JP6135919B2 - Process unit and image forming apparatus - Google Patents

Description

  The present invention relates to a process unit configured to be detachable from an image forming apparatus main body, and an image forming apparatus.

  In an electrophotographic image forming apparatus, there is known a system in which a process unit that is integrally provided with a photosensitive member, a developing device, and the like is configured to be detachable from the apparatus main body. This method is adopted in many products because of the advantage that the user can easily maintain the apparatus by exchanging the unit.

  In such a process unit, a part of the photoconductor is exposed from an opening formed in the case so that the photoconductor is brought into contact with a transfer member provided in the main body when mounted on the main body. doing. However, if a part of the photoconductor is exposed from the opening of the case, scratches or foreign matter may be attached to the exposed surface of the photoconductor when the process unit is removed from the main unit, or light fatigue may occur due to exposure. There is a risk of doing. Therefore, in order to prevent scratches, adhesion of foreign matters to the photoconductor, and light fatigue, a device provided with a shutter that covers the exposed surface of the photoconductor has been proposed (see Patent Documents 1 and 2).

  As shown in FIG. 39, when the process unit 1 is detached from the apparatus main body, the shutter 21 is closed and covers the photosensitive member 2 (see (a)), and the process unit 1 is mounted on the apparatus main body. When this occurs, the photosensitive member 2 is exposed in an open state (see (b)).

  By the way, with the recent increase in the speed of image forming apparatuses, the temperature of the process unit tends to increase, and this causes problems such as toner sticking in the process unit. One method for solving this problem is to cool the process unit by applying an airflow.

  However, when an air flow is generated to cool the process unit, the air flow enters through the gap S between the shutter 21 and the process unit 1 (case 20) as shown by the arrow in FIG. The behavior of the paper passing between the photosensitive member 2 and the transfer member 11 becomes unstable, and there is a possibility that wrinkles and jams may occur.

  Therefore, in view of such circumstances, the present invention intends to provide a process unit and an image forming apparatus capable of preventing the passage of airflow between a shutter and a case.

In order to solve the above-described problems, the present invention provides a photoconductor provided such that a part thereof is exposed from a case, a closed state that covers the exposed surface of the photoconductor, and an open state that opens the exposed surface of the photoconductor. In a process unit configured to be detachable from the main body of the image forming apparatus, the shutter is attached to the case and contacts the shutter when the shutter is in the open state. A shielding member that shields between the shutter and the case, and an elastic member is provided on an inner surface of the shutter facing the photoconductor, and the shielding member is the elastic member when the shutter is in the open state. When the shutter is switched from the open state to the closed state, a part of the shielding member comes into contact with the inner surface of the shutter, and the shielding is performed. Characterized in that the wood and the elastic member is configured to be non-contact.

  According to the present invention, since the space between the shutter and the case can be shielded by the shielding member, it is possible to prevent the passage of the airflow between the shutter and the case.

1 is a schematic configuration diagram illustrating an embodiment of an image forming apparatus to which the present invention is applied. It is the perspective view which looked at the process unit from diagonally downward. It is a figure which shows the attachment structure of an arm part. It is a figure which shows the attachment / detachment method of a process unit. It is a figure which shows the structure of the characteristic part of this invention, Comprising: (a) is a figure which shows the state which closed the shutter, (b) is a figure which shows the state which opened the shutter. It is a perspective view of a shielding member. It is the figure which looked at the state which shielded the crevice by the shielding member from the upper part. It is a figure for demonstrating the relationship between the urging | biasing force of a torsion spring, and a frictional resistance force. It is a figure which shows embodiment which provided the free piece intermittently. It is a figure which shows the state which shielded the clearance gap by the shielding member. It is a figure which shows the state which shielded the clearance gap by the shielding member. It is a figure which shows embodiment which aligned and attached the edge part of the block member to the bending part. It is a figure which shows the state which shielded the clearance gap by the shielding member. It is a figure which shows embodiment which adhered only a part of opposing surface of the free piece with the block member. (A) is a figure which shows the state immediately before a clearance gap is shielded with a shielding member, (b) is a figure which shows the state with which the clearance gap was shielded by the shielding member. (A) is a figure which shows the state immediately before a clearance gap is shielded with a shielding member, (b) is a figure which shows the state with which the clearance gap was shielded by the shielding member. It is a figure which shows embodiment which attached the block member to the outer surface side of the sheet | seat material. It is a figure which shows embodiment which provided the free piece intermittently in the structure which attached the block member to the outer surface side of the sheet | seat material. (A) is a figure which shows the state immediately before a clearance gap is shielded with a shielding member, (b) is a figure which shows the state with which the clearance gap was shielded by the shielding member. It is a figure which shows embodiment which comprised the shielding member with the sponge material. It is a figure which shows embodiment which provided the elastic member in the inner surface of the shutter. It is a perspective view of the shutter which provided the elastic member. It is a perspective view of the shutter which formed the exposed part. It is a perspective view of the shielding member which provided the convex part in the block member. It is a figure which shows the state which has a shutter in an open state. (A) is E1-E1 sectional drawing in FIG. 25, (b) is G1-G1 sectional drawing in FIG. It is a figure which shows the state at the time of starting to move a shutter to a closed state. (A) is E2-E2 sectional drawing in FIG. 27, (b) is G2-G2 sectional drawing in FIG. It is a figure which shows the relationship between the formation position of an exposed part, and the image support area | region of a photoreceptor. It is a perspective view of the shutter which provided the low friction member in the exposed part. It is a perspective view of the shielding member which provided the low friction member in the convex part. It is a perspective view of the shutter which provided the convex part. It is a figure which shows the state which has a shutter in an open state. It is a figure which shows the state at the time of starting to move a shutter to a closed state. It is a perspective view of the shutter which provided the low friction member in the convex part. It is a perspective view of the shielding member provided with the low friction member. 1 is a schematic configuration diagram of an indirect transfer type color image forming apparatus. 1 is a schematic configuration diagram of a direct transfer type color image forming apparatus. It is a figure which shows the structure of the conventional process unit.

  Hereinafter, the present invention will be described with reference to the accompanying drawings. In the drawings for explaining the present invention, components such as members and components having the same function or shape are denoted by the same reference numerals as much as possible, and once described, the description will be given. Omitted.

  FIG. 1 is a schematic configuration diagram showing an embodiment of an image forming apparatus to which the present invention is applied. First, the overall configuration and operation of the image forming apparatus will be described with reference to FIG.

  The image forming apparatus shown in FIG. 1 is a monochrome image forming apparatus. A process unit 1 as an image forming unit is detachably mounted on the apparatus main body (image forming apparatus main body) 100. The process unit 1 visualizes a photoreceptor 2 as an image carrier that carries an image on the surface, a charging roller 3 as a charging unit that charges the surface of the photoreceptor 2, and a latent image on the photoreceptor 2. A developing device 4 as a developing unit and a cleaning blade 5 as a cleaning unit for cleaning the surface of the photoreceptor 2 are provided. Further, an LED head array 6 as an exposure unit that exposes the surface of the photoconductor 2 is provided at a position facing the photoconductor 2.

  In addition, the image forming apparatus includes a transfer device 7 that transfers an image to a sheet as a recording medium, a paper feeding device 8 that supplies the sheet, a fixing device 9 that fixes the image transferred to the sheet, and a sheet outside the apparatus. And a paper discharge device 10 for discharging the paper.

  The transfer device 7 includes a transfer roller 11 as a transfer member. The transfer roller 11 is in contact with the photosensitive member 2 with the process unit 1 mounted on the apparatus main body 100, and a transfer nip is formed at the contact portion between the two. The transfer roller 11 is connected to a power source (not shown) so that a predetermined direct current voltage (DC) and / or alternating current voltage (AC) is applied.

  The paper feeding device 8 includes a paper feeding cassette 12 that contains paper P and a paper feeding roller 13 that feeds the paper P contained in the paper feeding cassette 12. A pair of registration rollers 14 are provided on the downstream side of the paper feeding direction with respect to the paper feeding roller 13 as timing rollers for feeding the paper to the secondary transfer nip at the timing of conveyance. The paper P includes cardboard, postcard, envelope, plain paper, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, and the like. Further, an OHP sheet, an OHP film, or the like can be used as a recording medium other than paper.

  The fixing device 9 includes a fixing roller 15 as a fixing member and a pressure roller 16 as a pressure member. The fixing roller 15 is heated by a heating source (not shown) such as a heater. The pressure roller 16 is pressed toward the fixing roller 15 and comes into contact with the fixing roller 15, and a fixing nip is formed at the contact portion.

  The paper discharge device 10 includes a pair of paper discharge rollers 17. The paper discharged out of the apparatus by the paper discharge roller 17 is stacked on a paper discharge tray 18 formed by denting the upper surface of the apparatus main body 100.

Next, an image forming operation of the image forming apparatus according to the present embodiment will be described with reference to FIG.
When the image forming operation is started, the photosensitive member 2 is rotationally driven, and the surface of the photosensitive member 2 is uniformly charged to a predetermined polarity by the charging roller 3. Then, an electrostatic latent image is formed on the charged surface of the photoreceptor 2 by exposure from the LED head array 6 based on image information from a reading device (not shown) or a computer. The toner is supplied by the developing device 4 to the electrostatic latent image formed on the photoreceptor 2 in this manner, whereby the electrostatic latent image is visualized (visualized) as a toner image.

  When the image forming operation is started, the paper feed roller 13 starts to rotate and the paper P is sent out from the paper feed cassette 12. The fed paper P is temporarily stopped by the registration rollers 14. Thereafter, rotation of the registration roller 14 is started at a predetermined timing, and the paper P is conveyed to the transfer nip in accordance with the timing at which the toner image on the photoconductor 2 reaches the transfer nip.

  At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the photoreceptor 2 is applied to the transfer roller 11, thereby forming a transfer electric field in the transfer portion. The toner image on the photoreceptor 2 is transferred onto the paper P by this transfer electric field. The residual toner on the photoreceptor 2 that could not be transferred onto the paper P is removed by the cleaning blade 5.

  The sheet P on which the toner image is transferred is conveyed to the fixing device 9 and is heated and pressed by passing through the fixing nip between the fixing roller 15 and the pressure roller 16, so that the toner image on the sheet P is transferred. Is established. Then, the paper P is discharged out of the apparatus by the paper discharge roller 17 and stocked on the paper discharge tray 18.

FIG. 2 is a perspective view of the process unit as viewed obliquely from below.
As shown in FIG. 2, an opening 20a is formed in the lower part of the case 20 constituting the exterior of the process unit 1, and a part of the photoreceptor 2 is exposed from the opening 20a. As described above, since a part of the photosensitive member 2 is exposed from the case 20, the photosensitive member 2 can come into contact with the transfer roller 11 (see FIG. 1) in a state where the process unit 1 is mounted.

  Further, a shutter 21 for protecting the exposed surface of the photosensitive member 2 is attached to the process unit 1. The shutter 21 is attached to the case 20 via a pair of arm members 22. Each arm member 22 is configured to be rotatable in a direction indicated by an arrow A in FIG. As described above, the arm member 22 rotates, so that the shutter 21 opens the closed state (the state indicated by the two-dot chain line in FIG. 2) covering the exposed surface of the photosensitive member 2 and the exposed surface of the photosensitive member 2. It can be switched to an open state (state indicated by a solid line in the figure).

  As shown in FIG. 3, in this embodiment, a rotation shaft 23 is provided on one end side of each arm member 22. On the other hand, the case 20 is provided with an insertion hole 24 into which the rotation shaft 23 can be inserted, and the rotation shaft 23 is rotatably inserted into the insertion hole 24. Further, a torsion spring 25 as a biasing member that biases the arm member 22 is attached to the rotation shaft 23. A portion of the torsion spring 25 wound in a cylindrical shape is attached to the outer periphery of the rotary shaft 23, one end is hooked on a hook portion 26 provided near the rotary shaft 23, and the other end is inserted in the insertion hole 24. It is hooked on a hook portion 27 provided in the vicinity. The elastic force of the torsion spring 25 urges the shutter 21 to be in a closed state.

FIG. 4 is a diagram showing a process unit attaching / detaching method.
As shown in FIG. 4, in the present embodiment, a cover 101 provided at the rear part of the apparatus main body 100 can be opened and closed. Further, when the cover 101 is opened, the LED head array 6 is retracted upward via a link mechanism (not shown). With this configuration, it is possible to remove the process unit 1 from the rear while avoiding interference with the LED head array 6 with the cover 101 opened. When the process unit 1 is removed, the shutter 21 is switched from the open state to the closed state by the resilient force of the torsion spring 25.

  On the other hand, when the process unit 1 is attached to the apparatus main body 100, when the process unit 1 is inserted into the apparatus main body 100 with the cover 101 opened, the shutter is brought into contact with the contact portion 102 provided in the apparatus main body 100. The arm member 22 holding 21 is brought into contact. By this contact, the arm member 22 rotates upward, and the shutter 21 is switched from the closed state to the open state. Thus, in the present embodiment, the shutter 21 is opened and closed as the process unit 1 is attached and detached. Further, after the process unit 1 is completely mounted, the cover 101 is closed, so that the LED head array 6 moves downward and is disposed at a position close to the photoreceptor 2.

As shown in FIG. 4, a fan 28 as an airflow generating means is provided on the upper part of the apparatus main body 100, and the process unit 1 is cooled by blowing the airflow from the fan 28 onto the process unit 1. Like to do. The airflow is also blown to the gap S between the shutter 21 and the case 20 in the open state. Therefore, if the airflow passes through the gap S and reaches the transfer nip, the behavior of the paper becomes unstable as described above, and wrinkles and jams may occur.
Therefore, in the present invention, the following measures are taken.

Hereafter, the characteristic part of this invention is demonstrated.
As shown in FIG. 5, the process unit 1 according to the present invention is provided with a shielding member 30 that prevents passage of airflow between the shutter 21 and the case 20 on the outer surface of the case 20. Specifically, the shielding member 30 is attached to the facing surface 20 a that faces the case 20 when the shutter 21 is in an open state (the state shown in FIG. 5B).

  As shown in FIG. 6, in this embodiment, the shielding member 30 includes an elastically deformable sheet material 31 attached to the outer surface of the case 20 and a block member 32 that is a rigid body attached to the sheet material 31. ing.

  The sheet material 31 is made of a resin sheet (including a film) such as PET formed in a longitudinal shape. The sheet material 31 has two pieces 31a and 31b which are bent at an intermediate portion in the short-side direction and form an acute angle with each other via the bent portion 31c. Of these two pieces 31 a and 31 b, the one piece 31 a is attached to the facing surface 20 a of the case 20 in the longitudinal direction (or the axial direction of the photoreceptor 2), and is fixed to the case 20. It is a piece 33. On the other hand, the other piece 31b is a free piece 34 that is elastically displaceable in a direction in which the other piece 31b is moved toward and away from the surface of the case 20 by swinging around the bent portion 31c.

  Further, in the sheet material 31, the opening direction of the fixed piece 33 and the free piece 34 is the same direction as the moving direction of the shielding member 30 to the open state (the direction indicated by the arrow C in FIG. 5B). Is attached. In other words, the end on the bent portion 31c side is disposed so as to face the moving direction of the shielding member 30 to the closed state (the direction indicated by the arrow B in FIG. 5A).

  The block member 32 is a long member having a triangular cross section formed of the same resin material as the case 20 of the process unit 1. The block member 32 is attached to a free piece 34 (elastically displaced portion) of the sheet material 31. In the present embodiment, the block member 32 is attached to the inner surface facing the fixed piece 33 of the free piece 34 and away from the bent portion 31c toward the leading end side where the free piece 34 swings. Double-sided tape is used for the attachment of the block member 32 to the sheet material 31 and the attachment of the sheet material 31 to the case 20, but other attachment methods can also be used.

  As shown in FIG. 5A, when the shutter 21 is in the closed state, the free piece 34 is not supported by anything, so the free piece 34 is loaded by its own weight and the weight of the block member 32. Receives the force in the opening direction (gravity direction). However, when the free piece 34 is opened to some extent, the free piece 34 is held at an acute angle with respect to the fixed piece 33 by an elastic return force that attempts to return in the closing direction. In this state, the free piece 34 is arranged on the movement path D when the shutter 21 is switched from the open state to the closed state.

  For this reason, as shown in FIG. 5B, when the shutter 21 moves so as to be switched to the open state, the shutter 21 comes into contact with the free piece 34 on the movement path D. By this contact, the free piece 34 is elastically displaced so as to approach the surface of the case 20, and the shutter 21 moves to the open position while being in contact with the free piece 34. Then, the free piece 34 is interposed between the shutter 21 and the case 20. In this state, the free piece 34 is in contact with the inner surface of the shutter 21 by an elastic return force acting in the opening direction, a weight due to the weight of the block member 32 itself, or both.

  As described above, when the shutter 21 is switched to the open state, the free piece 34 comes into contact with the inner surface of the shutter 21 so that the space between the shutter 21 and the case 20 is shielded by the shielding member 30. Therefore, in this state, even if the airflow from the fan 28 is blown into the gap S between the shutter 21 and the case 20, the airflow can be prevented from passing through the gap S by the shielding member 30. . This can reduce the influence of the air current applied to the paper at and near the transfer nip, so that the paper can be stably conveyed without causing wrinkles or jams.

FIG. 7 is a view of the state where the gap is shielded by the shielding member as seen from above.
In FIG. 7, the range indicated by reference sign Wp indicates the maximum sheet passing width (maximum recording medium passage width), and the range indicated by reference sign Ws indicates the maximum width through which airflow can enter the gap S between the shutter 21 and the case 20. Indicates. As shown in FIG. 7, the shielding member 30 (the sheet material 31 and the block member 32) is disposed in a width region larger than the maximum sheet passing width Wp. As described above, by disposing the shielding member 30 in the width region larger than the maximum sheet passing width Wp, it is possible to prevent the airflow from being blown to the sheet and to stabilize the behavior of the sheet. More preferably, as shown in FIG. 7, the shielding member 30 may be disposed in the same width region as the maximum width Ws into which the airflow can enter. Thereby, it is possible to reliably prevent the airflow from passing through the gap S, and it is possible to further stabilize the behavior of the paper. In addition, the arrangement | positioning area | region of the shielding member 30 may be the same as the largest sheet passing width Wp, or less. Also in this case, the passage of the air current can be prevented, and the influence of the air current received on the paper can be reduced.

  When the process unit 1 is removed, the shutter 21 is switched to the closed state by the urging force of the torsion spring 25. At this time, the shutter 21 is in sliding contact with the shielding member 30. Here, as shown in FIG. 8, the urging force of the torsion spring 25 for switching the shutter 21 to the closed state is F1, and the frictional resistance force due to sliding contact with the shielding member 30 when the shutter 21 is switched to the closed state. Is set so that F1> F2. In this way, by setting the relationship between F1 and F2, the shutter 21 can be reliably switched to the closed state by the urging force of the torsion spring 25.

  When the shutter 21 is in the closed state, the shielding member 30 is preferably in a non-contact state with respect to the shutter 21 (see FIG. 5A). When the shutter 21 is closed, that is, when the process unit 1 is detached from the apparatus main body 100, it is not affected by the airflow, so unnecessary contact between the shutter 21 and the shielding member 30 is avoided, and the shutter is released. It is desirable to reduce the switching load of 21.

  As shown in FIG. 9, the free piece 34 may be provided intermittently in the longitudinal direction. However, in this case, since there are gaps between the plurality of free pieces 34, the airflow cannot be shielded as in the above-described embodiment in which the free pieces 34 are continuously provided (the free pieces 34 There is a possibility that airflow leaks from the gap U).

  Therefore, in this case, as shown in FIG. 10, the block member 32 is brought into contact with both the shutter 21 and the case 20 with the shutter 21 being switched to the open state. Thereby, since the gap S between the shutter 21 and the case 20 can be shielded only by the block member 32, even if the free piece 34 is provided intermittently, the passage of the airflow is reliably prevented. Is possible.

  Further, as described above, not only the block member 32 is brought into direct contact with the shutter 21 and the case 20, but also the block member 32 is placed between the shutter 21 and the case via the sheet material 31 as in the example shown in FIG. 20 may be contacted indirectly. Even if it does in this way, in the structure by which the above free pieces 34 were provided intermittently, the leakage of the airflow from the clearance gap U between the free pieces 34 can be eliminated.

  In the embodiment shown in FIG. 12, the free piece 34 is provided intermittently. Here, the end of the block member 32 is attached in alignment with the bent portion 31 c of the sheet material 31. .

  In this case, as shown in FIG. 13, the gap S can be shielded without the block member 32 being in contact with the case 20. That is, by aligning and attaching the end portion of the block member 32 to the bent portion 31c, it is possible to close the gap U between the free pieces 34, so that the block member 32 does not contact the case 20, It is possible to prevent airflow leakage from the gap.

In addition, the gap U between the free pieces 34 can be blocked by the block member 32 even in the following configuration.
Specifically, as shown in FIG. 14, only a part 34 a (shaded portion in the figure) on the front end side of the facing surface of each free piece 34 facing the block member 32 is bonded to the block member 32, A portion 34 b on the base end side of the free piece 34 is a non-adhesive region that does not adhere to the block member 32. Further, in the fixed piece 33, a distal-side portion 33a indicated by hatching in the figure is an adhesion region with the case 20, and a proximal-side portion 33b is a non-adhesion region.

And it is operated as follows.
First, as shown in FIG. 15A, the free piece 34 swings upward while being in sliding contact with the shutter 21 due to the movement of the shutter 21 to the open state. Then, after the shutter 21 is moved in the opening direction, the shutter 21 is slightly moved in the reverse direction as shown in FIG. By the movement of the shutter 21 in the reverse direction, the block member 32 is pushed toward the case 20, and the end of the block member 32 on the case 20 side abuts against the case 20. At this time, the sheet material 31 is bent at a place other than the bent portion 31 c, and the free piece 34 and the fixed piece 33 are deformed so that the portions 34 b and 33 b of the non-adhesion region are separated from the block member 32 or the case 20. Thereby, the contact of the block member 32 with the case 20 is allowed. As a result, the gap U between the free pieces 34 is blocked by the block member 32, and the passage of the airflow is prevented.

  Moreover, as shown in FIG.16 (b), you may comprise so that it can deform | transform so that the parts 34b and 33b of the non-adhesion area | region of the free piece 34 and the fixed piece 33 may mutually overlap. Also in this case, the end portion of the block member 32 can be brought into contact with the case 20 by the pushing operation accompanying the movement of the shutter 21 in the reverse direction. Moreover, in this case, the entire surface of the free piece 34 facing the block member 32 can be adhered.

  In addition, when the free pieces 34 are provided intermittently, the sheet material 31 can be easily bent at a place other than the bent portion 31 c, so that the block member 32 can be allowed to contact the case 20. However, even in the configuration in which the free pieces 34 are provided intermittently, the sheet material 31 can be bent at a place other than the bent portion 31c.

  In each of the embodiments described above, the block member 32 is attached to the inner surface of the free piece 34 facing the fixed piece 33. However, the block member 32 is attached to the outer surface of the free piece 34 as in the embodiment shown in FIG. You may attach to the side. Also in this case, the gap S between the shutter 21 and the case 20 can be shielded by the block member 32 or both the block member 32 and the sheet material 31.

18 and 19 show an embodiment in which the free piece 34 is intermittently provided in the configuration in which the block member 32 is attached to the outer surface side of the sheet material 31. FIG.
Also in this configuration, among the opposing surfaces of each free piece 34 facing the block member 32, only a part 34a (shaded portion in the drawing) on the distal end side is bonded to the block member 32, and a part 34b on the proximal end side is attached. A non-adhesive region that does not adhere to the block member 32 is used.

  Then, as shown in FIG. 19, after the shutter 21 moves in the opening direction, the block member 32 is pushed to the case 20 side by moving slightly in the reverse direction, and the block member 32 side of the block member 32 is moved to the case 20 side. The end of the abuts against the case 20. At this time, the block member 32 is allowed to come into contact with the case 20 by being deformed so that the non-bonded region portion 34b of the free piece 34 is separated from the block member 32. Thereby, the gap U between the free pieces 34 is closed by the block member 32, and the passage of the airflow can be prevented.

FIG. 20 is a diagram showing an embodiment in which the shielding member is made of a sponge material.
Here, instead of the shielding member 30 composed of the sheet material 31 and the block member 32, a shielding member 30 made of an elastically deformable sponge material 35 is used. The sponge material 35 is attached to the facing surface 20 a where the shutter 21 faces the case 20. The sponge material 35 is attached over the longitudinal direction of the case 20 (or the axial direction of the photosensitive member 2), and is disposed on the movement path D when the shutter 21 is switched from the open state to the closed state.

  As shown in FIG. 20B, when the shutter 21 moves so as to be switched to the open state, the shutter 21 comes into contact with the sponge material 35, and the sponge material 35 is elastically deformed by this contact. Then, the shutter 21 moves to the open position, and the sponge material 35 is interposed between the shutter 21 and the case 20. In addition, the sponge material 35 is in close contact with the inner surface of the shutter 21 due to its elastic restoring force, so that the gap S between the shutter 21 and the case 20 is shielded.

  On the other hand, as shown in FIG. 20A, when the shutter 21 is in the closed state, the sponge material 35 is not in contact with the shutter 21 in order to reduce the opening / closing load of the shutter 21. Is good. Similarly to the above, the urging force F1 of the torsion spring 25 that switches the shutter 21 to the closed state, and the frictional resistance caused by sliding contact with the sponge material 35 (the shielding member 30) when the shutter 21 is switched to the closed state. The relationship with the force F2 is set so that F1> F2.

  Further, in order to reduce the frictional resistance between the shutter 21 and the sponge material 35, a low friction member such as a PET film is provided on the surface (sliding surface) of the sponge material 35, or the surface (sliding) of the sponge material 35. Surface) may be subjected to a low friction treatment.

  Next, in the embodiment shown in FIGS. 21 and 22, an elastic member 36 made of sponge or the like is provided on the inner surface of the shutter 21 facing the photosensitive member 2 over the entire length thereof. Thus, by providing the elastic member 36 on the inner surface of the shutter 21, when the shutter 21 is in the closed state (the state shown in FIG. 21A), the shutter 21 comes into contact with the surface of the photoreceptor 2. Scratches can be prevented from occurring. On the other hand, when the shutter 21 is in the open state (the state shown in FIG. 21 (b)), the shielding member 30 contacts the elastic member 36 over the entire length thereof, so that the shutter 21 and the shielding member 30 are in contact with each other. Adhesion is improved. Thereby, the clearance S between the shutter 21 and the case 20 can be shielded to a higher degree, and the passage of airflow can be more reliably prevented.

Further, the embodiment shown in FIGS. 23 to 28 is obtained by improving the embodiment shown in FIGS. 21 and 22.
23 is a view of the shutter as seen from the inner surface side, FIG. 24 is a view of the shielding member as seen from the block member side, FIG. 25 is a view showing a state where the shutter is in an open state, and FIG. 25 is a cross-sectional view taken along line E1-E1, FIG. 26B is a cross-sectional view taken along line G1-G1 in FIG. 25, and FIG. 27 is a view showing a state when the shutter starts to move to the closed state. FIG. 28 is a sectional view taken along line E2-E2 in FIG. 27, and FIG. 28B is a sectional view taken along line G2-G2 in FIG.

  In this embodiment, as shown in FIG. 23, both ends in the longitudinal direction of the elastic member 36 provided on the inner surface of the shutter 21 are cut out to form an exposed portion 37 that exposes the inner surface of the shutter 21. The shielding member 30 is composed of a sheet material 31 and a block member 32, and convex portions 38 are provided at both longitudinal ends of the block member 32.

  As shown in FIG. 25, when the shutter 21 is in the open state (stationary state), the block member 32 contacts the elastic member 36 over the entire length in the E1-E1 cross section where the exposed portion 37 is not formed. (See FIG. 26A). On the other hand, in the G1-G1 cross section where the exposed portion 37 is formed, both convex portions 38 of the block member 32 are in contact with the exposed portion 37 (the inner surface of the shutter 21) (see FIG. 26B). ). Here, the block member 32 is not in contact with the elastic member 36 in the G1-G1 cross section. However, as described above, since the block member 32 is in contact with the elastic member 36 over the entire length in the E1-E1 cross section, the gap S between the shutter 21 and the case 20 is shielded. And the passage of airflow is blocked.

  Also, as shown in FIG. 27, when the shutter starts to move to the closed state, in the E2-E2 cross section where the exposed portion 37 is not formed, unlike the open state, the block member 32 is It leaves | separates from the elastic member 36 and will be in a non-contact state mutually (refer Fig.28 (a)). On the other hand, in the G2-G2 cross section where the exposed portion 37 is formed, both convex portions 38 of the block member 32 are in contact with the exposed portion 37 (the inner surface of the shutter 21), as in the open state. The block member 32 is not in contact with the elastic member 36. (See FIG. 28 (b)).

  As described above, when the shutter 21 is switched to the closed state, the block member 32 does not come into contact with the elastic member 36 at all (becomes a non-contact state), so that frictional resistance due to contact with the elastic member 36 can be eliminated. As a result, the frictional resistance when the shutter 21 is moved to the closed state is reduced, so that the shutter 21 can be more reliably switched to the closed state by the urging force of the torsion spring 25.

  In particular, the urging force of the torsion spring 25 is maximum when the shutter 21 is in the open state, and the urging force decreases as the shutter 21 approaches the closed state. Accordingly, when the shutter 21 starts to close and the urging force of the torsion spring 25 starts to decrease, the frictional resistance is reduced as described above, so that the shutter 21 is caught in the middle of movement and is brought into the closed state. It is possible to effectively avoid the state in which switching is not possible.

  Further, when the static friction coefficient between the block member 32 and the elastic member 36 is μ1, and the static friction coefficient between the block member 32 (convex portion 38) and the inner surface (exposed portion 37) of the shutter 21 is μ2, By setting μ1> μ2, it is possible to make the reduction in frictional resistance more remarkable when the shutter 21 starts to close.

  Further, as shown in FIG. 29, the exposed portion 37 is desirably formed at a position corresponding to the outside of the image bearing area H of the photoreceptor 2. In such a position, even if the exposed portion 37 is formed, it is possible to protect the image carrying area H of the photoreceptor 2 by the elastic member 36.

  Further, as shown in FIGS. 30 and 31, low friction members 39, 40 such as Teflon (registered trademark) tape are provided on at least one of the sliding surfaces (sliding surfaces) of the exposed portion 37 and the convex portion 38. It may be provided, or at least one of the respective surfaces may be subjected to a low friction treatment. Thereby, the frictional resistance between the shutter 21 and the shielding member 30 can be further reduced.

  Further, as shown in FIG. 32, a convex portion 41 may be provided on the shutter 21 side. In this case, as shown in FIG. 33, when the shutter 21 is in the open state (stationary state), the block member 32 does not come into contact with the convex portion 41, and as shown in FIG. 34, when the shutter starts to move to the closed state, The block member 32 is in contact with the convex portion 41.

  With this configuration, when the shutter is in the open state, the block member 32 comes into contact with the elastic member 36 over the entire longitudinal direction to shield the gap S, and when the shutter starts to move to the closed state, the block member 32. Is in a non-contact state with respect to the elastic member 36 and can reduce the frictional resistance.

  Similarly to the above, in order to protect the image carrying area H of the photoconductor 2, it is desirable that the convex portion 41 is provided at a position corresponding to the outside of the image carrying area H of the photoconductor 2.

  Furthermore, as shown in FIGS. 35 and 36, low friction members 42 and 43 such as Teflon (registered trademark) tape are provided on at least one of the sliding surfaces (sliding surfaces) of the convex portion 41 and the block member 32. It may be provided, or at least one of the respective surfaces may be subjected to a low friction treatment. Thereby, the frictional resistance between the shutter 21 and the shielding member 30 can be further reduced.

  In the embodiment shown in FIGS. 21 to 36 in which the elastic member 36 is provided on the inner surface of the shutter 21, the block member 32 is attached to the outer surface side of the sheet material 31. It is also possible to attach to the inner surface side.

  As mentioned above, although each embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment, Of course, a various change can be added in the range which does not deviate from the summary of this invention.

  The image forming apparatus to which the present invention is applicable is not limited to a monochrome image forming apparatus as shown in FIG. The present invention relates to an indirect transfer type color image forming apparatus for indirectly transferring images on a plurality of photoreceptors 2 to a sheet via an intermediate transfer belt (intermediate transfer body) 50 as shown in FIG. As shown in FIG. 38, the present invention can also be applied to a direct transfer type color image forming apparatus that directly transfers images on a plurality of photosensitive members 2 onto a sheet conveyed by a conveyance belt (conveyance body) 51. . Further, the image forming apparatus to which the present invention can be applied includes a printer, a copying machine, a facsimile, or a complex machine thereof.

1 Process Unit 2 Photoconductor 20 Case 21 Shutter 25 Torsion Spring (Biasing Member)
30 Shielding member 31 Sheet material 32 Block member 35 Sponge material 36 Elastic member 37 Exposed portion 38 Convex portion 100 Image forming apparatus main body H Image carrying area Wp Maximum sheet passing width (maximum recording medium passage width)

Japanese Patent Laid-Open No. 10-333530 JP 2002-196649 A

Claims (4)

A photoconductor provided so that a part of the case is exposed;
A shutter that can be switched between a closed state that covers the exposed surface of the photoconductor and an open state that opens the exposed surface of the photoconductor,
In the process unit configured to be detachable from the image forming apparatus main body,
A shielding member that is attached to the case and contacts the shutter when the shutter is in the open state, and shields between the shutter and the case ;
An elastic member is provided on the inner surface of the shutter facing the photoconductor,
When the shutter is in the open state, the shielding member is in contact with the elastic member,
When the shutter is switched from the open state to the closed state, a part of the shielding member is in contact with the inner surface of the shutter, and the shielding member and the elastic member are not in contact with each other. Process unit to be executed. Providing a convex portion on the shielding member,
Forming an exposed portion by notching the elastic member to expose the inner surface of the shutter;
2. The process according to claim 1, wherein when the shutter is switched from the open state to the closed state, the convex portion comes into contact with the exposed portion, and the shielding member and the elastic member are not in contact with each other. unit. The process unit according to claim 2, wherein the exposed portion is formed at a position corresponding to the outside of the image bearing area of the photoconductor . An image forming apparatus comprising the process unit according to claim 1.

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