JPH1031407A - Air duct with projection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air duct with projections with which the assurance of high cooling efficiency is possible. SOLUTION: This air duct 11 with projections is installed near a fixing device (heat generating source) 9 and is constituted by projectingly providing the wall surface of a duct body 11a with >=3 projections 12 at approximately specified spacings S approximately perpendicularly to the flow direction of air. The arranging pitches S of the projections 12 are set according to the sectional shape of the projections 12. The optimum value of the arranging pitches S of the projections 12 for assuring the high cooling efficiency of the air duct 11 with the projections varies with the sectional shape of the projections 12; for example, it is experimentally ascertained that the assurance of the high cooling efficiency of the air duct 11 with the projections is possible if the arranging pitches S of the projections 12 are set at 5H<=S<=13H when the sectional shape of the projections 12 is square.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air duct with a projection for preventing a temperature rise around a heat source.

[0002]

2. Description of the Related Art Conventionally, for example, in a laser beam printer, an air duct is provided in the vicinity of a heat source such as a fixing device in order to prevent a temperature rise in the apparatus main body. There has been proposed an air duct with projections in which a plurality of projections are provided so as to project substantially perpendicularly to the direction of air flow.

[0003] In a conventional air duct with projections, the arrangement pitch of the projections is set substantially constant irrespective of the cross-sectional shape of the projections.

[0004]

However, according to the study of the present inventors, it has been found that the optimum value of the arrangement pitch of the projections for obtaining high cooling efficiency in the air duct with the projections differs depending on the cross-sectional shape of the projections. Was.

Therefore, in the conventional air duct with projections, the arrangement pitch of the projections is not always set to an optimum value with respect to the cross-sectional shape of the projections, and the air duct with projections can always ensure high cooling efficiency. The fact was not.

The inventor has also found that there is an optimum value of the closing ratio (the ratio of the cross-sectional area of the protrusion to the cross-sectional area of the duct body) for keeping the cooling efficiency of the air duct with the protrusion high. .

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an air duct with projections that can ensure high cooling efficiency.

[0008]

In order to achieve the above object, the invention according to claim 1 is installed near a heat source,
In an air duct with protrusions, in which three or more protrusions are provided on a wall surface of a duct body at substantially regular intervals at a substantially right angle to a flow direction of air, an arrangement pitch of the protrusions is set according to a cross-sectional shape of the protrusions. It is characterized by having done.

According to a second aspect of the present invention, in the first aspect of the present invention, when the cross-sectional shape of the projection is a square,
The arrangement pitch S of the projections with respect to the height H is 5H ≦ S ≦
13H.

According to a third aspect of the present invention, in the first aspect of the present invention, when the cross-sectional shape of the projection is a semi-elliptical shape, the arrangement pitch S of the projection is 6H ≦ H with respect to its height H.
It is characterized by setting S ≦ 10H.

According to a fourth aspect of the present invention, in the first aspect of the invention, when the cross-sectional shape of the projection is semicircular,
The arrangement pitch S of the projections with respect to the height H is 5H ≦ S ≦
11H.

According to a fifth aspect of the present invention, in the first aspect of the present invention, when the cross-sectional shape of the projection is a triangle,
The arrangement pitch S of the projections with respect to the height H is 5H ≦ S ≦
13H.

According to a sixth aspect of the present invention, in the first to fourth or fifth aspects, the ratio a / A of the cross-sectional area a of the projection to the cross-sectional area A of the duct body is set to a / A ≦ 0.07. It is characterized by having been set.

According to a seventh aspect of the present invention, in the sixth aspect of the present invention, the protrusion is formed over the entire width of the duct main body, and the height H of the protrusion is H ≦ 0.
07D.

According to an eighth aspect of the present invention, in the invention of the sixth aspect, when there are two or more heat sources, a projection is provided on a wall surface of the duct body facing each heat source, and each of the projections is cut off. The ratio Σa _i / A of the total area Σa _i (i = 1 to 4) to the cross-sectional area A of the duct body is expressed as Σa _i / A ≦ 0.
07 is set.

According to a ninth aspect of the present invention, in the invention of the eighth aspect, each of the projections is formed over the entire width of the duct body, and the sum of the heights of the projections ΣH _i (i = 1 to 4) is determined. It is characterized in that ΔH _i ≦ 0.07D with respect to the height D of the duct body.

The invention according to claim 10 is the invention according to claim 8 or 9.
In the described invention, the cross-sectional shapes of the projections provided on each wall surface are different from each other.

According to the present inventors, the optimum value of the arrangement pitch of the projections for ensuring high cooling efficiency in the air duct with projections differs depending on the cross-sectional shape of the projections, and the blockage for maintaining the cooling efficiency of the air duct with projections high. We found that there was an optimum value for the ratio (the ratio of the cross-sectional area of the projection to the cross-sectional area of the duct body), set the closing rate to 7% or less, and set the arrangement pitch of the projections to the cross-sectional shape of each projection. By setting each optimum value differently, high cooling efficiency could be secured for the air duct with projections.

[0019]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<First Embodiment> FIG. 1 is a cross-sectional view of a laser beam printer having an air duct with projections according to the present invention. FIG. 2 is a cross-sectional view showing the configuration of an air duct with projections according to Embodiment 1 of the present invention. FIG. 3 is a perspective view of the air duct with the protrusion, FIG. 4 is a diagram showing the relationship between the cross-sectional area of the protrusion and the cross-sectional area of the duct body, FIG. 5 is a diagram showing the relationship between the closing rate and the cooling efficiency, and FIG. FIG. 7 is a diagram illustrating the flow of air in the valley, and FIG. 7 is a diagram illustrating the relationship between the air volume and the cooling efficiency.

First, the schematic structure of a laser beam printer and its operation will be described with reference to FIG.

The main body 1 of the laser beam printer shown in FIG.
A photosensitive drum 1, which is an image carrier rotatably driven in the direction of the arrow in the figure, is disposed substantially at the upper center of the photosensitive drum 1. Around the photosensitive drum 1, a primary charger 2, a cleaner 3, and a transfer drum 4 are provided. And a developing unit 5 are provided. A laser scanner 6 is provided above the photosensitive drum 1 in the apparatus main body 10.
A cassette 7 in which a plurality of transfer materials P are stacked and housed is installed at the bottom of the apparatus main body 10.

Further, a paper feed roller 8 and a fixing device 9 are disposed above the cassette 7 in the apparatus main body 10, and an air duct with a projection according to the present invention is provided above the fixing device 9 which is a heat generating source. 11 are installed. The fixing device 9 includes a fixing roller 9 a having a built-in heater (not shown) and the fixing roller 9.
a and a pressure roller 9b that rotates in accordance with the rotation of the pressure roller 9a.

The photosensitive drum 1 is driven to rotate at a predetermined speed in the direction of the arrow shown in the figure, is uniformly charged by the primary charger 2, and the laser beam L from the laser scanner 6 is emitted.
, An electrostatic latent image is formed on the surface. Then, the electrostatic latent image is developed by the developing device 5 and visualized as a toner image.

On the other hand, the transfer material P is supplied one by one from the cassette 7 by the paper feed roller 8, and the transfer material P is attracted to the transfer drum 4 and rotates together with the transfer drum 4 in the direction of the arrow shown in FIG. In the process, the toner image formed on the photosensitive drum 1 is transferred.

The transfer material P to which the toner image has been transferred
Is separated from the transfer drum 4 and sent to the fixing unit 9 to fix the toner image by heat and pressure, and passes through a path shown by an arrow in FIG.
Is discharged on top.

The air duct 11 with projections according to the present invention has an inner wall surface (bottom wall surface) facing the fixing device 9 of the duct main body 11a having a rectangular cross section elongated in the direction perpendicular to the plane of FIG.
A plurality of projections 12 are provided at a predetermined interval S so as to be substantially perpendicular to the air flow direction. As shown in FIG. 2, a fan 13 for sucking air is provided near an opening on the downstream side (downstream side in the air flow direction) of the air duct 11 with protrusions.

As shown in detail in FIGS. 2 and 3, the projection 12 projecting from the inner wall surface (bottom wall surface) of the duct body 11a is a prismatic projection having a square section with a side length H. These are protruded over the entire width L of the duct body 11a, and they are arranged at a constant arrangement pitch (center-to-center distance) S
It is arranged in. The reason why the projections 12 are provided so as to be substantially perpendicular to the air flow direction is that if they are arranged in parallel to the air flow direction, the mixed development of the flow near the wall surface is unlikely to occur.

Next, a method of obtaining the height H of the projection 12 will be described with reference to FIGS.

Generally, in an air duct with a projection,
Blockage ratio (cross-sectional area a of the protrusion relative to cross-sectional area A of the duct body)
It is known that if the ratio a / A) is large, the protrusion becomes a resistance and air does not flow smoothly in the duct. Here, there is a relationship shown in FIG. 5 between the blocking ratio a / A (%) and the cooling efficiency η (%), and as shown in FIG. Does not appear, and a high cooling efficiency η is secured. However, if the closing ratio a / A exceeds 7%, the protrusion becomes a resistance and the air does not flow smoothly, so that the cooling efficiency η increases the closing ratio a / A. It gradually goes down with it.

Therefore, in order to ensure high cooling efficiency for the air duct with projections, it is necessary to set the closing ratio a / A to 7% or less.

That is, the following equation must be satisfied.

[0033]

A / A ≦ 0.07 (1) Here, as shown in FIGS. 3 and 4, the duct main body 11a
Is D, the sectional area A of the air duct body 11a is D = L. Since the sectional area a of the projection 12 is a = HL, the following equation is obtained by substituting these into the equation (1).

[0034]

A / A = (H · L) / (D · L) ≦ 0.07 H ≦ 0.07D (2) Accordingly, the height H of the projection 12 is equal to the height D of the duct body 11a.
Should be set to 7% or less.

Next, the setting of the arrangement pitch S of the projections 12 will be described.

FIG. 6 shows the flow of air over the protrusions 12 inside the valleys between the protrusions 12. If the distance between the protrusions 12 is small, as shown in FIG. As a result, the mixing phenomenon of the flow near the wall surface is not activated because the stable vortex is generated, and the mixing phenomenon of the flow near the wall surface is activated by appropriately setting the interval between the projections 12 as shown in FIG. It was required by experiment to do. In the protrusion 12 having a square cross section as in the present embodiment, the arrangement pitch S is represented by the following formula:

[0037]

## EQU3 ## It has been found that the setting of the range expressed by 5H ≦ S ≦ 13H (3) makes it possible to activate the mixing phenomenon of the flow near the wall without depending on the flow velocity of the air.

Accordingly, by setting the height H and the arrangement pitch S of the projections 12 so as to satisfy the above equations (2) and (3), it is possible to secure a high cooling efficiency η in the air duct 11 with projections. The temperature rise in the apparatus main body 10 of the laser beam printer shown in FIG. 1 can be effectively prevented.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 8 is a view showing various cross-sectional shapes of the protrusion.

The present inventor has found that the optimum value of the arrangement pitch S of the projections for ensuring high cooling efficiency in the air duct with the projections differs depending on the cross-sectional shape of the projections.
(A), a projection having a semi-elliptical cross section, (b) a projection having a semicircular cross section, (c) a projection having an isosceles triangle (triangle A) cross section, (d) ), The optimum arrangement pitch S for the projections having a right-angled isosceles triangle (triangle B) cross-section and the projections having a right-angled isosceles triangle (triangle C) cross-section as shown in FIG. The following results were obtained for each of them.

[0041]

[Formula 4] Semi-ellipse: 6H ≦ S ≦ 10H Semi-circle: 5H ≦ S ≦ 11H Triangle A: 5H ≦ S ≦ 13H (4) Triangle B: 5H ≦ S ≦ 13H Triangle C: 5H ≦ S ≦ 13H (2) for the projections having various cross-sectional shapes
By setting the height H and the arrangement pitch S so as to satisfy the expression and the expression (4), it is possible to secure a high cooling efficiency η in the air duct with projections.

Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 9 is a cross-sectional view showing the configuration of the air duct with projections according to Embodiment 3 of the present invention. In this figure, the same elements as those shown in FIG. The description of is omitted.

In this embodiment, the air duct 11 with projections
Shows an example in which the heat sources 9 and 19 are installed in the vicinity of the two heat sources 9 and 19, and the duct body 11 of the air duct 11 with protrusions.
a has a height H on the inner wall surface facing each of the heat generating sources 9 and 19.
_1, a plurality of projections 12, 22 having a rectangular cross-section of H ₂ is protruded at a pitch S _1, S ₂ substantially perpendicular aligned relative to the direction of flow of the air, respectively.

In this case, the closing rate of the air duct 11 with projections (the projections 12, 2 with respect to the sectional area A of the duct body 11a).
Ratio of the sum of the cross sectional area a of 2 (a ₁ + a ₂₎ is occupied (a ₁
+ A ₂ ) / A) should be set to 7% or less for the above reason, and therefore the heights H ₁ and H of the projections 12 and 22 are set.
₂ is set to satisfy the following equation.

[0045]

H ₁ + H ₂ ≦ 0.07D (5) Here, H ₁ and H ₂ do not necessarily have to be H ₁ = H ₂ , but are high according to the respective heat generation amounts of the heat sources 9 and 19. It is H _1, H
₂ may be set to a different value.

In this case, the projections 12,
The 22 array pitches S ₁ and S ₂ are set so as to satisfy the following equations.

[0047]

5H ₁ ≦ S ₁ ≦ 13H ₁ 5H ₂ ≦ S ₂ ≦ 13H ₂ (6) Accordingly, the height H ₁ of each of the projections 12 and 22 is set so as to satisfy the above equations (5) and (6). , H ₂ and arrangement pitches S ₁ , S ₂
, It is possible to secure a high cooling efficiency η in the air duct 11 with projections.

At this time, as shown in FIG. 10, the sectional shapes of the projections 12 and 32 may be changed for each wall surface. That is,
A protrusion 12 having a rectangular cross section is provided on the inner wall surface of the duct body 11a on the side facing one heat source 9, and the other heat source 19 is formed.
May be projected to the projection 32 of triangular cross section on the inner wall surface of the opposite side to, in this case, arrangement of the projections 32 Pitch S ₂
Is set so as to satisfy the following equation (see the above equation (4)).

[0049]

5H ₂ ≦ S ₂ ≦ 13H ₂ (7) By the way, in the present embodiment, the case where two heat sources are installed has been described, but more (up to 4) heat sources are required. is, it is also installed, as well as projecting a projection on the wall surface facing the respective heating source of the duct body, to the cross-sectional area a of the duct body of the sum Σa _{i (i} = 1~4) of the cross-sectional area of each projection It is necessary to set the ratio Δa _i / A (blockage rate) to 7% or less. That is, the following equation must be satisfied.

[0050]

Σa _i /A≦0.07 (8) When each projection is formed over the entire width of the duct body, the sum of the heights of each projection ΣH _i (i = 1 to 4) To 7% or less of the height D of the duct body, that is, the following equation;

[0051]

ΣH _i ≦ 0.07D (9)

[0052]

As is apparent from the above description, according to the present invention, three or more projections are provided near the heat source and formed on the wall surface of the duct main body substantially at right angles to the air flow direction. In an air duct with projections projecting at regular intervals, the arrangement pitch of the projections is set in accordance with the cross-sectional shape of the projections, so that an effect of ensuring high cooling efficiency in the air duct with projections can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a laser beam printer including an air duct with projections according to the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a protruding air duct according to Embodiment 1 of the present invention.

FIG. 3 is a perspective view of the air duct with projections according to Embodiment 1 of the present invention.

FIG. 4 is a diagram illustrating a relationship between a cross-sectional area of a protrusion and a cross-sectional area of a duct main body in the air duct with a protrusion according to Embodiment 1 of the present invention.

FIG. 5 is a diagram showing a relationship between a closing rate and cooling efficiency.

FIG. 6 is a diagram illustrating a flow of air in a protrusion valley.

FIG. 7 is a diagram illustrating a relationship between an air volume and a cooling efficiency.

FIG. 8 is a view showing various cross-sectional shapes of a projection.

FIG. 9 is a cross-sectional view illustrating a configuration of an air duct with projections according to Embodiment 3 of the present invention.

FIG. 10 is a sectional view of an air duct with projections showing a modification of the third embodiment of the present invention.

[Explanation of symbols]

9 fuser (heat source) 11 with projections air duct 11a duct body 12, 22, 32 protrusion 19 heat sources A duct body of the cross-sectional area a projection of the cross-sectional area D air duct body height H, H _1, the H ₂ projection height Length L Width of air duct body S, S ₁ , S ₂ Protrusion pitch

Claims (10)

[Claims] 1. An air duct with projections, which is installed in the vicinity of a heat source and has three or more projections projecting from a wall surface of a duct main body at substantially regular intervals at a substantially right angle to a flow direction of air. Characterized in that the arrangement pitch of the air ducts is set according to the cross-sectional shape of the projection. 2. When the cross-sectional shape of the projection is square, the arrangement pitch S of the projection is 5H ≦ H with respect to its height H.
2. The air duct with a projection according to claim 1, wherein S≤13H. 3. When the cross-sectional shape of the projection is a semi-elliptical shape, the arrangement pitch S of the projection is 6H ≦ H with respect to its height H.
2. The air duct with a projection according to claim 1, wherein S ≦ 10H is set. 4. When the cross-sectional shape of the projection is semicircular, the arrangement pitch S of the projection is 5H ≦ H with respect to its height H.
The air duct with a projection according to claim 1, wherein S≤11H is set. 5. When the cross-sectional shape of the projection is triangular, the arrangement pitch S of the projection is 5H ≦ H with respect to its height H.
2. The air duct with a projection according to claim 1, wherein S≤13H. 6. The projection according to claim 1, wherein a ratio a / A of the cross-sectional area a of the protrusion to the cross-sectional area A of the duct body is set to a / A ≦ 0.07. Air duct. 7. The projection is formed over the entire width of the duct main body, and the height H of the projection is H ≦ H with respect to the height D of the duct main body.
The air duct with a projection according to claim 6, wherein the air duct is set to 0.07D. 8. When there are two or more heat sources, a projection is provided on a wall surface of the duct body facing each heat source,
? A _i / A ≦ percentage? A _i / A to the cross-sectional area A of the duct body of the sum Σa _{i (i} = 1~4) of the cross-sectional area of each projection
7. The air duct with projections according to claim 6, wherein the air duct is set to 0.07. 9. Each of the projections is formed over the entire width of the duct main body, and the sum of the heights of the respective projections ΣH _i (i = 1 to 4) with respect to the height D of the duct main body is ΣH _i ≦ 0. The air duct with a protrusion according to claim 8, wherein the air duct is set to 07D. 10. The air duct with projections according to claim 8, wherein the projections projecting from the respective wall surfaces have different cross-sectional shapes.