JP7206927B2 - image forming device - Google Patents

Description

The present invention relates to an image forming apparatus.

2. Description of the Related Art Conventionally, in image forming apparatuses, a heat fixing method has been widely adopted in which an unfixed image (toner image) formed on a recording medium (for example, paper) is thermally fixed using a fixing member having a heat source. there is

In such a heat-fixing type image forming apparatus, a fixing member (fixing roller) having a heat source inside faces a pressure member (pressure roller) while being in contact with each other with a predetermined pressure. 2. Description of the Related Art There is known a technique in which a sheet having a toner image is transported to the abutted portion, and the unfixed toner image is fixed to the sheet by heating and pressurization. The fixing member is uniformly heated by, for example, an internal heater member such as a halogen lamp.

Temperature control at this time is extremely important for stabilizing paper transportability and image quality. Appropriate heating control is applied by

As a temperature detection sensor, a contact sensor (contact thermistor) has been widely used.
However, when a contact-type sensor is used, the surface state (temperature distribution and degree of wear) of the fixing member changes only in the area in contact with the sensor, so uneven gloss tends to occur in the fixed image.
In addition, if the contact sensor scratches the fixing member and the scratches are transferred to the image, or if minute toner stains or the like adhering to the fixing member accumulate on the contact sensor, the accumulated stains can be removed. In some cases, erroneous detection may occur due to the contamination, and in some cases, contamination may appear on the image when the contamination is peeled off.

On the other hand, a device using a non-contact sensor (for example, a thermopile, etc.) is known as a means for detecting the temperature of the fixing member.

However, since the non-contact type sensor is very expensive, if it is incorporated in a fixing device that is supposed to be replaced as a consumable item, the price of the consumable item will be directly affected.
Moreover, since it is a non-contact type, it must be arranged at a predetermined distance from the surface of the fixing member, and when it is incorporated in the fixing device, it is necessary to secure a suitable space inside the fixing device.

On the other hand, when a non-contact sensor is provided on the main body of the image forming apparatus and the temperature of the fixing member is detected through a detection opening provided in the cover member of the fixing device, in order to reduce the size of the device, The non-contact sensor is installed so as to dig into the fixing device so that the distance between the fixing member and the non-contact sensor is shortened. As a result, water vapor generated in the fixing device causes dew condensation on the measurement window of the non-contact sensor, resulting in erroneous temperature detection.

In order to solve such a problem, an image forming apparatus provided with a fan for removing water vapor has been proposed as dew condensation prevention means (see, for example, Japanese Unexamined Patent Application Publication No. 2002-100003).

According to the apparatus of Patent Document 1, even if the thermopile is used in an environment where a large amount of water vapor exists in the measurement environment, the air from the fan provided near the thermopile acts to remove the water vapor around the thermopile measuring portion. Therefore, it is said that it is possible to prevent dew condensation from occurring on the measurement window of the thermopile and to enable accurate measurement.

However, providing a special mechanism for removing water vapor complicates the structure of the device and makes it difficult to reduce the size of the device. Moreover, there is a problem that an increase in the number of parts leads to an increase in cost.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to prevent dew condensation from occurring in a non-contact type sensor that detects the temperature of a fixing member while reducing the size and cost with a simple configuration without increasing the number of parts, and by extension, erroneous temperature detection. An object of the present invention is to provide an image forming apparatus capable of preventing

In order to solve the above problems, the image forming apparatus of the present invention provides a fixing device having a fixing member, a heat source for heating the fixing member, and a pressure member for pressing the fixing member to form a nip portion, An image forming apparatus comprising at least a cover member that covers at least part of the fixing device, and temperature detection means that detects the temperature of the fixing member from outside the fixing device through an opening of the cover member in a non-contact manner. The temperature detecting means has a space above the cover member that does not overlap with the cover member in plan view, the fixing device has a flow path through which an air current can flow, and the flow path passes through the space. is communicated with the opening, and an air current flows through the flow path, whereby water vapor generated in the fixing device can be discharged through the opening, the space, and the flow path . is disposed above the temperature detection means and merges with the space above the temperature detection means .

According to the present invention, it is possible to prevent dew condensation occurring in a non-contact type sensor for detecting the temperature of a fixing member while achieving a reduction in size and cost with a simple structure without increasing the number of parts, thereby preventing an error in temperature. An image forming apparatus capable of preventing detection can be provided.

1 is a cross-sectional view showing a schematic configuration of an image forming apparatus according to an exemplary embodiment; FIG. 1 is a schematic diagram showing a schematic configuration of a main part including a fixing device of a conventional image forming apparatus; FIG. 7 is a graph showing temperature detection results obtained by a non-contact sensor mounted on a conventional image forming apparatus; 1 is a schematic diagram showing a schematic configuration of a main part including a fixing device of an image forming apparatus according to this exemplary embodiment; FIG. FIG. 2 is a schematic diagram showing a non-contact sensor installation section mounted on the image forming apparatus according to the present embodiment; 5 is a graph showing temperature detection results obtained by a non-contact sensor mounted in the image forming apparatus of the present embodiment;

An image forming apparatus according to the present invention will be described below with reference to the drawings. In addition, the present invention is not limited to the embodiments shown below, and can be changed within the scope of those skilled in the art, such as other embodiments, additions, modifications, deletions, etc. is also included in the scope of the present invention as long as the functions and effects of the present invention are exhibited.

FIG. 1 shows a cross-sectional view of a schematic configuration of a monochrome electrophotographic apparatus (monochrome laser printer), which is an example of an image forming apparatus according to the present embodiment. Note that the image forming apparatus is not limited to the example shown in FIG. 1, and may be a color printer, a multifunction machine, or the like. There is no particular limitation as long as it has hardware and software that can be implemented.

The image forming apparatus 1 includes a process cartridge 2 as a process unit for forming an image with developer.
The process cartridge 2 includes an image carrier (photosensitive drum) 3 that carries an image on its surface.
In addition, a charging roller as a charging means for charging the surface of the image carrier 3, an exposure device as an exposure means for irradiating the charged surface of the image carrier 3 with light such as a laser, and a developer on the image carrier 3 It has a developing device or the like as a developing means for supplying toner as a developer to form a developer image. It also has a drum cleaning device that removes excess toner after the transfer process is completed, and a static elimination device that eliminates static electricity on the surface.

A paper feeding device 12 having a paper feeding cassette 11 and feeding recording media placed in the paper feeding cassette 11 is arranged in the lower part of the image forming apparatus 1 . The recording medium is not limited to paper as long as it is a medium on which toner can be adhered, and may be, for example, an OHP sheet or cloth.
In addition, in FIG. 1, the conveying path of the recording medium is indicated by a dashed line.
A pair of timing rollers is arranged on the downstream side of the sheet feeder 12 in the conveying direction, for temporarily stopping the fed recording medium and then conveying it at a predetermined timing.

A transfer roller 70 is provided below the process cartridge 2 .
A fixing device 80 that fixes the image transferred to the recording medium is arranged downstream of the transfer roller 70 in the conveying direction.
The fixing device 80 includes a fixing member (fixing roller) 81 containing a heat source 83 and a pressure member (pressure roller) 82 rotating while contacting the fixing member 81 with a predetermined pressure. At least a portion of the fixing device 80 is covered with a cover member.

The image carrier 3 is rotated by a driving device installed in the image forming apparatus 1, and its surface photosensitive layer is uniformly charged to a high potential by a charging roller. The charged photosensitive layer is selectively exposed by an exposure device based on image data to form an electrostatic latent image consisting of a low potential area where the potential is attenuated by this exposure and a high potential area by initialization. Next, when the low potential portion (or high potential portion) of the electrostatic latent image comes to a position facing the developing roller, toner is transferred from the developing roller having a thin toner layer formed on its surface to develop the toner image. be.

When the toner image is formed on the image carrier 3, the pair of timing rollers and the feeding roller start to drive, and the recording medium is sent to the transfer nip in synchronization with the toner image on the image carrier 3. FIG. Then, the toner image on the image carrier 3 is transferred to the recording medium sent by the transfer roller 70 .

The recording medium onto which the toner image has been transferred is transported to the fixing device 80 through the post-transfer transport path.
The recording medium sent to the fixing device 80 is sandwiched between a fixing member (fixing roller) 81 and a pressure member (pressure roller) 82, and the unfixed toner image is heated and pressurized to be fixed on the recording medium.
Finally, the paper is discharged by the paper discharging device 15 to the paper discharging tray on the upper surface of the monochrome electrophotographic apparatus 1 .

4 and 5 are schematic diagrams showing the schematic configuration of the main part including the fixing device 80 of the image forming apparatus according to this embodiment.
The image forming apparatus of this embodiment includes a fixing device 80 having a fixing member 81, a heating source 83 for heating the fixing member 81, and a pressure member 82 for pressing the fixing member 81 to form a nip portion, and at least a fixing device. At least a cover member 80a covering a part of the fixing device 80 and a temperature detection means 91 for detecting the temperature of the fixing member 81 from the outside of the fixing device 80 in a non-contact manner through an opening of the cover member 80a.

Further, in the image forming apparatus of this embodiment, as shown in FIG. 5, the temperature detection means 91 has a space (hereinafter also referred to as "upper space") 92 that does not overlap the cover member 80a in plan view.
"Not overlapping in a plane" means that there is no overlapping region in the horizontal plane, and in this embodiment, it means that there is no overlapping region in plan view as viewed from above the device.
That is, there is no area covered by the cover member 80a of the fixing device, and an open space 92 is formed at least above the temperature detecting means 91 .

Moreover, as shown in FIG. 5, it is preferable that the temperature detection means 91 has a space (hereinafter also referred to as “lower space”) 93 below.
The temperature detection means 91 is attached to the housing 1a of the image forming apparatus facing the fixing device 80, but the lower part of the temperature detection means 91 preferably does not contact the attached housing 1a.

The temperature detection means 91 is a non-contact sensor capable of detecting the temperature of the fixing member 81, and is specifically a thermopile.
The temperature detection means 91 can detect the temperature of the fixing member 81 in a state of being separated from the fixing device 80 and disposed at a position where contact with water vapor can be avoided.

In FIG. 4, the flow of airflow is indicated by an arrow AF.
As shown in FIGS. 4 and 5, above the fixing device 80, it is preferable to have a flow path 94 through which the airflow AF can flow.

With the above-described configuration, in the image forming apparatus of the present embodiment, the area where the temperature detection means 91 is installed has a space 92 with an open top, so that water vapor can easily escape. Since it is arranged outside the device 80 and away from the cover member 80 a , water vapor generated inside the fixing device 80 is less likely to come into contact with the temperature detection means 91 .
For these reasons, it is possible to prevent water vapor from coming into contact with the surface of the temperature detecting means 91 and causing dew condensation.

In addition, by providing the space 93 also in the lower part, the air current flow AF is easily generated, the water vapor is more easily released, and the occurrence of dew condensation can be prevented more reliably.

Furthermore, by providing a flow path 94 through which the airflow AF can flow above the fixing device 80, and by flowing the airflow through this flow path, it is possible to more reliably release water vapor and prevent the occurrence of dew condensation. The flow path 94 communicates with the space 92 above the temperature detection means 91 .
This flow of airflow AF may be generated by an existing fan or the like in the device, or may be due to air circulation that occurs naturally within the device or air circulation that occurs due to the opening and closing of the housing, etc. good.

According to the image forming apparatus of the present embodiment, a fixing member, which is a fixing member, can be reduced in size and cost with a simple configuration without providing a special mechanism for releasing water vapor and without increasing the number of parts. It is possible to prevent dew condensation occurring in the non-contact sensor that detects the temperature of the member 81, and thus prevent erroneous temperature detection.

On the other hand, FIG. 2 shows an example of a conventional image forming apparatus.
In the image forming apparatus shown in FIG. 2, the temperature detection means 91 is arranged at a position biting into the fixing device 80, and the cover member 80a of the fixing device overlaps in a plane. For this reason, water vapor generated inside the fixing device 80 is likely to come into contact with the temperature detection means 91, and dew condensation is likely to occur on the surface.

FIG. 3 shows measurement data of the temperature detecting means 91 in the conventional image forming apparatus of FIG.
FIG. 3 shows the actual temperature (A), target temperature (C), and duty (D) of the fixing member 81 along with the detected temperature (B) of the fixing member 81 by the temperature detection means 91 .

From the graph of FIG. 3, there is a tendency that the temperature of the fixing member 81 to be measured is detected to be lower than the actual temperature. It can also be seen that the difference between the actual temperature (A) and the detected temperature (B) increases with the lapse of time. These are considered to be caused by dew condensation on the temperature detection means 91 over time.

On the other hand, FIG. 6 shows measurement data of the temperature detecting means 91 in the image forming apparatus according to the present invention.
6 shows the actual temperature (A), target temperature (C), and duty (D) of the fixing member 81 along with the temperature (B) of the fixing member 81 detected by the temperature detection means 91, similar to FIG. there is

From the graph of FIG. 6, there is almost no difference between the detected temperature (B) and the actual temperature (A) of the fixing member 81 to be measured. Moreover, since this tendency does not change over time, it can be seen that dew condensation does not occur in the temperature detection means 91 in the image forming apparatus of the present embodiment.

1 image forming apparatus 1a housing (image forming apparatus)
2 Process Cartridge 3 Image Carrier 11 Paper Feed Cassette 12 Paper Feed Device 15 Paper Discharge Device 70 Transfer Roller 80 Fixing Device 80a Cover Member 81 Fixing Member 82 Heat Source 83 Pressurizing Member 91 Temperature Detection Means (Thermopile)
92 space (upper space)
93 space (lower space)
94 flow path AF air flow

Japanese Patent Application Laid-Open No. 2003-297528

Claims (5)

a fixing device having a fixing member, a heat source for heating the fixing member, and a pressure member for pressing the fixing member to form a nip portion;
a cover member that covers at least part of the fixing device;
An image forming apparatus comprising at least temperature detecting means for detecting the temperature of the fixing member in a non-contact manner from the outside of the fixing device through an opening of the cover member,
The temperature detection means has a space above the cover member that does not overlap with the cover member in a plane,
The fixing device has a flow path through which an air current can flow upward,
the channel communicates with the opening through the space;
water vapor generated in the fixing device can be discharged through the opening, the space, and the flow path by flowing an air current through the flow path ;
The image forming apparatus according to claim 1, wherein the flow path is arranged above the temperature detection means and merges with the space above the temperature detection means . 2. An image forming apparatus according to claim 1, wherein said temperature detecting means has a space below it. 3. The image forming apparatus according to claim 1, wherein said temperature detecting means is a thermopile. 4. The image forming apparatus according to claim 1, wherein said temperature detection means is mounted in a housing of said image forming apparatus facing said fixing device. 5. The image forming apparatus according to claim 1, wherein said temperature detecting means is installed on an inner wall surface opposite to a side communicating with said opening in said space.

Images