JPH0769573B2 - Variable magnification image forming device - Google Patents

Description

The present invention relates to an improvement for stably operating a magnification conversion device of an image forming apparatus such as a copying machine.

[Conventional technology]

As a magnification conversion device for an image forming apparatus, there is a system that changes the total optical path length in addition to a system that uses a zoom lens. This is widely adopted because a wide variable range of magnification can be obtained at low cost compared to the zoom lens system. ing. An electronic copying machine using this method will be described with reference to FIGS. 3, 4, and 5.

This electronic copying machine is equipped with a light source lamp 2 for illuminating a document screen on a document table 80 and a mirror 4, and a first traveling table A as a first traveling means for traveling at a scanning speed u and a guide rail (see FIG. (Not shown), a mirror 5 and a mirror 6 (both mirrors 5 and 6 are generally referred to as a V mirror) are mounted, and are axially fixed together with the movable pulley 12 so as to move in the same direction as the first traveling platform A. A second traveling platform B as a second traveling unit, a guide rail (not shown), and a movable pulley platform 70 for changing the V mirror position that is movable in the same direction as the first traveling platform for magnification conversion. A lens moving table 40 equipped with the projection lens 7, a mirror 8 and a photosensitive drum 9 as an image forming surface are arranged.

By moving the lens moving base 40 and the moving pulley base 70, the V mirrors 5 and 6, that is, the initial position of the second traveling base B and the lens 7 are moved to a predetermined position for equal magnification or reduction or enlargement as shown in FIG. Are positioned respectively.

A pulley driven by a motor 10 as shown in FIG.
The first half W ₁ of the wire wound around 11 is wound around a moving pulley 12, passes through a pulley in the middle, and is wound around a pulley 14 on a moving pulley stand 70 and fixed on the moving pulley stand. The second half W _{2 of the} wire is wound around the pulleys 12 in the opposite direction of W ₁ after winding several pulleys on the way, and then the pulleys on the moving pulley stand 70 are passed through the intermediate pulleys. Wound on 22 and wire W ₂
The ends of are fixed on the moving pulley table 70. The above is set symmetrically as shown in FIG.

On the other hand, the lens 7 on the lens moving table 40 is positioned at a predetermined position according to the magnification, and its movement is performed as shown in FIG. That is, the latter half of the wire wound around the pulley 28 driven by the stepping motor 58 is connected to the pulley 32.
After that, it is fixed on the lens moving table 40. The first half of the wire is wound around the pulleys 29, 30, 31 and fixed on the lens moving base 40 in the same manner. A cam 85 is pivotally fixed on the rotary shaft of the pulley 30 so that it can rotate integrally with the pulley 30.
Therefore, by operating the stepping motor according to each magnification, the set position of the lens and the rotation angle of the cam 85 are determined. A cam follower 86 pressed by the cam 85 is fixed to the movable pulley table, and the initial position of the movable pulley block 70 is determined by the rotation angle of the cam 85. In this way, the initial position of the V mirror is set corresponding to the lens position of each magnification.

The magnification conversion is performed in this manner.

[Problems to be solved by the invention]

In the image forming apparatus having the magnification conversion mechanism as described above, a large difference occurs between the tensions of the wires fixed to the moving pulleys from different directions during exposure scanning, particularly when the movement of the exposure scanning member starts. In particular, if this difference in tension is in a direction opposite to the pressing force of the spring that presses the moving pulley base against the cam via the cam follower and is greater than this pressing force, This may result in separation of the cam follower. When the cam and the cam follower are separated, the position of the V mirror deviates from the normal position, the optical path length from the document surface to the lens no longer satisfies the correct image forming condition, and the image formed on the image carrier does not appear. The desired resolution cannot be maintained.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnification conversion mechanism of an image forming apparatus which eliminates such a problem, operates stably, and can obtain a high quality image.

Further, in the above-described magnification conversion mechanism, the movement amount of the movable pulley base 70 is doubled with respect to the movement amount of the second traveling base B, that is, the V mirror, for the magnification conversion at the initial position. The greater the change in magnification, the greater this amount. That is, the amount of movement of the V mirror at the initial position is about 60 mm between the magnifications M = 0.5 and M = 1.
The moving amount of the moving pulley table 70 is doubled to about 120 mm. Therefore, it cannot be said that the moving amount of the moving pulley, that is, the stroke amount of the cam 85, is a small proportion of the size of the device. Therefore, the space occupied by such members is very large, which is a serious obstacle to downsizing the device. And this becomes remarkable as the change in magnification increases. Therefore, a pulley is added on the moving pulley block, a fixed pulley is provided on the main frame corresponding to the adjacent pulleys, and the above-mentioned wire is wound around the pulley on the moving pulley block and the fixed pulley. It is conceivable that the amount of movement of the movable pulley and the stroke of the cam that operates the movable pulley are greatly reduced by using the pulley on the movable pulley as a moving pulley when the movable pulley is moved.

However, reducing the amount of movement of the movable pulley block in this manner contributes to downsizing of the apparatus, but the difference in tension applied to the movable pulley block is further amplified. Therefore, when a pulley is added on such a movable pulley stand to downsize the apparatus, the problem that the optical path length fluctuates during the exposure scanning becomes remarkable.

[Means for solving problems]

A variable-magnification image forming apparatus capable of forming a variable-magnification image on a document, including a first traveling unit having an exposure lamp and a reflecting mirror for scanning the surface of the document, and a scanning unit for scanning the first traveling unit. The second traveling unit that performs scanning in conjunction with each other and reflects the light from the first traveling unit, and the first traveling unit and the second traveling unit are reciprocally moved for scanning. A wire member, which is composed of a portion on the tension side and a portion on the tension side at the time of returning, which makes it possible to move and adjust the initial position of the second traveling means in accordance with the designated scaling factor, and the second traveling means to the designated scaling factor. A pulley as at least one movable pulley that moves with respect to the main body of the apparatus to adjust to a corresponding initial position and stretches a portion of the wire member that is a tension side when moving forward; Stretch the part And a movable pulley base provided with at least one pulley as a movable pulley, and the wire member has a portion which is a tension side at the time of the forward movement with respect to the pulley provided in the second traveling means, and The parts that will be the tension side at the time of returning are tensioned from different directions, and then each part is tensioned by pulleys as different fixed pulleys provided on the device main body side, and then each part is moved by the movable pulley. In a variable-magnification image forming apparatus suspended on different pulleys as moving pulleys provided on a table, the movable pulley table is a device when the second traveling means is moved and adjusted to an initial position according to a designated variable magnification. It has a control means that is movable with respect to the main body and that fixes the movable pulley base to the apparatus main body when the first traveling means and the second traveling means are scanned. Variable magnification image forming apparatus.

〔Example〕

One embodiment of the present invention will be described with reference to FIGS. 1 (a), (b) and FIG. In the figure, components having the same functions as those of the conventional example are designated by the same reference numerals.

FIG. 2 is a schematic view showing a relevant portion of an image forming apparatus incorporating the magnification conversion mechanism of the present invention.

In FIG. 2, the original image on the original table 80 is the first carriage A.
The reflected light emitted by the upper lamp 2 passes through the slit 3 and the mirror 4, and passes through the mirrors 5 and 6 of the second traveling base B which travels at half the traveling speed of the first traveling base A, An image is formed on the surface of the photosensitive drum 9 via the projection lens 7, the optical path restricting member 46, and the mirror 8.

The image projection mechanism in such an image forming apparatus is capable of changing the magnification M of the projected image with respect to the original, and determines the setting position of the projection lens 7 and the initial positions of the mirrors 5 and 6 for each magnification. I am doing it. At this time, the magnification M
In the case of = 1, the initial positions of the mirrors 5 and 6 before the start of exposure scanning and the set positions of the lens 7 are as shown by the solid line in FIG.

Further, the magnification M can be finely switched with almost no step, but here, in addition to M = 1, M = 1.55 for enlargement and M = 0.5 for reduction are exemplified. The initial positions of the lens 7 and the mirrors 5 and 6 at M = 1.55 and M = 0.5 are the positions shown by the dotted lines in FIG. The amount of change in the center position of the mirrors 5, 6 or the amount of change in the second carriage B is 5 between M = 1 and M = 0.5.
8.75 mm, 22.93 mm between M = 1 and M = 1.55, the amount of movement of the setting position of the projection lens 7 is 117.5 mm between M = 1 and M = 0.5, 129.25 between M = 1 and M = 1.55. It is in mm.

Next, a mechanism for converting the movement of the first and second carriages during exposure scanning and the initial position of the second carriage B and the setting position of the projection lens during magnification conversion will be described.

In FIG. 1 (a), for driving the scanning system, one wire is wound around a pulley 11 fixed to the shaft of a motor 10, and the first half W ₁ of the wire is wound around a pulley 12 and further a pulley 13, 1
It is fixed to the movable pulley base 70 by the stoppers 17 via 4, 15 and 16. The above-mentioned pulleys 14 and 16 are pulleys provided on the movable pulley stand, and except for the pulley 12 mounted on the second traveling platform B, are pulleys that rotate around an axis fixed to the main body 1. is there.

The latter half W ₂ of the wire wound around the pulley 11 is wound around the pulley 12 in the opposite direction to the first half W _{1 of the} wire through the pulleys 18 and 19, and the pulleys 21, 22, 23, 24 , 25, and is wound around a pulley 26 on a movable pulley 70 (the pulley 26 is adapted to apply tension to the wire (not shown)), and is connected to a substantially symmetrical wire described later. When the shaft of the motor 10 and the pulley 11 fixed to the shaft are integrally viewed, these wires form a closed loop. The pulleys 22, 24, 25 and 26 are provided on the movable pulley base 70, and each pulley is also provided at positions substantially symmetrical with respect to the optical axis of the lens as shown in FIG. 1 (a). The wires are stretched so that even driving force is applied to both sides.

Further, the first traveling base A incorporating the lamp 2, the slit 3 and the mirror 4 is attached to the first half W ₁ of the wire, and the pulley 12
Is rotatably pivoted on a shaft attached to a second traveling platform B composed of mirrors 5 and 6. Although the first and second traveling bases are not shown, the traveling direction of each traveling base (arrow X
It is designed to be moved by being guided by a rail provided in (). Further, the movable pulley base 70 is also movable in the arrow X direction by the rollers 72 attached thereto being guided by rails 73 on both sides as shown in FIG. 1 (a), for example.

On the other hand, the lens moving base 40 on which the projection lens and the optical path regulating member are mounted can also be moved in the arrow X direction by the rollers 54 provided therein being guided by the rails 55 and 56.

Further, a pulley 33 is provided on the lens moving base 40, and a wire whose one end is fixed on the lens moving base 40 via a spring 34 is wound around a pulley 28 driven by a drive motor 58 via the pulley 32. It is wound around the pulley 30 and the pulley 31 fixed to the shaft of the cam 85 via the pulley 29, and the other end is fixed again on the lens moving base 40.

Each time the setting of the magnification M is changed, the stepping motor 58 fixed to the main body frame 1 is actuated, the pulley 28 driven by this is rotated by a predetermined angle, and the pulley 28 is rotated.
The lens moving table having both ends of the wire wound around is moved in the X direction and set at a predetermined position. Then, the drive transmission of the wire causes the pulley 30 to rotate by a predetermined angle, the cam 85 that can rotate integrally with the pulley 30 to rotate to a predetermined position, and the cam on the moving pulley stand that is in contact with the cam 85. The follower 86 also moves the movable pulley table 70 in the X direction to set it at a predetermined position, thereby setting the initial position of the second traveling table B, that is, the mirrors 5 and 6 in the X direction. The cam 85 and the cam follower 86 are kept in contact with each other by a spring 71 stretched between the body frame 1 and the movable pulley base 70.

Further, during the conversion operation of the magnification M, the operation of the scanning drive motor 10 is stopped, so that the pulley 11 is stopped rotating and the first traveling platform is not moved, so that the predetermined position is always maintained. There is.

Thus, when the position of the lens moving base 40 is set according to the desired magnification M, the initial position of the moving pulley base 70 is determined. As a result, the positions of the second carriage, that is, the mirrors 5 and 6 are determined, and the light distribution adjustment described later is simultaneously performed by the optical path restricting member, and preparation corresponding to each magnification can be performed.

By the way, between the movable pulley base 70 and the main body 1, the single wire W ₁ or wire W ₂ from the pulley 13 or the pulley 21 on the main body 1 side is the pulley 14 or the pulley on the movable pulley base 70.
22 and the pulley 15 or the pulley 23 on the main body side are provided so as to extend in three lines.

Thus, with respect to the moving amount d of the moving pulley table 70, the amount of the wire wound or wound between the pulley 13 and the pulley 14 or between the pulley 21 and the pulley 22 is amplified to 3d.

Therefore, for example, the change range M of the aforementioned magnification M = 0.5 to 1 to 1.5
The maximum amount of movement of the initial positions of the mirrors 5 and 6 between 5 and 58.7
It is 5 mm, and the maximum movement of W ₁ and W ₂ is 58.75 × 2
= 117.5 mm, but the moving amount of the moving pulley block 70 is 117.5 at maximum.
÷ 3 = 39.16mm. Also, the cam 85 can be set to have such a short stroke amount. By thus providing the pulley base 70 and interposing the pulleys 15 and 23 fixed to the main body frame in the middle, the moving amount for changing the magnification of the moving pulley base 70 and the stroke amount of the cam 85 are also 117.5 m.
The size can be reduced from m to 1/3 of that, 39.16 mm, and it is possible to save a lot of space, which contributes to downsizing of the entire device.

In this way, the projection lens 7
When the exposure scanning is started, the set position of and the initial positions of the movable pulley base 70 and the mirrors 5 and 6 are determined, and even if the tension difference of the wire is small, the force is three times larger than the movable pulley base 70. In particular, in the acceleration stage immediately after the drive motor starts up, a force several to several tens of times that of constant speed driving is applied. For this reason, the cam follower and the cam of the movable pulley are separated during the scanning, and the separated two are returned to the contact state again with the impact force, or the contact and the separation are repeated. As a result, the positional relationship between the first carriage A having the light source lamp for exposure and the mirror 4 and the second carriage B having the mirrors 5 and 6 deviates from the prescribed one, and the resolution is low in image formation. Only images can be obtained.

In addition, dents may be formed on the cam and the cam follower, and in some cases, they may be deformed to seriously hinder the image formation state.

In one embodiment of the present invention, FIGS. 1 (a) and (b)
As shown in the perspective view of FIG. 3, a fixing means is provided so that the moving pulley table 70 does not move during scanning.

Therefore, in this embodiment, a friction member 74 made of rubber is attached to the side of the movable pulley base, and the friction member is attached to the main body frame side.
A friction member 75 that is pressed and released is provided opposite to 74. This friction member 75 is made of the same rubber as that bonded to the side portion of the moving pulley base, and when pressed, from a direction substantially perpendicular to the contact surfaces of both friction members 74, 75, A pressing force is applied by the spring 77, and both friction members
It has a structure that generates frictional force between 74 and 75.

On the other hand, as a mechanism for pressing and releasing the above friction part plate,
As shown in the figure, the solenoid 78 and the spring 77 are provided, and the solenoid is not energized except during the magnification conversion operation, and the pressing plate maintains the pressed state. The tension of the spring 77 is amplified by this principle using the support shaft 76 as a fulcrum and acts on the pressing portion to give a vertical reaction force between the friction members 74 and 75. Further, during the magnification conversion operation, the moving pulley needs to be moved to the position corresponding to the designated magnification in accordance with the cam shape. Therefore, the solenoid 78 is energized and the friction member 75 is pressed while the moving pulley is moving. It is supposed to be released. In this case, the attraction force of the solenoid 78 may be set to be slightly higher than the sum of the tension of the spring 77 and the slight frictional force of the movable portion during the pressure release operation.

In the present embodiment, the fixing means is provided on only one side as shown in FIG. 1, but of course, it may be provided on both sides of the movable pulley base in a substantially symmetrical manner.

In this embodiment, the number of mirrors on the second traveling platform B is two, but the number of mirrors is not limited to this.

Now, at the rear position of the projection lens 7 on the lens moving table 40,
As shown in FIG. 1, an optical path restricting member 46 that is rotatable around a shaft 46 'is provided.

The optical path restricting member 46 is moved to a predetermined position by the lens moving base 40 together with the projection lens 7 according to the magnification M as shown in FIG. The optical path regulating member 46 has its shaft 46 'as a bearing.
Lever 51 supported by 41, 42 and attached to the end of shaft 46 '
The cam follower 52 at the tip of the above moves on the rail cam 57 fixed to the main body frame 1. Therefore, the lever 51 is rotated in accordance with the movement of the lens moving base 40 according to the magnification M, and the angle of the optical path restricting member 46 also sequentially changes according to the magnification, so that the amount of light in the slit longitudinal direction after passing through the lens is increased. The distribution of is made uniform.

In this embodiment, the spring 71 may have a force required to press the cam follower 86 against the cam 85, that is, a winding resistance of the wire, and a tensile force slightly higher than the sum of some frictional force of the movable portion. The contact pressure between the cam and the cam follower can be set smaller than the conventional one.
For this reason, the resistance when the cam rotates decreases,
The torque generated by the stepping motor 58 for magnification conversion is now smaller than the conventional one.

From the above, the optical system of the image forming apparatus, which has a wide range of magnification change and does not require enlargement of the apparatus itself, can be reliably operated and obtained at low cost.

〔The invention's effect〕

According to the present invention, each element of the optical system that contributes to image formation when the optical system of the image forming apparatus operates the magnification conversion mechanism to set an arbitrary magnification and starts the exposure scanning, deviates from the normal image formation state. Is eliminated, and in particular, the reduction in resolution in the scanning direction has been eliminated.

[Brief description of drawings]

FIG. 1 (a) is a perspective view of an image projection mechanism of one embodiment of the present invention. FIG. 1 (b) is a perspective view showing a main part of the present invention. FIG. 2 is a schematic view showing a relevant portion of the image forming apparatus of one embodiment of the present invention. FIG. 3 is a schematic diagram of an image forming apparatus having a general optical path length changing type zooming mechanism. FIG. 4 is a schematic diagram of a conventional magnification conversion mechanism. FIG. 5 is a perspective view showing a winding state of a wire for operating exposure scanning. 1 ... Main frame, A ... 1st carriage 2 ... Light source lamp, B ... 2nd carriage 4,5,6,8 ... Mirror 7 ... Projection lens 9 ... Photoconductor 10 ... Scan Drive motor 58 …… Stepping motor 12,14,16,22,24 …… Pulley (for moving pulley) 11,13,15,18,19,21,23 …… Pulley (for fixing main body) 40 …… Lens movement Platform 70 …… Movable pulley 71,77 …… Spring 72 …… Roller, 73 …… Rail 74,75 …… Friction member 76 …… Spindle 78 …… Solenoid, 85 …… Cam 86 …… Cam follower

Claims (2)

[Claims] 1. A variable-magnification image forming apparatus capable of forming a variable-magnification image on a document, comprising: first traveling means having an exposure lamp and a reflecting mirror for scanning the surface of the document; Scanning is performed in conjunction with the scanning of the traveling means, and second traveling means for reflecting the light from the first traveling means, and the first traveling means and the second traveling means are reciprocally moved for scanning to reciprocate. A wire member that includes a portion that is a tension side when moving forward and a portion that is a tension side when returning, and that is capable of moving and adjusting the initial position of the second traveling means according to a specified scaling ratio; and the second traveling means. A pulley as at least one movable pulley that moves with respect to the apparatus main body in order to adjust the position of the wire member to an initial position according to a specified scaling ratio, and stretches a portion of the wire member that is a tension side at the time of forward movement; On the return side And a movable pulley base provided with at least one pulley serving as a movable pulley that stretches a portion of the wire member, and the wire member is stretched with respect to the pulley provided in the second traveling means during the forward movement. After the portion that becomes the side and the portion that becomes the tension side at the time of returning are stretched from different directions, the respective portions are stretched by pulleys as different constant pulleys provided on the apparatus main body side, and then, respectively. In a variable-magnification image forming apparatus in which a portion of the second traveling means is stretched around a pulley serving as the different movable pulley provided on the movable pulley base, when the second traveling unit is moved and adjusted to an initial position according to a designated variable magnification, The moving pulley table is movable with respect to the apparatus main body, and the control means for fixing the moving pulley table to the apparatus main body when the first traveling means and the second traveling means are scanned. Variable magnification image forming apparatus, characterized by. 2. The control means fixes the movable pulley base to the apparatus main body by pressing a friction member arranged on the apparatus main body side against the movable pulley base. Item 1. The variable-magnification image forming apparatus according to Item 1.