Image forming device

Abstract

To prevent occurrence of non-feed by controlling separating operation of a pair of conveyance rollers in accordance with a conveyance path of a sheet.SOLUTION: An image forming device comprises: a first storage cabinet (110); a second storage cabinet (111) provided below the first storage cabinet; a pair of conveyance rollers (120) for conveying a fed sheet; a pair of registration rollers (130) which are provided on the downstream in a conveyance direction of the pair of conveyance rollers and correct skew of a sheet to convey the sheet to an image forming part (150); a separation mechanism (140) for contacting or separating the pair of conveyance rollers; and control means (200) which controls the separation mechanism so as to, when an image is formed on the sheet fed from the first storage cabinet, let the pair of conveyance rollers contact regardless of the kind of the sheet stored in the first storage cabinet, and, when an image is formed on the sheet fed from the second storage cabinet, let the pair of conveyance rollers separate based on the kind of the sheet stored in the second storage cabinet.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] Conventionally, some image forming apparatuses include a skew correction unit that conveys paper fed from a paper storage unit to an image forming unit and corrects skew of the paper. The skew correction unit includes a pair of rollers called a registration roller pair, and performs skew correction by hitting the leading edge of the paper against a nip portion of the roller pair to bend the paper.

[0003] In recent years, image forming devices are also required to handle small-sized paper, and the spacing between the transport rollers in the transport path from the paper storage unit to the image forming unit tends to be narrower. If the spacing between the transport rollers is narrowed, the paper becomes more skewed when the skew correction unit corrects the skew of the paper, which can result in wrinkles on the paper.

[0004] Patent Document 1 proposes a method of temporarily separating a pair of conveying rollers (pre-registration conveying roller pair) arranged upstream of the registration roller pair when correcting skew by abutting the leading edge of the paper against the registration roller pair. By adopting the method of Patent Document 1, the grip of the pre-registration conveying roller pair is released, eliminating the distortion of the paper caused by skew correction and reducing the occurrence of wrinkles. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-26452 A Summary of the Invention [Problem to be solved by the invention]

[0006] According to the method of Patent Document 1, in order to reduce the occurrence of wrinkles in the paper, the pre-registration transport roller pair is separated when performing skew correction. However, when the pre-registration transport roller pair is separated, when the paper is fed to the registration roller pair, the transport force of the rollers provided upstream of the separated transport roller pair pushes the paper downstream of the transport path. Therefore, depending on the transport path, the paper may not be transported correctly to the registration roller pair, and paper jams may occur due to non-feeding. This problem is particularly noticeable for paper transported along a transport path with a short distance from the paper storage unit to the image forming unit.

[0007] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to suppress the occurrence of non-feeding by appropriately controlling whether or not to separate the pair of conveying rollers. [Means for solving the problem]

[0008] In order to achieve the above object, an image forming apparatus according to the present invention includes an image forming unit that forms an image on paper, a first storage case that stores paper, a first feeding and separating unit that feeds the paper stored in the first storage case and separates it into sheets one by one, a transport roller pair that transports the paper fed by the first feeding and separating unit, a registration roller pair that corrects skew of the paper transported by the transport roller pair and transports the paper with the skew corrected to the image forming unit, a first transport path that is provided between the first storage case and the transport roller pair in a sheet transport direction and through which a sheet passes, a second storage case that is provided below the first storage case and stores paper, a second feeding and separating unit that feeds the paper stored in the second storage case and separates it into sheets one by one, a pull-out roller pair that transports the paper fed by the second feeding and separating unit, and a front side of the second storage case in the sheet transport direction. a second transport path through which the sheet transported by the pull-out roller pair passes, the second transport path being provided between a first feeding and separating section in the first transport path and a junction section where the first and second transport roller pairs join upstream of the pair of transport rollers; a separation mechanism for bringing one roller of the pair of transport rollers into contact with or away from the other roller; and a control means for controlling the separation mechanism so that, when an image is formed on the sheet fed from the first storage case, the one roller is brought into contact with the other roller regardless of the type of sheet stored in the first storage case, and when an image is formed on the sheet fed from the second storage case, the one roller is separated from the other roller based on the type of sheet stored in the second storage case. In the first transport path, the first feeding and separating section is disposed closest to the pair of transport rollers in the sheet transport direction, Department The present invention is characterized in that the pair of pull-out rollers and other pairs of conveying rollers for conveying the sheet are not provided between the pair of conveying rollers and the pair of conveying rollers. Effect of the Invention

[0009] According to the present invention, the occurrence of non-feeding can be suppressed by controlling the separation operation of the pair of transport rollers depending on the feed source of the paper. [Brief description of the drawings]

[0010] [Figure 1] Simplified cross-sectional view of an image forming apparatus [Diagram 2] Block diagram of an image forming apparatus [Diagram 3] Schematic diagram of a pre-registration conveying roller pair in a separated state. [Figure 4] Schematic diagram of a state in which a pair of pre-registration transport rollers are in contact with each other [Diagram 5] Driving configuration diagram when the pre-registration conveying roller pair is separated [Figure 6] Driving configuration diagram when the pre-registration transport roller pair is in contact [Figure 7] Drive transmission diagram when rotating the pre-registration transport roller pair [Figure 8] Drive transmission diagram when operating the separation mechanism [Figure 9] Flowchart for explaining a paper feeding operation [Figure 10] FIG. 13 is a table showing a separation judgment table for a pair of pre-registration conveying rollers; [Figure 11] FIG. 13 is a schematic diagram for explaining the twisting of paper during skew correction; [Figure 12] FIG. 13 is a diagram showing an operation screen displayed on the operation unit for setting the front-of-register separation mode. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Example 1 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of an image forming apparatus 100 according to this embodiment. The image forming apparatus 100 forms an image on a sheet of paper based on image information received from an external device such as a PC or image information read from a document. The image forming apparatus 100 includes an apparatus main body 100A that houses an image forming section 150, and an image reading device 300 that is disposed above the apparatus main body 100A and reads image information from the document. The image forming section 150 includes four image forming stations Y, M, C, and K, an intermediate transfer belt 155, and a fixing device 160.

[0012] Each of the image forming stations Y to K executes an electrophotographic process to form a toner image on the surface of the photosensitive drum 151. That is, when the image forming stations Y to K are requested to form a toner image, the photosensitive drum 151 is rotated and the charging device uniformly charges the surface of the photosensitive drum 151. An exposure device 152 provided at the bottom of the apparatus main body 100A irradiates the photosensitive drum 151 with laser light corresponding to image information to expose the drum surface, and writes an electrostatic latent image on the photosensitive drum 151. A development device 153 supplies charged toner particles to the photosensitive drum 151 and develops the electrostatic latent image on the drum surface into a toner image. The toner images of each color formed by the image forming stations Y to K are primarily transferred from the photosensitive drum 151 to the intermediate transfer belt 155 by a primary transfer roller 154. Adherents such as toner remaining on the photosensitive drum 151 are removed by a cleaning unit provided at each of the image forming stations Y to K.

[0013] The intermediate transfer belt 155 is wound around a secondary transfer inner roller 156, a tension roller 157, and a tension roller 158, and is driven to rotate in the counterclockwise direction in FIG. 1. The toner image carried on the intermediate transfer belt 155 is secondarily transferred to the paper S at a secondary transfer portion formed between the intermediate transfer belt 155 and a secondary transfer roller 159 facing the secondary transfer inner roller 156. Adherents such as toner remaining on the intermediate transfer belt 155 are removed by a belt cleaner.

[0014] The paper S onto which the toner image has been transferred is delivered to the fixing device 160. The fixing device 160 has a fixing roller, a pressure roller which holds the paper S together with the fixing roller, and a halogen heater which heats the fixing roller. The fixing device 160 applies heat and pressure to the toner image while transporting the paper S to melt the toner, and then the toner is fixed to the paper S.

[0015] In parallel with this image forming process, sheets S are fed one by one from sheet feed cassettes 110 and 111 or manual sheet feed tray 112 toward image forming section 150.

[0016] The paper feed cassette 110 and the paper feed cassette 111 are an example of a paper storage that is provided so as to be removable from the apparatus main body 100A. The paper feed cassette 110 and the paper feed cassette 111 are arranged side by side in the vertical direction. The paper stored in the upper paper feed cassette 110 (first paper storage) is separated into individual sheets by the paper feed unit 113 (pickup roller 113a, feed roller 113b, retard roller 113c). The separated and transported paper is delivered to the pre-registration transport roller pair 120. In this embodiment, the transport path from the paper feed cassette 110, which is the first storage, to the pre-registration transport roller pair 120 is referred to as the first transport path for convenience. Since the length of the first transport path is relatively short, the paper transported on the first transport path is transported only by the transport force of the paper feed roller 113. In the first conveying path, the roller located most upstream in the conveying direction with respect to the pre-registration conveying roller pair 120 is the feed roller 113b, which is different from the second conveying path described later. In the following description, for convenience, the "pre-registration conveying roller pair" may be referred to as the "pre-registration conveying roller pair."

[0017] The paper feed cassette 111 provided below the paper feed cassette 110 is an example of a second paper storage. The paper in the paper feed cassette 111, which is an example of the second paper storage, is separated one by one by the paper feed unit 114 (pickup roller 114a, feed roller 114b, retard roller 115b) and delivered to the pull-out roller pair 121. The pull-out roller 121 conveys the paper received from the paper feed roller 114 toward the image forming unit 150. In this embodiment, the conveying path from the paper feed cassette 111, which is the second paper storage, to the pre-registration conveying roller pair 120 is called the second conveying path for convenience. The second conveying path is a conveying path with a shorter distance than the first conveying path, and if the paper fed by the paper feed roller 114 is a small-sized paper, the paper cannot be delivered to the pre-registration conveying roller pair 120. For this reason, the cassette pull-out roller 121 is arranged on the second conveying path.

[0018] Similarly, the sheets placed on the manual feed tray 112 are separated one by one by the feed roller 115 and delivered to the pull-out drive roller 122 .

[0019] The paper S that is fed from the paper feed cassettes 110, 111, or the manual feed tray 112 and reaches the pre-registration transport roller pair 120 is transported to the registration roller pair 130. The registration roller pair 130 corrects skew of the paper S and sends the paper S to the secondary transfer section at a timing synchronized with the image formation process by the image forming section 150. The registration roller pair will be described later.

[0020] The sheet S on which an image has been formed by passing through the secondary transfer unit and the fixing unit 160 is conveyed to a pair of discharge rollers 171 via a discharge path 172 in the discharge unit 170. In the case of single-sided printing, the sheet S is discharged by the pair of discharge rollers 171 to a discharge tray 180 provided between the apparatus main body 100A and the image reading device 300. In the case of double-sided printing, the sheet S on which an image has been formed on the first side is switched back and conveyed by the discharge rollers 171 and delivered to the double-sided conveying unit 190. Then, the sheet S reaches the pair of registration rollers 130 again, an image is formed on the second side by the image forming unit 150, and the sheet S is discharged to the discharge tray 180 by the pair of discharge rollers 171.

[0021] 2 is a control block diagram of the image forming apparatus 100. The image forming apparatus 100 has a control unit 200. The control unit 200 has at least one processor including a CPU 201, a read only memory (ROM) 202, a random access memory (RAM) 203, a motor drive circuit 204, and a sensor output detection circuit 205.

[0022] The ROM 202 stores a control program for controlling each process executed by the image forming apparatus 100. The RAM 203 is a system work memory used by the CPU 201 to execute the control program.

[0023] The motor drive circuit 204 is connected to the paper feed motor 181, the register drive motor 133, the pre-register transport drive motor 145, and the pull-out motor 116, and controls each of the connected motors. The motor drive circuit 204 outputs a control signal to each motor according to the rotation speed and direction of the motor instructed by the CPU 201. The motor drive circuit 204 specifies the rotation direction (CW / CCW) for the paper feed motor 113 and the pre-register transport drive motor 145. On the other hand, the motor drive circuit 204 specifies only one rotation direction (the transport direction) for the register drive motor 133 and the pull-out motor 116.

[0024] The sensor output detection circuit 205 outputs a high or low level signal to the CPU 201 based on the output signal of each connected sensor. Specifically, the sensor output detection circuit 205 outputs a high level signal if the amount of light received by each sensor is equal to or greater than the threshold value. On the other hand, if the amount of light received by each sensor is less than the threshold value, it outputs a low level signal. The CPU 201 recognizes that the separation sensor 129 is ON when the pre-registration transport roller pair 120 is in a separated state, and that the registration detection sensor 132 is ON when the paper reaches the registration roller position.

[0025] The operation unit 301 notifies the user of the state of the image forming apparatus 100 based on a signal received from the CPU 201. The operation unit 301 also receives an operation instruction for the image forming apparatus 100 from the user.

[0026] [Skew Correction and Wrinkles] The skew correction when the pre-registration transport roller pair 120 is in contact will be described with reference to Fig. 3. The paper S fed from each paper storage is transported downstream on the transport path by the pre-registration transport roller pair 120. The transported paper S is then abutted against the nip of the stopped registration roller pair 130 so that the leading edge of the paper S is aligned. As a result, a loop is formed for the paper S by the pre-registration transport roller pair 120 and the registration roller pair 130. This corrects the skew at the leading edge of the paper S.

[0027] FIG. 11 is a schematic diagram showing the state of a sheet when the skewed sheet is abutted against the registration roller pair 130 to correct the skew while the pre-registration conveying roller pair 120 is in contact with the sheet. The leading edge of the skewed sheet is abutted against the registration roller pair 130 to correct the skew, but the sheet is twisted between the registration roller pair 130 and the pre-registration conveying roller pair 120 to form a loop. The greater the input skew of the sheet S that reaches the registration roller pair 130, the greater the amount of twist. If the sheet S is conveyed downstream of the registration roller pair 130 in a twisted state, stress is applied to the sheet S, which may cause wrinkles. The occurrence rate of these wrinkles varies depending on the amount of twist, the basis weight of the sheet, the roller pitch in the section where the twist occurs, and other factors. If the roller pitch is widened, the stress on the sheet is dispersed, and the occurrence of these wrinkles can be avoided. For this reason, this patent has a separation mechanism for the pre-registration conveying rollers.

[0028] [Separation of transport rollers before registration] The configuration and operation of the pre-registration conveying roller pair 120 according to the present embodiment will be described with reference to Figs. 3 to 8. Figs. 3 and 4 are diagrams showing the cross-sectional configuration of the conveying path until the fed paper reaches the registration roller pair 130. Fig. 3 is a schematic diagram showing the state in which the pre-registration conveying roller pair 120 is in contact with each other. Fig. 4 is a schematic diagram showing the state in which the pre-registration conveying roller pair 120 is separated from each other. Fig. 5 is a perspective view showing the drive mechanism of the pre-registration conveying roller pair 120 corresponding to the state in which the pre-registration conveying roller pair 120 is in contact with each other. Fig. 6 is a perspective view showing the drive mechanism of the pre-registration conveying roller pair 120 corresponding to the state in which the pre-registration conveying roller pair 120 is separated from each other. Fig. 7 is a drive transmission diagram when the pre-registration conveying roller pair 120 is rotated, and Fig. 8 is a drive transmission diagram when the pre-registration conveying roller pair 120 is separated from each other.

[0029] 7 and 8, the rotation of the pre-registration conveyance roller pair 121 and the drive configuration for operating the separation mechanism 140 will be described. A one-way clutch (not shown) is provided on the pre-registration drive gear 147 so that the drive is transmitted to the output shaft only when the pre-registration conveyance drive motor 145 rotates CW. Also, a one-way clutch (not shown) is provided on the separation gear 146 so that the drive is transmitted to the output shaft only when the pre-registration conveyance drive motor 145 rotates CCW.

[0030] 7, when the pre-registration conveyance drive motor 145 rotates in the CW direction (first direction), a driving force is transmitted to the pre-registration conveyance roller pair 120 via the pre-registration drive gear 147. At this time, the driving force is not transmitted to the separation transmission shaft 148, and the separation mechanism 140 does not operate, so that the pre-registration roller pair 121 is maintained in a contact state or a separated state.

[0031] On the other hand, as shown in FIG. 8, when the pre-registration drive motor 145 rotates in the CCW direction (second direction, the direction opposite to the CW direction), the driving force is transmitted to the separation transmission shaft 148 via the separation gear 146. Then, the separation mechanism 140 switches the pre-registration conveying roller pair 120 between the abutment state and the separation state. At this time, the driving force is not transmitted to the drive shaft 121c, and the pre-registration conveying roller pair 120 is in a non-driven state. In this way, the drive configuration of the pre-registration conveying roller pair 120 can switch between the rotation drive of the pre-registration conveying roller pair 120 and the drive of the separation mechanism 140 by switching the rotation direction of the pre-registration drive motor 145, which is the drive motor.

[0032] The operation of the separation mechanism will be described in detail with reference to Figures 5 and 6. When the pre-registration transport roller pair 120 is kept in contact with each other, the pre-registration transport drive motor 145 is rotated in the CCW direction until the separation sensor 129 is turned OFF.

[0033] In more detail, the drive of the pre-registration conveyance drive motor 145 is transmitted to the separation gear 146, the separation transmission shaft 148, and the separation cam 149, and the separation cam 149 rotates. In conjunction with this, the angle of the separation operation lever 127, which is urged toward the separation cam 149 by the separation position determination spring 128, changes. By integrating the separation operation lever 127, the separation mechanism shaft 141, and the separation arm 142, the angle of the separation arm 142 also changes at the same time. When the pre-registration conveyance drive motor 145 is stopped at the timing when the separation operation lever 127 leaves the detection range of the separation sensor 129, the state shown in FIG. 5 is reached. The pre-registration conveyance driven roller 120b is urged toward the pre-registration conveyance drive roller 120a by the pre-registration pressure spring 143 held between the pre-registration pressure spring 143 and the spring seat metal plate 144, so that the pre-registration conveyance roller pair 120 comes into contact with each other. In this way, the separation mechanism 140 brings the pre-registration transport driven roller 120b, which is an example of one roller, into contact with or separates from the pre-registration transport drive roller 120a, which is an example of the other roller. In this embodiment, the pre-registration transport driven roller 120b is configured to come into contact with or separate from the pre-registration transport drive roller 120a. However, the pre-registration transport drive roller 120a may be configured to come into contact with or separate from the pre-registration transport driven roller 120b. Alternatively, both rollers may move to bring them into contact with or separate from each other.

[0034] To put the pre-registration conveying roller pair 120 into a separated state, the pre-registration conveying drive motor 145 is rotated in the CCW direction until the separation sensor 129 is turned ON. Specifically, the pre-registration conveying drive motor 145 is rotated and stopped at the timing when the separation operation lever 127 enters the detection range of the separation sensor 129, resulting in the state shown in FIG. 6, where the pre-registration conveying roller pair 120 is separated.

[0035] [Explanation of feeding operation from CST2 (transport path with independent pull-out rollers)] Using FIG. 4, an operation of conveying conveyed paper S to registration conveying roller pair 130 in a conveying path (second conveying path) in which cassette removal roller 121 is provided between paper feed roller 114 and pre-registration conveying roller pair 120 will be described.

[0036] The paper S sent downstream of the paper transport path by the paper feed roller 114a and separation roller 114b is sandwiched between the cassette pull-out rollers 121. The paper S sandwiched between the cassette pull-out rollers 121 is pulled further downstream. The paper S pulled downstream passes through or is sandwiched between the pre-registration transport rollers 120 and reaches the registration roller pair 130. Whether the pre-registration transport roller pair 120 is separated or contacted is determined based on the length and paper type, such as basis weight, of the paper S being transported. The separation or contact process is performed before the paper S in the cassette S is fed by the pickup roller 114a.

[0037] The pickup roller 114a and the separation roller 114b are rollers whose main purpose is to send out only one sheet of the topmost paper S of the paper feed cassette 111 to the transport path. Therefore, in general, the transport efficiency (amount of paper advancement relative to the amount of roller rotation) is lower than that of the cassette pull-out roller 121 and the pre-registration transport roller pair 120. Therefore, when the paper S is transported only by the pickup roller 114a and the separation roller 114b, it is difficult to precisely control the amount of paper advancement. On the other hand, the cassette pull-out roller 121 and the transport rollers downstream thereof are provided so that the transport efficiency of the paper is nearly 100%, and the amount of paper advancement can be precisely controlled. Therefore, the paper S pulled in by the cassette pull-out roller 121 can be correctly sent to the registration roller pair 130 without being sandwiched by the pre-registration transport roller pair 120, although this depends on the basis weight and length of the paper.

[0038] [Explanation of feeding operation from CST1 (transport path without independent pull-out rollers)] 3, an operation of conveying the paper S conveyed from the paper feed cassette 110 to the registration conveying roller pair 130 will be described. The conveying path (first conveying path) of the paper fed from the paper feed cassette 110 is different from the above-mentioned second conveying path in that no cassette removal roller is provided between the paper feed roller 113 and the pre-registration conveying roller 120.

[0039] The sheet S sent downstream of the sheet transport path by the pickup roller 113a and the separation roller 113b is sandwiched between a pair of pre-registration transport rollers 120 and reaches a pair of registration rollers .

[0040] As mentioned above, the amount of paper advance cannot be accurately controlled by the pickup roller 113a and separation roller 113b alone. Therefore, the amount of entry of the registration rollers cannot be accurately controlled, and skew correction cannot be performed correctly. Therefore, the pre-registration transport roller pair 120 must be in a contact state. The contact operation is performed before the pickup roller 113a feeds the paper S from the cassette S.

[0041] [Explanation regarding separation mode of the pre-registration transport roller pair] Next, the separation operation of the pre-registration conveying roller pair 120 will be described. In this embodiment, there are two modes related to the separation of the pre-registration conveying roller pair 120 (hereinafter, for convenience, may be referred to as "pre-registration separation mode"): a "wrinkle avoidance priority mode" and a "productivity priority mode". In this embodiment, the pre-registration separation mode is preset by a user or an administrator as a setting of the image forming apparatus 100. When the user selects the pre-registration separation mode, the user selects it via a user operation screen 200 shown in FIG. 12.

[0042] The "wrinkle avoidance priority mode" is a mode for preventing the occurrence of wrinkles in the paper. To prevent wrinkles in the paper, the pre-registration transport roller pair 120 is separated as necessary. The operating conditions and details of the "wrinkle avoidance priority mode" will be explained in the explanation of the flowchart in FIG. 9. The mechanism by which paper wrinkles occur has already been explained in FIG. 11.

[0043] The "productivity priority mode" is a mode for preventing a decrease in productivity due to the separation operation of the pre-registration conveying roller pair 120. When the pre-registration conveying roller pair is attached or detached, the conveyance of the paper must be interrupted, which reduces productivity. Therefore, in order to maintain productivity, this mode does not perform the separation operation of the pre-registration conveying roller pair 120. If the separation operation of the pre-registration conveying roller pair 120 is not performed, the paper may wrinkle depending on the setting state of the paper. Therefore, a message to prevent the paper from being wrinkled is displayed in 203 of FIG. 12 to encourage the user to avoid rough setting. The operating conditions and details of the "productivity priority mode" will be described in the explanation of the flowchart in FIG. 9.

[0044] [Explanation of the flow chart for paper feeding operation] 9 is a flowchart showing the processing executed by the CPU 201 in accordance with the programs stored in the ROM 202 and the RAM 203. This flowchart is executed in response to a print job being input. Note that size information and basis weight information of the sheets S stored in each paper storage is input in advance by the user from the operation unit 301, and the information is stored in the RAM 203.

[0045] First, it is determined whether to operate in a mode in which the pre-registration conveying roller pair 120 is separated to reliably avoid the occurrence of paper wrinkles, or to operate in a mode in which the pre-registration conveying roller pair 120 is not separated and prioritizes productivity (S1000). Specifically, it is determined whether the pre-registration separation mode is a "wrinkle avoidance priority mode" or a "productivity priority mode" (S1000). This determination is made based on the setting of the pre-registration separation mode input from the operation unit 301. If the pre-registration separation mode is not the "wrinkle avoidance priority mode" (if it is the "productivity priority mode"), the pre-registration conveying roller pair 120 always maintains a contact state. Therefore, the process proceeds to S1010 without performing the processes of S1001 to S1009, and the CPU 201 starts a paper feed operation from the paper feed cassette of the paper feed source. On the other hand, if the pre-registration separation mode is the "wrinkle avoidance priority mode", it is determined whether the paper storage unit of the paper feed source is "cassette 1" (S1001). The term "cassette 1" here corresponds to the paper feed cassette 110 in FIG. 1, and indicates that there is no independent cassette removal roller in the conveying path from the storage to the registration roller pair 130. If the result of S1001 is YES, the CPU 201 judges whether the pre-registration conveying roller pair 120 is in a contact state (S1002). If the pre-registration conveying roller pair 120 is in a contact state, the CPU 201 starts a paper feed operation (S1010). The paper feed operation is to drive the paper feed motor 181 to rotate the paper feed roller and the separation roller (113, 114). If the pre-registration conveying roller pair 120 is in a separated state, the CPU 201 judges whether the pre-registration conveying roller pair 120 is conveying a sheet (S1003). If it is judged that the pre-registration conveying roller pair 120 is conveying a sheet, the CPU 201 waits until the paper conveying by the pre-registration conveying roller pair 120 for that sheet is completed. Thereafter, the CPU 201 executes a contact operation of the pre-registration transport roller pair 120 (S1004). After the pre-registration transport roller pair 120 transitions to the contact state, the CPU 201 starts a paper feed operation (S1010).

[0046] In S1001, when paper is fed from a paper storage other than cassette 1, a separation / arrival judgment is executed (S1005), which will be described later. A paper storage other than cassette 1 corresponds to paper feed cassette 111 or manual feed tray 112 in FIG. 1. An independent pull-out roller is arranged on the transport path of paper fed from these paper storages, up to registration roller pair 130. If the judgment result in S1005 is "contact", proceed to S1002. If the judgment result is "separation", judge whether pre-registration transport roller pair 120 is in the separated state (S1007). If pre-registration transport roller pair 120 is in the separated state (YES in S1007), CPU 201 starts the paper feed operation (S1010). On the other hand, if the pre-registration transport roller pair 120 is in the contact state, the CPU 201 determines whether the pre-registration transport roller pair 120 is transporting a sheet (S1008). If the pre-registration transport roller pair 120 is transporting a sheet, the CPU 201 waits until the pre-registration transport roller pair 120 completes transporting the sheet. Then, the CPU 201 separates the pre-registration transport roller pair 120 (S1009). After the pre-registration transport roller pair 120 transitions to the contact state, the CPU 201 starts a sheet feeding operation (S1010).

[0047] [Separation / contact judgment processing] The judgment process of S1005 will be described below. In this embodiment, when the pre-registration separation mode is the "wrinkle avoidance priority mode", if the length of the paper in the conveying direction is X [mm] or more and the basis weight of the paper is less than M [gsm], the "separation" is selected. This allows the pre-registration conveying roller pair 120 to be separated, even if the paper has a basis weight of less than M [gsm] and is weak, so that the occurrence of wrinkles can be reduced. In addition, the pre-registration conveying roller pair 120 is always in a separated state, and the pre-registration conveying roller pair 120 does not switch between contact and separation while paper of the same size / basis weight is being continuously printed. Therefore, there is no need to stop conveying, and a decrease in productivity can be prevented.

[0048] Also, if the length of the paper in the conveying direction is less than X [mm] and the paper weight is M [gsm] or more, it is considered to be in "contact". In other words, if the paper weight is M [gsm] or more and the paper is stiff, it is determined that the occurrence rate of wrinkles is small, and the pre-registration conveying roller pair 120 is not separated and is always in contact. As a result, it is possible to prevent a decrease in productivity.

[0049] In addition, if the length of the paper in the transport direction is less than X [mm], it is considered to be in "contact" regardless of the basis weight of the paper. Since the length of the paper in the transport direction is less than X [mm], it is determined that even if the pre-registration transport roller pair 120 remains in contact, there is little twisting and wrinkles. As a result, by not separating the pre-registration transport roller pair 120 and keeping it in a constant contact state, it is possible to prevent a decrease in productivity.

[0050] The threshold value X, which is the threshold value of the length of the paper in the transport direction, is the length of the paper that can be transported by the upstream transport rollers (pulling drive roller 122 or cassette pull-out roller 121) even if the pre-registration transport roller pair 120 is separated. The threshold value of the paper basis weight, which is the basis weight M, is the boundary basis weight at which wrinkles may occur when the paper is transported without separating the pre-registration transport roller pair 120.

[0051] [effect] As described above, in this embodiment, the pre-registration transport roller pair 120 is switched between separation and contact depending on the configuration of the paper transport path. With this configuration, even in a paper transport path where the pre-registration transport roller pair and the cassette pull-out roller pair are used together, it is possible to transport the paper without causing a feed failure. Also, in the paper transport path where the paper is fed from the paper feed cassette 110, the pre-registration transport roller pair and the cassette pull-out roller pair can be used together, which makes it possible to reduce costs.

[0052] In addition, according to this embodiment, switching between separation and contact of the pre-registration conveying roller pair 120 has the disadvantage of reducing productivity. Therefore, by providing a mode setting that switches between the presence and absence of the separation operation, it is possible to avoid the reduction in productivity.

[0053] (Other Examples) The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions. [Explanation of symbols]

[0054] 100 Image forming device 110 Paper feed cassette (first storage unit) 111 Paper feed cassette (second storage unit) 113 Paper feed roller 114 Paper feed roller 116 Pulling motor 120 Pre-registration transport roller pair 121 Cassette pull-out roller 129 Distance Sensor 130 Registration roller pair 131 Cash register detection sensor 140 Separation mechanism 145 Pre-register conveyor motor 150 Image forming section 160 Fixing unit 181 Paper feed motor 133 Cash register drive motor 145 Pre-register conveyor drive motor 200 Control section 201 CPU 202 ROM 203 RAM 204 Motor drive circuit 205 Sensor output detection circuit 301 Operation section

Claims

1. an image forming unit that forms an image on a sheet; a first storage container for storing paper; a first feeding / separating unit that feeds the paper stored in the first storage case and separates the paper sheets one by one; a pair of conveying rollers for conveying the paper fed by the first feeding / separating unit; a pair of registration rollers that corrects skew of the paper conveyed by the pair of conveying rollers and conveys the paper whose skew has been corrected to the image forming unit; a first conveying path provided between the first storage case and the pair of conveying rollers in a sheet conveying direction, through which a sheet passes; a second storage unit provided below the first storage unit and configured to store paper; a second feeding / separating unit that feeds the paper stored in the second storage case and separates the paper sheets one by one; a pair of drawing rollers for conveying the paper fed by the second feeding / separating unit; a second transport path through which the sheet passes, the second transport path being provided in the sheet transport direction between the second storage and a junction where the sheet transported by the pair of pull-out rollers joins the first transport path downstream of the first feeding / separating portion and upstream of the pair of transport rollers; a separation mechanism for causing one roller of the pair of conveying rollers to come into contact with or separate from the other roller; a control means for controlling the separation mechanism so that when an image is formed on a sheet fed from the first storage chamber, the one roller is brought into contact with the other roller regardless of the type of sheet stored in the first storage chamber, and when an image is formed on a sheet fed from the second storage chamber, the one roller is separated from the other roller based on the type of sheet stored in the second storage chamber, In the first transport path, the first feeding / separating unit is disposed closest to the upstream of the transport roller pair in the sheet transport direction, The pull-out roller pair and other conveying roller pairs for conveying a sheet are not provided between the first feeding / separating portion and the conveying roller pair in the first conveying path; An image forming apparatus comprising:

2. A setting unit is provided for setting whether or not the pair of conveying rollers is to be separated, The image forming apparatus according to claim 1, characterized in that, when the setting means is set to not separate the pair of conveying rollers, the control means controls the separation mechanism to abut one of the rollers against the other roller regardless of the type of paper, even when an image is formed on paper fed from the second storage chamber.

3. 3. The image forming apparatus according to claim 1, further comprising a drive motor that rotates in a first direction to rotate the other roller and that rotates in a second direction opposite to the first direction to bring the one roller into contact with or away from the other roller.

4. 4. The image forming apparatus according to claim 1, wherein the type of paper includes a basis weight and a size of the paper.

Images