JPH05127465A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent deterioration in focusing performance from an image head by dividing the image head into a multiple number of sub heads and provid ing a mechanism to adjust spacing from inner surface of a photosensitive drum and the sub head. CONSTITUTION:The image head 6 is constituted by being divided into sub heads 8a and 8b, etc., and being connected to them. Furthermore, spacing rolls 16 provided on both ends of each sub head 8a and 8b is rotated in contact with an inner periphery of a transparent base 4. Then, the space rollers 16 are rotated along an inner periphery of the transparent substrate 4, and if the position of a housing 9 against a base 18 is varied by a spring 20, each sub head 8a and 8b are always head in the specified position against the inner periphery of the transparent substrate 4. Therefore, the influence of waves with a cycle longer than the sub heads 8a and 8b can be eliminated by positioning by the spacing roller 16 and the spring 20. In this case, the positions of the sub heads 8a and 8b can be adjusted utilizing a piezo actuator, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical back exposure type image forming apparatus, and more particularly to mounting an image head on a long photosensitive drum.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication (Kokai) No. 58-44445 discloses the basic principle of an optical back exposure system. Further, the optical backside exposure system has effects such as miniaturization and cost reduction of the image forming apparatus, improvement of safety by charging at low voltage, and prevention of ozone generation.

However, in the optical backside exposure method, the transparent substrate used for the photosensitive drum has a low cylindricity and has waviness.
Such undulation deteriorates the focus performance between the image head used for exposure and the photosensitive drum, and deteriorates the print quality. The problem of the undulation of the photosensitive drum becomes more serious as the length of the drum becomes longer, which becomes a particular problem in a large image forming apparatus compatible with A0 paper and A1 paper. As a problem related to this, since the image head is housed inside the photoconductor drum, it is difficult to position the image head and the drum, and if the length of the image head is increased, the accuracy of the head itself is deteriorated. is there.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to allow an image head to be accurately attached even to a transparent substrate having undulations and prevent deterioration of printing quality due to undulations of the substrate. Another object of the present invention is to provide a high-precision image head for a long photosensitive drum at low cost.

[0005]

According to the present invention, in an image forming apparatus in which an image head for exposure is housed inside a photosensitive drum having a photosensitive film provided on a transparent substrate, the image head is divided into a plurality of sub heads. It is characterized in that each sub head is provided with a mechanism for adjusting the distance between the inner surface of the drum and the sub head in order to keep the distance between the sub head and the image forming surface of the drum constant.

[0006]

According to the present invention, the image head is divided into a plurality of sub heads, and each sub head is provided with a mechanism for adjusting the distance to the inner surface of the drum so that the distance to the image forming surface is constant. As a result, even if the transparent substrate of the photosensitive drum has undulations,
The distance from the sub head is constant. Further, since the position of the sub head is automatically adjusted by the adjusting mechanism, the positioning of the image head is automatically performed. Furthermore, since the image head is divided into a plurality of sub heads, it is possible to easily obtain a long head with high accuracy.

[0007]

EXAMPLE An example is shown in FIGS. In FIGS. 1 and 2, reference numeral 2 denotes a photosensitive drum, in which a photosensitive film such as a-Si is provided on the surface of the transparent glass substrate 4. An image head 6 is divided into sub-heads 8a and 8b and the like, which are connected to each other. Reference numeral 9 denotes a housing for the sub heads 8a and 8b. 10 is a substrate of the LED array 12, 1
Reference numeral 4 denotes a lens array such as a self-focusing lens array. The lens array 14 is not divided into the sub heads 8a and 8b, but one for the entire image head 6. L
The ED array 12 is connected to the sub heads 8a and 8b at L
The substrates 10 are arranged up to both ends so that the pitch of the ED does not change. Numeral 16 is a space roller provided at both ends of each of the sub heads 8a and 8b, which is in contact with the inner circumference of the transparent substrate 4 and rotates. The support shaft of the space roller 16 is fixed to the base 9 such as the sub heads 8a and 8b. Reference numeral 18 is a base of the image head 6, 20 is a spring, and each sub head 8a, 8
For example, each b is provided at both ends.

FIG. 3 shows the mounting of the lens array 14. Reference numerals 22 and 24 are adjusting screws attached to the housing 9, and adjust the height of the lens array 14 for each of the sub heads 8a and 8b.

The operation of the embodiment will be described. The transparent substrate 4 made of glass has a waviness of about 200 μm in the longitudinal direction at a cycle of, for example, about 100 mm. If this waviness is left, the distance between the lens array 14 and the photoconductor film of the photoconductor drum 2 is about 200 μm, and LE is taken every 100 mm.
The beam diameter from D changes by about 15 to 20%. For this reason, the image printed on the photoconductor drum 2 has uneven density in a cycle of about 100 mm. On the other hand, the space roller 16 is rotated along the inner circumference of the transparent substrate 4 and the spring 20
By changing the position of the housing 9 with respect to the base 18, the sub heads 8a and 8b are always kept at predetermined positions with respect to the inner circumference of the transparent substrate 4. Sub heads 8a, 8
The length of b is determined according to the undulation period of the transparent substrate 4,
For example, if the undulation has a cycle of about 100 mm, the length of the sub heads 8a and 8b is also set to 100 mm or less. In this way, the effect of the undulation having a longer cycle than the sub heads 8a, 8b can be eliminated by the positioning by the space roller 16 and the spring 20.

Since the cylindricity of the transparent substrate 4 increases as the length increases, the embodiment is particularly effective for the long photosensitive drum 2, for example, the photosensitive drum corresponding to A0 paper and A1 paper. Further, the space between each of the sub heads 8a and 8b to the image forming surface of the photosensitive drum 2 is automatically adjusted by the space roller 16 and the spring 20, so that it is not necessary to consider the positioning of the image head 6. That is, the image head 6 includes the sub heads 8a and 8a.
It is automatically positioned for each b, etc. Next, by dividing the image head 6 into the sub heads 8a and 8b, the accuracy and productivity of the image head 6 itself are improved. The accuracy of the housing 9 and the accuracy of the substrate 10 become lower as the length becomes longer, but if this is divided into the sub heads 8a and 8b, the length can be kept within an appropriate range and a highly accurate one can be easily manufactured. You can

The lens array 14 is formed by bundling rod-shaped lenses and hardening the periphery with an adhesive. When the lens array 14 is divided into sub heads 8a, 8b, etc., an adhesive layer is required at both ends of the lens array 14 at the connecting portion of the sub heads 8a, 8b, so that a lens-free area is formed. Therefore, one lens array 14 is used for the entire image head 6. Since the lens array 14 is easily deformed, the sub heads 8a and 8b are screwed by using the screws 22 and 24.
Position each. That is, when both ends of the lens array 14 are positioned by the screws 22 and 24 for each of the sub heads 8a and 8b, the distance between the lens array 14 and the LED array 12 in each of the sub heads 8a and 8b becomes constant. When the positions of the sub heads 8a and 8b on the space roller 16 change, the lens array 14 also deforms accordingly. The lens array 14 is soft, and the interval with the lens array 12 can be made constant independently for each sub head 8a, 8b.

[0012]

[Embodiment 2] When the space roller 16 is used, the transparent substrate 4
The inner periphery of the transparent substrate 4 is easily polluted by damaging the inner periphery of the transparent substrate 4 or by adhering the toner or paper powder attached to the space rollers 16 to the inner periphery of the transparent substrate 4. Further, if it is used for a long time, the contact surface of the space roller 16 and the contact surface of the transparent substrate 4 with the space roller 16 may be worn and the accuracy may be lowered. Therefore, it is conceivable to adjust the positions of the sub heads 8a and 8b in a non-contact manner with the transparent substrate 4 using a piezo actuator or the like. FIG. 4 shows such an embodiment. In the figure, 22 is a piezo actuator, 24 is an electrode, 2
6 is an AC power supply, 28 is an amplifier, 30 is an output variable power supply, 3
2 is a control circuit, 34 is a transparent electrode of the photosensitive drum 2, 36
Is a photoconductor film.

In this embodiment, the electrode 24 is replaced by the transparent electrode 34.
The electrostatic capacitance between and is measured, amplified by the amplifier 28, the piezo actuator 22 is operated, the housing 9 is moved up and down, and the positions of the sub heads 8a, 8b and the like are adjusted. In other respects, it is similar to the embodiment of FIGS.

In this embodiment, without contacting the transparent substrate 4,
By the operation of the piezo actuator 22, the positions of the sub heads 8a and 8b can be adjusted. As a result, the transparent substrate 4
Prevents pollution of the inner circumference of the space, and the space roller 16 and the transparent belt 14
It is possible to prevent a decrease in accuracy due to wear of the.

In these embodiments, the space roller 16, the spring 20, and the piezo actuator 22 are used as a mechanism for adjusting the distance between the sub heads 8a, 8b and the image plane, but each sub head 8a, 8b etc. is automatically adjusted. The type is arbitrary as long as the distance can be adjusted.

[0016]

[Third Embodiment] In the adjacent portion of the sub heads 8a and 8b, the LED
In order to prevent the uneven light amount from the array 12, for example, the substrates 10 may be arranged in a staggered manner for each of the sub heads 8a and 8b as shown in FIG. 4 in the figure
Reference numeral 0 denotes a mirror, and both end portions are set as a half mirror portion where the light reflectance gradually decreases and the light transmittance increases. In this embodiment, since both end portions of the mirror 40 are half mirror portions,
The mirror 40 is arranged at 45 degrees with respect to the sub head 8a, and the sub head 8b is arranged at right angles to the sub head 8a.
The light from the sub head 8a is directly incident on the lens array 14 except for the LEDs at both ends, and the light from the sub head 8b is incident on the lens array 14 via the mirror 40 except at both ends. L at the right end of the adjacent sub head 8a
The ED array 12 and the LED array 12 at the left end of the sub head 8b are arranged so that the pitch of the LEDs at the boundary of the sub head does not change, and the left end of the mirror 40 is arranged so as to cover a part of the LED of the left sub head 8a. .. In this way, it is not necessary to arrange the LED array 12 to the literal end of the substrate 10. Next, the light transmission characteristics and the light reflection characteristics at both ends of the mirror 40 are set, for example, as shown in FIG. 6 so that the light reflectance and the light transmittance do not change drastically at the boundary between the sub heads 8a and 8b.

In FIG. 6, a part of the light from the LED near the left end of the sub head 8b is reflected by the half mirror part of the mirror 40 to enter the lens array 14, and part of the light is transmitted through the half mirror part, not shown. It is discarded inside the housing 9. Therefore, the light utilization rate of the LED at the left end of the sub head 8b becomes 1/2. Similarly, part of the light from the LED near the right end of the sub head 8a passes through the half mirror portion and enters the lens array 14, and part of the light is reflected by the half mirror portion and is discarded. Therefore, the sub heads 8a and 8b
The light utilization rate of the LED at the end of is 1/2. In order to compensate for the decrease in the amount of light due to the light utilization rate being halved, for example, for the LEDs at both ends of the sub heads 8a, 8b, the light emission time is lengthened or the light emission current is increased, and the both ends are taken. It is preferable to increase the amount of light so that the number of LEDs can be doubled.

If half mirror portions are not provided at both ends of the mirror 40, when the position of the mirror 40 or the like is displaced for some reason, the amount of light to the lens array 14 from the LEDs at both ends of the sub heads 8a and 8b is changed. The change is remarkable. For example, when the mirror 40 shifts to the right in the arrangements of FIGS. 5 and 6, when there is no half mirror portion, light from the LED at the left end of the right sub head 8b does not reach the lens array 14 because the mirror 40 shifts. Similarly, when the mirror 40 is displaced to the left, without the half mirror portion, the light from the LED at the right end of the left sub head 8a is reflected by the mirror 40,
It will not reach the lens array 14. On the other hand, if the half mirror portion is provided as shown in FIG. 6, even if the position of the mirror 40 is displaced, the change in the light amount is gentle and the influence on the print quality can be reduced as compared with the case where the half mirror portion is not provided.

[0019]

According to the present invention, a mechanism for adjusting the distance from the inner surface of the drum is provided for each sub head to keep the distance from the image forming surface constant. As a result, even if the transparent substrate of the photosensitive drum has undulations, the distance from the sub head is constant. Further, the position of the image head is automatically adjusted by automatically adjusting the position of the sub head by the adjusting mechanism. Further, the image head is divided into a plurality of sub heads to obtain a long and highly accurate image head.
As a result, it is possible to obtain a large-sized optical back exposure type image forming apparatus which is inexpensive and has high printing quality.

[Brief description of drawings]

FIG. 1 is a sectional view of an image forming apparatus according to an embodiment.

2 is a sectional view taken along line 2-2 of the embodiment shown in FIG.

FIG. 3 is a cross-sectional view showing the positioning of the lens array in the example.

FIG. 4 is a sectional view of another embodiment.

FIG. 5 is a perspective view showing the arrangement of the image heads in the embodiment in which the image heads are arranged in a staggered manner.

6 is a characteristic diagram of the half mirror used in the embodiment of FIG.

[Explanation of symbols]

 2 photoconductor drum 4 transparent substrate 6 image head 8a, 8b sub-head 9 housing 10 substrate 12 LED array 14 lens array 16 space roller 18 base 20 spring 22 piezo actuator 40 half mirror

Claims (1)

[Claims] 1. An image forming apparatus in which an image head for exposure is housed inside a photosensitive drum having a photosensitive film provided on a transparent substrate, and the image head is divided into a plurality of sub heads. An image forming apparatus, wherein a mechanism for adjusting a distance between the inner surface of the drum and the sub head is provided for each sub head in order to make a distance between the sub head and the image forming surface of the drum constant.