JP2008290326A - Led print head and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that, since higher accuracies of a component and assembling are necessary for making an imaging line formed by the light condensed with a lens array straight, a conventional LED print head is required for making the accuracies of component and manufacturing equipment higher and it results in the cost rise of the LED print head. <P>SOLUTION: The LED print head includes an LED array having two or more luminescence points, an LED substrate wherein two or more LED arrays are mounted, a base by which the LED substrate is fixed, a housing fixed on the base and the lens array fixed to the housing in facing the LED array. In the LED print head, when the LED print head is bent in the direction of light axis so that the variation in the imaging points formed by the convergence of the light radiated from the luminescence point through the lens array may become within a predetermined range, a plate for keeping the amount of bending of the LED print head constant is fixed to the rear surface of the base at least in both ends of the plate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an LED print head used in an image forming apparatus such as a copying machine or a printer, and a method for manufacturing the LED print head.

  Conventionally, in order to form an electrostatic latent image of an image on an electrostatic latent image carrier such as a photosensitive drum of an image forming apparatus, an LED print head having an LED array and a lens array as main components has been used. Yes.

  The LED print head includes a long LED substrate on which a plurality of LED arrays are mounted, a long base to which the LED substrate is fixed, a long housing fixed to the base, and a housing facing the LED array. And a long lens array fixed to the surface (for example, see Patent Documents 1 to 4).

  In order to form an electrostatic latent image on the surface of the photosensitive drum with high accuracy, the LED print head needs to minimize variations in image forming points. Here, the imaging point refers to a point (focal point) where light emitted from a plurality of light emitting points (LEDs) formed on the LED array converges through the lens array.

  A means generally employed to reduce the variation in the image forming point is to make the flatness and straightness of the base for fixing the LED substrate highly accurate and maintain this accuracy over a long period of time. Therefore, the LED print heads described in Patent Document 1 and Patent Document 2 are integrally formed with a base and a rigid body. In addition, the LED print heads described in Patent Documents 3 and 4 have a high height in the optical axis direction of the base.

JP 2006-289843 A JP 2005-193638 A JP 2000-141744 A Japanese Patent Laid-Open No. 11-266037

  However, the above-described conventional LED print head needs to increase the processing accuracy and assembly accuracy of the base and other parts in order to reduce the variation of the image formation point, which increases the cost of the LED print head. There is a problem of doing.

  Further, in the conventional LED print head, the height of the base is increased in order to maintain the flatness and straightness of the base with high accuracy and ensure rigidity. This is because if the height of the base is lowered, there is a problem that it is bent by its own weight (for example, JP-A-08-164631). For this reason, the conventional LED print head has a problem that the height in the optical axis direction of the LED print head is high, and thus the size cannot be reduced.

  The present invention has been made to solve such a problem, and is an inexpensive LED print head that does not bend due to the weight of the LED print head even when the height of the base is reduced, and realizes downsizing, and a method for manufacturing the same. The purpose is to provide.

  The present invention is directed to an LED array having a plurality of light emitting points, an LED substrate on which the plurality of LED arrays are mounted, a base to which the LED substrate is fixed, a housing fixed to the base, and the LED array. And an LED print head having a lens array fixed to the housing.

Then, when the LED print head is bent in the optical axis direction so that the variation of the image forming point where the light emitted from the light emitting point converges through the lens array is within a predetermined range, the deflection amount of the LED print head A plate for keeping the temperature constant is fixed to the back surface of the base at least at both ends of the plate.
The plate may be fixed to the base as long as it is strong, and a fixing method using an adhesive, a snap fit, a screw, or the like can be employed.

  With such a configuration, even if the LED print head is bent so that the variation in image formation point is reduced, the bent state can be maintained for a long period of time.

  In other words, the LED print head according to the present invention can be obtained after the LED print head is assembled even if the processing accuracy and assembly accuracy of each component constituting the LED print head are lowered and the height of the base in the optical axis direction is lowered. The variation in the image formation point can be maintained over a long period of time by bending the LED print head so that the variation in the image formation point falls within a predetermined range and fixing the plate to the back surface of the base.

  Here, the length of the plate is preferably equal to or longer than the length of the LED substrate. This is because the adjustment of the imaging point is desirably performed for all the light emitting points (LEDs). In other words, in order to reduce the variation of the image formation point and to make the image formation line formed by the plurality of image formation points straight (straight line), the LED substrate is formed over the entire length of the LED substrate. This is because it is desirable to maintain the bent state with the plate after bending.

  Further, the plate may be fixed to the base with screws through spacers at least at both ends of the plate. Even in this case, the effects described above can be obtained.

  The plate may be a printed wiring board, and if it is a printed wiring board, the LED array drive element mounted on the surface of the LED board can be mounted, thus simplifying the structure of the LED print head. can do. In this case, it is desirable to electrically connect the LED array of the LED board and the drive element of the printed wiring board with a flexible cable or the like.

  The present invention also fixes a long LED substrate on which a plurality of LED arrays are mounted on the surface of a long base, the lens array fixed to the long housing faces the LED array, The base is fixed, and the LED print head is bent so that the light emitted from the light emitting point (LED) of the LED array converges through the lens array so that the variation of the image forming point is within a predetermined range. The present invention relates to a method of manufacturing an LED print head having a plate fixed to the back surface.

  That is, after manufacturing the LED print head by fixing the LED substrate mounted with the LED array and the housing mounted with the lens array to the base with an adhesive or the like, the LED print head is set in a device capable of measuring the image point. . Then, with this device, each light emitting point of the LED array is caused to emit light, and the position of the image forming point (focal point) where the light emitted from each light emitting point is converged by the lens array is measured.

  As a result of the measurement, if the variation in the imaging point is within a predetermined range (for example, the variation in the optical axis direction is ± 50 μm), the plate is fixed to the back surface of the base with an adhesive or the like, and the LED print head is self-weighted. Avoid bending.

  As a result of the measurement, if the variation in the imaging point is outside the predetermined range, the LED print head is bent in the optical axis direction so as to be within the predetermined range, while maintaining the state within the predetermined range. Secure the plate to the back of the base.

  The plate may be fixed to the base as long as it is strong as described above, and can be performed using an adhesive, a snap fit, a screw, or the like.

From the viewpoint of man-hours required for adjusting the image formation point and readjustment, it is desirable to fix the plate to the base using screws at least at both ends of the plate.
That is, an LED print head in which an LED substrate on which an LED array is mounted and a housing on which a lens array is mounted are fixed to a base using an adhesive or the like, and a plate that supports at least two ends on the back surface of the base is temporarily fixed. After this is manufactured, this LED print head is set in an apparatus capable of measuring the image point.

  Then, with this device, each light emitting point of the LED array is caused to emit light, and the position of the image forming point where the light emitted from each light emitting point has converged through the lens array is measured, and this image forming point is within a predetermined range. The LED print head is bent so as to enter, and the state is maintained.

  Thereafter, the screws are finally tightened to firmly fix the plate to the back surface of the base. By doing so, the bent LED print head can be maintained for a long period of time, and a good image line state can be maintained. Moreover, since there is a plate on the back surface of the base, the LED print head does not bend further due to its own weight even when it is directed upward or downward.

  In the method of manufacturing the LED print head according to the present invention, it is desirable that the plate is longer than the length of the LED substrate, and at least both ends of the plate are fixed to the base with screws through spacers. May be. Furthermore, the plate may be a printed wiring board, and the LED array driving element may be mounted on the printed wiring board.

  According to the present invention, it is possible to provide an inexpensive LED print head that does not bend due to its own weight even if the height of the base is reduced and that is downsized and a method for manufacturing the same.

  Hereinafter, the present invention will be described in detail using examples.

A first embodiment according to the present invention will be described with reference to FIGS.
1 is a plan view of an LED print head according to the present invention, FIG. 2 is a front view of the LED print head according to the present invention, FIG. 3 is an enlarged view of a side of the LED print head according to the present invention, and FIG. FIG. 5 is a front view of the LED print head, FIG. 6 is a schematic view for explaining an image formation point (focal point), and FIG. 7 is a schematic view for explaining an adjustment operation of the image formation line of the LED print head. FIGS. 8A and 8B are schematic diagrams for explaining the adjustment operation of the image forming line of the LED print head.
The deflection amount of the LED print head is about several tens of μm. However, in order to make the explanation easy to understand, in FIG. 7 and FIG. 8, the LED print head 1 is greatly bent and illustrated.

(LED print head)
As shown in FIGS. 1 to 3, an LED print head 1 according to the present invention includes an LED array 2 having a plurality of light emitting points (LEDs) (not shown) and a long LED substrate 3 on which the plurality of LED arrays 2 are mounted. A long aluminum base 4 to which the LED substrate 3 is fixed by an adhesive, a long plastic housing 5 fixed to the base 4 by an adhesive, and the LED array 2. And a lens array 6 fixed to the housing 5 with an adhesive.

  A long plate 7 is attached to the back surface of the base 4 in a direction parallel to the longitudinal direction of the base 4. Since the plate 7 functions to prevent the base 4 from returning to its original state, the plate 7 needs to be made of a material that does not easily expand or contract even when a tensile force or a compressive force is applied. For example, a metal plate or the like. The plate 7 is temporarily fixed to the base 4 with two screws 8, and after the adjustment of the imaging line, which will be described later, is finished, the screws 8 are finally tightened and firmly fixed to the base 4. Is done.

(Image line adjustment work)
The above-described LED print head 1 can measure a plurality of imaging points (focal points) using a measuring device described in, for example, Japanese Patent Application Laid-Open Nos. 2006-289789 and 2006-289790. In many cases, an imaging line formed by connecting a plurality of measured imaging points has a concave shape as shown in FIG. 4 or a convex shape as shown in FIG.

  Here, as shown in FIG. 6, the imaging point (focal point) means that when the light emitting point (LED) 10 of the LED array 2 is caused to emit light, the light emitted from the light emitting point 10 is converged by the lens array 6 ( A point (position) where light is condensed. That is, if the conjugate length of the lens array 6 is TC, the distance from the light emitting point 10 to the focal position 11 is TC. The conjugate length TC is a length L from the upper surface of the lens array 6 to the focal position (condensing position), and a focal position (from the lower surface of the lens array 1) where T is the height of the lens array 6 in the optical axis direction. Since the length L to the light emission position) is equal, the relationship TC = T + 2L is established.

  As shown in FIG. 4, when the imaging line 9 of the LED print head 1 has a concave shape, the LED print head 1 is set on the column 13 of the jig 12 as shown in FIG. The LED print head 1 can be bent into a convex shape. If it does so, the imaging line 9 can be brought close to a straight line, and the variation in an imaging point can be made into a predetermined range.

  If the deflection of the LED print head 1 due to the weight of the LED print head 1 is small and the variation in the image formation point cannot be within a predetermined range, the back surface of the base is further formed at the substantially central portion of the LED print head 1. If an external force in the downward direction is applied, the variation of the imaging points can be set within a predetermined range.

  Thereafter, the screw 8 which has been temporarily tightened is finally tightened to maintain (maintain) a state in which the variation in the image forming point is within a predetermined range (the image forming line 9 is a straight line) for a long period of time. be able to.

  Further, when the imaging line 9 of the LED print head 1 has a convex shape as shown in FIG. 5, the LED print head 1 is set on the column 13 of the jig 12 as shown in FIG. The LED print head 1 can be bent into a concave shape by its own weight, and the variation of the image forming points can be within a predetermined range.

  If the deflection of the LED print head 1 due to the weight of the LED print head 1 is small and the variation of the image formation point cannot be within a predetermined range, the lens array is further formed at the substantially central portion of the LED print head 1. If a downward external force is applied from the upper surface, the variation of the imaging points can be made within a predetermined range. Then, the imaging line 9 can be brought close to a straight line.

  After that, the temporarily tightened screws 8 are finally tightened, and the plate 7 is firmly fixed to the base 4 to maintain (maintain) the imaging line 9 in a substantially straight line for a long period of time. it can.

  In Example 1, the length of the plate 7 in the longitudinal direction is the same as the length of the LED substrate 3 in the longitudinal direction. This is because the LED substrate 3 is bent over the entire LED substrate 3 having all the light emitting points, and this state is maintained by the plate 7. Therefore, the length of the plate 7 in the longitudinal direction may be equal to or longer than the length of the LED substrate 3 in the longitudinal direction.

(Method for manufacturing LED print head)
Hereinafter, a method for manufacturing the LED print head 1 will be described.
First, the LED substrate 3 on which the plurality of LED arrays 2 are mounted is fixed to the surface of the long base 4 with an adhesive. Then, the lens array 6 fixed to the housing 5 is opposed to the LED array 2 and the housing 5 is fixed to the base 4 with an adhesive. Then, the LED print head 1 in which the state of the imaging line 9 formed by the plurality of imaging points is unknown can be manufactured.

  Next, the LED print head 1 is set on the jig 12 described above, and the light emitting points (LEDs) of the LED array 2 mounted on the LED substrate 3 are turned on. The imaging line 9 formed by connecting the imaging points where the light emitted from the light emitting point of the LED array 2 converges through the lens array 6 is substantially straight (the variation in the optical axis direction of the imaging points is The LED print head 1 is bent (to be smaller).

  Here, when the imaging line 9 of the LED print head 1 is concave as shown in FIG. 4, the LED print head 1 is set by placing the LED print head 1 on the column 13 of the jig 12 as shown in FIG. 7. The LED print head 1 is bent into a convex shape by its own weight.

  If the amount of deflection of the LED print head 1 due to the weight of the LED print head 1 is small and the variation in the image formation point cannot be within a predetermined range, the base of the LED print head 1 is further reduced at the substantially central portion. When a downward external force is applied from the back surface to form a convex shape, the variation of the imaging points can be within a predetermined range.

  As shown in FIG. 5, when the imaging line 9 of the LED print head 1 has a convex shape, the LED print head 1 is set by placing the LED print head 1 on the column 13 of the jig 12 as shown in FIG. The LED print head 1 is bent into a concave shape by its own weight.

  If the amount of deflection of the LED print head 1 due to the weight of the LED print head 1 is small and the variation of the image formation point cannot be within a predetermined range, a lens array is further provided at the substantially central portion of the LED print head 1. If the LED print head 1 is formed in a concave shape by applying a downward external force from the upper surface, the variation of the imaging points can be made within a predetermined range.

  Then, after the variation in the optical axis direction of the image formation point is within a predetermined range (for example, ± 50 μm) and the image formation line 9 formed by connecting the image formation points becomes a straight line, a plate is formed on the back surface of the base 4. 7 is firmly fixed.

  Here, the plate 7 is fixed to the base 4 by providing at least two screw holes on the back surface of the base 4 and two holes at positions corresponding to the two screw holes on both ends of the plate 7. Is inserted into the hole and screw hole, and the screw 8 is tightened firmly. By doing so, the imaging line 9 that is a straight line can be held (maintained) for a long period of time.

  Further, since the deflection amount of the LED print head 1 is maintained by the plate 7 so as to be constant (so as not to change), the lens array 6 of the LED print head 1 is used when facing upward. Even when the lens array 6 is used with the lens array 6 facing downward, the LED print head 1 is not further bent by its own weight.

A second embodiment according to the present invention will be described below with reference to FIG.
FIG. 9 is a front view of the LED print head. Only differences from the first embodiment will be described, and the same parts as those of the first embodiment will be denoted by the same reference numerals and description thereof will be omitted.

  The difference between the second embodiment and the first embodiment is only that the plate 7 is a printed wiring board 15 and the driving elements 14 of the LED array 2 are mounted on the printed wiring board 15.

  Although it is necessary to select the plate 7 which is a material which does not easily expand and contract, a printed wiring board made of glass epoxy satisfies this requirement.

  Then, by mounting the driving element 14 such as an ASIC on the printed wiring board 15, the wiring of the LED print head 1 can be simplified, and the LED print head 1 can be reduced in size and made inexpensive. .

  Although the electrical connection between the LED board 3 and the printed wiring board 15 is not shown, a through hole extending from the front surface to the back surface of the base 4 is formed in a part of the base 4, and a flexible cable is formed in the through hole. It can be performed by connecting to each other through wiring such as.

A third embodiment according to the present invention will be described below with reference to FIGS.
FIG. 10 is a front view of the LED print head, and FIG. 11 is an enlarged view of a side surface of the LED print head. Only differences from the first embodiment will be described, and the same parts as those of the first embodiment will be denoted by the same reference numerals and description thereof will be omitted.

  The difference of the third embodiment from the first embodiment is only that the plate 7 is fixed to the base 4 via a resin spacer 16 as shown in FIGS. 10 and 11.

  Even in such a configuration, as in the first embodiment, the variation in the imaging point in the optical axis direction is reduced, the LED print head 1 is bent so that the imaging line 9 becomes a straight line, and then the screw 8 is tightened. Thus, by firmly fixing the plate 7 to the back surface of the base 4 via the spacers 16, the linear imaging line 9 can be maintained for a long period of time.

A fourth embodiment according to the present invention will be described below with reference to FIG.
FIG. 12 is a front view of the LED print head. Only differences from the third embodiment will be described, and the same parts as those of the third embodiment will be denoted by the same reference numerals and description thereof will be omitted.

  The difference between the fourth embodiment and the third embodiment is that, as shown in FIG. 12, a plurality of spacers 16 become one resin spacer 17, and the plate 7 is a printed wiring board 15 on which a driving element 14 is mounted. It is a point.

  Even with such a configuration, the image forming line 9 that has become a straight line by bending the LED print head 1 can be maintained over a long period of time as in the third embodiment, and the LED print head 1 can be reduced in size and size. It can be made cheap.

  The above-described embodiments have been illustrated for the purpose of explanation, and the present invention is not limited thereto. Those skilled in the art will recognize from the claims, the detailed description of the invention, and the drawings. Modifications and additions can be made without departing from the technical idea of the present invention.

  For example, in the above-described embodiment, the LED print head for fixing the plate 7 or the printed wiring board 15 to the base 4 with two screws provided at both ends thereof is shown, but a plurality of screws may be used.

  Further, the plate 7 needs to be fixed to the back surface of the base 4 at least at both ends of the plate 7 or the printed wiring board 15, but may be fixed at a plurality of other locations such as the central portion.

  In the above-described embodiment, the plate 7 or the printed wiring board 15 is fixed to the back surface of the base 4 with screws, but the plate 7 or the printed wiring board 15 is firmly fixed to the back surface of the base 4. What is necessary is just to fix using an adhesive agent, a snap fit, etc. Even in this case, it is necessary to fix at least both ends of the plate 7 or the printed wiring board 15 to the back surface of the base 4.

  The present invention is applied to an LED print head used in a copying machine, a printer, and the like and a manufacturing method thereof.

Plan view of LED print head (Example 1) Front view of LED print head (Example 1) Enlarged view of the side of the LED print head (Example 1) Front view of LED print head (Example 1) Front view of LED print head (Example 1) Schematic diagram for explaining an imaging point (focal position) (Example 1) Schematic diagram for explaining the adjustment operation of the imaging line of the LED print head (Example 1) Schematic diagram for explaining the adjustment operation of the imaging line of the LED print head (Example 1) Front view of LED print head (Example 2) Front view of LED print head (Example 3) Enlarged view of the side of the LED print head (Example 3) Front view of LED print head (Example 4)

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 LED print head 2 LED array 3 LED board 4 Base 5 Housing 6 Lens array 7 Plate 8 Screw 14 Drive element 15 Printed wiring board 16 Spacer 17 Spacer

Claims (11)

An LED array having a plurality of light emitting points;
An LED substrate mounted with a plurality of the LED arrays;
A base to which the LED substrate is fixed;
A housing fixed to the base;
In an LED print head having a lens array fixed to the housing opposite to the LED array,
When the LED print head is bent in the optical axis direction so that the variation of the image formation point where the light emitted from the light emitting point converges through the lens array is within a predetermined range,
An LED print head characterized in that a plate for keeping the bending amount of the LED print head constant is fixed to the back surface of the base at least at both ends of the plate.   The LED print head according to claim 1, wherein a length of the plate is equal to or longer than a length of the LED substrate.   The LED print head according to claim 1, wherein the plate is fixed to the base with screws at least at both ends of the plate.   The LED print head according to claim 3, wherein the plate is fixed to the base via a spacer at least at both ends of the plate.   The LED print head according to claim 1, wherein the plate is a printed wiring board.   The LED print head according to claim 5, wherein the LED array driving element is mounted on the printed wiring board. An LED substrate mounted with a plurality of LED arrays is fixed on the surface of the base,
A lens array fixed to a housing is opposed to the LED array, and the housing is fixed to the base.
After deflecting the LED print head such that the light emitted from the light emitting point of the LED array converges through the lens array and the variation of the imaging point is within a predetermined range,
A method of manufacturing an LED print head, wherein a plate is fixed to the back surface of the base.   The method for manufacturing an LED print head according to claim 7, wherein the plate has a length equal to or longer than a length of the LED substrate.   9. The method of manufacturing an LED print head according to claim 7, wherein the plate is fixed to the base by screws at least at both ends of the plate.   The method of manufacturing an LED print head according to claim 9, wherein the plate is fixed to the base via a spacer at least at both ends of the plate.   The method of manufacturing an LED print head according to claim 7, wherein the plate is a printed wiring board on which the driving element of the LED array is mounted.

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