The operation will be performed at / sec (OFF).

Next, the operation of the compressor 1 shown in FIG. 1 will be described. When the rotor 3a of the DC motor 3 rotates, the shaft 4 also rotates at the same time. The rotor 3a and the shaft 4 are completely fixed (by shrink fitting or press fitting). The rotation is supported by sliding on the fixed bearing 5.

An eccentric portion 4a is provided below the shaft 4, and eccentrically rotates as the shaft 4 rotates. This eccentric rotation is converted into reciprocating motion, and the piston 7 is reciprocatingly moved in the cylinder 8 to compress the refrigerant.

Further, an oil supply pump 6 is attached to the lower part of the eccentric portion 4a of the shaft, and in the case of this embodiment, the pump uses the centrifugal force of rotation. This pump is often used because it is structurally very simple and reliable.

This oil supply pump 6 is for supplying the lubricating oil accumulated in the bottom portion of the shell 2 to each part of the compressor, and particularly for the sliding portion between the shaft 4 and the bearing 5. An important refueling operation is performed.

On the other hand, a large number of refrigerators and air conditioners have been proposed and commercialized, in which an inverter is used to change the number of revolutions of the compressor to make the capacity of the refrigeration system variable depending on the state of the refrigeration load. A rotary type or scroll type machine is used.

The main reason for this is that the rotary type and scroll type use the rotary motion as it is for compression, so that the refrigerating capacity can be varied over a wide range in the case of a variable speed. This is because the refueling by the differential pressure refueling (limited to the high pressure shell type in which the pressure inside the shell is almost the same as the discharge gas) is less affected by the revolving speed.

However, as a result of the inventors analyzing various data and proceeding with the analysis, the following points were noted. That is, in the case of a rotary type or scroll type compressor, the efficiency decreases at a low rotation speed. In particular, it has been found that the efficiency decreases at a lower speed than the motor itself. Particularly, in a low temperature compressor having a high compression ratio such as a refrigerator compressor, this efficiency decrease is more noticeable.

Further detailed analysis revealed that it might be caused by leakage heat loss.
It is well known that refrigerant gas leaks from between a piston and a cylinder in a compressor. However, in the case of a rotary type or scroll type compressor in which the inside of the shell has a high pressure as in the conventional case, the direction of the leakage of the refrigerant gas is the direction from the inside of the shell to the inside of the compression chamber. Heat loss occurs due to heat loss, which reduces compression efficiency.

On the other hand, since the refrigerant gas leaks regardless of the number of revolutions, when the number of revolutions is low and the cooling capacity of the compressor is small, the rate of leakage heat loss due to leakage of the refrigerant gas becomes large and the efficiency is increased. It turned out that it is decreasing.

Therefore, the inventor has paid attention to the rotation speed control by a low-pressure shell (the pressure inside the shell is almost the same as the suction gas) type compressor. In the case of a low pressure shell type compressor, since the pressure inside the shell is low and the pressure inside the shell is always lower than the pressure inside the compression chamber, the leakage direction of the refrigerant gas is from the compression chamber to the inside of the shell. Although leakage leads to a decrease in volumetric efficiency, there is no heat loss to leak and compression efficiency does not decrease.

In order to verify the above contents, an experiment was conducted using a reciprocating compressor as a low pressure shell type compressor. The result is shown in FIG. FIG. 3 is a rotational speed characteristic diagram of the compressor. FIG. 3A is a characteristic diagram of the rotational speed and the relative efficiency (the efficiency at the rotational speed of 60 r / sec is 1), FIG.
(B) is the rotation speed and the relative refrigerating capacity (rotation speed 60 r / sec
It is a characteristic diagram of the refrigerating capacity at time 1).

In FIG. 3, the characteristic of the reciprocating compressor is shown by a solid line, and the characteristic of the rotary compressor is shown by a dotted line.
The reciprocating compressor here is a low pressure shell type, and the rotary compressor is a high pressure shell type.

First, the relative efficiency of FIG. 3A will be described. The efficiency of the rotary compressor reaches its peak at a rotational speed of 60 r / sec, and the lower the rotational speed becomes, the more the efficiency drops. On the other hand, the reciprocating compressor has a rotation speed of 40 r / se.
Although there was a peak of efficiency in the vicinity of c, the characteristics were almost flat from 60 r / sec to 40 r / sec.

Next, the relative refrigerating capacity shown in FIG. 3B will be described. The refrigerating capacity of the rotary compressor changes almost linearly with the change in the rotation speed. However, in the reciprocating compressor, a low rotation speed (30 r / sec to 60 r / se
(up to c), the refrigerating capacity changes almost linearly, but at 60 r / sec or more, it changes from the saturated state to the reduced state. This is because the suction valve into the cylinder has not responded sufficiently.

As a result, it was found that the rotational speed control of the reciprocating compressor was very efficient although the variable range of the refrigerating capacity was small. In other words, a very good system can be created if the use is limited. Therefore, we propose to install it in a refrigerator for this application.

The refrigerator is limited to a box of a certain size, and the internal load changes depending on the food or the like. However, when the load is sufficiently cooled, only heat intrusion from the box can be dealt with. It just needs the freezing capacity of. That is, there is no problem even if the change width of the refrigerating capacity is small.

Also, unlike other home appliances, the refrigerator is
The power is turned on and operating all year round, and the effect of saving energy is very large. Therefore, there is a need for a more efficient system.

Further, by operating the reciprocating compressor at a rotation speed lower than the commercial frequency, the condensation temperature of the condenser 11 is lowered and the evaporation temperature of the evaporator 13 is raised in the cooling system, so that the cooling system is used. Efficiency can be further improved and even greater energy savings can be realized.

Here, a reciprocating compressor is used as the low-pressure shell type compressor, but as is clear from the principle that the efficiency is high at a low rotation speed, the same can be said for all the low-pressure inside the shell. .

FIG. 4 shows a commutation circuit 25 in this embodiment.
6 is a circuit diagram of a synthesizing circuit 34. FIG. The logical expression of the output that drives the inverter 22 is defined by (Equation 1).

[0065]

(Equation 1)

Reference numeral 50 is a first logic circuit, which is U + (U
The ON / OFF signal of the phase upper arm switching element) is output, and the positive logic A of the position signal X and the negative logic A of the position signal Y are output.
It is composed of ND.

Reference numeral 51 is a second logic circuit, which is V + (V
The ON / OFF signal of the phase upper arm switching element) is output, and the positive logic of the position signal Y and the negative logic of the position signal Z are A.
It is composed of ND.

Reference numeral 52 is a third logic circuit, which is W + (W
The ON / OFF signal of the phase upper arm switching element) is output, and the positive logic of the position signal Z and the negative logic of the position signal X are A.
It is composed of ND.

53 is a fourth logic circuit, which is U- (U
The output signal is an ON / OFF signal of the phase lower arm switching element, and is configured by ANDing the negative logic of the position signal X, the positive logic of the position signal Y, and the positive logic of the duty signal CHOP.

Reference numeral 54 is a fifth logic circuit, which is V- (V
The output signal is an ON / OFF signal of the lower arm switching element, and is configured by ANDing the negative logic of the position signal Y, the positive logic of the position signal Z, and the positive logic of the duty signal CHOP.

55 is a sixth logic circuit, which is W- (W
The output signal is an ON / OFF signal of the lower arm switching element), and is configured by ANDing the negative logic of the position signal Z, the positive logic of the position signal X, and the positive logic of the duty signal CHOP.

Next, this operation will be described in more detail. FIG. 5 shows the commutation circuit 25 and the synthesis circuit 3 in this embodiment.
4 is an operation timing chart of FIG. All symbols in FIG. 5 are the same as those in FIG.

The position signals X, Y and Z are square waves at equal intervals, and their phases are shifted by 120 degrees. U
Each of +, V +, and W + has a waveform as shown in the figure from the above-mentioned logical expression. Each is turned on by 120 degrees, and the phases are shifted by 120 degrees.

Further, U-, V-, and W-have waveforms as shown in the figure from the above-mentioned logical expressions. Each is turned on by 120 degrees and the phase is shifted by 120 degrees,
It is ON only when the duty signal CHOP is ON.

The duty signal CHOP is a square wave having a constant ON width at constant intervals. This repetition period is generally called a carrier period, and its reciprocal is called a carrier frequency. The carrier frequency is set to a value that is sufficiently higher than the rotation speed, and is generally 2k.
The range of Hz to 20 kHz is often used.

The ratio of ON in the carrier cycle is called duty, and the duty varies from 0% (ON time = 0) to 100% (ON time = carrier cycle). The higher the duty value, the higher the voltage applied to the DC motor, and the higher the rotation speed.

The contents will be described in more detail.
FIG. 6 is a characteristic diagram showing the relationship between the torque and the rotation speed of the DC motor.

Generally, the characteristics of the DC motor have a downward sloping characteristic in which the rotational speed decreases as the torque increases when the applied voltage is constant. That is, as shown in FIG. 6, when the duty is D1 and the torque is T1, the rotation speed is R1.

When the torque is constant at T1 and the duty is D2 (<D1), the rotation speed is reduced to R2 (<R1). By utilizing this characteristic, the rotation speed can be controlled by adjusting the duty so that the rotation speed matches the target rotation speed under a constant load.

Next, the PWM control circuit 33 will be described in detail. FIG. 7 shows the PWM control circuit 33 in this embodiment.
It is a block diagram of.

In FIG. 7, a clock circuit 60 oscillates at a predetermined frequency. The frequency is represented by the product of the carrier frequency and the duty resolution. For example, the carrier frequency is 5 kHz, and when the resolution is 256, the oscillation is 1.28 MHz.

Reference numeral 61 is a counter circuit, which is an up-counter operating with the output of the clock circuit as a clock, and increments the output value CNT every time one clock pulse enters.

Reference numeral 62 denotes a first register circuit which stores a fixed predetermined value REG1. Reference numeral 63 is a first comparator, which compares the output value CNT of the counter circuit 61 with the set value REG1 of the first register circuit, and outputs an output when REG1≤CNT.

The output of the first comparator 63 is connected to the reset terminal RST of the counter circuit 61 and resets the count value of the counter circuit 61 (CNT = 0). That is, the count cycle (that is, the carrier cycle) of the counter circuit 61 is determined by the setting REG1 of the first register circuit.

Reference numeral 64 is a second register circuit, which has a predetermined value REG.
2 (0 ≦ REG1 ≦ REG2) is stored. A second comparator 65 compares the output value CNT of the counter circuit 61 with the set value REG2 of the second register circuit, and REG
When 2 ≧ CNT, the output of ON is sent. The output signal CHOP of the second comparator becomes a duty signal.

Reference numeral 66 is a main duty setting circuit, which sets the basic duty of the duty. At this time, the basic duty sets a value from 0 to the set value REG1 of the first register circuit.

Reference numeral 67 denotes a complementary duty setting circuit, which will be described here as one having two auxiliary bits. The number of times specified by the auxiliary bit (0 to 3 times) is set to be higher than the duty set by the main duty setting circuit for the four PWM waveforms.

Reference numeral 68 denotes a selection circuit, which selects the output from the main duty setting circuit 66 when the rotation speed difference of the output from the error detector 32 is 1 r / sec or more, and the rotation speed difference is 1 r.
When it is within / sec, the output from the complementary duty setting circuit 67 is selected.

Reference numeral 69 is an AND gate, which is a selection circuit 68.
From the second comparator at the timing of the output of the first comparator 63.
Set the value in the register circuit.

Next, the operation of the PWM control circuit 33 will be described in more detail. FIG. 8 shows the PW in this embodiment.
FIG. 9 is an operation timing chart of the M control circuit 33.

The output CNT of the counter circuit 61 is counted up by the output of the clock circuit 60. The output CNT of the counter circuit 61 and the set value RE of the first register circuit
The output RST of the first comparator 63 is sent out and the output CNT of the counter circuit 61 is reset when G1 and G1 match.

Further, the set value RE of the second register circuit 64
When the output value CNT of the counter circuit 61 is smaller than G2, the output of the second comparator 65 becomes H level. vice versa,
When the output value CNT of the counter circuit 61 is larger than the set value REG2 of the second register circuit 64, the second comparator 6
The output of 5 becomes L level.

Thus, the set value R of the second register circuit is
By changing EG2, the duty of the output of the PWM control circuit 33 can be changed. Therefore, the rotation speed of the DC motor can be controlled by changing the value of the set value REG2.

Therefore, in order to improve the accuracy of the rotation speed, the counter circuit 61 and the first register circuit 6 are provided.
2. This can be achieved by increasing the number of bits of the second register circuit 64. However, not only the circuit becomes complicated and the circuit becomes expensive, but also the oscillation frequency of the clock circuit 60 becomes considerably high, and the influence of noise or the like occurs. It becomes easy to receive.

Generally, the number of these bits is often set to about 8 bits in consideration of the reliability of the circuit, the cost and the like.
However, sufficient rotation speed control could not be performed with this number of bits. In order to solve this, a supplementary duty setting circuit 67 is provided.

Next, the operation when the complementary duty setting circuit is used will be described. FIG. 9 is an operation timing chart of the PWM control circuit 33 when the complementary duty is used.

Two bits are set as the auxiliary bits in the complementary duty setting circuit 67, and in this case, the auxiliary bit is set to 01B (binary notation). The set value of the main duty setting circuit 66 is D0.

In the section T, the duty signal is output four times, but since the value of the auxiliary bit is 01B, the set value REG2 of the first register circuit 64 is D0 + 1. That is, the duty signal CH at this time
OP is one bit wider than other cases.

For the other 2nd to 4th pulses, the set value REG2 is D0, and therefore the pulse width is the same as usual.

By doing so, the average duty in the section T is 1/4 as shown in (Equation 2).
It changes in bit units.

[0101]

(Equation 2)

Further, by increasing the number of wide pulses in the section T, it is possible to increase the duty by 2/4 or 3/4.

Motor characteristics when the complementary duty setting circuit 67 is used will be described. FIG. 10 is a characteristic diagram showing the relationship of torque = rotational speed of the DC motor when the complementary duty is used.

In FIG. 10, (a) shows the motor characteristics when the set value REG2 of the second register circuit 64 is D0. At this time, the rotation speed at the torque T1 is R1.

Further, (b) shows the motor characteristics when the value of the set value REG2 of the second register circuit 64 is D0 + 1. At this time, the rotation speed at the torque T1 is R5.

When only the normal main duty setting circuit 66 is used, it is impossible to realize the rotation speed between the rotation speeds R1 and R2 in this way.

Further, (c) shows the motor characteristics when the auxiliary bit is 01B, (d) shows the motor characteristics when the auxiliary bit is 10B, and (e) shows the motor characteristics when the auxiliary bit is 11B. Show. The rotational speeds at the torque T1 are R2, R3, and R4, respectively, and a finer rotational speed can be set.

As described above, in the present invention, by using the complementary duty, it is possible to easily perform the rotation speed control with higher accuracy. In this embodiment, the number of auxiliary bits is 2.
Although the case of bits has been described, it goes without saying that if the number of bits is larger than this, the accuracy can be further improved.

Next, the rotation speed control will be described in more detail. FIG. 11 is a flowchart of the processing of the rotation speed control in this embodiment.

In FIG. 11, the number of revolutions of the DC motor is measured in STEP 1 to detect the actual number of revolutions. Next,
In STEP 2, the target rotation speed and the actual rotation speed are compared.

Next, in STEP 3, as a result of comparison in STEP 2, it is determined whether the two match (within 0.1 r / sec). If they match, it is no longer necessary to change the duty, so the duty is fixed in STEP 4, and the process returns to STEP 1. If they do not match in STEP 3, the process proceeds to STEP 5.

Next, in STEP 5, as a result of comparison in STEP 2, it is determined whether the difference between the two is within 1 r / sec. If it is 1 r / sec or more, proceed to STEP 6,
The main duty is UP or DOWN (UP when the actual rotation speed is lower than the target rotation speed, UPM when the actual rotation speed is higher than the target rotation speed), and the process returns to STEP1. If it is within 1 r / sec, proceed to STEP 7.

Next, in STEP 7, the supplementary duty (auxiliary bit) is UP or DOWN (UP if the actual rotation speed is lower than the target rotation speed, and DOWM if the actual rotation speed is higher than the target rotation speed).

Next, in STEP 8, the result of UP or DOWN in STEP 7 is overflow (or borrow).
It is determined whether or not has occurred. If no overflow (or borrow) has occurred, the process returns to STEP 1.

If an overflow (or borrow) has occurred, the main duty is increased (or D) at STEP 9.
OWN) and returns to STEP1.

As described above, when the actual rotation speed and the target rotation speed are distant from each other, the main duty is operated, and when the actual rotation speed and the target rotation speed are close to each other, the auxiliary duty is operated to rotate the rotation speed. Smooth changes in numbers can be realized.

As described above, the control device for the refrigerator according to the present embodiment has the compressor 1 in which the inside of the shell has almost the same pressure as the suction gas, the DC motor 3 for operating the compression part of the compressor 1, and the DC motor 3. The counter electromotive voltage detection circuit 23 that detects the rotational position of the rotor 3a of the motor 3 from the counter electromotive voltage generated in the stator winding and the output of the counter electromotive voltage detection circuit 23 during normal operation performs commutation to drive the DC motor 3 The inverter 22 for variable speed operation, the temperature difference detection circuit 29 for detecting the temperature difference between the internal temperature and the set temperature, and the rotation speed are set from the output of the temperature difference detection circuit 29. When the rotation speed becomes smaller than the commercial power supply, the rotation speed setting circuit 30 that sets the rotation speed lower than the commercial power supply is compared with the target rotation speed of the rotation speed setting circuit 30 and the actual rotation speed of the DC motor. The PWM control circuit 33 for increasing / decreasing the duty width of the PWM control can prevent the efficiency of the compressor from being lowered due to heat loss due to leakage, and can provide a variable speed compressor having high efficiency even at a low rotation speed. Combined with the efficiency improvement of the cooling system at low speed, the power consumption of the refrigerator can be significantly reduced.

Further, the compressor 1, the DC motor 3 for operating the compressor of the compressor, and the rotation speed detection circuit 31 for detecting the rotation speed of the DC motor 3 by the output from the counter electromotive voltage detection circuit 23. A rotation speed setting circuit 30 for setting a target rotation speed, and a PWM control circuit 33 for comparing the target rotation speed with the actual rotation speed of the DC motor and increasing or decreasing the duty width of the PWM control of the inverter according to the result. And then PW
The M control circuit includes a main duty setting circuit 66 and a complementary duty setting circuit 67. The main duty setting circuit 66 determines the basic duty of a pulse for PWM control, and the complementary duty setting circuit 67 performs n times (n is an integer of 2 or more). By setting the PWM waveform of m times (m is an integer of 0 or more and less than n) to a duty higher than the duty set by the main duty setting circuit,
The rotation speed can be controlled with high accuracy and can be realized at a low cost with a simple circuit.

Further, the compressor 1, the DC motor 3 for operating the compression section of the compressor 1, and the counter electromotive voltage detection circuit 23.
The rotation speed detection circuit 31 that detects the rotation speed of the DC motor 3 based on the output from the rotation speed setting circuit 30 that sets the target rotation speed, and the target rotation speed and the actual rotation speed of the DC motor 3 are compared. A PWM control circuit 33 that increases or decreases the duty width of the PWM control of the inverter 22 according to the result is provided. The PWM control circuit 33 includes a main duty setting circuit 66 and an auxiliary duty setting circuit 67, and the main duty setting circuit 66 performs PWM control. The basic duty of the pulse is determined, and the main duty setting circuit 66 sets m times (m is an integer of 0 or more and less than n) for the PWM waveform of n times (n is an integer of 2 or more) by the complementary duty setting circuit 67. If the difference between the target rotation speed and the actual rotation speed of the DC motor is smaller than the specified value, set the duty higher than the specified duty. By providing the selection circuit 68 adapted to operate the supplementary duty setting circuit only in the case where the actual rotation speed is far from the target rotation speed, the change in the rotation speed is accelerated and the compressor It is possible to prevent noise and vibration from occurring due to resonance and the like, and when the number of rotations approaches, it is possible to control the number of rotations with high accuracy.

[0120]

As described above, the control device for a refrigerator according to the present invention comprises a compressor having a shell whose internal pressure is almost the same as that of the suction gas, a DC motor for operating the compressor of the compressor, and A counter electromotive voltage detection circuit that detects the rotational position of the rotor of the DC motor from the counter electromotive voltage that occurs in the stator windings, and during normal operation, commutation is performed by the output of the counter electromotive voltage detection circuit to make the DC motor a variable speed An inverter to be operated, a temperature difference detection circuit that detects the temperature difference between the internal temperature and the set temperature, and the number of revolutions is set from the output of the temperature difference detection circuit, especially when the temperature difference becomes smaller than a predetermined value. The rotation speed setting circuit that sets the rotation speed to a speed lower than the commercial power supply is compared with the target rotation speed by the rotation speed setting circuit and the actual rotation speed of the DC motor. Since it is configured with a PWM control circuit that increases or decreases the duty width of the compressor, it is possible to prevent the efficiency of the compressor from being reduced due to heat loss due to leakage, and to provide a variable speed compressor with high efficiency even at a low rotation speed, and cooling at low speed. Combined with the increase in system efficiency, the power consumption of the refrigerator can be significantly reduced.

Further, the compressor, the DC motor for operating the compressor of the compressor, the rotation speed detection circuit for detecting the rotation speed of the DC motor by the output from the counter electromotive voltage detection circuit, and the target rotation speed. The PWM control circuit has a rotation speed setting circuit for setting the number of revolutions, and a PWM control circuit for comparing the target rotation speed with the actual rotation speed of the DC motor and increasing or decreasing the duty width of the PWM control of the inverter according to the result. The circuit is composed of a main duty setting circuit and a complementary duty setting circuit. The main duty setting circuit determines a basic duty of a pulse for PWM control, and the complementary duty setting circuit makes a PWM waveform n times (n is an integer of 2 or more). In contrast,
By configuring the number of times m times (m is an integer of 0 or more and less than n) to be higher than the duty set by the main duty setting circuit, the rotation speed can be controlled with high accuracy and is simple. It can be realized at low cost with a circuit.

Further, the compressor, the DC motor for operating the compressor of the compressor, the rotation speed detection circuit for detecting the rotation speed of the DC motor by the output from the back electromotive force detection circuit, and the target rotation speed. The PWM control circuit has a rotation speed setting circuit for setting the number of revolutions, and a PWM control circuit for comparing the target rotation speed with the actual rotation speed of the DC motor and increasing or decreasing the duty width of the PWM control of the inverter according to the result. The circuit is composed of a main duty setting circuit and a complementary duty setting circuit. The main duty setting circuit determines a basic duty of a pulse for PWM control, and the complementary duty setting circuit makes a PWM waveform n times (n is an integer of 2 or more). In contrast,
m times (m is an integer of 0 or more and less than n) is set to a duty higher than the duty set by the main duty setting circuit, and the difference between the target rotation speed and the actual rotation speed of the DC motor is greater than a predetermined value. If the actual rotation speed is far from the target rotation speed by providing the selection circuit that operates the supplementary duty setting circuit only when the rotation speed is small, the change in the rotation speed is accelerated. It is possible to prevent noise and vibration from occurring due to the resonance of the compressor and the like, and it becomes possible to control the rotation speed with high accuracy when the rotation speed approaches.

[Brief description of the drawings]

FIG. 1 is a block diagram of a refrigerator control device according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram of a rotation speed setting circuit in this embodiment.

FIG. 3 (a) is a characteristic diagram showing the relative efficiency of the compressor. (B) is a characteristic diagram showing the relative refrigerating capacity of the compressor.

FIG. 4 is a circuit diagram of a commutation circuit and a synthesis circuit in this embodiment.

FIG. 5 is an operation timing chart of the commutation circuit and the synthesis circuit in the present embodiment.

FIG. 6 is a characteristic diagram showing the relationship between torque and rotation speed of a DC motor.

FIG. 7 is a block diagram of a PWM control circuit according to the present embodiment.

FIG. 8 is an operation timing chart of the PWM control circuit according to the present embodiment.

FIG. 9 is an operation timing chart of the PWM control circuit when the complementary duty is used.

FIG. 10 is a characteristic diagram showing a relationship between torque and rotation speed of a DC motor when a complementary duty is used.

FIG. 11 is a flow chart of processing of rotation speed control in the present embodiment.

[Explanation of symbols]

 1 Compressor 3 DC motor 22 Inverter

Claims (3)

[Claims] 1. A compressor in which the inside of the shell has almost the same pressure as the suction gas, a DC motor for operating a compression part of the compressor, and a reverse position in which a rotor winding position of the DC motor is generated in a stator winding. A counter electromotive voltage detection circuit that detects from the electromotive voltage, an inverter that performs commutation by the output of the counter electromotive voltage detection circuit during normal operation to operate the DC motor at a variable speed, and a refrigerator that detects the temperature inside the refrigerator. Inside temperature detecting means, inside temperature setting means for setting inside temperature, temperature difference detecting circuit for detecting temperature difference between the inside temperature detecting means and inside temperature setting means, and the temperature difference detecting circuit The rotation speed is set from the output of, and especially when the temperature difference becomes smaller than the predetermined value, the rotation speed setting circuit that makes the set rotation speed lower than the commercial power supply, and the target rotation speed and the actual rotation speed by the rotation speed setting circuit. DC model And a PWM control circuit that compares the number of revolutions of the inverter and increases or decreases the duty width of the PWM control of the inverter according to the result. 2. A compressor, a DC motor for operating a compressor of the compressor, and a counter electromotive voltage detection circuit for detecting a rotational position of a rotor of the DC motor from a counter electromotive voltage generated in a stator winding. During normal operation, an inverter that performs commutation by the output of the counter electromotive voltage detection circuit to operate the DC motor at a variable speed, and a rotation that detects the rotation speed of the DC motor by the output from the counter electromotive voltage detection circuit The speed detection circuit, the rotation speed setting circuit for setting the target rotation speed, and the target rotation speed by the rotation speed setting circuit are compared with the actual rotation speed of the DC motor.
A PWM control circuit for increasing or decreasing the duty width of control, wherein the PWM control circuit comprises a main duty setting circuit and an auxiliary duty setting circuit, and the main duty setting circuit determines a basic duty of a pulse for PWM control, With respect to the PWM waveform of n times (n is an integer of 2 or more) by the duty setting circuit, m times (m is an integer of 0 or more and less than n) is set to a duty higher than the duty set by the main duty setting circuit. Control device for the refrigerator. 3. A compressor, a DC motor for operating a compressor of the compressor, and a counter electromotive voltage detection circuit for detecting a rotational position of a rotor of the DC motor from a counter electromotive voltage generated in a stator winding. During normal operation, an inverter that performs commutation by the output of the counter electromotive voltage detection circuit to operate the DC motor at a variable speed, and a rotation that detects the rotation speed of the DC motor by the output from the counter electromotive voltage detection circuit The speed detection circuit, the rotation speed setting circuit for setting the target rotation speed, and the target rotation speed by the rotation speed setting circuit are compared with the actual rotation speed of the DC motor.
A PWM control circuit for increasing or decreasing the duty width of control, wherein the PWM control circuit comprises a main duty setting circuit and an auxiliary duty setting circuit, and the main duty setting circuit determines a basic duty of a pulse for PWM control, With respect to the PWM waveform of n times (n is an integer of 2 or more) by the duty setting circuit, m times (m is an integer of 0 or more and less than n) is set to a duty higher than the duty set by the main duty setting circuit. A refrigerator control device comprising a selection circuit that operates the auxiliary duty setting circuit only when the difference between the target rotation speed and the actual rotation speed of the DC motor is smaller than a predetermined value.