JPH1165360A - Image forming device - Google Patents

Abstract

(57) [Problem] To provide an image forming apparatus in which a pressure roller does not expand due to maturation and an image on a recording material does not expand. SOLUTION: Two cooling rollers for removing heat from a pressure roller 116a are held at an end of a holding lever 143,
The base end of the holding lever 143 is pivotally supported, and a lever gear 144 is arranged at the base end of the holding lever 143 via a spring clutch. A drive gear 16 that rotates clockwise when the temperature of the pressure roller is equal to or higher than the reference temperature is provided near the lever gear 144.
0, and the pendulum gear 145 meshes with the drive gear 160 via the idler gear 147 and the instruction arm 146. When the drive gear 160 rotates counterclockwise, the pendulum gear 145 rotates clockwise along the outer periphery of the idler gear 147. , So as to mesh with the lever gear 144. When the pendulum gear 145 and the lever gear 144 mesh with each other, the holding lever 143 swings toward the pressure roller 116a so that both cooling rollers come into contact with the pressure roller 116a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus for transferring an image formed on an image carrier to a recording material, and fixing the image by heating and pressing the recording material at a fixing unit. .

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus has been used
As described in Japanese Patent No. 43561, an image reading unit reads an image of a document and converts the image into a signal, a recording device unit having a laser beam printer to form an image on a recording material, a display unit, an input unit, and the like. And a control unit that controls the operation of each member.

The image reading section is a flat head scanner,
Some flat head scanners have a contact image sensor that reads images.The contact image sensor reads images such as characters and images on a document placed on the platen glass of the scanner, and sends the read image as a signal. Convert to
A pressure plate is provided on the upper surface of the platen glass. The pressure plate is used by a user to open and close the upper and lower sides to set a document, and to press a document placed on the platen glass.

Further, a document table for transporting a plurality of documents is provided above the pressure plate so that a plurality of documents can be stacked. The document table for transporting a plurality of sheets has a document transport unit that transports the documents while separating the documents one by one, and reads the documents while transporting the documents one by one to the sheet reading unit by the document transport unit. The read document is discharged to a document discharge tray and stacked. Here, the document feeder is provided in a part of the pressure plate, and opens and closes as the pressure plate opens and closes.

The recording device includes an electrostatic latent image carrier for forming an electrostatic latent image according to a signal from the image reading unit, a charging member for charging the surface of the electrostatic latent image carrier, and a charging member. Exposure means for exposing the electrostatic latent image carrier to form an electrostatic latent image, and developing the electrostatic latent image on the electrostatic latent image carrier with toner as a developer to visualize the latent image A developing device, a transfer device for transferring the visualized image on the electrostatic latent image carrier to a recording material, and heating and pressing of the recording material on which the developer image has been transferred to an unfixed recording material An image forming unit including a fixing unit for fusing and fixing an image, a cassette sheet feeding unit, a manual sheet feeding unit, a pair of sheet discharging rollers, a recording material discharge tray for stacking discharged recording materials, and the like. . Note that a recording material such as a recording paper or an OHP paper is used.

[0006] In the image formation by the recording device, first, the paper in the cassette, which is arranged at the lower portion of the device and in which the general-size paper is stacked and accommodated, is separated one by one by a feeding roller, and the paper is inclined by a pair of registration rollers. The line is corrected, and the sheet is conveyed upward and fed to the image forming unit in synchronization with the print signal from the control unit.

[0007] The surface of the photosensitive drum as an electrostatic latent image carrier is uniformly charged by a charging member, and the charged surface of the photosensitive drum is exposed based on image information by a laser scanner as exposure means. An electrostatic latent image is formed on the photosensitive drum. When an electrostatic latent image is formed on the photosensitive drum,
The toner in the developing device is transferred to an electrostatic latent image on the photosensitive drum by a developing sleeve serving as a developer carrier, and a toner image is formed on the photosensitive drum.

[0008] The toner image on the photosensitive drum is transferred to a sheet by a transfer roller as a transfer device.
The sheet is conveyed to a fixing unit provided at a predetermined position. In the fixing unit, the toner transferred on the paper is conveyed to a nip, which is a contact portion between a fixing roller rotatably provided in the fixing unit and a pressure roller, and the paper is passed through the nip to remove the toner. By applying heat and pressure to the toner, the toner is melted and fixed, and the image is fixed on the paper. The sheet on which the image has been fixed is discharged to a recording material discharge tray by a pair of discharge rollers.

On the other hand, when the paper is supplied from the manual paper feed unit, the paper stacked in the manual paper feed unit is separated into one sheet by a separation pad disposed at a position facing the paper feed roller, and the registration roller is separated. The skew of the sheet is corrected by the pair, the sheet is conveyed in the direction of the image forming unit, the toner image is transferred, the image is fixed by the fixing unit, and the sheet is discharged to the recording material discharge tray.

The fixing roller provided in the fixing section is provided with a coating layer in which a fluororesin for improving releasability is coated on a sleeve using a metal pipe or a primer is applied to cover a fluororesin tube. In addition, a heater is provided inside the sleeve so that the surface of the fixing roller can be heated, and the fixing roller can be rotated in a predetermined direction by a driving force from a driving unit.

The pressure roller is provided with a rubber layer as an elastic member on the outer periphery of the metal core in the longitudinal direction, and a coating layer in which the surface of the rubber layer is coated with a fluororesin or a fluororesin tube. It is configured. Further, the pressing roller is pressed against the fixing roller at a predetermined pressure by pressing means using a spring or the like so that a nip portion can be formed at a contact portion between the fixing roller and the pressing roller. Heat is transmitted from the surface of the fixing roller pressed into contact with the surface of the pressing roller to heat the surface of the pressing roller to a temperature required for fixing, and rotates in a predetermined direction following the rotation of the fixing roller. The paper passing through the nip can be conveyed at a predetermined speed in the direction of the paper discharge tray.

[0012]

However, when continuous copying is performed by the above-described conventional fixing unit, paper is conveyed continuously to the nip between the fixing roller and the pressure roller of the fixing unit.
Since the paper is continuously conveyed, the fixing roller is continuously heated, and the heat transmitted from the nip portion causes the rubber layer on the outer periphery of the core of the pressure roller to mature and expand, and the outer diameter of the pressure roller is increased. Becomes large. As a result, the conveyance speed of the pressure roller becomes faster than the conveyance speed of the transfer roller, and when the toner image on which the toner image is formed is transferred to the paper by the transfer roller, the recording material is pulled by the pressure roller. There was a problem that the growth.

Accordingly, the present invention provides a simple image forming apparatus in which even if heat is continuously applied in the fixing section during continuous copying, the pressure roller does not mature and expand, and the image on the recording material does not expand. It is intended to be provided in a configuration.

[0014]

According to a first aspect of the present invention, an object of the present invention is to provide a method for reading an image on a document and converting the image into a signal on an electrostatic latent image carrier by a signal from an image reading apparatus. Forming an electrostatic latent image on the electrostatic latent image carrier, developing the electrostatic latent image on the electrostatic latent image carrier with a developer, transferring the developed developer image on the electrostatic latent image carrier to a recording material, and fixing An image is formed by an electrophotographic method in which a recording material on which a developer image is transferred is passed through a fixing unit having a roller and a pressure roller, and the recording material is heated and pressed to fix the developer image on the recording material. In the image forming apparatus performed, the fixing unit is movable between a state in which the pressure roller is in contact with the pressure roller and a state in which the pressure roller is separated from the pressure roller. At least one that can rob temperature
Cooling means, and when the temperature of the pressure roller or the vicinity of the pressure roller is equal to or lower than a predetermined temperature, the cooling means can be moved to a state in which the cooling means and the pressure roller are separated from each other, and the pressure roller or the vicinity of the pressure roller can be moved. This is achieved by providing moving means for moving the cooling means so that the cooling means and the pressure roller are in contact with each other when the temperature is higher than a predetermined temperature.

Further, according to the second aspect of the present invention, the above object is to provide a temperature detection device capable of detecting the temperature of the pressure roller by contacting the pressure roller of the fixing section with the surface of the pressure roller. A cooling unit that abuts against the surface of the pressure roller and removes heat from the pressure roller, and an arbitrary position that is rotatably supported at one end and holds the end of the cooling unit at one end. 2
An elastic member for urging the two holding members in a direction in which the cooling unit held by the holding member is separated from the pressure roller, and a predetermined reference temperature. An operation signal in the case where the surface temperature of the pressure roller according to the temperature detection signal from the temperature detection means brought into contact with the pressure roller is compared with a predetermined reference temperature and the temperature is equal to or lower than the reference temperature. A comparison unit that issues an operation signal when the temperature is higher than the reference temperature; and a driving unit that separates or abuts the cooling unit and the pressure roller in accordance with a signal from the comparison unit. By receiving an operation signal when the surface temperature of the pressure roller is lower than the reference temperature, the holding member of the cooling unit is moved in the biasing direction by the elastic member to separate the pressure roller and the cooling unit,
By receiving an operation signal when the surface temperature of the pressure roller is higher than the reference temperature from the comparison unit, the holding member of the cooling unit is moved to the side opposite to the biasing direction by the elastic member, and the pressure roller and the cooling unit are moved. This is achieved by contacting

Further, according to the third aspect of the present invention, the above object is achieved by a cooling means which contacts a surface of the pressure roller to take heat of the pressure roller, and an arbitrary position is rotated. Two holding members that are rotatably supported and hold one end of the cooling unit at one end, and a moving unit that moves the cooling unit makes the cooling unit held by the holding member abut against the pressure roller. An elastic member for urging the two holding members in the directions, and a bimetal arranged near the pressure roller and curved when a predetermined temperature is reached, and at least a part of the bimetal contacts the holding member of the cooling means. When the bimetal is not bent due to contact, the movement of the holding member in the biasing direction by the elastic member is regulated to separate the pressure roller and the cooling unit, and when the bimetal is bent, the holding member is biased by the elastic member. Move the holding member in the direction It is accomplished by abutting the pressure roller and the cooling unit.

That is, according to the first aspect of the present invention, the pressure roller or the moving means for moving the cooling means according to the temperature in the vicinity of the pressure roller operates, and the pressure roller provided in the fixing section is operated. At least one cooling means movable between an abutting state and a state separated from the pressing roller, and capable of depriving the temperature of the pressing roller in a state of being in contact with the surface of the pressing roller, includes a pressing roller. Is moved to a state of being separated from or from a state of being in contact with the pressure roller. When the temperature of the pressure roller or the vicinity of the pressure roller is lower than a predetermined temperature, the cooling unit is moved away from the pressure roller, and the surface temperature of the pressure roller quickly and reliably rises to a temperature necessary for fixing. Let me do.
When the temperature of the pressure roller or the vicinity of the pressure roller is higher than a predetermined temperature, the pressure roller and the cooling means are brought into contact with each other, and the cooling means takes away the heat of the pressure roller. Prevention of expansion due to heat prevents elongation of the image in the fixing step due to a change in the peripheral speed of the pressure roller.

Further, according to the second aspect of the present invention, the surface temperature of the pressure roller is detected by the temperature detection means abutting on the pressure roller of the fixing unit, and the comparison unit provided in the moving means is provided. The surface temperature of the pressure roller from the temperature detection means is compared with the reference temperature, and the cooling unit provided in the cooling means is separated from the pressure roller by the driving means operating in response to a signal from the comparison unit. Alternatively, it is brought into contact with a pressure roller. The driving unit receives an operation signal from the comparison unit when the surface temperature of the pressure roller is lower than the reference temperature, and the urging direction of the elastic member provided on the holding member that holds the cooling unit of the cooling unit. By actuating the holding member of the cooling means to separate the pressure roller and the cooling unit, and receiving an operation signal from the comparison unit when the surface temperature of the pressure roller is higher than the reference temperature The pressure roller and the cooling unit are brought into contact by operating the holding member of the cooling unit to move in a direction opposite to the biasing direction of the elastic member provided on the holding member that holds the cooling unit of the cooling unit. Therefore, expansion of the pressure roller due to heat can be reliably prevented with a simple configuration without impairing the surface temperature required for fixing the pressure roller.

According to the third aspect of the present invention, when the temperature near the pressure roller is lower than the temperature at which the bimetal bends, the bimetal regulates the movement of the holding member and cools the pressure roller and the cooling member. The bimetal in the vicinity of the pressure roller is curved by increasing the temperature in the vicinity of the pressure roller, and the holding member is moved in the biasing direction by the elastic member of the holding member due to the bending of the bimetal. And the cooling unit are brought into contact with each other, so that expansion of the pressure roller due to heat can be prevented with a simple configuration without impairing the surface temperature required for fixing the pressure roller.

[0020]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an explanatory perspective view of a facsimile apparatus as an image forming apparatus according to a first embodiment of the present invention, and FIG. 2 is a schematic configuration diagram of the facsimile apparatus. The facsimile apparatus includes a flat head scanner unit 130 that is an image reading unit that reads an image of a document and converts it into a signal, a recording device unit 104 that forms an image on a recording material including a laser beam printer, a display unit, an input unit, and the like. The operation unit 105 includes a control unit 120 that controls the operation of each member. The facsimile apparatus according to the present embodiment has two modes: a mode for reading a sheet-shaped original, and a mode for reading a thick original such as a book.
It has different modes.

The flat head scanner section 130 is provided with a platen glass 130a on which an original is placed for reading a thick original such as a book in a stationary state, and a contact type image for reading an image. Sensor 10
8 is provided, and the platen glass 130a of the scanner is provided.
An image such as a character or an image on a document placed thereon is read by the contact image sensor 108, and the read image can be converted into a signal. Platen glass 130a
A pressure plate 102 is provided on the upper part of the
The user sets the original by opening and closing it up and down, and sets the original placed on the original platen glass 130a by the original holding white background 102e held on the surface of the pressure plate 102 facing the original platen glass 130a. 130a.

Here, the original platen glass 130a is connected to the frame 13 serving as a structure of the flat head scanner unit 130.
0b. Also, the pressure plate 102 and the frame 1
A hinge (not shown), which is a center of rotation, is provided between the pressure plate 30 and the pressure plate 1 so that the user can swing the pressure plate 102 by a predetermined angle with respect to the frame 130b.
02 is opened so that a document can be placed on the surface of the platen glass 130a.

The contact type image sensor 108 is driven by a sensor driving device (not shown) in the sub-scanning direction of the original placed on the original platen glass 130a as indicated by the arrow A in FIG. Platen glass 130a
When reading the original B on the document, the contact type image sensor 1
08 is moved in the sub-scanning direction to read the original. The contact type image sensor 108 is disposed on the lower surface of the platen glass 130a, and the distance between the contact type image sensor 108 and the platen glass 130a is always kept constant when moving in the sub-scanning direction by the sensor driving device. As a result, the height of the focal position of the contact type image sensor 108 on the platen glass 130a becomes constant, and a good image without a focal position shift can be obtained.

The close contact type image sensor 108 is provided with an illuminating means for illuminating the reading surface of the document, a selfoc lens through which the reflected light from the reading surface of the document passes, and an image formed immediately below the lens to form the reflected light. A sensor and a selfoc lens, a long focus type is used,
The focal point is set so as to be focused on the surface of the platen glass 130a having a thickness of 3 mm.

On the upper portion of the pressure plate 102, there is provided an original mounting table 102b for transporting a plurality of originals, which is configured to be able to stack a plurality of originals. The document mounting table 102b for transporting a plurality of sheets has a document transport unit 106 that transports the documents while separating the documents one by one. The document transport unit 106 transports the documents one by one toward the sheet reading unit 107. The document is read by the sheet reading unit 107. The read document is discharged to the document discharge tray 109 and stacked. Here, the document conveying unit 106 is provided in a part of the pressure plate 102 and is configured to open and close as the pressure plate 102 opens and closes.

The original transport section 106 is provided on the original table 102b.
The original S stacked thereon is transported by the preliminary transport roller 102d and the preliminary transport pressing plate 102c, separated one by one by the separation roller 106b pressed against the separation piece 106a, and further separated by the feeding roller 106f pressed by a pressing spring. The sheet is conveyed in the direction of the sheet reading unit 107.

When reading a sheet document by feeding the document from the document table 102b, the contact type image sensor 10
8 with the document holding roller 107a stationary under the document holding roller 107a and the document table glass 130a.
The original S is conveyed in between, and the image information of the original S is read by the close contact type image sensor 108 while the original S is conveyed onto the surface of the original platen glass 130a by the original pressing roller 107a. The read document is discharged to a document discharge tray 109 by a document discharge roller 106g and a document discharge roller 106h.

The document feeder 106 is provided at a part of the pressure plate 102, and when the pressure plate 102 is opened, the document feeder 106 also follows the pressure plate 102 and rises upward. The document conveyance path can be easily released to perform jam processing. A slider 1 slidable in the width direction of the document S, which is perpendicular to the direction in which the document S is transported, is placed on the document table 102b.
A document 02a is provided so that both sides of the document S placed on the document table 102b can be aligned by the slider 102a.

The recording unit 104 is disposed at the lower part of the apparatus. The image forming unit 111 forms an image on recording paper in accordance with a signal obtained by reading a document by the flat head scanner unit 130, a fixing roller 116b, and a pressure roller 116a. A fixing unit 116, a cassette paper feeding unit 112, and a manual paper feeding unit 125 that apply heat and pressure to the recording material onto which the image visualized by the developer has been transferred to fuse and fix an unfixed image on the recording material. , A paper discharge roller pair 117, a cassette 11 including a recording material discharge tray 113 on which discharged recording material is stacked, and a stack of general-purpose sheets P
2a are separated one by one by a feed roller 112b, the skew of the sheet P is corrected by a pair of registration rollers 124, and the sheet P is synchronized with a print signal from the control unit 120.
Are transported upward and fed to the image forming unit 111. The recording material is a recording paper or the like.

Image forming unit 11 for forming an image on a recording paper
1 is a photosensitive drum 111a which is an electrostatic latent image carrier that forms an electrostatic latent image according to a signal from the flat head scanner unit 130 on its surface, a charging member 111b which charges the surface of the electrostatic latent image carrier, A laser scanner 110, which is an exposure unit for exposing the charged electrostatic latent image carrier to form an electrostatic latent image, and developing the electrostatic latent image on the electrostatic latent image carrier with toner as a developer And a transfer roller 111f, which is a transfer device for transferring the visualized image on the electrostatic latent image carrier to a recording material.

To form an image on recording paper by the image forming unit 111, the photosensitive drum 1 is charged by the charging member 111b.
11a, the surface of the photosensitive drum 11a is charged uniformly.
The surface of the photosensitive drum 111a is exposed by exposing the surface of the photosensitive drum 11a based on the image information by the laser scanner 110 to form an electrostatic latent image. The electrostatic latent image on the photosensitive drum 111a transfers the toner from the developing sleeve 111c carrying the toner to the electrostatic latent image on the photosensitive drum 111a to form a toner image on the photosensitive drum 111a. Then, the toner image formed on the photosensitive drum 111a is transferred onto the sheet P by the transfer roller 111f, and the sheet P is further conveyed to the upper fixing unit 116.

In the fixing unit 116, the toner transferred on the paper P is fixed to the fixing unit 116 by a fixing roller 116b rotatably provided with a heating heater, and a fixing roller 1b.
The sheet P is conveyed to a nip portion that is in contact with a pressure roller 116a pressed against the sheet 16b, and the toner is melted and fixed by heating and pressing the toner on the sheet P by passing the sheet P through the nip. The image is fixed on the paper P. The sheet P on which the image has been fixed is discharged to a recording material discharge tray 113 by a discharge roller pair 117.

On the other hand, when the paper is supplied from the manual paper feed unit 125, the paper stacked on the manual paper feed unit 125 is separated into one sheet by a separation pad 125b arranged at a position facing the paper feed roller 125a. The registration roller pair 1
24, the skew of the sheet is corrected, and the sheet is
The sheet is conveyed in one direction to transfer the toner image, is fixed by the fixing unit 116, and is discharged to the recording material discharge tray 113.

Next, the configuration of the fixing unit 116 for fixing the unfixed toner on the sheet and the vicinity thereof will be described in detail with reference to FIGS. FIG. 3 is an explanatory view showing a main part in the vicinity of the fixing unit. FIG. 4 is a plan explanatory view showing the vicinity of the fixing unit in a state where the cooling roller and the pressure roller are in contact with each other. FIG. 6 is a schematic diagram illustrating a state in which the roller and the pressure roller are separated from each other. FIG. 6 is a schematic diagram illustrating a state in which the cooling roller and the pressure roller are in contact with each other.

The fixing section 116 has a heater (not shown) therein and has a fixing roller 116 heated by the heater.
b, a pressure roller 116a pressed against the fixing roller 116b by pressure means (not shown) such as a spring, and moves between a state in which the pressure roller 116a contacts the pressure roller 116a and a state in which the pressure roller 116a is separated from the pressure roller 116a. The pressing roller 116a is capable of contacting with the surface of the pressing roller 116a.
And a cooling unit 138 capable of moving the cooling unit 138 in a state where the cooling unit 138 and the pressing roller 116a are separated from each other when the temperature of the pressing roller 116a is equal to or lower than a predetermined temperature. A moving means 135 is provided for moving the cooling means 138 in a state where the cooling means 138 and the pressure roller are in contact with each other when the temperature of 116a is higher than a predetermined temperature.

The thermistor 140 serves as a temperature detecting means for detecting the surface temperature of the pressure roller 116a by contacting the surface of the pressure roller 116a. Thermistor 1 is in contact with the surface other than the contact part.
The detection signal from 40 is input to the control unit 120 so that the surface temperature of the pressure roller 116a can be detected.

As shown in FIGS. 4 to 6, the cooling means 138 is provided with, for example, two cooling rollers 141 and 142 as a cooling section which comes into contact with the surface of the pressure roller 116a and removes the heat of the pressure roller 116a. Has been
A holding lever 143, which is two holding members that are rotatably supported at an arbitrary position and hold the ends of the cooling rollers 141 and 142 at one end, is provided.

The holding lever 143 has a base end rotatably supported at an arbitrary position in the apparatus main body, and a holding portion 143a for the cooling roller 141 provided at the tip of the holding lever 143. The holding portion 143b of the cooling roller 142 is provided at a position slightly moved from the leading end to the center along the longitudinal direction of the holding lever 143, and the cooling rollers 141 and 142 are held by the two holding portions 143a and 143b. Holding lever 1
By rotating the holding lever 143 in the clockwise direction with the base portion of the base 43 as a fulcrum, the two cooling rollers 141 and 142 can be brought into contact with the surface of the pressure roller 116a. I have.

The cooling rollers 141 and 142 are formed of, for example, aluminum or iron having a large heat capacity, and extend from the surface of the pressure roller 116a to the pressure roller 116a.
Heat can be effectively removed. Although two cooling rollers are provided, the number of cooling rollers is not limited to this, and one or three or more cooling rollers may be provided.

As shown in FIG. 5, the moving means 135 for moving the cooling means includes two cooling rollers 141 and 142 held by a holding lever 143.
A tension spring 149, which is an elastic member for urging in a direction away from the pressure roller 16a, and a pressure roller according to a temperature detection signal from a thermistor 140 having a predetermined reference temperature and being brought into contact with the pressure roller 116a. A comparison unit 136 that compares the surface temperature with a preset reference temperature to generate an operation signal when the temperature is equal to or lower than the reference temperature and an operation signal when the surface temperature is higher than the reference temperature, and according to a signal from the comparison unit 136. Driving means 139 for separating or contacting the cooling means and the pressure roller is provided, and an operation signal when the surface temperature of the pressure roller 116a is higher than the reference temperature is transmitted from the comparison unit 136, thereby driving the cooling means. The means 139 moves the holding lever 143 in a direction opposite to the biasing direction of the tension spring 149, so that the pressing roller 116a and the two cooling rollers 141, 142 Are you to be able to contact.

More specifically, one end of a tension spring 149 is locked on the side slightly opposite to the holding portion 143b from the tip of the holding lever 143, and the other end of the tension spring 149 is connected to the other end. The holding lever 143 is locked at a position facing the holding lever 143 of the apparatus main body, so that the holding lever 143 can be urged in a direction in which the holding lever 143 is separated from the pressure roller 116a by the contraction force of the tension spring 149. In a normal state, as shown in FIG. 5, the two cooling rollers 141 and 142 and the pressure roller 116a are separated from each other. The holding lever 143 separated from the pressure roller 116a by the tension spring 149 comes into contact with a stopper 148 provided at an arbitrary position and is held in a separated state.

Further, the comparison unit 136 is provided with a reference temperature preset in consideration of use conditions and the like, and a thermistor 14.
The control unit 120 includes a comparator to which the surface temperature of the pressure roller according to the temperature detection signal from 0 is input. Further, the driving means 139 includes the driving motor 1
37, a driving gear 160 rotated by a driving force from a driving motor 137, an idler gear 147, an idler gear 1
It comprises a pendulum gear 145 that moves along the outer periphery of 47, and a lever clutch 144 that is connected to the holding lever 143 via a spring clutch 161.

The comparison section 136 is connected to the drive motor 137 via a drive motor control circuit (not shown) so that a signal can be input. The drive motor 137 includes a drive gear 16
0 is connected, the drive motor 137 receives an operation signal when the temperature is equal to or lower than the reference temperature from the comparison unit 136, and the drive gear 160 rotates in the clockwise direction, ie, the normal rotation direction. When the drive motor 137 receives an operation signal when the temperature is higher than the reference temperature, the drive gear 160 can rotate in the reverse direction, which is a counterclockwise direction.

Instead of rotating the drive gear 160 by the drive motor 137 provided for the drive means 139, a drive unit used for driving a paper transport mechanism or the like of the facsimile apparatus main body via a drive transmission means. Drive gear 160
May be rotated, in which case the comparison unit 13
6 by the drive transmission means in response to a signal from
The rotation direction of 0 can be appropriately changed.

The drive gear 160 includes an idler gear 147
Are meshed with each other so that the idler gear 147 rotates in a predetermined direction according to the rotation of the drive gear 160.
The idler gear 147 is meshed with a pendulum gear 145 supported by a support arm 146 rotatably supported on the rotation shaft of the idler gear 147, and the idler gear 147 rotates, thereby rotating in the opposite direction to the idler gear 147. The pendulum gear 145 can move along the periphery of the idler gear.

Further, as shown in FIG.
3 is connected to the lever gear 1 via a spring clutch 161.
When the lever gear 144 is rotated in a predetermined direction, the spring clutch 161 is tightened to connect the holding lever 143 and the lever gear 144, and the rotation of the lever gear 144 causes the holding lever 143 to press the pressing roller 1
The pressure roller 116a is swung in the direction of 16a.
The cooling levers 141 and 142 provided at the end of the holding lever 143 can contact with each other.

Here, when the drive gear 160 rotates in the reverse direction, the pendulum gear 145 supported via the idler gear 147 and the support arm 146 moves clockwise along the outer periphery of the idler gear 147. When the pendulum gear 145 and the lever gear 144 are engaged with each other and the drive gear 160 rotates in the normal rotation direction, the idler gear 147 and the support arm 146 are rotated.
The position and size of each gear are adjusted so that the pendulum gear 145 supported through the shaft moves counterclockwise along the outer circumference of the idler gear 147 to separate the pendulum gear 145 from the lever gear 144. ing.

When the drive gear 160 rotates in the forward direction, as shown in FIG. 5, the idler gear 147 rotates the pendulum gear 145 supported by the support arm 146, and the pendulum gear 145 is separated from the lever gear 144. Since the drive motor 137 is stopped and the rotation of the drive gear 160 is regulated by a fixing means (not shown), the disturbance of the drive motor 137 is not transmitted to the lever gear 144. The fixing means may restrict the rotation by hooking a claw on the tooth portion of the drive gear 160, or the drive gear 1
The rotation may be restricted by gripping the 60 rotation shafts.

When the drive gear 160 rotates in the reverse direction, as shown in FIG. 6, the pendulum gear 145 and the lever gear 144 mesh with each other, so that the driving force of the drive motor 137 is transmitted from the pendulum gear 145 to the lever gear 144. Is transmitted. Lever gear 144 to which drive has been transmitted
The lever gear 144 and the holding lever 143 are connected so that the rotation direction rotates in the tightening direction of the spring clutch 161, and the holding lever 143 swings in the direction opposite to the biasing direction of the tension spring 149. Then, the cooling rollers 141 and 142 rotate until they come into contact with the pressure roller 116a, and the rotation of the driving gear 160 is regulated in the state of contact. The spring clutch 161 is configured so that the spring clutch 161 is not further tightened by the end of the spring clutch 161 abutting on a stopper (not shown).

The cooling means 138 and the moving means 13 having the above structure
According to 5, the temperature detected by the thermistor 140 is
When the temperature is lower than the reference temperature of 36, the drive gear 160 to which the disturbance of the drive motor 137 is transmitted rotates in the normal rotation direction,
The idler gear 147 rotates the pendulum gear 145 supported by the support arm 146 in a direction away from the lever gear 144. As a result, the pendulum gear 145 and the lever gear 144 are separated from each other, so that the rotation of the drive gear 160 is not transmitted to the lever gear 144, and the holding lever 143 is urged in the direction of the stopper 148 by the contraction force of the extension spring 149, and the cooling is performed. The rollers 141 and 142 are the pressure roller 11
6a.

The temperature detected by the thermistor 140 is
6 is higher than the reference temperature, the rotation of the drive gear 160 is reversed, and the idler gear 147 rotates the pendulum gear 145 supported by the support arm 146 in the direction of the lever gear 144, and meshes the pendulum gear 145 and the lever gear 144. The rotation of the driving gear 160 is transmitted to the lever gear 144. Since the rotation direction of the lever gear 144 to which the rotation is transmitted is set to the tightening direction of the spring clutch 161, the lever gear 144 and the holding lever 143 are connected. When the lever gear 144 and the holding lever 143 are connected, the holding lever 14
3 is oscillated in a direction opposite to the direction in which the tension spring 149 is urged until the cooling rollers 141 and 142 and the pressure roller 116a come into contact with each other. At this time, the cooling rollers 141 and 142 come into contact with the outer peripheral surface of the pressure roller 116a other than the nip between the fixing roller 116b and the pressure roller 116a, so that the two are in close contact with each other. Cooling roller 14
The first and second rollers 142 take heat from the pressure roller 116a and dissipate the heat by being in close contact with the pressure roller 116a.

In the actual fixing step, the conveyed sheet P enters the nip between the fixing roller 116b and the pressure roller 116a, and if the temperature detected by the thermistor 140 at that time is low, the cooling rollers 141 and 142 The fixing roller 11 is separated from the pressure roller 116a.
6b, the pressure roller 116a is quickly warmed by the heat of the heater 6b, the temperature of the nip between the fixing roller 116b and the pressure roller 116a rises smoothly, and the paper P can be quickly and surely heated. Can be fixed on the paper P.

When the paper P is continuously conveyed to the fixing section, since the fixing roller 116a and the pressure roller 116b rotate while being in contact with each other for a long time, the pressure roller 116b is gradually heated. As a result, the temperature detected by the thermistor 140 provided on the pressure roller 116b increases. When the temperature detected by the thermistor 140 exceeds the reference temperature of the comparison unit 136, the cooling rollers 141 and 142 separated from the pressure roller 116a
The cooling rollers 141 and 142 take heat from the pressure roller 116a and dissipate the heat.

The pressure roller 116a radiated by the cooling rollers 141 and 142 does not expand its outer diameter due to heat accumulation, and the speed of the pressure roller 116a does not become faster than that of the transfer roller 111f. Is not pulled by the pressure roller 116a. Therefore, even if the paper P is continuously transported to the fixing unit in the continuous copy, the image on the paper P does not stretch.

According to this embodiment, even if the paper P is continuously conveyed to the fixing unit in the continuous copy, the thermistor 14
According to the temperature information from 0, the cooling rollers 141 and 142 separated from the pressure roller 116a are brought into contact with the outer peripheral surface of the pressure roller 116a via a plurality of gears to bring them into close contact with each other. An image forming apparatus in which the image on the sheet P is not stretched can be realized by a simple means such as removing heat from the heat 116a and dissipating the heat. In addition, by appropriately adjusting the gear ratio of each gear, the cooling roller can be reliably brought into contact with the pressure roller with a smaller driving force.

The holding lever for holding the cooling roller is swung from the drive motor by using a plurality of gear trains. However, the present invention is not limited to this. The holding lever is supported by the rotation shaft of the drive motor. Alternatively, the rotation of the drive motor may be directly transmitted to the holding lever. Further, a holding lever may be connected to the driving motor via a one-way clutch. In this case, the driving force of the driving motor is transmitted by the one-way clutch in a direction in which the holding lever swings toward the pressure roller. When the drive motor rotates in the reverse direction, the holding lever is separated from the pressure roller by a tension spring. Furthermore, instead of using a drive motor or a gear train as a moving means of the cooling roller, a solenoid clutch is provided at a predetermined position, and the holding lever is operated by operating the solenoid clutch by an operation signal when the temperature is higher than the reference temperature from the comparison unit. It may be possible to swing in the direction of the pressure roller.

(Second Embodiment) A second embodiment of the present invention will be described with reference to FIGS. In the present embodiment, instead of using a drive motor and a plurality of gears as the moving means for moving the cooling means in the first embodiment, the cooling means is brought into contact with the pressure roller using a bimetal bent at a predetermined temperature. The state is moved between a state and a state of being separated from the pressure roller. The other members such as the pressure roller and the fixing roller are the same as those in the first embodiment, and the detailed description is omitted.

In this embodiment, as shown in FIGS. 7 and 8,
As a moving means 135 'for moving the cooling means, the base end of a long rod-shaped support member 152 having a bimetal effect that curves at a predetermined temperature is fixed to the apparatus body near the pressure roller 116a. Further, as the cooling means 138 ', the cooling roller 1 having the same configuration as that used in the first embodiment is used.
41 and 142 are held at the ends of the two crank levers 150, so that the middle position of the crank lever 150 is rotatably supported at an appropriate position on the apparatus main body,
The distal end of the support member 152 is brought into contact with the end of the crank lever 150 opposite to the side on which the cooling rollers 141 and 142 are provided, and the cooling member of the crank lever 150 is bent by bending the support member 152. The end on the side can swing in the direction of the pressure roller.

The support member 152 is formed in a long rod shape, for example, by laminating copper as a material having a low thermal expansion coefficient on the upper side and ABS resin as a material having a high thermal expansion coefficient on the lower side. When the temperature of the support member 152 rises and heat is applied to the support member 152, the lower member having a large coefficient of thermal expansion greatly extends, and the end of the support member 152 on the side of the crank lever 150, which is the free end, warps upward. Has become.

The crank lever 150 is formed in a substantially rectangular shape, and its bent portion is rotatably supported at an appropriate position on the apparatus main body between the support member 152 and the pressure roller 116a. Further, the other end of the tension spring 151 whose one end is locked to the apparatus main body is connected to the support member 15 of the crank lever 150.
The crank lever 150 can be rotated in the clockwise direction by the contraction force of the tension spring 151, and the end of the crank lever 150 on the support member 152 side is locked to the end on the second side. Locking projection 150
c is projected and the locking projection 150c is locked to the end of the support member 152 on the crank lever side.

The holding portion 1 of the cooling roller 141 is attached to the tip of the crank lever 150 on the side of the pressure roller 116a.
50a is provided, and the holding portion 150 of the cooling roller 142 is located at a position slightly moved from the holding portion 150a to the pivotal support side along the longitudinal direction of the crank lever 150.
b, the cooling levers 141 and 142 are held by the two holding portions 150a and 150b, and the crank lever 150 is rotated in the clockwise direction around the shaft support portion of the crank lever 150 as a fulcrum.
The two cooling rollers 141 and 142 to the pressure roller 11
6a can be brought into contact with the surface.

Here, when the support member 152 is in a straight line, the end of the support member 152 on the side of the crank lever serves as a stopper so that the crank lever 150 does not rotate and the two cooling rollers 14 held by the crank lever 150 do not rotate.
When the support member 152 is curved while the pressure roller 116a is separated from the pressure roller 142, the crank lever 150 is rotated clockwise by the tension spring 151 following the curvature of the support member 152. Cooling rollers 1 held by crank lever 150
41, 142 can contact the pressure roller 116a.

Even when the support member 152 is curved and the pressure roller 116a and the two cooling rollers 141 and 142 are in contact with each other, the locking projection 150c of the crank lever 150 and the tip of the support member 152 are in contact with each other. As described above, the length of the locking projection 150c of the crank lever 150 and the degree of curvature of the support member 152 are adjusted.

According to the crank lever 150 and the support member 152 having the above configuration, as shown in FIG.
The free end of the support member 152 is locked to the end of the crank lever 150 until the temperature of the periphery of the support member 2 is low and the support member 152 is curved, and the support member 152 functions as a stop bar to restrict the rotation of the crank lever 150. Therefore, the pressure roller 116a and the cooling roller 141 are separated from each other.

On the other hand, when copying is performed continuously, the temperature of the pressure roller 116a rises, and
The temperature around 6a rises, and the temperature around the support member 152 provided near the pressure roller 116a rises. When the temperature at which the support member 152 is bent is reached, FIG.
As shown in FIG.
The end on the side of the crank lever 150 is bent so as to be lifted upward, and the crank lever 150 follows the curve of the support member 152, and the contraction force of the tension spring 151 causes the crank lever 150 to rotate in the clockwise direction about the shaft support portion. Rotate. When the crank lever 150 rotates clockwise, the cooling rollers 141 and 142 held by the two holding portions 150a and 150b of the crank lever 150 are pressed.
The two cooling rollers 141 and 142 remove the heat of the pressure roller 116a and dissipate the heat.

Since the pressure roller 116a is deprived of heat by the cooling rollers 141 and 142 and radiated heat, the outer diameter of the roller does not increase due to expansion due to heat storage of the pressure roller 116a. Since the transport speed of the transfer roller 116f does not become faster than the transport speed of the transfer roller 111f, the sheet is not pulled by the pressure roller 116a. Therefore, good image formation can be performed without the image on the paper being stretched.

Further, the copying is completed and the pressure roller 11
When the temperature of the supporting member 152 decreases, the temperature around the supporting member 152 also decreases, so that the supporting member 152 returns to the original linear shape, and the locking projection 150c at the end of the crank lever 150 changes to the supporting member 152. , The crank lever 150 rotates counterclockwise, and returns to the original position where the cooling rollers 141 and 142 and the pressure roller 116a are separated. Therefore, when the next copy is taken, the heat is not taken by the cooling rollers 141 and 142, so that the temperature of the pressure roller 116a rises smoothly, and the toner on the paper can be quickly fixed on the paper.

According to the present embodiment, the simple configuration of the bimetal and the cooling roller held by the crank lever can prevent the temperature of the pressure roller from rising and perform good image formation without image expansion. . In addition, the bimetal fixes the base end to the apparatus main body and locks the other end to the crank lever, but is not limited to this.
Both ends of the bimetal are fixed to the main body of the device, so that the middle of the rod-shaped bimetal is curved, and the end of the bimetal side of the crank lever is locked in the middle of the bimetal. It may be rotated. Instead of using a bimetal, a shape memory alloy that changes shape when the surrounding temperature reaches a predetermined temperature is used. May be contacted.

In the above two embodiments, the cooling unit and the moving unit are provided in the fixing unit in the facsimile apparatus to prevent the temperature of the pressure roller of the fixing unit from excessively rising.
However, the present invention is not limited to this, and a cooling unit and its moving unit may be provided in a fixing unit provided in an image forming apparatus such as a copying machine or a laser printer.

[0071]

As described above, according to the first aspect of the present invention, when the temperature of the pressure roller or the vicinity of the pressure roller is lower than the predetermined temperature, the cooling means is separated from the pressure roller. And the surface temperature of the pressure roller is quickly and reliably raised to the temperature required for fixing.
When the temperature of the pressure roller or the vicinity of the pressure roller is higher than a predetermined temperature, the pressure roller and the cooling means are brought into contact with each other, and the cooling means takes away the heat of the pressure roller. By preventing expansion due to heat, it is possible to prevent image expansion in the fixing step due to a change in the peripheral speed of the pressure roller, and it is possible to perform favorable image formation.

According to the second aspect of the present invention, the surface temperature of the pressing roller is detected by the temperature detecting means abutting on the pressing roller of the fixing unit, and the comparing unit provided in the moving means is provided. The surface temperature of the pressure roller from the temperature detection means is compared with the reference temperature, and a signal when the surface temperature of the pressure roller is lower than the reference temperature and a signal when the surface temperature of the pressure roller is higher than the reference temperature are driven from the comparison unit. Transmitted to the means, the driving means comprising:
By receiving the operation signal from the comparison unit when the surface temperature of the pressure roller is lower than the reference temperature, the cooling unit is biased by the elastic member provided on the holding member that holds the cooling unit of the cooling unit. By actuating the holding member to separate the pressure roller from the cooling unit, and receiving an operation signal from the comparison unit when the surface temperature of the pressure roller is higher than the reference temperature, the cooling unit is activated. Since the pressure roller and the cooling unit are brought into contact by operating to move the holding member of the cooling unit in a direction opposite to the biasing direction of the elastic member provided on the holding member holding the cooling unit, the pressure is applied. The expansion of the pressure roller due to heat can be reliably prevented with a simple configuration without impairing the surface temperature required for fixing the roller, and good image formation without expansion can be performed.

According to the third aspect of the present invention, when the temperature in the vicinity of the pressure roller is lower than the temperature at which the bimetal bends, the bimetal regulates the movement of the holding member to cool the pressure roller and the cooling roller. The bimetal in the vicinity of the pressure roller is curved by increasing the temperature in the vicinity of the pressure roller, and the holding member is moved in the biasing direction by the elastic member of the holding member due to the bending of the bimetal. And the cooling unit are in contact with each other, so that the expansion of the pressure roller due to heat can be prevented with a simple configuration without impairing the surface temperature required for fixing the pressure roller, and good image formation without elongation can be performed. Can be.

[Brief description of the drawings]

FIG. 1 is an explanatory perspective view showing a facsimile apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a facsimile machine.

FIG. 3 is an explanatory diagram of a main part showing a main part near a fixing unit.

FIG. 4 is an explanatory plan view showing the vicinity of a fixing unit in a state where a cooling roller and a pressure roller are in contact with each other.

FIG. 5 is a schematic explanatory view showing a state in which a cooling roller and a pressure roller are separated from each other.

FIG. 6 is a schematic explanatory view showing a state in which a cooling roller and a pressure roller are in contact with each other.

FIG. 7 is a schematic explanatory view showing a state in which a cooling roller and a pressure roller according to a second embodiment of the present invention are separated from each other.

FIG. 8 is a schematic explanatory view showing a state where a cooling roller and a pressure roller are in contact with each other.

[Explanation of symbols]

 116 fixing unit 116a pressure roller 116b fixing roller 135 moving unit 138 cooling unit 139 driving unit 140 thermistor (temperature detecting unit) 141, 142 cooling roller (cooling unit) 143 holding lever (cooling unit)

Claims (3)

[Claims] An electrostatic latent image is formed on an electrostatic latent image carrier by a signal from an image reading device that reads an image on a document and converts the image into a signal. The image is developed with a developer, the developed developer image on the electrostatic latent image carrier is transferred to a recording material, and the developer image is transferred to a fixing unit having a fixing roller and a pressure roller. In an image forming apparatus in which an image is formed by an electrophotographic method in which a developer image on a recording material is fixed by heating and pressurizing the recording material by passing through the fixing member, a state in which a fixing portion is brought into contact with a pressure roller is added. At least one cooling means movable between the pressure roller and the pressure roller and capable of depriving the temperature of the pressure roller in a state of contacting the surface of the pressure roller; and a pressure roller or a pressure roller. When the nearby temperature is below the specified temperature The cooling means can be moved to a state in which the cooling means and the pressure roller are separated from each other, and when the temperature of the pressure roller or the vicinity of the pressure roller is higher than a predetermined temperature, the cooling means is brought into contact with the pressure roller. An image forming apparatus, comprising: moving means for moving a cooling means. 2. A pressure roller of a fixing section, wherein a temperature detecting means is provided which is in contact with the surface of the pressure roller and is capable of detecting the temperature of the pressure roller, and the cooling means is provided on the surface of the pressure roller. A movement unit that has a cooling unit that contacts and removes the heat of the pressure roller, and two holding members that are rotatably supported at an arbitrary position and hold one end of the cooling unit at one end, and move the cooling unit. Means is an elastic member for urging the two holding members in a direction to separate the cooling unit held by the holding member from the pressure roller,
By comparing the surface temperature of the pressure roller according to the temperature detection signal from the temperature detection means brought into contact with the pressure roller with a predetermined reference temperature with a preset reference temperature, A comparison unit that issues an operation signal in the case and an operation signal when the temperature is higher than the reference temperature, and a driving unit that separates or abuts the cooling unit and the pressure roller in accordance with a signal from the comparison unit are provided, The driving unit moves the holding member of the cooling unit in the biasing direction of the elastic member by receiving an operation signal when the surface temperature of the pressure roller is lower than the reference temperature from the comparison unit, and By receiving an operation signal from the comparison section when the surface temperature of the pressure roller is higher than the reference temperature, the holding member of the cooling means is moved in a direction opposite to the biasing direction of the elastic member to be applied. Pressure roller and cold The image forming apparatus according to claim 1, characterized in that the parts can abut. 3. A cooling means for contacting the surface of the pressure roller to remove heat from the pressure roller, and a cooling means rotatably supported at an arbitrary position and holding one end of the cooling part at one end. Do 2
Moving means for moving the cooling means, an elastic member for urging the two holding members in a direction in which the cooling portion held by the holding member is brought into contact with the pressure roller, and a moving member for the pressure roller. A bimetal that is disposed in the vicinity and curves when a predetermined temperature is reached, and the bimetal is urged by an elastic member of the holding member when the bimetal is not bent when at least a part thereof abuts the holding member of the cooling unit. In the curved state, the holding member is moved in the biasing direction by the elastic member of the holding member to abut the pressing roller and the cooling portion while restricting the movement in the direction. The image forming apparatus according to claim 1, wherein the image forming apparatus can be used.