JPH04304155A - Movable magnet linear motor - Google Patents

Abstract

PURPOSE:To decrease the number of pole while suppressing ripple by disposing a magnetic sensor between armature coils of a movable magnet linear motor. CONSTITUTION:The movable magnet linear motor comprises a linear guide means 4, a plurality of armature coils 8 having a plurality of magnets 16 and mounted on the guide means 4, and a plurality of magnetic sensors 10 wherein the armature coils 8 are disposed while mutually spaced apart by a predetermined distance with the magnetic sensors interposed between.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving magnet type linear motor, and more particularly to a moving magnet type linear motor that can reduce the number of magnetic poles while suppressing the occurrence of thrust ripple.

2. Description of the Related Art In general, DC linear motors are known, such as a moving magnet type in which a moving element includes a magnet, and a moving coil type in which a moving element includes a coil. Taking a movable magnet type motor as an example,
For example, those described in JP-A-59-86473 and JP-A-59-122354 are known. In the above publication, a large number of armature coils are arranged side by side in contact with each other along the stator side base on which the mover runs, and a plurality of magnets with different magnetic poles are arranged on the back surface of the mover side. It is composed of A position detection element such as a Hall element that detects the magnetic pole of the magnet is placed on the upper surface of the armature coil or at a position where a conductor part that does not contribute to the thrust of the armature coil and a conductor part that contributes to the thrust intersect. It is set in. The position detection element detects the N and S magnetic poles of the magnet, and based on this, a current is passed in a predetermined direction to the armature coil, thereby moving the magnet, that is, the moving body, in a predetermined direction. There is. Furthermore, as another conventional example, a linear motor having a structure in which a position detection element is installed in a central space of a wound armature coil is also known.

0002

[Problem to be solved by the invention] By the way, in this type of linear motor, in order to realize smooth movement of a moving object, it is better to minimize the torque fluctuation, that is, the thrust ripple, and therefore the thrust ripple is large. In some cases, a compensation circuit is separately provided to compensate for this. In addition, in order to reduce the thrust ripple, it is possible to increase the number of magnetic poles of the magnet provided on the moving body, but in this case, the number of switching between N and S poles increases, and the flat part of the magnetic field decreases. As a result, a problem arises in that the thrust of the moving body cannot be increased. Furthermore, if the number of magnetic poles is increased and the magnetic pole pitch is reduced, the installation pitch of the electrode coils must be correspondingly reduced.
As a result, it becomes necessary to provide a large number of coils. Moreover,
The generation of thrust ripple is closely related to the ratio of the magnetic pole pitch to the coil pitch and other factors, and is currently determined by combining the various factors through trial and error.

However, in the linear motor with the above-mentioned conventional structure, even if the number of magnetic poles is reduced, the limit is 6 or 5 poles, and if the number of magnetic poles is reduced beyond that, the thrust ripple becomes very large, making it impractical. It disappears. For example, in FIGS. 2 and 3, when the position detection element is installed on the armature coil as in the above-mentioned document, the number of magnetic poles Nm is set to 5 and 4, and the ratio Lc of the coil pitch to the magnetic pole pitch is 1.45. This shows the thrust ripple when the simulation was performed with the setting set to 1.5, and when the number of magnetic poles Nm was set to 4,
The thrust ripple is too large to be practical. Furthermore, in FIGS. 4 and 5, when the position detection element is installed at the center of the wound coil, the number of magnetic poles Nm is set to 6 and 5, and the ratio Lc of the coil pitch and the magnetic pole pitch is 1.5, respectively. This figure shows the thrust ripple when a simulation was performed with the magnetic pole number Nm set to 5. If the number Nm of magnetic poles is set to 5, the thrust ripple is too large to be practical. The present invention has focused on the above-mentioned problems and has been devised to effectively solve them. An object of the present invention is to provide a movable magnet type linear motor that can reduce the number of magnetic poles while suppressing an increase in thrust ripple.

0004

[Means for Solving the Problems] The present invention provides a method for reducing the number of magnetic poles by installing a magnetic sensor between the coils and setting the ratio of the coil pitch to the magnetic pole pitch to a predetermined value.
This was achieved by discovering that thrust can be increased while suppressing an increase in thrust ripple. In order to solve the above-mentioned problems, the present invention includes a guide means formed in a linear shape, a movable body having a plurality of magnets arranged in parallel and provided so as to be able to run and move freely along the guide means.
A plurality of armature coils arranged in parallel in the guide means facing the magnet along the longitudinal direction thereof; and a plurality of magnetic sensors provided in the guide means to detect a magnetic field from the magnet of the movable body. In the movable magnet type linear motor, the movable magnet type linear motor is configured to move the movable body based on the output of the magnetic sensor, wherein the armature coils are arranged at a predetermined distance from each other, and the magnetic sensor is provided between the armature coils arranged in parallel.

[0005]

[Operation] Since the present invention is constructed as described above, the current supplied to the armature coils is controlled based on the output of the magnetic sensor installed between the armature coils, and as a result, the movable body is guided by the guide means. It moves smoothly along the top without receiving large thrust ripples.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a moving magnet type linear motor according to the present invention will be described in detail below with reference to the accompanying drawings. As shown in FIGS. 1, 6, and 7, the moving magnet linear motor 2 includes a guide means 4 formed in a straight line, a plurality of armature coils 8 fixed on the guide means 4, and a plurality of armature coils 8 fixed on the guide means 4. It is mainly composed of a plurality of magnetic sensors 10 provided on the upper surface of the guide means 4. Specifically, the guide means 4 has an elongated base 12, and guide paths 14 are formed on both sides of the upper surface thereof. At the center of the upper surface of the base 1, the plurality of armature coils 8 are wound at a predetermined distance from each other so that the overall width is, for example, about 25 mm.
For example, they are arranged in parallel in the longitudinal direction of the base 1 with a distance of 5 mm. The magnetic sensor 10 is composed of, for example, a Hall element that detects the strength and direction of a magnetic field, and the armature coils 8 are arranged in parallel or next to each other at a distance from each other.
It is located between 8.

On the other hand, the movable body 6 moving on the guide means 4 moves a pair of left and right running rollers 16, 16 forward and backward.
and engages with the guide path 14 of the base 12,
It is configured to be movable. On the back surface of the movable body 6, for example, four magnets 18 are arranged with N and S poles alternately facing the armature coil 8 on the base 12. Here, as mentioned above, when there are four magnetic poles Nm,
The ratio Lc of coil pitch L and magnetic pole pitch M is 1.40±1
It is set in the range of 0%, preferably in the range of ±5%, and set to 1.40 as the best mode. The opening angle width of the armature coil 8 and the magnetic pole width of the magnet 18 are set to be approximately equal. The magnetic sensor 10 that detects the magnetic field from the magnet 18 is wired as shown in FIG.
, 10 is taken by an amplifier 20, amplified and supplied to the corresponding armature coil 8 as a drive current. The wiring for driving each armature coil 8 is not limited to that shown in FIG. 8. For example, each armature coil 8 is connected in series as shown in FIG. It may be configured such that the output is amplified by the armature coils 8 and 8 and directly inputted to the connection point between the corresponding armature coils 8 and 8, and FIGS. 8 and 9 have an equivalent relationship.

Next, the operation of this embodiment configured as above will be explained. First, assuming that the linear motor 2 is powered on, the magnetic sensor 10 on which the moving body 6 is located senses the lines of magnetic force from the magnet 8 attached to the bottom surface of the moving body 6, and each magnetic field that senses the lines of magnetic force As shown in FIG. 8, the difference between the outputs of the sensors 10 that are adjacent to each other is calculated, and the difference value is amplified and supplied to the corresponding armature coil 8. Then, a current flows through the armature coil 8 and interacts with the magnetic field of the magnet 18 provided on the moving body 6, generating a thrust according to Fleming's law, causing the moving body 6 to travel along the guide means 4. do. To change the running direction, the polarity of the power supplied to the armature coil 8 is switched. Here, in the present invention, the armature coils 8, 8 installed in parallel are spaced apart from each other by an appropriate distance, and the magnetic sensor 10 is provided between the coils 8, 8. Since the number of poles of the provided magnet 18 is set to 4 and the ratio of the coil pitch to the magnetic pole pit is set to 1.40, the number of magnetic poles can be reduced while suppressing the increase in thrust ripple. I was able to do that. FIG. 10 shows the simulation results under the above conditions, and even though the number of magnetic poles was reduced to four, the magnetic sensor 10
By installing between the armature coils 8 and 8, and setting the ratio Lc of the coil pit to the magnetic pole pitch to 1.40,
It has been found that smooth movement is possible by suppressing the increase in thrust ripple. Further, good results can be obtained by setting the pitch ratio Lc in the range of ±10%, preferably ±5% around 1.40.

[0008] Furthermore, in the above simulation,
The generated magnetic field is handled as a sine wave, but in an actual linear motor, the shape of the generated magnetic field is close to a trapezoid, and FIG. 11 shows the results of a simulation using this trapezoidal magnetic field, which is closer to the actual machine. Figure 12 shows the linear motor shown in Figure 2, which used a similar trapezoidal magnetic field and was thought to have a small number of magnetic poles (5) and low thrust ripple, which was considered to be good. The results of a simulation of a motor are shown. Comparing Figures 11 and 12, Figure 1 assumes the actual machine.
In this embodiment shown in FIG. 1, the thrust itself increases, but the thrust ripple hardly increases and a smooth thrust is obtained, giving a good result. In contrast, in FIG. 12, although the thrust itself increases, It turns out that the thrust ripple increases accordingly, giving unfavorable results.

As described above, in the above embodiment, the number of magnetic poles is 4.
Although the case where the number of magnetic poles is set is described above, the number of magnetic poles is not limited to this, and the number of magnetic poles may be set to 5, 6, or 8, for example. When the number of magnetic poles is changed to 5, 6, and 8 in this way, the ratio LC of the coil pitch to the magnetic pole pitch is changed sequentially to 1.48, 1.60, and 1.37, respectively. The results of simulations performed under such conditions (the generated magnetic field is set as a sine wave) are shown in FIGS. 13 to 15. As shown in the figure, it has been found that under the above conditions, thrust ripple is extremely small and smooth movement can be achieved. Also, in the cases shown in FIGS. 13 to 15, the LC
The allowable range is ±10%, preferably ±5% around each set value. In addition, in the diagrams showing each thrust ripple characteristic, the lower curve shows the current efficiency (thrust force constant).

0010

As described above, according to the present invention, the following excellent effects can be achieved. By locating the magnetic sensor between the armature coils, the number of magnetic poles can be reduced without increasing thrust ripple. Since the number of magnetic poles can be reduced for the same length of the moving body, the number of armature coils required for the same movement stroke can be reduced, contributing to cost reduction.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a moving magnet type linear motor according to the present invention.

FIG. 2 is a diagram showing thrust ripple characteristics of a conventional linear motor.

FIG. 3 is a diagram showing thrust ripple characteristics of a conventional linear motor.

FIG. 4 is a diagram showing thrust ripple characteristics of a conventional linear motor.

FIG. 5 is a diagram showing thrust ripple characteristics of a conventional linear motor.

FIG. 6 is a plan view showing the linear motor of the present invention.

FIG. 7 is a side view showing the linear motor of the present invention.

FIG. 8 is a wiring diagram showing a linear motor of the present invention.

FIG. 9 is another wiring diagram showing the linear motor of the present invention.

FIG. 10 is a diagram showing thrust ripple characteristics of the linear motor of the present invention.

FIG. 11 is a diagram showing thrust ripple characteristics when a trapezoidal magnetic field is used in the linear motor of the present invention.

FIG. 12 is a diagram showing thrust ripple characteristics when a trapezoidal magnetic field is used in a conventional linear motor.

FIG. 13 is a diagram showing thrust ripple characteristics when the number of magnetic poles is five.

FIG. 14 is a diagram showing thrust ripple characteristics when the number of magnetic poles is six.

FIG. 15 is a diagram showing thrust ripple characteristics when the number of magnetic poles is 8.

[Explanation of symbols]

2 Linear motor 4 Guidance means 6. Mobile object 8 Armature coil 10 Magnetic sensor 12 Base 18 Magnet

Claims (5)

[Claims] 1. A guide means formed in a straight line, a movable body having a plurality of magnets arranged in parallel and movable along the guide means; a plurality of armature coils arranged in parallel facing the magnet along the guide means, and a plurality of magnetic sensors provided on the guide means to detect a magnetic field from the magnet of the moving body, the magnetic sensor In the movable magnet type linear motor that moves the movable body based on the output of A moving magnet type linear motor characterized by having coils installed between each other. 2. When the number of magnetic poles of the magnet of the moving body is 4, the ratio of the pitch of the armature coil to the magnetic pole pitch of the magnet is within a range of 1.40±10%. The linear motor according to claim 1. 3. When the number of magnetic poles of the magnet of the moving body is 5, the ratio of the pitch of the armature coil to the magnetic pole pitch of the magnet is within a range of 1.48±10%. The linear motor according to claim 1. 4. When the number of magnetic poles of the magnet of the moving body is 6, the ratio of the pitch of the armature coil to the magnetic pole pitch of the magnet is within a range of 1.60±10%. The linear motor according to claim 1. 5. When the number of magnetic poles of the magnet of the moving body is 8, the ratio of the pitch of the armature coil to the magnetic pole pitch of the magnet is within a range of 1.37±10%. The linear motor according to claim 1.