Medium conveyance device, image formation apparatus, and image formation system

Abstract

To provide a medium conveyance device which maintains conveyance power for a medium varying in accordance with a conveyance load.SOLUTION: A medium conveyance apparatus comprises: plural conveyance mans along a conveyance passage; conveyance state detection means for detecting the conveyance state of a medium; conveyance power variable means for changing conveyance power applied to the medium by the conveyance means; and control means for controlling the conveyance power variable means so that the conveyance power applied to the medium from the specified conveyance means is changed. When a result of determining the conveyance state of the medium based on a first detection result from the first conveyance state detection means corresponding to the first conveyance means arranged relatively upstream and a second detection result from the second conveyance state detection means corresponding to the second conveyance means arranged relatively downstream is the one showing the reduction of the conveyance power to the medium, the control means controls the conveyance power variable mean corresponding to the second conveyance means so that the conveyance power applied to the medium by the second conveyance means is increased.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a medium conveying device, an image forming device, and an image forming system. [Background technology]

[0002] 2. Description of the Related Art Media conveying devices are known for conveying sheet-like media along a predetermined conveyance path. Image forming apparatuses that include the media conveying devices and image forming systems that operate in conjunction with the media conveying devices are also known.

[0003] In order for a media transport device to transport a medium, the transport force applied to the medium is often applied by roller pairs arranged at predetermined intervals along the transport path. The medium is then transported along the transport path in a predetermined state by the appropriately applied transport force. For example, the transport force causes the medium to pass through a specific section of the transport path in a predetermined time. Therefore, transport control to maintain the optimal media transport state is achieved by controlling the transport force applied to the medium by the roller pairs.

[0004] On the other hand, the shape of the transport path of a medium transport device, etc., is not only linear but also includes curved sections with multiple curvatures. When a medium to which a predetermined transport force is applied passes through a curved section, the transport resistance of the medium is greater than when the medium passes through a linear section.

[0005] That is, the conveying force applied by the roller pair at a predetermined magnitude decreases and fluctuates due to friction or collision with the conveying path, etc. The conveying force applied to the medium also fluctuates depending on the contact state (friction state) with the roller pair.

[0006] Therefore, when transporting media in an optimal condition in a media transport device, various factors are to be considered, such as transport loads arising from structural factors and loads that fluctuate depending on the condition of the media, and it is desirable to maintain the transport force that fluctuates due to these factors at a predetermined state.

[0007] In a conveying mechanism for conveying sheet-like media, a technique is known in which the deflection of the media between a pair of rollers that convey the media is detected and the pressure with which the pair of rollers clamp the media is reduced or released (see Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0008] The conventional technology disclosed in Patent Document 1 reduces and releases the pressure applied by the upstream roller pair when it detects that the medium is sagging between the roller pair arranged in the conveying path. However, it is known that the conveying force applied to the medium can be reduced due to the conveying load, which can cause conveying problems.

[0009] In this regard, conventional techniques are unable to recover the media transport force that decreases as the transport load increases due to factors in the transport path, and have a problem in suppressing the causes of transport failures.

[0010] An object of the present invention is to provide a medium transport device that maintains a medium transport force that varies depending on the transport load. [Means for solving the problem]

[0011] In order to solve the above problem, one aspect of the present invention relates to a media processing device comprising: conveying means arranged at multiple locations along a conveying path for conveying media; conveying state detection means arranged corresponding to each of the conveying means and detecting the conveying state of the media; conveying force variable means for changing the conveying force applied to the media from at least one of the conveying means; and control means for controlling the conveying force variable means arranged corresponding to a specific conveying means so that the conveying force applied to the media by a specific conveying means is changed in accordance with the detection results of the multiple conveying state detection means; and when the result of determining the conveying state of the media based on a first detection result from a first conveying state detection means corresponding to a first conveying means arranged relatively upstream in the conveying direction and a second detection result from a second conveying state detection means corresponding to a second conveying means arranged relatively downstream in the conveying direction indicates a decrease in the conveying force applied to the media, the control means controls the conveying force variable means corresponding to the second conveying means so as to increase the conveying force applied to the media by the second conveying means. [Effects of the Invention]

[0012] According to the present invention, it is possible to maintain the medium transport force that fluctuates depending on the transport load. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a diagram showing the overall configuration of an example of an image forming system according to the present invention; [Figure 2] 1 is a diagram showing an example of the configuration of a transport mechanism as a medium transport device according to the present invention; [Figure 3] 5A to 5C are diagrams illustrating an example of the operation of the transport mechanism. [Figure 4] 10 is a flowchart showing an example of the flow of a control process of the transport mechanism. [Figure 5] 6A and 6B are diagrams showing examples of changes in a detection signal used to control the transport mechanism. [Figure 6] 10 is a flowchart showing another example of the flow of the control process of the transport mechanism. [Figure 7]10 is a flowchart showing another example of the flow of the control process of the transport mechanism. [Figure 8] 10 is a flowchart showing another example of the flow of the control process of the transport mechanism. [Figure 9] 10A and 10B are diagrams showing another example of the configuration of a transport mechanism as a medium transport device according to the present invention. [Figure 10] 6A and 6B are diagrams showing examples of changes in a detection signal used to control the transport mechanism. [Figure 11] 10A and 10B are diagrams showing another example of the configuration of a transport mechanism as a medium transport device according to the present invention. [Figure 12] 10A and 10B are diagrams showing another example of the configuration of a transport mechanism as a medium transport device according to the present invention. [Figure 13] 10A and 10B are diagrams showing another example of the configuration of a transport mechanism as a medium transport device according to the present invention. [Figure 14] 6A and 6B are diagrams showing examples of changes in a detection signal used to control the transport mechanism. [Figure 15] 10A and 10B are diagrams showing another example of the configuration of a transport mechanism as a medium transport device according to the present invention. [Figure 16] 10A and 10B are diagrams showing another example of the configuration of a transport mechanism as a medium transport device according to the present invention. [Figure 17] 6A and 6B are diagrams showing examples of changes in a detection signal used to control the transport mechanism. [Figure 18] 10A and 10B are diagrams showing another example of the configuration of a transport mechanism as a medium transport device according to the present invention. [Figure 19] 10A and 10B are diagrams showing another example of the configuration of a transport mechanism as a medium transport device according to the present invention. [Figure 20] 10 is a flowchart showing another example of the flow of the control process of the transport mechanism. [Figure 21] 10 is a flowchart showing another example of the flow of the control process of the transport mechanism. [Figure 22] 10 is a flowchart showing another example of the flow of the control process of the transport mechanism. [Figure 23] FIG. 2 is a hardware configuration diagram of a control block that controls the operation of the transport mechanism. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, reference numerals are used to distinguish between components. Components with the same reference numerals generally represent similar components, but some exceptions will be explained separately.

[0015] [Embodiment of Image Forming System 1] Fig. 1 is a diagram showing the overall configuration of an image forming system 1. The image forming system 1 has an image forming function for forming an image on paper P, which corresponds to a type of sheet-like medium, and a post-processing function for performing post-processing on the paper P on which the image has been formed as a process after the image formation. As shown in Fig. 1, the image forming system 1 is configured so that an image forming device 2 and a post-processing device 3 work together.

[0016] Furthermore, the image forming system 1 is connected to a large-capacity medium supply device 22 as a medium supply device that supplies media to the image forming device 2.

[0017] In this embodiment, the medium to be processed in the image forming system 1 is assumed to be sheet-like "paper," but the medium to be processed is not limited to paper, and is any medium on which an image can be formed using a conventionally known image forming process, and which can be subjected to folding and binding processes, regardless of material or specifications.

[0018] The image forming device 2 forms an image on a sheet P and discharges the sheet P with the image formed thereon to the post-processing device 3. The image forming device 2 includes a storage tray 201 that stores the sheet P, a transport unit 202 that transports the sheet P stored in the storage tray 201, and an image forming unit 203 that forms an image on the sheet P transported by the transport unit 202. The image forming device 2 includes an operation display panel 110 on the exterior of its housing. The operation display panel 110 is a type of user interface that inputs instructions for processing content to the image forming device 2. The operation display panel 110 also has the function of displaying information indicating the operating status of the image forming device 2 and the entire image forming system 1, and information to notify the user if an operational malfunction occurs. Therefore, if a malfunction occurs in the transport of the sheet P in the medium transport device, an error notification is displayed on the operation display panel 110.

[0019] The image forming unit 203 may be an inkjet type that forms an image using ink, or an electrophotographic type that forms an image using toner. The image forming apparatus 2 also includes a control unit 100 that controls various operations of the conveying unit 202 and the image forming unit 203. The configuration of the image forming apparatus 2 is already well known, so a detailed description thereof will be omitted, but a detailed description of the control unit 100 will be given later.

[0020] The medium conveying device according to the present invention can be applied to, for example, the conveying section 202 inside the image forming device 2. It can also be applied to a conveying mechanism that conveys paper P to a predetermined position inside the post-processing device 3, and a conveying mechanism provided in the large-capacity medium supply device 22.

[0021] [First embodiment] Fig. 2 illustrates an example of an embodiment of a medium conveying device according to the present invention, illustrating a portion of a conveying mechanism 200 serving as a medium conveying unit. The conveying mechanism 200 shown in Fig. 2 includes a first conveying roller pair 210 serving as a first conveying means and a second conveying roller pair 220 serving as a second conveying means, among a plurality of conveying means arranged along a conveying path 250. Note that, since the conveying mechanism 200 has a plurality of conveying means arranged along the conveying path 250, the number of conveying means is not limited to two.

[0022] The present invention relates to transport control when a sheet P is transported across two transport means arranged at specific positions among a plurality of transport means. In this explanation, for convenience, one of the two transport means will be defined as the "upstream transport means" and the other as the "downstream transport means." In FIG. 2, the upstream transport means is the first transport roller pair 210 as the first transport means. The downstream transport means is the second transport roller pair 220 as the second transport means.

[0023] In this specification, the terms "upstream" and "downstream" are used relative terms, and the terms "upstream side" and "downstream side" may be interchanged even for the same configuration depending on the position of interest. The terms "upstream" and "downstream" are used based on the transport direction of paper P, which is the medium to be transported. In the case of the transport mechanism 200 shown in FIG. 2, the right side of the first transport roller pair 210 corresponds to the upstream side when facing the drawing. The paper P is transported from the first transport roller pair 210 on the upstream side through the transport path 250 to the second transport roller pair 220 on the downstream side. The paper P is then transported downstream of the second transport roller pair 220.

[0024] A first medium sensor 211 is disposed near the first conveying roller pair 210 as a corresponding first conveying state detection means. Furthermore, a second medium sensor 221 is disposed near the second conveying roller pair 220 as a corresponding second conveying state detection means. Detection signals from the first medium sensor 211 and the second medium sensor 221 are notified to the control unit 100 and are used to determine the conveying state of the paper P.

[0025] Therefore, the conveying mechanism 200 optimizes the conveying condition of the paper P by having the first media sensor 211 detect the paper P to which a conveying force is applied by the first pair of conveying rollers 210 located relatively upstream, and then having the second media sensor 221 detect the same paper P.

[0026] In the conveying mechanism 200 according to this embodiment, the second pair of conveying rollers 220 is provided with a second pressure change means 222 as a conveying force change means for changing the conveying force applied to the paper P.

[0027] In this embodiment, the specific section is the section of the conveying path 250 located between the first conveying roller pair 210 and the second conveying roller pair 220. When the conveying load of the paper P increases in this specific section and the conveying force of the paper P decreases, the conveying mechanism 200 is characterized in that it has a function of operating the second pressure force changing means 222 to restore the decreased conveying force.

[0028] Factors that reduce the conveying force of paper P include a portion of the conveying path 250 having a curvature, as shown in FIG. 2. It is expected that conveying resistance will increase when paper P passes through this curvature. That is, in a specific section with a curvature, paper P moves downstream while experiencing friction and collision with components of the conveying path 250. As a result, the conveying force applied by the first conveying roller pair 210 located upstream decreases, and the controller 100 determines the situation when the medium detected by the first medium sensor 211 is detected by the second medium sensor 221, and estimates the degree of decrease in conveying force. When this estimation determines that the conveying force has fallen below a certain level, the controller 100 operates to increase the conveying force applied by the second conveying roller pair 220 located downstream.

[0029] The control unit 100, which will be described later, estimates a decrease in the conveying force of the paper P based on the detection results of the first medium sensor 211 and the second medium sensor 221. If the conveying force indicates a certain decrease, the control unit 100 operates the second pressure force changing means 222 to control the conveying force applied to the paper P by the second conveying roller pair 220 to increase.

[0030] 2, one of the causes of the transport load that reduces the transport force of the paper P is the presence of curvature in part of the transport path 250. That is, starting from a specific section having a curvature, when there is a situation in which the transport force applied to the paper P by the first transport roller pair 210 arranged upstream is estimated to have decreased when the paper P passes through the curvature portion, the transport force applied by the second transport roller pair 220 is increased.

[0031] Here, an example of the conveying state in Fig. 2 will be described. The sheet P to which a conveying force is applied by the first conveying roller pair 210 is detected by the first medium sensor 211, then detected by the second medium sensor 221, and conveyed by the second conveying roller pair 220.

[0032] If the transport load increases at a curved portion (corner) of the transport path 250 after the paper P transported by the first transport roller pair 210 is detected by the first medium sensor 211, the time that elapses until the second medium sensor 221 detects the paper P will be delayed beyond the first elapsed time constant value Tht1, which is a predetermined first threshold time. Therefore, the control unit 100 determines whether the time that has elapsed since the first medium sensor 211 detected the paper P has exceeded the first elapsed time constant value Tht1.

[0033] Then, when the control unit 100 determines that the elapsed time has exceeded the first elapsed time constant value Tht1, that is, when the paper P to which the conveying force has been applied by the first conveying roller pair 210 has not reached a predetermined position (a position detected by the second media sensor 221) within a specific time, it estimates that the conveying force of the paper P has decreased due to the conveying load.

[0034] Therefore, the control unit 100 operates the second pressure change unit 222 to increase the conveying force applied by the second conveying roller pair 220. Note that, in order to increase the conveying force applied by the second conveying roller pair 220, it is only necessary to increase the contact pressure between the rollers constituting the second conveying roller pair 220. Therefore, as illustrated in Fig. 3, the second pressure change unit 222 operates to increase the force that presses one roller constituting the second conveying roller pair 220 toward the other roller.

[0035] In this embodiment, a solenoid is used as the second pressure change means 222. However, the configuration of the second pressure change means 222 is not limited to a solenoid. For example, a cam mechanism may be used to apply pressure by pressing one roller against the other roller, or a housing that holds the second conveying roller pair 220 may be applied with pressure to increase the contact pressure between the rollers. Alternatively, any method that can change the pressure, such as switching the pressure between the rollers by rotating a motor forward or backward, may be used.

[0036] [First example of processing flow according to the first embodiment] Next, the flow of control processing according to this embodiment will be described using the flowchart in Fig. 4. Fig. 4 illustrates a transport job for transporting paper P along the transport path 250 illustrated in Fig. 2 and Fig. 3. Note that the transport job executed in the transport mechanism 200 may include various processes in addition to the process illustrated in Fig. 4, but only the process that includes the features of the present invention will be described here.

[0037] In the following description, it is assumed that when the first medium sensor 211 or the second medium sensor 221 detects the paper P, the detection signal level outputted is "V2 or higher." When the paper P is not detected, the detection signal level is "V1." And, V1 <V2とする。

[0038] First, a transport job is started, and the process of determining whether a transport abnormality exists continues (S405) until the detection signal level of the first medium sensor 211 reaches V2 (S401: NO). Step S405 corresponds to the process of determining whether a transport abnormality exists based on whether the time elapsed from the start of the transport job until the first medium sensor 211 detects the sheet P exceeds the abnormality determination threshold The1. If the time elapsed until the first medium sensor 211 detects the sheet P exceeds the abnormality determination threshold The1 (S405: YES), it is determined that a transport abnormality has occurred, and the control unit 100 stops the transport process (S406). Then, an error notification is sent to the operation display panel 110 (S407), and the transport job is terminated. The error notification in step S407 may be a display indicating an error on the operation display panel 110, or an alarm may be sounded, as long as the user can be notified of the abnormality.

[0039] After the level of the detection signal from the first medium sensor 211 becomes V2 (S401: YES), and thereafter, until the level of the detection signal from the second medium sensor 221 becomes V2 (S402: NO), if the elapsed time during this period does not exceed the first elapsed time constant Tht1 (S403; NO), step S402 is looped. In other words, after the level of the detection signal from the first medium sensor 211 becomes V2 (S401: YES), and thereafter, when it is determined based on the second detection result that the leading edge of the paper P in the transport direction has reached the second medium sensor 221 (S402: NO), if the elapsed time during this period does not exceed the first elapsed time constant Tht1 (S403; NO), step S402 is looped.

[0040] Starting from the time when the level of the detection signal from the first medium sensor 211 becomes equal to or greater than V2 (S401: YES), when the time elapses until the level of the detection signal from the second medium sensor 221 becomes equal to or greater than V2 (S402: NO), and the first elapsed time constant Tht1 has elapsed (S403: YES), it is estimated that the conveying force applied to the paper P by the first conveying roller pair 210 has decreased. Therefore, the control unit 100 controls the operation of the second pressure force change means 222 to increase the conveying force applied by the second conveying roller pair 220 (S404).

[0041] [Relationship between the outputs of the first medium sensor 211 and the second medium sensor 221] Figure 5 shows how the pressure applied by the second pressure change means 222 corresponding to the second conveying roller pair 220 is changed when the second conveying roller pair 220 is unable to detect the paper P within a fixed value (until the first elapsed time fixed value Tht1 has elapsed) after the first media sensor 211 detects the paper P.

[0042] For example, in Fig. 5, when t3 is the time corresponding to the first elapsed time constant value Tht1, the level of the output signal of the second medium sensor 221 does not reach V2 by t3 after the first medium sensor 211 reaches V1. That is, in the example of Fig. 5, it is estimated that the conveying force of the paper P that has passed through the first conveying roller pair 210 has decreased. In this case, the pressure is changed by the second pressure change unit 222.

[0043] 5, even after the output signal level of the second medium sensor 221 changes from V1 to V2, the output signal level of the first medium sensor 211 remains at V2. This is because the example illustrates a case where the length of the paper P in the transport direction is longer than the arrangement distance between the first medium sensor 211 and the second medium sensor 221.

[0044] [Second example of processing flow according to the first embodiment] Next, another example of the flow of the control process according to this embodiment will be described using the flowchart of Fig. 6. Fig. 6 illustrates the flow of a transport job including a process of transporting paper P along the transport path 250 illustrated in Fig. 2 and Fig. 3. In this example, when the second medium sensor 221 does not detect paper P until a second elapsed time constant value Tht2, which is a predetermined second threshold time, has elapsed after the first medium sensor 211 detects paper P, the transport force applied by the first transport roller pair 210 is increased.

[0045] First, a transport job is started, and processing to determine whether a transport abnormality has occurred continues (S605) until the detection signal level of the first medium sensor 211 reaches V2 (S601: NO). Step S605 corresponds to processing to determine whether a transport abnormality has occurred, based on whether the time elapsed from the start of the transport job until the first medium sensor 211 detects the sheet P exceeds the abnormality determination threshold The1. If the abnormality determination threshold The1 has been exceeded by the time the first medium sensor 211 detects the sheet P (S605: YES), an error notification is issued (S606), and the transport job is terminated. Note that the error notification in step S606 is the same as the error notification in step S407, and therefore a description thereof will be omitted.

[0046] After the level of the detection signal of the first medium sensor 211 becomes V2 (S601: YES), if the output of the second medium sensor 221 becomes V2 (S604: YES) before the second elapsed time constant value Tht2 is exceeded (S602: NO), the processing ends.

[0047] After the level of the detection signal from the first medium sensor 211 reaches V2 (S601: YES), but before the output of the second medium sensor 221 reaches V2 (S604: NO), when the second elapsed time Tht2 has elapsed (S602: YES), it can be assumed that the conveying force applied by the first conveying roller pair 210 is decreasing. Therefore, the conveying speed by the first conveying roller pair 210 is accelerated, and the pressure applied by the first conveying roller pair 210 and the second conveying roller pair 220 is also increased, and the process ends. To accelerate the conveying speed, the rotation speed of the first conveying roller pair 210 can be increased.

[0048] [Third example of processing flow according to the first embodiment] Next, another example of the flow of control processing according to this embodiment will be described using the flowchart of Fig. 7. Fig. 7 illustrates a transport job in which paper P is transported along the transport path 250 illustrated in Fig. 2 and Fig. 3. In this example, the first medium sensor 211 and the second medium sensor 221 each have a threshold value for the elapsed time until they detect paper P, and when this threshold value is reached, the transport forces applied by the corresponding first transport roller pair 210 and second transport roller pair 220 are increased.

[0049] First, a conveying job is started, and the process loops until the detection signal level of the first medium sensor 211 reaches V2 (S701: NO) or until a fourth elapsed time Tht4 serving as a predetermined fourth threshold value has elapsed (S705: NO). Also, when the elapsed time until the detection signal level of the first medium sensor 211 reaches V2 (S701: NO) exceeds the fourth elapsed time Tht4 (S705: YES), the pressure of the first conveying roller pair 210 is increased (S706), and the process ends.

[0050] If the detection signal level of the first media sensor 211 becomes V2 (S701: YES) and the detection signal level of the second media sensor 221 becomes V2 (S702: NO), and the third elapsed time constant value Tht3 as the predetermined third threshold time has not elapsed (S703: NO), the processing loops.

[0051] Furthermore, when the detection signal level of the first media sensor 211 becomes V2 (S701: YES) and the elapsed time until the detection signal level of the second media sensor 221 becomes V2 (S702: NO) exceeds the third elapsed time constant value Tht3 (S703: YES), the pressure of the second conveying roller pair 220 is also increased (S704), and the process is terminated.

[0052] [Fifth example of processing flow according to the first embodiment] Next, another example of the flow of the control process according to this embodiment will be described with reference to the flowchart of Fig. 8. Fig. 8 illustrates the process after the pressure change process (e.g., S404) is executed in a transport job for transporting paper P along the transport path 250 illustrated in Figs. 2 and 3.

[0053] This example is a process that is executed after the control unit 100 changes, for example, the pressure force in accordance with the detection results of the first medium sensor 211 and the second medium sensor 221. In other words, after the pressure force change process has been executed once, if the paper P that has passed the first medium sensor 211 is not detected by the second medium sensor 221 before the elapsed time thereafter reaches the first elapsed time constant Tht1, the process executes a change in the pressure force again.

[0054] After the pressure change process is executed during the transport job, if the output of the first medium sensor 211 or the second medium sensor 221 becomes V2 (S801: YES), the process ends.

[0055] After the pressure force change process is executed during a transport job, if the output of the first media sensor 211 or the second media sensor 221 has not yet reached V2 (S801: NO), the change limit value Thc as the limit value for the number of times the pressure force can be changed has not been exceeded (S802: YES), and the elapsed time after the pressure force change process has been executed has not exceeded the fifth elapsed time constant value Tht5 as the predetermined fifth threshold value (S803: NO), the process loops.

[0056] In the determination of step S803, if the elapsed time after the pressure change process is executed exceeds the fifth elapsed time constant value Tht5 (S803: YES), the pressure of the second conveying roller pair 220 is changed again to be one level higher (S804), the number of pressure change times is incremented, and the process proceeds to step S801.

[0057] As in this example, when the number of pressure force changes is equal to or less than the change limit value Thc, the pressure force is changed in stages until the paper P is detected by the first medium sensor 211 and the second medium sensor 221. It is assumed that a solenoid or the like capable of adjusting the protrusion amount in stages will be used as the second pressure force change means 222 that changes the pressure force in stages.

[0058] [Second embodiment] 9 illustrates another embodiment of a medium conveying device according to the present invention. As shown in FIG. 9, a conveying mechanism 200a includes a first current detection unit 214 that detects the drive current of the first conveying roller pair 210 without using the first medium sensor 211 and the second medium sensor 221.

[0059] The first conveying roller pair 210 rotates together with the pair of driven rollers and drive roller when the drive roller is rotated by the first driving unit 213 controlled by the control unit 100. When the paper P passes between this pair of rollers, the paper P is conveyed from upstream to downstream. At this time, a conveying force is applied to the paper P by the first conveying roller pair 210.

[0060] When the paper P is thicker than a predetermined thickness or has a large basis weight, or when the transport resistance is high, the value of the drive current applied from the first drive unit 213 to the drive roller becomes high.

[0061] The first current detection unit 214 detects the value of the drive current supplied to the drive roller by the first drive unit 213, and when the value of this drive current exceeds a predetermined current threshold, it is estimated that the transport load is high and the transport force applied to the paper P will decrease.

[0062] Therefore, in the conveying mechanism 200a, the control unit 100 monitors the drive current value detected by the first current detection unit 214, and when it exceeds a predetermined current threshold, controls the second pressure force change means 222 to increase the pressure force.

[0063] In this embodiment, too, a solenoid is used as the second pressure change means 222. However, the configuration of the second pressure change means 222 is not limited to a solenoid. For example, a cam mechanism may be used to apply pressure by pressing one roller against the other roller, or a housing that holds the second conveying roller pair 220 may be applied with pressure to increase the contact pressure between the rollers. Alternatively, any method that can change the pressure, such as switching the pressure between the rollers by rotating a motor forward or backward, may be used.

[0064] [Example of Output Fluctuation of First Current Detection Unit 214] FIG. 10 is a diagram illustrating the relationship between the change in the driving current of the first conveying roller pair 210 detected by the first current detection unit 214 and the pressure force changing process.

[0065] 10, the current threshold is set to V3. Furthermore, if there is no increase in conveyance resistance that would lead to an estimation of a decrease in conveyance force, as in pattern A, the value of the current voltage when the first conveyance roller pair 210 conveys the paper P changes from I1 to I2. When the conveyance resistance due to the paper P increases, the drive current applied to the first conveyance roller pair 210 exceeds I3 (pattern B).

[0066] Therefore, the control unit 100 monitors whether the drive current exceeds I3, and when the drive current exceeds I3, controls the second pressure change unit 222 to increase the pressure of the second conveying roller pair 220.

[0067] [Third embodiment] Fig. 11 illustrates another embodiment of a medium conveying device according to the present invention. As shown in Fig. 3, a conveying mechanism 200b according to this embodiment, like the conveying mechanism 200 already described, includes a first conveying roller pair 210 as a first conveying means and a second conveying roller pair 220 as a second conveying means, both of which are arranged along a conveying path 250. The conveying mechanism 200b differs from the conveying mechanism 200 in that it includes a first pressure change means 212 for increasing the conveying force applied by the first conveying roller pair 210.

[0068] The sheet P to which the conveying force is applied by the first conveying roller pair 210 is detected by the first medium sensor 211 , and then detected by the second medium sensor 221 and conveyed by the second conveying roller pair 220 .

[0069] If the transport load increases at a curved portion (corner) of the transport path 250 after the paper P transported by the first transport roller pair 210 is detected by the first medium sensor 211, the time elapsed until the paper P is detected by the second medium sensor 221 will be longer than the first elapsed time constant value Tht1, which is a predetermined first threshold time. The control unit 100 determines whether the elapsed time has exceeded the first elapsed time constant value Tht1.

[0070] When the control unit 100 determines that the elapsed time has exceeded the first elapsed time constant value Tht1, it assumes that the conveying force of the paper P has decreased due to the conveying load on the paper P, and increases the conveying force applied by the first conveying roller pair 210 using the first pressure force changing unit 212. At the same time, it increases the conveying force applied by the second conveying roller pair 220 using the second pressure force changing unit 222.

[0071] In this embodiment, solenoids are used as the first pressure change means 212 and the second pressure change means 222. However, the configuration of the first pressure change means 212 and the second pressure change means 222 is not limited to solenoids. For example, a cam mechanism may be used to apply pressure by pressing one roller against the other roller, or a housing that holds the first pressure change means 212 and the second conveying roller pair 220 may be applied to increase the contact pressure between the rollers. Alternatively, any method that can change the pressure, such as switching the pressure between the rollers by rotating a motor forward or backward, may be used.

[0072] [Fourth embodiment] Fig. 12 illustrates another embodiment of a medium conveying device according to the present invention. As shown in Fig. 12, a conveying mechanism 200c according to this embodiment, like the conveying mechanism 200a described as the second embodiment, is provided with a first conveying roller pair 210 as a first conveying means and a second conveying roller pair 220 as a second conveying means, both arranged along a conveying path 250. Furthermore, in addition to a first medium sensor 211 and a second medium sensor 221, the conveying mechanism 200c is also provided with a first current detection unit 214 that detects the drive current of the first conveying roller pair 210 and a second current detection unit 224 that detects the drive current of the second conveying roller pair 220.

[0073] The first conveying roller pair 210 rotates together with the pair of driven rollers and drive roller when the drive roller is rotated by the first driving unit 213 controlled by the control unit 100. When the paper P passes between this pair of rollers, the paper P is conveyed from upstream to downstream. At this time, a conveying force is applied to the paper P by the first conveying roller pair 210.

[0074] The second conveying roller pair 220 rotates together with the pair of driven rollers and drive roller when the drive roller is rotated by the second driving unit 223 controlled by the control unit 100. When the paper P passes between this pair of rollers, the paper P is conveyed from upstream to downstream. At this time, a conveying force is applied to the paper P by the second conveying roller pair 220.

[0075] When the paper P is thicker than a predetermined thickness or has a large basis weight, or when the conveyance resistance is high, the first drive unit 213 and the second drive unit 223 apply a high value of the drive current to each drive roller.

[0076] The first current detection unit 214 detects the value of the drive current supplied to the drive roller by the first drive unit 213. The second current detection unit 224 detects the value of the drive voltage supplied to the drive roller by the second drive unit 223. Therefore, when these drive voltage values exceed predetermined voltage thresholds, it is estimated that the transport load is high and the transport force applied to the paper P will decrease.

[0077] Therefore, in the conveying mechanism 200v, the control unit 100 monitors the value of the drive current detected by the first current detection unit 214 and the second current detection unit 224, and when it exceeds a predetermined current threshold, controls the first pressure force changing means 212 and the second pressure force changing means 222 to increase the pressure force.

[0078] This embodiment is an effective configuration when the conveying methods of the first conveying roller pair 210 and the second conveying roller pair 220 are different, such as when the drive parts of the first conveying roller pair 210 and the second conveying roller pair 220 are different, when the conveying forces of the first conveying roller pair 210 and the second conveying roller pair 220 are different, or when the drive part operates the first conveying roller pair 210 when rotating forward and the second conveying roller pair 220 when rotating reverse.

[0079] In this embodiment as well, solenoids are used as the first pressing force change means 212 and the second pressing force change means 222. However, the configurations of the first pressing force change means 212 and the second pressing force change means 222 are not limited to solenoids. This point is the same as in the other embodiments, so a description thereof will be omitted.

[0080] [Fifth embodiment] 13 illustrates another embodiment of a medium transport device according to the present invention. As shown in FIG. 13, a transport mechanism 200d according to this embodiment includes a first vibration sensor 215 instead of a first medium sensor 211 as a medium state detection unit corresponding to a first transport roller pair 210 arranged along a transport path 250.

[0081] The first vibration sensor 215 is disposed near the first conveyor roller pair 210. It detects a detection signal based on vibrations generated when the first conveyor roller pair 210 conveys the paper P and notifies the control unit 100. Based on the notified detection signal, the control unit 100 estimates whether the first conveyor roller pair 210 is applying a proper conveying force. That is, if the vibration of the first conveyor roller pair 210 detected by the first vibration sensor 215 exceeds a predetermined vibration threshold, it can be assumed that the conveying force applied by the first conveyor roller pair 210 is decreasing. In this case, the control unit 100 changes the pressure applied by the first conveyor roller pair 210 using the first pressure force changing unit 212, or changes the pressure applied by the second conveyor roller pair 220 using the second pressure force changing unit 222. Note that the increase in the pressure by the first pressure force changing unit 212 and the increase in the pressure by the second conveyor roller pair 220 may be used in combination.

[0082] In this example, solenoids are used as an example of the first pressure change means 212 and the second pressure change means 222. However, the present invention is not limited to this, and any other means capable of changing the pressure may be used, such as a method of applying pressure using a cam, a method of applying pressure to a housing that holds the second conveying roller pair 220, or a method of switching the pressure by rotating a motor forward or backward.

[0083] [Example of output fluctuation of first vibration sensor 215] FIG. 14 is a diagram illustrating the relationship between the vibration of the first conveying roller pair 210 detected by the first vibration sensor 215 and the pressure force changing process.

[0084] 14, the vibration threshold is set to F3. As in pattern A, if no vibration that would lead to an estimation of a decrease in conveying force occurs, the amplitude of vibration when the first conveying roller pair 210 conveys the paper P is assumed to be below F3. As in pattern B, if the amplitude of vibration exceeds F3, it is estimated that the conveying resistance of the paper P is high and the conveying force applied by the first conveying roller pair 210 is decreasing.

[0085] Therefore, the control unit 100 monitors whether the vibration exceeds F3, and when the vibration exceeds F3, controls the second pressure change means 222 to increase the pressure of the second conveyor roller pair 220.

[0086] When monitoring vibrations and estimating a decrease in the conveying force, the determination may be based not only on the magnitude of the amplitude as illustrated in FIG. 14, but also on the number of vibrations (frequency) within a unit time.

[0087] Furthermore, the cause of the increased vibration as in pattern B is when the conveying force is insufficient when conveying the paper P, causing the paper P to slip and the first conveying roller pair 210 to make an abnormal noise.

[0088] [Sixth embodiment] 15 illustrates another embodiment of a medium transport device according to the present invention. As shown in FIG. 15, a transport mechanism 200e according to this embodiment includes a first vibration sensor 215 instead of a first medium sensor 211 as a medium state detection means corresponding to a first pair of transport rollers 210 arranged along a transport path 250, and a second vibration sensor 225 instead of a second medium sensor 221 as a medium state detection means corresponding to a second pair of transport rollers 220.

[0089] When the vibration detected by the first vibration sensor 215 or the second vibration sensor 225 exceeds a vibration threshold, the pressure is changed by the first pressure change means 212 provided on the first conveying roller pair 210 and the second pressure change means 222 provided on the second conveying roller pair 220. Note that the first vibration sensor 215 is disposed near the first conveying roller pair 210 and the second vibration sensor 225 is disposed near the second conveying roller pair 220, but the vibration detection means may be disposed somewhere other than near the conveying roller pairs.

[0090] As in the other embodiments, the first pressure change means 212 and the second pressure change means 222 may be configured using a device other than a solenoid.

[0091] [Seventh embodiment] Fig. 16 illustrates another embodiment of a medium transport device according to the present invention. As shown in Fig. 16, a transport mechanism 200f according to this embodiment includes a first temperature sensor 216 instead of a first medium sensor 211 as a medium state detection unit corresponding to a first pair of transport rollers 210 arranged along a transport path 250.

[0092] The first temperature sensor 216 is disposed near the first conveyor roller pair 210. It detects a detection signal based on the temperature of the first conveyor roller pair 210 and notifies the control unit 100. The control unit 100 estimates whether a proper conveying force is being applied from the temperature of the first conveyor roller pair 210 based on the notified detection signal. That is, if the temperature of the first conveyor roller pair 210 detected by the first temperature sensor 216 exceeds a predetermined temperature threshold, it can be estimated that the conveying force applied by the first conveyor roller pair 210 is decreasing. In this case, the control unit 100 changes the pressure applied by the first conveyor roller pair 210 using the first pressure force changing unit 212, or changes the pressure applied by the second conveyor roller pair 220 using the second pressure force changing unit 222. Note that the increase in the pressure applied by the first pressure force changing unit 212 and the increase in the pressure applied by the second conveyor roller pair 220 may be used in combination.

[0093] There are various possible causes for the temperature rise in the first conveying roller pair 210. For example, if the paper P slips on the roller, the temperature of the roller will rise. In this case, it is estimated that the conveying force applied to the paper P is insufficient.

[0094] As in the other embodiments, the first pressure change means 212 and the second pressure change means 222 may be formed using a means other than a solenoid.

[0095] [Example of output fluctuation of first temperature sensor 216] FIG. 17 is a diagram illustrating the relationship between the temperature of the first conveying roller pair 210 detected by the first temperature sensor 216 and the pressure force changing process.

[0096] 17, the temperature threshold is set to T3. As in pattern A, if no factors that would lead to an estimation of a decrease in conveying force have occurred and the temperature fluctuation is equal to or less than the temperature threshold, it is assumed that slippage or the like has not occurred when the first conveying roller pair 210 conveys the paper P, resulting in a decrease in the conveying force applied. On the other hand, as in pattern B, if the temperature exceeds T3, the temperature of the first conveying roller pair 210 has risen due to factors such as an increase in the conveying resistance of the paper P. At this time, it is estimated that the conveying force applied by the first conveying roller pair 210 has decreased.

[0097] Therefore, the control unit 100 monitors whether the temperature exceeds T3, and when the temperature exceeds T3, changes the pressure applied by the first conveying roller pair 210 by the first pressure change means 212, or changes the pressure applied by the second conveying roller pair 220 by the second pressure change means 222. Note that the increase in the pressure applied by the first pressure change means 212 and the increase in the pressure applied by the second conveying roller pair 220 may be used in combination.

[0098] [Eighth embodiment] 18 illustrates another embodiment of a medium transport device according to the present invention. As shown in FIG. 18, a transport mechanism 200g according to this embodiment includes a first temperature sensor 216 instead of a first medium sensor 211 as a medium condition detection means corresponding to a first pair of transport rollers 210 arranged along a transport path 250, and a second temperature sensor 226 instead of a second medium sensor 221 as a medium condition detection means corresponding to a second pair of transport rollers 220.

[0099] When the temperature detected by the first temperature sensor 216 or the second temperature sensor 226 exceeds the temperature threshold, the pressure is increased by the first pressure change means 212 provided on the first conveying roller pair 210 and the second pressure change means 222 provided on the second conveying roller pair 220. Note that although the first temperature sensor 216 is disposed near the first conveying roller pair 210 and the second temperature sensor 226 is disposed near the second conveying roller pair 220, the temperature detection means may be disposed somewhere other than near the conveying roller pairs.

[0100] As in the other embodiments, the first pressure change means 212 and the second pressure change means 222 may be configured using a device other than a solenoid.

[0101] [Ninth embodiment] 19 illustrates another embodiment of a medium transport device according to the present invention. As shown in FIG. 19, a transport mechanism 200h according to this embodiment includes a plurality of medium state detection units corresponding to a first transport roller pair 210 and a second transport roller pair 220 arranged along a transport path 250.

[0102] For example, a first vibration sensor 215 and a first temperature sensor 216 are provided as medium condition detection means corresponding to the first conveyor roller pair 210. Also, a second vibration sensor 225 is provided as medium condition detection means corresponding to the second conveyor roller pair 220.

[0103] In this way, by using multiple medium state detection means in combination, it is possible to more accurately grasp the transport state of the paper P. Note that the types and number of medium state detection means do not have to be as shown in Figure 19, and the required types and number may be arranged wherever desired.

[0104] As in the other embodiments, the first pressure change means 212 and the second pressure change means 222 may be configured using a device other than a solenoid.

[0105] [Tenth embodiment] Next, another example of processing that can be executed by a media processing device according to the present invention will be described using the flowchart in Figure 20. In the processing described below, for example, after executing a pressure change process in the transport mechanism 200 (S2001), the change is maintained until the transport job is completed (S2002: NO). Then, when the transport job is completed (S2002: YES), the change in pressure is reset (S2003).

[0106] That is, when the transport load increases during the execution of a transport job, the pressure force of the second pressure force changing means 222 or the like is changed, but when the transport job ends with the pressure force changed, it is not necessary to maintain the change. That is, after a new transport job is started, when the transport force decreases, the pressure force can be changed (increased) again.

[0107] [Eleventh embodiment] Next, another example of processing that can be performed by the media processing device according to the present invention will be described using the flowchart in Figure 21. The processing described below involves, for example, performing a pressure force change process in the transport mechanism 200 (S2101), resetting the change in pressure force (S2203) when the image forming device 2 is turned off (S2102).

[0108] Regardless of whether the transport job is completed, the pressure setting once changed is maintained until the device is turned off. Therefore, according to this embodiment, good transport control can be continued when the factors that cause a decrease in transport force are relatively fixed.

[0109] [Twelfth embodiment] Next, another example of processing that can be executed by the media processing device according to the present invention will be described using the flowchart in Figure 22. The processing described below resets the pressure change when the power is turned on in the transport mechanism 200 (S2301), for example. This processing allows the settings of the transport mechanism 200 to be returned to their initial values.

[0110] [Explanation of the control unit 100] Next, the control block configuration of the conveying mechanism 200 provided in the image forming apparatus 2 will be described with reference to Fig. 23. Fig. 23 is a hardware configuration diagram for executing control processing in the image forming apparatus 2. As shown in Fig. 23, the image forming apparatus 2 has a configuration in which a CPU (Central Processing Unit) 101, a RAM (Random Access Memory) 102, a ROM (Read Only Memory) 103, an HDD (Hard Disk Drive) 104, and an I / F 105 are connected via a common bus 109.

[0111] The CPU 101 is a computing unit that controls the overall operation of the image forming apparatus 2. The RAM 102 is a volatile storage medium that can read and write information at high speed, and is used as a work area when the CPU 101 processes information. The ROM 103 is a read-only nonvolatile storage medium that stores programs such as firmware. The HDD 104 is a nonvolatile storage medium that can read and write information and has a large storage capacity, and stores an OS (Operating System), various control programs, application programs, etc.

[0112] The image forming apparatus 2 processes a control program stored in ROM 103, an information processing program (application program) loaded into RAM 102 from a storage medium such as HDD 104, and the like using the arithmetic functions of the CPU 101. This processing constitutes a software control unit including various functional modules of the post-processing device 3. The combination of the software control unit thus constituted and hardware resources installed in the image forming apparatus 2 constitutes functional blocks that realize the functions of the image forming apparatus 2. In other words, the CPU 101, RAM 102, ROM 103, HDD 104, and I / F 105 constitute a control unit 100 (control means) that controls the operation of the image forming apparatus 2.

[0113] The control process of the transport mechanism 200 and the like that has already been described is an example of a process executed by the control unit 100.

[0114] The I / F 105 is an interface that connects the first conveying roller pair 210, the first media sensor 211, the first pressure change means 212, the first drive unit 213, the first current detection unit 214, the first vibration sensor 215, the first temperature sensor 216, the second conveying roller pair 220, the second media sensor 221, the second pressure change means 222, the second drive unit 223, the second current detection unit 224, the second vibration sensor 225, the second temperature sensor 226, and the operation display panel 110 to the common bus 109.

[0115] The control unit 100 operates the first conveying roller pair 210, the second conveying roller pair 220, the first pressure change means 212, and the second pressure change means 222 via the I / F 105.

[0116] In addition, the control unit 100 acquires detection results from the first medium sensor 211, the first current detection unit 214, the first vibration sensor 215, the first temperature sensor 216, the second medium sensor 221, the second current detection unit 224, and the second vibration sensor 225.

[0117] As shown in FIG. 1, the image forming apparatus 2 includes an operation display panel 110. The operation display panel 110 includes an operation unit that accepts operations from a user and a display (notification unit) that notifies the user of information. The operation unit includes, for example, hard keys, a touch panel superimposed on the display, etc. The operation display panel 110 acquires information from the user through the operation unit and provides the information to the user through the display. Note that the notification unit is not limited to a display, and may be an LED lamp, a speaker, etc. The post-processing device 3 may also be provided with an operation display panel 110 similar to the above.

[0118] As described above, the image forming apparatus 2 uses the hardware resources of the control unit 100 to realize the function of controlling operations related to liquid deposition by software (control program) executed by the CPU 101.

[0119] As already explained, the control processing method by the control unit 100 described above is realized by cooperation between the hardware resources of a computer and a program as computer software. That is, the control method is a method executed by a computer by causing an arithmetic unit, a storage unit, an input unit, an output unit, and a control unit to operate in cooperation with each other based on the program. The program may also be written to a storage unit or a storage medium, etc., and distributed, or distributed via a telecommunications line, etc.

[0120] The present invention is not limited to the above-described embodiments, but various modifications are possible without departing from the technical gist thereof, and all technical matters included in the technical concept described in the claims are covered by the present invention. The above-described embodiments are preferred examples, but a person skilled in the art can realize various modifications from the disclosed content. Such modifications are also included in the technical scope described in the claims.

[0121] [Aspects of the present invention] The contents of the present invention are as follows, for example. <1> conveying means disposed at a plurality of locations along a conveying path for conveying the medium; a conveyance state detection unit disposed corresponding to each of the conveyance units and detecting a conveyance state of the medium; a conveying force varying means for varying a conveying force applied to the medium from at least one of the conveying means; a control means for controlling the conveying force varying means arranged corresponding to a specific conveying means so as to vary the conveying force applied to the medium by the specific conveying means in accordance with the detection results of the plurality of conveying state detection means; Equipped with The control means When the result of determining the transport state of the medium based on a first detection result from a first transport state detection means corresponding to a first transport means arranged relatively upstream and a second detection result from a second transport state detection means corresponding to a second transport means arranged relatively downstream indicates a decrease in the transport force applied to the medium, the transport force variable means corresponding to the second transport means is controlled so as to increase the transport force applied to the medium by the second transport means. The medium transport device is characterized by the above. <2> The control means When the second transport state detection means does not detect the medium before a first threshold time has elapsed since the first transport state detection means detected the medium transported by the first transport means, the transport force variable means is controlled so as to increase the transport force applied by the second transport means. The aforementioned <1> 2 is a medium conveying device according to the first embodiment. <3> The control means after the conveying force of the conveying means is increased by the conveying force variable means, if the second conveying state detection means does not detect the medium even when the elapsed time since the first conveying state detection means detected the medium exceeds the first threshold time, the conveying force of the second conveying means is further increased. The aforementioned <2> 2 is a medium conveying device according to the first embodiment. <4> The control means When the conveying force variable means increases the conveying force applied to the medium, the corresponding pair of rollers constituting the conveying means increases the pressure with which the medium is sandwiched. The aforementioned <1> and above <3> 10. The medium transport device according to claim 9, wherein: <5> The control means When the conveying force variable means increases the conveying force applied to the medium, the rotation speed of the corresponding roller pair constituting the conveying means is increased. The aforementioned <1> and above <4> 10. The medium transport device according to claim 9, wherein: <6> The control means When the first conveying state detecting means does not detect the medium within a second threshold time from the start of a job including a predetermined process on the medium, increasing the conveying force of the first conveying means; When the second conveying state detection means does not detect the medium within a third threshold time from the start of the job, the conveying force of the second conveying means is increased. The aforementioned <1> and above <5> 10. The medium transport device according to claim 9, wherein: <7> the conveying state detecting means detects at least one of a current value for driving the corresponding conveying means, vibrations in the vicinity of the corresponding conveying means, and a temperature of the corresponding conveying means; the control means controls the conveying force variable means to increase the conveying force of at least one of the conveying means when the detection result exceeds a predetermined threshold value. The aforementioned <1> and above <6> 10. The medium transport device according to claim 9, wherein: <8> When the conveying force applied by the first conveying means is increased, the conveying force applied by the second conveying means is also increased at the same time. The aforementioned <1> and above <7> 10. The medium transport device according to claim 9, wherein: <9> an image forming unit that forms an image on a medium; a medium transport unit that transports the medium to the image forming unit, The medium transport unit is <1> and above <8> The medium conveying device according to any one of the above items. The image forming apparatus is characterized by the above. <10> an image forming device that forms an image on a medium; The image forming apparatus includes: <1> and above <8> a medium transport device according to any one of the above items; The image forming system is characterized by comprising:

[0122] Further, another example of the contents of the present invention is as follows. (First Invention) a transport unit that transports the medium in a transport direction; a first conveying means provided in the conveying section; a second conveying means provided downstream of the first conveying means; a first detection means provided downstream of the first transport means for detecting the transported medium; a second detecting means provided upstream of the second conveying means; a pressure change means for changing the pressure of the second conveying means; When the second detection means fails to detect the medium within a predetermined time after the first detection means detects the medium, the pressure change means changes the pressure applied by the second conveyance means. The medium transport device is characterized by the above.

[0123] (Second Invention) This medium conveying device is characterized in that if the medium conveyed by the first conveying means cannot be detected by the second detection means within a predetermined value after being detected by the first detection means, in addition to changing the pressure force of the second conveying means by a pressure force changing means, the conveying speeds of the second conveying means and the first conveying means are changed.

[0124] (Third explanation) This is a medium conveying device described in the first invention or the first invention, characterized in that if the medium conveyed by the first conveying means is not detected by the first detection means or the second detection means, the pressure force is changed by the pressure force changing means when it exceeds a threshold value.

[0125] (Fourth explanation) This is a medium conveying device described in the first to third inventions, characterized in that if the first detection means or the second detection means does not detect the medium even after the pressure force is changed by the pressure force changing means, the pressure force is increased stepwise at regular intervals.

[0126] (Fifth Explanation) a transport unit that transports the medium in a transport direction; a first conveying means provided in the conveying section; a second conveying means provided downstream of the first conveying means; a pressure change means for changing the pressure of the second conveying means; a first detection unit for measuring a current value of the first conveying means; The medium conveying device is characterized in that, when the first detection unit exceeds a threshold value, the pressure change unit changes the pressure applied to the first conveying unit and the second conveying unit.

[0127] (Sixth Invention) The first conveying means is provided with the pressure changing means, The pressure applied by the first conveying means is changed simultaneously with the pressure applied by the second detecting means. The medium transport device according to any one of the first to fifth aspects of the present invention is characterized by the above.

[0128] (Seventh Invention) a second detection unit for measuring a current value of the second conveying means; When the second detection unit exceeds a threshold value, the pressure change unit changes the pressure of the first conveying unit and the pressure change unit. The present invention is effective in cases where the rollers that are operated in the forward and reverse directions are separated, or where the motors are separated by the rollers, etc.

[0129] (Eighth Invention) a transport unit that transports the medium in a transport direction; a first conveying means provided in the conveying section; a second conveying means provided downstream of the first conveying means; a pressure change means for changing the pressure applied by the first conveying means and the second conveying means; a vibration detection means provided in the transport section for detecting vibrations; This is a medium conveying device characterized in that when the vibration detected by the vibration detection means exceeds a threshold value, the pressure change means changes the pressure applied to the first conveying means and the second conveying means, or the pressure applied to the first conveying means or the second conveying means.

[0130] (Ninth Invention) In the medium transport device according to an eighth aspect of the present invention, a plurality of the vibration detection means are provided.

[0131] (Tenth Invention) a transport unit that transports the medium in a transport direction; a first conveying means provided in the conveying section; a second conveying means provided downstream of the first conveying means; a pressure change means for changing the pressure applied by the first conveying means and the second conveying means; a temperature detection means for detecting the temperature of the first conveying means; This medium conveying device is characterized in that when the temperature detection unit exceeds a threshold value, the pressure change means changes the pressure of the first conveying means and the second conveying means, or the pressure of the first conveying means or the second conveying means.

[0132] (Eleventh Invention) In a tenth aspect of the present invention, the medium transport device is characterized in that a plurality of the temperature detection means are provided.

[0133] (Twelfth Invention) This is a medium conveying device described in the first to eleventh inventions, characterized in that it has a combination of any two or more detection means from the first detection means, the second detection means, the first detection unit, the second detection unit, the vibration detection means, and the temperature detection means.

[0134] (Thirteenth Invention) In the medium transport device according to any one of the first to twelfth aspects of the invention, the pressure force changed by the pressure force changing means is returned to the original pressure force when transport of the medium is completed.

[0135] (Fourteenth Invention) In the medium transport device according to any one of the first to twelfth aspects of the invention, the pressure force changed by the pressure force changing means is returned to the original pressure force when the power to the device is turned off.

[0136] (Fifteenth Invention) In the medium transport device according to any one of the first to twelfth aspects of the invention, the pressure change means returns to its initial position after power is turned on. [Explanation of symbols]

[0137] 1: Image forming system 2: Image forming device 100: Control unit 110: Operation display panel 200: Transport mechanism 210: First conveying roller pair 211: First media sensor 212: First pressure change means 213: First drive unit 214: First current detection unit 215: First vibration sensor 216: First temperature sensor 220: Second conveying roller pair 221: Second media sensor 222: Second pressure force changing means 223: Second drive unit 224: Second current detection unit 225: Second vibration sensor 226: Second temperature sensor 250: Transport path [Prior art documents] [Patent documents]

[0138] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-013352

Claims

1. conveying means disposed at a plurality of locations along a conveying path for conveying the medium; a conveyance state detection unit disposed corresponding to each of the conveyance units and detecting a conveyance state of the medium; a conveying force varying means for varying a conveying force applied to the medium from at least one of the conveying means; a control means for controlling the conveying force varying means arranged corresponding to a specific conveying means so as to vary the conveying force applied to the medium by the specific conveying means in accordance with the detection results of the plurality of conveying state detection means; Equipped with The control means When the result of determining the transport state of the medium based on a first detection result from a first transport state detection means corresponding to a first transport means arranged relatively upstream and a second detection result from a second transport state detection means corresponding to a second transport means arranged relatively downstream indicates a decrease in the transport force applied to the medium, the transport force variable means corresponding to the second transport means is controlled so as to increase the transport force applied to the medium by the second transport means. A medium transport device characterized by:

2. The control means When the second transport state detection means does not detect the medium before a first threshold time has elapsed since the first transport state detection means detected the medium transported by the first transport means, the transport force variable means is controlled so as to increase the transport force applied by the second transport means. The media transport device of claim 1 .

3. The control means after the conveying force of the conveying means is increased by the conveying force variable means, if the second conveying state detection means does not detect the medium even when the elapsed time since the first conveying state detection means detected the medium exceeds the first threshold time, the conveying force of the second conveying means is further increased. The medium transport device of claim 2 .

4. The control means When the conveying force variable means increases the conveying force applied to the medium, the corresponding pair of rollers constituting the conveying means increases the pressure with which the medium is sandwiched. The media transport device of claim 1 .

5. The control means When the conveying force variable means increases the conveying force applied to the medium, the rotation speed of the corresponding roller pair constituting the conveying means is increased. The media transport device of claim 1 .

6. The control means When the first conveying state detecting means does not detect the medium within a second threshold time from the start of a job including a predetermined process on the medium, increasing the conveying force of the first conveying means; When the second conveying state detection means does not detect the medium within a third threshold time from the start of the job, the conveying force of the second conveying means is increased. The media transport device of claim 1 .

7. the conveying state detecting means detects at least one of a current value for driving the corresponding conveying means, vibrations in the vicinity of the corresponding conveying means, and a temperature of the corresponding conveying means; the control means controls the conveying force variable means to increase the conveying force of at least one of the conveying means when the detection result exceeds a predetermined threshold value. The media transport device of claim 1 .

8. When the conveying force applied by the first conveying means is increased, the conveying force applied by the second conveying means is also increased at the same time. The media transport device of claim 1 .

9. an image forming unit that forms an image on a medium; a medium transport unit that transports the medium to the image forming unit, The medium transport unit is the medium transport device according to claim 1. An image forming apparatus characterized by:

10. an image forming device that forms an image on a medium; a medium transport device according to claim 1 that transports the medium to the image forming device; An image forming system comprising:

Images