JP3222605B2 - Linear drive - 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 drive device using a linear motor applicable to a copying machine, a printer, an optical disk device and the like.

[0002]

2. Description of the Related Art Conventionally, a linear motor has been widely known as a driving means for performing a linear reciprocating motion.

FIG. 6 shows the structure of a three-phase linear DC motor as an example of a linear motor. The stator 50 includes a field magnet 51 and a stator yoke 52, and generates a magnetic field necessary for driving a motor. The mover 60 includes three-phase coils 61a, 61b, and 61c, a moving yoke 63, and position detecting elements 62a, 62b, and 62c corresponding to the coils of each phase, and a mover is connected to the mover. Position detecting elements 62a, 62b, 6
In general, a Hall element, a Hall IC, or the like that converts a magnetic flux density into a potential difference is used for 2c, and a coil 6c according to outputs from the position detection elements 62a, 62b, 62c.
By energizing 1a, 61b, 61c, thrust is generated in the mover according to Fleming's left-hand rule.

FIG. 7 shows a simple schematic diagram for obtaining the thrust of a motor. Assuming that the mass of the movable part 70 is Ma and the acceleration of the movable part is α, the necessary thrust F is expressed by the following equation of motion of the object: F = Maα (1)

[0005]

However, in the conventional method, when a large thrust is required, for example, when a heavy moving part is accelerated with a larger acceleration, the amount of current flowing through the coil is increased or the field is increased. It is necessary to take measures such as increasing the magnetomotive force of the magnet to increase the magnetic flux density, and there are problems such as an increase in power consumption due to an increase in the amount of current and an increase in the size of the field magnet in order to increase the magnetomotive force. .

In view of the above, it is an object of the present invention to provide a linear drive device having an increased thrust while reducing power consumption and miniaturizing a field magnet.

[0007]

As shown in FIG. 1, a means for solving the problems according to the present invention comprises a movable portion 1 and a stator 2 which can move linearly and reciprocally, and the movable portion 1 and the stator 2 constitute a linear motor. The movable part 1 and the stator 2 are mechanically connected at an arbitrary reduction ratio.

When the mass of the movable part is Ma and the mass of the stator is My, the reduction ratio i is i> My / Ma.

[0009]

In the above means for solving the above problems, a case is considered where the movable part 1 having the mass Ma is moved linearly at an acceleration α. Movable part 1
Assuming that the required thrust applied to the stator 2 is F ′, a counterforce F ′ of the same magnitude and opposite direction is applied to the stator 2. Assuming that the reduction ratio is i, the forces received by the movable portion 1 are T ₁ and T ₂ , and the mass of the stator is My, the acceleration of the stator 2 is α / i, and the forces received by the stator 2 are iT ₁ and iT ₂ .

The equations of motion of the movable part 1 and the stator 2 are as follows.

Maα = F ′ + (T ₁ −T ₂ ) (2) Myα / i = F′−i (T ₁ −T ₂ ) (3) From equations (2) and (3), T ₁ and T ₂ And F ′ is obtained to obtain F ′ = {Mai / (i + 1) + My / i (i + 1)} α (4)

If the reduction ratio is set so that i> My / Ma, the equation (4) is as follows: F ′ <{Mai / (i + 1) + Ma / (i + 1)} α = Maα (5) From equation (1), the thrust required by the conventional method is F =
Since Maα, F ′ <F (6), and the required thrust is smaller than that of the conventional method.

As a result, in realizing the same movable portion weight and the same acceleration, the thrust required to move the movable portion 1 can be reduced as compared with the case where the conventional stator is fixed. .

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a linear drive device according to the present invention comprises a movable portion 1 and a stator 2 which are capable of linearly reciprocating movement, and a linear motor is constituted by the movable portion 1 and the stator 2. And the stator 2 are mechanically connected by a connecting means 4 via a speed reducing means 3 having an arbitrary speed reduction ratio.

The deceleration means 3 comprises a timing pulley which is a pair of left and right two-stage pulleys, and the coupling means 4 comprises timing belts 4a, 4a wound around the large and small pulleys 3a, 3b of the pair of left and right timing pulleys. 4b. The movable part 1 is a timing belt 4a on the side of the large pulley 3a.
, The stator 2 is fixed to the lower half of the timing belt 4b on the side of the small pulley 3b, and moves in opposite directions.

Now, consider a case where the movable part 1 having the mass Ma is linearly moved at an acceleration α. Assuming that the required thrust applied to the movable portion 1 is F ', a counterforce F' having the same magnitude and the opposite direction is applied to the stator 2. Let the reduction ratio of the reduction means 3 be i (= φda
/ Φdy), the force which the movable part 1 receives by the connecting means 4 is T
Assuming that ₁ , T ₂ and the mass of the stator are My, the acceleration of the stator 2 is α / i, and the forces received by the connecting means 4 by the stator 2 are iT ₁ and iT ₂ .

The equations of motion of the movable part 1 and the stator 2 are as follows.

Maα = F ′ + (T ₁ −T ₂ ) (2) Myα / i = F′−i (T ₁ −T ₂ ) (3) From equations (2) and (3), T ₁ and T ₂ And F ′ is obtained to obtain F ′ = {Mai / (i + 1) + My / i (i + 1)} α (4)

If the reduction ratio is set so that i> My / Ma, the equation (4) is as follows: F ′ <{Mai / (i + 1) + Ma / (i + 1)} α = Maα (5) From equation (1), the thrust required by the conventional method is F =
Since Maα, F ′ <F (6), and it can be seen that the required thrust is smaller than that of the conventional method.

FIGS. 2 to 4 show an embodiment in which the linear drive device of the present invention is applied to a scanning optical system unit for a copying machine of a slit exposure system.

The linear drive device of the present embodiment shows a first movable body 10a equipped with an optical unit such as a mirror and a lamp and a second movable body 10b equipped with an optical unit such as a mirror at a speed ratio of 2: 1. 2 is provided on a base frame 11 inside the copying machine main body so as to linearly reciprocate in the direction of A or B in FIG.

The first movable body 10a and the second movable body 10b are
One side is slidably supported via bearings 14a and 14b on a shaft 13 fixedly mounted on a base frame 11 via a holder 12. The other side is slidably supported via sliding members 16a and 16b which slide on rails 15 fixed to the base frame 11.
The base frame 11 is movable in the directions A and B in the figure.

The first movable body 10a and the second movable body 1
Linear encoders 17a and 17b for detecting the respective movement positions are attached to the upper surface of Ob. On the other hand, the linear scale 18 is fixed to the base frame 11 via a fixing member 19.

The first movable body 10a, the second movable body 10
The movable parts 20a and 20b are respectively attached to one side of b. Both movable parts 20a and 20b are formed in a rectangular cross section, and include three-phase coils.

A stator 30 is provided around the movable parts 20a and 20b. The stator 30 includes a back yoke 31 having a U-shaped cross section, upper and lower field magnets 32 attached to the back yoke 31 so as to face the upper and lower surfaces of the movable portions 20a and 20b, and hollow portions of the movable portions 20a and 20b. And a center yoke 33 for forming a closed magnetic circuit together with the back yoke 31 and the field magnet 32.
Consists of As shown in FIG. 5, both ends of the center yoke 33 are attached to the back yoke 31 via the center yoke support plate 33a.

A roller 34 is provided below the back yoke 31.
Are attached to the base frame 11 by the holder 35, and the roller 34 is in contact with the lower surface of the back yoke 31. This allows the stator 30 to move with respect to the base frame 11.

Further, a support 3 is provided above the first movable body 10a.
6 is attached toward the direction of the stator 30, and the tip thereof projects outward through an upper lateral groove 37 formed in the base frame 11. A column 38 is also protruded from the side surface of the back yoke 31 of the stator 30, and penetrates a lower lateral groove 39 formed in the base frame 11 and protrudes outward.

As shown in FIG. 4, a pair of left and right timing pulleys 40 as reduction means, which are two-stage pulleys having a reduction ratio i, are rotatably mounted outside the base frame 11. The large pulley 40a and the small pulley 40b of both timing pulleys 40 are connected by timing belts 41 and 42, respectively.

The timing belt 41 on the large pulley side includes
The support 36 of the first movable body 10a is fastened, and the support 38 of the stator 30 is fastened to the timing belt 42 on the small pulley side. That is, when the first movable body 10a is driven, the timing pulley 40 and the timing belt 41,
42, the stator 30 also moves in conjunction therewith.
1 and 42 constitute a connecting means.

When the combined mass of the first movable body 10a and the movable portion 20a is Ma and the mass of the stator 30 is My, the timing pulley 40 is designed so that the reduction ratio i is i> My / Ma. ing.

In the above configuration, when scanning the original by the optical unit, the first and second movable bodies 10a, 10b are detected in accordance with the position detection from the linear encoders 17a, 17b.
The first movable body 10a and the second movable body 10b have a speed ratio of 2:
1. Synchronous operation is performed.

At this time, as the first movable body 10a moves in the direction B, the timing belt 41 moves and the timing pulley 40 rotates. Then, the timing belt 42 on the small pulley 40b side also moves in the same direction, and the stator 3
0 moves in the opposite direction A at a moving speed of 1 / i times the moving speed of the first movable body 10a.

At the time of return, the first and second movable bodies 10a and 10b move in the direction A by the same operation, and the stator 30 moves in the direction B.

As described above, in order to achieve the same mass of the movable body and the same acceleration with respect to the case where the conventional stator is fixed, the stator can be linearly reciprocated in the opposite direction to the movable body, and the movable body can be moved. The required thrust can be reduced by mechanically connecting the body and the stator at a reduction ratio i, and by setting i> My / Ma. Therefore,
It is possible to realize a linear drive device that can save power and reduce the size of a field magnet as compared with a conventional linear drive device.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that many modifications and changes can be made to the above-described embodiment within the scope of the present invention.

The linear drive device according to the present invention can be applied not only to a copying machine but also to a printer, a magneto-optical disk device, and the like.

In this embodiment, the connecting means is a timing belt, and the speed reducing means is a timing pulley. However, a combination of a wire and a two-stage pulley or a rack and a pinion may be used.

The structure of the stator and the movable body may be reversed so that the movable body includes a permanent magnet, and the stator includes a winding and a yoke.

[0039]

As is apparent from the above description, according to the present invention, the stator can be linearly reciprocated, the movable part and the stator are mechanically connected, and the reduction ratio is set within a predetermined range. In order to realize the same mass of the movable part and the same acceleration as compared with the case where the conventional stator is fixed, the required thrust can be reduced. Therefore, it is possible to realize a linear drive device that can save power and reduce the size of the field magnet as compared with the conventional linear drive device.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the mechanical outline of a linear drive device according to the present invention

FIG. 2 is a plan view of a scanning optical system of a slit exposure type copying machine to which the linear driving device of the present invention is applied.

FIG. 3 is a sectional view taken along line XX of FIG. 2;

FIG. 4 is a front view of a scanning optical system.

FIG. 5 is a perspective view of a stator.

FIG. 6 is a structural diagram of a general three-phase linear DC motor.

FIG. 7 is an explanatory diagram of a dynamic outline of a conventional linear motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Movable part 2 Stator 3 Timing pulley 4 Timing belt 10a 1st movable body 10b 2nd movable body 20a, 20b Movable part 30 Stator 31 Back yoke 32 Field magnet 33 Center yoke 35, 37 Prop 40 Timing pulley 41, 42 Timing belt

Claims (2)

(57) [Claims] 1. A linear drive device comprising a movable portion capable of linearly reciprocating movement and a stator, wherein a linear motor is constituted by the movable portion and the stator . And a connecting means for mechanically connecting at a given reduction ratio. 2. The mass of the movable part is Ma and the mass of the stator is My.
2. The linear drive device according to claim 1, wherein the speed reduction ratio i is set to i> My / Ma.