JP2013234023A - Image forming apparatus having paper thickness detection means for recording paper, and thickness detection method for recording paper in image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect a thickness of recording paper even if a conveying speed of the recording paper changes.SOLUTION: An image forming apparatus has a paper thickness detection means 160 for detecting a thickness of recording paper based on displacement amount between a driving roller 164 and a driven roller 170 which convey the recording paper. The paper thickness detection means 160 has a sampling means and a calculation means. The sampling means samples a displacement amount twice or more at timing when a conveying surface of the driving roller 164 moves by a fixed length in a rotation cycle of the driving roller 164 in each case that the recording paper exists between the driving roller 164 and the driven roller 170 and it does not exist between them. The calculation means averages the sampled displacement amounts and also detects the thickness of the recording paper based on a difference of the averaged displacement amount.

Description

  The present invention relates to an image forming apparatus having a paper thickness detecting means for a recording paper and a recording paper thickness detecting method in the image forming apparatus.

There are numerous types of recording paper used in image forming apparatuses. For this reason, it is a common practice to set characteristics of recording paper to be used in the apparatus in advance and output an image under process conditions and a conveyance speed corresponding to the characteristics.
In particular, in the case of an electrophotographic output device, since the correlation between the recording paper thickness information and the fixing conditions and transfer conditions is high, it is desirable to set the recording paper thickness information accurately. In addition, in an inkjet output device, the gap between the print head and the recording paper changes depending on the thickness of the recording paper, so that the output is controlled in such a manner that the gap amount becomes constant according to the thickness of the recording paper. Is required.

Setting of the recording paper thickness information can be realized by inputting the recording paper thickness information used by the user to the image forming apparatus. However, considering the prevention of setting mistakes and reducing the burden on the user, a sensor that automatically measures the thickness is placed in the image forming device so that the optimum image forming conditions can be automatically set according to the detection results. It is desirable to do.
Further, in order to detect double feeding of recording sheets or to protect the image forming apparatus from use of recording sheets that are not supported, it is necessary to detect the thickness of each recording sheet. In that case, it is necessary to measure the recording paper during conveyance in the conveyance path.

  When measuring the thickness of the recording paper in the transport path, the behavior of the recording paper directly affects the detection accuracy, so it is preferable to measure in a state where the behavior of the recording paper is regulated. For this purpose, it is already known to accurately measure the thickness of the recording paper by sandwiching the recording paper between a pair of rollers installed in the conveyance path and measuring the displacement amount of the roller or roller shaft with a sensor.

However, in the conventional thickness detection system in which the recording paper is sandwiched between a pair of rollers and the displacement amount of the roller or the roller shaft is measured, there is a problem that the detection accuracy deteriorates because the eccentric component of the roller is superimposed on the detection value.
With respect to this problem, in Patent Document 1, for the purpose of detecting the displacement of the conveying member (roller) with high accuracy, the thickness of the recording paper is determined for a predetermined time in a section of one or more rotations of the detection roller using a sensor. It is disclosed that an eccentric component is removed by detecting at intervals and averaging the output.

  This method is similar to the present invention described below in that the detection accuracy is improved by removing the influence of eccentricity. However, in this process, if the conveyance speed changes during the period during which the thickness is detected, the detection interval changes with respect to one rotation of the roller. Therefore, even if the averaging process is performed, the eccentric component is canceled (offset) well. ) And the detection accuracy of the thickness of the recording paper deteriorates.

  An object of the present invention is to detect the thickness of a recording paper with high accuracy even when the conveyance speed of the recording paper changes during measurement in the paper thickness detection in the image forming apparatus.

  The present invention is an image forming apparatus having a recording paper thickness detecting means for detecting a thickness of a recording paper based on a displacement amount between a pair of rotary conveyance bodies that convey the recording paper, the paper thickness detecting means comprising: In each of the cases where the recording paper is present between the pair of rotating transport bodies and the case where the recording sheet is not present, the amount of displacement between the pair of rotating transport bodies is determined by the transport surface of the rotating transport body within the rotation period of the rotating transport body. Sampling means for sampling a plurality of times at the timing of moving a certain length, and a computing means for averaging the sampled displacement amount and detecting the thickness of the recording paper from the difference of the averaged displacement amount An image forming apparatus having a detection unit.

  In the present invention, the amount of displacement between the rotary transport bodies is detected at a timing at which the transport surface of the rotary transport body moves by a certain length within the rotation cycle of the rotary transport bodies. Even if the rotation speed of the recording medium changes during the measurement, the thickness of the recording paper can be detected without deteriorating the accuracy.

1 is a front view showing a mechanism part of an image forming apparatus according to an embodiment of the present invention. 1 is a block diagram schematically showing a structure of an image forming apparatus according to an embodiment of the present invention. It is a perspective view which shows the structure of the paper thickness detection means in this embodiment. It is a side view which shows the structure of the paper thickness detection means in this embodiment. 5 is a time chart showing the displacement amount of the driven roller shaft detected by the paper thickness detection means on the vertical axis and the rotation amount of the driving roller on the horizontal axis. 6 is a time chart similar to FIG. 5 in which an error component due to roller eccentricity is removed from the displacement amount of the driven roller shaft shown in FIG. 5. FIG. 6 is an enlarged waveform at the time of “with recording paper” in FIG. 5, and is a time chart showing a case where 8 points are sampled in a period variation section of one cycle. FIG. 8 is a time chart schematically showing a case where sampling is performed at the same time interval as in FIG. 7 when the speed fluctuates, and the speed is accelerated and returns to the original speed again. It is a time chart which shows the case where sampling is performed by embodiment of this invention.

FIG. 1 is a front view showing a mechanism part of an image forming apparatus according to an embodiment of the present invention.
The printer unit 1 of the image forming apparatus has an intermediate transfer unit in the center in the figure, and an intermediate transfer belt 10 that is an endless belt is disposed in the intermediate transfer unit.
The intermediate transfer belt 10 is stretched around first to third support rollers 14 to 16 and is driven to rotate clockwise.

On the left side of the third support roller 16, an intermediate transfer member cleaning unit 17 that removes residual toner remaining on the intermediate transfer belt 10 after image transfer is disposed.
The intermediate transfer belt 10 between the first support roller 14 and the second support roller 15 has black (K), yellow (Y), magenta (M), and cyan (C) along the moving direction. The image forming device 20 including the photosensitive drum 40, the charger unit 18, the developing unit, and the cleaning unit for each color is disposed.

The image forming device 20 is detachably attached to the printer unit 1. A writing unit 21 for irradiating each photosensitive drum 40 with laser light for image formation is disposed above the image forming device 20.
A secondary transfer unit 22 is disposed below the intermediate transfer belt 10. The secondary transfer unit 22 includes a secondary transfer belt 24, which is an endless belt, or a single roller between two rollers 23. The image on the intermediate transfer belt 10 is transferred onto a recording sheet. You may transcribe.

Next to the secondary transfer unit 22, a fixing unit 25 for fixing the transfer image on the recording paper is disposed, and the recording paper on which the toner image is transferred is sent to the fixing unit 25. The fixing unit 25 includes a fixing belt 26 that is an endless belt, and a heating / pressure roller 27 pressed against the fixing belt 26.
Below the secondary transfer unit 22 and the fixing unit 25, a sheet reversing unit 28 that reverses the front and back and sends out the image in order to record the image on the back surface of the recording paper immediately after the image is formed on the front surface is disposed. .

Next, document reading will be described.
Here, when there is a document on the document feeder 30 of the ADF (automatic document feeder) 4, the document is conveyed onto the contact glass 32 by operating a start button of an operation unit (not shown). When there is no document on the document feed tray 30 of the ADF 4, the scanner of the image reading unit 3 is driven to scan the first carriage 33 and the second carriage 34 in order to read a manually placed document on the contact glass 32. Drive for. At that time, when the contact glass 32 is irradiated with light from the light source on the first carriage 33, the reflected light from the document surface by this light is reflected by the first mirror on the first carriage 33 and directed to the second carriage 34. Then, the light is reflected by a mirror on the second carriage 34 and forms an image on a CCD (Charge Coupled Device) 36 as a reading sensor through an imaging lens 35. The CCD 36 converts an optical signal into an electric signal, and K, Y, M, and C color recording data are generated based on the image signal obtained by this conversion.

  When the start switch is operated, the intermediate transfer belt 10 is driven to rotate. At the same time, preparation for image formation of each unit of the image forming apparatus 20 is started, and an image formation sequence for each color image is started. That is, an exposure laser modulated based on the recording data of each color is projected onto the photosensitive drum 40 for each color, and each color toner image is superimposed on the intermediate transfer belt 10 as one image by each color image forming process. Is transcribed. The recording sheet is sent to the secondary transfer unit 22 at a timing so that the leading edge of the toner image enters the secondary transfer unit 22 at the same time as the leading edge of the toner image enters the secondary transfer unit 22. As a result, the toner image on the intermediate transfer belt 10 is transferred to the recording paper, and the recording paper on which the toner image has been transferred is sent to the fixing unit 25 where the toner image is fixed.

  The above-described recording paper is fed as follows. That is, by selecting and rotating one of the paper feed rollers 42 of the paper feed table 2, the recording paper (sheet) is fed out from one of the paper feed trays 44 provided in multiple stages in the paper feed unit 43, and the separation roller At 45, only one sheet is separated and put into the conveyance path 46. The recording sheet that has entered the conveyance path 46 is conveyed by the conveyance roller 47 and guided to the conveyance path 48 in the printer unit 1. The recording sheet abuts against the registration roller 49 in the conveyance path 48, and then temporarily stops at the timing described above. It is sent out to the transfer unit 22.

Paper can also be fed by inserting a recording paper on the manual feed tray 51.
That is, when the user inserts a recording sheet on the manual feed tray 51, the printer unit 1 rotates the paper feed roller 50 to separate one of the recording sheets on the manual feed tray 51, and the transport roller 52 records. The paper is drawn into the manual feed path 53 and is abutted against the registration roller 49 and stopped.

  The paper feed table 2 is mounted with a sensor (not shown) made of, for example, a photo sensor, and the sensor is a paper end sensor that detects the remaining amount or the presence of recording paper stored in the paper feed tray 44. There are a size detection sensor for detecting the size and orientation of the recording paper, and a tray set detection sensor for detecting whether or not each tray is mounted on the printer unit 1 of the image forming apparatus. Each paper feed tray 44 is provided with a paper conveyance sensor that detects whether or not the recording paper is suitably conveyed during conveyance of the paper and whether or not a conveyance jam (paper jam) has occurred.

In the case of single-sided recording, the recording paper discharged after the fixing process by the fixing unit 25 is guided to the discharge roller 56 by the switching claw 55 and stacked on the discharge tray 57. When performing double-sided recording, the switching claw 55 guides the sheet to the sheet reversing unit 28, reverses it there, guides it to the transfer position again, records the image on the back side, and then discharges the paper on the discharge tray 57 by the discharge roller 56 To discharge.
On the other hand, residual toner remaining on the intermediate transfer belt 10 after image transfer is removed by the intermediate transfer body cleaning unit 17 to prepare for the next image formation.

FIG. 2 is a block diagram schematically showing the structure of the image forming apparatus according to the embodiment of the present invention.
The image forming apparatus has a configuration represented by blocks as shown in FIG. 2, and includes an engine control unit 100, a controller control unit 140, and an operation unit together with a paper feeding unit 110, a fixing unit 120, an image forming unit 130, and the like. A display unit 150 is provided.

  The engine control unit 100 includes a CPU (Central Processing Unit) 101, a non-volatile memory (not shown), and the like. In the non-volatile memory, a detection output and recording of a paper thickness detection unit 160 (displacement sensor unit 162), which will be described later, are recorded. A paper thickness data table corresponding to the paper thickness of the paper and an image forming data table corresponding to the recording paper thickness and the image forming conditions are stored in advance. The engine control unit 100 controls the paper feeding unit 110, the fixing unit 120, the image forming unit 130, and the like, which are the engine units of the image forming apparatus, and the engine control processing program for forming an image and the detection result of the paper thickness detecting unit 160 The image forming control process corresponding to the paper thickness for performing image formation under the image forming conditions suitable for the paper thickness of the recording paper is executed with reference to the paper thickness data table and the image forming data table of the nonvolatile memory based on .

The image forming conditions include the fixing temperature of the fixing unit 120, the transfer bias value for transferring the toner image on the intermediate transfer belt 10 to the recording paper by the secondary transfer roller, the conveyance speed of the recording paper by the paper supply unit 110, and the like. is there.
A CPU (functioning as an image forming condition setting unit) 101 has an analog port, and analog detection voltages from the various sensors and paper thickness detection unit 160 described above are input to the analog port. The CPU 101 sets an image forming condition suitable for the paper thickness of the recording paper based on the detection voltage of the detection result of the paper thickness detecting unit 160 (displacement sensor unit 162), and executes an image forming control process according to the image forming condition. To do.

The controller control unit 140 controls each unit of the image forming apparatus to execute processing of the image forming apparatus and controls the operation display unit 150. The operation display unit (designating unit) 150 includes various keys necessary for operating the image forming apparatus, and includes a lamp such as a display (for example, a liquid crystal display) or an LED (Light Emitting Diode).
The operation display unit 150 uses an operation key to perform various operations necessary for various image processing such as copying processing, printing processing, and scanner processing using the image forming apparatus, in particular, operation for specifying the paper type of the recording paper used for image formation. On the display, the contents of commands input from the operation keys and various types of information notified from the image forming apparatus to the operator are displayed.

FIG. 3 is a perspective view showing the configuration of the paper thickness detection means 160 in the present embodiment. Here, recording paper or paper (paper) is used as a general term for recording media on which images can be formed.
The paper thickness detection means 160 is a conveyance roller that is rotatably supported for conveying a recording sheet (here, for convenience of explanation, the case where the conveyance roller 52 is used as a detection roller will be described as an example) 52, conveyance A displacement sensor unit 162 that detects a displacement of the roller 52 when the recording paper is conveyed; a sampling unit that samples the detected value of the position displacement while the conveyance roller 52 makes one or more rotations; A recording sheet thickness calculation unit (not shown) that calculates the amount of position fluctuation of the transport roller 52 by calculating an average value of the detection values for one rotation of the roller 52 is provided.

  The transport roller 52 includes a pair of opposed driving rollers 164 and driven rollers 170 having the same diameter, a driving roller shaft 166 of the driving roller 164, and a driven roller shaft 172 of the driven roller 170. A pressure contact portion N is formed between the rollers 170.

A gear 184 that meshes with a gear 182 provided on a drive shaft 180 of a drive source (motor) 178 that drives the drive roller 164 is provided at one end of the drive roller shaft 166.
The displacement sensor unit 162 is connected to the actuator 186 in contact with the driven roller shaft 172 and one end of the actuator 186 so that the displacement follows the direction in which the driving roller 164 and the driven roller 170 are separated from each other. A displacement sensor (here, a magnetic linear sensor) 188 for detecting a displacement angle is configured.

FIG. 4 is a side view showing the configuration of the paper thickness detecting means 160 in the present embodiment.
Between the driving roller 164 and the driven roller 170, a conveyance path 190 including a pair of flat plates is provided at a predetermined interval so that the recording paper is conveyed.
A paper detection sensor 192 that detects the presence or absence of recording paper is provided on the downstream side of the transport roller 52.

FIG. 5 shows the amount of displacement between the driving roller 164 and the driven roller 170 detected by the paper thickness detecting means 160, specifically, the amount of displacement of the driven roller shaft 172 in this case, the driving roller 164 as the vertical axis. It is the time chart which showed the amount of rotations on the horizontal axis.
Since the displacement level of the driven roller shaft 172 changes according to the thickness of the recording paper, the difference value of the data (displacement amount) when the recording paper is between the driving roller 164 and the driven roller 170 and when there is no recording paper is calculated. It is detected as the thickness of the recording paper.
However, in actuality, as shown in FIG. 5, the displacement sensor unit is affected by the eccentric component of the transport roller 52 (drive roller 164, driven roller 170) or its roller shaft (drive roller shaft 166, driven roller shaft 172). The output waveform 162 does not have a constant value regardless of the presence or absence of recording paper in the paper thickness detection unit 160, that is, between the driving roller 164 and the driven roller 170, and mainly has one rotation period of the transport roller 52 as a cycle. The periodic fluctuation is detected as a waveform superimposed on the output waveform of the displacement sensor unit 162.

Since the periodic fluctuation component of the output waveform of the displacement sensor unit 162 can be removed by performing an averaging process in a section that is an integral multiple of one period, in order to remove the influence of the periodic fluctuation component, the recording paper Sampling data of at least one rotation of the driven roller shaft 172 in the period when the paper thickness detection means 160 is present and when it is not present, and calculating a difference value between the values (displacement amounts) obtained by averaging the data. It is detected as the thickness of the recording paper.
By this measure, the waveform has less fluctuation as shown in FIG. 6 and the error component due to the eccentricity of the transport roller 52 (drive roller 164, driven roller 170) can be removed, so that the detection accuracy of the recording paper can be improved.

Whether the recording paper has entered the paper thickness detection means 160 is determined by monitoring the paper detection sensor 192.
At the timing when the leading edge of the recording paper starts to pass through the paper detection sensor 192, a part of the recording paper is already between the driving roller 164 and the driven roller 170, so the data when “recording paper is present” is driven from this timing. Data for one rotation or more of the roller shaft 172 may be collected.

FIG. 7 is an enlarged waveform at the time of “with recording paper” in FIG. 5, and is a time chart showing a case where 8 points are sampled in a period variation section of one period.
Circles in the figure are measurement (sampling) points. By averaging the sampled value (displacement amount) in the section of one cycle, the averaged value becomes the same value in the cycles (1) to (3). That is, if the conveyance speed is constant, as shown in FIG. 7, by sampling at equal time intervals, the position of the equal phase of the driven roller shaft 172 is detected every time. The eccentric component can be removed.

Incidentally, in general, during the period in which the image is transferred to the recording paper, the speed of the transfer belt on the image forming side and the conveyance speed of the recording paper are the same and constant. For this reason, if the thickness of the recording paper is measured during image transfer, it is possible to accurately detect the paper thickness by removing the periodic variation component even by processing by a conventional method.
In order to change the image forming condition based on the thickness of the recording paper and form an image under the optimum conditions, it is preferable to determine the thickness information of the recording paper before the image is transferred to the recording paper. For this purpose, it is preferable to detect the thickness of the recording sheet on the upstream side of the conveyance path, and to detect it using a conveyance roller arranged on the upstream side of the conveyance path.

  In the case of using the transport roller arranged on the upstream side of the transport path, there is no problem in the same process as the conventional method as long as the thickness of the recording paper is measured within a period when the transport speed is constant. However, in the paper conveyance section from when the recording paper is fed to the registration roller 49, the speeds of the conveyance rollers 47 and 52 are subjected to acceleration / deceleration control. That is, before the passage of the registration sensor (not shown) in the paper transport section, the recording paper is transported at a speed higher than the image forming linear speed in order to shorten the recording paper feeding interval. In order to stop at the registration roller 49, the sheet is decelerated and conveyed.

This is to reduce power consumption and extend the life while maintaining productivity by reducing the distance between recording papers as much as possible in order to reduce power consumption and extend the life of life parts such as photoconductors. It is.
However, if sampling is performed at equal time intervals in the paper conveyance section to be accelerated / decelerated and the averaging process is performed, the following problems occur.

FIG. 8 illustrates a case where sampling is performed at the same time interval as in FIG. 7 when the speed fluctuates, and is a time chart schematically showing a case where the speed is accelerated and returns to the original speed again.
When sampling is performed at regular time intervals in the state where the conveyance speed is changed, the amount of displacement of the driven roller shaft 172 is detected at short intervals when considering the position on the recording paper in the low-speed paper conveyance section. On the other hand, in the paper transport section where the speed is fast, the displacement amount is detected at long intervals.
In the section (1) in FIG. 8, the displacement amount of the driven roller shaft 172 appears in the same amount on the plus side and the minus side, so that it becomes the center value by performing the averaging process, but the section (2), ( In 3), since the detected value (displacement amount) appears biased toward the plus side, the value after the averaging process is also a large value with respect to the result of the section (1). That is, even if the averaging process is performed, different detection values are output at the measurement points, and the eccentric component of the driving roller 164 cannot be removed, and the residual component remains as an error.

FIG. 9 is a time chart showing a case where sampling is performed according to the embodiment of the present invention.
FIG. 9 also schematically shows a case where the speed is accelerated and returns to the original speed again as in FIG. That is, in this embodiment, data is not sampled at equal time intervals as in the prior art, but as shown in FIG. 9, the measurement positions on the conveyed recording paper are at equal intervals, that is, the conveyance roller. 52 is different from the conventional sampling method in that the detection is performed at the timing when the peripheral surface (conveying surface) of the driving roller 164 constituting 52 moves by a certain length along with the rotation. That is, the sampling interval is lengthened when the transport speed is changed in the slow direction, and conversely, the measurement position on the transported recording paper is always equal by shortening the sampling interval in the high speed section. To control.

In this way, by changing the sampling interval according to the change in the speed of the recording paper being conveyed, as shown in FIG. . Thereby, by averaging the sampled values in the section of one cycle, the averaged values become the same values in the cycles (1) to (4).
That is, even when the recording sheet conveyance speed changes, sampling is performed at a timing at which the detection interval on the recording sheet is equal, as shown in FIG. Since the detection is performed every time, the eccentric component can be removed by averaging over one period.

  The detection timing used here is generated from a control signal corresponding to the amount of movement of the motor that drives the transport roller 52 (drive roller 164 thereof). Since the amount of movement of the motor and the amount of rotation of the transport roller 52 (the driving roller 164) are in a proportional relationship, no matter how the speed changes, by averaging the prescribed number of pulses, it is always on the recording paper. Data of a certain distance period = a period in which the driving roller 164 rotates by a certain angle (= a period in which the conveyance surface (circumferential surface) of the driving roller 164 moves by a certain distance) can be sampled.

  The detection timing is not generated by a special circuit, but a circuit is added by generating a frequency after dividing the control signal of the motor that drives the transport roller 52 to a required resolution using a reference signal. The required signal can be generated without using it.

Next, an embodiment in which the drive motor that drives the transport roller 52 is a DC motor will be described.
When the drive motor that drives the transport roller 52 is a DC motor, 1 of the transport roller 52 is obtained from a signal synchronized with an encoder signal (or an FG (Frequency Generator) signal proportional to the drive speed of the DC motor) of the output shaft of the DC motor. A signal that is about 1/10 to 1/100 of the rotation time is generated, and the paper timing detection timing of the displacement sensor unit 162 is generated using the signal timing as a trigger.

  When the specification of the encoder of the motor output shaft is 200 pulses / rotation and the reduction ratio between the motor output shaft and the shaft of the transport roller 52 (drive roller shaft 166) is 2, the transport roller 52 of the motor output shaft rotates twice. The roller (drive roller 164) rotates once.

For this reason, since the transport roller 52 rotates once when the encoder outputs 400 pulses, the output of the displacement sensor unit 162 is sampled at the timing when one pulse is input from the encoder of the motor output shaft. 400 points of data can be collected per rotation of the roller 52.
There is no upper limit on the number of samplings per rotation of the transport roller 52, but when mounted on an actual device, if the sampling cycle is short, the influence on other processing may be considered. Therefore, the detection timing is set so that the number of samplings is about 10 to 100 per rotation of the transport roller 52.

The outer periphery of the transport roller 52 is 50 [mm], the transport speed of the recording paper is 200 [mm / s], the specification of the encoder of the motor output shaft is 200 pulses / rotation, and the reduction ratio between the motor output shaft and the shaft of the transport roller 52 When 2 is 2, since the motor output shaft rotates 8 times per second, when the transport speed reaches 200 [mm / s], 1600 [pps (pulses / second)] is output from the encoder.
In the above conveyance speed setting, the conveyance speed is 200 [mm / s] by detecting the output of the displacement sensor unit 162 (the displacement amount of the driven roller shaft 172) at the timing of every 16 pulses to 160 pulses of the output pulse of the encoder. ], Data of 10 to 100 samples can be collected per rotation of the transport roller 52.
According to the present embodiment, the encoder output signal used for motor control is divided to create a sampling timing signal, so that the thickness of the recording paper can be detected at an accurate timing without adding new parts. Can do.

Next, an embodiment in which the drive motor that drives the transport roller 52 is a stepping motor will be described.
When the drive motor that drives the transport roller 52 is a stepping motor, a signal that is about 1/10 to 1/100 of the rotation time of the shaft of the transport roller 52 (drive roller shaft 166) is generated from the drive pulse signal of the stepping motor. The detection timing of the displacement sensor unit 162 is generated using the signal timing as a trigger.
When the specification of the stepping motor is 200 pulses / rotation and the reduction ratio between the motor output shaft and the transport roller 52 is 2, the transport roller 52 rotates once for every two motor output shaft rotations. For this reason, since the transport roller 52 rotates once by outputting 400 pulses of the driving pulse signal of the stepping motor, when the output of the displacement sensor unit 162 is sampled at the timing of outputting one pulse to the stepping motor, the transport roller 400 points of data can be collected per rotation.

  There is no upper limit on the number of samplings per rotation of the transport roller 52, but when mounted on an actual device, if the sampling cycle is short, the influence on other processing may be considered. Therefore, the detection timing is set so that the number of samplings is about 10 to 100 per rotation of the transport roller 52.

The outer circumference of the conveyance roller 52 is 50 [mm], the conveyance speed of the recording paper is 200 [mm / s], the specification of the stepping motor is 200 pulses / rotation, between the motor output shaft and the shaft of the conveyance roller 52 (drive roller shaft 166). When the reduction ratio of the motor is 2, the motor output shaft rotates 8 times per second. Therefore, when the conveyance speed reaches 200 [mm / s], the stepping motor must be driven with the drive pulse signal 1600 [pps]. become.
In the above-described conveyance speed setting, the conveyance speed is 200 [mm / mm] by detecting the output of the displacement sensor unit 162 (the displacement amount of the driven roller shaft 172) at the timing of every 16 pulses to 160 pulses of the driving pulse of the stepping motor. s], 10 to 100 samples of data can be collected per rotation of the transport roller 52.
In this embodiment, since the timing signal is generated by dividing the drive pulse signal of the stepping motor, the output of the displacement sensor unit 162 can be detected at an accurate timing without adding new parts.

Next, the case where the drive of the conveyance roller 52 is separated from other drives by a clutch or the like will be described.
When the transport roller 52 provided with the displacement sensor unit 162 that detects the thickness of the recording paper is driven by an independent motor as in the embodiment described above, the detection timing is generated from the motor control signal, Although the output of the displacement sensor unit 162 (the amount of displacement of the driven roller shaft 172) can be sampled at that timing, the driving of the transport roller 52 is not necessarily independent.

If the drive of the transport roller 52 is common to other drive sources, a speed reduction gear is interposed between the drive source and the shaft that drives the transport roller 52, and a sensor that detects one rotation of the gear before speed reduction is added. The number of rotations of the driving roller 164 can be detected for the number of times of the final reduction ratio with respect to one rotation of the gear before deceleration. Using the output of this sensor, as a timing signal for sampling, for example, it is possible to perform sampling in the displacement sensor unit 162 with a timing signal for each rotation of the gear.
According to this, a function for generating an accurate timing signal with a simple configuration can be realized regardless of the type of motor.

Next, a roller used for detecting the thickness of the recording paper will be described.
In this embodiment, the displacement sensor unit 162 for detecting the thickness of the recording paper has been described as measuring the amount of displacement of the transport roller 52 (driven roller shaft 172).
When the conveyance rollers 47 and 52 are used as recording sheet thickness detection rollers as described above, the conveyance rollers 47 and 52 are located upstream of the conveyance path. Since the arrival time to the part becomes long, there is an advantage that the time for FB (feedback) can be secured.
Here, the detection roller installed on the upstream side of the transport path is not limited to the transport roller, but may be the registration roller 49. In this case, since the registration roller 49 has a function for temporarily stopping the conveyance of the recording sheet during the conveyance, the registration roller 49 is composed of a pair of rollers having high rigidity and is not easily affected by the fluctuation in the behavior of the recording sheet. This is advantageous in terms of accuracy. The detection roller may be arranged in the transport path.

As for the detection roller, when using a roller whose surface is made of a soft material such as rubber in order to ensure transportability, the diameter changes greatly due to environmental variations such as deformation amount and temperature of the roller itself. There is a possibility. For this reason, it is advantageous in terms of accuracy to use a hard roller made of a material having a small linear expansion coefficient.
In addition, regarding the roller diameter of the detection roller, if the diameter is relatively large, the time required for one rotation becomes longer, and the time required for the averaging process also becomes longer. Therefore, it is advantageous in time to use a roller having a relatively small diameter.
In the present invention, the “rotary conveyance body” is a generic term for a rotation body having a function of conveying a recording sheet including the pair of driving rollers and driven rollers.

Next, the displacement sensor 188 of the displacement sensor unit 162 will be described.
In the present embodiment, a magnetic linear sensor is used as the displacement sensor 188 of the displacement sensor unit 162 for detecting the thickness of the recording paper, but the displacement sensor unit 162 is not limited to this.
As long as the target displacement amount can be detected, a known sensor such as an optical distance measuring sensor, a capacitance type sensor, a strain sensor, a lever type encoder sensor or the like may be used. it can. The output format of the displacement sensor unit 162 not only detects the analog output with an A / D converter, but also outputs the displacement amount converted into a frequency, or outputs the displacement amount as a count number, and counts it with a counter to count the paper. It may be converted into a thickness and used.

  Regardless of which sensor is used, the thickness of the recording paper can be detected without deteriorating the accuracy even when the recording paper transport speed is changing by detecting at the above detection timing.

  DESCRIPTION OF SYMBOLS 1 ... Printer part, 2 ... Paper feed table, 3 ... Image reading unit, 4 ... ADF, 10 ... Intermediate transfer belt, 14-16 ... Support roller, 17 ... Intermediate transfer body cleaning unit, 18 ... charger unit, 20 ... image forming device, 21 ... writing unit, 22 ... secondary transfer unit, 23 ... roller, 24 ... secondary transfer Belt, 25... Fixing unit, 26... Fixing belt, 27... Heating / pressure roller, 28... Sheet reversing unit, 30. 33 ... 1st carriage, 34 ... 2nd carriage, 35 ... Imaging lens, 36 ... CCD (reading sensor), 40 ... Photosensitive drum, 42 ... Paper feed roller, 43 ... Paper feed unit 44 ... feed tray, 45 ... separation roller, 46 ... conveyance path, 47 ... conveyance roller, 48 ... conveyance path, 49 ... registration roller, 50 ... feed roller , 51 ... Bypass tray, 52 ... Transport roller, 55 ... Switching claw, 56 ... Discharge roller, 57 ... Discharge tray, 100 ... Engine control unit, 110 ... Feed Paper part 120... Fixing part 130... Image forming part 140... Controller control part 150 .. Operation display part 160. 164... Driving roller, 166... Driving roller shaft, 170... Driven roller, 172... Driven roller shaft, 178. ... Gear, 186 Actuator, 188 ... displacement sensor.

JP 2009-227404 A

Claims (6)

An image forming apparatus having recording sheet thickness detecting means for detecting the thickness of a recording sheet based on a displacement amount between a pair of rotary conveying members that convey the recording sheet,
The paper thickness detection means is configured to calculate a displacement amount between the pair of rotary transport bodies within a rotation cycle of the rotary transport body in each of the cases where the recording paper is between the pair of rotary transport bodies and the recording paper is not present. Sampling means that samples a plurality of times at a timing when the conveyance surface of the rotary conveyance body moves a certain length; an arithmetic means that averages the sampled displacement amount and detects the thickness of the recording paper from the difference of the averaged displacement amount; An image forming apparatus having a sheet thickness detecting means for recording paper. An image forming apparatus having a recording paper thickness detecting means according to claim 1.
The timing at which the conveyance surface of the rotary conveyance body moves by a certain length has a recording paper thickness detection means based on a timing signal synchronized with a rotation control signal for controlling the rotation of the drive source of the rotary conveyance body. Image forming apparatus. An image forming apparatus having a recording paper thickness detecting means according to claim 2.
The timing signal synchronized with the rotation control signal for controlling the rotation of the driving source of the rotating carrier is generated by dividing the encoder output signal for controlling the motor that is the driving source of the rotating carrier, Alternatively, an image forming apparatus having a sheet thickness detecting unit for a recording sheet, which is generated by dividing a drive pulse signal of a stepping motor that is a drive source of the rotary conveyance body. An image forming apparatus having a recording paper thickness detecting means according to claim 1.
The timing at which the transport surface of the rotary transport body moves a certain length is the output of a sensor that detects one rotation of the gear before deceleration of the gear reducer interposed between the drive source of the rotary transport body and the rotary transport body. An image forming apparatus having a paper thickness detecting means for the recording paper generated in the above. 5. An image forming apparatus having a recording paper thickness detecting means according to claim 1.
The image forming apparatus having a recording paper thickness detection unit, wherein the rotary conveyance body is a conveyance roller or a registration roller arranged in a conveyance path of the recording paper. A method for detecting the thickness of a recording paper in an image forming apparatus having a paper thickness detecting step for detecting the thickness of the recording paper based on a displacement amount between a pair of rotary conveyance bodies that convey the recording paper,
In the paper thickness detection step, the amount of displacement between the pair of rotary transport bodies in the case where the recording paper is present between the pair of rotary transport bodies and the case where there is no recording paper is within the rotation period of the rotary transport body, A sampling step of sampling a plurality of times at a timing when the transport surface of the rotary transport body moves by a certain length, an arithmetic step of averaging the sampled displacement amount, and detecting the thickness of the recording paper from the difference of the averaged displacement amount, A method for detecting the thickness of a recording sheet in an image forming apparatus.

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