JP2019168648A - Conveying and driving device and image forming apparatus - Google Patents

Abstract

To provide a conveying and driving device that can appropriately control conveyance of various types of sheets with a simple configuration without providing a new sensor.SOLUTION: A conveying and driving device of the present invention comprises: a first motor; a second motor; a detection unit; and a control unit. The first motor drives a first conveyance roller that conveys a sheet. The second motor drives a second conveyance roller that is adjacent to the first conveyance roller and arranged on the downstream side in the conveyance direction of the first conveyance roller. The detection unit detects, for at least one of the first motor and second motor, a current value of a current flowing in the motor. The control unit controls the first and second motors to operate such that the conveyance speed of the first conveyance roller becomes faster than the conveyance speed of the second conveyance roller, and estimates the rigidity of the sheet to be conveyed on the basis of the current value detected by the detection unit in a state where the sheet is in contact with the first conveyance roller and second conveyance roller.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a conveyance driving device and an image forming apparatus.

  In an image forming apparatus, a technique for determining whether a sheet to be transported is plain paper or thick paper based on a current value output to a motor that drives a transport roller that transports the sheet is known (for example, Patent Documents). 1).

  According to the technique as described above, it is possible to determine the thickness of the paper and to estimate the load when the paper is transported on a straight transport path.

  However, since the load when the sheet is conveyed in the bent conveyance path depends on the rigidity of the sheet, the conveyance of the sheet cannot be appropriately controlled over the entire conveyance path only by determining the thickness of the sheet.

Japanese Patent Laid-Open No. 2006-179870

  In relation to the above problem, a paper loop is formed by providing a speed difference between adjacent conveyance rollers, and the height of the loop is measured using a dedicated sensor to determine the paper stiffness. A detection method has also been proposed.

  However, the above method has a problem that it is necessary to newly provide a dedicated sensor. Moreover, since the height of the loop that can be formed is limited due to the limitation of the space in the apparatus, there is also a problem that the range of stiffness that can be detected is limited. Furthermore, when the conveyance speed difference between adjacent conveyance rollers is small, a paper loop with high rigidity cannot be formed. Conversely, when the conveyance speed difference is large, a paper loop with high rigidity can be formed, but the rigidity of the paper is not high. There is a risk that paper wrinkles will occur on low paper. For this reason, in order to properly convey a sheet while ensuring a detectable rigidity range, it is necessary to prepare a plurality of patterns of speed differences depending on the type of the sheet, which complicates the configuration and processing. There is also a problem of end.

  The present invention has been made in view of the above-described problems. Therefore, an object of the present invention is to provide a transport driving device and an image forming apparatus that can appropriately control transport of various types of paper with a simple configuration without providing a new sensor.

  The above object is achieved by the following means.

  (1) a first motor that drives a first transport roller that transports paper in the paper transport path, and is adjacent to the first transport roller along the paper transport path, more than the first transport roller The current value of the current flowing through the motor can be detected for at least one of the second motor that drives the second transport roller disposed downstream in the transport direction, and the first motor and the second motor. And a sheet conveyed while operating the first motor and the second motor so that the conveyance speed of the first conveyance roller is faster than the conveyance speed of the second conveyance roller. Estimating the stiffness of the paper based on the current value detected by the detection unit in contact with the first transport roller and the second transport roller Transport driving device comprising a control unit.

  (2) The control unit calculates an average value of current values detected by the detection unit within a predetermined time in a state in which a sheet to be conveyed is in contact with the first conveyance roller and the second conveyance roller. Then, the conveyance drive device according to (1), wherein the stiffness of the sheet is estimated based on the calculation result.

  (3) The control unit is configured to detect the first sheet detected by the detection unit within a predetermined time in a state where the first sheet to be conveyed is in contact with the first conveyance roller and the second conveyance roller. The average value of the current value of the motor is detected by the detection unit within a predetermined time in a state where the second sheet to be conveyed is in contact with the first conveyance roller and the second conveyance roller. When the current value of the motor is larger than the average value of the motors, the conveyance driving device according to (2), wherein the first sheet is determined to have higher rigidity than the second sheet.

  (4) The control unit is configured to detect the second sheet detected by the detection unit within a predetermined time in a state where the first sheet to be conveyed is in contact with the first conveyance roller and the second conveyance roller. The average value of the current value of the motor is detected by the detection unit within a predetermined time in a state where the second sheet to be conveyed is in contact with the first conveyance roller and the second conveyance roller. When the current value of the current value of the motor is smaller than the average value, the conveyance driving device according to (2) or (3) described above, wherein the first sheet is determined to have higher rigidity than the second sheet.

  (5) The control unit can switch between a print mode for printing on a sheet and a test mode for conveying and testing a reference sheet, which is a predetermined type of sheet, unlike the print mode. The current value detected by the detection unit in a state where the reference paper is in contact with the first transport roller and the second transport roller when transporting the reference paper is previously stored in the storage unit as a reference current value. Storing the current value detected by the detection unit in a state where the reference paper is in contact with the first transport roller and the second transport roller when transporting the reference paper in the test mode; The reference current value stored in the storage unit is compared, and based on the comparison result, the correspondence between the current value and the paper stiffness when estimating the paper stiffness is corrected. 1) conveyor driving device according to any one of to (4).

  (6) The transport driving device according to any one of (1) to (5), wherein the control unit registers the estimated stiffness of the sheet in the storage unit as a sheet profile.

  (7) a first motor that drives a first transport roller that transports paper in the paper transport path, and is adjacent to the first transport roller along the paper transport path, more than the first transport roller A current value of a current flowing during operation can be detected for at least one of the second motor that drives the second transport roller disposed downstream in the transport direction, and the first motor and the second motor. The sheet to be conveyed while operating the first motor and the second motor so that the conveyance speed of the detection unit and the first conveyance roller is faster than the conveyance speed of the second conveyance roller. Based on the current value detected by the detection unit in contact with the first transport roller and the second transport roller, the first transport roller or Conveying drive unit and a control unit for controlling the operation of the third motor for driving the third transport roller than the second transport roller.

  (8) A conveyance driving device applied to an image forming apparatus including an air sheet feeding mechanism, the first motor driving a first conveyance roller that conveys a sheet in a sheet conveyance path, and the sheet conveyance path A second motor that drives a second transport roller that is adjacent to the first transport roller and is disposed downstream of the first transport roller in the transport direction, and the first motor and For at least one of the second motors, the detection unit capable of detecting the current value of the current flowing through the motor, and the transport speed of the first transport roller is higher than the transport speed of the second transport roller. While the first motor and the second motor are operated, the sheet to be conveyed is in contact with the first conveyance roller and the second conveyance roller. On the basis of the current value detected by the detection unit, the transport drive unit and a control unit that adjusts the air volume of the air feed in the air sheet feeding mechanism.

  (9) The transport driving device according to any one of (1) to (8), wherein at least one of the first motor and the second motor is a stepping motor or a brushless motor.

  (10) The transport driving device according to any one of (1) to (9), wherein the first transport roller is a loop roller, and the second transport roller is a registration roller.

  (11) The conveyance according to any one of (1) to (10), wherein a space capable of forming a paper loop is provided between the first conveyance roller and the second conveyance roller. Drive device.

  (12) An image forming apparatus having the transport driving device according to any one of (1) to (11).

  According to the present invention, the stiffness of the paper is estimated based on the current value of the motor in a state where the paper is in contact with two adjacent transport rollers. Thereby, the rigidity of the paper can be estimated with a simple configuration without providing a new sensor.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. It is a figure which illustrates a mode that a sheet | seat is contacting 2 pairs of adjacent conveyance rollers. It is a figure which shows the example of the combination of an upstream conveyance roller and a downstream conveyance roller. 4 is a flowchart illustrating a procedure of processing executed by the image forming apparatus according to the first embodiment. It is a figure for demonstrating the relationship between the electric current value which flows into an upstream motor, and the rigidity of a paper. It is a figure which shows the table which matched the electric current value which flows into an upstream motor, and the rigidity of a paper. It is a figure which shows the example of the time change of the electric current value which flows into an upstream motor. It is a figure for demonstrating the relationship between the electric current value which flows into a downstream motor, and the rigidity of a paper. It is a figure which shows the example of the time change of the electric current value which flows into a downstream motor. 10 is a flowchart illustrating a procedure of processes executed by the image forming apparatus according to the second embodiment. 10 is a flowchart illustrating a procedure of processing executed by an image forming apparatus according to a third embodiment. 10 is a flowchart illustrating a procedure of processing executed by an image forming apparatus according to a fourth embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

<First Embodiment>
FIG. 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus 100 according to an embodiment of the present invention. As shown in FIG. 1, the image forming apparatus 100 of this embodiment includes a control unit 110, a storage unit 120, an image reading unit 130, an image forming unit 140, a fixing unit 150, a paper feeding unit 160, and a paper transport unit 170. ing.

  The control unit 110 is a CPU (Central Processing Unit), and controls the above-described units and performs various arithmetic processes according to a program.

  The storage unit 120 stores a ROM (Read Only Memory) that stores various programs and various data in advance, a RAM (Random Access Memory) that temporarily stores programs and data as a work area, and stores various programs and various data. It consists of a hard disk. The storage unit 120 stores information such as a calculation formula and a table for estimating the stiffness of the paper 500 from the current value.

  The image reading unit 130 includes a light source such as a fluorescent lamp and an image sensor such as a CCD (Charge Coupled Device) image sensor. The image reading unit 130 applies light from a light source to a document set at a predetermined reading position, photoelectrically converts the reflected light with an image sensor, and generates image data from the electric signal.

  The image forming unit 140 includes image forming units 141Y to 141K corresponding to toners of Y (yellow), M (magenta), C (cyan), and K (black). The toner images formed through the charging, exposure, and development processes by the image forming units 141Y to 141K are sequentially superimposed on the intermediate transfer belt 142 and transferred onto the paper 500 by the secondary transfer roller 143.

  The fixing unit 150 includes a heating roller and a pressure roller as the fixing roller 151, and heats and presses the paper 500 conveyed to the fixing nip of the fixing roller 151 to melt the toner image on the paper 500 on the surface. To settle.

  The paper feed unit 160 includes a plurality of paper feed trays 161, 162, and 163, and the paper 500 accommodated in the paper feed trays 161, 162, and 163 one by one on the downstream side is referred to simply as “ It is also called “conveyance path”.

  The paper transport unit 170 includes a plurality of transport rollers for transporting the paper 500, and transports the paper 500 between the image forming unit 140, the fixing unit 150, and the paper feed unit 160. Each transport roller is configured as a pair of rollers facing each other across the transport path. Each roller pair rotates while pinching the paper, so that the paper 500 is conveyed. At least one roller of each roller pair is driven by a motor (see FIG. 2). The roller that is paired with the driven roller may be a roller that is driven in accordance with the movement of the conveyed paper. In the present embodiment, the paper transport unit 170 and the control unit 110 constitute a transport drive device.

  In this embodiment, in two pairs of transport rollers adjacent along the transport path, the transport speed of the upstream transport roller (first transport roller) is the transport speed of the downstream transport roller (second transport roller). The drive of each motor is controlled so as to be faster.

  FIG. 2 is a diagram illustrating a state in which a sheet is in contact with two adjacent pairs of transport rollers.

  In FIG. 2, the sheet 500 is conveyed in the conveyance direction indicated by the arrow in the conveyance path indicated by the broken line. The upstream side conveyance roller 170a (first conveyance roller) is arranged on the upstream side in the conveyance direction in the conveyance path. The downstream-side transport roller 170b (second transport roller) is adjacent to the upstream-side transport roller 170a along the transport path, and is disposed downstream of the upstream-side transport roller 170a in the transport direction.

  The upstream motor 180a (first motor) drives the upstream conveying roller 170a, and the downstream motor 180b (second motor) drives the downstream conveying roller 170b. Since the upstream motor 180a and the downstream motor 180b are controlled independently by the control unit 110, the upstream transport roller 170a and the downstream transport roller 170b are also driven independently. The upstream motor 180a and the downstream motor 180b can be configured by a stepping motor capable of operating at a high speed or a brushless motor capable of controlling the speed.

  The detection unit 190 detects the value of the current flowing through the upstream motor 180a and the downstream motor 180b. The detection unit 190 may detect a current value for both the upstream motor 180a and the downstream motor 180b, or may detect a current value for either the upstream motor 180a or the downstream motor 180b. .

  A paper detection sensor 200 that detects the presence or absence of the paper 500 at a predetermined location in the transport path is provided in the vicinity of the upstream transport roller 170a. The paper detection sensor 200 is a photo sensor, for example. In the example shown in FIG. 2, the paper detection sensor 200 is provided on the downstream side in the transport direction of the upstream transport roller 170a, but the place where the paper detection sensor 200 is provided is not limited to this, and the transported paper 500 is used. It may be installed anywhere as long as it can be detected. The number of paper detection sensors 200 is not limited to one, and a plurality of paper detection sensors 200 may be provided.

  In the present embodiment, the operations of the upstream motor 180a and the downstream motor 180b are controlled so that the transport speed of the upstream transport roller 170a is faster than the transport speed of the downstream transport roller 170b. As a result, when the paper 500 is in contact with both the upstream side transport roller 170a and the downstream side transport roller 170b, the paper 500 is placed between the upstream side transport roller 170a and the downstream side transport roller 170b as shown in FIG. It floats from the transport path and a loop is formed. A space in which the paper 500 can form a loop is provided between the upstream conveyance roller 170a and the downstream conveyance roller 170b.

  FIG. 3 is a diagram illustrating an example of a combination of an upstream conveyance roller and a downstream conveyance roller.

  In FIG. 3, the example of the combination of an upstream conveyance roller and a downstream conveyance roller is shown as roller sets S1-S4.

  The roller set S1 is a first intermediate transport roller 171 and a second intermediate transport roller 172. The first intermediate conveyance roller 171 is a conveyance roller that is arranged on the most upstream side in the conveyance path of the paper conveyance unit 170 and is the conveyance roller closest to the paper supply unit 160 or the paper supply device. By applying the processing of the present embodiment to the roller set S1, the stiffness of the paper 500 can be detected at an early timing, and when the paper 500 is transported downstream, the transport is appropriately controlled based on the detected stiffness. it can.

  The roller set S2 is a loop roller 173 and a registration roller 174. In the rotation stopped state, the registration roller 174 stops the conveyance of the paper 500 by abutting the conveyed paper 500, and resumes rotation at a predetermined timing to resume the conveyance of the paper 500. As a result, the registration roller 174 corrects the skew of the paper 500, aligns the toner image transferred onto the paper 500, and the like. The loop roller 173 is disposed adjacent to the upstream side of the registration roller 174. The loop roller 173 continues to rotate while the leading edge of the sheet 500 is stopped from being conveyed by the registration roller 174, and forms a loop on the sheet 500 by continuing to convey the rear end of the sheet 500. When applying the processing of the present embodiment to the roller set S2, the registration roller 174 temporarily stops the paper 500 and performs high-precision processing, so that the rigidity of the paper 500 can be detected stably.

  The roller set S3 is a secondary transfer roller 143 and a fixing roller 151. When the processing of this embodiment is applied to the roller set S3, the rigidity of the paper 500 can be detected without stopping the conveyance by the fixing roller 151 that is a downstream conveyance roller.

  The roller set S4 is an ADU pre-registration roller 176 and an ADU intermediate transport roller 175 provided on the most downstream side in an ADU (Auto Duplex Unit). The ADU intermediate transport roller 175 is a transport roller provided adjacent to the upstream side of the ADU pre-registration roller 176 in the transport direction. The ADU pre-registration roller 176 is a transport roller for correcting the paper bending of the paper 500 and adjusting the transport timing before returning the paper 500 from the transport path in the ADU to the original transport path. When the processing of this embodiment is applied to the roller set S4, the ADU pre-registration roller 176 temporarily stops the paper 500 and performs high-precision processing, so that the rigidity of the paper 500 can be detected stably.

  Hereinafter, the conveyance driving process in the present embodiment will be described as being performed in the upstream conveyance roller 170a, the downstream conveyance roller 170b, and the upstream motor 180a and the downstream motor 180b that drive them.

  Note that the image forming apparatus 100 may include components other than the above-described components, or some of the above-described components may not be included.

  In the image forming apparatus 100 configured as described above, the transport speed of the upstream transport roller 170a is controlled to be faster than that of the downstream transport roller 170b. Then, the stiffness of the paper 500 is estimated based on the current value of at least one of the upstream motor 180a and the downstream motor 180b while the paper 500 is in contact with both transport rollers. Hereinafter, the operation of the image forming apparatus 100 according to the present embodiment will be described in detail with reference to FIGS. 4 to 9.

  FIG. 4 is a flowchart illustrating a procedure of processing executed by the image forming apparatus according to the first embodiment. Note that the algorithm shown in the flowchart of FIG. 4 is stored as a program in the storage unit 120 and executed by the control unit 110.

  As shown in FIG. 4, the control unit 110 determines whether or not the conveyance of the paper 500 has been started (step S101). For example, the control unit 110 determines whether the conveyance of the paper 500 has been started based on the detection result of the paper presence / absence by the paper detection sensor 200.

  When the conveyance is not started (step S101: NO), the control unit 110 stands by until the conveyance is started.

  When the conveyance is started (step S101: YES), the control unit 110 is in a state where the conveyed paper 500 is in contact with the upstream conveyance roller 170a and the downstream conveyance roller 170b that are two adjacent conveyance rollers. It is determined whether or not there is (step S102). For example, when the paper detection sensor 200 detects the leading edge of the paper 500 and the predetermined time elapses, the control unit 110 comes into contact with both the upstream-side transport roller 170a and the downstream-side transport roller 170b. I can judge. The predetermined time in this case can be calculated from, for example, the distance from the detection location on the conveyance path by the paper detection sensor 200 to the downstream conveyance roller 170b and the conveyance speed of the upstream conveyance roller 170a. Note that the state in which the paper 500 is in contact with both the upstream-side transport roller 170a and the downstream-side transport roller 170b is, for example, the state in which the paper 500 is biting the two adjacent transport rollers, that is, the two adjacent transport rollers A state in which the paper 500 is sandwiched between the pairs is included. Further, when the paper 500 is in contact with both the upstream-side transport roller 170a and the downstream-side transport roller 170b, for example, the leading edge of the paper 500 is abutted against the stopped downstream-side transport roller 170b, and the paper 500 A state in which the rear end side is sandwiched and transported by the upstream transport roller 170a is also included.

  When the paper 500 is not in contact with two adjacent transport rollers (step S102: NO), the control unit 110 controls the paper transport unit 170 until the paper 500 comes into contact with the two adjacent transport rollers. The conveyance of the paper 500 is continued.

  When the sheet 500 is in contact with two adjacent transport rollers (step S102: YES), the control unit 110 controls the detection unit 190 to determine the current value of the current flowing through the upstream motor 180a and the downstream motor 180b. Detection is performed (step S103). The control unit 110 stores the detected current value in the storage unit 120. As the current value, for example, an average value of values detected within a predetermined time or an RMS (Root Mean Square) value of a current waveform is used. Here, in the present embodiment, as described above, since the transport speed of the upstream transport roller 170a is controlled to be faster than the transport speed of the downstream transport roller 170b, a loop is formed on the paper 500. The

  Subsequently, the control unit 110 determines whether or not the trailing end of the conveyed paper 500 has passed through the upstream transport roller 170a, which is an upstream roller (step S104). That is, the control unit 110 determines whether or not the sheet 500 is no longer in contact with two adjacent transport rollers. For example, the control unit 110 detects that the leading edge of the paper 500 has arrived at the paper detection sensor 200, and after the predetermined time has elapsed, the trailing edge of the paper 500 has left (separated) the upstream-side transport roller 170a. It can be judged. The predetermined time in this case can be calculated from, for example, the length of the paper 500 in the transport direction and the transport speed of the upstream transport roller 170a. Alternatively, when the paper detection sensor 200 detects the trailing edge of the paper 500, the control unit 110 may determine that the trailing edge of the paper 500 has passed through the upstream conveyance roller 170a.

  When the trailing edge of the sheet 500 has not passed through the upstream transport roller 170a (step S104: NO), the control unit 110 continues the process of step S103, and the trailing edge of the sheet 500 exits the upstream transport roller 170a. Until the paper 500 is conveyed.

  When the trailing edge of the sheet 500 has passed through the upstream transport roller 170a (step S104: YES), the control unit 110 estimates the stiffness of the sheet 500 based on the current value detected in the process of step S103 (step S104). S105). The control unit 110 may associate the estimated stiffness of the paper 500 with the type of the paper 500 and register it in the storage unit 120 as a paper profile that is information indicating an attribute for each paper type. Processing for estimating the stiffness of the paper 500 based on the current value will be described in detail below.

<Stiffness estimation processing>
FIG. 5 is a diagram for explaining the relationship between the current value flowing through the upstream motor and the stiffness of the paper.

  In FIG. 5, six plots display actual measured values, and a curve displays an approximate expression obtained from the above plot.

As shown in FIG. 5, when the stiffness of the paper 500 increases, the value of the current flowing through the upstream motor 180a that drives the upstream conveying roller 170a increases. When the paper 500 is bent to form a loop, a load is applied to the upstream motor 180a, and the load increases as the stiffness of the paper 500 increases. As a result, the current value flowing through the upstream motor 180a also increases. Thus, there is a correlation between the stiffness of the paper 500 and the value of the current flowing through the upstream motor 180a. In the present embodiment, an approximate expression corresponding to this correlation is calculated in advance from experimental results and stored in the storage unit 120. In the example of FIG. 5, an approximate expression of y = −0.0016x ² + 5.7437x−3578.4 is calculated, where x is a current value (mA) and y is stiffness. The control unit 110 can calculate the stiffness of the paper 500 as y by substituting the current value detected by the detection unit 190 for x in the above approximate expression.

  Note that the method of estimating the stiffness of the paper 500 based on the current value is not limited to the above example. For example, instead of calculating an approximate expression of stiffness and current value, a table indicating the correspondence between stiffness and current value may be used.

  FIG. 6 is a diagram showing a table in which the value of the current flowing through the upstream motor is associated with the stiffness of the paper.

  The table shown in FIG. 6 selects representative values for different stiffnesses depending on the type of the paper 500, and previously determines the current value that flows through the upstream conveying roller 170a when a loop is formed on the paper 500 having the stiffness. The stiffness and the current value are associated with each other. By storing a table as shown in FIG. 6 in the storage unit 120, the control unit 110 determines the stiffness of the conveyed paper 500 based on the current value flowing through the upstream motor 180 a detected by the detection unit 190. Can be estimated. For example, when a value that matches the detected current value is not stored in the table, the closest current value may be selected from the table, and the stiffness corresponding to the selected current value may be employed. At this time, if the difference between the detected current value and the current value stored in the table is larger than a predetermined threshold value, a warning may be output as an error.

  The process for estimating the stiffness of the paper 500 based on the current value will be described in more detail.

  FIG. 7 is a diagram illustrating an example of a temporal change in a current value flowing through the upstream motor. The solid line in FIG. 7 shows the waveform when the paper stiffness is high, and the broken line shows the waveform when the paper stiffness is low. The predetermined time shown in FIG. 7 can be set to any time in a period in which the conveyed paper 500 is in contact with the upstream side transport roller 170a and the downstream side transport roller 170b.

  As shown in FIG. 7, the sum of the current values detected by the upstream motor 180a is larger when the rigidity indicated by the solid line is higher within a predetermined time than when the rigidity indicated by the broken line is lower. Therefore, for example, the control unit 110 calculates the average value of the current values detected by the detection unit 190 within a predetermined time, and the sheet 500 has a high rigidity when the average value is large, and the sheet when the average value is small. It can be determined that the stiffness of 500 is low. That is, when the average value of the current value of the upstream motor 180a detected for the first sheet 500 is larger than the average value of the current value of the upstream motor 180a detected for the second sheet 500, the first value It can be determined that the paper 500 has higher rigidity than the second paper 500.

  Also, as shown in FIG. 7, the rate of change of the value at the rising edge of the current waveform is larger when the stiffness indicated by the solid line is higher than when the stiffness indicated by the broken line is low. Therefore, the control unit 110 calculates, for example, the rate of change of the value at the rising edge of the current waveform detected by the detection unit 190. When the rate of change is large, the stiffness of the sheet 500 is high, and when the rate of change is small, the sheet 500 It may be determined that the stiffness of is low.

  7 is an example of a current waveform when a stepping motor is used, and the peak value of the current waveform does not change depending on the stiffness of the paper 500. However, for example, in a current waveform in the case of using a brushless motor, the peak value of the current waveform is larger when the stiffness is high than when the stiffness is low. In this case, for example, the control unit 110 acquires the peak value of the current waveform detected by the detection unit 190, and the stiffness of the paper 500 is high when the peak value is large, and the stiffness of the paper 500 is high when the peak value is small. You may judge that it is low.

  In the above description, the example in which the stiffness of the paper 500 is estimated based on the current value flowing through the upstream motor 180a has been described. However, the stiffness of the paper 500 may be estimated based on the current value flowing through the downstream motor 180b. Good. Hereinafter, an example in which the stiffness of the paper 500 is estimated based on the value of the current flowing through the downstream motor 180b will be described in detail.

  FIG. 8 is a diagram for explaining the relationship between the current value flowing through the downstream motor and the stiffness of the paper.

  In FIG. 8, seven plots display actual measured values, and a curve displays an approximate expression obtained from the above plot.

As shown in FIG. 8, when the stiffness of the paper 500 increases, the value of the current flowing through the downstream motor 180b that drives the downstream transport roller 170b decreases. When the paper 500 is bent to form a loop, the paper 500 tries to return to its original shape, and the downstream side transport roller 170b is pushed by the paper 500 and rotates. Thereby, the load concerning the downstream motor 180b becomes small. This load decreases as the stiffness of the paper 500 increases, and as a result, the value of the current flowing through the downstream motor 180b also decreases. Thus, there is a correlation between the stiffness of the paper 500 and the value of the current flowing through the downstream motor 180b. In the present embodiment, an approximate expression corresponding to this correlation is calculated in advance from experimental results and stored in the storage unit 120. In the example of FIG. 8, an approximate expression of y = −0.0062x ² + 89.727x−29200 is calculated, where x is a current value (mA) and y is stiffness. The control unit 110 can calculate the stiffness of the paper 500 as y by substituting the current value detected by the detection unit 190 for x in the above approximate expression.

  FIG. 9 is a diagram illustrating an example of a temporal change in a current value flowing through the downstream motor. The solid line in FIG. 9 shows the waveform when the paper stiffness is high, and the broken line shows the waveform when the paper stiffness is low.

  As shown in FIG. 9, the total sum of current values is smaller when the rigidity indicated by the solid line is higher within a predetermined time than when the rigidity indicated by the broken line is lower. Therefore, for example, the control unit 110 calculates the average value of the current values detected by the detection unit 190 within a predetermined time. When the average value is small, the rigidity of the sheet 500 is high, and when the average value is large, the sheet It can be determined that the stiffness of 500 is low.

  As shown in FIG. 9, the rate of change of the value at the rising edge of the current waveform is smaller when the rigidity indicated by the solid line is higher than when the rigidity indicated by the broken line is low. Therefore, the control unit 110 calculates, for example, the rate of change of the value at the rising edge of the current waveform detected by the detection unit 190. When the rate of change is small, the stiffness of the sheet 500 is high, and when the rate of change is large, the sheet 500 It may be determined that the stiffness of is low. 9 is an example of a current waveform when a stepping motor is used, and the peak value of the current waveform does not change depending on the stiffness of the paper 500. However, for example, in a current waveform when a brushless motor is used, the peak value of the current waveform is smaller when the stiffness is high than when the stiffness is low. In this case, for example, the control unit 110 acquires the peak value of the current waveform detected by the detection unit 190, and the stiffness of the paper 500 is high when the peak value is small, and the stiffness of the paper 500 is high when the peak value is large. You may judge that it is low.

  As described above, according to the image forming apparatus 100 of the first embodiment, the transport speed of the upstream transport roller 170a is controlled to be higher than that of the downstream transport roller 170b. The image forming apparatus 100 estimates the stiffness of the paper 500 based on the current value of at least one of the upstream motor 180a and the downstream motor 180b in a state where the paper 500 is in contact with both transport rollers. Thereby, the rigidity of the paper 500 can be estimated with a simple configuration without providing a new sensor. For example, the image forming apparatus 100 can suppress the step-out of each motor by controlling the values of the currents flowing to the upstream motor 180a and the downstream motor 180b based on the estimated stiffness, and appropriately transport the paper 500. The productivity of the image forming apparatus 100 can be improved by controlling.

  In addition, the image forming apparatus 100 calculates an average value of current values detected within a predetermined time, and estimates the stiffness of the paper 500 based on the calculation result. Thereby, the rigidity of the paper 500 can be estimated with higher accuracy.

  Further, in the image forming apparatus 100, the average value of the current value of the upstream motor 180a detected for the first sheet is larger than the average value of the current value of the upstream motor 180a detected for the second sheet. The first sheet is determined to have higher rigidity than the second sheet. Thus, the stiffness of the paper 500 can be easily determined by simply comparing the average values of the current values of the upstream motor 180a.

  Further, in the image forming apparatus 100, the average value of the current value of the downstream motor 180b detected for the first sheet is smaller than the average value of the current value of the downstream motor 180b detected for the second sheet. The first sheet is determined to have higher rigidity than the second sheet. Thus, the stiffness of the paper 500 can be easily determined by simply comparing the average values of the current values of the downstream motor 180b.

  Further, at least one of the upstream motor 180a and the downstream motor 180b can be a stepping motor or a brushless motor. Thereby, the rigidity of the paper 500 can be estimated while appropriately controlling the conveyance of the paper 500.

  Further, the upstream transport roller 170 a can be the loop roller 173, and the downstream transport roller 170 b can be the registration roller 174. Thereby, since the paper 500 is stopped once in the registration roller 174, the rigidity of the paper 500 can be estimated stably.

  Further, a space in which the paper 500 can form a loop can be provided between the upstream side conveyance roller 170a and the downstream side conveyance roller 170b. Accordingly, the paper 500 can surely form a loop, and the rigidity of the paper 500 can be estimated more stably.

  In addition, the image forming apparatus 100 associates the estimated stiffness of the paper 500 with the type of the paper 500 and registers it in the storage unit 120 as a paper profile. Thus, the stiffness registered in the paper profile can be used for the same type of paper 500 as the paper 500 whose stiffness is estimated, and the processing can be simplified.

  In the above embodiment, the method for estimating the stiffness of the paper 500 based on the current value of the upstream motor 180a and the method of estimating the stiffness of the paper 500 based on the current value of the downstream motor 180b are separately performed. As described above, the stiffness of the paper 500 may be estimated by combining the two methods. Thereby, the rigidity of the paper 500 can be estimated with higher accuracy.

  In the above embodiment, the paper detection sensor 200 has been described as detecting the presence or absence of paper at a predetermined location in the conveyance path, but the present invention is not limited to this. For example, the paper detection sensor 200 determines the distance between the paper detection sensor 200 and the paper 500 based on the time from when light is emitted toward the conveyance path to when the reflected light is received, the amount of reflected light, and the like. It may be determined that the loop is formed. Alternatively, the paper detection sensor 200 determines that the loop of the paper 500 is formed by detecting the presence or absence of the paper 500 at a location where the paper 500 exists only when the loop of the paper 500 is formed. Also good.

Second Embodiment
In the first embodiment, the example in which the image forming apparatus 100 estimates the stiffness of the paper 500 in the print mode in which the normal printing is performed on the paper 500 has been described. However, the image forming apparatus 100 is detected by the detection unit 190 even when the paper 500 having the same stiffness is transported due to aging, changes in use environment, motor performance variations, individual differences in friction in the transport path, and the like. The current value to be changed may vary. In the second embodiment, the correspondence between the current value when estimating the stiffness of the paper 500 and the stiffness of the paper 500 in a test mode in which a reference paper, which is a predetermined type of paper, is conveyed to test the image forming apparatus 100. An example of correcting the relationship will be described.

  The configuration of the image forming apparatus 100 of the second embodiment is the same as the configuration of the image forming apparatus 100 of the first embodiment.

  In the storage unit 120, when the reference paper 510, which is a predetermined type of paper 500, is conveyed, the detection unit 190 detects that the reference paper 510 is in contact with the upstream conveyance roller 170a and the downstream conveyance roller 170b. Current value is stored in advance as a reference current value. The reference current value is measured and stored at an arbitrary timing when the image forming apparatus 100 is in a normal state, for example, when the image forming apparatus 100 is shipped from the factory, initially installed, or when maintenance is performed. Further, since the reference current value differs depending on the type of paper used as the reference paper 510, a plurality of reference current values may be stored for each paper type. Hereinafter, processing executed by the image forming apparatus 100 according to the second embodiment will be described.

  FIG. 10 is a flowchart illustrating a procedure of processes executed by the image forming apparatus according to the second embodiment. Note that the algorithm shown in the flowchart of FIG. 10 is stored as a program in the storage unit 120 and executed by the control unit 110.

  First, the control unit 110 switches the operation mode of the image forming apparatus 100 to the test mode and starts conveying the reference paper 510. The processing in steps S201 to S205 in FIG. 10 is the same as the processing in steps S101 to S105 in FIG. 4 except that the processing is performed using the reference sheet 510 in the test mode, and thus description thereof is omitted.

  Subsequently, the control unit 110 compares the current value detected in step S203 with a reference current value stored in advance in the storage unit 120 (step S206).

  Subsequently, the control unit 110 corrects the correspondence between the current value when estimating the stiffness of the paper 500 and the stiffness of the paper 500 based on the comparison result in step S206 (step S207).

  For example, when the current value detected in the upstream motor 180a is larger than the reference current value, the control unit 110 changes the correspondence relationship between the current value and the stiffness as shown in FIGS. The stiffness value corresponding to is corrected so as to be low. On the other hand, when the current value detected in the upstream motor 180a is smaller than the reference current value, the control unit 110 changes the correspondence between the current value and the stiffness as shown in FIGS. The stiffness value corresponding to is corrected so as to increase.

  When the current value detected in the downstream motor 180b is larger than the reference current value, the control unit 110 changes the correspondence relationship between the current value and the stiffness as shown in FIG. 8 to correspond to the current value. Correct the stiffness value to be higher. On the other hand, when the current value detected in the downstream motor 180b is smaller than the reference current value, the control unit 110 changes the correspondence relationship between the current value and the stiffness as shown in FIG. 8 to correspond to the current value. Correct the stiffness value to be low.

  As described above, according to the image forming apparatus 100 of the second embodiment, the current value detected by the detection unit 190 and the reference current stored in the storage unit 120 when the reference sheet 510 is conveyed in the test mode. Compare the value. Then, the image forming apparatus 100 corrects the correspondence between the current value and the stiffness when estimating the stiffness of the paper 500 based on the comparison result. As a result, it is possible to appropriately estimate the stiffness of the paper 500 while suppressing the influence of aging deterioration, change in use environment, and the like.

  In the above-described embodiment, an example in which the image forming apparatus 100 performs correction by conveying one sheet of the reference sheet 510 is described, but the present invention is not limited to this. The image forming apparatus 100 may carry out correction by conveying a plurality of reference sheets 510 having different types of sheets and integrating the processing results of the respective reference sheets 510. Thereby, correction can be performed with higher accuracy.

<Third Embodiment>
In the first embodiment described above, the example in which the image forming apparatus 100 estimates the stiffness of the paper 500 based on the detected current value has been mainly described. However, the image forming apparatus 100 not only estimates the stiffness of the paper 500 based on the detected current value, but also transports the paper 500 based on the detected current value and the stiffness estimated from the current value. You may control the electric current of the motor which drives a conveyance roller. In the third embodiment, an example will be described in which the image forming apparatus 100 controls the current value of the motor that drives the transport roller that transports the paper 500 based on the detected current value and the stiffness estimated from the current value. .

  The configuration of the image forming apparatus 100 according to the third embodiment is the same as the configuration of the image forming apparatus 100 according to the first embodiment. Hereinafter, processing executed by the image forming apparatus 100 according to the third embodiment will be described.

  FIG. 11 is a flowchart illustrating a procedure of processes executed by the image forming apparatus according to the third embodiment. Note that the algorithm shown in the flowchart of FIG. 11 is stored as a program in the storage unit 120 and executed by the control unit 110.

  The processing in steps S301 to S305 in FIG. 11 is the same as the processing in steps S101 to S105 in FIG.

  Based on the stiffness of the paper 500 estimated in the process of step S305, the control unit 110 controls the value of the current passed through the upstream motor 180a and the downstream motor 180b that detected the current value (step S306). For example, when the stiffness of the sheet 500 is high, the control unit 110 increases the output torque by increasing the value of the current passed through each motor. Thereby, the paper 500 can be appropriately conveyed.

  Further, the control unit 110 may control the value of the current that flows to other motors other than the upstream motor 180a and the downstream motor 180b.

  For example, when the upstream transport roller 170a and the downstream transport roller 170b are the loop roller 173 and the registration roller 174, respectively, the control unit 110 drives another motor (third transport roller) that drives another transport roller (third transport roller). This also controls the value of the current flowing to the motor. Specifically, the control unit 110 controls each motor that drives the loop roller 173, the secondary transfer roller 143 and the fixing roller 151, the ADU pre-registration roller 176, the ADU intermediate transport roller 175, and the like that are downstream of the registration roller 174. You may control the value of the electric current to flow. In this case, it is possible to appropriately control the conveyance on the downstream side of the point where the stiffness is estimated for the paper 500 being conveyed whose stiffness is estimated.

  In addition, the control unit 110 may control the value of the current that flows to each motor that drives the first intermediate conveyance roller 171 and the second intermediate conveyance roller 172 that are upstream of the loop roller 173 and the registration roller 174. . In this case, when the paper 500 of the same type as the paper 500 whose stiffness is estimated is transported next time, the transport of the paper 500 can be appropriately controlled even upstream from the point where the stiffness is estimated.

  In the above description, the control unit 110 estimates the stiffness of the paper 500 based on the detected current value, and controls the value of the current passed through each motor based on the estimated stiffness. The method for appropriately controlling the conveyance of the paper 500 is not limited to this. For example, the control unit 110 may control the value of the current flowing through each motor based on the detected current value without performing the process of estimating the stiffness.

  As described above, the image forming apparatus 100 according to the third embodiment uses the detected current value and the current value of each motor that drives each transport roller that transports the paper 500 based on the stiffness estimated from the current value. To control. Thereby, the output torque of each motor can be appropriately controlled to prevent step-out and the like, and the paper 500 can be appropriately conveyed.

<Fourth embodiment>
In the third embodiment, the example in which the image forming apparatus 100 controls the current value that flows through the motor based on the detected current value and the stiffness estimated from the current value has been described. The method of appropriately controlling the above is not limited to this. In the fourth embodiment, an example will be described in which the image forming apparatus 100 controls the air flow rate of air feeding in the paper feeding unit 160 or the paper feeding device based on the detected current value and the stiffness estimated from the current value. .

  The configuration of the image forming apparatus 100 according to the fourth embodiment is the same as the configuration of the image forming apparatus 100 according to the first embodiment, except that an air sheet feeding mechanism is provided in the sheet feeding unit 160. Hereinafter, processing executed by the image forming apparatus 100 according to the fourth embodiment will be described.

  FIG. 12 is a flowchart illustrating a procedure of processes executed by the image forming apparatus according to the fourth embodiment. 12 is stored as a program in the storage unit 120 and executed by the control unit 110.

  The processes in steps S401 to S405 in FIG. 12 are the same as the processes in steps S101 to S105 in FIG.

  Based on the stiffness of the paper 500 estimated in the process of step S405, the control unit 110 controls the air supply air volume in the paper supply unit 160 or the paper supply device (step S406). For example, the control unit 110 increases the air supply air volume when the paper 500 has high rigidity, and decreases the air supply air volume when the paper 500 has low rigidity. As a result, it is possible to appropriately adjust the air volume of air feeding according to the stiffness of the paper, and it is possible to appropriately transport the paper 500 from the paper feeding unit 160 or the paper feeding device.

  In the above description, the control unit 110 estimates the stiffness of the paper 500 based on the detected current value, and controls the air feed amount based on the estimated stiffness. However, the method for appropriately controlling the conveyance is not limited to this. For example, the control unit 110 may control the air supply air volume based on the detected current value without performing the process of estimating the stiffness.

  As described above, the image forming apparatus 100 according to the fourth embodiment controls the air feeding amount of air in the paper feeding unit 160 or the paper feeding device based on the detected current value and the stiffness estimated from the current value. To do. Thereby, the air volume of air feeding can be adjusted appropriately, and the paper 500 can be appropriately conveyed from the paper feeding unit 160 or the paper feeding device.

  In addition, although said 1st-4th embodiment was demonstrated separately as separate embodiment, each process in these embodiment may be performed combining arbitrarily. For example, by combining all the processes in the first to fourth embodiments, estimating the stiffness of the paper based on the current value of the motor, performing the current control of the other motor and the air volume control of the air feeding, and further the reference current value Each process may be corrected based on the above.

  The means and method for performing various processes in the image forming apparatus according to the above-described embodiments can be realized by either a dedicated hardware circuit or a programmed computer. The program may be provided by a computer-readable recording medium such as a flexible disk and a CD-ROM, or may be provided online via a network such as the Internet. In this case, the program recorded on the computer-readable recording medium is usually transferred to and stored in a storage unit such as a hard disk. The program may be provided as a single application software, or may be incorporated in the software of the apparatus as a function of the image forming apparatus.

100 image forming apparatus,
110 control unit,
120 storage unit,
130 image reading unit,
140 Image forming unit,
143 secondary transfer roller,
150 fixing section,
151 fixing roller,
160 paper feeder,
170 paper transport section,
170a upstream transport roller,
170b downstream transport roller,
171 1st intermediate conveyance roller,
172 second intermediate transport roller,
173 loop roller,
174 Registration roller,
175 ADU intermediate transport roller,
176 ADU pre-registration roller,
180a upstream motor,
180b downstream motor,
190 detector,
200 Paper detection sensor,
500 paper,
510 Reference paper.

Claims (12)

A first motor for driving a first transport roller for transporting paper in the paper transport path;
A second motor that drives a second transport roller that is adjacent to the first transport roller along the paper transport path and is disposed downstream of the first transport roller in the transport direction;
For at least one of the first motor and the second motor, a detection unit capable of detecting a current value of a current flowing through the motor;
The sheet to be transported is operated while the first motor and the second motor are operated so that the transport speed of the first transport roller is faster than the transport speed of the second transport roller. A control unit that estimates the stiffness of the paper based on a current value detected by the detection unit in a state in contact with the transport roller and the second transport roller;
A conveyance driving device having   The control unit calculates an average value of current values detected by the detection unit within a predetermined time in a state in which a sheet to be conveyed is in contact with the first conveyance roller and the second conveyance roller. The conveyance drive device according to claim 1, wherein the stiffness of the sheet is estimated based on a result.   The control unit is configured to detect the current of the first motor detected by the detection unit within a predetermined time in a state where the first sheet to be conveyed is in contact with the first conveyance roller and the second conveyance roller. An average value of the first motor detected by the detection unit within a predetermined time in a state where the second sheet to be conveyed is in contact with the first conveyance roller and the second conveyance roller. The transport driving apparatus according to claim 2, wherein when the current value is larger than an average value, the first paper sheet is determined to have higher rigidity than the second paper sheet.   The control unit is configured to detect the current of the second motor detected by the detection unit within a predetermined time in a state where the first sheet to be conveyed is in contact with the first conveyance roller and the second conveyance roller. The average value of the second motor detected by the detection unit within a predetermined time in a state in which the second sheet to be transported is in contact with the first transport roller and the second transport roller. 4. The transport driving device according to claim 2, wherein when the current value is smaller than an average value, the first sheet is determined to have higher rigidity than the second sheet. 5. The controller is
It is possible to switch between a print mode for printing on paper and a test mode for transporting and testing a reference paper, which is a predetermined type of paper, unlike the print mode,
When the reference paper is conveyed, the current value detected by the detection unit in a state where the reference paper is in contact with the first conveyance roller and the second conveyance roller is previously stored in the storage unit as a reference current value. And
A current value detected by the detection unit when the reference paper is in contact with the first transport roller and the second transport roller when transporting the reference paper in the test mode; 5 is compared with the reference current value stored in the sheet, and based on the comparison result, the correspondence between the current value and the sheet stiffness when the sheet stiffness is estimated is corrected. The conveyance drive device according to item.   The transport controller according to claim 1, wherein the control unit registers the estimated stiffness of the sheet in a storage unit as a sheet profile. A first motor for driving a first transport roller for transporting paper in the paper transport path;
A second motor that drives a second transport roller that is adjacent to the first transport roller along the paper transport path and is disposed downstream of the first transport roller in the transport direction;
A detection unit capable of detecting a current value of a current flowing during operation for at least one of the first motor and the second motor;
The sheet to be transported is operated while the first motor and the second motor are operated so that the transport speed of the first transport roller is faster than the transport speed of the second transport roller. Driving the third transport roller other than the first transport roller or the second transport roller based on the current value detected by the detection unit in contact with the transport roller and the second transport roller A control unit for controlling the operation of the third motor
A conveyance driving device having A transport driving device applied to an image forming apparatus provided with an air feeding mechanism,
A first motor for driving a first transport roller for transporting paper in the paper transport path;
A second motor that drives a second transport roller that is adjacent to the first transport roller along the paper transport path and is disposed downstream of the first transport roller in the transport direction;
For at least one of the first motor and the second motor, a detection unit capable of detecting a current value of a current flowing through the motor;
The sheet to be transported is operated while the first motor and the second motor are operated so that the transport speed of the first transport roller is faster than the transport speed of the second transport roller. A control unit that adjusts an air feed amount of the air feeding mechanism in the air feeding mechanism based on a current value detected by the detection unit in contact with the transport roller and the second transport roller;
A conveyance driving device having   The conveyance drive device according to any one of claims 1 to 8, wherein at least one of the first motor and the second motor is a stepping motor or a brushless motor.   The transport driving device according to claim 1, wherein the first transport roller is a loop roller, and the second transport roller is a registration roller.   The transport driving device according to any one of claims 1 to 10, wherein a space capable of forming a paper loop is provided between the first transport roller and the second transport roller.   An image forming apparatus comprising the transport driving device according to claim 1.