JP7625403B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming device.

Conventionally, some image forming devices are equipped with a skew correction section that conveys paper fed from a paper storage section to an image forming section and corrects skew in the paper. The skew correction section is equipped with a pair of rollers called a registration roller pair, and performs skew correction by hitting the leading edge of the paper against the nip of this roller pair to bend the paper.

In recent years, image forming devices have been 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 become narrower. If the spacing between the transport rollers is narrowed, the paper will become more twisted when the skew correction unit corrects the skew of the paper, which can result in wrinkles on the paper.

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

JP 2019-26452 A

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 with paper transported along a transport path with a short distance from the paper storage unit to the image forming unit.

The present invention was made in consideration of the above problems, and its purpose is to prevent non-feeding by appropriately controlling whether or not to separate the conveying roller pair.

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 unit that stores paper, a first feeding and separating unit that feeds the paper stored in the first storage unit 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 unit and the transport roller pair in a sheet transport direction and through which a sheet passes, a second storage unit that is provided below the first storage unit and stores paper, a second feeding and separating unit that feeds the paper stored in the second storage unit 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 pair of pull-out rollers that transports the paper fed by the second storage unit in the sheet transport direction, the first feeding and separation section is disposed upstream of the pair of conveying rollers in the first conveying path, the second feeding and separation section being disposed between the pair of conveying rollers and a junction where the two rollers join upstream of the pair of conveying rollers, the second feeding and separation section being disposed between the pair of conveying rollers and the junction where the two rollers join upstream of the pair of conveying rollers, the second feeding and separation section being disposed between the pair of conveying rollers and the junction where the two rollers join upstream of the pair of conveying rollers, the second feeding and separation section being disposed between the pair of conveying rollers and the junction where the two rollers join upstream of the pair of conveying rollers, the second feeding and separation section being disposed between the pair of conveying rollers and the pair of conveying rollers in the first conveying path, the first feeding and separation section being disposed upstream of the pair of conveying rollers in the sheet conveying direction, the second feeding and separation section being disposed between the pair of conveying rollers and the pair of conveying rollers in the first conveying path, the first feeding and separation section being disposed upstream of the pair of conveying rollers and the junction where the two rollers join

According to the present invention, the occurrence of non-feeding can be suppressed by controlling the separation operation of the conveying roller pair depending on the paper feed source.

Simplified cross-sectional view of an image forming apparatus Block diagram of an image forming apparatus Schematic diagram of a pre-registration conveying roller pair in a separated state. Schematic diagram of a state in which a pair of pre-registration transport rollers are in contact with each other Driving configuration diagram when the pre-registration conveying roller pair is separated Driving configuration diagram when the pre-registration transport roller pair is in contact Drive transmission diagram when rotating the pre-registration transport roller pair Drive transmission diagram when operating the separation mechanism Flowchart for explaining a paper feeding operation FIG. 13 is a table showing a separation judgment table for a pair of pre-registration conveying rollers; FIG. 13 is a schematic diagram for explaining the twisting of paper during skew correction; FIG. 13 is a diagram showing an operation screen displayed on the operation unit for setting the front-of-register separation mode.

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 a PC, which is an external device, 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.

Each image forming station Y-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-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. The exposure device 152 provided at the bottom of the device 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. The 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-K are primarily transferred from the photosensitive drum 151 to the intermediate transfer belt 155 by the primary transfer roller 154. Adherents such as toner remaining on the photosensitive drum 151 are removed by a cleaning unit provided at each image forming station Y-K.

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 a counterclockwise direction in FIG. 1. The toner image carried on the intermediate transfer belt 155 is secondarily transferred to paper S at a secondary transfer section formed between the intermediate transfer belt 155 and a secondary transfer roller 159 that faces the secondary transfer inner roller 156. Toner and other deposits remaining on the intermediate transfer belt 155 are removed by a belt cleaner.

The paper S with the transferred toner image is passed to the fixing device 160. The fixing device 160 has a fixing roller, a pressure roller that holds the paper S together with the fixing roller, and a halogen heater that heats the fixing roller. The fixing device 160 applies heat and pressure to the toner image while transporting the paper S, melting the toner, and then the toner is fixed to the paper S.

In parallel with this image formation process, paper S is fed one sheet at a time from paper feed cassettes 110, 111 or manual feed tray 112 toward image forming section 150.

The paper feed cassette 110 and the paper feed cassette 111 are examples of paper storage units that can be pulled out from the device main body 100A. The paper feed cassette 110 and the paper feed cassette 111 are arranged vertically side by side. The paper stored in the upper paper feed cassette 110 (first paper storage unit) is separated into sheets by the paper feed unit 113 (pickup roller 113a, feed roller 113b, retard roller 113c). The separated and transported paper is handed over 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 unit, 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 transport path, the roller located most upstream in the transport direction relative to the pre-registration transport roller pair 120 is the feed roller 113b, which differs from the second transport path described below. In the following description, for convenience, the "pre-registration transport roller pair" may be referred to as the "pre-registration transport roller pair."

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 a second paper storage, is separated one by one by the paper feed unit 114 (pickup roller 114a, feed roller 114b, retard roller 115b) and handed over to the pull-out roller pair 121. The pull-out roller 121 transports the paper received from the paper feed roller 114 toward the image forming unit 150. In this embodiment, the transport path from the paper feed cassette 111, which is the second paper storage, to the pre-registration transport roller pair 120 is called the second transport path for convenience. The second transport path is a transport path that is shorter in distance than the first transport path, and if the paper fed by the paper feed roller 114 is a small-sized paper, the paper cannot be handed over to the pre-registration transport roller pair 120. For this reason, a cassette removal roller 121 is placed on the second transport path.

Similarly, the paper placed on the manual feed tray 112 is separated one by one by the feed roller 115 and delivered to the pull-out drive roller 122.

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

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

Figure 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.

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

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 control signals 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, it specifies only one rotation direction (the transport direction) for the register drive motor 133 and the pull-out motor 116.

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 sensor ON when the pre-registration conveying roller pair 120 is in a separated state, and that the registration detection sensor 132 is sensor ON when the paper reaches the registration roller position.

The operation unit 301 notifies the user of the status of the image forming device 100 based on a signal received from the CPU 201. The operation unit 301 also receives operation instructions for the image forming device 100 from the user.

[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 sheet S fed from each sheet storage is transported downstream on the transport path by the pre-registration transport roller pair 120. The transported sheet S is then abutted against the nip of the stopped registration roller pair 130 so that the leading edge of the sheet S is aligned. As a result, a loop is formed for the sheet 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 sheet S.

Figure 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. 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 may be applied to the sheet S, causing 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 distributed, and the occurrence of these wrinkles can be avoided. For this reason, this patent has a separation mechanism for the pre-registration conveying rollers.

[Separating Operation of Conveyance Roller Before Registration]
The configuration and operation of the pre-registration conveying roller pair 120 according to this embodiment will be described with reference to Figures 3 to 8. Figures 3 and 4 are diagrams showing the cross-sectional configuration of the conveying path until the fed paper reaches the registration roller pair 130. Figure 3 is a schematic diagram showing the state in which the pre-registration conveying roller pair 120 is in contact. Figure 4 is a schematic diagram showing the state in which the pre-registration conveying roller pair 120 is separated. Figure 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. Figure 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. Figure 7 is a drive transmission diagram when the pre-registration conveying roller pair 120 is rotated, and Figure 8 is a drive transmission diagram when the pre-registration conveying roller pair 120 is separated.

First, the rotation of the pre-registration transport roller pair 121 and the drive configuration for operating the separation mechanism 140 will be described with reference to Figures 7 and 8. The pre-registration drive gear 147 is provided with a one-way clutch (not shown) so that drive is transmitted to the output shaft only when the pre-registration transport drive motor 145 rotates CW. In addition, the separation gear 146 is provided with a one-way clutch (not shown) so that drive is transmitted to the output shaft only when the pre-registration transport drive motor 145 rotates CCW.

As shown in FIG. 7, when the pre-registration transport drive motor 145 rotates in the CW direction (first direction), the drive force is transmitted to the pre-registration transport roller pair 120 via the pre-registration drive gear 147. At this time, the drive force is not transmitted to the separation transmission shaft 148, and the separation mechanism 140 does not operate, so the pre-registration roller pair 121 remains in contact or separated state.

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 drive force is transmitted to the separation transmission shaft 148 via the separation gear 146. Then, the separation mechanism 140 switches the pre-registration transport roller pair 120 between a contact state and a separated state. At this time, the drive force is not transmitted to the drive shaft 121c, and the pre-registration transport roller pair 120 is in a non-driven state. In this way, the drive configuration of the pre-registration transport roller pair 120 can switch between the rotation drive of the pre-registration transport 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.

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, the pre-registration transport drive motor 145 is rotated CCW until the separation sensor 129 turns OFF.

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 biased 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 biased against the pre-registration conveyance drive roller 120a by the pre-registration pressure spring 143 held between the spring seat sheet metal 144 and the pre-registration conveyance roller pair 120, so that the pre-registration conveyance roller pair 120 comes into contact. 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 away 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 away 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 away from the pre-registration transport driven roller 120b. Also, both rollers may move to come into contact with or away from each other.

When the pre-registration transport roller pair 120 is put into a separated state, the pre-registration transport drive motor 145 is rotated CCW until the separation sensor 129 is turned ON. Specifically, the pre-registration transport 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 transport roller pair 120 is separated.

[Description of the paper feeding operation from CST2 (conveying path with independent pull-out rollers)]
Using Figure 4, we will explain the operation of transporting the transported paper S to the registration transport roller pair 130 in the transport path (second transport path) in which the cassette removal roller 121 is provided between the paper feed roller 114 and the pre-registration transport roller pair 120.

The paper S sent downstream of the paper transport path by the paper feed roller 114a and separation roller 114b is clamped by the cassette pull-out roller 121. The paper S clamped by the cassette pull-out roller 121 is pulled further downstream. The paper S pulled downstream passes through or is clamped by the pre-registration transport roller 120 and reaches the registration roller pair 130. Note that whether the pre-registration transport roller pair 120 is separated or contacted is determined based on the length and paper type, such as the basis weight, of the transported paper S. The separation or contact process is performed before the pickup roller 114a feeds the paper S from the cassette S.

The pickup roller 114a and the separation roller 114b are rollers whose main purpose is to send only one sheet of paper S from the top 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 transporting paper S using only the pickup roller 114a and the separation roller 114b, it is difficult to accurately control the amount of paper advancement. On the other hand, the cassette pull-out roller 121 and the downstream transport rollers are set so that the paper transport efficiency is almost 100%, and the amount of paper advancement can be accurately 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, depending on the basis weight and length of the paper.

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

The paper S sent downstream of the paper transport path by the pickup roller 113a and separation roller 113b is sandwiched between the pre-registration transport roller pair 120 and reaches the registration roller pair 130.

As mentioned above, the amount of paper advance cannot be accurately controlled using only the pickup roller 113a and separation roller 113b. As a result, the amount of insertion of the registration rollers cannot be accurately controlled, and skew correction cannot be performed correctly. For this reason, 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.

[Explanation regarding separation mode of pre-registration conveying roller pair]
Next, a 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 a user selects the pre-registration separation mode, the user selects it via a user operation screen 200 shown in FIG. 12.

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" are explained in the explanation of the flowchart in Figure 9. The mechanism by which paper wrinkles occur has already been explained in Figure 11.

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 conveying 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, there is a risk of the paper becoming wrinkled depending on the setting state of the paper. Therefore, a message to prevent the paper from becoming wrinkled is displayed at 203 in FIG. 12 to encourage the user to avoid rough setting. The operating conditions and details of the "productivity priority mode" will be explained in the explanation of the flowchart in FIG. 9.

[Explanation of Flowchart of 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 when a print job is 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.

First, it is determined whether the pre-registration conveying roller pair 120 is separated to reliably avoid the occurrence of paper wrinkles, or whether the pre-registration conveying roller pair 120 is not separated and the mode prioritizes productivity. Specifically, it is determined whether the pre-registration separation mode is the "wrinkle avoidance priority mode" or the "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" (it is the "productivity priority mode"), the pre-registration conveying roller pair 120 always maintains abutment. Therefore, the processing of S1001 to S1009 is not performed, and the process proceeds to S1010, where 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 pull-out roller in the conveying path from the storage to the registration roller pair 130. If the answer is YES in S1001, 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. After that, the CPU 201 executes the contact operation of the pre-registration conveying roller pair 120 (S1004). After the pre-registration conveying roller pair 120 transitions to the contact state, the CPU 201 starts the paper feed operation (S1010).

In S1001, when paper is fed from a paper storage other than cassette 1, a separation/attachment judgment is performed (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. The transport path of paper fed from these paper storages is configured to have an independent pull-out roller arranged between the registration roller pair 130. If the judgment result in S1005 is "contact", proceed to S1002. If the judgment result is "separation", it is judged whether the pre-registration transport roller pair 120 is in a separated state (S1007). If the pre-registration transport roller pair 120 is in a separated state (YES in S1007), the CPU 201 starts the paper feed operation (S1010). On the other hand, if the pre-registration conveying roller pair 120 is in the contact state, the CPU 201 determines whether the pre-registration conveying roller pair 120 is conveying a sheet (S1008). If the pre-registration conveying roller pair 120 is conveying a sheet, the CPU 201 waits until the pre-registration conveying roller pair 120 has completed conveying the sheet. The CPU 201 then performs a separation operation of the pre-registration conveying roller pair 120 (S1009). After the pre-registration conveying roller pair 120 transitions to the contact state, the CPU 201 starts a sheet feeding operation (S1010).

[Separation/contact determination process]
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 paper is set to "separated". As a result, even if the paper has a basis weight of less than M [gsm] and is weak, the occurrence of wrinkles can be reduced by separating the pre-registration conveying roller pair 120. 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.

In addition, if the length of the paper in the transport direction is less than X [mm] and the paper has a basis weight of M [gsm] or more, it is considered to be in "contact." In other words, if the paper has a basis weight of M [gsm] or more and is stiff, it is determined that the occurrence rate of wrinkles is low, and the pre-registration transport roller pair 120 is not separated and is kept in a constant contact state. As a result, a decrease in productivity can be prevented.

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. Because 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 them in a constant contact state, it is possible to prevent a decrease in productivity.

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. In addition, basis weight M, which is the threshold value of the paper basis weight, is the boundary basis weight at which wrinkles may occur if the paper is transported without separating the pre-registration transport roller pair 120.

[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 in combination, it is possible to transport the paper without causing non-feeding. 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 in combination, which makes it possible to reduce costs.

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 separation operation, it is possible to avoid a reduction in productivity.

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.

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

Claims (4)

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: 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. The image forming apparatus according to claim 1 or 2, further comprising a drive motor that rotates in a first direction to rotate the other roller and rotates in a second direction opposite to the first direction to bring the one roller into contact with or away from the other roller. The image forming device according to any one of claims 1 to 3, characterized in that the type of paper includes the basis weight and size of the paper.

Images