JP4126598B2 - Operation control device for vibration compressor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an operation control device for a vibration compressor applied to a refrigerator of a gas cycle engine such as a Stirling refrigerator or a pulse tube refrigerator.
[0002]
[Prior art]
In the above-mentioned Stirling refrigerator and pulse tube refrigerator, as a compressor that is a mechanism for generating the pressure vibration, a configuration in which a piston is reciprocally driven by a moving coil linear motor is known. (For example, refer to Patent Document 1).
[0003]
In addition, a pair of pistons are arranged opposite to each other across a compression / expansion space for working gas (refrigerant such as helium) in a cylinder with both ends open, and the pistons are synchronized with each other in the opposite directions by driving a linear motor. A split-type linear drive compressor that is reciprocated is also known. (For example, patent document 2).
[0004]
Next, FIG. 2 shows a detailed structure of the above-described split type linear drive compressor.
[0005]
In FIG. 2, 1 is a compressor, 2 is a sealed casing that constitutes a pressure-holding vessel for working gas, 3 is a cylindrical cylinder that also serves as a yoke for a linear motor to be described later, and 4A and 4B are working gas compression spaces. A pair of left and right pistons 5 fitted to both ends of the cylinder 3 facing each other across the cylinder 3a, 5 are disk-shaped suspension springs that support the pistons 4A and 4B so as to be movable in the axial direction, 6A. Reference numeral 6B denotes a moving coil linear motor that individually drives the pistons 4A and 4B.
[0006]
The linear motors 6A and 6B include a yoke 7 that is integrated with the outer peripheral side of the cylinder 3 to form a magnetic circuit, and a ring-shaped permanent magnet that is magnetized in the radial direction and attached to the inner peripheral surface of the yoke 7. 8 and a movable coil 9 that faces the permanent magnet 8 and a bobbin 10 that supports the movable coil 9 and is connected to the pistons 4A and 4B. 3b is a working gas passage that passes through the cylinder 3 in the radial direction and communicates with the gas compression space 3a, and 11 is a pipe between the gas passage 3b and a displacer built in a cold head (not shown) of the refrigerator. Capillary tube.
[0007]
Although not shown, the lead wire connected to the movable coil 9 of the linear motor 6A, 6B passes through the casing 2 in an airtight manner and is pulled out to the outside, and then connected to a power supply unit described later to supply power. ing.
[0008]
The operation of the vibration compressor having such a configuration is well known. When an AC voltage is applied to the movable coil 9, an electromagnetic force acting between the current flowing through the movable coil 9 and the magnetic flux of the permanent magnet 8 linked to the coil is used. The movable coils 9 of the linear motors 6A and 6B reciprocate in opposite directions in synchronization with each other. As a result, the pistons 4A and 4B supported by the suspension spring 5 reciprocate alternately in the compression direction and the expansion direction in the cylinder 3 and are enclosed in the gas compression space 3a in the cylinder 3 sandwiched between the left and right pistons. Gas compresses and expands, generating pressure oscillations. The disc-shaped suspension spring 5 holds the piston 3 at the neutral position shown in the figure with the current of the movable coil 9 being zero.
[0009]
Next, a conventional power supply and control circuit used in the compressor 1 is shown in FIG. In FIG. 3, reference numeral 12 denotes a single-phase inverter (power supply device) composed of switching elements Q1 to Q4. The AC output of the inverter 12 is supplied to the movable coils 9 of the linear motors 6A and 6B of the compressor 1 to supply the piston 4A. , 4B are driven back and forth.
[0010]
Here, in order to control the amplitudes (reciprocating strokes) and reciprocating cycles of the pistons 4A and 4B during the operation of the compressor 1 in accordance with the command values given from the outside, The position sensor 13 corresponding to the piston 4A is provided, and based on the position information of the piston obtained by the position sensor 13, the output of the inverter 12 is adjusted as follows.
[0011]
That is, the inverter output frequency command is given to the sine wave generator 14 to obtain a control signal (sine wave signal) having a desired frequency. Then, a product of the sine wave signal and the piston amplitude command is obtained by a multiplier 15, and each is multiplied by a coefficient to obtain an output voltage command. Further, the output voltage command is compared with the triangular wave generated by the carrier generator 16 by the comparator 17 and converted into a PWM waveform. Further, the dead time is added by the dead time generation circuit 18 and then the gate driver 19 The switching elements Q1 to Q4 are ON / OFF controlled, and an output voltage having a desired frequency and voltage value is obtained from the inverter 12.
[0012]
On the other hand, the piston position control of the compressor 1 is performed by comparing the piston position detected by the DC component detector 20 with the position command based on the position information obtained by the position sensor 13 and a position adjuster (proportional controller or proportional integration). Controller 21) and its output (DC voltage) is superimposed on the output voltage command described above. In this case, if a positive DC voltage is superimposed on the output voltage command, the pistons 4A. Assume that 4B moves outward.
[0013]
[Patent Document 1]
JP-A-5-288419 (p3-4, FIG. 14)
[Patent Document 2]
Japanese Patent Laid-Open No. 6-257871 (p3, FIG. 1)
[0014]
[Problems to be solved by the invention]
By the way, in the conventional operation control system for the above-described vibration compressor, the coil is disconnected in one of the two left and right linear motors 6A and 6B during the operation of the compressor, or the piston is driven by the linear motor. When an abnormal situation occurs such as the motor being locked due to cylinder turn or the like, the amplitude of the piston driven by the other linear motor becomes abnormally large and the piston collides with the casing of the compressor. There is a risk of progressing to a serious accident that breaks.
[0015]
That is, in the operation control system described in FIG. 3, the output voltage from the inverter 12 is adjusted based on the position information of the position sensor 13 for the linear motors 6A and 6B of the compressor 1. If the linear motor 6A detecting the piston position is locked due to a broken coil or the piston 4A driven by the linear motor 6A, the piston 4A stops in the middle of a reciprocating stroke. Or, because of the restraint, the position sensor 13 cannot normally obtain the piston position information. In addition, in this case, feedback acts so as to increase the output voltage of the inverter 12 from the relationship between the position command and the position information of the piston 4A in the restrained state. For this reason, the amplitude of the piston 6B driven by the other linear motor 6B that operates by receiving a high output voltage is abnormally increased. As a result, the piston 4B collides with the casing 2 of the compressor, or the linear motor 6B. The bobbin 10 collides with the end face of the cylinder 3, and in the worst case, it is damaged and the compressor 1 cannot be operated.
[0016]
Therefore, it is conceivable to limit the upper limit of the output voltage of the inverter 12 in advance so as to prevent the piston from running away, but even with this method, it is difficult to suppress the abnormal amplitude of the piston.
[0017]
In other words, when the output voltage of the inverter 12 is limited, if an abnormality such as the linear motor 6A being locked as described above occurs, the piston 4A remains restrained, and the other piston is restricted due to the limitation of the output voltage of the inverter 12. Since the thrust of the linear motor 6B that drives 4B is also restricted, the compression pressure of the working gas in the gas compression space 3a in FIG. 2 decreases during the compression stroke of the compressor. On the other hand, the amplitude of the piston in the compression stroke of the compressor is determined by the balance condition between the gas pressure in the gas compression space 3a and the suspension spring 5 supporting the piston, in addition to the thrust of the linear motor.
[0018]
For this reason, when the gas pressure in the gas compression space 3a compressed in the compression stroke is lowered as described above, the drag of the gas pressure acting on the piston is also weakened. Receiving the thrust of 6B, it further proceeds in the compression direction, and the amplitude of the piston 4B becomes larger than that in the steady operation. Moreover, since the piston of the compressor is designed to swing at the resonance frequency of the vibration system in order to keep power consumption low, even if the upper limit of the output voltage of the inverter 12 is limited as described above, In this situation, the amplitude of the piston 4B increases self-excitingly, causing the piston 4B to collide with the casing, and in the worst case, there is a danger of destruction.
[0019]
Further, a pair of left and right pistons 4A. 4B, if the piston 4B on the right side that has not been detected by the position sensor 13 constrains and stops the reciprocating movement of the piston due to coil disconnection, piston stroke, etc. 4A reciprocates with the same amplitude as during steady operation by the output voltage of the inverter 12 based on the position information detected by the position sensor 13, but the right piston 4B is restrained and stopped during the reciprocating stroke by the motor lock. Therefore, the working gas pressure discharged from the compressor is lowered, and the capacity of the refrigerator is lowered.
[0020]
The present invention has been made in view of the above points. The object of the present invention is to solve the above-mentioned problems, and when the amplitude of the piston increases due to an abnormality of the linear motor during the operation of the compressor, this is electrically fastened. It is an object of the present invention to provide an operation control device for a vibration compressor that can detect and avoid a piston from running away and colliding with a casing.
[0021]
[Means for Solving the Problems]
In order to achieve the above-described object, according to the present invention, a pair of pistons fitted into opposite ends of a cylinder with a working gas compression / expansion space sandwiched inside a casing of the compressor, and each piston individually. Vibration that is configured to drive two sets of linear motors, supplying the AC output of the power supply to each linear motor, and reciprocally driving the pistons in opposite directions to generate pressure oscillations in the working gas As a compressor operation control device,
According to a first aspect of the present invention, the linear motor power supply circuit includes a current detection means for a coil current flowing through each linear motor, a calculation means for obtaining the current difference, and an output adjustment means for the power supply device. When the detection value corresponding to the difference in coil current flowing through each linear motor exceeds a preset threshold value, it is determined that an abnormal amplitude has occurred in the piston, and an abnormal signal is output from the calculation means to the output adjustment means of the power supply device Then, based on this abnormal signal, the power supply to the linear motor is stopped to stop the operation of the compressor (claim 1).
[0022]
In the second invention, when the detected value corresponding to the difference between the coil currents flowing through the respective linear motors during the operation of the compressor exceeds a preset threshold value, power is supplied to the linear motor based on the abnormal signal. The output voltage of the power supply device is lowered from that during steady operation to reduce the piston amplitude so that it does not collide with the casing, and the compressor is continuously operated with the output of the compressor lowered (claim 2).
[0023]
In the above, when an abnormality such as disconnection or motor lock occurs in one of the two linear motors during operation of the compressor, the coil current flowing in the linear motor and the coil current flowing in the other linear motor are A large current difference occurs between the two. Therefore, this current difference is detected, and when the detected value (absolute value) corresponding to the current difference exceeds the above-described threshold value, it is determined that an abnormal amplitude has occurred in the piston, and the compressor operation is forced. By operating the compressor in a state where the output voltage of the power supply device is lowered than in the steady operation and the amplitude of the piston is suppressed, the emergency situation where the piston collides with the casing and breaks, The compressor can be safely operated and controlled.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described based on the example shown in FIG. In the drawing of the embodiment, portions corresponding to those in FIG.
[0025]
The power supply and control circuit of FIG. 1 are basically the same as those of FIG. 3, but a current detector 24, a current difference calculator 25, and an inverter output adjustment circuit 26 are newly added as compared with FIG.
[0026]
That is, for the power feeding circuit 22 wired between the output terminal of the inverter (power supply device) 12 and the compressor 1, the branch power feeding circuits 22 </ b> A and 22 </ b> B corresponding to the two sets of linear motors 6 </ b> A and 6 </ b> B equipped in the compressor 1. CT 23 is provided to measure coil currents I _A and I _B flowing through the linear motors 6A and 6B. The current detector 24 converts the currents I _A and I _B measured by the CT 23 into voltages V _A and V _B and outputs them to the current difference calculator 25 at the subsequent stage. On the other hand, the current difference calculator 25 calculates the difference between the output voltages V _A and V _B of each current detector 24 and outputs an abnormal signal to the inverter output adjustment circuit 26 when the absolute value of the difference exceeds a threshold value to be described later. Output to. Further, when receiving an abnormal signal output from the current difference calculator 25, the inverter output adjustment circuit 26 turns off the switching elements Q1 to Q4 of the inverter 12 to completely stop the power supply to the compressor 1, or Alternatively, the output voltage of the inverter 12 is lowered to cause the compressor 1 to operate at a low output, and at the same time, an alarm signal is issued to notify the outside of the occurrence of abnormality.
[0027]
Next, the above threshold value setting will be described. That is, the amplitude (reciprocating stroke) of the pistons 4A and 4B built in the compressor 1 depends on the magnitudes of the currents I _A and I _B flowing in the movable coils of the linear motors 6A and 6B that individually drive the pistons. Since the maximum amplitude of the pistons 4A and 4B in steady operation is L _MAX and the coil current flowing through the linear motors 6A and 6B at that time is I _MAX , the detected voltage detected by the current detector 24 is V _MAX. The margin dimension remaining between the piston position of the maximum amplitude L _MAX and the casing 2 (see FIG. 2) of the compressor 1 is L ₀ , and the piston is expanded to the margin dimension L ₀ exceeding the maximum amplitude L _MAX . In this case, when the increment of the detection voltage corresponding to the increase in the coil current flowing through the linear motor is V ₀ , V ₀ is obtained by the following equation (1).
[0028]
V ₀ = V _MAX + V ₀ −V _MAX (1)
Accordingly, the V ₀ which said as a threshold, the current detector 24 of FIG. 1 during operation of the compressor, the output voltage V _A detected by the current difference calculator 25, the difference V _B (absolute value) a threshold value V ₀ If the operation of the compressor 1 is forcibly stopped as described above, the situation where the piston collides with the casing due to an abnormal amplitude can be avoided.
[0029]
Further, depending on the environment of the refrigerator to which this compressor is applied, it is possible to continue the operation with the compressor in a low output state without forcibly stopping the operation of the compressor. In this case, the threshold value is set to about 80% of the V ₀ value, for example, and the difference (absolute value) between the output voltages V _A and V _B during the operation of the compressor is the threshold value (0.8 V ₀ ). If the output voltage of the inverter 12 is adjusted so as to be lowered to 90% of that in the steady operation when the pressure exceeds), the output of the compressor is lower than that in the steady operation, but the piston collision is avoided. It is possible to continue operation in the state.
[0030]
As a case where an abnormality occurs in one of the linear motors 6A and 6B, if the movable coil of the linear motor 6A is disconnected, the coil current I _A becomes zero, so I _A <I _B , and the linear motor 6A When the motor is locked, the coil current I _A increases, so that I _A > I _B. Further, when an abnormality occurs in the linear motor 6B, the magnitude relationship between the coil currents I _A and I _B is opposite to the above, but in either case, by monitoring the coil currents I _A and I _B , The risk of the piston of the compressor colliding with the casing can be avoided by detecting the abnormality in the amplitude quickly and adjusting the output of the inverter (power supply device) 12 based on this.
[0031]
Further, as a method of detecting the coil currents I _A and I _B of the linear motors 6A and 6B, in the illustrated embodiment, the power feeding branch circuits 22A and 22B of the power feeding circuit 22 are equipped with a CT 23 and a current detector 24, and the coil currents I _A , While detecting the I _B, and the feeding circuit 22 through which the total current I _{a + B} of the coil current I _a and I _B of separate linear motors 6A and 6B is this one feeder branch circuits, for example, 22A The CT 23 and the current detector 24 can be provided, and the coil current I _B of the linear motor 6B can be obtained by calculation (I _B = I _{A + B} −I _A ).
[0032]
【The invention's effect】
As described above, according to the present invention, a pair of pistons that are fitted opposite to both ends of the cylinder across the compression / expansion space of the working gas inside the casing of the compressor, and each piston are individually driven. A vibration compressor that has two sets of linear motors, supplies the AC output of the power supply to each linear motor, and drives the pistons to reciprocate in opposite directions to generate pressure vibrations in the working gas. The power supply circuit of the linear motor includes a current detection means for the coil current that flows to each linear motor, a calculation means for obtaining the current difference, and an output adjustment means for the power supply device, and flows to each linear motor during operation of the compressor. When the detected value corresponding to the difference in coil current exceeds a preset threshold, it is determined that an abnormal amplitude has occurred in the piston, and the supply to the linear motor is made. One of the two sets of linear motors during the operation of the compressor by stopping the compressor and stopping the operation of the compressor, or lowering the output voltage of the power supply unit that supplies power to the linear motor and continuing the compressor operation. Even if an abnormality such as coil disconnection or motor lock occurs in the linear motor of this type, this abnormality is electrically detected quickly, and an emergency situation in which the piston collides with the casing and breaks can be avoided to operate the compressor safely. It can be controlled, and this makes it possible to cope with accident prevention of the vibration compressor.
[Brief description of the drawings]
FIG. 1 is a power supply and control circuit diagram of a vibration compressor according to an embodiment of the present invention. FIG. 2 is a structural cross-sectional view showing a detailed structure of the compressor in FIG. Circuit diagram [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Compressor 2 Casing 3 Cylinder 3a Compression space of working gas 4A, 4B Piston 5 Suspension spring 6A, 6B Linear motor 9 Moving coil 12 Inverter (power supply device)
22 Power supply circuit 23 Current detection CT
24 Current detector 25 Current difference calculator 26 Inverter output adjustment circuit I _A , I _B Linear motor coil current V _A , V _B Coil current detection voltage

Claims (2)

The compressor casing is equipped with a pair of pistons fitted opposite to both ends of the cylinder across the compression / expansion space of the working gas, and two linear motors that individually drive each piston. An operation control device for a vibration compressor that feeds alternating current output of a power supply device to each linear motor and drives the piston to reciprocate in opposite directions to generate pressure vibration in the working gas,
Coil current flowing through each linear motor during operation of the compressor, comprising: current detection means for coil current flowing through each linear motor in the power supply circuit of the linear motor; calculation means for obtaining the current difference; and output adjustment means for the power supply device. When the detected value corresponding to the difference exceeds a preset threshold value, it is determined that an abnormal amplitude has occurred in the piston, and the compressor is stopped by stopping power supply to the linear motor. Machine operation control device. The compressor casing is equipped with a pair of pistons fitted opposite to both ends of the cylinder across the compression / expansion space for the working gas, and two linear motors that individually drive each piston. An operation control device for a vibration compressor that feeds alternating current output of a power supply device to each linear motor and drives the piston to reciprocate in opposite directions to generate pressure vibration in the working gas,
Coil current flowing through each linear motor during operation of the compressor, comprising: current detection means for coil current flowing through each linear motor in the power supply circuit of the linear motor; calculation means for obtaining the current difference; and output adjustment means for the power supply device. When the detected value corresponding to the difference exceeds a preset threshold, it is judged that an abnormal amplitude has occurred in the piston, and the output voltage of the power supply unit that supplies power to the linear motor is lowered to continue the compressor operation. An operation control apparatus for a vibration compressor.

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