JPH05116404A - Pressure-contacting structure of pinch roller in image forming device - Google Patents

Abstract

PURPOSE:To provide pressure-contacting structure of a pinch roller in an image forming device which can prevent defective image forming to be caused by a hollow, by preventing that the hollow of a press mark is generated in the surface of a platen roller by pressure-contacting of the pinch roller. CONSTITUTION:A head operation Cam 41 and roller pressure-contacting cam 42 are fixed to a cam shaft 43, a thermal transfer head 50 is rocked and operated by the head operation cam 41 and a pinch roller 22 is provided on a guide arm 20 connected with an operation arm 33, which is rocked and operated by the roller pressure-contacting cam 42, through a spring 32. The title structure is constituted so that pressure-contacting force of the pinch roller 22 to a platen roller 34 is varied by interlocking with a movement of the thermal transfer head 50 and the pressure-contacting force of the pinch roller 22 to the platen roller 34 is mitigated when recording paper is carried and driven so that the same is allowed to held by a clamper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus in which a recording paper is held by a movable recording paper holding means and one-way scanning for forming an image on the recording paper is performed by the movement. The present invention relates to a pinch roller pressure contact structure in which a pinch roller is arranged in pressure contact with a platen roller, and the recording paper is nipped between the platen roller and the pinch roller by rotation to convey and drive the recording paper to a holding position by a recording paper holding means.

[0002]

2. Description of the Related Art As one of recording (image forming) systems in image forming apparatuses such as copiers, printers, and facsimiles, a recording head movable in the width direction of the recording paper or the entire width direction of the recording paper is provided. There is a recording head in which recording elements are arranged, and an image is formed while moving the recording paper in the moving direction of the recording head or in the direction orthogonal to the element arrangement direction. That is, the main scanning is performed by the recording head or the like, and the sub scanning is performed by moving the recording paper. As a moving / conveying structure of the recording paper in the image forming apparatus for performing sub-scanning by moving the recording paper, a holding means (clamper) capable of holding the leading end of the recording paper is provided so as to be movable in the scanning direction of the recording paper. There is a configuration in which the recording paper is moved and driven by holding and moving the front end of the recording paper with the clamper. Since this configuration can accurately manage the movement of the recording paper at the time of image formation, it is often used especially in a color image forming apparatus that needs to form an image a plurality of times on the same recording paper. ..

A platen roller whose surface is made of a material having a predetermined elasticity such as rubber is arranged opposite to the recording head so that the recording paper can be pressed against the recording head with a uniform pressing force. The recording paper, which is held by the platen roller and moved and driven (sub-scanning) by the platen roller, is brought into pressure contact with and in close contact with the platen roller, and the recording head is configured so as to be movable in and out of contact with the platen roller. When holding the recording paper, the recording head can be separated from the platen roller. In addition, the platen roller is configured to be rotatable and a pinch roller is arranged in pressure contact, and the pinch roller presses the recording paper against the platen roller and rotationally drives the platen roller, so that the recording paper is clamped by the clamper. It can be transported to the holding position.

[0004]

However, in the conventional structure as described above, the pinch roller continues to be pressed against the same position on the outer periphery of the platen roller when the platen roller is stopped, and as a result, the surface of the platen roller is The elastic body is dented by the pinch roller pushing mark. The depression gradually returns to its original state when the pressure of the pinch roller is released. However, until the depression is returned after the image formation is started, the pressing force of the recording paper to the recording head is reduced by the platen roller. There is a problem that unevenness occurs in the circumferential direction (sub-scanning direction) (the pressing force decreases when the recessed portion is located at a position facing the recording head), which causes defective image formation.

[0005]

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to prevent a press mark from being formed on the surface of a platen roller due to the pressure contact of a pinch roller, to prevent defective image formation due to the recess, and to provide a high quality image. An object is to provide a pressure contact structure of a pinch roller in an image forming apparatus capable of forming an image.

[0006]

In order to achieve the above object, the pinch roller pressure contact structure in the image forming apparatus according to the present invention is as follows.
A pinch roller is arranged in pressure contact with the platen roller, and the recording paper is nipped between the platen roller and the pinch roller by the rotation of the platen roller to be driven to the holding position of the recording paper holding means, and the recording paper is held by the recording paper holding means. An image forming apparatus that scans and moves between a platen roller and a recording head pressed against the platen roller by the movement of the recording paper holding means to form an image, wherein the recording head is provided on a rotary shaft. One cam member is supported by a head support member that is rockably operated, and the head support member is rocked by the rotation of a cam to move between an image forming operation position close to the platen roller and a retracted position separated from the platen roller. It is movable and the recording head is separated from the platen roller at least when the recording paper is conveyed and driven to the holding position of the recording paper holding means. In the configuration, the pinch roller is provided with a variable pressure contact force with respect to the platen roller by swinging the arm member via the arm member swingably driven by the second cam member provided on the rotating shaft. The pressure contact force is reduced in association with the movement of the recording head except when driving the recording paper holding means. According to this configuration, the pressure contact force of the pinch roller with respect to the platen roller is reduced except when the recording paper requiring the pressure contact force of the pinch roller with the platen roller is driven to the holding position by the recording paper holding means. The dents of the push marks of the pinch roller do not occur on the elastic body on the surface of the platen roller.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram corresponding to a longitudinal section of an image forming apparatus to which an embodiment of a pinch roller pressure contact structure in an image forming apparatus according to the present invention is applied. The illustrated image forming apparatus 1 is a so-called color image forming apparatus, and a plurality of times (magenta, cyan, yellow, black of magenta, cyan, yellow, and black are printed on the same recording paper based on image information separated into three colors of red, blue, and green. A color image is formed by performing image formation four times). The illustrated apparatus 1 is provided with a paper feed section 10 to which a recording paper cassette 2 accommodating recording papers 4 ... Can be attached and detached at the lower part of one end (the left end in the figure), and is ejected above the paper feed section 10. A paper tray 3 is provided, and the recording paper 4 accommodated in the recording paper cassette 2 is introduced from the paper feed unit 10, conveyed to the end side opposite to the paper feed unit 10, and inverted to the upper side. The sublimation dye of the ink ribbon 63 is transferred by a thermal transfer head 50, which will be described later, to form an image, and the image is discharged onto the paper discharge tray 3.

The paper feed section 10 is provided with an opening into which the recording paper cassette 2 can be inserted, and the recording paper is introduced above the front end of the recording paper cassette 2 inserted into the opening. A roller 11 is provided, and at a position adjacent to the front end of the recording paper cassette 2, an introducing roller pair 12 in which the rollers are arranged in pressure contact with each other is provided. A conveyance roller pair 31 in which the rollers are arranged in pressure contact with each other is provided in front of the introduction roller pair 12 in the conveyance direction of the recording paper (on the right side in the drawing). The guide arm 20 having the guide portion 21 of the
It is pivotally supported by 3 and is approximately above it,
A platen roller 34 is provided. The outer peripheral surface of the platen roller 34 is formed of an elastic member having a predetermined elasticity such as rubber, and is driven in both forward and reverse directions (clockwise and counterclockwise in the figure) by a drive motor (not shown).
In addition to being rotationally drivable, a friction clutch that idles at a torque of a predetermined value or more is interposed in the rotational driving force transmission path.

The lower end of the guide arm 20 is connected via a spring 32 to the lower end of an operation arm 33 as an arm member which is swingably provided by a pin 14 on the right side of the drawing, and the elasticity of the spring 32 is provided. By the restoring force, the guide arm 20 is oscillated and urged counterclockwise in the figure, and the operation arm 33 is urged in the clockwise direction in the figure. A pinch roller 22 is rotatably provided at the upper end of the guide arm 20, and the pinch roller 22 is pressed against the platen roller 34 in the horizontal direction by the urging force of a spring 32, whereby the guide arm 20 swings. Is regulated to be in a substantially vertical state, and the lower end of the guide portion 21 is positioned in the conveyance path of the recording paper conveyed by the conveyance roller pair 31.

A cam follower 33A is rotatably provided at the upper end of the operation arm 33, and the spring 3
By the urging force of 2, the cam follower 33A abuts on the outer peripheral cam surface of the roller pressure contact cam 42 as the second cam member fixed to the cam shaft 43 provided at the right end portion of the device 1 in the drawing, thereby operating. The swing of the arm 33 is restricted. That is, the elastic return force of the spring 32 urges the pinch roller 22 provided at the upper end of the guide arm 20 to the platen roller 34 and the cam follower 33 A of the operation arm 33 to the roller pressure contact cam 42. The roller pressure contact cam 4
The cam follower 33A is attached to the displacement of the cam surface due to the rotation of 2.
The amount of deformation of the spring 32 changes due to the swinging of the operation arm 33 due to the following, and as a result, the pressure contact force of the pinch roller 22 to the platen roller 34 changes.

The roller pressing cam 42 has a large-diameter portion and a small-diameter portion formed in a predetermined angle range as shown in enlarged views of the relevant portion in FIGS. 2 to 4, and is operated when the cam follower 33A corresponds to the large-diameter portion. The arm 33 swings counterclockwise and the amount of deformation of the spring 32 increases, and the pressure contact force of the pinch roller 22 to the platen roller 34 increases. On the other hand, when the cam follower 33A corresponds to the small diameter portion, the pinch roller 22
The contact pressure of the platen roller 34 with the platen roller 34 is weakened. As a result, the pressure contact force of the pinch roller 22 to the platen roller 34 can be changed into two levels, strong and weak, by the rotation of the roller pressure contact cam 42 (that is, the rotation of the cam shaft 43). The cam shaft 43 is rotationally driven by a motor (not shown), and the motor is drive-controlled by the control device of the image forming apparatus in synchronization with image formation.

A recording paper guide plate 3 for supporting the recording paper to be conveyed is provided between the introducing roller pair 12 and the conveying roller pair 31, and between the conveying roller pair 31 and the guide arm 20.
5 are arranged, and the upper side of each of them and the recording paper introducing roller 1
1 above the recording paper support plate 3 in parallel with each other at a predetermined distance.
6 are provided. Guide part 2 of the guide arm 20
A recording paper withdrawal restricting member 37 formed of an elastic member is attached to an end of the recording paper support plate 36 facing the recording paper supporting plate 1, and the recording paper withdrawal restricting member 37 is directed obliquely upward toward the guide portion 21. , Its tip is provided in contact with the guide portion 21.

Above the platen roller 34, there is provided a thermal transfer head 50 as a recording head in which a thermal head array 51 extending in the width direction of the recording paper is supported by a head frame 52 as a head supporting member. The thermal transfer head 50 is pivotally supported on a chassis (not shown) of the apparatus 1 so as to be swingable by a pivot shaft 53 at substantially the center of the head frame 52, and is urged to rotate clockwise in the figure by a spring (not shown). .. A roller-like cam follower 54 is rotatably attached to the end opposite to the thermal head array 51 with the pivot shaft 53 interposed therebetween.
4 contacts the outer peripheral cam surface of the head operating cam 41 as a first cam member fixed to the same cam shaft 43 to which the roller pressure contact cam 42 described above is fixed, and the head operating cam 41
The rotation operation of the outer peripheral cam surface due to the rotation (i.e., the rotation of the cam shaft 43) is followed to perform the rocking operation.

As shown in FIGS. 2 to 4, the head operating cam 41 is formed as an outer diameter (outer peripheral cam surface) whose radii differ in three steps within a predetermined angle range. As shown in FIG. 4, the cam follower 54 is the most. In a state corresponding to the large-diameter cam surface, the thermal head array 51 faces the upper side of the platen roller 34 and becomes a transfer operation position where the thermal head array 51 is brought into pressure contact with a predetermined pressing force,
As shown in FIG. 3, the thermal head array 51 is positioned slightly above the platen roller 34 in a state corresponding to the second-stage medium-diameter cam surface, and the thermal head array 51 is spaced from the outer periphery of the platen roller 34 and the thermal head array 51. 2, the thermal transfer head 50 swings largely clockwise and the thermal head array 51 largely separates from the platen roller 34 in the state corresponding to the smallest diameter cam surface as shown in FIG. It is supposed to be.

Here, the relationship between the cam surface displacement of the head operation cam 41 and the roller pressure contact cam 42 with which the cam follower of the operation arm 33 comes into contact (that is, the position of the thermal transfer head 50 and the pressure contact of the pinch roller 22 with the platen roller 34). The relationship of the force change) is substantially the pressure contact force of the pinch roller 22 to the platen roller 34 when the thermal transfer head 50 is in the transfer action position and in the retracted position (the state shown in FIGS. 2 and 4). Is weak, and the pressure contact force of the pinch roller 22 to the platen roller 34 is set to be strong when the thermal transfer head 50 is at the sheet feeding position (in the state shown in FIG. 3).
In the standby state shown in FIG. 1, the thermal transfer head 50 is in the retracted position, and the pinch roller 22 is the platen roller 34.
The pinch roller 22 is not pressed by the platen roller 34 in the standby state.

An ink ribbon reel 61 on the delivery side is arranged below the thermal transfer head 50, and is rotationally driven by a motor (not shown) at a position substantially symmetrical to the ink ribbon reel 61 on the delivery side with the platen roller 34 interposed therebetween. The ink ribbon reel 62 on the take-up side is arranged. The ink ribbon reel 61 on the delivery side is wound with an ink ribbon 63 in which ribbons of each color to be transferred are sequentially connected by one page (one sheet) of recording paper, and the ink ribbon 63 on the take-up side is wound. It is adapted to be wound up on the ink ribbon reel 62. Thermal transfer head 5
At the time of image formation in which 0 is at the transfer operation position, the ink ribbon 63 overlaps the recording paper and is sandwiched between the platen roller 34 and the thermal head array 51 (the recording paper is on the platen roller 34 side, It is sandwiched between the thermal head array 51 side) and the recording paper, and is taken up from the sending side ink ribbon reel 61 to the take-up side ink ribbon reel 62 in synchronization with the movement of the recording paper.

Platen roller 34 and thermal transfer head 50
On the left side in the figure, a clamper 70 is slidably movable by a pair of left and right widthwise guide shafts 90 supported by a chassis (not shown) of the apparatus 1 and horizontally arranged in the front-rear direction. The clamper 70 is configured to include a holding roller pair 80 in which a metal upper roller 82 is arranged in pressure contact by a spring (not shown) on the upper side of a rotatable lower roller 81 having a rubber layer of a predetermined thickness formed on the surface thereof. ing. The clamper 70 is driven to move by a driving unit (not shown) and can move left and right along the guide shaft 90 in the figure, and has a sheet feeding position located at the right end in the figure adjacent to the platen roller 34 and the thermal transfer head 50. , And can be located at the discharge position at the left end in the figure.

Clamper drive gears (not shown), which are rotationally driven by drive means, are arranged at the portions corresponding to the front and rear ends (paper feed position and paper discharge position) of the stroke of the clamper 70 along the guide shaft 90. A gear (not shown) connected to the lower roller 81 of the clamper 70 meshes with the clamper drive gear at the paper feed position and the paper discharge position, and the lower roller 81 rotates counterclockwise in the figure by the rotation of the clamper drive gear. It is designed to be driven to rotate. That is, when the clamper 70 is located at the sheet feeding position and the sheet discharging position, the lower roller 81 can be driven to rotate. Also, on the left side of the clamper 70 at the paper discharge position in the drawing,
A paper discharge roller pair 38 in which rollers are arranged in pressure contact with each other is provided.

Thus, the image forming apparatus constructed as described above operates as follows to form an image. First, from the standby state shown in FIG. 1, the head operating cam 41 and the roller pressure contact cam 42 are rotated by the rotation of the cam shaft 43, so that the thermal transfer head 50 is slightly moved from the thermal transfer position of the thermal head array 51 as shown in FIG. The pinch roller 22 is set to the sheet feeding position located above and the platen roller 34
The recording paper 4 housed in the recording paper cassette 2 is introduced into the apparatus 1 by the driving of the recording paper introducing roller 11, and is conveyed by driving the introducing roller pair 12 and the conveying roller pair 31. .. At this time, the clamper 7
0 is the sheet feeding position closest to the thermal transfer head 50 in the moving stroke.

The leading edge of the recording paper 4 is a guide arm 20.
Is guided by the circular arc-shaped guide portion 21 and deforms the recording paper retreat restricting member 37 while being bent and conveyed upward, and is caught between the platen roller 34 and the pinch roller 22.
The platen roller 34 is driven to rotate counterclockwise in the figure, and is conveyed, and is guided by the thermal transfer head 50 toward the pressure contact portion of the upper and lower rollers 81 and 82 of the holding roller pair 80 of the clamper 70 at the sheet feeding position. At this time, the pinch roller 22 presses the recording paper 4 against the platen roller 34 with a large force, so that reliable conveyance driving can be performed. The leading end of the recording paper 4 has a pair of support rollers 8 of the clamper 70.
When the pressure contact portion of the upper and lower rollers 81 and 82 of 0 is reached, the lower roller 81 is rotationally driven counterclockwise in the drawing to engage the recording paper 4 between the pair of support rollers 80, and a predetermined amount of engagement is achieved. Then, the rotation drive of the lower roller 81 is stopped. As a result, the leading edge of the recording paper 4 is held by the support roller pair 80 of the clamper 70 (FIG. 6).

After that, the thermal transfer head 50 is moved to the transfer operating position by the rotation of the head operation cam 41, and the pressure contact force of the pinch roller 22 to the platen roller 34 is weakened, and the clamper 70 is moved to the left side in the drawing. Then, the recording paper 4 is driven to move, the ink ribbon 63 is wound in synchronization with the movement of the recording paper 4, and an image is formed (transferred) on the recording paper 4 by the thermal head array 51 (FIG. 7). .. At this time, the platen roller 34 is not rotationally driven but is rotated following the movement of the recording paper by the action of the friction clutch provided in the drive system described above.
Since the pressure contact force of the pinch roller 22 to the platen roller 34 is weak, the platen roller 34 does not hinder the movement of the recording paper.

Since this embodiment is a color image forming apparatus, this transfer process is carried out four times for magenta, cyan, yellow and black as described above. That is, after the first transfer process is completed, the clamper 70 is returned to the paper feeding position (the recording paper 4), and then the clamper 70 is driven to the left side in the drawing (the recording paper 4 is driven to move). ) The next transfer process is performed, and thereafter, this process is repeated a predetermined number of times. When the clamper 70 is returned to the paper feed position, the thermal transfer head 50 is set to the paper feed position, and the platen roller 34 rotates in the opposite direction (clockwise direction in the figure) to the case where the clamper 70 holds the recording paper. Driven. Further, the trailing end of the recording paper 4 is changed by the recording paper retreat restricting member 37 to reach the recording paper support plate 36 as shown in FIG. 8 and does not return to the paper feed section 10 side.

The clamper 70 is at the paper discharge position in a state where the transfer process of a predetermined number of times is completed (transfer of all colors is completed),
Here, the lower roller 81 of the clamper 70 is rotated counterclockwise in the drawing to convey the recording paper 4 held by the holding roller pair 80 to the paper discharge side (left side in the drawing) as shown in FIG. Is. The recording paper 4 sent from the clamper 70 is conveyed by the paper discharge roller pair 38 and discharged onto the paper discharge tray 3.

[0024]

As described above, according to the pressure contact structure of the pinch roller in the image forming apparatus according to the present invention, the pinch roller is pressed against the recording paper holding means in association with the recording head which moves according to the operating state. The pressure contact force of the pinch roller to the platen roller is reduced except when the conveyance drive is performed, and it is possible to prevent the depression of the pinch roller pushing trace from being generated on the surface of the platen roller. Occurrence can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram corresponding to a longitudinal section of a standby state of an image forming apparatus to which an embodiment of a pinch roller pressure contact structure in an image forming apparatus according to the present invention is applied.

FIG. 2 is an enlarged view of a main part in which a thermal transfer head is in a retracted position.

FIG. 3 is an enlarged view of a main part in which a thermal transfer head is at a sheet feeding position.

FIG. 4 is an enlarged view of a main part in which a thermal transfer head is at a transfer position.

FIG. 5 is an explanatory diagram of an operation during image formation.

FIG. 6 is an explanatory diagram of an operation during image formation.

FIG. 7 is an explanatory diagram of an operation during image formation.

FIG. 8 is an explanatory diagram of an operation during image formation.

FIG. 9 is an explanatory diagram of an operation during image formation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 4 ... Recording paper 22 ... Pinch roller 33 ... Operation arm (arm member) 34 ... Platen roller 41 ... Head operation cam (first cam member) 42 ... Roller pressure contact cam (second cam member) 43 ... Cam Shaft (rotating shaft) 50 ... Thermal transfer head (recording head) 51 ... Thermal head array 52 ... Head frame (head support member) 70 ... Clamper (recording paper holding means)

Claims (1)

[Claims] 1. A pinch roller is arranged in pressure contact with a platen roller, the recording paper is nipped between the platen roller and the pinch roller and driven to a holding position of a recording paper holding means, and the recording paper is also moved. An image forming apparatus for performing image formation by carrying out scanning movement between a platen roller and a recording head pressed against the platen roller by holding the recording paper holding means and moving the recording paper holding means. Is supported by a head support member that is rockably operated by a first cam member provided on the rotary shaft,
By swinging the head support member by the rotation of the cam, the head supporting member is movable between an image forming operation position close to the platen roller and a retracted position separated from the platen roller, and at least a recording paper is held. When the recording head is separated from the platen roller when it is conveyed and driven to the holding position of the means, the pinch roller is oscillated by a second cam member provided on the rotating shaft. The pressure contact force with respect to the platen roller is variably provided by swinging the arm member via the arm member, and the pressure contact force is reduced in association with the movement of the recording head except when the recording sheet holding means is driven to be conveyed. The pinch roller pressure contact structure in an image forming apparatus, characterized in that