JPH05531A - Image forming device - Google Patents

Abstract

PURPOSE:To record beautifully additional information in density which is always easy to be seen by cooling a thermal head by a method wherein temperature of the thermal head is detected and when said temperature reaches not less than stop temperature which has been preliminarily determined, operation of a second image recording means including the thermal head is temporarily stopped. CONSTITUTION:When additional information is recorded, the temperature of a thermal head 39 is detected. Where the temperature of the thermal head has risen excessively by continuous use, the operation of an additional information recording mechanism 8 is prohibited. That is, where temperature (t) to be detected with a thermistor 84 exceeds, for example, 50 deg.C by increase in temperature inside a copying machine, continuous use, etc., the operation of the additional information recording mechanism 8 is temporality stopped until its temperature (t) falls to 48 deg.C or lower. It never happens thereby that a thermal transfer ribbon 37 is accidentally heated with the thermal head 39 of which the temperature is high and paper is stained.

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 such as an electrophotographic copying machine, a laser beam printer and a facsimile machine, and more particularly to a desired character or mark on a sheet on which an original image is formed by electrophotography. The present invention relates to an image forming apparatus having an additional information recording mechanism for recording additional information by thermal transfer.

[0002]

2. Description of the Related Art Conventionally, in addition to a so-called electrophotographic image forming function of developing an electrostatic latent image formed on the surface of a photosensitive member into a toner image and then transferring it to a sheet, a thermal head and a thermal transfer ribbon are provided. There has been proposed an image forming apparatus having an additional information recording function for recording additional information such as the number of pages and the date on the above-mentioned paper (for example, JP-A-59-774).
59, JP-A-60-258575 or JP-A-61-53665).

[0003]

However, in the above-mentioned conventional image forming apparatus, the paper on which the image is formed by the electrophotographic method is heated and pressed to fix the toner image on the paper. Therefore, the heated paper for fixing and the heated paper are supplied to the additional information recording means. For this reason, particularly when performing image formation by electrophotography and recording additional information by the additional information recording mechanism continuously on a plurality of sheets, the thermal head of the additional information recording mechanism generates heat for additional information recording. However, there was a case where it was heated by the heat of the paper. As a result, there is a problem in that the thermal transfer ribbon is erroneously heated and the paper is soiled, and when the additional information is recorded, bleeding or flow occurs in the recorded content.

Further, the thermal head has a problem that if it is heated to a high temperature for a long time, its deterioration is accelerated and its life is shortened. The present invention has been made in view of the above circumstances, and provides an image forming apparatus capable of properly operating the additional information recording mechanism and recording the additional information neatly at a density that is always easy to see. It is an object.

[0005]

According to the present invention, a first image recording means for forming an image by an electrophotographic system and recording the image on a sheet, and an image recorded by the first image recording means. A second image recording unit for recording an additional image on the sheet, the second image recording unit including a thermal transfer ribbon containing ink and the thermal transfer ribbon being in contact with the thermal transfer ribbon; In an image forming apparatus including a thermal head that selectively heats and transfers the ink of a heated portion onto a sheet, a temperature detection unit for detecting the temperature of the thermal head and a detection temperature of the temperature detection unit are set in advance. The protective means is provided for stopping the operation of the second image recording means when the temperature becomes equal to or higher than a predetermined stop temperature.

In the image forming apparatus of the present invention, the temperature detecting means includes a thermistor built in the thermal head. Furthermore, the invention is characterized in that, in the image forming apparatus, the temperature detecting means includes a temperature detecting means for detecting an ambient temperature around the thermal head.

According to the present invention, in the image forming apparatus, the temperature detected by the temperature detecting means is preset to be lower than the stop temperature after the operation of the second image recording means is stopped by the protecting means. It is characterized in that it includes an activation means for bringing the second image recording means into an operable state when the temperature becomes equal to or lower than the operation restart temperature.

Further, in the present invention, in the image forming apparatus, the second image recording means is made operable after a lapse of a predetermined time after the operation of the second image recording means is stopped by the protection means. It is characterized in that it includes an activating means for operating.

[0009]

In the image forming apparatus according to the present invention, the temperature of the thermal head is detected by the temperature detecting means,
When the detected temperature exceeds the predetermined stop temperature, the operation of the second image recording means including the thermal head is temporarily stopped by the protection means. The thermal head is cooled by this stop processing. The temperature detecting means for detecting the temperature of the thermal head may be a thermistor built in the thermal head or a temperature sensor for detecting the ambient temperature around the thermal head.

The operation of the second image recording means may be restarted when the temperature detected by the temperature detecting means becomes equal to or lower than a predetermined temperature, or after the stop time has passed a certain time.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An electrophotographic copying machine will be described in detail below as an embodiment of the present invention. Figure 1
FIG. 1 is a schematic sectional view showing an overall configuration of an electrophotographic copying machine according to an embodiment of the present invention. This copying machine includes a contact glass 2 for placing a document on the upper surface of a main body case 1.
Is provided. Inside the main body case 1, the optical system 3, the image processing unit 4, the paper feed path 5, the paper transport path 6, the fixing device 7,
An additional information recording mechanism 8 and a punching mechanism 9 are provided.

The optical system 3 illuminates and scans a document (not shown) set on the contact glass 2 and guides the reflected light to the image processing section 4, as indicated by the one-dot chain line in the figure,
This is for forming a document image on the photosensitive drum 10 provided in the image processing section 4. The image processing unit 4 is for reproducing an original image by an electrophotographic method. Specifically, after the surface of the photosensitive drum 10 is uniformly charged by the charging charger 11, the drum surface is exposed by the reflected light of the document guided by the optical system 3, and the electrostatic latent image corresponding to the document image is exposed. Is formed. Then, the electrostatic latent image is visualized as a toner image by the developing device 12, the toner image is transferred onto the surface of the paper by the transfer charger 13, and the paper on which the toner image is transferred by the separation charger 14 is transferred from the photosensitive drum 10. It is peeled off.

The paper feed path 5 is a mechanism for supplying a paper for transferring a toner image to the photosensitive drum 10.
The sheet feeding path 5 takes in sheets one by one from a sheet feeding cassette 15 or 16 or a stacking bypass 17 which is detachably attached to a predetermined position of the main body case 1, and is fixed in synchronization with the image processing operation in the image processing section 4. The paper is supplied to the photoconductor drum 10 at the timing and the speed.

The paper transport path 6 is for transporting the paper, on which the toner image separated from the photosensitive drum 10 is transferred, to the fixing device 7. The fixing device 7 includes a fixing roller 18
The fixing roller 18 fixes the toner image on the paper by pressing or heating the paper.

The additional information recording mechanism 8 arranged on the downstream side of the fixing device 7 with respect to the sheet conveying direction is for recording additional information on the copied sheet on which the toner image is fixed. The punching mechanism 9 is for forming punched holes in the sheet discharged to the discharge tray 20 by the discharge roller 19.

FIG. 2 is a sectional view of the punching mechanism 9. Figure 2
Referring to, the punching mechanism 9 has a holder 21 and a punch blade 22 vertically movably held by the holder 21.
A coil spring 23 for holding the punch blade 22 in a raised position, and a punch die 24 which also serves as a lower guide plate for the paper transport path.
And a cam 25 for displacing the punch blade 22 downward.

The holder 21 includes an upper horizontal frame 26 and an upper horizontal frame 2.
Vertical frame 27 and vertical frame 27 extending downward from one end of 6
And a lower horizontal frame 28 that extends horizontally from the lower end of the. Holes are formed in the upper horizontal frame 26 and the lower horizontal frame 28, and the punch blade 22 is inserted into the holes. The punch blade 22 is formed of a columnar body, and a blade 29 is provided at the lower end thereof.

The punch blade 22 is provided with a collar 30. When the punch blade 22 moves upward, the brim 30 is in contact with the lower surface of the upper horizontal frame 29 to prevent the punch blade 22 from moving further upward. On the other hand, a bush 31 is formed in the lower horizontal frame 28 around the hole so as to surround the punch blade 22. And
A coil spring 23 is fitted between the bush 31 and the collar 30 of the punch blade 22. The coil spring 23 is fitted so as to surround the punch blade 22. Therefore, the punch blade 22 has an upper horizontal frame 26 and a lower horizontal frame 28.
Is held so as to be movable up and down by the coil spring 23 and is always held at the highest position by the coil spring 23.

The punch die 24 has a hole 32 through which the punch blade 22 can enter at a position corresponding to the punch blade 22.
Are formed. In addition, the punch die 24 and the lower horizontal frame 2
8 are opposed to each other at a predetermined interval, and the punch die 24 and the lower horizontal frame 28 form a sheet passage. The holder 21 and the punch die 24 are attached to the unit material 33.

On the other hand, a rotating shaft 34 is provided in a mounting member (for example, a frame fixed to the main body case 1 or the like, not shown) different from the unit material 33, and the cam 25 is rotated by the rotating shaft 34. It is eccentrically fixed to the shaft 34.
When the rotary shaft 34 is rotated and the cam 25 rotates approximately 180 degrees from the illustrated state, the peripheral surface of the cam 25 contacts the upper surface of the punch blade 22 and pushes the punch blade 22 downward. The lower end of the punch blade 22 is a punch die 24.
It goes down to the position where it enters into the hole 32 of the. As a result, when there is a sheet in the sheet path, punch holes are formed in the sheet.

FIG. 3 is a perspective view of the additional information recording mechanism 8. Referring to FIG. 3, the additional information recording mechanism 8 has a casing 35 and a ribbon cassette 36 detachably attached to the casing 35. A ribbon-shaped thermal transfer ribbon 37 is housed inside the ribbon cassette 36. The additional information recording mechanism 8 further includes a casing 35.
A support member 38 rotatably attached to the
8 and a thermal head moving mechanism 40 that pushes the thermal head 39 toward a platen roller (to be described later) that is arranged opposite to the thermal head 39 across the paper path.

The casing 35 is a box body 4 having an open upper surface.
1 and side plates 42a, 42 fixed to both ends of the box 41
It consists of b and. Both of the side plates 42a and 42b have a substantially triangular shape, and support shafts 43a and 43b (43b not shown in FIG. 3) protruding outward are provided at the lower ends of the side plates 42a and 42b. And, these support shafts 43a, 4
The casing 35 is attached to the main body case 1 of the copying machine or a frame (not shown) fixed to the main body case 1 by 3b.

The ribbon cassette 36 includes a body 45 and a delivery reel 46 rotatably attached to the body 45.
And the take-up reel 47, and the thermal transfer ribbon 37 sent from the delivery reel 46 is taken up by the take-up reel 47. The body 45 has an opening 48 located between the reels 46 and 47. In addition, the bottom plate 4 of the box 41
An opening 50 is formed at 9 to match the opening 48.

Inside the box 41, the ribbon cassette 36 is
A drive device 51 for driving the take-up reel 47 to wind the thermal transfer ribbon 37 is provided. The drive device 51 includes a motor 52 and a torque limiter mechanism 53 that transmits the rotational force of the motor 52 to the take-up reel 47. A lock member 54 for locking the attached state of the ribbon cassette 36 is provided in the box 41. The lock member 54 includes a shaft 55 that is planted on the bottom plate 49.
And an L-shaped member 56 rotatable about a shaft 55. By bringing the end portion 57 of the L-shaped member 56 into contact with the body 45 of the ribbon cassette 36, the ribbon cassette 36 can be held at a predetermined position.
6 is prevented from falling out of the box 41.

The thermal head 39 has a large number of minute heating elements 391, 39 as shown in an enlarged view surrounded by the circle.
2, ... are provided. During recording, the heating element corresponding to the pattern of additional information is selectively energized to melt the portion of the thermal transfer ribbon 37 that contacts the heating element, and the melted ink is transferred to the paper. In the thermal head 39,
As a temperature sensor for measuring the temperature of the thermal head 39, for example, a thermistor (not shown) is incorporated.

The support member 38 includes a support shaft 58 having one end attached to the side plate 42a and the other end attached to the side plate 42b, and the plate 5.
9 and 9 are included. The thermal head 39 is attached to the upper portion of the plate 59, and the lower end portion of the plate 59 is attached to the central portion of the support shaft 58. FIG. 4 shows a mounting structure of the plate 59 and the support shaft 58. Referring to FIG. 4, a pair of elongated holes 60a and 60b extending in a direction orthogonal to the axis of support shaft 58 are formed at the lower end of plate 59. Further, the support shaft 58 has screw holes 61a, 61b.
(61b is not shown in FIG. 4B) is formed. Then, the screw holes 61
Screws 62a and 62b are screwed into a and 61b.

Therefore, the position of the thermal head 39 mounted on the upper portion of the plate 59 is adjusted by loosening the two screws 62a and 62b and shifting the plate 59 in the direction orthogonal to the axis of the support shaft 58. You can Referring back to FIG. 3, the thermal head moving mechanism 40 includes a shaft 63, a cam 64, a coil spring 65, leaf springs 66 and 67, and a coil spring 68.

Although not shown, both ends of the shaft 63 are directly or indirectly supported by the copying machine main body case 1. A long hole 69 is formed in the cam 64, and the shaft 63 passes through the long hole 69. Further, a coil spring 65 is arranged in the space left over from the long hole 69. Cam 6
4 is rotated by the action of the coil spring 65 while being eccentric from the rotation center of the shaft 63. It should be noted that, for example, the shaft 63 is
A portion of the cam 64 that penetrates the long hole 69 is processed into a square section or the like.

One end 70 of the leaf spring 66 is attached to the support shaft 58. The leaf spring 66 extends in a direction orthogonal to the axial direction of the support shaft 58, and the other end (tip) 71 of the leaf spring 66 contacts the bottom plate 49 of the box 41 when the support shaft 58 rotates. It is supposed to touch. One end 72 of the leaf spring 67 is attached to the support shaft 58, extends in a direction orthogonal to the axial direction of the support shaft 58, and is in contact with the peripheral surface of the cam 64.

The coil spring 68 has one end fitted to the plate 59, and constantly pulls the plate 59 in a direction away from the bottom plate 49 of the box 41. 5, 6 and 7 are sectional views showing the positional relationship between the additional information recording mechanism 8 and the punching mechanism 9. In particular, FIG. 5 shows the additional information recording mechanism 8 in the standby state, and FIG. 6 shows the additional information recording mechanism 8 in the operating state. Also,
FIG. 7 shows that the punching mechanism 9 is opened for maintenance and the like.
FIG. 8 is a cross-sectional view showing a state in which the thermal transfer ribbon 37 of the additional information recording mechanism 8 can be replaced.

Referring to FIGS. 5, 6 and 7, a fixing discharge roller 74 is arranged at the outlet of the fixing device 7,
A fixing completion detection switch 75 is provided on the downstream side of the fixing device 7 with respect to the sheet conveying direction. When the leading edge of the paper is ejected from the fixing ejection roller 74, the detection switch 75 changes from the solid line state shown in the figure to a tilted ON state, and the trailing edge of the paper has finished passing over the detection switch 75. It is a switch that is instantly returned to the solid line state and turned off. Therefore, the fixing completion detection switch 7
The trailing edge of the paper can be detected by detecting the switching edge of the switch 5 from ON to OFF.

An additional information recording mechanism 8 and a perforation mechanism 9 are sequentially provided in the passage of the sheet discharged from the fixing discharge roller 74. In the state where the additional information is not recorded, as shown in FIG. 5, the coil spring 65 is located on the upper right side of the shaft 63, and no pressing force is generated between the cam 64 and the leaf spring 67. .. Therefore, the support member 38 is
The tensile force of the coil spring 68 and the elastic force of the plate spring 66 urge the clockwise direction to urge the thermal head 39 to the released position.

On the other hand, when the mode for recording the additional information on the sheet is set, the shaft 6 is rotated by the clutch described later.
3, the coil spring 65 comes to the lower left of the shaft 63 as shown in FIG. This causes the leaf spring 67 to move to the cam 6
Pressed by 4. The support shaft 58 to which the plate spring 67 is attached is rotated counterclockwise mainly against the pressing force of the plate spring 66 against the bottom plate 49. Therefore, the plate 59 fixed to the support shaft 58 also rotates counterclockwise, and the thermal head 3 provided above the plate 59 is rotated.
9 is displaced to the recording position.

Then, the discharging roller 19 and the platen roller 76 are temporarily stopped on the basis that the fixing completion detecting switch 75 is switched from ON to OFF by the trailing edge of the sheet discharged from the fixing device 7, and thereafter, a predetermined period. Of the discharge roller 19 and the platen roller 76 intermittently at a low speed
Is driven. In this state, the additional information recording mechanism 8 records the additional information.

A platen roller 76 is arranged on the sheet conveying path corresponding to the additional information recording mechanism 8. As shown in FIG. 5, the thermal head 39 provided in the additional information recording mechanism 8 is in a state of being raised from the platen roller 76,
As shown in FIG. 6, the platen roller 76 is displaceable in a lowered state in which the platen roller 76 is in contact with the peripheral surface. In the descent state,
The thermal head 39 has openings 48 and 50 shown in FIG.
The thermal transfer ribbon 37 is extruded below the casing 35, and the thermal transfer ribbon 37 is brought into contact with the platen roller 76. When the thermal head 39 is brought into contact with the platen roller 76, the contact force thereof is kept constant by the action of the leaf spring 66.

In the state shown in FIG. 5, the thermal transfer ribbon 37 is retracted from the paper path so that the thermal transfer ribbon 37 does not accidentally come into contact with the paper passing through this path and the paper is not contaminated. There is. When the thermal head 39 is in the lowered state, as shown in FIG. 6, the thermal transfer ribbon 37 is in contact with the head line of the thermal head 39, and when the thermal head 39 is operated, the ink of the thermal transfer ribbon 37 causes the platen roller 76 to move. Side, that is, the paper side.

The thermal transfer ribbon 37 is preferably colored red, for example, when the original image is recorded in a color different from the color on which the original image is recorded. Of course, the thermal transfer ribbon 37 having the same color as the original image may be used. As shown in FIGS. 5 and 6, the punching mechanism 9 is arranged between the additional information recording mechanism 8 and the discharge roller 19, and a plurality of (for example, two) binding devices are provided on the trailing end side of the sheet. It is for punching holes. The punching mechanism 9 except the cam 25 is attached to a unit material 33 that can rotate outwardly of the copying machine main body 1 about a shaft 77 at the lower end, as shown in FIG. When the unit material 33 is rotated to the outside of the copying machine main body 1, the engagement between the punch blade 22 and the cam 25 is released, and the punch blade 22 becomes free. Therefore, the jam processing is easy.

When the unit material 33 is rotated to the outside of the main body 1 of the copying machine, the additional information recording mechanism 8 provided inside the unit is exposed. Therefore, maintenance of the additional information recording mechanism 8 becomes easy. When the unit material 33 is opened, the casing 35 of the additional information recording mechanism 8 is
As shown in FIG. 7, centering around the support shafts 43a and 43b,
It is possible to rotate from the set position shown by the two-dot chain line to the open position where the ribbon cassette 36 shown by the solid line can be taken out.

FIG. 8 is a block diagram showing the electrical construction of the electrophotographic copying machine described above. This copier is provided with a CPU 78 as a control center. CPU78
The temperature of the operation panel 80, the main motor 81, the step motor 82, the thermal head 39, the head lifting clutch 83, the motor 52 of the driving device 51 (see FIG. 3), and the temperature of the thermal head 39 via the input / output interface 79. Detection thermistor 84 and cam 2 of the punching mechanism 9
A cam clutch 95 for driving 5 is connected.

The operation panel 80 has a mode selector switch 89 for changing the operation mode of the copying machine, a display 90 made of a liquid crystal display for displaying the number of copies, numerical data and other data, and the number of copies. An input key (numeric keypad) 91, a clear key 92, a print key 93, and a paper rank input key 94 are provided. The main motor 81 includes the image processing unit 4, the fixing device 7, and the paper transport path 6.
(See FIG. 1) and the like.

The step motor 82 is for driving the discharge roller 19 and the platen roller 76 independently of each part driven by the main motor 81. That is, by changing the speed of the step motor 82, when the additional information recording mechanism 8 records the additional information, the additional information recording mechanism 8 can record the conveyance speed of the sheet by the discharge roller 19 and the platen roller 76. Can be up to late. When the punching mechanism 9 is used to form punch holes by stopping the step motor 82, the discharge roller 19 and the platen roller 76 are temporarily stopped with the trailing edge of the sheet facing the punch blade 22. Can be made

The head lifting clutch 83 uses the shaft 63 of the thermal head moving mechanism 40 described above as the main motor 81.
It is for connecting to and disconnecting from the power transmission mechanism from. By connecting the shaft 63 to a power transmission mechanism from the main motor 81 and rotating the shaft 63, the thermal head 39 can be moved up and down. In addition, CP
Various drive mechanisms constituting the copying machine are further connected to the U78 via the input / output interface 79, but they are omitted in FIG. 8 because they are not particularly related to the description of this embodiment.

The CPU 78 also includes a control ROM 85,
A font ROM 86 and a RAM 87 are connected. The control ROM 85 is a read-only memory in which the control program of this copying machine is stored. Font ROM
A read-only memory 86 stores character data. A specific logo mark by the additional information recording mechanism 8,
When the designed characters, numbers, etc. are recorded, the particular logo mark, the designed characters, numbers, etc. are read from the font ROM 86 and stored in the buffer area 88 of the RAM 87.

Next, the control operation at the time of recording additional information in the present invention will be described. In the control operation described below, the temperature of the thermal head 39 is detected during additional information recording, and if the temperature of the thermal head 39 rises excessively due to continuous use, etc., the additional information recording mechanism 8 The operation is prohibited. 9 and 10 are flowcharts showing the contents of such protection control.

First, referring to FIG. 9, the CPU 78 determines whether or not it is the additional information recording mode in which the additional information recording mechanism 8 operates (step S41). If it is not the additional information recording mode, the additional information recording is performed. The mechanism 8 is not operated, and normal copying is performed (step S42). When the additional information recording mode is selected, the temperature t of the thermal head 39 is measured (step S43).

The temperature of the thermal head 39 is measured according to the flow chart shown in FIG. And
Based on the measured temperature t, a prohibition flag for prohibiting the operation of the additional information recording mechanism 8 is set or reset in the buffer area 88. Then, the thermal transfer time T4 + β according to the measurement temperature t (β is a value that changes depending on the measurement temperature)
Is determined (step S44). Then, it is judged whether or not the prohibition flag is set (step S4).
5) If the prohibition flag is set, the operation of the additional information recording mechanism 8 is stopped (step S46).
Then, until the prohibition flag is reset, step S
The processing of steps 43 to S46 is repeated, and the operation of the additional information recording mechanism 8 is stopped until the temperature of the thermal head 39 falls below a predetermined temperature.

If the prohibition flag is not set in step S45, the additional information recording mechanism 8 is operated and additional information is recorded for the determined thermal transfer time T4 + β (step S47). After this, it is judged whether or not the copy is a continuous copy (step S48), and if it is a single copy, the operation is ended.

On the other hand, in the case of continuous copying, it is judged whether or not the number of copies reaches a predetermined number (step S
49) Until the number of copies reaches a predetermined number, the processes of steps S43 to S48 are repeated and the additional information is continuously recorded on the paper. Next, referring to FIG. 10, first, in step S43, it is determined whether or not the prohibition flag is set (step S43).
1) When the prohibition flag is not set, the temperature detected by the thermistor 84 (that is, the temperature of the thermal head 39) t is a preset upper limit temperature (for example, 50 ° C.).
It is determined whether or not the following (step S432).

If the temperature t of the thermal head 39 is less than or equal to the upper limit temperature of 50 ° C., step S44 is performed as it is.
(See FIG. 9). On the other hand, when the temperature t of the thermal head 39 exceeds the upper limit temperature of 50 ° C., the prohibition flag is set (step S433), and the process proceeds to step S44 described above.

If the prohibition flag is set in step S431, it is determined whether or not the temperature t detected by the thermistor 84 has become a predetermined temperature, for example, 48 ° C. or lower (step S434). If the temperature t is not lower than 48 ° C., the process is step S.
Proceed to 44. On the other hand, when the detected temperature t falls below 48 ° C., the prohibition flag is reset (step S43).
5), the process proceeds to step S44.

As described above, when the temperature t detected by the thermistor 84 exceeds a predetermined temperature, for example, 50 ° C. due to the temperature rise inside the copying machine or continuous use, the temperature t is increased. For example, until the temperature drops below 48 ° C
The operation of the additional information recording mechanism 8 is temporarily stopped. By doing so, the thermal transfer ribbon 37 is mistakenly heated by the high temperature thermal head 39, and the paper is not contaminated.
Further, there is no fear that the recorded contents by the thermal head 39 will be blurred or flow, and it is possible to always record the additional information neatly.

Further, the thermal head 39 deteriorates rapidly when used at high temperature for a long time. Therefore, this deterioration can be prevented and the life of the thermal head 39 can be extended. The control method for changing the thermal transfer time T4 + β is basically the same as the control method for changing the thermal transfer time T3 + α described later. The difference is that the respective values of “T3” and “T4” are different, and “α” is a value that changes based on the sheet rank, and “β” is a temperature variable.

In the above description, the operation of the additional information recording mechanism 8 is stopped when the temperature of the thermal head 39 exceeds a predetermined temperature, and the additional information recording mechanism is stopped when the temperature of the thermal head 39 falls below the predetermined temperature. Although the operation of No. 8 is restarted, the following operation may be performed, for example. When the temperature detected by the thermistor 84 exceeds a predetermined temperature, the operation of the additional information recording mechanism 8 is stopped. Then, from that point of time, a timer may be operated to measure a predetermined time, and when the predetermined time has elapsed, the operation of the additional information recording mechanism 8 may be restarted.

In the above embodiment, the temperature of the thermal head 39 is directly measured by the thermistor 84, but the temperature of the thermal head 39 may be indirectly estimated. For example, it is possible to detect the temperature of the thermal head 39 based on the ambient temperature inside the copier body.
Alternatively, when a predetermined number of copies with additional information recording are continuously performed, it is presumed that the temperature of the thermal head 39 has become equal to or higher than a predetermined temperature, and the operation of the additional information recording mechanism 8 is temporarily stopped. Good.

Next, still another control operation of this embodiment will be described. In the control operation described below, the heating time T3 by the thermal head 39 depends on the type of paper.
+ Α (α is variable) can be changed. By doing this, even if the type of paper is changed, the additional information is recorded with a density that is easy to read according to the type of paper.

Regarding the type of paper, various papers used for copying are ranked in several stages according to the level of thermal transfer property, and are stored in advance in the control ROM 85. An example is as follows.

[0057]

[Table 1]

When any one of the paper type numbers (1) to (5) is input by the input key 94, the CPU 78
The control ROM 8 according to the input paper type number.
The rank stored in 5 is read. Then, the thermal transfer time (heating time) T3 + α is calculated based on the read rank. Here, T3 + α is 0.5, and T3 is the basic time.
It is 12 msec, α is a variable time, and α ₀ × rank.

Α ₀ = 0.032 msec. Therefore, for example, (1) When Japanese high-quality paper is input, the rank is "1". The thermal transfer time T3 + α is T3 + α = 0.512 + 0.032 × 1 = 0.544 msec. When (5) rough paper is input, the rank is "10". The thermal transfer time T3 + α is T3 + α = 0.512 + 0.032 × 10 = 0.832 msec.

In this embodiment, the ranks are "1" to "1".
There are 12 steps up to 2 ".
This will be described with reference to FIGS. 11 and 12. Input key 9
When a paper type having good transferability such as copy paper specified by the manufacturer (high quality paper made in Japan) is input as the paper type by 4, the thermal transfer time T3 + α1 is determined and the RAM 8
Stored in 7.

Next, as shown in FIG. 11, when data for one row is given, the data is stored in the thermal head 39 by the latch signal. The thermal head 39 includes a large number of heating elements 391, 392, ... (See FIG. 3) as described above. These many heating elements are, for example, 7
It is divided into one group and is sequentially energized by the strobes 1-7. Each strobe is a control ROM85
The thermal transfer time T3 + α1 read from the RAM 87 and stored in the RAM 87 is given. Accordingly, the heating element is sequentially energized for a time T3 + α1 for each groove to perform thermal transfer.

On the other hand, when the type of paper having poor transferability such as rough paper is input by the input key 94, the thermal transfer time T3 + α10 of the paper having poor transferability is determined and stored in the RAM 87. Next, as shown in FIG. 12, when data for one row is given, the data is stored in the thermal head 39 by the latch signal. Subsequently, the seven heating element groups are sequentially energized by the strobes 1 to 7. The low active time of each strobe 1 to 7 is the time T3 stored in the RAM 87.
It is + α10. Therefore, the heating elements are sequentially energized for a time T3 + α10 for each group, and thermal transfer is performed.

The time from the low edge of the preceding strobe (eg strobe 1) to the low edge of the next strobe (eg strobe 2) is always constant even if the thermal transfer time T3 + α changes. Therefore, the time required to record one row of information processed by the strobes 1 to 7 is always constant. The strobes 1 to 7 may be repeatedly output two or more times to record information for one row without extending the low active times of the strobes 1 to 7, respectively.

In the above description, a large number of heating elements are divided into seven groups, and the strobes 1 to 7 are used to sequentially energize them. This is because the drive current becomes too large in the configuration in which all the heating elements are energized at the same time. However, when the operating power source is large, all the heating elements may be energized at the same time.

The number of heating elements is not limited to seven, and the heating elements can be divided into arbitrary groups. In that case, strobes are sequentially output for the number of divided groups. Further, in the case of a sheet having good transferability, raising the heating temperature of the platen roller 76 will further improve the transferability. Therefore, when selecting the rank of the sheet having good transferability,
While raising the heating temperature of the platen roller 76,
The additional information recording mechanism 8 may record the additional information by setting the heating and transfer times shorter than T3.

[0066]

The image forming apparatus according to the present invention is configured as described above, and when the temperature of the thermal head exceeds a predetermined temperature, the protection means stops the operation of the second image recording means, and the thermal head Is prohibited from being energized to cool the thermal head. Therefore, the thermal head does not deteriorate due to excessive use, and the thermal transfer ribbon may be erroneously transferred by the heated thermal head to stain the paper, or additional information may bleed or flow during recording. Absent.

When the temperature of the thermal head drops below a predetermined temperature, the additional information can be recorded again, so there is no need to restart the operation, and the device should be easy to use. You can

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an overall configuration of an electrophotographic copying machine according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a configuration of a punching mechanism in this embodiment.

FIG. 3 is a perspective view of an additional information recording mechanism in this embodiment.

FIG. 4 is a view showing a mounting structure of a plate and a support shaft.

FIG. 5 is a cross-sectional view when the additional information recording mechanism is in a standby state.

FIG. 6 is a cross-sectional view when the additional information recording mechanism is in an operating state.

FIG. 7 is a cross-sectional view in which the punching mechanism is opened and the thermal transfer ribbon of the additional information recording mechanism is replaceable.

FIG. 8 is a block diagram showing an electrical configuration of this embodiment.

FIG. 9 is a flowchart showing a control operation for protecting the thermal head.

FIG. 10 is a flowchart showing a control operation for protecting the thermal head.

FIG. 11 is a timing chart showing control for changing the thermal transfer time according to the type of paper.

FIG. 12 is a timing chart showing control for changing the thermal transfer time according to the paper type.

[Explanation of symbols]

 37 Thermal Transfer Ribbon 39 Thermal Head 78 CPU 84 Thermistor

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location G03G 15/00 114 7369-2H 8305-2H B41M 5/26 M

Claims (1)

Claim: What is claimed is: 1. A first image recording unit for forming an image by an electrophotographic method and recording the image on a sheet, and a sheet on which the image is recorded by the first image recording unit. On the other hand, it has a second image recording means for recording an additional image, and the second image recording means is in contact with the thermal transfer ribbon containing the ink and the thermal transfer ribbon to selectively select the thermal transfer ribbon. In an image forming apparatus including a thermal head that heats the ink to a sheet and transfers the ink in the heated portion to the paper,
Temperature detection means for detecting the temperature of the thermal head, and protection means for stopping the operation of the second image recording means when the detected temperature of the temperature detection means exceeds a predetermined stop temperature are provided. An image forming apparatus characterized by the above. 2. The image forming apparatus according to claim 1, wherein the temperature detecting means includes a thermistor built in the thermal head. 3. The image forming apparatus according to claim 1, wherein the temperature detecting means includes a temperature detecting means for detecting an ambient temperature around the thermal head. 4. The image forming apparatus according to claim 1, 2 or 3, further, after the operation of the second image recording means is stopped by the protection means, the temperature detected by the temperature detecting means is the stop temperature. When the temperature becomes lower than a predetermined operation restart temperature, which is lower than the lower limit, the activation means is provided for making the second image recording means operable. 5. The image forming apparatus according to claim 1, 2 or 3, further comprising: when a predetermined time elapses after the operation of the second image recording means is stopped by the protection means, the second image recording means is turned on. It is characterized in that it includes an activation means for making it operable.