JPH0433565A - Polyphase drive type linear brushless dc motor - Google Patents

Abstract

PURPOSE:To reduce a variation in a thrust force by functionally separating a position information permanent magnet and a field permanent magnet, and forming a field distribution by the magnet in a sine waveshape state. CONSTITUTION:Positions of pole detecting Hall elements 31 - 33 are moved outside in a direction perpendicular to the moving direction of a movable element on a movable element board 1, and disposed outside from the opposed parts of field permanent magnets 51 - 58 and 71 - 78. A magnetic field distribution is in a trapezoidal wave state inside the opposed part, but becomes near a sine wave toward the outside. The winding width of armature coils 21 - 23 is T/3 when a magnet pitch is T. If the width is large, a variation in a thrust force upon change of the position of the coil is not abrupt but made uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multipolar DC linear motor used for positioning robots, XY stages, etc.

[Conventional technology]

The basic structure of a multi-polar DC linear motor and its driving method are described, for example, in "IEE of Japan: Linear Motors and Their Applications," IEEJ (1982), pp. 9-10. This motor uses multi-pole magnetized permanent magnets,
It is composed of multiple coils and moves by generating thrust in a constant direction over a long stroke.In order to minimize the fluctuation of thrust due to position, the drive current is adjusted according to the change in relative position with the magnet. Efforts are being made to change this.

A specific example of this type of linear motor configured as a movable armature three-phase brushless motor is shown in FIG. Figure 4 (
a) is a perspective view showing the arrangement of a stator (field permanent magnet), a mover (armature coil), and a Hall element for magnetic pole detection;
FIG. 4(b) is a side view showing the relative positional relationship in more detail.

In FIG. 4, 1 is a mover substrate made of an insulator, 21
, 22.23 is the armature coil placed thereon, 31
, 32 and 33 are Hall elements for magnetic pole detection. Also, 4
, 6 are stator yokes, 51 to 58 are field permanent magnets arranged on the stator yoke 4, and 71 to 78 are field permanent magnets arranged on the second side of the stator yoke 6. The stator yokes 4 and 6 are configured to sandwich the movable base plate 1, and the movable base plate 1 is attached to a linear slider (not shown) so as to be able to reciprocate in the direction of the arrow.

Since the field permanent magnets are arranged as shown in the figure, for example, in the area between magnets 56 and 76, there is a magnetic field I in two directions.
(Also, a downward magnetic field 11- is generated between the magnets 57 and 77, and an alternating magnetic field in the vertical direction is generated similarly between the other magnets.The repetition pitch is T is equal to the width of the magnet.

Next, a circuit for exciting the armature coil 31 etc. will be explained with reference to FIG. In this configuration example shown in Fig. 4,
There are three sets of armature coils and Hall elements, and three-phase drive is possible, and this circuit corresponds to one phase of them.

In the figure, 21 is an armature coil, 31 is a Hall element,
10 is an operational amplifier, and 11 and 12 are output I transistors. The circuits for the other two phases are similar, and the power supply V
cc and -Vcc are shared, and command voltage E is also commonly applied.

It is now assumed that a command voltage E corresponding to a certain required thrust force and its direction is being applied. When the Hall element 31 receives a magnetic field, an output voltage proportional to the magnetic field appears, which is amplified by the operational amplifier 10, and further by transistors 11 and 1.
．． 2, a driving current flows through the armature coil 21. The magnitude and direction of this current are determined by the Hall element 31
The output voltage is proportional to the magnitude and polarity of the output voltage. Therefore, the magnitude and direction of this current are proportional to the magnitude and direction of the command voltage E and the magnitude and direction of the magnetic field received by the Hall element 31.

Further details will be described using FIG. 4(b). When the relative positions of the mover and stator are as shown in the figure, the armature coil 21 is in a state spanning both the magnets 51.71 and 52.72. The part 21A of the coil 21 perpendicular to the movable direction of the armature is placed in the downward magnetic field H- generated by the magnet 51.71, and the part 21B of the armature coil is placed in the downward magnetic field H- generated by the magnet 52. It is placed in an upward magnetic field H+ generated by .72. Also,
The Hall element 31 is also placed in the upward magnetic field 1, like the armature coil portion 21B.

In this state, the direction of the current in the armature coil generated by the output of the Hall element 31 (generated by being amplified by the circuit in FIG. 5) is shown in FIG. 4(b).

If the command voltage E is set as shown by ×, then the armature coil parts 21A and 21B
Both receive force in the right direction. This force moves the mover to the right, but when it moves by T/2, the armature coil part 2
1A, 21B and the Hall element 31 are all in the magnetic field -0 region of the alternating magnetic field, so the Hall element output is zero.
Therefore, the drive current flowing through the armature coil also becomes zero, and no thrust is generated at this point. When the mover moves further to the right due to inertia, it enters the area next to the alternating magnetic field, so the magnetic field received by the armature coil parts 2LA, 2] and B is reversed, but the magnetic field received by the Hall element 31 is also reversed. Therefore, since the drive current of the armature coil is also reversed, the force received by the armature coil 21 is still directed to the right, and the movable element continues to move to the right.

Looking only at the armature coil 21, its rightward force repeatedly fluctuates between the maximum value and zero.

The period of variation is the magnet width T. However, armature coils 22 and 23 are also attached to the mover, and their relative positions with respect to the magnets are phase-shifted by T/3, so that fluctuations in the total rightward thrust are averaged out. In particular, if the alternating magnetic field is configured to vary sinusoidally between 10 → 0 → I-(-), no fluctuation will appear in the total thrust.

If the polarity of the command voltage is reversed, the direction of thrust will be to the left. Further, the magnitude of the thrust changes in proportion to the command voltage.

The above description has been made using a so-called three-phase driving force type as an example, in which there are three armature coils, and the relative positions of the armature coils with respect to the magnets are shifted by T/3. If N armature coils are provided and their relative positions with respect to the magnets are shifted by T/N, the thrust becomes more average as N becomes smaller than 3, and especially when the alternating magnetic field from the field magnet becomes a sine wave. If the configuration is configured so that the thrust force changes in a consistent manner, no thrust fluctuations will occur at all.

[Problem that the invention seeks to solve]

A specific example of the configuration of a multi-phase drive type linear precision motor is shown below. This system can provide excellent characteristics with extremely small thrust fluctuations if the distribution of the alternating magnetic field caused by the field permanent magnet can be made close to a sine wave.

However, there are downsides to making the distribution closer to a sine wave. Although it is possible to approximate this by optimizing the shape, size, arrangement, etc. of the field permanent magnets, this results in an increase in the processing cost of the magnetic circuit and a decrease in the efficiency of magnet use.

Furthermore, even if the distribution of the alternating magnetic field is close to a trapezoidal wave,
By increasing the number of phases, it is possible to reduce thrust fluctuations.

However, in order to increase the number of phases, it is necessary to increase the number of armature coils, which leads to an increase in cost.

[Means for solving problems]

The inventors attempted to solve the problem by separating the field permanent magnet and the position information permanent magnet that applies a magnetic field to the magnetic pole detection Hall element. That is, according to the conventional technology, the field permanent magnet and the position information permanent magnet are generally used together, and the magnetic field distribution in the operating direction of the field permanent magnet is close to a trapezoidal wave. In this case, the fluctuation of the thrust force is large, but based on the results of experiments and computer simulations, the inventors have functionally separated the permanent magnet for position information and the field permanent magnet, and They discovered that by making the distribution into a sine wave or an appropriate shape close to this, thrust fluctuations could be significantly reduced. In addition, permanent magnets for field use are usually configured to use strong magnets with saturation magnetization in order to obtain large thrust, but permanent magnets for position information use holes for magnetic pole detection. Since the magnetization is sufficient to operate the element p, it is possible to adjust the magnetization so that the magnetic field distribution is close to a sine wave, or select a shape that is easy to select, giving a large degree of freedom. Become.

Before explaining the embodiments, the basic idea of the present invention will be described.

First, FIG. 6 shows a typical example of the magnetic field distribution due to the field permanent magnet. Figure (a) shows the magnetic field distribution, and figure (1)) shows the magnetic field distribution. The magnetic field distribution is shown in the same figure (b).
Measurements were made along the central axis indicated by the dashed-dotted line, but the results were approximately the same at the periphery. This example shows a trapezoidal wave distribution in which the magnetic field is at its maximum in a section of approximately 10 mm for a magnet width of 15 mm. The present invention has made it possible to reduce thrust fluctuations in response to such a trapezoidal wave magnetic field distribution. Below, thrust fluctuations in the conventional configuration are shown in FIGS. Thrust force fluctuations when using the configuration of the invention will be explained using FIGS. 10 and 11.

FIG. 7 shows only one phase of the coil of the conventional linear motor described above with reference to FIGS. 4 and 5. The operating principle is as described above.

Figure (a) is a side view showing the positional relationship of the movable armature coil 21', fixed field permanent magnets 51' to 54', and magnetic field detection Hall element 31', and figure (b) is a side view of the movable armature coil 21', fixed field permanent magnets 51' to 54', and magnetic field detection Hall element 31'. 2
FIG. 1 is a sectional view showing the state of the magnetic field caused by field permanent magnets 51' to 54' applied to Hall element r3'' and Hall element r3'' for magnetic field detection. As shown in Figure (a), the armature coil 21' has a winding width W, but this will be omitted in explaining the basic operation, and as shown in Figure (b), there is no winding width and the coil center Assume that the current flows in a concentrated manner in the area).

In FIG. 7, the thrust force F acting on the coil 21' is F--
is expressed as +N iBi (1).

Here, 1 is a constant, N is the number of turns of the coil, i is the current flowing through the coil, and I3I is the magnetic flux density of the part where the coil is placed.

Also, the current j flowing through the coil is 1 = K 2 I32 (2)
It is. Here, N2 is a constant, B2 is the Hall element 31'
is the magnetic flux density in the area where is placed.

Therefore, if we put together (]−)(2), we get F=
1 to 2 N BI32 (3). K
,,2. N will be determined once the structure is determined, but Y? is transformed into the product of B1 and I32.

In a linear motor with a conventional configuration, the field permanent magnet and the position information permanent magnet are both used, so I32-f
3, and therefore, F is proportional to B,2.

FIG. 8 shows X, Bl, B2, . This is the J1 calculation result showing the relationship between F and F. I3□, B2. All F is dimensionless and is expressed as a ratio with the maximum possible value being 1. Also, the degree of trapezoid is
Similar to the example shown in FIG. 6, it is assumed that the flat part of the trapezoid has a magnet pitch of 2T/3, where 'r is the magnet pitch. As is clear from equation (3), in the case of such a trapezoidal magnetic flux distribution, the thrust force F repeatedly fluctuates periodically from 0 to the maximum value = 1]-, but the result of calculation using equation (3) is , the fluctuations are repeated in a pattern as shown in FIG.

In order to average out such large thrust fluctuations, a so-called multi-phase drive system is adopted in which a large number of armature coils are arranged in a slightly shifted manner. FIG. 9 shows the N1 calculation results showing the relationship between position and thrust when using a three-phase driving force formula. Thrust fluctuations are still quite large.

Next, a calculation example showing the effects of the present invention will be shown.

In Figure 10, the field permanent magnet and the permanent magnet for position information are separate, and the change in B1 that marks the position is the same trapezoidal wave as in Figure 8, and the change in B2 with respect to the position is a sine wave. The coil position X and B+, Ba, F when
This is a calculation of the relationship between Moreover, FIG. 11 shows calculation results showing the relationship between position and thrust when this is set as a three-phase driving force formula. It is clear that this configuration has a greater effect in reducing thrust fluctuations than the conventional configurations shown in FIGS. 8 and 9.

〔Example〕

(Example 1) A first embodiment of the invention described above is shown in FIG.

This is a movable armature three-phase linear brushless motor having a similar structure to the conventional motor shown in FIG. 4.

The difference between this embodiment and the conventional motor is that the positions of the magnetic pole detection Hall elements 31-33 are moved outward on the mover substrate 1 in a direction perpendicular to the moving direction of the mover. This is because the permanent magnets 51 to 58 and 71 to 78 are located outside of the opposing portions. The magnetic field distribution is trapezoidal wave-like inside the armpit, but as it goes outside, the magnetic field distribution becomes closer to a sine wave. Therefore, the present invention does not require a separate permanent magnet for position information. The desired effect can be obtained.

Furthermore, in this embodiment, the winding width of the armature coils 21 to 23 was set to T/3 as shown in FIG. Since the thrust force fluctuations are averaged instead of being averaged, the thrust fluctuations were able to be made even smaller than the calculation results shown in FIG. Figure 2 shows the thrust force fluctuations while the armature coil moves by one pitch of the field permanent magnet (that is, the T dimension) in the case of this embodiment, and
Although the diagram shows the conventional configuration, it can be seen that the thrust fluctuation reduction effect of the present invention is remarkable. Although the thrust is slightly reduced, it is slightly larger than when the magnetic field distribution pattern of the field permanent magnet is made to be a sine wave.

(Example 2) FIG. 33 shows a second example of the present invention. This is a movable magnet type three-phase brush 1/motor. Figure (a) is a perspective view showing this configuration, and figure (b) shows the magnetization pattern of the magnet in the mover and the fixed armature coil hole. It is a figure explaining the relative positional relationship with an element.

In the figure (a), 10 is a mover/board, 6 is a yoke made of a soft magnetic material provided thereon, and 81 to 85 are permanent magnets for position information. In addition, field permanent magnets 51~
・There is 54, but it is not visible in the same figure (a,).

Reference numeral 11 denotes a fixed yoke made of soft magnetic material, on which an armature/coil is arranged, and 21 to 27 are shown. A Hall element for magnetic pole detection is also arranged, and 3
1 to 37 are illustrated.

In addition, in FIG. 3(b), 11 is a stator yoke, 21
26 are armature coils thereon, and 31 to 36 are Hall elements for detecting magnetic poles, and their arrangement is shown in a top view. Reference numeral 10 denotes a movable element substrate facing this, which is shown as a top view for ease of understanding when explaining the operation. 51 to 54 are field permanent magnets arranged on the fifth surface side of 10, and 81 to 85 are position information permanent magnets similarly arranged on the lower surface side of 10. Both the field permanent magnet and the position information magnet are magnetized in the direction perpendicular to the plane of the paper, and the magnetic pole symbols N and S shown in Fig. 3 indicate the lower side of the magnet, i.e., the armature coil or The magnetic pole symbol on the surface facing the magnetic pole detection Hall element is shown. (Please refer to and compare the magnetization directions of the magnets 81 to 85 partially shown in FIG. 3(a).) Furthermore, although the position information magnets 81 to 85 are shown separately, the As is clear from the purpose of the above, the strongest magnetic field is generated near the area where the tree fertilizer number is displayed, and the boundary between the categories is
It goes without saying that it is constructed to provide a sinusoidal magnetic field distribution that becomes zero in the near future.

The movable board 10 has the magnets arranged in this way, and the relative position with respect to the fixed P yoke 11 is shown in FIG. 33(b).
Starting from the position indicated by the dashed dotted line, it is possible to move to the right. Although omitted since the diagram is complicated, when the mover board is at the position indicated by the two-dot chain line, the field permanent magnets 51 to 54 are opposed to the armature coils 21 to 23, and the position information is It will be understood that the magnets 81 to 85 are located opposite 31 to 33 of the magnetic pole detection ball elements.

Next, we will discuss the operation. In FIG. 3(1)), it is assumed that the movable board J-0 is at the reference position indicated by the two-dot chain line. When the magnetic pole detection Hall element (for example, 31) is facing the N pole of the position information magnet, current flows in the direction shown by the solid line in the opposing armature coil (21 in this example), and the magnetic pole When the detection Hall element faces the S pole of the position information magnet, a current flows in the corresponding armature coil in the direction indicated by the dotted line 1, and the magnitude of the coil current is determined by the magnitude of the coil current applied to the Hall element. It is assumed that the magnetic field is configured so that it is proportional to the strength of the applied magnetic field.

It goes without saying that such a configuration can be realized by using the circuit shown in FIG. 5 and setting the command voltage E to an appropriate polarity and magnitude.

In this state, the Hall element 32 is located approximately at the center of the position information magnet 83 and faces the strongest N-pole portion, so current flows through the corresponding Vg armature coil in the direction of the solid line, resulting in A thrust force is generated between the armature coil and the field permanent magnet that moves the magnet L) 2 + J J to the right side. In addition, the Hall elements 31 and 33 are
In order to face the S poles of the position information magnets 82 and 84, electric current flows in the direction of the broken line in the electric machine p coils 2] and 23, and as a result, the field permanent magnets 51, 52 and 53, 54
A partner will appear that will move these to the right.

As the mover/substrate moves to the right, the armature coil current is also sequentially switched to maintain the rightward movement.

Unlike the conventional structure, in this embodiment (2), the position of the magnetic pole detection element is shifted by T/2 and placed on the extension of the center line of each coil, but the position information magnet also has a permanent field. Since it is placed at a position shifted by T/2 from the magnet, the relative position of the magnetic pole detection element and the position information magnet remains the same as before, and the operation is performed without any problem. Furthermore, by arranging the position information magnets wider than the field permanent magnets as in this example, it is possible to flow the drive current to the armature coils that are adjacent to but not opposed to the field permanent magnets. Therefore, the effect of increasing thrust can also be obtained.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to reduce fluctuations in the thrust force during the operation of the movable element, and it is possible to obtain a near motor with good performance and suitable for servo control. Also,
Since the thrust fluctuation is reduced, the number of phases can be reduced to obtain the same performance, and the cost can also be reduced.

Furthermore, as described in the embodiment (2), it is also possible to excite the armature coil adjacent to the field permanent magnet, which is not facing the field permanent magnet, and the effect of increasing the thrust force can also be obtained.

[Brief explanation of the drawing]

FIG. 1 shows a perspective view, a side view, and a sectional view of a ten-type multiphase linear motor for a movable electric machine according to the first embodiment of the present invention, and FIG. 2 shows the thrust fluctuations of the configuration shown in FIG. FIG. 3 is a perspective view of a movable magnet linear motor according to a second embodiment of the present invention, and FIG.
4 is a perspective view and a side view of a conventional movable armature three-phase linear motor; FIG. 5 is a diagram showing a circuit for exciting the electric machine p-coil; FIG. The figure shows a typical example of the magnetic field distribution due to field permanent magnets.
The figure shows the positional relationship between the field permanent magnet, the armature coil, and the Hall element for magnetic pole detection, and the magnetic field distribution generated by the field permanent magnet. Figure 8 shows the coil of one phase of the linear motor with the conventional configuration. Figure 9-19 is a diagram showing the thrust fluctuation when the configuration shown in Figure 8 is used as a three-phase drive, and Figure 10 is a diagram showing the results of calculating the magnetic field distribution and thrust fluctuation according to the present invention. FIG. 11 is a diagram showing the results of calculation of thrust fluctuations for the one-phase coil of the linear motor having the configuration, and FIG. 11 is a diagram showing thrust fluctuations when the configuration shown in FIG. 1o is driven in three phases. 1 and 10: Mover board, 4 and 6: Yoke for field permanent magnet, 11: Yoke for armature coil, 21 to 27:
Armature coil, 31-37: Hall element for magnetic pole detection, 5
1-58 and 71-78: field permanent magnet, 81-85
: Magnet for location information. Figure 1 (α) /-7-/7=7-/l Hua/'/'/'/'/'/'/'/' /
/////////1 5 5221421B 57 5
81 /7 □Birch 1 diagram (C
) Figure 2 Figure 1 (b)

Claims (3)

[Claims] (1) A field permanent magnet that is alternately magnetized with N and S poles and whose magnetization pitch is T, and a field permanent magnet with an opposing opening angle of T (N is 1 or more). The N armature coils are arranged so that the relative position in the operating direction with respect to the field permanent magnet is slightly different for each system, so that so-called multiphase drive is performed. In a linear brushless DC motor configured such that either the field permanent magnet or the armature coil serves as the stator and the other serves as the mover, in addition to the field permanent magnet, there is also a magnetic pole detection A permanent magnet for position information is provided to operate the sensor, and the magnetization pitch of the permanent magnet for position information is equal to the magnetization pitch of the field permanent magnet, and the permanent magnet for position information is used as the magnetic pole detection sensor. A multiphase drive type linear brushless DC motor characterized in that the applied magnetic field pattern has a sine wave or an appropriate shape to reduce thrust ripple. (2) The field permanent magnet and the position information permanent magnet are magnetized with a deviation of T/2 from the traveling direction, and the magnetic pole detection sensor element is located at the center of the opening angle T of each armature coil. 2. The multiphase drive type linear brushless DC motor according to claim 1, wherein the motor is provided with a multiphase drive type linear brushless DC motor. (3) Rather than making the permanent magnet for position information separate from the field permanent magnet, use a part of the field permanent magnet, and partially change the distance between the magnet and the magnetic pole detection sensor and the shape and dimensions of the magnet. 2. The multiphase drive type linear brushless DC motor according to claim 1, wherein the magnetic field distribution applied to the magnetic pole detection sensor is sinusoidal.