JPH10274893A - Medium heating/carrying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To impart optimum tensile force to various kinds of mediums. SOLUTION: Shafts 4a and 4b inserted/fixed in both ends of a backup roller 3 made of an elastic material are held by freely rotatably fitted bearings 6a and 6b. A gear 10 engaged with the bearing 6b is rotated in synchronization with a gear 9 engaged with the bearing 6a. When the gears 9 and 10 are rotated in the directions of A and B by specific amounts respectively, the bearings 6a and 6b are rotated in the directions of C and D by the specific amounts respectively. The backup roller 3 is curved in the direction of carrying a paper sheet 11 and simultaneously, the contact part, of a heating roller not shown by the figure, with the backup roller 3 is curved in the same direction as well. Even if the backup roller 3 is curved, it is in press-contact with the heating roller by elasticity, in the axial direction of the backup roller 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a medium heating / transporting apparatus for holding and transporting a medium while applying heat and pressure by a heat roller and a backup roller pressed against the heat roller.

[0002]

2. Description of the Related Art A heating and fixing device provided as a medium heating and transporting device in, for example, an electrophotographic printer generally includes:
It has a heat roller and a backup roller that is in pressure contact with the heat roller. The medium is nipped and conveyed while applying heat and pressure by the heated heat roller and the backup roller to fix the toner image.

[0003]

When the medium is paper, the fibers of the paper are stretched by heating the heat roller. At this time, if the sheet is pressed against the heat roller by the backup roller, the sheet cannot extend in the longitudinal direction (axial direction) of both rollers, and "wrinkles" will be generated on the sheet. Therefore, in the conventional heat fixing device, the diameter of the heat roller is not made uniform in the axial direction, but, for example, the diameter of the central portion is made larger than the diameter of both ends, thereby applying the axial tension of both rollers to the paper. , "Wrinkles" were prevented.

However, the proper tension applied to the medium changes depending on the thickness of the medium, and therefore, it is possible to apply the optimum tension to various media while keeping the diameter distribution of the heat roller fixed. Did not.

[0005]

In order to solve the above-mentioned problems, a solution taken by the present invention is that a backup roller is formed to be elastic and bendable, and a contact portion between the backup roller and the heat roller is formed. A bending mechanism for bending the backup roller so as to draw a curve is provided.

According to the above solution, the backup roller is bent by the bending mechanism. In this state, the medium is nipped and transported by the heat roller and the backup roller. Due to the curvature of the backup roller, tension is applied to the medium in the axial direction of both rollers. Therefore, when the material of the medium is extended by heat, the medium can be extended in the axial direction of both rollers.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the present embodiment, a heating and fixing device incorporated in an electrophotographic printer will be described as an example of a medium heating and transporting device. Elements common to the drawings are denoted by the same reference numerals.

[0008] block diagram of a first embodiment Figure 1 of the backup roller provided in the heat fixing apparatus of the first embodiment according to the present invention, FIG 2 is first
FIG. 3 is a schematic perspective view showing a heat fixing device according to the first embodiment, and FIG.
FIG. 4 is a diagram illustrating a state of a contact portion of the heat roller with the backup roller according to the first embodiment. 2 and 4
Indicate the contact portions between the heat roller and the backup roller, respectively.

The heat fixing device 1 shown in FIG. 3 includes a heat roller 2 and a backup roller 3. The heat roller 2 is formed of a hard metal and has a hollow pipe shape. A heater 2a is provided inside the heat roller 2, and is heated by the heater 2a to generate heat. The heat roller 2 is rotated in a direction indicated by an arrow E by transmitting a rotational force from a drive source (not shown).

The backup roller 3 is made of a heat-resistant elastic material and has a columnar shape. The backup roller 3 is in pressure contact with the heat roller 2, and is rotated in the direction of arrow F by the rotation of the heat roller 2 in the direction of arrow E. Accordingly, the sheet 11 held between the heat roller 2 and the backup roller 3 is transported in the direction of arrow G.

A shaft 4 is provided at each end of the backup roller 3.
(4a, 4b) are inserted and fixed. The shafts 4a and 4b do not pass through to the center of the backup roller 3, respectively.
Therefore, the backup roller 3 can freely change the degree of curvature. The shafts 4a and 4b are rotatably held by bearings 6 (6a and 6b) attached to the base 5 of the heat fixing device 1 shown in FIGS.

The bearings 6a and 6b are respectively supported on a base 5 by a fulcrum 7
It is rotatably attached with a and 7b as pivot points. The bearings 6a and 6b have teeth 8 (8a and 8b), respectively.
Are formed. The teeth 8a mesh with a gear 9 provided on a rotating shaft of a motor described later. The teeth 8b are
The gear 10 meshes with the gear 10 which rotates by transmitting the torque of the motor.

In the present embodiment, the gear 10 rotates in synchronization with the gear 9, and the rotation amounts of the gears 9 and 10 are the same and the rotation directions are opposite. Therefore, when the gear 9 rotates by a predetermined amount in the direction of arrow A, the gear 10 rotates by the same amount in the direction of arrow B, whereby the bearing 6a rotates by a predetermined amount in the direction of arrow C.
b rotates a predetermined amount in the direction of arrow D,
Are curved in the transport direction of the sheet 11 (the direction of arrow G). That is, the state of FIG. 1 changes to the state of FIG.

When the backup roller 3 curves, the contact portion where the heat roller 2 and the backup roller 3 come into contact changes from the contact portion J to the contact portion K (see FIGS. 2 and 4). The contact portion K is curved in the sheet transport direction, similarly to the backup roller 3. That is, even if the backup roller 3 is curved, the backup roller 3 is elastically pressed against the heat roller 2 in the axial direction. Therefore, the backup roller 3 can press the heat roller 2 not only at the center but also at both ends of the sheet 11 in the same manner as when the sheet is not curved.

Next, a control system according to the first embodiment will be described with reference to FIG. FIG. 5 is a block diagram of the first embodiment.

The overall operation of the heat fixing device 1 is controlled by a control unit 12.
Is controlled by The operation unit 13 and the movable bearing drive circuit 14 shown in FIG. The operation unit 13 has input keys and the like, and is operated by an operator. The movable bearing drive circuit 14 is a circuit that generates a signal for driving the motor 15 by a predetermined amount based on information input from the operation unit 13. Information input from the operation unit 13 is information such as the thickness of the sheet 11.

When heat is applied to the paper 11, the fibers of the paper expand. At this time, if the sheet 11 is pressed against the heat roller 2 by the backup roller 3, the sheet 11 cannot extend in the longitudinal direction of the rollers 2 and 3 (the axial direction indicated by arrows L and M). "Wrinkles" are generated on the surface. Therefore, in the present embodiment, at the time of the fixing operation, the backup roller 3 is curved as shown in FIG. 2 according to the thickness of the paper 11, and tension is applied to the paper 11 to be nipped and conveyed (the paper 11 in the directions of arrows L and M). Pulling force).

The tension applied to the paper 11 is determined by the type (thickness, etc.) of the paper. Therefore, in the present embodiment, the optimal tension on the plurality of types of paper 11 handled by the heat fixing device 1 and the amount of curvature of the backup roller 3 (rotation angle of the motor 15) for applying the tension are determined in advance by experiments and the like. These rotation angles are stored in a non-volatile memory or the like (not shown). When the operator selects the type of paper 11 by key input from the operation unit 13, the rotation angle of the motor 15 corresponding to the selected paper type is called from the memory, and the movable bearing drive circuit 14 is called from the memory. A signal for driving the motor 15 by the rotation angle is generated.

Further, the tension applied to the paper 11 may be input by the operator each time.

Next, the operation of the heat fixing device 1 of the present embodiment will be described with reference to FIGS.

The heat roller 2 is maintained at a predetermined temperature by a heater 2a. In this state, the operator first inputs the type of the paper 11 to be used from the operation unit 13.
The control unit 12 obtains the rotation angle of the motor 15 according to a key input from the operation unit 13 and sends the rotation angle to the movable bearing drive circuit 14. The movable bearing drive circuit 14 generates a signal based on the input rotation angle and outputs the signal to the motor 15. The motor 15 is driven, the gear 9 rotates in the direction of arrow A, and the gear 10
Rotate in the direction. At the same time, the bearing 6a rotates in the direction of arrow C, and the bearing 6b rotates in the direction of arrow D.

Accordingly, the backup roller 3 is curved. The contact portion between the heat roller 2 and the backup roller 3 changes from the contact portion J to the contact portion K (see FIG. 2).

Thereafter, when the sheet 11 to which the unfixed toner image is attached is sent to the heat fixing device 1, the sheet 11 is nipped and conveyed by the heat roller 2 and the backup roller 3. At this time, the unfixed toner image on the paper 11 is melted and fixed on the paper 11 by heat and pressure, and the paper 11 is conveyed while being pulled in the directions of the arrows L and M by the curvature of the backup roller 3.

Since the paper 11 is pulled and conveyed in the directions of the arrows L and M, the linear velocity of the central part of the paper 11 which comes into contact with the center of the backup roller 3 is higher than the linear velocity of both ends on the bearing 6 side. Become. This is the same as when the diameter of the central portion of the backup roller 2 is larger than the diameter of the end portion. Therefore, even if heat is applied and the paper fibers stretch,
Since the paper 11 can extend in the directions of the arrows L and M,
No wrinkles occur.

In the first embodiment, by changing the rotation angle of the motor in accordance with the type (thickness) of the paper 11,
That is, the curvature of the contact portion between the heat roller 2 and the backup roller 3 can be changed by changing the magnitude of the curvature of the backup roller 3. Thereby, the tension applied to the paper 11 can be set arbitrarily,
The flexibility of the paper 11 handled by the heat fixing device 1 can be expanded more than before.

In the first embodiment, the backup roller 3 is curved in the direction in which the sheet 11 is transported. However, the center of the backup roller 3 is not limited to the transport direction, but is curved in the direction away from the heat roller 2. Is also good. Hereinafter, a modification of the first embodiment will be described with reference to FIG. FIG. 6 is a schematic configuration diagram illustrating a heat fixing device according to a modified example of the first embodiment.

The heat fixing device 100 includes a heat roller 2
00 and a backup roller 300 are provided.
The heat roller 200 is a metal pipe having a surface coated with a resin and having elasticity, and has a surface shape at the time of molding, which is the metal pipe itself. As in the first embodiment, a heater (not shown) is provided inside the heater, and the heater is heated by the heater to generate heat. Further, the heat roller 200 is transmitted with a rotational force by a drive source (not shown) and rotates in the direction of arrow E shown in FIG.

The backup roller 300 is formed by coating a rubber on a shaft 400. It has a columnar shape as in the first embodiment. Backup roller 300
Is constantly in pressure contact with the heat roller 200 by the pressure spring 500, and the heat roller 200 rotates to rotate in the opposite direction to the rotation direction of the heat roller 200.

In this modification, both ends of the shaft 400 are held by, for example, a bending mechanism (not shown), and both ends of the backup roller 300 are heated by the bending mechanism.
0, that is, the central portion of the backup roller 300 is curved in a direction away from the heat roller 200 (the direction of the arrow T).

The magnitude of the curvature (deflection amount δ) of the central portion of the backup roller 300 can be approximated by a dynamic model as shown in FIG. FIG.
(A) is a figure explaining the curvature of the axis of the backup roller of a 1st embodiment by a dynamic model. The deflection amount δ can be expressed by the following equation.

[0031]

(Equation 1)

Incidentally, d shown in the figure corresponds to the diameter of the shaft 400, and the longitudinal elasticity coefficient E is determined by the material of the backup roller 300. In this modification, the longitudinal elastic modulus E is 210
00 [Kg / mm ² ].

For example, the external force W is 2.5 [Kg], the length L1 of the shaft 400 projecting from both ends of the backup roller 300 is 12 [mm], and the backup roller length L2 is 22 [mm].
When the diameter d is obtained in order to obtain the deflection amount δ of 0.2 [mm], assuming that the deflection amount is 0 [mm], the following expression is obtained from the above equation.

[0034]

(Equation 2)

Therefore, the shaft 4 of the backup roller 300
If the diameter of 00 is 5.45 [mm], the deflection amount δ
Can obtain 0.2 [mm].

That is, by combining the set values of the external force W, the lengths L1 of the shafts at both ends, the length L2 of the backup roller, and the diameter d, the amount of deflection near the center of the backup roller 300 can be obtained without particular processing. δ = 0.1 ~
0.3 [mm] can be obtained. Also, the heat roller 2 is located at the center of the pressure contact portion with the heat roller 200.
Since 00 has elasticity, the deflection amount X shown in FIG.
= 0.1 to 0.3 [mm] is obtained.

In this modification, the backup roller 30
0 is curved in a direction away from the heat roller 200, so that when the sheet 11 is nipped and conveyed by the heat roller 200 and the backup roller 300, both ends parallel to the conveying direction of the sheet 11
It is conveyed while being held down by 0 and 300. Therefore, similarly to the first embodiment, even if the fiber of the sheet 11 is stretched by applying heat, the stretched portion of the sheet 11 escapes to the center of the rollers 200 and 300, and no wrinkles are generated.

Further, as shown in FIG. 7B, the same effect can be obtained by bending the central portion of the backup roller 300 in the direction approaching the rotation center of the heat roller 200.
FIG. 7B is a diagram illustrating the curvature of the shaft of the backup roller according to the first embodiment using a mechanical model. In this case, when the sheet 11 is nipped and conveyed at the central portion between the rollers 200 and 300, the sheet 11
Due to the curvature of 0, the sheet is conveyed so as to escape in the directions of arrows L and M. Therefore, no wrinkles are generated even if heat is applied and the fibers of the paper 11 are stretched.

Second Embodiment In the first embodiment, the gear 10 is rotated by the same amount in synchronization with the gear 9, but in the second embodiment, the gear 9 is rotated.
And the rotation amount of the gear 10 are made different. Less than,
The second embodiment will be described with reference to FIGS. 1, 3, 8, and 9. FIG. FIG. 8 is a block diagram of the second embodiment, and FIG. 9 is a diagram illustrating a state of a contact portion of the heat roller with the backup roller according to the second embodiment.

The heat fixing device 1 includes a control unit 20 shown in FIG.
Controls the overall operation. An operation unit 13 similar to that of the first embodiment is connected to the control unit 20. The control unit 20 further includes a first movable bearing drive circuit 21 and a second movable bearing drive circuit 21.
Of the movable bearing drive circuit 22 is connected. A first motor 23 is connected to the first movable bearing drive circuit 21, and a second motor 24 is connected to the second movable bearing drive circuit 22. First and second movable bearing drive circuits 21, 2
Reference numeral 2 denotes a circuit for generating a signal for driving the first and second motors 23 and 24 by a predetermined amount based on information input from the operation unit 13 as in the first embodiment.

The gear 9 is provided on the motor shaft of the first motor 23, and the gear 10 is provided on the motor shaft of the second motor 24. Accordingly, the gear 9 and the gear 10 are separately driven and controlled.

In the second embodiment, paper 11 such as an envelope having a window for the purpose of seeing through an address or paper 11 to which a non-carbon chemical for copying is partially adhered, that is, paper 11 In contrast, the optimum tension is applied by changing the rotation angle of the first motor 23 and the rotation angle of the second motor 24.

That is, since the tension applied to the paper 11 is determined by the type (thickness) of the paper,
Distribution of tension and the rotation angle of the motor 15 are obtained in advance, and the obtained rotation angle is calculated in the same manner as in the first embodiment.
It is stored in a non-volatile memory (not shown) or the like. Then, when the operator selects the type of the paper 11 by key input from the operation unit 13, the control unit 20 calls the rotation angles of the motor 23 and the motor 24 corresponding to the type of the paper 11 from the memory, respectively, and stores the first and second rotation angles. Second movable bearing drive circuit 2
1 and 22, and signals for driving the motors 23 and 24 corresponding to the rotation angle are transmitted to the first and second movable bearing drive circuits 21 and 22.
Is generated.

The other configuration is the same as that of the first embodiment, and the description is omitted.

Next, the operation of the heat fixing device 1 according to the second embodiment will be described with reference to FIGS. 1, 3, 8, and 9.

The heat roller 2 is maintained at a predetermined temperature by a heater 2a. In this state, as in the first embodiment, the operator first inputs the type of the paper 11 to be used from the operation unit 13. The control unit 20 obtains the rotation angles of the first motor 23 and the second motor 24 according to the key input from the operation unit 13, and sends them to the first and second movable bearing drive circuits 21 and 22. The first and second movable bearing drive circuits 21 and 22 generate signals based on the input rotation angles, respectively, and the first movable bearing drive circuit 21
3 and the second movable bearing drive circuit 22 outputs
Of the motor 24 is output.

For example, when the thickness of the end of the sheet 11 in the direction of arrow L is smaller than the thickness of the end of the sheet 11 in the direction of arrow M, the controller 20 The rotation angle of the first motor 23 is made larger than the rotation angle of the second motor 24 via the first and second movable bearing drive circuits 21 and 22 so that the first and second motors 23 and 24
Drive. Therefore, the backup roller 3 on the arrow L direction side is curved. That is, the curvature of the contact portion on the arrow L direction side is larger than the curvature of the contact portion on the arrow M direction side. Therefore, the contact portion between the heat roller 2 and the backup roller 3 changes from the contact portion J to the contact portion N as shown in FIG.
In this case, the tension on the paper 11 is greater at the end in the direction of arrow L than at the end in the direction of arrow M.

Thereafter, when the sheet 11 to which the unfixed toner image is attached is sent to the heat fixing device 1, the sheet 11 is nipped and conveyed by the heat roller 2 and the backup roller 3. At this time, the unfixed toner image on the paper 11 is melted and fixed on the paper 11 by heat and pressure, and the paper 11 is conveyed while being pulled in the directions of the arrows L and M by the curvature of the backup roller 3. Since the sheet 11 is pulled and conveyed in the directions of the arrows L and M, the linear velocity of the end of the sheet 11 that comes into contact with the backup roller 3 in the direction of the arrow L is the linear velocity of the central part and the end of the side in the arrow M direction. Faster than. Therefore, even if heat is applied and the fibers of the paper are stretched, the paper 11 can be stretched in the directions of the arrows L and M, so that no wrinkles occur.

In the second embodiment, since the bearings 6a and 6b can be driven separately, the tension applied to the paper 11 can be set even if the paper 11 is not uniform in thickness. Therefore, the adaptability of the paper 11 handled by the heat fixing device 1 can be expanded as compared with the first embodiment.

Third Embodiment In the third embodiment, the drive amount of the bearing 6 (the rotation angle of the motor) is determined by a print command. Hereinafter, FIG.
The third embodiment will be described with reference to FIGS. FIG. 10 is a block diagram of the third embodiment.

In the heat fixing apparatus 1 according to the third embodiment, the optimum tension on the paper 11 and the rotation angle of the motor 15 are determined in advance by an experiment or the like, as in the first embodiment. Is stored in a non-volatile memory or the like (not shown).

The control unit 30 shown in FIG.
Controls the overall operation of. The receiving unit 31, the command processing unit 32, and the movable bearing drive circuit 14 are connected to the control unit 30. The receiving unit 31 receives a print command output from the host device 33. The command processing unit 32 is connected to the receiving unit 31, and determines whether the print command input by the receiving unit 32 includes a command related to the thickness of the sheet 11, and outputs a signal to the control unit 30 when it determines that there is a command. . The control unit 30 determines the type of paper based on the command relating to the thickness, retrieves the corresponding rotation angle of the motor 15 from the memory, and outputs the rotation angle to the movable bearing drive circuit 14.

In this embodiment, when the paper 11 is a special paper such as a polycarbonate paper used in the overhead projector, the angle of the bearing 6 is specified in the command.

The movable bearing drive circuit 14 generates a signal for driving the motor 15 by the input rotation angle, as in the above-described embodiment.

The other configuration is the same as that of the first embodiment, and the description is omitted.

Next, the heat fixing device 1 according to the third embodiment will be described.
Will be described with reference to FIG. FIG. 11 is a flowchart according to the third embodiment.

The heat roller 2 is maintained at a predetermined temperature by a heater 2a. In this state, when a command is received from the host device 33, the control unit 30 determines whether or not the received command is a print command (Step S).
1). If it is determined that the command is a print command, the print command is sent to the command processing unit 32 (step S2). The command processing unit 32 adds the paper 11 to the input print command.
It is determined whether there is a command related to the thickness of the sheet (step S).
3) If it is determined that there is, a signal is output to the control unit 30. The control unit 30 determines the type of paper based on the command (step S4).

When the control unit 30 determines that the command is a command indicating thick paper, the control unit 30 calls the rotation angle of the motor 15 corresponding to the thick paper from the memory (step S5). When the paper 11 is thick paper, the amount of expansion when heat is applied is small, so the control unit 30 issues a command to the movable bearing drive circuit 14 so that the rotation angle of the bearing 6 becomes “small”.

If the control unit 30 determines that the command is a command indicating plain paper in step S6, the control unit 30 calls the rotation angle of the motor 15 corresponding to the plain paper from the memory (step S7). When the paper 11 is plain paper, the amount of elongation when heat is applied is moderate, so the control unit 30 issues a command to the movable bearing drive circuit 14 so that the rotation angle of the bearing 6 becomes “medium”.

If it is not plain paper, in step S8, when the control unit 30 determines that the command is a command indicating thin paper, the control unit 30 calls the rotation angle of the motor 15 corresponding to the thin paper from the memory (step S9). When the paper 11 is plain paper,
Since the amount of elongation when heat is applied is large, the control unit 30 controls the movable bearing drive circuit 1 so that the rotation angle of the bearing 6 becomes “large”.
Issue a command to 4.

When the paper 11 is a special paper such as polycarbonate paper used in an overhead projector,
Since the rotation angle of the bearing 6 is specified in the command, the control unit 30 calls the rotation angle of the motor 15 corresponding to the input rotation angle of the bearing 6 from the memory (Step S).
11).

Then, the control unit 30 controls the called motor 1
5 is output to the movable bearing circuit 14, and the movable bearing drive circuit 14 generates a signal based on the input rotation angle and outputs the signal to the motor 15. The subsequent operation is the same as in the first embodiment, and a description thereof will not be repeated.

Thereafter, the heat fixing device 1 proceeds to another command processing (step S10).

If it is determined in step S1 that the command is not a print command, and if it is determined in step S3 that the command is not a thickness command, the process proceeds to step S10, and the control unit 30 performs the processing indicated by the command.

In the third embodiment, the heat fixing device 1 determines the type of the thickness of the sheet 11 by a command relating to the type of the sheet from the host device 33, that is, the motor 1.
Since the rotation angle of No. 5 is determined by a command from the host device 33, the operator does not need to input the type of paper or the tension on the paper from the operation unit or the like. Operator operation is simplified.

Fourth Embodiment In the fourth embodiment, the heat fixing device determines the type of the thickness of the sheet 11 by a thickness detecting mechanism provided in the heat fixing device. Hereinafter, description will be made with reference to FIGS. 1 to 4 and FIGS. 12 to 14. FIG. 12 is a schematic configuration diagram showing an electrophotographic printer including a fixing device according to a fourth embodiment, FIG. 13 is a block diagram of the fourth embodiment, and FIG. 14 is a circuit block diagram of the fourth embodiment. It is.

The electrophotographic printer 40 shown in FIG. 12 has a paper cassette 41 for accommodating the paper 11, a feeding mechanism 42 for feeding the paper 11 from the paper cassette 41, and a thickness of the fed paper 11 from the upstream to the downstream in the transport direction. A sheet thickness detection mechanism 43 for detecting, an entrance sensor 44 for detecting passage of the sheet 11, an image forming apparatus 45, and a fixing device 1 similar to the fixing device shown in the first embodiment are provided.

The sheet thickness detecting mechanism 43 comes into contact with the conveyed sheet 11 in the thickness direction of the sheet 11 (arrows P and Q directions).
A contact roller 46 that freely moves up and down, a magnetoresistive element 47, and a crank 48 that transmits the up and down movement of the contact roller 46 to the magnetoresistive element 47 and rotates the shaft of the magnetoresistive element 47.

The output of the paper thickness detecting mechanism 43 is input to a mechanism control processing section 49 shown in FIG. The mechanism control processing unit 49 converts the output of the sheet thickness detection mechanism 43 from an analog value to a digital value, and converts constants D1 and D2 (D1 <D) described later.
By comparing with 2), the type of the thickness of the paper 11 is detected, and the rotation angle of the motor 15 corresponding to the type of the paper 11 is output to the movable bearing drive circuit.

Here, the mechanism control processing section 49 will be described with reference to FIG.
Will be described.

The mechanism control processing section 49 includes the A / D converter 5
0, an input port to which the output (d) of the A / D converter 50 and the output of the entrance sensor 44 are input, constants D1, D2
And a ROM 52 storing an angle of rotation of the motor 15 and an operation program of the electrophotographic printer 40, an output port 53, and a CPU 54.

The input side of the A / D converter 50 receives a reference voltage (Vref) and an output obtained by dividing the voltage by a magnetic resistor 56 and a fixed resistor 55 incorporated in the magnetoresistive element 47.

The input port 51, the ROM 52 and the output port 53 are connected to the CPU 54 by a bus 57. The CPU 54 controls the overall operation of the electrophotographic printer 40 based on the operation program stored in the ROM 52.

FIG. 15 is an explanatory diagram showing the relationship between the output of the magnetoresistive element and the rotation angle of the paper thickness detecting mechanism according to the fourth embodiment. As shown in FIG. The resistance value (MR) changes in a sine curve as the rotation angle (φ) of the axis of the magnetoresistive element 47 increases.

By the way, the paper 11 is transferred to the paper thickness detecting mechanism 4.
9, the contact rollers 46 by the paper 11
Is small, and the resistance value (MR) and the rotation angle (φ) change in a narrow range R surrounded by a dotted line in FIG. The relationship between the thickness of the sheet 11 and the resistance value (MR) in this range R is approximated by a straight line as shown in FIG. Therefore, the relationship between the thickness of the sheet 11 and the output (d) of the A / D converter 50 also changes linearly, and the constants D1 and D2 are set based on this. FIG. 16 is an explanatory diagram showing the relationship between the output of the magnetoresistive element according to the fourth embodiment and the thickness of the sheet.

Next, the operation of the fourth embodiment will be described with reference to FIG. FIG. 17 is a flowchart of the fourth embodiment.

When a print command is issued from a higher-level device (not shown), the CPU 54 drives the feeding mechanism 42 to cause the paper 11
In the direction of arrow G (step S20). CPU5
4 monitors a change in the output of the entrance sensor 44 (step S21). When the leading end of the sheet 11 passes through the entrance sensor 44 and the output of the entrance sensor 44 changes, the feeding mechanism 42 is stopped (step S22). ).

The CPU 54 reads the output (d) of the A / D converter 50 and compares it with the constants D1 and D2. In step S24, when the CPU 54 determines that the output (d) is smaller than the constant D1, the CPU 54 determines that the sheet 11 is a thick sheet.
The rotation angle of the motor 15 corresponding to the cardboard is called from the ROM 52, and a command is issued to the movable bearing drive circuit 14 so that the rotation angle of the bearing 6 becomes "small" (step S25).

If it is determined in step S24 that the output (d) is equal to or greater than the constant D1, the output (d) is further compared with the constant D2 (step S26). When the CPU 54 determines that the output (d) is equal to or greater than the constant D1 and equal to or less than the constant D2, the CPU 11 determines that the paper 11 is plain paper, calls the rotation angle of the motor 15 corresponding to the plain paper from the ROM 52, and rotates the bearing 6. Movable bearing drive circuit 1 so that the angle is "medium"
4 (step S27).

In step S26, when the CPU 54 determines that the output (d) is larger than the constant D2,
Is determined to be thin paper, the rotation angle of the motor 15 corresponding to the thin paper is called from the ROM 52, and a command is issued to the movable bearing drive circuit 14 so that the rotation angle of the bearing 6 becomes "large" (step S28).

When the operation of step S25 or step S27 or step S28 is completed, the CPU 54 drives the feeding mechanism 42 again and sends the paper 11 to the image forming apparatus 45. After the toner image is attached to the sheet 11 by the image forming apparatus 45, the sheet 11 is sent to the fixing device 1.

The subsequent fixing operation is the same as that of the first embodiment, and the description is omitted.

In the fourth embodiment, the paper thickness detecting mechanism 43 is provided in the electrophotographic printer 40, and the rotation angle of the motor 15 is determined by the output of the paper thickness detecting mechanism 43. As in the first embodiment, the operator does not input the type of paper or the tension on the paper from the operation unit or the like, so that the operator's operation is simpler than in the first embodiment.

By the way, the third and fourth embodiments are described in the second embodiment.
May be applied to the embodiment.

In the first to fourth embodiments, the gears 9 and 10 for rotating the bearing 6 are used as a part of the bending mechanism. The backup roller 3 may be curved by pressing the backup roller 3 in a direction in which the shafts 4a and 4b approach each other.

In the first to fourth embodiments, examples of the heat fixing device applied to the electrophotographic printer have been described.
As the medium heating and transporting device for adjusting the surface state of the material by heating, for example, a banknote sterilizing mechanism or a shaping mechanism provided in an automatic cash dispenser or the like, or an iron or the like used for shaping clothes, the first to fourth above-mentioned. Embodiments are applicable.

[0087]

As described in detail above, the present invention provides
The backup roller is formed to have elasticity and bendable, and a bending mechanism for bending the backup roller is provided so that the contact portion between the backup roller and the heat roller draws a curve. Even if the tension changes, an optimum tension can be applied to various media.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a backup roller provided in a heat fixing device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a backup roller according to the first embodiment.

FIG. 3 is a schematic perspective view illustrating the heat fixing device according to the first embodiment.

FIG. 4 is an explanatory diagram of a contact portion state of the heat roller according to the first embodiment.

FIG. 5 is a block diagram of the first embodiment.

FIG. 6 is a schematic configuration diagram illustrating a heat fixing device according to a modification of the first embodiment.

FIG. 7 is an explanatory diagram of a mechanical model of a shaft of a backup roller according to a modification of the first embodiment.

FIG. 8 is a block diagram of a second embodiment.

FIG. 9 is a diagram illustrating a contact portion state of a heat roller according to a second embodiment.

FIG. 10 is a block diagram of a third embodiment.

FIG. 11 is a flowchart of the third embodiment.

FIG. 12 is a schematic configuration diagram illustrating an electrophotographic printer according to a fourth embodiment.

FIG. 13 is a block diagram of a fourth embodiment.

FIG. 14 is a circuit block diagram according to a fourth embodiment.

FIG. 15 is a diagram illustrating the relationship between the output and the rotation angle of the magnetoresistive element according to the fourth embodiment.

FIG. 16 is a diagram illustrating the relationship between the output of the magnetoresistive element according to the fourth embodiment and the thickness of a sheet.

FIG. 17 is a flowchart of the fourth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 100 Heat fixing apparatus 2, 200 Heat roller 3, 300 Backup roller 6 Bearing 11 Paper 12, 20, 30 Control part 14 Movable bearing drive circuit 15 Motor 40 Electrophotographic printer 43 Paper thickness detection mechanism 49 Mechanism control processing part

Claims (11)

[Claims] 1. A medium heating / conveying apparatus for nipping and conveying a medium while applying heat and pressure by a heat roller and a backup roller pressed against the heat roller, wherein the backup roller is formed to have elasticity and bendable. A medium heating / conveying device, further comprising a bending mechanism for bending a backup roller so that a contact portion between the roller and the heat roller draws a curve. 2. The medium heating / transporting apparatus according to claim 1, wherein the bending mechanism holds both ends of the backup roller and rotates both ends in opposite directions to bend the backup roller. 3. The medium heating and conveying apparatus according to claim 1, wherein the bending mechanism holds both ends of the backup roller and urges both ends in a direction to approach each other to bend the backup roller. 4. The medium heating and transporting device according to claim 2, wherein the bending mechanism curves the backup roller so that a contact portion between the backup roller and the heat roller bends in a direction in which the medium is transported. 5. The medium heating / conveying apparatus according to claim 4, wherein both ends of said backup roller are biased by different forces. 6. A thickness detection mechanism that is provided upstream of the backup roller and the heat roller in the medium conveyance direction and detects a thickness of the medium; and a type of the medium is determined based on a detection result of the thickness detection mechanism. 6. The medium heating and conveying device according to claim 2, further comprising: a drive control unit configured to drive and control the bending mechanism. 7. The medium heating and conveying device according to claim 6, wherein the medium heating and conveying device is a heat fixing device. 8. The medium heating / conveying device is a heating / fixing device, a command determination unit for inputting a print command from a host and determining the content of the command; 6. The medium heating and transporting device according to claim 2, further comprising: a control unit that controls the drive of the bending mechanism according to the type of the medium when the command is determined to be the command to be specified. apparatus. 9. The medium heating and conveying apparatus according to claim 1, wherein a surface of the heat roller has elasticity, and the bending mechanism curves a part of the backup roller in a direction in which the backup roller is pressed against the heat roller. 10. The medium heating and conveying apparatus according to claim 9, wherein the bending mechanism bends the backup roller in a direction away from the heat roller. 11. The medium heating / conveying apparatus according to claim 9, wherein the amount of deflection of the backup roller due to the curvature is set according to a configuration size of the backup roller.