JP3049750B2 - Scanning optical system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a scanning optical system used in an image forming apparatus that forms an image by scanning a document image on a photoconductor and exposing the same in a copying machine. The slider is supported on the guide so as to support the scanning optical member and reciprocate in the scanning direction, a pulley supported by the slider, and the extension and contraction of the folded portion folded back through the pulley. The present invention relates to a scanning optical system including a drive cable that exerts a moving force in the scanning direction with rotation on a pulley to reciprocate the slider in the scanning direction.

(Prior Art) Conventionally, a scanning optical system having a first slider a and a second slider b as shown in FIGS. 5 and 6 is widely used. The first slider a is moved in the direction of the arrow at the system speed, and scans the image of the original by the light source and the first mirror supported by the first slider a, and the second slider b is 1/1 of the first slider a.
The scanning light is moved at a speed of 2 and the scanning light is directed to a projection lens (not shown) by the second and third mirrors supported by the scanning lens, and the optical path length of the exposure optical path by the projection lens is kept constant, so that image exposure is performed. Achieve at a given magnification.

Such a first slider a and a second slider b
Is driven by a driving cable c stretched as shown in FIG. The driving cable c is driven by the rotation of a driving pulley d whose length is equal to or longer than the scanning distance, and is moved on a pair of pulleys e and f. As a result, the driving ropes c are individually turned around pulleys i and j on the second slider b near both ends g and h fixed to the fixed portion, and are formed with folded portions u opposite to each other. , V extend and the other contracts, and pulleys i and j follow this to move the second slider b. The speed of extension and contraction of the folded portions u and v of the driving rope c is 1/2 of the moving speed of the driving rope c itself, and is the moving speed of the second slider b. On the other hand, the first slider “a” is fixed at one place in the middle of the driving cable “c”,
It is moved at the same speed as the driving cable. Therefore, it is possible to satisfy the 2: 1 driving condition of the first and second sliders a and b only by driving one driving line c.

(Problems to be Solved by the Invention) However, a copied image formed by performing image exposure with the above-described scanning optical system may have a distortion or an unclear portion.
This is because when the second slider b is scanned and moved in the direction indicated by the arrow m, the second slider b floats on the front side in the scanning direction, and the positions of the second and third mirrors fluctuate. Cause.

In recent years, the above-described scanning optical system has been reduced in size with the copier, and in order to make the scanning range as small as possible without reducing the scanning range, the first and second sliders a and b are used.
It is desired to set the shape to be as small as possible and to be able to approach as much as possible while avoiding mutual interference. Due to such a request, the second slider b is set to a side shape as shown in FIG. 6, and the second and third mirrors k,
1 is provided at a position deviated rearward when viewed from the scanning direction indicated by the arrow m.

For this reason, the center of gravity n of the second slider b is located rearward of the center s between the receiving portions q and r of the second slider b on the guide p. It can be seen that it has a rotational moment w that falls down. In addition, when the turn-up portion v extends when the driving cable c moves the second slider b forward, the pulley i,
6 is rotated in the direction of the arrow in FIG. 6 by the driving cable c, and the pulley j on the rear side in the scanning direction rotates near the center of gravity n in the same direction as the rotational moment w of the second slider b. The friction caused by rotation at this time
Works on the slider b, so that the tendency to fall backward due to the rotational moment w is further strengthened. It is considered that this actually caused the receiver to fall, causing the receiving portion q to float.

Accordingly, an object of the present invention is to provide a scanning optical system that can solve the above-described problem by only slightly improving the way of extending the driving cable.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a slider supported on a guide so as to support a scanning optical member and reciprocate in a scanning direction. A pulley that is pivotally supported by the pulley, and a drive rope that applies a moving force in the scanning direction with rotation to the pulley by the expansion and contraction of the folded portion that is turned back through the pulley, and reciprocates the slider in the scanning direction. In the scanning optical system provided, when the slider moves forward, the drive cable is stretched so that the pulley is rotated in the direction opposite to the direction of the rotational moment that is caused by the deviation of the center of gravity of the slider on the guide. It is characterized by having been provided.

(Operation) According to the above configuration of the present invention, when the drive rope moves the slider in the scanning direction via the pulley provided on the slider, the slider is moved along with the movement of the pulley in the forward direction. The pulley is stretched so as to rotate the pulley in the direction opposite to the direction of the rotational moment possessed by the deviation of the center of gravity on the guide, so that when the slider is moved forward, the rotational moment it has The rotational acting force of the pulley acting in the opposite direction cancels the rotational moment, thereby preventing the slider from falling backward during forward movement.

Embodiment An embodiment of the present invention shown in FIGS. 1 to 4 will be described below.

In the present embodiment, the structure for extending the driving cable 3 for driving the first slider 1 and the second slider 2 is improved. As shown in FIG. 4, the drive cable 3 has one end 3a fixed at a point P substantially at the center of the optical box 4 in the scanning direction, and is rotatably supported on the second slider 2 from the point P. After the first folded portion 6 is formed via the left pulley 5, it is fixed at the point Q of the first slider 1.
The driving cable 1 is further wound from the point Q to the driving pulley 8 via the idle pulley 7 at the left end of the optical box 4 by a length equal to or longer than the maximum scanning distance. Right pulley 10 rotatably supported on second slider 2 via pulley 9
The second folded portion 12 is formed through
Is stopped by a lever 13 that can apply tension to the driving cable 1 provided at the right end of the optical box 4.

The first and second sliders 1 and 2 are arranged in the optical box 4 as shown in FIGS. The first slider 1 has slide bushes 15 provided before and after both ends thereof mounted on a first guide rail 16 on the inner surface of the side wall of the optical box 4 and supported so as to be able to reciprocate in the scanning direction. In the second slider 2, slide bushes 17 provided before and after both ends thereof are received on a second guide rail 18 on the inner surface of the side wall of the optical box 4,
It is supported so that it can reciprocate in the scanning direction.

The driving cable 1 is applied to both ends of the first and second sliders 1 and 2. The left and right idle pulleys 7 and 9 are installed in a window 21 formed on a side wall of the optical box 4, and a drive pulley 8 provided outside the optical box 4.
And the bridging portion of the driving cable 1 between them is exposed to the outside of the optical box 4 to enable the bridging as described above.

In addition, if comprised in this way, the intensity | strength of the optical box 4 can be maintained and the installation of the driving cable | cord to the driving pulley 8 can be facilitated.

When the drive rope 1 is driven in the direction of the arrows in FIGS. 1 and 2, the first slider 1 moves forward in the scanning direction at the same speed as the drive stripe 1, whereas the second slider 1 moves in the scanning direction. The slider 2 contracts the first folded portion 6 of the driving cable 1 and the second folded portion 12
As the pulleys 5 and 10 move to the left along with the rotation of the first slider 1, the pulleys 5 and 10 move forward in the scanning direction at half the speed of the first slider 1. As a result, an image of a document (not shown) is scanned by the illumination lamp 31 on the first slider 1 and the first mirror 32. Then, the second slider 2 receives the scanning light from the first slider 1 and sends it to the second and third mirrors 3.
Image exposure is performed to a projection lens (not shown) by 3 and 34, and the optical path length of the exposure light path by the projection lens is kept constant so that image exposure is achieved at a predetermined magnification.

When the driving cable 1 is driven in the direction opposite to the above, the first and second sliders 1 and 2 are moved in the direction opposite to the above and in the same speed relationship as described above, and move to the home position. Is returned.

By the way, the second slider 2 is the first slider 1
The second slider 2 is designed to have the same structure and shape as the above-described conventional case in order to prevent interference and minimize the size.
Its own center of gravity N is deviated to the rear side in the scanning direction from the center S between the slide bushes 17 which is a receiving portion on the guide rail 18. For this reason, a rotational moment W that gives the second slider 2 a tendency to fall backward is generated. However, in the case of this embodiment, when the second slider 2 moves forward,
The pulley 10 located near the center of gravity N is
Is rotated in the counterclockwise direction in accordance with the extension operation of the second folded portion 12 of FIG.
The second slider 2 is provided with a guide rail
It is moved forward stably without floating from 18. Therefore, it is possible to prevent the second slider 2 from floating from the guide rail 18 and causing distortion or unclearness in the exposed image.

In addition, since the pulley 10 at the time of return of the second slider 2 is rotated in the opposite direction to the above, the pulley 10 works in combination with the rotational moment W of the second slider 2 itself, and the second slider 2 is moved by the guide rail 18. It is easy to float from,
No image exposure is performed and no problem occurs.

Also, due to the bearing structure between the pulley 10 and the shaft that pivotally supports the pulley 10 or the shaft that is integral with the pulley 10 and the portion that rotatably supports the shaft on the second slider 2, the larger the friction, the more the characteristic Is often exhibited. Therefore, it is advantageous to use a plain bearing for the bearing.

(Effects of the Invention) According to the present invention, when the driving cable moves the slider in the scanning direction through the pulley provided on the slider, the slider is guided along with the movement of the pulley in the moving direction. It is stretched to rotate the pulley in the direction opposite to the direction of the rotational moment that has due to the deviation of the center of gravity above, and when the slider is moved forward, it is in the opposite direction to the rotational moment it has The rotating pulling force of the working pulley cancels out the rotating moment, so that it is possible to prevent the slider from falling backward during the forward movement, so that it is possible to avoid distortion or unclearness in the image to be exposed.

[Brief description of the drawings]

1 is a perspective view showing a main part of an embodiment of the present invention, FIG. 2 is a partially enlarged view, FIG. 3 is a cross-sectional view showing a state of being mounted on an optical box, and FIG. 4 is an optical box. FIG. 5 is a vertical cross-sectional view showing a state of mounting on a conventional device, FIG.
The figure is a partially enlarged view. DESCRIPTION OF SYMBOLS 1 ... 1st slider 2 ... 2nd slider 3 ... Drive rope 4 ... Optical box 5, 10 ... Pulley 7, 9 ... Idle pulley 6, 12 ... Folding part 16, 18 ... Guide rail 17… Slide bush 31… Illumination lamp 32-34 …… Turning moment

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-164757 (JP, A) JP-A-61-203440 (JP, A) Fully open Showa 56-74452 (JP, U) Really open show 59- 134148 (JP, U) JP-A-3-80446 (JP, U) JP-A 64-55938 (JP, U) JP-A 2-48611 (JP, U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) G03G 15/04-15/04 120 G03B 27/50

Claims (1)

(57) [Claims] 1. A slider mounted on a guide so as to support a scanning optical member and reciprocate in a scanning direction, a pulley pivotally supported by the slider, and a folded portion folded back through the pulley. A driving cable that exerts a moving force in the scanning direction with rotation on the pulley by extension and contraction, and a driving cable that reciprocates the slider in the scanning direction, wherein the guide of the slider is moved when the slider moves forward. A scanning optical system characterized in that the drive cable is stretched so that the pulley is rotated in a direction opposite to the direction of the rotational moment that is caused by the deviation of the center of gravity.