JPH01185626A - Optical system moving device for copying machine - Google Patents

Abstract

PURPOSE:To move an optical system at a high speed and with high accuracy by allowing a driving current to flow so that specific requirements are met between the mass of each of a mirror base for original scanning and a mirror base for drum projection and the driving force of a needle. CONSTITUTION:The movable part mass values of the mirror base (a) for original scanning and the mirror base (b) for drum projection are denoted as m1 and m2 and the driving forces of needles 12a and 12b, and 12c and 12d are denoted as F1 and F2. Then the driving current which satisfies 2m1.F2not equal to m2.F1 is supplied to the linear motor 10a consisting of a stator 11a and the needle 12 in the beginning of the return accelerating operation of the mirror bases (a) and (b). Consequently, unbalance which impedes the ideal return acceleration between the driving forces is generated, but the driving force corresponding to the unbalance is transmitted to other needles through a pulley mechanism 20 and converged speedily into ideal driving force relation. Consequently, the return acceleration is carried out positively and fast, high-accuracy movement is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an optical system moving device for a copying machine (hereinafter referred to simply as an optical system moving device) that is installed in a copying machine with a fixed document table.

<Prior art> In a copying machine with a fixed document table, the optical path distance from the surface of the document to the exposure position of the photoreceptor must be constant regardless of the scanning position. An optical system moving device is provided that moves the first mirror and the second mirror that reflects the reflected light from the first mirror toward the drum projection lens in the document scanning direction at a speed ratio of 2:1. There is.

Such optical system moving devices have long had a configuration in which the first mirror and the second mirror are moved by a method using a wire pulley mechanism, but since an elastic member is interposed in the middle, There is a limit to the ability to move at higher speeds and with higher precision than is currently possible, and this has been a serious obstacle to increasing the speed of recent copying machines. In order to overcome this technical problem, various creative efforts have been made, but a typical conventional example that applies a linear motor is Japanese Patent Application Laid-Open No. 56-87065 (hereinafter referred to as the first conventional example). ), Japanese Patent Application Laid-Open No. 60-136731 (hereinafter referred to as No. 2
(hereinafter referred to as conventional examples).

In the first conventional example, as shown in FIG.
The first mirror 41 and the second mirror 4 whose movement is restricted at 0
2 are moved in the document scanning direction by a voice coil motor 43. Voice coil motor 4
3 will be explained in detail. A plate-shaped permanent magnet 433 is provided between an upper yoke plate 431 and a lower yoke plate 432 which are connected with an interval. , a first bobbin 411 fixed to the end of the first mirror 41, and a second mirror 4
A second bobbin 421 fixed to the end of each of the two bobbins 421 is provided so as to be slidable in the document scanning direction. Moreover, the first
A first excitation coil 434 and a second excitation coil 435 are provided on the inner peripheral surfaces of the bobbin 411 and the second bobbin 421, respectively. In other words, when a predetermined drive current is passed through the first excitation coil 434 and the second excitation coil 435, which are interlinked with the field magnetic flux from the permanent magnet 433, an electromagnetic force is generated. The configuration is such that the first mirror 41 and the second mirror 42 are moved at a speed ratio of 2:1.

In the second embodiment, as shown in FIG. 10, a first mirror 51 and a second mirror 52 whose movements are restricted by a guide rail 50 are moved in the document scanning direction by a linear pulse motor 53. ing. To explain in more detail, the stator 531 of the linear pulse motor 53 is common, but the first movable element 532 and the second movable element are fixed to one end of the first mirror 51 and the second mirror 52, respectively. 533 independently, the first mirror 5
The configuration is such that the first mirror 52 and the second mirror 52 are moved at a speed ratio of 2:1. However, since the principle of the linear pulse motor is well known, the explanation will be omitted.

<Problems to be Solved by the Invention> However, in the case of the first conventional example, since the magnetic flux is concentrated at the end of the stator, the cross-sectional area of the end yoke is large (and the entire surface of the opposing yoke is A magnetic attraction force acts on the voice coil motor 43, and it is necessary to have mechanical strength that can withstand this attraction force. This makes it impossible to make the voice coil motor 43 smaller than the current size, and this poses a limit in making the copying machine more compact. ing.

In the case of conventional method 2, although it is possible to reduce the size and weight of the entire device, the movement state during document scanning is unstable due to large thrust ripples, etc., and the optical system is moved at high speed and with high precision. There are still limits to how fast copying machines can operate, and the current situation is that it is not possible to sufficiently meet the current demands for faster copying machines.

The present invention was devised in view of the above circumstances, and an object of the present invention is to provide an optical system moving device that can reduce the size and weight of the entire device and move the optical system at high speed and with high precision. do.

Means for Solving the Problems> The optical system moving device according to the present invention moves the first and second movers provided on the mirror stand for document scanning and the mirror stand for drum projection, respectively, on a common stator. A linear motor that moves independently in the document scanning direction, a wire pulley mechanism that regulates the movement of the document scanning mirror stand and drum projection mirror stand at a speed ratio of 2:1, and the document scanning mirror stand and drum projection mirror stand. When the masses of the movable parts of are respectively m, , mz, and the respective thrust forces of the first and second movers are F1 and F2, respectively, 2m+ at the initial stage of return acceleration of the mirror stand for document scanning and the mirror stand for drum projection.・F! ≠m2 ·Fl A linear motor control unit is provided that applies drive currents to the first and second movable elements, respectively, satisfying the relationship: ≠m2 ·Fl.

The conditions for ideally returning and accelerating the document scanning mirror stand and the drum projection mirror stand, whose movement is restricted by a wire pulley mechanism at a speed ratio of 2:1, are as follows: Each thrust of the child F,,F.

It is necessary that the following relational expression be satisfied.

F2/F1=mt/(2・ml)...■Furthermore, if drive currents that do not satisfy the relationship of formula (■) are applied to the first and second movable elements at the initial stage of return acceleration, the first and second movers An unbalance occurs in the thrust of the mover that prevents ideal return acceleration, but the unbalanced thrust is transmitted to other movers via the wire pulley mechanism. The thrust of the first and second movers is expressed by the formula ■
It quickly converges to satisfy the relational expression, and as a result, the ideal return acceleration of the document scanning mirror stand and the drum projection mirror stand is actively performed.

<Example> Hereinafter, an example of the optical system moving device according to the present invention will be described with reference to the drawings. Figure 1 is a mechanical schematic diagram of the optical system moving device, Figure 2 (a) is a layout diagram of the linear motor in the mirror stand for document scanning, and Figure 2 (b) is the arrangement of the linear motor in the mirror stand for drum projection. Layout diagram, Figure 3 is a front view of the mover in the beam near motor, Figure 4 is a partial front view of the stator in the beam near motor, Figure 5 is an explanatory diagram of the connection of the wire pulley mechanism, and Figure 6 is each air core in the mover. FIG. 7 is an electrical connection diagram of the coil, FIG. 7 is an electrical configuration diagram of the optical system moving device, and FIG. 8 is a copy cycle diagram of a mirror stand for document scanning and a mirror stand for drum projection.

The optical system to be moved by such an optical system moving device includes an original scanning mirror stand a on which a first mirror (not shown) for scanning the original surface is mounted, and a mirror table a for projecting the reflected light from the first mirror onto a drum. This is a mirror stand for drum projection on which a second mirror (none of which is shown) is placed to reflect the image toward the lens.

The optical system moving device described here moves the original scanning mirror stand a and the drum projection mirror stand at a speed of 2:1 by controlling four linear motors 10a to 10d, which are three-phase brushless linear motors. The basic configuration is such that the document is moved in the document scanning direction (X direction in the figure) at a ratio of
Furthermore, from the viewpoint of improving the return acceleration after scanning, the movement of the document scanning mirror stand a and the drum projection mirror stand is restricted by a wire boolean mechanism 20. Of the four linear motors 10, linear motors 10a and 10b are used to move the document scanning mirror stand a, while linear motors 10c to 10d are used to move the drum projection mirror stand, respectively. However, linear motor 1
The subscripts attached to the part numbers of the stator 11 and mover 12 in 0 correspond to the alphabets of the near motors 10a to 10d.

To explain in more detail, movers 12a and 12b are respectively disposed on the lower right side and left side in the figure of the document scanning mirror stand a, while on the other hand, on the lower right side and left side of the mirror stand for drum projection. Also, movers 12c and 12d are provided, respectively. Also, movers 12a, 12c, mover 12b
, 12d, the stator 118111b corresponds to X
They are arranged on the main body of the copying machine at intervals in the X direction and facing in the X direction. In other words, linear motor 10a, 1
0c, the stator 11a is in the - direction near a motor 1
0b and 10d, the stator 11b is shared, and is configured to reciprocate the document scanning mirror stand a and the drum projection mirror stand in the X-axis direction (the second (see figure). However, mirror stand a for document scanning
Also, guide rails for regulating the position of the drum projection mirror, rollers for regulating the distance between the stator 11 and the movable element 12 in the near motor 10, etc. are not shown.

Next, the mover 12 will be explained in detail with reference to FIG. 3.

On the upper surface of the yoke plate 121, three-phase air-core coils Pv 122U, 122V, 1 in a three-phase brushless linear motor are shown.
Hall elements 1230.123V, 123K are installed in the center of the air-core coils 122U to 122-, which are magnetic field detection elements for detecting excitation switching in a three-phase brushless linear motor. are fixed respectively. Further, a reflective photodetector 124 for detecting the position and speed of the movable element 12 is provided at the lower part of the yoke plate 121. However, the mover 12b
, 12d includes a photodetector 124 and a Hall element 123U, 1
23v, 123- are not provided.

Next, the stator 11 will be explained in detail with reference to FIG.

A yoke 111 that is placed in the copying machine body and forms a magnetic path.
On the top surface, permanent magnets 112 are magnetized alternately with north pole and south pole, and below this magnetized surface is a linear scale depicting a repeating black and white pattern that is the detection target of the photodetector 124. 113 is formed. In addition, the permanent magnet 11
2, the magnetization pitch in each of the opposing air-core coils 122
The pitch is set to be 375 times the pitch of U to 122-. However, the stator 11b is not equipped with the linear scale 113 (in addition, the Hall elements 123υ, 123v
, 123 enemy , air core coil 1220 , 122L 12
2W, the subscript attached to the photodetector 124 corresponds to the alphabet of the near motors 10a to 10d)
.

Next, the air-core coils 122U to 122- in the mover 12
The connection method will be explained with reference to FIG.

Air core coil 122Ua ~ 122W of linear motor 10a
a are Y-connected, and air-core coils 122Ub to 122Wb of the linear motor 10b are connected in series for each phase. Similarly, the air-core coils 122Uc to 122Wc of the linear motor 10c are also Y-connected.
Air core coil 122tld of linear motor 10d for each phase
~122 Wd are each connected in series. In other words, the same thrust force is always generated in the linear motors 10a and 10b, and the document scanning mirror stand a is moved in parallel in the X direction. linear motor 10c
, 10d.

Next, the wire pulley mechanism 20 will be explained in detail with reference to FIG.

Pulleys 21 and 22, which are respectively pivotally supported on the copying machine body near both ends of the stator 11b, have wires 24 for pulling the original scanning mirror stand a and the drum projection mirror stand.
．． 25 (steel wire, etc.) are each turned. Furthermore, a wire 24, 25 is wound around a pulley 23 which is pivotally supported on the upper surface of the drum projection mirror stand two to three times. Note that, as shown in FIG. 2(b), the pulley 23 is composed of two boozes IJ 231 and 232 that are pivotally supported by the same shaft.

To explain in more detail, the wire 25 whose end Ae is connected to the front side of the original scanning mirror stand a in the figure is wound around a pulley 231 in the middle, and the end that is returned toward the original scanning mirror stand is fixed. It is designed to be connected to the rear base frame of the child 11b (see Fig. 5(a)).
. On the other hand, the wire 24 whose end Be is connected to the side surface of the document scanning mirror stand a on the far side in the figure is connected to a pulley 21,
Wrap the end around the pulley 22 one after another, wrap it around the pulley 232, and then return the end toward the pulley 22 to the stator 1.
It is designed to be connected to the front base frame of 1b (see FIG. 5(b)).

In other words, the wire pulley mechanism 20 mechanically connects the mirror stand a for document scanning and the mirror stand for drum projection. The structure is such that the movement is restricted so that the speed ratio with respect to the mirror stand is 2:1 (see FIG. 5(C)).The movable part mass m1 of the mirror stand a for document scanning is It also includes a first mirror and movers 12a and 12b (not shown), and the same applies to the movable part mass m2 of the drum projection mirror stand.

The electrical configuration of the optical system moving device will be described below with reference to FIG.

The near motor control unit 30 that controls the speed of the original scanning mirror stand a and the drum projection mirror stand is mainly composed of a microcomputer 31 called a software servo, and includes photodetectors 124a and 124c.
The pulse signals 313 and 314 are introduced into the microcomputer 31, which generates a PWM speed signal 311 and a PWM speed signal 312 corresponding to the moving speeds of the document scanning mirror stand a and the drum projection mirror stand. The speed commands are given to the three-phase drivers 32 and 33, respectively.

Moreover, the Hall element 123υa 5123Va, 12
The signal 322 from 3Wa is switched in the three-phase driver 32 into which the signal 322 is introduced, and here a three-phase drive current according to the duty ratio is produced, and the produced three-phase drive current is sent to the mover 12a via the signal 321
, 12b, respectively. Note that the same applies to the three-phase driver 33, so a description thereof will be omitted.

In other words, the linear motor control unit 30 controls the three-phase drive current to control the thrust F of the movers 12a, 12b in the linear motors 10a, 10b, and the movers 12c, 12d in the linear motors 10c, 10d.
The configuration is such that the thrust force F2 of the two thrusters is controlled respectively.

Hereinafter, a detailed explanation of the operation of the optical system moving device configured as described above will be explained with reference to FIG. In the figure, the solid line shown in the figure shows the speed pattern of the mirror stand a for document scanning, and the dotted line shows the speed pattern of the mirror stand for drum projection.

First, for convenience of explanation, we will start with the document reading period. At time t1 in the document reading period, the mover 12
After generating a predetermined initial thrust in the movers 12c and 12d, respectively, the original scanning mirror table a
, the drum projection mirror stand is controlled at a constant speed of V and V/2, respectively. However, ■ is the document scanning speed.

Furthermore, at time t2 when the document reading period ends, the movable elements 12a, 12b, and 12c and 12d generate thrust necessary to return the original scanning mirror stand a and the drum projection mirror stand in the opposite direction. .

At this time, movers 12a, 12b, mover 12c
, 12d, the thrust forces F+ and Fz generated respectively are F
It is set in advance so that the relationship 2/F l ≠m, /(2·ml) holds true.

In other words, the conditions regarding the thrust forces F3 and Fz required to ideally return at high speed the document scanning mirror stand a and the drum projection mirror stand whose movements are regulated at a speed ratio of 2:1 by the wire pulley mechanism 20 are as follows. ,F2/F,=mt/
(2·m,), but at the initial stage of return acceleration, this condition does not hold true, that is, the mover 12a
, 12b, and the thrust forces F+ and Fz generated in the movers 12c and 12d, respectively, are set to be unbalanced.

However, the unbalanced thrust generated in this way is quickly transmitted to the other movers 12 via the wire pulley mechanism 20, so that the thrust force F+ of the movers 12a, 12b, movers 12c, 12d,... Fz is FZ /
F + = m! / (2・m+) will be actively returned in a direction that satisfies the condition. This is
This means that transient vibrations that occur when the document scanning mirror stand a and the drum projection mirror stand are returned at high speed can be rapidly brought to a halt. The relationship between the surplus thrust Fs corresponding to the unbalanced thrust described above and the initial tension F0 of the wire 24.25 is Fo,>Fs
It's Nishide.

Furthermore, at time t3 during the return, a reverse thrust force necessary to stop the document scanning mirror stand a and the drum projection mirror stand is applied to the movers 12a, 12b, mover 12c,
12d, the case is exactly the same as the above case except that the direction of acceleration is changed.

After the time t4 when the return is completed and the original scanning mirror stand a and the drum projection mirror stand stop, there is a slight margin period, and then the original scanning mirror stand a is returned to the origin position. Accelerate the drum projection mirror stand again and return it to the original reading position. This completes a series of copy cycles.

Therefore, in the case of this embodiment, since the configuration is such that the transient vibrations that occur at the initial stage of return acceleration of the mirror stand a for document scanning and the mirror stand for drum projection can be actively converged, the return acceleration can be reduced as a result. It will be possible to raise it even higher than the current level. Moreover, since the linear motor 10 employs a three-phase brushless linear motor, the weight of the movable element 12 can be reduced, and the movement of the document scanning mirror stand a and the drum projection mirror stand can be controlled at high speed and with high precision. will be possible.

Note that the optical system moving device according to the present invention is not limited to the configuration of the wire pulley mechanism or the type and number of near motors.

<Effects of the Invention> As described above, in the case of the optical system moving device of the present invention, the transient vibration that occurs at the initial stage of return acceleration of the mirror stand for document scanning and the mirror stand for drum projection can be actively converged. As a result, a large return acceleration can be achieved, and the optical system can be moved at high speed and with high precision. Moreover, since the thrust forces generated in the first movable element and the second movable element are complemented by each other via the wire pulley mechanism, the thrust forces generated in the first movable element and the second movable element are substantially complementary to each other. The child can be made smaller,
Therefore, the entire device can also be downsized. Therefore, it is possible to sufficiently cope with the recent increase in speed and compactness of copying machines.

[Brief explanation of the drawing]

1 to 8 are explanatory views of embodiments of the optical system moving device according to the present invention. Figure 1 is a schematic mechanical configuration diagram of the optical system moving device, Figure 2 (a) is a layout diagram of the linear motor in the mirror stand for document scanning, Figure 2 (b)
Figure 3 is a layout diagram of the linear motor in the mirror stand for drum projection, Figure 3 is a front view of the mover in the linear motor, Figure 4
Figure 5 is a partial front view of the stator in the near motor, Figure 5 is an explanatory diagram of the connection of the wire pulley mechanism, Figure 6 is the electrical connection diagram of the winter air core coil in the mover, and Figure 7 is the electrical connection diagram of the optical system moving device. FIG. 8 is a copying cycle diagram of a mirror stand for document scanning and a mirror stand for drum projection. 9th
10 are diagrams for explaining the schematic configuration of a conventional optical system moving device, FIG. 9 is a perspective view of the first conventional example, and FIG. 10 is a perspective view of the second conventional example. be. 10a, 10b, 10C, 10d --- Linear motor 11a, llb --- Stator 12a, 12b, 12c, 12d ---
- Mover 20...Wire pulley mechanism 30...Linear motor control unit a...Mirror stand for document scanning b...Mirror stand for drum projection Patent applicant Sharp Corporation

Claims (1)

[Claims] (1) A linear motor for independently moving first and second movers provided on a mirror stand for document scanning and a mirror stand for drum projection in the document scanning direction on a common stator; a wire pulley mechanism for regulating the movement of the mirror stand and the mirror stand for drum projection at a speed ratio of 2:1, and masses of the movable parts of the mirror stand for document scanning and the mirror stand for drum projection, respectively, being m_1 and m_2; When the respective thrust forces of the first and second movers are F_1 and F_2, respectively, 2m_1・F_2≠m_2・F_1 at the initial stage of return acceleration of the document scanning mirror stand and the drum projection mirror stand.
An optical system moving device for a copying machine, comprising: a linear motor control section that applies drive currents to the first and second movers, respectively, satisfying the following relationship.