JP3188332B2 - Image forming device - Google Patents

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 laser beam printer, a copying machine and a facsimile.

[0002]

2. Description of the Related Art A conventional electrophotographic image forming apparatus will be described with reference to FIG.

The photosensitive drum 1 as an image carrier has a grounded conductive core covered with an OPC photosensitive layer.

The photosensitive drum 1 rotates in the direction shown by the arrow,
The surface of the photoreceptor drum 1 is pressed by a charging roller 2 which is a charging rotator that is driven to rotate in the direction of the arrow by being pressed.
Uniform and uniform charging is achieved. Here, the charging roller 2 serves as a pressing means for a pressing contact portion between the photosensitive drum 1 and the charging roller 2.
The compression spring 20 is used between the bearing supporting the frame and the frame.

The charging roller 2 has at least a conductive rubber layer on a core to which a voltage is applied.

Thereafter, an electrostatic latent image is formed on the surface of the photosensitive layer by image exposure 3, and a developing device 4 having a developing sleeve 40 is provided.
Thus, a visible image is formed by selectively attaching the developer.

On the other hand, a plurality of recording materials P, for example, made of paper, are stacked from the accommodation box 10 and fed only by the paper feed rollers 11.
The visible image on the photosensitive drum 1 and the leading edge of the photosensitive drum 1 are made to substantially coincide with each other by a pair of registration rollers 13 that are pressed and contacted with each other, and are further fed through the transport unit 12. Is transferred to the nip portion with the transfer roller 5 which comes into pressure contact with the transfer roller 5.

[0008] The recording material P loaded here is applied to a spring 101 via an intermediate plate 102 on which the recording material P is loaded.
Is in contact with the paper feed roller 11 due to the pressing force. The registration roller pair 13 is in pressure contact with each other via the bearing by the pressing force of the spring 130. The transfer roller 5 is attached to the photosensitive drum 1 via its bearing by a spring 5.
There is a pressure contact with a pressing force of 0.

The transfer guide 14 functions to feed the recording material P to the photosensitive drum 1 and the transfer roller 5 at a predetermined angle.

Further, the recording material P is charged from the back by a transfer roller 5 rotating in the direction of the arrow, with a polarity opposite to that of the visible image, and the visible image on the photosensitive drum 1 is transferred to the recording material P.

The transfer roller 5 has at least a conductive rubber layer on a core to which a voltage is applied.

After the transfer, the developer and paper dust remaining on the photosensitive drum 1 are removed by a cleaning blade 6, and the photosensitive drum 1 is repeatedly used in an image forming process.

On the other hand, the recording material P on which the visible image is placed is separated from the photosensitive drum 1, and the charge on the back surface of the recording material P is removed by the discharging needle 15.

Next, the recording material P is guided by a conveyance guide 16 and a fixing entrance guide 17 to a nip portion of a heating roller 7 and a pressure roller 9 which are a pair of fixing rotating bodies and are in pressure contact with each other. The recording material P is heated and pressurized by rotating in the direction of the arrow to fix a visible image. Here, the pressure roller 9 is in pressure contact with the heating roller 7 via the bearing by the pressing force of the spring 90.

The pressure roller 9 has rubber on the outer periphery of the cored bar, and the heating roller 7 has a heater 8 as a heating element for heating the heating roller 7. The surface temperature of the heating roller 7 is determined by a temperature detecting element 71 that contacts the heating roller 7.
Is detected by the surface temperature by causing intermittently actuate Therefore heater 8 to a temperature control means (not shown) is controlled to a predetermined temperature.

A series of image forming steps such as charging, exposure, development, transfer, cleaning, paper feeding, and fixing are performed by inputting an image formation start signal to an image forming apparatus by a copy button or the like. Reference numeral 300 denotes a controller that controls the instruction system of the image signal.
Reference numeral 01 denotes a leg for supporting the image forming apparatus on the installation surface.

[0017]

However, in the above-mentioned prior art, each pressing contact portion requires a dedicated urging member such as a spring member as a pressing means as described above.

Particularly, in the fixing unit, the nip pressure is 0.5
kgf / cm (20 kgf / cm
/ Cm) Because of the necessity, a strong spring was required.

An object of the present invention is to provide an image forming apparatus provided with a pressing means of a pressing contact portion which does not use a spring member or reduces a load of the spring member.

[0020]

According to a first aspect of the present invention, there is provided an image forming apparatus having a pressing contact portion, wherein the pressing contact portion applies at least a part of the weight of the image forming apparatus main body as a pressing force to a pressing source. The image forming apparatus is characterized in that the image forming apparatus further comprises a pressurizing unit which is a part or all of the unit, and the pressurizing unit also serves as a leg for supporting the image forming apparatus on an installation surface.

According to a second aspect of the present invention, the pressing contact portion comprises:
The image forming apparatus according to the first aspect, wherein the image forming apparatus is a fixing device that makes an unfixed image on a recording material a permanent fixed image.

According to a third aspect of the present invention, the pressing contact portion comprises:
The image forming apparatus according to the first aspect, wherein the image forming apparatus is a paper feeder for feeding a recording material.

According to a fourth aspect of the present invention, the pressing contact portion includes:
The image forming apparatus according to the first aspect of the present invention is a charging roller that rotates by pressing and contacting an image carrier in the image forming apparatus.

According to a fifth aspect of the present invention, the pressing contact portion comprises:
The image forming apparatus according to claim 1, wherein the transfer roller is a transfer roller that transfers a visible image on the image carrier to a recording material by pressing the image carrier in the image forming apparatus.

In a sixth aspect of the present invention, the pressurizing means includes a receiving portion for receiving a reaction force from the installation surface of the image forming apparatus main body weight, and a pressurizing portion for applying a pressing force to the pressing contact portion. The image forming apparatus according to any one of the first to fifth aspects of the present invention, wherein the image forming apparatus comprises a receiving portion and a connecting portion connecting the pressing portion.

According to a seventh aspect of the present invention, in the connecting portion, the pressing portion applies to the pressing contact portion a magnitude of a reaction force received from an installation surface of the image forming apparatus main body weight in the receiving portion. An image forming apparatus according to a sixth aspect of the present invention, further comprising a force conversion unit that changes the magnitude of the pressing force so as to be different.

According to an eighth aspect of the present invention, there is provided the first to seventh aspects of the present invention, further comprising switch means for selecting whether the pressing means receives a reaction force from the installation surface or not. An image forming apparatus according to any one of the above.

[0028]

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

Embodiment 1 FIG. 1 is a diagram showing Embodiment 1 of the present invention. The same reference numerals are given to the same parts as in the conventional example, and the description is omitted.

A bearing 72 for supporting the rotation of the heating roller 7 in the direction of the arrow is fixed to a frame (not shown) of the fixing device 800. A bearing 91 for axially supporting the rotation of the pressure roller 9 in the direction of the arrow is engaged with a guide surface 801 parallel to a line connecting the respective rotation centers of the heating roller 7 and the pressure roller 9. The guide surface 801 is provided on a frame (not shown) of the fixing device. Thereby, the bearing 91 is connected to the heating roller 7.
Is slightly slidable in a direction parallel to a line connecting the rotation center of the pressure roller 9 and the rotation center of the pressure roller 9.

A pressing means 2010 for pressing the pressing roller 9 against the heating roller 7 also serves as a leg for supporting the image forming apparatus main body on the installation surface. Here, the pressurizing means 2010 applies a pressing force F11 to the pressure roller bearing 91 at a point P11 on the receiving portion 2013 which receives a reaction force F1 from the installation surface against the image forming apparatus main body weight W at a point P1. Pressurizing section 2011, receiving section 2013 and pressurizing section 20
11 connected to each other and having a projection 2014 in a part thereof
012.

The pressing means 2010 further includes a protrusion 2014
A constricted portion 2015 between the image forming apparatus and the receiving portion 2013.
It is in a relationship slidable in the direction of gravity with 0.

Further, the position of the other leg 200 receiving the reaction force F2 from the installation surface against the image forming apparatus main body weight W is point P2, the center of gravity of the image forming apparatus main body weight W is G, The horizontal distances between the point of action P1 and the center of gravity G and between the point of action P2 and the center of gravity G are a and b, respectively. The action point P1 and the action point P11 are on a straight line in the vertical direction.

The pressing means 2010 and the leg 200
It is assumed that another set is located at a position symmetrical with respect to the center line in the direction perpendicular to the paper surface, that is, in the depth direction of the image forming apparatus.

Investigation of the relationship between F1, F2, F11 and the weight W in the above configuration reveals that, due to the balance of forces in the direction of gravity, the pressing means 2010 and the leg 200 on the same side in the front and rear directions perpendicular to the plane of the drawing are shown. F1 = W × {b / 2 (a + b)} (1) F2 = W × {a / 2 (a + b)}・ (2) F11 = F1 × {b / 2 (a + b)} (3) Therefore, the above equation is obtained from the fixing device pressing force F11 and the image forming apparatus main body weight W which are designated in advance. If a and b are determined so as to satisfy (1), (2), and (3), that is, the fixing device 80
0 and the position of the receiving portion 2013 of the pressing means 2010 may be determined.

With this setting, the receiving portion 2013 of the pressurizing means 2010 also serves as a leg for supporting the image forming apparatus on the installation surface. Therefore, the pressing force generating member of the fixing device 800, such as a spring member, is eliminated. Alternatively, it is possible to provide an image forming apparatus capable of reducing the cost by reducing the spring.

Embodiment 2 FIG. 2 is a view showing Embodiment 2 of the present invention. The same reference numerals are given to the same parts as in the first embodiment, and the description will be omitted.

A pressing means 2020 for pressing the pressing roller 9 against the heating roller 7 also serves as a leg for supporting the image forming apparatus main body on the installation surface. Further, the pressing means 2020 includes a receiving portion 2023 that receives a reaction force F3 from the installation surface against the image forming apparatus main body weight W at a point P3, and a pressing force that applies a pressing force F31 to the pressing roller bearing 91 at an action point P31. Part 2021, receiving part 2023, and pressing part 2021
And a connecting portion 2022 for connecting and integrating the above, and the points P3 and P31 are separated in the horizontal direction. Further, a fulcrum P32 is formed by a member fixed to the image forming apparatus main body, and the fulcrum P32 supports an end of the pressing portion 2021 distant from the action point P31.
It is configured to be able to swing about the first action point P31.

The application point P3 and the center of gravity G of the receiving portion 2023 of the pressing means 2020, the application point P4 and the center of gravity G of the leg 200, the support point P32 for supporting the application point P3 and the pressing means 2020, and the pressing section 202 Point of action P31 and fulcrum P3
The horizontal distances to 2 are c, d, e, and f, respectively.

When the relationship between the forces F3, F4, F31 and the weight W in the above configuration is examined, the balance of the forces in the direction of gravity indicates that the pressing means 2020 and the leg portions 2020 on the same side in the front and rear directions perpendicular to the plane of FIG. For 200, F3 = W × {d / 2 (c + d)} (4) F4 = W × {c / 2 (c + d)} (5) F31 = F3 × (e / 2f) = W × {d / 2 (c + d)} × (e / 2f) (6) Therefore, the fixing device designated in advance Is determined from the pressure F31 applied to the pressure roller 9 and the weight W of the image forming apparatus to satisfy the above expressions (4), (5) and (6), that is, the fixing device 800 and pressing means 2020
The position of the swing center of the receiving portion 2023 and the pressing means 2020 may be determined.

With this setting, the receiving portion 2023 of the pressurizing means 2020 also serves as a leg for supporting the image forming apparatus on the installation surface, so that a member for generating a pressing force of the fixing device 800, such as a spring member, is eliminated. Alternatively, it is possible to provide an image forming apparatus in which the cost can be reduced by reducing the size of the spring member. Further, according to the present embodiment, the position of the leg portion can be set to an appropriate position as the leg portion, and the pressing force to the pressure roller can be set to an appropriate value.

Further, in the case of the present embodiment, as shown in the equation (6), the pressing means 2020 applies the reaction force F3 received from the point P3 of the installation surface of the image forming apparatus main body weight W in the receiving portion 2023.
Is multiplied by a predetermined ratio (e / 2f)
1 has a lever mechanism which is a force conversion means for enlarging the magnitude of the pressing force F31 applied to the fixing roller bearing 91, and has two more determination parameters than in the case of the first embodiment. It is possible to provide a high-quality image forming apparatus.

Third Embodiment FIGS. 3 and 4 show a third embodiment of the present invention. The same reference numerals are given to the same parts as in the first embodiment, and the description will be omitted.

The pressing unit 2010 of the fixing device 800 includes a switch unit 2100 that can select whether or not to use a reaction force F1 received from a point P1 on the installation surface of the image forming apparatus main body weight W as a pressing force. Here, switch means 2
Reference numeral 100 denotes a lever 2110 which is fitted to a shaft 2111 fixed to the image forming apparatus main body and is capable of swinging about the shaft 2111.

Further, the switch means 2100 is connected to the lever 21
When the end portion 1012 is pushed perpendicularly to the installation surface as shown in FIG. 4 by pushing in the direction of the arrow in FIG.
3 and the lever 21 so that the
The distance to ten end portions 2113 is set.

In the above configuration, switch means 2100
Is set to a state perpendicular to the installation surface as shown in FIG. 4 by manual or mechanical operation.

The pressurizing means 2010 descends in the direction of gravity until the projection 2014 abuts against the bottom of the image forming apparatus while sliding the constriction 2015 against the guide 2200. At this time, there is a gap 2016 between the receiving portion 2013 and the installation surface.
Therefore, both are in a non-contact state.

Accordingly, the receiving portion 2013 does not receive a reaction force from the installation surface against the weight W of the image forming apparatus main body. Therefore, the pressing roller 9 does not receive the pressing force from the pressing unit 2010, and the pressing roller 20 uses its own weight.
Along with 10, the pressure roller bearing 91 descends while sliding on the guide surface 801.

Then, a gap 710 is formed between the heating roller 7 and the pressure roller 9. For example, when taking out the jammed recording material P in the fixing device 800, the image forming apparatus does not have to open the exterior, It can be removed directly from the outside of the forming device.

Further, there is no need for a mechanism for driving the pressure roller 9 when the jammed recording material P is taken out.

Next, the lever 211 of the switch means 2100
It is assumed that 0 is manually or mechanically operated to swing and rotate in a direction indicated by an arrow from a state perpendicular to the installation surface as shown in FIG.

First, the receiving portion 2013 contacts the installation surface,
Next, the pressure means 2010 is pushed up. Then, the pressure roller 9 in which the pressure roller bearing 91 is in contact with the point P11 of the pressure portion 2011 is moved to the guide surface 801 by the pressure roller bearing 91.
It is pushed up while sliding.

The outer periphery of the pressure roller 9 is
When the contact is made with the outer periphery of the push-up operation, the push-up operation ends. At this time, the fixing device 800 applies a pressing force F1 by a reaction force F1 to the pressing means 2010 from an installation surface corresponding to the weight W of the image forming apparatus main body.
1 from the pressing means 2010, the image forming apparatus can perform a normal image forming and fixing operation in this state.

Therefore, in the present embodiment, as in the case of the first embodiment, the receiving portion 2013 of the pressing means 2010 is provided.
Is also used as a leg for supporting the image forming apparatus on the installation surface, so that the pressing force generating member of the fixing device 800, such as a spring member, is eliminated, or the cost of the image forming apparatus can be reduced by reducing the spring member. It is possible to provide.

In this embodiment, the switching means 210
The lever 2100 is used as 0, but a screw member (not shown) is used instead, and the tip of the screw member protrudes or retracts from the bottom of the image forming apparatus by manual or mechanical rotation. However, it is clear that similar effects are produced under similar operations.

As a modification of this embodiment, a fixing device 800
Has its own pressurizing means, for example, a pressurizing spring (not shown), and adds or does not add the pressurizing force by the pressurizing means 2010 by the on / off operation of the switch means 2100 (FIGS. 3 and 3). 4 outline).

In this case, the fixing device 800 can change the pressing force in two stages.

That is, for a normal recording material, the switching means is turned off and fixing is performed only by the pressing force of the pressing device of the fixing device 800 itself. Is turned on, and fixing is performed with a pressing force obtained by combining the pressing force of the pressing unit of the fixing device 800 itself and the pressing force of the pressing unit 2010.

Therefore, it is possible to provide an image forming apparatus capable of controlling fine fixing properties suitable for the characteristics of the recording material by using the weight W of the image forming apparatus itself.

In the first to third embodiments,
Although the fixing device is shown as the pressing contact portion, the sheet feeding / conveying portion for sending out the recording material, the charging roller which rotates by pressing against the image carrier, and the image bearing member on the image carrier by pressing against the image carrier It is apparent that the same effect can be obtained under the same operation even when the present invention is applied to a transfer roller for transferring the visible image to a recording material.

[0061]

The first invention of the present invention has the above-mentioned configuration,
Each pressing contact portion includes a pressing unit that utilizes at least a part of the weight of the image forming apparatus main body as a pressing force, and a receiving unit of the pressing unit also serves as a leg that supports the image forming apparatus on an installation surface. It is possible to provide an image forming apparatus capable of reducing cost by eliminating a pressing force generating member such as a spring member or the like of each pressing contact portion, or reducing a spring.

The first invention of the present invention is suitable for application to any one of a fixing device, a paper feeder, a charging roller and a transfer roller as in the second to fifth inventions.

According to a sixth aspect of the present invention, in any one of the first to fifth aspects, a pressing force is applied to the receiving portion receiving the reaction force from the weight installation surface of the image forming apparatus main body and the pressing contact portion. Since the pressure unit and the connection unit that connects the receiving unit and the pressure unit are provided, the pressure unit and the leg unit can be combined.

According to a seventh aspect of the present invention, in the sixth aspect, there is provided a force converting means for changing the magnitude of the reaction force received from the installation surface to be different from the magnitude of the pressing force applied to the pressing contact portion by the pressing portion. Therefore, there is an effect that the pressing force can be set differently from the reaction force received from the installation surface.

According to an eighth aspect of the present invention, in any one of the first to seventh aspects, the image forming apparatus main body pressurizing means includes switch means for selecting whether or not to receive a reaction force from the installation surface. Therefore, the pressing force of the pressing contact portion can be changed or the pressing force can be released.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a second embodiment of the present invention.

FIG. 3 is a longitudinal sectional view showing a state when a switch is turned on in Embodiment 3 of the present invention.

FIG. 4 is a longitudinal sectional view showing a state when a switch is turned off in Embodiment 3 of the present invention.

FIG. 5 is a longitudinal sectional view showing a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum 2 charging roller 5 transfer roller 7 heating roller 9 pressure roller 11 paper feed roller 200 leg 800 fixing device 2010 pressure device 2100 switch device

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 13/02 G03G 13/16 G03G 13/20 G03G 15/00 510-550 G03G 15/02 G03G 15/16 G03G 15/20 G03G 21/16-21/18

Claims (8)

(57) [Claims] 1. An image forming apparatus having a pressing contact portion, wherein said pressing contact portion has a pressing means for applying at least a part of a weight of said image forming apparatus main body to a part or all of a pressing source as a pressing force. An image forming apparatus, wherein the pressing unit also serves as a leg for supporting the image forming apparatus on an installation surface. 2. The image forming apparatus according to claim 1, wherein the pressing contact unit is a fixing device that converts an unfixed image on a recording material into a permanently fixed image. 3. The image forming apparatus according to claim 1, wherein the pressing contact unit is a paper feed unit for feeding a recording material. 4. The image forming apparatus according to claim 1, wherein the pressing contact portion is a charging roller that rotates while pressing and contacting an image carrier in the image forming apparatus. 5. The image forming apparatus according to claim 1, wherein the pressing contact portion is a transfer roller that transfers a visible image on the image carrier to a recording material by pressing the image carrier in the image forming apparatus. 2. The image forming apparatus according to 1. 6. The pressurizing unit includes: a receiving unit that receives a reaction force of the weight of the image forming apparatus main body from the installation surface; a pressurizing unit that applies a pressing force to the pressing contact unit; The image forming apparatus according to claim 1, further comprising a connection unit that connects the pressure unit. 7. The connecting portion may be configured such that a magnitude of a pressing force applied to the pressing contact portion by the pressing portion with respect to a magnitude of a reaction force received from the mounting surface of the image forming apparatus main body weight at the receiving portion. The image forming apparatus according to claim 6, further comprising a force conversion unit that changes the image forming apparatus differently. 8. The image forming apparatus according to claim 1, further comprising switch means for selecting whether the pressing means receives a reaction force from an installation surface or not. apparatus.