Light irradiation device, fixing device, and image forming apparatus

Provided is a light irradiation device including plural first irradiation units that irradiate an irradiation target area on a surface to be irradiated with light beams and are disposed in a specific direction, and plural second irradiation units that irradiate an outside of the irradiation target area with light beams and are disposed at an outer side of the first irradiation units in the specific direction, wherein light beams emitted from two adjacent irradiation units among the plural first irradiation units and the plural second irradiation units are superimposed with each other in the specific direction, and a first irradiation width that is not superimposed with the light beam from the adjacent first irradiation unit is smaller than a second irradiation width that is not superimposed with the light beam from the other adjacent first irradiation unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2014-173117 filed Aug. 27, 2014.

BACKGROUND

Technical Field

The present invention relates to a light irradiation device, a fixing device, and an image forming apparatus.

SUMMARY

According to an aspect of the invention, there is provided a light irradiation device including:

plural first irradiation units that irradiate an irradiation target area on a surface to be irradiated with light beams and are disposed in a specific direction; and

plural second irradiation units that irradiate an outside of the irradiation target area with light beams and are disposed at an outer side of the first irradiation units in the specific direction,

wherein light beams emitted from two adjacent irradiation units among the plural first irradiation units and the plural second irradiation units are superimposed with each other in the specific direction, and

a first irradiation width that is not superimposed with the light beam from the adjacent first irradiation unit among irradiation width of the surface to be irradiated that is irradiated with the light beam from the second irradiation unit in the specific direction is smaller than a second irradiation width that is not superimposed with the light beam from the other adjacent first irradiation unit among the irradiation width of the surface to be irradiated that is irradiated with the light beam from the adjacent first irradiation unit in the specific direction.

DETAILED DESCRIPTION

First Exemplary Embodiment

Examples of a light irradiation device, a fixing device, and an image forming apparatus according to the first exemplary embodiment will be described.

Overall Configuration

FIG. 1shows an image forming apparatus10of the first exemplary embodiment. The image forming apparatus10, for example, includes a transportation unit12that transports a sheet P, an image forming unit14that forms a toner image G on the transported sheet P using a toner T, and a fixing device20that fixes the toner image G onto the sheet P. The sheet P is an example of a recording medium. The toner T is an example of a developer. The toner image G is an example of a developer image. The image forming unit14is an example of a developer image forming unit. In addition, the image forming unit14, for example, performs each step of charging, exposing, developing, transferring, and cleaning by an electrophotographic method.

Main Configuration

Next, the fixing device20will be described.

As shown inFIG. 2, the fixing device20includes a transportation belt22as an example of a transportation unit that transports the sheet P to which the toner T is attached, and a light irradiation unit30as an example of a light irradiation device that irradiates the toner T with a laser light beam Bm as an example of light to melt the toner T.

Transportation Belt

The transportation belt22, for example, is configured with a polyimide tubular body and is wound on two rolls24(seeFIG. 1). One of the two rolls24is rotatably driven by a gear and a motor (not shown). Accordingly, the sheet P is transported by the transportation belt22. The laser light beam Bm is emitted to a surface PA of the sheet P on the transportation belt22. The surface PA is an example of a surface to be irradiated.

In the description hereinafter, a direction in which the sheet P is transported is set as an X direction, a direction which is orthogonal to the X direction and in which the laser light beam Bm is emitted is set as a Y direction, and a direction orthogonal to the X direction and the Y direction is set as a Z direction. The Z direction is a width direction of the sheet P. In a case where it is necessary to differentiate one side and the other side of each of the X direction, the Y direction, and the Z direction, the upper side is set as a Y side, the lower side is set as a negative Y side, the right side is set as an X side, the left side is set as a negative X side, the rear side is set as a Z side, and the front side is set as a negative Z side, when the light irradiation unit30is seen in the Z direction. The right side is the upstream side in the X direction and the left side is the downstream side in the X direction.

Light Irradiation Unit

Next, the light irradiation unit30will be described.

As shown in (A) ofFIG. 3, the light irradiation unit30, for example, includes plural first irradiation units32that are disposed in the Z direction at set intervals, and two second irradiation units34that are disposed in the Z direction with the plural first irradiation units32nipped therebetween.FIG. 3shows the four first irradiation units32, but the number of the first irradiation units32may be one or 4 or more.

As shown in (B) ofFIG. 3, the laser light beam Bm emitted to the surface PA of the sheet P from the first irradiation units32(see (A) ofFIG. 3) is a first light flux A in a linear line shape that is short in the X direction and long in the Z direction when seen in the Y direction. In addition, the laser light beam Bm emitted to the surface PA of the sheet P from the second irradiation units34(see (A) ofFIG. 3) is a second light flux B in a linear line shape that is short in the X direction and long in the Z direction when seen in the Y direction. The Z direction is an example of a specific direction.

First Irradiation Unit

As shown in (A) ofFIG. 3, the first irradiation unit32includes a laser light source36A as an example of a first light source, and a first lens38that guides the laser light beam Bm from the laser light source36A to the surface PA of the sheet P. In addition, the first irradiation unit32includes a collimate lens37and a condensing lens39. In the first irradiation unit32, the laser light source36A, the collimate lens37, a second lens42, and the condensing lens39are disposed in this order according to an optical axis of the laser light beam Bm.

Laser Light Source

As shown in (A) ofFIG. 3, the plural laser light sources36A are disposed in the Z direction at set intervals on the Y side of the sheet P. In addition, the laser light source36A emits the laser light beam Bm to the surface PA of the sheet P. In the exemplary embodiment, an optical axis direction of the laser light beam Bm is the Y direction.

The collimate lens37is disposed on the optical axis (not shown) of the laser light beam Bm and on the negative Y side (sheet P side) of the laser light source36A. As shown inFIG. 2, the collimate lens37is, for example, a cylindrical lens, and converts the laser light beam Bm which is a diverging light beam into a parallel light beam, when seen in an X-Y plane. As shown inFIG. 3, the collimate lens37has the laser light beam Bm as the diverging light, when seen in a Z-Y plane.

First Lens

The first lens38is disposed on the optical axis of the laser light beam Bm and on the negative Y side of the collimate lens37. In addition, the first lens38is, for example, a plane-concave lens, of which the Y side has a concave shape and the negative Y side has a flat shape, when seen in the X direction, and causes the laser light beam Bm to be diverged in the Z direction.

Condensing Lens

The condensing lens39is disposed on the optical axis of the laser light beam Bm and on the negative Y side of the first lens38. In addition, the condensing lens39is commonly used by the first irradiation unit32and the second irradiation unit34(is provided as one body). As shown inFIG. 2, the condensing lens39condenses the laser light beam Bm in the X direction, when seen in the X-Y plane. Furthermore, the condensing lens39is, for example, a cylindrical lens, and condenses the laser light beam Bm in the X direction. However, as shown inFIG. 3, the condensing lens has the laser light beam Bm as the diverging light beam without being condensed, when seen in the Z-Y plane.

Herein, an irradiation width in the Z direction of the laser light beam Bm emitted to the surface PA of the sheet P by the first irradiation unit32is set as W1. The plural first irradiation units32are disposed so that a part of the laser light beam Bm (first light flux A) emitted to the surface PA of the sheet P is superimposed with a part of the laser light beam Bm (first light flux A) emitted by the adjacent first irradiation unit32, in the Z direction.

Second Irradiation Unit

Next, the second irradiation unit34will be described. The members basically same as those of the first irradiation unit32will have the same reference numerals and description thereof will be omitted.

As shown in (A) ofFIG. 3, the second irradiation unit34includes a laser light source36B as an example of a second light source, and the second lens42that guides the laser light beam Bm from the laser light source36B to the surface PA of the sheet P. The laser light source36B, for example, has the same configuration as the laser light source36A. The same configuration means to have the same optical characteristics and light irradiation performance. In addition, the second irradiation unit34includes the collimate lens37and the condensing lens39. In the second irradiation unit34, the laser light source36B, the collimate lens37, the second lens42, and the condensing lens39are disposed in this order according to an optical axis of the laser light beam Bm.

Second Lens

The second lens42is, for example, a plane-concave lens, of which the Y side has a concave shape and the negative Y side has a flat shape, when seen in the X direction, and causes the laser light beam Bm to be diverged in the Z direction. In addition, the second lens42has a smaller irradiation width (range) of the surface PA of the sheet P in the Z direction which is to be irradiated with the laser light beam Bm from the laser light source36B, compared to that of the first lens38. That is, when the irradiation width of the surface PA of the sheet P in the Z direction to be irradiated with the laser light beam Bm by the second irradiation unit34is set as W2, an expression of W2<W1is satisfied. The second lens42has a narrow range for the laser light beam Bm to be emitted to the surface PA of the sheet P, by setting a focal length to be longer compared to that of the first lens38.

The two second irradiation units34are disposed at the outer side of the first irradiation unit32in the Z direction, so that a part of the laser light beam Bm (second light flux B) emitted to the surface PA of the sheet P is superimposed with a part of the laser light beam Bm (first light flux A) emitted by the adjacent first irradiation unit32in the Z direction. In the exemplary embodiment, both of the Z side and the negative Z side are the outer sides in the Z direction. In addition, an interval (pitch) in the Z direction between the adjacent second irradiation unit34and the first irradiation unit32is shorter than the interval in the Z direction between the first irradiation units32. This is for causing the width of the laser light beam Bm of the second irradiation unit34and the laser light beam Bm of the first irradiation unit32superimposed in the Z direction, to be close to W4(to match the superimposed width), by setting the width of the laser light beams Bm of the adjacent first irradiation units32superimposed in the Z direction as W4.

In addition, an irradiation target area (fixing area) of the laser light beam Bm on the surface PA of the sheet P is set as S. The width of the irradiation target area S in the Z direction is set as W3(>W1). In addition, an optical axis of the laser light source36B of the second irradiation unit34is set as K. Herein, the two laser light sources36B of the second irradiation unit34are disposed so that two optical axes K are positioned in the irradiation target area S in the Z direction. The second irradiation unit34irradiates not only the irradiation target area S but also the outside of the irradiation target area S in the Z direction with the laser light beam Bm.

In addition, among the irradiation width of the surface PA irradiated with the laser light beam Bm from the second irradiation unit34in the Z direction, a first irradiation width that is not superimposed with the laser light beam Bm from the adjacent first irradiation unit32is set as W5. Among the irradiation width of the surface PA irradiated with the laser light beam Bm in the Z direction from the first irradiation unit32adjacent to the second irradiation unit34, a second irradiation width that is not superimposed with the laser light beam Bm from the other first irradiation unit32adjacent to the first irradiation unit32is set as W6. Herein, an expression of W5<W6is satisfied.

Comparative Example

A unit in which the two second irradiation units34of the exemplary embodiment are replaced with the two first irradiation units32(all configured with the first irradiation units32) is set as a light irradiation unit of a comparative example. In addition, in the light irradiation unit of the comparative example, six first irradiation units32are disposed at regular intervals in the Z direction. Herein,FIG. 11shows a simulation result of the light intensity [W/mm] with respect to the irradiation position [mm] of the laser light beam Bm of the light irradiation unit of the comparative example.

Trapezoidal graphs G1, G2, G3, G4, G5, and G6ofFIG. 11show light intensity distribution of six first irradiation units32(seeFIG. 3). In addition, a graph GB shown with a bold line ofFIG. 11shows the total six light intensities of the graphs G1, G2, G3, G4, G5, and G6. Herein, in order to obtain the necessary light intensity from the center and both ends of the irradiation target area S in the Z direction using the light irradiation unit of the comparative example, it is necessary to dispose the first irradiation units32at both ends so that the light intensity becomes maximum in the positions corresponding to both ends (boundary) of the irradiation target area S.

However, in the light irradiation unit of the comparative example, the first irradiation unit32having the irradiation width W1(seeFIG. 3) that is the same as that of the center portion is used on both ends in an arrangement direction. Accordingly, in the light irradiation unit of the comparative example, when the first irradiation unit32is disposed so that the light intensity becomes to be the maximum in the positions corresponding to both ends of the irradiation target area S, the laser light beam Bm, the area of which is more than half of the irradiation width in the graphs G1and G6is emitted to the outside of the irradiation target area S. Accordingly, in the light irradiation unit of the comparative example, a loss of light energy at the outside of the irradiation target area S is increased.

Operation

An operation of the first exemplary embodiment will be described.

FIG. 4shows a simulation result of the light intensity [W/mm] with respect to the irradiation position [mm] of the laser light beam Bm of the light irradiation unit30of the exemplary embodiment (seeFIG. 3).

Trapezoidal graphs G2, G3, G4, and G5ofFIG. 4show light intensity distribution of the four first irradiation units32(seeFIG. 3). In addition, trapezoidal graphs G7and G8ofFIG. 4show light intensity distribution of the two second irradiation units34(seeFIG. 3). Further, a graph GA shown with a bold line ofFIG. 4shows the total six light intensities of the graphs G2, G3, G4, G5, G7, and G8.

In order to obtain the necessary light intensity from the center and both ends of the surface PA of the sheet P in the Z direction using the light irradiation unit30of the exemplary embodiment shown inFIG. 3, it is necessary to dispose a portion of the second irradiation unit34having the highest light intensity on both ends of the irradiation target area S of the laser light Bm. This is because the light intensity is insufficient only by the first irradiation units32.

Herein, in the light irradiation unit30, the first irradiation width W5is smaller than the second irradiation width W6. The second irradiation units34having a irradiation width smaller than the first irradiation units32disposed in the center portion in the Z direction are disposed at both end portions in the Z direction. Accordingly, in the light irradiation unit30, even when the second irradiation units34are disposed so that a portion having the highest light intensity is positioned at both ends of the irradiation target area S, a quantity of light (integration value) of the laser light beam Bm emitted to the outside of the irradiation target area S becomes (is decreased) to be smaller than a quantity of light (integration value) of the comparative example. Accordingly, in the light irradiation unit30, a loss of light energy at the outside of the irradiation target area S is decreased, compared to the light irradiation unit of the comparative example.

In the light irradiation unit30, the number of members configuring the first irradiation unit32and the number of members configuring the second irradiation unit34are the same as each other. That is, no members are added to the second irradiation unit34of the light irradiation unit30, when compared with the first irradiation unit32. Accordingly, the light irradiation unit30has a small number of components, compared to a configuration of reflecting the laser light beam Bm that is supposed to be emitted to the outside of the irradiation target area S to the inside of the irradiation target area S by adding a mirror.

In addition, the second irradiation unit34of the light irradiation unit30uses the laser light source36B having the same configuration as that of the laser light source36A and uses the second lens42having a different focal length from that of the first lens38of the first irradiation unit32to have a smaller (narrower) irradiation width. Accordingly, since the configurations of the light sources of the first irradiation unit32and the second irradiation unit34are the same, the assembly of the light irradiation unit30is easy, compared to a configuration of not using the light source having the same configuration as that of the laser light source36A as the light source of the second irradiation unit34.

In the fixing device20shown inFIG. 2, the light irradiation unit30irradiates the toner T on the sheet P transported by the transportation belt22with the laser light beam Bm. The toner T (toner image G) is heated and melted by absorbing the laser light beam Bm, and is fixed onto the sheet P. Herein, in the fixing device20, the loss of light energy of the light irradiation unit30is decreased, compared to that of the light irradiation unit of the comparative example, and accordingly, the energy necessary for the fixation of the toner T is reduced compared to the case of the comparative example.

In the image forming apparatus10shown inFIG. 1, the image forming unit14forms the toner image G on the sheet P and the fixing device20fixes the toner image G onto the sheet P. Here, in the image forming apparatus10, since the energy necessary for the fixation of the toner T is reduced by using the fixing device20, the energy necessary for the image forming onto the sheet P is reduced, compared to the case of using the fixing device including the light irradiation unit of the comparative example.

Second Exemplary Embodiment

Next, examples of a light irradiation device, a fixing device, and an image forming apparatus according to the second exemplary embodiment will be described. The members and parts basically same as those of the first exemplary embodiment will have the same reference numerals as those of the first exemplary embodiment and description thereof will be omitted.

FIG. 5shows a light irradiation unit50as an example of a light irradiation device of the second exemplary embodiment. In the second exemplary embodiment, a point of providing the light irradiation unit50instead of the light irradiation unit30(seeFIG. 1) in the image forming apparatus10and the fixing device20of the first exemplary embodiment is different from the first exemplary embodiment, and the other configurations thereof are same as those of the first exemplary embodiment.

The light irradiation unit50includes the plural first irradiation units32that are disposed in the Z direction at intervals, and two second irradiation units52that are disposed in the Z direction with the plural first irradiation units32nipped therebetween.FIG. 5shows, for example, the four first irradiation units32, but the number of the first irradiation units32may be other than four.

The second irradiation unit52includes the laser light source36B, and a second lens54that guides the laser light beam Bm from the laser light source36B to the surface PA of the sheet P. In addition, the second irradiation unit52includes the collimate lens37and the condensing lens39. In the second irradiation unit52, the laser light source36B, the collimate lens37, the second lens54, and the condensing lens39are disposed in this order according to an optical axis of the laser light beam Bm.

Second Lens

As shown inFIG. 6A, the second lens54is, for example, a plane-concave lens which includes a first concave surface54A and a second concave surface54B on the Y side which is the side of the laser light source36B (seeFIG. 5) and of which the negative Y side has a flat shape. An optical axis K of the laser light beam Bm is positioned in the center of the second lens54in the Z direction.FIG. 6Ashows the second lens54positioned in end portion of the Z side. Herein, the second lenses54on the Z side and the negative Z side have the same configuration and are disposed to be symmetrical with each other using the center position of the irradiation target area S as the center, and accordingly the second lens54on the Z side will be described and the second lens54on the negative Z side will be omitted.

The first concave surface54A is disposed on the negative Z side which is the first lens38side with respect to the optical axis K, using the optical axis K as a boundary, when the second lens54is seen in the X direction. The second concave surface54B is disposed on the Z side with respect to the optical axis K, when the second lens54is seen in the X direction. The first concave surface54A and the second concave surface54B are connected to each other in the Z direction. A curvature of the first concave surface54A is greater than a curvature of the second concave surface54B.

The curvature and a focal length of the first concave surface54A are set so that the irradiation width W4on the surface PA of the sheet P is irradiated with the laser light beam Bm incident to the first concave surface54A, from the optical axis K to the negative Z side. The curvature and a focal length of the second concave surface54B are set so that the first irradiation width W5(<W4) on the surface PA of the sheet P is irradiated with the laser light beam Bm incident to the second concave surface54B, from the optical axis K to the Z side. For example, the sum of the irradiation width W4and the first irradiation width W5is substantially equivalent to the irradiation width W2(seeFIG. 3).

As shown inFIG. 6B, in a case where the second lens54is used, distribution of the light intensity I with respect to the light irradiation position (Z direction position) has a left-right asymmetric shape with the optical axis K as the center, as shown in a graph G10. Specifically, the laser light beam Bm penetrating the first concave surface54A (seeFIG. 6A) is diverged to the negative Z side. In addition, the laser light beam Bm penetrating the second concave surface54B (seeFIG. 6A) is diverged to the Z side to have a smaller width, compared to the laser light beam Bm penetrating the first concave surface54A. The graph of the light intensity I of the laser light beam Bm diverged by the second concave surface54B has the smaller width in the Z direction and a larger maximum value (peak), compared to a graph of the light intensity I of the laser light beam Bm penetrating the first concave surface54A (seeFIG. 6A).

As shown inFIG. 5, the two second irradiation units52are disposed so that a part of the laser light beam Bm emitted to the surface PA of the sheet P is superimposed with a part of the laser light beam Bm emitted by the adjacent first irradiation unit32. In addition, the two laser light sources36B of the second irradiation unit52are disposed so that two optical axes K are positioned in the irradiation target area S in the Z direction. The second irradiation unit52irradiates not only the irradiation target area S but also the outside of the irradiation target area S in the Z direction with the laser light beam Bm.

In addition, from the irradiation width of the surface PA irradiated with the laser light beam Bm from the second irradiation unit52in the Z direction, a first irradiation width that is not superimposed with the laser light beam Bm from the adjacent first irradiation unit32is set as W5. From the irradiation width of the surface PA irradiated with the laser light beam Bm in the Z direction from the first irradiation unit32adjacent to the second irradiation unit34, a second irradiation width that is not superimposed with the laser light beam Bm from the other first irradiation unit32adjacent to the first irradiation unit32is set as W6. Herein, an expression of W5<W6is satisfied.

Operation

An operation of the second exemplary embodiment will be described.

FIG. 7shows a simulation result of the light intensity [W/mm] with respect to the irradiation position [mm] of the laser light beam Bm of the light irradiation unit50of the exemplary embodiment (seeFIG. 5).

As described above, trapezoidal graphs G2, G3, G4, and G5ofFIG. 7show light intensity distribution of the four first irradiation units32(seeFIG. 5). In addition, graphs G9and G10ofFIG. 7show light intensity distribution of the two second irradiation units52(seeFIG. 5). Further, a graph GC shown with a bold line ofFIG. 7shows the total six light intensities of the graphs G2, G3, G4, G5, G9, and G10.

In order to obtain the necessary light intensity from the center and both ends of the surface PA of the sheet P in the Z direction using the light irradiation unit50of the exemplary embodiment shown inFIG. 5, it is necessary to dispose a portion of the second irradiation unit52having the highest light intensity on both ends of the irradiation target area S of the laser light Bm. This is because the light intensity is insufficient only by the first irradiation units32.

Herein, in the light irradiation unit50, the second irradiation units52having a irradiation width smaller than the first irradiation units32disposed in the center portion in the Z direction are disposed at both end portions in the Z direction. Accordingly, in the light irradiation unit50, even when the second irradiation units52are disposed so that a portion having the highest light intensity is positioned at both ends of the irradiation target area S, a quantity of light (integration value) of the laser light beam Bm emitted to the outside of the irradiation target area S becomes (is decreased) to be smaller than a quantity of light (integration value) of the comparative example (seeFIG. 11). Accordingly, in the light irradiation unit50, a loss of light energy at the outside of the irradiation target area S is decreased, compared to the light irradiation unit of the comparative example.

In addition, the second irradiation unit52of the light irradiation unit50uses the laser light source36B having the same configuration as that of the laser light source36A and uses the second lens54having a different focal length from that of the first lens38of the first irradiation unit32to have a smaller (narrower) irradiation width. Accordingly, since the configurations of the light sources of the first irradiation unit32and the second irradiation unit52are common, the assembly of the light irradiation unit50is easy, compared to a configuration of not using the light source having the same configuration as that of the laser light source36A as the light source of the second irradiation unit52.

As shown inFIG. 6A, in the light irradiation unit50, the second concave surface54B having a small curvature and a long focal length is positioned at the outer side in the Z direction (the side opposite to the first lens38side) with respect to the first concave surface54A having a large curvature and a short focal length. Accordingly, the light intensity of the laser light beam Bm emitted to the surface PA of the sheet P by the second lens54on the first lens38side is low, and the light intensity thereof on the boundary portion of the irradiation target area S is high. The sum of the light intensity of the laser light beam Bm penetrating the first lens38and the light intensity of the laser light beam Bm penetrating the first concave surface54A of the second lens54is close to the light intensity of the laser light beam Bm penetrating the second concave surface54B of the second lens54. Therefore, as shown inFIG. 7, a difference between the light intensity on end portion in the irradiation target area S in the Z direction and the light intensity in the center thereof in Z direction is decreased.

In the fixing device20including the light irradiation unit50, the light irradiation unit50irradiates the toner T on the sheet P transported by the transportation belt22with the laser light beam Bm. The toner T (toner image G) is heated and melted by absorbing the laser light beam Bm, and is fixed onto the sheet P. Herein, in the fixing device20, the loss of light energy of the light irradiation unit50is decreased, compared to that of the light irradiation unit of the comparative example, and accordingly, the energy necessary for the fixation of the toner T is reduced compared to the case of the comparative example.

In the image forming apparatus10, the image forming unit14forms the toner image G on the sheet P and the fixing device20fixes the toner image G onto the sheet P. Here, in the image forming apparatus10, since the energy necessary for the fixation of the toner T is reduced by using the fixing device20, the energy necessary for the image forming onto the sheet P is reduced, compared to the case of using the fixing device including the light irradiation unit of the comparative example.

Third Exemplary Embodiment

Next, examples of a light irradiation device, a fixing device, and an image forming apparatus according to the third exemplary embodiment will be described. The members and parts basically same as those of the first exemplary embodiment will have the same reference numerals as those of the first exemplary embodiment and description thereof will be omitted.

FIG. 8shows a light irradiation unit60as an example of a light irradiation device of the third exemplary embodiment. In the third exemplary embodiment, a point of providing the light irradiation unit60instead of the light irradiation unit30(seeFIG. 1) in the image forming apparatus10and the fixing device20of the first exemplary embodiment is different from the first exemplary embodiment, and the other configurations thereof are same as those of the first exemplary embodiment.

In the light irradiation unit60, for example, the six first irradiation units32are disposed at set intervals in the Z direction. The light irradiation unit60does not include the second irradiation units34(seeFIG. 3). In the light irradiation unit60, the two first irradiation units32at both ends in the Z direction are disposed in a position close to the surface PA of the sheet P, compared to the other four first irradiation units32. That is, the four first irradiation units32in the center in the Z direction are disposed in the position to have the irradiation width W1on the surface PA, and the two first irradiation units32at both ends in the Z direction are disposed in the position to have the irradiation width W2on the surface PA. In addition, the two laser light sources36A at both ends in the Z direction are disposed so that two optical axes K are positioned in the irradiation target area S in the Z direction. The second irradiation unit34irradiates not only the irradiation target area S but also the outside of the irradiation target area S in the Z direction with the laser light beam Bm.

In addition, from the irradiation width of the surface PA irradiated with the laser light beam Bm from the first irradiation units32at both ends in the Z direction, a first irradiation width that is not superimposed with the laser light beam Bm from the adjacent first irradiation unit32is set as W5. From the irradiation width of the surface PA irradiated with the laser light beam. Bm in the Z direction from the first irradiation unit32adjacent to the first irradiation units32at both ends in the Z direction, a second irradiation width that is not superimposed with the laser light beam. Bm from the other first irradiation unit32adjacent to the first irradiation unit32is set as W6. Herein, an expression of W5<W6is satisfied.

Operation

An operation of the third exemplary embodiment will be described.

In the light irradiation unit60shown inFIG. 8, the irradiation widths at both ends in the Z direction are smaller than those in the center portion. Accordingly, in the light irradiation unit60, even when the first irradiation units32are disposed so that a portion having the highest light intensity is positioned at both ends of the irradiation target area S, a quantity of light (integration value) of the laser light beam Bm emitted to the outside of the irradiation target area S is decreased to be smaller than a quantity of light (integration value) of the comparative example. Therefore, in the light irradiation unit60, a loss of light energy at the outside of the irradiation target area S is decreased, compared to the light irradiation unit of the comparative example.

In the light irradiation unit60, the first irradiation units32at both ends in the Z direction among the plural first irradiation units32are close to the surface PA of the sheet P. Accordingly, it is not necessary to use the irradiation unit having the different configuration, and therefore, the first irradiation unit and the second irradiation unit are configured with the same elements. The operations of the fixing device20and the image forming apparatus10are the same as those in the first exemplary embodiment, and therefore the description thereof will be omitted.

The invention is not limited to the exemplary embodiments described above. For example, the following modification examples may be employed.

First Modification Example

A fixing device is not limited to a device that performs fixation of the toner T in a non-contact manner as the fixing device20shown inFIG. 2, and may be a device that performs fixation of the toner T in a contact manner as a fixing device70shown inFIG. 9.

The fixing device70includes an opposite roll72as an example of the transportation unit and a light irradiation unit80as an example of the light irradiation device. The opposite roll72is rotatably provided using the Z direction as an axial direction.

In the light irradiation unit80, a lens pad74and a transparent tube76having the Z direction as a longitudinal direction are provided instead of the condensing lens39(seeFIG. 3) in the first irradiation unit32and the second irradiation unit34of the first exemplary embodiment. The lens pad74is nipped and supported between a support frame78A and a support frame78B. The transparent tube76is rotatably disposed on the outer side of the lens pad74, the support frame78A, and the support frame78B.

The transparency of the transparent tube76means sufficiently high transmittance in a wavelength region of the laser light beam Bm. That is, the transparent tube76may be any component as long as it transmits the laser light beam Bm, and the higher transmittance as much as possible is preferable, in order to realize efficiency for light utilization and to prevent the heating of the lens pad74. The transmittance is, for example equal to or greater than 90 [%] and desirably equal to or greater than 95 [%].

As the material of the lens pad74, a material having heat resistance may be generally selected from the materials used for the lens, and an optical transparent plastic resin is used, for example. Examples of the optical transparent plastic resin include materials including polydiethylene glycol bisallyl carbonate (PADC), polymethyl methacrylate (PMMA), and polystyrene (PSt). In addition, examples of the optical transparent plastic resin include materials including a polymer formed of a methyl methacrylate unit and a styrene unit (MS resin), a polycarbonate resin, a cycloolefin resin, and a fluorene resin, for example.

The laser light beam Bm penetrating the first lens38or the second lens42is incident to the Y side of the transparent tube76. The laser light beam Bm penetrating the lens pad74and the transparent tube76is output from the negative Y side of the transparent tube76. In addition, silicone oil permeated in a felt material82is, for example, applied to the inner surface of the transparent tube76. Further, the outer circumferential surface of the transparent tube76and the outer circumferential surface of the opposite roll72come into contact with each other, to form a nip portion N that pressurizes the toner T.

The lens pad74causes the laser light beam Bm emitted by penetrating the transparent tube76to be converged in the X direction and concentrates the laser light beam on the nip portion N. The lens pad74supports the transparent tube76passing the nip portion N from the inside. As described above, the fixing device70may pressurize the toner T by bringing the transparent tube76into contact with the toner T, irradiates the toner T with the light by the light irradiation unit80to heat and melt the toner. The laser light beam Bm is diverged in the Z direction by the first lens38and the second lens42.

Second Modification Example

A method of changing the irradiation width and the light intensity distribution of the laser light beam Bm on the surface PA of the sheet P is not limited to the method using the first lens38, and the second lenses42and54. For example, a light irradiation unit90of a second modification example shown inFIG. 10may be used.

The light irradiation unit90has a configuration of replacing the second irradiation units34at both ends in the Z direction (seeFIG. 3) in the light irradiation unit30of the first exemplary embodiment (seeFIG. 3) with second irradiation units35. The second irradiation unit35is configured with the same member as that of the first irradiation unit32, but is different in a point that the second irradiation unit is inclined so that the laser light beam Bm (optical axis K) emitted to the surface PA of the sheet P from the second irradiation unit35faces the first irradiation unit32side.

When the irradiation width of the surface PA of the sheet P in the Z direction to be irradiated with the laser light beam Bm by the second irradiation unit35is set as W7, an expression of W7<W1is satisfied. In addition, when the width where the laser light beam Bm of the second irradiation unit35and the laser light beam Bm of the first irradiation unit32are superimposed in the Z direction is set as W8, an expression of W8>W4is satisfied.

In addition, from the irradiation width of the surface PA irradiated with the laser light beam Bm from the second irradiation unit35in the Z direction, a first irradiation width that is not superimposed with the laser light beam Bm from the adjacent first irradiation unit32is set as W9. Further, from the irradiation width of the surface PA irradiated with the laser light beam Bm in the Z direction from the first irradiation unit32adjacent to the second irradiation unit35, when a second irradiation width that is not superimposed with the laser light beam Bm from the other adjacent first irradiation unit32is set as W10, an expression of W9<W10is satisfied.

Herein, in the light irradiation unit90, a quantity of light (integration value) of the laser light beam Bm emitted to the outside of the irradiation target area S becomes (is decreased) to be smaller than a quantity of light (integration value) of the comparative example (seeFIG. 11). Accordingly, in the light irradiation unit90, the quantity of light emitted to the outside of the irradiation target area S on the surface PA is decreased and a loss of light energy at the outside of the irradiation target area S is decreased, compared to the light irradiation unit of the comparative example.

Other Modification Example

The light irradiation units30,50,60, and80are not limited to be used in the fixing devices20and70, and may be used in a heat treatment device that performs annealing for removing processing strain. In addition, the light irradiation units30,50,60, and80may be used as an inline sensor that performs the image forming on the sheet P, emits light to the toner image G, receives the reflected light from the toner image G, and evaluates the toner image G. Further, the light irradiation units30,50,60, and80may be used as a light irradiation unit of a scanner.

The first lens38and the second lenses42and54are not limited to be configured with a diffusion optical system (concave lens), and may be configured with a condensing optical system (convex lens). When the first lens38and the second lenses42and54are configured with a condensing optical system, the first lens38and the second lenses42and54may be disposed so that the condensed divergent light is emitted to the surface of the sheet P.

Regarding the light source, the first irradiation unit and the second irradiation unit are not limited to have the same configuration, as the laser light sources36A and36B. As long as they are configured to have the same melting state of the toner T, the laser light source having the different configurations between the first irradiation unit and the second irradiation unit may be used.