JP5392605B2 - Image forming apparatus - Google Patents

Description

  The present invention comprises two or more latent image carriers such as photoconductors whose surfaces revolve around along the surface movement direction of a transfer medium such as an intermediate transfer member or a recording material, and a latent image on the surface of each latent image carrier. The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, etc., in which visible images obtained by developing are transferred onto a transfer target body so as to overlap each other to obtain a final image.

  Conventionally, as this type of image forming apparatus, for example, a tandem type image provided with four photoconductors (latent image carriers) for forming visible images of four colors of yellow, magenta, cyan, and black, respectively. Known as a forming device. As described above, in the image forming apparatus that transfers the visible images formed on the photosensitive members onto the transfer target body so as to overlap each other, the relative transfer position shift between the visible images on the transfer target member is different. It is important in terms of image quality improvement to reduce (hereinafter referred to as “color shift” as appropriate).

  Among the color misregistrations, there is a color misregistration caused by the outer peripheral deflection of the photosensitive member driving gear caused by the eccentricity of the photosensitive member driving gear (driven transmission rotating member) fixed to the rotating shaft of the photosensitive member. This color shift will be described in detail. The photosensitive member drive gear has an outer periphery due to its eccentricity, and the slowest rotational angular velocity when the radius of the longest part meshes with the motor gear or idler gear that transmits the rotational driving force to the photosensitive member drive gear. Rotate with. As a result, unless other fluctuation components that can fluctuate the linear velocity of the photosensitive member are taken into consideration, the rotational angular velocity of the photosensitive member provided with the photosensitive member driving gear is the slowest at this time, and the linear velocity of the photosensitive member is Sometimes the slowest. Similarly, when the portion of the photoconductor drive gear having the shortest radius meshes with the motor gear or idler gear, the photoconductor drive gear rotates at the highest rotational angular velocity, and the line of the photoconductor on which the photoconductor drive gear is provided. The speed is the fastest. The former part where the linear speed of the photosensitive member is the slowest and the latter part where the linear speed of the photosensitive member is the fastest are point-symmetrical with respect to the rotational center of the photosensitive member drive gear, that is, the rotational position is 180 °. In different positions. For this reason, the rotational angular velocity of the photosensitive member driving gear has a sine wave fluctuation component having a period corresponding to one rotation, and the linear velocity of the photosensitive member has a period corresponding to one rotation of the photosensitive member driving gear. A fluctuation component of a sine wave appears. The toner image (visible image) transferred from the photosensitive member to the transfer member when the photosensitive member is rotating at a linear velocity near the upper limit of the fluctuation component is more sub-scanning (transferred) than the original. The shape is contracted in the direction of body surface movement. Conversely, the toner image transferred from the photosensitive member to the transfer member when the photosensitive member is rotating at a linear velocity near the lower limit of the fluctuation component has a shape extending in the sub-scanning direction from the original. As a result, the most contracted toner image transferred from one of the two photoconductors and the most elongated toner image transferred from the other photoconductor are transferred onto the transfer target. When transferred to the same point, the maximum color shift occurs.

  Usually, since the same photosensitive member driving gears are provided on the respective photosensitive members, it can be said that the amplitude values of the outer peripheral deflections of the photosensitive member driving gears due to the eccentricity are the same. Therefore, the amplitude value of the fluctuation component appearing in the linear velocity of the photosensitive member due to the eccentricity is the same, and the maximum amount of expansion and contraction of the toner image transferred onto the transfer target due to this is the same. Accordingly, the relative rotational positions of the photosensitive member driving gears so that the toner images having the most contracted shapes or the toner images having the most extended shapes are transferred to the same point on the transfer target. In theory, it is possible to prevent color misregistration caused by the eccentricity of the photosensitive member driving gear.

  Conventionally, as a configuration for driving three or more photoconductors, a motor gear (drive transmission rotor) connected to a drive source is directly connected to each photoconductor drive gear provided on each photoconductor, One that drives a photoreceptor is known. With this configuration, the photosensitive member driving gear of the one photosensitive member has a point at which a specific point on the transferred member (any point in the moving direction of the transferred member surface) passes through the transfer portion of the one photosensitive member. Theoretically, the phase of eccentricity is adjusted so that it matches the phase of the eccentricity of the photosensitive member driving gear of the other photosensitive member when the specific point passes through the transfer portion of the other photosensitive member. It is possible to prevent color misregistration caused by the eccentricity of the body drive gear. However, this configuration requires at least two drive sources, resulting in a problem that the cost increases and it is difficult to downsize the apparatus.

  On the other hand, as a configuration for driving three or more photoconductors, a motor gear connected to a drive source is directly connected to some photoconductor drive gears, and the remaining photoconductor drive gears are connected to other photoconductor drive gears. What connects via an idler gear (following rotary body) is also known (patent document 1, patent document 2, etc.). Since this configuration can drive all the photoconductors with a single drive source, compared to the configuration described above in which the motor gear is directly connected to each photoconductor drive gear without using an idler gear. Therefore, it is possible to realize low cost and downsizing of the apparatus.

  However, in the conventional configuration using the idler gear, even if the relative rotational position of these photosensitive member driving gears is adjusted as described above between the two photosensitive member driving gears connected via the idler gear, the photosensitive member. There has been a problem that color misregistration due to eccentricity of the drive gear occurs.

  With respect to this problem, two photoconductor drive gears connected via an idler gear are directly connected to a motor gear of a drive source (hereinafter referred to as “second photoconductor drive gear”), and this second. An example will be described in which the photosensitive member driving gear includes a photosensitive member driving gear (hereinafter referred to as a “first photosensitive member driving gear”) to which a rotational driving force is transmitted from an idler gear that is driven to rotate by rotating the photosensitive member driving gear. . In this case, an eccentricity of the photosensitive member driving gear that affects the fluctuation component of the photosensitive member linear velocity in the photosensitive member (hereinafter referred to as “second photosensitive member”) provided in the second photosensitive member driving gear is provided. Only the eccentricity of the second photoconductor driving gear. On the other hand, the eccentricity of the photosensitive member driving gear that affects the fluctuation component of the photosensitive member linear velocity in the photosensitive member (hereinafter referred to as “first photosensitive member”) provided in the first photosensitive member driving gear is related to this. In addition to the eccentricity of the first photosensitive member driving gear provided, the eccentricity of the second photosensitive member driving gear transmitted through the idler gear is also included. That is, the rotational angular velocity of the first photoconductor driving gear includes a composite wave of fluctuation components due to the eccentricity of the two photoconductor drive gears (hereinafter referred to as “synthetic wave fluctuation component”). In the linear velocity, this synthesized wave fluctuation component appears as a linear velocity fluctuation component.

  When the above-described adjustment is performed in this configuration, the phase of the combined wave fluctuation component of the rotational angular velocity of the first photoconductor driving gear at the time when a specific point on the transfer medium passes through the transfer portion of the first photoconductor is the second. The first photoconductor driving gear and the first photoconductor driving gear and the phase of the fluctuation component of the rotational angular velocity of the second photoconductor driving gear due to the eccentricity of the second photoconductor driving gear when the specific point passes through the transfer portion of the photoconductor The relative rotational position of the second photoconductor driving gear is set. Thereby, the toner images having the most contracted shapes or the toner images having the most extended shapes are transferred to the same point on the transfer target.

  If the distance between the transfer portions between the first photoconductor and the second photoconductor is set to be an integral multiple of the circumference of these photoconductors, the first photoconductor drive gear can be used even if the same one is used. The amplitude value of the composite wave fluctuation component of the rotational angular velocity of the photosensitive member driving gear can be matched with the amplitude value of the fluctuation component of the rotational angular velocity of the second photosensitive member driving gear due to the eccentricity of the second photosensitive member driving gear. Therefore, with this configuration, the above-described adjustment can prevent color misregistration caused by the eccentricity of the photosensitive member driving gear.

  However, such a configuration greatly restricts the internal layout of the image forming apparatus. For example, due to other restrictions, the distance between the transfer portions is desired to be larger than an integral multiple of the circumference of the photosensitive member. The request cannot be met, and such a configuration may not be adopted due to other restrictions in the first place. Therefore, the conventional image forming apparatus is generally configured such that the distance between the transfer portions between the first photoconductor and the second photoconductor deviates from a value that is an integral multiple of the peripheral length of these photoconductors. In this case, the amplitude value of the combined wave fluctuation component of the rotation angular velocity of the first photoconductor driving gear does not match the amplitude value of the fluctuation component of the rotation angular velocity of the second photoconductor driving gear due to the eccentricity of the second photoconductor driving gear. . As a result, the amplitude value of the linear speed fluctuation component of the first photoconductor and the amplitude value of the linear speed fluctuation component of the second photoconductor do not coincide with each other, so that the toner image having the most contracted shape on the transfer body. The amount of contraction in the sub-scanning direction or the amount of extension in the sub-scanning direction of the toner image having the most extended shape differs between the first photoconductor and the second photoconductor. Therefore, even if adjustment is performed so that toner images having the most contracted shapes or toner images having the most extended shapes are transferred to the same point on the transfer target, the amount of contraction or extension is reduced. Difference color deviation (hereinafter referred to as “specific color deviation”) remains.

  This specific color shift can be achieved by using separate rotating bodies having different eccentric amounts as the first photoconductor drive gear and the second photoconductor drive gear, and eliminating the specific color shift of the first photoconductor drive gear. If the amount is set, it is possible to prevent the specific color deviation from occurring by performing the above-described adjustment. However, the use of gears having different eccentric amounts as the first photosensitive member driving gear and the second photosensitive member driving gear causes an increase in cost and has an eccentric amount that can eliminate the specific color deviation. It is difficult to manufacture the first photoconductor driving gear, which causes an increase in cost.

  The present invention has been made in view of the above problems, and the object of the present invention is that the distance between the transfer portions between the first latent image carrier and the second latent image carrier is such a latent image carrier due to some restrictions. Specific color misregistration that may occur between driven transmission rotating bodies such as two photosensitive member driving gears connected via a driven rotating body such as an idler gear when configured to deviate from an integral multiple of the peripheral length of The present invention is to provide an image forming apparatus that can alleviate the problem even when the same rotating body is used as these driven transmission rotating bodies.

ただし、Ｙの周期はＬ／πＲである。
また、上記式（１）中のＡ、Ｂ及びＣは、それぞれ下記の式（２）〜（４）により定義されるものである。
Ａ＝cos（−Ｘ＋α−β）−Ｚ×cos(θ＋β−１８０) ・・・（２）
Ｂ＝sin（−Ｘ＋α−β）−Ｚ×sin(θ＋β−１８０) ・・・（３）

また、上記式（２）及び上記式（３）中のＸは下記の式（５）により定義され、上記式（２）及び上記式（３）中のＺは下記の式（６）により定義されるものである。

ただし、Ａ_Ｍは上記第２被駆動伝達用回転体の偏心振幅であり、θ_Ｍ＝１８０−αであり、θ_Ｉ＝βである。
また、請求項２の発明は、請求項１の画像形成装置において、上記理想振幅比率Ｙから１を差し引いた値の絶対値が、０．７以下となるように、上記２つの潜像担持体の直径Ｒ、該２つの潜像担持体の転写部間距離Ｌ、上記角度α及び上記角度βが設定されていることを特徴とするものである。
また、請求項３の発明は、請求項２の画像形成装置において、上記理想振幅比率Ｙから１を差し引いた値の絶対値が、０．０６以下となるように、上記２つの潜像担持体の直径Ｒ、該２つの潜像担持体の転写部間距離Ｌ、上記角度α及び上記角度βが設定されていることを特徴とするものである。
また、請求項４の発明は、請求項１乃至３のいずれか１項に記載の画像形成装置において、上記２つの潜像担持体の表面が所定の潜像形成箇所から被転写体への転写部までを移動する間に、上記駆動伝達用回転体及び上記従動回転体が整数回、回転するように構成したことを特徴とするものである。
また、請求項５の発明は、請求項１乃至４のいずれか１項に記載の画像形成装置において、上記第１被駆動伝達用回転体及び上記第２被駆動伝達用回転体の相対的な回転位置を調整するための回転位置調整手段を設けたことを特徴とするものである。
また、請求項６の発明は、請求項５の画像形成装置において、上記回転位置調整手段は、上記第１被駆動伝達用回転体及び上記第２被駆動伝達用回転体として用いられる上記同一の回転体上に形成された、該回転体の回転により周回移動する第１マーク及び第２マークで構成されており、上記第１マーク及び上記第２マークは、上記相対的な回転位置が調整された後における上記第１被駆動伝達用回転体上の第１マークと上記第２被駆動伝達用回転体上の第２マークとが互いに同じ回転位置となるように、該同一の回転体上に形成されていることを特徴とするものである。
また、請求項７の発明は、請求項５の画像形成装置において、上記回転位置調整手段は、上記第１被駆動伝達用回転体及び上記第２被駆動伝達用回転体として用いられる上記同一の回転体上に形成された、該回転体の回転により周回移動する第１マーク及び第２マークと、該第１被駆動伝達用回転体及び該第２被駆動伝達用回転体を支持する支持部材上に形成された、該第１マークに対応する第３マーク及び該第２マークに対応する第４マークとで構成されており、上記第１マークは、その回転体が上記第１被駆動伝達用回転体として用いられる場合に、上記相対的な回転位置が調整された後における回転位置が上記支持部材上の第３マークに最も近接する位置となるように、該同一の回転体上に形成されており、上記第２マークは、その回転体が上記第２被駆動伝達用回転体として用いられる場合に、上記相対的な回転位置が調整された後における回転位置が上記支持部材上の第４マークに最も近接する位置となるように、該同一の回転体上に形成されていることを特徴とするものである。 In order to achieve the above object, the invention according to claim 1 is provided with at least two latent image carriers whose surface circulates in the direction of surface movement of the transferred body, and each driven image provided for each latent image carrier. A latent image on the surface of each latent image carrier formed at a predetermined latent image forming position is obtained by rotating the surface of each latent image carrier by transmitting a rotational driving force from a driving source to the transmission rotor. In the image forming apparatus for obtaining the final image by transferring the visible images obtained by developing the image onto the transfer target body so as to overlap each other, the distance L between the transfer portions of the two latent image carriers having the same diameter R is The first latent image carrier is configured to deviate from a value that is an integral multiple of the circumferential length πR of the two latent image carriers, and is located on the downstream side of the surface to be transferred in the moving direction of the two latent image carriers. The first driven transmission rotating body provided on the body and the surface of the transferred body in the direction of movement The second driven transmission rotating body provided on the second latent image carrier positioned on the side is composed of the same rotating body, and the transfer portion of the first latent image carrier is placed on the transferred body. The phase of the fluctuation component of the rotational angular velocity of the first driven transmission rotator due to the eccentricity of the first driven transmission rotator and the eccentricity of the second driven transmission rotator when the specific point passes And the phase of the fluctuation component of the rotational angular velocity of the second driven transmission rotating body due to the eccentricity of the second driven transmission rotating body when the specific point passes through the transfer portion of the second latent image carrier. The relative rotational positions of the first driven transmission rotator and the second driven transmission rotator are set so that they coincide with each other, and the drive transmission rotation connected to the drive source side is set. A driven rotating body that is directly connected to the second driven transmission rotating body and is driven to rotate Are directly connected to the first driven transmission rotator and the second driven transmission rotator, so that the first latent image carrier and the first latent image carrier are transmitted by the rotational driving force transmitted from the drive transmitting rotator. When both of the second latent image carriers are driven and viewed from the direction of the rotation axis of the driven rotator, the rotation center of the driven rotator is the rotation center of the first driven transmission rotator and the first driven transmission rotator. (2) the driven rotating body is arranged so that the driven rotating body is located downstream of the first virtual straight line connecting the rotation center of the driven driven rotating body with respect to the rotational direction of the second driven transmitting rotating body; When viewed from the rotation axis direction of the rotating body, a second virtual line connecting the first virtual straight line, the rotation center of the second driven transmission rotating body, and the rotation center of the driving transmission rotating body. The angle formed with the straight line is defined as α with the rotation direction of the second driven transmission rotating body as positive, and the above A third imaginary straight line connecting the first imaginary straight line, the rotation center of the first driven transmission rotator and the rotation center of the driven rotator as viewed from the rotation axis direction of the dynamic rotator. Is defined as β with the rotation direction of the first driven transmission rotating body being positive, the second driven transmission rotating due to the eccentricity of the second driven transmission rotating body. The first latent image carrier and the second latent image carrier due to the eccentricity of the first driven transmission rotating body and the second driven transmission rotating body with respect to the actual amplitude of the outer peripheral shake of the rotating body An ideal amplitude ratio Y indicating the ratio of the ideal amplitude of the outer peripheral deflection of the first driven transmission rotating body that can theoretically make the relative transfer position deviation generated between the first and second rotating bodies zero is defined by the following equation (1): Then, the absolute value of the value obtained by subtracting 1 from the ideal amplitude ratio Y is the outer peripheral vibration of the second driven transmission rotating body. The diameter R of the two latent image carriers and the transfer of the two latent image carriers so that the ratio is equal to or less than a maximum allowable amplitude ratio indicating a ratio of 10 μm that is a maximum allowable amount of the transfer position deviation with respect to the actual amplitude. The inter-part distance L, the angle α, and the angle β are set.

However, the period of Y is L / πR.
A, B, and C in the above formula (1) are defined by the following formulas (2) to (4), respectively.
A = cos (−X + α−β) −Z × cos (θ + β−180) (2)
B = sin (−X + α−β) −Z × sin (θ + β−180) (3)

X in the above formula (2) and the above formula (3) is defined by the following formula (5), and Z in the above formula (2) and the above formula (3) is defined by the following formula (6). It is what is done.

However, A _M is the eccentric amplitude of the second driven transmission rotating body, θ _M = 180−α, and θ _I = β.
According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the two latent image carriers are arranged so that an absolute value of a value obtained by subtracting 1 from the ideal amplitude ratio Y is 0.7 or less. The diameter R, the distance L between the transfer portions of the two latent image carriers, the angle α, and the angle β are set.
According to a third aspect of the present invention, in the image forming apparatus of the second aspect, the two latent image carriers are arranged so that an absolute value of a value obtained by subtracting 1 from the ideal amplitude ratio Y is 0.06 or less. The diameter R, the distance L between the transfer portions of the two latent image carriers, the angle α, and the angle β are set.
According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the surfaces of the two latent image carriers are transferred from a predetermined latent image forming portion to a transfer target. During the movement to the part, the drive transmission rotator and the driven rotator are configured to rotate an integer number of times.
According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the first driven transmission rotating body and the second driven transmission rotating body are relative to each other. Rotational position adjusting means for adjusting the rotational position is provided.
According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, the rotational position adjusting means is the same as the first driven transmission rotating body and the second driven transmission rotating body. The first mark and the second mark are formed on the rotating body and move around by the rotation of the rotating body, and the relative rotation position of the first mark and the second mark is adjusted. After that, the first mark on the first driven transmission rotating body and the second mark on the second driven transmission rotating body are on the same rotating body so that they are in the same rotational position. It is characterized by being formed.
According to a seventh aspect of the present invention, in the image forming apparatus according to the fifth aspect, the rotational position adjusting means is the same as the first driven transmission rotating body and the second driven transmission rotating body. The first mark and the second mark which are formed on the rotator and move around by the rotation of the rotator, and the support member for supporting the first driven transmission rotator and the second driven transmission rotator. The first mark is composed of a third mark corresponding to the first mark and a fourth mark corresponding to the second mark, and the first mark has a rotating body that is the first driven transmission. Formed on the same rotating body so that the rotational position after the relative rotational position is adjusted is closest to the third mark on the support member. The second mark is When a body is used as the second driven transmission rotating body, the rotational position after the relative rotational position is adjusted is the closest position to the fourth mark on the support member. It is formed on the same rotating body.

In the present invention, since the toner images having the most contracted shapes or the toner images having the most extended shapes are adjusted to be transferred to the same point on the transfer target, The relative transfer position deviation caused between the first latent image carrier and the second latent image carrier due to the eccentricity of the driven transmission rotor and the second driven transmission rotor is theoretically: Only the specific color shift described above is present. As described above, the specific color misregistration uses individual rotating bodies having different eccentric amounts as the first driven transmission rotating body and the second driven transmission rotating body, and the first driven transmission rotating body. Is set to an amount that can eliminate the specific color misalignment.
As will be described in detail later, the inventors of the present invention are ideal of the outer peripheral runout of the first driven transmission rotator that can theoretically make the specific color shift zero relative to the actual amplitude of the outer peripheral runout of the second driven transmission rotator. The ideal amplitude ratio Y, which is the ratio of the amplitudes, represents the diameter R of the two latent image carriers and the distance L between the transfer portions between these latent image carriers as shown in the above formulas (1) to (6). And the angle α (hereinafter referred to as “motor input angle α”) and the angle β (hereinafter referred to as “idler input angle β”). The maximum amount of the specific color shift is the ideal amplitude ratio Y and the ratio of the actual amplitude of the outer peripheral shake of the first driven transmission rotating body to the actual amplitude of the outer peripheral shake of the second driven transmission rotating body. It is proportional to the difference value (absolute value) from the actual amplitude ratio. Specifically, the maximum amount of the specific color shift is obtained by multiplying the difference value by the actual amplitude of the outer peripheral deflection of the second driven transmission rotating body. In recent years, it is assumed that the maximum allowable amount of the specific color shift is set to about 10 μm due to a demand for high image quality. In order to make the maximum amount of the specific color shift equal to or less than the maximum allowable amount (10 μm), the difference value is the ratio of the maximum allowable amount (10 μm) to the actual amplitude of the outer peripheral deflection of the second driven transmission rotating body. What is necessary is just to make it become below the maximum allowable amplitude ratio. In the present invention, since the same rotating body is used as the first driven transmission rotating body and the second driven transmission rotating body, the actual amplitude ratio is 1. Accordingly, the diameter R of the latent image carrier, the distance L between the transfer portions, the motor, and the motor are obtained so that the ideal amplitude ratio Y is obtained such that the absolute value obtained by subtracting 1 from the ideal amplitude ratio Y is equal to or less than the maximum allowable amplitude ratio. According to the present invention in which the input angle α and the idler input angle β are set, the maximum amount of the specific color shift can be 10 μm or less.

  As described above, according to the present invention, the distance between the transfer portions between the first latent image carrier and the second latent image carrier is deviated from a value that is an integral multiple of the circumference of these latent image carriers due to some restrictions. In this case, the amount of specific color misregistration that can occur between two driven transmission rotating bodies connected via the driven rotating body is determined even when the same rotating body is used as these driven transmission rotating bodies. The excellent effect that it can reduce to 10 micrometers or less is acquired.

1 is a schematic configuration diagram illustrating a printer according to an embodiment. FIG. 2 is a schematic configuration diagram illustrating one of process units of the printer. FIG. 2 is a perspective view of a driving device for three color photoconductors provided in the printer when viewed from the opposite side to FIG. 1. FIG. 6 is a perspective view of a color photoconductor in which a photoconductor drive gear is fixed to a rotation shaft. It is a perspective view showing a printer main body side driving force transmission unit constituting the driving force transmission unit. FIG. 6 is a perspective view showing a photosensitive member side driving force transmission unit constituting a driving force transmission unit. It is explanatory drawing for demonstrating the relationship between the distance of an exposure part and a transfer part, and a transfer position shift (color shift). FIG. 3 is a front view showing the arrangement of photosensitive member driving gears, motor gears, and idler gears when viewed from the rotation axis direction of three color photosensitive members. FIG. 5 is a schematic diagram showing a relative arrangement relationship of motor gears and idler gears with respect to three photosensitive member driving gears. FIG. 6 is an explanatory diagram showing a phase relationship of outer peripheral deflection caused by eccentricity of the photosensitive member driving gear between two photosensitive member driving gears directly connected to the motor gear. FIG. 6 is an explanatory diagram showing a phase relationship of an eccentric component of a photosensitive member driving gear between two photosensitive member driving gears directly connected to an idler gear. FIG. 6 is an explanatory diagram showing a phase relationship between a combined eccentric component of a Y photoconductor driving gear and an eccentric component of an M photoconductor driving gear. FIG. 6 is an explanatory diagram showing a positional relationship between an eccentric component of an M photoconductor drive gear and an eccentric component of an M photoconductor drive gear transmitted to an Y photoconductor drive gear via an idler gear. FIG. 6 is an explanatory diagram showing a relative rotation position (assembly position) of the Y photoconductor drive gear with respect to the M photoconductor drive gear. The ideal amplitude ratio indicating the ratio of the ideal amplitude of the eccentric component of the Y photoconductor drive gear that can theoretically eliminate the specific color shift of the eccentric component of the M photoconductor drive gear with respect to the actual amplitude, and the distance between these transfer portions / It is a graph which shows the relationship with a photoreceptor circumference. It is explanatory drawing which shows an example of the phase adjustment means which can be used by embodiment. It is explanatory drawing which shows the other example of the phase adjustment means which can be used by embodiment. It is explanatory drawing which shows the further another example of the phase adjustment means which can be used by embodiment. It is explanatory drawing for demonstrating the usage example of the same phase adjustment means. It is a schematic diagram which shows the relative arrangement | positioning relationship of the motor gear with respect to the three photoreceptor drive gears in a modification, and an idler gear. FIG. 10 is an explanatory diagram showing a phase relationship of outer peripheral deflection caused by the eccentricity of the photosensitive member driving gear between two photosensitive member driving gears directly connected to the motor gear in a modified example. FIG. 11 is an explanatory diagram showing a phase relationship of eccentric components of a photosensitive member driving gear between two photosensitive member driving gears directly connected to an idler gear in a modified example. FIG. 11 is an explanatory diagram showing a phase relationship between a combined eccentric component of a Y photoconductor drive gear and an eccentric component of an M photoconductor drive gear in a modification. FIG. 9 is an explanatory diagram showing a positional relationship between an eccentric component of an M photoconductor drive gear and an eccentric component of an M photoconductor drive gear transmitted to an Y photoconductor drive gear via an idler gear in a modified example. In the modification, an ideal amplitude ratio indicating the ratio of the ideal amplitude of the eccentric component of the Y photoconductor driving gear that can theoretically make the specific color shift with respect to the actual amplitude of the eccentric component of the M photoconductor driving gear, and the transfer thereof. 6 is a graph showing the relationship between the distance between parts / photoreceptor circumference.

Hereinafter, as an image forming apparatus to which the present invention is applied, an embodiment of an electrophotographic printer (hereinafter simply referred to as “printer”) will be described.
FIG. 1 is a schematic configuration diagram illustrating a printer according to an embodiment.
In the drawing, the printer according to the embodiment includes four process units for generating toner images (visible images) of yellow, magenta, cyan, and black (hereinafter referred to as Y, M, C, and K, respectively). 6Y, 6M, 6C, 6K. These use Y, M, C, and K toners as the image forming substances, but other than that, they have the same configuration and are replaced when the lifetime is reached. Taking a process unit 6Y for generating a Y toner image as an example, as shown in FIG. 2, a drum-shaped photosensitive member 1Y, which is a latent image carrier, a drum cleaning device 2Y, a charge eliminating device (not shown), and a charging device. 4Y, developing unit 5Y, and the like. The process unit 6Y, which is an image forming unit, can be attached to and detached from the printer body, so that consumable parts can be replaced at a time.

  The charging device 4Y uniformly charges the surface of the photoreceptor 1Y that is rotated clockwise in the drawing by a driving unit (not shown). The uniformly charged surface of the photoreceptor 1Y is exposed and scanned by the laser beam L to carry an electrostatic latent image for Y. The electrostatic latent image of Y is developed into a Y toner image by a developing device 5Y using a Y developer containing Y toner and a magnetic carrier. Then, intermediate transfer is performed on an intermediate transfer belt 8 serving as a transfer target, which will be described later. The drum cleaning device 2Y removes the toner remaining on the surface of the photoreceptor 1Y after the intermediate transfer process. The static eliminator neutralizes residual charges on the photoreceptor 1Y after cleaning. By this charge removal, the surface of the photoreceptor 1Y is initialized and prepared for the next image formation. In the other color process units 6M, 6C, and 6K, M, C, and K toner images are similarly formed on the photoreceptors 1M, 1C, and 1K, respectively, and are intermediately transferred onto the intermediate transfer belt 8.

  The developing device 5Y has a developing roll 51Y disposed so as to be partially exposed from the opening of the casing. Also included are two conveying screws 55Y, a doctor blade 52Y, a toner density sensor (hereinafter referred to as “T sensor”) 56Y, and the like, which are arranged in parallel with each other.

  In the casing of the developing device 5Y, a Y developer (not shown) including a magnetic carrier and Y toner is accommodated. The Y developer is frictionally charged while being agitated and conveyed by the two conveying screws 55Y, and then carried on the surface of the developing roll 51Y. Then, after the layer thickness is regulated by the doctor blade 52Y, the layer is transported to the developing region facing the Y photoreceptor 1Y, where Y toner is attached to the electrostatic latent image on the photoreceptor 1Y. This adhesion forms a Y toner image on the photoreceptor 1Y. In the developing unit 5Y, the Y developer that has consumed Y toner by the development is returned into the casing as the developing roll 51Y rotates.

  A partition wall is provided between the two conveying screws 55Y. By this partition wall, the first supply unit 53Y that accommodates the developing roll 51Y, the right conveying screw 55Y in the figure, and the second supply unit 54Y that accommodates the left conveying screw 55Y in the figure are separated in the casing. . The conveying screw 55Y on the right side in the drawing is driven to rotate by a driving means (not shown), and supplies the Y developer in the first supply unit 53Y to the developing roll 51Y while being conveyed from the near side to the far side in the drawing. The Y developer conveyed to the vicinity of the end of the first supply unit 53Y by the right conveyance screw 55Y in the drawing enters the second supply unit 54Y through an opening (not shown) provided in the partition wall. In the second supply unit 54Y, the conveyance screw 55Y on the left side in the drawing is driven to rotate by a driving means (not shown), and the Y developer sent from the first supply unit 53Y is the conveyance screw 55Y on the right side in the drawing. Transport in the reverse direction. The Y developer conveyed to the vicinity of the end of the second supply unit 54Y by the conveyance screw 55Y on the left side in the drawing passes through the other opening (not shown) provided in the partition wall, and the first supply unit. Return to 53Y.

  The above-described T sensor 56Y composed of a magnetic permeability sensor is provided on the bottom wall of the second supply unit 54Y and outputs a voltage having a value corresponding to the magnetic permeability of the Y developer passing therethrough. Since the magnetic permeability of the two-component developer containing toner and magnetic carrier shows a good correlation with the toner concentration, the T sensor 56Y outputs a voltage corresponding to the Y toner concentration. This output voltage value is sent to a control unit (not shown). This control unit includes a RAM that stores a Vtref for Y that is a target value of an output voltage from the T sensor 56Y. The RAM also stores M Vtref, C Vtref, and K Vtref data, which are target values of output voltages from a T sensor (not shown) mounted in another developing device. The Y Vtref is used for driving control of a Y toner conveying device to be described later. Specifically, the control unit drives and controls a Y toner conveying device (not shown) so that the value of the output voltage from the T sensor 56Y is close to the Y Vtref, and the Y toner in the second supply unit 54Y. To replenish. By this replenishment, the Y toner concentration in the Y developer in the developing device 5Y is maintained within a predetermined range. The same toner replenishment control using the M, C, and K toner conveying devices is performed for the developing units of the other process units.

  In FIG. 1 shown above, an optical writing unit 7 as a latent image forming unit is disposed below the process units 6Y, 6M, 6C, 6K in the drawing. The optical writing unit 7 scans the respective photosensitive members in the process units 6Y, 6M, 6C, and 6K with the laser light L emitted based on the image information. By this scanning, electrostatic latent images for Y, M, C, and K are formed on the photoreceptors 1Y, 1M, 1C, and 1K. The optical writing unit 7 is a photosensitive member that passes through a plurality of optical lenses and mirrors while deflecting the laser light L emitted from the light source in the main scanning direction by reflection on a polygon mirror that is rotationally driven by a motor. Is irradiated.

  On the lower side of the optical writing unit 7 in the figure, paper storage means having a paper feed cassette 26, a paper feed roller 27 incorporated therein, and the like are disposed. The paper feed cassette 26 stores a plurality of transfer papers P, which are sheet-like recording materials, and a paper feed roller 27 is in contact with each uppermost transfer paper P. When the paper feeding roller 27 is rotated counterclockwise in the drawing by a driving means (not shown), the uppermost transfer paper P is sent out toward the paper feeding path 70.

  A registration roller pair 28 is disposed near the end of the paper feed path 70. The registration roller pair 28 rotates both rollers so as to sandwich the transfer paper P, but temporarily stops rotating immediately after sandwiching. Then, the transfer paper P is sent out toward a later-described secondary transfer nip at an appropriate timing.

  Above the process units 6Y, 6M, 6C, and 6K in the drawing, a transfer unit 15 that moves the endlessly while the intermediate transfer belt 8 as an intermediate transfer body as a transfer target is stretched is disposed. This transfer unit 15 includes a secondary transfer bias roller 19 and a cleaning device 10 in addition to the intermediate transfer belt 8. Also provided are four primary transfer bias rollers 9Y, 9M, 9C, 9K, a driving roller 12, a cleaning backup roller 13, a tension roller 14, and the like. The intermediate transfer belt 8 is endlessly moved counterclockwise in the figure by the rotational drive of the driving roller 12 while being stretched around these seven rollers. The primary transfer bias rollers 9Y, 9M, 9C, and 9K hold the intermediate transfer belt 8 that is moved endlessly in this manner between the photoreceptors 1Y, 1M, 1C, and 1K to form primary transfer nips. Yes. In these systems, a transfer bias having a polarity opposite to that of toner (for example, plus polarity) is applied to the back surface (inner circumferential surface of the loop) of the intermediate transfer belt 8. All the rollers except the primary transfer bias rollers 9Y, 9M, 9C, and 9K are electrically grounded. The intermediate transfer belt 8 sequentially passes through the primary transfer nips for Y, M, C, and K along with its endless movement, and Y, M, and C on the photoreceptors 1Y, 1M, 1C, and 1K. , K toner images are superimposed and primarily transferred. As a result, a four-color superimposed toner image (hereinafter referred to as “four-color toner image”) is formed on the intermediate transfer belt 8.

  The drive roller 12 sandwiches the intermediate transfer belt 8 between the secondary transfer roller 19 and forms a secondary transfer nip. The visible four-color toner image formed on the intermediate transfer belt 8 is transferred to the transfer paper P at the secondary transfer nip. Then, combined with the white color of the transfer paper P, a full color toner image is obtained. Untransferred toner that has not been transferred onto the transfer paper P adheres to the intermediate transfer belt 8 after passing through the secondary transfer nip. This is cleaned by the cleaning device 10. The transfer paper P on which the four-color toner images are collectively transferred at the secondary transfer nip is sent to the fixing device 20 via the post-transfer conveyance path 71.

  The fixing device 20 forms a fixing nip by a fixing roller 20a having a heat source such as a halogen lamp inside, and a pressure roller 20b that rotates while contacting the roller with a predetermined pressure. The transfer paper P fed into the fixing device 20 is sandwiched between the fixing nips so that the unfixed toner image carrying surface is in close contact with the fixing roller 20a. Then, the toner in the toner image is softened by the influence of heating and pressurization, and the full color image is fixed.

  The transfer sheet P on which the full-color image is fixed in the fixing device 20 exits the fixing device 20 and then reaches a branch point between the paper discharge path 72 and the pre-reversal conveyance path 73. At this branch point, a first switching claw 75 is swingably disposed, and the path of the transfer paper P is switched by the swing. Specifically, by moving the tip of the claw in the direction approaching the pre-reverse feed path 73, the path of the transfer paper P is changed to the direction toward the paper discharge path 72. Further, by moving the tip of the claw in a direction away from the pre-reversal conveyance path 73, the path of the transfer paper P is changed to the direction toward the pre-reversal conveyance path 73.

  When the path to the paper discharge path 72 is selected by the first switching claw 75, the transfer paper P is disposed outside the apparatus after passing through the paper discharge roller pair 100 from the paper discharge path 72. Are stacked on a stack 50a provided on the upper surface of the printer housing. On the other hand, when the path toward the conveyance path 73 before reversal is selected by the first switching claw 75, the transfer paper P enters the nip of the reversing roller pair 21 via the conveyance path 73 before reversal. The reversing roller pair 21 conveys the transfer paper P sandwiched between the rollers toward the stack portion 50a, but reversely rotates the rollers immediately before the rear end of the transfer paper P enters the nip. Due to this reverse rotation, the transfer paper P is transported in the opposite direction, and the rear end side of the transfer paper P enters the reverse transport path 74.

  The reverse conveyance path 74 has a shape extending while curving from the upper side to the lower side in the vertical direction, and the first reverse conveyance roller pair 22, the second reverse conveyance roller pair 23, and the third reverse conveyance in the path. A roller pair 24 is provided. The transfer paper P is transported while sequentially passing through the nips of these roller pairs, so that the upper and lower sides thereof are reversed. After the transfer paper P is turned upside down, it is returned to the paper feed path 70 and then reaches the secondary transfer nip again. Then, this time, the image transfer surface enters the secondary transfer nip while bringing the non-image carrying surface into close contact with the intermediate transfer belt 8, and the second four-color toner image of the intermediate transfer belt is collectively transferred to the non-image carrying surface. The Thereafter, the sheet is stacked on the stack unit 50a outside the apparatus via the post-transfer conveyance path 71, the fixing device 20, the paper discharge path 72, and the paper discharge roller pair 100. A full color image is formed on both sides of the transfer paper P by such reverse conveyance.

  A bottle support portion 31 is disposed between the transfer unit 15 and the stack portion 50a located above the transfer unit 15. The bottle support portion 31 is equipped with toner bottles 32Y, 32M, 32C, and 32K that are toner storage portions for storing Y, M, C, and K toners. The toner bottles 32Y, 32M, 32C, and 32K are arranged so as to be arranged at an angle slightly inclined from the horizontal, and the arrangement positions are higher in the order of Y, M, C, and K. The Y, M, C, and K toners in the toner bottles 32Y, 32M, 32C, and 32K are appropriately replenished to the developing units of the process units 6Y, 6M, 6C, and 6K by toner transfer devices that will be described later. These toner bottles 32Y, 32M, 32C, and 32K are detachable from the printer main body independently of the process units 6Y, 6M, 6C, and 6K.

  This printer drives only the K photoconductor 1K among the four photoconductors 1Y, 1M, 1C, and 1K in a monochrome mode print job. At this time, by adjusting the posture of the transfer unit 15, the intermediate transfer belt 8 is brought into contact with only the K photoconductor 1K among the four photoconductors 1Y, 1M, 1C, and 1K. On the other hand, in the color mode print job, all of the four photoconductors 1Y, 1M, 1C, and 1K are driven. At this time, the intermediate transfer belt 8 is brought into contact with all of the four photosensitive members 1Y, 1M, 1C, and 1K by adjusting the posture of the transfer unit 15.

Hereinafter, the driving device for the color photoconductors 1Y, 1M, and 1C, which is a characteristic part of the present invention, will be described.
FIG. 3 is a perspective view of the color photoconductors 1Y, 1M, and 1C as viewed from the opposite side to FIG.
The driving device 80 mainly includes a motor 81 that is a driving source, a driving force transmission unit (to be described later) for transmitting a rotational driving force from the motor 81 to each of the photoreceptors 1Y, 1M, and 1C. It is comprised from the holding members 82a and 82b for doing.

FIG. 4 is a perspective view of the photoreceptors 1Y, 1M, and 1C in which the photoreceptor drive gears 83Y, 83M, and 83C are fixed to the rotation shaft.
FIG. 5 is a perspective view showing the printer main body side driving force transmitting portion constituting the driving force transmitting portion.
FIG. 6 is a perspective view showing the photosensitive member side driving force transmitting portion constituting the driving force transmitting portion.
The driving force transmission unit is mainly driven driven portions 84Y, 84M, and 84C provided on the rotation shafts of the photosensitive members 1Y, 1M, and 1C, and the photosensitive members fixed to the driven connected portions 84Y, 84M, and 84C. It comprises body drive gears 83Y, 83M, 83C, a motor gear 85 fixed on the motor shaft of the motor 81, and an idler gear 86. In the present embodiment, the photoreceptor driving gears 83Y, 83M, and 83C are the same. The driven connecting portions 84Y, 84M, 84C on the rotation shafts of the photoreceptors 1Y, 1M, 1C are coaxially connected to the drive connecting portions 87Y, 87M, 87C on the rotation shafts of the photoreceptor driving gears 83Y, 83M, 83C. To do. As a result, the photoreceptors 1Y, 1M, and 1C rotate integrally with the respective photoreceptor drive gears 83Y, 83M, and 83C. The driven connecting portions 84Y, 84M, and 84C provided on the rotation shafts of the photoreceptors 1Y, 1M, and 1C and the photoreceptor drive gears 83Y, 83M, and 83C may be integrally formed as in the present embodiment. It may be formed separately.

Here, with reference to FIG. 7, an example of the photoreceptor 1 </ b> Y for generating a Y toner image with respect to the relationship between the distance between the exposure unit and the transfer unit, which is a latent image forming portion, and the transfer position shift (color shift). I will give a description.
If the rotational angular velocity of the photoconductor 1Y fluctuates for some reason, the position on the photoconductor in the electrostatic latent image portion formed by the exposure unit when the rotational angular velocity is high is shifted to the downstream side in the direction of movement of the photoconductor surface. It becomes the position. Further, the position on the intermediate transfer belt 8 in the toner image portion transferred by the transfer portion when the rotational angular velocity of the photoreceptor 1Y is high is shifted to the upstream side of the intermediate transfer belt surface movement direction from the original position. Conversely, when the rotational angular velocity of the photosensitive member 1Y is low, the position on the photosensitive member in the electrostatic latent image portion formed at the exposure portion is shifted to the upstream side in the moving direction of the photosensitive member surface relative to the original, and the photosensitive member 1Y The position on the intermediate transfer belt 8 in the toner image portion transferred at the transfer portion when the rotational angular velocity is low is shifted to the downstream side of the intermediate transfer belt surface movement direction from the original position.

  However, even when the rotational angular velocity of the photoconductor 1Y varies, if there is no difference between the rotational angular velocity at the time of exposure and the rotational angular velocity at the time of transfer for a specific point on the photoconductor. The toner image is transferred to the original position on the intermediate transfer belt 8. This is because, for example, the electrostatic latent image portion exposed when the rotational angular velocity of the photoconductor 1Y is high is formed at a position shifted to the downstream side in the photoconductor surface movement direction as described above. When the rotational angular velocity when the toner image portion corresponding to the portion is transferred by the transfer portion is also fast (same speed), the toner image portion moves in the direction of the intermediate transfer belt surface than the original as described above. This is because, as a result of the transfer to the position shifted to the upstream side, the shift at the time of exposure and the shift at the time of transfer cancel each other. Therefore, if the rotational angular velocity fluctuation does not cause a difference in rotational angular velocity between the exposure time and the transfer time, there will be no color shift between the photoconductors.

Next, the gear configuration of the color photoreceptors 1Y, 1M, and 1C in the present embodiment will be described.
FIG. 8 is a front view showing the arrangement of the photosensitive member driving gears 83Y, 83M, 83C, the motor gear 85, and the idler gear 86 when viewed from the rotation axis direction of the color photosensitive members 1Y, 1M, 1C.
FIG. 9 is a schematic diagram showing a relative arrangement relationship of the motor gear 85 and the idler gear 86 with respect to the photosensitive member driving gears 83Y, 83M, and 83C.
In this embodiment, the motor gear 85, which is a drive transmission rotator connected to the motor 81, is an M photoconductor drive gear 83M as a second driven transmission rotator and a third driven transmission rotator. The Y photoconductor drive gear 83Y is directly connected. The idler gear 86 as a driven rotating body is directly connected to a C photoconductor driving gear 83C and an M photoconductor driving gear 83M as first driven transmission rotating bodies. Thus, the three photosensitive members including the C photosensitive member 1C as the first latent image carrier and the M photosensitive member 1M as the second latent image carrier by the rotational driving force of the motor 81 transmitted from the motor gear 85. 1Y, 1M, and 1C can be driven.

As shown in FIG. 9, in this embodiment, when viewed from the direction of the rotation axis of the idler gear 86, the rotation center of the idler gear 86 is the rotation center of the C photoconductor drive gear 83C and the M photoconductor drive gear 83M. An idler gear 86 is arranged so as to be downstream in the rotation direction of the M photoconductor driving gear 83M with respect to the first virtual straight line D1 connecting the rotation center.
In the present embodiment, the angle (idler input angle) formed by the first virtual straight line D1 and the third virtual straight line D3 connecting the rotation center of the C photoconductor drive gear 83C and the rotation center of the idler gear 86. ) Is defined as β, with the rotation direction of C photoconductor drive gear 83C (clockwise direction in FIG. 9) being positive. Therefore, in the present embodiment, the idler input angle β takes a negative value.

As shown in FIG. 9, in the present embodiment, when viewed from the direction of the rotation axis of the motor gear 85, the rotation center of the motor gear 85 is greater than the first imaginary straight line D1 of the M photoconductor drive gear 83M. A motor gear 85 is arranged so as to be downstream in the rotational direction.
In the present embodiment, an angle formed by the first virtual straight line D1 and a second virtual straight line D2 connecting the rotation center of the M photoconductor drive gear 83M and the rotation center of the motor gear 85 (motor input angle). ) Is defined as α, with the rotation direction (clockwise direction in FIG. 9) of the M photoconductor drive gear 83M being positive. Therefore, in this embodiment, the motor input angle α takes a positive value.

FIG. 10 is an explanatory diagram showing the phase relationship of the outer peripheral shake due to the eccentricity of the photosensitive member driving gear between the two photosensitive member driving gears 83M and 83Y directly connected to the motor gear 85. FIG.
Symbols E _M and E _Y in the figure are vectors representing the peripheral deflection (hereinafter referred to as “eccentric component”) due to the eccentricity of the respective photosensitive member driving gears 83M and 83Y. The phase reference is the radial direction (the radial direction having the longest radius) in which the outer peripheral runout due to the 83Y eccentricity is maximum. Therefore, the direction of the vector indicated by symbols E _M and E _Y in the figure indicates the reference phase. In addition, the magnitudes of the vectors indicated by the symbols E _M and E _Y in the figure indicate the magnitude of the outer runout according to the amount of eccentricity in that direction. Therefore, the magnitudes of the vectors indicated by the symbols E _M and E _Y in the figure indicate the actual amplitude of the eccentric phase. However, the directions and sizes of the illustrated vectors are assumed, and do not correspond exactly to the configuration in the present embodiment. The same applies to the vectors described below.

In order to make the amount of color misregistration between the two photoconductors 1M and 1Y provided with these photoconductor drive gears 83M and 83Y zero, the transfer portion of one photoconductor 1M is placed on the intermediate transfer belt 8. a phase of the eccentric component E _M of the photoconductor driving gear 83M at the time specific point (any point in the intermediate transfer belt surface moving direction) passes, at the time of the transfer portion that particular point passes the other of the photoreceptor 1Y it may be adjusted so that the phase of the eccentric component E _Y of the photoconductor driving gear 83Y coincide with each other.

ただし、上記式（７）において、「ｓｔ＿ｎｕｍ」は、Ｙ用感光体駆動ギヤ８３Ｙが色ズレの基準となる感光体（本実施形態ではＭ用感光体１Ｍ）から何個目の感光体かを示すもので、ここでは１である。
また、上記式（７）中、「Ｌ」は２つの感光体１Ｍ，１Ｙの転写部間距離であり、「Ｒ］は２つの感光体１Ｍ，１Ｙの直径である。
なお、本実施形態では、少なくともカラー感光体１Ｙ，１Ｍ，１Ｃ間において、それぞれの転写部間距離はいずれのＬであり、同一の感光体が用いられているのでいずれの直径もＲである。 Each photoconductor driving gear 83M, 83Y, when the respective eccentric component E _M, the reference phase E _Y facing direction of the motor gear 85, the rotational angular velocity becomes minimum. Therefore, considering the time when the reference phase of the eccentric component E _M of the photoconductor driving gear 83M of M photoconductor 1M located intermediate transfer belt surface moving direction downstream side is directed toward the motor gear 85 to the reference, a photosensitive for Y body drive gear 83Y, the reference phase of the eccentric component E _Y may be adjusted to face in a direction rotated by X ° which is calculated by the addition of the following formula from the rotational position facing the direction of the motor gear 85 (7) .

However, in the above formula (7), “st_num” indicates the number of the photoconductors from the photoconductor (M photoconductor 1M in this embodiment) on which the Y photoconductor drive gear 83Y is a reference for color misregistration. It is shown and is 1 here.
In the above formula (7), “L” is the distance between the transfer portions of the two photoconductors 1M and 1Y, and “R” is the diameter of the two photoconductors 1M and 1Y.
In this embodiment, at least between the color photoconductors 1Y, 1M, and 1C, the distance between the transfer portions is L, and the same photoconductor is used, so that the diameter is R.

FIG. 11 is an explanatory diagram showing the phase relationship of the eccentric component of the photosensitive member driving gear between the two photosensitive member driving gears 83C and 83M directly connected to the idler gear 86.
What is indicated by a symbol E _C in the figure is a vector representing the outer peripheral runout due to the eccentricity of the photoconductor drive gear 83C, that is, the eccentric component of the photoconductor drive gear 83C, and the radius at which the outer peripheral runout due to the eccentricity of the photoconductor drive gear 83C is maximized. The direction (radial direction with the longest radius) is used as a phase reference. Therefore, the direction of the vector indicated by the symbol E _C in the figure indicates the reference phase. In addition, the magnitude of the vector indicated by the symbol E _C in the figure indicates the magnitude of the outer peripheral shake according to the amount of eccentricity in that direction. Therefore, the magnitude of the vector indicated by symbol E _C in the figure indicates the actual amplitude of the eccentric component.

  As described above, in the photoconductors 1M and 1Y provided in the photoconductor drive gears 83M and 83Y to which the rotational driving force is directly transmitted from the motor gear 85, the photoconductor drive that affects the fluctuation components of the respective photoconductor linear speeds. The eccentricity of the gears is only the eccentricity of the respective photosensitive member driving gears 83M and 83Y. On the other hand, in the photosensitive member 1C provided in the C photosensitive member driving gear 83C to which the rotational driving force is transmitted from the idler gear 86, the eccentricity of the photosensitive member driving gear that affects the fluctuation component of the photosensitive member linear velocity is as follows. This includes not only the eccentricity of the C photoconductor driving gear 83C provided thereto, but also the eccentricity of the M photoconductor driving gear 83M transmitted via the idler gear 86. That is, the rotational angular velocity of the C photoconductor drive gear 83C includes a fluctuation component due to a composite wave of the eccentric components of the two photoconductor drive gears 83C and 83M. As a result, the linear velocity of the C photoconductor 1C The fluctuation component due to the combined wave appears as a linear velocity fluctuation component.

In FIG. 11, the eccentric component of the M photoconductor drive gear 83M transmitted through the idler gear 86 is indicated by reference symbol E _M ', and this eccentric component E _M ' and the eccentric component E _{C of the C} photoconductor drive gear 83C The combined wave (hereinafter referred to as “synthetic eccentric component”) is denoted by E _C ′. Therefore, when the reference phase of the composite eccentric component E _C ′ is directed toward the idler gear 86, the _C angular photoreceptor driving gear 83C has the smallest rotational angular velocity. Therefore, as shown in FIG. 12, given in reference to the time when the reference phase of the eccentric component E _M of the photoconductor driving gear 83M of M photoconductor 1M is directed toward the motor gear 85, C photosensitive body drive gear 83C If the reference phase of the composite eccentric component E _C ′ is further adjusted from the rotational position in the direction of the idler gear 86 to the direction rotated by X ° calculated by the above equation (7), the color photoconductor Between 1Y, 1M, and 1C, the toner images having the most contracted shapes or the toner images having the most extended shapes are transferred to the same point on the intermediate transfer belt 8.

FIG. 13 shows the positions of the eccentric component E _M of the M photoconductor drive gear 83M and the eccentric component E _M ′ of the _M photoconductor drive gear 83M transmitted to the C photoconductor drive gear 83C via the idler gear 86. It is explanatory drawing which shows a relationship.
The rotational angular velocity of the M photoconductor driving gear 83M is the slowest, that is, the rotational angular velocity of the M photoconductor 1M is the slowest, as described above, as the eccentric component E of the M photoconductor driving gear 83M. _This is a time when the reference phase of _M faces the direction of the motor gear 85 (direction indicated by reference sign E1 _M in FIG. 13). Further, the angular velocity of the M photosensitive body drive gear 83M is slowest transmitted to the idler gear 86, 180 ° opposite to the direction of the reference phase idler gear 86 of the eccentric component E _M of M photosensitive body drive gear 83M it is when facing (direction indicated in FIG. 13 code E2 _M). From this, the rotational angular velocity of the idler gear 86 is slowest, the reference of the eccentric component E _M of M photosensitive body drive gear 83M in a direction located in the middle between the direction indicated by the direction and code E2 _M indicated at E1 _M When the phase is correct. At this time, the lowest rotational angular velocity of the idler gear 86 means that the linear speed of the C photoconductor drive gear 83C is the slowest. Therefore, at this time, the reference phase of the eccentric component E _M ′ of the _M photoconductor drive gear 83M transmitted to the C photoconductor drive gear 83C via the idler gear 86 is directed toward the idler gear 86.

ただし、「Ａ_Ｍ」はＭ用感光体駆動ギヤ８３Ｍの偏心振幅であり、θ_Ｍ＝１８０−αであり、θ_Ｉ＝−βである。 From the above, the rotation angle θ when the rotation angular velocity of the idler gear 86 is the slowest can be expressed by the following equation (8). The amplitude amplification factor Z when the amplitude of the eccentric component E _M of M photosensitive body drive gear 83M is transmitted to the C photosensitive body drive gear 83C is defined by the following equation (9).

However, “A _M ” is the eccentric amplitude of the M photoconductor driving gear 83M, θ _M = 180−α, and θ _I = −β.

FIG. 14 is an explanatory diagram showing the relative rotation position (assembly position) of the C photoconductor drive gear 83C with respect to the M photoconductor drive gear 83M.
When the eccentric component E _M of the M photoconductor driving gear 83M is defined by the following equation (10), the combined eccentric component E _C ′ on the C photoconductor driving gear 83C is expressed by the following equation (11), and the idler gear: The eccentric component E _M ′ of the _M photoconductor drive gear 83M transmitted from 86 to the C photoconductor drive gear 83C is expressed by the following equation (12).

ただし、Ｅ_Ｃの周期はＬ／πＲである。また、上記式（１３）中のＡ、Ｂ及びＣは、それぞれ下記の式（１４）〜（１６）により定義されるものである。
Ａ＝cos（−Ｘ＋α−β）−Ｚ×cos(θ＋β−１８０) ・・・（１４）
Ｂ＝sin（−Ｘ＋α−β）−Ｚ×sin(θ＋β−１８０) ・・・（１５）

The eccentric component E _C of the C photoconductor driving gear 83C is obtained by subtracting the eccentric component E _M ′ transmitted through the idler gear 86 from the combined eccentric component E _C ′. The component E _C is represented by the following formula (13).

However, the period of E _C is L / πR. A, B and C in the above formula (13) are defined by the following formulas (14) to (16), respectively.
A = cos (−X + α−β) −Z × cos (θ + β−180) (14)
B = sin (−X + α−β) −Z × sin (θ + β−180) (15)

When the above formula (10) is compared with the above formula (13), if the amplitude (A ² + B ² ) ^1/2 of the eccentric component E _C of the C photoconductor drive gear 83C is other than 1, it is for C it is not possible to match the amplitude of the eccentric component E _M amplitude and M photosensitive body drive gear 83M synthetic eccentric component E _C of the photoconductor driving gear 83C _'. If these amplitudes cannot be matched, the toner images having the most contracted shapes or the toner images having the most extended shapes are intermediately transferred between the color photoconductors 1Y, 1M, and 1C. Even if the image is transferred to the same point on the belt 8, a specific color shift corresponding to the amplitude difference remains.

As a method of setting the amplitude (A ² + B ² ) ^1/2 of the eccentric component E _C of the C photoconductor drive gear 83C to 1, the C photoconductor drive gear 83C is different from the M photoconductor drive gear 83M. A method using a separate gear having an eccentric amount can be mentioned. However, this method is not preferable because the manufacturing cost increases as described above. Therefore, if the amplitude (A ² + B ² ) ^1/2 can be set to 1 by another method, or can be as close to 1 as possible, the C photoconductor drive gear 83C and the M photoconductor drive gear are used. With the configuration using the same gear as 83M, the specific color shift can be eliminated or reduced.

Therefore, in the present embodiment, in the configuration in which the same gear is used as each photoconductor driving gear 83Y, 83M, 83C of the color photoconductors 1Y, 1M, 1C, the following configuration is adopted, so that each photoconductor driving gear is used. The specific color shift due to the eccentric components E _Y , E _M , and E _C of 83Y, 83M, and 83C is eliminated or reduced. Note that no specific color shift occurs between the two photoconductor drive gears 83M and 83Y directly connected to the motor gear 85, and therefore, the specific color between the two photoconductor drive gears 83C and 83M directly connected to the idler gear 86. If the color deviation can be eliminated or reduced, the specific color deviation between the color photoreceptors 1Y, 1M, 1C can be eliminated or reduced.

  Note that the rotational angular velocities of the photoconductors 1Y, 1M, and 1C may also be affected by the outer peripheral shake due to the eccentricity of the motor gear 85 and the idler gear 86. The motor gear 85 and the idler gear 86 can be canceled by being configured to rotate an integral number of times during the rotation. With this configuration, the point where the photosensitive member passes through the exposure portion when the rotational angular velocity (linear velocity) of the outer periphery due to the eccentricity of the motor gear 85 or idler gear 86 is the fastest is the transfer portion when the photosensitive member has the fastest linear velocity. Will pass. Therefore, with this configuration, there is no difference between the rotational angular velocity at the time of exposure and the rotational angular velocity at the time of transfer, which is caused by the eccentricity of the motor gear 85 and the idler gear 86 as described with reference to FIG. Color misregistration does not occur.

  Here, since it is not normally considered that the motor gear 85 and the idler gear 86 are larger than the photosensitive member driving gear, the motor input angle α that can be substantially taken in the present embodiment is in the range of 0 ° to + 60 °. The idler input angle β is in the range of 0 ° to −60 °.

15, in the structure of the present embodiment, the ideal of the eccentric component E _C of C photosensitive body drive gear 83C which may a specific color shift for real amplitude of the eccentric component E _M of M photosensitive body drive gear 83M theoretically zero 6 is a graph showing a relationship between an ideal amplitude ratio Y indicating an amplitude ratio and the distance L between the transfer parts / photoreceptor circumferential length πR. Y-axis of the graph is the ratio of the amplitude of the eccentric component E _C of C photosensitive body drive gear 83C to the amplitude of the eccentric component E _M of M photosensitive body drive gear 83M.

The graph F1 depicted in FIG. 15 is an ideal drawn by swinging the transfer portion distance L / photoreceptor circumference πR when the motor input angle α is 10 ° and the idler input angle β is −40 °. The locus of the amplitude ratio Y is shown. When the values of the motor input angle α and the idler input angle β are changed, the relationship between the ideal amplitude ratio Y and the transfer portion distance L / photoreceptor peripheral length πR changes. In either case, the eccentric component E _{M is} always used. The ratio of the amplitude of the eccentric component E _{C to} the amplitude of 1 is 1 and the distance L between the transfer parts / photoreceptor circumferential length πR passes through a natural number. This is so that even if the same gear having the same eccentric component is used as the C photoconductor drive gear 83C and the M photoconductor drive gear 83M, the distance L between the transfer portions is an integral multiple of the photoconductor peripheral length πR. If configured, it means that the specific color shift can be eliminated regardless of the values of the motor input angle α and the idler input angle β. However, such a configuration may cause the distance L between transfer portions to be larger than a value that is an integral multiple of the photoreceptor circumferential length πR due to some restrictions in the printer.

Here, in the graph F1 shown in FIG. 15, the distance L between the transfer portions is larger than a value that is an integral multiple of the photoreceptor circumferential length πR. Specifically, the distance L between the transfer portions / the photoreceptor circumferential length πR = Around 1.1, a point where the ratio of the amplitude of the eccentric component E _{C to} the amplitude of the eccentric component E _M is 1 is passed. In the present embodiment, since the same gear is used as the C photoconductor drive gear 83C and the M photoconductor drive gear 83M, the ratio of the amplitude of the eccentric component E _{C to} the amplitude of the eccentric component E _M is 1. Therefore, in the example of the graph F1, the motor input angle α is set to 10 °, the idler input angle β is set to −40 °, and the transfer portion distance L / photoreceptor circumferential length πR is represented by the Y axis ( as the ratio of the amplitudes of the eccentric components E _C with respect to the amplitude of the eccentric component E _M) is the value of X-axis when the 1, by setting the distance L and the photosensitive member circumference πR between the transfer unit, the photosensitive for C Even if the same gear is used as the body driving gear 83C and the M photoconductor driving gear 83M, the distance L between the transfer portions is set to be larger than a value that is an integral multiple of the circumferential length of the photosensitive body πR, and specific color deviation is eliminated. Can do.

In general, it is not necessary to completely eliminate the specific color shift, and it is sufficient that the specific color shift can be within an allowable range of the required specific color shift amount. The maximum allowable amount of the specific color misregistration amount is assumed to be set to about 10 μm due to the recent demand for higher image quality. Therefore, in the present embodiment, the maximum indicating an ideal absolute value of the amplitude ratio Y value obtained by subtracting 1 from the, 10 [mu] m ratio of a the maximum allowable amount for actual amplitudes of the eccentric components E _M of M photosensitive body drive gear 83M The diameter R of the photoreceptors 1Y, 1M, and 1C, the transfer portion distance L, the motor input angle α, and the idler input angle β are set so as to be less than the allowable amplitude ratio.

Assuming that the real amplitude of the eccentric component E _M of M photosensitive body drive gear 83M is assumed to be 15 [mu] m, the maximum permissible amplitude ratio is approximately 0.7. In this case, the diameter R of the photoreceptors 1Y, 1M, and 1C, the distance L between the transfer portions, the motor input angle α, and the idler input angle β are set so that the ideal amplitude ratio Y is in the range of 0.3 to 1.7. Thus, even if the same gear is used as the C photoconductor drive gear 83C and the M photoconductor drive gear 83M, the distance L between the transfer portions is set to be larger than the integral multiple of the photoconductor peripheral length πR. The specific color misregistration amount can be suppressed to 10 μm or less.

Next, an example of phase adjusting means, which is rotational position adjusting means for adjusting the relative rotational positions (assembly positions) of the photosensitive member driving gears 83Y, 83M, 83C, will be described.
FIG. 16 is an explanatory diagram showing an example of phase adjusting means that can be used in the present embodiment.
In this phase adjusting means, a mark 88 serving as a phase alignment reference is formed on an axial end face of a gear used as the photosensitive member driving gears 83Y, 83M, 83C. The mark 88 is provided at a position that moves around the gear shaft as the photoconductor drive gears 83Y, 83M, and 83C rotate. On the other hand, on the holding member 82a side, the mark 89Y is located at a portion (the closest portion) that faces the mark 88 when the rotational positions of the photoconductor driving gears 83Y, 83M, and 83C are adjusted as described above. , 89M, 89C are formed. Therefore, when assembling these photosensitive member driving gears 83Y, 83M, and 83C, the photosensitive member driving gears 83Y, 83M are simply assembled by adjusting the rotational position so that the mark 88 faces the marks 89Y, 89M, and 89C, respectively. , 83C can be adjusted as described above, and color shifts (including specific color shifts) caused by the eccentricity of the photoreceptor drive gears 83Y, 83M, 83C can be eliminated or reduced.

FIG. 17 is an explanatory diagram showing another example of phase adjusting means that can be used in the present embodiment.
In the phase adjusting means shown in FIG. 16, the positions of the marks 89Y, 89M, and 89C provided on the holding member 82a side are limited, and the marks 89Y, 89M, and 89C are hidden by other parts and visible to the assembly operator. It may be difficult to form the marks 89Y, 89M and 89C.
The phase adjusting means shown in FIG. 17 has three phase alignment reference marks R corresponding to the photosensitive member driving gears 83Y, 83M and 83C on the axial end surfaces of the gears used as the photosensitive member driving gears 83Y, 83M and 83C. , C, L are formed. The marks R, C, and L are adjusted on the mark R on the Y photoconductor drive gear 83Y, the mark C on the M photoconductor drive gear 83M, and the photoconductor drive gear 83C after the rotational position is adjusted. The mark L is formed at a position on the axial end face of the gear that is the same rotational position (for example, the lower position in the drawing in the drawing). Therefore, when assembling these photosensitive member driving gears 83Y, 83M, 83C, the rotational positions of the photosensitive member driving gears 83Y, 83M, 83C are adjusted so that the corresponding marks R, C, L are at the same rotational position. As a result, the rotational positions of the photosensitive member driving gears 83Y, 83M, and 83C can be adjusted as described above, and color shifts (including specific color shifts) caused by the eccentricity of the photosensitive member driving gears 83Y, 83M, and 83C. .) Can be eliminated or reduced.

FIG. 18 is an explanatory diagram showing still another example of the phase adjusting means that can be used in the present embodiment.
In this example, similar to the example shown in FIG. 17, three phases corresponding to the photosensitive member driving gears 83Y, 83M, and 83C are provided on the axial end surfaces of the gears used as the photosensitive member driving gears 83Y, 83M, and 83C. Alignment reference marks R, C, and L are formed. Further, on the holding member 82a side, when the rotational positions of the respective photosensitive member driving gears 83Y, 83M, and 83C are adjusted as described above, portions that are opposed to the corresponding marks R, C, and L (closest to each other). The same marks R, C, and L are respectively formed on the portion). Therefore, when assembling these photosensitive member driving gears 83Y, 83M, 83C, R is associated with the Y photosensitive member driving gear 83Y, C is associated with the M photosensitive member driving gear 83M, and C photosensitive member driving gear 83C is associated with. The rotational positions of the photosensitive member driving gears 83Y, 83M, and 83C can be adjusted as described above only by adjusting the rotational positions so that the Ls are opposed to each other, and the photosensitive member driving gears 83Y, 83M, A color shift (including a specific color shift) due to the eccentricity of 83C can be eliminated or reduced.

  Further, according to this example, when one of the marks R, C, L on the holding member 82a side (for example, the mark of the Y photoconductor driving gear 83Y) is to be moved, as shown in FIG. The mark corresponding to the Y photoconductor driving gear 83Y and the mark corresponding to the C photoconductor driving gear 83C are exchanged. Then, on the holding member 82a side, when the rotational positions of the respective photosensitive member driving gears 83Y, 83M, and 83C are adjusted as described above, portions that face the corresponding marks L, C, and R after the replacement ( The same marks L, C, and R are formed in the closest part. As a result, the mark position on the holding member 82a cannot be changed while the rotational positional relationship of the photoconductor drive gears 83Y, 83M, 83C remains the same as that shown in FIG. That is, the mark position on the holding member 82a side can be freely changed by changing the mark position on the gear side. Therefore, it is possible to arrange the mark without hiding the mark on the gear side or the mark on the holding member 82a side from other parts.

[Modification]
Next, a modification of the driving device for the color photoconductors 1Y, 1M, and 1C in the above embodiment will be described.
FIG. 20 is a schematic diagram showing a relative arrangement relationship of the motor gear 85 and the idler gear 86 with respect to the photoreceptor driving gears 83Y, 83M, and 83C in the present modification.
In this modification, when viewed from the rotation axis direction of the motor gear 85, the motor gear 85 is arranged such that the rotation center of the motor gear 85 is upstream of the first virtual straight line D1 in the rotation direction of the M photoconductor drive gear 83M. Is arranged. Therefore, the angle (motor input angle) α formed between the first virtual straight line D1 and the second virtual straight line D2 ′ connecting the rotation center of the M photoconductor drive gear 83M and the rotation center of the motor gear 85 is As in the embodiment, if the rotation direction of the M photoconductor driving gear 83M (clockwise direction in FIG. 9) is positive, it takes a negative value. The idler input angle β takes a negative value as in the above embodiment. In addition, about another structure, it is the same as the said embodiment.

FIG. 21 is an explanatory diagram showing the phase relationship of the outer peripheral deflection caused by the eccentricity of the photosensitive member driving gear between the two photosensitive member driving gears 83M and 83Y directly connected to the motor gear 85 in the present modification.
Given the time the reference phase of the eccentric component E _M of the photoconductor driving gear 83M of the intermediate transfer belt surface moving direction downstream M photoconductor located side 1M is directed toward the motor gear 85 to the reference, the photosensitive member driving Y gear 83Y may be adjusted to face in a direction in which the reference phase is rotated by X ° which is calculated by further above equation from the rotational position facing the direction of the motor gear 85 (7) of the eccentric component E _Y.

FIG. 22 is an explanatory diagram showing the phase relationship of the eccentric component of the photosensitive member driving gear between the two photosensitive member driving gears 83C and 83M directly connected to the idler gear 86 in the present modification.
As in the above-described embodiment, when the reference phase of the combined eccentric component E _C ′ is directed toward the idler gear 86, the C photoconductor drive gear 83C has the smallest rotational angular velocity. Therefore, as shown in FIG. 23, given in reference to the time when the reference phase of the eccentric component E _M of the photoconductor driving gear 83M of M photoconductor 1M is directed toward the motor gear 85, the photosensitive body driving gear 83C for C If the reference phase of the composite eccentric component E _C ′ is adjusted so that it is directed in the direction rotated in the reverse direction by X ° calculated by the above equation (7) from the rotational position directed in the direction of the idler gear 86, the color Between the photoreceptors 1Y, 1M, and 1C, the toner images having the most contracted shapes or the toner images having the most extended shapes are transferred to the same point on the intermediate transfer belt 8.

FIG. 24 shows the eccentric component E _M of the M photoconductor drive gear 83M and the eccentric component E of the _M photoconductor drive gear 83M transmitted to the C photoconductor drive gear 83C via the idler gear 86 in this modification. It is explanatory drawing which shows the positional relationship with _M '.
In this modification, the rotation angular velocity of the idler gear 86 is slowest, the code E1 direction indicated by _M and a code E2 eccentric component of M photosensitive body drive gear 83M in a direction located in the middle between the direction indicated by _M E _{This is when the M} reference phase is oriented. At this time, the lowest rotational angular velocity of the idler gear 86 means that the linear speed of the C photoconductor drive gear 83C is the slowest. Therefore, at this time, the reference phase of the eccentric component E _M ′ of the _M photoconductor drive gear 83M transmitted to the C photoconductor drive gear 83C via the idler gear 86 is directed toward the idler gear 86.

The rotation angle θ when the rotational angular velocity is slowest of the idler gear 86, as in the embodiment described above, can be expressed by the equation (8), amplitude photoconductor drive C of the eccentric components E _M of M photosensitive body drive gear 83M The amplitude amplification factor Z when transmitted to the gear 83C is also defined by the above equation (9), as in the above embodiment. Further, when the eccentric component E _M of M photosensitive body drive gear 83M is defined by the equation (10), synthesized eccentric component E _{C 'are} on C photosensitive body drive gear 83C, as in the above embodiment, the above formula ( 11), and the eccentric component E _M ′ of the M photoconductor drive gear 83M transmitted from the idler gear 86 to the C photoconductor drive gear 83C is also expressed by the above equation (12) as in the above embodiment. Therefore, also in this modification, when the amplitude (A ² + B ² ) ^1/2 of the eccentric component E _C of the C photoconductor driving gear 83C is other than 1, the combined eccentricity of the C photoconductor driving gear 83C is obtained. The amplitude of the component E _C ′ and the amplitude of the eccentric component E _M of the M photoconductor driving gear 83M cannot be matched. If these amplitudes cannot be matched, the toner images having the most contracted shapes or the toner images having the most extended shapes are intermediately transferred between the color photoconductors 1Y, 1M, and 1C. Even if the image is transferred to the same point on the belt 8, a specific color shift corresponding to the amplitude difference remains.

Also in this modified example, in the configuration using the same gear as each photoconductor driving gear 83Y, 83M, and 83C of the color photoconductors 1Y, 1M, and 1C, by adopting the same configuration as in the above embodiment, each photoconductor drive The specific color shift due to the eccentric components E _Y , E _M , E _C of the gears 83Y, 83M, 83C is eliminated or reduced. Since the motor gear 85 and the idler gear 86 are not normally considered larger than the photosensitive member driving gear, the motor input angle α that can be substantially taken in the present embodiment is in the range of 0 ° to −60 °. The idler input angle β is also in the range of 0 ° to −60 °.

Figure 25 is the structure of this modification, the ideal of the eccentric component E _C of C photosensitive body drive gear 83C which may a specific color shift for real amplitude of the eccentric component E _M of M photosensitive body drive gear 83M theoretically zero 6 is a graph showing a relationship between an ideal amplitude ratio Y indicating an amplitude ratio and the distance L between the transfer parts / photoreceptor circumferential length πR. Y-axis of the graph is the ratio of the amplitude of the eccentric component E _C of C photosensitive body drive gear 83C to the amplitude of the eccentric component E _M of M photosensitive body drive gear 83M.

A graph F2 showing the locus of the ideal amplitude ratio depicted in FIG. 25 is obtained when the motor input angle α is −10 ° and the idler input angle β is −40 °. However, also in this modification, when the values of the motor input angle α and the idler input angle β are changed, the relationship between the ideal amplitude ratio Y and the distance L between the transfer parts / the photoreceptor peripheral length πR changes. However, as described above, changing the value of the motor input angle α and the idler input angle beta, always a proportion of the amplitude of the eccentric component E _C with respect to the amplitude of the eccentric component E _M is 1 and the transfer unit The distance L / photoreceptor circumference πR also passes through a natural number. This is so that even if the same gear having the same eccentric component is used as the C photoconductor drive gear 83C and the M photoconductor drive gear 83M, the distance L between the transfer portions is an integral multiple of the photoconductor peripheral length πR. If configured, it means that the specific color shift can be eliminated regardless of the values of the motor input angle α and the idler input angle β. However, such a configuration may cause the transfer portion distance L to be larger than an integral multiple of the photoreceptor circumferential length πR due to some restrictions in the printer, and is not employed in the present modification.

In the graph F2 shown in FIG. 25, the distance L between the transfer portions is larger than an integral multiple of the photoreceptor circumferential length πR. Specifically, the distance L between the transfer portions / the photoreceptor circumferential length πR = 1.2. Around the point where the ratio of the amplitude of the eccentric component E _{C to} the amplitude of the eccentric component E _M is 1. In this modification, since it uses the same gear as C photosensitive body drive gear 83C and the photosensitive body driving gear 83M for M, the ratio of the amplitude of the eccentric component E _C with respect to the amplitude of the eccentric component E _M is 1. Therefore, according to this modification, the motor input angle α is set to −10 °, the idler input angle β is set to −40 °, and the inter-transfer portion distance L / photoreceptor circumferential length πR is represented by the Y axis ( as the ratio of the amplitudes of the eccentric components E _C with respect to the amplitude of the eccentric component E _M) is the value of X-axis (around 1.2) when the 1, setting the distance L and the photosensitive member circumference πR between the transfer unit Even if the same gear is used as the C photoconductor drive gear 83C and the M photoconductor drive gear 83M, the distance L between the transfer portions is set to be larger than an integral multiple of the photoconductor circumferential length πR. Specific color shift can be eliminated.

Here, as described above, since it is usually not necessary to completely eliminate the specific color shift, in this modification, the absolute value of the value obtained by subtracting 1 from the ideal amplitude ratio Y is the M photoconductor driving gear 83M. so as not to exceed the maximum allowable amplitude ratio indicating a ratio of a the maximum allowable amount for actual amplitudes of the eccentric components E _M 10 [mu] m, the photoreceptor 1Y, 1M, 1C diameter R, the transfer unit distance L, the motor input angle α And the idler input angle β is set. Assuming that the real amplitude of the eccentric component E _M of M photosensitive body drive gear 83M is assumed to be 15 [mu] m, the maximum permissible amplitude ratio is approximately 0.7. In this case, the diameter R of the photoreceptors 1Y, 1M, and 1C, the distance L between the transfer portions, the motor input angle α, and the idler input angle β are set so that the ideal amplitude ratio Y is in the range of 0.3 to 1.7. Thus, even if the same gear is used as the C photoconductor drive gear 83C and the M photoconductor drive gear 83M, the distance L between the transfer portions is set to be larger than the integral multiple of the photoconductor peripheral length πR. The specific color misregistration amount can be suppressed to 10 μm or less.

As described above, the printer according to the present embodiment (including the above-described modification example, the same applies hereinafter) has an intermediate transfer belt in which the photoreceptors 1Y, 1M, 1C, and 1K serving as latent image carriers whose surfaces move around are transferred. Rotation from a motor 81 as a driving source with respect to the photosensitive member driving gears 83Y, 83M, 83C, and 83K as a driven transmission rotating member provided for each photosensitive member. Visible images obtained by developing the latent images on the surfaces of the photoreceptors formed at predetermined latent image formation locations by rotating the surfaces of the photoreceptors 1Y, 1M, 1C, and 1K by transmitting the driving force. This is a so-called tandem type image forming apparatus that obtains a final image by transferring (toner images) onto the intermediate transfer belt 8 so as to overlap each other. This printer is configured such that the distance L between the transfer portions of two photoconductors 1C and 1M having the same diameter R deviates from a value that is an integral multiple of the circumferential length πR of the two photoconductors 1C and 1M. Among the two photoconductors 1C and 1M, a C photoconductor as a first driven transmission rotator provided on a C photoconductor 1C as a first photoconductor located downstream of the intermediate transfer belt surface movement direction. A drive gear 83C and an M photoconductor drive gear 83M as a second driven transmission rotating body provided on the M photoconductor 1M as the second photoconductor located on the upstream side of the intermediate transfer belt surface movement direction. The same gear (rotating body) is used. In this printer, the C photoconductor is driven by the eccentricity of the C photoconductor driving gear 83C and the eccentricity of the M photoconductor driving gear 83M when a specific point on the intermediate transfer belt 8 passes through the transfer portion of the C photoconductor 1C. The phase of the fluctuation component of the rotational angular velocity of the body drive gear 83C is the rotation of the M photoconductor drive gear 83M due to the eccentricity of the M photoconductor drive gear 83M when the specific point passes through the transfer portion of the M photoconductor 1M. The relative rotational positions of the C photoconductor drive gear 83C and the M photoconductor drive gear 83M are set so as to coincide with the phase of the fluctuation component of the angular velocity. Thereby, between the two photoconductors 1C and 1M, the toner images having the most contracted shapes or the toner images having the most extended shapes are transferred to the same point on the intermediate transfer belt 8. It becomes like this. Further, a motor gear 85 as a drive transmission rotator connected to the motor 81 side is directly connected to the M photoconductor drive gear 83M, and an idler gear 86 as a driven rotator that is driven to rotate is connected to a C photoconductor drive gear. By directly connecting to 83C and M photoconductor drive gear 83M, both C photoconductor 1C and M photoconductor 1M are driven by the rotational driving force transmitted from motor gear 85. Therefore, as described above, a specific color shift can occur. Therefore, in this embodiment, when viewed from the rotation axis direction of the idler gear 86, the rotation center of the idler gear 86 connects the rotation center of the C photoconductor drive gear 83C and the rotation center of the M photoconductor drive gear 83M. When the idler gear 86 is arranged so as to be downstream of the first imaginary straight line D1 in the rotation direction of the M photoconductor driving gear 83M, when viewed from the rotation axis direction of the idler gear 86, the first imaginary straight line D1 and , The angles D2 and D2 ′ formed by the second imaginary straight line connecting the rotation center of the M photoconductor drive gear 83M and the rotation center of the motor gear 85 are defined with the rotation direction of the M photoconductor drive gear 83M as positive. The first imaginary straight line D1, the rotation center of the C photoconductor drive gear 83C, and the rotation center of the idler gear 86 are connected to each other when viewed from the rotation axis direction of the idler gear 86. Is defined as β with the rotation direction of the C photoconductor drive gear 83C being positive, the M photoconductor drive gear 83M due to the eccentricity of the M photoconductor drive gear 83M. between the relative actual amplitude of the eccentric component E _M which is the outer peripheral shake, and C photosensitive body drive gear 83C and the C photoconductor 1C due to the eccentricity of the M photosensitive body drive gear 83M and the M photoconductor 1M of When the ideal amplitude ratio Y indicating the ratio of the ideal amplitude of the eccentric component of the C photoconductor drive gear 83C that can theoretically make the relative transfer position shift (specific color shift) generated zero is defined by the above equation (1). , the absolute value of the reference amplitude ratio Y value obtained by subtracting 1 from the maximum allowable indicating a ratio of 10μm which is the maximum allowable amount of the specific color shift for real amplitude of the eccentric component E _M of M photosensitive body drive gear 83M Amplitude ratio or less Sea urchin, the two photoreceptor 1C, the diameter R of 1M, the two photoreceptor 1C, the transfer unit distance L of 1M, the motor input angle α and the idler input angle β is set. As a result, even when the distance L between the transfer portions deviates from a value that is an integral multiple of the photosensitive member circumferential length πR due to some restrictions, between the two photosensitive member driving gears 83C and 83M connected via the idler gear 86. The amount of specific color misregistration that can occur can be reduced to 10 μm or less.
In particular, if the absolute value of the value obtained by subtracting 1 from the ideal amplitude ratio Y is 0.7 or less, even when a gear having a general eccentric amount is used as the photosensitive member driving gears 83C and 83M, the specific value is specified. The amount of color misregistration can be reduced to 10 μm or less.
If the absolute value of the value obtained by subtracting 1 from the ideal amplitude ratio Y is 0.06 or less, the specific color misregistration amount can be greatly reduced, so that higher image quality can be realized. In addition, as a result of greatly reducing the specific color misregistration amount, it is possible to relatively increase the allowable amount of color misregistration due to other color misregistration variation factors, thereby increasing the degree of freedom in designing and the like for the entire apparatus. The effect is obtained.
In this embodiment, the motor gear 85 and the idler gear 86 are integers while the surfaces of the two photoconductors 1C and 1M move from a predetermined latent image forming portion (exposure portion) to the transfer portion to the intermediate transfer belt 8. It is configured to rotate. Thereby, it is possible to prevent the influence of the eccentricity of the motor gear 85 and the idler gear 86 from appearing as color misalignment.
Further, as in the present embodiment, by providing phase adjusting means as rotational position adjusting means for adjusting the relative rotational positions of the C photoconductor drive gear 83C and the M photoconductor drive gear 83M, The adjustment can be facilitated.
In particular, as described above, as the phase adjusting means, the first mark R and the first mark R which move around by the rotation of the gear on the same gear used as the C photoconductor drive gear 83C and the M photoconductor drive gear 83M. 2 marks C are formed, and the first mark R and the second mark C are formed on the first mark R and the M photoconductor on the C photoconductor driving gear 83C after the relative rotational position is adjusted. By forming the second mark C on the drive gear 83M so as to be in the same rotational position, adjustment can be easily performed without being obstructed by other components.
Further, as described above, the first mark R and the first mark R that move around by the rotation of the gear on the same gear used as the C photoconductor drive gear 83C and the M photoconductor drive gear 83M as the phase adjusting means. The second mark C is formed, and the third mark R corresponding to the first mark R and the third mark R are formed on the holding member 82a as a support member for supporting the C photoconductor drive gear 83C and the M photoconductor drive gear 83M. A fourth mark C corresponding to the second mark C is formed, and the first mark R rotates after the relative rotational position is adjusted when the gear is used as the C photoconductor driving gear 83C. The position is formed so as to be closest to the third mark R on the holding member 82a, and the second mark C has a gear used as the M photoconductor driving gear 83M. By forming the rotational position after the relative rotational position is adjusted so as to be the closest position to the fourth mark C on the holding member 82a, the mark on the holding member 82a is marked with a gear mark. Adjustment is possible only by combining the two, and the adjustment becomes easy.

1Y, 1M, 1C, 1K Photoconductor 7 Optical writing unit 8 Intermediate transfer belt 80 Drive device 81 Motor 82a, 82b Holding member 83Y, 83M, 83C, 83K Photoconductor drive gear 85 Motor gear 86 Idler gear 88 Mark 89Y, 89M, 89C Mark R, C, L Mark D1 First imaginary straight line D2, D2 ′ Second imaginary straight line D3 Third imaginary straight line E _Y Eccentric component of Y photoconductor driving gear E _M M Eccentric photoconductor driving gear E _C C Photosensitive member drive gear eccentric component E _C 'Composite eccentric component α Motor input angle β Idler input angle

JP 2003-329090 A JP 2004-117386 A

Claims (7)

Two or more latent image carriers whose surfaces move around are provided along the surface movement direction of the transfer target, and the rotational driving force from the drive source is applied to the driven transmission rotating member provided for each latent image support. By transmitting, the surface of each latent image carrier is circulated, and the visible images obtained by developing the latent images on the surface of each latent image carrier formed at a predetermined latent image formation site are overlapped with each other. In an image forming apparatus that obtains a final image by transferring onto a transfer body,
The distance L between the transfer portions of two latent image carriers having the same diameter R is deviated from a value that is an integral multiple of the circumferential length πR of the two latent image carriers,
Of the two latent image carriers, a first driven transmission rotator provided on the first latent image carrier located on the downstream side in the moving direction of the transferred surface, and an upstream side in the moving direction of the transferred surface. The second driven transmission rotating body provided on the second latent image carrier is composed of the same rotating body,
The eccentricity of the first driven transmission rotator and the eccentricity of the second driven transmission rotator when a specific point on the transferred material passes through the transfer portion of the first latent image carrier. The phase of the fluctuation component of the rotational angular velocity of the first driven transmission rotator and the eccentricity of the second driven transmission rotator when the specific point passes through the transfer portion of the second latent image carrier. The relative rotational positions of the first driven transmission rotating body and the second driven transmission rotating body are such that the phase of the fluctuation component of the rotational angular velocity of the second driven transmission rotating body coincides with each other. Is set,
The drive transmission rotator connected to the drive source side is directly connected to the second driven transmission rotator, and the driven rotator driven by rotation is connected to the first driven transmission rotator and the second driven transmission rotator. By directly connecting to the drive transmission rotator, both the first latent image carrier and the second latent image carrier are driven by the rotational driving force transmitted from the drive transmission rotator,
When viewed from the rotation axis direction of the driven rotor, the rotation center of the driven rotor connects the rotation center of the first driven transmission rotor and the second driven transmission rotor. The driven rotator is arranged so as to be on the downstream side in the rotation direction of the second driven transmission rotator with respect to the first virtual straight line,
When viewed from the rotational axis direction of the driven rotating body, the second virtual line connecting the first virtual straight line, the rotation center of the second driven transmission rotating body, and the rotation center of the driving transmission rotating body. Is defined as α with the rotation direction of the second driven transmission rotator being positive, and when viewed from the rotation axis direction of the driven rotator, The angle formed by the virtual straight line and the third virtual straight line connecting the rotation center of the first driven transmission rotating body and the rotation center of the driven rotating body is the rotation of the first driven transmission rotating body. When the direction is positive and β is defined, the first driven transmission for the actual amplitude of the outer peripheral deflection of the second driven transmission rotating body due to the eccentricity of the second driven transmission rotating body The first latent image carrier and the second latent image carrier due to the eccentricity of the rotor and the second driven transmission rotor An ideal amplitude ratio Y indicating the ratio of the ideal amplitude of the outer peripheral deflection of the first driven transmission rotating body that can theoretically make the relative transfer position deviation generated between the first and second rotating bodies zero is defined by the following equation (1): Then, the absolute value of the value obtained by subtracting 1 from the ideal amplitude ratio Y is a ratio of 10 μm which is the maximum allowable amount of the transfer position deviation with respect to the actual amplitude of the outer peripheral runout of the second driven transmission rotating body. The diameter R of the two latent image carriers, the distance L between the transfer portions of the two latent image carriers, the angle α, and the angle β are set so as to be equal to or less than the maximum allowable amplitude ratio shown. An image forming apparatus.

However, the period of Y is L / πR.
A, B, and C in the above formula (1) are defined by the following formulas (2) to (4), respectively.
A = cos (−X + α−β) −Z × cos (θ + β−180) (2)
B = sin (−X + α−β) −Z × sin (θ + β−180) (3)

X in the above formula (2) and the above formula (3) is defined by the following formula (5), and Z in the above formula (2) and the above formula (3) is defined by the following formula (6). It is what is done.

However, A _M is the eccentric amplitude of the second driven transmission rotating body, θ _M = 180−α, and θ _I = β. The image forming apparatus according to claim 1.
The diameter R of the two latent image carriers, the distance L between the transfer portions of the two latent image carriers, so that the absolute value of the value obtained by subtracting 1 from the ideal amplitude ratio Y is 0.7 or less. An image forming apparatus in which the angle α and the angle β are set. The image forming apparatus according to claim 2.
The diameter R of the two latent image carriers, the distance L between the transfer portions of the two latent image carriers, and the absolute value of the value obtained by subtracting 1 from the ideal amplitude ratio Y is 0.06 or less. An image forming apparatus in which the angle α and the angle β are set. The image forming apparatus according to any one of claims 1 to 3,
While the surfaces of the two latent image carriers are moved from a predetermined latent image forming position to a transfer portion to the transfer target, the drive transmission rotating body and the driven rotating body are rotated an integer number of times. An image forming apparatus characterized by comprising. The image forming apparatus according to any one of claims 1 to 4, wherein:
An image forming apparatus comprising a rotation position adjusting means for adjusting a relative rotation position of the first driven transmission rotating body and the second driven transmission rotating body. The image forming apparatus according to claim 5.
The rotational position adjusting means is formed on the same rotator used as the first driven transmission rotator and the second driven transmission rotator. It consists of 1 mark and 2nd mark,
The first mark and the second mark are the first mark on the first driven transmission rotating body and the second driven transmission rotating body after the relative rotational position is adjusted. An image forming apparatus, wherein the two marks are formed on the same rotating body so that the two marks are at the same rotational position. The image forming apparatus according to claim 5.
The rotational position adjusting means is formed on the same rotator used as the first driven transmission rotator and the second driven transmission rotator. A first mark, a second mark, a third mark corresponding to the first mark, and a third mark formed on a support member that supports the first driven transmission rotating body and the second driven transmission rotating body; It consists of a fourth mark corresponding to the second mark,
In the case where the rotating body is used as the first driven transmission rotating body, the first mark has a rotational position that is most similar to the third mark on the support member after the relative rotational position is adjusted. It is formed on the same rotating body so as to be close to each other,
When the rotating body is used as the second driven transmission rotating body, the rotational position after the relative rotational position is adjusted is the second mark on the fourth mark on the support member. An image forming apparatus, wherein the image forming apparatus is formed on the same rotating body so as to be close to each other.

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