JPH0241027B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable-magnification copying machine, and more particularly to a copying machine having a copying function of reduction and enlargement in addition to the same-size copying function.

In recent years, as the use of copying machines has increased, various additional functions have been required. One example of this is the request for reduction or enlargement of a document in addition to the same size copy.

On the other hand, apart from the demand for additional functions of copying machines, demands for energy saving, miniaturization, and cost reduction of copying machines have also increased.

In view of these various circumstances, it is an object of the present invention to provide a copying machine that is equipped with the functions of reducing and enlarging copies in addition to the same size, and which is energy-saving, compact, and low-cost. shall be.

In conventional variable magnification copying machines, the speed of the photoreceptor is constant during full-size copying, reduction copying, and enlargement copying, and when reducing copying, the optical scanning system of the original (for example, in a moving optical system copying machine, the mirror It was customary to adopt a configuration in which the speed of the optical system (or document table in movable document table type copying machines) was increased in accordance with the reduction ratio.
Furthermore, since the amount of exposure of the photoreceptor is naturally higher than when the magnification is the same, the diaphragm or optical slit in the lens has been adjusted to make it equal to the value when the magnification is the same.

On the other hand, during enlargement copying, the speed of the optical scanning system is slowed down in accordance with the enlargement ratio, contrary to when reducing the size.
Furthermore, since the amount of exposure of the photoreceptor is naturally insufficient, the amount of light from the original illumination lamp is increased accordingly.

By the way, in general, variable-resolution copying machines are overwhelmingly used for same-resolution copying. Therefore, when designing a variable magnification copying machine, it is ideal to have reduction/enlargement copying functions within the performance range of its component parts and equipment, based on the design specifications of a normal full-size copying machine.

However, in conventional variable magnification copying machines, when making reduction copies, it is necessary to increase the speed of the optical scanning system compared to when making copies at full magnification, so in order to guarantee reliability against this increase in speed, for example, the bearings, supporting members, and driving force of the optical scanning system must be increased. It was necessary to increase the rigidity of the transmission means, that is, to increase the performance of each component in response to the increased speed.

In addition, when making enlarged copies, it is necessary to provide the document illumination lamp, power supply, etc. with a margin so that the amount of light can be increased compared to when making copies at the same size, so that the same amount of exposure can be given as when making copies at the same size. Ta.

In other words, it would be wasteful to improve the performance of parts and equipment as described above or to provide extra margin in order to enable reduced or enlarged copying, which is much less frequently used than full-size copying, and it would be wasteful and increase the cost of the entire device. This is a major cause of high

In addition, increasing the speed of the optical scanning system compared to when the image is magnified requires that the run-up distance be increased in advance in order to prevent blurring at the leading edge of the image, which goes against miniaturization of the apparatus.

Furthermore, increasing the speed of the optical scanning system or increasing the brightness of the illumination lamp compared to the same magnification is undesirable from the viewpoint of energy saving and consumption.

The present invention is a copying machine that eliminates the drawbacks of the conventional variable magnification copying machine as described above.

That is, the present invention provides a variable magnification copying apparatus having an original scanning means for scanning an original and projecting and exposing the original image onto a moving photoreceptor surface, and a magnification conversion means capable of equal magnification, reduction, and enlargement of the original image projected onto the photoreceptor. For reduced copying, the reduction rate is m (m < 1), the photoreceptor speeds for full-size copying and reduced copying are v ₀ and v ₁ , respectively, and the document scanning speeds are u ₀ and u ₁ , respectively. , when v ₁ = mv ₀ u ₁ = u ₀ , when enlarging the copy, the enlargement ratio is n (n > 1), and the photoreceptor speed during full-size copying and enlarged copying is When v ₀ and v ₂ are respectively, and the document scanning speed during enlarged copying is u ₂ , v ₂ = (4/(1+n ² )×v ₀ u ₂ = (4/(n×(1+n) ² ))× This variable magnification copying machine is characterized in that it is executed under the condition of v ₀ .

FIG. 1 shows an embodiment of a variable magnification copying machine to which the present invention is applied.

Reference numeral 1 denotes an original such as a book, 2 a document mounting table (fixed) such as a transparent glass plate, and the original 1 is placed on the table 2 with its copy side facing downward. The placed original is illuminated by an illumination lamp 3, and a first mirror 4 moves integrally with the lamp 3, and a second mirror 5 moves in the same direction at 1/2 the speed of the first mirror 4. The scanned image is formed on a drum 10 rotating in the direction of the arrow by an optical system consisting of a transmission lens 6, a third mirror 7, a fourth mirror 8, and an exposure slit 9. The exposure slit 9 has a constant opening width at any copying magnification, and is disposed near the image forming part of the drum 10 to regulate the amount of exposure to the drum 10.

The surface of the drum 10 is an electrophotographic photosensitive surface formed by laminating an electrically grounded conductive layer, photoconductive layer, and surface insulating layer, and a well-known method can be used to form a latent image thereon. . For example, the residual charge on the surface of the drum 10 is uniformly erased by the pre-charger 11, then it is uniformly charged by the primary charger 12, and then when it reaches the imaging section 13, the original image is formed as described above. At the same time as the drum 10 is exposed, the static electricity is removed by the static eliminator 14, and then the entire surface is exposed by the full surface exposure lamp 15, and an electrostatic latent image is formed on the surface of the drum 10. The latent image on the drum 10 is then visualized by the developing device 16.

The latent image on drum 10 is usually made visible by toner contained in a developer. The visible image on the drum is sent out from the paper feed section 18 at the transfer charger 17 position, and is transferred to the register rollers 19, 20, 2.
1 and 22 onto copy paper 23, which is fed out in synchronization with the rotation of the drum so that its leading edge coincides with the leading edge of the visible image on the drum. The copy paper on which the image has been transferred is then separated from the drum 10 by a separating section 24, guided to a fixing section 25, fixed thereon, and then discharged onto a tray 26 as a copy.

On the other hand, the drum surface after the copy paper has been peeled off is cleaned by a cleaner blade 27 pressed against the drum surface so that the next copying cycle can be applied.

In the figure, the solid line positions of the first mirror 4 and the second mirror 5 indicate the travel start position (forward movement start position) for scanning the original, and the two-dot chain line positions 4' and 5' indicate the maximum size original. Indicates the end position of the forward movement when scanning. When the scanning of the original on the original platen 2 is completed, the mirrors 4 and 5 move back from the positions 4' and 5' to the start position indicated by the solid line.

The magnification can be changed by moving the positions of the inner lens 6 and mirrors 7 and 8 of the optical system.
It is desirable to move the mirrors 7 and 8 integrally in the case of the illustrated example apparatus, since it is easier to perform optical adjustment and the like and the reliability of the apparatus is increased when the number of moving members during magnification conversion is as small as possible.

In FIG. 1, the solid line positions of the lens 6 and mirrors 7 and 8 indicate the positions when copying at the same magnification. When changing the magnification for reduction or enlargement copying, move the lens 6 from the solid line position along the optical axis in the direction of arrow c or d, and move the mirrors 7 and 8 in the direction of arrow e without changing the relative angle of the mirror surfaces. Good.

The position of the lens 6a indicated by the chain line is the position at the time of reduction copying, and at this time the mirrors 7 and 8 are
It will be in position a.

Also, the lens 6b position is the position at the time of enlarged copying, and at this time mirrors 7 and 8 are respectively 7b and 8.
It will be in position b.

If the reduction ratio is the reciprocal of the enlargement ratio, the positions of lenses 6a and 6b will be symmetrical with exactly the same distance from position 6 at the same magnification, and furthermore, mirror positions 7a and 7b and 8a and 8b will be at exactly the same position. Become.

Note that the optical system and magnification changing method in the present invention are not limited to those described above, and the present invention may also be replaced with other optical systems such as an optical system composed of a mirror and an in-mirror lens, or an optical system using a zoom lens. The gist of this will not be lost in any way. Furthermore, in this embodiment, an optical system that can perform one type of reduction and enlargement in addition to the same magnification is shown, but the optical system of a copying machine is not limited to this, and has two or more levels of reduction and enlargement functions. It doesn't matter if it is. Furthermore, although this embodiment has described a copying machine with a moving optical system,
Exactly the same effect can be expected for copying machines with a moving document table.

Design conditions such as the amount of light of the illumination lamp of the copying machine, the circumferential speed of the photoreceptor, and other charging conditions are set on the basis of full-size copying. That is, the amount of lamp light, the circumferential speed of the photoreceptor, etc. are set so that the number of copies is maximized during full-size copying. Even if the number of copies is reduced when enlarging or reducing, this does not pose any problem since the purpose of the present invention is to provide a low-cost, compact, and energy-saving copying machine. This method is based on the idea that since the amount of copies (usage) is much smaller than that of full-size copying, it does not cause much inconvenience to the users of the copying machine.

Now, reduction copying is possible by displacing the members constituting the optical system as described above. However, it is necessary to convert the relationship between the speed of the optical system and the speed of the photoreceptor when reducing the size. Therefore, the speed of the optical system is set to be the same as the speed for full-size copying, and the speed of the photoreceptor 10 is reduced to a value proportional to the reduction ratio (m<1). That is, u ₁ = u ₀ ... (1) v ₁ = mv ₀ (= mu ₀ ) ... (2) Here, u ₀ and u ₁ are the speeds of the optical system at equal magnification and reduction, respectively, and v ₀ and v ₁ are the speeds of the photoreceptor when it is magnified and reduced, respectively.

In this way, there is no part that is mechanically faster when reduced than when it is at the same size, so in terms of design, it is better to guarantee the rigidity, durability, etc. of the parts based on the speed at the same size. good. Furthermore, since there is no need to increase the run-up distance, there is no need to increase the size of the copying machine even though it has a reduction function.

Regarding the amount of exposure of the photoreceptor, if the light amount of the original illumination lamp is constant, it will naturally be larger than the value at the same magnification when the image is reduced, so it is necessary to reduce it until it becomes the same as the value at the same magnification. For this purpose, well-known means such as a method of narrowing down an aperture in a lens or a method of reducing the amount of light from an illumination lamp can be used.

In this way, in any case, there is nothing that consumes more energy than in the case of the original size, so it is possible to obtain an extremely energy-saving copying machine despite having a reduction function.

A method of compensating process conditions for the photoreceptor speed, which is slower than when copying at full size, will be described later.

Next, the case of enlarged copying will be described. When making an enlarged copy, it is necessary to change the relationship between the speed of the photoreceptor and the speed of the optical scanning system from the relationship when making a full-size copy, as in the case of copying. In the case of enlarged copying, the speed of the optical scanning system must generally be made smaller than the speed of the photoreceptor by the reciprocal of the enlargement ratio. Therefore, in a conventional copying machine with an enlargement function, the speed of the photoconductor is the same as the speed at 1:1 magnification, and the speed of the optical scanning system is conversely reduced to satisfy the speed relationship between the photoconductor and the optical scanning system. I'm letting you do it. In this way, the speed of both the photoreceptor and the optical scanning system will not be increased compared to when the magnification is the same, so the copying machine can save energy.

However, with regard to the amount of exposure on the surface of the photoreceptor, such conventional copying machines have the following problems.

In other words, if the speed of the photoconductor during enlarged copying is made equal to that when copying at full magnification, and if all factors related to the exposure amount of the photoconductor, such as the light intensity of the original illumination lamp and the slit width, remain unchanged, then the exposure on the photoconductor will be The amount will be smaller than when copying at the same size. To solve this problem, it is necessary to increase the light intensity of the illumination lamp or widen the exposure slit width. Increasing the width of the slits from the original magnification means further widening the slits that are optimally arranged at the original magnification, making it easier for flare to occur, and thus not producing desirable results.

On the other hand, the method of increasing the amount of light from the illumination lamp deviates from the viewpoint of providing an energy-saving copying machine, which is one of the main objectives of the present invention.

Therefore, in the copying machine of the present invention, the speed of the photoreceptor is reduced to such a speed that the amount of exposure on the photoreceptor during enlarged copying becomes equal to that during full-size copying. The optical scanning system may be moved at a speed commensurate with the magnification factor for the photoreceptor speed determined in this way.

To illustrate this with an example, if the magnification is n (n>1) in the copying machine shown in Figure 1, and the illuminance of the original image on the surface of the photoreceptor is E(n), then E (n)=A/(1+n) ² ...(3) There is a relationship. Here, A is a constant determined by the brightness of the lamp, the type of original, lens transmittance, etc. Therefore, if the drum illuminance at the same magnification is E(1), E(n)/E(1)=A/(1+n) ² )/(A/
(1 + 1) ² ) = 4/(1 + n) ² ...(4) On the other hand, since the amount of exposure onto the photosensitive drum needs to be constant between the original magnification and enlargement, the width of light irradiation onto the drum must be Let w ₂ be the magnification, w ₀ be the same magnification, and let the drum circumferential speeds be v ₀ and v ₂ respectively when the magnification is the same and when the drum is magnified, then E(n)×w ₂ /v ₂ = E(1)×w ₀ /v ₀ ...(5) However, in a copying machine like the one shown in Figure 1, the exposure slit width is constant and is placed near the photoreceptor, so the width of light irradiation onto the photoreceptor can be magnified or magnified. In other words, w ₁ = w ₀ ...(6) Substituting (4) and (6) into equation (5) to find v ₂ gives v ₂ = (4/(1+n) ² ) x v ₀ ...(7) That is, when enlarging when the magnification rate is n (n>1), if the photoconductor is run at a circumferential speed that is 4/(1+n) ² times the circumferential speed of the photoconductor at the same magnification, it will be the same as at the same magnification. The same exposure is obtained on the scan. Also, if the speed of the optical scanning system is u ₂ at this time, then u ₂ = 1/n x v ₂ = (4/(n x (1 + n) ² )) x v ₀ ... (8) From (7) and (8) As is obvious, since n>1, both 4/(1+n) ² and 4/(n(1+n) ² ) are smaller than 1, that is, v ₂ < v ₀ (=u ₀ ), u ₂ < v ₀ ( = u ₀ ), and the speeds of the photoreceptor and the optical scanning system during magnification are both smaller than those during full magnification, making it possible to create an energy-saving copying machine.

Furthermore, as mentioned above, the present invention allows for enlarged copying to be carried out in an extremely simple manner since the other factors other than the speed of the photoreceptor and the optical scanning system are completely unchanged, and the means for achieving this is also low cost. It can be done. Another advantage is that the amount of light from the lamp only needs to be lit in an optimal state.

In this way, the copying machine of this embodiment can achieve the above-mentioned purpose by simply changing the speed of the photoreceptor and the optical scanning system when performing true-size, reduction, and enlargement copies.

This speed switching can be performed as shown in FIG.

The speed change explanatory diagram in FIG. 2 corresponds to the copying machine shown in FIG. In the figure, when copying at the same size, the driving force from the drive motor 28 is transferred to the clutch 29.
It is sufficient to transmit the information to the drum 10, the transfer paper conveying system 31, and the pulley 32 by turning on the signals 30 and 30.

Here, the pulley 32 has a wire etc. (not shown).
is wound around the pulley 32, and the optical scanning system can be moved via a wire or the like by the rotational force of the pulley 32.

At the time of reduction copying, by turning on the clutch 34 via the clutch 30 and the transmission section 33, it is possible to transmit the original speed to the optical scanning system and the reduced speed to the photoreceptor 10 and the transport system 31. .

During enlarged copying, the clutch 3 via the transmission section 35
By turning ON 6 and 37, a speed reduced from the original magnification can be transmitted to the drum 10 and the conveyance system 31, and a speed reduced by the reciprocal of the magnification rate can be transmitted to the pulley 32.

As described above, in the copying machine of this embodiment, the speed of the photoreceptor 10 is reduced during reduction and enlargement compared to when copying at the same size, but this is due to the introduction of the photoreceptor surface potential control means as described below. This makes it possible to maintain the same image quality as when magnifying the image at the same magnification even during such magnification changes.

That is, by changing the electric field strength between the corona dischargers 12, 14 and the photoreceptor 10 to an intensity corresponding to the selected photoreceptor speed and controlling the corona discharge applied to the photoreceptor 10, the photoreceptor speed can be increased. Regardless of the conversion, ie, the process speed, a good copy image of the same quality is always obtained.

As the means and method for controlling the surface potential of the photoreceptor, those already disclosed in detail in Japanese Patent Application No. 53-103038 can be used, so only a brief explanation will be given here. In this control method, the surface potential of the photosensitive drum 10 is measured by the surface potential sensor 38 during the previous rotation of the drum, and this is fed back and corrected to maintain a constant surface potential of the drum when the original image is exposed. This is a method to keep it within the standards. Note that the pre-rotation of the drum 10 refers to the predetermined rotation of the drum 10 before scanning the original and projecting and exposing the image onto the photoreceptor when copying the desired number of sheets from the desired original. After the pre-rotation is completed, the original is scanned a set number of times, and the image thereof is exposed to the photoreceptor to obtain the desired number of copies.

Now, in FIG. 3, while rotating the drum 10 at a speed corresponding to the selected copying magnification, a reference current is applied to the primary charger 12 and the static eliminator 14, respectively, to determine the bright and dark potentials of the drum surface. are alternately measured by the sensor 38. The blank exposure lamp 39 is turned on when measuring the bright area potential, and is turned off when measuring the dark area potential. The bright area potential and dark area potential signals detected by the sensor 38 are amplified by an amplifier circuit 40 and input to an arithmetic control circuit 41. The control circuit 41 compares a preset target potential constant 42 with the signal detected by the sensor 38, calculates the difference, and adds a correction current calculated according to a preset correction formula to the reference current. Then, this added current is applied to the primary charger 12 and the static eliminator 14 via the primary high voltage power supply 43 and the static eliminator power supply 44, respectively. In this way, of the reference current plus the correction current, one corresponding to the dark potential is applied to the primary charger, and one corresponding to the dark potential is applied to the static eliminator. The reference current plus the correction current is the reference current for the next control (the next time the drum front rotates). After repeating the above-described control during the pre-rotation of the drum, the surface potential of the drum 10 will eventually fall within a predetermined specification. After this state is reached, scanning of the original and projection of its image onto the photoreceptor at the selected magnification is started.

Target potential constant signal generation means 42 in the control device
The signal is converted according to the copy magnification. That is,
As described above, this signal is converted so as to reduce the voltage applied to the corona dischargers 12 and 14 by a value corresponding to the magnification ratio when the photoreceptor speed is slow during variable magnification copying compared to when copying at the same magnification.

In this way, both when copying at the same size and when copying at variable magnification, the bright area potential of the latent image for the same original is the bright area potential, and the dark area potential is within the specified standard range, so that good copies are always obtained. An image is obtained.

As described above, the present invention is a copying machine that has the same magnification, reduction, and enlargement functions, but it can be made small and simple in structure, and is extremely significant from an energy-saving perspective. can be provided.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the configuration of an embodiment of a copying machine embodying the present invention, FIG. 2 is an explanatory diagram of speed switching, and FIG.
The figure is a diagram for explaining potential control on the drum surface. 3 is a document illumination lamp, 4 and 4' are first mirrors,
5, 5' are second mirrors, 6, 6a, 6b are transmission lenses, 7, 7a, 7b are third mirrors, 8, 8a,
8b is a fourth mirror, 9 is an exposure slit, and 10 is a photosensitive drum.

Claims (1)

[Scope of Claims] 1. A variable magnification device having a document scanning means for scanning a document and projecting and exposing the document image onto a moving photoconductor surface, and a magnification converting device capable of equal magnification, reduction, and enlargement of the document projected image onto the photoconductor. It is a copying machine, and for reduced copying, the reduction rate is m (m<1), the photoreceptor speeds during full size copying and reduced copying are v ₀ and v ₁ , respectively, and the document scanning speeds are u ₀ and u, respectively. ₁ , it is executed under the conditions of v ₁ = mv ₀ u ₁ = u ₀ , and when making enlarged copies, the enlargement ratio is n (n>1), and the photoreceptor speed is When v ₀ and v ₂ are respectively, and the document scanning speed during enlarged copying is u ₂ , v ₂ = (4/(1+n) ² ×v ₀ u ₂ = (4/(n×(1+n) ² )) A variable magnification copying machine characterized in that it is executed under the condition of xv ₀ .