IMAGE FORMING APPARATUS AND NON-TRANSITORY COMPUTER READABLE MEDIUM

An image forming apparatus includes: a first rotating body pair that transports a recording medium; a second rotating body pair that transports the recording medium transported by the first rotating body pair; a first detection unit that detects the recording medium at a first position in a transporting width direction of the recording medium; a second detection unit that detects the recording medium at a second position, the second position being different from the first position in the transporting width direction; and a modification unit that modifies a shape of an image to be formed on the recording medium in accordance with a difference between a detection time during which the recording medium is detected at the first position and a detection time during which the recording medium is detected at the second position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2016-059018 filed on Mar. 23, 2016.

BACKGROUND

Technical Field

The present invention relates to an image forming apparatus, and a non-transitory computer readable medium,

SUMMARY

According to an aspect of the invention, there is provided an image forming apparatus including: a first rotating body pair that transports a recording medium; a second rotating body pair that transports the recording medium transported by the first rotating body pair; a first detection unit that detects the recording medium at a first position in a transporting width direction of the recording medium, the transporting width direction being a direction that is perpendicular to a transporting direction of the recording medium; a second detection unit that detects the recording medium at a second position, the second position being different from the first position in the transporting width direction; and a modification unit that modifies a shape of an image to be formed on the recording medium in accordance with a difference between a detection time during which the recording medium is detected at the first position and a detection time during which the recording medium is detected at the second position.

DETAILED DESCRIPTION

Hereinafter, an image forming apparatus according to exemplary embodiments will be described in detail with reference to the accompanying drawings. A case where a direct transfer type monochromic image forming apparatus is employed as an image forming apparatus according to each of the exemplary embodiments will be described.

First Exemplary Embodiment

As illustrated inFIG. 1, an image forming apparatus10according to the first exemplary embodiment includes a housing12which accommodates components of the image forming apparatus10. A paper feeding unit14is provided on a lower side of the inside of the housing12. In the paper feeding unit14, pieces of paper P which is a recording medium are stacked and accommodated so as to have a shape of a bundle. In the exemplary embodiment, a case where paper P is used as a recording medium will be described. However, the recording medium is not limited to the paper P, and the recording medium may be a film and the like. A pickup roll16is disposed right over an entrance and outlet port of paper P in the paper feeding unit14, The pickup roll16is in pressure contact with an end portion of an upper surface of paper P, and carries the paper P from the paper feeding unit14.

A registration roll pair18is provided over the pickup roll16. The registration roll pair18is used for performing skew correction on paper P. A photoconductor drum20and a transfer roll22are provided over the registration roll pair18. The registration roll pair18is an example of a first rotating body pair and a second rotating body pair.

A cleaning device26, a charging roll24, an exposure device28, and a developing roll30are provided on the outer circumference of the photoconductor drum20, in this order.

The cleaning device26, the charging roll24, the exposure device28, and the developing roll30are provided along an A direction which is a rotation direction of the photoconductor drum20.

The cleaning device26removes a toner remaining on the photoconductor drum20. The charging roll24charges a surface of the photoconductor drum20. The exposure device28includes a laser generation unit28awhich generates a laser beam. The laser generation unit28airradiates the photoconductor drum20which has uniformly charged by the charging roll24, with laser LB, so as to form an electrostatic latent image on the photoconductor drum20. The developing roll30develops the electrostatic latent image which has been formed on the photoconductor drum20, by using a toner, so as to form a toner image on the photoconductor drum20.

The transfer roll22nips paper P between the transfer roll22and the photoconductor drum20, and transfers the toner image which has formed on the photoconductor drum20, to the paper P. The photoconductor drum20and the transfer roll22are an example of the second rotating body pair.

A fixing roll pair32is provided over the photoconductor drum20and the transfer roll22. The fixing roll pair32is used for fixing the toner image which has been transferred, onto the paper P. The fixing roll pair32includes a heat source. The fixing roll pair32presses and heats the paper P to which the toner image has been transferred, and thus fixes the toner image to the paper P. The fixing roll pair32is an example of the first rotating body pair.

A carrying-out roll pair34for carrying the paper P outwardly is provided over the fixing roll pair32.

Next, the entire flow of forming an image on paper P in the image forming apparatus10will be described.

Firstly, paper P is carried out from the paper feeding unit14. The carried-out paper P is transported to the registration roll pair18by plural transport roll pairs. The paper P is subjected to skew correction in a state of being nipped on the registration roll pair18. The paper P is transported upwardly in a state of being nipped on the registration roll pair18. Transporting the paper is temporarily stopped by the registration roll pair18, and then the paper is transported to a transfer position by the transfer roll22at a predetermined timing. The transfer position is positioned between the photoconductor drum20and the transfer roll22. A toner image formed on the photoconductor drum20is transferred to the paper P which has been transported to the transfer position, by the transfer roll22. Thus, a toner image is formed. The paper P on which the toner image has been formed is transported to the fixing roll pair32. The toner image which has been transferred is fixed by the fixing roll pair32, in a state where the paper P is nipped on the fixing roll pair32. The paper which has the fixed toner image is transported to the carrying-out roll pair34. Then, the paper P is output to the outside of the housing12by the carrying-out roll pair34.

Next, a transporting path H of paper P will be described.

A transporting path H which is gently curved upwardly is formed between the entrance and outlet port of the paper feeding unit14and the registration roll pair18. The transporting path H is extended upwardly with passing through the photoconductor drum20, the transfer roll22, the fixing roll pair32, and the carrying-out roll pair34in this order, and the transporting path H is linked to the outside of the housing12. While paper P accommodated in the paper feeding unit14which is disposed on the lower side of the housing12is transported toward an upper part of a vertical direction along the transporting path H, a toner image is formed by the photoconductor drum20and the transfer roll22. After the toner image is fixed by the fixing roll pair32, the paper P is output to the outside of the housing12,

As illustrated inFIGS. 1 and 2, the image forming apparatus10according to the exemplary embodiment includes paper sensors62A and62B between the registration roll pair18and the transfer roll22on the transporting path H. The paper sensors62A and62B detect paper P. As illustrated inFIG. 2, in the exemplary embodiment, the paper sensor62A is provided on one end side (for example, on the left side in the front view (below referred to as “an in-side”)) of a transporting width direction of the transporting path H. The paper sensor62A detects an area of the in-side of the paper P. The paper sensor62B is provided on another end side (for example, on the right side in the front view (below referred to as “an out-side”)) of the transporting width direction of the transporting path H.

The paper sensor62B detects an area of the out-side of the paper P. The paper sensor62A is an example of a first detection unit, and the paper sensor62B is an example of a second detection unit.

A detection time during which paper P is continuously detected by the paper sensor62A corresponds to a transporting period of the in-side of the paper P. A detection time during which the paper P is continuously detected by the paper sensor62B corresponds to a transporting period of the out-side of the paper P. In the exemplary embodiment, parallelism of an image formed on the paper P is corrected based on a difference between the detection time during which the paper P is continuously detected by the paper sensor62A, and the detection time during which the paper P is continuously detected by the paper sensor62B.

The length of the transporting path H from the registration roll pair18to the transfer roll22is configured so as to be less than the length of paper P in a transporting direction B. Thus, the paper P is in a state of being nipped on the transporting path H by both of the photoconductor drum20and the transfer roll22.

The length of the transporting path H from the transfer roll22to the fixing roll pair32is configured so as to be less than the length of paper P in the transporting direction B. Thus, the paper P is in a state of being nipped on the transporting path H by both of the fixing roll pair32and the transfer roll22.

Here, when the image forming apparatus10forms an image on paper P, the paper P is transported along the transporting path11, and is detected by the paper sensors62A and62B during a period from when the paper P passes through the registration roll pair18until the paper P reaches the transfer roll22.

At this time, as illustrated inFIGS. 3 and 4as an example, the paper may be inclined with respect to the transporting direction B due to a difference of a transporting speed of the paper P in the transporting width direction thereof. As illustrated inFIG. 3, in a case where the transporting speed of the out-side is faster than the transporting speed of the in-side, an end portion of the out-side of the paper P is detected prior to an end portion of the in-side, and a detection time of the end portion on the out-side of the paper P is shorter than a detection time of the end portion on the in-side thereof. As illustrated inFIG. 4, in a case where the transporting speed of the in-side is faster than the transporting speed of the out-side, the end portion of the in-side of the paper P is detected prior to the end portion of the out-side thereof, and a detection time of the end portion on the in-side of the paper P is shorter than a detection time of the end portion on the out-side.

Here,FIG. 5illustrates a table which shows a relationship between a detection time difference, the transporting period of paper P, the transporting speed of the paper P, the length of an image to be formed, and parallelism. The detection time difference is obtained by subtracting a detection time by the paper sensor62B (out-side) from a detection time by the paper sensor62A (in-side).

As illustrated inFIG. 5, in a case where the detection time difference is positive, the detection time of the paper P on the in-side is long and the detection time of the paper on the out-side is short. That is, in a case where the detection time difference is positive, the transporting speed of the paper P on the in-side becomes slow, and the transporting speed of the paper P on the out-side becomes fast. Thus, in a case where the detection time difference is positive, the length of the formed image on the in-side becomes short, and the length of the formed image on the out-side becomes long. Accordingly, parallelism is negative.

In a case where the detection time difference is negative, the detection time of the paper P on the in-side is short and the detection time of the paper on the out-side is long. That is, in a case where the detection time difference is negative, the transporting speed of the paper P on the in-side becomes fast, and the transporting speed of the paper P on the out-side becomes slow. Thus, in a case where the detection time difference is negative, the length of the formed image on the in-side becomes long, and the length of the formed image on the out-side becomes short. Accordingly, parallelism is positive.

Next, an electrical configuration of the image forming apparatus10according to the exemplary embodiment will be described.

As illustrated inFIG. 6, the image forming apparatus10according to the exemplary embodiment includes a central processing unit (CPU)50, and a read only memory (ROM)52. The CPU50performs various types of processing which includes adjustment processing (will be described later). The ROM52stores a program and various types of information which are used for processing of the CPU50. The image forming apparatus10includes a random access memory (RAM)54, and a memory56such as a nonvolatile memory. The RAM54temporarily stores various types of data, as a work area of the CPU50. The memory56stores various types of information which are used for processing of the CPU50. The image forming apparatus10includes a communication line I/F unit58which inputs and outputs data from and to an external device. The CPU50is connected to the communication-line I/F unit58. The image forming apparatus10includes an operation display60which displays various types of information, and inputs information based on a user operation. The CPU50is connected to the operation display60.

The CPU50is connected to the paper sensors62A and62B which have been described above. If the paper sensors62A and62B detect paper P, each of the paper sensors62A and62B outputs a detection signal which indicates that the paper P is detected, to the CPU50.

The image forming apparatus10includes a first driving unit64. The first driving unit64drives a mechanism which includes a cam and a motor for changing an angle (simply referred to as “an angle” below) of the registration roll pair18of paper P with respect to the transfer roll22in a transporting surface of the paper P. The CPU50is connected to the first driving unit64. The image forming apparatus10includes a second driving unit66. The second driving unit66drives a mechanism which includes a cam and a motor for changing an angle of the fixing roll pair32with respect to the transfer roll22. The CPU50is connected to the second driving unit66. The first driving unit64and the second driving unit66are controlled by the CPU50.

Next, a flow of processing when the CPU50of the image forming apparatus10according to the exemplary embodiment performs adjustment processing will be described with reference to a flowchart illustrated inFIG. 7. In the exemplary embodiment, a program of the adjustment processing is stored in the memory56in advance. However, it is not limited thereto. For example, the program of the adjustment processing may be received from an external device through the communication line I/F unit58, and be stored in the memory56. The program of the adjustment processing which has been recorded in a recording medium such as a CD-ROM may be read by a CD-ROM drive, and thus the adjustment processing may be performed.

In Step S101, the CPU50acquires a detection time of the paper P on the in-side, which has been detected by the paper sensor62A.

In Step S103, the CPU50acquires a detection time of the paper P on the out-side, which has been detected by the paper sensor62B.

In Step S105, the CPU50calculates a difference between the detection times of the in-side and the out-side.

In Step S107, the CPU50determines whether or not the difference of the detection time is equal to or more than a predetermined threshold value. Here, the threshold value is set to be an upper limit value of the difference, so that a distortion amount of an image is in an allowable range. The threshold value is set to have a value which is obtained in advance by a test and the like.

In Step S107, in a case where it is determined that the difference of the detection time is equal to or more than the predetermined threshold value (S107, YES), the process proceeds to Step S109. In Step S107, in a case where it is determined that the difference of the detection time is less than the predetermined threshold value (S107, NO), execution of the program of the adjustment processing is ended.

In Step S109, the CPU50determines whether or not the detection time on the in-side is long. As described above, in a case where the detection time on the in-side is long, the in-side of an image formed on paper P is shorter than the out-side thereof. In a case where the detection time on the out-side is long, the out-side of an image formed on paper P is shorter than the in-side thereof.

In Step S109, in a case where it is determined that the detection time on the in-side is long (S109, YES), the process proceeds to Step S111. In Step S109, in a case where it is determined that the detection time on the out-side is long (S109, NO), the process proceeds to Step S113.

In Step S111, the CPU50changes a positional relationship between the fixing roll pair32and the transfer roll22, so that a distance of the fixing roll pair32of the in-side from the transfer roll22becomes far. Then, execution of the program of the adjustment processing is ended.

In the exemplary embodiment, as illustrated inFIG. 8, as an example, an angle of the fixing roll pair32with respect to the transfer roll22is changed, and thus adjustment is performed so that a distance on the in-side between the registration roll pair18and the fixing roll pair32in the transporting width direction is increased. At this time, the angle of the fixing roll pair32with respect to the transfer roll22is changed so as to remove the difference between the detection time on the in-side and the detection time on the out-side.

That is, the distance on the in-side between the transfer roIl22and the fixing roll pair32in the transporting width direction is increased, and thus the in-side of paper P is stretched by the fixing roll pair32, and is transitioned to the out-side. Thus, the in-side of the formed image becomes long.

In Step S113, the CPU50changes the positional relationship between the fixing roll pair32and the transfer roll22, so that the distance of the fixing roll pair32on the in-side from the transfer roll22becomes far. Then, execution of the program of the adjustment processing is ended.

In the exemplary embodiment, as illustrated inFIG. 9, as an example, an angle of the fixing roll pair32with respect to the transfer roll22is changed, and thus adjustment is performed so that a distance on the in-side between the transfer roll22and the fixing roll pair32in the transporting width direction is increased. At this time, the angle of the fixing roll pair32with respect to the transfer roll22is changed so as to remove the difference between the detection time on the in-side and the detection time on the out-side.

That is, the distance on the in-side between the transfer roll22and the fixing roll pair32in the transporting width direction is increased, and thus the out-side of paper P is stretched to the fixing roll pair32, and is transitioned to the in-side. Thus, the out-side of the formed image becomes long.

FIG. 10illustrates an example of parallelism of an image to be formed in a case where at least one of the distance on the in-side between the registration roll pair18and the fixing roll pair32, and the distance on the out-side between the registration roll pair18and the fixing roll pair32is changed. As illustrated inFIG. 10, the followings are understood. In a case where the distance on the in-side is equal to the distance on the out-side (Case A), parallelism is set to be −0.7. In this case, in a case where an angle of the fixing roll pair32with respect to the registration roll pair18is changed so that the distance of the inside is longer than the distance on the out-side by 0.6 mm (Case B), the parallelism is −1.1, that is, the parallelism is decreased. In a case where the angle of the fixing roll pair32with respect to the registration roll pair18is changed so that the distance on the in-side is shorter than the distance on the out-side by 0.6 mm (Case C), the parallelism is 0.4, that is, the parallelism is increased.

In the exemplary embodiment, a case where the angle of the fixing roll pair32with respect to the transfer roll22is adjusted is described. However, the target of the adjusting is not limited thereto. As illustrated inFIG. 11as an example, instead of the angle of the fixing roll pair32with respect to the transfer roll22, an angle of the registration roll pair18with respect to the transfer roll22may be adjusted. As illustrated inFIG. 11, in a case where the distance of the registration roll pair18from the transfer roll22on the out-side becomes far, the distance on the out-side between the registration roll pair18and the transfer roll22in the transporting width direction of the out-side becomes long. Thus, the out-side of paper P is stretched to the transfer roll22, and is transitioned to the in-side. Accordingly, the out-side of an image to be formed becomes long. In a case where the distance of the registration roll pair IS from the transfer roll22on the inside becomes far, the distance on the in-side between the registration roll pair18and the transfer roll22in the transporting width direction of the in-side becomes long. Thus, the in-side of paper P is stretched to the transfer roll22, and is transitioned to the out-side. Accordingly, the in-side of an image to be formed becomes long.

As illustrated inFIG. 12as an example, both of the angle of the fixing roll pair32with respect to the transfer roll22, and the angle of the registration roll pair18with respect to the transfer roll22may be changed, and the relative angle between the fixing roll pair32and the transfer roll22may be adjusted.

Second Exemplary Embodiment

Next, an image forming apparatus according to a second exemplary embodiment will be described.

In the first exemplary embodiment, a case where the angle of the fixing roll pair32with respect to the transfer roll22is adjusted in accordance with the detection time difference which is obtained by subtracting the detection time by the paper sensor62B from the detection time by the paper sensor62A is described. However, in the second exemplary embodiment, a case where the detection time difference obtained by subtracting the detection time by the paper sensor62B from the detection time by the paper sensor62A is suggested, and the angle of the fixing roll pair32with respect to the transfer roll22is adjusted by a user will be described.

Since other components of the image forming apparatus according to the second exemplary embodiment are the same as those of the image forming apparatus10according to the first exemplary embodiment, descriptions of the same components will be omitted.

Next, a flow of processing when the CPU50of the image forming apparatus10according to the exemplary embodiment performs adjustment processing will be described with reference to a flowchart illustrated inFIG. 13. In the exemplary embodiment, a program of the adjustment processing is stored in the memory56in advance. However, it is not limited thereto. For example, the program of the adjustment processing may be received from an external device through the communication line I/F unit58, and be stored in the memory56. The program of the adjustment processing which has been recorded in a recording medium such as a CD-ROM may be read by a CD-ROM drive, and thus the adjustment processing maF be performed.

In Step S201, the CPU50acquires a detection time of the paper P on the in-side, which has been detected by the paper sensor62A.

In Step S203, the CPU50acquires a detection time of the paper P on the out-side, which has been detected by the paper sensor62B.

In Step S205, the CPU50calculates a difference between the detection times of the in-side and the out-side.

In Step S207, the CPU50displays the calculated difference between the detection times of the in-side and the out-side, or an adjustment amount depending on the difference, in the operation display60.

Then, the CPU50ends execution of the program of the adjustment processing. A user confirms the difference between the detection times of the in-side and the out-side, or the adjustment amount depending on the difference and manually adjusts the angle of the fixing roll pair32with respect to the transfer roll22based on the adjustment amount depending on the difference.

Third Exemplary Embodiment

Next, an image forming apparatus according to a third exemplary embodiment will be described.

In the first exemplary embodiment, the case where the angle of the fixing roll pair32with respect to the transfer roll22is adjusted in accordance with the detection time difference which is obtained by subtracting the detection time by the paper sensor62B from the detection time by the paper sensor62A is described. However, in the third exemplary embodiment, a case where a correction coefficient for correcting an image to be formed is adjusted in accordance with the detection time difference which is obtained by subtracting the detection time by the paper sensor62B from the detection time by the paper sensor62A will be described.

Since other components of the image forming apparatus according to the third exemplary embodiment are the same as those of the image forming apparatus10according to the first exemplary embodiment, descriptions of the same components will be omitted.

In the exemplary embodiment, the correction coefficient for correcting an image to be formed has been stored in the memory56in advance. When the image forming apparatus10forms an image, a shape of an image to be formed is corrected by using the correction coefficient which is stored in the memory56. The correction coefficient is a correction coefficient for correcting the shape of an image to be formed so that the length of the shape of an image to be formed on one side of which the detection time is long becomes short.

The correction coefficient is used when the correction is performed considering a point that the length of paper P on one side of which the detection time is long among the inside and the out-side of the paper P is short in the image to be formed.

Next, a flow of processing when the CPU50of the image forming apparatus10according to the exemplary embodiment performs adjustment processing will be described with reference to a flowchart illustrated inFIG. 14. In the exemplary embodiment, a program of the adjustment processing is stored in the memory56in advance. However, it is not limited thereto. For example, the program of the adjustment processing may be received from an external device through the communication line I/F unit58, and be stored in the memory56. The program of the adjustment processing which has been recorded in a non-transitory recording medium such as a CD-ROM may be read by a CD-ROM drive, and thus the adjustment processing may be performed.

In Step S301, the CPU50acquires a detection time of the paper P on the in-side, which has been detected by the paper sensor62A.

In Step S303, the CPU50acquires a detection time of the paper P on the out-side, which has been detected by the paper sensor62B.

In Step S305, the CPU50calculates a difference between the detection times of the in-side and the out-side.

In Step S307, the CPU50calculates a correction coefficient for correcting an image to be formed, through image processing.

The CPU50stores the calculated correction coefficient in the memory56, and ends execution of the program of the adjustment processing. Regarding an image formed on paper P, parallelism is corrected based on the correction coefficient which is stored in the memory56.

In the first exemplary embodiment to the third exemplary embodiment, a case where the paper sensors62A and62B are provided between the registration roll pair18and the transfer roll22is described.

However, it is not limited thereto. It is preferable that detection by the paper sensors62A and62B is performed before a toner image is transferred to paper P.

However, the paper sensors62A and62B may be provided at any position on the transporting path H on which paper P is transported.

In the first exemplary embodiment to the third exemplary embodiment, correction of parallelism which is performed, for example, by adjusting the angle of the fixing roll pair32with respect to the transfer roll22may be applied from paper P of which parallelism has been measured, or may be applied from paper P which is the next to the paper P of which parallelism has been measured.

In the first exemplary embodiment to the third exemplary embodiment, a case where a direct transfer type monochromic image forming apparatus is employed as the image forming apparatus is described.

However, it is not limited thereto. For example, a tandem type color image forming apparatus in which a toner image of each color is primarily transferred to the photoconductor body may be employed as the image forming apparatus.