JPH0448207B2 - - Google Patents

Description

[Detailed Description of the Invention] A. Field to which the Invention Pertains The present invention provides a method for moving a stationary original image using a moving optical system.
The present invention relates to an optical scanning type exposure apparatus that performs slit exposure on the surface of an object to be projected, such as a photoreceptor, which is driven in surface movement. More specifically, the present invention relates to an improved structure of a light shielding member provided for opening and closing an exposure section.

B. Prior art There are various structures of optical scanning exposure devices.
It is used as an exposure mechanism and means in image forming devices such as copying machines, printers, and image reading devices, as well as in various other optical devices.

As a specific example, FIG. 1 shows a slit that is equipped with a moving optical system and enlarges and projects a microfilm frame image as an original onto the surface of a rotating drum-type electrophotographic photoreceptor (hereinafter abbreviated as photosensitive drum) as a projection object. This figure shows a schematic configuration of a microfilm enlarging printer that prints by exposing it to light.

In this example printer, 3 is microfilm F.
This is the frame image portion to be printed, and is positioned at a predetermined position on a setting table (not shown). The film image 3 is illuminated from the back side of the film by an illumination lamp 1 and a condensing lens 2, and the illumination light transmitted through the film is transmitted through a projection lens 4, a movable first plane mirror 5, a movable second plane mirror 6, and a slit member. The film image 3 is incident on the exposure section 20a surface of the photosensitive drum 20, which is rotationally driven in the direction of arrow C at a circumferential speed V, through a moving optical system consisting of 8, etc., and the film image 3 is enlarged with respect to the surface of the rotating photosensitive drum 20. Projection slit exposures are made sequentially.

That is, the movable first plane mirror 5 and the second plane mirror 6 are mounted and supported by a common movable support member 35 so that their surfaces including the reflective surfaces intersect with each other at right angles. Both the mirrors 5 and 6 are also driven forward to the right and back to the left by a drive mechanism (not shown), so that the mirrors 5 and 6 are also moved forward (E) and back (E). Regarding mirrors 5 and 6 in Fig. 1, the two-dot chain line indicates the forward movement start point position (home position) of both mirrors, the three-dot chain line indicates the forward movement end position, and the solid line indicates the forward movement start position of both mirrors. This shows the state at the time when the forward movement position is exactly at the halfway point between the same end point position. In response to the exposure start signal, the first and second plane mirrors 5 and 6 are driven forward from the forward movement start point position at a speed of 1/2 of the rotational circumferential speed V of the rotating photosensitive drum 20. Until reaching the end point of the forward movement, enlarged images of the film image 3 are sequentially slit-exposed onto the circumferential surface of the rotary drum 20 from one end to the other in synchronization with the moving speed of the drum circumferential surface. The slit member 8 is for regulating the exposure area on the circumferential surface of the photosensitive drum into a band shape in the drum generatrix direction using the slit portion 8a. When the mirrors 5 and 6 reach the forward movement end point, they immediately switch to the backward movement E' and are returned to the initial forward movement start position and wait. The optical principle of slit exposure using the above-mentioned first and second movable plane mirrors 5 and 6 is well known, so its explanation will be omitted.

The print execution process in the printer of this example follows the electrophotographic process disclosed in Japanese Patent Publication No. 42-23910 or Japanese Patent Publication No. 43-24748. It has a three-layer structure consisting of a conductive layer (for example, a CdS layer) and a conductive layer as a base, and is uniformly charged in advance by a charger 10, and is simultaneously exposed to an image slit by the moving optical system at an exposure position 20a using a charger 1.
The electrostatic latent image corresponding to the film image 3 is formed on the surface of the photosensitive drum 20 by being neutralized by a charge 9 having a polarity opposite to 0, and then uniformly exposed by a light irradiation lamp 11 over the entire surface. This electrostatic latent image is then developed with toner 17 of the developing device 12. The toner image is then transferred to a transfer discharger 1.
4 onto the transfer material 13. After the transfer, the transfer material 13 is sent to a fixing device (not shown) and the image is fixed thereon.
It is printed and ejected outside the machine. On the other hand, although a small amount of untransferred toner remains on the surface of the photosensitive drum after passing through the transfer section, these residual toners are scraped off by the blade 16 of the cleaner 15 and collected.

In such devices, especially in the case of printers that produce positive images from negative film, in order to prevent wasteful toner consumption, it is necessary to limit the exposure of the photosensitive drum circumferential surface to only the image area corresponding to the size of the transfer material. It is desirable to form an image using the photosensitive drum, and to block light as much as possible from the non-image area on the circumferential surface of the photosensitive drum to prevent toner from adhering to that area.

As shown in FIG. 1, one method for this is to apply a mask B to a portion of the surface of the film F other than the image area corresponding to the size of the transfer material, and to cut off the light projected onto the photosensitive drum surface in that portion. is possible. However, when printing is performed by arbitrarily changing the magnification of the projection lens 4, there is a corresponding projection position on the photosensitive drum surface of the scanning start side tip A of the film image 3 positioned and set on the film set table. If the scanning mirrors 5 and 6 are at the _a1 position on the surface of the photosensitive drum 20 in FIG. 1 at the selected projection magnification, then when a projection lens with a higher magnification is used, the scanning mirror 5 , 6 are at the same position, the corresponding projection position of the leading end A of the film image on the photosensitive drum surface is shifted to position _a2 where exposure starts earlier than position _a1 . this a ₂
The position corresponds to the position away from the leading edge of the transfer material applied to the surface of the photosensitive drum 20 in the transfer unit 14, and originally the light should be cut off to prevent toner from adhering _.
The light will hit the area between ~a and ₂ . This problem can be solved by changing the position of the mask B in accordance with the magnification conversion of the projection lens 4, or by shifting the optical axis by moving the position of the projection lens 4 in a direction perpendicular to the optical axis. However, it is troublesome to perform these operations every time the lens is converted (magnification conversion), and the mechanism becomes complicated.

Therefore, the slit portion 8a is usually used as a second means.
There is a method in which a light shielding member 7 (hereinafter referred to as a shutter) is provided to open and close the shutter, and exposure to the circumferential surface of the photosensitive drum 20 is limited to only an image area corresponding to the size of the transfer material by controlling the opening and closing of the shutter. Be taken. FIG. 2 is an enlarged view of the shutter section, and the shutter 7 is rotated counterclockwise and clockwise about a shaft 7a by a drive mechanism (not shown) to open and close the slit section 8a. The figure shows the shutter in the middle of opening and rotation. In the case of this shutter method, it is necessary that the shutter opening speed at the start of image exposure to the photosensitive drum 20 is substantially synchronized with the rotational peripheral speed of the photosensitive drum 20. However, even if the synchronization is not perfect, it is acceptable for practical purposes even if it is approximate to some extent.

To explain this with reference to FIG. 2, when the slit opening speed D of the tip 7b of the shutter 7 is faster than the circumferential speed V of the photosensitive drum 20 and the projection position of the image tip A on the drum surface reaches the _a1 position. , assuming that the shutter 7 has already finished opening, the end of the exposed area area beyond the a ₁ position is the a ₃ position (the position of the regulation line on the downstream side in the drum rotation direction of the photosensitive drum exposure area 20 a that is defined by going up to the slit part 8 a). ) is also exposed. At this time, the exposure amount for the drum surface area between the _a3 position and the _a1 position becomes as shown by the slope line shown in the graph of FIG. 5a. That is, even if the amount of irradiated light is constant, the actual amount of light on the photosensitive drum surface changes, and the image density changes. Furthermore, if the opening speed of the shutter 7 is slower than the circumferential speed V of the photosensitive drum 20, for example, if the projected position of the leading edge A of the image on the drum surface is at the _a4 position when the shutter ₇ finishes opening, then The drum surface area between the _three positions from a to a will not be completely exposed. That is, the exposure amount for this drum surface area becomes like the slope line shown in the graph of FIG. 5b, and a situation similar to that described above occurs at the beginning of the image. In the above case, the density change does not appear on the printed image, but in this case, this density change appears on the printed image, resulting in a poor quality image and degrading the image quality. Of course, you should be prepared to waste toner and open the shutter before the transient state when the shutter 7 is opened affects the printed image, but in this case, the leading edge of the transfer material Since the area becomes an image area and toner adheres to it, the transfer material becomes more likely to wrap around the fixing roller of the fixing device.

Therefore, in order to prevent jams and the like from occurring due to such causes and to allow the printer to function stably, the image exposure start point for the drum 20 is slightly shifted from the leading edge of the transfer material to create an area where toner does not adhere to the leading edge of the transfer material. (hereinafter referred to as a leading edge margin) is formed. In such a case, the above-mentioned phenomenon cannot be avoided. Therefore, the opening speed D of the shutter 7 must always be approximately synchronized with the rotational circumferential speed of the drum 20.

Therefore, as a synchronization means, it is possible to adjust the shutter opening speed by braking with a flywheel and synchronize the shutter opening speed with the drum circumferential speed. It is possible to obtain a shutter opening speed that is always stable and substantially synchronized with the circumferential speed of the photosensitive drum 20 by minimizing the influence of stabilizing factors. However, in this flywheel type device, the rotational energy of the flywheel must be quickly absorbed when the shutter opening operation or light shielding is completed. If I do not,
At each point in time, the shutter rebounds due to the reaction of the flywheel and jumps out into the exposed area, causing problems such as vignetting and light leakage due to incomplete light shielding. Using a damper such as a dart pot is considered to be the most effective method for quickly absorbing the rotational energy of the flywheel, but the device becomes complicated and expensive. Furthermore, it is possible to provide sufficient margin in the movable range of the shutter so that there is no problem even if the shutter rebounds, but this is not so desirable as it causes space problems and requires a large stroke of the solenoid for moving the shutter.

C. Object/Structure of the Invention The present invention provides the latter second means described above, that is, the shutter 7 is provided, and the photosensitive drum 2 is opened and closed by opening and closing the shutter.
Regarding an optical scanning type exposure device that controls the exposure area for 0 within the necessary range and also uses a flywheel to approximately synchronize the opening speed D of the shutter with the circumferential speed V of the photosensitive drum, when the shutter opening operation is completed or the light shielding is completed. The purpose is to provide this type of exposure apparatus with a simple and compact structure at low cost by devising a simple structure that reliably absorbs the rotational energy of the flywheel.
The gist of the present invention is the configuration described in the claims.

D. Example A detailed description will be given below based on an example shown in FIGS. 3 and 4.

FIG. 3 is a partially cutaway perspective view of the shutter opening/closing mechanism, and FIG. 4 is a partially cutaway side view of the shutter opening/closing mechanism. The slit member 8 is fixedly supported by a stationary member such as a device chassis (not shown). Reference numerals 8b and 8b denote side plates bent upward on the longitudinal front side and back side of the slit member 8, respectively.
The opening/closing rotation center shaft 7a of the shutter 7 is provided on the outer surface of the shutter 7, respectively.
7a has been planted. Reference numerals 7c and 7c are arm plates bent upward on the longitudinal front side and rear side of the shutter 7, respectively, and the upper ends of the arm plates 7c and 7c are implanted in the slit member side plates 8b and 8b, respectively. The shafts 7a and 7a are connected and supported so as to be freely rotatable about the shafts.

Reference numerals 33 and 34 denote first and second stopper members provided on the lower surface of the slit member 8 to restrict the rotational movement range of the shutter 7. Shutter 7 is the fourth
The shaft 7 until its tip side 7b abuts and is received by the first stopper member 33 as shown by the solid line
Clockwise around a and 7a (shutter closing direction)
When the slit portion 8a of the slit receiving member 8 is rotated, the shutter 7 is located below the slit portion 8a of the slit receiving member 8, and the shutter 7 completely closes the slit portion 8a (completely blocking light). On the other hand, when the shutter 7 is rotated counterclockwise (shutter opening direction D) until the rear end side 7d abuts and is received by the second stopper member 34, as shown by the two-dot chain line in FIG. The slit portion 8a becomes completely open due to the relief of the portion 7.

Reference numeral 27 denotes a spring which is fixed with one end fixed to the arm plate 7c of the shutter 7 and the other end fixed to the side plate 8b of the slit member 8, and the shutter 7 is constantly rotated in the shutter opening direction D by the tensile force of this spring 27. Receive a moving force.

Reference numeral 26 denotes an electromagnetic solenoid plunger mounted and supported on the outer surface of the slit member side plate 8b, and its advance/retreat plunger 26a' and shutter arm plate 7c are connected via a connecting rod 25. When the solenoid is energized, the plunger 26a is retracted, and the shutter 7 is connected to the shafts 7a, 7a via the connecting rod 26.
The shutter is rotated about the shutter in the shutter closing direction against the spring 27.

Reference numeral 28 denotes a half-moon-shaped gear that is loosely fitted onto one shutter rotation center shaft 7a and is integrally attached to the outer surface of the shutter arm plate 7c. It rotates around the shaft 7a.

29 is a shaft implanted on the outer surface of the slit member side plate 8b adjacent to and parallel to the shaft 7a;
A small gear 3 that meshes with the semicircular gear 28 is connected to this shaft.
0 is loosely supported. Reference numeral 30a designates a boss portion integral with the small gear, into which a flywheel 32 is press-fitted via a one-way clutch 31. The flywheel 32 is rotatable clockwise above the boss 30a via the one-way clutch 31.

Next, the operation will be explained. Simultaneously with the ON operation of the print button provided on the device operation panel (not shown), the solenoid 26 is turned on (energized), and the shutter 7 rotates clockwise around the shafts 7a, 7a against the tension spring 27. Thus, the slit portion 8a is kept closed. Then, when the scan mirrors 5 and 6 reach the starting point of the image (actually, there is a time delay in the operation of the solenoid 26, so the timing must take this into account), the solenoid 26 is turned off, and the tension is The shutter 7 moves in the direction of arrow D due to the spring 27.
It begins to open in the direction. At this time, the half-moon gear 28 also rotates counterclockwise together with the shutter 7, causing the small gear 30 meshing therewith to rotate clockwise. Furthermore, a clockwise rotational force is applied to the flywheel fitted onto the boss portion 30a of the small gear 30 via the one-way clutch 31. This direction of rotation is between the one-way clutch 31 and the flywheel 3.
2, the small gear 30 and flywheel 32 rotate clockwise as one. When the shutter 7 rotates open and reaches an open position where its rear side 7d abuts the second stopper member 34, further rotation of the shutter 7 is stopped. At the same time, the small gear 30 also stops. At this time, the flywheel 32 also receives a force in the direction of stopping, but the action of the one-way clutch 31 allows the flywheel 32 to freely rotate relative to the boss portion 30a of the small gear 30 until the rotational energy is absorbed in some way. Continue rotating. Normally, this rotational energy is absorbed by the frictional force generated between the boss portion 30a of the small gear 30 and the one-way clutch 31. Therefore, when the shutter 7 stops at the open position, no reaction force is generated by the flywheel. In addition, the frictional force generated between the boss portion 30a of the small gear 30 and the one-way clutch 31 always acts on the shutter 7 in the opening direction.
Acts in the direction of pressing against the reaction force received when it comes into contact with 4. Therefore, there is no need to provide a special cushioning material such as moltoprene or rubber between the rear end 7d of the shutter 7 and the second stopper member 34.

Next, when the exposure is completed, the solenoid 26 is turned on, and the shutter 7 is rotated in the closing direction against the tension spring 27. At the same time, the half-moon gear 28 attached to the shutter 7 rotates clockwise.
Furthermore, the small gear 3 meshing with the half-moon gear 28
Rotate 0 counterclockwise. At this time, small gear 3
0 and the one-way clutch 31 are in a free state, and the inertial force of the flywheel 32 does not act as a load on the rotation of the shutter.
Although the frictional force generated between the two acts as a load, it can be ignored compared to the inertial force when the flywheel 32 is connected. ). It is desirable that the shutter 7 be closed at a fast speed in order to minimize the exposed area and reduce toner consumption. Therefore, it is preferable that the load acting on the shutter 7 be as small as possible. Therefore, the device according to the present invention meets these requirements. Furthermore, Shyatsuta 7
When the flywheel 32 rebounds in the D direction due to the reaction force generated when it comes into contact with the first stopper member 33 in the closed position, the inertial force of the flywheel 32 acts in a direction to press it down, so the shock absorbing force described above is also applied to this part. The material is no longer needed.

In the above embodiment, the one-way clutch 3 is used to give the flywheel 32 one-way rotation.
1 was used, but the same effect can be obtained by using a ratchet mechanism, a coil spring, or the like.

Effect As described above, according to the present invention, the flywheel 3
The end point of the opening/closing movement of the light shielding member 7 can be achieved with a simple structure in which a one-way torque transmitting member is inserted so that the light shielding member 7 rotates in conjunction with the opening/closing operation of the light shielding member 7 only in one direction and is free to rotate in the other direction. This eliminates the inconsistency caused by the rotational inertia of the flywheel at the time of arrival, and the intended purpose can be well achieved, making it an effective and suitable improvement for this type of optical scanning exposure device with a built-in shutter and flywheel. be.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of an example of a microfilm enlarging printer with a built-in optical scanning exposure device.
Fig. 2 is an enlarged side view of the shutter section, Figs. 3 and 4 are partially cutaway slope views and partially cutaway side views of the shutter opening/closing mechanism constructed according to the present invention, and Fig. 5a. , b are graphs showing the relationship between the exposure starting point position on the photosensitive drum surface and the exposure amount. 32 is a flywheel, 31 is a one-way clutch, 7 is a shutter, and 8a is a slit portion.

Claims (1)

[Scope of Claims] 1. In an optical scanning exposure device that slit-exposes a stationary original image onto the surface of an object to be projected, such as a photoreceptor, which is driven to move in plane, by means of a moving optical system, an exposure unit is opened and closed. A unidirectional rotational force transmitting member is provided so that the flywheel, which rotates in conjunction with the operation of the provided light shielding member, rotates in conjunction with the opening/closing operation of the light shielding member only in one direction, and is rotatable in the other direction. An exposure apparatus characterized in that the exposure apparatus is connected to a light shielding member side through a light shielding member.