Active guidance system for linear motor mover

Abstract

An active guidance system for a linear motor mover. The invention relates to a rotor guide system for a linear motor, which system generates a force (lateral force) perpendicular to the direction of movement by means of a magnetic field distribution, the same as the rotor, which also utilizes a stator. When the mover is stationary or moving, the lateral force can be used to adjust the clearance between the mover and the stator.

Description

TECHNICAL FIELD

[0001] The present invention relates to a mover guiding system for a linear motor, which generates a force perpendicular to the direction of motion (side force) by a magnetic field distribution, which also utilizes the stator, with the same mover. The side force can be used to adjust the gap between the mover and the stator when the mover is stationary or in motion. BACKGROUND

[0002] Linear motor movers are mechanically guided by rollers along a track, by linear bearings or similar methods. The gap between the stator and the mover must be small to achieve high efficiency, but this requires a precise guiding mechanism along which the mover travels. These are passive methods that cannot compensate for irregularities in the construction, nor can they respond to changing conditions by automatically adjusting the gap between the mover and the stator or increasing the guiding force. If active adjustment of the stator-mover gap could be provided, a mover guide with lower precision could be installed, thereby reducing initial and operating costs. Similarly, in Japan and many other countries, earthquakes occur frequently, and they can cause sudden shocks. Especially in elevators, such shocks can cause the linear motor mover to collide with the linear motor stator, causing damage and endangering passengers.

[0003] There is a known double-sided fixed stator in linear generators - with similar operation to linear oscillatory motion electric machines in the prior art. Here, the plate-type mover in the double-sided fixed stator of the linear generator is driven by the acoustic power output of the acoustic line of a thermoacoustic engine. The main originality of the structure is the linear guide for the moving parts. The mover consists of a plate of sandwiched magnets - between two stators. The plate is in magnetic equilibrium between the two stators by a controlled friction device. However, this mover cannot automatically adjust the gap between the mover and the stator, or increase the guiding force, to respond to changing conditions.

[0004] US patent document US9621097B2 discloses a linear conveyor, the drive source of which is a linear motor and includes a plurality of electromagnets, a plurality of conveyor carriages (each comprising a linear motor mover); a linear scale and detector; a plurality of motor controllers and a data storage unit. Here, each motor controller controls the conduction of the electromagnets using position correction data stored in the data storage. However, the application does not disclose automatically adjusting the gap between the mover and the stator or increasing the guiding force to respond to changing conditions.

[0005] Japanese patent document JP 4581313 B2 discloses a linear motor support device in a linear motor driven elevator. The invention comprises a linear motor primary coil on the shaft side, a permanent magnet of the linear motor on the car side, and a linear motor which causes the car to travel by the propulsion force generated between the primary coil and the permanent magnet, wherein the primary coil and the permanent magnet are arranged to face each other. The invention provides a support device in which, despite the simple structure, the support can be reliably performed, and the gap adjustment peculiar to the linear motor can be automatically performed.

[0006] Therefore, since the solutions are not sufficient to meet the needs mentioned above, it is necessary to develop in the related art. SUMMARY

[0007] The present invention is inspired by the current situation and aims to solve the disadvantages mentioned above.

[0008] The object of the present invention is to disclose an active guiding system for linear motor movers, which is constituted of a structure that utilizes the existing stator armature, creates a specific magnetic field distribution, and can create a force perpendicular to the direction of movement. The lateral force can be used to adjust the gap between the mover and the stator when the mover is stationary or moving.

[0009] Another object of the present invention is to create an electromagnetic force between the stator and the mover, which is perpendicular to the stator surface and proportional to the driving current. By sensing the air gap width and controlling the driving current in the feedback loop, it becomes possible to actively resist the dynamic forces and impacts acting on the mover and maintain a safe constant air gap.

[0010] Another object of the present invention is to ensure the safety of the linear motor even in the case where the stator is shaken due to an earthquake, a storm, or any other reason.

[0011] In order to achieve the above-mentioned objects, the present invention comprises:

[0012] • a long armature linear motor having thrust force generating movers,

[0013] • lateral force generating movers placed between the thrust force generating movers in sufficient number and creating a magnetic field distribution to generate a lateral force; wherein the magnetic field is parallel to the stator surface, thus the force due to the stator current acts to force the mover sideways, which is perpendicular to the stator surface and the direction of travel,

[0014] • a sensor that detects the distance between the mover and the stator coil, wherein the air gap width is maintained at the desired value by triggering the stator current in the feedback loop, and wherein the sensor measures the air gap to control the excitation current for the force generating movers and detects the longitudinal position of the force generating movers to control the excitation phase.

[0015] The structure and typical features of the invention, as well as all its advantages, will become clearer by studying the accompanying drawings and the detailed description written with reference to these drawings. Therefore, these drawings and detailed description should be taken into consideration for evaluation. Attached Figure Description

[0016] Figure 1 A linear motor and its magnetic field distribution using existing methods without originality are shown.

[0017] Figure 2 The active guide for a linear motor and its field of the present invention are shown.

[0018] Figure 3 The magnetic yoke-type lateral force generating mover of the present invention and its magnetic field distribution are shown.

[0019] Figure 4 The Helbeck-type lateral force generating mover of the present invention and its magnetic field distribution are shown.

[0020] Description of component reference numerals

[0021] 1. Stator coil

[0022] 2. Thrust generates a mover.

[0023] 3. Magnetic field distribution used to generate thrust

[0024] 4. Lateral force generates a moving part.

[0025] 5. Magnetic field distribution used to generate lateral force

[0026] 6. Sensors

[0027] 7. Yoke-type lateral force generates a mover.

[0028] 8. Halbach-type lateral force generating mover

[0029] 9. Magnet

[0030] 10. Magnetic yoke

[0031] 11. Direction of movement

[0032] 12. Lateral force Detailed Implementation

[0033] This invention relates to an active guidance system for a linear motor mover, comprising utilizing the structure of an existing stator armature that generates a specific magnetic field distribution and is capable of generating a force perpendicular to the direction of motion. When the mover is stationary or in motion, the lateral force can be used to adjust the clearance between the mover and the stator.

[0034] The present invention proposes a novel magnetic circuit to be attached to the mover of a linear motor and a novel method to drive the part of the linear motor facing the magnetic circuit. This will allow to generate an electromagnetic force between the stator and the mover that is perpendicular to the stator surface and proportional to the stator drive current. By sensing the air gap width and controlling the drive current in the feedback loop it becomes possible to actively resist dynamic forces and impacts acting on the mover and to maintain a safe constant air gap. Even if the stator is shaken due to an earthquake, a storm or any other reason, this arrangement will ensure the safety of the linear motor.

[0035] The important concept of the guiding system of the present invention is to generate a magnetic field distribution (5) for generating a sideways force that is not perpendicular but parallel to the direction of motion (11). The magnetic field of the sideways force generating mover (4) is parallel to the stator surface, so the direction of the sideways force (12) generated due to the stator current is perpendicular to the stator, thus acting to force the mover sideways.

[0036] The main contribution of the present invention is to generate a magnetic field by the mover (4) on the stator coils (1) so that the direction of the sideways force (12) perpendicular to the direction of motion (11) can be achieved. The current in the stator coils (1) generates an attractive or repulsive force on the novel mover, which can cause a sideways force (12). On a long armature synchronous linear motor, a part of the mover is modified so that its magnetic flux in the air gap is parallel to the direction of motion (11) or contains a flux component that is essentially parallel to the direction of motion (11), which is contrary to the thrust force generating mover (2), in which the flux (3) is perpendicular to the direction of travel. If such sideways force generating movers (4) are placed in sufficient number between the thrust force generating movers (2), by sensing the mover position and adjusting the current applied to the appropriate stator coils (1) in the feedback loop, the direction of the sideways force (12) can be actively controlled.

[0037] Figure 1 - Concept of an air-cored linear motor and its field. (Plan view section)

[0038] Figure 1 A linear motor with a mover using a magnetic circuit is shown schematically, as well as an example of a magnetic field distribution (3) generating a thrust force. The magnetic field distribution (3) is mainly perpendicular to the stator coils (1); therefore, the stator current generates a force in the direction of motion (11) that is parallel to the stator surface and perpendicular to the magnetic flux (3). This is an existing method without originality.

[0039] Figure 2 - Concept of the active guide of the present invention for linear motors and its field. (Plan view section)

[0040] In the present invention, the magnets are arranged such that the generated magnetic flux is mostly parallel to the stator surface, as Figure 2 is shown, a lateral force (12) is obtained, and the current in the stator coil (1) will generate a force perpendicular to the stator surface and the direction of motion (11). In Figure 1 the system, the stator current needs to be maximum at the center of the pole where the maximum flux is located, to maximize the thrust. In contrast, in Figure 2 the system, the stator current needs to be maximum in the region around the center of the lateral force generating mover where the magnetic flux is maximum. The direction of the lateral force (12) will depend on the polarity of the stator current, while its strength is proportional to the size of the stator current.

[0041] The proposed active guiding system can be incorporated into the mover structure, for example at both ends of the mover. With the guiding elements at both ends, not only the direction of the lateral force (12) perpendicular to the stator can be generated, but also a torque vector to counteract the torsional dynamic forces and impacts.

[0042] In an alternative embodiment of the invention, sensors (6) for sensing the air gap width along the mover are preferably located on the stator side. For example, ToF (time-of-flight) optical distance sensors can provide sufficient sensitivity and sampling speed at relatively low cost. Such sensors (6) can be arranged along the stator at appropriate locations to continuously cover the motion of one or more movers. By sensing the distance between the lateral force generating mover (4) and the stator coil (1), the air gap can be kept at a desired value by triggering the stator current in a feedback loop.

[0043] In an embodiment of the invention, a sensorless air gap control system based on the induced EMF in the stator coil (1) can be used alone or together with distance sensors (6).

[0044] Various embodiments of the invention are disclosed by the accompanying drawings.

[0045] Figure 3 - Concept of active guiding elements for magnetic yoke type lateral force generating movers and their field. (Plan view section)

[0046] In an embodiment of the invention, a magnetic yoke type lateral force generating mover (7) is used. The magnets (9) are arranged such that the generated magnetic flux is mostly perpendicular to the stator surface, as Figure 3The shown polarity is mounted on the Halbach-type lateral force generating mover (7) to generate flux parallel to the stator surface. By changing the size and position of the magnets (9), e.g. permanent magnets, on the Halbach (10), the magnetic field distribution (5) on the stator coil (1) for generating lateral forces can be adjusted to be strongest in the appropriate area. By controlling the stator current in the closed loop, depending on the position of the Halbach-type lateral force generating mover (7), a lateral force (12) can be generated. The magnetic field of the lateral force generating mover (4) is parallel to the stator surface, so the direction of the lateral force (12) caused by the stator current is perpendicular to the stator surface and the direction of motion (11), acting as a force to urge the mover sideways.

[0047] Figure 4 - Concept of active guiding of the Halbach-type lateral force generating mover and its field. (Plan view cross section)

[0048] In another embodiment of the invention, a Halbach-type lateral force generating mover (8) is used. The permanent magnets (9) are mounted with their poles Figure 4 The shown polarity is mounted on the Halbach-type lateral force generating mover (8) to generate flux parallel to the stator surface. By changing the size and position of the magnets (9), the magnetic field distribution on the stator coil (1) for generating lateral forces (12) can be adjusted to be strongest in the appropriate area. The magnetic field of the lateral force generating mover (4) is parallel to the stator surface, so the direction of the lateral force (12) caused by the stator current is perpendicular to the stator surface and the direction of motion (11), acting as a force to urge the mover sideways.

[0049] Figure 3 and Figure 4 The magnetic arrangements in Figs. 1-8 are only illustrative examples; the invention can be implemented in many other embodiments, including a single pair of magnets arranged staggered on the stator, or by inclined permanent magnets, etc.

Claims

1. An active guiding system capable of generating a lateral force (12) on a mover, wherein the lateral force is perpendicular to the surface of a stator coil (1) and proportional to the stator current, characterized in that, The active guiding system comprises: • Long armature linear motor with thrust producing movers (2), • Lateral force producing movers (4) placed in sufficient number between the thrust producing movers (2) and its magnetic field distribution (5) for producing lateral forces to cause lateral forces; where the magnetic field is parallel to the stator surface, thus the direction of the lateral forces (12) caused by the stator current is perpendicular to the stator surface and the direction of motion (11), acting as a force to push the movers sideways.

2. The active guidance system of claim 1, wherein, Including sensors (6) to detect the distance between the lateral force producing movers (4) and the stator coils (1), where the air gap width is kept at a desired value by triggering the stator current in a feedback loop, and where the sensors (6) measure the air gap in order to control the excitation current of the lateral force producing movers (4) and detect the lateral position of the lateral force producing movers (4) in order to control the excitation phase.

3. The active guidance system of claim 1, wherein, Including yoke type lateral force producing movers (7) that produce the lateral forces (12) by ferromagnetic yokes (10) and magnets (9).

4. The active guidance system of claim 1, wherein, Including Halbach type lateral force producing movers (8) that generate the lateral forces (12) by Halbach arrangement of permanent magnets (9).

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