JPH03198072A - Multicolor image forming device - Google Patents

Abstract

PURPOSE:To prevent adhering of carrier to an image carrier due to decreasing of toner before it occurs by periodically cleaning a toner residue quantity detection part inside a toner residue quantity detecting means provided in the developing means with a cleaning member. CONSTITUTION:A piezo-oscillator 20, like a piezo element, is installed as the toner residue quantity detecting means, and when the toner exists on the upper surface of the piezo element 20, outputted voltage from the piezo element 20 cannot be obtained, but when the toner is consumed and the toner quantity inside the toner containing room 6 is decreased to an amount where there is none existant on the upper surface of the piezo element 20, outputted voltage from the piezo element can be obtained, and from the variation of this voltage value, the residue toner quantity in the toner constaining room 6 can be detected. Elastic members 22 are installed in both edge parts of a toner agitating stick 21 of a strip state with an axis 00' as a rotating axis, and the upper surface of the piezo element 20 is periodically cleaned along with the rotation of the toner agitating stick 21. Thus, decreasing of the toner can be detected with accuracy, and the carrier can be prevented from adhering before it occurs.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. The present invention relates to an electrophotographic or electrostatic recording image forming apparatus, and particularly to an image forming apparatus that is capable of forming a multicolor image in one image forming process. The present invention relates to a multicolor image forming apparatus that can perform multicolor image forming.

At present, electrophotographic or electrostatic recording image forming apparatuses are often used as printers for terminal devices of information equipment such as computers, facsimiles, and CAD. In particular, in electrophotographic printers, information signals are written on a photosensitive drum as an electrostatic latent image carrier using a laser beam, LED, LCD, etc., this is made into a visible image by a developing device, and then transferred to transfer paper. A recorded image is obtained through the transfer and fixing process, and in conventional printers, the recorded image is of one color, for example, black.

However, in recent years, recorded images have become clearer and information has become easier to understand, so for example, the color of the format and the color of the calculated value or data value are expressed in different colors, or It is desired that the drawings be distinguished using two or more colors, such as outputting a part of a drawing in a different color.

Among electrophotographic image forming apparatuses capable of such multicolor recording, two-color image forming apparatuses have two sets of latent image forming means and developing means, and form two-color printed images in one image forming process. An example of an electrophotographic apparatus is shown in FIG.

In FIG. 2, a photosensitive drum 101 serving as an image carrier rotates in the direction of arrow A, and a first electrostatic latent image is formed by a latent image forming means. In other words, the photosensitive drum 101 is
First, after being uniformly negatively charged by the primary charger 102, a first image exposure is performed using a laser beam 1 or the like from a first exposure means (not shown). This first image exposure is an image exposure that exposes an image area,
A negative electrostatic latent image is formed on the photosensitive drum 101. This electrostatic latent image is reversely developed by a developing means, that is, a first developing device 103, using negatively charged chromatic toner, for example, red, to obtain a first visible image.

Next, in the same manner, a second visible image is formed on the photosensitive drum 101 by the second latent image forming means and the second developing means. That is, after the photosensitive drum 101 is uniformly negatively charged again by the secondary charger 104, a second image exposure is performed by a laser beam 2 or the like from a second exposure means (not shown). . Similar to the first image exposure, this second image exposure is an image exposure that exposes an image area, and forms a negative electrostatic latent image on the photosensitive drum 101. This electrostatic latent image is reversely developed with negatively charged black toner by the second developing device 105 to obtain a second visible image. As a result, a multicolor recorded image is formed on the photosensitive drum 101.

After that, the multicolor recorded image on the photosensitive drum 101.

The image is transferred onto the transfer paper P by the transfer charger 106 and further fixed by the fixing device 107. Note that the photosensitive drum 10
The toner remaining on the photosensitive drum 101 is removed from the photosensitive drum 101 by a cleaner 108.

By the way, in such a two-color electrophotographic apparatus, the first
The toner visible image on the photosensitive drum 101 of a different color adheres to the photosensitive drum 101 due to the reflection force, but if this adhesion is weak, the toner of the first color may fall into the second developing device when developing the second color. There is a problem with mixing. In order to solve this problem, it is said that a two-component magnetic brush development method using a developer containing a non-magnetic toner and magnetic particles (carrier) is suitable for the first color development. When using two-component magnetic brush development method,
Compared to the one-component development method using magnetic toner, the amount of charge of the toner is higher, so the mirroring force with the photosensitive drum 101 is stronger, and the above-mentioned problem is less likely to occur. If the image is recharged with the same polarity as the toner, the amount of charge on the toner will increase, the adhesion between the toner layer and the photosensitive drum 101 will become stronger, and the toner of the first color will be transferred to the second developing device. 105 can be more effectively prevented from being mixed in.

Next, regarding the developing method of the second developing device 105, it is preferable to use a non-contact developing method so as not to disturb the first color toner image on the photosensitive drum 101.
For example, a jumping development method using a magnetic component toner is said to be suitable.

However, when a two-component developing method such as a magnetic brush developing method is used as the developing method as in the conventional example, the toner in the developing device decreases due to multiple image formations, and the T/ As the C ratio, that is, the weight ratio of toner to carrier decreases, carrier adhesion to the photosensitive drum becomes more likely to occur, making it impossible to obtain a good image.

This was a problem in conventional monochrome electrophotographic devices, but in the case of monochrome electrophotographic devices, the carrier attached to the photosensitive drum is either transferred to transfer paper or removed from the photosensitive drum by a cleaner. Ru. Then, it was possible to continue forming good images by replenishing toner to a developing device that was depleted of toner, or by replacing the cartridge if the developing device was configured as a cartridge.

However, in the multicolor electrophotographic apparatus described in connection with FIG.
The carrier deposited on the second developing device 1
The developing sleeve 105a is attracted by the magnet in the developing sleeve 105a as a developer carrier of 05, and the developing sleeve 105a is
It will stick to. Once the carrier has adhered to the developing sleeve 105a, it is difficult to easily remove it, making it impossible to obtain good images in the future.

In order to deal with such problems, conventionally, the first developing device 10
Proposals have been made to dispose a carrier recovery magnetic roller (not shown) near the photosensitive drum 101 between the photosensitive drum 101 and the second developing device 105 to remove the carrier attached to the photosensitive drum 101. There is.

However, in such a method, the apparatus becomes large and it is difficult to remove all the carrier attached to the photosensitive drum 101.

Therefore, the purpose of the present invention is not to collect carrier adhering to an image bearing member such as a photosensitive drum, but to accurately detect a decrease in toner in a developing means, which is the cause of carrier adhesion to an image bearing member. However, it is an object of the present invention to provide a multicolor image forming apparatus that can prevent carrier adhesion and obtain high quality images.

The above objects are achieved by a multicolor image forming apparatus according to the present invention. In summary, the present invention includes a plurality of sets of latent image forming means and developing means arranged around an image carrier, and a latent image formed by the latent image forming means being developed by a plurality of color developers of the developing means. In a multicolor image forming apparatus that visualizes a multicolor recorded image and transfers the multicolor recorded image onto a transfer material at one time, at least one of the developing means is configured to generate a nonmagnetic toner and magnetic particles. The developing means includes a developer having non-magnetic toner and magnetic particles, and includes a remaining toner amount detecting means for detecting the remaining amount of toner, and a remaining toner amount detecting means for stirring the toner and detecting the remaining toner amount. a rotating toner stirring means having a cleaning member that periodically cleans the remaining toner amount detection section of the means, and the cleaning member detects the remaining toner amount at least once in one image forming process. This is a multicolor image forming apparatus characterized by cleaning the parts.

1 Retrospect 1 Next, the multicolor image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

In this embodiment, the present invention is explained in conjunction with FIG.
Since the present invention is implemented in a color electrophotographic apparatus, and its overall configuration and image forming operation are the same as those of the prior art, a detailed explanation will be omitted and only a brief explanation will be given here.

FIG. 1 shows an enlarged embodiment of a developing means constructed according to the present invention, that is, a first developing device 103. In this embodiment, a photosensitive drum 10 as an image carrier is shown.
1 rotates in the direction of arrow A, and the electrostatic latent image formed on the photosensitive drum 1 by the latent image forming means (primary charger 102 and exposure means L1 in FIG. 2) is transferred to the first developing device. 10
3, it is visualized with red toner, for example.

In this embodiment, the first developing device 103 includes a developing chamber 3, a developing sleeve 103 as a developer carrier rotating in the direction of arrow C, a magnet roll 103b, a toner storage chamber 6, a magnetic blade 7, and The developing chamber 3 contains red non-magnetic toner (particle size approximately 10 μm) and magnetic particles (particle size approximately 1 μm) as a carrier.
00 μm) is stored in the toner storage chamber 6, and only toner is stored in the toner storage chamber 6.

The developing chamber 3 and the toner storage chamber 6 are separated by a mesh member 9 through which only toner can pass, and the toner in the developing chamber 3 consumed by developing the electrostatic latent image is replenished. , the toner in the toner storage chamber 6 is gradually sent to the developing chamber 3.

Further, a transparent window 1 is provided in a part of the outer wall of the toner storage chamber 6.
0, and near the outside thereof, a light emitting element 11, such as an LED, as a toner remaining amount detection means, and a light receiving element 12, which is a photoelectric conversion element such as a photodiode, are arranged.

Then, the light emitted from the light emitting element 11 is transmitted to the window 10.
The reflected light reaches the light receiving element 12.

Here, when the toner is sufficiently stored in the toner storage chamber 6 and the toner is present near the window 10, the amount of reflected light is large (and the current value obtained by the photodiode is also large. However, When the toner is consumed by repeating the image forming process many times and the amount of toner in the toner storage chamber 6 decreases to such an extent that no toner exists near the window 10, the amount of reflected light decreases; The current value obtained by the photodiode also becomes smaller.In other words, this change in current value makes it possible to detect the remaining amount of toner in the toner storage chamber 6. The state of the change is shown in Figure 3, and a large change appears in the current value when the remaining amount of toner approaches approximately Og.It would be good if it were possible to accurately detect this change, but in reality In this case, false detections often occur due to causes such as toner adhering to the inner surface of the window 10.

Therefore, in this embodiment, a transparent elastic member 14, for example, urethane rubber, is attached to the tip of the toner stirring rod 8, so that the inner surface of the window 1O is moved by the toner stirring rod 8.
The device is configured to periodically clean the device as the device rotates.

Changes in the output current of the light receiving element 12 in this configuration will be explained with reference to FIG. 4, taking as an example a state in which there is almost no toner in the toner storage chamber 6.

First, immediately after cleaning the window 10 with the elastic member 14, almost no reflected light is obtained, so the current value is small (Fig. 4,
As the elastic member 14 approaches the window 10 again, more toner is brought to the window 10, more reflected light is obtained, and the current value increases (Fig. 4, part 1).
6).

The method for detecting the remaining amount of toner in this configuration will be explained below with reference to FIGS. 5 and 6.

In this embodiment, it is assumed that the two-color electrophotographic apparatus requires 4 seconds for one image forming process, and the rotation period of the toner stirring rod 8 is set to 2.5 seconds. An example of a change in the output current of the photoelectric conversion element 12 of the remaining toner amount detecting means at this time is shown in FIG. 6(A).

First, the current detected by the reflected light irradiated on the light receiving element 12 is amplified by the amplifier 17 and then passed through the integrator 1.
8, one rotation period of the toner stirring rod 8 is integrated for 2.5 seconds from the image formation start time 1+ (the shaded area in FIG. 6(a)).

Next, this integral value is compared with a preset reference value 20 by a comparator 19, and if the integral value is larger than the reference value, it is determined that toner is present, and whether the integral value is equal to the reference value or not. If it is smaller than the standard value, it is determined that there is no toner,
Inform the user that there is no toner.

According to the present invention, in one image forming process, the toner stirring rod 8 always rotates at least once and the output of the light receiving element 12 for one rotation period of the toner stirring rod 8 is integrated. As shown in FIGS. 6(B) and 6(C), even if the position of the toner stirring rod 8 at the image formation start time t1 is different, the same integral value is obtained. Stable detection becomes possible.

Further, according to the present invention, since the output from the light receiving element 12 is integrated, the detection error is reduced compared to the case where the current value outputted from the light receiving element 12 at a certain point is immediately taken as the detected value. becomes possible.

Another embodiment of the present invention will be described with reference to FIG. In this embodiment, one image forming process takes 4 seconds, and the rotation period of the toner stirring rod 8 is 1.5 seconds. That is, the toner stirring rod 8 is set to rotate two or more times during one image forming process.

FIG. 7 shows an example of a change in the output current of the light receiving element 12 of the remaining toner amount detection means in the remaining toner amount detection method in this embodiment.

First, after the start of image formation and after a certain period of time has elapsed from the time tx, ts when the elastic member 14 provided at the tip of the toner stirring rod 8 cleans the window 10, a time t2° t3, for example, one second later. The current values P and Q detected by the reflected light irradiated onto the light receiving element 12 are detected at .

Note that the following method is an example of a method for detecting the times ts and ts. That is, if the output deformation shown in Fig. 7 (a) is differentiated by a differentiating circuit, the output deformation shown in Fig. 7 (a) is differentiated using a differentiating circuit.
A differential waveform like (b) is obtained. That is, at the moment when the elastic member 14 cleans the window 10, the differential value decreases significantly. Therefore, we define this reduced moment as tg, ja
It's fine if you do this. For this purpose, the differential value is compared with a preset threshold value S, and the time point when the differential value becomes equal to or less than the threshold value S is determined as ti,js.

Next, the previously detected current values P and Q are respectively input to the amplifier 17.
After amplification, the average value of these is calculated, and this average value is compared with a preset reference value 20 by a comparator 19. If the average value is larger than the reference value, it is determined that toner is present, and , if the average value is equal to the reference value or smaller than the reference value, it is determined that there is no toner, and the user is notified that there is no toner.

By taking the average value in this manner, it is possible to reduce the detection error compared to the case where the current value at one point outputted from the light receiving element 12 is immediately taken as the detected value.

FIG. 8 shows another embodiment according to the invention. Components in FIG. 8 that are common to those in FIG. 1 are given the same reference numerals.

In this embodiment, a piezoelectric vibrator 20 such as a piezo element is provided as a toner remaining amount detection means. If toner is sufficiently stored in the toner storage chamber 6 and toner is present on the top surface of the piezo element 20,
No output voltage is obtained from the piezo element 20, but when the toner is consumed by repeating the image forming process many times and the amount of toner in the toner storage chamber 6 decreases to the extent that it does not exist on the top surface of the piezo element 20, the piezo element 20 An output voltage can now be obtained from the element 20.

In other words, it is possible to detect the remaining amount of toner in the toner storage chamber 6 based on this change in voltage value. FIG. 9 shows how the voltage value changes as the toner amount changes.

As can be understood from FIG. 9, a large change appears in the voltage value when the remaining amount of toner approaches approximately Og. It would be good if it were possible to accurately detect this change, but in reality, toner may adhere to the top surface of the piezo element 20, which often causes false detection.

For this purpose, in this embodiment, elastic members 22, such as urethane rubber, are provided at both ends of a rectangular toner stirring rod 21 whose rotation axis is 00° as shown in FIG. The upper surface of the piezo element 20 is periodically cleaned as the toner stirring rod 21 rotates. Regarding the change in the output voltage of the piezo element 20 in this configuration, take as an example a state where there is almost no toner in the toner storage chamber 6.
This will be explained with reference to FIG.

First, immediately after cleaning the top surface of the piezo element 20 with the elastic member 21, since there is no toner on the top surface of the piezo element 20, the voltage value is large ((part 23 in FIG. 11)), and the elastic member 21 As it approaches the piezo element 20 again, the toner is carried to the top surface of the piezo element 20, and the voltage value becomes approximately O (11th
Figure, part 24).

Now, assume that the two-color electrophotographic apparatus of this embodiment requires 4 seconds for one image forming process, and the rotation period of the toner stirring rod 21 is set to 3 seconds. In addition, the output voltage of the piezo element 20 is determined by the amplifier 1 in a circuit configured as shown in FIG.
After being amplified by step 7, the integrator 18 integrates one cycle of rotation of the toner stirring rod 21 for 3 seconds from the start of image formation. This integral value is then compared with a preset reference value 20 by a comparator 19, and if the integral value is smaller than the reference value, it is determined that toner is present, and if the integral value is equal to the reference value or is less than the reference value. If it is also large, it is determined that there is no toner, and the user is notified that there is no toner.

By using the toner stirring rod 21 as shown in this embodiment, the rotation period of the toner stirring rod 21 is not increased (
It becomes possible to speed up the period of cleaning the piezo element surface, and the present invention can be easily applied to a multicolor image forming apparatus in which the time required for one image forming process is short.

As described above, the multicolor image forming apparatus according to the present invention periodically cleans the remaining toner amount detecting section in the remaining toner amount detecting means provided in the developing means with a cleaning member. Configure it to
In addition, the cleaning member cleans a small amount of toner in the developing means (at least once in one image forming process; It becomes possible to detect the remaining amount,
For example, a first developing device containing red toner, which usually mainly forms monochrome images using only black toner, and forms two-color images using red toner only once every few times. Even when the toner operates intermittently, it is possible to reliably detect the remaining amount of toner, and it is possible to prevent carrier from adhering to the image carrier due to a decrease in toner. You can get quality multicolor images.

[Brief explanation of drawings]

FIG. 1 is a partial detailed configuration diagram showing an embodiment of a multicolor image forming apparatus according to the present invention. FIG. 2 is a schematic diagram of a two-color electrophotographic apparatus that can embody the present invention. FIG. 3 is a diagram showing the remaining toner amount detection output using reflected light. FIG. 4 is a diagram showing the remaining toner amount detection output using reflected light and a stirring rod. FIG. 5 is a block diagram of an electric circuit implementing a method for detecting the amount of remaining toner using reflected light and a stirring rod. FIG. 6 is an example diagram showing the remaining toner amount detection output configured according to the present invention. FIG. 7 is a diagram of another embodiment showing the remaining toner amount detection output constructed according to the present invention. FIG. 8 is a partial configuration diagram of another embodiment of the multicolor image forming apparatus according to the present invention. FIG. 9 is a diagram showing the remaining toner amount detection output using a piezo. FIG. 10 is a perspective view of one embodiment of a stirring bar. FIG. 11 is a diagram showing the toner remaining amount detection output using a piezo and a stirring rod. 8.21: Toner stirring rod lO: Transparent window 11: Light emitting element 12: Light receiving element 20: Piezo element 101: Image carrier 102.104: Charger Figure 2 Figure 3 Toner remaining amount (9) 4th Figure 5 Figure 6 Figure 1--2.5 seconds-m- Time Figure 7 Figure 8 Figure 9 Toner remaining amount (9) Figure 10 Figure 11 Rotation period

Claims (1)

[Claims] 1) A plurality of sets of latent image forming means and developing means are disposed around the image bearing member, and the latent image formed by the latent image forming means is visualized by a plurality of color developers of the developing means to produce a multicolored image. In a multicolor image forming apparatus that forms a color recorded image and transfers the multicolor recorded image onto a transfer material at one time, at least one of the developing means contains a developer having a nonmagnetic toner and magnetic particles. The developing means, which has a developer having non-magnetic toner and magnetic particles, includes a remaining toner amount detecting means for detecting the remaining amount of toner, and a toner remaining amount detecting means for stirring the toner and detecting the remaining toner amount by the toner remaining amount detecting means. a rotating toner stirring means having a cleaning member that periodically cleans the detection section, the cleaning member cleaning the remaining toner amount detection section at least once in one image forming process; A multicolor image forming device featuring: