JPH06337568A - Image recorder - Google Patents

Abstract

PURPOSE:To provide an image recorder that prevents the start of an image recording processing for the following recording sheet from being delayed due to a decrease in fixing speed and prevents a decrease in image recording speed as much as possible. CONSTITUTION:The image recorder transfers toner images in separate colors on a photosensitive drum 20 to a recording sheet 30 held on a transfer drum 31, by one on top of the other, and then passes the recording sheet 30, peeled off the transfer drum 31, through a heat fixing device 50. In the image recorder, at least before the recording sheet 30 peeled off the transfer drum 31 is forced through the heat fixing device 50, the fixing speed of the heat fixing device 50 is switched to a low speed according to the type of the recording sheet 30, and, after a transfer process for the final color is finished, the rotating speed of the transfer drum 31 is switched to a low speed corresponding to the fixing speed of the heat fixing device 50. Further, right after the recording sheet 30 is completely peeled off the transfer drum 31, the rotating speed of the transfer drum 31 is returned to the normal speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus for forming a color image by multiple-transferring toner images of respective color components formed on an image carrier onto a recording sheet held on a transfer body, and more particularly to an image recording apparatus. The present invention relates to improvement of an image recording apparatus of a type in which the fixing speed is switched according to the type of recording sheet.

[0002]

2. Description of the Related Art Conventionally, as this type of image recording apparatus, for example, one disclosed in Japanese Patent Laid-Open No. 4-3377751 is known. Specifically, the photoconductor drum (image carrier)
And a transfer drum (transfer body) are synchronously rotated by a single servo motor drive system, and toner images of respective colors sequentially formed on the photosensitive drum are multi-transferred onto a recording sheet held on the transfer drum to form a color image. After being formed, the recording sheet is inserted into a heat fixing device to fix the toner image on the recording sheet.

In this image recording apparatus, sufficient thermal energy can be applied to the recording sheet when an image is recorded on a recording sheet having a large heat capacity such as a sheet for overhead projector (hereinafter abbreviated as OHP) or thick paper. As described above, the fixing speed of the heat fixing device is switched to a low speed according to the type of the recording sheet.At this time, in order to match the conveyance speed of the recording sheet to the heating fixing device with the fixing speed, the toner of the final color is used. After the image is transferred from the photosensitive drum to the recording sheet on the transfer drum, the speed of the transfer drum is switched from the transfer speed to a low speed corresponding to the fixing speed.

[0004]

Even when the fixing speed is switched to the low speed to fix the toner image in this way, it is necessary to discharge the recording sheet to the discharge tray at a high speed to some extent. If the discharge speed of the recording sheet remains low, as shown in FIG.
Is not completely accommodated in the discharge tray 11, and its rear end is caught in the discharge port 12 and curls.

For this reason, in the conventional image recording apparatus having the fixing speed switching means, an exit roll for sending the recording sheet passing through the heat fixing device to the discharge tray is provided so that the recording sheet completely passes through the heating fixing device. At this point, the speed of the exit roll is increased to a predetermined discharge speed, and the recording sheet is urged and sent to the discharge tray.

However, in the image recording apparatus disclosed in JP-A-4-337751, since the exit roll is connected to the same servo motor drive system as the transfer drum, there are the following problems. That is, from the viewpoint of improving the image recording speed, it is preferable that the transfer drum switched to the low speed returns to the original transfer speed immediately after the recording sheet is peeled off, but it is connected to the same servo motor drive system. Since the exit roll is required to be driven at a low speed until the recording sheet completely passes through the heating and fixing device, the transfer drum has to be driven at a low speed during this period. Therefore, while the recording sheet is passing through the heat fixing device at a low speed, a new toner image cannot be formed on the photosensitive drum and transferred to the recording sheet on the transfer drum. There was a problem that it was significantly slowed down.

The present invention has been made in view of the above problems, and an object of the present invention is to record an image by lowering the fixing speed when the fixing speed is switched to a low speed according to the type of the recording sheet. To prevent the start of
Accordingly, it is an object of the present invention to provide an image recording apparatus capable of preventing a decrease in image recording speed as much as possible.

[0008]

In order to achieve the above object, an image recording apparatus of the present invention has an image carrier and a transfer member, which are rotated in synchronization with each other, so that a recording sheet held on the transfer member is mounted on the image carrier. In the image recording apparatus in which the recording sheets separated from the transfer body are inserted into the heat fixing means after the toner images of the respective colors are multiple-transferred, and the recording sheets are sent to the discharge tray by the exit roll, Before the recording sheet separated from the recording sheet enters the heating and fixing means, the fixing speed switching means for switching the fixing speed of the heating and fixing means and the delivery speed of the exit roll to a low speed according to the type of the recording sheet, and the transfer of the final color After the process is completed, transfer member speed switching means for switching the rotation speed of the transfer member to a low speed corresponding to the fixing speed of the heat fixing means, and the recording sheet is completely peeled off from the transfer member. Immediately after the transfer body speed returning means for returning the rotation speed of the transfer body to the normal speed, and an exit roll speed returning means for returning the rotation speed of the exit roll to the normal speed immediately after the recording sheet passes through the heat fixing means. And is provided.

[0009]

According to the above technical means, the fixing speed switching means switches the fixing speed of the heating fixing means to a low speed according to the type of the recording sheet at least before the recording sheet enters the heating fixing means, while the final fixing speed is changed. When the color transfer process is completed, the transfer member speed switching means switches the speed of the transfer member to a speed corresponding to the low speed fixing speed, so that the recording sheet is decelerated to the conveying speed corresponding to the low speed fixing speed and then separated from the transfer member. Then, it rushes into the heat fixing means.

Immediately after the recording sheet passes through the heating and fixing means, the exit roll speed restoring means increases the rotation speed of the exit roll to the normal speed, and the recording sheet is urged and discharged to the discharge tray. On the other hand, the transfer member speed returning means restores the rotational speed of the transfer member to the normal speed immediately after the recording sheet is completely separated from the transfer member, and prepares for transfer of the toner image to the next recording sheet.

Therefore, even while the recording sheet is passing through the heat fixing means at a low fixing speed, a toner image is formed on the image carrier and is transferred to the next recording sheet held on the transfer body. Transfer is possible, and the image recording speed can be improved.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The image recording apparatus of the present invention will be described in detail below with reference to the accompanying drawings. 1 and 2 show an embodiment of a color printer to which the present invention is applied. In the figure, reference numeral 20 is a photosensitive drum, 21 is a photosensitive drum 20.
, A laser scanning unit for writing an electrostatic latent image on the photoconductor drum 20 charged by the charging corotron 21, and 23 for black (K), cyan (C), and magenta (M). ), Yellow (Y)
Four developing units 23B, 23C, in which the respective toners of
The rotary developing units 23M and 23Y are rotatably arranged and are appropriately switched and selected. 24 is a pre-transfer corotron for removing the potential on the photosensitive drum 20. 25 is a residual toner on the photosensitive drum 20. A cleaner, 26 is an erase lamp that removes residual charges on the photosensitive drum 20.

Further, 31 is a recording sheet 30 (OH
This is a transfer drum in which a P sheet or plain paper) is wound and held, and toner images of respective color components sequentially formed on the photoconductor drum 20 are transferred to the recording sheet 30 in a multiple transfer manner. As shown in FIGS. 3 and 4, the transfer drum 31 forms a drum frame 32 by connecting a pair of ring bodies 33 with one tie bar 34, and for example, polyvinylidene fluoride or the like is attached to the drum frame 32. The drum sheet 35 consisting of the above is wound and its both ends are fixed by the fixing members 36, and the recording sheet 30 is electrostatically attracted to the peripheral surface by precharging the drum sheet 35. In this embodiment, an adjuster plate 37 for preventing the drooping of the drum sheet 35 is disposed at a portion adjacent to the tie bar 34 on the side opposite to the rotation direction. The adjuster plate 37 has a ladder-shaped through hole. 38
When the adjuster plate 37 is opened, a recess 39 is formed on the surface of the adjuster plate 37 on the side of the tie bar 34, which is inclined downward toward the through hole 38, as a space for entering a peeling finger 47 described later.

Further, in this embodiment, as shown in FIGS. 3 and 4, the approximate center line of the adjuster plate 37 is set as the tip reference P _A of the sheet holding surface A, and from this tip reference P _A A line deviated by 180 ° is set as the front end reference P _B of the sheet holding surface B, and the recording sheet 30 made of plain paper is held on the normal sheet holding surface A. In the mode (a mode in which the two recording sheets 30 are held on the transfer drum 31 and the transfer operation is performed on the two recording sheets 30), the sheet holding surfaces A and B are made of plain paper, respectively. The seat 30 is held.

In this embodiment, the recording sheet 30 made of the OHP sheet is also used. However, the recording sheet 30 made of the OHP sheet on the sheet holding surface A is used.
When the sheet holding surface is held, the leading edge of the recording sheet 30 rises due to its rigidity, which causes a tacking error. Therefore, a predetermined distance e from the leading edge reference P _A of the sheet holding surface A.
Position shifted backward by (is approximately 180mm in this example) is set to be front end reference P _C of OHP sheet holding surface C.

Further, as shown in FIGS. 2 and 3, the transfer drum 31 has an adsorption corotron 41 for charging the drum sheet 35 when holding the recording sheet 30, and the photosensitive drum 2.
On the transfer corotron 42 for transferring the toner image on the recording sheet 30 to the recording sheet 30 side, the static elimination corotron 43 for discharging the recording sheet 30 after the final color transfer step, and the drum sheet 35 for the final color transfer step. A cleaning charge-eliminating corotron 44 for removing charges, a cleaning brush 45 for cleaning paper dust and the like adhering to the drum sheet 35 after the transfer process of the final color, and the recording sheet 30 held on the sheet holding surfaces B, C are peeled off. Drum sheet 35 when doing
Is provided from the inside, and a peeling finger 47 that peels the recording sheet 30 pushed alone or when the recording sheet 30 is peeled off is provided. Reference numeral 48 is an adsorption corotron 41.
A sheet conveying system that conveys the recording sheet 30 to a part.

Further, reference numeral 50 is a fixing device for inserting the recording sheet 30 after the transfer process and fixing the unfixed toner image on the recording sheet 30. In this embodiment, a heating device having a heater built therein is used. The recording sheet 30 from the transfer drum 31 is conveyed to the fixing device 50 via the guide plate 53. The recording sheet 30 is composed of a roll 51 and a pressure roll 52 arranged in pressure contact with the heating roll 51. Further, reference numeral 54 is a fuser outlet roll that conveys the recording sheet 30 having passed through the fixing device 50, and 55 is the fixing device 50.
The fuser outlet switch for detecting the trailing edge of the recording sheet 30 that has passed through the recording sheet 30, 56 is a discharge tray in which the fixed recording sheet 30 is accommodated, and 57 is a discharge tray 56.
Is an exit roll for sending out.

Further, the photosensitive drum 2 in this embodiment
FIG. 5 shows a drive control system for 0, the transfer drum 31, the fixing device 50, and the like. In the figure, reference numeral 61 is a drum motor for synchronously rotating the photosensitive drum 20 and the transfer drum 31, and 62.
Is a motor driver thereof, 63 is a main motor for driving the fixing device 50, the outlet roll 57 and the fuser outlet roll 54 (see FIG. 1), 64 is a motor driver thereof, and 68 is for driving the sheet conveying system 48. A sheet conveying motor 69 is a motor driver for the sheet conveying motor. Further, a half moon plate 65 is provided coaxially with the transfer drum 31, and an optical sensor 66 including a light emitting portion and a light receiving portion is arranged at a position crossing the half moon plate 65. The output of the optical sensor 66 is repeatedly turned on and off for each rotation.
The rising and falling points of the output of the edge detection circuit 67
It will be detected at.

Reference numeral 70 denotes a CPU 71, a ROM 72 in which various programs such as a color print execution program (normal mode, OHP mode) and a color printer stop program are stored in advance, and data is temporarily stored when the CPU 71 executes the programs. Which is a microcomputer in which a RAM 73 and an I / O port 74 that are temporarily stored are mutually connected by a system bus 75, and a detection pulse TR0 from the edge detection circuit 67 and a detection signal from the fuser outlet switch 55 are I / O ports. A reference timing signal and a speed return timing signal are fetched into the microcomputer 70 via 74, and a motor control signal from the microcomputer 70 is sent to each motor driver 62, 64, 69 via the I / O port 74. Drum motor 61, Inmota 63 and the sheet conveying motor 68 are controlled.

Next, the operation of the color printer according to this embodiment will be described. ◎ Normal mode (normal print mode using the recording sheet 30 made of plain paper) At the start of printing, the start switch 8
When 1 is turned on, the microcomputer 70 sends a drum motor ON signal and a drum motor H signal (high-level drive of the drum motor: equivalent to normal rotation speed) to the motor drive 62, causing the drum motor 61 to move to the speed V1 (this operation). In the example, it is driven at 160 mm / sec). still,
The sheet conveying motor 68 and the main motor 63 are also driven in synchronization with the drum motor 61.

The copy mode (four color mode,
The exposure, development, and transfer processes of the respective color components are executed according to the three-color mode, the mono-black mode, etc.
The toner images of the respective color components above are transferred to the recording sheet 30 held on the transfer drum 31 in a multiple manner.
The recording sheet 30 separated from the sheet is discharged to the discharge tray 56 via the fixing device 50.

OHP mode (print mode using recording sheet composed of OHP sheet) FIG. 6 is a flow chart showing the processing steps in the OHP mode. In the figure, when the start switch 81 and the OHP mode switch 82 (see FIG. 5) are turned on at the start of printing, the CPU 71 causes the drum motor 61, the main motor 63, and the sheet conveying motor 68 to rotate at the normal rotation speed V1 as in the normal mode. Is set, and the exposure, development, and transfer processes of each color component are executed according to the copy mode (four-color mode, three-color mode, mono-black mode), etc., and the toner image of each color component on the photosensitive drum 20 is transferred. Multiple transfer is performed on the recording sheet 30 held on the drum 31 (step 1).

At this time, as shown in FIG. 7, first, the suction corotron 41 holds the recording sheet 30 composed of the OHP sheet on the sheet holding surface C of the transfer drum 31, and in this state, the pre-transfer treatment corotron 24 is held. While constantly operating, the transfer corotron 42 is operated at a predetermined operation timing to execute the transfer process of each color component.

Next, the CPU 71 checks whether or not the final color transfer process is completed (step 2), and as shown in FIG. 8, when the final color transfer process is completed, the drum motor 61 and the main The motor 63 is decelerated from the normal rotation speed V1 to a low speed V2 (corresponding to the fixing speed in the OHP mode) (steps 3 and 4). At this time, the sheet conveying motor 68 is still rotating at the normal rotation speed V1.

In this embodiment, the following timing is used as the deceleration timing. That is, FIG.
As shown in, after the final transfer reference timing signal TR0 indicating the transfer pitch of the final color toner image is fetched from the edge detection circuit, the leading end reference P _A of the sheet holding surface A reaches the transfer corotron (TC) 42 position. Is t ₁ , the time from the leading edge reference P _A of the sheet holding surface _A to the leading edge reference P _C of the sheet holding surface C to the transfer corotron (TC) 42 position is t ₂ , and the maximum size OHP sheet (this In the embodiment, if the transfer time of the A4 plate is set to t ₃ and the delay time when the transfer corotron (TC) 42 is turned off is t ₄ , the final transfer reference timing signal TR 0 to T = t ₁ + t ₂ + t.
_{When 3} + t ₄ (in this embodiment, about 3400 msec) has elapsed, it is determined that the transfer process of the final color has ended, and the drum motor 61 and the main motor 63 are decelerated at this timing. Since the deceleration may be completed before the front end of the transferred recording sheet 30 reaches the fixing point,
FCOT (First Copy Out Time)
In order to speed up, the start of deceleration should be delayed as much as possible.

At this time, the transfer drum 31 idles while the recording sheet 30 on which the toner images of the respective color components have been transferred is held (dummy cycle), and the recording sheet 30 on which the toner image is held is again rotated. Photoconductor drum 2
Pass 0 site.

In this case, the toner image on the recording sheet 30 may be transferred to the photosensitive drum 20 side again. In this embodiment, the transfer corotron 42 is used even in the dummy cycle.
Is operated to prevent the toner image on the recording sheet 30 from being transferred to the photosensitive drum 20 side. At this time, the transfer corotron 42 current flows only 98 (the first color is 100), but the transfer drum 31 is rotated at the normal rotation speed V.
₁ (160 mm / sec) substantially 1/3 of the speed V ₂ (6
Since it rotates at 0 mm / sec), the substantial amount of electric charge applied to the recording sheet 30 is larger than the amount of electric charge of the transfer corotron 42 of the fourth color. Therefore, the toner image on the recording sheet 30 is reliably electrostatically attracted onto the recording sheet 30 without being transferred to the photosensitive drum 20 side again, and the disturbance of the toner image on the recording sheet 30 is prevented. To be done.

After that, the CPU 71 checks whether or not the recording sheet 30 has reached the peeling point (for example, whether or not a predetermined time has elapsed from the reference timing signal TR0 from the transfer drum 31) (step). 5) When the recording sheet 30 reaches the peeling point, the recording sheet 3
A peeling operation of 0 is executed (step 6).

At this time, immediately before the tip of the recording sheet 30 reaches the position of the static elimination corotron 43, the static elimination corotron 43 operates, and as shown in FIG. 9, when the tip of the recording sheet 30 reaches the vicinity of the position of the internal pressing roll 46. Then, the inner pressing roll 46 operates to lift the leading end of the recording sheet 30 on the drum sheet 35, and in this state, the peeling finger 47 operates to peel the recording sheet 30 from the transfer drum 31.

Then, the peeled recording sheet 30 is conveyed to the fixing device 50 through the guide plate 53, but since the speeds of the transfer drum 31 and the fixing device 50 are both switched to the low speed V2, the recording sheet 30. Rushes into the fixing device 50 smoothly without jamming on the way. Therefore, since the recording sheet 30 passes through the fixing device 50 at a low speed, sufficient thermal energy is applied to the recording sheet 30 which is an OHP sheet, so that each toner image on the recording sheet 30 is reliably fixed and each toner image is fixed. The light transmittance of the image can be kept good.

When the peeling operation is performed, the sheet charge-removing corotron 44 is activated after a lapse of a predetermined time to remove the charges on the drum sheet 35, and the cleaning brush 45 causes the paper dust on the drum sheet 35. Is cleaned, and preparation for electrostatically adhering the next recording sheet 30 onto the transfer drum 31 is made.

On the other hand, as shown in FIG. 10, the CPU 71 determines whether or not the recording sheet 30 has been completely peeled from the transfer drum 31, that is, whether or not the rear end of the recording sheet 30 has been peeled from the transfer drum 31. It is checked (step 7), and when completely separated, the drum motor 61 is accelerated to the original normal speed V1 (step 8). Whether or not the trailing edge of the recording sheet 30 is separated from the transfer drum 31 is determined by, for example, whether or not a predetermined time set for each recording sheet size has elapsed from the reference timing signal TR0.

At this stage, the recording sheet 30 is still passing through the fixing device 50 at a low speed, but in this embodiment, at this time, the rotational speed of the photosensitive drum 20 and the transfer drum 31 has already changed from the low speed V2 to the normal speed V1. The second recording sheet 30 is supplied to the transfer drum 31 by the sheet conveying system 48 which is also driven at the normal speed V1, and the formation of the toner image on the photosensitive drum 20 is started. can do. Therefore, the time required for the first recording sheet 30 to pass through the fixing device 50 at the low speed V2 (2.5 times or more of that at the normal speed V1) is not wasted, and the toner is supplied to the next recording sheet 30. The image can be transferred, and the image recording processing speed is significantly improved.

Thereafter, as shown in FIG. 11, the CPU 71 causes the rear end of the recording sheet 30 to move to the fuser outlet switch 5.
5 is checked (step 9), and when the trailing edge of the recording sheet 30 passes the fuser outlet switch 55, the main motor 63 is accelerated to the original normal speed V1 (step 10). At this time, the main motor 6
The acceleration timing of 3 is at least the exit roll 5
In FIG. 7, the predetermined timing after passing through the fuser outlet switch 55 is selected so as to secure a margin (about 16 mm in this embodiment) for sending the recording sheet 30 at the normal speed v1.

As a result, as shown in FIG. 11, the fixing device 5
0 and the exit roll 57 return to the normal speed V1, and the recording sheet 30 is discharged to the discharge tray 56 while being urged by the exit roll 57. Therefore, it is possible to effectively avoid the situation where the recording sheet 30 is not completely accommodated in the discharge tray 56 and the rear end is caught in the discharge port.

In this embodiment, the transfer drum 3
Although the sheet conveying system 48 that conveys the recording sheet 30 to the first sheet is driven by the sheet conveying motor 68, the sheet conveying motor 68 may be omitted by driving this with the drum motor 61. At this time, the speed of the sheet conveying system 48 varies with the acceleration / deceleration of the drum motor 61, but since the sheet conveying system 48 always accelerates / decelerates together with the transfer drum 31, there is no support for supplying the recording sheet 30 to the transfer drum 31. Does not happen.

[0037]

As described above, according to the present invention, immediately after the recording sheet is completely peeled from the transfer body, the rotational speed of the transfer body is changed from the low speed corresponding to the speed of the heat fixing means to the normal speed. Since a recording sheet having a large heat capacity, such as an OHP sheet, is passing through the heating and fixing means at a low fixing speed, a toner image is formed on the image carrier and is transferred to the transfer body. It is possible to transfer the image to the next recording sheet held on the sheet, and it is possible to perform the image recording process on the next recording sheet without wasting the long processing time required for fixing the recording sheet having a large heat capacity. Therefore, it is possible to significantly improve the image recording processing speed.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of a color printer to which an image recording apparatus of the present invention is applied.

FIG. 2 is an explanatory diagram showing details around the transfer drum according to the embodiment.

FIG. 3 is an explanatory diagram showing details of a part III in FIG.

FIG. 4 is an explanatory diagram showing a holding position of a recording sheet with respect to a transfer drum.

FIG. 5 is a block diagram showing a drive control system for a photosensitive drum, a transfer drum, and a fixing device.

FIG. 6 is a flowchart showing an image recording operation in the OHP mode.

FIG. 7 is an explanatory diagram showing a first step of an image recording operation in the OHP mode.

FIG. 8 is an explanatory diagram showing a second step of the image recording operation in the OHP mode.

FIG. 9 is an explanatory diagram showing a third step of the image recording operation in the OHP mode.

FIG. 10 is an explanatory diagram showing a fourth step of the image recording operation in the OHP mode.

FIG. 11 is an explanatory diagram showing a fifth step of the image recording operation in the OHP mode.

FIG. 12 is an explanatory diagram showing a specific setting example of deceleration timing in the OHP mode.

FIG. 13 is an explanatory diagram showing a problem in a state where a recording sheet is stored in a discharge tray.

[Explanation of symbols]

20 ... Photosensitive drum (image bearing member), 30 ... Recording sheet,
31 ... Transfer drum (transfer body), 50 ... Fixing device (heat fixing unit), 56 ... Discharge tray, 57 ... Exit roll

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location G03G 15/20 109

Claims (1)

[Claims] 1. An image carrier and a transfer member are synchronously rotated to multiple-transfer the toner images of respective colors on the image carrier to the recording sheet held on the transfer member, and then the recording sheet separated from the transfer member is removed. In an image recording apparatus in which the recording sheet is passed through the heating and fixing means and is fed to an ejection tray by an exit roll, at least before the recording sheet separated from the transfer body enters the heating and fixing means. Fixing speed switching means for switching the fixing speed and the delivery speed of the exit roll to a low speed according to the type of the recording sheet, and the rotation speed of the transfer member after the completion of the final color transfer process to the fixing speed of the heat fixing means. A transfer body speed switching means for switching to a corresponding low speed, and a transfer body speed recovery means for returning the rotational speed of the transfer body to the normal speed immediately after the recording sheet is completely separated from the transfer body. It means a recording sheet an image recording apparatus characterized by comprising an exit roll speed returning means for returning the rotational speed of the outlet rolls to the normal speed immediately after passing through the heat fixing means.