The present invention relates to an exposure device and an image forming apparatus.
A conventional image forming apparatus such as a printer, a copier, a facsimile machine, a complex machine or the like is configured to form an image as follows. A surface of a photosensitive drum is uniformly charged by a charging roller. The surface of the photosensitive drum is exposed by an LED (Light Emitting Diode) head as an exposure device so that a latent image is formed on the surface of the photosensitive drum. Then, a toner layer formed on a developing roller adheres to the latent image, and a toner image formed. The toner image is transferred to a recording medium by a transfer roller. The toner remaining on the surface of the photosensitive drum after the transferring is removed by a cleaning device.
A general LED head includes an LED array chip that emits light and a rod lens array that focuses the light on the surface of the photosensitive drum. The LED array chip includes LED chips arranged on an elongated substrate.
On the assembling of the LED head, the substrate (with the LED chips) is mounted to a lens array holder (as a supporting member) holding the rod lens array. More specifically, the substrate is inserted into the lens array holder so that both ends of the substrate in the widthwise direction are placed on contact surfaces formed inside the lens array holder. Then, a base made of metal is placed on the substrate, and a plurality of clamps are attached to the lens array holder so as to force the substrate against the contact surfaces via the base. The clamps protrude outwardly from the lens array holder (see, Japanese Laid-open Patent Publication No. H7-115511).
The present invention is intended to provide an exposure device and an image forming apparatus capable of reducing size and capable of simplifying an operation for mounting a substrate to a supporting member.
The present invention provides an exposure device including a substrate on which a light emitting element array is provided, a focusing lens that focuses light emitted by the light emitting element array, and a supporting member that supports the substrate and the focusing lens. The supporting member has a contact surface. The exposure device further includes a base for forcing the substrate against the contact surface of the supporting member. The base has a first engaging portion that engages a second engaging portion formed on an inner wall of the supporting member. The base is mounted to the supporting member by engagement of the first engaging portion and the second engaging portion.
With such an arrangement, the base can be mounted to the supporting member without using clamps, and the size of the exposure device can be reduced. Further, the substrate can be forced against the contact surface by the base, and the operation for mounting the substrate to the supporting member can be simplified.
The present invention also provides an exposure device including a substrate on which a light emitting element array is provided. The substrate has a first surface and a second surface opposite to the first surface. The exposure device further includes a focusing lens that focuses light emitted by the light emitting element array. The focusing lens faces the first surface of the substrate. The exposure device further includes a supporting member including a lens-supporting portion that supports the focusing lens and a substrate-supporting portion that supports the substrate at a predetermined distance from the focusing lens. The substrate supporting portion is disposed between the substrate and the focusing lens. A forcing member forces the substrate against the substrate-supporting portion from the second surface side of the substrate. The forcing member has a first surface facing the substrate and a second surface opposite to the first surface. The supporting member has an engaging portion that engages the forcing member from the second surface side of the forcing member.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
In the attached drawings:
Hereinafter, embodiments of the present invention will be described with reference to the attached drawings. A printer as an example of an image forming apparatus will be described.
First Embodiment
As shown in
The image forming units 12Bk, 12Y, 12M and 12C respectively include photosensitive drums 13Bk, 13Y, 13M and 13C as image bearing bodies, charging rollers 14Bk, 14Y, 14M and 14C that uniformly charge surfaces of the photosensitive drums 13Bk, 13Y, 13M and 13C, developing rollers 16Bk, 16Y, 16M and 16C (i.e., developer bearing bodies) that develop latent images formed on the surfaces of the photosensitive drums 13Bk, 13Y, 13M and 13C with not-shown toners (i.e., developers) to form visible toner images of respective colors, and the like. Toner supplying rollers 18Bk, 18Y, 18M and 18C (i.e., developer supplying members) are disposed so as to be pressed against the developing rollers 16Bk, 16Y, 16M and 16C. The toner supplying rollers 18Bk, 18Y, 18M and 18C supply the toner from toner cartridges 20Bk, 20Y, 20M and 20C to the developing rollers 16Bk, 16Y, 16M and 16C. Developing blades 19Bk, 19Y, 19M and 19C are disposed so as to be pressed against the developing rollers 16Bk, 16Y, 16M and 16C. The developing blades 19Bk, 19Y, 19M and 19C form thin layers of the toner supplied by the toner supplying rollers 18Bk, 18Y, 18C and 18M on the surfaces of the developing rollers 16Bk, 16Y, 16M and 16C.
LED heads 15Bk, 15Y, 15M and 15C (i.e., exposure devices) are disposed above the photosensitive drums 13Bk, 13Y, 13M and 13C of the image forming units 12Bk, 12Y, 12M and 12C. The LED heads 15Bk, 15Y, 15M and 15C face the photosensitive drums 13Bk, 13Y, 13M and 13C, and expose the surfaces of the photosensitive drums 13Bk, 13Y, 13M and 13C to form latent images thereon based on image data of the respective colors.
A transfer unit is disposed below the photosensitive drums 13Bk, 13Y, 13M and 13C of the image forming units 12Bk, 12Y, 12M and 12C. The transfer unit includes a conveying belt 21 (i.e., a conveying member) capable of moving in a direction shown by an arrow “e” in
A sheet feeding mechanism is provided on a lower part of the printer 11, for feeding the sheet to the conveying path. The sheet feeding mechanism includes a hopping roller 22, a registration roller pair 23, a sheet storing cassette 24 (i.e., a medium storing portion) and the like. The sheet stored in the sheet storing cassette 24 is individually picked up by the hopping roller 22 and is fed along a feeding path P1 to the registration roller pair 23. The sheet is fed by the registration roller pair to the conveying belt 21. The sheet is further conveyed by the movement of the conveying belt 21. When the sheet passes the image forming portions 12Bk, 12Y, 12M and 12C, the toner images of the respective colors are transferred to the sheet by the transfer rollers 17Bk, 17Y, 17M and 17C, and the color toner image is formed. The sheet on which the color toner image is formed is further conveyed to a fixing unit 28. The fixing unit 28 fixes the color toner image to the sheet. The sheet with the color toner image being fixed is further conveyed by an ejection roller pair (not shown) along an ejection path P2, and is ejected outside the printer 11.
Next, relationships between the photosensitive drums 13Bk, 13Y, 13M and 13C and the LED heads 15Bk, 15Y, 15M and 15C will be described. The relationships between the photosensitive drums 13Bk, 13Y, 13M and 13C of the image forming units 12Bk, 12Y, 12M and 12C and the respective LED heads 15Bk, 15Y, 15M and 15C are the same as each other, and therefore the relationship between the photosensitive drum 13Bk and the LED head 15Bk will be described.
In
The lens array holder 34 has an internal space that penetrates from the bottom to the top of the lens array holder 34. The internal space includes a first area R1 in which the rod lens array 32 is held, a second area R2 disposed above the first area R1 so as to be communicated with the first area R1, and a third area R3 disposed above the second area R2 so as to be communicated with the second area R2. The third area R3 has a width wider than the second area R2. Two step portions are formed on inner walls of the second area R2. Contact surfaces S1 are defined on the upper surfaces of the step portions.
The rod lens array 32 is disposed in the first area R1 and is fixed to the lens array holder 34. After the rod lens array 32 is fixed to the lens array holder 34, a gap between the rod lens array 32 and the lens array holder 34 is sealed by a silicon agent 41 for preventing entry of light or foreign material.
A base 35 (i.e., a forcing member) is provided in the lens array holder 34 for forcing the substrate 33 against the contact surfaces S1 of the lens array holder 34. The base 35 is formed of a material having a resiliency and flexibility, for example, a thermoplastic resin. To be more specific, the base 35 is composed of a general-purpose engineering plastic such as polyamide reinforced with glass fibers. With this, it becomes possible to enhance heat resistivity, heat deflection temperature properties or the like of the base 35, and to maintain stable resilient force for a long time.
Here, a distance L11 represents a distance between a surface of the LED array chip 31 and an end surface (i.e., an incident end surface) of the rod lens array 32 on which light is incident, i.e., a distance between the LED array chip 31 and the rod lens array 32. A distance L12 represents a distance between a surface (i.e., an emitting end surface) of the rod lens array 32 from which light is emitted and the surface of the photosensitive drum 13Bk, i.e., a distance between the rod lens array 32 and the photosensitive drum 13Bk. In order to correctly focus the light on the surface of the photosensitive drum 13BK, it is necessary to adjust the distance L12 to satisfy the following relationship:
L11=L12
For this purpose, eccentric cam mechanisms 42 and 43 (i.e., an adjusting mechanism) are provided in the vicinities of both ends of the lens array holder 34 in the longitudinal direction thereof as shown in
Coil springs 37 are provided on both ends of the base 35. The coil springs 37 forces the LED head 15Bk in the direction toward the photosensitive drum 13Bk so that the eccentric cam mechanisms 42 and 43 contact the surfaces of the spacers 38a and 38b to thereby keep constant the distance L12. In this regard, the eccentric cam mechanisms 42 and 43 are configured to adjust the position of the lens array holder 34 with respect to the spacers 38a and 38b by rotating main bodies of the eccentric cam mechanisms 42 and 43.
As shown in
As shown in
L2>L1.
Further, as shown in
In order to mount the base 35 to the lens array holder 34, grooves 34b (i.e., second engaging portions) are formed on the inner walls of the lens array holder 34. The grooves 34b are disposed on positions corresponding to the respective positions of the protrusions 35a of the base 35. Each groove 34b has a shape corresponding to the protrusion 35a, more specifically has an arc-shaped inner surface in this embodiment. The grooves 34b are formed to be slightly larger than the protrusions 34a. The distance L6 (
L6>L2.
In this regard, the contact surfaces S1 are formed below the grooves 34b as shown in
L4<L8.
Next, the mounting operation of the base 35 will be described.
As shown in
The distance L2 between the tips of the protrusions 35a varies from L2 (
As shown in
As described above, according to the first embodiment of the present invention, when the base 35 is mounted to the lens holder 34, the protrusions 35a move into the grooves 34b due to the resilient force of the bridge portions 35d so that the protrusions 35a engage the grooves 34b. Therefore, it is not necessary to use clamps (see
Further, the substrate 33 is directly forced against the contact surfaces S1 (
Second Embodiment
In the above described first embodiment, it is necessary that the distance L11 from the surface of the LED array chip 31 to the incident end surface of the rod lens array 32 is the same as the distance L12 from the emitting end surface of the rod lens array 32 to the surface of the photosensitive drum 13Bk, in order to correctly focus the light on the surface of the photosensitive drum 13Bk. Since the distance L12 can be adjusted by the eccentric cam mechanism 42 and 43 as described above, it is preferable that the distance L11 is kept constant.
In this regard, if there are variations in the positions of the upper ends of the grooves 34b of the lens array holder 34, the thickness L4 of the base 35 or the like, it is difficult to stably force the substrate 33 against the contact surfaces S1.
Therefore, the second embodiment of the present invention is intended to stably force the substrate 33 against the contact surfaces S1 even when there are variations in dimensions as described above.
Components that are the same as those of the first embodiment are assigned the same reference numerals. Regarding advantages obtained by configurations which are the same as those of the first embodiment, the descriptions of the advantages in the first embodiment are herein incorporated.
As shown in
As shown in
L2>L1.
Further, as shown in
As shown in
In order to mount the base 35 to the lens array holder 34, grooves 34b (i.e., second engaging portions) are formed on the inner walls of the lens array holder 34. The grooves 34b are disposed on positions corresponding to the respective positions of the protrusions 35a of the base 35. Each groove 34b has a shape corresponding to the protrusion 35a, more specifically has an arc-shaped inner surface in this embodiment. The grooves 34b are formed to be slightly larger than the protrusions 34a (see
L6>L2.
In this regard, contact surfaces S1 of the lens array holder 34 are formed below the grooves 34b as shown in
L4>L8.
Next, the mounting operation of the base 35 will be described.
As shown in
The distance L2 between the tips of the protrusions 35a varies from L2 (
Further, as shown in
In this state, the deflecting amount L9 of each bridge portion 35d, the distance L4′ from the bottom surface (i.e., a forcing surface) of the base 35 to the upper surface of the bridge portions 35d and the thickness L4 (
L4′=L4−L9<L8
In this case, the bridge portions 35d are going to return to their original shapes due to resilient forces, and therefore the base 35 continuously generates a constant force to force the substrate 33 against the contact surfaces S1.
As described above, according to the second embodiment of the present invention, when the base 35 is mounted into the lens holder 34, the protrusions 35a engage the grooves 34b by causing the bridge portions 35d to be deflected downwardly. Therefore, in addition to the advantages of the first embodiment, it becomes possible to stably force the substrate 33 against the contact surfaces S1.
Comparative Example
The LED head of the comparative example includes an LED array chip 51 that emits light and a rod lens array 52 that focuses the light on the surface of a photosensitive drum 13. The rod lens array 52 is held by a lens array holder 54. The LED array chip 51 is formed on a substrate 53 mounted in the lens array holder 54.
The substrate 53 is placed on contact surfaces S1 formed inside the lens array holder 54. Further, a base made of metal is placed on the substrate 53. A plurality of clamps 58 are attached to the lens array holder 54 for forcing the substrate 53 against the contact surfaces S1 via the base 50.
In the configuration shown in
In contrast, according to the first and second embodiments of the present invention (
The first and second embodiments have been described as being employed in the printer as an example of an image forming apparatus. It is also possible to apply the present invention to a copier, a facsimile machine, a complex machine or the like.
While the preferred embodiments of the present invention have been illustrated in detail, it should be apparent that modifications and improvements may be made to the invention without departing from the spirit and scope of the invention as described in the following claims.
Number | Date | Country | Kind |
---|---|---|---|
2007-244094 | Sep 2007 | JP | national |
Number | Name | Date | Kind |
---|---|---|---|
6025863 | Nakajima et al. | Feb 2000 | A |
6809752 | Nagamine | Oct 2004 | B2 |
Number | Date | Country |
---|---|---|
4-138262 | May 1992 | JP |
06-198957 | Jul 1994 | JP |
7-115511 | May 1995 | JP |
2002-144624 | May 2002 | JP |
2003-285470 | Oct 2003 | JP |
2005-074677 | Mar 2005 | JP |
2005-153362 | Jun 2005 | JP |
Number | Date | Country | |
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20100195079 A1 | Aug 2010 | US |
Number | Date | Country | |
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Parent | 12230240 | Aug 2008 | US |
Child | 12662324 | US |