JPS63170672A - Color image forming device - Google Patents

Abstract

PURPOSE:To miniaturize a device, and to obtain it at a low cost by driving two pieces of developing devices by shifting the driving time of one developing device and the other developing device during about one rotation of an image forming body by a common driving source through a switching means. CONSTITUTION:A controller turns on an ON-OFF switch 43 while the development by a developing device 23 or 24 is being executed, and rotates a motor 44 by a motor power source, and also, turns on a clutch power source and switches a changeover switch 45 to an A contact point while the developing device 23 executes development, and changes over said switch to a B contact point while the developing device 24 executes development. As a result, while the changeover switch 45 is changed over to the A contact point, the rotation of the motor 44 is transmitted to a sleeve 32 through a magnet body 33 of the developing device 23 and a worm, a worm, gear, etc., and while said switch is changed over to the B contact point, said rotation is transmitted to the magnet body 33 of the developing device 24 and the sleeve 32. In such a way, the device is miniaturized and constituted at a low cost, and also, a forming speed of a color image is comparatively high, and a faithful color image can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color image forming apparatus, and in particular, an apparatus in which an electrostatic image forming means and three or four developing devices are arranged around an image forming body. The present invention relates to an apparatus that repeatedly develops an electrostatic image formed on an image forming body by an electrostatic image forming means into a toner image using a developing device, thereby forming a color image consisting of a composite of toner images on the image forming body.

[Background of the invention]

In the color image forming apparatus as described above, a photoreceptor drum is used as an image forming member, and an electrostatic image forming means forms a color-separated electrostatic image on the photoreceptor drum on the upstream side of each developing device. In some cases, a color image is formed in one revolution of the photoreceptor drum by developing the electrostatic image in a developing device on the downstream side, and in other cases, the electrostatic image forming means is installed at one location on the upstream side of the developing device, forming a color image on the photoreceptor drum. It is known to form a color image by forming color-separated electrostatic images with each rotation and developing these electrostatic images with corresponding developing devices. The former can form a color image at a high speed, but the device tends to be large and expensive, whereas the latter has the opposite characteristics.

In order to make these color image forming apparatuses more compact and cost-effective, if we consider driving the developing devices by switching from a common drive source using a switching means, in the former case, the driving timings of the developing devices overlap with each other. Otherwise, the device will become extremely large, so a common drive source must have a large capacity that can stably drive multiple developing devices. Since this can be done without increasing the size of the device, a common drive source with the capacity to drive one developing device is sufficient, but the time from electrostatic image formation to development is longer than the developing device on the most upstream side. Since the developing device and the developing device on the most downstream side are equivalent components, if the same bias voltage is applied to the sleeve of the developing device from a common bias power source, color images with different color balances are likely to be formed. Another problem is that switching and driving the moving members of three or more developing units using a common motor makes the transmission mechanism significantly larger and more complex than when driving one or two developing units. There is also.

[Purpose of the invention]

The present invention has been made based on the above-mentioned background, and an object of the present invention is to provide a color image forming apparatus that has a relatively high color image forming speed, is small in size, is configured at low cost, and is capable of forming faithful color images. shall be.

[Structure of the invention]

In the present invention, an electrostatic image forming means and three or four developing devices are arranged around an image forming body, and the electrostatic image formed on the image forming body by the electrostatic image forming means is transferred to toner by the developing device. In an apparatus that forms a color image by combining toner images on an image forming body by repeating development into an image, an electrostatic image forming means is installed upstream of a developing device and one developing device and two developing devices. An electrostatic image shall be formed at two places between the developing devices or between two developing devices, and the above-mentioned one developing device and two developing devices or two developing devices and The two developing devices are each driven by a separate driving source, and the driving timing of one developing device and the other developing device is controlled by a common driving source through a switching means. The color image forming apparatus is characterized in that the color image forming apparatus is driven with a shift of one rotation, and this configuration achieves the above object.

〔Example〕

The present invention will be explained below using illustrated examples.

FIG. 1 is a schematic side view showing an example of the color image forming apparatus of the present invention, FIG. 2 is a partial view showing an example of a developing device, and FIGS. 3 and 4 respectively show the drive mechanism of the moving member of the developing device. FIG. 2 is a perspective view showing an example of the main part configuration.

In FIG. 1, A is a reading unit, B is a writing unit, C is an image forming section, D is a paper feeding section, and E is a fixing section.

The reading unit A scans and exposes a document 2 placed on a platen glass 1 using a scanning optical system consisting of an illumination lamp 4 that moves along a slide rail 3, a first mirror 5, and a V-mirror 6 that moves at a moving speed of Then, the resulting reflected light from the original 2 is imaged on image sensors 9 to 11 for each wavelength, such as blue, green, and red, via an imaging lens 7 and a spectroscopic prism 8, respectively. As a result, the image sensor 9
The blue, green, and red image signals outputted by 11 are processed by a signal processing section (not shown) into image signals for each toner color to be outputted to the writing unit B, and are temporarily stored in a memory. It is preferable to use a commercially available warm white fluorescent lamp as the illumination lamp 4 to prevent emphasis or attenuation of specific colors as it is used as a light source when reading the color image of the document 2, and to prevent flickering. , 40klLzO high frequency power source, and preferably a heater using a resistor to keep the tube at a constant temperature or to promote warm-up. The scanning optical system is configured to expose the standard white plates 12 and 13 before and after scanning and exposing the original 2. The information output by the image sensors 9 to 11 based on the reflected light from the standard white plates 12 and 13 is used to set the developing bias and to send signals to the signal processing section in order to prevent fogging and adjust color balance. Used for processing, etc.

The writing unit) B has a configuration as described in Japanese Patent Application Laid-open No. 56-161566 and Japanese Patent Application Laid-open No. 57-19764, in which a laser beam output from two semiconductor lasers is rotated by a motor 14. The reflected light that is scanned by the polygon mirror 15 is f-
After passing through the θ lens 16, each laser beam enters the photosensitive drum 21 at different positions via a cylindrical lens 17 for scanning line correction and a mirror 18 or mirrors 19 and 20. When the laser beams output from the two semiconductor lasers start scanning with the polygon mirror 15, the beams are detected by the index sensor, so that, for example, the cyan image signal and the yellow image signal from the signal processing section of the reading unit A are detected. Modulation using the image signal or magenta image signal and black image signal is started. This modulation starts with the start of modulation by the cyan image signal or magenta image signal of one laser beam, and the yellow image of the other laser beam is delayed by the time required for the photoreceptor drum 21 to pass between the incident positions of both laser beams. The time required for the photoreceptor drum 21 to make one rotation from the start of modulation by the signal or black image signal, and from the start of modulation of one laser beam by the cyan image signal or the start of modulation of the other laser beam by the yellow image signal. The timing is shifted so that the modulation of one laser beam by the magenta image signal or the start of modulation of the other laser beam by the image signal is delayed by a certain amount of time.

In the image forming section C, the photoreceptor drum 21 rotates at a constant speed in the direction of the arrow before the laser beam from the writing unit B enters, and the charger 22 charges the photoreceptor drum 21.
A laser beam modulated with, for example, a cyan image signal and scanned is incident on the charged surface. As a result, an electrostatic image is formed on the surface of the photoreceptor drum 21, and the electrostatic image is developed into a cyan toner image by a developing device 23 using cyan toner as a developer. The charger 27 uniformly charges the surface on which the toner image has been formed, and a laser beam modulated by a yellow image signal and scanned is incident on the charged surface to form an electrostatic image again. This electrostatic image is developed by a developing device 25 using yellow toner as a developer, thereby forming a two-color image consisting of a combination of a cyan toner image and a yellow toner image on the surface of the photosensitive drum 2. . The transfer device 282 and the separator 29, in which this two-color imaged surface is placed in an inactive state. Static eliminator 30. After passing through the cleaning device 31 and reaching the charger 22, the charger 22 uniformly charges its surface again, and a scanned laser beam modulated with a magenta image signal is incident on the charged surface. Ru.

The electrostatic image thus formed is developed by a developing device 24 using magenta toner as a developer, thereby forming a three-color image on the surface of the photoreceptor drum 21 consisting of a combination of cyan, yellow, and magenta toner images. It is formed. This 3
The charger 27 uniformly charges the surface on which the color image has been formed again, and a laser beam modulated with a black image signal and scanned is incident on the charged surface. The electrostatic image thus formed is developed by a developing device 26 using black toner as a developer, thereby forming a contrast consisting of a combination of cyan, yellow, magenta, and black toner images on the surface of the photoreceptor drum 21. Excellent color images are formed. This color image is transferred to the recording paper P fed from the paper feed section by the transfer unit 2.
8, the transferred recording paper P is transferred to the separator 29.
The image is separated from the surface of the photoreceptor drum 21, the color image is fixed in the fixing section E, and the image is discharged outside the machine. The surface of the photoreceptor drum 21 on which the color image has been transferred is made easy to remove residual toner by a static eliminator 30, and is then removed by a cleaning device 31 to be ready for repeating the next image forming process. return.

That is, according to this image forming apparatus, four colors or three colors can be used.
A color image consisting of a combination of colored toner images can be formed by two rotations of the photoreceptor drum 21, and a color image consisting of a combination of two-color toner images as well as a single color image can be formed in one rotation.

The developing units 23 to 26 in this image forming apparatus do not damage previously formed toner images and can be easily switched between a developing state and an inactive state.
A second step in which development is performed under non-contact jumping development conditions.
A developing device as shown in the figure is preferably used.

In the developing device shown in FIG. 2, a developing roller consisting of a sleeve 32 and a magnet 33 inside the sleeve 32 attracts the developer in a developer reservoir 34 to the surface of the sleeve 32 by the magnetic force of the magnet 33. At least one of the sleeves 33 rotates in the direction of the arrow to convey the adsorbed two-component developer consisting of a mixture of carrier and toner in the same direction as the rotation direction of the sleeve 32, and during the conveyance, the layer thickness regulating blade 35
forms a layer of developer thinner than the gap between the photoreceptor drum 21 and the sleeve 32, and applies a developing bias voltage, which is a superimposition of an AC voltage and a DC voltage, to the sleeve 32 from a bias power source including an AC power source and a DC power source. By doing so, toner flies from the developer layer and adheres to the electrostatic image in the development area where the sleeve 32 faces the photoreceptor drum 21, thereby performing development. The developer layer that has passed through the development area is scraped off from the surface of the sleeve 32 by a cleaning blade 36 made of a thin Mylar plate and returned to the developer reservoir 34, and the developer reservoir 34 is replenished with toner from the toner chamber 37. The developer in the developer reservoir 34 is replenished by the container 38 and the sponge roller 39, and the developer in the developer reservoir 34 is supplied by the stirring rollers 40 and 41.
The toner is uniformly agitated and triboelectrically charged. In addition, to make this developing device inoperable,
This is done by grounding or floating the sleeve 32, by actively applying a DC voltage of opposite polarity to the charging of the toner to the sleeve 32, or by stopping the conveying rotation of the developing roller.

The developing rollers of the developing devices 23 and 24 shown in FIG. 1 are driven by the circuit shown in FIG. A developing bias voltage is applied by connecting the switch 42 to the A contact at least while the developing device 23 is performing development, and by connecting it to the B contact while the developing device 24 is performing development.

That is, the timing of developing devices 23 and 24 differs by one rotation of photoreceptor drum 21 and the time it takes for photoreceptor drum 21 to move between developing devices 23 and 24, and there is no overlap. The output of the common bias power supply can be switched by the changeover switch 42 and applied to each developing roller as shown in FIG. can. Furthermore, since the developing units 23 and 24 are adjacent to each other and the distance between them can be shortened, the attenuation of the electrostatic image potential between them can be reduced, and therefore the developing bias voltage applied to each developing roller can be kept the same. It is also possible to form color images with unchanged color balance,
The bias power supply can be easily controlled by the control device. Of course, the present invention is not limited to this, and the developing bias voltage may be adjusted in accordance with the developing conditions of each developing device. Application of bias voltage to the developing units 25 and 26 is performed in the same manner.

Further, the movement of the moving members such as the developing rollers and stirring rollers of the developing devices 23 and 24 shown in FIG. 1 is carried out by a common motor by a drive device as shown in FIG. 3 or 4.

In the drive device shown in FIG.
During development, the ON-OFF switch 43 is turned on and the motor 42 is rotated by the motor power, and the clutch power is turned on and the selector switch 45 is turned on to rotate the motor 42.
While the developing device 24 is developing, the contact is switched to the A contact, and while the developing unit 24 is developing, the contact is switched to the B contact. Accordingly, the changeover switch 4
5 is switched to the A contact, the rotation of the motor 42 is transmitted to the sleeve 32 by the electromagnetic clutch 46 via the magnet 33 of the developing unit 23, the worm, the worm gear, etc., and while the switch is switched to the B contact, The electromagnetic clutch 47 transmits the signal to the magnet body 33 and sleeve 32 of the developing device 24 . Note that the stirring roller and the like are also rotated in the same way as the magnet body 33 by a gear train, etc., not shown. Further, the movement of the moving members of the developing units 25 and 26 is similarly performed by the motor 48.

In the drive device shown in FIG. 4, a motor 49 rotates in the same direction as the motor 44 shown in FIG. 3 during development by the developing device 23, and rotates in the opposite direction during development by the developing device 24. Reference numerals 50 and 51 transmit the rotation in the same direction and the rotation in the opposite direction to the developing units 23 and 24, respectively, and this also drives the developing units 23 and 24 in the same manner as the drive device shown in FIG. The same applies to the developing units 25 and 26.

As described above, even when the moving members of the developing units 23 and 24 and 25 and 26 are driven by a common motor,
Since the developing timings of the developing units 23 and 24 or 25 and 26 do not overlap, the common motor only needs to have a small capacity to drive one developing unit, and a small motor can drive adjacent developing units. Since it is driven, the transmission mechanism can be easily and compactly constructed.

The color image forming apparatus of the present invention is not limited to the example described above, and may be one in which image exposure to the photosensitive drum is performed by a slit exposure device, or one in which three developing units are provided. For images in which image exposure is performed by a slit exposure device, Japanese Patent Applications No. 61-63856 and No. 61-6526
2 As described in each publication, the photoreceptor drum is equipped with a color separation function, and a primary latent image including a latent image of each color separation is formed by -times of image exposure, and the -second latent image forming surface is It is preferable that the color-separated electrostatic image is drawn out by uniformly exposing the image to specific light.In addition, in the case where three developing units are installed, the most upstream or downstream developing unit is connected to the other one. It goes without saying that the two developing units are driven separately by a drive source different from that of the two developing units.

〔Effect of the invention〕

The color image forming apparatus of the present invention is compact.

It is inexpensive, has a relatively fast color image formation speed, and has the excellent effect of being able to form faithful color images.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view showing an example of the color image forming apparatus of the present invention, FIG. 2 is a partial view showing an example of a developing device, and FIGS. 3 and 4 respectively show the drive mechanism of the moving member of the developing device. FIG. 2 is a perspective view showing an example of the main part configuration. A...Reading unit, B...Writing unit, C...Image forming section, D...Paper feeding section, E...
-Fixing unit, 21...photosensitive drum, 22,
27... Charger, 23-26... Developer, 4
2, 45... Selector switch, 44.48.49...
Motor, 46, 47... Electromagnetic clutch, 50.51.
...One-way clutch. Patent applicant: Konishiroku Photo Industry Co., Ltd., agent patent attorney
Haru Yasutaka ゛-Figure 2 Figure 3 4G Figure 4

Claims (3)

[Claims] (1) Three or four electrostatic image forming means around the image forming body.
A color image is created by composing a toner image on an image forming body by repeatedly developing an electrostatic image formed on an image forming body by an electrostatic image forming means into a toner image using the developing unit. In an image forming apparatus, an electrostatic image forming means is installed upstream of the developing device and between one developing device and two developing devices, or between two developing devices and two developing devices. An electrostatic image is formed at two locations, and the one developing device and the two developing devices or the two developing devices and the two developing devices are driven by separate drive sources, and each of the two developing devices is driven by a separate drive source. A color image forming apparatus characterized in that the developing devices are driven by a common driving source via a switching means, with the driving timings of one developing device and the other developing device being shifted by approximately one rotation of the image forming body. . (2) Claim 1, wherein the common drive source is a bias power supply that applies a bias voltage to a developing roller of a developing device, and the switching means is a power supply circuit including a changeover switch.
The color image forming apparatus described in 1. (3) The color image forming apparatus according to claim 1, wherein the common drive source is a motor that drives a moving member of a developing device, and the switching means is a transmission mechanism including a clutch.