Patent Application
20070047604
This application claims priority under 35 USC 119 from Japanese Patent Application Nos. 2005-242796, 2005-282205, and 2006-53201, the disclosures of which are incorporated by reference herein.
1. Technical Field
The present invention relates to an optical apparatus having a laser light source unit which emits a laser beam in a predetermined direction and is mounted on a holding member via a temperature control portion, and to an image recording apparatus.
2. Related Art
Generally, among optical scanning apparatuses provided at an optical apparatus such as a digital copier or a laser printer or the like, there are optical scanning apparatuses carrying out operation as follows. A laser beam emitted from a semiconductor laser light source is converted into parallel light by a collimator lens. The laser beam which has been made into parallel light is imaged as a line image which is long in a direction corresponding to the main scanning, and is deflected at a uniform angular velocity by a light deflector having deflecting/reflecting surfaces in a vicinity of the imaging position of the line image. Thereafter, the deflected laser beam is collected onto a surface-to-be-scanned by an imaging optical system, and optical scanning of the surface-to-be-scanned is carried out.
Among such optical apparatuses, there are those using a light source unit having a structure in which a collimator lens is set near and made integral with the light-emitting surface of the semiconductor laser light source, in order to efficiently collect the laser light emitted at the semiconductor laser light source and to make the laser light exit in a predetermined direction after it has been made into parallel light.
As disclosed in Japanese Patent Application Laid-Open (JP-A) No. 9-73056, there has conventionally been proposed a structure in which, at an optical apparatus provided with a light source unit, in order to oscillate a semiconductor laser in a stable state and obtain a stable collimated beam by keeping the temperature of the entire light source unit constant, the light source unit is mounted to a heat sink (radiator) via a Peltier element (heat exchange element), and this heat sink is structured as the holding member of the light source unit.
As described above, by energizing the Peltier element, temperature control with respect to the light source unit which is mounted to the holding member via the Peltier element is carried out, and the light source unit is maintained at a constant temperature.
However, it is easy for the temperature of a holding member serving as a radiator to fluctuate due to the temperature of the surrounding environment and the heat exchange operation of the Peltier element. For example, in a case in which the environmental temperature is higher than the set temperature of the light source unit, the light source unit is cooled by the Peltier element, whereas the temperature of the holding member becomes higher than the temperature of the light source unit because the holding member is heated. Conversely, in a case in which the environmental temperature is lower than the set temperature of the light source unit, because the holding member is cooled whereas the light source unit is heated, the temperature of the holding member is lowered.
In this way, when temperature control with respect to the light source unit is carried out, the states of thermal expansion of the light source unit and the holding member vary in accordance with changes in the environmental temperature. Therefore, a temperature difference arises between the light source unit and the holding member. Due to this temperature difference, the light source unit is affected by the thermal strain arising at the time when the light source unit expands or contracts with respect to the holding member, and deforms. The posture at which the light source unit is held at the holding member also changes. Therefore, the optical axis of the laser beam exiting from the light source tilts with respect to a predetermined exiting direction, and the problem that the beam position fluctuates arises. (Due to the fluctuations in the beam position, the alignment of the optical system is thrown off, and aberration and eclipse arise. Therefore, the beam quality deteriorates, and there is the concern that the image quality of an image formed on a photosensitive material will be deteriorated.)
In view of the aforementioned, an object of the present invention is to newly provide an optical apparatus having a laser light source unit, and an image recording apparatus, which emit a laser beam such that the optical axis of the laser beam exiting from a light source unit does not tilt, even in cases in which a temperature difference arises between the light source unit and a holding member due to temperature control being carried out with respect to the light source unit which is mounted on the holding member.
The present invention has been made in view of the above circumstances and provides an optical apparatus having a laser light source unit, and an image recording apparatus, which emit a laser beam without tilting of the optical axis of the laser beam exiting from a light source unit due to temperature control being carried out with respect to the light source unit which is mounted on a holding member.
Preferred embodiments of the present invention will be described in detail based on the following figures, wherein:
A first embodiment of an optical apparatus having a laser light source unit, and an image recording apparatus, relating to the present invention will be described with reference to
The image recording apparatus 10 is structured to have a light source unit 12 which emits a laser beam (light beam) having a predetermined color wavelength and a predetermined output, a polygon mirror 14 rotating in the direction of arrow A, a first cylindrical lens 16, an fθ lens 18, a second cylindrical lens 20, and a reflecting mirror 22 disposed in the main scanning direction of the laser beam.
These structural elements are disposed at predetermined positions within a case 26, so as to structure an optical system which illuminates the laser beam, which exits from the light source unit 12, to a predetermined position on a photosensitive drum 24.
In the image recording apparatus 10, a laser beam which includes image information is emitted from the light source unit 12 and is adjusted, and thereafter, is incident on the polygon mirror 14 which rotates at a constant speed. After passing through the fθ lens 18 in order to carry out adjustment for scanning, the laser beam is, via the second cylindrical lens 20, reflected at the reflecting mirror 22 and incident on the photosensitive drum 24.
In the image recording apparatus 10, due to the movement of the photosensitive drum 24 and the deflection due to the rotation of the polygon mirror 14, the photosensitive drum 24 is scan-exposed by the laser beam, such that an electrostatic latent image is formed on the photosensitive drum 24. The electrostatic latent image is developed by toner. Due to the toner image being transferred onto a transfer medium such as a recording sheet or the like, an image is formed and recorded.
As shown in
The semiconductor laser 28 is disposed at one end side (the left side in
Due to the collimator lens 30 and the semiconductor laser 28 being disposed near to one another with a predetermined short interval therebetween, the light source unit 12 is structured so as to aim for efficient collection, via the collimator lens 30, of the light emitted by the semiconductor laser 28, as well as compactness of the members and a reduction in the number of members.
The housing of the light source unit 12 is fastened on a holding member (platen) 48 via a displacement avoiding portion. The holding member 48 may be structured as a portion of the case 26 of the image recording apparatus 10 for placement of the housing of the light source unit 12.
As shown in
In order to structure the aforementioned displacement avoiding portion, an insert-through hole 38, which is a through hole for fixing, is formed in the one pedestal portion 34 (the pedestal portion at the right side in
The insert-through hole 38 for fixing is formed to a size such that a screw part 46 is inserted therethrough, and such that, at the time of fastening the light source unit 12 to the holding member through the screw part 46, the position of the light source unit 12 can be fixed so as to not fluctuate.
The play-insertion hole 40 for insertion with play is formed to a size which is such that the screw part 46 is inserted therethrough, and which has leeway of a range which allows fluctuations in the fastened position at the time when the housing main body of the light source unit 12 thermally expands or thermally contracts and allows fluctuations in the fastened position at the time when positioning is carried out by using the insert-through hole 38 for fixing as a reference.
Further, in order to structure the displacement avoiding portion, a screw hole 50, which is for the screwing-in of the screw part 46 which passes through the insert-through hole 38 for fixing, and a screw hole 52, which is for the screwing-in of the screw part 46 which passes through the play-insertion hole 40 for insertion with play, are formed at predetermined positions of the holding member (platen) 48 which is fastened with the housing of the light source unit 12 which is structured as described above.
A positioning pin 54, which serves as a guide portion for abutting and positioning the front end surface of the housing main body of the light source unit 12, stands erect at a predetermined position of the holding member 48 near the screw hole 52.
The light source unit 12 is disposed on the holding member 48 via the displacement avoiding portion and a temperature control portion. The temperature control portion can be structured by using a Peltier element 56 and thermally insulating members 58 which suppress heat conduction. Note that, in the present embodiment, the temperature control portion is structured by simultaneously using both the Peltier element 56 and the thermally insulating members 58, but the temperature control portion may be structured by only the Peltier element 56.
The thermally insulating members 58 function as spacers which keep the interval between the holding member 48 and the housing of the light source unit 12 constant. The thermally insulating members 58 are formed of a material having low heat conductivity such as ceramic or the like, and prevent heat conduction between the holding member 48 and the housing of the light source unit 12.
The one thermally insulating member 58, which is disposed at the portion of the insert-through hole 38 for fixing, is formed by a rectangular member having a thickness corresponding to the set interval between the holding member 48 and the housing of the light source unit 12. An insert-through hole 60 for the screw part 46 is formed in the central portion of the thermally insulating member 58.
Further, in order to structure the displacement avoiding portion, the other thermally insulating member 58 which is disposed at the play-insertion hole 40 side is formed in the shape of a rectangle having a thickness corresponding to the set interval between the holding member 48 and the housing of the light source unit 12 (the same thickness as the one thermally insulating member 58), by a combination of a spacer 62 for thermal insulation and a slide plate 64. Insert-through holes 60, 66 for the screw part 46 are formed so as to communicate with one another in the central portions of the spacer 62 for thermal insulation and the slide plate 64. Note that the slide plate 64 may be structured by a metal plate.
Further, in order to structure the displacement avoiding portion, an auxiliary slide plate 68 is disposed on the pedestal portion 36, at which the play-insertion hole 40 is provided, at the housing of the light source unit 12. An insert-through hole 70 for the screw part 46, which communicates with the play-insertion hole 40, is formed in the central portion of the auxiliary slide plate 68.
Washers 42, 44, which are formed of metal or plastic, are disposed on the auxiliary slide plate 68, which is disposed at the pedestal portion 36 side where the play-insertion hole 40 is provided, and on the pedestal portion 34 at which the insert-through hole 38 for fixing is provided.
When the light source unit 12 is to be mounted on the holding member 48, first, one of the screw parts 46 is passed through the washer 44, the insert-through hole 38 for fixing at the housing of the light source unit 12, and the insert-through hole 60 of the thermally insulating member 58, and is screwed-into and fastened to the screw hole 50 of the holding member 48.
Next, rotational adjustment is carried out with respect to the light source unit 12, such that the front end portion of the housing of the light source unit 12 is made to abut the positioning pin 54 which serves as a guide portion, in the state in which the one screw part 46 is fastened to the screw hole 50, and positioning of the light source unit 12 in the rotational direction around the screw hole 50 is carried out.
Then, when the other screw part 46 for structuring the displacement avoiding portion is to be fastened, this other screw part 46 is passed through the washer 42, the insert-through hole 70 of the auxiliary slide plate 68, the play-insertion hole 40 for insertion with play of the pedestal portion 36, the insert-through hole 66 of the slide plate 64, and the insert-through hole 60 of the spacer 62 for thermal insulation, and is screwed-into and fastened to the screw hole 52 of the holding member 48.
In this case, by applying a lubricant such as high pressure grease or the like to the surfaces of sliding contact between the slide plate 64 and the spacer 62 for thermal insulation, sliding is easily carried out between the slide plate 64 and the spacer 62 for thermal insulation via the lubricant at the time when slight displacement arises between the holding member 48 and the housing of the light source unit 12. Therefore, it is possible to prevent stress, which deforms or tilts the housing of the light source unit 12, from working.
Note that the lubricant such as high pressure grease or the like may be applied between the slide plate 64 and the bottom surface of the housing of the light source unit 12, and between the surface of the pedestal portion 36 and the auxiliary slide plate 68.
For example, a high pressure grease product which contains particulates (“NEVER-SEEZ” manufactured by Bostik), or a high-temperature, high pressure-resistant grease which contains metal particulates of copper, nickel, stainless, or the like, can be used as the lubricant such as high pressure grease or the like which is used here.
As shown in
In this way, when the flexible gaskets 72 or the like are disposed between the Peltier element 56 and the housing of the light source unit 12 and between the holding member 48 and the Peltier element 56 respectively, by making the surfaces of contact fit closely together by the flexible gaskets 72, it is possible to prevent air layers which have a thermally insulating effect from being interposed, and to improve the efficiency of the conductive heat transfer.
The Peltier element 56 is a heat exchange element which is structured to make one surface low temperature and the other surface high temperature, due to current flowing thereto. When dc current is applied to the Peltier element 56 which is structured by a pair of semiconductor elements which are an N-type semiconductor element and a P-type semiconductor element, the heat radiation amount and the heat absorbing amount vary proportionately to the current.
In the image recording apparatus 10, by controlling the current flowing to the Peltier element 56, temperature control is carried out such that the temperature of the housing of the light source unit 12 is maintained at a predetermined temperature. Note that, at this time, because the housing of the light source unit 12 is insulated from the holding member 48 by the thermally insulating members 58, it is possible for heat exchange to not take place between the holding member 48 and the housing of the light source unit 12, and therefore, the light source unit 12 can efficiently be maintained at a constant temperature.
Further, in the image recording apparatus 10, the Peltier element 56 is disposed so as to be sandwiched between the pair of flexible gaskets 72 in a state in which it can slide by a slight distance. Therefore, even if the Peltier element 56 deforms so as to warp slightly due to changes in its own temperature when current is made to flow to the Peltier element 56, this deformation is absorbed by the pair of flexible gaskets 72, and it is possible to prevent stress which tilts the housing of the light source unit 12 from arising due to this deformation.
In this way, for example, in a case in which the light source unit 12 is heated so as to be maintained at temperature of 30° C. by the Peltier element 56 which serves as the temperature control portion, the holding member 48 is cooled by the Peltier element 56 to a temperature which is lower than the air temperature of the atmosphere in which the image recording apparatus 10 is set, and a state arises in which a large temperature difference has arisen between the holding member 48 and the housing of the light source unit 12.
When determining, by a simulation, the state of deformation which arises when the housing of the light source unit 12 is heated and thermally expands and the holding member 48 is cooled and thermally contracts in this state in which a large temperature difference has arisen in a case in which the housing of the light source unit 12 is fixed to the holding member 48 without a displacement avoiding portion being provided, it is clear that the deformation is as schematically shown in
In the results of this simulation, because the housing of the light source unit 12 is heated and thermally expands and the holding member 48 is cooled and thermally contracts, the bottom portion of the housing of the light source unit 12 elastically deforms so as to become convex upwardly in
In the state shown in
Thus, in the image recording apparatus of the present invention, by mounting the housing of the light source unit 12 to the holding member 48 via the displacement avoiding portion, relative deformation arising at the time when the housing of the light source unit 12 is heated and thermally expands and the holding member 48 is cooled and thermally contracts is avoided, and it is possible to prevent stress from working on the housing of the light source unit 12. Therefore, the housing of the light source unit 12 deforming, and the mounted posture of the light source unit 12 tilting, can be prevented.
In the structure of the displacement avoiding portion shown in
Therefore, in this structure of the displacement avoiding portion, if, due to thermal expansion or thermal contraction, the distance between the screw hole 50 and the screw hole 52 of the holding member 48, and the distance between the insert-through hole 38 for fixing and the play-insertion hole 40 for insertion with play at the housing of the light source unit 12, become different, it is possible to prevent stress, which is in the direction of extending or contracting the interval between the insert-through hole 38 for fixing and the play-insertion hole 40 for insertion with play, from working on the housing main body of the light source unit 12, due to the screw part 46 moving within the play-insertion hole 40 at the housing of the light source unit 12. Note that this operation of the screw part 46 moving within the play-insertion hole 40 is carried out smoothly due to the screw part 46 sliding smoothly between the spacer 62 for thermal insulation and the slide plate 64 due to the working of the grease for lubrication.
When this operation is carried out, the light source unit 12 is guided so as to move along a line which connects the screw hole 50 and the screw hole 52, by the positioning pin 54 which serves as a guide portion and which abuts the front end surface of the housing of the light source unit 12. Therefore, even if the optical axis of the laser beam exiting from the light source unit 12 moves parallel to the laser beam optical path as designed, it does not tilt.
Here, the light source unit 12 makes the laser light, which is emitted by the semiconductor laser 28, into a laser beam of parallel light by the collimator lens 30, and emits the laser beam. Therefore, even if this emitted laser beam which is parallel light moves parallel on a predetermined optical path, the position at the time when the laser beam travels the optical path leading to the photosensitive drum 24 and is imaged on the photosensitive drum 24, does not fluctuate. Therefore, a predetermined optical performance can be maintained. In this way, a high-quality image can be formed.
Next, explanation will be given of another structural example of a displacement avoiding portion provided between the holding member 48 and the housing of the light source unit 12 in the image recording apparatus 10.
In the structural example of the displacement avoiding portion shown in
Further, in the structural example of the displacement avoiding portion shown in
The roller members 74 which are roller bearings are solid-cylindrical members which are precisely machined to predetermined diameters, and are disposed so as to be able to roll along directions of lines which are radial with respect to a central line of the screw hole 50 and the insert-through hole 38. Namely, the central line of rotation of each of the roller members 74 is disposed in a direction orthogonal to radial lines whose center is the screw hole 50 and the insert-through hole 38.
In the structural example of the displacement avoiding portion which is shown in
Next, explanation will be given of a structural example shown in
In the structural example of the displacement avoiding portion shown in
V-shaped grooves 78, which extend in directions of lines which are radial with respect to a central line of the screw hole 50 and the insert-through hole 38, are formed at both sides of the screw hole 52 of the holding member 48. The ball bearings 76, which can roll along the directions of radial lines whose center is the screw hole 50 and the insert-through 38, are disposed within the V-shaped grooves 78. Note that the ball bearings 76 may be disposed so as to roll within a plane of a predetermined range.
In the structural example of the displacement avoiding portion which is shown in
Note that, in the structural example of the displacement avoiding portion shown in
Next, explanation will be given of a structural example shown in
In the structural example of the displacement avoiding portion shown in
A screw hole 84, which is a through hole which communicates with the screw hole 52, is formed in the pedestal member 80. The small ball bearings 82 are disposed at the both sides of the screw hole 84 and the play-insertion hole 40. These small ball bearings 82 are formed in the shapes of spheres which are precisely machined to predetermined small diameters.
Generally, the small ball bearings 82 shown in
V-shaped grooves 86, which extend in radial line directions with respect to a central line of the screw hole 50 and the insert-through hole 38, are formed at both sides of the screw hole 84 of the pedestal member 80. The small ball bearings 82, which can roll along the directions of radial lines whose center is the screw hole 50 and the insert-through hole 38, are disposed within the V-shaped grooves 86.
In the structural example of the displacement avoiding portion which is shown in
Next, explanation will be given of a structural example shown in
In the structural example of the displacement avoiding portion shown in
Further, in this structural example of the displacement avoiding portion shown in
In the structural example of the displacement avoiding portion shown in
In the structural example of the displacement avoiding portion shown in
In the structural example of the displacement avoiding portion which is shown in
Next, explanation will be given of a structural example shown in
In the structural example of the displacement avoiding portion shown in
The thermally insulating, elastically deforming member 90 is formed as a relatively large parallelepiped having a predetermined thickness. A screw hole 92 which fastens the screw part 46, and an insert-through hole 96 through which a screw part 94 is inserted, are formed in a line at the thermally insulating, elastically deforming member 90.
A thin groove 98, which opens so as to pass between the screw hole 92 and the insert-through hole 96 from one end portion and extend to near the other end portion, and a thin groove 100, which opens so as to pass between the screw hole 92 and the insert-through hole 96 from the other end portion and extend to near the one end portion, are formed between the screw hole 92 and the insert-through hole 96 of the thermally insulating, elastically deforming member 90. Note that the thin groove 98 and the thin groove 100 may be structured by openings of needed configurations which are formed so as to changeably elastically deform the interval between the screw hole 92 and the insert-through hole 96.
In the structural example of the displacement avoiding portion shown in
In the structural example of the displacement avoiding portion shown in
In the structural example of the displacement avoiding portion which is shown in
Next, explanation will be given of a structural example shown in
In the structural example of the displacement avoiding portion shown in
In the structural example of the displacement avoiding portion shown in
Further, in the structural example of the displacement avoiding portion shown in
In the structural example of the displacement avoiding portion shown in
In addition, a positioning member 108, which is solid-cylindrical, is disposed at a position which corresponds to on the optical path of the laser beam on the holding member 48 and which is separated from the positioning pin 54 by a distance corresponding to the optical path direction length of the light source unit 12. The positioning member 108 is, by a compression coil spring 110 which is stretched between the positioning member 108 and a supporting member 112 which projects-out at the holding member 48, guided so as to go along the optical path of the laser beam and urged to move toward the positioning pin 54.
In the structural example of the displacement avoiding portion shown in
In the structural example of the displacement avoiding portion which is shown in
In addition, if the holding member 48 and the light source unit 12 become respectively different temperatures and thermally expand or thermally contract, stress, which causes the light source unit 12 main body to expand or contract or to tilt, is prevented from working from the holding member 48 side, due to the respective screw parts 46 being moved within the play-insertion hole 40 of the pedestal portion 34 and the play-insertion hole 40 of the pedestal portion 36 at the housing of the light source unit 12. Note that this operation of the screw parts 46 moving within the play-insertion holes 40 is carried out smoothly due to the screw parts 46 sliding smoothly between the spacers 62 for thermal insulation and the slide plates 64 due to the working of the grease for lubrication.
A second embodiment of the present invention will be described next with reference to
As shown in
The semiconductor laser 231 which is the light source is provided at one end side (the right end side in
The collimator lens 232 and the semiconductor laser 231 are disposed near to one another at a predetermined interval. In this way, the laser light emitted from the semiconductor laser 231 can be efficiently collected, and compactness of the members and a reduction in the number of members can be aimed for.
As shown in
Spacers 234 are provided between the base member 210 and the holding holes 238 of the light source unit 203, and keep the interval between the light source unit 203 and the base member 210 constant. The spacers 234 are formed of a material having low heat conductivity such as ceramic or the like, and prevent the heat which is generated at the light source unit 203 from being conducted to the base member 210.
A Peltier element 235 serving as a temperature control portion is disposed between the base member 210 and the holding holes 238 of the light source unit 203. The Peltier element 235 is a heat exchange element which, due to current flowing thereto, can make one surface be a low temperature and the other surface be a high temperature.
The semiconductor laser 231 of the light source unit 203 generates heat due to driving current during exposure. Thus, the temperature of the light source unit 203 can be kept constant due to the Peltier element 235 absorbing the heat generated at the light source unit 203.
Slits, which are formed in the shape of the letter H and structure the displacement avoiding portion, are formed at the portion where the Peltier element 235 is disposed, i.e., at the base member 210. There are three of the slits, and two thereamong are provided parallel to one another at a width which is wider than the opposing sides of the rectangular Peltier element 235 which run along the direction in which the laser light exits. The remaining one slit is provided so as to connect the central portions of the two slits which are provided in parallel. Further, the thickness of the base member 210 is thinner than that of the other portions of the case.
The portions of the base member 210 which are surrounded by the three slits are structures which easily deform with respect to stress from above the base member 210.
These slits can be formed by applying wire cut electric discharge machining. Wire cut electric discharge machining uses an electrode wire of an electric discharge machine, and is an electric discharge machining method which causes a discharging phenomenon to occur while relatively moving a slender wire electrode which is stretched perpendicularly by an NC apparatus through a metal object of machining and, and carries out cutting machining in a needed shape such as a fret sawing machine.
As shown in
Accordingly, when such a structure is employed, the positional relationship of the light source unit 203 is kept constant, the optical path of the light beam exiting from the light source unit 203 is stabilized, and an image of high image quality can be formed.
Note that, when the positional relationship of the light source unit 203 becomes offset, up until the light beam reaches the photosensitive drum 24, this offset increases, and there is the concern that the image formed on the photosensitive drum 24 will deteriorate. In contrast, in cases in which there is no offset in the positional relationship of the light source unit 203, even if some offset arises in the positional relationship of the optical members up until the light beam reaches the photosensitive drum 24, the desired optical performance can be maintained. Therefore, maintaining the positional relationship of the light source unit 203 constant is important for ensuring the optical performance.
Heat radiating sheets 236, 237, which are formed of a material having high thermal conductivity, are disposed between the light source unit 203 and the Peltier element 235, and between the Peltier element 235 and the base member 210. Generally, if surfaces which contact one another are hard, the surfaces of contact contact one another at points when viewed microscopically, and an air layer which has a thermally insulating effect exists between the surfaces of contact. Thus, by filling-in the gaps of the air layers by the heat radiating sheets 236, 237, the efficiency of conductive heat transfer can be increased.
Another example of the configuration of the slits of the base member will be described with reference to
As shown in
When such a structure is employed, the base member 220 elastically deforms in accordance with the deformation of the Peltier element 235, the positional relationship of the light source unit 203 is maintained, the optical path of the light beam exiting from the light source unit 203 is stabilized, and an image of high image quality can be formed.
Further, in the embodiment shown in
In the present invention, the heat of the light source unit which is a source of heat generation is absorbed at the Peltier element. Therefore, it suffices for the light source unit to include a semiconductor laser. Even if the semiconductor laser is not structured integrally with a collimator lens, a rise in the temperature of the light source unit is suppressed, the positional relationship of the light source unit is maintained, and an image of high image quality can be formed on a photosensitive material.
Next, a third embodiment of the present invention will be described with reference to
As shown in
At the housing of the light source unit 312, insert-through holes 338, which are through holes for fastening through which screw parts 346 pass respectively, are formed in the pedestal portions 334.
In order to structure a displacement avoiding portion which suppresses offset of at least the angle of the optical axis of the laser beam exiting from the light source unit 312, screw holes 350, which are for the screwing-in of the screw parts 346, are formed at two predetermined positions on a holding member (platen) 348 at the portion of the holding member 348 to which the housing of the light source unit 312 is fastened.
Further, in order to structure the displacement avoiding portion, two slits 301 for assisting deformation, which are a predetermined length, are formed between the two screw holes 350 so as to be parallel to one another. The slits 301 for assisting deformation are formed as rectilinear slits of the same length which open at one end portion of the holding member 348 and which pass by the positions of the two screw holes 350 and extend toward the other end side of the holding member 348 (thin cut-out grooves which pass-through in the direction of thickness of the holding member 348).
In this way, at the holding member 348, the screw holes 350 are formed at positions which are separated by the same distances from proximal end portions of the slits 301 for assisting deformation of elastically deforming beam pedestal portions 302 which are shaped as cantilevered beams having the same cross-sectional configurations and which are demarcated by the slits 301 for assisting deformation.
At the holding member 348 which is structured in this way, when forces of the same magnitude are applied between the two screw holes 350 in directions of making them approach or move away from one another, as shown in
Further, as shown in
The light source unit 312 is set on the holding member 348 via the displacement avoiding portion and a temperature control portion. The temperature control portion can be structured by using a Peltier element 356 which is a heat exchange element, and thermally insulating members 358 which suppress thermal conduction. Note that, in the present third embodiment, the temperature control portion is structured by using both the Peltier element 356 and the thermally insulating members 358 at the same time, but it suffices for the temperature control portion to be structured by only the Peltier element 356.
The thermally insulating members 358 are structured as spacers which keep the interval between the holding member 348 and the housing of the light source unit 312 constant. Because the thermally insulating members 358 are formed of a material which has low thermal conductivity such as ceramic or the like, they prevent thermal conduction between the holding member 348 and the housing of the light source unit 312.
Further, the thermally insulating members 358, which are disposed at the insert-through hole 338 portions, are formed as rectangular members having a thickness corresponding to the set interval between the holding member 348 and the housing of the light source unit 312. Insert-through holes 360 for the screw parts 346 are formed in the central portions of the thermally insulating members 358.
As shown in
When the light source unit 312 is to be mounted on the holding member 348, the respective screw parts 346 are passed through the washers 344, the insert-through holes 338 at the housing of the light source unit 312, and the insert-through holes 360 of the thermally insulating members 358, and are screwed-in and fastened to the screw holes 350 of the holding member 348.
As shown in
Further, silicon grease is applied and interposed in the form of a layer of a predetermined thickness between one surface of the Peltier element 356 and the bottom surface of the housing of the light source unit 312, and between the other surface of the Peltier element 356 and the surface of the holding member 348. By making these surfaces of contact fit against one another closely by the silicon grease, air layers which have a thermally insulating effect are prevented from existing therebetween, and the efficiency of the conductive heat transfer can be increased.
Further, by placing the silicon grease thereat, when the Peltier element 356 deforms as a bimetal, the deformation of the Peltier element 356 is absorbed at the portions of the silicon grease layers. Therefore, it is possible to suppress thermal stress working on the light source unit 312 and deforming the housing, and displacement due to thermal stress arising in the state in which the light source unit 312 is mounted, and the housing of the light source unit 312 tilting due to deformation of the Peltier element 356.
In this image recording apparatus, by controlling the current that flows to the Peltier element 356, control which maintains the housing of the light source unit 312 at a constant temperature is carried out. Note that, at this time, the housing of the light source unit 312 is thermally insulated from the holding member 348 by the thermally insulating members 358, and it is possible to prevent heat exchange from arising between the holding member 348 and the housing of the light source unit 312. Therefore, control which keeps the light source unit 312 at a constant temperature can be carried out efficiently.
Firstly, the slits 301 for assisting deformation, which structure the displacement avoiding portion, are formed so as to be substantially perpendicular to a straight line joining the centers of the two screw holes 350 formed in the holding member 348.
With such a structure, even if a state arises in which, at the time of temperature adjustment at the Peltier element 356, a temperature difference arises between the light source unit 312 and the holding member 348 and the amounts of thermal deformation differ, the respective elastically deforming beam pedestal portions 302 which are the same shape elastically deform symmetrically and by uniform amounts. Therefore, it is possible to suppress the light source unit 312 deforming and the optical axis of the laser beam moving so as to become offset from a predetermined position.
Secondly, the pair of slits 301 for assisting deformation which structure the displacement avoiding portion, together with the light source unit 312 and the holding member 348, are structured in symmetric shapes with respect to a plane which includes the optical axis of the laser beam exiting from the lens barrel 332 of the light source unit 312, and which is perpendicular to a holding surface which is the surface of the holding member 348 which holds the light source unit 312.
Due to such a structure, the deformation due to the heat of the light source unit 312 itself, and the deformation due to the heat of the holding member 348 itself, are generated symmetrically with respect to the laser beam exiting from the light source unit 312, and cancel one another out. Therefore, it is possible to suppress occurrence of offset of the optical axis of the laser beam (here, offset of the angle of the optical axis of the laser beam exiting from the light source unit 312, and positional offset which is such that the optical axis moves substantially parallel).
Thirdly, the slits 301 for assisting deformation are structured such that the elastically deforming beam pedestal portions 302 for supporting and fixing the light source unit 312 at the holding member 348, and the receiving piece portion 303 which is the portion which the Peltier element 356 abuts, are separated, and even if the receiving piece portion 303 elastically deforms due to the bimetal-like deformation of the Peltier element 356, the stress from this elastic deformation is not applied to the elastically deforming beam pedestal portions 302.
Namely, in the structure of this displacement avoiding portion, even if the Peltier element 356 deforms as a bimetal for the temperature adjusting operation, the receiving piece portion 303, which is elastically deformed by the deformed Peltier element 356, is separated from the respective elastically deforming beam pedestal portions 302 by the respective slits 301 for assisting deformation. Therefore, it is possible for the deformation of the Peltier element 356 to not affect the fixed state of the light source unit 312 by the respective elastically deforming beam pedestal portions 302.
Accordingly, in this image recording apparatus, by providing the displacement avoiding portion in accordance with thermal stress between the light source unit 312 and the holding member 348, effects, which are due to relative deformation arising at the time when a state arises in which the housing of the light source unit 312 is heated and thermally expands and the holding member 348 is cooled and thermally contracts, or the opposite state arises, are avoided. The optical axis of the laser beam exiting from the light source unit 312 is prevented from becoming offset, and the position at the time when the laser beam travels on the predetermined optical path and is imaged on the photosensitive drum does not fluctuate. In this way a predetermined optical performance is maintained, and an image of high image quality can be formed.
Next, explanation will be given, with reference to
In the structural example of the displacement avoiding portion in accordance with thermal stress shown in
The thermally insulating, elastically deforming member 390 is formed as relatively large parallelepiped of a predetermined thickness. A screw hole 392 for fastening the screw part 346, and an insert-through hole 396 through which a screw part 394 is inserted, are formed in a line at the thermally insulating, elastically deforming member 390.
A slit 398, which is open so as to pass between the screw hole 392 and the insert-through hole 396 from one end portion and extend to near the other end portion, and a slit 399, which is open so as to pass between the screw hole 392 and the insert-through hole 396 from the other end portion and extend to near the one end portion, are formed between the screw hole 392 and the insert-through hole 396 at the thermally insulating, elastically deforming member 390. The slit 398 and the slit 399 may be structured by slits of needed configurations which open so as to changeably elastically deform the interval between the screw hole 392 and the insert-through hole 396.
In this structural example shown in
Further, the screw parts 394 are passed through washers 395, are inserted through the insert-through holes 396 of the thermally insulating, elastically deforming members 390, and are screwed-in and fastened to the screw holes 350.
In the structural example of the displacement avoiding portion in accordance with thermal stress which is shown in
In addition, in the structural example of the displacement avoiding portion in accordance with thermal stress which is shown in
Next, explanation will be given, with reference to
In the structural example of the displacement avoiding portion in accordance with thermal stress shown in
Further, in the structural example of the displacement avoiding portion in accordance with thermal stress shown in
In this structural example of the displacement avoiding portion in accordance with thermal stress which is shown in
In the structural example of the displacement avoiding portion in accordance with thermal stress which is shown in
In addition, in the structural example of the displacement avoiding portion in accordance with thermal stress which is shown in
Note that structures, operations and effects in the present third embodiment, other than those described above, are similar to those of the previously-described first embodiment, and therefore, description thereof will be omitted.
The present invention is not limited to the above-described embodiments, and various other structures can of course be adopted within a scope which does not deviate from the gist of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-242796 | Aug 2005 | JP | national |
| 2005-282205 | Sep 2005 | JP | national |
| 2006-053201 | Feb 2006 | JP | national |
