JPS6247666A - White frame forming device for electrophotographic copying machine - Google Patents

Abstract

PURPOSE:To improve reliability by moving a shutter member which adjusts an area to be discharged electrostatically by irradiating a photosensitive body with light through a mechanism which converts the linear motion of a zoom lens in magnification varying operation into the corresponding nonlinear motion. CONSTITUTION:A optical magnification variation system which has the zoom lens 25 is provided and this lens 25 is moved to vary the magnification. The shutter member 50 which adjusts the area on the photosensitive body 10 irradiated with light from the light source 46 in the axial direction of the photosensitive body 10 is moved by the mechanism consisting of the light source 46 which irradiates the photosensitive body 10 with the light, a shutter member 50, grooves 52 and pins 53 which convert the linear motion of the zoom lens 25 during variable power operation into corresponding nonlinear motion, etc., associatively with the movement of the zoom lens 25, thereby forming a while frame.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a white frame forming device for an electrophotographic copying machine, and particularly for forming an inner frame outside an image area in an electrophotographic copying machine with variable copying magnification. This relates to a device for doing so.

(Prior Art) Generally, in a copying machine capable of variable magnification, when a reduced copy is made, a larger non-image area is generated on one or both sides of the photoreceptor in the axial direction than when a copy is made at the same size.

Since this non-image area is not exposed to light, it is in a charged state, and if left as is, it will be developed and toner will adhere to it.

As a result, toner consumption increases, cleaning failure due to increased load on the cleaning device, insufficient capacity of the cleaning device, and furthermore, when transferring to transfer paper that is larger than the image, toner from non-image areas may adhere to the transfer paper. This causes various problems such as a black frame being formed and the appearance being degraded.

Conventionally, in this type of copying machine, a plurality of lamps are arranged along the axial direction of the photoreceptor, and by selectively lighting these lamps, non-image areas are exposed to light and discharged, thereby preventing toner from adhering. A white frame forming device is used to prevent this. In this case, since the area illuminated by one lamp is wide,
It is not possible to change the exposure area to a focal level. Therefore, in stepless variable magnification copying machines, instead of lamps, light sources such as LED elements that can expose only a small area are closely arranged, and strictly speaking, in a stepwise manner. The exposure area is being switched to .

However, in this case, since the exposed area changes stepwise, the exposed area overlaps the image forming area, resulting in a problem that the image becomes missing or unclear. Furthermore, since a large number of LED elements are required, reliability is lowered due to failure of individual parts and lifespan, and an electric circuit for control is required, making the device complicated.

Therefore, the following white frame forming apparatus has been proposed for use in a stepless variable magnification copying machine. That is, a light source that irradiates light along the axial direction is arranged on the photoreceptor, a window for forming a white frame is provided between the light source and the photoreceptor, and a part or all of the window can be opened and closed. Install a shutter. However, by moving the shutter with a motor and controlling the drive of the motor with an electric circuit or a microcomputer according to the set magnification, the exposure area for forming the white frame was continuously adjusted and rotated. It is something.

In this case, a motor and a motor control circuit are required, which increases costs, and since braking control is impossible when using a normal motor, highly accurate control is difficult and reliability is reduced. In addition, if a pulse motor that can be controlled by braking is used, reliability will be improved, but if the power is turned off,
Then, since it can rotate freely, it is easy to shift the position, and it is difficult to turn off the power.
Each time the shutter is turned to N, it is necessary to move the shutter to detect the reference position and then move it again to the set position, which makes the operation complicated.

Therefore, we focused on the fact that there is a correlation between the amount of lens movement during zooming and the amount of change in the exposure area for forming a white frame, and mechanically transmitted the amount of lens movement without using a motor etc. A structure in which the shutter is moved by moving the shutter has also been proposed.

Next, based on FIG. 7, the relationship between the amount of lens movement and the width of the exposure area for forming a white frame when a variable optical path length optical system is used will be explained. FIG. 7(a) is a diagram of the optical layout when the magnification is the same, and FIG. 7(b) is a diagram of the optical layout when the lens is reduced.
Let f be the focal length of

At 0 equal magnification, the position p corresponds to the position of the original table a, and the position q corresponds to the position of the photoconductor. When the lens 101 is at a magnification of 0, the lens 101 is located at the center position r between the position of the document table p and the photoconductor position q. An image having a length h on the document table forms an image having a length h' on the photoreceptor. Here, h'=
It is h. Fig. 7(b) shows lens 1 for reduction copying.
01 is moved toward the photoreceptor by a length of 100 cm. Manuscript′? An image of length h on the L device will be of length h on the photoreceptor.
”, and let K be the 0 magnification that satisfies the following relationship.

Therefore, the width of the exposure area for forming a white frame is expressed by the following equation.

b = h - h '' Therefore, the lens movement distance and the width of the exposure area for forming a white frame are proportional to h/f. If h is the maximum document width on the document table A, h/f becomes a constant. By the way, since the width of the exposure area for forming a white frame is equal to the moving distance of the shutter, the lens moving distance and the shutter moving distance are directly proportional, and the shutter can be moved by moving the lens with a simple conversion mechanism.Especially If the maximum original Il@h and the lens focal length f are determined so that , h=f, the mechanism becomes even simpler.

However, in this case, although it is possible to continuously adjust the exposure area for forming a white frame using a simple mechanism, it is necessary to move the mirror to change the optical path length when changing the magnification. Therefore, there is a problem that the mechanism of the copying machine becomes complicated.

Therefore, recently, zoom lenses have been used in variable magnification optical systems in electrophotographic copying machines.

If a zoom lens is used, the optical path length remains constant even when changing the magnification, so there is no need to change the optical path length by moving a mirror, which simplifies the mechanism of the copying machine.

(Problems to be Solved by the Invention) However, such prior art has the following problems. That is, when a zoom lens is used in a variable magnification optical system, the relationship between the lens movement distance and the width of the exposure area for forming a white frame is different from that of a variable optical path length type, as shown below. FIG. 8(a) is an optical arrangement diagram when using the zoom lens 102 at the same magnification, and FIG. 8(b) is an optical arrangement diagram when the zoom lens is reduced.The focal length of the zoom lens 102 at the same magnification is f, In the illustrated example, one end of the image on the photoreceptor position q in the width direction is always fixed as a one-sided reference.

In the case of a central reference, simply multiplying b by the station will basically not change the relationship between the text and b.Also, even if the lens 102 does not move parallel to the optical axis, the basic relationship between the text and b will not change. do not have.

At the time of reduction, with respect to the movement amount IL3 of the zoom lens 102,
The image length h'' of the photoreceptor 1 for an image of length h on the document table is expressed by the following equation.

Therefore, the width of the exposure area for forming a white frame is expressed by the following equation.

b = h − h ” In other words, the width of the exposure area for forming a white frame is the lens movement amount 9
．． 3, 0 is expressed as a hyperbola on the graph. Therefore, since the exposure area width is equal to the amount of shutter movement, when the shutter is moved by lens movement,
A linear conversion mechanism such as a variable optical path length type cannot be used.
Therefore, the movement of the shutter must be performed by a newly provided motor and an electric circuit for controlling the motor, resulting in problems such as high cost and complicated control.

Therefore, the present invention has been made to solve the above-mentioned problems of the prior art, and its purpose is not only to be able to accurately form a white frame in response to stepless magnification. To provide a white frame forming device for an electrophotographic copying machine, which can simplify the mechanism of the electrophotographic copying machine by using a zoom lens, and can also move a shutter member with a simple mechanism.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an electrophotographic copying machine that is equipped with a variable magnification optical system having a zoom lens and that changes magnification by moving the zoom lens. , a light source that irradiates light onto the photoreceptor, and a region where the light from the light source irradiates the photoreceptor.

a shutter member adjustable along the axial direction of the photoreceptor;
a mechanism for converting a linear motion of the zoom lens during zooming into a non-linear linear movement corresponding thereto, and configured to move the shutter member in response to movement of the zoom lens by the mechanism. There is.

(Embodiment) The present invention will be explained below based on the illustrated embodiment. Fig. 2 is a schematic diagram showing an electrophotographic copying machine to which a white frame forming device according to the present invention is applied. The upper document 2 is illuminated by an illumination lamp 3.

1st for scanning. Second. A third mirror 4,5.6 and a fourth mirror for projection. Fifth. It is projected onto the photoreceptor drum 10 via the sixth mirror 7.8.9. Around the photoreceptor drum 10, there is a primary charger 11. which is a known image forming means. Developer 1
2. Transfer/separation charger 13.14, cleaning device 15
is located. The transfer paper P, which is the final image carrier, is selectively sent out from the paper feed cassette 16, 17 by rotating either of the paper feed rollers 18, 19. Further, the transfer paper P is conveyed by a pair of registration rollers 20 in synchronization with the toner image formed on the photoreceptor drum IO, and after image transfer, the transfer paper P is conveyed onto an ejection tray 24 by a conveyance belt 21, a fixing device 22, and an ejection roller 23. In the figure, 70 indicates a document pressure plate, and 71 indicates a fan for preventing temperature rise of the optical system.

This electrophotographic copying machine allows stepless magnification by changing the position and focal length of the zoom lens 25 without changing the optical path length.

FIG. 3 shows the movement mechanism of the variable magnification optical system. 2
6 is a motor for moving the mirror, and a wire 28 is wound around a pulley 27 fixed to the shaft of the motor 26. This wire 28 is wound around pulleys 29 and 30 that are rotatably supported on the main body of the copying machine, and is further rotatably supported on a support 31 for the second and third mirrors 5 (the third mirror is not shown). It is wound around the 2idi pulley 32 so as to be folded back, and both ends thereof are fixed to the main body. on the other hand,
The first mirror 4 and the support body 33 of the illumination lamp 3 are fixed to the wire 28 by a mounting bracket 34. This support body 33 is provided with a convex portion 33a, and the mechanical operation is controlled by a sensor 35 that detects passage of the convex portion 33a. While the first mirror 4 is moved at a moving speed V by the above mechanism, the second mirror 4 is moved at a moving speed V. 3rd mirror 5
is moved at a moving speed of V/2. The motor 26 may be a C motor or a pulse motor with speed control 1, in order to make the scanning speed of the optical system correspond to the circumferential speed of the photoreceptor at an accurate predetermined ratio.

Next, the moving mechanism of the zoom lens will be explained. The zoom lens 25 is supported by a lens holder 36, and the lens holder 36 is movable by a rail shaft 37 and rollers 38. Further, the lens holder 36 is connected to a wire 40 by a mounting bracket 39, and by moving the wire 40 by a pulley 42 that is rotationally driven by a motor 41, the zoom lens 25 is moved. Note that the bulge at the other end of the wire 40 is not shown in the figure, and the stop position of the zoom lens 25 is determined by calculation from the position where the position detection section 36a provided on the holder 36 passes the sensor 43. Ru. Furthermore, the focal length of the zoom lens 25 can be changed by using a gear 44 attached to a zoom ring (not shown) on the rack 4.
This is done by rotating the zoom ring as the zoom lens 25 moves. Here, since the stopping precision of the zoom lens 25 has a large influence on the image, the motor 41 needs to be capable of braking control, and a pulse motor is generally used.

FIG. 1 shows an embodiment of a white frame forming apparatus according to the present invention. Reference numeral 46 denotes a rod-shaped exposure lamp disposed on the photoreceptor drum IO along its axial direction. A light shielding plate 47 protruding in a substantially U-shape is provided. At the tip 47a of this light shielding plate 47,
An opening 49 (only one side is shown in the figure) is provided so that light from the exposure lamp 46 can illuminate the exposure area for forming a white frame located at both ends of the photoreceptor drum 10. A shutter 50 for opening and closing 49 is provided. As shown in FIG. 2, the exposure lamp 46 and the opening 49 are arranged between the negative charger 11 and the image exposure section, while the lens stand 51 to which the zoom lens 25 is fixed is provided. , a groove 52.52 for driving the shutter is cut into the groove 52.52, and a pin 53.53 protruding from the shutter 50 is engaged with the groove 52.52. Said groove 52.5
2, from position A to position B is formed perpendicular to the axis of the photoreceptor drum IO, and the shutter 50 does not move in this part.

This area corresponds to a portion that does not require exposure for forming a white frame during enlarged copying and same-size copying. However, in order to prevent the toner from going around and adhering to the outside of the image area during full-size copying and enlarged copying, part of the light from the exposure lamp 46 is transmitted to the photoreceptor drum 10 through the opening 49 at this time. irradiated on top. The groove 52 from position B to position C is provided so as to move the shutter 50 and form a predetermined exposure area width for forming a white frame in accordance with the lens movement distance. Since the exposure is based on the center, exposure is performed to form a white frame on both sides of the image.
The shape of the groove 52 is the same as that of the lens mentioned above. 11 to 1
-, the shafter 50 is moved by a distance equal to the frost light radiation b'=-'b (b+s described above) on one side.

In the above configuration, in the electrophotographic copying machine according to this embodiment, the white frame is formed in a first order manner. That is, as shown in FIG.
When a reduction copy is performed in accordance with a.a, non-image areas which are not exposed to light are generated at both axial ends of the photoreceptor drum IO. By the way, since the entire width of the photosensitive drum 10 is charged by the primary charger 11, the non-image area will be developed.
When the zoom lens 25 is moved, as shown in FIG.
．． 53, the shutter 50 moves in the E direction by the exposure area width b' for forming a white frame. Therefore, the exposure lamp 4
6 illuminates an exposure area for forming a white frame on the photoreceptor drum 10 through the opening 49, and charges in this area are discharged to form a white frame on the photoreceptor drum 10. Therefore, toner is not unnecessarily consumed and the cleaning device 15 is not burdened, and even when an image is transferred to a large size transfer paper P, a black frame is not formed. Further, the lens stand 51 to which the zoom lens 25 is fixed has a groove 5.
Since it is engaged with the shutter 50 through 2°52 and pins 53 and 53, the lens drive motor is set to 0FFL,
Even in such a case, the position of the zoom lens 25 can be prevented from shifting to an unsteady position.

Note that the formation of the inner frame in the circumferential direction of the photoreceptor drum 1O is
This is done by a well-known method.

FIG. 4 shows another embodiment of the white frame forming apparatus according to the present invention, and the same parts as in the previous embodiment are given the same reference numerals and will be explained. In addition to being exposed, the mechanism for moving the shutter 50 is different. That is, a light shielding plate 47 disposed between the exposure lamp 46 and the photoreceptor drum IO
An opening 49 is provided only on one end of the photoreceptor drum in the axial direction. When the zoom lens 25 and the lens stand 51 move in the direction of arrow G, the movement of the lens stand 51 is controlled by the rack 54 attached to the lens stand 51.
．． 57 and a rack 58 provided on the shutter 50. However, gear 57
The amount of movement of the shutter 50 in the H direction is adjusted by the rack 58. That is, the rack 58 meshing with the gear 57
As shown in FIG. 5, the pitch P of the south 58a gradually changes in the X direction, and satisfies the above-mentioned nonlinear relationship between the amount of lens movement and the exposure area for forming a white frame. The opening 4
9 is blocked by the shutter 50, and the exposure lamp 46
The light is transmitted to the photosensitive drum 1 only through the opening 49 in the appropriate area.
0 is irradiated.

FIG. 6 shows still another embodiment of the white frame forming apparatus according to the present invention, and the same parts as those in the embodiment shown in FIG. Now, instead of moving the shutter 50.50 by the linear movement of the lens base 51 that moves together with the zoom lens 25, the shutter 50.50 is moved by changing the movement of the zoom lens 25 into a rotational amount. There is.

That is, a rack 59 is attached to the zoom lens 25, and a pinion 60 meshes with the rack 59. A cam plate 62 rotatably supported via a shaft 61 is connected to this pinion 60.
2 has cam grooves 63 and 64 carved therein. Pins 53.53 protruding from the shutters 50.50 are engaged with the cam grooves 63.64. Position A of the cam groove 63
to position B and from position A' to position B' of the cam groove 64.
Up to this point, the zoom lens 25 is arranged concentrically with respect to the axis 61, and corresponds to when the zoom lens 25 is positioned at magnification or equal magnification. Further, the cam groove 63 from position B to position IC and the cam groove 64 from position IB' to position f1G' are provided so as to satisfy the nonlinear relationship of shutter movement with respect to lens movement, as described above.

In the illustrated embodiment, the case where the shutter is moved nonlinearly using cams, gears, racks, etc. has been explained, but the invention is not limited to this, and any mechanism that performs nonlinear conversion can be used to Of course, it is also possible to use a device using a bobbin and a wire, a link mechanism, or the like.

(Effect of the invention) The present invention consists of the above configuration and operation.

Through a mechanism that converts the linear movement of the zoom lens when changing magnification into linear movement that corresponds non-linearly, the shutter member that illuminates the photoconductor to determine the area where static electricity is removed is moved. As a result, it is compatible with electrophotographic copying machines that use a zoom lens to perform stepless magnification with a simple mechanism.Moreover, the movement of the shutter member can be easily performed without using a motor or electric control circuit. This can be done mechanically, making it possible to reduce costs and improve reliability.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an embodiment of the white frame forming device according to the present invention, Fig. 2 is a schematic diagram showing an electrophotographic copying machine to which the white frame forming device is applied, and Fig. 3 is a movement of the optical system. FIG. 4 is a perspective view showing another embodiment of the white frame forming device according to the present invention; FIG. 5 is a front view showing the main parts of FIG. 4;
The figure is a plan view showing still another embodiment of the white frame forming apparatus according to the present invention, FIGS. 7(a) and (b) are explanatory diagrams showing a variable optical path length type optical system, and FIG. 8(a) , (b) is an explanatory diagram showing an optical system using a zoom lens. Explanation of symbols

Claims (1)

[Claims] In an electrophotographic copying machine that is equipped with a variable magnification optical system having a zoom lens and that changes magnification by moving the zoom lens, a light source that irradiates light onto the photoreceptor, and light from the light source irradiates the photoreceptor. a shutter member that can adjust the area to be zoomed along the axial direction of the photoreceptor; and a mechanism that converts the linear movement of the zoom lens during zooming into a linear movement nonlinearly corresponding thereto; A white frame forming device for an electrophotographic copying machine, characterized in that the shutter member is moved in response to movement of a lens.