JP2012047810A - Transfer mechanism and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect variations in the quantity of toner per unit area of a toner image transferred by a transfer roll in a shaft direction of the transfer roll when suppressing the variations.SOLUTION: In order to apply an electric voltage between a primary transfer roll 110 and a photoreceptor drum 4, electric current supplied from a power source is controlled to be changed to first electric current or second electric current whose quantity is smaller than that of the first electric current. When the electric current supplied from the power source is the second electric current, a quantity of toner per unit area of a toner image transferred to an intermediate transfer belt 10 is detected. According to the detected quantity of toner, adjustment means 120 causes a position of a shaft of the primary transfer roll 110 to be adjusted to control a pressing force by which the primary transfer roll 110 presses the intermediate transfer belt 10 to the photoreceptor drum 4.

Description

  The present invention relates to a transfer mechanism and an image forming apparatus.

  In Patent Document 1, the change rate of primary transfer bias applied to an image carrier is measured while measuring the potential change data of the image carrier, and the transfer rate derived from the measured potential change data is higher than a reference value. A technique for determining the temporary transfer bias value as a voltage target of the image carrier is disclosed. Patent Document 2 discloses a technique for optimizing the amount of toner on a transfer material by varying the amount of toner on the transfer material, detecting a difference in abnormal flying phenomenon of the toner by an image reading unit. Patent Document 3 discloses a technique for adjusting a transfer bias current to be supplied to a transfer roll in accordance with temperature and humidity in order to prevent a transfer failure caused by a change in resistance value of the transfer roll.

JP 2003-280298 A JP 2004-0778030 A JP 2006-047331 A

  An object of the present invention is to accurately detect a variation in a toner image transferred by a transfer roll when suppressing a variation in toner amount per unit area in the axial direction of the transfer roll.

  In order to solve the above-described problems, a transfer mechanism according to claim 1 of the present invention is a transfer roll that contacts a transfer destination member of a toner image and presses the transfer destination member against the transfer source member of the toner image. A transfer roll that applies a voltage between the roll and the transfer source member to transfer the toner image from the transfer source member to the transfer destination member; and the transfer roll and the transfer source A current for controlling the current supplied from the power source to apply a voltage to the first member to the first current or a second current having a smaller amount than the first current. When the current supplied from the power source is the second current, the supply control means and the current supply control means are transferred to the transfer destination member by supplying the second current. The amount of toner per unit area of the toner image A detecting means for taking out, an adjusting means for adjusting the position of the shaft of the transfer roll, and causing the adjusting means to adjust the position of the shaft of the transfer roll according to the toner amount detected by the detecting means, Control means for controlling the pressing force with which the transfer roll presses the transfer-destination member against the transfer-source member, and the current supply control means has the pressing force with which the transfer roll is controlled by the control means. Then, when the transfer destination member is pressed against the transfer source member, the current supplied from the power source is controlled to be the first current.

  The transfer mechanism according to claim 2 is the transfer mechanism according to claim 1, wherein the detection means is transferred to a plurality of detection positions different in the axial direction of the transfer roll in the transfer destination member. The toner amount per unit area of the toner image is detected, and the control unit reduces the toner amount difference according to the toner amount difference detected by the detection unit at each detection position. The pressing force is controlled.

  The transfer mechanism according to claim 3 is the transfer mechanism according to claim 1 or 2, wherein the control means changes the pressing force into a plurality of magnitudes, and each time the change is made, the detection means Based on the detected change in the toner amount, the pressing force at which the ratio of the change in the toner amount to the change in the pressing force is less than a threshold is specified, and the transfer roll transfers the transfer destination member to the transfer destination The adjustment unit is configured to adjust the position of the shaft of the transfer roll so that the force pressing the original member becomes the specified pressing force.

  According to a fourth aspect of the present invention, in the transfer mechanism according to the third aspect, the control unit is configured such that the ratio of the change in the toner amount with respect to the change in the pressing force is smaller than the threshold value. The pressure is specified, and the position of the shaft of the transfer roll is adjusted by the adjusting means so that the force by which the transfer roll presses the transfer destination member against the transfer source member becomes the specified pressing force. It is characterized by making it.

  Further, in the transfer mechanism according to claim 5, in the transfer mechanism according to any one of 1 to 4, the second current is an amount of current smaller than 50% of the amount of the first current. It is characterized by that.

  The transfer mechanism according to claim 6 is the transfer mechanism according to any one of claims 1 to 4, wherein the second current is supplied from the power source to the transfer destination. The amount of toner per unit area of the toner image transferred to the member is greater than the amount of toner per unit area of the toner image transferred to the transfer destination member when the first current is supplied from the power source. The current is reduced by 20% or more.

  The transfer mechanism according to claim 7 is the transfer mechanism according to any one of 1 to 6, wherein the adjustment unit adjusts the position of one end of the shaft of the transfer roll, and the detection unit includes: The transfer destination member detects the toner amount at a position closer to the one end than the center in the axial direction of the transfer roll, and the control means detects the toner amount detected by the detection means. Accordingly, the adjustment means adjusts the position of one end of the shaft of the transfer roll, and controls the pressing force with which the transfer roll presses the transfer destination member against the transfer source member. And

  The transfer mechanism according to claim 8 is the transfer mechanism according to any one of 1 to 6, wherein the adjusting means adjusts the positions of one end and the other end of the shaft of the transfer roll, respectively. The detecting means is a member of the transfer destination, and is closer to the one end than the center in the axial direction of the transfer roll and closer to the other end than the center in the axial direction of the transfer roll. The control unit detects the toner amount at a position, and the control unit detects the detection position on the one end side detected by the detection unit and the toner amount detected by the detection unit on the other end side. Accordingly, the adjusting means adjusts the positions of one end and the other end of the shaft of the transfer roll so that the transfer roll presses the transfer destination member against the transfer source member. Characterized by controlling That.

  The image forming apparatus according to claim 9 functions as a forming unit that forms a toner image and a primary transfer unit that primarily transfers the toner image formed by the forming unit onto a transfer body. The transfer mechanism according to any one of the above, a secondary transfer unit that secondary-transfers the toner image primary-transferred to the transfer body by the transfer mechanism onto a transfer material, and a secondary transfer unit that is secondary-transferred by the secondary transfer unit. And a fixing unit for fixing the toner image to the transfer material.

  The image forming apparatus according to claim 10 includes: a forming unit that forms a toner image; a primary transfer unit that primarily transfers the toner image formed by the forming unit to a transfer member; and the primary transfer unit that The transfer mechanism according to claim 1, which functions as a secondary transfer unit that secondary-transfers the toner image transferred to the transfer body to a transfer material, and the toner secondarily transferred by the transfer mechanism. Fixing means for fixing the image on the transfer material.

  According to the transfer mechanism of claim 1, the unit area in the axial direction of the transfer roll is compared with a case where a configuration in which a second current having a current amount lower than the first current is supplied to the transfer roll is not employed. It is possible to accurately detect variations in the amount of toner per unit.

  According to the transfer mechanism of claim 2, the unit in the axial direction of the transfer roll is compared with the case where the configuration in which the pressing force by the transfer roll is controlled so as to reduce the difference in the toner amount at the plurality of detection positions is not adopted. The variation in the toner amount per area can be detected with higher accuracy.

  According to the transfer mechanism of the third aspect, the pressing force at which the ratio of the change in the toner amount to the change in the pressing force is smaller than the threshold is specified, and the pressing force by the transfer roll becomes the specified pressing force. Transfer defects can be suppressed as compared to a case where the configuration of controlling the pressing force by the transfer roll is not adopted.

  According to the transfer mechanism of the fourth aspect, the minimum pressing force at which the change rate of the toner amount is less than the threshold value is specified, and the pressing force by the transfer roll is determined to be the specified pressing force. Transfer defects can be suppressed as compared with the case where the configuration of controlling the pressing force is not adopted.

  According to the transfer mechanism of the fifth aspect, the variation in the toner amount is suppressed as compared with the case where the configuration in which the second current is smaller than 50% of the first current is not employed. I can do it.

  According to the transfer mechanism of the sixth aspect, the toner amount detected when the second current is used is less than 20% less than the toner amount detected when the first current is used. As compared with the case where the configuration of defining the current of 2 is not adopted, the variation in the toner amount can be suppressed.

  According to the transfer mechanism of the seventh aspect, the toner amount varies as compared with the case where the configuration in which the toner amount at the detection position on one end side is detected and the position of the one end portion is adjusted is not employed. Can be suppressed with a simpler configuration.

  According to the transfer mechanism of claim 8, the toner amount at each detection position on both the one end side and the other end side is detected, and at least one of the one end and the other end is detected. Compared with the case where the configuration of adjusting the position is not adopted, the pressing force by the transfer roll can be adjusted more finely.

  According to the image forming apparatus of the ninth aspect of the present invention, compared to the case where the configuration in which the second current having a current amount lower than the first current is supplied to the transfer roll is not adopted in the primary transfer unit, the primary transfer is not performed. In this case, the variation in the toner amount per unit area in the axial direction of the transfer roll can be accurately detected.

  According to the image forming apparatus of the tenth aspect, the secondary current is supplied to the transfer roll with a second current having a current amount lower than that of the first current, as compared with the case where the secondary transfer means is not employed. It is possible to accurately detect a variation in toner amount per unit area in the axial direction of the transfer roll during transfer.

1 shows an internal configuration of an image forming apparatus 1. The external appearance of the primary transfer mechanism 100 is shown. The side surface of the primary transfer mechanism 100 is shown. The front of the primary transfer mechanism 100 is shown. The relationship between the pressing force of the primary transfer roll 110 and the toner amount is shown. A change in toner amount accompanying a change in pressing force is shown for each current value. The front of the primary transfer mechanism 100 which concerns on 2nd Embodiment is shown. 6 shows a change in toner amount distribution accompanying a change in pressing force.

(First embodiment)
The first embodiment of the present invention will be described below. First, the internal configuration of the image forming apparatus 1 will be described. FIG. 1 shows an internal configuration of the image forming apparatus 1. The image forming apparatus 1 is provided with four image forming units 2Y, 2M, 2C, and 2K of yellow (Y), magenta (M), cyan (C), and black (K), and the plurality of image forming units. A full-color printer 2 is arranged in parallel along the intermediate transfer belt 10.

  The image forming unit 2 is an example of a forming unit that forms a toner image, and includes a photosensitive drum 4 and a developing device 5. An image exposure device 6 is provided below the image forming unit 2 in the direction of gravity. The image exposure device 6 irradiates the photosensitive drum 4 with a laser beam corresponding to the image data. The laser beam emitted from the image exposure device 6 scans the surface of the photosensitive drum 4 to form an electrostatic latent image on the photosensitive drum 4. The electrostatic latent image formed on the photosensitive drum 4 is developed by the developing device 5 with a developer containing toner of a color corresponding to the image forming unit 2 to become a toner image. The toner image formed on the photosensitive drum 4 is primarily transferred from the photosensitive drum 4 to the intermediate transfer belt 10 by the primary transfer mechanism 100 provided to face the outer peripheral surface of the photosensitive drum 4. The intermediate transfer belt 10 is a belt-like member that is stretched by a plurality of rolls such as a drive roll 12, a tension roll 13, and an idler roll 14. The intermediate transfer belt 10 is driven by a drive roll 12 to move in a predetermined direction (direction A in FIG. 1). The intermediate transfer belt 10 is an example of a transfer member, and the primary transfer mechanism 100 is an example of a primary transfer unit that primarily transfers a toner image to a transfer member.

  The transfer paper 18 (transfer material) is stored in the tray 24 in advance, and is taken out from the tray 24 when printing is performed, and is transported to the secondary transfer position by the transport roll 25 and the resist roll 28. At the secondary transfer position, a secondary transfer roll 17 is provided as an example of secondary transfer means for secondary transfer of the toner image to the transfer material. The secondary transfer roll 17 is pressed by a pressing means such as a spring (not shown) to press the transfer paper 18 against the intermediate transfer belt 10 from the back side of the transfer paper 18. In this state, a secondary transfer bias supplied from a power supply (not shown) is applied between the secondary transfer roll 17 and a roll facing the secondary transfer roll 17, thereby being transferred onto the surface of the intermediate transfer belt 10. The existing toner image is secondarily transferred to the transfer paper 18. Thereafter, the transfer paper 18 is heated and pressed by a fixing device 19 (fixing means) that is an example of a fixing unit that fixes the toner image to the transfer paper 18, and the toner image is fixed. It is discharged outside the main body of the forming apparatus 1. The so-called residual toner remaining on the intermediate transfer belt 10 without being secondarily transferred to the transfer paper 18 is recovered by the toner recovery unit 50.

  Next, the configuration of the primary transfer mechanism 100 will be described. 2 to 4 show the configuration of the primary transfer mechanism 100. Among these, FIG. 2 shows the external appearance of the primary transfer mechanism 100. FIG. 3 shows a side view of the primary transfer mechanism 100. FIG. 4 shows the front of the primary transfer mechanism 100. Here, the “side surface of the primary transfer mechanism 100” indicates the primary transfer mechanism 100 when the axial direction of the primary transfer roll 110 is the direction of the line of sight. The “front surface of the primary transfer mechanism 100” indicates the primary transfer mechanism 100 when the traveling direction of the intermediate transfer belt 10 is the direction of the line of sight. As shown in FIG. 1, the image forming apparatus 1 includes four primary transfer mechanisms 100 corresponding to each of the image forming units 2Y, 2M, 2C, and 2K, all of which have the same configuration as the primary transfer mechanism 100 described below. Have

  The primary transfer mechanism 100 transfers the toner image formed on the photosensitive drum 4 to the intermediate transfer belt 10. That is, in the primary transfer mechanism 100, the photosensitive drum 4 is a transfer source member, and the intermediate transfer belt 10 is a transfer destination member. The primary transfer mechanism 100 includes a primary transfer roll 110, an adjustment unit 120, a detection unit 130, a control unit 140, and a current supply control unit 150.

  The primary transfer roll 110 sandwiches the intermediate transfer belt 10 between the intermediate transfer belt 10 and the photosensitive drum 4 from the back surface (the surface on which the toner image is not transferred). The primary transfer roll 110 is pressed against the photosensitive drum 4 via the intermediate transfer belt 10, and is supplied between a primary transfer roll 110 and the photosensitive drum 4 from a power supply (not shown). When the transfer bias is applied, the toner image formed on the surface of the photosensitive drum 4 is primarily transferred to the intermediate transfer belt 10. The primary transfer roll 110 has a shaft portion 112. Both ends of the shaft portion 112, that is, both the end portion 112A and the end portion 112B are supported in a rotatable state by a bearing portion or the like (not shown).

  The adjusting unit 120 adjusts the pressing force of the primary transfer roll 110 against the photosensitive drum 4 by adjusting the position of the shaft portion 112 of the primary transfer roll 110. In the first embodiment, the adjusting unit 120 adjusts the pressing force of the primary transfer roll 110 by adjusting the position of the end portion 112 </ b> A that is one end portion of the shaft portion 112 of the primary transfer roll 110. That is, the position of the end 112B, which is the other end of the shaft 112 of the primary transfer roll 110, does not change.

  Specifically, it is as follows. As described above, in the primary transfer roll 110, both one end portion 112A and the other end portion 112B of the shaft portion 112 are supported in a rotatable state by the bearing portion or the like. The adjusting unit 120 adjusts the pressing force of the primary transfer roll 110 by adjusting the vertical position of the end 112A. The “up and down direction” here will be described. The direction in which the pressing force of the primary transfer roll 110 is increased (that is, the direction in which the primary transfer roll 110 is brought closer to the photosensitive drum 4) is “upward”, and the pressing force of the primary transfer roll 110 is set. Is a “downward” direction (ie, a direction in which the primary transfer roll 110 is moved away from the photosensitive drum 4).

  The adjusting means 120 includes a pressing spring 122, an elastic member 122, and a cam 126. The pressing spring 122 presses the shaft portion 112 from below to above. The support plate 124 supports the lower end portion of the elastic member 122. The cam 126 is in contact under the support plate 124 and adjusts the vertical position of the support plate 124. In the adjustment means 120 configured as described above, the vertical position of the support plate 124 is adjusted by rotating the cam 126 by driving a motor (not shown). As a result, the pressing force of the pressing spring 122 whose lower end is supported by the support plate 124 is adjusted, and as a result, the pressing force of the primary transfer roll 110 is adjusted.

  In the operation mode of the image forming apparatus, an adjustment mode for adjusting the pressing force of the primary transfer roll 110 against the photosensitive drum 4 and an image corresponding to the image data are formed based on the pressing force adjusted in the adjustment mode. There is a normal mode. In the adjustment mode, an image having a predetermined density (for example, toner coverage per unit area) is formed by the image forming unit 2 and transferred to the intermediate transfer belt 10. The unit area may be an area having any size as a unit, and may be an area having a predetermined size. The detection unit 130 detects the toner amount per unit area of the toner image transferred onto the surface of the intermediate transfer belt 10. The detection unit 130 is, for example, a reflection type or scattering type optical sensor, and detects, for example, a ratio (area coverage) that the toner covers the unit area as the toner amount per unit area of the toner image. The toner constituting the detected toner image is collected by, for example, the toner collecting unit 50. The control unit 140 controls the pressing force of the primary transfer roll 110 by operating the adjustment unit 120 based on the toner amount detected by the detection unit 130. In particular, in the first embodiment, the detection means 130 is provided for each of a plurality of detection positions on the surface of the intermediate transfer belt 10 in the width direction of the intermediate transfer belt 10 (the axial direction of the primary transfer roll 110). The toner amount of the toner image transferred to the detection position is detected. Here, the width direction of the intermediate transfer belt 10 (the axial direction of the primary transfer roll 110) is the main scanning direction in the image exposure apparatus 6.

  Based on the toner amount at each of the plurality of detection positions detected by the detection unit 130, the control unit 140 causes the adjustment unit 120 to have a shaft portion so that the toner amount distribution on the surface of the intermediate transfer belt 10 is uniform. The pressing force of the primary transfer roll 110 is controlled by adjusting the position 112. Specifically, the control unit 140 controls the pressing force of the primary transfer roll 110 so that the toner amounts at the plurality of detection positions are as equal as possible. Note that “equal” refers to a state in which the difference in toner amount per unit area is smaller than an allowable value.

  Specifically, as shown in FIGS. 2 and 4, three detection means 130 (detection means 130 </ b> A, detection means 130 </ b> B, and detection means 130 </ b> C) are formed on the front surface (toner image is formed) of the intermediate transfer belt 10. (Side surface) side by side in the width direction. Among these, the detection unit 130 </ b> B is provided at a detection position P <b> 2 that is a center detection position in the width direction of the intermediate transfer belt 10. The detection unit 130A is provided at a detection position P1, which is a detection position on the end 112A side of the center of the intermediate transfer belt 10 in the width direction. The detection unit 130 </ b> C is provided at a detection position P <b> 3 that is a detection position closer to the end 112 </ b> B than the center in the width direction of the intermediate transfer belt 10. In short, the detection unit 130B detects the toner amount at the detection position P2, the detection unit 130A detects the toner amount at the detection position P1, and the detection unit 130C detects the toner amount at the detection position P3. Yes. Then, the control unit 140 controls the pressing force of the primary transfer roll 110 by operating the adjustment unit 120 so that the toner amounts at these three detection positions are as equal as possible. The control unit 140 is realized by, for example, an IC (Integrated Circuit) configured by a CPU (Central Processing Unit), a memory, and the like.

  Here, a specific example of control by the control means 140 will be shown. FIG. 5 shows the relationship between the pressing force of the primary transfer roll 110 and the toner amount detected at each detection position. The pressing force is represented by linear pressure (gf / cm), and the toner amount is represented by a dimensionless index value that means that the larger the numerical value, the larger the toner amount, and the smaller the numerical value, the smaller the toner amount. In the example illustrated in FIG. 5, when the linear pressure indicating the pressing force of the primary transfer roll 110 is “16 (gf / cm)”, that is, when the toner amount is detected before the linear pressure of the primary transfer roll 110 is adjusted. The toner amount detected at the detection position “P1” by the detection unit 130A is “1.5”. At this time, the toner amount detected at the detection position “P2” by the detection unit 130B is “1.55”. At this time, the toner amount detected at the detection position “P3” by the detection unit 130C is “1.6”.

  As already described, the control unit 140 causes the adjusting unit 120 to adjust the position of the end portion 112 </ b> A that is one end portion of the shaft portion 112 of the primary transfer roll 110. As the pressing force of the primary transfer roll 110 increases, the amount of toner transferred from the photosensitive drum 4 to the intermediate transfer belt 10 increases. Therefore, when the control unit 140 wants to increase the amount of toner transferred to the intermediate transfer belt 10, To increase the pressing force of the transfer roll 110 and conversely to reduce the amount of toner transferred to the intermediate transfer belt 10, the pressing force of the primary transfer roll 110 is decreased. For example, in the example shown in FIG. 5, the toner amount at the detection position “P1” is “1.5”, whereas the toner amount at the detection position “P3” is “1.6”. The adjusting means 120 can adjust only the position of the end 112A from the detection position “P1”. Therefore, the control unit 140 operates the adjustment unit 120 to move the end 112A upward, thereby increasing the linear pressure at the detection position “P1” and setting the toner amount at the detection position “P1” to “1. The adjustment of the position of the shaft portion 112 by the adjusting means 120 is controlled so that the toner amount distribution on the surface of the intermediate transfer belt 10 approaches a uniform state.

  At this time, the control unit 140 determines the amount of increase in the linear pressure of the primary transfer roll 110 (the amount of movement of the end portion 112A) for setting the toner amount at the detection position “P1” to “1.6” by experiment or calculation in advance. If it is known, the increase amount may be stored in advance, and the adjusting unit 120 may be controlled so as to increase the linear pressure of the primary transfer roll 110 by the stored increase amount. On the other hand, when the increase amount of the linear pressure of the primary transfer roll 110 is not known in advance, the control unit 140 increases the linear pressure of the primary transfer roll 110 step by step, and the toner amount detected at the detection position “P1” each time. Until the toner amount at the detection position “P1” reaches “1.6” or falls within a range determined around “1.6” (for example, 1.6 ± 0.05). Further, the adjusting means 120 may be controlled so as to increase the linear pressure of the primary transfer roll 110.

  For example, in FIG. 5, when the linear pressure of the primary transfer roll 110 is “20 (gf / cm)”, the toner amount at the detection position “P1” is changed from “1.5” to “1.6”. It is shown that. When this is known in advance, the control unit 140 may control the adjustment unit 120 so as to increase the linear pressure of the primary transfer roll 110 by “4 (gf / cm)” at a stroke. On the other hand, if this is not known in advance, for example, while increasing the linear pressure of the primary transfer roll 110 by “2 (gf / cm)” step by step, the toner amount detected at the detection position “P1” is increased each time. The adjustment unit 120 may be controlled so as to increase the linear pressure of the primary transfer roll 110 until the toner amount at the detection position “P1” becomes “1.6”.

  Incidentally, as described above, in order to bring the toner amount distribution close to an even state, it is necessary to accurately detect the amount of toner at each detection position. Therefore, the current supply control unit 150 controls the amount of current supplied for voltage application between the primary transfer roll 110 and the photosensitive drum 4 (hereinafter, the primary transfer roll 110, the photosensitive drum 4 and the like). The amount of current supplied to apply a voltage during the period is referred to as “current amount supplied to the primary transfer roll 110”). Specifically, the current supply control unit 150 controls the amount of current supplied to the primary transfer roll 110 so that the first current is supplied to the primary transfer roll 110 during normal use. Further, when adjusting the pressing force of the primary transfer roll 110, the current supply control unit 150 supplies the primary transfer roll 110 with a second current lower than the first current supplied to the primary transfer roll 110. Control the amount of current that is generated. “During normal use” means not actual adjustment of the pressing force of the primary transfer roll 110 but actual image formation (during actual operation). In this way, by making the amount of current when adjusting the pressing force of the primary transfer roll 110 lower than the amount of current during normal use, it is easy to detect variations in the amount of toner.

  Here, the current supply control unit 150 sets the amount of the second current to be smaller than 50% of the amount of the first current so that the second current is supplied to the primary transfer roll 110. Good control. For example, the current supply control unit 150 performs control so that the second current in an amount corresponding to 40% of the current amount of the first current is supplied to the primary transfer roll 110. This is because by making the amount of the second current smaller than 50% of the amount of the first current, the variation in the toner amount can be easily detected. Preferably, the amount of the second current is set to the first amount. This is based on an experimental result that variation in the toner amount at each detection position can be detected more easily by setting 40% of the current amount of 1 current. The current supply control means 150 is realized by an IC (Integrated Circuit) composed of a CPU (Central Processing Unit), a memory, and the like.

  FIG. 6 shows, for each current value, a change in the toner amount per unit area accompanying a change in the pressing force of the primary transfer roll 110. FIG. 6 shows that as the amount of current supplied to the primary transfer roll 110 decreases, the change in the toner amount per unit area accompanying the change in the linear pressure of the primary transfer roll 110 increases. For example, when the linear pressure of the primary transfer roll 110 is changed between “16 to 22 (gf / cm)”, if the current supplied to the primary transfer roll 110 is the first current, the toner amount is “1”. .75 to 1.77 ". On the other hand, if the current supplied to the primary transfer roll 110 is the second current, the toner amount changes within the range of “1.5 to 1.63”. That is, if the current supplied to the primary transfer roll 110 is the first current, the fluctuation amount of the change in the toner amount is “0.02.” As described above, if the fluctuation amount of the change in the toner amount is small, it may be determined that there is no variation in the toner amount due to a detection error of the toner amount. On the other hand, if the current supplied to the primary transfer roll 110 is the second current, the fluctuation amount of the change in the toner amount is “0.13”. Thus, if the fluctuation amount of the change in the toner amount is large, even if a detection error of the toner amount occurs, it is easy to detect the variation in the toner amount.

  As described above, in the adjustment mode, the pressing force of the primary transfer roll 110 against the photosensitive drum 4 is adjusted. In the normal mode, an image corresponding to the image data is formed by the image forming unit 2 under the pressing force adjusted in the adjustment mode, transferred to the intermediate transfer belt 10, and further transferred to a transfer material and fixed. The

(Second Embodiment)
Next, a second embodiment of the present invention will be described. In the second embodiment, the primary transfer roll 110 presses the intermediate transfer belt 10 against the photosensitive drum 4 by adjusting the positions of both the end 112A and the end 112B of the shaft portion 112 of the primary transfer roll 110. An example of adjusting the will be described.

  The front of the primary transfer mechanism 100 which concerns on 2nd Embodiment is shown. The primary transfer mechanism 100 according to the second embodiment is such that the adjusting unit 120 adjusts the positions of both the end 112A and the end 112B of the shaft 112 of the primary transfer roll 110 according to the first embodiment. Different from the mechanism 100. The end portion 112B can move in the vertical direction in the same manner as the end portion 112A. That is, the adjusting means 120 can adjust the vertical positions of both the end portion 112A and the end portion 112B. In response to this, the control unit 140 adjusts the position of one or both of the end 112A and the end 112B by the adjusting unit 120 so that the toner amount distribution on the surface of the intermediate transfer belt 10 approaches an even state. Thus, the adjusting unit 120 is operated to control the pressing force of the primary transfer roll 110.

  For example, when only the position of the end 112A can be adjusted as in the first embodiment, the toner detection amount at the detection position P1 is “1.5”, and the toner detection amount at the detection position P3 is “1.6”. If the position of the end 112A is adjusted so that the toner detection amount at the detection position P1 is “1.6”, the toner detection amount at the detection position P3 is less than “1.6”. It may increase. Even in such a case, in the primary transfer mechanism 100 of the second embodiment, for example, the position of the end 112B is lowered, the toner detection amount at the detection position P3 is returned to “1.6”, and the toner is Keep the quantity distribution even. Further, in the primary transfer mechanism 100 according to the second embodiment, both the position of the end portion 112A and the position of the end portion 112B are moved up and down, so that the primary transfer roll 110 can be pressed while maintaining a uniform toner amount distribution. Increase or decrease the pressure.

  In the first embodiment, the toner amount distribution is brought close to an even state. With this alone, the pressing force by the primary transfer roll 110 is not always appropriate. Even if the toner amount distribution is brought close to an even state, if the pressing force by the primary transfer roll 110 is too high, a part of the toner is not transferred in the line-shaped image area constituting the character (image defect ( This is called character omission). Therefore, in the second embodiment, not only the toner amount distribution is equalized, but also the pressing force by the primary transfer roll 110 is more appropriate for maintaining the image quality. An example of controlling the pressure will be described.

  In the second embodiment, first, the detecting unit 130 controls the toner amount at each detection position for each of the plurality of pressing forces while changing the pressing force of the primary transfer roll 110 a plurality of times by controlling the adjusting unit 120. Detect it. Then, the control unit 140 changes the pressing force of the primary transfer roll 110 based on the toner amount detected by the detecting unit 130 every time the pressing force of the primary transfer roll 110 is changed to a plurality of pressing forces. The pressing force of the primary transfer roll 110 (referred to as an appropriate pressing force) at which the rate of change in the ratio is smaller than the threshold is specified. Then, the control unit 140 controls the pressing force by the primary transfer roll 110 so that the pressing force of the primary transfer roll 110 becomes an appropriate pressing force.

For example, in FIG. 6, the linear pressures of the primary transfer roll 110 are “16 (gf / cm)”, “18 (gf / cm)”, “20 (gf / cm)”, and “22 (gf / cm)”, respectively. The amount of toner detected by the detecting means 130 is shown. Here, in both cases where the first current is supplied to the primary transfer roll 110 and the second current is supplied to the primary transfer roll 110, the linear pressure of the primary transfer roll 110 is set to “20 (gf / It is shown that when changing from “cm” to “22 (gf / cm)”, the toner amount does not change greatly. If the linear pressure of the primary transfer roll 110 is increased to “22 (gf / cm)” or more, the amount of toner will not change, and the resistance during driving of the primary transfer roll 110 will increase. Problems arise. Therefore, in this way, when changing from “20 (gf / cm)” to “22 (gf / cm)”, the ratio of the change in the toner amount to the change in the linear pressure of the primary transfer roll 110 is greater than the threshold value. If it decreases, the control means 140 specifies “20 (gf / cm)” or “22 (gf / cm)” as the appropriate pressing force, and the linear pressure of the primary transfer roll 110 becomes this appropriate pressing force. Thus, the linear pressure by the primary transfer roll 110 is controlled. In particular, if the minimum “20 (gf / cm)” of these “20 (gf / cm)” or “22 (gf / cm)” is set as an appropriate pressing force, the above-described problem hardly occurs.
The above is the contents of the second embodiment, but since the contents other than the above are the same as those of the first embodiment, description thereof will be omitted.

(Modification)
The present invention is not limited to the embodiment described above, and may be modified as follows. Further, the following modifications may be combined.
(Modification 1)
In the first embodiment, the position of the end 112A is adjusted based on the detected amount of toner at each of the center detection position, the detection position closer to the end 112A than the center, and the detection position closer to the end 112B. It was decided. Here, when adjusting the position of one end portion of the shaft portion 112, a detection position is provided only on the one end portion side from the center, and based on the toner amount of the detection position on the one end portion side. The position of one end portion of the shaft portion 112 may be adjusted. For example, when the position of the end 112A is adjusted as in the first embodiment, the detection position is provided only on the end 112A side from the center, and the control unit 140 sets the toner at the detection position on the end 112A side. For example, the position of the end 112A is adjusted based on the amount.

  FIG. 8 shows a change in toner amount distribution accompanying a change in pressing force on the end 112A side. In the graph shown in FIG. 8, the vertical axis represents the toner amount. On the other hand, in the graph shown in FIG. 8, the horizontal axis indicates the position on the surface of the intermediate transfer belt 10 in the width direction, “0” indicates the position on the end 112A side, and “300” indicates the end 112B side. Indicates the position. As shown in FIG. 8, when the pressing force on the end 112A side is changed, the toner amount on the end 112A side changes greatly, but the toner amount on the end 112B side does not change greatly. This is because when the pressing force on the end 112A side is adjusted by adjusting the position of the end 112A based on the toner amount detected on the end 112A side, the pressing on the end 112B side is performed at the same time. This means that the pressure is adjusted moderately, and as a result, the pressing force of the entire primary transfer roll 110 is adjusted appropriately and efficiently.

  Therefore, for example, in the first embodiment, even when the configuration is such that only the toner amount on the end 112A side is detected and the position of the end 112A is adjusted based on this, the entire primary transfer roll 110 is pressed. The pressure is adjusted. In addition, the configuration of the adjustment unit 120 and the detection unit 130, the control logic of the control unit 140, and the like are simpler than configurations other than this configuration, and an increase in cost can be suppressed.

  In the second embodiment in which the positions of both the end 112A and the end 112B are adjusted, only the toner amount on one end side is detected, and the position of one end is adjusted based on the detected toner amount. However, the pressing force of the entire primary transfer roll 110 is adjusted. Also in this case, the control logic of the control means 140 is simpler than the configuration other than this configuration, and the increase in cost can be suppressed. In the above case, only the pressing force on one end side may be adjusted, the pressing force on one end side is adjusted preferentially, and the pressing force on the other end side is adjusted auxiliary. You may make it do.

(Modification 2)
In the first and second embodiments, in order to easily detect the variation in the toner amount, a current value smaller than 50% of the first current may be set as the second current. Although it is preferable that the current value of 40% be the second current, the present invention is not limited to this. The second current may be any value as long as it is lower than the first current.

(Modification 3)
In the first and second embodiments, the current value when the toner amount when the current value is changed from the first current becomes smaller than the threshold may be set as the second current. For example, the control unit 140 detects the toner amount each time the current value of the current supplied to the primary transfer roll 110 is decreased from the first current, and the current value when the toner amount becomes 20% lower is set to the second current value. The current is good. This is because the current value at which the toner amount is 20% or less smaller than that at the first current is used as the second current, so that the fluctuation in the toner amount when the pressing force of the primary transfer roll 110 is changed is changed. This is based on the experimental result that the width is increased and the variation in the toner amount is easily detected. For example, in the example of FIG. 6, when the current value when the linear pressure of the primary transfer roll 110 is “16 (gf / cm)” is changed from the first current to the second current of 40%, It is shown that the toner amount changes from “1.75” to “1.5”, which indicates that the toner amount is reduced by about 20%. As a result, as shown in FIG. 6, the fluctuation amount of the change in the toner amount due to the change in the pressing force of the primary transfer roll 110 is increased, and the uneven distribution of the toner amount is easily detected. That is, by setting the current value at which the toner amount is 20% or more smaller than that at the first current as the second current, the fluctuation amount of the change in the toner amount when the pressing force of the primary transfer roll 110 is changed. Becomes larger and it becomes easier to detect unevenness in the toner amount distribution.

(Modification 4)
In each embodiment, the functions of the control unit 140 and the current supply control unit 150 are realized by an IC. However, the present invention is not limited to this, for example, without providing an IC for the control unit 140 and an IC for the current supply control unit 150, the main control unit already installed in the image forming apparatus 1 can be used as the control unit 140 and the current supply control unit 150. You may comprise so that this function may be implement | achieved. In short, as long as the functions of the control unit 140 and the current supply control unit 150 are realized, the operation subject may be any hardware or software.

(Modification 5)
In each embodiment, an intermediate transfer belt is used as an example of a transfer destination member. However, the transfer destination member may be a member other than the intermediate transfer belt, such as an intermediate transfer roll.

(Modification 6)
In each embodiment, the example in which the transfer mechanism of the present invention is employed as the primary transfer unit has been described. However, the present invention is not limited thereto, and may be employed as the secondary transfer unit. In this case, the transfer roll is a secondary transfer roll. The transfer source member is an intermediate transfer body transfer member such as an intermediate transfer belt or an intermediate transfer roll. The transfer destination member is a transfer material such as transfer paper.

(Modification 7)
In each embodiment, it has been described that the detection unit 130 is, for example, a reflection type or a scattering type photosensor. The detection unit 130 is not limited to this, and any detection unit 130 may be used as long as it detects the toner amount of the toner image transferred onto the surface of the intermediate transfer belt 10.

(Modification 8)
In each embodiment, the adjustment unit 120 automatically adjusts the position of the shaft portion 112 under the control of the control unit 140. Not limited to this, the user may adjust the position of the shaft portion 112 by the adjusting means 120. In this case, the primary transfer mechanism 100 has information necessary for adjusting the position of the shaft portion 112, such as the distribution state of the toner amount, whether or not the unevenness of the toner amount distribution has been eliminated, and the amount of adjustment of the position of the shaft portion 112. It is good to provide the notification means to notify a user.

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 4 ... Photosensitive drum, 10 ... Intermediate transfer belt, 100 ... Primary transfer mechanism, 110 ... Primary transfer roll, 112 ... Shaft part, 114 ... Support part, 120 ... Adjustment means, 122 ... Bearing part, 130: detecting means, 140: control means, 150: current supply control means

Claims (10)

A transfer roll that is in contact with a transfer destination member of a toner image and presses the transfer destination member against the transfer source member of the toner image, and a voltage is applied between the own roll and the transfer source member. A transfer roll for transferring the toner image from the transfer source member to the transfer destination member;
A current supplied from a power source for applying a voltage between the transfer roll and the transfer source member is a first current or a second current that is smaller than the amount of the first current. Current supply control means for performing control to be changed to
When the current supply control means sets the current supplied from the power source as the second current, the second current is supplied, and the toner image transferred to the transfer destination member is supplied from the toner image. Detecting means for detecting toner amounts per unit area at a plurality of different positions in the axial direction of the transfer roll;
Adjusting means for adjusting the position of the shaft of the transfer roll;
The adjustment unit adjusts the position of the shaft of the transfer roll in accordance with each toner amount detected by the detection unit, and the transfer roll presses the transfer destination member against the transfer source member. Control means for controlling the pressing force,
The current supply control means is configured such that when the transfer roll presses the transfer destination member against the transfer source member with the pressing force controlled by the control means, the current supplied from the power source is A transfer mechanism characterized in that the first current is controlled. The control means includes
2. The transfer mechanism according to claim 1, wherein the pressing force is controlled so as to reduce the difference between the toner amounts according to the difference between the toner amounts detected by the detection unit. The control means includes
Based on the change in the toner amount detected by the detection means for each change, the ratio of the change in the toner amount to the change in the pressing force is less than a threshold value. The pressing force to be reduced is specified, and the force of the transfer roll pressing the transfer destination member against the transfer source member becomes the specified pressing force, so that the adjusting means is connected to the shaft of the transfer roll. The transfer mechanism according to claim 1, wherein the position is adjusted. The control means includes
The minimum pressing force at which the ratio of the change in the toner amount to the change in the pressing force is less than a threshold value is specified, and the force with which the transfer roll presses the transfer destination member to the transfer source member is specified The transfer mechanism according to claim 3, wherein the adjustment means adjusts the position of the shaft of the transfer roll so that the pressing force is achieved. The second current is:
5. The transfer mechanism according to claim 1, wherein the transfer mechanism is an amount of current smaller than 50% of the amount of the first current. The second current is:
The amount of toner per unit area of the toner image transferred to the transfer destination member when the second current is supplied from the power source, and the transfer amount when the first current is supplied from the power source. The transfer mechanism according to any one of claims 1 to 4, wherein the current is an amount that is 20% or more less than the toner amount per unit area of the toner image transferred to the previous member. The adjusting means includes
Adjusting the position of one end of the shaft of the transfer roll;
The detection means includes
The transfer destination member detects the toner amount at a position closer to the one end than the center in the axial direction of the transfer roll;
The control means includes
In accordance with the amount of toner detected by the detection means, the adjustment means adjusts the position of one end of the shaft of the transfer roll so that the transfer roll moves the transfer destination member to the transfer source member. The transfer mechanism according to any one of claims 1 to 6, wherein a pressing force to be pressed is controlled. The adjusting means includes
Adjusting the position of one end and the other end of the shaft of the transfer roll,
The detection means includes
The transfer destination member detects the toner amount at a position closer to the one end than the center in the axial direction of the transfer roll and a position closer to the other end than the center in the axial direction of the transfer roll. And
The control means includes
According to the detection position on the one end side detected by the detection means and the toner amount detected by the detection means on the other end side, one of the shafts of the transfer roll is supplied to the adjustment means. The position of the edge part of this and the other edge part is adjusted, The pressing force by which the said transfer roll presses the member of the said transfer destination to the said member of the transfer origin is controlled. The transfer mechanism according to any one of the above. Forming means for forming a toner image;
The transfer mechanism according to claim 1, which functions as a primary transfer unit that primarily transfers the toner image formed by the forming unit to a transfer body;
Secondary transfer means for secondary transfer of the toner image primarily transferred to the transfer body by the transfer mechanism onto a transfer material;
An image forming apparatus comprising: a fixing unit that fixes the toner image secondarily transferred by the secondary transfer unit to the transfer material. Forming means for forming a toner image;
Primary transfer means for primarily transferring the toner image formed by the forming means to a transfer body;
The transfer mechanism according to any one of claims 1 to 8, which functions as a secondary transfer unit that secondarily transfers the toner image transferred to the transfer body by the primary transfer unit onto a transfer material;
An image forming apparatus comprising: a fixing unit that fixes the toner image secondarily transferred by the transfer mechanism to the transfer material.

Images