JP2012205398A - Linear drive device and linear generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress eccentricity of a mover which reciprocates with respect to a stator in a linear drive device and a linear generator.SOLUTION: Stator cores 12 and stator coils 14 are stacked in an axial direction in a cylindrical stator 10 and a mover core 22 and a mover permanent magnet 24 are provided on a mover 20. Levitation coils 16, which are provided on a tip of the stator core 12 and sandwich the mover 20 oppositely, are connected with each other by null flux wires. When eccentricity of the mover 20 is generated, the mover 20 is restored to a central axis by an electromagnetic force due to induction current generated in the levitation coil 16. Power is supplied from the outside to the levitation coil 16 on an end position where moving velocity of the mover 20 is low.

Description

  The present invention relates to a linear drive / power generation device, and more particularly to a configuration of a floating coil.

  Conventionally, linear drive devices such as linear motors and linear power generation devices using free pistons are known.

  In the following Patent Document 1, in a linear motor composed of a rod-shaped stator in which permanent magnets are arranged in the axial direction and a mover equipped with an armature coil arranged on the outside thereof, contact due to deflection of the stator, etc. A configuration including an aerostatic bearing for protecting and maintaining a constant gap between the stator and the mover is disclosed.

  Further, in Patent Document 2, in a linear motor including a rod-shaped stator in which permanent magnets are arranged in the axial direction and a mover equipped with an armature coil arranged on the outside thereof, contact due to deflection of the stator or the like is avoided. In order to protect, the structure provided with the coil protection pipe made from aluminum between a needle | mover and a stator is disclosed.

  Patent Document 3 discloses a configuration of a free-piston engine-driven linear power generator, and discloses that a rotating unit that rotates the shaft about its central axis is provided.

  Patent Document 4 discloses a linear motor and a press molding apparatus using this as a drive source. A coil unit including a core extending along the inner peripheral surface of the stator and extending in the axial direction and a plurality of coils arranged in the core is mounted, and linear bushes mounted on both ends of the stator are linearly reciprocated in the axial direction. The permanent magnet unit is attached to the outer peripheral surface of the rod supported so as to be movable.

  Furthermore, Non-Patent Document 1 discloses a linear permanent magnet generator for a free piston energy converter, in which a stator is formed by laminating a stator core and a coil in the axial direction, and each row of stators. The iron core is divided and arranged in the circumferential direction.

JP 2009-225640 A JP 2007-174804 A JP 2004-11777 A JP 2001-352747 A

“Design and Experimental Verification of a Linear Permanent Magnet Generator for a Free-Piston Energy Converter”, Jiabin Wang et al, IEEE Transaction on Energy Conversion, Vol. 22, No. 2, June 2007

  In a linear drive / power generation device in which the mover reciprocates in the axial direction, the moving direction of the mover and the direction of the magnetic flux are orthogonal to each other, so that the position of the mover can be supported in the radial direction (direction orthogonal to the traveling direction). Have difficulty.

  In Patent Document 1, the movable element is supported by an aerostatic bearing. However, even if the aerostatic bearing alone can protect the stator from bending or the like, it can be protected from contact due to external force, such as vibration. It is difficult to protect because of its relatively low support. Moreover, since it is necessary to process a hard member with high precision in order to comprise an air bearing, there exists a problem which cannot be manufactured cheaply also in cost.

  Moreover, in patent document 2, the coil protection pipe made from aluminum arrange | positioned between a stator and a needle | mover is for protecting a coil from a contact, and is not for supporting a needle | mover. Moreover, since it is made of conductive aluminum, even if an electromagnetic force is generated by electromagnetic induction, the generated supporting force is offset. Further, the electromagnetic force and the induced current at this time are lost, and the efficiency is reduced.

  An object of the present invention is to maintain the radial position of the mover by efficiently suppressing the eccentricity of the mover with a simple configuration in a linear drive / power generation device.

  The present invention is a linear drive / power generation device, which includes a cylindrical stator and a mover including a magnet that reciprocally moves in the stator in the axial direction, and the stator includes the shaft A stator core and a stator coil stacked in a direction, and a levitation coil provided at an end of the stator core on the mover side, and the levitation coil at least sandwiching the mover. It consists of a set of opposing coils, and the set of coils are connected to each other by a null flux wire.

  In one embodiment of the present invention, there is provided means for applying a current to the levitating coil located at the end of the reciprocating movement of the mover in the levitating coil.

  In another embodiment of the present invention, there is provided means for applying a current to the levitation coil at a position where the moving speed of the mover is relatively small in the levitation coil.

  In another embodiment of the present invention, the stator core and the levitation coil are divided into a plurality in the circumferential direction of the stator.

  In another embodiment of the present invention, the levitation coil is divided into four in the circumferential direction of the stator, and the four divided levitation coils are opposed to each other across the mover. The coil includes a second set of coils that are opposed to each other with the mover interposed therebetween and are disposed in a direction orthogonal to the first set of coils.

  According to the present invention, even if the mover is eccentric, a restoring force is generated in the mover by at least one set of floating coils connected by a null flux wire, and the eccentricity can be suppressed. In addition, according to the present invention, even when the moving speed of the mover is low, it is possible to compensate for the lack of restoring force by supplying current to the levitation coil.

It is a block diagram of the linear electric power generating apparatus in 1st Embodiment. It is the partially expanded view and sectional drawing of FIG. It is arrangement | positioning explanatory drawing of a floating coil. It is a connection diagram of the levitation coil in the x-axis direction. It is a connection diagram of a floating coil in the y-axis direction. It is a graph which shows the relationship between a needle | mover position and a needle | mover speed. It is a system configuration figure in a 2nd embodiment. It is a graph which shows the relationship between the needle | mover speed | rate and levitation | floating force in 2nd Embodiment. It is division | segmentation explanatory drawing of the stator core and the floating coil in other embodiment. It is division | segmentation explanatory drawing of the stator core and the floating coil in other embodiment. It is division | segmentation explanatory drawing of the stator core and the floating coil in other embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Basic principle>
First, the basic principle of this embodiment will be described.

  In a linear drive device or linear power generator in which a shaft-like mover reciprocates in a cylindrical stator, a levitating coil is provided at the end of the stator core, that is, the end of the stator core on the mover side. Suppresses radial eccentricity. That is, when the mover is eccentric in the radial direction, the magnetic flux interlinked with the levitating coil in the eccentric direction increases, while the magnetic flux interlinked with the levitating coil in the position facing the mover decreases, The electromagnetic forces generated by the induced currents of the pair of opposed levitation coils cancel each other in opposite directions, and cannot be used as a restoring force for restoring the mover to the center position.

  Therefore, in the present embodiment, a pair of floating coils facing each other with the mover interposed therebetween are connected to each other by a null flux wire. The null flux system is connected so that the winding directions of the respective levitation coils constituting one set of levitation coils intersect with each other, whereby one set of levitation coils is connected to electromagnetic waves in a direction opposite to the eccentric direction of the mover. A force is generated, and the eccentricity of the mover is effectively prevented.

  The levitation coils are arranged opposite to each other so as to sandwich the mover in the eccentric direction of the mover. However, if the mover can be eccentric in any direction, at least two sets of levitation coils that are orthogonal to each other are used. It is desirable. That is, assuming that the directions perpendicular to each other are the x direction and the y direction, one set of levitation coils is arranged in the x direction, and another set of levitation coils is arranged in the y direction. One set of levitation coils in the x direction are connected to each other by a null flux method, and another set of levitation coils in the y direction are also connected to each other by a null flux method. Thereby, the eccentricity of the mover is suppressed in the two directions of xy.

  Hereinafter, the present embodiment will be described more specifically.

<First Embodiment>
FIG. 1 shows the configuration of the linear drive device according to this embodiment. The linear drive device includes a stator 10 and a mover 20. The stator 10 has a hollow cylindrical shape, and the mover 20 has a shaft shape and reciprocates along the axial direction of the hollow cylindrical stator 10.

  The stator 10 includes a stator core 12, a stator coil 14, and a levitation coil 16. The stator core 12 and the stator coil 14 are laminated in the axial direction. The levitation coil 16 is disposed at the tip of the stator core 12, that is, the end of the stator core 12 on the side of the mover 20.

  The mover 20 includes a mover iron core 22 and a permanent magnet 24. The mover iron core 22 and the permanent magnet 24 are laminated in the axial direction in the same manner as the stator iron core 12 and the stator coil 14 of the stator 10. The mover 10 is driven to reciprocate by, for example, a free piston engine. That is, one piston engine of a pair of free piston engines arranged opposite to both ends of the mover 20 repeats expansion, gas exchange, compression, and combustion, and the other piston engine is shifted in timing from one piston engine. The mover 20 reciprocates by repeating expansion, gas exchange, contraction, and combustion. Due to the reciprocating movement of the mover, an induced electromotive force is generated in the stator coil 16 and an induced current flows to generate power. The levitation coil 16 is a coil for preventing contact between the stator 10 and the mover 20 and maintaining a radial relative positional relationship between the stator 10 and the mover 20.

  In FIG. 2, the arrangement | positioning state of the stator core 12, the stator coil 14, and the floating coil 16 of the stator 10 is shown. 2A is a partially enlarged view of the stator 10 in FIG. 1, FIG. 2B is a cross-sectional view taken along line BB in FIG. 2A, and FIG. 2C is FIG. 2A. It is CC sectional drawing of. As shown in FIGS. 2B and 2C, the stator core 12 is divided in the circumferential direction, and is divided into four in the circumferential direction in this embodiment. In the part where the stator coil 12 does not exist, as shown in FIG. 2C, the stator core 12 is divided in the circumferential direction and arranged radially, so that a cross-shaped arrangement is formed as a result. The stator coil 14 is wound in the circumferential direction. Further, the levitation coil 16 is also divided into four in the circumferential direction, like the stator core 12. The levitation coil 16 is a set of two coils at positions facing each other among the four divided coils. Assuming that two axes orthogonal to each other in a plane viewed from the radial direction are an x-axis and a y-axis, the position of the mover 20 in the x-direction is determined by one set of two sets of coils that are opposed to each other among the four divisions. It adjusts and the y direction position of the needle | mover 20 is adjusted with the other group of two sets of coils.

  FIG. 3 shows the arrangement position of the levitation coil 16. The stator core 12 divided into four in the circumferential direction is referred to as stator cores 12a, 12b, 12c, and 12d. The stator cores 12a and 12b face each other, and the stator cores 12c and 12d face each other. As shown in the figure, if the two orthogonal axes are the x-axis and the y-axis, the stator cores 12a and 12b are the stator cores in the x-axis direction, and the stator cores 12c and 12d are the stator cores in the y-axis direction. Become. Of the levitation coil 16, a levitation coil 16x + in the x-axis direction is wound around the stator core 12a. Further, the other levitation coil 16x− in the same x-axis direction among the levitation coils 16 is wound around the stator iron core 12b facing the stator iron core 12a. When the mover 20 is displaced with respect to the stator 10 in the x-axis direction, a current corresponding to the displacement flows through the floating coils 16x + and 16x− in the x-axis direction. That is, when the mover 20 is displaced with respect to the stator 10 in the x-axis direction, a relative displacement is generated between the mover permanent magnet 24 of the mover 20 and the levitation coils 16x + and 16x−. Inductive currents occur at 16x + and 16x-. Specifically, when the mover 20 is decentered in the direction of the levitation coil 16x +, the magnetic flux of the mover permanent magnet 24 linked to the levitation coil 16x + increases, and an induced current flows through the levitation coil 16x + in a direction that prevents this. On the other hand, the magnetic flux of the mover permanent magnet 24 interlinking with the levitation coil 16x− decreases, and an induced current flows through the levitation coil 16x− in a direction that prevents this.

  Of the levitation coil 16, a levitation coil 16y + in the y-axis direction is wound around the stator core 12c. Further, the other floating coil 16y− in the same y-axis direction among the floating coils 16 is wound around the stator core 12d facing the stator core 12c. When the mover 20 is displaced with respect to the stator 10 in the y-axis direction, a current corresponding to the displacement flows through the floating coils 16y + and 16y− in the y-axis direction. That is, when the mover 20 is displaced with respect to the stator 10 in the y-axis direction, a relative displacement is generated between the mover permanent magnet 24 of the mover 20 and the levitation coils 16y + and 16y−. An induced current is generated at 16y + and 16y−. Specifically, when the mover 20 is decentered in the direction of the levitation coil 16y +, the magnetic flux of the mover permanent magnet 24 linked to the levitation coil 16y + increases, and an induced current flows in the levitation coil 16y + in a direction that prevents this. On the other hand, the magnetic flux of the mover permanent magnet 24 interlinking with the levitation coil 16y− decreases, and an induced current flows through the levitation coil 16y− in a direction that prevents this.

  In this way, when the mover 20 is eccentric in the radial direction, induced currents flowing in opposite directions flow through the levitating coil in the eccentric direction and the levitating coil opposite thereto, so that the levitating coil in the eccentric direction is opposed to this. Since the electromagnetic force generated by the induced current of the floating coil that is generated is opposite to each other and cancels out, the electromagnetic force generated by the induced current cannot be used as the support force of the mover 20 as it is.

  Therefore, in the present embodiment, two levitation coils facing each other are connected by null flux wires.

  FIG. 4 shows a method for connecting the levitation coils 16x + and 16x− in the x-axis direction. The levitation coils 16x + and 16x− are connected by a null flux wire 17x. As a result, a current corresponding to the difference between the induced electromotive forces of the two closed circuits formed by the levitation coils 16x + and 16x− flows through the null flux wire 17x, and the phases of the levitation coils 16x + and 16x− are changed. Align the direction of the electromagnetic force generated by the induced current. Thereby, the restoring force which returns to the center axis direction arises in the needle | mover 20, and eccentricity is suppressed.

  FIG. 5 shows a method of connecting the floating coils 16y + and 16y− in the y-axis direction. The levitation coils 16y + and 16y− are connected by a null flux wire 17y. As a result, a current corresponding to the difference between the induced electromotive forces of the two closed circuits formed by the levitation coils 16y + and 16y− flows through the null flux wire 17y, and the phases of the levitation coils 16y + and 16y− are changed. Align the direction of the electromagnetic force generated by the induced current. Thereby, the restoring force which returns to the center axis direction arises in the needle | mover 20, and eccentricity is suppressed.

Second Embodiment
In the first embodiment, two levitation coils 16x + and 16x− facing each other in the x-axis direction are connected by the null flux wire 17x, and two levitation coils 16y + and 16y− facing each other in the y-axis direction are connected. By connecting with the null flux wire 17y, the electromagnetic force generated by the induced current is used to suppress the eccentricity of the mover 20, but the induced current generated in the levitation coil 16 depends on the relative speed with the mover 20. As it changes, the moving speed of the mover 20 is relatively large at the center of the reciprocating motion and relatively small at both ends of the reciprocating motion.

  FIG. 6 shows the relationship between the axial position of the mover 20 and the speed of the mover 20. The position of the mover 20 is normalized by setting one end of the reciprocating motion to 0 and the other end to 1.0. Further, in the figure, the mover speed on the forward path is indicated by a solid line, and the mover speed on the return path is indicated by a broken line. As shown in the figure, the mover speed increases from one end of the reciprocating motion toward the center, reaches a maximum at the center, and decreases from the center toward the other end. The same characteristics are shown for both the outbound and inbound routes.

  Since the mover speed is relatively high at the center of the reciprocating motion, the electromagnetic force of the levitation coil 16 generated by the induced current is also large, and the eccentricity of the mover 20 can be suppressed. However, since the mover speed is relatively small at the end of the reciprocating motion, the electromagnetic force of the levitation coil 16 generated by the induced current is also small, and this alone may make it difficult to suppress the eccentricity of the mover 20. .

  Therefore, in this embodiment, electric power is supplied from the outside to the levitation coils 16 at both ends where the speed of the mover 20 is reduced and sufficient electromagnetic force cannot be obtained, and current is forced to flow from the outside to electromagnetically. Generates a force and reinforces the electromagnetic force generated by the induced current.

  FIG. 7 shows a system configuration diagram of the present embodiment. The electric power from the battery 50 is supplied to the levitation coils 16 at both ends of the stator 10 via the switching controller 52. Switching of the switching controller 52 is controlled by the controller 54. The controller 54 outputs a command to turn on the switch of the switching controller 52 when it is detected that the mover 20 is positioned at the end based on a signal from a sensor that detects the position of the mover 20. Thereby, the electric power from the battery 50 is supplied to the levitation coil 16 at the end portion to compensate for the insufficient electromagnetic force. Further, the controller 54 outputs a command to turn off the switch of the switching controller 52 when it is detected that the mover 20 is located at the center based on a signal from a sensor that detects the position of the mover 20. Thereby, the electric power from the battery 50 is not supplied to the floating coil 16 at the end, and the eccentricity of the mover 20 is suppressed by the electromagnetic force generated by the induced current of the central floating coil 16.

  FIG. 8 shows the relationship between the mover speed and the levitation force, that is, the electromagnetic force caused by the induced current. When the mover speed is low, the levitating force is small, and when the mover speed is high, the levitating force is also large. Therefore, if electric power is not supplied to the levitation coil 16 from the outside, the levitation force is insufficient at the end portion where the mover speed is low, as indicated by a one-dot chain line 100 in the figure.

  On the other hand, if a current is forced to flow from the external battery 50 to the levitation coil 16 at the end where the mover speed is low, the levitation force at the end increases as shown by the solid line 200 in the figure, resulting in a mover speed. Regardless of this, that is, a levitating force of a certain value or more is obtained regardless of the axial position of the mover 20, and the eccentricity of the mover 20 can be suppressed.

<Other embodiments>
As mentioned above, although embodiment of this invention was described, this invention is not limited to this, A various change is possible.

  For example, in the first and second embodiments described above, the stator core 12 is divided into four parts in the circumferential direction, but it can be further divided. In addition, the levitation coil 16 can also be divided into four or more parts in the same manner as the stator core 12. The number of divisions of the stator core 12 and the levitation coil 16 is not necessarily the same, and may be different.

  FIG. 9 shows a case where the stator core 12 and the levitation coil 16 are divided into six in the circumferential direction. FIG. 10 shows a case where the stator core 12 and the levitation coil 16 are divided into eight in the circumferential direction. Further, FIG. 11 shows a case where the stator core 12 is divided into eight in the circumferential direction and the levitation coil 16 is divided into four in the circumferential direction. All the figures correspond to FIG. 2 (b) and show a BB cross section of the stator 10. Generally, as the number of divisions of the stator core 12 and the levitation coil 16 increases, the position of the mover 20 can be more accurately brought closer to the center. However, since the number of parts increases as the number of divisions increases, it is desirable to consider the balance with cost. In the form of FIG. 11, the number of parts can be reduced by suppressing the number of divisions of the levitation coil 16 to 4 and manufacturing can be performed at low cost.

  In this embodiment, the mover 20 is reciprocated by a pair of free pistons. However, the present invention is not necessarily limited to this, and the mover 20 is reciprocated by another engine or drive mechanism. May be. However, a linear power generator using a free piston, in other words, a free-piston energy converter (FREC), is excellent in the efficiency of converting chemical energy into electric energy, and is desirable.

  In the present embodiment, as the mover speed decreases at the end of the reciprocating movement of the mover 20, electric power is supplied from the external battery 50 to the levitation coil 16 located at the end of the reciprocating movement. However, instead of detecting the position of the mover 20, the speed of the mover 20 is detected, and when the speed of the mover 20 decreases, an external battery 50 is connected to the floating coil 16 at that position. Electric power may be supplied to forcibly flow current. In this case, the levitation coil 16 through which current flows by external power is not necessarily limited to the end of the reciprocating movement.

  Furthermore, when this embodiment is applied to a linear drive device, the stator coil 14 may be used as a drive coil instead of a power generation coil, and a drive current may be passed.

  DESCRIPTION OF SYMBOLS 10 Stator, 12 Stator iron core, 14 Stator coil, 16 Levitation coil, 20 Movable element, 22 Movable iron core, 24 Movable element permanent magnet

Claims (5)

A linear drive / power generator,
A cylindrical stator,
A mover including a magnet that reciprocates in the stator in the axial direction; and
Have
The stator is
A stator core and a stator coil laminated in the axial direction;
A levitation coil provided at an end of the stator core on the mover side;
Have
The levitation coil includes a pair of coils facing each other with at least the mover interposed therebetween, and the one set of coils is connected to each other by a null flux wire. The linear drive / power generation device according to claim 1,
A linear drive / power generation device comprising: means for applying a current to a floating coil located at an end of the reciprocating movement of the mover in the floating coil. The linear drive / power generation device according to claim 1,
A linear drive / power generation device comprising: means for applying a current to the levitation coil at a position where the moving speed of the mover is relatively small in the levitation coil. The linear drive / power generation device according to claim 1,
The stator core and the levitation coil are divided into a plurality in the circumferential direction of the stator. The linear drive / power generation device according to claim 4.
The levitation coil is divided into four in the circumferential direction of the stator,
The four-part levitation coil is disposed in a direction perpendicular to the first set of coils and the first set of coils facing each other with the mover interposed therebetween, and the first set of coils opposed to each other with the mover interposed therebetween. A linear drive / power generation device comprising a second set of coils.

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