JPH04355477A - Image forming device - Google Patents

Abstract

PURPOSE:To highly precisely detect the residual quantity of a developer within each developing vessel of a plurality of developing vessels having nonmagnetic toners. CONSTITUTION:A first stick antenna conductor 48 is laid near the bottom part within a developing vessel body 41, a second stick antenna conductor 49 is laid opposite to the first antenna conductor 48, and a developing bias voltage in which DC voltage and AC voltage from a high voltage power source are superposed to each other is applied also to the first antenna conductor 48. The dielectric voltage changed according to the electrostatic capacity between the antenna conductors 48 and 49 is taken from the second antenna conductor 49, rectified and amplified in the detecting part of a developer residual quantity detecting circuit, and converted into a DC voltage output. This DC voltage output is compared with a standard voltage corresponding to a predetermined standard developer quantity level in a control part, and when the DC voltage output is lower than the standard voltage, the residual quantity of the developer is judged less, and an alarm is displayed in a display part.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to image forming apparatuses such as electrophotographic or electrostatic recording type copying machines and printers, and in particular is equipped with a plurality of developing units of different colors, and is capable of producing multi-color images, full-color images, etc. The present invention relates to a multicolor image forming apparatus that forms a multicolor image.

0002

[Prior Art] Currently, computers, facsimiles, C
2. Description of the Related Art Electrophotographic and electrostatic recording image forming apparatuses are often used as printers for terminal devices of information devices such as ADs. In particular, in electrophotographic printers, information signals are written on a photoreceptor drum as an electrostatic latent image carrier using a laser beam, LED, LCD, etc., this is visualized by a developing device, and then a transfer material is used. A recorded image is obtained by the process of transferring and fixing the image, but in conventional printers, the recorded image is of one color, for example, black.

However, recently, for reasons such as recording images becoming clearer and information easier to understand, for example, the color of the format and the color of calculated values and data values are expressed in different colors, and CAD It is desired that recorded images be distinguished by two or more colors, such as by outputting a part of an outputted drawing in a different color.

FIG. 8 shows an example of an electrophotographic image forming apparatus that enables such multicolor recording. A photoreceptor drum 121 having a photoconductive layer coated on a drum-shaped conductive substrate is used as an electrostatic latent image carrier.
21 rotates in the direction of the arrow in the figure in synchronization with a transfer drum 126 as a transfer material carrier which rotates in the direction of the arrow in the figure. Around the photoreceptor drum 121, there is a charger 122 that charges the photoreceptor drum 121 to a predetermined polarity, and a charger 122 that develops the electrostatic latent image formed on the photoreceptor drum 121 into a visible image, such as magenta M, for example. developing device 124A storing cyan C, yellow Y, and black BK toners, respectively;
124B, 124C, 124D, and cleaners 125 for removing residual toner on the photosensitive drums 121 are respectively provided.

First, the photoreceptor drum 121 is uniformly charged to a predetermined polarity by a charger 122, and image exposure 123 is performed by an exposure means (not shown) based on image information of a first color, for example, magenta. A magenta first latent image is formed on 121. Next, this latent image is developed by the magenta developing device 124A, and a first toner image of magenta M is formed on the photoreceptor drum 121. On the other hand, a transfer material P is held on the transfer drum 126, and by applying a transfer voltage having a polarity opposite to that of the toner to the transfer charger 128 at the transfer position, the magenta toner image on the photoreceptor drum 121 is transferred. The image is transferred to the material P. Thereafter, the remaining magenta toner is removed from the photoreceptor drum 121 by a cleaner 125, and the photoreceptor drum 121 is prepared for the next color latent image formation and development process.

Next, the photosensitive drum 121 is uniformly charged again by the charger 122, and image exposure 123 is performed based on image information of a second color, for example, cyan.
A cyan second latent image is formed on the photoreceptor drum 121. Next, this latent image is developed by the cyan developing device 124B, and a second toner image of cyan C is formed on the photoreceptor drum 121. Note that after the development is completed, the magenta developing device 124A is temporarily retracted downward as shown by arrow a.
Next, the cyan developing device 124B moves along with the other developing devices as indicated by the arrow b.
The cyan latent image is moved to a position facing the photoreceptor drum 121, and as described above, the cyan latent image is transferred to the cyan developing device 124.
Developed by B. This cyan toner image is aligned with the magenta toner image previously transferred to the transfer material P, and is transferred onto the transfer material P held by the transfer drum 126 in an overlapping manner. Thereafter, the remaining cyan toner is removed from the photoreceptor drum 121 by a cleaner 125, and the photoreceptor drum 121 is prepared for the next color latent image formation and development process.

Similarly, yellow, black third,
Each fourth latent image is sequentially formed on the photoreceptor drum 121,
Yellow and black developing devices 124C and 12, respectively.
The third color of cyan, black, and
The toner images of the fourth color are sequentially transferred, and thus the toner images of the four colors are transferred onto the transfer material P in an overlapping state.

The transfer material P on which toner images of magenta, cyan, yellow, and black are superimposed is separated from the transfer drum 121 by a separation mechanism (not shown) and conveyed to the fixing device 127, where the toner images on the transfer material are The toner image is fused into a permanent image. A full color print is thus obtained.

By the way, as the above-mentioned color developing device, a two-component magnetic brush developing device using a mixture of non-magnetic toner and magnetic particles has conventionally been used. For this reason, as shown in FIG. 8 described above, only the developing unit that performs the developing operation is moved in advance to a position facing the photosensitive drum, and during development, it is further moved toward the photosensitive drum side and the magnetic brush is moved to the photosensitive drum side. During this time, other developing devices are placed at a position apart from the photosensitive drum. When developing a latent image of the next color, the previous developing device is temporarily retracted from the position facing the photoreceptor drum, the developing device of the next color is moved to the position facing the photoreceptor drum, and the developing device is moved to a position facing the photoreceptor drum. Sometimes, it is necessary to move the developing device further toward the photosensitive drum and bring the magnetic brush into contact therewith.

[0010] The mechanism for moving the four developing units is complicated and takes up a considerable amount of space, so a one-component developing unit using a non-contact developing method that does not require the movement of each developing unit has been developed. and is used. In this non-contact one-component developing device, the developing sleeve carrying the developer does not come into contact with the photosensitive drum, so there is no need to evacuate or move the non-operating developing devices from the photosensitive drum. It can be fixedly installed around the photoreceptor drum, which has the advantage of simplifying the device and reducing costs. Furthermore, in order to eliminate the hassle of replenishing developer and replacing consumables such as photoreceptor drums, process cartridge technology, which integrates the developer, photoreceptor drum, charger, etc. into an integrated unit, can be applied. be. FIG. 9 shows an example of a conventional color cartridge for an electrophotographic color image forming apparatus to which this process cartridge technology is applied.

The color cartridge 10 includes a photosensitive drum 1, a charger 2, a yellow developer 40a, a cyan developer 40b, a magenta developer 40c, and a black developer 40.
d. It has a structure in which the cleaner 5 is integrated into the cartridge container 10a, and is detachable from the apparatus main body. When the cartridge 10 is installed in the apparatus main body, as shown in the figure, the photoreceptor The drum 1 is arranged to face the transfer drum 4. For example, when the photosensitive drum 1 reaches the end of its life, when the toner in one of the developing devices is used up, or when the cleaner 5 is full of waste toner, the entire cartridge 10 can be replaced. This is intended to facilitate maintenance.

Each of the developing devices 40a to 40d stores non-magnetic toner (
Container body 4 containing a one-component developer (without carrier)
1, a developing sleeve 42 that faces the photosensitive drum 1 in a non-contact state and rotates in a fixed direction to supply the carried toner toward the photosensitive drum 1, and an application roller that applies toner to the developing sleeve 42. 43, a feeding member 44 that moves the toner in the container body 41 toward the application roller 43, an elastic blade 45 that regulates the layer thickness of the toner on the developing sleeve 42, and a gap between the developing sleeve 42 and the container body 41. A sealing member 46 and the like prevents toner from leaking out. The developing operation by these developing devices is performed by toner flying and adhering to the electrostatic latent image formed on the photoreceptor drum 1 from the developing sleeve of the developing device containing the necessary color toner.

[0013]

As described above, from the viewpoint of the color tone of a color image, it is necessary to use a non-magnetic toner as a color toner when forming a color image. Since conventional single-color, particularly black, image forming apparatuses can use magnetic toner, it has been possible to supply and convey the toner to the developing sleeve by the magnetic force of the magnet contained in the developing sleeve. However, since magnetic force cannot be used for non-magnetic toner, a member is required to supply the toner to the developing sleeve, and the application roller 43 shown in FIG. 9 corresponds to this member. By rotating the application roller 43, it is possible to apply the non-magnetic toner onto the developing sleeve, but in order to achieve good application, the application roller 43 must be processed into a spongy, knurling, or brush-like process. It is preferable to apply

By the way, in a color image forming apparatus using a process cartridge as in the above-mentioned conventional example, the amount of toner in the developing device decreases due to a large number of image formations, and eventually it becomes impossible to form an image. It ends up.

This has been a problem in conventional monochrome image forming apparatuses, but in the case of monochrome image forming apparatuses, especially when the developing device is a cartridge, ``running out of toner'' means ``running out of toner'' immediately. It was concluded that the cartridge had reached the end of its service life, and it was possible to continue forming good images by replacing the cartridge. This also applies to color image forming apparatuses, but it is very inconvenient from the user's perspective that the toner runs out without prior notice and image formation becomes impossible.

Therefore, it has been proposed to apply the remaining developer amount detection means, which is often used in conventional monochrome image forming apparatuses, to each developing device of a color image forming apparatus to indicate the remaining amount of toner.

FIG. 10 shows an example of a conventional monochrome image forming apparatus in which a monochrome developer using magnetic one-component toner is provided with a developer remaining amount detection means. A rod-shaped antenna conductor 47 is provided parallel to the sleeve 42 to form a capacitor with the developing sleeve 42 as one electrode and the antenna conductor 47 as the other electrode, and the capacitance of this capacitor is interposed between the electrodes. The remaining amount of toner is detected based on the amount of toner T that changes depending on the amount of toner T that is applied to the developing sleeve 4.
2, and the induced voltage generated in the antenna conductor 47 via the toner T by this bias voltage is extracted as a remaining amount detection signal, and this signal is compared with a reference voltage in a developer remaining amount detection circuit to detect the developing device. It is configured to detect the amount of toner remaining in the printer. In addition, the developing sleeve 4
2 includes a magnet 48. Further, the antenna conductor 47 is grounded via a resistor R. In the figure, reference numeral 49 indicates a blade that regulates the toner adhering to the developing sleeve 42 into a layer of a predetermined thickness.

When the developer remaining amount detecting means shown in FIG. 10 is applied to each developer of the color image forming apparatus shown in FIG. 9, the configuration is as shown in FIG. 11. Note that since each developing device has the same configuration, only one developing device is illustrated as a representative example 40 in FIG. On the other hand, the developer remaining amount detection circuit that processes the remaining amount detection signal from the antenna conductor 47 is configured as shown in FIG. When the above-described developing bias obtained by superimposing the DC voltage and the AC voltage is applied to the developing sleeve 42 from the high-voltage power supply 50, the remaining amount detection signal (voltage) obtained from the antenna conductor 47 is detected by the detection section 51 of the developer remaining amount detection circuit. rectified at,
It is amplified and converted to a DC voltage output. This DC voltage output is compared with a reference voltage corresponding to a predetermined reference developer amount level in the control unit 52, and when the DC voltage output from the antenna conductor 47 becomes lower than the reference voltage, the remaining amount of developer is low. It is determined that the developer has run out (almost all of the developer has run out), and the display unit 53 operates to display a warning.

However, as described above, the developing units 40a to 40 of the color image forming apparatus using non-magnetic toner
d requires an application roller 43 for supplying and applying toner to the developing sleeve 42, so the placement position of the antenna conductor 47 is naturally limited. Moreover, in the case of the color cartridge 10 in which a plurality of developing devices 40a to 40d are arranged around the photoreceptor drum 1, each developing device must be a thin developing device due to its arrangement.
As shown in FIG. 11, the antenna conductor 47 is attached to the developing sleeve 4.
If it is placed near the developing sleeve 42, the toner flow will be greatly affected, and the toner may not be stably supplied to the developing sleeve 42, resulting in image defects.
5. The flow of toner becomes stagnant in the area surrounded by the application roller 43 and the antenna conductor 47, causing the toner to deteriorate, or in the worst case, causing the toner to aggregate and solidify.

Accordingly, an object of the present invention is to provide a cartridge that includes at least an image bearing member and a plurality of developing devices arranged around the image bearing member, and is configured to be removably attached to the main body of the apparatus. An object of the present invention is to provide an image forming apparatus that can accurately detect the amount of developer remaining in each developing device and can stably form high-quality color images.

[0021]

Means for Solving the Problems The above objects are achieved by an image forming apparatus according to the present invention. In summary, the present invention provides an image that is equipped with a plurality of developing devices and that can form a multicolor image by developing a latent image formed on an endlessly running image carrier into a visible image by the developing devices. In the forming apparatus, at least two conductors are arranged to face each of the developing units, and one of the facing conductors is configured to detect an impedance change that changes depending on the amount of developer present between the conductors. A signal applying means for applying a signal for detecting impedance, and a signal for detecting the remaining amount of developer induced in the other of the opposing conductors by circuit processing to generate a signal indicating the remaining amount of developer in each of the developing units. An image forming apparatus is characterized in that it includes a circuit for detecting a remaining amount of developer.

In one embodiment of the present invention, the amount of developer remaining in each of the developing units is determined by one of the opposing conductors.
It is measured by applying a developing bias.

[0023] In another embodiment of the present invention,
The remaining amount of developer in each developing device is measured by applying an impedance detection signal from a separately provided signal generator to one of the opposing conductors.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing a developing unit of an embodiment of an image forming apparatus according to the present invention, and each developing unit 40a to 40d in a color cartridge 10 included in the electrophotographic image forming apparatus shown in FIG. The present invention is applied to the developing device, and since each developing device has substantially the same configuration as described above, one of the developing devices is illustrated as a representative example 40. Therefore, parts corresponding to those in FIG. 11 are given the same reference numerals.

As mentioned above, it is difficult to provide a rod-shaped antenna conductor for extracting the induced voltage at an appropriate position facing the developing sleeve 42. A rod-shaped first antenna conductor 48 to which a voltage is applied is horizontally stretched in parallel to the developing sleeve 42 near the bottom of the container body 41 of the developing device 40. A rod-shaped second antenna conductor 49 for extracting the induced voltage is stretched parallel to the developing device 40 at a predetermined interval, and the capacitance between the first and second antenna conductors is detected. The device is configured to detect the amount of toner remaining in the printer. Further, in this embodiment, the first antenna conductor 48 is electrically connected to the developing sleeve 42, and a developing bias voltage containing an AC component (usually a voltage that is a superimposition of an AC voltage and a DC voltage) is applied to the developing sleeve 42. ) are applied to the first antenna conductor 48 simultaneously. Furthermore, the arrangement positions of the first and second antenna conductors 48 and 49 are
The second antenna conductor is positioned as far away from the developing sleeve 42 as possible so that the capacitance between the second antenna conductor and the developing sleeve 42 is smaller than the capacitance between both antenna conductors, and it is hardly affected by the developing sleeve 42. I have to.

On the other hand, the developer remaining amount detection circuit that processes the remaining amount detection signal guided to the second antenna conductor 49 is constructed as shown in FIG. A developing bias voltage obtained by superimposing the above-mentioned DC voltage and AC voltage is applied from the high voltage power supply 50 to the developing sleeve 42 , and at the same time, this developing bias voltage is also applied to the first antenna conductor 48 . A voltage that varies depending on the capacitance between the antenna conductor and the second antenna conductor 49 (ie, a voltage representing the amount of toner between these antenna conductors) is induced in the second antenna conductor 49. The remaining amount detection signal (voltage) obtained from this second antenna conductor 49 is transmitted to the detection section 51 of the developer remaining amount detection circuit.
It is rectified, amplified, and converted into a DC voltage output. This DC voltage output is compared with a reference voltage corresponding to a predetermined reference developer amount level in the control unit 52, and when the DC voltage output becomes lower than the reference voltage, it is determined that the remaining amount of developer is low (developer It is determined that the amount of water has almost disappeared), and a warning is displayed on the display unit 53.

As described above, in this embodiment, a dedicated conductor for applying a voltage for detecting the remaining amount of toner is provided separately from the developing sleeve, and an antenna conductor is arranged parallel to this conductor. Since the structure is configured to extract the induced voltage that changes depending on the amount of toner remaining from the conductor, the placement positions of the dedicated voltage application conductor and antenna conductor can be selected quite freely, and the positions that have a large effect on the flow of toner can be selected. It can be avoided. Therefore, toner can be stably supplied to the developing sleeve 42, and there is no possibility of image defects or stagnation of toner flow.

In the above embodiment, a pair of conductors is provided in each developing device, but due to the structure of the developing device, it may not be possible to provide the pair of conductors at appropriate detection positions. In this case, since only a two-dimensional distribution of toner within the developing device can be detected, there is a possibility that the amount of toner remaining within the developing device cannot be accurately measured.

FIG. 3 shows a second embodiment of the present invention, in which four primary voltages are used exclusively for applying a voltage for detecting the remaining amount of toner.
antenna conductors 60, 61, 62, and 63 are disposed in parallel in the upper part of the developing device 40 at a predetermined interval in the horizontal direction;
4 so as to form a pair with each antenna conductor 60 to 63, respectively.
Four second antenna conductors 64, 65, 66, and 67 are arranged in parallel in the lower part of the developing device 40 at a predetermined interval in the horizontal direction, and each of the four first and second antenna conductors The structure is such that four capacitors are formed. However, as shown in Figure 4,
The first antenna conductors 60 to 63 are commonly connected to the developing sleeve 42, and when a developing bias is applied to the developing sleeve 42 from the high-voltage power supply 50, this developing bias is also applied to each of the first antenna conductors at the same time due to the amount of remaining toner. On the other hand, each second antenna conductor 6
4 to 67 are each connected to the detection unit 51 separately, and the second
The remaining power detection voltage induced in each antenna conductor can be extracted in parallel and processed in the circuit.

In this way, by arranging the four capacitors in parallel, the amount of toner remaining between the electrodes of these capacitors can be reliably detected as a three-dimensional distribution, so the amount of toner in the developing device can be accurately detected. can be measured. In addition, by appropriately combining the extracted four remaining amount detection voltages and calculating the sum, difference, etc., it is possible to detect the remaining amount of toner even more accurately. Furthermore, the capacitance between the first and second antenna conductors 60 to 63 and 64 to 67 is greater than that between the first and second antenna conductors and the developing sleeve 4.
It is extremely easy to arrange both antenna conductors at positions where the capacitance between them is greater than that between the antenna conductors. Components corresponding to those in FIGS. 1 and 2 are given the same reference numerals, and their explanations will be omitted.

FIG. 5 shows a third embodiment of the present invention. In this embodiment, a first antenna conductor 68 dedicated to applying a voltage for detecting the remaining amount of toner and an induced voltage for detecting the remaining amount of toner are used. The second antenna conductors 69 to be taken out are each formed into a plate shape and placed on the outside of the upper and lower walls of the developing device 40. It is also possible to arrange these plate-shaped antenna conductors 68 and 69 inside the developing device, but since they are plate-shaped and wide, there is a risk that their surfaces will come into contact with the feeding member 44 and wear out. It is placed outside. In this case, the antenna conductor 68,
As the material 69, for example, one in which aluminum is vapor-deposited on the outer surface of the developing device may be used. As shown in FIG. 6, the first antenna conductor 68 is commonly connected to the developing sleeve 42, and when a developing bias is applied to the developing sleeve 42 from the high voltage power supply 50, the first antenna conductor 68 is also connected to the developing sleeve 42 at the same time. This developing bias is applied as a voltage for detecting the remaining amount of toner, while the second antenna conductor 69
is connected to the detection unit 51, and performs circuit processing on the voltage for detecting the remaining amount induced in the second antenna conductor in the same manner as in the first embodiment.

In this way, the pair of plate-shaped antenna conductors 68
, 69, the area of the electrodes constituting the capacitor becomes larger, ensuring that the remaining amount of toner interposed between the electrodes is reduced to 3.
It can be detected as a dimensional distribution, and therefore the amount of toner in the developing device can be accurately measured. Further, both antenna conductors are placed in a position such that the capacitance between the first and second antenna conductors 68 and 69 is larger than the capacitance between the first and second antenna conductors and the developing sleeve 42. It is extremely easy to install. Components corresponding to those in FIGS. 1 and 2 are given the same reference numerals, and their explanations will be omitted.

In each of the above embodiments, the developing bias voltage applied to the developing sleeve 42 is used as the signal for detecting the remaining amount, but the signal for detecting the remaining amount is not limited to the developing bias. For example, as shown in FIG. 7, a signal generator 70 that generates an AC signal such as a sine wave voltage is connected to a high voltage power supply 5.
0, and the signal generator 70 outputs an AC signal for detecting the remaining amount to the first antenna conductor 48 in FIG. 1, the first four antenna conductors 60 to 63 in FIG. 3, or the first four antenna conductors 60 to 63 in FIG. 1st of
to the antenna conductor 68 and the second antenna conductor 49
, 64 to 67, or 69 may be taken out as the remaining amount detection signal and sent to the detection section 51 of the developer remaining amount detection circuit for circuit processing, as described above.

By providing a separate dedicated signal generator 70 and applying it to the first antenna conductor separately from the developing bias, the remaining amount can be detected when each developing device is not in an operating state and is not developing. By setting the mode, it is possible to detect the remaining amount of developer in each developing device. Since a rectangular wave is normally used as the developing bias, it has many harmonic components and at the same time is a high voltage of about 2 KV, which becomes a source of noise. However, if the remaining amount of developer is detected by operating a separate signal generator during non-development, it will not become a noise source since the development bias is turned off. Furthermore, since the developing sleeve and stirring member are not driven, and the paper feed motor and the like are also stopped, the noise source when detecting the remaining amount can be further reduced. Therefore, there is an advantage that detection accuracy is further improved. In addition, in multicolor image forming apparatuses, different developing biases may be used for each developing unit, and in such cases, detection accuracy decreases, but it is possible to use separate signal generators as described above. If the remaining amount is detected, a stable constant voltage can be applied, so the detection accuracy does not deteriorate.

It should be noted that the above embodiments are merely illustrative of the present invention, and it goes without saying that various modifications and changes can be made as necessary. For example, the present invention can also be applied to multicolor image forming apparatuses such as copying machines and printers other than those using electrophotography.

[0036]

As explained above, according to the image forming apparatus of the present invention, a signal for detecting the amount of developer remaining in the developing device is applied separately from the developer carrier to which a developing bias is applied. A dedicated first conductor is provided, a second conductor is arranged parallel to this conductor, and an induced voltage that changes depending on the remaining amount of developer is extracted from this second conductor.
Even for a developing device with a thin structure such as a color process cartridge, the placement positions of the first and second conductors can be selected quite freely, and positions that greatly affect the flow of developer can be avoided. It can be placed at a position where the remaining amount of the agent can be accurately detected. Therefore, not only can the remaining amount of developer be detected with high precision, but also the developer can be stably supplied to the developer carrier, preventing image defects and toner flow stagnation. . Furthermore, since the cost of the remaining amount detection member can be minimized, there are also effects such as miniaturization of the device, reduction in cost, and improvement in reliability.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the configuration of a developing device in a first embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a block diagram showing a developer remaining amount detection circuit used in the first embodiment of FIG. 1;

FIG. 3 is a schematic diagram showing the configuration of a developing device in a second embodiment of the image forming apparatus according to the present invention.

FIG. 4 is a block diagram showing a developer remaining amount detection circuit used in the second embodiment of FIG. 3;

FIG. 5 is a schematic diagram showing the configuration of a developing device in a third embodiment of the image forming apparatus according to the present invention.

FIG. 6 is a block diagram showing a developer remaining amount detection circuit used in the third embodiment of FIG. 5;

FIG. 7 is a block diagram showing a developer remaining amount detection circuit used in a fourth embodiment of the image forming apparatus according to the present invention.

FIG. 8 is a schematic diagram showing an example of a conventional electrophotographic multicolor image forming apparatus.

FIG. 9 is a schematic diagram showing an example of a conventional color cartridge for an electrophotographic color image forming apparatus.

FIG. 10 is a schematic diagram showing an example of a developing device equipped with a conventional developer remaining amount detection means.

11 is a schematic diagram showing the configuration of the developing device of the color cartridge shown in FIG. 8 in which a developer remaining amount detecting means is incorporated; FIG.

FIG. 12 is a block diagram showing a developer remaining amount detection circuit used in a conventional image forming apparatus.

[Explanation of symbols]

Claims (3)

[Claims] 1. An image forming apparatus comprising a plurality of developing devices and capable of forming a multicolor image by developing a latent image formed on an endlessly running image carrier by the developing devices into a visible image. , at least two conductors disposed facing each of the developing devices, and detecting an impedance change that changes depending on the amount of developer present between the conductors,
Signal applying means for applying an impedance detection signal to one of the opposing conductors, and circuit processing of the remaining amount detection signal induced to the other of the opposing conductors to detect the amount of developer in each developing device. An image forming apparatus comprising: a developer remaining amount detection circuit that generates a signal indicating the remaining amount of developer. 2. A developing bias applied to each of the developing devices is applied to one of the opposing conductors as the impedance detection signal to measure the amount of developer remaining in each of the developing devices. The image forming apparatus according to claim 1. 3. A signal for detecting the impedance is generated from a signal generating means provided separately from the developing bias generating means, and the signal is applied to one of the opposing conductors to detect the developer in each developing unit. The image forming apparatus according to claim 1, wherein the image forming apparatus measures the remaining amount of the image forming apparatus.