JP6809295B2 - Image forming device and program - Google Patents

Description

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

Conventionally, an electrostatic latent image formed on a photoconductor is developed with toner to form a toner image, the formed toner image is transferred to paper by a transfer roller, and the transferred toner image is sandwiched and conveyed by a fixing roller. There is known an electrophotographic image forming apparatus that forms an image on paper by heating and fixing.

In such an image forming apparatus, image defects such as color shift and shock noise may occur due to a difference in transfer speed between the transfer roller and the fixing roller. Even if the transfer roller and the fixing roller are set to transfer paper at the same speed, the transfer speed of the fixing roller actually deviates from the set value. When the paper is sandwiched and conveyed by both the fixing roller and the transfer roller, if the rotation speed of the fixing roller becomes faster than the rotation speed of the transfer roller, the paper is pulled between the two and the transfer shift occurs. appear.
In addition, a post-processing device may be provided on the downstream side of the image forming apparatus in the paper transport direction, but the transport roller of the post-processing device is generally set to transport paper at the same speed as the transfer transport speed. Is the target. Therefore, if the above-mentioned pulling of the paper occurs between the fixing roller and the transport roller of the aftertreatment device, roller marks or the like may be generated on the paper.

In order to deal with such a problem, a technique for changing the paper transport speed by the fixing roller is disclosed. For example, the image forming apparatus described in Patent Document 1 causes a paper loop to be formed between the fixing roller by making the conveying speed of the fixing roller slower than the conveying speed of the transfer roller. Then, the loop amount is detected by a loop detection sensor composed of an actuator arranged on the transfer path between the transfer roller and the fixing roller, and when the loop amount exceeds a predetermined loop amount, the transfer speed of the fixing roller is increased. It suppresses excessive loosening of the paper.
However, although the loop detection sensor is arranged so as to detect one point in the width direction of the paper, the loop detection sensor may not detect even if the paper is loose. Ideally, the transfer roller and the fixing roller should be aligned in parallel, but in reality they will be misaligned, and depending on the paper type, the paper will not loosen evenly and only a part of it will be misaligned. This is probably because it loosens and does not come into contact with the loop detection sensor well.

Therefore, in the image forming apparatus described in Patent Document 2, the transfer transfer speed and the fixing transfer speed are detected without using a loop detection sensor such as an actuator. That is, the passage of the paper is detected by using the registration sensor arranged near the transfer roller, and the transfer transfer speed is calculated based on the detection time and the length of the paper in the transport direction. Further, the paper discharge sensor arranged downstream of the fixing roller is used to detect the passage of the paper, and the fixing transfer speed is calculated in the same manner.
The loop amount is calculated based on these speed differences, and the fixing transfer speed is controlled so that the loop amount becomes appropriate.

Japanese Unexamined Patent Publication No. 10-97154 Japanese Unexamined Patent Publication No. 2011-237656

However, in the configuration described in Patent Document 2, since there is no measurement data of the transfer transfer speed and the fixing transfer speed for the first sheet, it is not possible to control the loop amount to an appropriate level. Therefore, there is a demand for an image forming apparatus capable of controlling the loop amount for all sheets of paper.
On the other hand, in order to prevent the paper from being pulled between the fixing roller and the transport roller of the post-processing device, when the paper reaches the post-processing device, the fixing transfer speed should be the same as the paper transport speed of the post-processing device. Need to be controlled.

The present invention has been made in view of the above problems, and controls an appropriate loop amount for all papers including the first sheet, and controls the amount of the paper between the fixing roller and the other rollers. It is an object of the present invention to provide an image forming apparatus and a program capable of suppressing tension.

In order to achieve the above object, the image forming apparatus according to claim 1 is
A transfer roller that forms a toner image on paper,
A fixing roller that heats and fixes the toner image formed on the paper,
A first detecting means for detecting the passage of the leading edge of the paper at the first position on the upstream side of the transfer roller in the paper transport direction.
A second detecting means for detecting the passage of the leading edge of the paper at a second position on the downstream side of the fixing roller in the paper transport direction,
A speed control means for controlling the paper transport speed by the transfer roller and the fixing roller, and
When the paper is transported by the speed control means with the paper transport speed of the transfer roller as the first speed and the paper transport speed of the fixing roller as the second speed slower than the first speed, A first calculation means for calculating the first time required from the detection of the tip by the first detection means to the detection by the second detection means, and
The transfer roller at the time when the tip of the paper is detected by the second detecting means based on the first time, the transport distance between the first position and the second position, and the first speed. And a second calculation means for calculating the amount of slack in the paper between the fixing rollers, and
A third calculation means for calculating the second time required for the slack amount to reach a predetermined slack amount after the tip of the paper is detected by the second detection means based on the slack amount is provided.
The speed control means is characterized in that the paper transport speed by the fixing roller is changed to the first speed after the lapse of the second time after the tip of the paper is detected by the second detection means.

The invention according to claim 2 is the image forming apparatus according to claim 1.
The second calculation means is characterized in that the amount of slack is calculated from the following formula (1).
A = V1 * T1-D1 ... (1)
However,
A: The amount of slack [mm]
V1: The first speed [mm / s]
T1: The first time [s]
D1: Distance [mm] between the first detection means and the second detection means
Is.

The invention according to claim 3 is the image forming apparatus according to claim 2.
The third calculation means is characterized in that the second time is calculated from the following formula (2).
T2 = (Aref-A) / (V1-V2) ... (2)
However,
T2: The second time [s]
Aref: The predetermined amount of slack [mm]
V2: The second speed [mm / s]
Is.

The invention according to claim 4 is the image forming apparatus according to any one of claims 1 to 3.
The speed control means is characterized in that the paper transport speed of the fixing roller is changed to the first speed after the lapse of the second time.

The invention according to claim 5 is the image forming apparatus according to any one of claims 1 to 3.
A transport roller arranged on the downstream side of the fixing roller in the paper transport direction,
A fourth calculation means for calculating the third time required from the tip of the paper reaching the fixing roller to reaching the transport roller.
A fifth calculation means for calculating the fourth time required from when the front end of the paper reaches the fixing roller to when the rear end of the paper passes through the transfer roller is provided.
When the second time is longer than the third time and the third time is longer than the fourth time, the speed control means has the paper transport speed of the fixing roller after the lapse of the fourth time. Is changed to the first speed.

The invention according to claim 6 is the image forming apparatus according to any one of claims 1 to 3.
A transport roller arranged on the downstream side of the fixing roller in the paper transport direction,
A fourth calculation means for calculating the third time required from the tip of the paper reaching the fixing roller to the transfer roller is provided.
When the second time is longer than the third time, the speed control means changes the paper transport speed of the fixing roller to a third speed slower than the second speed, and the second time After the lapse of time, the paper transport speed of the fixing roller is changed to the first speed.

The invention according to claim 7 is the image forming apparatus according to claim 5 or 6.
The fourth calculation means is characterized in that the third time is calculated from the following formula (3).
T3 = D2 / V2 ... (3)
However,
T3: The third time [s]
D2: Distance [mm] between the fixing roller and the conveying roller
Is.

The invention according to claim 8 is the image forming apparatus according to claim 5.
The fifth calculation means is characterized in that the fourth time is calculated from the following formula (4).
T4 = (S-D3) / V1 ... (4)
However,
T4: The fourth hour [s]
S: Paper transport direction length [mm]
D3: Distance [mm] between the transfer roller and the fixing roller
Is.

The invention according to claim 9 is the image forming apparatus according to any one of claims 1 to 8.
The speed control means is characterized in that at least one of the predetermined slack amount, the first speed, and the second speed is corrected according to the paper length, the paper type, and the weight of the paper.

The program according to claim 10
The passage of the tip of the paper is detected at the transfer roller that forms the toner image on the paper, the fixing roller that heats and fixes the toner image formed on the paper, and the first position on the upstream side of the transfer roller in the paper transport direction. A computer of an image forming apparatus including a first detecting means and a second detecting means for detecting the passage of the tip of the paper at a second position on the downstream side in the paper transport direction of the fixing roller.
A speed control means for controlling the paper transport speed by the transfer roller and the fixing roller,
When the paper is transported by the speed control means with the paper transport speed of the transfer roller as the first speed and the paper transport speed of the fixing roller as the second speed slower than the first speed, A first calculation means for calculating a first time required from the time when the tip is detected by the first detection means until the tip is detected by the second detection means.
The transfer roller at the time when the tip of the paper is detected by the second detecting means based on the first time, the transport distance between the first position and the second position, and the first speed. And a second calculation means for calculating the amount of slack in the paper between the fixing rollers,
A third calculation means for calculating a second time required for the amount of slack to reach a predetermined amount of slack after the tip of the paper is detected by the second detection means based on the amount of slack.
To function as.

According to the present invention, an image forming apparatus capable of controlling an appropriate loop amount for all sheets including the first sheet and suppressing the tension of the sheets between the fixing roller and the other rollers. And programs can be provided.

It is a figure which shows the schematic structure of the image forming apparatus which concerns on this invention. It is a block diagram which shows the functional structure of an image forming apparatus. It is a figure explaining the loop amount control method of a paper. It is a flowchart which shows the fixing transfer speed control in 1st Embodiment. It is a flowchart which shows the fixing transfer speed control in 2nd Embodiment. It is a figure which shows an example of the correction value of the paper transport speed based on a paper type and a weight. It is a figure which shows an example of the image quality adjustment screen of a long paper.

[First Embodiment]
First, a first embodiment of the image forming apparatus according to the present invention will be described. In the embodiment of the present invention, a color image forming apparatus will be described as an example, but the present invention is not limited to this, and can be applied to, for example, a monochrome image forming apparatus.

FIG. 1 is a schematic configuration diagram of an image forming apparatus 100.
The image forming apparatus 100 is an image forming apparatus that forms a color image by an electrophotographic method based on the image data obtained by reading an image from a document or the image data received from an external device.
The image forming apparatus 100 includes an operation unit 15, a display unit 20, a document reading unit 30, an image forming unit 40, a paper feeding unit 50, a post-processing unit 60, a conveying unit 70, and the like.

The operation unit 15 includes a touch panel formed so as to cover the display screen of the display unit 20, various operation buttons such as a number button and a start button, and controls an operation signal based on the user's operation with the control unit 81 (see FIG. 2). ) Is output.

The display unit 20 is composed of an LCD (Liquid Crystal Display), and displays various screens according to an instruction of a display signal input from the control unit 81.

The document reading unit 30 includes an ADF (automatic document feeding device), a scanner, and the like, and outputs the image data obtained by scanning the image of the document to the control unit 81.

The image forming unit 40 forms an image on the paper supplied from the paper feeding unit 50.
The image forming unit 40 includes photoconductor drums 41Y, 41M, 41C, 41K, intermediate transfer belts 42, and secondary transfer rollers corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (K). 43, a fixing portion 44, a reversing mechanism 45, and the like are provided.

The photoconductor drum 41Y is uniformly charged and then scanned and exposed by a laser beam based on the yellow image data to form an electrostatic latent image. Then, yellow toner is adhered to the electrostatic latent image on the photoconductor drum 41Y, and development is performed.
The photoconductor drums 41M, 41C, and 41K are the same as the photoconductor drum 41Y except that the colors to be handled are different, and thus the description thereof will be omitted.

The toner images of each color formed on the photoconductor drums 41Y, 41M, 41C, and 41K are sequentially transferred onto the rotating intermediate transfer belt 42 (primary transfer). That is, a color toner image in which four color toner images are superimposed is formed on the intermediate transfer belt 42.
The color toner image on the intermediate transfer belt 42 is collectively transferred onto the paper by the secondary transfer roller 43 (secondary transfer).

The fixing unit 44 includes a fixing roller 441 that heats and pressurizes the paper on which the color toner image is transferred, and fixes the color toner image on the paper by heating and pressing.

The image forming unit 40 includes a reversing mechanism 45 that reverses the front and back sides of the paper that has been fixed by the fixing unit 44 and conveys the paper to the secondary transfer roller 43. In the image forming apparatus 100, when an image is formed on both sides of the paper, the front and back sides of the paper are inverted by the reversing mechanism 45 to form an image on both sides, and then the paper is conveyed to the post-processing unit 60. When the image is formed on only one side of the paper, the paper on which the image is formed on one side is conveyed to the post-processing unit 60 without the front and back sides of the paper being reversed by the reversing mechanism 45.

The paper feed unit 50 includes paper feed trays t1 to t3, and supplies paper to the image forming unit 40. Paper types and sizes predetermined for each paper feed tray are stored in the paper feed trays t1 to t3.

The post-processing unit 60 discharges the paper on which the image is formed by the image forming unit 40 to the output trays t11 and t12, or stores the paper in the large-capacity stacker 61. If necessary, another post-processing device that performs post-processing such as sorting processing, staple processing, punching hole processing, folding processing, and bookbinding processing may be connected.

The transport unit 70 is provided with a plurality of paper transport rollers for transporting paper by rotating while sandwiching the paper, and supplies the paper stored in the paper feed trays t1 to t3 of the paper feed unit 50 to the image forming unit 40. The paper is conveyed in the image forming apparatus 100 until the image-formed paper is conveyed to the output trays t11, t12 or the large-capacity stacker 61.

On the paper transport path of the post-processing unit 60, a carry-in roller 72 for carrying the paper into the post-processing unit 60 and a drive motor (not shown) are arranged, whereby the image-formed paper is conveyed to the post-processing unit 60. Will be done.
The drive motor adjusts the rotational drive speed of the carry-in roller 72 by rotationally driving the carry-in roller 72 according to the instruction of the control unit 81.

Further, the transport unit 70 includes a resist roller 71 and a first sensor SE1 upstream of the secondary transfer roller.
Before the paper is conveyed to the secondary transfer roller 43, the image forming apparatus 100 temporarily stops the transfer of the paper when the tip of the paper hits the resist roller 71, and starts the transfer again (hereinafter, the registration start). Notation).
The first sensor SE1 (first detecting means) is provided in the vicinity of the resist roller 71 (first position), detects the presence or absence of paper in the resist roller 71, and outputs it to the control unit 81. As a result, the control unit 81 can detect the time when the tip of the paper has passed through the resist roller 71. The first sensor SE1 includes, for example, a light emitting element such as a light emitting diode (LED: Light Emitting Diode) and a light receiving element such as a photodiode (PD: Photodiode), and is composed of a reflective light sensor that detects the reflected light of the paper. Will be done.

Further, a second sensor SE2 (second detection means) capable of detecting the passage of the leading edge of the paper is arranged downstream of the fixing roller 441 (second position). The second sensor SE2 detects the presence or absence of paper in the second sensor SE2 and outputs it to the control unit 81. As a result, the control unit 81 can detect the time when the tip of the paper has passed through the second sensor SE2. The second sensor SE2 may use an existing sensor for the image forming apparatus 100 such as a JAM detection sensor, or may be composed of a reflective light sensor that detects the reflected light of the paper. In this embodiment, a JAM detection sensor is used as the second sensor SE2.

FIG. 2 is a block diagram showing a functional configuration of the image forming apparatus 100.
As shown in FIG. 2, the image forming apparatus 100 includes an operation unit 15, a display unit 20, a document reading unit 30, an image forming unit 40, a paper feeding unit 50, a post-processing unit 60, a conveying unit 70, a control unit 81, and a storage unit. A unit 82, a communication unit 83, and the like are provided. The functional parts already described will be omitted.

The control unit 81 is composed of a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The CPU reads various processing programs stored in the ROM in response to an operation signal input from the operation unit 15 or an instruction signal received by the communication unit 83, expands the RAM, and images according to the expanded program. The operation of each part of the forming device 100 is centrally controlled.

The storage unit 82 is composed of storage means such as a DRAM (Dynamic Random Access Memory) and an HDD (Hard Disk Drive), which are semiconductor memories, and is external via the image data acquired by the document reading unit 30 and the communication unit 83. The image data and the like input from are stored.

The communication unit 83 transmits / receives data to / from an external device connected to a communication network such as a LAN (Local Area Network).

Next, a method of controlling the paper transport speed of the image forming apparatus 100 in the first embodiment will be described. In the first embodiment, the paper to be conveyed is shorter than the distance from the secondary transfer roller 43 to the carry-in roller 72.

FIG. 3 shows a schematic configuration of the image forming unit 40.
The paper P is conveyed in the direction a in the drawing, but at the time of image formation, the paper transfer speed of the fixing roller 441 (hereinafter referred to as the fixing transfer speed) is the paper transfer speed of the secondary transfer roller 43 (hereinafter, transfer). (Notation as transport speed) It is set to V2 [mm / s] (second speed), which is slower than V1 [mm / s] (first speed). By doing so, a loop based on the transfer speed difference is formed between the two.

When the tip of the paper P hits the resist roller 71, the control unit 81 temporarily stops the transport of the paper P and starts the resist. The first sensor SE1 detects the passage of the resist roller 71 at the tip of the paper P at the start of the resist.
A second sensor SE2 capable of detecting the passage of the tip of the paper P is arranged downstream of the fixing roller 441, and when the paper P passes through the fixing roller 441, the second sensor SE2 passes through the tip of the paper P. To detect.

Based on the passing time difference of the tip of the paper P detected by the first sensor SE1 and the second sensor SE2, the control unit 81 passes through the second sensor SE2 after the tip of the paper P passes through the first sensor SE1. The time required to complete T1 [s] (first time) is calculated.
Here, assuming that the distance from the first sensor SE1 to the second sensor SE2 is D [mm], originally D = V1 * T1.
However, in this embodiment, the fixing transfer speed is V2 (second speed), which is slower than the transfer transfer speed V1 (first speed).
D <V1 * T1
Will be.

Therefore, assuming that the loop amount (slack amount) formed between the secondary transfer roller 43 and the fixing roller 441 is A [mm], A can be obtained from the following formula (1).
A = V1 * T1-D ... (1)
Here, there is an appropriate range for the loop amount A of the paper P. If the loop amount A is too small, the paper P may be pulled between the secondary transfer roller 43 and the fixing roller 441, resulting in transfer misalignment. On the contrary, if the loop amount A is too large, the unfixed toner on the paper P may come into contact with the sheet metal in the image forming apparatus 100 to cause toner rubbing. Therefore, an appropriate loop amount (predetermined slack amount) Aref [mm] is set, and the transfer transfer speed and the fixing transfer rate are controlled so that the loop amount becomes the predetermined loop amount Aref.

Based on the difference in paper transport speed, the control unit 81 takes T2 [s] (second time) from when the tip of the paper P reaches the fixing roller 441 until the loop amount A grows to a predetermined loop amount Aref. ) Is calculated using the following formula (2).
T2 = (Aref-A) / (V1-V2) ... (2)
After the elapse of T2, the control unit 81 changes the fixing transfer speed to V1. As a result, the paper can be conveyed while the loop amount A does not exceed the predetermined loop amount Aref and the loop amount close to the predetermined loop amount Aref is maintained.

Here, the carry-in roller 72 provided in the post-processing unit 60 is rotated at a paper transport speed V1 by a drive motor.
The time T3 [s] (third time) required for the tip of the paper P to reach the carry-in roller 72 after the tip of the paper P reaches the fixing roller 441 is calculated using the following formula (3). To do.
T3 = D2 / V2 ... (3)
D2 [mm] is the distance from the fixing roller 441 to the carry-in roller 72. If the tip of the paper reaches the carry-in roller 72 before the fixing transfer speed is changed to V1, that is, if T2 is larger than T3, the paper is pulled between the fixing roller 441 and the carry-in roller 72. Therefore, it is necessary to change the fixing and conveying speed to V1 before the tip of the paper P reaches the carry-in roller 72.

Here, if the rear end of the paper P has passed through the secondary transfer roller 43, there is no possibility that the paper P will be pulled between the secondary transfer roller 43 and the fixing roller 441.
Therefore, when T2 is larger than T3, the time from when the front end of the paper P reaches the fixing roller 441 until the rear end of the paper P passes through the secondary transfer roller 43 is T4 [s] (fourth). Time) is calculated using the following formula (4).
T4 = (S-D3) / V1 ... (4)
Note that S [mm] is the length of the paper P in the transport direction, and D3 is the distance from the secondary transfer roller 43 to the fixing roller 441.
That is, when T2> T3, the fixing transfer speed may be changed to V1 when the shorter time of T2 or T4 elapses.

Next, the paper transport operation of the image forming apparatus 100 will be described with reference to the flowchart of FIG.
First, when image formation is started (step S401), the control unit 81 (speed control means) sets the fixing transfer speed to V2 (step S402). When the paper is conveyed to the image forming unit 40, the first sensor SE1 (first detecting means) detects the passage of the tip of the paper (step S403). When the paper passes through the secondary transfer roller 43 and the fixing roller 441 and a toner image is formed on the paper, the paper is conveyed downstream of the fixing roller 441, and the second sensor SE2 (second detecting means) uses the paper. The passage of the tip of the paper is detected (step S404).

Next, the control unit 81 (first calculation means) calculates T1 based on the passing time of the tip of the paper by the first sensor SE1 and the second sensor SE2 (step S405).
Further, the control unit 81 (second calculation means) calculates the loop amount A based on T1 (step S406). Subsequently, the control unit 81 (third calculation means, fourth calculation means, fifth calculation means) calculates T2, T3, and T4 (step S407).

Next, the control unit 81 determines whether T2> T3 (step S408). If the control unit 81 determines that T2> T3 (step S408: Yes), the process proceeds to step S409, and if it determines that T2> T3 is not (step S408: No), the process proceeds to step S410.

In step S409, the control unit 81 determines whether T4> T2.
When the control unit 81 determines that T4> T2 (step S409: Yes), the control unit 81 determines whether T2 has elapsed (step S410). When the control unit 81 determines that T2 has not passed (step S410: No), the process of step S410 is repeated, but when it is determined that T2 has passed (step S410: Yes), that is, the loop amount is a predetermined loop amount. If it is determined that the Aref has been reached, the process proceeds to step S412.

In step S409, if the control unit 81 determines that T4> T2 does not exist (step S409: No), the control unit 81 determines whether T4 has elapsed (step S411). When the control unit 81 determines that T4 has not passed (step S411: No), the process of step S411 is repeated, but when it is determined that T4 has passed (step S411: Yes), that is, the loop amount is a predetermined loop amount. If it is determined that the Aref has been reached, the process proceeds to step S412.

In step S412, the control unit 81 (speed control means) changes the fixing transfer speed to V1 and makes the transfer transfer speed and the fixing transfer speed equal to each other.

Next, in step S413, the control unit 81 determines whether or not the rear end of the paper has passed through the fixing roller 441. When the control unit 81 determines that the paper has not passed (step S413: No), the process of step S413 is repeated, but when it determines that the paper has passed (step S413: Yes), that is, the image forming process for the paper is completed. When the determination is made, the control unit 81 determines whether or not the paper is the final page (step S414). When the control unit 81 determines that it is the final page (step S414: Yes), it ends the control, but when it determines that it is not the final page (step S414: No), it returns to step S402 and repeats the subsequent processing. ..

As described above, the image forming apparatus 100 according to the first embodiment controls the secondary transfer roller 43, the fixing roller 441, the first sensor SE1 and the second sensor SE2 for detecting the passage of the tip of the paper. A unit 81 is provided. The control unit 81 calculates the time T1 required from the detection of the tip of the paper by the first sensor SE1 to the detection by the second sensor SE2, and based on T1, the tip of the paper is detected by the second sensor SE2. The loop amount A of the paper between the secondary transfer roller 43 and the fixing roller 441 at the time of detection is calculated, and based on the loop amount A, the loop amount is increased after the tip of the paper reaches the fixing roller 441. The time T2 required to reach the predetermined loop amount Aref is calculated, and the paper transport speed of the fixing roller 441 is controlled so that the loop amount A becomes the predetermined loop amount Aref.
Therefore, according to the image forming apparatus 100 in the present embodiment, since a loop detecting means such as an actuator is not used, the configuration can be realized without being complicated, and the alignment between the secondary transfer roller 43 and the fixing roller 441 can be realized. It can be carried out without being affected by misalignment. Further, since the control is performed without using the actually measured values of the paper transport speeds of the secondary transfer roller 43 and the fixing roller 441, it can be performed on the first sheet of paper.

Further, in the image forming apparatus 100 according to the first embodiment, the control unit 81 changes the fixing transfer speed from V2 to V1 after the passage of T2, that is, after the loop amount A reaches a predetermined loop amount Aref.
As a result, the paper can be conveyed to the fixing roller 441 while maintaining a loop amount close to the predetermined loop amount Aref, and the paper reaches the carry-in roller 72 at a speed of V1, so that the carry-in roller 72 and the fixing roller There is no possibility that the paper will be pulled together with the 441.

Further, in the image forming apparatus 100 according to the first embodiment, the control unit 81 calculates the time T3 required from when the tip of the paper reaches the fixing roller to when it reaches the carry-in roller 72, and the tip of the paper reaches the fixing roller. The time T4 required for the rear end of the paper to pass through the secondary transfer roller 43 after reaching 441 is calculated, and when T2> T3 and T2> T4, the paper is conveyed by the fixing roller 441 after passing T4. Change the speed to V1.
That is, when the tip of the paper reaches the carry-in roller 72 before the lapse of T2, the secondary transfer roller 43 is fixed and conveyed at the timing when the rear end of the paper comes off before the front end of the paper reaches the carry-in roller 72. Since the speed is changed from V2 to V1, there is no possibility that the paper will be pulled between the carry-in roller 72 and the fixing roller 441.

[Second Embodiment]
Next, a second embodiment to which the present invention is applied will be described. In the second embodiment, the paper to be conveyed is a so-called long paper or the like, which is longer than the distance from the secondary transfer roller 43 to the carry-in roller 72.
Since the image forming apparatus 100 in the second embodiment has the same configuration as the image forming apparatus 100 shown in the first embodiment, FIGS. 1 and 2 are incorporated, and illustration and description of the configuration will be omitted. Hereinafter, the processing characteristic of the second embodiment will be described.

As described above, when the tip of the paper reaches the carry-in roller 72 before T2 elapses, that is, when T2> T3, the fixing transfer speed is still V2, so the paper is conveyed at the speed of V1. Paper is pulled together with the carry-in roller 72. However, if the paper to be conveyed is longer than the distance between the secondary transfer roller 43 and the carry-in roller 72, the paper may be sandwiched between the secondary transfer roller 43, the fixing roller 441, and the carry-in roller 72. At this time, unlike the first embodiment, it is not possible to control to change the fixing transfer speed to V1 when the rear end of the paper passes through the secondary transfer roller 43.

In the second embodiment, when T2> T3, the value of T2 is reduced until T2 ≦ T3. Here, since T2 is represented by the above-mentioned equation (2), the value of T2 can be reduced by setting the fixing transfer speed to V3 (third speed), which is even slower than V2. The control unit 81 calculates V3 such that T2 ≦ T3, and sets it as the fixing transfer speed. V3 can be calculated using the above-mentioned equations (2) and (3).

Next, the paper transport operation of the image forming apparatus 100 according to the second embodiment will be described with reference to the flowchart of FIG. Since the processing of steps S501 to S507 is the same as the processing of steps S401 to S407 in FIG. 4, detailed description thereof will be omitted.
In step S508, the control unit 81 determines whether T2> T3. If the control unit 81 determines that T2> T3 (step S508: Yes), the process proceeds to step S511, and if it determines that T2> T3 is not (step S508: No), the process proceeds to step S509.

In step S509, the control unit 81 calculates V3 such that T2 ≦ T3, and then the control unit 81 (speed control means) sets the fixing transfer speed to V3 (step S510).
Next, the control unit 81 determines whether or not T2 has elapsed (step S511). When the control unit 81 determines that T2 has not passed (step S511: No), the process of step S511 is repeated, but when it is determined that T2 has passed (step S511: Yes), that is, the loop amount is a predetermined loop amount. If it is determined that the Aref has been reached, the process proceeds to step S512.

Since the processing of steps S512 to S514 is the same as the processing of steps S421 to S414 in FIG. 4, detailed description thereof will be omitted.

As described above, in the image forming apparatus 100 according to the second embodiment, when T2> T3, the control unit 81 changes the paper transport speed of the fixing roller 441 to V3, which is slower than V2, and the progress of T2. Later, the paper transport speed of the fixing roller 441 is changed to V1.
Therefore, in order to shorten the time required for the loop amount A to reach the predetermined loop amount Aref and to change the fixing transfer speed from V2 to V1 before the tip of the paper reaches the carry-in roller 72, a long paper is used. Even if there is, it is possible to suppress the pulling of the paper between the secondary transfer roller 43 and the fixing roller 441, and the fixing roller 441 and the carry-in roller 72.

[Correction of fixing transfer speed]
In the above embodiment, the control unit 81 controls the fixing and conveying speed at the time of image formation to be V1 or V2, but the speed at which the fixing roller 441 actually advances changes depending on the paper type and the weight of the paper. Therefore, in order to improve the accuracy of control, V1 and / or V2 used when calculating T2 can be corrected depending on the paper type and the weight.

FIG. 6 shows an example of the correction value of the fixing and conveying speed depending on the paper type and the weight. Specifically, the values of V1 and V2 used when calculating T2 are corrected to the values shown in FIG.
As the weight increases, the actual paper transport speed in the fixing roller 441 becomes slower than V1 or V2. Therefore, the larger the weight, the smaller the values of V1 and V2 used in the calculation of T2.
Further, the actual paper transport speed of the coated paper on the fixing roller 441 is slower than that of V1 or V2 on the coated paper than on the plain paper. Therefore, in the case of coated paper, the values of V1 and V2 used for calculating T2 are corrected so as to be smaller than those of plain paper.
The same effect can be obtained by correcting a predetermined loop amount Aref instead of V1 and V2.

Further, as the paper length becomes longer, the loop amount A deviates from the predetermined loop amount Aref with time after the fixing transfer speed is increased to V1. This is because there is an error between the actual transfer speed at the transfer transfer speed V1 and the actual transfer speed at the fixing transfer speed V1. Therefore, when printing long paper, it is desirable to control the fixing and conveying speed according to the state of the image forming apparatus 1.
FIG. 7 shows an example of an image quality adjustment screen when printing on long paper. The image forming apparatus 1 displays a screen as shown in FIG. 7 on the display unit 20 during or after printing on the long paper, and prompts the user to adjust the image quality. Specifically, when "2. Image is rubbed" in FIG. 7 is selected, toner is rubbed due to an excessive amount of loop, so in addition to the correction of V2 in FIG. 6, further −0. Correct by 05%. When "3. There is a scratch on the image" in FIG. 7 is selected, the fixing transfer speed after speeding up is slower than V1, and paper tension occurs between the secondary transfer roller 43 and the fixing roller 441. Therefore, the drive motor speed of the fixing roller 441 is increased by +0.05.

[Other Embodiments]
Although the above embodiments have been specifically described based on the embodiment of the present invention, the above-described embodiment is a preferable example of the present invention and is not limited thereto.

For example, the second embodiment has been described as a control performed when the paper to be conveyed is a long paper or the like longer than the distance from the secondary transfer roller 43 to the carry-in roller 72, but the same applies even if the paper is not a long paper. It is possible to control. That is, the program can be simplified by uniformly setting the paper transport control in the image forming apparatus 100 regardless of the size of the paper.

Further, in the above embodiment, the carry-in roller 72 provided in the post-processing unit 60 has been used as the transport roller downstream of the fixing roller 441, but the present invention is not limited to this.
For example, in the case of an image forming system in which a plurality of image forming devices are connected in series, the paper that has passed through the fixing portion of the image forming device on the upstream side is conveyed to the image forming device on the downstream side on the downstream side. Control may be performed on the paper transport roller on the paper transport path of the image forming apparatus.

In addition, the detailed configuration of each device constituting the image forming apparatus and the detailed operation of each device can be appropriately changed without departing from the gist of the present invention.

20 Display unit 40 Image forming unit 43 Secondary transfer roller (transfer roller)
44 Fixing section 441 Fixing roller 60 Post-processing section 70 Transport section 71 Resist roller 72 Carry-in roller (conveyor roller)
81 Control unit (1st calculation means, 2nd calculation means, 3rd calculation means, 4th calculation means, 5th calculation means, speed control means)
100 Image forming apparatus SE1 1st sensor (1st detecting means)
SE2 2nd sensor (2nd detection means)

Claims (10)

A transfer roller that forms a toner image on paper,
A fixing roller that heats and fixes the toner image formed on the paper,
A first detecting means for detecting the passage of the leading edge of the paper at the first position on the upstream side of the transfer roller in the paper transport direction.
A second detecting means for detecting the passage of the leading edge of the paper at a second position on the downstream side of the fixing roller in the paper transport direction,
A speed control means for controlling the paper transport speed by the transfer roller and the fixing roller, and
When the paper is transported by the speed control means with the paper transport speed of the transfer roller as the first speed and the paper transport speed of the fixing roller as the second speed slower than the first speed, A first calculation means for calculating the first time required from the detection of the tip by the first detection means to the detection by the second detection means, and
The transfer roller at the time when the tip of the paper is detected by the second detecting means based on the first time, the transport distance between the first position and the second position, and the first speed. And a second calculation means for calculating the amount of slack in the paper between the fixing rollers, and
A third calculation means for calculating the second time required for the slack amount to reach a predetermined slack amount after the tip of the paper is detected by the second detection means based on the slack amount is provided.
The speed control means is characterized in that the paper transport speed by the fixing roller is changed to the first speed after the second time has elapsed after the tip of the paper is detected by the second detection means. apparatus. The image forming apparatus according to claim 1, wherein the second calculation means calculates the amount of slack from the following formula (1).
A = V1 * T1-D1 ... (1)
However,
A: The amount of slack [mm]
V1: The first speed [mm / s]
T1: The first time [s]
D1: Distance [mm] between the first detection means and the second detection means
Is. The image forming apparatus according to claim 2, wherein the third calculation means calculates the second time from the following formula (2).
T2 = (Aref-A) / (V1-V2) ... (2)
However,
T2: The second time [s]
Aref: The predetermined amount of slack [mm]
V2: The second speed [mm / s]
Is. The image forming according to any one of claims 1 to 3, wherein the speed control means changes the paper transport speed of the fixing roller to the first speed after the lapse of the second time. apparatus. A transport roller arranged on the downstream side of the fixing roller in the paper transport direction,
A fourth calculation means for calculating the third time required from the tip of the paper reaching the fixing roller to reaching the transport roller.
A fifth calculation means for calculating the fourth time required from when the front end of the paper reaches the fixing roller to when the rear end of the paper passes through the transfer roller is provided.
When the second time is longer than the third time and the third time is longer than the fourth time, the speed control means has a paper transport speed of the fixing roller after the lapse of the fourth time. The image forming apparatus according to any one of claims 1 to 3, wherein the speed is changed to the first speed. A transport roller arranged on the downstream side of the fixing roller in the paper transport direction,
A fourth calculation means for calculating the third time required from the tip of the paper reaching the fixing roller to the transfer roller is provided.
When the second time is longer than the third time, the speed control means changes the paper transport speed of the fixing roller to a third speed slower than the second speed, and the second time The image forming apparatus according to any one of claims 1 to 3, wherein the paper transport speed of the fixing roller is changed to the first speed after the lapse of time. The image forming apparatus according to claim 5 or 6, wherein the fourth calculation means calculates the third time from the following formula (3).
T3 = D2 / V2 ... (3)
However,
T3: The third time [s]
D2: Distance [mm] between the fixing roller and the conveying roller
Is. The image forming apparatus according to claim 5, wherein the fifth calculation means calculates the fourth time from the following formula (4).
T4 = (S-D3) / V1 ... (4)
However,
T4: The fourth hour [s]
S: Paper transport direction length [mm]
D3: Distance [mm] between the transfer roller and the fixing roller
Is. The speed control means is characterized in that it corrects at least one of the predetermined slack amount, the first speed, and the second speed according to the paper length, the paper type, and the weight of the paper. The image forming apparatus according to any one of Items 1 to 8. The passage of the tip of the paper is detected at the transfer roller that forms the toner image on the paper, the fixing roller that heats and fixes the toner image formed on the paper, and the first position on the upstream side of the transfer roller in the paper transport direction. A computer of an image forming apparatus including a first detecting means and a second detecting means for detecting the passage of the tip of the paper at a second position on the downstream side in the paper transport direction of the fixing roller.
A speed control means for controlling the paper transport speed by the transfer roller and the fixing roller,
When the paper is transported by the speed control means with the paper transport speed of the transfer roller as the first speed and the paper transport speed of the fixing roller as the second speed slower than the first speed, the paper is fed. A first calculation means for calculating a first time required from the time when the tip is detected by the first detection means until the tip is detected by the second detection means.
The transfer roller at the time when the tip of the paper is detected by the second detecting means based on the first time, the transport distance between the first position and the second position, and the first speed. And a second calculation means for calculating the amount of slack in the paper between the fixing rollers,
A third calculation means for calculating a second time required for the amount of slack to reach a predetermined amount of slack after the tip of the paper is detected by the second detection means based on the amount of slack.
A program that functions as.

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