JP2010078730A - Image forming apparatus - Google Patents

Abstract

An image forming apparatus capable of maintaining a gap between a developer carrying member and an image carrying member and increasing the stability of image quality without increasing the pressure more than necessary during operation of the device.
SOLUTION: A first unit device 1, a second unit device 2 that performs an approaching / separating operation with respect to the first unit device 1, and an abutment provided in at least one place of the second unit device 2. Pressurizing means 503 that presses and abuts the portion 203 against the abutting portion 102 provided in the first unit device 1, and the first unit device 1 and the second unit device 2 by the pressurizing means 503 Pressure force adjusting means M for adjusting the pressure force. Measure the applied pressure of the first unit device 1 and the second unit device 2 in at least one place in the contact portion between the first unit device 1 and the second unit device 2 or in the vicinity of the contact portion. A pressure measuring means 601 is provided.
[Selection] Figure 2

Description

  The present invention relates to an image forming apparatus such as an electrophotographic printer or a copier, and particularly has a feature in a positioning and pressurizing mechanism of a developing device that moves close to and away from an image carrier. .

  2. Description of the Related Art Conventionally, a non-contact developing method is often used in a developing device in an image forming apparatus such as an electrophotographic printer or a copying machine. In the non-contact development system, a developing roller as a developer carrying member is disposed with a predetermined gap between a drum-shaped electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) as an image carrying member. . Then, the toner on the developing roller is caused to fly to the electrostatic latent image on the photosensitive drum, so that the electrostatic latent image becomes visible as a toner image.

  FIG. 13 is a schematic cross-sectional view of the periphery of a conventional photosensitive drum 101 and developing device 2. In the developing device 2 employing the non-contact developing method as described above, the abutting member 203 provided on the developing roller 202 side is provided on the abutting member 102 (or the photosensitive drum 101) provided on the photosensitive drum 101 side. Butt it and make it come into contact. Next, the developing device 2 is pressurized to the photosensitive drum 101 side by a pressing unit (not shown), and the gap between the developing roller 202 rotatably supported by the developing container 201 and the photosensitive drum 101 is maintained with high accuracy. In the developing device 2 that employs the non-contact development method, such a contact method is common.

  Also in a so-called tandem type multi-color image forming apparatus, each of which is a unit device, and has a plurality of pairs of photosensitive drums and developing devices, the unit device can be installed and replaced at the time of maintenance and maintenance. The close-and-separated operation occurs. Also in the image forming apparatus having such a configuration, the abutting method as described above is employed for positioning the photosensitive drum and the developing device.

  As another example, in recent years, with the increase in copying and printer speeds, a developing apparatus provided with two developing rollers so as to be compatible with high speed has been tried. 14 is a cross-sectional view of the periphery of the developing device 2 provided with the conventional photosensitive drum 101 and two developing rollers, and FIG. 15 is a developing device provided with the conventional photosensitive drum 101 and two developing rollers. It is a perspective view of 2 periphery.

  In FIG. 14, the photosensitive drum 101 is rotated in the direction of arrow R in the drawing to form an image.

  In the conventional developing device 2, a developing roller (hereinafter referred to as “developing upper roller”) 202a located on the upstream side and a developing roller located on the downstream side (hereinafter referred to as “developing lower roller”) in the image forming process. 202b is fixed to the developing container 201 between the shafts and is rotatably supported. The developing device 2 pressurizes in the direction of the photosensitive drum 101 by a pressurizing unit (not shown) via a pressurizing spring 501. Then, a total of four abutting members 203 provided at two front and rear coaxial positions of the upper developing roller 202a and the lower developing roller 202b are abutted against the photosensitive drum 101 (or a not-shown abutting member). Make contact. Accordingly, the gap between the upper developing roller 202a and the lower developing roller 202b and the photosensitive drum 101 is maintained with high accuracy.

  In such a developing device 2, as disclosed in Patent Document 1, a configuration in which the abutting member 203 is provided on the lower developing roller 202b and the abutting member 203 is not provided on the upper developing roller 202a is exemplified. Yes.

  In a multi-color image forming apparatus having a plurality of developing devices for one photosensitive drum, only the developing device having a desired toner is moved close to the photosensitive drum side from the standby position to the developing position and is placed on the photosensitive drum. After the toner image is formed, the separating operation is performed up to the standby position. Next, a multicolor image is formed by sequentially switching a plurality of developing devices to form a plurality of toner images on the photosensitive drum.

  Also in this case, the positioning of the photosensitive drum and the developing device is performed by abutting the abutting members provided at the two front and rear positions on the developing roller side with the abutting members provided at the two front and rear positions on the photosensitive drum side opposite thereto. Make contact. And the structure which pressurizes a developing device to the photosensitive drum side is implemented.

Further, in such a developing device, as disclosed in Japanese Patent Application Laid-Open No. 2004-228561, the approaching / separating speed of the developing device is reduced before and after the developing device contacts the photosensitive drum to reduce noise and vibration associated with the approaching operation. A configuration has been proposed.
JP 2003-307930 A JP-A-6-317980

  However, the above prior art has the following problems.

  In the conventional example, as described above, the gap between the developing roller and the photosensitive drum is maintained by bringing the abutting member into contact with the abutting member and applying pressure, but the abutting member contacts the abutting member. There was no means for detecting whether or not they were in contact.

  On the other hand, the periphery of the developing device is a place where dust such as toner scattering is generated, and the dust tends to cause a sliding failure in the pressurizing mechanism. For this reason, when the applied pressure is low, there is a problem that the abutting member does not contact the abutted member and the gap between the developing roller and the photosensitive drum cannot be maintained.

  Further, in the conventional developing device provided with two developing rollers, a total of four abutting members, which are fixed between the shafts, come into contact with the photosensitive drum on the same circumferential surface. If the applied pressure is low at this time, there is a problem that at least one abutting member has a gap between the photosensitive drum and the gap between the developing roller and the photosensitive drum cannot be maintained.

  If the pressurizing force is set high in order to avoid such poor contact, the rotational torque of the developing roller and the photosensitive drum may be increased. Furthermore, there are cases in which the abutting member is elastically deformed due to the applied pressure, or wear due to long-term use, resulting in a problem that the gap between the developing roller and the photosensitive drum cannot be maintained.

  Further, in a multicolor image forming apparatus having a plurality of developing devices for one photosensitive drum, only the developing device having a desired toner is moved from the standby position to the developing position toward the photosensitive drum, and the abutting member and the target member are covered. A gap between the developing roller and the photosensitive drum is maintained via the abutting member. Here, with the speeding up of copying and printers, there is a demand for shortening the time required for the switching operation of the developing device. Therefore, it is necessary to move the developing device close to and away from the photosensitive drum at high speed.

  However, when the proximity speed is increased, the impact at the time of abutment increases, and vibration is generated by the impact, and the vibration propagates to the photosensitive drum and the like in addition to the developing device itself and appears as so-called “image blur”. This was a major factor in image quality degradation.

  In order to reduce the impact at the time of abutting as described above, it is effective to control so that the proximity speed of the developing device to the photosensitive drum is reduced at a timing before the abutting member contacts the abutted member. is there.

  In the prior art disclosed in Patent Document 2, a configuration in which a detection flag and a photosensor are provided in the drive gear portion of the pressurizing mechanism is exemplified as means for detecting the timing at which the abutting member contacts the abutted member. ing. However, the periphery of the developing device is a place where there is a lot of dust such as toner, and it is necessary to take sufficient dust countermeasures so as not to hinder the operation of the photosensor.

  Therefore, an object of the present invention is to maintain a gap between the two unit devices, for example, between the developer carrying member and the image carrying member without increasing the pressing force more than necessary during operation of the device, thereby improving the stability of the image quality. It is an object of the present invention to provide an image forming apparatus.

The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention is provided in at least one location of the first unit device, the second unit device that performs a proximity / separation operation with respect to the first unit device, and the second unit device. A pressurizing means for pressurizing and abutting the abutting portion against the abutted portion provided in the first unit device, and the first unit device and the second unit device by the pressurizing device. In the image forming apparatus having a pressure adjusting means for adjusting the pressure,
Proximity / separation acceleration between the first unit device and the second unit device at least at one position in the contact portion between the first unit device and the second unit device or in the vicinity of the contact portion. An image forming apparatus is provided with a measuring unit.

  According to the present invention, based on the measurement result of the proximity / separation acceleration between the abutting portion of one unit device and the abutted portion of another unit device, the abutting portion and the abutted portion abut on each other. It is possible to detect whether or not there is. This makes it possible to maintain, for example, the gap between the developer carrier and the image carrier without increasing the pressure more than necessary during operation of the device, thereby improving the stability of image quality. Can be increased.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Example 1
FIG. 1 shows a schematic configuration of a first embodiment of an image forming apparatus according to the present invention. In this embodiment, the image forming apparatus is an electrophotographic image forming apparatus, and includes an image reading unit 8 and an image writing unit 9. The image reading unit 8 reads an image of a document, and the image writing unit 9 exposes the surface of the image carrier, that is, the photosensitive drum 101 according to a command from a controller (not shown) based on the read image data. Then, an electrostatic latent image is formed on the photosensitive drum 101.

  The surface of the photosensitive drum 101 is uniformly charged to a predetermined potential by the charger 3 before exposure, and image writing is performed on the uniformly charged photosensitive drum 101 as described above. An electrostatic latent image is formed on the photosensitive drum 101 by irradiating laser light or the like from the unit 9.

  The electrostatic latent image formed on the photosensitive drum 101 is developed by applying toner as a developer by the developing device 2, and then the developed toner image is transferred to the transfer device 4 by the rotation of the photosensitive drum 101. It is conveyed to the facing part.

  On the other hand, the sheet S as a recording medium is fed one by one from the sheet cassette by the pickup roller 32 corresponding to the conveyance of the developed toner image. When the sheet S passes through a facing portion between the photosensitive drum 101 and the transfer device 4 at a timing by the registration roller pair 35, the developed toner image on the photosensitive drum 101 is transferred onto the sheet S by the transfer device 4. Is done.

  The sheet S on which the toner image has been transferred is conveyed to the position of the fixing roller pair 7 by a predetermined conveying device, pressed against the fixing roller pair 7, and heated by a heater (not shown) provided in the fixing roller. Thus, the toner on the sheet S is melted and fixed on the sheet S. Thereafter, the sheet S on which the toner image is fixed is stored in the tray 15 outside the apparatus main body by the discharge roller 11, and a series of image forming processes is completed.

  In this embodiment, each of the photosensitive drum 101 and the developing device 2 constitutes a unit device. In this embodiment, in particular, the unit device on the side that carries and drives the photosensitive drum 101 is referred to as the image carrier device 1. I will call it. Further, it is assumed that the developing device 2 operates in contact with the image carrier device 1.

  Next, an image carrier device (first unit device) 1 and a developing device (second unit device) 2 which are first and second unit devices in this embodiment will be described.

  FIG. 2 is a schematic cross-sectional plan view of the vicinity of the contact portion on the front side of the image forming apparatus (that is, the front operation side of the image forming apparatus) when the image carrier device 1 and the developing device 2 are separated from each other in this embodiment. is there.

  Referring to FIG. 2, an image carrier device 1 is provided with a photosensitive drum 101 and an abutting member 102 that is provided at two positions on the front and rear of the photosensitive drum 101 and constitutes an abutting portion in this embodiment. And. Further, the image carrier device 1 is a pressure-sensitive measuring means that is a pressure measurement means having a contact convex portion 601c fixed inside the abutted member 102 and projecting outward from the surface of the abutted member 102. A conductive elastomer sensor 601 is provided. The pressure-sensitive conductive elastomer sensor 601 includes a sensor portion 601a made of a pressure-sensitive conductive elastomer having a contact convex portion 601c formed at the tip, and a flexible substrate 601b connected to the sensor portion 601a.

  On the other hand, the developing device 2 includes a developing container 201, a developing roller 202 rotatably supported by the developing container 201, and an abutting portion provided in two places on the front and rear of the developing roller 202 on the same axis. The abutting member 203 is configured.

  Here, the pressure-sensitive conductive elastomer sensor 601 is obtained by mixing and dispersing conductive particles such as metal and granulated carbon in an insulator made of rubber or elastomer. The characteristic is that the conductive particles are insulative because they are separated from each other when no pressure is applied. However, when the pressure is applied, the conductive particles approach each other or come into contact with each other, and the electric resistance value (volume resistance) Value and surface resistance value) continuously decrease, and as a result, conductivity is exhibited.

  When image formation is performed, the developing device 2 performs a proximity operation in the direction of the image carrier device 1 in order to form a predetermined gap between the photosensitive drum 101 and the developing roller 202. The approaching operation is performed by driving the camshaft 504 by an actuator such as a motor M to operate the pressure cam 503 connected to the camshaft 504 and operating the pressure spring 501 via the pressure plate 502. Done. The pressure spring 501, the pressure cam 503, etc. constitute a pressure means, and the actuator such as a motor constitutes a pressure adjustment means.

  The electrical resistance value measurement result by the pressure-sensitive conductive elastomer sensor 601 is input to a control board (not shown) on which the amplification circuit, the output result calculation unit, and the like of the pressure-sensitive conductive elastomer sensor 601 are mounted, and calculation is performed. Based on the calculation result, by driving the pressure cam 503 by controlling the driving of an actuator such as the motor M, the approaching and separating operation of the image carrier device 1 and the developing device 2 can be controlled. .

  FIG. 3 is a schematic cross-sectional plan view of the vicinity of the contact portion on the front side of the image forming apparatus in a state where the image carrier device 1 and the developing device 2 according to the present embodiment are in the process of approaching and separating.

  In the state shown in FIG. 3, the abutting member 203 pressurizes the sensor unit 601 a by contacting the contact convex portion of the sensor unit 601 a of the pressure-sensitive conductive elastomer sensor 601. As described above, the sensor unit 601a is made of rubber or elastomer, and the elastic coefficient in the mechanical characteristics thereof can be selected to be sufficiently smaller than the material forming the abutting member 203. is there.

  By setting the elastic coefficient of the sensor unit 601a to be sufficiently smaller than the material forming the abutting member 203, the sensor unit 601a can be elastically deformed without elastically deforming the abutting member 203. . Therefore, the proximity operation is continued until the abutting member 203 abuts against the abutted member 102 while elastically deforming the sensor unit 601a.

  When the elastic modulus of the sensor unit 601a cannot be selected to be sufficiently small, when the pressure-sensitive conductive elastomer sensor 601 is fixed inside the abutted member 102, the abutted member 102 and the pressure-sensitive conductivity You may make it the structure fixed via arbitrary elastic members, such as a leaf | plate spring, between the elastomer sensors 601.

  FIG. 4 is a schematic cross-sectional plan view of the vicinity of the contact portion on the front side of the image forming apparatus when the image carrier device 1 and the developing device 2 are close to each other in this embodiment.

  In the state shown in FIG. 4, the abutting member 203 is abutted against the abutting member 102 in a state where the contact convex portion 601 c of the sensor portion 601 a of the pressure-sensitive conductive elastomer sensor 601 is elastically deformed and pressed. Is done. As a result, a predetermined gap is maintained between the photosensitive drum 101 and the developing roller 202.

  Although the image carrier device 1 and the developing device 2 repeatedly perform the approaching and separating operations as necessary, the sensor unit 601a has a characteristic of quickly returning to the state before pressurization when the load due to the applied pressure is released. Have. Therefore, after the state shown in FIG. 4, the developing device 2 returns to the state shown in FIG. 2 by performing a separation operation from the image carrier device 1.

  FIG. 5 shows the electric resistance value of the pressure-sensitive conductive elastomer sensor 601 with the elapsed time from the separated state to the contact state of the image carrier device 1 and the developing device 2 in this embodiment. It is an example of the graph which showed the measurement result on the vertical axis | shaft.

  In the separated state shown in FIG. 2 described above, the sensor unit 601a and the abutting member 203 are not in contact with each other, and the electrical resistance value is detected as a no-load state. The electrical resistance value measurement result output in such a no-load state corresponds to the elapsed time range indicated by region A in FIG.

  When the proximity operation is performed and the sensor unit 601a and the abutting member 203 come into contact with each other, the sensor unit 601a starts elastic deformation. This amount of elastic deformation varies until the abutting member 203 abuts against the abutted member 102 and a predetermined gap is maintained between the photosensitive drum 101 and the developing roller 202. A state in which the electric resistance value of the sensor unit 601a continuously changes according to the elastic deformation amount is detected. The electrical resistance value output corresponds to the elapsed time range indicated by region B in FIG.

  When the approaching operation is continued and the contact state shown in FIG. 4 is reached, the abutting member 203 abuts against the abutted member 102, whereby the fluctuation of the elastic deformation of the sensor unit 601a stops and is constant. This is detected as a state in which the applied pressure is maintained. The electrical resistance value measurement result output in a state in which a constant pressure is maintained corresponds to the elapsed time range indicated by region C in FIG.

  Next, based on the output of the pressure-sensitive conductive elastomer sensor 601 shown in FIG. 5, a means for detecting whether or not the abutting member 203 is in contact with the abutted member 102 and optimum pressure control are performed. The means will be described.

  The acceleration of the waveform can be calculated by differentiating the waveform shown in FIG. 5 with respect to the time axis by an arithmetic unit (not shown). When the sensor output exceeds the arbitrarily set threshold value indicated by the dotted line in FIG. 5 and the waveform acceleration falls below the arbitrarily set threshold value for a certain period of time, the fluctuation of the elastic deformation of the sensor unit 601a is Judged to have stopped. That is, it is possible to determine that the abutting member 203 is in contact with the abutted member 102.

  Next, the operation amount of the pressure cam 503 after it is determined that the abutting member 203 is in contact with the abutted member 102 is arbitrarily set.

  Here, the pressing force of the unit device is determined from the amount of movement of the pressure plate 502 and the spring constant of the pressure spring 501. Therefore, it is possible to perform a desired pressure control by setting the operation amount of the pressure cam 503 optimally.

  Whether or not the abutting portion of one unit device (developing device 2 in this embodiment) is in contact with the abutting portion of another unit device (image carrier device 1 in this embodiment) by the above-described means. Can be detected. Accordingly, it is possible to maintain the gap between the developing roller 202 of the developing device 2 and the photosensitive drum 101 of the image carrier device 1 without increasing the pressure more than necessary during operation of the device, and the stability of the image quality. Can be increased.

  Next, a means for controlling the approaching / separating speed between the image carrier device 1 and the developing device 2 based on the output of the pressure-sensitive conductive elastomer sensor 601 shown in FIG. 5 will be described.

  FIG. 6 is a graph showing the elapsed time from the separated state to the contact state between the image carrier device 1 and the developing device 2 in the present embodiment on the horizontal axis and the driving frequency of the motor M on the vertical axis. It is an example.

  In the elapsed time range indicated by the area A in FIG. 5, the motor M first accelerates to the drive frequency S1, as shown in FIG. 6, and then drives at a constant speed at the speed S1 to move the developing device 2 to the image carrier device 1. Operate close to. When the proximity operation is performed and it is detected that the sensor output exceeds an arbitrarily set threshold value indicated by a dotted line in FIG. 5, control for decelerating the driving frequency of the motor M to S2 shown in FIG. 6 is started.

  The deceleration operation performs the drive frequency control of the motor M so as to be performed within the elapsed time range indicated by the region B in FIG. That is, control is performed so as to decelerate the drive frequency of the motor M before reaching the contact state shown in FIG.

  With the above-described configuration, it is possible to control the apparatus proximity speed to a low speed before the abutting portion of the developing device 2 contacts the abutted portion of the image carrier device 1. Accordingly, it is possible to reduce the impact at the time of contact while minimizing the loss of time required for the proximity operation, and it is possible to reduce the deterioration of the image quality due to the image blur.

  That is, as described above, according to this embodiment, the proximity separation acceleration measuring means has the structure having the contact convex portion that protrudes outward from the surface of the unit device contact portion, so that at the time of the unit proximity operation, It is possible to detect the timing at which the abutting part comes into contact with the abutted part. As a result, the unit approach speed can be controlled before contact, and the impact during contact can be reduced while minimizing the loss of time required for close operation, thereby reducing image quality degradation due to image blurring. It becomes. Here, as a means for detecting the proximity / separation acceleration, a differential transformer type contact displacement sensor, an optical non-contact displacement sensor, or the like may be used. However, by using a pressure-sensitive conductive elastomer sensor as the detection means, it is sufficient to use a differential transformer type displacement sensor with a moving part or an optical photo sensor that causes a problem of light quantity reduction due to dust. It is no longer necessary to take special dust countermeasures.

Example 2
Next, a second embodiment of the image forming apparatus of the present invention will be described. The overall configuration of the image forming apparatus according to the present embodiment is the same as that of the image forming apparatus according to the first embodiment. Therefore, the description of the first embodiment is used and the description thereof is omitted here.

  FIG. 7 is a schematic sectional plan view showing the periphery of the image carrier device 1 and the developing device 2 in this embodiment.

  The present embodiment is an application of the first embodiment, and differs from the first embodiment in that the pressure-sensitive conductive elastomer sensor 601 is provided only at one of the front and rear instead of two at the front and rear of the apparatus.

  In the configuration of this embodiment, a developing roller gear 204 is connected to either the front or rear end of the developing roller 202, and the developing roller 202 is driven by a developing driving gear 205 driven from an image forming apparatus main body (not shown). ing.

  In general, in the image forming apparatus, the radial component force generated in the developing roller shaft due to the engagement between the developing roller gear 204 and the developing driving gear 205 is designed to press the abutting member 203b against the abutting member 102. Therefore, the abutting portion on the side to which the developing roller gear 204 is connected can often maintain a stable contact state.

  On the other hand, due to the radial direction component force, a force acts on the developing roller 202 in a direction in which the abutting member 203a is separated from the abutting member 102 with the abutting member 203b as a fulcrum. Therefore, the pressure-sensitive conductive elastomer sensor 601 is provided only on the abutting member 203a side. As a result, the pressure-sensitive conductive elastomer sensor 601 can be reduced by one with respect to the first embodiment, and the cost can be reduced.

Example 3
Next, a third embodiment of the image forming apparatus of the present invention will be described. The overall configuration of the image forming apparatus according to the present embodiment is the same as that of the image forming apparatus according to the first embodiment. Therefore, the description of the first embodiment is used and the description thereof is omitted here.

  FIG. 8 is a schematic cross-sectional front view showing the periphery of the image carrier device 1 and the developing device 2 according to another embodiment in the image forming apparatus of this embodiment, and FIG. 9 is the image carrier device 1 and the developing device 2. It is a perspective view which shows the periphery.

  The present embodiment is an application of the first embodiment, and is a case where the present invention is applied to the developing device 2 provided with two developing rollers.

  That is, in this embodiment, the pressure-sensitive conductive elastomer sensor corresponds to each position of a total of four abutting members 203 provided at two front and rear coaxial positions of the upper developing roller 202a and the lower developing roller 202b. 601 is provided in the same number as the abutting member 203.

  In the developing device 2 of the present embodiment, the upper developing roller 202a and the lower developing roller 202b are rotatably supported with the shaft fixed to the developing container 201, so that a gap between the two rollers 202a and 202b is formed. Guaranteed. However, as described above, the developing device 2 in which the two developing rollers 202a and 202b are fixed between the shafts in the same container 201 has the following problems.

  A total of four abutting members 203 provided at two front and rear positions on the same axis of the two developing rollers are in contact with the same cylindrical surface of the abutting member 102 provided at two front and rear positions on the same axis as the photosensitive drum 101. Touch. For this reason, when the applied pressure is low, at least one abutting member 203 has a poor contact state with a gap with the abutted member 102. That is, when the gap between the photosensitive drum 101 and the developing rollers 202a and 202b becomes larger than a desired value, image quality may be deteriorated.

  In order to prevent the contact failure as described above, the developer container 201 is deformed by increasing the applied pressure, thereby improving the dimensional accuracy of the developer container 201, the abutting member 203, and the abutting member 102 and the like. It is necessary to eliminate the contact failure caused accordingly.

  However, since the dimensional accuracy of the developing container and the like varies depending on the apparatus, it is difficult to predict in advance where the contact failure occurs among the four contact portions. Therefore, if the contact pressure is set high assuming any contact failure, the gap between the developing roller and the photosensitive drum cannot be maintained due to the elastic deformation of the abutting member 203. Furthermore, there is a problem that the rotational torque of the developing roller is increased.

  In the third embodiment, it is possible to detect the contact state of each of the four contact portions. By operating the plurality of pressure cams 503 according to the detection result and controlling the pressure applied to each contact portion, the gap between the developing roller and the photosensitive drum is maintained without increasing the pressure more than necessary. It is possible to improve the stability of image quality.

Example 4
Next, a description will be given of a fourth embodiment of the image forming apparatus of the present invention. The overall configuration of the image forming apparatus according to the present embodiment is the same as that of the image forming apparatus according to the first embodiment. Therefore, the description of the first embodiment is used and the description thereof is omitted here.

  FIG. 10 is a schematic cross-sectional plan view of the vicinity of the contact portion on the front side of the image forming apparatus when the image carrier device 1 and the developing device 2 in the image forming apparatus of the present embodiment are close to each other.

  The present embodiment is an application of the first embodiment, and the pressure-sensitive conductive elastomer sensor 601 is not fixed to the abutted member 102 but is fixed to the front and rear side plates 103 of the image carrier device 1 in the vicinity of the contact portion. is doing. That is, the present embodiment is different from the first embodiment in that the pressure-sensitive conductive elastomer sensor 601 is provided between the front and rear side plates 103 and the developing container 201.

  In the fourth embodiment, the gap between the photosensitive drum 101 and the developing roller 202 is abutted on the photosensitive drum 101 constituting the abutted portion so as to be rotatable at two positions on the same axis before and after the developing roller 202. It is maintained by abutting the member 203, that is, the abutting portion.

  In a state where the photosensitive drum 101 and the abutting member 203 are in contact with each other, the sensor unit 601 provided on the front and rear side plate 103 in the vicinity of the contact portion is a contact convex portion of the sensor unit 601a that protrudes outward from the front and rear side plate 103. 601 c is pressurized by the developing container 201. The developing container 201 is disposed so as not to contact the front and rear side plates 103.

  Also in the fourth embodiment, it is possible to detect whether the abutting member 203 is in contact with the photosensitive drum 101 based on the output of the pressure-sensitive conductive elastomer sensor 601 as in the first embodiment. In this embodiment, the pressure-sensitive conductive elastomer sensor 601 may be provided on the developing container 201 side.

Example 5
FIG. 11 shows a schematic configuration of the fifth embodiment of the image forming apparatus according to the present invention. In this embodiment, the image forming apparatus is an electrophotographic multicolor image forming apparatus, and includes an image reading unit 8 and an image writing unit 9 as in the image forming apparatus of the first embodiment.

  However, unlike the image forming apparatus of the first embodiment, in the multi-color image forming apparatus of the present embodiment, the transfer drum 300 that supports and conveys the sheet S is disposed facing the photosensitive drum 101. A plurality of developing devices 2, that is, a yellow developing device 2Y, a cyan developing device 2C, a magenta developing device 2M, and a black developing device 2K are arranged facing the photosensitive drum 101. Any one of the developing devices 2 (2Y, 2C, 2M, 2K) among the plurality of developing devices is configured to perform a contact operation with respect to the image carrier device 1 including the photosensitive drum 101.

  The image forming operation is performed in the same manner as in the first embodiment. That is, the image reading unit 8 reads an image of an original, and the image writing unit 9 exposes the surface of the photosensitive drum 101 in response to a command from a controller (not shown) based on the read image data. An electrostatic latent image is formed on 101. Of course, the surface of the photosensitive drum 101 is uniformly charged to a predetermined potential by the charger 3 before exposure, and laser light is emitted from the image writing unit 9 onto the uniformly charged photosensitive drum 101. Etc., an electrostatic latent image is formed on the photosensitive drum 101.

  The electrostatic latent image formed on the photosensitive drum 101 is developed by applying toner by any of the developing devices 2 (2Y, 2C, 2M, 2K), and then the developed toner image is converted into the photosensitive drum. The sheet is conveyed to a portion facing the transfer device 4 by the rotation of 101.

  On the other hand, the sheet S as a recording medium is fed one by one from the sheet cassette by the pick-up roller 32 corresponding to the conveyance of the developed toner image, and is carried on the transfer drum 300. When the sheet S carried on the transfer drum 300 passes through a facing portion between the photosensitive drum 101 and the transfer device 4, the developed toner image on the photosensitive drum 101 is transferred onto the sheet S by the transfer device 4. .

  The above image forming operation is repeated by replacing the developing device 2 (2Y, 2C, 2M, 2K), and a yellow color image, a cyan color image, a magenta color image, and a black color image formed on the photosensitive drum 101 are displayed. Then, the image is transferred onto the sheet S carried and conveyed by the transfer drum 300.

  The sheet S on which the toner images of four colors are superimposed and transferred is conveyed to the position of the fixing roller pair 7 by a predetermined conveying device, pressed against the fixing roller pair 7, and a heater (not shown) provided in the fixing roller. The toner on the sheet S is melted and fixed on the sheet S. Thereafter, the sheet S on which the toner image is fixed is stored in the tray 15 outside the apparatus main body by the discharge roller 11, and a series of image forming processes is completed.

  FIG. 12 is a schematic cross-sectional front view around the image carrier device 1 and the developing device 2 (2Y, 2C, 2M, 2K) in the present embodiment.

  The fifth embodiment is an application of the first embodiment and shows an embodiment in a multicolor image forming apparatus including a plurality of developing devices 2 (2Y, 2C, 2M, and 2K) around one image carrier device 1. It is. Each developing device 2 (2Y, 2C, 2M, 2K) has the same configuration as the developing device of the first embodiment. Accordingly, members having the same configuration function are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the multi-color image forming apparatus shown in FIG. 11 and FIG. 12, only the developing device having the desired toner moves from the standby position to the development position to develop the photosensitive drum 101, and then performs the separation operation to the standby position. Do.

  In this embodiment, as described above, a plurality of developing devices are sequentially switched to perform development on the photosensitive drum 101, and a plurality of toner images are superimposed to form a multicolor image.

  In the image forming apparatus that repeatedly switches the developing device 2 as described above, when the pressure force is large, the abutting member 203 may be worn when the developing device 2 contacts the image carrier device 1. .

  Therefore, in the fifth embodiment, a plurality of positions are provided at positions corresponding to the positions where the abutting members 203 of the plurality of developing devices 2 come into contact with the abutting members 102 provided at two front and rear positions on the same axis as the photosensitive drum 101. The pressure-sensitive conductive elastomer sensor 601 was provided.

  Also in the fifth embodiment, similarly to the first embodiment, the operation of the pressurizing cam (pressurizing means) 503 is changed based on the output of the pressure-sensitive conductive elastomer sensor 601 (not shown) such as an actuator (pressurizing pressure adjusting means). By controlling with, there is no need to increase the pressure more than necessary. That is, the wear of the abutting member 203 is reduced, and the stability of the image quality can be enhanced by maintaining the gap between the photosensitive drum and the developing roller with high accuracy.

1 is a schematic cross-sectional view of an embodiment of an image forming apparatus according to the present invention. FIG. 3 is a schematic cross-sectional view illustrating an apparatus configuration around a contact portion in a state where the developing device is separated from the photosensitive drum in the first exemplary embodiment. FIG. 3 is a schematic cross-sectional view illustrating an apparatus configuration around an abutting portion when the developing device is in the middle of the approaching / separating operation with respect to the photosensitive drum according to the first exemplary embodiment. FIG. 2 is a schematic cross-sectional view illustrating an apparatus configuration around a contact portion in a state where the developing device is in contact with the photosensitive drum in Embodiment 1. It is explanatory drawing which shows the electrical resistance value measurement result waveform of a pressure-sensitive conductive elastomer sensor. It is a figure which shows the drive frequency control of the motor which performs pressurizing pressure adjustment. FIG. 10 is a schematic cross-sectional view illustrating an apparatus configuration around a contact portion in a state where the developing device is separated from the photosensitive drum in Embodiment 2. FIG. 10 is a schematic cross-sectional view illustrating a configuration of a photosensitive drum and a developing device in Embodiment 3. FIG. 10 is a perspective view illustrating a configuration of a photosensitive drum and a developing device in Embodiment 3. FIG. 10 is a schematic cross-sectional view illustrating a configuration of a photosensitive drum and a developing device in Embodiment 4. FIG. 5 is a schematic cross-sectional view of another embodiment of an image forming apparatus according to the present invention. FIG. 10 is a schematic cross-sectional view illustrating a configuration of a photosensitive drum and a developing device in Embodiment 5. FIG. 6 is a schematic cross-sectional view of a conventional photosensitive drum and a peripheral portion of a developing device. FIG. 6 is a schematic cross-sectional view of the periphery of a developing device provided with two conventional photosensitive drums and developing rollers. It is a schematic perspective view of the periphery of a developing device provided with a conventional photosensitive drum and two developing rollers.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image carrier apparatus 2 Developing apparatus 3 Charger 8 Image reading part 9 Image writing part 101 Photosensitive drum (abutting part)
102 Abutted member (abutted part)
202 Developing roller 203 Abutting member (abutting portion)
204 Development roller gear 205 Development drive gear 501 Pressure spring (pressure means)
502 Pressurizing plate (pressurizing means)
503 Pressurizing cam (pressurizing means)
504 Camshaft (Pressurizing means)
601 Pressure-sensitive conductive elastomer sensor (pressure measuring means)
601a Sensor part 602b Flexible substrate 601c Contact convex part M Motor (pressure adjusting means)

Claims (2)

A first unit device; a second unit device that performs a proximity / separation operation with respect to the first unit device; and an abutting portion provided in at least one location of the second unit device. Pressurizing means for pressurizing and abutting against the abutted portion provided in the unit device, and pressurizing adjustment for adjusting the pressurizing force between the first unit device and the second unit device by the pressurizing device And an image forming apparatus comprising:
Proximity / separation acceleration between the first unit device and the second unit device at least at one position in the contact portion between the first unit device and the second unit device or in the vicinity of the contact portion. An image forming apparatus comprising a measuring unit.   The first unit device is an image carrier device provided with an image carrier, and the second unit device is a developing device that performs an approaching and separating operation with respect to the image carrier device. The image forming apparatus according to claim 1.

Images