JP2008139690A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device which controls the press-contact and separation of a pressure roller by detecting the present position of a rotating body one by one, and to provide an image forming apparatus provided with the fixing device. <P>SOLUTION: The fixing device includes: a drive means 005 which rotates the rotating body 004; a moving means which is engaged with the rotating body 004 in a part of the moving means, moves the position of a first roller 001 by another part of the moving means, brings the first roller 001 into press-contact with a second roller 002, fixes an image and then, separates the first roller 001 from the second roller 002; a position instruction means 007 which is provided to the side surface of the rotating body 004; a sensor substrate 008 on which a plurality of loop coils are arranged side by side on a path where the position instruction means 007 is rotated; a position detecting means 009 which detects the position of the arrangement of the loop coils of the position instruction means 007, as the present position from the characteristic distribution of a signal; a rotation amount deciding means 010 which obtains the rotation amount of the rotating body 004, on the basis of the present position; and a control means 006 which performs control until the rotation amount of the rotating body 004 coincides with a target rotation amount. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fixing device that heats and fixes an image on a recording sheet with a pair of rollers, and an image forming apparatus including the same. More specifically, the present invention relates to a technique for performing pressure contact and separation between a pair of rollers.

  An electrophotographic image forming apparatus includes a fixing device that fixes an image on a recording sheet. As a fixing device, a roller system that includes a roller pair including a fixing roller and a pressure roller, and that fixes an image by passing a recording sheet through a nip portion of the roller pair is widely used. In this roller type fixing device, a heat source (halogen heater or the like) is provided in at least one of the roller pair, and the image is fixed on the recording paper by the heat and the pressure of the roller.

  Furthermore, in order to improve the fixing performance according to the transfer paper, in recent years, it has been required to adjust the pressing force according to the thickness of the transfer paper using a sensor for measuring the thickness of the transfer paper.

  Conventionally, in these image forming apparatuses, the above-described roller pair is provided such that at least one of the rollers rotates about a predetermined fulcrum, so that the rollers can be pressed and separated from each other. Here, as a configuration in which the pressure roller side is moved to perform pressure contact and separation, an apparatus in which the pressure roller is provided to be rotatable around a predetermined support shaft has been proposed (for example, Patent Documents). 1). When the toner image is fixed, the pressure roller is in pressure contact with the fixing roller (pressure contact mode), and the pressure contact is released in the standby state (separation mode). In addition, there is a type in which the low pressure contact mode can be set for passing an envelope or cardboard.

JP 2006-184364 A

  However, to control the rotation angle of the gear in the cam mechanism used for the pressure contact and separation operation of the pressure roller in the conventional fixing device, the number of pulses based on a predetermined amount of movement is received and the number of pulses is used as the reference position. Therefore, the absolute position of the pressure roller after movement cannot be grasped, and even if excessive pressure contact or separation, or insufficient pressure contact or separation is made, It was difficult to control the position to an appropriate position.

  The present invention has been made in view of such circumstances, and provides a fixing device that detects the current position of a rotating body one by one and controls the pressure contact and separation of a pressure roller, and an image forming apparatus including the same. The purpose is to do.

  In order to achieve the above object, a fixing device according to a first aspect of the present invention relates to a movable first roller, a fixed second roller, a driving unit that rotates the rotating body, and a part of the fixing device. The other part of the first roller moves the position of the first roller, presses the first roller against the second roller to fix the image on the transfer paper, and after fixing the image, the first roller Moving means for separating the second roller from the second roller, position indicating means having a resonance circuit provided on a side surface of the rotating body, and a plurality of paths on a path along which the position indicating means rotates as the rotating body rotates. A signal is transmitted from the loop coil in the transmission state to the sensor substrate on which the loop coils are arranged and the position instruction means by electromagnetic coupling, and the signal received by the position instruction means is switched to the reception state. Receive at Position detecting means for detecting the position on the loop coil array of the position indicating means as the current position from the characteristic distribution of the received signal, and the current of the position indicating means received from the position detecting means. A rotation amount determining means for obtaining a rotation amount of the rotating body based on a position; and a rotation amount determining means for receiving the rotation amount of the rotating body, the rotation amount being a predetermined target rotation amount for each of pressure contact and separation. And a control means for controlling until they coincide with each other.

  According to a second aspect of the present invention, in the fixing device according to the first aspect, the rotation amount determining unit corresponds to the predetermined position when the position indicating unit is at a predetermined position on the path. Storage means for storing a reference position which is a position on the array of the loop coils is provided, and the amount of rotation is obtained based on the reference position and the current position of the position indicating means.

  According to a third aspect of the present invention, in the fixing device according to the first or second aspect, the sensor substrate receives the scanning by sequentially scanning the loop coils in series. .

  According to a fourth aspect of the present invention, in the fixing device according to any one of the first to third aspects, the rotating body is a gear, and the moving means is part of the gear. Engaging, receiving the amount of rotation of the gear, rotating around a fulcrum, receiving a force from the rotating member to reciprocate, and engaging the first roller at the other part; And a reciprocating member that is separated from the second roller by pressing the first roller and is in pressure contact with the second roller by pulling the first roller.

  The image forming apparatus according to claim 5, comprising: an image forming unit that transfers an image onto a transfer sheet; and a fixing unit that fixes the transferred image. A movable first roller, a fixed second roller, a driving means for rotating the rotating body, and a part of the first roller engages the rotating body, and the other part moves the position of the first roller; The first roller is pressed against the second roller to fix the image on the transfer paper, and after the image is fixed, moving means for separating the first roller from the second roller, and a side surface of the rotating body Transmission to a position indicating means having a provided resonance circuit, a sensor substrate in which a plurality of loop coils are arranged on a path along which the position indicating means rotates as the rotating body rotates, and the position indicating means Electromagnetic coupling from the loop coil in the state Therefore, the signal is sent, and the signal received by the position indicating means is received by the loop coil switched to the receiving state, and the position on the array of the loop coils of the position indicating means is determined from the characteristic distribution of the received signal. Position detection means for detecting the current position; rotation amount determination means for obtaining the rotation amount of the rotating body based on the current position of the position indicating means received from the position detection means; and the rotation amount of the rotating body And a control means for controlling the drive means until the rotation amount coincides with a predetermined target rotation amount for each of the press contact and separation.

  According to the fixing device according to claim 1, the fixing device according to claim 4, and the image forming device according to claim 5, since the current position of the rotating body is detected step by step, an accurate rotation amount is set. Can do. Thereby, accurate pressure contact and separation are possible by controlling toward the target rotation amount. Further, by performing accurate press contact and separation, the fixing operation is improved, and a more beautiful image can be formed.

  According to the fixing device of the second aspect, since the current position of the rotator is represented by the amount of rotation from a predetermined reference position, the amount of rotation of the rotator can be accurately measured. As a result, the pressure contact force can be controlled with higher accuracy.

  According to the fixing device of the third aspect, since the loop coils are arranged in series, the configuration of the fixing device is simplified. Furthermore, the loop coil only needs to be arranged on the path of the position indicating means, and it is not necessary to arrange the loop coil over the entire surface. Therefore, the loop coil can be used effectively, and the manufacturing cost can be reduced.

[First Embodiment]
A fixing device according to a first embodiment of the present invention will be described. FIG. 1 is a block diagram showing functions of a fixing device according to the present invention. The control unit 006, the position detection unit 009, the rotation amount determination unit 010, and the image forming unit 012 in FIG. 1 are composed of a CPU and a program that defines its operation. Further, the position instruction means 007 has a resonance circuit. Further, solid line arrows in FIG. 1 represent signal exchange, and dotted line arrows represent physical action relationships. Further, the transfer paper 011 in FIG. 1 passes between the first roller 001 and the second roller 002 and indicates that the image is fixed. FIG. 2 is a schematic cross-sectional view of the fixing device according to the present invention. 1 and 2, the first roller 001 is the pressure roller 201, the second roller 002 is the fixing roller 202, the moving unit 003 is the gear 203, the rotating member 204, the reciprocating member 205, and the holding member 209. Further, the position instruction means 007 corresponds to the position instruction means 207, and the sensor substrate 008 corresponds to the sensor substrate 208, respectively. FIG. 3 is a diagram for explaining the position detection of the position instruction unit 007 (position instruction unit 207) in the fixing device according to the present embodiment. FIG. 4 is a diagram for explaining a modified example of the arrangement of the sensor substrates 008 (sensor substrate 208).

  First, the physical operation of the fixing device according to the present embodiment will be described with reference to FIG. 2A is a cross-sectional view for explaining a state in which the fixing device according to the present invention is separated, and FIG. 2B is a cross-sectional view for explaining a state in which the fixing device according to the present invention is in pressure contact. FIG. 2C is an enlarged view of a portion of the gear 203 in the fixing device according to the present invention. Here, in any of FIGS. 2A, 2B and 2C, the actual position indicating means 207 provided on the gear 203 is smaller than the figure.

[When separating the pressure roller 201 and the fixing roller 202]
First, as shown in FIG. 2A, the gear 203 rotates in the direction of the arrow 210.

  The rotating member 204 has a gear 204 a that meshes with the gear 203 at a part thereof. The rotating member 204 rotates around the fulcrum in the direction of the arrow 211 by the rotation of the gear 204 a and the gear 203. The fulcrum is provided between the end of the rotating member 204 opposite to the gear 204a. Thereby, the opposite side also rotates in the direction of the arrow 211 around the fulcrum.

  The reciprocating member 205 is attached to a side opposite to the gear 204a sandwiching the fulcrum of the rotating member 204 via a conversion device (not shown) that converts the rotating store motion to the reciprocating motion. The reciprocating member 205 is pushed in the direction of the arrow 212 by the rotation of the rotating member 204 in the direction of the arrow 210. As a result, the reciprocating member 205 pushes the holding member 209 covering the pressure roller 201 away from the fixing roller 202, that is, in the direction of the arrow 212.

  The holding member 209 is held so as to rotate the pressure roller 201 around the fulcrum 206. The holding member 209 receives the force in the direction of the arrow 212 of the reciprocating member 205 and rotates around the fulcrum 206 in the direction of the arrow 212 to move the holding pressure roller 201 away from the fixing roller 202.

  The pressure roller 201 is separated from the fixing roller 202 and the gap a is opened. This makes it easier to pass the transfer paper 011 through.

[When the pressure roller 201 and the fixing roller 202 are in pressure contact]
First, as shown in FIG. 2B, the gear 203 rotates in the direction of the arrow 213.

  The rotating member 204 rotates around the fulcrum in the direction of the arrow 214 by the rotation of the gear 204a and the gear 203. As a result, the rotating member 204 rotates in the direction of the arrow 214 around the end fulcrum opposite to the gear 204a.

  The reciprocating member 205 is pulled in the arrow 215 direction by the rotation of the rotating member 204 in the arrow 214 direction. As a result, the reciprocating member 205 pulls the holding member 209 covering the pressure roller 201 in the direction approaching the fixing roller 202, that is, in the direction of the arrow 215.

  The holding member 209 receives the force of the reciprocating member 205 in the direction of the arrow 215, rotates about the fulcrum 206 in the direction of the arrow 215, and moves the holding pressure roller 201 in a direction approaching the fixing roller 202.

  The pressure roller 201 is in pressure contact with the fixing roller 202 and is in close contact with the contact surface b. As a result, a nip pressure (pressure sandwiched between the pressure roller 201 and the fixing roller 202) is applied to the transfer paper 011 passing through the contact surface b, and the image is fixed by further applying heat.

  Further, the position indicating means 207 is attached to the side surface of the gear 203 as shown in FIG. 2C, and rotates together with the gear 203 in accordance with the movement of the separation and press-contact described above. Furthermore, the sensor substrate 208 is installed in the casing of the fixing device so as to face the path along which the position instruction unit 207 rotates. Here, in all of FIGS. 2A, 2B, and 2C, the sensor substrate 208 is described in a disk shape, but this is a schematic one, and actually a loop coil that will be described later. Are arranged in a disk shape on the housing side.

  Next, control of the rotating body 004 (gear 203) in the fixing device according to the present embodiment will be described with reference to FIGS.

  In the fixing device according to the present invention, the position on the array of the loop coils of the sensor substrate 008 of the position indicating unit 007 corresponding to the position of the position indicating unit 007 known at the time of shipment (for example, the position in the state of maximum separation) is detected. The position is detected by means 009 and the detected position is stored in a storage unit (not shown) of the rotation amount determination means 010. Hereinafter, the stored position indicating unit 007 is referred to as a reference position.

  The image forming unit 012 has an image forming unit, and after transferring the image to the transfer paper 011, sends the transfer paper 011 to the fixing device, and receives information on the thickness of the transfer paper 011 based on the input from the user. Come to control means 006. In this embodiment, the thickness information of the transfer paper 011 is acquired based on the thick paper setting input by the user or the setting of special paper such as OHP. When the thickness of 011 can be measured, information on the thickness of the transfer paper 011 may be acquired from the sensor.

  The 1st roller 001 and the 2nd roller 002 are provided in the position which opposes, and the 1st roller 001 is provided so that the movement to the direction which leaves | separates from the 2nd roller 002, and the approaching direction. The first roller 001 and the second roller 002 sandwich the transfer paper 011 between them, apply a nip pressure, and further extrude while applying heat to fix the image on the transfer paper 011.

  The moving unit 003 moves the first roller 001 in a direction away from or closer to the second roller 002 according to the rotation amount of the rotating body 004.

  A part of the rotating body 004 is in contact with the moving unit 003 and transmits the rotating motion to move the moving unit 003.

  The driving unit 005 receives a command from the control unit 006 and rotates the rotating body 004.

  The position indicating means 007 is provided on the side surface of the rotating body 004 and rotates on the moving path indicated by the dotted line 301 in FIG. 3 together with the rotating body 004.

  The sensor substrate 008 is arranged on the housing side of the fixing device so that the loop coils overlap at a predetermined interval along the moving path 301 represented by the dotted line of the position indicating means 007 as shown in FIG. ing. Here, in this embodiment, as shown in FIG. 3, the loop coils of the sensor substrate 008 are arranged circumferentially so that detection is possible even when the position indicating means 007 rotates to an angle close to one rotation. However, this changes depending on the movement path of the position indicating means 007. For example, if the rotation range of the position indicating means 007 is a part of the circumference, loop coils are arranged in a sector shape as shown in FIG. May be. In this case, the position indicating means 007 needs to rotate only within the fan-shaped range.

  Also, each loop coil of the sensor substrate 008 shown in FIG. 3 can be switched between a loop coil for transmitting and a loop coil for receiving. Further, on the sensor substrate 008, the loop coils are arranged so as to scan and receive in order in series.

  The position detection unit 009 switches the loop coil of the sensor substrate 008 to the transmission state. Next, the position detecting unit 009 causes the position indicating unit 007 to transmit a signal by electromagnetic coupling between the loop coil of the sensor substrate 008 and the position indicating unit 007, and generates electromagnetic induction in the coil of the position indicating unit 007. A signal is stored in a coil and a capacitor in the resonance circuit of the position indicating unit 007, and thereafter, while the signal is stored, the coil of the resonance circuit and a nearby loop coil are coupled, and the signal is detected by the position detection unit 009. Is received by all the loop coils switched to the reception state. Then, the position detection unit 009 scans all the loop coils of the sensor substrate 008, and acquires the characteristic distribution of the returned signal. The characteristic distribution of the signal is represented by the received signal strength with respect to the position on the loop coil array on the horizontal axis and the position on the loop coil array on the vertical axis. The current position of the position indicating means 007 can be obtained from the peak position of the characteristic distribution of the signal. Here, when a signal is sent from the loop coil of the sensor substrate 008, if the loop coil closest to the position indicating unit 007 can be predicted, the signal may be sent from the loop coil.

  Further, the position detecting unit 009 sends the acquired position indicating unit 007 to the rotation amount determining unit 010. Here, the position of the position instruction means 007 detected and transmitted by the position detection means 009 is a position on the array of loop coils, and is information on a relative position with respect to the loop coils. For example, the loop coil c in FIG. 3 is the first loop coil, and the number of loop coils arranged on the circumference is stored by sequentially numbering each loop coil (for example, clockwise). Thus, the position of the position indicating means 007 is detected with the number. In the following, a case will be described where 1000 loop coils are arranged on the circumference at a constant interval that provides the required accuracy.

  The rotation amount determination unit 010 stores the reference position in advance in its own storage unit (not shown). This is stored with the loop coil number at the reference position being 0 degrees. In the following description, the reference position is assumed to be the position of the position indicating means 007 in the most separated state, and the position indicating means 007 will be described when it is directly above the No. 500 loop coil.

  The rotation amount determination means 010 receives the information on the current position of the position indicating means 007, and if the position indicating means 007 is between the coils, the number of coils from the reference position to the position indicating means 007 Based on the sum of the ratios between them, the angle (rotation amount) between them is calculated. For example, when the current position of the position indicating unit 007 is directly above the 700th coil under the above-described conditions, the angle (rotation amount) from the reference position is (700−500) × 360/1000 = 72. It can be calculated as a degree. This can be calculated in the same manner even when the current position of the position indicating means 007 is not directly above the coil.

  The control unit 006 receives information on the thickness of the transfer paper 011 from the image forming unit 012, and based on the thickness of the transfer paper 011 stored in its own storage unit (not shown) and the reference position of the rotation unit 004 corresponding thereto. The target rotation amount of the rotating means 004 is obtained with reference to the table of the rotation angles of the rotation means 004. Here, the control unit 006 according to the present invention does not need to receive the actual thickness of the transfer paper 011 and may be any signal that can determine the target rotation amount.

  The control unit 006 instructs the driving unit 005 to rotate the rotating body 004 by the target rotation amount.

  While the rotating body 004 is rotating, the control unit 006 receives the current rotation amount of the rotating body 004 from the rotation amount determination unit 010 and compares it with the target rotation amount. If the current rotation amount is less than the target rotation amount, the control unit 006 continues to rotate the driving unit 005 and rotate the rotating body 004 as it is, and the current rotation amount exceeds the target rotation amount. If it is, the driving means 005 is reversed and the rotating body 004 is rotated in the reverse direction. The control unit 006 stops the driving unit 005 and stops the rotation of the rotating body 004 when the target rotation amount and the current rotation amount become equal.

  Here, the detection of the current position of the position indicating unit 007 in the present embodiment is a conventional technique, and can be realized by using the technique disclosed in, for example, Japanese Patent Application Laid-Open No. 8-161100.

  Next, the control operation of the rotating body 004 in the fixing device according to the present embodiment will be described with reference to FIG. FIG. 5 is a flowchart of control of the rotator 004 in the fixing device according to the present embodiment.

  Step S001: The control unit 006 receives information on the thickness of the transfer paper 011 from the image forming unit 012 and obtains a target rotation amount.

  Step S002: The control means 006 issues a drive command to the drive means 005, and the drive means 005 starts to rotate the rotating body 004.

  Step S003: The position detection unit 009 scans the sensor substrate 008 and acquires the current position of the position instruction unit 007. The rotation amount determination unit 010 obtains the current rotation amount of the rotating body 004 from the current position of the position instruction unit 007.

  Step S004: The control means 006 compares the current rotation amount with the target rotation amount. If the current rotation amount has not reached the target rotation amount, the process proceeds to step S005, and the current rotation amount has exceeded the target rotation amount. If so, the process proceeds to step S006.

  Step S005: The control unit 006 drives the drive unit 005 as it is and rotates the rotating body 004 as it is.

  Step S006: The control means 006 reverses the drive means 005 and reversely rotates the rotating body 004.

  Step S007: The position detection unit 009 determines whether or not the current rotation amount and the target rotation amount match. If they match, the process proceeds to step 008. If they do not match, step S003 to step S006 are repeated.

  Step S008: The control unit 006 stops the driving unit 005 and ends the rotating operation of the rotating body 004.

  Actually, in the fixing device and the image forming apparatus according to the present invention, the transfer paper 011 is passed between the first roller 001 and the second roller 002 pressed by the above control to fix the image, and then the paper is discharged. Is done.

  As described above, in the present embodiment, since the current rotation amount of the rotating body 004 is fed back and controlled toward the target rotation amount, accurate press-contact can be performed and further separated. As a result, the fixing operation can be performed satisfactorily, and a beautiful image can be formed.

  In the present embodiment, the description has been made using the gear 203 in FIG. 2 as the rotating body 004 in FIG. 1, but this moves the first roller 001 through the moving means 003 by rotating. For example, a belt-like structure that has a plurality of rollers and is rotated by the rollers may be used.

Block diagram of a fixing device according to the present invention (A) A cross-sectional view schematically illustrating a separation state of the fixing device according to the first embodiment. (B) A cross-sectional view schematically illustrating a pressure contact state of the fixing device according to the first embodiment. The enlarged view of the gear part of the fixing device which concerns on embodiment FIG. 6 is a diagram for explaining position detection of a position instruction unit in the fixing device according to the first embodiment. The figure for demonstrating the modification of the arrangement | sequence of a sensor board | substrate. Flowchart of control of rotating body in fixing device according to first embodiment

Explanation of symbols

001 First roller 002 Second roller 003 Moving unit 004 Rotating body 005 Driving unit 006 Control unit 007 Position indicating unit 008 Sensor substrate 009 Position detecting unit 010 Rotation amount determining unit 011 Transfer paper 012 Image forming unit 201 Pressure roller 202 Fixing roller 203 Gear 204 Rotating member 205 Reciprocating member 206 Support point 207 Position indicating means 208 Sensor substrate 209 Holding member

Claims (5)

A movable first roller and a fixed second roller;
Driving means for rotating the rotating body;
One part is engaged with the rotating body, the other part is moved the position of the first roller, the first roller is pressed against the second roller to fix the image on the transfer paper, and the image is Moving means for separating the first roller from the second roller after fixing;
Position indicating means having a resonance circuit provided on a side surface of the rotating body;
A sensor substrate in which a plurality of loop coils are arranged on a path along which the position indicating means rotates in accordance with the rotation of the rotating body;
A signal is sent from the loop coil in a transmission state to the position indication means by electromagnetic coupling, and a signal received by the position indication means is received by the loop coil switched to a reception state. Position detecting means for detecting a position on the loop coil array of the position indicating means as a current position from a characteristic distribution;
A rotation amount determination means for determining a rotation amount of the rotating body based on a current position of the position instruction means received from the position detection means;
A fixing device comprising: a control unit that receives the rotation amount of the rotating body and controls the driving unit until the rotation amount matches a predetermined target rotation amount for each of press contact and separation. The rotation amount determination means includes
Storage means for storing a reference position that is a position on the array of the loop coils corresponding to the predetermined position when the position indicating means is at the predetermined position on the path;
The fixing device according to claim 1, wherein the rotation amount is obtained based on the reference position and the current position of the position instruction unit.   The fixing device according to claim 1, wherein the sensor substrate scans and receives the loop coils sequentially in series. The rotating body is a gear;
The moving means is
A rotating member that engages with the gear at the part, receives a rotation amount of the gear, and rotates around a fulcrum;
The reciprocating motion is received by the force from the rotating member, the other part is engaged with the first roller, the first roller is pushed to be separated from the second roller, and the first roller is pulled. 4. The fixing device according to claim 1, further comprising: a reciprocating member that press-contacts the second roller. 5. Image forming means for transferring an image to transfer paper;
An image forming apparatus comprising: a fixing unit that fixes a transferred image;
The fixing means is
A movable first roller and a fixed second roller;
Driving means for rotating the rotating body;
One part is engaged with the rotating body, the other part is moved the position of the first roller, the first roller is pressed against the second roller to fix the image on the transfer paper, and the image is Moving means for separating the first roller from the second roller after fixing;
Position indicating means having a resonance circuit provided on a side surface of the rotating body;
A sensor substrate in which a plurality of loop coils are arranged on a path along which the position indicating means rotates in accordance with the rotation of the rotating body;
A signal is sent from the loop coil in a transmission state to the position indication means by electromagnetic coupling, and a signal received by the position indication means is received by the loop coil switched to a reception state. Position detecting means for detecting a position on the loop coil array of the position indicating means as a current position from a characteristic distribution;
A rotation amount determination means for obtaining a rotation amount of the rotating body based on a current position of the position instruction means received from the position detection means;
An image forming apparatus comprising: a control unit that receives the rotation amount of the rotating body and controls the driving unit until the rotation amount matches a predetermined target rotation amount for each of press contact and separation. .