JP3322686B2 - Linear motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear motor used for moving and positioning a movable member in, for example, optoelectronics equipment, precision equipment, and the like. The present invention relates to a linear motor capable of preventing shaking (yawing) in a direction perpendicular to a moving direction, improving positioning accuracy and shortening a settling time.

[0002]

2. Description of the Related Art Conventionally, a driving device for positioning an object within a long stroke range of 10 cm to 100 cm is disclosed in, for example, Japanese Patent Publication No. 58-49100 and Japanese Utility Model Laid-Open Publication No. 63-93783. Such moving coil type linear motors are frequently used. In this linear motor, a plurality of permanent magnets magnetized in the thickness direction are arranged to face each other with different magnetization directions, and move in a direction perpendicular to the magnetic flux in a gap formed between the facing permanent magnets. It has a structure in which a movable coil assembly is provided.

In such a linear motor, the magnetic flux forms a plurality of closed loops in the air gap so that the magnetic flux does not concentrate on a part of the magnetic path, so that the magnetic flux is uniform over a long stroke. A magnetic flux density can be generated.

When moving and positioning a table or other movable member in precision equipment or the like using the linear motor as a drive source, a lubricating oil is used instead of a conventional mechanical bearing means to prevent vibration and improve accuracy. Instead, a gas bearing using a gas such as air or nitrogen gas as a medium is used.

FIGS. 7 and 8 are a partial sectional side view and a partial sectional plan view, respectively, showing an example of a conventional linear motor using the above gas bearing. 7 and FIG.
Is a linear motor, a center yoke 2 made of a ferromagnetic material, an outer yoke 4 made of a ferromagnetic material and magnetically coupling the center yoke 2 and an outer end, and a magnetized magnet in the thickness direction. It comprises a permanent magnet 3 fixed to the inner surface of an outer yoke 4 and a movable member 5. The movable member 5
A coil 7 is wound around the outer periphery of a magnetic gap 6 formed by the permanent magnet 3, and is disposed so as to be movable in the left and right directions in FIGS.

Reference numeral 8 denotes a suspending member which is fixed to the upper outer yoke 4 to suspend and hold the linear motor 1. Next, reference numeral 9 denotes a guide, which has a rectangular cross-sectional profile, connects the left end to the lower end of the hanging member 8, and is disposed substantially coaxially with the center yoke 2. Numeral 10 denotes a slider, which is formed in a hollow rectangular tube shape and is movable in the axial direction through a small gap with the guide 9. A left end of the slider 10 is connected to the movable member 5 via a connecting member 11, and a connecting member 12 to a driven member (not shown) is fixed to a right end. The guide 9 is provided with an air supply port 13 and an air supply hole 14, and the slider 10 is provided with an exhaust port 15, thereby constituting a gas bearing.

With the above configuration, if the coil 7 constituting the movable member is energized in the forward and reverse directions, the movable member 5 can be moved according to Fleming's left hand rule, and the slider 10 can be moved in the left and right direction. Can be. In this case, since the compressed air supplied to the air supply port 13 blows out from the air supply hole 14 into the slider 10, the slider 10 is in a floating state with respect to the guide 9, and the friction between the two can be maintained without any friction. is there.

However, in the configuration shown in FIGS. 7 and 8, the length including the linear motor 1 and the gas bearing portion is large, so that the entire device becomes large and the occupied area becomes large. There is a point. Further, since the distance between the gas bearing portion and the movable member 5 is large, the guide 9 and the slider 1 which constitute the gas bearing depending on the moving position of the movable member 5
Since the length of the overlapped portion with 0 changes, it is necessary to delicately control the pressure and / or flow rate of the air to be supplied, and there is a problem that the operation is complicated. On the other hand, the requirements for downsizing and weight reduction of this type of device are becoming increasingly strict, and the above-mentioned requirements are satisfied if the driving portion and the supporting portion are separately configured as described above. There is a problem that it is not possible.

In order to solve the above problems, there has been proposed a linear motor having a structure in which a driving portion and a gas bearing portion are integrated. FIG. 9 is a perspective view of an essential part showing an example of such a linear motor. In FIG. 9, 21 is a guide,
The cross-sectional outline is formed in a square shape. Reference numeral 22 denotes a slider, which is formed in a hollow rectangular cylindrical shape so as to be interposed with the guide 21 via a minute gap, and is provided so as to be axially movable with respect to the guide 21. The guide 21 and the slider 22 constitute a gas bearing similar to that shown in FIGS. 7 and 8.

Reference numeral 23 denotes a drive unit, which is configured as a linear motor incorporating a coil (not shown), for example.
It is provided integrally with the lower end of the slider 22. A permanent magnet group 24 is magnetized in, for example, the thickness direction, and is configured such that N and S magnetic poles appear alternately on the surface of a yoke (not shown) made of a ferromagnetic material. The coil in the drive unit 23 is configured to be present in a magnetic gap formed on the surface of the permanent magnet group 24.

[0011]

The device constructed as shown in FIG. 9 has the advantage that the whole device is more compact than those shown in FIGS. 7 and 8, but has the following problems. There is.

That is, since the drive unit 23 is provided below the slider 22, when the slider 22 is moved and / or stopped in the axial direction of the guide 21, the swinging in the axial direction (pitching) and the swing in the direction perpendicular to the axis are performed. (Yawing), or swaying (rolling) around the axis occurs. This is because the slider 22 is in a floating state with respect to the guide 21. The above-mentioned sway is not a problem if the device is used only for moving the load and the stopping accuracy is rough. However, accuracy in the submicron range as in optical equipment or precision equipment is required. This is a fatal problem.

In addition, there is a problem that the damping characteristic is low in relation to the stop accuracy, that is, the time until the vibration is attenuated (settling time) is long. As described above, since the slider 22 and the guide 21 which constitute the gas bearing are engaged in a non-contact floating state, once the above-mentioned shaking occurs, the shaking is attenuated to a predetermined value or less. It takes a long time to work. In order to shorten the settling time, it is conceivable to suppress the shaking or vibration via electrical means or mechanical means. However, the apparatus becomes complicated and the operation becomes complicated. is there.

Further, in the conventional device, no consideration is given to the position where the load or external force acting on the gas bearing portion acts, and the device is constructed based on the idea that these act equally and symmetrically. However, the load or external force acting on the gas bearing portion generally acts in an uneven manner in most cases. On the other hand, the gas bearing part is engaged in a non-contact floating state microscopically as described above.
There is a problem that the effect of the above-mentioned eccentric load greatly affects the stopping accuracy and the accuracy of the slider in the submicron region.

The present invention solves the above-mentioned problems in the prior art, is compact, prevents undesired shaking of the movable member, improves positioning accuracy, and can drastically shorten the settling time. An object is to provide a linear motor.

[0016]

In order to achieve the above object, according to a first aspect of the present invention, two rod-shaped guides provided in parallel are provided movably in the longitudinal direction of the guides via gas bearings. Carriage, a yoke made of a ferromagnetic material provided between the guides, a permanent magnet provided on the surface of the yoke so that different poles alternately appear in the longitudinal direction of the guides, and the permanent magnets And a flat coil provided opposite to the magnetic pole in a magnetic gap formed by the magnet. One of the yoke and the coil is fixed, and the other is fixed to the carriage. The point of action of the resultant force of the thrust generated between the two
And the balance on the carriage
A weight is provided, and the position of the center of gravity of the carriage is
Plane perpendicular to the plane containing the point of action and the axis of the guide
Ru provided within adopts the technical means of.

Next, in the second aspect of the present invention, the parallel
The length of the guide through a gas bearing to two rod-shaped guides
A carriage provided so as to be movable in the
A yoke made of a ferromagnetic material provided between
Different polarity alternately in the longitudinal direction of the guide
And a permanent magnet formed to appear in
Therefore, it is provided facing the magnetic pole in the magnetic gap formed.
The yoke or the coil.
And fix the other to the carriage
Thrust generated between the permanent magnet and the coil
The point of action of the resultant force is within the plane containing the axis of the guide.
And the loading section
The center of gravity of the carriage, including wood, set <br/> that only in a plane perpendicular to the plane including the axis of the guide includes a point of action of the resultant force of the thrust, adopting the technical means of. In the present invention described above, a plurality of end faces of the coil may be provided in parallel, and each coil may be provided in the magnetic gap of the permanent magnet so as to face the magnetic pole.

[0018]

According to the above construction, since the point of application of the resultant force of the thrust generated between the permanent magnet and the coil coincides with the support center of the gas bearing, the starting point and / or the movement of the carriage, which is a movable member, can be achieved. Also, it is possible to prevent undesired shaking or vibration from occurring in the movable member.

[0019]

FIG. 1 is a perspective view of a main part showing an embodiment of the present invention, and FIG. 2 is a front view of a main part of a partial cross section showing the vicinity of a movable member in FIG. 1 and 2, reference numeral 31 denotes a support plate on which a linear motor 32 and an encoder 3 are mounted.
3 are provided in parallel. Numeral 34 denotes a position sensor provided on the movable portion of the linear motor 32, which is provided to face the encoder 33 and detects the position of the movable portion of the linear motor 32.

Next, the configuration of the linear motor 32 will be described. Reference numeral 35 denotes a substrate, for example, formed in a rectangular flat plate shape and fixed to the surface of the support plate 31. 36 is a side plate,
Two guides 37 formed in a round bar shape are provided in parallel between the side plates 36, standing on the short side edge of the substrate 35.
Numeral 38 denotes a carriage, which is engaged with the guide 37 via a minute gap and forms a gas bearing;
And a top plate 40 for integrally connecting the sliders 39, 39.

Reference numeral 41 denotes a yoke which has a substantially E-shaped cross section made of a ferromagnetic material such as a steel material, and is provided on the surface of the substrate 35 at an intermediate portion between the guides 37, 37.
7 is provided in parallel. On the inner peripheral surface of the yoke 41, permanent magnets 42 which are magnetized in the thickness direction and are formed in a plate shape are arranged. It is arranged as follows. Reference numeral 43 denotes a flat-shaped coil, one side of which is supported by a support member 44 fixed to the slider 39 and / or the top plate 40.
Further, it is provided so as to face the magnetic poles N and S in the magnetic gap formed by the permanent magnet 42.

With the above configuration, if the coil 43 is energized in the forward and reverse directions, the carriage 38 is moved in the axial direction of the guide 37 according to Fleming's left-hand rule, as in the linear motor having the conventional configuration. Can be.
In this case, the center of the resultant force of the thrust generated between the permanent magnet 42 and the coil 43 exists in a plane including the axes of the guides 37, 37, and equally divides the distance between the axes of the guides 37, 37. Configure to be in place. With this configuration, when the carriage 38 is started and / or
Alternatively, occurrence of undesired shaking or vibration during movement can be prevented.

FIGS. 3 and 4 are diagrams showing the relationship between the error of the stop position and time in the embodiment of the present invention and the conventional linear motor, respectively. As is clear from FIG. 3, in the embodiment of the present invention, the error is within ± 0.02 μm. Compared to the conventional example shown in FIG. 4 having an error of ± 0.1 μm, it can be seen that the example of the present invention shown in FIG. 3 has extremely high accuracy.

[0024]

[Table 1]

Table 1 is a table showing the characteristics of the present invention and the conventional one. As is clear from Table 1, the apparatus of the present invention has excellent stopping accuracy, and has a short moving and settling time. In other words, in the state where it has moved from the stop state,
It can be seen that the vibration attenuates to a smaller amplitude within a shorter time than the conventional one. It is also recognized that other characteristics have been improved.

FIG. 5 is a partial sectional front view showing another embodiment of the present invention, and the same parts are denoted by the same reference numerals as in FIG. 5 is different from that shown in FIG. 2 in that the yoke 41, the permanent magnet 42, and the coil 43 are provided in such a manner that they are respectively rotated by 90 °, and the other configuration is shown in FIG. Same as the one. Therefore, the stop accuracy, the movement / settling time, and other characteristics are also the same as those shown in FIG.

FIG. 6 is a partial cross-sectional front view showing still another embodiment of the present invention, and the same portions are denoted by the same reference numerals as in FIGS. 1, 2 and 5. In FIG. 6, reference numeral 45 denotes a balance weight which is formed to have substantially the same weight as the position sensor 34, is provided at a position symmetrical to the position sensor 34, and has a center of gravity of the entire carriage 38 which is a coil 43 and a permanent magnet (not shown, FIG. 2 (see reference numeral 42 in FIG. 2), and includes an action point of a resultant force of thrust generated between the guides 37 and 37, and exists in a plane orthogonal to a plane including the axis of the guides 37.

With the above configuration, it is possible to prevent an eccentric load from acting on the carriage 38, and to further improve the stopping accuracy of the linear motor, the movement / settling time, and other characteristics.
Instead of the balance weight 45 in FIG. 6, the position of the components mounted or mounted on the carriage 38 may be adjusted so that the center of gravity of the entire carriage 38 is at the above-described position.

In this embodiment, an example in which the coil is configured in two stages has been described. However, the coil may be formed in a single stage or in three or more stages. The operation is the same even when the cross-sectional profile of the guide is set to a shape other than the circular shape. Further, the guides may be provided not only horizontally but also vertically. Further, a so-called movable magnet type linear motor in which a yoke and a permanent magnet are provided on the carriage and the coil is fixed may be used.

[0030]

As described above, the present invention has a configuration and an operation as described above.
In addition to the high stopping accuracy in the submicron range, there is an effect that the occurrence of undesired shaking and vibration of the movable member can be prevented, and the settling time can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part showing an embodiment of the present invention.

FIG. 2 is a partial cross-sectional front view showing the vicinity of a movable member in FIG.

FIG. 3 is a diagram illustrating a relationship between an error of a stop position and time according to the embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between a stop position error and time in a conventional linear motor.

FIG. 5 is a partial cross-sectional front view showing another embodiment of the present invention.

FIG. 6 is a partial cross-sectional front view showing still another embodiment of the present invention.

FIG. 7 is a partial cross-sectional side view showing an example of a conventional linear motor using a gas bearing.

FIG. 8 is a partially sectional plan view showing an example of a conventional linear motor using a gas bearing.

FIG. 9 is a perspective view of a main part showing another example of a conventional linear motor using a gas bearing.

[Explanation of symbols]

 37 Guide 41 Yoke 42 Permanent magnet 43 Coil

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-161228 (JP, A) JP-A-3-218249 (JP, A) Japanese Utility Model Application No. Sho 61-288770 (JP, U) Japanese Utility Model Application No. Sho 62- 165772 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H02K 41/02

Claims (3)

(57) [Claims] 1. A carriage provided on two parallel bar-shaped guides via a gas bearing so as to be movable in the longitudinal direction of the guides, and a yoke made of a ferromagnetic material provided between the guides. A permanent magnet provided on the surface of the yoke so that different poles alternately appear in the longitudinal direction of the guide; and a flat magnet provided in a magnetic gap formed by the permanent magnet so as to face the magnetic pole. A coil, wherein one of the yoke and the coil is fixed and the other is fixed to the carriage, and the point of action of the resultant force of the thrust generated between the permanent magnet and the coil is a plane including the axis of the guide. as well as configured to be located in the central portion between the guide of the inner, the balance weight on the carriage
The position of the center of gravity of the carriage
Linear motor, wherein the digits set in a plane perpendicular to the plane including the guide axis comprises. 2. A gas is introduced into two rod-shaped guides provided in parallel.
It is provided so that it can move in the longitudinal direction of the guide via the bearing
Is the ferromagnetic material provided between the carriage and the guide
And a guide provided on the surface of the yoke.
A pole formed so that different poles appear alternately in the longitudinal direction of the
In the magnetic air gap formed by the permanent magnet and the permanent magnet
And a flat coil provided opposite to the magnetic pole.
To fix either the yoke or the coil.
And the other is fixed to the carriage, and the permanent magnet is
The point of action of the resultant of the thrust generated between the coil and the
Located between the guides in the plane containing the axis of the
Together constitute urchin, the center of gravity of the carriage, including the loading member, a plane that is provided in the plane perpendicular to the characteristics and to Brighter two <br/> the containing guide axis comprises a point of action of the resultant force of the thrust Amota. 3. An end face of a coil is provided in a plurality of stages in parallel.
3. The linear motor according to claim 1 , wherein the coil is provided in the magnetic gap of the permanent magnet so as to face the magnetic pole .