JPH0623906B2 - Color copier - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color copying machine using an electrophotographic process, and more particularly, a heating type fixing means for fixing a toner image on a transfer sheet by heating. The present invention relates to an improvement of a color copying machine equipped with.

[Prior art]

As a conventional color copying machine of this type, there is one shown in FIG. 1, for example. This scans the document (2) on the platen (1) with the exposure lamp (3), and the reflected light from the document (2) is divided into red, green, and blue color components by the three-color separation filter (4). Along with color separation, the above-mentioned color components are exposed on the photosensitive drum (5) at a time, and toner development is carried out at each of cyan, magenta, and yellow developing machines (6) (7) (8) corresponding to each color component. On the other hand, one transfer sheet (10) is wound around the transfer roll (9) which rotates in synchronization with the photosensitive drum (5), and the transfer sheet (1
0) sequentially transfer each toner image to the transfer roll.
The transfer sheet (10) separated from (9) is conveyed to a heating type fixing device (12) by a conveying belt (11), and the three layers of toner on the transfer sheet (10) are conveyed in the fixing device (12). The image is heat-melted and fixed to obtain a color copy. still,
In FIG. 1, (13) and (14) are mirrors and lenses of an optical system forming an exposure optical path, (15) is a pre-charging device that pre-charges the photosensitive drum (5) before exposure, and (16) is a photosensitive member. A cleaner that removes static electricity from the drum (5) and removes residual toner, (17) and (18) are cassettes for feeding transfer paper (10) of different sizes, and (19) and (20) are paper feed cassettes. Roller, (21) is the cassette (1
7) A conveyor roll that conveys the transfer paper from (18) to the transfer roll (9), and (22) is a peeling unit that separates the transfer paper (10) wound around the transfer roll (9) from the transfer roll (9). ,(twenty three)
Numerals (24) are a sheet and a feeding roller for feeding the transfer sheet (10) having passed through the fixing device (12) to the storage tray (25).

[Problems to be Solved by the Invention]

By the way, in the color copying machine as described above, since the toner layer on the transfer paper (10) becomes thicker than that in the case of black-and-white copying, it is necessary to keep the toner fixability on the transfer paper (10) good. The amount of heat required is relatively large. However, in the above-mentioned conventional color copying machine, in order to keep the transfer paper (10) transferred smoothly in the process of transferring the transfer paper (10) from the transfer roll (9) to the fixing device (12), Transfer belt (11) transfer speed is transfer roll
Since the peripheral speed of the transfer roll (9) is set to be substantially equal to the peripheral speed of (9), and the peripheral speed of the transfer roll (9) is set to be relatively high to increase the copying speed, the transfer paper (10) is relatively It will be sent by the fixing device (12) at a high speed. Therefore, the transfer paper (10) passes through the fixing device (12) for a relatively short time, and accordingly, the fixing device (12) generates a large amount of heat in a relatively short time. ). Therefore, the power consumption of the fixing device (12) is significantly increased, and due to the short transit time of the transfer paper (10) to the fixing device (12), the fixing failure of the toner on the transfer paper (10) occurs. There is a fear that it will be easy.

The present invention has been made from the above viewpoints,
The purpose is to reduce the power consumption of the fixing unit and to stabilize the fixing property of the toner while maintaining a good transfer condition of the transfer sheet from the transfer process to the fixing process. To provide.

[Means for Solving the Problems]

The basic configuration of the present invention is that the transport length of the transport means between the transfer means and the fixing means is set to be at least the maximum usable size of the transfer paper, and the transport means is set to at least the transfer paper of the transfer paper. Before the rear end is separated from the transfer means and the front end of the transfer paper reaches the fixing means, the transfer speed of the transfer means is switched to a speed lower than the normal speed, and after the transfer paper passes through the fixing means, the transfer means moves. A transport speed switching means for switching the transport speed to the normal speed is additionally provided.

[Action]

According to the technical means as described above, the transfer paper is smoothly guided from the transfer means to the transfer means by the switching of the transfer speed switching means, and the rear end of the transfer paper is separated from the transfer means and the front end of the transfer paper. Since the transfer paper transport speed is set to a speed slower than the normal speed before the transfer paper reaches the fixing means, the transfer paper passes through the fixing means at a slow speed, and the fixability of the color toner image on the transfer paper is good. Keep on.

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.

In the embodiment shown in FIG. 2, the basic structure of the color copying machine is substantially the same as the conventional one, but a conveyor belt different from the conventional one.
It is equipped with (30). This conveyor belt (30) is
(31) and the driven pulley (32), and the transport length (l) of this transport belt (30) is approximately equal to the maximum usable size (Amax) of the transfer paper (10). Is set to.

Further, the conveyor belt (30) is provided with a switching means (40) for switching the transportation speed of the transportation belt (30) between a normal speed and a speed lower than the normal speed, and this switching means (40) is provided. The driving force from the driving source is transmitted to the conveyor belt (30) via the driving belt, and a driving motor (not shown) for driving the photosensitive drum (5) is commonly used as the driving source. There is. In this embodiment, as shown in FIG. 3, the switching means (40) fixes the drive gear (42) to one end of the drive shaft (41) of the drive pulley (31), and the drive gear (42) is fixed. 42) is engaged with a pair of transmission gears (43) (44) having a gear ratio of about 3: 1, and the transmission gears (43) (44)
Is fixed to each of the transmission shafts (45) (46), and further, each of the transmission shafts (49) (50) is rotated by a driving force from the drive motor at a predetermined rotational speed. (45) (4
6) is connected intermittently via clutches (47) (48). The on / off state of each clutch (47) (48) is controlled by the clutch control circuit (51).
A pair of timing signals (S ₁ ) and (S ₂ ) for switching the transport speed of the transport belt (30) is given to (51).

That is, in this embodiment, one of the timing signals
(S ₁ ) is a detection signal from the detection switch (52) that detects when scanning of the original (2) is completed, delayed by a timer (53) for a certain period of time. While it occurs when completely peeled from (9),
For the other timing signal (S ₂ ), the transfer paper (10) is the fuser (12).
Using the detection signal from the detection switch (54) that detects the time when it has completely passed through, the detection switch (54) is
For example, it is composed of a micro switch in which a switch piece (54a) is projectingly arranged in the short (23), and when the transfer paper (10) passes through the short (23), the rear end of the transfer paper (10) is the above-mentioned switch. A detection signal is output when the vehicle gets over the piece (54a).

Then, the clutch control circuit (51)
(S ₁ ) cuts off one clutch (47) and continues the other clutch (48), and the timing signal (S ₂ ) reverses the intermittent state of the clutches (47) (48). .

Further, in this embodiment, the fixing device (12) is composed of, for example, a fixing roll (12a) having a heat source and the fixing roll (12b), and the fixing roll (12a) and the pressure roll (12b).
The peripheral speed of is set in correspondence with the slow transfer speed of the transfer belt (30).

It should be noted that the same components as those of the related art are denoted by the same reference numerals as those of the related art, and detailed description thereof will be omitted here.

Next, the operation of the color copying machine according to this embodiment will be described.

Now, in the case of taking color copy, if an operation button for color copy (not shown) is operated at time (t ₀ ) (see FIG. 4), it is wound around the transfer roll (9) through the same process as the conventional one. Toner images corresponding to the respective color components are sequentially transferred to the transferred transfer paper (10), and the transferred transfer paper (10) is sequentially peeled from the transfer roll (9) by the peeling means (22), and the conveyor belt ( 30). At this time, since the one clutch (47) maintains the continuous state and the other clutch (48) maintains the disconnected state, the rotational force of the rotating shaft (49) is transmitted by the clutch (47) and the transmission shaft. (45), transmission gear (43), drive gear (42) and drive shaft (41).
As shown in FIG. 4, the transport speed of the transport belt (30) is set to the normal speed v _α which is approximately equal to the peripheral speed of the transfer roll (9). For this reason, the transfer paper (10) does not sag from the transfer roll (9) to the conveyor belt (3
It moves smoothly to 0).

Then, when the rear end of the transfer paper (10) is peeled off from the transfer roll (9), the timing signal (S ₁ ) is applied to the clutch at the time (t ₁ ) as shown in FIGS. 3 and 4. Control circuit
Given to (51), the clutch control circuit (51) cuts off one clutch (47) and takes over the other clutch (48). Then, the rotational force of the rotating shaft (50) is changed to the clutch (4
8), the transmission shaft (46), the transmission gear (44), the drive gear (42) and the drive shaft (41) are transmitted to the drive pulley (31). At this time, the number of teeth of the transmission gear (44) is the same as that of other transmission gears.
Since it is approximately one-third of the number of teeth of (43), the conveyor belt (3
As shown in FIG. 4, the transport speed of (0) is switched to the slow speed v _b corresponding to approximately one third of the normal speed v _a . In this state, the transfer length (l) of the transfer belt (30) is equal to the transfer paper (10).
Since the transfer paper (10) is set to be approximately equal to the maximum use size (Amax), even if the transfer paper (10) is the maximum use size (Amax), the transfer paper (10) as a whole has the transfer belt (10). The transfer sheet (10) is placed on the sheet (30), and the leading end of the transfer sheet (10) has not reached the fixing device (12). Therefore, the conveyor belt (3
The transfer paper (10) on (0) is not sent to the fixing device (12) at the normal speed v _a , and the transfer paper (10) is always sent to the fixing device (12) at a slow speed v _b. To be

After that, the transfer paper (10) passes through the fixing device (12), but since the transfer speed of the transfer paper (10) becomes slower than before, the transfer paper (10) is fixed accordingly. It takes longer to pass through the vessel (12). For this reason, the fixing device (12) is configured to transfer the heat required for toner fixing to the transfer paper (1
Therefore, the amount of heat from the fixing device (12) per unit time can be smaller than that in the conventional case. Therefore, the power consumption of the fixing device (12) is small,
Since the toner fixing time in the fixing device (12) can be extended to some extent, the multi-layered toner layer is reliably and gently heated and melted, and the situation in which the toner is not fixed properly can be effectively avoided. Will be done. After that, the transfer sheet (10) having passed through the fixing device (12) is sent out to the storage tray (25) through the sheet (23) and the feed roller (24), and a predetermined color copy is obtained. At this time,
The transfer paper (10) is detected by the switch piece (54).
After passing through a), as shown in FIGS. 3 and 4, at that time (t ₂ ), the timing signal (S ₂ ) is given from the detection switch (54) to the clutch control circuit (51), and the clutch is turned on. The control circuit (51) will once again join one clutch (47) and disconnect the other clutch (48). Then, the rotational force of the rotation shaft (49) is applied to the clutch (47), the transmission shaft (45),
It is transmitted to the drive pulley (31) via the transmission gear (43), the drive gear (42) and the drive shaft (41), and the transport speed of the transport belt (30) is as shown in FIG. , Again switch to normal speed v _a . In this case, even if the color copying operation is continuously performed, in this embodiment, the preceding transfer paper (10) is completely peeled off from the transfer roll (9), and the fixing device is fixed.
Since the time until it finishes passing through (12) is set within the time when the next transfer paper (10) is being transferred on the transfer roll (9), the previous transfer paper (10) The next transfer sheet (10) is not delivered onto the conveyor belt (30) before passing through the fixing device (12). Therefore, the conveyor belt (3
There is no concern that the transfer paper (10) is sent from the transfer roll (9) onto the transfer belt (30) in a state where the transfer speed of (0) is different from the peripheral speed of the transfer roll (9). 10) will always be smoothly delivered from the transfer roll (9) onto the conveyor belt (10) when the conveyor belt (30) is at the normal speed v _a .

In the above embodiment, the transport length of the transport belt (30)
Although (l) is set to be substantially equal to the maximum usable size (Amax) of the transfer sheet (10), it does not matter if the conveyance length (l) is set larger than the maximum usable size (Amax). Further, in the above embodiment, a combination of a gear and a clutch is used as the transfer speed switching means (40), but the transfer speed switching means (40) is not necessarily limited to this, and for example, a dedicated drive motor whose rotational speed can be switched. Can be used. Furthermore, regarding the timing of switching the transport speed of the transport belt (30),
The transfer speed of the transfer belt (30) is not limited to that shown in the above embodiment, and at least while the transfer paper (10) is passing through the fixing device (12), the transfer speed is lower than the normal speed. It may be switched. Furthermore, the conveyor belt (3
The method for detecting the transfer timing of (0) is not limited to that shown in the above embodiment, and the position of the transfer sheet may be directly detected by using, for example, a proximity switch. Further, the change in the transfer speed of the transfer belt (30) is not limited to that shown in the above embodiment, and the transfer condition of the transfer paper (10) is impaired at least when performing a continuous color copying operation. Set it so that it does not break. Further, in the above embodiment, the present invention is applied to a color copying machine provided with the photosensitive drum (5), the transfer roll (9), and the conveyor belt (30). It is needless to say that the present invention can be applied to a color copying machine provided with the transfer means, the transfer means such as a chain gripper, and the like.

〔The invention's effect〕

As described above, according to the color copying machine of the present invention, the transfer speed of the transfer means for transferring the transfer paper is slowed while the transfer paper passes through the fixing means. Is relatively long, the amount of heat applied to the transfer paper by the fixing unit per unit time can be reduced accordingly, the power consumption of the fixing unit can be reduced, and the fixing property of the toner can be stabilized. Also,
According to the present invention, since the transfer sheet does not reach the fixing unit in the process of being sent out from the transfer unit,
Even if the transport speed of the transport means changes, there is no possibility of impairing the transport condition of the transfer sheet.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of a conventional color copying machine, FIG. 2 is an explanatory view of an essential part showing an embodiment of a color copying machine according to the present invention, and FIG. 3 is a concrete example of a conveying speed switching means. 4A and 4B are timing charts showing changes in the transport speed of the transport means. References (5) …… Photosensitive drum (photoconductor) (9) …… Transfer roll (transfer means) (10) …… Transfer paper (11) (30) …… Conveying belt (conveying means) (12) …… Fixing device (fixing means) (40) …… Conveying speed switching means (l) …… Conveying length (Amax) …… Maximum size of transfer paper

Claims (1)

[Claims] 1. A transfer unit for sequentially transferring a toner image corresponding to each color component on a photoconductor onto a transfer sheet, a fixing unit for heating and melting and fixing a multilayer toner image transferred onto the transfer sheet, In a color copying machine provided with a conveying unit that conveys the transfer sheet sent from the transfer unit to the fixing unit, the conveying length of the conveying unit is set to at least the maximum usable size of the transfer sheet, and Means that at least the rear end of the transfer paper is separated from the transfer means and the transfer speed of the transfer means is switched to a speed lower than the normal speed before the front end of the transfer paper reaches the fixing means to fix the transfer paper. A color copying machine characterized in that a transport speed switching means for switching the transport speed of the transport means to a normal speed after passing through the means is attached.