WO2009101781A1

WO2009101781A1 - Control device of compressor and refrigerator having the same

Info

Publication number: WO2009101781A1
Application number: PCT/JP2009/000493
Authority: WO
Inventors: Katsumi Endo
Original assignee: Panasonic Corporation
Priority date: 2008-02-15
Filing date: 2009-02-09
Publication date: 2009-08-20

Abstract

A control device of a compressor of the present invention calculates the rotating speed in rotating speed arithmetic unit (109), compares a command rotating speed with the calculated rotating speed of DC motor (104), rotating speed controller (108) controls the rotating speed of DC motor (104) so as to be equal to the command rotating speed, and when the applied voltage to DC motor (104) reaches an upper limit, a rotating speed lower than the command rotating speed is selected from a prescribed rotating speed stored in prescribed rotating speed storage unit (115), and it is controlled so as to be equal to the selected rotating speed, and by operating at the command rotating speed when the temperature of the inverter circuit drops. Therefore, compressor (114) does not rotate at its resonance rotating speed, thereby minimizing the decline of cooling capacity, and enhancing the reliability.

Description

CONTROL DEVICE OF COMPRESSOR AND REFRIGERATOR HAVING THE SAME

The present invention relates to a control device of a compressor, and more particularly to an inverter circuit for driving a motor by a PWM-controlled switching element, and is especially preferable for driving of closed type motor compressor for refrigerator.

Hitherto, in this kind of control device of a compressor, by detecting the motor rotating speed, the rotating speed of the motor was controlled by varying the duty ratio of PWM (pulse width modulation) signal (see, for example, patent document 1).
Referring now to the drawings, a conventional control device of a compressor is explained below.
FIG. 5 is a block diagram of a conventional control device of a compressor disclosed in patent document 1, and FIG. 6 is a flowchart explaining the operation of raising or lowering the rotating speed of a DC motor in the conventional control device of the compressor.
In FIG. 5, AC/DC converter 1 is connected to commercial power source 2, and converts the commercial alternating-current voltage into direct-current voltage. Inverter circuit 3 is connected to AC/DC converter 1, and its output is connected to a motor, that is, DC motor 4.
As shown in FIG. 5, DC motor 4 is assembled in compressor 14 for cooling a refrigerator or the like.
Inverter circuit 3 is composed of six switching elements T1, T2, T3, T4, T5, T6, and the six switching elements are connected in a three-phase bridge.
Control circuit 5 is composed of position detector 6, commutation unit 7, rotating speed controller 8, rotating speed arithmetic unit 9, command rotating speed detector 10, rotating speed comparator 11, synthesizing unit 12, and drive unit 13.
Position detector 6 detects the position of a rotor from the counter electromotive voltage of DC motor 4, and sends out the position detection signal to commutation unit 7, rotating speed arithmetic unit 9, rotating speed comparator 11, and rotating speed controller 8.
Commutation unit 7 sends out commutation pulses for driving synthesizing unit 12 depending on the output from position detector 6.
Rotating speed arithmetic unit 9 counts the position detection signals of position detector 6 for a specific period, or measures the pulse intervals, and calculates the rotating speed of DC motor 4, and sends out the rotating speed of operating DC motor 4 to rotating speed comparator 11.
On the other hand, command rotating speed detector 10 detects the command rotating speed sent out from the refrigerator or the like, and sends out this command rotating speed to rotating speed comparator 11.
Rotating speed comparator 11 compares the rotating speed of DC motor 4 from rotating speed arithmetic unit 9, with the command rotating speed from command rotating speed detector 10.
When the rotating speed of DC motor 4 is smaller than the command rotating speed, an output for increasing the duty ratio is sent to rotating speed controller 8, and rotating speed controller 8 increases the duty ratio, and increases the voltage applied to DC motor 4, and thereby the rotating speed of DC motor 4 is raised.
When the rotating speed of DC motor 4 is larger than the command rotating speed, an output for decreasing the duty ratio is sent to rotating speed controller 8, and rotating speed controller 8 decreases the duty ratio, and decreases the voltage applied to DC motor 4, and thereby the rotating speed of DC motor 4 is lowered.
Herein, the duty ratio is the ratio of the ON time to the total time of ON time when voltage pulse is applied and OFF time when voltage pulse is not applied. The total time of ON time and OFF time is constant.
Synthesizing unit 12 issues the logic product of outputs from commutation unit 7 and rotating speed controller 8 to drive unit 13. Drive unit 13 drives switching elements T1 to T6 for composing inverter circuit 3.
In the control device of compressor 14 having such configuration, the operation of raising and lowering the rotating speed of DC motor 4 is described specifically below while referring to FIG. 5 and FIG. 6.
The control device of compressor 14 receives a change in command rotating speed from the control device of the refrigerator or the like by command rotating speed detector 10 during operation of DC motor 4. As a result, the control device of compressor 14 controls to change the rotating speed of DC motor 4.
As shown in FIG. 6, at STEP 1, rotating speed arithmetic unit 9 calculates the rotating speed of DC motor 4 by the signal from position detector 6. At STEP 2, rotating speed comparator 11 compares the command rotating speed detected by command rotating speed detector 10 with the rotating speed calculation result of DC motor 4 calculated by rotating speed arithmetic unit 9.
At STEP 3, when the rotating speed calculation result is smaller than the command rotating speed, going to STEP 4, rotating speed controller 8 raises the duty ratio, the ratio of the ON time to the total time of ON time and OFF time. As the duty ratio is raised, the ON time is increased, and the voltage applied to DC motor 4 is elevated, and thereby the rotating speed of DC motor 4 is elevated.
On the other hand, when the rotating speed calculation result is not smaller than the command rotating speed at STEP 3, the process skips to STEP 5.
At STEP 5, when the rotating speed calculation result is larger than the command rotating speed, going to STEP 6, rotating speed controller 8 lowers the duty ratio. As a result, the ON time is decreased, and the voltage applied to DC motor 4 is lowered, and thereby the rotating speed of DC motor 4 declines.
By such operation, when a command rotating speed higher than the present rotating speed is applied, rotating speed controller 8 gradually raises the duty ratio in the sequence of STEP 1, STEP 2, STEP 3, STEP 4, STEP 5 according to the flowchart in FIG. 6. As a result, the rotating speed of DC motor 4 is raised, and the command rotating speed and the rotating speed calculation result are equalized. In the sequence of STEP 1, STEP 2, STEP 3, STEP 5, rotating speed controller 8 no longer changes the duty ratio, and the rotating speed of DC motor 4 is maintained at the command rotating speed.
In the case of an input of command rotating speed smaller than present rotating speed, in the sequence of STEP 1, STEP 2, STEP 3, STEP 5, STEP 6, rotating speed controller 8 lowers the duty ratio gradually. As a result, the rotating speed of DC motor 4 is lowered, and the command rotating speed and the rotating speed calculation result are equalized. Then, in the sequence of STEP 1, STEP 2, STEP 3, STEP 5, rotating speed controller 8 no longer changes the duty ratio, and the rotating speed of DC motor 4 is maintained at the command rotating speed.
In this conventional configuration, however, in an overloaded state of refrigerator load or the like, if a maximum rotating speed is applied as the command rotating speed, rotating speed controller 8 raises the voltage applied to DC motor 4. However, if the applied voltage becomes the maximum applied voltage, the voltage to be applied to DC motor 4 cannot be raised further. Therefore, the command rotating speed does not reach the maximum rotating speed, and the operation is maintained at a specified rotating speed determined by the load and the applied voltage.
Generally, compressor 14 has a resonating rotating speed, and the operating rotating speed of DC motor 4 in compressor 14 is not continuous, but it is designed to operate at a rotating speed while avoiding this resonance rotating speed. However, when the applied voltage to DC motor 4 reaches the upper limit, there is a risk of compressor 14 rotating at resonance rotating speed. If compressor 14 resonates at a specific rotating speed, for example, the discharge pipe may be broken.
Japanese Unexamined Patent Application Publication No. S62-66080

The present invention is devised to solve the conventional problems, and it is hence an object thereof to present a control device of compressor for controlling to operate the motor at a command rotating speed by changing the voltage applied to the motor, or more specifically a control device of compressor for controlling, in the case of an overload, so that the rotating speed of the DC motor may not coincide with the rotating speed resonating with the compressor.
The control device of compressor of the present invention commands, when the rotating speed of the motor does not reach the command rotating speed, to operate the motor at a prescribed rotating speed which is lower than the command rotating speed and in a range of rotating speed either higher than or lower than a resonance rotating speed of the compressor.
In this configuration, when the applied voltage to the DC motor reaches the maximum, a prescribed rotating speed lower than the command rotating speed and avoiding the resonance of the compressor is commanded. Therefore, the compressor does not rotate at the resonance rotating speed, and breakage of discharge pipe of the compressor can be prevented, and the reliability of the compressor is enhanced. As a result, decline of cooling performance of refrigerator using such compressor can be avoided, and the reliability of the refrigerator is enhanced.

FIG. 1 is a block diagram of a control device of a compressor in exemplary embodiment 1 of the present invention. FIG. 2 is a block diagram of a resonance system of a freezing apparatus including the control device of the compressor in exemplary embodiment 1 of the present invention. FIG. 3 is a flowchart of operation of the control device of the compressor in exemplary embodiment 1 of the present invention. FIG. 4 is a block diagram of a refrigerator including the control device of the compressor in exemplary embodiment 1 of the present invention. FIG. 5 is a block diagram of a conventional control device of a compressor. FIG. 6 is a flowchart of operation of the conventional control device of compressor.

Explanation of Reference

103 Inverter circuit
104 DC motor
106 Position detector
107 Commutation unit
108 Rotating speed controller
109 Rotating speed arithmetic unit
111 Temperature sensor
113 Drive unit
114 Compressor
115 Prescribed rotating speed storage unit
116 Temperature detector
117 Temperature storage unit
118 Temperature comparator

An exemplary embodiment of a control device of a compressor of the present invention is described specifically below while referring to the accompanying drawings. However, the present invention is not limited by the exemplary embodiment alone. In the following drawings, like elements are identified with like reference numerals and duplicate explanations may be omitted.

Mode for the Embodiment 1

FIG. 1 is a block diagram of a control device of a compressor in exemplary embodiment 1 of the present invention, FIG. 2 is a block diagram of a resonance system of a freezing apparatus including the control device of the compressor in exemplary embodiment 1, and FIG. 3 is a flowchart of operation elevating and lowering the rotating speed of the DC motor in the control device of the compressor in exemplary embodiment 1.
In FIG. 1, AC/DC converter 101 is connected to commercial power source 102, and converts the commercial alternating-current voltage into direct-current voltage. Inverter circuit 103 is connected to AC/DC converter 101, and its output is connected to DC motor 104. DC motor 104 is incorporated in compressor 114 for cooling, for example, a refrigerator.
Inverter circuit 103 is composed of six switching elements T101, T102, T103, T104, T105, T106, and these six switching elements are connected in a three-phase bridge.
Temperature sensor 111 is attached to inverter circuit 103, and detects the temperature of inverter circuit 103, and sends out a temperature detection signal to temperature detector 116.
Control circuit 105 is composed of, as shown in FIG. 1 for example, position detector 106, commutation unit 107, rotating speed controller 108, rotating speed arithmetic unit 109, command rotating speed detector 110, synthesizing unit 112, drive unit 113, temperature detector 116, temperature storage unit 117, temperature comparator 118, and prescribed rotating speed storage unit 115.
Position detector 106 detects the position of a rotor from the counter electromotive voltage of DC motor 104, and sends out the position detection signal to commutation unit 107 and rotating speed arithmetic unit 109.
Commutation unit 107 sends out a commutation pulse for driving synthesizing unit 112 depending on the output of position detector 106.
Rotating speed arithmetic unit 109 counts the position detection signals from position detector 106 for a specific period, or measures the pulse intervals, and calculates the rotating speed of DC motor 104, and sends out the rotating speed for operating DC motor 104 to rotating speed controller 108.
On the other hand, command rotating speed detector 110 detects the command rotating speed sent from, for example, the refrigerator, and sends out the detection signal to rotating speed controller 108.
Rotating speed controller 108 compares the rotating speed of DC motor 104 from rotating speed arithmetic unit 109 with the command rotating speed from command rotating speed detector 110, and when the rotating speed of DC motor 104 is smaller than the command rotating speed, the rotating speed of DC motor 104 is raised. At this time, to elevate the applied voltage to DC motor 104, the duty ratio is increased, and issued to synthesizing unit 112.
When the rotating speed of DC motor 104 is larger than the command rotating speed, the rotating speed of DC motor 104 is lowered. At this time, to lower the applied voltage to DC motor 104, the duty ratio is decreased, and is issued to synthesizing unit 112.
Synthesizing unit 112 issues the logic product of outputs of commutation unit 107 and rotating speed controller 108 to drive unit 113. Drive unit 113 drives switching elements T101 to T106 for composing inverter circuit 103.
Temperature detector 116 calculates the temperature of the inverter circuit from the detection signal issued from temperature sensor 111, and sends out a value of the temperature to temperature storage unit 117.
Rotating speed controller 108 selects a rotating speed lower than the rotating speed calculated in the rotating speed arithmetic unit 109 and closest to this rotating speed (the rotating speed calculated in the rotating speed arithmetic unit 109) from prescribed rotating speed storage unit 115 when the rotating speed calculated in rotating speed arithmetic unit 109 is lower than the command rotating speed. Rotating speed controller 108 compares the selected rotating speed with the rotating speed calculated in rotating speed arithmetic unit 109, and controls the duty ratio so as to conform to the selected rotating speed.
At the same time, when the rotating speed is selected, rotating speed controller 108 issues an output indicating the completion of selection to temperature storage unit 117.
Temperature storage unit 117, when receiving the output from rotating speed controller 108, stores the temperature of inverter circuit 103 as the detection signal from temperature detector 116.
Prescribed rotating speed storage unit 115 stores a plurality of prescribed rotating speeds avoiding the resonance rotating speed of compressor 114. That is, it stores a plurality of prescribed rotating speeds lower than the command rotating speed and in a range of rotating speed either higher than or lower than the resonance rotating speed.
Temperature comparator 118 is connected to the outputs of temperature storage unit 117 and temperature detector 116. When the temperature of inverter circuit 103 detected by temperature detector 116 is lower than the temperature stored in temperature storage unit 117 by more than a specified value, temperature comparator 118 issues the result to rotating speed controller 108. Hence, rotating speed controller 108 compares the command rotating speed with the rotating speed calculated in rotating speed arithmetic unit 109.
Reciprocating compressor 114 shown in FIG. 2 contains DC motor 104 and compression element 120 to be driven by DC motor 104 in closed container 130. In discharge connection pipe 121 fixed in closed container 130, discharge pipe 122 communicating between compression element 120 and discharge connection pipe 121 is connected. Vibration control coil spring 123 is fitted at a specified position of discharge pipe 122, and the resonance frequency of discharge pipe 122 is adjusted, and the vibration of discharge pipe 122 is attenuated. DC motor 104 is operated by inverter circuit 103.
In reciprocating compressor 114 having such configuration, compression element 120 is driven as DC motor 104 is operated by inverter circuit 103, and compression gas compressed by compression element 120 is guided out of discharge connection pipe 121 by way of discharge pipe 122. At this time, vibration generated from compression element 120 is transmitted to discharge pipe 122, but if resonance occurs, the resonance is attenuated by coil spring 123 fitted to discharge pipe 122.
However, discharge pipe 122 has its own natural resonance frequency, and may resonate at certain operating rotating speeds. In prescribed rotating speed storage unit 115, a plurality of prescribed rotating speeds not resonating with discharge pipe 122 have been stored preliminarily.
In the control device of compressor 114 having such configuration, the operation of elevating and lowering the rotating speed of DC motor 104 is explained by referring to FIG. 3.
The control device of compressor 114 controls to change the rotating speed of DC motor 104 as follows when receiving a change of command rotating speed from the control device of the refrigerator or the like in command rotating speed detector 110 during operation of DC motor 104.
First, at STEP 101, the command rotating speed is stored as reference rotating speed.
At STEP 102, rotating speed arithmetic unit 109 calculates the rotating speed of DC motor 104 from the signal of position detector 106. At STEP 103, the reference rotating speed determined at STEP 101 and the rotating speed calculation result of DC motor 104 calculated at STEP 102 are compared.
At STEP 104, if the reference rotating speed is larger than the rotating speed calculation result, going to STEP 105, rotating speed controller 108 judges if the applied voltage is at the upper limit or not. If not at the upper limit, advancing to STEP 108, rotating speed controller 108 raises the duty ratio at STEP 108 and goes to STEP 111. By raising the duty ratio, the ON time increases, and the applied voltage to DC motor 104 is elevated, and the rotating speed of DC motor 104 is elevated.
At STEP 105, when the duty ratio is at the upper limit, that is, when the applied voltage is at the upper limit, the process goes to STEP 107. At STEP 107, the reference rotating speed is set lower than the command rotating speed, and lower than and closest to the rotating speed calculated in rotating speed arithmetic unit 109 is selected from prescribed rotating speed storage unit 115, and is determined, and the process goes to STEP 108.
At STEP 106, if an output is given from rotating speed controller 108, temperature storage unit 117 stores the temperature of inverter circuit 103 issued from temperature detector 116, and advances to STEP 111.
At STEP 104, if the reference rotating speed is smaller than the rotating speed calculation result, the process goes to STEP 109.
At STEP 109, if the reference rotating speed and the rotating speed calculation result are not the same, the process goes to STEP 110, and rotating speed controller 108 lower the duty ratio. As the duty ratio is lowered, the ON time decreases, and the applied voltage to DC motor 104 declines, and the rotating speed of DC motor 104 is lowered.
At STEP 109, if the reference rotating speed and the rotating speed calculation result are the same, the process advances to STEP 111.
At STEP 111, if the reference rotating speed is not smaller than the command rotating speed, returning to STEP 101, the command rotating speed is stored again as the reference rotating speed. Otherwise, advancing to STEP 112, temperature comparator 118 compares the temperature values between temperature detector 116 and temperature storage unit 117. By judging if the temperature value of temperature detector 116 is lower than the temperature value of temperature storage unit 117 by more than a specified amount, the process returns to STEP 102 if not lowered more than the specified amount.
At STEP 112, if the temperature value of temperature detector 116 is lower than the temperature value of temperature storage unit 117 by more than the specified amount, returning to STEP 101, the command rotating speed is stored again as the reference rotating speed.
Thus, if the duty ratio does not reach 100% as a result of input of command rotating speed larger than the present rotating speed, the process advances to STEP 101, STEP 102, STEP 103, STEP 104, STEP 105, STEP 108, STEP 111. As a result, rotating speed controller 108 gradually raises the duty ratio, and the rotating speed of the DC motor 104 is elevated.
When the reference rotating speed and the rotating speed calculation result are equal to each other, the process advances to STEP 101, STEP 102, STEP 103, STEP 104, STEP 109, STEP 111. As a result, rotating speed controller 108 no longer changes the duty ratio, and the rotating speed of DC motor 104 is maintained at the reference rotating speed.
When the applied voltage reaches the upper limit, the process advances to STEP 101, STEP 102, STEP 103, STEP 104, STEP 105, STEP 107, STEP 106. The reference rotating speed is set to a rotating speed lower than the rotating speed calculated in rotating speed arithmetic unit 109, and is selected at a rotating speed most close to this rotating speed, and the process returns to STEP 102. Then going to STEP 103, at STEP 104, since the reference speed is lower than the rotating speed calculated at rotating speed arithmetic unit 109, and the process goes to STEP 109. Going to STEP 110, the duty ratio is lowered, and rotating speed controller 108 gradually lowers the duty ratio, and thereby the rotating speed of DC motor 104 is lowered.
When the reference rotating speed and the rotating speed calculation result are equal to each other, the process advances to STEP 102, STEP 103, STEP 104, STEP 109, STEP 111. As a result, rotating speed controller 108 no longer changes the duty ratio, and the rotating speed of DC motor 104 can be maintained at reference rotating speed.
When such operation continues, for example, if the compartment of the refrigerator is cooled, and the overload state is gradually canceled, and in the case that the voltage applied to DC motor 104 is decreased, the rotating speed can be maintained. Therefore, the motor current decreases, and the temperature of inverter circuit 103 declines, and not only the reliability of the compressor is enhanced, but also the reliability of the refrigerator is enhanced.
Therefore, when the reference rotating speed at STEP 107 is lower than the rotating speed calculated in rotating speed arithmetic unit 109, and is set at a rotating speed most close to this rotating speed, at STEP 112, suppose the temperature of inverter circuit 103 becomes lower than the value stored in temperature storage unit 117. Then, going to STEP 101, the reference rotating speed is set at the command rotating speed, and usual control is executed.
On the other hand, when a command rotating speed lower than the present rotating speed is applied, the process advances to STEP 101, STEP 102, STEP 103, STEP 104, STEP 109, STEP 110. Then, rotating speed controller 108 gradually lowers the duty ratio, and the rotating speed of DC motor 104 declines, and when the reference rotating speed becomes equal to the rotating speed calculation result, the process advances to STEP 101, STEP 102, STEP 103, STEP 104, STEP 109, STEP 111. As a result, rotating speed controller 108 no longer changes the duty ratio, and the rotating speed of DC motor 104 is maintained at reference rotating speed.
Therefore, it is usually controlled so that the duty ratio is increased or decreased so that the rotating speed of DC motor 104 may be the same as the command rotating speed. When the applied voltage reaches the upper limit, decline of cooling performance is minimized, and compressor 114 is controlled to operate at a predetermined rotating speed so as not to rotate at the resonance rotating speed. As a result, breakage of discharge pipe 122 is prevented, and the reliability of compressor 114 can be enhanced.
Besides, the temperature of inverter circuit 103 is detected, and when it is judged it is possible to operate DC motor 104 at command rotating speed, DC motor 104 can be securely operated at command rotating speed.
That is, when the rotating speed of the motor does not reach the command rotating speed, the control device of the compressor of the present invention commands to operate the motor at a prescribed rotating speed which is lower than the command rotating speed and in a range of rotating speed either higher than or lower than the resonance rotating speed of the compressor.
In this configuration, as the motor does not rotate at resonance rotating speed causing resonance with the compressor, the reliability of the compressor can be enhanced.
FIG. 4 is a block diagram of a refrigerator incorporating the control device of the compressor in exemplary embodiment 1 of the present invention.
As shown in FIG. 4, refrigerator 200 of the present invention includes compressor 201, control device 202 of the above-mentioned compressor for controlling this compressor 201, cooling compartment 203, and refrigerating cycle 204 for cooling this cooling compartment 203. The refrigerant compressed by compressor 201 circulates refrigerating cycle 204 to cool the cooling compartment 203, and the food stored in the cooling compartment 203 is cooled. In FIG. 4, compressor 201 and control device 202 of compressor are disposed inside of refrigerator casing 205, but they may be disposed outside of refrigerator casing 205 depending on the application.
Control device 202 of compressor is designed to command, when the rotating speed of the motor (not shown) is lower than the command rotating speed, to operate the motor at a prescribed rotating speed which is lower than the command rotating speed and in a range of rotating speed either higher than or lower than the resonance rotating speed of compressor 201.
In this configuration, the motor does not rotate at the resonance rotating speed causing resonance with compressor 201, and the reliability of refrigerator 200 can be enhanced.
The control device of the compressor of the present invention includes an inverter circuit having a plurality of semiconductor switches connected in bridge wiring, a temperature sensor provided in the inverter circuit for detecting the temperature of the inverter circuit and sending out its detection signal, and a control circuit. This control circuit includes a rotating speed arithmetic unit for calculating the rotating speed of the motor from an output of a position detector, and a prescribed rotating speed storage unit for storing a prescribed rotating speed not causing resonance with the compressor. The control circuit further includes a temperature detector for detecting the temperature of the inverter circuit from the detection signal of the temperature sensor, a temperature storage unit for storing the value of the temperature detected by the temperature detector, and a temperature comparator for comparing the temperature of the inverter circuit stored in the temperature storage unit with the temperature of the inverter circuit during operation of the motor.
The control device of the compressor operates the motor at a specified rotating speed, when the motor rotating speed calculated in the rotating speed arithmetic unit does not reach the command rotating speed, by selecting a specified rotating speed lower than the command rotating speed from the prescribed rotating speed storage unit. At this time, the temperature of the inverter circuit is stored, and when the temperature of the inverter circuit becomes lower by a specified threshold than the stored temperature of the inverter circuit, the operation is returned to the command rotating speed.
In this configuration, the motor does not rotate at the resonance rotating speed causing resonance with the compressor, and the reliability of the compressor can be enhanced. When the overload state is canceled, the operating rotating speed of the DC motor is immediately returned to the command rotating speed, and the operation at the command rotating speed can be executed securely.
In the control device of the compressor of the present invention, the control circuit further includes a commutation unit for outputting a commutation pulse of the inverter circuit based on the output from position detector, a rotating speed controller, and a drive unit for operating the inverter circuit by the output of the commutation unit and the output of the rotating speed controller. The rotating speed controller compares the command rotating speed with the rotating speed of the motor calculated in the rotating speed arithmetic unit, and controls the voltage so as to vary the rotating speed of the motor so that the rotating speed of the motor may be equal to the command rotating speed.
In this configuration, the motor does not rotate at resonance rotating speed causing resonance with the compressor, and the reliability of the compressor can be enhanced. When the overload state is canceled, the operating rotating speed of the DC motor is immediately returned to the command rotating speed, and the operation at the command rotating speed can be executed securely.
In the control device of the compressor of the present invention, if the rotating speed calculated in the rotating speed arithmetic unit does not reach the command rotating speed, it is designed to select the rotating speed lower than and closest to the rotating speed calculated in the rotating speed arithmetic unit from prescribed rotating speeds in the prescribed rotating speed storage unit.
In this configuration, decline of cooling performance of the refrigerator is further minimized, and the compressor does not rotate at the resonance rotating speed. Therefore, the reliability of the compressor and the refrigerator using the same can be enhanced. At the same time, decline of cooling performance of the refrigerator can be prevented.
The control device of the compressor of the present invention is designed to control the refrigerator by using the above-mentioned control device of the compressor. In such configuration, the control device of compressor high in quality and reliability can be presented, and the reliability of the control device of the compressor and the refrigerator having the same can be enhanced. At the same time, decline of cooling performance of the refrigerator can be prevented.
In the control device of the compressor of the prevent invention, the motor does not rotate at the resonance rotating speed causing resonance with the compressor if the applied voltage to the DC motor reaches the maximum of applied voltage to the maximum DC motor, and breakage of discharge pipe of the compressor can be prevented, and the reliability of the compressor can be enhanced.
When the overload state of the motor is canceled, the motor current to the DC motor is lowered, and hence the temperature of the inverter circuit drops. When the temperature of the inverter circuit drops, the rotating speed of the DC motor is quickly returned to the command rotating speed. As a result, the reliability of the compressor can be enhanced, and decline of cooling performance of the refrigerator can be prevented.
The refrigerator of the present invention includes a compressor, a control device of the compressor for controlling this compressor, a cooling compartment, and a refrigeration cycle for cooling this cooling compartment. The control device of the compressor is composed to command, when the rotating speed of the motor is lower than the command rotating speed, so as to operate the motor at a prescribed rotating speed which is lower than the command rotating speed and in a range of rotating speed higher than the resonance rotating speed of the compressor or in a range of specified rotating speed lower than the resonance rotating speed.
In such configuration, the motor does not rotate at the resonance rotating speed causing resonance with the compressor, and the reliability of the refrigerator can be enhanced.

Thus, in the control device of the compressor of the present invention, the compressor does not rotate at resonance rotating speed, and breakage of discharge pipe is prevented, and the reliability of the compressor is enhanced, and hence it is very useful for controlling the inverter drive device of the compressor or the refrigerator.

Claims

A control device of a compressor for controlling to operate a motor at a command rotating speed by varying a voltage applied to the motor,
wherein, when the rotating speed of the motor does not reach the command rotating speed, the control device commands to operate the motor at a prescribed rotating speed lower than the command rotating speed and in a range of rotating speed either higher than or lower than a resonance rotating speed of the compressor.
The control device of the compressor of claim 1, comprising:
an inverter circuit having a plurality of semiconductor switches connected in bridge wiring,
a temperature sensor provided in the inverter circuit for detecting a temperature of the inverter circuit, and sending out its detection signal, and
a control circuit including:
a rotating speed arithmetic unit for calculating the rotating speed of the motor from an output of a position detector;
a prescribed rotating speed storage unit for storing the prescribed rotating speed not resonating with the compressor;
a temperature detector for detecting a temperature of the inverter circuit from the detection signal of the temperature sensor;
a temperature storage unit for storing a value of the temperature detected by the temperature detector; and
a temperature comparator for comparing the temperature of the inverter circuit stored in the temperature storage unit with the temperature of the inverter circuit during operation of the motor,
wherein the motor is operated at the prescribed rotating speed by selecting the prescribed rotating speed lower than the command rotating speed from the prescribed rotating speed storage unit when the rotating speed of the motor calculated in the rotating speed arithmetic unit does not reach the command rotating speed,
the temperature of the inverter circuit at this time is stored, and
when the temperature of the inverter circuit becomes lower by a specified threshold than the temperature stored in the inverter circuit, the operation is returned to the command rotating speed.
The control device of the compressor of claim 2,
wherein the control circuit includes
a commutation unit for outputting a commutation pulse of the inverter circuit based on the output of the position detector,
a rotating speed controller for comparing the command rotating speed with the rotating speed of the motor calculated in the rotating speed arithmetic unit, and controlling the voltage so as to vary the rotating speed of the motor until the rotating speed of the motor becomes equal to the command rotating speed, and
a drive unit for operating the inverter circuit by the output of the commutation unit and the output of the rotating speed controller.
The control device of the compressor of claim 3,
wherein when the rotating speed of the motor calculated in the rotating speed arithmetic unit is lower than the command rotating speed, a rotating speed lower than and closest to the rotating speed calculated in the rotating speed arithmetic unit is selected from prescribed rotating speeds stored in the prescribed rotating speed storage unit.
The control device of the compressor of any one of claims 1 to 4, wherein the control device of the compressor is designed to control a refrigerator.
A refrigerator comprising:
a compressor,
a control device for controlling the compressor,
a cooling compartment, and
a refrigeration cycle for cooling the cooling compartment,
wherein the control device varies a voltage applied to the motor to operate at a command rotating speed, and
when the rotating speed of the motor does not reach the command rotating speed, the control device commands to operate the motor at a prescribed rotating speed lower than the command rotating speed and in a range of rotating speed either higher than or lower than a resonance rotating speed of the compressor.
The refrigerator of claim 6,
the control device comprising:
an inverter circuit having a plurality of semiconductor switches connected in bridge wiring,
a temperature sensor provided in the inverter circuit for detecting the temperature of the inverter circuit, and sending out its detection signal, and
a control circuit including:
a rotating speed arithmetic unit for calculating the rotating speed of the motor from the output of the position detector;
a prescribed rotating speed storage unit for storing the prescribed rotating speed not resonating with the compressor;
a temperature detector for detecting a temperature of the inverter circuit from the detection signal of the temperature sensor;
a temperature storage unit for storing a value of the temperature detected by the temperature detector; and
a temperature comparator for comparing the temperature of the inverter circuit stored in the temperature storage unit with the temperature of the inverter circuit during operation of the motor,
wherein the motor is operated at the prescribed rotating speed by selecting the prescribed rotating speed lower than the command rotating speed from the prescribed rotating speed storage unit when the rotating speed of the motor calculated in the rotating speed arithmetic unit does not reach the command rotating speed,
the temperature of the inverter circuit at this time is stored, and
when the temperature of the inverter circuit becomes lower by a specified threshold than the temperature stored in the inverter circuit, the operation is returned to the command rotating speed.
The refrigerator of claim 7,
wherein the control circuit includes
a commutation unit for outputting a commutation pulse of the inverter circuit based on the output of the position detector,
a rotating speed controller for comparing the command rotating speed with the rotating speed of the motor calculated in the rotating speed arithmetic unit, and controlling the voltage so as to vary the rotating speed of the motor until the rotating speed of the motor becomes equal to the command rotating speed, and
a drive unit for operating the inverter circuit by the output of the commutation unit and the output of the rotating speed controller.
The refrigerator of claim 8,
wherein when the rotating speed of the motor calculated in the rotating speed arithmetic unit is lower than the command rotating speed, a rotating speed lower than and closest to the rotating speed calculated in the rotating speed arithmetic unit is selected from prescribed rotating speeds stored in the prescribed rotating speed storage unit.