JP2019017175A - Linear motor system - Google Patents

Abstract

To provide a linear motor system capable of avoiding collision of a movable element without a need for a sensor for detecting collision.SOLUTION: A linear motor system 100 comprises a linear motor 104 having a movable element 6 at least connected with a coil 8 applied with an AC voltage and an elastic body 23, and has a linear motor drive device 101 that detects variation in amplitude of an AC current flowing in the coil 8, and detects that the movable element 6 goes beyond the maximum displacement in a case where the detected amplitude becomes larger than a predetermined value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a linear motor system, and more particularly to a linear motor system including a linear motor having a mover to which an elastic body is connected.

  For example, a technique described in Patent Document 1 is known as a so-called linear compressor in which a piston is reciprocated by a linear motor. Patent Document 1 discloses a reciprocating piston, a linear motor that drives the piston, and a linear compressor that has a motor control unit that controls the linear motor so that the stroke of the piston differs according to the required cooling force. Yes. The linear compressor described in Patent Document 1 includes a collision proximity sensing unit that detects whether or not the piston passes the collision proximity position, and the return time of the collision proximity point is determined according to a predetermined allowable time for each cooling power. The thrust of the linear motor is changed.

JP 2005-195026 A

However, the collision proximity detection unit described in Patent Document 1 needs to have a sensor such as a laser or an optical sensor in order to detect the position of the piston, and wiring is complicated and it is difficult to realize space saving. Become.
Therefore, the present invention provides a linear motor system that can avoid the collision of the mover without requiring a sensor for detecting the collision.

  In order to solve the above problems, a linear motor system according to the present invention includes a linear motor having at least a winding to which an AC voltage is applied and a mover to which an elastic body is connected, and an amplitude of an AC current flowing through the winding. And a linear motor driving device that detects that the movable element has exceeded a maximum displacement when the detected amplitude exceeds a predetermined value.

ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the linear motor system which can avoid the collision of a needle | mover, without requiring the sensor which detects a collision.
Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

1 is an overall schematic configuration diagram of a linear motor system according to a first embodiment of the present invention. It is a perspective view of the structural example of an armature. It is a schematic diagram which shows the longitudinal cross-section of a magnetic pole, and the flow of magnetic flux. It is explanatory drawing of the polarity which generate | occur | produces in a magnetic pole tooth. It is explanatory drawing of the external mechanism connected to a needle | mover. It is explanatory drawing which shows the structural example of the voltage command value preparation device which comprises the control part of the linear motor drive device shown in FIG. It is a figure which shows the structural example of the power converter circuit which comprises the linear motor drive device shown in FIG. It is explanatory drawing of the example of an electric current waveform when the needle | mover which comprises a linear motor collides with the stop which restrict | limits a stroke. It is explanatory drawing which shows the structural example of the low frequency component detector which comprises the control part of the linear motor drive device shown in FIG. It is explanatory drawing which shows the structural example of the collision determination device which comprises the control part of the linear motor drive device shown in FIG. It is explanatory drawing which shows the time change of the various values at the time of a collision and collision avoidance. It is a longitudinal cross-sectional view of the hermetic compressor of Example 2 which concerns on the other Example of this invention. It is a whole schematic block diagram of the linear motor system of Example 2. It is explanatory drawing which shows the structural example of the collision determination device which comprises the control part of the linear motor drive device shown in FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Similar components are denoted by the same reference numerals, and redundant description is omitted.
The various components of the present invention do not necessarily have to be independent of each other. A plurality of components are formed as a single member, and a single component is formed of a plurality of members. It is allowed that a certain component is a part of another component, a part of a certain component overlaps a part of another component, and the like.

  In this embodiment, for convenience of explanation, the terms front-rear direction, left-right direction, and up-down direction that are orthogonal to each other are used, but the gravitational direction is not necessarily parallel to the lower direction. It can be parallel to other directions.

<Linear motor system 100>
FIG. 1 is an overall schematic configuration diagram of a linear motor system according to a first embodiment of the present invention. The linear motor system 100 includes a linear motor driving device 101 and a linear motor 104. As will be described later, the linear motor 104 has an armature 9 and a mover 6 that move relative to each other.
In this embodiment, the mover 6 moves in the vertical direction, but the armature 9 and the mover 6 (field element) may move relative to each other, and the armature 9 may move in the vertical direction. In the following, the case where the movable element 6 reciprocates in the vertical direction will be described as an example, but the direction of reciprocation is not limited to the vertical direction. For example, the movable element 6 may be configured to reciprocate in the horizontal direction, or the movable element 6 may be configured to reciprocate in a direction having an arbitrary angle with respect to the vertical direction. The same applies to the armature 9.
The control unit 102 outputs an output voltage command value to the power conversion circuit 105 or a drive signal (pulse signal) for driving the power conversion circuit 105 according to the detection result of the current detector 107. Details of the control unit 102 will be described later.
Although details will be described later, the power conversion circuit 105 is an example of a power conversion unit that converts the voltage of the DC voltage source 120 (FIG. 21) and outputs an AC voltage. Note that a DC current source may be used instead of the DC voltage source 120.

<Linear motor 104>
FIG. 2 is a perspective view of the linear motor 104 (a perspective view of a configuration example of the armature). The linear motor 104 of the present embodiment has a mover 6 that can move relative to the armature 9 in the direction (front-rear direction) in which the permanent magnets 2 (2a, 2b) are arranged. The armature 9 has two magnetic poles 7 that face each other in the vertical direction through a gap, and a winding 8 wound around the magnetic pole 7. The mover 6 is disposed in this gap. The magnetic pole 7 has magnetic pole teeth 70 (also referred to as teeth) as end faces facing the mover 6.
The armature 9 can apply a force in the front-rear direction (hereinafter referred to as thrust) to the mover 6. For example, as will be described later, the thrust can be controlled so that the mover 6 reciprocates in the front-rear direction.
The mover 6 includes two flat permanent magnets 2 (2a, 2b) magnetized in the vertical direction. The rear permanent magnet 2a and the front permanent magnet 2b are magnetized in opposite directions. In this embodiment, the rear permanent magnet 2a has an N pole on the upper side, and the front permanent magnet 2b has an S pole on the upper side. In FIG. 2, the permanent magnets 2a and 2b are shown, but the mover 6 is not shown. As the mover 6, for example, a flat plate with a flat permanent magnet 2 fixed can be adopted.
The control unit 102 outputs a drive signal so that the mover 6 reciprocates in a range where the permanent magnets 2 a and 2 b face the armature 9.

  FIG. 3 is a cross-sectional view taken along the line A-A ′ of FIG. 2 (A-A ′ cross-sectional view). As shown in FIG. 3, the magnetic pole 7 and the yoke 7e are integrally formed of a magnetic material such as iron to constitute a magnetic circuit. The arrow lines in FIG. 3 show an example of magnetic flux lines when current is passed through the two windings 8. The direction of the flow of magnetic flux is not limited to that shown in the figure because it can be reversed depending on the direction of the current flowing through the winding 8. The magnetic pole teeth 70 are magnetized by the magnetic flux lines.

[Thrust applied to the mover 6]
FIG. 4 is a diagram for explaining the thrust received by the mover 6 due to the magnetization of the magnetic pole teeth 70. The polarities of the magnetic pole teeth 70 generated by the current flowing in the winding 8 are represented by “N” and “S” attached in the vicinity of the magnetic pole teeth 70 in the drawing. Further, in FIG. 4, the white arrow indicates the direction of the current flowing through the winding 8. The left diagram of FIG. 4 shows that the upper magnetic pole tooth 70a is magnetized to “S” and the lower magnetic pole tooth 70b is magnetized to “N” by the current flowing through the winding 8, so that the movable element 6 exerts a force in the forward direction. An example is shown in which the mover 6 has moved forward. The right diagram in FIG. 4 shows that the upper magnetic pole tooth 70a is magnetized to “N” and the lower magnetic pole tooth 70b is magnetized to “S” by the current flowing through the winding 8, so that the movable element 6 exerts a force in the backward direction. In this example, the mover 6 is moved backward.

  In this way, by applying a voltage or current to the winding 8, magnetic flux is supplied to the magnetic circuit including the two magnetic poles 7, and the two opposing magnetic pole teeth 70 (magnetic pole teeth set) can be magnetized. By applying an alternating voltage or current such as a sine wave or rectangular wave (square wave) as the voltage or current, a thrust for reciprocating the mover 6 can be applied. Thereby, the movement of the mover 6 can be controlled.

Note that the thrust applied to the mover 6 can be changed by changing the amplitude of the applied alternating current or alternating voltage. Moreover, the displacement of the mover 6 can be changed as desired by appropriately changing the thrust applied to the mover 6 using a known method. Here, when the mover 6 reciprocates (for example, a movement that occurs in the mover 6 by sequentially repeating the magnetization of the magnetic pole teeth 70 as shown in the left and right diagrams of FIG. 4), it changes in an alternating waveform. The amount of change in the displacement of the mover 6 is called a stroke.
Since the magnetic pole teeth 70 are magnetic bodies, a magnetic attractive force that attracts the permanent magnet 2 acts. In the present embodiment, since the two magnetic pole teeth 70 are opposed to each other with a gap so as to sandwich the mover 6, the resultant magnetic attraction force acting on the mover 6 can be reduced.

  When converting the rotary motion of the rotary motor into a linear motion, for example, a crankshaft is used as the conversion mechanism. With a crankshaft, the linear motion stroke is mechanically limited. On the other hand, the mover 6 of the linear motor is not mechanically limited. Therefore, the stroke of the mover 6 may exceed a predetermined value. Therefore, the linear motor driving device 101 constituting the linear motor system 100 according to the present embodiment has a configuration for detecting that the stroke exceeds a predetermined value.

[Mechanism outside the mover 6]
FIG. 5 is an explanatory diagram of an external mechanism connected to the mover 6. For example, an external mechanism constituted by a resonance spring 23 (assist spring) that is a coil spring is connected to one end of the mover 6, and its spring force It is a figure explaining the mechanism in which the needle | mover 6 is returned by FIG. One end of the resonance spring 23 is connected to the mover 6 via the intermediate portion 24, and the other end is fixed to the base portion 25. Further, a side portion 26 that extends substantially parallel to the extending direction of the resonance spring 23 and guides or supports the resonance spring 23 is provided. When the linear motor 104 is reciprocated, acceleration and deceleration are repeated each time the moving direction of the mover 6 changes. During deceleration, the velocity energy of the mover 6 is converted into electrical energy (regenerative operation), but loss occurs due to the resistance of the wiring to the linear motor 104. On the other hand, as shown in FIG. 5, when a resonance spring 23 (assist spring) is added to the mover 6 and the mover 6 is reciprocated at a mechanical resonance frequency determined from the mass of the mover 6 and the spring constant, the mover 6 is movable. The speed energy of the child 6 can be effectively used, and a highly efficient linear motor drive system can be configured. Instead of the resonance spring 23, for example, a leaf spring or an elastic body such as rubber having an appropriate Young's modulus and expanding and contracting similarly to the case of using a coil spring may be used. With this configuration, the movable element 6 (field element 6) is configured as a movable element (field element) moving type that moves in the vertical direction, but an elastic body is connected to the armature 9 instead of the movable element 6. The armature 9 may be configured as an armature moving type that moves the armature 9 in the vertical direction.

  For example, when the stroke of the mover 6 becomes excessive, the resonance springs 23 are contracted too much and contact each other, or the mover 6 collides with a stopper (not shown) that limits the stroke, thereby vibrating. Cause noise. Therefore, it is desirable to detect that the stroke has exceeded a predetermined value.

<Outline of Control Unit 102>
As shown in FIG. 1, the control unit 102 receives a current detection value Im from the current detector 107 and outputs a low-frequency component amplitude value. The low-frequency component detector 130 outputs a low-frequency component amplitude value. A collision determination unit 131 that performs a collision determination based on the amplitude value of the component and outputs a collision determination signal, which will be described later, and a stroke command value l ^* and a collision determination unit 131 input from a host controller (not shown) are input. Based on these, a voltage command value generator 133 that outputs a voltage command value Vm ^* to be applied to the linear motor 104, and a PWM signal that outputs a drive signal that drives the power conversion circuit 105 based on the input voltage command value Vm ^*. And a creator 134.
Hereinafter, the configuration and operation of each of the above-described units constituting the control unit 102 will be described.

<Voltage command value generator 103>
FIG. 6 is an explanatory diagram illustrating a configuration example of the voltage command value generator 133 that configures the control unit 102 of the linear motor driving apparatus 101 illustrated in FIG. 1. The voltage command value generator 133 outputs a single-phase AC voltage command value Vm ^* based on a stroke command value l ^* input from a host controller (not shown) or the like and a collision determination signal described later. Here, the voltage command value Vm ^* applied to the linear motor 104 can be adjusted by changing either or both of the stroke command value l ^{* and the} frequency command value ω ^* . That is, by adjusting the amplitude and frequency of the applied voltage, the drive frequency ω can be controlled to the resonance frequency and the stroke can be controlled.
6, first, the frequency command value omega ^* or preset by the voltage command value generator 133, another controller integrates the frequency command value input (not shown) or the like omega ^* phase The command value θ ^* is created by the integrator 140. Next, the phase command value θ ^* is input to the cosine calculator 82b (the cosine of the input value is output) to obtain the cosine (cos θ ^* ) with respect to the phase command value θ ^* . The cosine (cos θ ^* ) and the stroke command value l ^* are multiplied by a multiplier 92a. By doing so, it is possible to obtain the speed command value vm ^* of the mover 6 without performing a differentiation operation. In general, one of the position command value xm ^* and the speed command value vm ^* can be a sine and the other can be a cosine. Depending on the combination, it is necessary to add a negative sign.

Further, the speed command value vm ^* of the mover 6 is multiplied by the induced voltage constant Ke ^* by the multiplier 92b to obtain a single-phase AC voltage command value Vm ^* .
In addition to the above, a known synchronous motor drive voltage command method can be applied to the voltage command value generator 133. Further, for example, the frequency command value ω ^* may be fixed to the mechanical resonance frequency of the vibrating body including the mover 6.
The stroke command switch 150 will be described later.

<PWM signal generator 133>
The PWM signal generator 134 constituting the control unit 102 of the linear motor driving apparatus 101 shown in FIG. 1 is known by comparing the triangular wave carrier signal with the voltage command value Vm ^* output from the voltage command value generator 133. Drive signal corresponding to the voltage command value Vm ^* is generated, and the generated drive signal is output to the power conversion circuit 105.

<Power conversion circuit 105>
FIG. 7 is a diagram illustrating a configuration example of the power conversion circuit 105 included in the linear motor driving apparatus 101 illustrated in FIG. The full bridge circuit 126 switches the DC voltage source 120 according to the drive signal input by the control unit 102 and outputs a voltage to the linear motor 104. The full bridge circuit 126 includes four switching elements 122, a first upper and lower arm (hereinafter referred to as U phase) having switching elements 122a and 122b connected in series, and a second upper and lower arm having switching elements 122c and 122d. And an arm (hereinafter referred to as a V phase). The switching element 122 can perform a switching operation in accordance with a pulsed gate signal (124a to 124d) output from the gate driver circuit 123 based on a voltage command value Vm ^* generated by the control unit 102 or a drive signal by pulse width modulation. .
By controlling the conduction state (ON / OFF) of the switching element 122, a voltage corresponding to the AC voltage of the DC voltage source 120 can be output to the winding 8. Note that a DC current source may be used instead of the DC voltage source 120. As the switching element 122, for example, a semiconductor switching element such as IGBT or MOS-FET can be employed.

[Connection with linear motor 104]
The linear motor 104 is connected between the switching elements 122 a and 122 b of the first upper and lower arms and between the switching elements 122 c and 122 d of the second upper and lower arms of the power conversion circuit 105. Although FIG. 7 shows an example in which the windings 8 of the upper and lower armatures 9 are connected in parallel, the windings 8 can also be connected in series.

<Current detector 107>
For example, a current detector 107 such as a CT (current transformer) can be provided on the U-phase lower arm and the V-phase lower arm. Thereby, the current Im flowing through the winding 8 of the linear motor 104 can be detected.
As the current detector 107, for example, instead of CT, a phase shunt current method is adopted in which a shunt resistor 125 is added to the lower arm of the power conversion circuit 105 and a current flowing through the linear motor 104 is detected from a current flowing through the shunt resistor 125. it can. In place of or in addition to the current detector 107, a single shunt current detection method for detecting the current on the AC side of the power conversion circuit 105 from the DC current flowing in the shunt resistor 125 added to the DC side of the power conversion circuit 105. It may be adopted. The single shunt current detection method utilizes the fact that the current flowing through the shunt resistor 125 changes with time depending on the energization state of the switching element 122 constituting the power conversion circuit 105.

[Current waveform at the time of collision]
FIG. 8 is an explanatory diagram of an example of a current waveform when the mover 6 constituting the linear motor 104 collides with a stopper that restricts the stroke. In FIG. 8, time is plotted on the horizontal axis and motor current is plotted on the vertical axis, and the time variation of the motor current is shown. The upper diagram in FIG. 8 shows the motor current waveform when the electric machine time constant is short, and the lower diagram in FIG. 8 shows the motor current waveform when the electric machine time constant is long. As shown in the upper diagram of FIG. 8, when the electric machine time constant including the load system is short, the amplitude of the current waveform of the motor current at the time of collision appears alternately. This can be explained as follows. When the mover 6 collides with the stopper, the speed of the mover 6 decreases, and the induced voltage decreases. Therefore, the applied voltage becomes excessive and the current amplitude increases. Since the mover 6 of this embodiment reciprocates, it eventually moves in the opposite direction. At this time, the phase relationship between the position of the mover 6 and the applied voltage is shifted, and the thrust is reduced. Therefore, in the next cycle, the stroke falls within a predetermined value, and the current amplitude of the motor current returns. Thereafter, the phase relationship between the position of the mover 6 and the applied voltage is eliminated, and the mover collides with the stopper again.

On the other hand, as shown in the lower diagram of FIG. 8, when the electromechanical time constant including the load system is long, it takes time until the deviation of the phase relationship between the position of the movable element 6 and the applied voltage converges. Therefore, the fluctuation of the current amplitude of the motor current is lower than that in the upper diagram of FIG.
As shown in the upper diagram of FIG. 8, when the electric machine time constant is short, the amplitude of the current waveform of the motor current when the mover 6 collides with the stopper is alternately large and small. The fact that the amplitudes are alternately large and small can be regarded as a half of the drive frequency. In other words, the driving cycle can be regarded as being doubled. On the other hand, as shown in the upper diagram of FIG. 8, when the electric machine time constant is long, it can be regarded as a frequency lower than ½ of the drive frequency. The example in the lower diagram of FIG. 8 can be regarded as a frequency that is 1/3 of the drive frequency. In other words, it can be considered that the driving period is three times. In the present embodiment, it is detected that the stroke exceeds a predetermined value by specifying a current waveform having a frequency component that is ½ of the driving frequency or a frequency component that is lower than ½ of the driving frequency. If the current waveform at the time of collision is acquired in advance, it can be understood which frequency component should be acquired. In this embodiment, the drive frequency is shown as an example of 1/2 of the drive frequency and 1/3 of the drive frequency, but the present invention is not limited to this. For example, it can be appropriately set by acquiring a current waveform at the time of collision such as ¼ of the driving wave number in advance. In other words, it is possible to detect that the stroke exceeds a predetermined value by detecting the current (motor current) flowing through the winding 8 having a frequency component of N times (N ≧ 2) the driving cycle.

<Low frequency component detector 130>
FIG. 9 is an explanatory diagram illustrating a configuration example of the low-frequency component detector 130 included in the control unit 102 of the linear motor driving apparatus 101 illustrated in FIG. In addition, in FIG. 9, the case where the electric machine time constant including the load system shown in the upper figure of the above-mentioned FIG. Therefore, the current waveform of the frequency component that is 1/2 of the drive frequency (twice the drive cycle) is specified. When the frequency to be specified is changed, a coefficient of a division period 156 described later may be changed as appropriate.

First, the frequency command value omega ^* or preset by the voltage command value generator 133, another controller (not shown) is multiplied by 1/2 by the frequency command value omega ^* the frequency divider 156 obtained from such, integration Then, the phase command value θ2 ^* is created by the integrator 140a.
Next, the phase command value θ2 ^* is input to the sine calculator 81c (outputs the sine of the input value) and the cosine calculator 82c (outputs the cosine of the input value), and the sine (sin θ2 ^* ) with respect to the phase command value θ2 ^* , respectively. And cosine (cos θ2 ^* ). The sine (sin θ2 ^* ) and the current detection value Im are multiplied by a multiplier 92c, and the cosine (cos θ2 ^* ) and the current detection value Im are multiplied by a multiplier 92d. These results are obtained by LPFs (low-pass filters) 157a and 157b, which are lower than the cutoff frequency of the LPF (low-pass filter). Note that these LPFs (low-pass filters) 157a and 157b have a delay similar to the first-order lag filter or the second-order lag filter.

Further, using the multiplier 92e and the multiplier 92f, the adder 90, and the square root calculator 96, the square sum of squares of the output values of the LPF 157a and the LPF 157b is taken to obtain the current amplitude.
By doing so, it is possible to obtain a current amplitude (Im_1 / 2) of a desired frequency component (here, a frequency component that is ½ of the drive frequency).

  If the mover 6 collides with a stopper or the like that limits the stroke, and the current waveform has alternating amplitudes as shown in the upper diagram of FIG. A two-frequency current amplitude (Im_1 / 2) is detected. When there is no change in the amplitude of the current flowing through the linear motor 104, the output of the square root calculator 96 is near zero.

<Collision detector 131>
FIG. 10 is an explanatory diagram illustrating a configuration example of the collision determination unit 131 included in the control unit 102 of the linear motor driving apparatus 101 illustrated in FIG. As shown in FIG. 10, when the current amplitude (Im_1 / 2) input from the low frequency component detector 130 is equal to or less than a predetermined value A, the determination unit 164 included in the collision determination unit 131 is a low level signal (digital In the case of output, for example, “0”) is output as a collision determination signal, and when it is larger than the predetermined value A, a high level signal (for example, “1” in the case of digital output) is output as a collision determination signal. .
For example, the determination value (predetermined value A) may be changed according to the elapsed time, or may be changed from an upper controller (not shown). Further, by providing a hysteresis width to the determination value (predetermined value A), it is possible to change the determination timing when the stroke exceeds the predetermined value and the determination timing when the stroke becomes equal to or less than the predetermined value. Thereby, erroneous detection can be prevented. This is particularly effective, for example, when the current detection value includes a lot of noise.

[Operation at collision judgment]
FIG. 11 is an explanatory diagram showing temporal changes of various values at the time of collision and collision avoidance. Hereinafter, a series of operations at the time of collision determination will be described with reference to FIGS. 6 and 11 showing a configuration example of the voltage command value generator 133 constituting the control unit 102 of the linear motor driving apparatus 101. FIG. In FIG. 11, in order from the top, the time change of the motor current (current waveform), the time change of the stroke of the mover 6, the time change of the voltage / current phase difference, the time change of the low frequency component current amplitude, the state of the collision determination signal The change and the time change of the voltage amplitude are shown. In FIG. 11, as an example, a case where the current waveform of the motor current at the time of the collision has a short electric machine time constant including the load system shown in the upper diagram of FIG. 8 will be described. That is, the case where the current waveform of the frequency component of 1/2 of the drive frequency (twice the drive cycle) is specified is shown as an example.

In the normal operation state, the time change of the motor current detected by the current detector 107 and the stroke of the mover 6 is a sinusoidal waveform having substantially the same phase and a constant amplitude. The voltage / current phase difference is zero, the low frequency component current amplitude output from the low frequency component detector 130 is near zero, and the collision determination signal output from the collision detector 131 is a low level signal (L). The voltage amplitude of the voltage command value Vm ^* output from the voltage command value generator 133 is constant.

  When the mover 6 collides with the stopper, the amplitude of the motor current increases, and the amplitude difference increases as shown in FIG. 11 rather than the amplitude of the motor current in the normal operation state. In addition, when the mover 6 collides with the stopper, the speed of the mover 6 decreases, so that the induced voltage decreases, the applied voltage becomes excessive, the current amplitude increases, and the voltage / current phase difference becomes steep. To increase. After that, since the movable element 6 reciprocates, it eventually moves in the opposite direction, and the voltage / current phase difference gradually decreases and becomes zero in the next cycle. In the example shown in FIG. 11, these waveform changes are alternately repeated three times. During this period, the low-frequency component current amplitude output from the low-frequency component detector 130 has a delay in the LPFs (low-pass filters) 157a and 157b constituting the low-frequency component detector 130 as described above. Therefore, the waveform becomes a gradually increasing waveform. Here, the low-frequency component current amplitude output from the low-frequency component detector 130 is a current amplitude (Im_1 / 2) of a frequency component that is ½ of the drive frequency.

As described above, the collision determination unit 131 has the current amplitude (Im_1 / 2) of the frequency component input from the low frequency component detector 130, that is, the low frequency component current amplitude value exceeds the predetermined value A in FIG. When this is detected, a high level signal (H) is output as a collision determination signal. When the voltage command value generator 133 receives a high level signal (H) as a collision determination signal from the collision determiner 131, the stroke command switch 150 that constitutes the voltage command value generator 133 as shown in FIG. Switch from side to side B. Then, the value decreased from stroke command value l ^* by a stroke subtraction value .DELTA.l ^* by the subtractor 91 becomes the stroke command value l ^*. A value obtained by reducing the stroke command value l ^* by the stroke subtraction value Δl ^* is multiplied by the stroke command value l ^* and the cosine (cos θ ^* ) by the multiplier 92a. Further, the speed command value vm ^* of the mover 6 is multiplied by the induced voltage constant Ke ^* by the multiplier 92b to output a single-phase AC voltage command value Vm ^* . That is, as shown in the time variation of the voltage amplitude in FIG. 11, the amplitude of the voltage applied to the motor decreases, and a collision avoidance operation is performed.

  When the current amplitude (Im_1 / 2) of the frequency component input from the low frequency component detector 130 reaches the predetermined value C after the collision avoidance operation described above, the collision determiner 131 uses the low level signal (L) as the collision determination signal. Is output to the voltage command value generator 133. Then, as shown in FIG. 11, the normal operation state is restored.

As described above, according to the present embodiment, it is possible to provide a linear motor system that can avoid the collision of the mover without requiring a sensor for detecting the collision.
Further, if the configuration of this embodiment is used, it is possible to reduce the wiring and reduce the size of the linear motor system that can detect that the stroke exceeds a predetermined value.

  The configuration of the present embodiment can be the same as that of the first embodiment except for the following points. The present embodiment relates to a hermetic compressor 50 as an example of a device on which a linear motor system 200 described later is mounted.

<Sealed compressor 50>
FIG. 12 is a longitudinal sectional view of a hermetic compressor of Example 2 according to another embodiment of the present invention, and is an example of a longitudinal sectional view of a hermetic compressor 50 having a linear motor 104. The hermetic compressor 50 is a reciprocating compressor in which the compression element 20 and the electric element 30 are arranged in the hermetic container 3. The compression element 20 and the electric element 30 are elastically supported in the sealed container 3 by a support spring 49. The electric element 30 includes a mover 6 and an armature 9.
The compression element 20 includes a cylinder block 1 that forms a cylinder 1a, a cylinder head 16 that is assembled to an end face of the cylinder block 1, and a head cover 17 that forms a discharge chamber space. The working fluid supplied into the cylinder 1a is compressed by the reciprocating motion of the piston 4, and the compressed working fluid is sent to a discharge pipe (not shown) communicating with the outside of the compressor. For example, air or a refrigerant of a refrigeration cycle can be adopted as the working fluid.

A piston 4 is attached to one end of the mover 6. In this embodiment, the movable body 6 and the piston 4 reciprocate to compress and expand the working fluid. This corresponds to a load in which work required for compression and expansion fluctuates. A compression element 20 is disposed at one end of the electric element 30. The cylinder block 1 has a guide rod that guides the reciprocating motion of the mover 6 along the front-rear direction.
When the linear motor 104 is installed in the hermetic container 3, an airtight connector called a hermetic connector or a hermetic seal may be used. In order to maintain airtightness, it is desirable to minimize the number of connectors.

  When a resonance spring 23 (not shown in FIG. 12) is added to the mover 6 and the mover 6 is reciprocated at a mechanical resonance frequency determined by the mass of the mover 6 and the spring constant, resonance by the compression element 20 is performed. It is necessary to consider the influence on the frequency. That is, since the spring action of the working fluid is applied by the suction pressure of the compression element 20 and the pressure of the discharge space, the frequency at which the resonance state is reached changes. That is, when the pressure of the cylinder 1a is high, it is equivalent to a high spring constant of the resonance spring 23 added to the mover 6, and the resonance frequency becomes high. On the contrary, when the pressure of the cylinder 1a is low, the spring constant of the resonance spring 23 added to the mover 6 becomes dominant, and the resonance frequency is a mechanical resonance frequency determined from the mass of the mover 6 and the spring constant. Close to.

  The piston 4 is fixed to the base 25 via the mover 6 and the resonance spring 23, but the stroke is not mechanically limited. Therefore, if the stroke of the mover 6 becomes larger than expected, the piston 4 may collide with the cylinder head 16. Alternatively, the side opposite to the cylinder 1a of the piston 4 or the mover 6 may collide with the magnetic pole 7 or the winding 8 of the linear motor 104, for example. When the piston 4 collides with the cylinder head 16, it not only makes noise, but in the worst case, the piston 4 and the cylinder head 16 may be damaged. Therefore, it is desirable to appropriately control the stroke even during a transition such as startup, and it is necessary to detect it in the event of a collision.

  When the linear motor 104 is used as the power of the compression element 20, the resonance frequency changes depending on the condition of the compression element 20. Thus, even if the same voltage is applied to the linear motor 104, the stroke changes. Therefore, it is necessary to detect where the piston 4 and the movable element 6 collide even under a wide range of load conditions. Therefore, the linear motor system 200 of the present embodiment detects the fluctuation of the amplitude of the alternating current flowing through the linear motor 104, and detects that the maximum displacement of the mover 6 has been exceeded when the amplitude fluctuation exceeds a predetermined value. In addition, wiring and space can be saved, and highly efficient linear motor drive can be realized.

<Linear motor system 200>
FIG. 13 is an overall schematic configuration diagram of the linear motor system 200 of the present embodiment. The linear motor system 200 includes a linear motor driving device 201 and a linear motor 104.
The linear motor driving device 201 includes a power conversion circuit 105, a current detector 106, and a control unit 202. The control unit 202 includes a low frequency component detector 130, a collision determiner 131 a, a voltage command value generator 133, and a PWM signal generator 134.
When the hermetic compressor 50 is driven, the suction pressure and the discharge pressure change. In particular, since the rate of change in pressure is large at the time of startup, there is a problem that the collision determination device 131a may be erroneously detected. Therefore, in this embodiment, the determination value (predetermined value) is switched according to the elapsed time or the load condition.

FIG. 14 is an explanatory diagram illustrating a configuration example of the collision determination unit 131a included in the control unit 202 of the linear motor driving apparatus 201 illustrated in FIG. As illustrated in FIG. 14, the collision determination unit 131a includes two determination units 164a and 164b, an integrator 94, and a coefficient unit 159. The determination unit 164a included in the collision determination unit 131 is a low level signal (in the case of a digital output, for example, when the current amplitude (Im_1 / 2) is not more than a predetermined value A, for example, input from the low frequency component detector 130. "0") is output, and when it is larger than the predetermined value A, a high level signal (for example, "1" in the case of digital output) is output. The output from the determiner 164a is a value obtained by multiplying the coefficient K_coll by the coefficient unit 159, and further integrated by the integrator 94.
The output of the integrator 94 is input to the determiner 164b. When the output from the integrator 94 exceeds a predetermined value B (determination value), the determiner 164b outputs a high level signal (for example, “1” in the case of digital output) as a collision determination signal. In the following cases, a low level signal (for example, “0” in the case of digital output) is output as a collision determination signal.
Thereby, when the current amplitude of a desired frequency component exceeds a determination value (predetermined value) for a predetermined period, it can be detected that the stroke has exceeded a predetermined value.

As described above, according to the present embodiment, in the hermetic compressor 50, by applying the linear motor system 200 that detects that the stroke exceeds a predetermined value, it is possible to realize wiring saving and miniaturization. It becomes. By changing the determination value (predetermined value) during operation, or by providing hysteresis to the determination value (predetermined value), it is possible to provide a linear motor system that can reduce erroneous detection and realize stable driving.
Further, by appropriately switching the determination value (predetermined value) according to the elapsed time and the load of the linear motor 104 (eg, proportional to the difference between the suction pressure and the discharge pressure of the pressure element 20), no load (pressure It is possible to provide a linear motor system capable of appropriately detecting a collision even under a wide range of load conditions, such as a condition where the suction pressure and discharge pressure of the element 20 are equalized) to a heavy load.
Further, the compressor shown in the present embodiment can be applied to a compressor that compresses a working fluid in order to adjust the vehicle height in an air suspension.

The present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described.
Each of the above-described configurations, functions, processing units, processing procedures, and the like may be realized by hardware by designing a part or all of them with, for example, an integrated circuit. Each of the above-described configurations, functions, and the like may be realized by software by interpreting and executing a program that realizes each function by the processor.
The power conversion circuit 105 may be configured to output current. In this case, a current command value generator may be provided instead of the voltage command value generator 103.

DESCRIPTION OF SYMBOLS 1 ... Cylinder block 1a ... Cylinder 2 ... Permanent magnet 3 ... Sealed container 4 ... Piston 6 ... Movable element 7 ... Magnetic pole 8 ... Winding 9 ... Armature 16 ... Cylinder head 17 ... Head cover 20 ... Compression element 23 ... Resonant spring (assist Spring)
30 ... Electric element 50 ... Hermetic compressor 100, 200 ... Linear motor system 101, 201 ... Linear motor driving device 102, 202 ... Control unit 104 ... Linear motor 105 ... Power conversion circuit 106, 107 ... Current detector 126 ... Full Bridge circuit 130 ... Low frequency component detector 131, 131a ... Collision determiner 133 ... Voltage command value generator 134 ... PWM signal generator 140 ... Integrator 150 ... Stroke command switch

Claims (14)

A linear motor having at least a winding to which an AC voltage is applied and a mover to which an elastic body is connected;
A linear motor drive device that detects a change in amplitude of an alternating current flowing through the winding and detects that the movable element has exceeded a maximum displacement when the detected amplitude exceeds a predetermined value. Motor system. The linear motor system according to claim 1,
The linear motor driving device is:
A low frequency component detector for inputting an alternating current flowing in the winding and detecting a current amplitude of a frequency component lower than the driving frequency;
A linear motor system, comprising: a collision determination unit that detects that the mover has exceeded a maximum displacement when a current amplitude detected by the low frequency component detector exceeds a predetermined value. The linear motor system according to claim 2,
The low-frequency component detector detects fluctuations in the period of the amplitude of the alternating current flowing in the winding;
When the amplitude detected by the low frequency component detector exceeds a predetermined value, the collision determination unit detects that the mover has exceeded a maximum displacement. The linear motor system according to claim 2,
The low frequency component detector detects a current amplitude of a current flowing through the winding having a frequency component equal to or less than ½ of a driving frequency,
When the current amplitude detected by the low frequency component detector exceeds a predetermined value, the collision determination unit detects that the mover has exceeded a maximum displacement. The linear motor system according to claim 2,
The low frequency component detector detects a current amplitude of a current flowing through the winding having a frequency component equal to or less than ½ of a driving frequency,
When the current amplitude detected by the low frequency component detector exceeds a predetermined value for a predetermined period, the collision determination unit detects that the mover has exceeded a maximum displacement. The linear motor system according to claim 2,
The low frequency component detector detects a current amplitude of a current flowing through the winding having a frequency component of N times (N ≧ 2) of a driving cycle,
When the current amplitude detected by the low frequency component detector exceeds a predetermined value, the collision determination unit detects that the mover has exceeded a maximum displacement. The linear motor system according to claim 2,
The low frequency component detector detects a current amplitude of a current flowing through the winding having a frequency component of N times (N ≧ 2) of a driving cycle,
When the current amplitude detected by the low frequency component detector exceeds a predetermined value for a predetermined period, the collision determination unit detects that the mover has exceeded a maximum displacement. In the linear motor system according to claim 4 or 6,
The linear motor system, wherein the collision determination device changes the predetermined value based on an elapsed time or a load condition. The linear motor system according to claim 8,
The linear motor driving device is:
A linear voltage characterized by having a voltage command value generator for outputting a voltage command value for changing a voltage applied to the winding when the mover detects that the movable element has exceeded a maximum displacement by the collision determiner. Motor system. The linear motor system according to claim 8,
The linear motor driving device is:
A linear voltage characterized by having a voltage command value generator for outputting a voltage command value for decreasing the voltage applied to the winding when the movable element detects that the movable element has exceeded a maximum displacement by the collision determiner. Motor system. The linear motor system according to claim 9, wherein
The collision determiner is
When the current amplitude detected by the low frequency component detector is less than or equal to the predetermined value, a low level signal is output to the voltage command value generator as a collision determination signal,
When the current amplitude detected by the low frequency component detector exceeds the predetermined value, a high level signal is output to the voltage command value generator as a collision determination signal. The linear motor system according to claim 10,
The collision determiner is
When the current amplitude detected by the low frequency component detector is less than or equal to the predetermined value, a low level signal is output to the voltage command value generator as a collision determination signal,
When the current amplitude detected by the low frequency component detector exceeds the predetermined value, a high level signal is output to the voltage command value generator as a collision determination signal. The linear motor system according to claim 11,
The voltage command value generator is
An integrator for obtaining a phase command value by integrating a frequency command value set in advance or input from the outside;
A cosine calculator for obtaining a cosine for the phase command value;
A stroke command switch for selecting one of a stroke command value of a stroke which is a change amount of the displacement of the mover and a value obtained by subtracting a predetermined stroke subtraction value from the stroke command value;
A multiplier that multiplies the output of the cosine calculator and the stroke command value or a value obtained by subtracting a predetermined stroke subtraction value from the stroke command value;
The stroke command switch selects the stroke command value when the collision determination signal is a low level signal, and subtracts a predetermined stroke subtraction value from the stroke command value when the collision determination signal is a high level signal. A linear motor system characterized by selecting a value. The linear motor system according to claim 12, wherein
The voltage command value generator is
An integrator for obtaining a phase command value by integrating a frequency command value set in advance or input from the outside;
A cosine calculator for obtaining a cosine for the phase command value;
A stroke command switch for selecting one of a stroke command value of a stroke which is a change amount of the displacement of the mover and a value obtained by subtracting a predetermined stroke subtraction value from the stroke command value;
A multiplier that multiplies the output of the cosine calculator and the stroke command value or a value obtained by subtracting a predetermined stroke subtraction value from the stroke command value;
The stroke command switch selects the stroke command value when the collision determination signal is a low level signal, and subtracts a predetermined stroke subtraction value from the stroke command value when the collision determination signal is a high level signal. A linear motor system characterized by selecting a value.

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