JPH06253526A - Linear driver - Google Patents

Abstract

PURPOSE:To lower necessary thrust by a constitution wherein the stator is reciprocal linearly, the movable part is coupled mechanically with the stator, and the deceleration rate is set within a predetermined range. CONSTITUTION:A linear motor comprises a movable section 1 and a stator 2 mechanically coupled by a coupling means 4 through a deceleration means 3 having deceleration ratio i>My/Ma, where Ma and My represent masses of the movable section and the stator, respectively. The decelerating means 3 comprises a pair of double stage pulley, i.e., a timing pulley, whereas the coupling means 4 comprises timing belts 4a, 4b entrained about large and small pulleys 3a, 3b of the timing pulley 3. The movable section 1 is secured to the upper half side of the timing belt 4a whereas the stator 2 is secured to the lower half side of the timing belt 4b and move reversely each other. This constitution reduces required thrust.

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 which can be applied 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 the linear motor. The stator 50 includes a field magnet 51 and a stator yoke 52, and generates a magnetic field necessary for driving the motor. The mover 60 includes three-phase coils 61a, 61b, 61c, moving yoke 63 and position detection elements 62a, 62b, 62c corresponding to the coils of each phase, and the mover is connected to the movable body. Position detecting elements 62a, 62b, 6
A Hall element, a Hall IC, or the like that converts the magnetic flux density into a potential difference is generally used for 2c, and the coil 6 is responsive to the outputs from the position detecting elements 62a, 62b, and 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 the motor. When the mass of the movable portion 70 is Ma and the acceleration of the movable portion is α, the necessary thrust F is expressed by F = Maα (1) from the equation of motion of the object.

[0005]

However, in the conventional method, when a large thrust is required, such as accelerating a heavy moving part with a large 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 magnet to increase the magnetic flux density, which causes problems such as an increase in power consumption due to an increase in the amount of current, and an increase in size of the field magnet to increase the magnetomotive force. .

In view of the above, an object of the present invention is to provide a linear drive device in which thrust is increased while achieving low power consumption and miniaturization of a field magnet.

[0007]

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

When the mass of the movable portion 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 problem, consider a case where the movable portion 1 of the mass Ma is linearly moved by the acceleration α. Moving part 1
Assuming that the necessary thrust force applied to F is F ′, a reaction force F ′ of the same magnitude and in the opposite direction is applied to the stator 2. When the reduction ratio is i, the forces received by the movable portion 1 are T ₁ and T ₂ , and the stator mass 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 formulas (2) and (3), T ₁ , T ₂ When F'is found by erasing, F '= {Mai / (i + 1) + My / i (i + 1)} α (4)

When the reduction ratio is set so that i> My / Ma, the equation (4) becomes 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 achieving the same weight of the movable part and the same acceleration, the thrust required to move the movable part 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 of the present invention comprises a movable part 1 and a stator 2 which are linearly reciprocally movable, and the movable part 1 and the stator 2 constitute a linear motor. And the stator 2 are mechanically connected by the connecting means 4 via the speed reducing means 3 having an arbitrary reduction ratio.

The speed reducing means 3 is composed of a pair of left and right timing pulleys, which are two-stage pulleys, and the connecting means 4 is a timing belt 4a wound around the large and small pulleys 3a, 3b of the pair of left and right timing pulleys 3, respectively. It consists of 4b. The movable portion 1 is the timing belt 4a on the side of the large pulley 3a.
The stator 2 is fixed to the upper half side, and the stator 2 is fixed to the lower half side of the timing belt 4b on the small pulley 3b side so as to move in opposite directions.

Now, consider a case where the movable portion 1 of the mass Ma is linearly moved at the acceleration α. Assuming that the necessary thrust force applied to the movable portion 1 is F ′, a reaction force F ′ of the same magnitude and in the opposite direction is applied to the stator 2. The speed reduction ratio of the speed reducer 3 is i (= φda
/ Φdy), the force that the movable part 1 receives by the connecting means 4 is T
₁ , T ₂ and the mass of the stator are My, the acceleration of the stator 2 is α / i, and the force that the stator 2 receives by the connecting means 4 is 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 formulas (2) and (3), T ₁ , T ₂ When F'is found by erasing, F '= {Mai / (i + 1) + My / i (i + 1)} α (4)

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

Next, an embodiment in which the linear driving device of the present invention is applied to a scanning optical system unit for a slit exposure type copying machine is shown in FIGS.

The linear drive device of the present embodiment shows a first movable body 10a having optical units such as mirrors and lamps and a second movable body 10b having optical units such as mirrors at a speed ratio of 2: 1. It is provided on the base frame 11 inside the main body of the copying machine so as to be linearly reciprocated in the direction A or B in FIG.

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

Then, the first movable body 10a and the second movable body 1
On the upper surface of 0b, linear encoders 17a and 17b for detecting respective moving positions are attached. On the other hand, the linear scale 18 is fixed to the base frame 11 via a fixing member 19.

Further, the first movable body 10a and the second movable body 10
The movable parts 20a and 20b are attached to one side of b. Both movable parts 20a and 20b are formed in a square cross-section and are provided with 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 the hollow portions of the movable portions 20a and 20b. A center yoke 33 which is located at a portion and forms a closed magnetic circuit 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 center yoke support plates 33a.

Below the back yoke 31, a roller 34 is provided.
Is 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. As a result, the stator 30 is movable with respect to the base frame 11.

In addition, on the upper part of the first movable body 10a, the column 3
6 is attached toward the direction of the stator 30, and the tip thereof penetrates the upper lateral groove 37 formed in the base frame 11 and projects outward. A pillar 38 is also provided on the side surface of the back yoke 31 of the stator 30 so as to project, and penetrates a lower lateral groove 39 formed in the base frame 11 to project to the outside.

As shown in FIG. 4, a pair of left and right timing pulleys 40, which are two-stage pulleys having a speed reduction ratio i and serving as speed reducing means, are rotatably attached to the outside of 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 pillar 36 of the first movable body 10a is fastened, and the pillar 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 also has a structure in which the stator 30 also moves in conjunction with each other.
The connecting means is composed of 1, 42.

When the 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 arrangement, when scanning an original by the optical unit, the first and second movable bodies 10a and 10b are detected according to the position detection by the linear encoders 17a and 17b.
By the well-known method of switching the excitation of the three-phase coil, the speed ratio of the first movable body 10a and the second movable body 10b is 2:
1 runs synchronously.

At this time, as the first movable body 10a moves in the B direction, 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 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 A direction and the stator 30 moves in the B direction by the same operation.

As described above, in order to realize the same mass and the same acceleration of the movable body as compared with the case where the conventional stator is fixed, the stator is allowed to move linearly in the opposite direction to the movable body, and is movable. The thrust force required 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 consumes less power and is smaller in size than a conventional linear drive device.

The present invention is not limited to the above embodiments, and it goes without saying that many modifications and changes can be made to the above embodiments within the scope of the present invention.

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

In this embodiment, the connecting means is the timing belt and the speed reducing means is the timing pulley. However, other combinations such as 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 is provided with a permanent magnet and the stator is composed of 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 portion and the stator are mechanically connected, and the reduction ratio is set within a predetermined range. As compared with the case where the conventional stator is fixed, the required thrust force can be reduced in achieving the same mass and the same acceleration of the movable portion. Therefore, it is possible to realize a linear drive device that consumes less power and is smaller in size than the conventional linear drive device.

[Brief description of drawings]

FIG. 1 is a principle explanatory view of a mechanical outline of a linear drive device of 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.

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 3-phase linear DC motor.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 movable part 2 stator 3 timing pulley 4 timing belt 10a first movable body 10b second movable body 20a, 20b movable part 30 stator 31 back yoke 32 field magnet 33 center yoke 35, 37 strut 40 timing pulley 41, 42 timing belt

Claims (2)

[Claims] 1. In a linear drive device including a movable portion that is linearly reciprocally movable and a stator, and a linear motor is configured by the movable portion and the stator, the stator is linearly reciprocally movable, and the movable portion and the stator are A linear drive device characterized by being mechanically connected at an arbitrary reduction ratio. 2. The movable part mass is Ma and the stator mass is My.
The linear drive device according to claim 1, wherein the reduction ratio i is i> My / Ma.