JP2001171884A - Image recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image recording device having a low cost double-side recording mechanism and improved processing efficiency. SOLUTION: This image recording device comprises a reverse path for reversing the conveying direction of a sheet recorded with an image, a reverse conveying means disposed downstream of the reverse path, a re-feeding path connected to the upstream of the reverse path, and a guide means disposed in the re-feeding path for guiding the reversed sheet, and records images on both sides of the sheet. While a front sheet is reversed and conveyed in the reverse path, a rear sheet is intruded into the reverse path.

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 having a double-sided recording mechanism capable of recording images on the front and back of a sheet, and more particularly to an improvement in processing efficiency by shortening a sheet interval.

[0002]

2. Description of the Related Art Conventionally, in an image recording apparatus such as a laser printer, a double-sided recording mechanism for recording images on the front and back of a sheet is mainly attached to a relatively large, high-speed, high-cost apparatus. there were. As described above, the apparatus to be additionally mounted as a unit needs to newly provide a transport path for reversing the sheet, which has been a major factor in increasing the size and cost of the entire apparatus.

[0003]

However, in recent years, the number of companies that instruct employees to record on both sides of a sheet has been increasing for environmental protection. The desire for a two-sided recording mechanism is growing. However, a small-sized, low-speed, low-cost image forming apparatus naturally requires a low-cost double-sided recording apparatus.

[0004] In addition, the operation of reversing a sheet cannot transport the succeeding sheet until the reversed sheet has passed, and requires a predetermined sheet interval. For this reason, there has been a problem that the processing efficiency is greatly reduced during double-sided recording.

It is an object of the present invention to provide an image recording apparatus having a low-cost double-sided recording mechanism and having improved processing efficiency.

[0006]

In order to solve the above-mentioned problems, an image recording apparatus according to the present invention includes a reversing path for reversing a conveying direction of a sheet on which an image is recorded, and a reversing path disposed downstream of the reversing path. Reversing conveyance means, a re-feeding path connected to the upstream side of the reversing path, and a guiding means arranged in the re-feeding path to guide the reversed sheet, and record images on both sides of the sheet. In the image recording apparatus, while a previous sheet is reversely conveyed in the reverse pass, a subsequent sheet is caused to enter the reverse pass.

[0007]

[First Embodiment] A first embodiment of an image recording apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the overall configuration of the image recording apparatus according to the present embodiment. In the present embodiment, a description will be given using a laser beam printer as an image recording apparatus. The apparatus main body 1 shown in FIG. 1 has an image forming unit 2 at an upper part, a double-sided recording conveyance path 3 at a central part, and a sheet cassette 4 at a lower part.

In the image forming section 2, after the image carrier 5 is uniformly charged by the primary charging device 6, the laser beam is raster-scanned from the laser scanner unit 7 based on the image information, and the image carrier is returned by the return mirror 7a. 5, an electrostatic latent image is formed while scanning. The electrostatic latent image applied to the image carrier 5 is visualized by the developing device 8 to form a toner image.

A sheet presence / absence detection sensor S1 is arranged in the sheet cassette 4, and detects the presence / absence of a sheet in the cassette. At the time of image recording, the stacked sheets are sent out by a pickup roller 11, the sheets are separated and fed one by one by a feed roller 12 and a retard roller 13, and are conveyed to a registration roller pair 14. A feed sensor S2 is disposed downstream of the registration roller pair 14, and detects the image writing timing and the leading and trailing edges of the sheet.

The registration roller pair 14 conveys the sheet in synchronism with the image carrier 5, and the toner image formed on the image carrier 5 is transferred to the sheet by the copying section 9. The toner image on the sheet is fixed on the sheet by the heat fixing device 15. Thermal fixing device 15
Is composed of a heating element (not shown) and a thermistor for detecting the temperature of the heating element, and applies heat and pressure to the sheet after the transfer process to fix the toner image on the sheet.

In the apparatus main body 1, a face-up tray 17 for discharging the recording surface upward is disposed on the side of the apparatus, and a face-down tray 20 for discharging the recording surface downward is disposed on the upper surface of the apparatus. When the timing at which the sheet has passed the thermal fixing device 15 is detected by the discharge sensor S3, the sheet is conveyed by the face-up discharge roller pair 16 and discharged to the face-up tray 17 or the face-down tray 20.

The face-up tray 17 is configured to be openable and closable with respect to the apparatus main body 1. When the tray detection sensor S4 detects that the sheet is open, the sheet is discharged to the face-up tray 17. When the face-up tray 17 is closed as shown in FIG. 1, the closed face-up tray 17 forms a discharge conveyance path 18, and a sheet is discharged to the face-down tray 20 by a face-down discharge roller pair 19. , Be loaded.

When performing double-sided recording, the face-up tray 17 is closed, the discharge conveyance path 18 constitutes a reverse path, and the face-down discharge roller pair 19 constitutes a reverse conveyance means. The sheet conveyed by the face-down discharge roller pair 19 in the direction of the face-down tray 20 for a predetermined period of time changes the conveyance direction by switching the drive of the face-down discharge roller pair 19 in a state where the sheet is engaged with the face-down discharge roller pair 19. The sheet is reversed, and is conveyed to the re-feeding path 22 under the guidance of the pair of reversing sheet guide rollers 21 as guide means.

The reversing sheet sensor S5 can detect the timing at which the sheet is conveyed to the re-feeding path 22 and the leading and trailing ends of the sheet. After the sheet guided to the re-feeding path 22 is conveyed by the reversing sheet conveying roller pair 23, the sheet is stopped in front of the reversing sheet re-feeding roller pair 24,
It waits until it is re-fed as a sheet for the second side (back side) of double-sided recording. The stop and re-feeding of the reversing sheet are performed at the detection timing of the re-feed sensor S6.

When the sheet waiting in the re-feeding path 22 is re-fed by the driving of the pair of reversing sheet conveying rollers 23 and the pair of reversing sheet re-feeding rollers 24, the sheet is moved to the second side similarly to the first side. The image is recorded, and the sheet recorded on the face down tray 20 on both sides is discharged. The refeed path 22 is configured to open and close, and the refeed sensor S6 can detect a jam on the refeed path 22 when the reverse sheet is jammed, and open the refeed path 22. As a result, the sheet on the double-sided conveyance path can be removed.

Next, a case where continuous double-sided printing is performed will be described. As shown in the figure, the sheet P1 on which the recording operation on the first side has been completed is moved to the face-down discharge roller pair 19.
The sheet is once protruded from the sheet, the conveyance direction is reversed, the sheet is engaged with the reversing sheet guide roller pair 21, and is guided to the re-feeding path 22.
Then, while the preceding sheet P1 is in the above state, the succeeding sheet P2 is caused to enter the discharge conveyance path 18.

That is, while the previous sheet P1 exists in the discharge conveyance path 18 between the face-up discharge roller pair 16 and the face-down discharge roller pair 19, the subsequent sheet P2 enters, and the previous sheet P1 enters. And subsequent sheet P2
Are transported while rubbing in the reverse direction and the discharge direction, respectively.

With this configuration, since the preceding sheet P1 does not occupy the discharge conveyance path 18, the following sheet P1
2 can be narrowed, and the processing efficiency in continuous double-sided recording can be improved.

[Second Embodiment] Next, a second embodiment of the image recording apparatus according to the present invention will be described with reference to the drawings.
FIG. 2 is a diagram illustrating a configuration of a discharge unit of the image recording apparatus according to the present embodiment. FIG. 3 is a timing chart illustrating an operation of the image recording apparatus. The same reference numerals are given and the description is omitted.

In FIG. 2, the sheet conveyance distance from the discharge sensor S3 to the face-up discharge roller pair 16 is D1,
The sheet conveyance distance from the face-up discharge roller pair 16 to the reversal position R is D2, the sheet conveyance distance from the reversal position R to the face-down discharge roller pair 19 is D3, and the reversal position R
The sheet conveyance distance from the reverse sheet guiding roller pair 21 to the reversing sheet guiding roller pair 21 is D4, and the sheet conveying distance from the reversing sheet guiding roller pair 21 to the reversing sheet sensor S5 is D5. Each of the distances is a distance along the sheet conveyance path, not a linear distance. The conveying speed of the preceding sheet P1 and the conveying speed of the succeeding sheet P2 are equal to Amm / sec, and both lengths are set to Bmm.

The previous sheet P1 on which an image is recorded on the first surface
Is reversed when the rear end passes the reversing position R, and is conveyed to the reversing sheet guide roller pair 21. Here, the operation timing of the discharge sensor S3, the reversing sheet sensor S5, and the face-down discharge roller pair 19 will be described.

In FIG. 3, first, at time t1, the preceding sheet P1 is detected at the position of the discharge sensor S3. And time t
2, the rear end of the previous sheet P1 passes through the discharge sensor S3,
At time t3 when the rear end of the sheet reaches the reversing position R, the rotation of the face-down discharge roller pair 19 is reversed. The leading edge of the inverted sheet P1 is detected by the inverted sheet sensor S5 at time t4.

At time t5, the succeeding sheet P2 reaches the discharge sensor S3. At time t6, the preceding sheet P1 passes through the face-down discharge roller pair 19, and the reverse rotation ends. At time t7, the reversing sheet sensor S5 detects the previous sheet P1.
At the time t8, the discharge sensor S3 detects the rear end of the succeeding sheet P2.

Here, at time t5 when the subsequent sheet P2 reaches the discharge sensor S3, first, the face-down discharge roller pair
19, it is necessary that both the preceding sheet P1 and the succeeding sheet P2 have a timing that is not involved. This is because the preceding sheet P1 should be reversed and the subsequent sheet P2 should be conveyed in the discharge direction, so that both of them cannot be conveyed.

At time t3, the leading edge of the preceding sheet P1 after the reversal is at the reversing position R, and (B-D3) / A before the trailing edge passes through the face-down discharge roller pair 19.
(sec) On the other hand, it takes (D1 + D2 + D3) / A (sec) until the sheet P2 after passing the discharge sensor S3 reaches the face-down discharge roller pair 19. Therefore, at time t5, t5> t3 + (B-D1-D2-2D3)...

At the same time, at time t5 when the succeeding sheet P2 reaches the discharge sensor S3, the reverse sheet guiding roller pair 21
Must be after the previous sheet P1 is engaged. This is because the reversal conveyance of the preceding sheet P1 may be hindered by the friction of the succeeding sheet P2, and in an extreme case, the sheet may collide against each other and cause a jam.

Here, the sheet P1 from the position at time t3
Time until it is engaged with the reversing sheet guide roller pair 21 is D
4 / A (sec), while the succeeding sheet P2 is at the reversal position R
Is (D1 + D2) / A (sec). Accordingly, by setting the timing of the time t5 so as to satisfy t5> t3 + (D4−D1−D2) / A (Equation 2), such an adverse effect can be prevented.

With the above configuration, it is possible to improve the processing efficiency at the time of double-sided recording, and it is possible to reliably perform the recording / transporting operation without causing a problem of causing a jam.

[0029]

As described above, in the image recording apparatus according to the present invention, while the previous sheet is being reversely conveyed in the reversing pass, the subsequent sheet enters the reversing pass, thereby improving the processing efficiency. Improvement can be achieved.

The timing at which the next sheet enters the reversing path while the previous sheet is being reversed and conveyed is the timing when both sheets are not engaged with the reversing conveyance means, or the timing when the preceding sheet is engaged with the guiding means. By doing so, it is possible to improve the processing efficiency at the time of double-sided recording, and it is possible to reliably perform the recording and transporting operation without any adverse effect of causing a jam.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an overall configuration of an image recording apparatus according to a first embodiment.

FIG. 2 is a diagram illustrating a configuration of a discharge unit of an image recording apparatus according to a second embodiment.

FIG. 3 is a timing chart illustrating the operation of the image recording apparatus.

[Explanation of symbols]

 S1 ... Sheet presence / absence detection sensor S2 ... Feed sensor S3 ... Ejection sensor S4 ... Tray detection sensor S5 ... Reverse sheet sensor S6 ... Refeed sensor 1 ... Main unit 2 ... Image forming unit 3 ... Double-sided recording conveyance path 4 ... Sheet cassette DESCRIPTION OF SYMBOLS 5 ... Image carrier 6 ... Primary charging device 7 ... Laser scanner unit 7a ... Mirror 8 ... Developer 9 ... Transfer part 11 ... Pickup roller 12 ... Feed roller 13 ... Retard roller 14 ... Registration roller pair 15 ... Heat fixing device 16 ... Face-up discharge roller pair 17… Face-up tray 18… Discharge transport path 19… Face-down discharge roller pair 20… Face-down tray 21… Reverse sheet guide roller pair 22… Re-feed path 23… Reverse sheet transport roller pair 24… Reverse Sheet re-feed roller pair

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H028 BA06 BA09 BA16 BB04 2H072 BA03 BA08 BA12 BB08 CA01 CB01 CB03 CB07 FB02 3F053 BA03 BA27 LA03 LA07 LB01 3F100 AA02 BA05 CA03 CA06 CA12 CA13 CA14 CA15 CA18 EA02 EA03

Claims (4)

[Claims] 1. A reversing path for reversing the conveying direction of a sheet on which an image has been recorded, a reversing conveyance unit arranged downstream of the reversing path, and a re-feeding path connected upstream of the reversing path. Guiding means for guiding a reversed sheet arranged in the re-feeding path, wherein the image recording apparatus records an image on both sides of the sheet; An image forming apparatus for causing a subsequent sheet to enter the reversing path. 2. The timing at which a subsequent sheet enters the reversing path while the preceding sheet is being reversed and conveyed,
2. The image recording apparatus according to claim 1, wherein the timing is such that both sheets are not involved in the reverse conveyance unit. 3. The timing at which a subsequent sheet enters the reversing path while the preceding sheet is reversingly conveyed,
The image recording apparatus according to claim 1, wherein after the previous sheet is engaged with the guiding unit, the image is recorded. 4. The apparatus according to claim 1, wherein the reversing path is a discharge conveyance path for discharging the sheet out of the apparatus.
The image recording device according to any one of claims 1 to 3, wherein