JP2024135140A - Media thickness detection device and image forming apparatus - Google Patents

Abstract

[Problem] To detect the thickness of a medium by utilizing the rigidity of the medium. [Solution] A medium thickness detection device comprising: a transport means (Rr) for transporting a medium (S), a load applying means (1) arranged downstream of the transport means (Rr) in the transport direction of the medium (S) and contacting the transported medium (S) to apply a transport load to the medium (S), and a thickness detection means (C7) for detecting the thickness of the medium (S) based on the drive current of the transport means (Rr) after the medium (S) comes into contact with the load applying means (1). [Selected Figure] Figure 3

Description

The present invention relates to an image forming apparatus having a media thickness detection device and a post-processing device.

The technologies described in the following Patent Documents 1 and 2 are known in the art for a medium thickness detection device that detects the thickness of a medium on which an image is recorded by an image recording device.

Patent document 1 (JP 2016-136194 A) describes a technology that determines the thickness of the recording material (P) from the value of the drive torque that rotates the pressure member (4) of the fixing device (20) and corrects the set temperature of the fixing member according to the paper thickness.

Patent document 2 (JP Patent Publication 2003-285484A) describes a technology for measuring the thickness of paper by measuring the total torque applied to the motor unit (2) that drives the vertical path roller (71), pre-registration roller (72), registration roller (73), and transfer roller (74) from the supply current value (IA).

JP 2016-136194 A (Claim 1, "0024"-"0035", Figures 1-3) JP 2003-285484 A ("0024"-"0039", Figs. 3-7, 14)

The technical objective of this invention is to detect the thickness of a medium by utilizing the stiffness of the medium.

In order to solve the above technical problem, the medium thickness detection device of the present invention as set forth in claim 1 comprises:
A conveying means for conveying a medium;
a load applying means arranged downstream of the conveying means in a medium conveying direction, the load applying means contacting the conveyed medium to apply a conveying load to the medium;
a thickness detection means for detecting a thickness of the medium based on a drive current of the transport means after the medium comes into contact with the load application means;
The present invention is characterized by comprising:

The present invention relates to a medium thickness detection device, comprising:
the load applying means having a curved shape along the medium transport direction and configured as a guide means for guiding the medium;
The present invention is characterized by comprising:

The present invention relates to a medium thickness detection device, comprising:
the load applying means moving between a contact position where the medium being conveyed comes into contact with the load applying means and a retracted position where the load applying means is retracted from the medium, the load applying means moving to the contact position when detecting the thickness of the medium;
The present invention is characterized by comprising:

The present invention provides a medium thickness detection device according to claim 3, further comprising:
the load applying means moving to the contact position when there is a possibility of changing the type of medium;
The present invention is characterized by comprising:

The present invention relates to a medium thickness detection device, comprising:
the load applying means moving to the contact position when the insertion or removal of the storage means storing the medium is detected as a possibility of a change in the type of the medium;
The present invention is characterized by comprising:

The present invention provides a medium thickness detection device according to claim 6, further comprising:
A guide means for guiding the medium;
the load applying means being disposed at a position where the medium being supported by and transported by the guide means comes into contact with the load applying means, the load applying means having a friction coefficient greater than that of the guide means;
The present invention is characterized by comprising:

The present invention provides a medium thickness detection device according to claim 1,
a medium detection means disposed between the conveying means and the load applying means and configured to detect a medium;
a contact time determination means for determining a time when the medium comes into contact with the load application means based on a detection result of the medium detection means;
The present invention is characterized by comprising:

The present invention relates to a medium thickness detection device, comprising:
The present invention is characterized in that it comprises a contact time determination means which detects the time when the medium enters the transport means based on the drive current and determines the time when the medium will come into contact with the load application means from the entry time.

The present invention provides a medium thickness detection device according to claim 9, further comprising:
a calibration means for calibrating the drive current based on a predetermined calibration condition;
the thickness detection means for detecting a thickness of a medium based on the calibrated driving current;
The present invention is characterized by comprising:

The present invention provides a medium thickness detection device according to claim 9,
The calibration condition is a size in a width direction of the medium.

In order to solve the above technical problem, an image forming apparatus according to the present invention includes:
An image holding means;
a transfer means for transferring the image held on the image holding means to a medium;
A fixing means for fixing the image transferred to the medium;
a medium thickness detection device according to claim 1 , the medium thickness detection device being disposed upstream of the transfer means in a medium transport direction;
The present invention is characterized by comprising:

According to the first and eleventh aspects of the present invention, the thickness of the medium can be detected by utilizing the rigidity of the medium.
According to the second aspect of the present invention, the guide means can be used as the load applying means, and the number of parts can be reduced, and costs can be suppressed, compared to the case where the load applying means is provided separately.
According to the third aspect of the present invention, even if the guide means cannot apply a load, the thickness of the medium can be detected by using the load applying means that moves between the contact position and the retracted position.
According to the fourth aspect of the present invention, the processing load for detecting the thickness of the medium can be reduced compared to when the thickness of the medium is detected every time.

According to the invention described in claim 5, when insertion or removal of the storage means, which may have resulted in the medium being replaced, is detected, the thickness can be detected, and the processing load for detecting the thickness of the medium can be reduced compared to detecting the thickness every time.
According to the sixth aspect of the present invention, even if the guide means has a low coefficient of friction, the thickness of the medium can be detected by using the load applying means having a high coefficient of friction.
According to the seventh aspect of the present invention, detection errors in the contact timing of the medium can be suppressed compared to when the medium detection means is not used.

According to the eighth aspect of the present invention, the entry time can be detected by the drive current, no medium detection means is required, and the number of parts can be reduced.
According to the ninth aspect of the present invention, the accuracy of detecting the thickness of the medium can be improved compared to the case where calibration is not performed.
According to the tenth aspect of the present invention, the driving current that varies depending on the size of the medium in the width direction can be calibrated.

FIG. 1 is an overall explanatory diagram of an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a diagram illustrating a main part of the image recording unit of the first embodiment. FIG. 3 is a functional block diagram of the control unit according to the first embodiment. FIG. 4 is an explanatory diagram of an example of the detection result of the drive current in the first embodiment. FIG. 5 is a diagram illustrating a main portion of a medium thickness detection device according to a second embodiment. FIG. 6 is a diagram illustrating a main portion of a medium thickness detection device according to a third embodiment.

Next, examples of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following examples.
In order to make the following explanation easier to understand, in the drawings, the front-to-rear direction is defined as the X-axis direction, the left-to-right direction is defined as the Y-axis direction, and the up-down direction is defined as the Z-axis direction, and the directions or sides indicated by arrows X, -X, Y, -Y, Z, and -Z are defined as the front, rear, right side, left side, upper side, and lower side, or the front side, rear side, right side, left side, upper side, and lower side, respectively.
In addition, in the figures, a "・" inside a "○" means an arrow going from the back to the front of the page, and an "X" inside a "○" means an arrow going from the front to the back of the page.
In the following description using the drawings, illustrations of components other than those necessary for the description are omitted as appropriate to facilitate understanding.

FIG. 1 is an overall explanatory diagram of an image forming apparatus according to a first embodiment of the present invention.
1, a copier U as an example of an image forming apparatus according to the first embodiment of the present invention has a printer unit U1 as an example of an image recording means and an example of an image recording device. A scanner unit U2 as an example of a reading means and an example of an image reading device is supported above the printer unit U1. An auto feeder U3 as an example of a document conveying device is supported above the scanner unit U2.

A document tray TG1, which is an example of a medium storage means, is disposed above the auto feeder U3. A stack of multiple documents Gi to be copied can be stored in the document tray TG1. A document discharge tray TG2, which is an example of a document discharge section, is formed below the document tray TG1. A document transport roller U3b is disposed between the document tray TG1 and the document discharge tray TG2 along the document transport path U3a.

A platen glass PG, which is an example of a transparent document table, is disposed on the upper surface of the scanner unit U2. In the scanner unit U2 of Example 1, a reading unit U2a, which is an example of a reading unit, is disposed below the platen glass PG. The reading unit U2a of Example 1 is supported along the lower surface of the platen glass PG so as to be movable in the left-right direction, which is an example of a sub-scanning direction. The reading unit U2a is electrically connected to the image processing unit GS.

FIG. 2 is a diagram illustrating a main part of the image recording unit of the first embodiment.
The image processing section GS is electrically connected to a writing circuit DL of the printer section U1. The writing circuit DL is electrically connected to exposure devices LHy, LHm, LHc, and LHk, which are an example of a latent image forming means.
The exposure devices LHy to LHk in the first embodiment are configured, for example, with an LED head in which a plurality of LEDs are arranged in the main scanning direction. The exposure devices LHy to LHk are configured to be able to output writing light corresponding to each of the colors Y, M, C, and K in response to a signal input from a writing circuit DL.
The write circuit DL and the power supply circuit E have their write timing and power supply timing controlled in response to control signals from a control section C, which is an example of a control means.
In Fig. 1, photoconductors PRy, PRm, PRc, and PRk as an example of an image holding means are disposed above the exposure devices LHy to LHk. In Fig. 1 and Fig. 2, writing areas Q1y, Q1m, Q1c, and Q1k are configured by areas on the photoconductors PRy to PRk where the writing light is irradiated.

Charging rollers CRy, CRm, CRc, and CRk as an example of a charging means are disposed upstream of the writing areas Q1y to Q1k with respect to the rotation direction of each of the photoconductors PRy to PRk. The charging rollers CRy to CRk in the first embodiment are supported in contact with the photoconductors PRy to PRk so as to be rotatable by the photoconductors PRy to PRk.
Developing devices Gy, Gm, Gc, and Gk, which are an example of developing means, are disposed downstream of the writing areas Q1y to Q1k with respect to the rotation direction of the photoconductors PRy to PRk. The developing areas Q2y, Q2m, Q2c, and Q2k are formed by the areas where the photoconductors PRy to PRk and the developing devices Gy to Gk face each other.

Primary transfer rollers T1y, T1m, T1c, and T1k, which are an example of a primary transfer means, are disposed downstream of the developing devices Gy to Gk with respect to the rotation direction of the photoconductors PRy to PRk. Primary transfer regions Q3y, Q3m, Q3c, and Q3k are formed by regions where the photoconductors PRy to PRk and the primary transfer rollers T1y to T1k face each other.
Photoconductor cleaners CLy, CLm, CLc, and CLk, which are an example of a cleaning unit, are disposed downstream of the primary transfer rollers T1y to T1k with respect to the rotation direction of the photoconductors PRy to PRk.
Dischargers Jy, Jm, Jc, and Jk, which are an example of a discharge means and an example of a discharge device, are disposed downstream of the photoconductor cleaners CLy to CLk with respect to the rotation direction of the photoconductors PRy to PRk.

The Y-color photoconductor PRy, charging roller CRy, exposure device LHy, development device Gy, primary transfer roller T1y, photoconductor cleaner CLy, and static eliminator Jy constitute a Y-color image forming unit Uy as an example of a Y-color visible image forming means in Example 1 that forms a Y-color toner image. Similarly, the M-, C-, and K-color image forming units Um, Uc, and Uk are constituted by the photoconductors PRm, PRc, and PRk, charging rollers CRm, CRc, and CRk, exposure devices LHm, LHc, and LHk, development devices Gm, Gc, and Gk, primary transfer rollers T1m, T1c, and T1k, photoconductor cleaners CLm, CLc, and CLk, and static eliminators Jm, Jc, and Jk.

A belt module BM, which is an example of an intermediate transfer device, is disposed above the photoconductors PRy to PRk. The belt module BM is an example of an image holding means, and has an intermediate transfer belt B, which is an example of an intermediate transfer means. The intermediate transfer belt B is made of an endless belt-like member.
The intermediate transfer belt B in the first embodiment is rotatably supported by a tension roller Rt as an example of a tensioning means, a walking roller Rw as an example of a deviation correcting means, an idler roller Rf as an example of a driven means, a backup roller T2a as an example of an opposing means in the secondary transfer region, primary transfer rollers T1y to T1k, and a drive roller Rd as an example of a drive member. In the first embodiment, when drive is transmitted to the drive roller Rd, the intermediate transfer belt B rotates.

A secondary transfer roller T2b as an example of a secondary transfer means is disposed at a position facing the backup roller T2a across the intermediate transfer belt B. The backup roller T2a and the secondary transfer roller T2b constitute a secondary transfer unit T2 of the first embodiment as an example of a transfer device. A secondary transfer area Q4 is constituted by an area where the secondary transfer roller T2b and the intermediate transfer belt B contact each other.
A belt cleaner CLb is disposed downstream of the secondary transfer area Q4 in the rotation direction of the intermediate transfer belt B, as an example of a cleaning device for the intermediate transfer body.
The primary transfer rollers T1y to T1k, the intermediate transfer belt B, the secondary transfer unit T2, etc., constitute a transfer device T1+T2+B of the first embodiment as an example of a transfer means. The image forming units Uy to Uk and the transfer device T1+T2+B constitute an image recording unit Uy to Uk+T1+T2+B of the first embodiment.

1, four pairs of left and right guide rails GR as an example of a guide means are provided below the imaging units Uy to Uk. Each guide rail GR supports paper feed trays TR1, TR2, TR3, and TR4 as an example of a medium storage means so that they can be moved in and out in the front-rear direction. The paper feed trays TR1 to TR4 store recording paper S as an example of a medium.
A pickup roller Rp, which is an example of a removal means, is disposed above and to the left of each of the paper feed trays TR1 to TR4. A separation roller Rs, which is an example of a separation means, is disposed downstream of the pickup roller Rp in the transport direction of the recording paper S. A paper feed path SH1, which extends upward and is an example of a medium transport path, is formed downstream of the separation roller Rs in the transport direction of the recording paper S. A plurality of transport rollers Ra, which are an example of a transport means, are disposed on the paper feed path SH1.

A manual feed tray TR0 as an example of a medium storage means is disposed in the lower left portion of the copier U. A pickup roller Rp0 is disposed in the upper right portion of the manual feed tray TR0, and a manual feed path SH0 extends from the manual feed tray TR0. The manual feed path SH0 merges with the feed path SH1.
In the sheet feed path SH1, a registration roller Rr as an example of a conveyance timing adjustment unit is disposed upstream of the secondary transfer area Q4. A conveyance path SH2 extends from the registration roller Rr toward the secondary transfer area Q4.

A fixing device F as an example of a fixing means is disposed downstream of the secondary transfer area Q4 in the conveying direction of the recording paper S. The fixing device F has a heating roller Fh as an example of a fixing member for applying heat, and a pressure roller Fp as an example of a fixing member for applying pressure. A fixing area Q5 is formed by a contact area between the heating roller Fh and the pressure roller Fp.
A lower discharge tray TRh, which is an example of a medium discharge section, is formed on the upper surface of the printer unit U1. In the first embodiment, a finisher U4, which is an example of a post-processing device, is installed in the lower discharge tray TRh. A discharge path SH3, which is an example of a transport path, extends toward the lower discharge tray TRh above the fixing device F. Discharge rollers Rh, which are an example of a medium transport means, are disposed at the downstream end of the discharge path SH3.

An upper discharge tray TRh2 as an example of a medium discharge section is disposed above the lower discharge tray TRh. An upper transport path SH4 is formed above the fixing device F, branching off from the discharge path SH3 and extending toward the upper discharge tray TRh2.
A reversible roller Rb, which is an example of a medium transport means, is disposed on the upper transport path SH4. A reversible path SH6, which is an example of a medium transport path, branches off to the lower left from the upper transport path SH4 above the branching position of the paper discharge path SH3 and the upper transport path SH4.

A gate GT1 as an example of a switching means is disposed across a branching portion between the discharge path SH3 and the upper transport path SH4 and a branching portion between the upper transport path SH4 and the reversing path SH6. The gate GT1 guides the recording paper S from the fixing device F toward the lower discharge tray TRh and is supported switchably between a first guide position (second position) for guiding the recording paper S from the upper transport path SH4 to the reversing path SH6 and a second guide position (first position) for guiding the recording paper S from the fixing device F to the upper transport path SH4.
A plurality of transport rollers Ra, which are an example of a medium transport means, are arranged on the reversing path SH6. The downstream end of the reversing path SH6 joins the paper feed path SH1 on the upstream side of the registration rollers Rr.

(Explanation of Image Forming Operation)
In the copying machine U of the first embodiment having the above-mentioned configuration, when an operator places an original Gi on the platen glass PG by hand to perform copying, the reading unit U2a moves from the initial position in the left-right direction, and the original Gi on the platen glass PG is scanned while being exposed to light. When the automatic feeder U3 is used to automatically transport the original Gi to perform copying, the multiple originals Gi accommodated in the original tray TG1 are transported sequentially to the original reading position on the platen glass PG, pass through it, and are discharged to the original discharge tray TG2. Each original Gi that sequentially passes through the reading position on the platen glass PG is exposed to light and scanned by the reading unit U2a. The reflected light from the original Gi is received by the reading unit U2a. The reading unit U2a converts the received reflected light of the original Gi into an electrical signal. When double-sided reading of the original Gi is performed, the original Gi is also read by the reading sensor.

The image processing unit GS receives the electrical signals output from the reading unit U2a. The image processing unit GS converts the electrical signals of the R, G, and B color images read by the reading unit U2a into image information of yellow (Y), magenta (M), cyan (C), and black (K) for forming a latent image. The image processing unit GS outputs the converted image information to the writing circuit DL of the printer unit U1. Note that, when the image is a single-color image, that is, a monochrome image, the image processing unit GS outputs image information of only black (K) to the writing circuit DL.
The writing circuit DL outputs a control signal corresponding to the input image information to the exposure devices LHy to LHk, which in turn output writing light corresponding to the control signal.

When image formation starts, each photoconductor PRy-PRk is rotated. A charging voltage is applied to the charging rollers CRy-CRk from the power supply circuit E. Therefore, the surfaces of the photoconductors PRy-PRk are charged by the charging rollers CRy-CRk. An electrostatic latent image is formed on the surface of the charged photoconductors PRy-PRk by the exposure devices LHy-LHk in the writing areas Q1y-Q1k. The electrostatic latent image on the photoconductors PRy-PRk is developed into a toner image, an example of a visible image, by the developing devices Gy-Gk in the development areas Q2y-Q2k.

The developed toner image is transported to a primary transfer area Q3y-Q3k that contacts an intermediate transfer belt B, which is an example of an intermediate transfer body. In the primary transfer area Q3y-Q3k, a primary transfer voltage having a polarity opposite to the charge polarity of the toner is applied from a power supply circuit E to the primary transfer rollers T1y-T1k. Therefore, the toner images on the photoconductors PRy-PRk are transferred to the intermediate transfer belt B by the primary transfer rollers T1y-T1k. In the case of a multi-color toner image, the toner image on the downstream side is transferred and superimposed on the toner image transferred to the intermediate transfer belt B in the upstream primary transfer area.
After the primary transfer, residues and deposits on the photoconductors PRy to PRk are cleaned by photoconductor cleaners CLy to CLk. The surfaces of the photoconductors PRy to PRk after cleaning are neutralized by neutralizers Jy to Jk. The surfaces of the photoconductors PRy to PRk after neutralization are recharged by charging rollers CRy to CRk.
The single-color or multi-color toner images transferred onto the intermediate transfer belt B by the primary transfer rollers T1y to T1k in the primary transfer areas Q3y to Q3k are transported to the secondary transfer area Q4.

The recording paper S on which an image is recorded is picked up by the pickup roller Rp of the paper feed tray TR1 to TR4 being used. If the recording paper S picked up by the pickup roller Rp is a stack of multiple sheets of recording paper S, they are separated one by one by the separation roller Rs. The recording paper S separated by the separation roller Rs is transported along the paper feed path SH1 by the transport roller Ra. The recording paper S transported along the paper feed path SH1 is sent to the registration roller Rr. The recording paper S loaded on the manual feed tray TR0 is also sent to the paper feed path SH1 by the pickup roller Rp0 via the manual feed path SH0 by the manual feed path SH0.
The registration roller Rr transports the recording paper S to the secondary transfer area Q4 in time with the toner image formed on the intermediate transfer belt B being transported to the secondary transfer area Q4. A secondary transfer voltage having a polarity opposite to the charge polarity of the toner is applied to the secondary transfer roller T2b by the power supply circuit E. Therefore, the toner image on the intermediate transfer belt B is transferred from the intermediate transfer belt B to the recording paper S.

After the secondary transfer, the intermediate transfer belt B has any adhering matter or the like on its surface cleaned by a belt cleaner CLb.
The recording paper S onto which the toner image has been secondarily transferred is heated and fixed when passing through a fixing area Q5.
When post-processing is performed on the recording paper S with the image fixed thereon, the recording paper S is transported to a finisher U4, which is an example of a post-processing device installed in the lower paper discharge tray TRh. When post-processing is not performed on the recording paper S, the recording paper S is transported to the upper paper discharge tray TRh2. When the recording paper S is transported to the lower paper discharge tray TRh, the gate GT1 moves to the first guide position. Therefore, the recording paper S sent out from the fixing device F is transported along the paper discharge path SH3. The recording paper S transported along the paper discharge path SH3 is transported by the paper discharge rollers Rh toward the finisher U4 and the lower paper discharge tray TRh.
The finisher U4 performs a binding process, which is an example of post-processing, on the recording paper S, and then discharges the recording paper S onto a lower paper discharge tray TRh.

When the recording paper S is discharged onto the upper discharge tray TRh2, the gate GT1 moves to the second guiding position, and the recording paper S is discharged onto the upper discharge tray TRh2.
When the recording paper S is printed on both sides, the gate GT1 moves to the second guide position. Then, when the trailing edge of the recording paper S passes through the gate GT1, the gate GT1 moves to the first guide position and the reversing roller Rb rotates in the reverse direction. Therefore, the recording paper S is guided by the gate GT1 and sent to the reversing path SH6. The recording paper S transported through the reversing path SH6 is sent to the registration roller Rr in an inverted state.

(Description of thickness detection device)
2, in the copying machine U of the first embodiment, a paper guide 1, which is an example of a load applying means and an example of a guiding means, is disposed downstream of a registration roller Rr, which is an example of a conveying means. The paper guide 1 of the first embodiment has a curved shape with respect to the paper sending-out direction (medium conveying direction) from the registration roller Rr, and extends toward the secondary transfer area Q4 on the downstream side.
Further, near the downstream side of the registration rollers Rr, a paper sensor SN1 that detects the recording paper S is disposed as an example of a medium detection means.
The registration roller Rr in the first embodiment is driven by a registration motor M1 as an example of a driving means. A torque ammeter 2 as an example of a detection means for detecting a drive current (load current, current consumption) is connected to the registration motor M1. Note that, in the first embodiment, a case where a dedicated registration motor M1 is used to drive the registration roller Rr is illustrated, but this is not limiting. It is also possible to use a motor common to other conveying rollers Ra, etc., and to control the driving/stopping of the registration roller Rr by turning a clutch on/off. When a common motor is used, it is possible to detect the change in the drive current of the common motor during the period when the clutch is on as the drive current of the registration roller Rr.

(Description of the control unit of the first embodiment)
FIG. 3 is a functional block diagram of the control unit according to the first embodiment.
In Fig. 3, the control unit (controller) C, which is an example of a control means of the copier U, has an input/output interface I/O for inputting and outputting signals from and to the outside. The control unit C also has a ROM (read-only memory) in which programs and information for performing necessary processing are stored. The control unit C also has a RAM (random access memory) for temporarily storing necessary data. The control unit C also has a CPU (central processing unit) for performing processing according to the programs stored in the ROM or the like. Thus, the control unit C in the first embodiment is configured with a small information processing device, a so-called microcomputer. Thus, the control unit C can realize various functions by executing programs stored in the ROM or the like.
The control unit C in the first embodiment receives a signal from the signal output element and outputs a signal to the controlled element to control it.

(Description of signal output elements)
The control unit C receives signals from signal output elements such as a user interface UI, a paper sensor SN1, a tray sensor SN2, a torque ammeter 2, and other sensors (not shown).
The user interface UI inputs the contents input by the user or the worker to the control unit C. In the first embodiment, as an example, when an input to change the type of recording paper S (plain paper, thin paper, thick paper, etc.) contained in the paper feed trays TR1 to TR4 is made through the user interface UI, a control signal is input to the control unit C.
The paper sensor SN1 detects the presence or absence of the recording paper S, thereby detecting the passage of the recording paper S.
The tray sensor SN2, which is an example of a storage means attachment/detachment detection means, is provided for each of the paper feed trays TR1 to TR4 and detects attachment/detachment of each of the paper feed trays TR1 to TR4 to the copier U.
The torque ammeter 2 detects a torque current which is a driving current for the registration roller Rr.

(Description of Controlled Elements)
The control unit C outputs signals to a power supply circuit E, a registration roller control circuit, and other controlled elements (not shown).
The power supply circuit E controls the charging bias of the charging rollers CRy to CRk, the developing bias of the developing devices Gy to Gk, the primary transfer bias of the primary transfer rollers T1y to T1k, the secondary transfer bias of the secondary transfer roller T2b, and the power supply to the heater of the fixing device F, etc.
The registration roller control circuit controls the driving/stopping of the registration roller Rr via a registration motor M1.

(Functions of control unit C)
The control unit C of the first embodiment has the following functional means (functional modules, program modules) C1 to C8.
The passage determination section C1 determines whether the recording paper S has passed the position of the paper sensor SN1 based on the detection result of the paper sensor SN1.
The tray attachment/detachment detection means C2 detects the attachment/detachment of each of the paper feed trays TR1 to TR4 based on the detection result of the tray sensor SN2.
The paper type setting unit C3 sets the type of recording paper S stored in each of the paper feed trays TR1 to TR4 based on an input from the user interface UI. The types of recording paper S include paper types such as plain paper, thin paper, thick paper, postcards, coated paper, and OHP sheets, as well as sizes such as A4, B5, and A3. When the setting of the type of recording paper S is changed, the paper type setting unit C3 of the first embodiment also detects that the change has been made.

The calibration means C4 calibrates the output result of the torque ammeter 2. The torque current detected by the torque ammeter 2 increases with an increase in the transport load of the recording paper S. Therefore, even if the paper type is the same, the transport load is larger for a recording paper S of a large size (especially the size in the width direction) than for a recording paper S of a small size, and the transport load is larger for a heavy recording paper S (large basis weight) such as thick paper than for a light recording paper S (small basis weight) such as thin paper. Also, the transport load is larger when the recording paper S is transported while in contact with the paper guide 1 (under load) than before the front end of the recording paper S contacts the paper guide 1 (under no load). Therefore, for the drive current value detected by the torque ammeter 2, for example, the drive current value of a large-sized thick paper under no load and the drive current value of a small-sized thin paper under load may happen to coincide. Therefore, in the calibration means C4 of the first embodiment, the drive current value (drive current value at no load, reference current value) before contact with the paper guide 1 is derived in advance by experiment or the like for each type (paper type, size) of recording paper S, and based on the settings made by the paper type setting means C3, the reference current value of the drive current value detected by the torque ammeter 2 is set and calibrated according to the type of recording paper S contained in the paper feed trays TR1 to TR4 from which paper is fed.

The contact time determination means C5 determines the time when the recording paper S contacts the paper guide 1 based on the detection result of the paper sensor SN1. In the contact time determination means C5 of the first embodiment, the transport speed at which the registration roller Rr transports the recording paper S is predetermined, and calculates the time when the leading edge of the recording paper S will reach the paper guide 1 from the time when the paper sensor SN1 detects the recording paper S, the distance from the paper sensor SN1 to the paper guide 1, and the transport speed, and determines the calculated time as the time of contact.

FIG. 4 is an explanatory diagram of an example of the detection result of the drive current in the first embodiment.
The driving current detection means C6 detects the driving current at the registration roller Rr based on the detection result of the torque ammeter 2. In FIG. 4, at time t1 when the recording paper S enters the registration roller Rr, a temporarily high driving current value is detected due to the impact at the time of entry. After that, the recording paper S contacts the curved paper guide 1, and is conveyed while bending along the curve of the paper guide 1 when guided by the paper guide 1. For recording paper S of the same paper type and size, if the thickness is thick, the paper stiffness (paper rigidity, paper stiffness) is high, and the conveying load becomes large when the recording paper S bends. When the conveying load becomes large, a large driving current of the registration roller Rr is detected. Therefore, as shown in FIG. 4, after contact time t2 when the recording paper S contacts the paper guide 1, a difference in the driving current value detected between thick paper and thin paper is likely to occur.

The thickness detection means C7 detects the thickness of the recording paper S based on the drive current of the registration roller Rr after the recording paper S contacts the paper guide 1. After the contact time determined by the contact time determination means C5, the thickness of the recording paper S is determined based on the drive current detected by the drive current detection means C6. As described above, the drive current increases as the thickness of the recording paper S increases, so it is possible to detect (estimate, estimate) the thickness of the recording paper S from the detected drive current value.

As an example, the thickness detection means C7 of the first embodiment detects the thickness of the recording paper S based on the drive current value during the period from the contact time until the recording paper S reaches the downstream secondary transfer area Q4. Here, at the moment t2a when the front end of the recording paper S contacts the paper guide 1, a temporary localized transport load may occur due to the impact at the time of contact, and a noise-like value may be measured in the drive current value. Therefore, it is preferable not to use the measurement result immediately after the start of the contact time t2 (the moment of contact) t2a, but to use the drive current value after the impact of a predetermined time has elapsed from immediately after the start of the contact time t2a. In other words, it is possible to detect the thickness of the recording paper S based on the drive current value at the time after the contact time, taking into account a margin.

In addition, the thickness detection means C7 of the first embodiment detects the thickness of the recording paper S every time the recording paper S passes, but is not limited to this. For example, when multiple sheets are printed continuously, it is also possible to configure the thickness to be detected only for the first sheet. In this way, it is possible to suppress the processing load of thickness detection in the control unit C. In addition, it is also possible to configure the thickness of the recording paper S to be detected when there is a possibility of a change in the type of the recording paper S in the paper feed trays TR1 to TR4. For example, when the attachment/detachment (insertion/removal) of the paper feed trays TR1 to TR4 is detected, the recording paper S in the paper feed trays TR1 to TR4 may have been replaced, and the type of the recording paper S may have changed, so it is also possible to configure the thickness of the recording paper S fed after the attachment/detachment of the paper feed trays TR1 to TR4 is detected. In addition, when the setting of the paper type is changed in the user interface UI, there is a possibility of a change in the type of the recording paper S, so it is also possible to configure the thickness of the recording paper S fed thereafter to be detected. When the paper type setting is changed via the user interface UI, there is a possibility of erroneous input by the user, and even if the set paper type is correct, there may be manufacturing errors due to the lot. Therefore, in the first embodiment, the thickness information input via the user interface UI is not used as is, but the thickness is detected by the thickness detection means C7.
The registration roller Rr, the paper guide 1, the paper sensor SN1, the torque ammeter 2, the means C1 to C7 of the control section C, and the like constitute the medium thickness detection device of the first embodiment.

The image formation condition adjustment means C8 adjusts the image formation conditions based on the detection results of the thickness detection means C7. In the first embodiment, the image formation condition adjustment means C8 adjusts the secondary transfer bias in the secondary transfer area Q4 and the fixing temperature in the fixing device F, which are examples of image formation conditions, according to the thickness of the recording paper S detected by the thickness detection means C7. For example, when the recording paper S is thick, the secondary transfer bias is increased and the fixing temperature is increased, compared to when the recording paper S is thin.

(Function of Example 1)
In the copying machine U of the first embodiment having the above-mentioned configuration, after the recording paper S comes into contact with the paper guide 1, the transport load that changes according to the thickness of the recording paper S is detected by the drive current value of the registration roller Rr, and the thickness of the recording paper S is detected. In other words, the thickness of the recording paper S is detected by utilizing the stiffness of the recording paper S that changes according to the thickness of the recording paper. Then, the image forming conditions are adjusted according to the detected thickness.
In Patent Document 1, the thickness of the recording paper is detected by the fixing device after the recording paper has passed the transfer area, and there is a problem in that the transfer conditions cannot be adjusted according to the thickness of the paper. In contrast, in Example 1, the thickness of the recording paper S is detected downstream of the registration roller Rr, and it is possible to adjust the secondary transfer conditions and fixing conditions.

In Patent Document 2, since the total torque is measured, the torque current value when the recording paper enters the conveying roller, the torque current value when the recording paper is not in contact with the paper guide 1, and the torque current value after the recording paper reaches the downstream conveying roller are also added together for judgment. A locally large value is observed for the torque current value when the recording paper enters, and the thickness of the recording paper is hardly related to the driving current value before contact with the paper guide 1. Furthermore, after the recording paper reaches the downstream conveying roller, the recording paper is pulled or loosened due to the difference in peripheral speed between the upstream conveying roller and the downstream conveying roller, so the conveying load fluctuates due to factors other than the thickness of the recording paper. Therefore, in the technology described in Patent Document 2, the torque current value in a state not related to the thickness of the recording paper S is also taken into account, which may reduce the accuracy of thickness detection.
In contrast to this, in the first embodiment, the thickness of the recording paper S is detected based on the drive current value after the contact time, which is the period during which the drive current value closely related to the thickness of the recording paper S is detected. Therefore, compared to the technology described in Patent Document 2, the thickness detection accuracy is improved.

In addition, in the first embodiment, the curved paper guide 1 is used to create a situation in which a transport load that depends on the thickness of the recording paper S is generated, and the thickness is detected from the drive current. Therefore, there is no need to provide a dedicated member that generates the transport load, and an increase in manufacturing costs is suppressed compared to when a dedicated member is used.
Furthermore, in the first embodiment, the time when the recording paper S reaches the paper guide 1 is determined from the detection result of the paper sensor SN1. Although it is possible to calculate the arrival time from the time when the recording paper S is sent out by the pickup roller Rp, by using the paper sensor SN1 on the upstream side of the paper guide 1, it is possible to suppress the influence of errors during transport due to slippage between the recording paper S and each of the rollers Rp, Rs, and Ra.
In the first embodiment, the time when the recording paper S reaches the paper guide 1 is determined based on the detection result of the paper sensor SN1, but the present invention is not limited to this. For example, by utilizing the fact that a large drive current value is detected when the recording paper S enters the registration rollers Rr, it is possible to determine that the leading edge of the recording paper S has entered the registration rollers Rr when a drive current value higher than a predetermined threshold value is detected, and to determine the time when the recording paper S comes into contact with the paper guide 1 based on the elapsed time from the entering time.

In addition, in the first embodiment, the driving current is calibrated based on the size of the recording paper S, etc. Therefore, it is possible to improve the detection accuracy of the thickness of the recording paper S compared to the case where calibration is not performed. Note that if the size or type of recording paper S used is limited to one specific type, it is also possible not to perform calibration.

FIG. 5 is a diagram illustrating a main portion of a medium thickness detection device according to a second embodiment.
Next, a second embodiment of the present invention will be described. The differences from the first embodiment will be described. The same reference numerals will be used to designate the same components as those in the first embodiment, and detailed description thereof will be omitted.

In FIG. 5, in the medium thickness detection device of the second embodiment, the paper guide 1' downstream of the registration roller Rr is not curved and does not function as a load applying means. In the second embodiment, a movable gate 11 is disposed downstream of the registration roller Rr as an example of a load applying means. The movable gate 11 is configured to be movable between a contact position (see solid line in FIG. 5) where the transported recording paper S comes into contact with the movable gate 11 and a retracted position (see dashed line in FIG. 5) where the movable gate 11 is retracted from the recording paper S. In the second embodiment, the movable gate 11 enters the transport path SH2 at the contact position, and retracts to the outside of the transport path SH2 at the retracted position. In the second embodiment, the movable gate 11 that has moved to the contact position is configured to narrow the cross-sectional area of the transport path SH2 without completely blocking the transport path SH2.

The movable gate 11 in the second embodiment moves to the contact position when detecting the thickness of the recording paper S, and moves to the retracted position when not detecting the thickness. Therefore, when detecting the thickness every time a recording paper S passes, the movable gate 11 continues to move to the contact position, and when detecting the thickness of only the first recording paper S in successive printing processes or only when the attachment or detachment of paper feed trays TR1 to TR4 is detected, the movable gate 11 moves to the contact position when the first recording paper S is transported and is then held in the retracted position.

(Function of Example 2)
In the medium thickness detection device of the second embodiment having the above-mentioned configuration, when the recording paper S comes into contact with the movable gate 11, the recording paper S bends, generating a transport load according to the thickness and rigidity of the recording paper S. Then, the thickness of the recording paper S is detected from the drive current value after the recording paper S comes into contact with the movable gate 11.
Depending on the device configuration of the copier U, it may be difficult to provide a curved paper guide 1 as in Example 1, or the configuration may be such that it is difficult to provide a curved paper guide 1 due to the risk of paper jams. Even in these cases, by providing a movable gate 11 as in Example 2, it is possible to detect the thickness of the recording paper S by utilizing the rigidity of the recording paper S, and it is possible to reduce the risk of paper jams, etc., compared to when measuring every time.

FIG. 6 is a diagram illustrating a main portion of a medium thickness detection device according to a third embodiment.
Next, a third embodiment of the present invention will be described. The differences from the first embodiment will be described. The same reference numerals will be used to designate the same components as those in the first embodiment, and detailed description thereof will be omitted.
6, in the medium thickness detection device of the third embodiment, a high friction sheet 21 as an example of a load applying means is supported on the inner surface of the curved paper guide 1 downstream of the registration roller Rr, corresponding to the position where the recording paper S comes into contact. The high friction sheet 21 is configured so that the surface friction coefficient is higher than the surface friction coefficient of the paper guide 1. Any method can be used to increase the friction coefficient, such as using a high friction material for the high friction sheet 21 or processing the surface to make it rough.

(Function of Example 3)
In the medium thickness detection device of Example 3 having the above-mentioned configuration, when the recording paper S comes into contact with the high friction sheet 21, the recording paper S bends, generating a transport load according to the thickness and rigidity of the recording paper S. Then, the thickness of the recording paper S is detected from the drive current value after the recording paper S comes into contact with the high friction sheet 21.
Depending on the device configuration, parts configuration, material selection, etc. of the copier U, the curved paper guide 1 may be configured to be only slightly curved, or the friction coefficient of the surface of the paper guide 1 may be small, resulting in only a small deflection of the recording paper S upon contact. Even in these cases, it is possible to detect the thickness of the recording paper S by utilizing the rigidity of the recording paper S using the high friction sheet 21 as in the third embodiment.

(Example of change)
Although the embodiment of the present invention has been described above in detail, the present invention is not limited to the above embodiment, and various modifications can be made within the scope of the gist of the present invention described in the claims. Modifications (H01) to (H05) of the present invention are illustrated below.
(H01) In the above embodiment, a copying machine U is shown as an example of an image forming apparatus, but the present invention is not limited to this and may be configured as, for example, a printer, a FAX, or a multifunction machine having multiple or all of these functions. Also, the present invention is not limited to an electrophotographic image forming apparatus and may be applied to any image forming apparatus such as an inkjet type or a thermal transfer type.

(H02) In the above embodiment, a configuration in which four color developers are used as the copier U is exemplified, but this is not limited to this and the present invention is also applicable to, for example, a monochrome image forming apparatus or a multi-color image forming apparatus having three or less colors or five or more colors.
(H03) In the above embodiment, an endless intermediate transfer belt B was used as an example of an image holding means, but the present invention is not limited to this. For example, the present invention can be applied to a cylindrical intermediate transfer drum, a photosensitive drum, or a photosensitive belt. The present invention can also be applied to a configuration that does not have an intermediate transfer body and records an image directly from a photosensitive body onto recording paper S.

(H04) In the above embodiment, the thickness of the recording paper S is detected downstream of the registration roller Rr, but this is not limiting. For example, it is also possible to detect the thickness at a position such as the transport roller Ra, pickup roller Rp, or separation roller Rs upstream of the registration roller Rr. Note that when detecting at the pickup roller Rp, it is necessary to separately install the paper sensor SN1 and torque ammeter 2, which may increase costs, but when detecting at the registration roller Rr, one is sufficient, which is advantageous.

(H05) In the above embodiment, the secondary transfer bias and fixing temperature are adjusted according to the thickness, but this is not limiting. It is also possible to adjust image formation conditions such as the primary transfer bias, development bias, charging bias, and the rotation speed of the photoconductors PRy to PRk.

(Additional Note)
(((1)))
A conveying means for conveying a medium;
a load applying means arranged downstream of the conveying means in a medium conveying direction, the load applying means contacting the conveyed medium to apply a conveying load to the medium;
a thickness detection means for detecting a thickness of the medium based on a drive current of the transport means after the medium comes into contact with the load application means;
A media thickness detection device comprising:
(((2)))
the load applying means having a curved shape along the medium transport direction and configured as a guide means for guiding the medium;
The medium thickness detection device according to ((1)) above,
(((3)))
the load applying means moving between a contact position where the medium being conveyed comes into contact with the load applying means and a retracted position where the load applying means is retracted from the medium, the load applying means moving to the contact position when detecting the thickness of the medium;
The medium thickness detection device according to ((1)) above,
(((4)))
the load applying means moving to the contact position when there is a possibility of changing the type of medium;
The medium thickness detection device according to ((3)) above,
(((5)))
the load applying means moving to the contact position when the insertion or removal of the storage means storing the medium is detected as a possibility of a change in the type of the medium;
The medium thickness detection device according to ((4))),
(((6)))
A guide means for guiding the medium;
the load applying means being disposed at a position where the medium being supported by and transported by the guide means comes into contact with the load applying means, the load applying means having a friction coefficient greater than that of the guide means;
The medium thickness detection device according to ((1)) above,
(((7)))
a medium detection means disposed between the conveying means and the load applying means and configured to detect a medium;
a contact time determination means for determining a time when the medium comes into contact with the load application means based on a detection result of the medium detection means;
The medium thickness detection device according to any one of ((1)) to ((6)) above, comprising:
(((8)))
The medium thickness detection device described in any one of ((1)) to ((6)) is characterized by comprising a contact time determination means for detecting the time when the medium enters the transport means based on the drive current and determining the time when the medium contacts the load application means from the entry time.
(((9)))
a calibration means for calibrating the drive current based on a predetermined calibration condition;
the thickness detection means for detecting a thickness of a medium based on the calibrated driving current;
The medium thickness detection device according to any one of ((1)) to ((8))), comprising:
(((10)))
The medium thickness detection device described in ((9))) is characterized in that the calibration condition is a size of the medium in a width direction.
(((11)))
An image holding means;
a transfer means for transferring the image held on the image holding means to a medium;
A fixing means for fixing the image transferred to the medium;
a medium thickness detection device according to any one of ((1)) to ((10))) that is disposed upstream of the transfer means in a medium transport direction;
An image forming apparatus comprising:

According to the medium thickness detection device of (((1))), the stiffness of the medium can be utilized to detect the thickness of the medium.
According to the medium thickness detection device of (((2))), the guide means can be used as the load applying means, and the number of parts can be reduced, and costs can be suppressed, compared to a case in which the load applying means is provided separately.
According to the medium thickness detection device of ((3)), even if the guide means cannot apply a load, the thickness of the medium can be detected by using a load application means that moves between a contact position and a retracted position.
According to the medium thickness detection device of (((4))), the processing load for detecting the medium thickness can be reduced compared to when the medium thickness is detected every time.
According to the medium thickness detection device of ((5)), when the insertion or removal of the storage means, which may have resulted in the medium being replaced, is detected, the thickness can be detected, and the processing load for detecting the thickness of the medium can be reduced compared to when the thickness is detected every time.
According to the medium thickness detection device of (((6))), even if the guide means has a low coefficient of friction, the thickness of the medium can be detected by using the load applying means having a high coefficient of friction.
According to the medium thickness detection device of ((7)), detection errors in the timing of medium contact can be reduced compared to when a medium detection means is not used.
According to the medium thickness detection device of (((8))), the approach time can be detected by the drive current, no medium detection means is required, and the number of parts can be reduced.
According to the medium thickness detection device of ((9)), the accuracy of detecting the medium thickness can be improved compared to a case where calibration is not performed.
The medium thickness detection device of ((10)) can calibrate the drive current that varies with the size of the medium in the width direction.
According to the image forming apparatus of ((11)), the thickness of the medium can be detected by utilizing the stiffness of the medium.

1...Guidance means,
1, 11, 21 ... load applying means,
C4...calibration means,
C5...Contact time determination means,
C7: thickness detection means,
B...image holding means,
F: fixing means,
Rr: conveying means,
S…medium;
SN1: medium detection means,
T2: Transfer means,
TR1 to TR4: storage means,
U...Image forming device.

Claims (11)

A conveying means for conveying a medium;
a load applying means arranged downstream of the conveying means in a medium conveying direction, the load applying means contacting the conveyed medium to apply a conveying load to the medium;
a thickness detection means for detecting a thickness of the medium based on a drive current of the transport means after the medium comes into contact with the load application means;
A media thickness detection device comprising: the load applying means having a curved shape along the medium transport direction and configured as a guide means for guiding the medium;
The media thickness detection device according to claim 1 , further comprising: the load applying means moving between a contact position where the medium being conveyed comes into contact with the load applying means and a retracted position where the load applying means is retracted from the medium, the load applying means moving to the contact position when detecting the thickness of the medium;
The media thickness detection device according to claim 1 , further comprising: the load applying means moving to the contact position when there is a possibility of changing the type of medium;
4. The media thickness detection device according to claim 3, further comprising: the load applying means moving to the contact position when the insertion or removal of the storage means storing the medium is detected as a possibility of a change in the type of the medium;
The media thickness detection device according to claim 4, further comprising: A guide means for guiding the medium;
the load applying means being disposed at a position where the medium being supported by and transported by the guide means comes into contact with the load applying means, the load applying means having a friction coefficient greater than that of the guide means;
The media thickness detection device according to claim 1 , further comprising: a medium detection means disposed between the conveying means and the load applying means and configured to detect a medium;
a contact time determination means for determining a time when the medium comes into contact with the load application means based on a detection result of the medium detection means;
The media thickness detection device according to claim 1 , further comprising: 2. The medium thickness detection device according to claim 1, further comprising: a contact time determination means for detecting a time when the medium enters the transport means based on the drive current, and determining a time when the medium comes into contact with the load application means from the time when the medium enters the transport means. a calibration means for calibrating the drive current based on a predetermined calibration condition;
the thickness detection means for detecting a thickness of a medium based on the calibrated driving current;
The media thickness detection device according to claim 1 , further comprising: The medium thickness detection device according to claim 9 , wherein the calibration condition is a size in a width direction of the medium. An image holding means;
a transfer means for transferring the image held on the image holding means to a medium;
A fixing means for fixing the image transferred to the medium;
a medium thickness detection device according to claim 1 , the medium thickness detection device being disposed upstream of the transfer means in a medium transport direction;
An image forming apparatus comprising:

Images