JP2004120884A - Control device for linear motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent damage to a motor by immediately getting out of a situation where a movable body has a collision, if any. <P>SOLUTION: This control device for a linear motor is driven by a single-phase inverter 2 and reciprocates pistons 5A, 5B as movable bodies. The control device for linear motor has the collision detection sensor for detecting the collision of the piston 5A, a down counter 25 for changing the magnitude of the output voltage of the inverter 2 at the time of the collision detection by the sensor 8; an adder 26, a counter 27 for changing offset voltage superimposed on the output voltage; a multiplier 28, and an adder 24. At the time of the collision detection, the output voltage is decreased immediately, and the offset voltage is increased, and the output voltage is returned. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a linear motor control device, and more particularly, to a linear motor for a compressor (so-called linear compressor) that is driven by a power converter and compresses gas by reciprocating a piston or the like as a movable portion of the linear motor. More particularly, the present invention relates to a control device for preventing collision of a movable part without using a position detection sensor of the movable part.
[0002]
[Prior art]
FIG. 9 shows a driving system of a conventional linear compressor driven by a power converter. In this conventional technology, a single-phase inverter is used as a power converter, and a single-phase voice coil motor is used as a linear motor. . Note that this type of linear compressor is used in a cooling device such as a refrigerator when the expanded refrigerant gas is compressed by reciprocating motion of a piston in a cylinder.
[0003]
9, 1 is a DC power source, 2 is a single-phase inverter having a semiconductor switching element _Q 1 to Q _4, 3 is a linear compressor, 4A, 4B is a linear motor, 5A, 5B are driven motors 4A, respectively, by 4B Reference numeral 6 denotes a cylinder as a movable part for compressing gas, 6 denotes a cylinder, and 7 denotes a position sensor such as a magnetic sensor for obtaining position information of the piston.
[0004]
The operation of this conventional technique will be briefly described.
A single-phase inverter 2 connected to a DC power supply 1 supplies a single-phase AC voltage having a desired frequency and amplitude to the linear motors 4A and 4B. The pistons 5A and 5B connected to the motors 4A and 4B reciprocate in the left-right direction (x direction) in the figure according to the frequency output from the single-phase inverter 2 to compress the gas in the cylinder 6.
[0005]
In such a linear compressor 3, if the average pressure on the pistons 5A and 5B is different between when the gas is compressed and when the gas is expanded, the center position of the pistons 5A and 5B along the x-direction changes. As a result, in the worst case, the pistons 5A and 5B may collide with each other and damage the linear motors 4A and 4B.
[0006]
In order to avoid the above inconvenience, the position information of the piston 5A detected by the position sensor 7 is conventionally used for control.
Here, FIG. 10 shows a control block diagram of the single-phase inverter 2. An output frequency command of the inverter 2 is input to the sine wave oscillator 11, and a sine wave signal of a desired frequency is obtained by referring to a sine wave table or the like from a phase angle command obtained by integrating the frequency command. The sine wave signal is multiplied by the output voltage command (amplitude command) of the inverter 2 by the multiplier 12, and the result is multiplied by coefficients by the coefficient units 13 and 14 to obtain the output voltage command. The output voltage command output from the coefficient unit 13 is input to the comparator 16 via the adder 24, and the output voltage command output from the coefficient unit 14 is input directly to the comparator 17.
[0007]
In the comparators 16 and 17, each output voltage command is compared with a triangular wave output from the carrier generator 15, and a PWM pulse is generated. The PWM pulse is input to the gate driver 20 after a dead time for preventing a short circuit between the upper and lower arms is added by the dead time generator 19 via the distributor 18. In the gate driver 20 generates gate signals of the single-phase inverter 2 to the switching element _Q 1 to Q ₄ based on the PWM pulse, turns on the switching element _Q 1 to Q ₄ by these gate signal, by turning off the desired And outputs the AC voltage having the amplitude and frequency to the linear motors 4A and 4B.
[0008]
In this prior art, the control of the piston position is performed as follows.
That is, the position information detected by the position sensor 7 is input to the DC component detecting means 21 to detect the center position of the piston in the x direction. Further, a deviation between the average piston position command and the center position of the piston detected by the DC component detecting means 21 is obtained by the adder 22. The deviation is input to a position adjuster (proportional adjuster or proportional-integral adjuster, etc.) 23, and the output DC bias is superimposed on the output voltage command of one comparator 16 by an adder 24 as an offset voltage. By doing so, a change in the center position of the pistons 5A and 5B is prevented.
Here, it is assumed that when a positive offset voltage is superimposed on the output voltage command on the comparator 16 side, the pistons 5A and 5B move outward in the axial direction.
[0009]
In addition, there are various conventional techniques of a linear compressor including a position sensor for controlling the position of a piston as described below (for example, see Patent Documents 1 to 3). On the other hand, it is necessary to arrange the position sensor 7 in the cylinder 6. However, since the pressure inside the cylinder 6 is high, it is structurally difficult to draw out the signal line of the position sensor 7, and the cost increases. Also. In view of such a point, a method and apparatus for measuring the piston position of a free piston compressor, which estimates the piston position by measuring the voltage and current of a linear motor without using a position sensor, are already known. (See Patent Document 4).
[0010]
[Patent Document 1]
JP-A-9-291889 (paragraph [0024], etc., [FIG. 1])
[Patent Document 2]
JP 2001-90661 A (paragraphs [0032], [0033], etc., [FIG. 1], [FIG. 2], [FIG. 10])
[Patent Document 3]
JP-A-2002-155869 (paragraphs [0028] to [0034], [0050], [0058], etc., [FIG. 1, FIG. 3, and FIG. 7])
[Patent Document 4]
Japanese Patent Publication No. Hei 8-508558 (Pages 7-8, "Simple Disclosure of the Invention", page 9, lines 11-16)
[0011]
[Problems to be solved by the invention]
As described above, when a position sensor is used to prevent the collision of the piston, there are structural problems and cost problems.
Further, according to the related art in which the piston position is controlled without using the position sensor as in Patent Literature 4, the inconvenience of disposing the piston in the cylinder can be avoided, but the variation in the motor constant and the filling of the cylinder can be avoided. In the unlikely event that the piston falls into a collision state due to gas deterioration, spring deterioration, or the like, the piston may not be able to escape quickly, and if the collision state continues for a long time, the motor may be damaged.
[0012]
Therefore, the present invention provides a linear motor that controls the position of a movable part without using a position sensor of the movable part such as a piston. Even if the movable part collides, the linear motor immediately escapes from the collision state and prevents damage to the motor. It is an object of the present invention to provide a control device for a linear motor.
[0013]
[Means for Solving the Problems]
In order to solve the above problem, an invention according to claim 1 is a collision detection that detects a collision of the movable part in a linear motor driven by a power converter and reciprocating a movable part as a load. A sensor, means for changing the magnitude of the output voltage of the power converter when a collision is detected by the sensor, and means for changing an offset voltage superimposed on the output voltage, wherein the output voltage is immediately reduced when a collision is detected And the offset voltage is increased, and then the output voltage is restored.
[0014]
According to a second aspect of the present invention, in a linear motor driven by a power converter and reciprocating a movable portion as a load, a collision detection sensor for detecting a collision of the movable portion, and a collision by the sensor At the time of detection, if the output voltage of the power converter at that time is smaller than the output voltage at the time of the previous collision detection, the output voltage is reduced, and the offset voltage superimposed on this output voltage is reduced. Means for reducing the output voltage and increasing the offset voltage when the output voltage of the power converter is higher than the output voltage at the time of the previous collision detection.
[0015]
According to a third aspect of the present invention, in the linear motor control device according to the first or second aspect, an offset voltage superimposed on an output voltage is corrected when a collision of the movable portion is detected.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, FIG. 1 shows a drive system of a linear compressor 3 'to which the first embodiment of the present invention is applied, and the same components as those in FIG. 9 are denoted by the same reference numerals.
As is clear from the figure, in the linear compressor 3 ', a position sensor for detecting the position of the piston is removed, and instead, the piston 5A is attached to the rear end of one piston 5A. And a collision detection sensor 8 for detecting collision with the inner walls of both ends of the cylinder 6. Here, the collision detection sensor 8 includes, for example, a proximity switch or the like that detects that the piston 5A has moved a predetermined distance or more in the direction of the other piston 5B. It may be a sensor that detects sound.
[0017]
FIG. 2 is a control block diagram of the single-phase inverter 2 in the present embodiment, and corresponds to the first aspect of the present invention. In this figure, the same components as those in FIG. 10 are denoted by the same reference numerals, and the configuration and operation will be described below focusing on the portions different from FIG.
[0018]
In FIG. 2, a collision detection signal output from the collision detection sensor 8 is input to a down counter 25, and its output is input to an adder 26 with an output voltage command (amplitude command) of the inverter 2 by a sign shown in the drawing. I have. The output signal of the adder 26 is input to the multiplier 12, and is multiplied by the sine wave signal from the sine wave oscillator 11 as in the related art.
On the other hand, the collision detection signal is input to the counter 27, the output of which is multiplied by the gain K _off in the multiplier 27, and then input to the adder 24 on the output side of the coefficient unit 13.
[0019]
In the above configuration, the down counter 25 acts so as to reduce the magnitude of the output voltage command when, for example, the piston 5A collides with the other piston 5B, and the counter 27 and the multiplier 28 control the offset applied to the output voltage command. It acts to increase the voltage.
[0020]
The reason why not only the offset voltage is added but also the output voltage command, that is, the voltage applied to the motor during the collision of the piston is reduced is that the response of the piston position to the step change of the offset voltage is slow. Generally, the piston of the linear motor is operated at the resonance frequency of the gas, and the position response of the piston at a frequency other than the resonance frequency is extremely slow. Therefore, first, since the amplitude of the piston is immediately reduced by reducing the voltage applied to the motor, it is possible to quickly escape from the collision state, and at the same time, the offset voltage is increased.
The output voltage command reduced immediately after the collision is slowly restored thereafter.
[0021]
FIG. 3 is a diagram showing an operation at the time of a piston collision in FIG. 2, and FIG. 4 is a diagram showing an operation of the down counter 25 at the time of a piston collision.
The down counter 25 in FIG. 2 generates a sawtooth waveform as shown in FIG. 4 by subtracting from a preset value using the collision detection signal as a trigger. The output voltage is reduced as shown in FIG. 3 by subtracting the output of the down counter 25 from the output voltage command (the magnitude before collision is V1). On the other hand, the counter 27 counts the collision detection signal, multiplies the output thereof by a gain K _off by a multiplier 28 to increase the offset voltage at the time of collision, and adds the offset voltage to the output voltage command by the adder 24.
[0022]
Next, FIG. 5 is a control block diagram of a single-phase inverter 2 to which the second embodiment of the present invention is applied, and corresponds to the second aspect of the present invention. The drive system of the linear compressor 3 'has the same configuration as that of FIG.
In the first embodiment described above, it is mainly assumed that the piston moves toward the center of the cylinder 6 and the pistons 5A and 5B collide with each other. This is mainly because the pistons 5A and 5B move toward the center of the cylinder 6 because the pressure in the cylinder 6 is higher during compression than during expansion. However, in consideration of aging, the pistons 5A and 5B may collide with the inner walls of both ends of the cylinder 6 in some cases. Therefore, it is necessary to immediately escape from the collision state even in such a case.
[0023]
Therefore, in the second embodiment, the pistons 5A and 5B move in the center direction and collide with each other (referred to as a central collision for convenience), and move in the outward direction and collide with the inner walls at both ends of the cylinder 6 ( For convenience, an outside collision is determined), and an offset voltage according to the situation is superimposed on the output voltage to escape from the collision state.
A stopper may be provided on the cylinder 6 in order to prevent the collision between the pistons 5A and 5B beforehand. In such a case, the case where the pistons 5A and 5B collide with the stopper is also included in the central collision in the present invention. .
[0024]
In FIG. 5, focusing on the differences from FIG. 2, in the embodiment of FIG. 5, a collision detection signal is input to a down counter 25 and a counter (up / down counter) 27, and a central collision determination unit 29. Is also entered. The central collision judging device 29 discriminates between a central collision and an outside collision based on a collision detection signal and an output voltage command, and sends an up-count command or a down-count command to the counter 27 according to the discrimination result. Output.
Other configurations in FIG. 5 are the same as those in FIG.
[0025]
Here, FIG. 6 shows the principle of determining an outside collision. As described above, the discrimination between the center collision and the outside collision is performed by the inside / outside collision judging device 29.
Since the output voltage is decreased and the offset voltage is increased at the time of the center collision, as shown in FIGS. 3 and 6, it is possible to return to at least the output voltage V1 at the time of the collision. However, when the offset voltage is increased, the piston is displaced outward, so that at the time of an outside collision, the collision again occurs at the output voltage V2 'before returning to the output voltage V1 at the time of the previous collision as shown in FIG. .
[0026]
Therefore, in the present embodiment, the output voltage V1 at the time of the previous collision is compared with the output voltage V2 at the time of the current collision,
If V1> V2, it is determined that an outside collision has occurred, and the offset voltage is reduced.
If V1 <V2, it is determined that the center collision has occurred, and the offset voltage is increased.
Thereby, the offset voltage superimposed on the output voltage at the time of the center collision or the outer collision is adjusted.
[0027]
The inside / outside collision judging device 29 performs the above judgment operation based on the collision detection signal and the output voltage command, and outputs an up-count command or a down-count command to the counter 27 according to the discrimination result. The counter 27 changes the offset voltage superimposed on the output voltage command by, for example, decreasing the value by two at the time of an outside collision and outputting a value obtained by adding one at the time of a center collision.
Thus, in any of the case of the center collision and the case of the outer collision, it is possible to quickly escape from the collision state by superimposing an appropriate offset voltage on the output voltage command.
[0028]
Next, FIG. 7 is a control block diagram of the single-phase inverter 2 to which the third embodiment of the present invention is applied, and corresponds to the third aspect of the present invention. The drive system of the linear compressor 3 'has the same configuration as that of FIG.
The difference between FIG. 7 and FIG. 2 will be mainly described. In FIG. 7, the output of the multiplier 28 and the output voltage command are input to the correction table 30, and the output is added to the adder 24 on the coefficient unit 13 side. ing.
[0029]
The correction table 30 is configured as shown in FIG.
That is, at the time of the collision of the piston, the relationship between the output voltage command and the offset voltage superimposed thereon is corrected according to the direction of the collision (center collision or outer collision). Specifically, assuming that the broken line in FIG. 8 indicates the relationship between the two before the collision, the ratio of the offset voltage to the output voltage is increased at the time of the central collision, and the ratio of the offset voltage to the output voltage is increased at the time of the outer collision. The relationship between the two is corrected so as to decrease the offset voltage, and the offset voltage increased or decreased by the relationship is output to the adder 24.
[0030]
As a result, even when a voltage higher than the voltage at the time of the collision is output next as a command, the vehicle can be operated without colliding again in both cases of the center collision and the outer collision.
Although the correction table 30 in this embodiment is a table that defines the relationship between the output voltage and the offset voltage, the relationship between the output current and the offset voltage superimposed on the output current and the output power and the offset voltage superimposed on this May be a table that defines the relationship with the table.
[0031]
【The invention's effect】
As described above, according to the present invention, even if the linear compressor does not have a position sensor for a movable part such as a piston, it is possible to reliably detect a center collision or an outer collision of the movable part and immediately escape from the collision state. Thus, the motor can be prevented from being damaged, and the life can be extended. Further, since the collision detection sensor does not necessarily need to be disposed in the cylinder, there is an effect that there is no problem in structure and cost as in the case of using a position sensor.
[Brief description of the drawings]
FIG. 1 is a diagram showing a drive system of a linear compressor to which a first embodiment of the present invention is applied.
FIG. 2 is a control block diagram of a single-phase inverter according to the first embodiment.
FIG. 3 is a view showing an operation at the time of a piston collision in FIG. 2;
FIG. 4 is a diagram showing an operation of a down counter at the time of a piston collision in FIG. 2;
FIG. 5 is a control block diagram of a single-phase inverter according to a second embodiment of the present invention.
FIG. 6 is a diagram illustrating a principle of determining an outside collision in the second embodiment.
FIG. 7 is a control block diagram of a single-phase inverter according to a third embodiment of the present invention.
FIG. 8 is an explanatory diagram of a correction table in a third embodiment.
FIG. 9 is a diagram showing a drive system of a conventional linear compressor.
FIG. 10 is a control block diagram of a single-phase inverter according to the related art.
[Explanation of symbols]
1: DC power supply 2: Single-phase inverter 3 ': Linear compressors 4A, 4B: Linear motors 5A, 5B: Piston 6: Cylinder 8: Collision detection sensor 11: Sine wave oscillators 12, 28: Multipliers 13, 14: Coefficient units 15: carrier generator 16, 17: comparator 18: distributor 19: dead time generating means 20: gate driver 24, 26: adder 25: down counter 27: counter 29: central collision determiner 30: correction table _{Q 1} ~Q _4: semiconductor switching element

Claims (3)

In a linear motor driven by a power converter and reciprocating a movable part as a load,
A collision detection sensor that detects a collision of the movable portion; a unit that changes a magnitude of an output voltage of the power converter when a collision is detected by the sensor; and a unit that changes an offset voltage superimposed on the output voltage. ,
A control device for a linear motor, characterized in that at the time of collision detection, the output voltage is immediately reduced, the offset voltage is increased, and then the output voltage is restored. In a linear motor driven by a power converter and reciprocating a movable part as a load,
A collision detection sensor that detects a collision of the movable portion, and at the time of collision detection by this sensor, when the output voltage of the power converter at that time is smaller than the output voltage at the time of the previous collision detection, The offset voltage superimposed on the output voltage is reduced, and when the output voltage of the power converter at the time of collision detection is higher than the output voltage at the time of the previous collision detection, the output voltage is reduced and the offset voltage is reduced. A control device for a linear motor, comprising: means for increasing. The control device for a linear motor according to claim 1 or 2,
A control device for a linear motor, wherein an offset voltage superimposed on an output voltage is corrected when a collision of the movable portion is detected.

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