JP2001150729A - Writing unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the inter-dot pitch at the joint of a plurality of light emitting element array boards from being disturbed by such an extent as causing a defective image even when the environmental temperature of a writing unit is varied. SOLUTION: Light emitting element array boards 1A, 1B, 1C have light emitting element arrays 2a, 2b, 2c each comprising a plurality of light emitting elements arranged in line in the main scanning direction on each board 5a, 5b, 5c. The three light emitting element array boards 1A, 1B, 1C are staggered in two rows so that a desired writing width can be obtained and adjacent boards are linked through connecting members 8a, 8b in the vicinity of switching positions D01, D02 of the writing dots of respective light emitting elements. The light emitting element array boards 1A, 1B, 1C are provided with corresponding self-converging rod lens arrays 3A-3C and packaged integrally using a package case 4 and a housing 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a writing apparatus using a light emitting element array, and more particularly to a writing apparatus suitable for use in an image forming apparatus such as a printer and a digital copying machine.

[0002]

2. Description of the Related Art Conventionally, light emitted from a light-emitting element array unit (light-emitting element array substrate) in which a plurality of light-emitting elements such as LEDs are arranged on a substrate in a straight line is charged on a charged surface of a photosensitive member to be written. There is a writing device which irradiates a latent image and writes a latent image thereon. When writing a wide image such as an A0 size with such a writing apparatus, a light emitting element array unit having a length of about 1 m or more, which is equal to or larger than the writing width of the image, is required.

However, when a light emitting element array unit as long as 1 m is to be manufactured at, for example, 400 dpi (dot pitch: 63.5 μm), a wide LE is required.
Expensive equipment such as a D-chip mounter and a wire bonding machine are required for exclusive use. In addition, the self-focusing rod lens array (Selfoc lens array: SLA) provided corresponding to the light emitting element row generally has a higher price per unit length as the width becomes wider. Was.

[0004] In order to solve such a problem, a conventional writing apparatus includes a light emitting element array unit formed in a relatively short length such as a width of A3 size, and the light emitting element arrays are arranged side by side. In some cases, a plurality of light emitting element array units are configured as a whole by arranging a plurality of light emitting element array units in the longitudinal direction (for example, see Japanese Utility Model Application Laid-open No.
No. 16342).

[0005]

However, in the case where a plurality of light emitting element array units are arranged in the longitudinal direction to form a long light emitting element array unit, the unit of the plurality of light emitting element array units is used. The problem is the dot alignment between them. That is, 400 dp
The dot pitch at i is 63.5 μm, but usually, unless the dot pitch error is smaller than about 5 μm,
Vertical black and white streaks are likely to occur in the image.

[0006] However, if the seam portion is formed by simply connecting a plurality of light emitting element array units as in a conventional writing device, for example, the environmental temperature may change or
When the temperature inside the image forming apparatus rises due to the heat generated by the LEDs, which are the light emitting elements provided in the light emitting element array unit, the temperature of the joints between the plurality of light emitting element array units also increases. There was a problem that the inter-pitch changed due to the elongation of the material.

That is, assuming that the distance between joints of connecting members connecting a plurality of light emitting element array units is 20 mm, the material is iron having a linear expansion coefficient of 0.000012 / deg, and the temperature rise is 30 deg, the temperature calculated by simple calculation is A pitch shift of 7.2 μm will occur only by the change. Therefore, if the initial positioning accuracy of the plurality of light emitting element array units is added to this, the dot pitch error further increases, so that the seam portion of the light emitting element array unit may cause a defect in an image formed thereby. Is generated, resulting in a dot pitch error.

[0008] Further, the substrate on which the light emitting element is mounted and the casing for holding the substrate are usually made of different materials, so that their linear expansion coefficients are different. Since the temperature distribution is usually different, simply connecting the housings of the light emitting element array units tends to greatly shift the pitch between dots at the joint between adjacent light emitting element array units. Further, there is a problem that a dot shift occurs at the joint in a direction (sub-scanning direction) orthogonal to the array direction due to a temperature change.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and changes the environmental temperature in which the apparatus is placed, or causes a light emitting element or the like on a light emitting element array substrate (light emitting element array unit) to generate heat. Accordingly, even if the temperature inside the image forming apparatus changes, the pitch between dots at the joint portion of the plurality of light emitting element array substrates does not become so disturbed that image failure occurs.

[0010]

In order to achieve the above object, the present invention provides a plurality of light emitting element array substrates in which a plurality of light emitting elements are arranged in a straight line on a substrate, and the plurality of light emitting element array substrates are provided. Along with being arranged in parallel so that a desired writing width can be obtained in the arrangement direction of the light emitting elements, adjacent ones of the light emitting element array substrates are connected near a switching position of the writing dot of the light emitting element, A self-focusing rod lens array is provided corresponding to each light-emitting element array of each light-emitting element array substrate, and a plurality of the light-emitting element array substrates and a plurality of self-focusing rod lens arrays are integrally packaged by a package member. It is.

In the writing apparatus, the light emitted from each of the light emitting elements of the plurality of light emitting element array substrates may be located at one position in the sub scanning direction on a writing surface of a writing object moving in the sub scanning direction. The light emitting elements and the self-focusing rod lens arrays may be arranged so that an image is formed in a straight line along the main scanning direction. Further, each of the light-emitting elements and each of the self-focusing rods are arranged such that an optical axis of light emitted from each of the light-emitting elements and passing through the self-focusing rod lens array is perpendicular to a writing surface of a writing object. It is also effective to arrange the lens arrays respectively.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing a writing apparatus according to an embodiment of the present invention, FIG. 2 is an exploded perspective view for explaining the configuration of the writing apparatus, and FIG.
It is sectional drawing which follows the -A line.

The writing apparatus shown in FIG. 1 has a plurality of light emitting elements arranged on each of the substrates 5a, 5b, 5c on a straight line in the main scanning direction indicated by an arrow B as shown in FIG. 2
Light-emitting element array substrate 1 having a, 2b, and 2c, respectively
A, 1B, and 1C (four or more may be arranged) are provided, and the three light emitting element array substrates 1A, 1B, and 1C can obtain a desired writing width in the direction in which the light emitting elements are arranged (the direction of arrow B). Thus, as shown in FIG. 1, a part of them is wrapped with each other and arranged in parallel in two rows in a zigzag manner.

Then, the light emitting element array substrates 1A and 1B and the substrates 5a and 5b and 5b and 5c of the light emitting element arrays 1B and 1C which are adjacent to each other are connected to the light emitting element arrays 2a and 2b and 2b and 2c.
Switching position Do1 of the writing dot of each light emitting element
And Do2 near each other by plate-like connecting members 8a and 8b.

That is, the substrates 5a and 5b and the substrates 5b and 5c
The switching positions Do1 and D of the respective writing dots on the back surface where the light emitting element rows 2a, 2b and 2c are not provided, respectively.
In the vicinity of o2, connecting members 8a and 8a having a shape as shown in FIG.
By fixing 8b by bonding, the light emitting element array substrates 1A and 1B are connected to each other, and the light emitting element array substrates 1B and 1C are also connected to each other. The light emitting elements constituting each of the light emitting element rows 2a to 2c are, for example, those in which a plurality of LED array chips in which a plurality of dots are integrated are mounted on the substrates 5a to 5c.

Further, the light emitting element array substrates 1A to 1C
The self-focusing rod lens arrays 3A to 3C are provided corresponding to the light emitting element rows 2a to 2c, respectively. The three light emitting element array substrates 1A to 1C and the three self-focusing rod lens arrays 3A to 3C are shown in FIG. As shown in FIG. 3, the package is integrally packaged with a package case 4 and a housing 6 which are package members.

That is, as shown in FIG. 2, a projecting portion 4a is formed on the package case 4 so as to be continuous at a predetermined length along the longitudinal direction of the package case 4, and the light emitting element array 2a is formed on the projecting portion 4a. Self-focusing rod lens arrays 3A to 3C
C are inserted so that the front ends thereof slightly protrude as shown in FIG.
It is fixed to.

In the positional relationship shown in FIG. 1, the light emitting element array substrates 1A and 1B are bonded and fixed to each other with a connecting member 8a, and the light emitting element array substrates 1B and 1C are bonded and fixed to each other with a connecting member 8b. An integrated light emitting element array substrate of a length is sandwiched between the edge of the package case 4 and the housing 6 as shown in FIG. It is fixed with screws. Thereby, the light emitting element array substrates 1A to 1C and the self-focusing rod lens arrays 3A to 3A
3C is packaged integrally with the package case 4 and the housing 6.

The packaged writing apparatus is in a state in which the tip side of each of the self-focusing rod lens arrays 3A to 3C is located at a predetermined distance from the surface of the photosensitive drum 7 to be written as shown in FIG. And is fixed to the apparatus main body of the image forming apparatus so as to face each other.

In the set state, the light emitted from each of the light emitting elements of the light emitting element rows 2a and 2c and passed through the self-focusing rod lens arrays 3A and 3C is written on the surface of the photosensitive drum 7. Image at position a,
Light emitted from each light emitting element of the light emitting element row 2b and passing through the self-focusing rod lens array 3B is
The image is formed at the writing position b on the surface of.

As described above, in the writing apparatus according to the present embodiment, the image forming position of light irradiated through the self-focusing rod lens arrays 3A and 3C on the photosensitive drum 7 (a portion in FIG. 3) Self-focusing rod lens array 3B
The position of the light irradiated through the photosensitive drum 7 on the photosensitive drum 7 (portion b in FIG. 3) is shifted in the double scanning direction indicated by arrow C.

Therefore, in this writing apparatus, when writing one scanning line in the main scanning direction (the direction indicated by the arrow B in FIG. 2) on the surface of the photosensitive drum 7, it is upstream in the rotation direction of the photosensitive drum 7. The light from the light emitting element array 2b positioned on the side is irradiated to the writing position b, and the light emitting element is turned on at the timing when the writing position b reaches the position a by the rotation of the photosensitive drum 7 in the direction of arrow E. By irradiating the light from the columns 2a and 2c to the writing position a, even if the self-focusing rod lens arrays 3A to 3C are arranged in a zigzag manner, one scanning line can be written in the same straight line. I have to.

As described above, this writing device is arranged in a zigzag manner and the light emitting element array substrates 1A and 1A adjacent to each other are arranged.
B substrates 5a and 5b, and light emitting element array substrates 1B and 1
C substrates 5b and 5c are connected to light emitting element arrays 2a, 2b and 2b.
And 2c are connected by plate-shaped connecting members 8a and 8b in the vicinity of the switching positions of the write dots of the light emitting elements, respectively.

For this reason, the substrates 5a to 5c are provided with light emitting elements (LEDs) constituting the light emitting element arrays 2a to 2c,
Although the temperature rises and expands due to heat generated from various heat-generating components provided in the image forming apparatus, the substrates 5a and 5b adjacent to each other as described above.
, And 5b and 5c are write dot switching positions Do1 and D
Since the vicinity of o2 is connected and fixed by the connecting members 8a and 8b, the fluctuation of the dot interval at the switching positions Do1 and Do2 becomes very small, so that no problem occurs.

As shown in FIG. 2, the light emitting element rows 2a and 2c in which a large number of light emitting elements are
a, 5c are respectively arranged near the edge of the substrate 5b side,
Since the light emitting element rows 2b on the substrate 5b are also arranged close to the edges on the side of the substrates 5a and 5c, the distance between the light emitting elements on the adjacent light emitting element rows 2a and 2b and between the light emitting elements on the lines 2b and 2c is reduced. Overwhelmingly small. Therefore, even when the environmental temperature rises as described above, the deviation of the dot position in the sub-scanning direction (the direction indicated by the arrow C in FIG. 3) in addition to the main scanning direction is remarkably small.

Furthermore, as the self-focusing rod lens arrays 3A to 3C for forming an image of the light emitted from each light emitting element on the photosensitive drum 7, three light emitting elements which are relatively short in the arrangement direction of the light emitting elements are used. However, since they are all fixed at predetermined positions in the same package case 4, their positional relationship is maintained with high accuracy. Accordingly, the same accuracy (imaging accuracy of the imaging position) as when one long self-focusing rod lens array which is inexpensive and very expensive is provided is provided.
Is obtained.

FIG. 4 is a plan view similar to FIG. 1 showing an embodiment of a writing device in which a plurality of light emitting element array substrates are arranged stepwise, and portions corresponding to FIG. 1 are denoted by the same reference numerals. I have. Thus, even if the light emitting element array substrates 1A to 1C are arranged stepwise, the substrates 5a and 5b of the light emitting element array substrates 1A and 1B and the substrates 5b and 5c of the light emitting element array substrates 1B and 1C are not Switching positions Do1, D of the respective write dots of the light emitting elements in columns 2a, 2b, 2c
In the vicinity of o2, they are connected by connecting members 8a and 8b, respectively, and they are connected to the package case 4 'and the housing 6'
(Corresponding to the housing 6 in FIG. 3 and below the package case 4 'in FIG. 4), if the package is integrally packaged, even when the environmental temperature rises, the switching positions Do1, It is possible to make the fluctuation of the dot interval at Do2 small enough to be acceptable.

FIG. 5 is a sectional view similar to FIG. 3, showing another embodiment of the writing device according to the present invention. In FIG. 5, the same reference numerals are used to simplify the description if the functions are the same as those of the writing device shown in FIG. This writing device is configured such that light emitted from each light emitting element provided on each of the light emitting element array substrates 1A to 1C forms an image linearly in the main scanning direction on the surface (writing surface) of the photosensitive drum 7. , Each light emitting element and each self-focusing rod lens array 3A to 3C are arranged.

According to this writing device, the image forming position of the light emitted from each light emitting element of the light emitting element array substrates 1A, 1B and 1C coincides in the sub-scanning direction of the photosensitive drum 7 (the rotation direction of the drum). Therefore, the light emitting element array substrates 1A, 1
There is no need to delay the light emission timing of each light emitting element on C by a predetermined time with respect to the light emission timing of the light emitting elements on the light emitting element array substrate 1B. Therefore, even when the speed of the photosensitive drum 7 fluctuates, the light emitting element array substrate 1A,
There is no deviation between the write line 1C and the write line on the light emitting element array substrate 1B.

FIG. 6 is a sectional view similar to FIG. 3 showing another embodiment of the writing apparatus according to the present invention.
In FIG. 6 as well, the same reference numerals are used to simplify the description if the functions are the same as those of the writing device shown in FIG.

In this writing device, the optical axes 10a to 10c of the light emitted from the respective light emitting elements and passing through the self-focusing rod lens arrays 3A to 3C are respectively applied to the surface of the photosensitive drum 7 serving as the writing surface. So that each light emitting element array 2a-2c and each self-focusing rod lens array 3
A to 3C are arranged respectively. In this way, the shift of the scanning line can be reduced as compared with the writing apparatus according to the embodiment shown in FIG.

That is, in the case of the writing device described with reference to FIG. 5, light emitted from each light emitting element is applied to the surface of the photosensitive drum 7 and to a line La perpendicular to the surface as shown in FIG. Incident at an angle θ. In this case, as shown in the figure, the distance between the surface of the photosensitive drum 7 and the writing device (the distance in the left-right direction in FIG. 7) is reduced due to the eccentricity of the peripheral surface of the photosensitive drum 7, for example. If the position of the peripheral surface fluctuates by ± δ as shown by the broken line and the imaginary line in the figure (generated by the rotational fluctuation of the photosensitive drum), the writing position of the light in the sub-scanning direction becomes regular. The position fluctuates by δtanθ.

At this time, the image forming position of the light passing through the self-focusing rod lens arrays 3A and 3C on the photosensitive drum 7 and the light passing through the self-focusing rod lens array 3B on the photosensitive drum 7 Is formed, the angle of incidence of the light on the photosensitive drum 7 is different from the perpendicular line La by an angle θ in a direction different from each other. Therefore, the shift of the scanning line on the photosensitive drum 7 is 2δtan θ. .

On the other hand, in the writing apparatus of FIG. 6, the optical axes 10a to 10c of the light passing through the self-focusing rod lens arrays 3A to 3C are respectively perpendicular to the surface of the photosensitive drum 7. 8, the distance between the peripheral surface of the photosensitive drum 7 and the writing device is different from the case where the peripheral surface of the photosensitive drum 7 is eccentric as shown by a virtual line in FIG. Even if it changes, the imaging position d of each light on the photosensitive drum 7 through the self-focusing rod lens arrays 3A and 3C does not shift in the sub-scanning direction (the direction of arrow C).
Similarly, the image forming position e of the light passing through the self-focusing rod lens array 3B on the photosensitive drum 7, even if the peripheral surface of the photosensitive drum 7 is eccentric as shown by a virtual line in FIG. There is no shift in the sub-scanning direction (arrow C direction).

[0035]

As described above, according to the present invention, the following effects can be obtained. According to the writing device of the present invention, an inexpensive narrow light emitting element array is generally used without using a long light emitting element array substrate requiring an extremely expensive LED chip mounter, a wire bonding machine or the like. In addition to using a plurality of substrates, a plurality of self-focusing rod lens arrays, which are generally used in a narrow width, are used, so that they can be manufactured at low cost.

Further, by integrally packaging the whole with a package member, a plurality of narrow light emitting element array substrates are arranged in a state where the distance between the light emitting elements provided thereon is very short. The adjacent ones of the light emitting element array substrates are connected near the switching position of the writing dot of the light emitting element, so that the fixed distance between the light emitting elements is also small. Therefore, even if the temperature inside the device rises due to a change in environmental temperature or heat generation of the light emitting element,
The dot positions do not shift in both the main scanning direction and the sub-scanning direction.

According to the second aspect of the present invention, the light emitted from each of the light emitting elements of the plurality of light emitting element array substrates moves in the sub scanning direction on the writing surface of the writing object in the sub scanning direction. Are all aligned to form an image in a straight line along the main scanning direction, so that it is possible to eliminate the deviation of the writing line in the sub-scanning direction between the light emitting element rows due to the fluctuation of the moving speed of the writing object.

According to the writing device of the third aspect, the optical axis of light emitted from each light emitting element and passing through the self-focusing rod lens array is perpendicular to the writing surface of the writing object. When the writing surface fluctuates in the direction of approaching / separating from the self-focusing rod lens array when the writing target moves, causing a change in the distance between the writing surface and the self-focusing rod lens array. However, it is possible to prevent the writing line shift between the light emitting element rows in the sub-scanning direction.

[Brief description of the drawings]

FIG. 1 is a plan view showing a writing device according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view for explaining the configuration of the writing device.

FIG. 3 is a sectional view taken along line AA of FIG. 1;

FIG. 4 is a plan view similar to FIG. 1, showing an embodiment of a writing device in which a plurality of light emitting element array substrates are arranged stepwise.

FIG. 5 is a sectional view similar to FIG. 3, showing another embodiment of a writing device according to the present invention;

FIG. 6 is a sectional view similar to FIG. 3, showing another embodiment of a writing device according to the present invention.

FIG. 7 shows a case where the photosensitive drum is eccentric in the case of the writing device of FIG. 5, the image forming position of light passing through the self-focusing rod lens array is shifted in the sub-scanning direction on the photosensitive drum. It is the schematic for demonstrating the appearance.

FIG. 8 does not deviate in the sub-scanning direction on the photosensitive drum even if the photosensitive drum is eccentric, even if the photosensitive drum is eccentric; It is a schematic diagram for explaining a situation.

[Explanation of symbols]

 1A, 1B, 1C: Light emitting element array substrate 2a, 2b, 2c: Light emitting element array 3A, 3B, 3C: Self-focusing rod lens array 4: Package case 5a, 5b, 5c: Substrate 6: Housing 7: Photoconductor Drum (object to be written) 8a, 8b: connecting member 10a, 10b, 10c: optical axis

Claims (3)

[Claims] 1. A plurality of light emitting element array substrates each having a plurality of light emitting elements arranged in a straight line on a substrate, and a desired writing width can be obtained in a direction in which the plurality of light emitting element array substrates are arranged. Along with arranging in parallel so that adjacent ones of the light emitting element array substrate are connected near the switching position of the writing dot of the light emitting element,
A self-focusing rod lens array is provided corresponding to each of the light-emitting element rows of each light-emitting element array substrate, and a plurality of the light-emitting element array substrates and a plurality of the self-focusing rod lens arrays are integrally packaged by a package member. A writing device characterized by performing writing. 2. The light emitted from each light emitting element of the plurality of light emitting element array substrates moves in the sub-scanning direction, and the position in the sub-scanning direction coincides with the position on the writing surface of the writing object in the main scanning direction. 2. The writing device according to claim 1, wherein each of the light emitting elements and each of the self-focusing rod lens arrays are arranged so as to form an image in a straight line along the line. 3. The light-emitting elements and the light-emitting elements such that an optical axis of light emitted from each of the light-emitting elements and passing through the self-focusing rod lens array is perpendicular to a writing surface of a writing object. 2. The writing device according to claim 1, wherein a self-focusing rod lens array is arranged.