JPH0439670B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color electronic copying machine for obtaining a recording speed corresponding to the size of recording paper.

[Prior art]

FIG. 1 is a side view showing an example of the configuration of a conventional color copying machine, including a platen 1, a light source lamp 2,
A scan exposure system consisting of reflection mirrors 30 to 35, a focusing lens 4, and a three-color separation filter 5, a photosensitive drum 6, and different colors of yellow, magenta, and cyan (hereinafter referred to as Y) arranged successively on the circumferential surface of the photosensitive drum 6. A developing system consisting of developing machines 7, 8, and 9 containing toner of each color (abbreviated as M and C), a transfer drum 11 having a gripper 10 for gripping recording paper, and a transfer corotron 12 installed inside the transfer drum 11. A transfer system consisting of a transfer system, a paper feed system consisting of paper feed trays 13 and 14 loaded with recording paper of different sizes, a paper feed system consisting of a paper feed roller 15, an endless conveyor belt 16, a fixing roller 17, a paper ejection roller 18, and a paper ejection tray 19. The fixing and paper discharging system consists of: Also the second
Figures a, b, and c are timing charts showing the operations of the scan exposure system, development system, and transfer system, respectively, in the conventional apparatus. In these figures 1 and 2, when the recording start operation is performed, the time
From t ₀ to the light source lamp 2, the reflecting mirrors 30, 3
Three reciprocating scans of 1 and 32 are performed, and the photosensitive drum 6 is exposed to light through the blue, green, and red filters of the three-color separation filter 5 sequentially interposed in the scanning optical path during each scan. (See Figure 2a). The electrostatic latent image of each color component image information formed on the photosensitive drum 6 by this three-color separation exposure is developed by opposing complementary color toners Y, M, and C, respectively, when passing through the development system. Time after a certain period of time has elapsed from the start of exposure t ₀
At _t1 , the leading edges of these Y, M, and C toner images sequentially reach a transfer position T where the photosensitive drum 6 and transfer drum 11 are in contact (see FIG. 2b). On the other hand, the transfer drum 11 is also connected to the photosensitive drum 6 from the start of the exposure.
A recording paper of a predetermined size, which is rotated at the same circumferential speed as the paper feed system, is gripped by the gripper 10 and rotated so that the leading edge of the recording paper is also at the transfer position T at the time _t1 . (see Figure 2c). Thereafter, while rotating the photosensitive drum 6 and the transfer drum 11 at the same circumferential speed, the above operation is repeated 3 times.
Y formed on the photosensitive drum 6 repeatedly,
Color copies were obtained by sequentially transferring M and C toner images from the same position each time onto the recording paper and mixing these Y, M and C toners. Note that L in FIG. 2 is a length corresponding to the circumferential length of the photosensitive drum 6 and the transfer drum 11. In this way, in a device that sequentially transfers each Y, M, and C toner image onto a single sheet of recording paper and obtains a color copy by mixing them, scanning is performed to prevent these transfer positions from shifting and to improve the print quality. Drive system, photosensitive drum 6, transfer drum 1
It is important to synchronize the drives of the two. In this respect, conventionally, the photosensitive drum 6 and the transfer drum 11 are connected by a gear with little collision and are driven integrally, and the scan drive system is driven by a servo motor or the like that is highly responsive to speed control and the synchronization is performed. A method was used to increase the accuracy of the take. As an example of selecting the circumferential length L of the transfer drum 11 based on such a driving method, a length corresponding to the scanning reciprocating time of the maximum size A3 original is used, or a length equivalent to the scanning reciprocating time of the maximum size A3 original is used. There are two possible methods: using a long one, but in either case, the circumferential speed of the transfer drum 11 depends on the circumferential speed of the photosensitive drum 6 and is constant due to the above conditions. In the former method of circumference selection,
The recording speed is the same for B5 to A3 sizes, and in the case of the latter, when recording A3 size, it is necessary to idle the transfer drum 11 once during the scan back, so the recording speed is approximately twice that of B5 and A4 sizes. The disadvantage was that it took a long time to record.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide a color copying machine that can establish an appropriate printing time depending on the size of recording paper and can efficiently proceed with printing work.

[Structure of the invention]

Therefore, the present invention performs scanning and scanback in an amount corresponding to the paper size for each color component, and also performs scanning and scanning back during the transfer and copying of the developed toner image of the electrostatic latent image of each color component on the photosensitive drum formed by the scanning. The rotational speed of the transfer drum is varied according to the paper size so that the leading edge of the toner image of the next color and the leading edge of the recording paper coincide at the transfer position, thereby achieving an appropriate recording speed according to the paper size. I'm trying to get it.

〔Example〕

Embodiments of the present invention will be described in detail below based on the accompanying drawings. FIG. 3 is a schematic diagram of a color copying machine showing an embodiment of the present invention, and parts corresponding to those of the conventional apparatus shown in FIG. 1 are designated by the same reference numerals. According to the apparatus of the present invention shown in FIG. 3, independent servo motors 200, 210, 220 are connected.

Here, only the servo motor 220 connected to the capstan shaft 22 is capable of forward and reverse rotation.

In addition, the scan start timing and the trailing edge of the transfer recording paper are detected near the standby position of the light source lamp 2 before the scan start in the scan mechanism system and near the circumferential surface of the transfer drum 11 immediately before the above-mentioned transfer position T, respectively. Optical sensors 23 and 24 are provided.

The control unit of this device also includes a reference pulse circuit 25 that provides a reference pulse for rotating the servo motor 200 at a constant speed, servo circuits 26 and 27 that drive and control the servo motors 210 and 220, and the servo circuit. Paper size setting circuit 2 that issues recording paper size commands to 26 and 27
8. Furthermore, Fig. 4 a, b,
c, d, and e are the scan mechanism, sensor 23, photosensitive drum 6, and transfer drum 1 in the above device, respectively.
1. This is a timing chart showing each operation of the sensor 24. Hereinafter, the control operation of the apparatus of the present invention will be explained in detail with reference to FIG. 4.

In the figure, L, I, and R correspond to the circumferential length of the photosensitive drum 6 or the transfer drum 11, the recording paper length, and the scan back length, respectively.

First, prior to a printing operation, the size of the recording paper used for the printing is set in the paper size setting circuit 28, and a paper size signal based on the setting is input to the servo circuits 26 and 27. Next, when a recording start operation is performed, the reference pulse circuit 2
5 supplies a reference pulse to a servo motor 200, and the servo motor 200 always rotates the photosensitive drum 6 at a constant circumferential speed based on the reference pulse. The rotation signal of this servo motor 200 is input to the servo circuit 27, and the servo circuit 27 uses this rotation signal and the paper size signal input from the paper size setting circuit 28 as described above to start the rotation of the servo motor from time _t0 . 220 is rotated forward to perform a scan of a length corresponding to the paper size (corresponding to time _t1 ), and then reversed to perform scanback at a preset speed (corresponding to time _t2 ). The above scanning operation is repeated for each of the blue, green, and red filters of the three-color separation filter 5 sequentially interposed in the scanning optical path on one color document placed on the platen 1, Three-color separation exposure of the respective color component image information is performed on the photosensitive drum 6 (see FIG. 4a). The scan operation at this time is not to wait for the photosensitive drum 6 to complete one rotation and then start scanning from the same position for each of the color components, as in the conventional case, but to start the next scan immediately after the scan back is completed. . At the start of scanning for each color component for such three-color separation exposure, the sensor 23 detects the start of scanning according to the movement of the light source lamp 2 (see FIG. 4b), and the detection output is sent to the servo circuit. 2
6 is input. Next, when the electrostatic latent image of each color component image information formed on the photosensitive drum 6 by the three-color separation exposure passes through the above-mentioned developing section, the developing devices 7, 8, and 9 move the opposing complementary color toner Y. , M, and C in sequence. Through this operation, the leading edge of the Y toner image developed first is transferred to the transfer drum after a certain period of time _t3 corresponding to the circumferential speed of the photosensitive drum 6 has elapsed from the time _t0 when scanning of the blue component image information starts. 11 (see FIG. 4c). On the other hand, the servo circuit 2
6 also receives a rotation signal from the servo motor 200 as described above, drives the servo motor 210, rotates the transfer drum 11 at the same circumferential speed as the photosensitive drum 6, and supplies paper from the paper feed system during the rotation. The gripper 10 grips the recording paper, and when a time t ₃ has elapsed from the initial scan start time t ₀ , conveyance control is performed such that its leading edge meets the leading edge of the Y toner image at the transfer position T. (See Figure 4d).

From this transfer position, the transfer of the Y toner image formed on the photosensitive drum 6 onto the recording paper that is conveyed in close contact with the transfer drum 11 is started. The transfer of the Y toner image is completed at time _t6 by rotating the photosensitive drum 6 and the transfer drum at the same circumferential speed and transporting the recording paper by the length l, but at time _t4 immediately before the transfer is completed. The trailing edge of the recording paper is detected by the sensor 24 (Fig. 4e).
), the detection signal is input to the servo circuit 26. Therefore, the servo circuit 26 transfers the recording paper to the sensor 2 from the rear edge detection signal input time _t4 .
4. By counting the time _t5 required for conveyance from the placement position to the transfer position T, the above-mentioned transfer end time _t6 is detected, and from this time _t6 , the rotational speed of the servo motor 210 is determined as the paper size signal. The leading edge of the recording paper, on which the Y toner image has already been transferred, is then driven at the leading edge of the M toner image, which is formed on the photosensitive drum 6 and reaches the transfer position T, at this transfer position T. The speed is controlled so as to meet the target (see Figure 4 d). That is, as is clear from FIGS. 4c and 4d, while the photosensitive drum 6 advances the distance R from the Y toner image transfer end time _t6 to the M toner image to be formed next, that is, within the time _t7 . In the transfer drum 11, it is necessary to advance the difference between the circumferential length L and the recording paper length l, that is, (L-l). Now, if the constant speed of the photosensitive drum 6 and the rotational speed of the transfer drum 11 during fast rotation are v ₀ and v ₁ , respectively, then from the above conditions, R/v ₀ = (L-l)/v ₁ = t ₇ . . . …(1) holds true. Therefore, rearranging the equation (1) gives the transfer drum 11 a rapid rotation speed v ₁ as follows: v ₁ =(L-l)/Rv ₀ (2).

In the above equation (2), the peripheral speed v ₀ of the photosensitive drum 6
and circumferential length L are determined in advance, and the paper length l of the recording paper and the amount of rotation R at the time of scanback can be recognized from the paper size signal given from the paper size setting circuit 27, respectively. It can be driven at a rotational speed suitable for the paper size. Note that the servo circuit 26
Similarly to the first scan operation via the blue filter, the transfer drum 11, which has been rotated at the speed _v1 described above from the time _t6 , is transferred to the sensor 23.
In other words, when time _t7 is counted after the scan start detection signal via the green filter is input, rotation control is performed to return the speed _v1 to the normal speed _v0 .

Thereafter, at time _t8 , transfer of the M toner image to the recording paper conveyed by the transfer drum 11 starts. After that, the servo circuit 26
is the transfer end time detected from the trailing edge detection signal of the recording paper by the sensor 24 and the sensor 23 as described above.
The leading edge of the C toner image and the leading edge of the paper are aligned at the transfer position by rapidly rotating the transfer drum 11 at a speed _v1 between the transfers determined by the transfer start time detected from the scan start detection signal. By rotating the drum at a speed _v0 , the C toner image is also transferred, and the desired color copy is completed by mixing these Y, M, and C toners.

As a result of such rotational speed control of the transfer drum 11, compared to the conventional printing time, the time _t9 , which is sufficient to convey the difference between (L-l) and R at the circumferential speed _v0 , for each color toner image transfer is The printing time can be shortened by _t9 =L-l-R/ _v0 . In the above example, the circumferential length of the transfer drum 11 is set to the length equivalent to the scanning reciprocating time of the largest size recording paper, and when the paper is the largest size, the transfer drum 11 is always driven to rotate at a constant speed v ₀ to print. The speed v ₁ is applied between transfers only when the paper size is smaller than this.
This is to speed up the rotation.

〔Effect of the invention〕

As explained above, according to the color copying machine of the present invention, scanning and scanback are performed for each color component according to the paper size, and the electrostatic latent image of each color component formed on the photoreceptor drum by the scanning is This is because the rotational speed of the transfer drum is varied depending on the paper size so that the leading edge of the next toner image and the leading edge of the recording paper coincide at the transfer position between each transfer of the developed toner image. This provides an excellent effect in that an appropriate recording speed can be obtained depending on the paper size, allowing efficient printing work to be performed.

[Brief explanation of drawings]

Fig. 1 is a side view showing the configuration of a conventional color copying machine, Fig. 2 is a timing chart showing the operation of each part in this conventional device, and Fig. 3 is a conceptual diagram of a color copying machine showing an embodiment of the present invention. The configuration diagram and FIG. 4 are timing charts showing the operation of each part in the device of the present invention. 6...Photosensitive drum, 11...Transfer drum, 2
0, 21, 22...rotation axis, 200, 210, 2
20... Servo motor, 23, 24... Optical sensor, 25... Reference pulse circuit, 26, 27... Servo circuit, 28... Paper size setting circuit.

Claims (1)

[Scope of Claims] 1. A color original is sequentially exposed to multiple color separations on a photosensitive drum rotated at a constant speed by repeated scanning with a scan optical system, and this is developed each time with complementary color toner, and then A color copying machine that obtains color copies by repeatedly transferring images onto recording paper on a transfer drum that rotates in contact with the photosensitive drum, comprising: a first sensor that detects the start of scanning of the scan optical system; a second sensor that detects the trailing edge of the recording paper, and detects a transfer start time and a transfer end time from the detection outputs of the first and second sensors, respectively, and detects the transfer start time and transfer end time between the detected end and start of transfer. . A color copying machine, comprising: control means for increasing the rotational speed of the transfer drum so that the leading edge of the recording paper on the transfer drum and the leading edge of each of the color toner images coincide with each other.