JPH10171225A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which has a simple and space saved developing part cooling means, unncessitate a seal member causing inconvenience at the time of executing maintenance and to increase the cooling efficiency of a developing part by directly hitting a flow of cooling air against a developing part housing, without providing a guiding member and further, discharging the flow of cooling air outside an image forming device, without retaining the flow of cooling air. SOLUTION: This image forming device is provided with a nearly closed space using at least a part of the developing part housing 1 including a stirring member for stirring/mixing carriers and toner, as a component. A suction fan 41 for taking outdoor air in the space is provided in one component of the space and a discharge fan 42 for discharging air in the space to the outside of a device is arranged in a position comparatively far from the suction fan 41 of another component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, such as a copying machine, a plain paper facsimile, and a printer, for forming an image using a two-component developer composed of a carrier and a toner. The present invention relates to an image forming apparatus having means for performing the above.

[0002]

2. Description of the Related Art In a developing section of an image forming apparatus for forming an image using a two-component developer, a stirring member is provided in a housing to sufficiently stir a two-component developer composed of a toner and a carrier. Therefore, heat is generated by the friction at that time. If the heat is trapped in the developing section, the toner during development starts to soften (becomes in a state of melting), so that so-called toner filming that enters into a bearing or the like and is locked may occur. In addition, the heat may increase the temperature of the photoconductor, causing a problem such as changing the potential of the photoconductor.

In order to avoid these problems, the housing of the developing unit has conventionally been made of a material having high thermal conductivity, and the surface of the housing has been blown by a fan to cool the developing unit.
However, due to space limitations, it is often not possible to arrange a fan in the vicinity of the agitating member, which is a heat generating part. However, it is difficult to take a wide air path due to space limitations, the pressure loss during ventilation increases, and the fan must be increased in capacity to obtain the required cooling effect. there were.

In order to eliminate this drawback and enable efficient cooling, Japanese Patent Application Laid-Open No. 63-184774 discloses
It has been proposed to provide a guide member made of a heat conductive material, one end of which contacts the developing unit housing and the other end of which is located near the exhaust port of the cooling fan. In this known configuration, heat generated in the developing section is transmitted to the guide member via a developing section housing made of a heat conductive material. On the other hand, cooling air sucked from the outside of the image forming apparatus by the cooling fan flows through an air passage formed between the guide member and the structural member. Therefore, it was expected that the developing unit housing would be efficiently cooled by heat exchange between the wide surface of the guide member exposed to the cooling air and the lower part of the developing unit housing.

However, in many cases, a sufficient installation space for the guide member cannot be secured, and in some cases, no installation space can be obtained at all.
This device also has disadvantages common to those generally used in the prior art. Also, by installing the guide member, the flow path becomes narrow, and the airflow around the developing device is weakened.
Instead, it can even have a negative effect on cooling.

On the other hand, if the cooling air sucked by the fan flows in another direction, it causes a decrease in the amount of light due to the adhesion of toner to the eraser surface. In addition, cooling air after cooling the developing unit housing disturbs the toner image formed on the surface of the photoreceptor, or lowers the sensitivity by attaching toner to the light receiving surface of the density sensor. May cause it to occur. Therefore, in the apparatus disclosed in JP-A-63-184774, in order to prevent these inconveniences, the entire width of the image forming apparatus (the entire axial length of the photosensitive drum).
Measures were required to seal the gap between the upper end of the guide member and the optical base with a seal member, and to provide a seal member over the entire width between the vicinity of the lowermost portion of the developing unit housing and the structural member. . However, if the gap between the developing device and the main body structure is closed by the seal member, it becomes difficult to attach and detach the developing device from the main body structure, which causes a great inconvenience during maintenance.

[0007]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an image forming apparatus having a simple and space-saving cooling means for a developing unit, which does not require a sealing member which causes inconvenience during maintenance. And Another object is to increase the cooling efficiency of the developing unit by directing the airflow of the cooling air to the developing unit housing without providing a guide member and discharging the airflow to the outside of the image forming apparatus without stopping the airflow. I do.

[0008]

According to the present invention, there is provided a substantially closed space including at least a part of a developing unit housing including a stirring member for stirring and mixing a carrier and a toner. A suction fan for sucking outside air into the space is provided in one component of the space, and a discharge fan for discharging air in the space to the outside of the device is relatively far from the suction fan of another component. The problem is solved by an image forming apparatus characterized by being arranged at a position.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described based on the illustrated embodiment. FIG. 1 illustrates an image forming apparatus including a developing unit cooling unit according to an embodiment of the present invention.
1 shows a schematic cross-sectional view from the front. FIG. 2 is a schematic partial view when the inside of the image forming apparatus is viewed from above. FIG. 2 shows only the minimum members necessary for explanation.

Inside the image forming apparatus, a developing unit housing 1 (FIGS. 1 and 2) containing a stirring member 2 for stirring the carrier and the toner, a structural member 5 (FIG. 1), and a casing of the toner replenishing unit 7 are provided. 8 (FIGS. 1 and 2), a front plate 21 (FIG. 2) of the image forming apparatus, a rear plate 22 (FIG. 2) of the image forming apparatus, and an inner cover 23 (FIGS. 1 and 2) of the image forming apparatus. A closed space is formed. The space need not be airtightly closed. The inner cover 23 has a suction fan 41 for sucking outside air (cooling air) from outside the image forming apparatus into the space.
The rear plate 22 is provided with a discharge fan 42 for discharging air in the space to the outside of the image forming apparatus.

The cooling air sucked from the outside of the image forming apparatus by the suction fan 41 passes under the casing 8 in the space as shown by an arrow A in FIG. And heat exchange is performed to cool the developing unit housing 1 and thus the developing unit. Therefore, the airflow of the cooling air is drawn by a discharge fan 42 provided on the rear side plate 22 to change the flow direction by about 90 °, and as shown by a plurality of continuous arrows A in FIG. The heat flows along the developing unit housing 1 in the axial direction without stagnation toward the discharge fan 42 while performing heat exchange, and is discharged again to the outside of the image forming apparatus by the discharge fan 42. Therefore, there is no inconvenience that the airflow passing through the lower part of the developing unit disturbs the toner image formed on the surface of the photosensitive drum 3.
For efficient cooling of the developing unit, it is advantageous to arrange the exhaust fan 42 near the developing unit so that the widest possible area of the developing unit housing 1 is exposed to the cooling airflow. As an example, when the exhaust fan 42 is provided on the rear plate 22 as shown in FIG. 2, it is advantageous that the suction fan 41 is arranged at a position as close to the front plate 21 of the inner cover 23 as possible. is there.

If the exhaust fan 42 is provided on the front plate 21, the suction fan 41 may be arranged as close to the rear plate 22 of the inner cover 23 as possible. Further, the suction fan and the discharge fan may be provided near the developing portions of the front plate 21 and the rear plate 22 so as to face each other.

Although a suction fan is provided as in the device known from Japanese Patent Application Laid-Open No. 63-184774, if the discharge side is not a discharge fan but a mere discharge hole, the cooling fan sucked from the suction fan is used. The air for use leaks out of the apparatus from a gap near the suction fan due to negative pressure generated around the fan outside the image forming apparatus due to the influence of the suction fan. As a result, the flow rate of the cooling air in the space is reduced, and thus the air flow is weakened.
The airflow in the space also stagnates, and only a very small amount of the intake air is discharged from the discharge hole. Therefore, the cooling effect is poor.

[0014] On the other hand, although a discharge fan is provided, if the suction side is a mere suction hole, a negative pressure near the discharge fan in the space caused by the discharge fan causes a gap from the vicinity of the discharge fan to decrease. Since the air flows into the space, the amount of air flowing in from the suction hole becomes smaller than the amount discharged from the discharge fan, and it is difficult to obtain the airflow of the cooling air necessary for cooling the developing unit. .

That is, as proposed by the present invention, an additional seal member can be provided only by providing fans on both the suction side and the discharge side so that both cooperate to suction and discharge air. It is possible to form a sufficiently smooth cooling airflow for cooling the developing unit without using the airtightness of the space.

If the amount of air exhausted by the exhaust fan 42 is larger than the amount of air intake by the intake fan 41,
In addition to the cooling airflow from 1, the intake of air into the space from the gap near the exhaust fan 42 naturally occurs. Since such air is warm air in the machine, warm air in the machine mixes between the developing unit housing 1 and the discharge fan 42, thereby causing a temperature rise, and cooling of the developing unit housing 1 around it. Can be counterproductive.
Therefore, it is necessary to select both fans so that the suction amount of the suction fan 41 and the discharge amount of the discharge fan 42 are at least equal. In this case, there is a cost advantage in that the same fan can be used. However, if importance is placed on the cooling function, the flow rate of the suction fan 41 is reduced, although the cost is slightly disadvantageous.
It is desirable to select both fans so that the flow rate is greater than

[0017]

According to the present invention, it is not necessary to fill the gap between the developing device and the main assembly of the image forming apparatus with a sealing member. became. Further, since there is no need to provide an obstacle such as a guide member, the sucked cooling airflow can directly hit the developing unit housing, and the airflow is sucked out by the exhaust fan. Since the stagnation does not occur near the developing section, the developing section can be cooled more effectively.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an image forming apparatus including a developing unit cooling unit according to one embodiment of the present invention as viewed from the front side.

FIG. 2 is a schematic partial view showing a flow of cooling air when the image forming apparatus shown in FIG. 1 is viewed from above.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Developing part housing 5 Structural member 8 Toner supply part casing 21 Front side plate 22 Rear side plate 23 Inner cover 41 Suction fan 42 Discharge fan

Claims (4)

[Claims] 1. A suction fan that has a substantially closed space including at least a part of a developing unit housing that includes a stirring member that stirs and mixes a carrier and a toner, and that sucks outside air into the space. Provided in one component of the space,
An image forming apparatus, wherein a discharge fan for discharging air in the space to the outside of the apparatus is disposed at a position relatively far from the suction fan of another component. 2. The image forming apparatus according to claim 1, wherein at least one of a suction fan and a discharge fan is provided in a component near the developing device that forms the space. 3. The flow rate of the suction fan is equal to the flow rate of the discharge fan.
The image forming apparatus according to claim 1. 4. The image forming apparatus according to claim 1, wherein a flow rate of the suction fan is larger than a flow rate of the discharge fan.