JP2008011583A - Linear motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a linear motor in which an impact of flux leakage on a magnetic encoder can be reduced without enlarging a device. <P>SOLUTION: In a linear motor comprising a housing, a permanent magnet contained and arranged in the housing, a slider installed slidably on the housing, and a magnetic linear encoder composed of a coil fixed to the slider and a head having a magnetic scale fixed to the housing and a sensor fixed to the slider, a magnetic shield member composed of a soft magnetic material is interposed between the magnetic linear encoder and the permanent magnet and the head is made of a soft magnetic material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  In the present invention, a permanent magnet is installed on the housing side, while a coil is installed on the slider side that is movably installed with respect to the housing, and a current is passed through the coil so that the slider is controlled by the relationship between the permanent magnet and the coil. In particular, a magnetic shield member for blocking leakage magnetic flux from the permanent magnet side is installed between the magnetic linear encoder used in the linear motor and the permanent magnet. The present invention relates to a linear encoder that can be prevented from malfunctioning due to the influence of leakage magnetic flux.

  A conventional linear motor has a configuration as shown in FIG. 5, for example. Fig.5 (a) is a cross-sectional view of a linear motor, FIG.5 (b) is a cross-sectional view which expands and shows the b section of Fig.5 (a). First, there is a housing 101, and the housing 101 is composed of a base 103 and a case 105 installed above the base 103. A plurality of permanent magnets 107 are stacked and disposed in the center position of the case 105 in a state where the permanent magnets 107 are accommodated in the cylindrical body 109.

  On the other hand, an opening 111 is formed in the upper part of the case 105, and a slider 113 is installed so as to be movable in the axial direction along the opening 111. A bracket 115 is attached to the lower surface side of the slider 113, and a coil 117 is attached to the bracket 115. The coil 117 is installed on the outer peripheral side of the permanent magnet 105.

  Then, by passing a current in an appropriate direction through the coil 117, the slider 113 moves in an appropriate direction depending on the relationship between the permanent magnet 107 and the coil 117.

  A magnetic encoder 119 is installed between the slider 113 and the base 103. The magnetic encoder 119 includes a head 121, a sensor 123 incorporated in the head 119, and a magnetic scale 125 attached to the base 103 side. The magnetic scale 125 is multipolarized with a magnetization pitch αmm. The position of the slider 113 is detected by the relationship between the sensor 123 and the magnetic scale 125.

  That is, when the slider 113 moves, the sensor 123 attached to the slider 113 detects a change in magnetic flux with the magnetic scale 125 over the entire stroke. The detected signal is amplified in the head 121 and output. Specifically, they are an A phase (sine wave), a B phase (cosine wave) that is 90 ° out of phase with respect to the A phase, and two Z phase signals positioned at the approximate stroke length at both ends.

Note that there are optical encoders other than the magnetic encoders as described above. In the case of an optical linear encoder, since it is configured to use reflection of light, when a foreign object such as oil, dust, or dust adheres to the scale, the optical sensor emits reflected light. It becomes impossible to detect, so the scale must be kept clean at all times.
On the other hand, in the case of a magnetic linear encoder, there is an advantage that such management is unnecessary.

  A guide mechanism installed between the slider 113 and the housing 101 will be described. First, the base 103 has a shallow concave shape, and a pair of guide rails 131 and 131 are provided on both the left and right inner surfaces thereof. On the other hand, guide members 133 and 133 are installed at the lower end on the slider 113 side and on both the left and right sides. A plurality of balls 135 are installed between the guide rails 131 and 131 and the guide members 133 and 133. The slider 113 moves along the guide rails 131 and 131 via the guide members 133 and 133 and the balls 135 and 135.

The conventional configuration has the following problems. That is, since the coil 117 is installed on the outer periphery of the permanent magnet 107 and the yoke is not present, the magnetic circuit is not closed, and as a result, a large magnetic flux leakage occurs. . When such a magnetic flux leakage occurs, there is a problem that it affects the magnetic encoder 119 and the detection accuracy of the magnetic encoder 119 is lowered.
In order to solve such a problem, it can be considered that the magnetic encoder 119 is largely separated from the permanent magnet 107. However, this would increase the size of the device. Further, simply separating the magnetic encoder 119 from the permanent magnet 105 has not eliminated the influence of magnetic flux leakage.

  The present invention has been made based on such points, and an object thereof is to provide a linear motor capable of reducing the influence of magnetic flux leakage on a magnetic encoder without increasing the size of the apparatus. It is in.

  As a prior art of the present invention, for example, there is Patent Document 1.

JP 2004-343874 A

To achieve the above object, a linear motor according to a first aspect of the present invention includes a housing, a permanent magnet housed and installed in a shaft shape in the housing, a slider movably installed in the housing, and the slider A magnetic linear encoder comprising a coil attached to the outer periphery of the permanent magnet and surrounding the outer periphery of the permanent magnet; a magnetic scale attached to the housing; and a head attached to the slider and provided with a sensor. In this linear motor, a magnetic shield member made of a soft magnetic material is installed between the magnetic linear encoder and the permanent magnet, and the head is made of a soft magnetic material. .
The linear motor according to claim 2 is the linear motor according to claim 1, wherein the housing is composed of a base and a case attached to the base, and the magnetic scale is attached to the base. The magnetic shield member is installed between the magnetic scale and the base.
According to a third aspect of the present invention, there is provided the linear motor according to the second aspect, wherein another magnetic shield member is provided between the head and the permanent magnet.
The linear motor according to claim 4 is the linear motor according to any one of claims 1 to 3, wherein the soft magnetic material has a relative magnetic permeability of 1,000 to 1,000,000.
The holding power is about 0.01 to 10 (KA / m).

As described above, the linear motor according to claim 1 of the present invention includes a housing, a permanent magnet housed and installed in a shaft shape in the housing, a slider movably installed in the housing, and the slider. A magnetic linear encoder comprising a coil attached to surround the outer periphery of the permanent magnet, a magnetic scale attached to the housing, and a head attached to the slider and provided with a sensor. In the linear motor, a magnetic shield member made of a soft magnetic material is installed between the magnetic linear encoder and the permanent magnet, and the head is made of a soft magnetic material. By installing a magnetic shield member, leakage magnetic flux from the permanent magnet side is applied to the magnetic linear encoder. Impact can be reduced to that. Thereby, the accuracy of position detection by the magnetic linear encoder can be improved.
In addition, since the head itself is made of the same soft magnetic material as the magnetic shield member, the influence of the leakage magnetic flux on the magnetic linear encoder can be reduced, and the above effect can be further enhanced. it can.
Further, since the leakage magnetic flux can be cut off, the magnetic linear encoder does not need to be separated and arranged with respect to the permanent magnet, so that the apparatus is not increased in size.
Further, when the housing is composed of a base and a case attached to the base, the magnetic scale is attached to the base, and the magnetic shield member is installed between the magnetic scale and the base, the above effects are obtained. Can be made more reliable.
Further, when another magnetic shield member is installed between the head and the permanent magnet, the above effect can be further enhanced.
The soft magnetic material has a relative magnetic permeability of 1000 to 1000000,
When the holding force is about 0.01 to 10 (KA / m), the above-described effect is more reliable.

Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a side sectional view showing a configuration of a part of a linear motor according to the present embodiment, and FIG. 2 is a sectional view taken along line II-II in FIG. First, there is a housing 1, and the housing 1 is composed of a base 3 and a case 5 installed above the base 3. At the center position of the case 5, a plurality of permanent magnets 7 are stacked and arranged in a state of being accommodated in the cylindrical body 9.

  On the other hand, an opening 11 is formed in the upper part of the case 5, and a slider 13 is installed so as to be movable in the axial direction along the opening 11. A bracket 15 is attached to the lower surface side of the slider 13, and a coil 17 is attached to the bracket 15. The coil 17 is installed on the outer peripheral side of the permanent magnet 7.

  Then, by passing a current in an appropriate direction through the coil 17, the slider 13 moves in an appropriate direction depending on the relationship between the permanent magnet 7 and the coil 17.

A magnetic encoder 19 is installed between the slider 13 and the base 3. The magnetic encoder 19 includes a head 21 attached to the slider 13 side, a sensor 23 incorporated in the head 21, and a magnetic scale 25 attached to the base 3 side. The magnetic scale 25 is subjected to multipolar magnetization at a magnetization pitch α mm. The position of the slider 13 is detected by the relationship between the head 21 and the magnetic scale 25.
Although the head 21 and the sensor 23 are shown in FIG. 3, the sensor 23 is built in the head 21 as shown in FIG.

  When the slider 13 moves, the sensor 23 attached to the slider 13 detects a change in magnetic flux with the magnetic scale 25 over the entire stroke. The detected signal is amplified in the head 21 and output. Specifically, they are an A phase (sine wave), a B phase (cosine wave) that is 90 ° out of phase with respect to the A phase, and two Z phase signals positioned at the approximate stroke length at both ends.

A magnetic shield member 31 is installed between the magnetic scale 25 and the base 3. The magnetic shield member 31 has a plate shape and is extended and installed in a direction orthogonal to the paper surface in FIG. This magnetic shield member 31 also blocks the influence of the leakage magnetic flux from the permanent magnet 7 side on the magnetic scale 25. The magnetic shield member 31 is made of a soft magnetic material, and the soft magnetic material has a relative permeability of 1000 to 1000000,
The holding power is about 0.1 to 100.

  In this embodiment, the head 21 is also made of the same soft magnetic material. Therefore, the sensor 23 and the magnetic scale 25 are configured to be sandwiched between the magnetic shield member 31 made of a soft magnetic material and the head 21, so that the leakage magnetic flux sensor 23 and the magnetic scale from the permanent magnet 7 side can be obtained. The influence on 25 is cut off.

  The guide mechanism installed between the slider 13 and the housing 1 has the following configuration. First, the base 3 has a shallow concave shape, and a pair of guide rails 51, 51 are provided on both the left and right inner surfaces thereof. On the other hand, guide members 53, 53 are provided at the lower end portion on the slider 13 side and on the left and right side portions. A plurality of balls 55 are installed between the guide rails 51 and 51 and the guide members 53 and 53. The slider 13 moves along the guide rails 51 and 51 via the guide members 53 and 53 and the balls 55 and 55.

As described above, according to the present embodiment, the following effects can be obtained.
First, by installing the magnetic shield member 31, it is possible to block the influence of the leakage magnetic flux from the permanent magnet 7 side on the sensor 23 and the magnetic scale 25. Thereby, the accuracy of position detection by the magnetic linear encoder 19 can be improved.
In this embodiment, since the head 23 itself is made of the same soft magnetic material as the magnetic shield member 31, the leakage magnetic flux from the permanent magnet 7 side is given to the sensor 23 and the magnetic scale 25. The impact can be reduced. Thereby, the above-mentioned effect can be made more reliable.
Further, since the leakage magnetic flux from the permanent magnet 7 side can be cut off, the magnetic linear encoder 19 does not need to be separated and arranged with respect to the permanent magnet 7, so that the size of the apparatus is not increased.

Next, a second embodiment of the present invention will be described with reference to FIG. In the case of the second embodiment, in addition to the configuration of the first embodiment, another magnetic shield member 41 is installed. This is installed between the head 21 and the permanent magnet 7. As shown in the drawing, the cross-sectional shape is L-shaped, and at least in the direction perpendicular to the paper surface in the figure, the magnetic scale. It is extended and installed in a range that can cover 25.
Other configurations are the same as those in the case of the first embodiment, and the same reference numerals are given to the same portions in the drawing, and the description thereof is omitted.
Therefore, the same effect as in the case of the first embodiment can be obtained, and the effect can be further enhanced by installing another magnetic shield member 41.

The present invention is not limited to the first and second embodiments.
For example, the number, shape, and installation location of the magnetic shield members are not particularly limited.
In addition, the illustrated configuration is merely an example and is not limited thereto.

In the present invention, a permanent magnet is installed on the housing side, while a coil is installed on the slider side that is movably installed with respect to the housing, and a current is passed through the coil so that the slider is controlled by the relationship between the permanent magnet and the coil. In particular, a magnetic shield member for blocking leakage magnetic flux from the permanent magnet side is installed between the magnetic linear encoder used in the linear motor and the permanent magnet. The linear encoder is devised so that it can be prevented from malfunctioning due to the influence of leakage magnetic flux, and is suitable for various uniaxial actuators, for example.

It is a figure which shows the 1st Embodiment of this invention, and is a partial sectional side view which shows the structure of a linear motor. 2A and 2B are views showing a first embodiment of the present invention, in which FIG. 2A is a cross-sectional view taken along the line II-II in FIG. 1, and FIG. 2B is a cross-sectional view showing an enlarged portion b of FIG. It is. FIG. 3A is a side view of the head, and FIG. 3B is a cross-sectional view taken along line bb in FIG. 3A, illustrating the first embodiment of the present invention. 4A and 4B are diagrams showing a second embodiment of the present invention, in which FIG. 4A is a cross-sectional view showing a configuration of a part of a linear motor, and FIG. 4B is an enlarged view of a portion b in FIG. FIG. FIG. 5A is a cross-sectional view of a linear motor, and FIG. 5B is an enlarged cross-sectional view of a portion b of FIG. 5A.

Explanation of symbols

1 Housing
3 Base 5 Case 7 Permanent magnet 13 Slider
17 Coil 19 Magnetic Linear Encoder 21 Head 23 Sensor 25 Magnetic Scale 31 Magnetic Shield Member 41 Magnetic Shield Member

Claims (4)

A housing, a permanent magnet housed and installed in a shaft shape in the housing, a slider movably installed in the housing, and a coil installed on the slider so as to surround the outer periphery of the permanent magnet; A magnetic linear encoder comprising a magnetic scale attached to the housing and a head attached to the slider and provided with a sensor.
A linear motor comprising a magnetic shield member made of a soft magnetic material between the magnetic linear encoder and the permanent magnet, and the head made of a soft magnetic material. The linear motor according to claim 1,
The housing is composed of a base and a case attached to the base, the magnetic scale is attached to the base, and the magnetic shield member is installed between the magnetic scale and the base. A linear motor characterized by The linear motor according to claim 2,
A linear motor, wherein another magnetic shield member is installed between the head and the permanent magnet. In the linear motor according to any one of claims 1 to 3,
The soft magnetic material has a relative permeability of 1000 to 1000000,
A linear motor having a holding force of about 0.01 to 10 (KA / m).

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