JP2005241864A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To intermediate a plurality of image carriers on which toner images of different colors are respectively formed, an intermediate transfer member rotating while being in contact with each image carrier, and a toner image formed on each image carrier A primary transfer device for primary transfer to the transfer member, a secondary transfer device for secondary transfer of the superimposed toner image transferred to the intermediate transfer member to the recording medium, and a contact for contacting or separating the intermediate transfer member from the image carrier. In an image forming apparatus comprising separation drive means and contact / separation detection means for detecting that the intermediate transfer member is in contact with or separated from the image carrier, the contact / separation drive means and contact / separation detection means as a whole Simplify the configuration and reduce its cost.
The contact / separation drive means has a cam that is rotationally driven by a motor 27, and the rotation of the cam causes the intermediate transfer member to contact or separate from the image carrier. The detection member 36 that rotates together with the detection member 36 is detected, and the rotation position of the detection member 36 detects that the intermediate transfer member is in contact with or separated from the image carrier.
[Selection] Figure 4

Description

  The present invention forms a toner image of a different color on each of a plurality of image carriers, transfers each of the toner images to an intermediate transfer member by a primary transfer device, and transfers the superimposed toner image to a secondary transfer device The present invention relates to an image forming apparatus that obtains a recorded image by transferring to a recording medium.

  An image forming apparatus of the above type configured as an electronic copying machine, a printer, a facsimile machine, or a multifunction machine having at least two of these functions has been conventionally known (for example, see Patent Document 1). Further, in this type of image forming apparatus, contact / separation driving means for bringing the intermediate transfer member into contact with and separating from the image carrier and detection of whether the intermediate transfer member is in contact with or separated from the image carrier are detected. Providing contact / separation detection means is also well known. However, in the conventional image forming apparatus, since the contact / separation drive means and the contact / separation detection means are provided completely separately, the entire structure of these means is increased in size and the cost thereof is unavoidable. It was.

  In addition, a contact / separation drive unit that makes the secondary transfer device contact and separate from the intermediate transfer member and a contact / separation detection unit that detects that the secondary transfer device is in contact with or separated from the intermediate transfer member are provided. Image forming apparatuses are also conventionally known. However, in this case as well, in the conventional image forming apparatus of this type, the contact / separation drive means and the contact / separation detection means are provided completely separately, which increases the overall structure of these means, and its cost. Could not escape the rising drawbacks.

JP 2001-134111 A

  An object of the present invention is to provide an image forming apparatus of the type described at the beginning, which eliminates the above-mentioned conventional drawbacks.

  In order to achieve the above object, the present invention provides a plurality of image carriers on which toner images of different colors are respectively formed, an intermediate transfer member that rotates while contacting each image carrier, and an image on each image carrier. A primary transfer device that primarily transfers the toner image formed on the intermediate transfer member, a secondary transfer device that secondarily transfers the superimposed toner image transferred to the intermediate transfer member to a recording medium, and the intermediate transfer member. Image formation comprising contact / separation driving means for making contact with or separating from the image carrier and contact / separation detection means for detecting that the intermediate transfer member is in contact with or separated from the image carrier. In the apparatus, the contact / separation driving unit includes a motor and a cam that is rotationally driven by the motor, and the rotation of the cam causes the intermediate transfer member to contact or separate from the image carrier. The contact / separation detecting means is shared with the cam. An image forming apparatus having a rotating detection member and detecting that the intermediate transfer member is in contact with or separated from the image carrier by a rotation position of the detection member is proposed. (Claim 1).

  In the image forming apparatus according to claim 1, the contact / separation driving unit contacts or separates the intermediate transfer body from an image carrier other than the specific image carrier, and the contact / separation detection unit includes: It can be configured to detect that the intermediate transfer member is in contact with or separated from an image carrier other than the specific image carrier.

  In order to achieve the above object, the present invention provides a plurality of image carriers on which toner images of different colors are formed, an intermediate transfer member that rotates while contacting each image carrier, and each image carrier. A primary transfer device that primarily transfers a toner image formed on the body to the intermediate transfer member; a secondary transfer device that secondarily transfers the superimposed toner image transferred to the intermediate transfer member to a recording medium; and the secondary transfer device. Contact / separation driving means for bringing the transfer device into contact with or separating from the intermediate transfer member, and contact / separation detecting means for detecting that the secondary transfer device is in contact with or separated from the intermediate transfer member. In the image forming apparatus, the contact / separation driving unit includes a motor and a cam that is rotationally driven by the motor, and the secondary transfer device is brought into contact with or separated from the intermediate transfer member by the rotation of the cam. The contact / separation detecting means An image forming apparatus comprising: a detection member that rotates together with a cam; and detecting that the secondary transfer device is in contact with or separated from the image carrier according to a rotation position of the detection member. (Claim 3).

  In the image forming apparatus according to any one of claims 1 to 3, it is advantageous that the intermediate transfer member is made of a polyimide or polyamide-imide endless belt (claim 4).

  Further, in the image forming apparatus according to any one of claims 1 to 4, it is advantageous that the toner attached to the surface of the secondary transfer device is electrostatically returned to the intermediate transfer member. (Claim 5).

  Further, in the image forming apparatus according to any one of claims 1 to 5, it is advantageous that the secondary transfer device comprises a transfer roller (claim 6).

  Further, in the image forming apparatus according to claim 6, it is advantageous that the transfer roller is configured to rotate following the rotation of the intermediate transfer member (claim 7).

  The image forming apparatus according to claim 7, wherein the intermediate transfer member includes an endless belt that is wound around a plurality of support rollers and rotates, and the transfer roller is interposed via an intermediate transfer member including an endless belt. It is advantageous that the supporting roller in contact is a driving roller for driving the endless belt.

  According to the present invention, it is possible to achieve downsizing of the entire structure of the contact / separation driving means and the contact / separation detection means and reduction of the cost.

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

  FIG. 1 is a schematic cross-sectional view showing an example of an image forming apparatus. The image forming apparatus shown here has a plurality of image carriers 2Y, 2C, 2M, and 2BK made up of drum-shaped photoconductors in a main body 1 thereof. An intermediate transfer member 3 made of an endless belt wound around the support rollers 4, 5, 6 is disposed. Here, four image carriers 2Y to 2BK are provided, and each image carrier 2Y to 2BK is rotationally driven in the clockwise direction in FIG. The body 3 is also rotationally driven in the direction of arrow A.

  The configuration in which a toner image is formed on each image carrier 2Y, 2C, 2M, 2BK and the toner image is transferred to the intermediate transfer member 3 is substantially the same except that the color of the toner image is different. Therefore, only a configuration in which a toner image is formed on one of the image carriers 2Y and the toner image is transferred to the intermediate transfer member 3 will be described. When the image carrier 2Y is rotationally driven in the clockwise direction in FIG. 1, the image carrier 2Y is charged to a predetermined polarity by a charging device including a charging roller 7 to which a charging voltage is applied. The charged image carrier 2Y is irradiated with a light-modulated laser beam L emitted from the optical writing device 8, thereby forming an electrostatic latent image on the image carrier 2Y. This electrostatic latent image is visualized as a yellow toner image by the developing device 9.

  A primary transfer device 10 composed of a transfer roller is arranged on the opposite side of the intermediate transfer member 3 from the image carrier 2Y, and a transfer voltage is applied to the primary transfer device 10 to form the image on the image carrier 2Y. The toner image is primarily transferred onto the intermediate transfer member 3 that rotates in the direction of arrow A. The transfer residual toner adhering to the image carrier 2Y after the toner image transfer is removed by the cleaning device 11.

  In the same manner as described above, a cyan toner image, a magenta toner image, and a black toner image are respectively formed on the image carriers 2C, 2M, and 2BK shown in FIG. 1, and these toner images are transferred to the yellow toner image. The toner images are sequentially transferred onto the intermediate transfer body 3 by the action of each primary transfer device, and a superimposed toner image is formed on the intermediate transfer body 3. The transfer residual toner on each of the image carriers 2C, 2M, 2BK after the toner image transfer is removed by the cleaning device is the same as in the case of the first image carrier 2Y.

  On the other hand, a paper feed cassette 12 containing a recording medium P made of, for example, transfer paper or a resin sheet and a paper feed device 14 having a paper feed roller 13 are arranged at the lower part in the image forming apparatus main body 1. The uppermost recording medium P is sent out in the direction of arrow B by the rotation of the roller 13. The sent recording medium is transferred between a portion of the intermediate transfer body 3 wound around the support roller 4 at a predetermined timing by the registration roller pair 15 and a secondary transfer device 16 composed of a transfer roller placed on the support roller 4. To be sent to. At this time, a predetermined transfer voltage is applied to the secondary transfer device 16, whereby the superimposed toner image on the intermediate transfer body 3 is transferred to the recording medium P.

  The recording medium P to which the superimposed toner image has been transferred is further conveyed upward and passes between the fixing roller 18 and the pressure roller 19 of the fixing device 17. At this time, the toner image on the recording medium is subjected to the action of heat and pressure. It is fixed by. The recording medium that has passed through the fixing device 17 is discharged by the paper discharge roller pair 20 to the paper discharge unit 21 at the top of the image forming apparatus main body 1. Further, the transfer residual toner adhering to the intermediate transfer body 3 after the toner image transfer is removed by the cleaning device 22. In this way, a recording medium on which a full color image is formed can be obtained.

  As described above, the image forming apparatus of this example includes a plurality of image carriers 2Y to 2BK on which toner images of different colors are formed, and an intermediate transfer member 3 that rotates while contacting each image carrier. A primary transfer device 10 that primarily transfers a toner image formed on each image carrier to the intermediate transfer body 3, and a secondary transfer that secondary-transfers the superimposed toner image transferred to the intermediate transfer body 3 to the recording medium P. Device 16.

  By the way, the above-described intermediate transfer member 3 is normally in contact with the image carriers 2Y to 2BK. However, the intermediate transfer member 3 can be separated from the image carriers 2Y to 2BK as necessary. . For example, when the image carriers 2Y to 2BK are configured such that they can be set by pulling out or pushing in the front direction perpendicular to the paper surface of FIG. 1, the intermediate transfer body 3 is imaged prior to the attachment / detachment operation. It can be separated from the supports 2Y to 2BK. Thereby, when the image carriers 2Y to 2BK are attached / detached, it is possible to prevent the image carrier from sliding on the intermediate transfer member 3 and scratching the surfaces thereof. Hereinafter, a specific example of the configuration related to the contact and separation of the intermediate transfer body 3 with respect to the image carriers 2Y to 2BK will be clarified.

  As schematically shown in FIGS. 2A and 2B, the support rollers 4, 5 and 6 around which the intermediate transfer member 3 is wound are freely rotatable at the end portions in the longitudinal direction on the front and rear side plates 23, respectively. These side plates 23 are supported by the image forming apparatus main body via a support shaft 24 so as to be swingable in the directions of arrows C and D. In addition, the image forming apparatus of this example brings the intermediate transfer member 3 into contact with the image carriers 2Y to 2BK as shown in FIG. 2A, or as shown in FIG. It has contact / separation driving means for separating the intermediate transfer member 3 from the image carriers 2Y to 2BK, and the intermediate transfer member 3 is in contact with or separated from the image carriers 2Y to 2BK. Contact / separation detecting means for detecting

  FIG. 3 is an external perspective view of the contact / separation drive means 25. The contact / separation drive means 25 shown here includes a case body 26A and a case 26 having a cover 26B detachably fixed to the case body 26A. It comprises. FIG. 4 is a view showing the inside of the case 26 with the cover 26B removed. As can be seen from this figure, a motor 27 is fixed to the case body 26A. The output gear 28 of the motor 27 meshes with the first intermediate gear 29, and the second intermediate gear 30 fixed concentrically with the first intermediate gear 29 meshes with the third intermediate gear 31. A fourth intermediate gear 32 fixed concentrically to the third intermediate gear 31 meshes with the fifth intermediate gear 33. The first and second intermediate gears 29 and 30 and the third and fourth intermediate gears 31 and 32 are rotatably supported by the case 26, respectively, and the fifth intermediate gear 33 is rotatable by the case 26. It is fixed to a supported shaft 34. As shown in FIG. 3, the shaft 34 extends to the outside of the case 26, and a cam 35 is fixed to the tip thereof.

  When the motor 27 shown in FIG. 4 operates and the output gear 28 rotates, the rotation of the gear 28 is transmitted to the shaft 34 via the first to fifth intermediate gears 29 to 33, and the shaft 34 The center axis is rotated in the direction of arrow E, whereby the cam 35 is rotated in the direction indicated by arrow E in FIG. As shown in FIGS. 2A and 2B, the lower edge portion of the side plate 23 is placed on the cam 35. Accordingly, when the cam 35 rotates as described above, the side plate 23 swings around the support shaft 24 in the directions of the arrows C and D, and the intermediate transfer member 3 is separated from the image carriers 2Y to 2BK or is in contact therewith. To do.

  That is, as shown in FIG. 2A, when the side plate 23 is placed on the small diameter portion 35A of the cam 35, the side plate 23 occupies the lowest position. At this time, the intermediate transfer member 3 comes into contact with the peripheral surfaces of the image carriers 2Y to 2BK, and in this state, the image forming operation is performed as described above.

  On the other hand, when the intermediate transfer member 3 is separated from the image carriers 2Y to 2BK, the cam 27 is rotated by 180 ° in the direction of arrow E by operating the motor 27. Thereby, as shown in FIG. 2B, the large-diameter portion 35B of the cam 35 raises the side plate 23 in the arrow C direction. As a result, the intermediate transfer member 3 is separated from the image carriers 2Y to 2BK. When the cam 35 is further rotated 180 ° in the direction of arrow E, the cam 35 occupies the rotational position shown in FIG. 2A, whereby the surface of the intermediate transfer member 3 is brought into contact with the peripheral surfaces of the image carriers 2Y to 2BK. Contact.

  As described above, the contact / separation driving means 25 of this example includes the motor 27 and the cam 35 that is rotationally driven by the motor 27. The rotation of the cam 35 causes the intermediate transfer member 3 to move to the image carrier 2Y. Thru | or 2BK, it is comprised so that it may space apart.

  On the other hand, as shown in FIG. 4, the contact / separation detecting means for detecting that the intermediate transfer body 3 is in contact with or separated from the image carriers 2Y to 2BK is a detection member made of a disk-shaped conductor. The detection member 36 is fixed to the shaft 34 so as to rotate together with the cam 35. Moreover, a cutout 39 is formed in the detection member 36. Further, the base end portions of the first to third contacts 37A, 37B, and 37C shown in FIG. 3 are fixed to the cover 26B shown in FIG. 3, and the first and third contacts as shown in FIG. The contacts 37A and 37C are connected to the CPU 38.

As shown in FIG. 2A, when the small diameter portion 35A of the cam 35 hits the lower edge of the side plate 23 and the intermediate transfer body 3 is in contact with the image carriers 2Y to 2BK, as shown in FIG. The first contact 37A is located at the notch 39, and the second and third contacts 37B and 37C are in contact with the detection member 36 made of a conductor. In this case, the X portion is applied a voltage of, for example 5V, by which, via the detection member 36, the second contact 37B current flows to the third contact 37C, the first signal _{S 1} to the CPU38 Entered. On the other hand, since the first contact 37A is located in the notch 39 of the detection member 36, no current flows to the first contact 37A, and therefore a signal is input from the first contact 37A to the CPU 38. There is nothing. As a result, it is detected that the intermediate transfer member 3 is in contact with the image carriers 2Y to 2BK.

On the other hand, when the motor 27 shown in FIG. 4 operates and the cam 35 starts to rotate, the detection member 36 fixed to the cam 35 via the shaft 34 also starts to rotate in the same arrow E direction as the cam 35. . When the detection member 36 occupies the position shown in FIG. 6, the first to third contacts 37A, 37B, and 37C all come into contact with the detection member 36. At this time, since a voltage is applied to the X portion, a current flows from the second contact 37B to the first and third contacts 37A and 37C, and the CPU 38 receives the first and second signals S ₁ and S ₁ . ₂ is input.

Next, when the detection member 36 rotates 180 ° together with the cam 35 and the intermediate transfer body 3 moves away from the image carriers 2Y to 2BK as shown in FIG. 2B, the detection member 36 is shown in FIG. The notch 39 coincides with the third contact 37C. At this time, the first contact 37 </ b> A remains in contact with the detection member 36. Therefore, the current from the second contact 37B to the first contact 37A flows, the second signal _S only ₂ are input to the CPU 38. It is not that the first signal _{S 1} is input to the CPU 38. Thereby, it is detected that the intermediate transfer body 3 is separated from the image carriers 2Y to 2BK, and the rotation of the motor 27 is thereby stopped.

When the motor 27 starts operating again and the detection member 36 rotates together with the cam 35 by 180 ° in the direction of arrow E, the first contact 37A is brought into the notch 39 of the detection member 36 as shown in FIG. matched, third contact 37C is kept in contact with the sensing member 36, only the first signal _{S 1} is input to the CPU 38. As a result, as shown in FIG. 2A, it is detected that the intermediate transfer body 3 has come into contact with the image carriers 2Y to 2BK, whereby the rotation of the motor 27 is stopped.

  As described above, whether the intermediate transfer body 3 is in contact with or separated from the image carriers 2Y to 2BK is detected based on the rotational position of the detection member 36. Since the detection member 36 is configured to rotate together with the cam 35, the detection member 36 can be incorporated into the contact / separation drive means 25 as shown in FIG. 4. The contact / separation drive means 25 and the contact / separation detection means are integrated to simplify the overall configuration and reduce the overall cost.

  The image forming operation described above with reference to FIG. 1 is a color mode for forming a full-color image on the recording medium P. In addition to this color mode, a specific single-color image is formed on the recording medium. The monochrome mode can be selected. For example, a black monochrome image is formed on the recording medium P in the monochrome mode. In this case, in the monochrome mode, as shown in FIG. 8, the intermediate transfer member 3 is separated from the image carriers 2Y, 2C, 2M on which the chromatic toner images are formed, and the image carrier on which the black toner images are formed. Abuts only on 2BK. A black toner image is formed on the image carrier 2BK in the same manner as described above, and this toner image is transferred to the surface of the intermediate transfer member 3 that is rotationally driven in the direction of arrow A by the primary transfer device. Subsequently, the black toner image is fed from the paper feeding device 14 and transferred onto the recording medium P fed by the registration roller pair 15 at a predetermined timing by the action of the secondary transfer device 16. This recording medium also passes through the fixing device 17. At this time, the black toner image on the recording medium P is fixed, and then the recording medium P is discharged to the paper discharge unit 21. In the monochrome mode, the intermediate transfer member 3 is not in contact with the image carriers 2Y, 2C, and 2M, so that the life of the image carrier can be extended.

  When such a configuration is adopted, as shown in FIGS. 9A and 9B, the first side plate 23A on which the support roller 5 is rotatably supported and the support rollers 4 and 6 are rotatable. The second side plate 23B is supported, the second side plate 23B is fixed to the image forming apparatus main body, and the first side plate 23A is attached to the second side plate 23B via pins 40 with arrows C and D. Connect to swing in the direction. Then, as shown in FIGS. 9A and 9B, the first side plate 23A is supported by the cam 35 of the contact / separation drive means configured similarly to the contact / separation drive means shown in FIGS. Then, the rotation of the cam 35 brings the intermediate transfer body 3 into contact with the image carriers 2Y to 2BK as shown in FIG. 9A, or the intermediate transfer body 3 as shown in FIG. 9B. Is separated from the image carriers 2Y to 2BK. Also in this case, the contact / separation detecting means is configured in the same manner as shown in FIGS. 3 to 7, and detects that the intermediate transfer member 3 is in contact with or separated from the image carriers 2Y to 2BK.

  As described above, the contact / separation driving unit in this example is configured so that the image carrier (color toner image in the example in the figure) other than the specific image carrier (image carrier 2BK on which the black toner image is formed in the example in the figure). The intermediate transfer member 3 is brought into contact with or separated from the image carrier 2Y, 2C, 2M) to be formed, and the contact / separation detecting means is connected to the image carriers 2Y, 2C, 2M other than the specific image carrier 2BK. The intermediate transfer body 3 is configured to detect contact or separation.

  Further, if the position of the toner image of each color transferred to the intermediate transfer body 3 is shifted, color shift occurs in the completed image, and the image quality is deteriorated. Therefore, in the image forming apparatus shown in FIG. 1, a sensor 41 is disposed so as to face the intermediate transfer body 3, and the pattern toner images formed on the image carriers 2 </ b> Y to 2 </ b> BK are primarily transferred to the intermediate transfer body 3. Each pattern toner image is detected by the sensor 41, and the phase of each image carrier 2Y to 2BK is adjusted based on the detection result, so that no color shift occurs in the final image. The photosensor 41 can also be used to detect the image density of the toner image and adjust the image forming conditions based on the detection result.

  In order to enable the sensor 41 to detect the pattern toner image transferred onto the intermediate transfer member 3 as described above, the secondary transfer device 16 is separated from the intermediate transfer member 3 as indicated by an arrow F in FIG. It is necessary to prevent the pattern toner image from being disturbed by the secondary transfer device 16. That is, contact / separation driving means for bringing the secondary transfer device 16 into contact with or separating from the intermediate transfer member 3 and contact for detecting that the secondary transfer device 16 is in contact with or separated from the intermediate transfer member 3. Although it is necessary to provide the separation detection means, the contact / separation driving means and the contact / separation detection means can also be configured in the same manner as the respective means described above with reference to FIGS. That is, also in this case, the contact / separation driving means has a motor 27 and a cam 35 that is rotationally driven by the motor 27, and the secondary transfer device 16 is moved relative to the intermediate transfer body 3 by the rotation of the cam 35. The contact / separation detection means includes a detection member 36 that rotates together with the cam 35, and the secondary transfer device 16 contacts or separates from the intermediate transfer body 3 depending on the rotational position of the detection member 36. It is configured to detect that it is.

  Also, a contact / separation drive means for contacting / separating the intermediate transfer body 3 to / from the image carrier and a contact / separation detection means thereof, a contact / separation drive means for contacting / separating the secondary transfer device 16 to / from the intermediate transfer body 3, When both the contact / separation detection means are provided, it is preferable to use the contact / separation drive means and the contact / separation detection means having exactly the same configuration. Thus, the cost of the image forming apparatus can be reduced by using a common apparatus.

  The intermediate transfer member 3 of the image forming apparatus shown in FIGS. 1 and 8 is composed of an endless belt. In this case, if a polyimide or polyamideimide endless belt is used, the durability can be improved.

  In addition, it is inevitable that toner adheres to the secondary transfer device 16 shown in FIGS. 1 and 8, and if this is left as it is, the possibility that the toner attached to the secondary transfer device 16 may contaminate the recording medium P is avoided. Absent. Therefore, for example, at appropriate times such as after the image forming operation is completed, positive and negative biases are applied to the secondary transfer device 16 to electrostatically transfer the toner adhering to the surface of the secondary transfer device 16 to the intermediate transfer member. It is preferable to make it return to the surface of 3. Thereby, it is possible to prevent a problem that the recording medium P is stained with toner. In addition, since there is no need for a cleaning member such as a blade that contacts the secondary transfer device, an increase in the cost of the image forming apparatus can be suppressed. The toner returned onto the intermediate transfer member 3 is removed by the cleaning device 22.

  In the image forming apparatus of this example, since the secondary transfer device 16 includes a transfer roller, the transfer device 16 can be downsized and its cost can be kept low. Further, when the transfer roller is configured to rotate following the rotation of the intermediate transfer member 3, a transfer roller driving gear or the like is not required, and the intermediate transfer member 3 and the transfer roller are rotated at a constant speed. And generation of banding images can be prevented.

  In the image forming apparatus of this example, the intermediate transfer body 3 is composed of an endless belt that is wound around a plurality of support rollers 4, 5, and 6, but the secondary transfer device 16 that is composed of a transfer roller is endless. When the support roller 4 that is in contact with the intermediate transfer member 3 made of a belt is a drive roller that drives the endless belt, color misregistration and generation of banding images can be more effectively prevented.

It is a schematic sectional drawing which shows an example of an image forming apparatus. FIG. 3 is an explanatory diagram illustrating a configuration in which an intermediate transfer member is brought into contact with and separated from an image carrier. It is an external appearance perspective view of an approach / separation drive means. It is a figure which shows the structure inside a contact / separation drive means. FIG. 6 is a diagram for explaining whether an intermediate transfer body is in contact with or separated from an image carrier by a detection member and first to third contacts. FIG. 6 is a diagram for explaining whether an intermediate transfer body is in contact with or separated from an image carrier by a detection member and first to third contacts. FIG. 6 is a diagram for explaining whether an intermediate transfer body is in contact with or separated from an image carrier by a detection member and first to third contacts. FIG. 3 is a diagram showing a state where an intermediate transfer member is separated from an image carrier for color. FIG. 3 is an explanatory diagram showing a configuration for bringing an intermediate transfer member into and out of contact with a color image carrier.

Explanation of symbols

2Y, 2C, 2M, 2BK Image carrier 3 Intermediate transfer body 4, 5, 6 Support roller 10 Primary transfer device 16 Secondary transfer device 25 Contact / separation drive means 27 Motor 35 Cam 36 Detection member

Claims (8)

A plurality of image carriers on which toner images of different colors are respectively formed, an intermediate transfer member that rotates while being in contact with each image carrier, and a toner image formed on each image carrier is transferred to the intermediate transfer member. A primary transfer device for primary transfer, a secondary transfer device for secondary transfer of the superimposed toner image transferred to the intermediate transfer member to a recording medium, and the intermediate transfer member in contact with or separated from the image carrier. In an image forming apparatus comprising contact / separation drive means and contact / separation detection means for detecting that the intermediate transfer member is in contact with or separated from the image carrier,
The contact / separation drive means includes a motor and a cam that is rotationally driven by the motor, and the rotation of the cam causes the intermediate transfer member to contact or separate from the image carrier, thereby detecting contact / separation. The means includes a detection member that rotates together with the cam, and detects that the intermediate transfer member is in contact with or separated from the image carrier depending on a rotation position of the detection member. Image forming apparatus. The contact / separation driving unit contacts or separates the intermediate transfer body from an image carrier other than the specific image carrier, and the contact / separation detection unit is configured to contact the image carrier other than the specific image carrier. The image forming apparatus according to claim 1, wherein it is detected that the intermediate transfer body is in contact with or separated from the intermediate transfer body. A plurality of image carriers on which toner images of different colors are respectively formed, an intermediate transfer member that rotates while being in contact with each image carrier, and a toner image formed on each image carrier is transferred to the intermediate transfer member. A primary transfer device for primary transfer, a secondary transfer device for secondary transfer of the superimposed toner image transferred to the intermediate transfer member to a recording medium, and the secondary transfer device in contact with or away from the intermediate transfer member. In an image forming apparatus comprising contact / separation drive means and contact / separation detection means for detecting that the secondary transfer device is in contact with or separated from the intermediate transfer member,
The contact / separation driving means includes a motor and a cam that is rotationally driven by the motor, and the rotation of the cam causes the secondary transfer device to contact or separate from the intermediate transfer body, thereby detecting the contact / separation. The means includes a detection member that rotates together with the cam, and detects that the secondary transfer device is in contact with or separated from the intermediate transfer body according to a rotation position of the detection member. Image forming apparatus. The image forming apparatus according to claim 1, wherein the intermediate transfer member is formed of a polyimide or polyamideimide endless belt. The image forming apparatus according to claim 1, wherein the toner attached to the surface of the secondary transfer device is electrostatically returned to the intermediate transfer member. The image forming apparatus according to claim 1, wherein the secondary transfer device includes a transfer roller. The image forming apparatus according to claim 6, wherein the transfer roller rotates following the rotation of the intermediate transfer member. The intermediate transfer member is composed of an endless belt that is wound around a plurality of support rollers and rotates, and the support roller with which the transfer roller contacts via the intermediate transfer member composed of an endless belt is a drive roller that drives the endless belt. The image forming apparatus according to claim 7.

Images