JPH09204105A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform efficient trickle according to the amount of toner consumption, in an image forming device equipped with a developing device which trickles two-component developer. SOLUTION: The developer D as a mixture of toner T and carrier C is stored in a developer container 41. After held on a developing roll 411, the developer D is supplied to a photoreceptor. Then, according to the amount of toner T consumed for development, amounts of toner T and carrier C to be added to the developer container 41 are properly controlled to balance efficiently the overflow of the deteriorated developer D and the trickle of the fresh developer D by the supply.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic copying machine or a printer, and more particularly to an image forming apparatus provided with a developing device using a two-component developer composed of toner and carrier. Regarding

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine or a printer, in a developing device using a two-component developer composed of a mixture of toner and carrier, the toner is consumed by the developing operation while the carrier is consumed. It is not left in the developing device. Therefore, the carrier stirred with the toner in the developing device deteriorates as the stirring frequency increases. Deterioration of the carrier is caused by contamination or the like in which a part of the toner adheres to the carrier due to friction or impact of the toner, and usually causes deterioration of the charging performance of the developer.

Therefore, in order to suppress the deterioration of the developer, Japanese Patent Publication No. 2-21591 proposes a so-called trickle system. In addition to replenishing the toner consumed by the developing operation, a new carrier is replenished in the developing unit, and the developer in the developing unit that has become excessive due to the replenishment is discharged. A method of maintaining the development characteristics of the developer in the developing device by replacing the deteriorated developer in the developing device with newly supplied toner and carrier by sequentially replenishing and discharging the developer. Is. As a result, the charging performance of the developer is maintained and the deterioration of copy image quality is suppressed.

In general, the developing device has a developing roll inside the developer tank for storing the developer, which faces the image carrier on which an electrostatic latent image is formed, and agitates the developer. And a stirring member for supplying the developing roll to the developing roll. The carrier is supplied from the carrier supply tank by driving a dispensing member provided in the carrier supply tank in synchronization with the developing roll and the stirring member. That is, the carrier is replenished according to the operating time of the developing device.

Further, Japanese Patent Laid-Open No. 4-66984 proposes an image forming apparatus which replenishes a carrier in accordance with the number of image formed sheets, that is, the number of recording sheets on which development is transferred. However, since the number of formed images is proportional to the operating time of the developing device, there is substantially no difference from the above method.

[0006]

However, the deterioration of the charging performance of the carrier has a large relationship not only with the operating time of the developing device but also with the toner consumption amount. The larger the toner consumption amount, the faster the deterioration. FIG. 8A shows a change in the charge amount of the carrier with respect to the operating time of the developing device. FIG. 8B shows changes in the amount of toner adhered to the carrier. The developing roll is configured to rotate a non-magnetic sleeve around a fixed magnet, and the peripheral speed is 320 mm / s. The dotted line shows the toner consumption of 50 g / h, and the solid line shows the triple consumption of 150 g / h. The carrier charging performance initially increases, but then begins to decrease, and a difference of about 15 μC / g occurs at 15 hours. At this time, the amount of toner adhered to the carrier is about doubled. In other words, since the new toner has a larger amount of toner attached to the carrier, if the toner consumption is large, the amount of contact between the carrier and the new toner increases, the amount of toner attached to the carrier increases, and the charging performance of the carrier deteriorates. To do.

This means that when the above-mentioned trickle system is adopted, when the toner consumption is large, that is, when a document having a high image density is continuously copied or printed, carrier replenishment and developer discharge result in carrier deterioration. The image quality deteriorates without catching up. Conversely, if the toner consumption is low, that is, if you copy or print a document with a low image density continuously, the supply of carrier and the discharge of developer exceed the deterioration of the carrier, that is, the deterioration of the carrier is still small and the carrier can be used. This means that the carrier will be discharged and the trickle will be less efficient.

The present invention has been made in view of the above circumstances, and even if the toner consumption varies depending on the input image,
It is an object of the present invention to provide an image forming apparatus that can perform trickle effectively and efficiently.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above object, and comprises an image carrier on which an input image is formed as a latent image on the surface by image writing means, a toner and a carrier. In the developer tank which stores the developer which is the mixed agent of and which contains the developer carrier facing the image carrier, by the toner replenishing member from the toner replenishing tank,
Further, while the toner and the carrier are respectively replenished from the carrier replenishing tank by the carrier replenishing member, the developer is discharged from the developer tank, and the developer in the developer tank is further conveyed to the developer carrier side by the conveying member. In an image forming apparatus comprising: a developer carrying a developer, the developer carrying member carrying the developer, and a developer for developing the latent image by supplying the developer from the developer carrying body to the surface of the image carrying body, A toner consumption amount measuring means for measuring a consumption amount of toner required for development from the inside of the developer tank, and from the carrier replenishing tank to the inside of the developer tank according to a measurement result of the toner consumption amount measuring means. It is characterized by controlling the supply amount of carrier. The toner consumption amount measuring means for measuring the consumption amount of the toner required for the development from the developer tank and the developing device operating time measuring means for measuring the operating time of the developing device are provided. It is characterized in that the replenishment amount of the carrier from the carrier replenishing tank into the developer tank is controlled according to the measurement results of the measuring means and the developing device operating time measuring means.

According to the present invention, when the amount of toner consumption is large, such as when a document having a high image density is continuously copied or printed, the carrier supply amount is increased to prevent a decrease in image density, and conversely, the image density is reduced. When the amount of toner consumption is small, such as when copying or printing a document having a low temperature, the amount of carrier replenishment can be reduced to reduce the developer discharge amount, and efficient trickle can be performed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an image forming apparatus according to an embodiment. In FIG. 1, reference numeral 1 is a negatively charged photosensitive member (image carrier) that rotates in the a direction, 2 is a charger (for example, scorotron) that charges the photosensitive member 1, and 3 is an electrostatic latent image formed on the photosensitive member 1. Image writing means, 4 is a developing device, 5 is a transfer charger (transfer means) for transferring the toner image developed by the developing device 4 onto the surface of the photoconductor 1, and 6 is a photoconductor after the transfer. A peeling charger for peeling the recording paper 9 from the photosensitive member 1, a cleaner 7 for removing the residual toner on the photosensitive member 1, and a discharging lamp 8 for removing the residual electric charge on the photosensitive member 1.

In this image forming apparatus, the developing device 4 is
A contact magnetic brush development method using a two-component developer composed of toner and carrier is used, and the toner is replaced, that is, toner is replenished for trickle, carrier is replenished, and developer is discharged. This developing device 4 is, as shown in FIG.
Developer tank 41 for developing while circulating a two-component developer
And a toner replenishing tank 42 containing new toner T,
A carrier replenishing tank 43 containing a new carrier C,
Deteriorated developer discharge tank 4 for discharging deteriorated developer D
4 is provided.

In the developer tank 41, a non-magnetic sleeve 411a having a circumferential groove formed on the surface and rotatable in the b direction,
A developing roll 411 (developer carrier) in which a magnet roll 411b is arranged and which adsorbs the developer D on the sleeve 411a.
And a layer thickness regulating member 4 made of a non-magnetic material which is disposed with a constant gap from the developing roll 411 and regulates the layer thickness of the developer D on the developing roll 411 (on the sleeve 411a).
12 and the developer D are agitated to put the developer D on the developing roll 41.
1 and the paddle 413 supplied to the upper surface of the developer D
A plurality of (two in this case) augers (conveying members) 414 to be conveyed to the third side are incorporated. The interior of the developer tank 41 is partitioned by a partition wall 415 into an upstream side and a downstream side in the transport direction of the developer D. Each auger 414 is a partition wall 415
Are arranged on the upstream side and the downstream side, respectively. As shown in FIG. 5, both ends of the partition wall 415 do not reach the inner side surface of the developer tank 41, and the upstream side and the downstream side communicate with each other. The circumferential groove of the sleeve 411a has, for example, a pitch of 1.3 mm, a depth of 0.15 mm, and a width of 0.
It is set to 3 mm.

The magnet roll 411b is a developing pole S that effectively forms a spike of the developer D at a position facing the photoconductor 1.
1. To form a thin layer of a pick-off magnetic pole N2 for peeling the developer D after passing through the developing area from the developing roll 411, a pickup magnetic pole N3 for adsorbing the developer D on the developing roll 411, and a developer D. Trimming magnetic pole S
2. It has a magnetic pole N1 for adjusting the number of magnetic poles in order to favorably convey the developer D.

Further, the layer thickness regulating member 412 is arranged at a position near the magnetic pole S2 of the developing roll 411 with a predetermined gap maintained. The paddle 413 is the developer D separated from the developing roll 411 by the pick-off magnetic pole N3.
Has a function of sending out to the auger 414 side. The auger 414 has a function of stirring the separated developer D and stirring the toner T supplied from the toner supply tank 42 and the developer D in the developer tank 41. FIG. 5 shows a developer tank 4.
1 viewed from above (developing roll 411 in the developer tank 41)
The components other than those are omitted), and the developer tank 41
The developer D therein is conveyed in the direction of the arrow in the figure.

A toner dispensing member (toner replenishing member) 421 is provided in the toner replenishing tank 42.
When the toner dispensing member 421 is driven in accordance with the toner consumption amount, as shown in FIG.
The toner T is replenished into the developer tank 41 from No. 2 through the toner replenishing port 422. A carrier dispensing member (carrier supplying member) 431 is provided in the carrier supplying tank 43. When the carrier dispensing member 431 is driven according to the toner consumption amount or the toner consumption amount and the driving time of the developing device 4, the developer is passed from the carrier replenishing tank 43 through the carrier replenishing port 432 as shown in FIG. The carrier C is replenished in the tank 41.

From the carrier replenishment tank 43 to the carrier C
When the volume of the developer D is increased by replenishing the developer D, as shown in FIG. 4, the developer D (degraded developer) in the developer tank 41 becomes
Trickle is performed by overflowing from the developer discharge port 441 to the deteriorated developer discharge tank 44. As shown in FIG. 5, the developer discharge port 441.
Is provided on one end side in the longitudinal direction of the developer tank 41 (vertical direction in FIG. 5, front-back direction in FIGS. 2 to 4). Further, the toner replenishing port 422 and the carrier replenishing port 432 are provided on the downstream side of the developer discharge port 441 in the transport path of the developer D by the auger 414 and are spaced apart from each other.

As described above, the developer D in the developer tank 41
Is conveyed by the auger 414 as shown by the arrow in FIG. On the auger 414 side of the developing roll 411, the paddle 413 picks up the developer D to the developing roll 411 and the pickoff magnetic pole N2 of the magnet roll 411b picks up the developer D from the developing roll 411. It circulates as shown by the solid arrow in FIG. The toner supply port 422 is provided on the downstream side of the developer discharge port 441 so that the toner T which has just been supplied is not immediately discharged from the developer discharge port 441. Further, the toner T is sufficiently agitated with the carrier C at a position as far as possible from the developing roll 411 until the toner T is conveyed to the developing roll 411. Similarly, the carrier replenishing port 432 is preferably located far from the developer discharge port 441. Then, when the carrier C is replenished and the volume of the developer D is increased, the developer D (degraded developer) is discharged from the developer discharge port 441 in accordance with the carrier replenishment amount, as shown by the broken line arrow in FIG. It is like this.

Next, the image forming process of the image forming apparatus will be described. In the charging step, the surface of the photoconductor 1 is uniformly charged by the charger 2 (charging potential Vh), and in the exposure step, the image portion of the original document (not shown) is exposed by the image writing means 3 to eliminate static electricity. Electric latent image (image part potential is V
In the developing step, the image portion of the electrostatic latent image is reversely developed (developing bias potential Vb) by the developing device 4 with the toner T having the same polarity as the charging polarity of the photoconductor 1. A toner image is formed on the photoconductor 1 through these steps.

Here, an experiment in the above image forming process was conducted under the following conditions. (1) Photoreceptor 1 Organic photoreceptor (negative charging type), drum outer diameter 84 mm (2) Process speed (rotational speed of photoreceptor 1) 160 mm
/ S (3) Developer (toner concentration 4.0%)-Two-component system-Magnetic carrier (positive charging) Ferrite carrier with an average particle size of 85 μm-Black toner (negative charging) Styrene-n-butylmethacrylate copolymer 91 parts, 7 parts of carbon black, and 2 parts of a charge control agent (P-51, manufactured by Orient Chemical Co., Ltd.) were melted and kneaded, and then finely pulverized to have an average particle size of 9 μm. (4) Parameter of developing device 4 (contact type development) -DRS (gap between photoconductor 1 and recording paper 9) 0.7 mm-MSA (developing main pole setting angle: point of magnet roll 411b closest to photoconductor 1) And the developing pole S1 of the magnet roll 411b) +5 degrees ・ TG (gap between the layer thickness regulating member 412 and the sleeve 411a) 0.8 mm ・ Outer diameter of the sleeve 411a 24.5 mm ・ Rotation speed of the sleeve 411a 320 mm / s ・ Rotation direction of sleeve 411a “With (photoreceptor 1
In addition, the potential condition for latent image formation is −700 for the charging potential Vh.
V, the image portion potential Vl is -120 V, the developing bias potential V
b was set to -520V. The following is a specific example of obtaining the toner consumption amount.

A. Example 1A-1. Application of image forming apparatus to digital copying machine Photoreceptor 1 in digital copying machine
The flow of the image information until the latent image is formed is shown in FIG. In this case, first, the image information of the document is read by the image reading means 51 including an optical lens system and a CCD sensor. Next, the image processing means 52 performs pictogram separation and halftone processing, and the image writing means 3 including an optical system and a semiconductor laser exposes the photoconductor 1 to form an electrostatic latent image on the photoconductor 1.

A-2. Application of Image Forming Device to Printer FIG. 6B shows the flow of image information until a latent image is formed on the photoconductor 1 in the printer. In this case, first, the image information output from the interface 62 of the terminal 61 such as a personal computer is received by the printer interface 64 via the net 63. Then, the image processing means 65 performs pictogram separation, halftone processing, etc., and the image writing means 3 including an optical system and a semiconductor laser exposes the photoconductor 1 to form an electrostatic latent image on the photoconductor 1. In some cases, all or part of image processing is performed on a personal computer.

A-3. Application of Image Forming Apparatus to Facsimile FIG. 6C shows a flow of image information until a latent image is formed on the photoconductor 1 in a facsimile which is an image transmission unit. In this case, in the facsimile on the transmitting side, after the image reading means 71 reads the image information of the document, the image information is output from the interface 72 and transmitted to the facsimile on the receiving side via a line 73 such as a telephone line. The facsimile on the receiving side receives image information from the interface 74, performs pictogram separation and halftone processing by the image processing means 75, exposes the photoconductor 1 by the image writing means 3 including an optical system and a semiconductor laser, and exposes it. An electrostatic latent image is formed on the body 1. In some cases, all or part of the image processing is performed by the facsimile on the transmitting side.

In the image forming apparatus as described above, since the image read or the image received before the image processing is converted into an electric signal, the image density can be easily calculated. In the developing process, the toner T is attached to the pixel portion of the electrostatic latent image on the photoconductor 1, so that the image density and the toner consumption amount are in a substantially proportional relationship. Therefore, the toner consumption can be estimated by measuring the image density. Similarly, the toner consumption can be estimated by measuring the image density of the image information after the image processing.

For example, in a digital copying machine, the image density of an original is set to three types of 1%, 5% and 15%, and the image density before image processing is measured. The carrier replenishment amount was 1/2 at 1% and 2.5 times at 15%, and was copied on the recording paper 9. Here, the carrier replenishment amount is not a value proportional to the image density.
This is because if the sleeve 411a rotates, the toner T and the carrier C are agitated without replenishing the toner T.
The carrier C may be deteriorated. This contribution is large when the toner consumption is small and small when the toner consumption is large. Therefore, when the image density is 1%, the carrier supply amount is larger than the ratio, and when the image density is 15%, the carrier supply amount is smaller than the ratio. In addition, as a comparative example, the carrier replenishment amount was set to be the same as the standard 5%.

The results are shown in FIG. The solid line shows an example in which the carrier supply amount is controlled, and the dotted line shows a comparative example in which the carrier supply amount is constant. As shown in FIG. 7A, when the carrier replenishment amount is 1%, the image density is not decreased in both the embodiment and the comparative example, but the developer D is discharged in the embodiment in which the carrier replenishment amount is small. Of course, there are few, and the trickle efficiency is good. As shown in FIG. 7B, at the image density of 5%, the carrier replenishment amounts of the example and the comparative example are the same, and thus represent the example. As shown in FIG. 7C, when the image density is 15%, the discharge amount of the developer D is smaller in the comparative example, but the image density is reduced. Conversely, in the example, the developer D
The discharge amount of is increased, but the image density can be maintained. Even if the discharge amount of the developer D is small, it cannot be said that the purpose of the trickle is fulfilled because the image density is lowered, and the embodiment is superior.

B. Second Embodiment Similar to the digital copying machine of the first embodiment, the toner consumption is measured by measuring the number of pixels of the image before the image processing with the image density of the original being set to 1%, 5%, 15%, and developing. The operating time of the developing device was calculated from the On time of the developing device operating time drive control signal to calculate the toner consumption amount per unit time of the developing device 4 operating from both, and the carrier replenishment amount was controlled by the result. At this time, when the toner consumption amount per unit time is small, the carrier replenishment amount is small, and when the toner consumption amount per unit time is large, the carrier replenishment amount is large. That is, when the image density of the original is low, the carrier replenishment amount is reduced, and when the image density is high, the carrier replenishment amount is increased.

Here, in the first embodiment, the amount of deterioration of the carrier C even if toner is not replenished is generated by the rotation of the sleeve 411a, the paddle 413, and the auger 414. Usually, the components of these developing devices 4 are
The driving time of the developing device 4 coincides with the driving time of each component, because the driving force is linked with one driving transmission means. Therefore, the carrier replenishment amount is not set to a value proportional to the toner consumption amount per unit time. When the original pixel density is 5%, the toner consumption per unit time when the original pixel density is 1% is about 1 /
5, the carrier replenishment amount was halved, and the toner consumption amount per unit time when the original pixel density was 15% was almost three times, but the carrier replenishment amount was 2.5 times. did. The results were the same as in Example 1.

C. Embodiment 3 The amount of toner replenished from the toner replenishing tank 42 is almost equal to the amount of toner consumed from the developer tank 41. Further, since the amount of toner replenished from the toner replenishing tank 42 is substantially proportional to the driving time of the toner dispensing member 421, the toner consumption amount can be estimated by measuring the driving time of the toner dispensing member. Therefore, the toner consumption amount per unit time of the operating developing device 4 is obtained from the toner consumption amount obtained from the operating time of the developing device 4 and the driving time of the toner dispensing member 421, and the carrier supply amount is controlled. The results were the same as in Example 2.

D. Fourth Embodiment If the remaining amount in the toner replenishing tank 42 can be detected, the toner replenishing amount from the toner replenishing tank 42 can be obtained. Therefore, as shown in FIG.
Displacement sensor 81 for measuring the upper surface position of the displacing toner T
Was provided. The operating time of the developing device 4 and the toner T within that time
The amount of toner consumption was obtained from the amount of displacement of the upper surface of the toner, the amount of toner consumption of the operating developing device 4 per unit time was obtained, and the carrier replenishment amount was controlled. The results were similar to those in Example 2.

E. Fifth Embodiment The operating time of the developing device 4 is almost proportional to the number of image forming sheets such as the number of recording sheets 9 although there are times for various control processes. Therefore, in the above-described Example 2, the operating time of the developing device 4 was obtained from the number of recording sheets 9 required for copying, and the operating time of the developing device 4 was evaluated in the same manner. Became.

The means for measuring the toner consumption amount is not limited to the above embodiments as long as it has a function of measuring the toner consumption amount.
A method of measuring and obtaining the image on the photoreceptor 1 or the recording paper 9 on which the image is formed may be used. Further, in each of the above-described embodiments, the developer D is discharged by the overflow method. However, a shutter is provided at the developer discharge port 441 to open and close the shutter, and the discharge amount of the developer D is determined by the opening time of the shutter. It may be controlled. Further, the supply of the carrier C and the discharge of the developer D may be continuously performed,
You may go intermittently. Further, generally, the carrier C is largely deteriorated by stirring with the new toner T, but depending on the material, the stirring degree with the old toner, that is, the toner T having a long residence time in the developing device may be more deteriorated. . In this case, contrary to the above embodiments, the smaller the toner consumption amount, the larger the carrier replenishment amount, and the larger the toner consumption amount, the smaller the carrier replenishment amount. Further, the present invention can be applied to not only the above copying machine, printer, and facsimile but also any image forming apparatus for developing while performing a trickle of a two-component developer.

[0033]

As described above, according to the present invention,
The toner consumption amount measuring means measures the toner consumption amount from the inside of the developing device, and the carrier replenishment amount is controlled according to the measurement result. Therefore, the carrier replenishment amount and the developer are determined according to the toner consumption amount. Emissions are controlled accurately,
As a result, it is possible to efficiently perform the trickle according to the deterioration of the carrier.

[Brief description of drawings]

FIG. 1 is a schematic side view showing an embodiment of an image forming apparatus of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG. 5, showing the developing device of the embodiment.

3 is a sectional view taken along line III-III in FIG.

4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 is a top view of a developer tank that constitutes a developing device.

FIG. 6 is a diagram showing a case where the embodiment of the present invention is applied to (a) a flow of image information when applied to a copying machine, (b) a flow of image information when applied to a printer, and (c) applied to a facsimile. It is a flow of image information.

FIG. 7 is a diagram showing a change in image density and developer discharge amount in an example in which the carrier replenishment amount into the developer tank is controlled according to the toner consumption amount and in a comparative example in which the amount is not controlled;
(A) Carrier replenishment amount 1%, (b) Carrier replenishment amount 5%, (c) Carrier replenishment amount 15%.

FIG. 8A is a diagram showing that the relationship between the operating time of the developing device and the charging ability of the carrier varies depending on the toner consumption amount;
FIG. 6B is a diagram showing that the relationship between the operating time of the developing device and the amount of toner attached to the carrier varies depending on the amount of toner consumed.

[Explanation of symbols]

1 ... Photosensitive member (image bearing member), 3 ... Image writing means, 4 ...
Developing device, 5 ... Transfer charging device (transfer means), 9 ... Recording paper, 4
DESCRIPTION OF SYMBOLS 1 ... Developer tank, 42 ... Toner supply tank, 43 ... Carrier supply tank, 411 ... Development roll (developer carrying body), 414 ...
Auger (conveying member), 421 ... Toner dispensing member (toner replenishing member), 431 ... Carrier dispensing member (carrier replenishing member), C ... Carrier, D ... Developer,
T ... toner.

Claims (8)

[Claims] 1. A developer that stores an image carrier on which an input image is formed as a latent image on the surface by an image writing unit, and a developer that is a mixture of toner and carrier and that faces the image carrier. Toner and carrier are replenished by the toner replenishing member from the toner replenishing tank and by the carrier replenishing member from the carrier replenishing tank, respectively, while the developer is discharged from the developer replenishing tank into the developer tank containing the carrier. , Further, the developer in the developer tank,
Development for developing the latent image by carrying the developer to the developer carrying body by carrying the developer by the carrying member and supplying the developer from the developer carrying body to the surface of the image carrying body An image forming apparatus comprising: a toner consumption amount measuring means for measuring a consumption amount of toner required for development from the developer tank, wherein the toner consumption amount measuring means measures the toner consumption amount according to a measurement result of the toner consumption amount measuring means. An image forming apparatus for controlling the amount of carrier replenished from a carrier replenishment tank into the developer tank. 2. A developer that stores an image carrier on which an input image is formed as a latent image on the surface by an image writing unit, and a developer that is a mixture of toner and carrier and that faces the image carrier. Toner and carrier are replenished by the toner replenishing member from the toner replenishing tank and by the carrier replenishing member from the carrier replenishing tank, respectively, while the developer is discharged from the developer replenishing tank into the developer tank containing the carrier. , Further, the developer in the developer tank,
Development for developing the latent image by carrying the developer to the developer carrying body by carrying the developer by the carrying member and supplying the developer from the developer carrying body to the surface of the image carrying body An image forming apparatus including: a toner consumption amount measuring means for measuring an amount of consumption of the toner required for development from the developer tank; and a developing device operation time measurement for measuring an operation time of the developing device. And a means for controlling the replenishment amount of the carrier from the carrier replenishing tank into the developer tank according to the measurement results of the toner consumption measuring means and the developing device operating time measuring means. Forming equipment. 3. The image forming apparatus according to claim 1, wherein the toner consumption amount measuring unit determines the toner consumption amount required for development based on the area of the input image. 4. The toner consumption amount measuring unit obtains the toner consumption amount required for development from the number of pixels corresponding to the input image written in the image carrier by the image writing unit. 2. The image forming apparatus according to any one of 2 above. 5. The image forming apparatus according to claim 1, wherein the toner consumption amount measuring unit determines the toner consumption amount from the operating time of the toner supply member. 6. The image forming apparatus according to claim 1, wherein the toner consumption amount measuring unit obtains the toner consumption amount from the remaining amount of the toner replenishing tank. 7. The image according to claim 2, wherein the developing device operating time measuring means determines at least one of an operating time of the developer carrying member and an operating time of the conveying member. Forming equipment. 8. The image forming apparatus according to claim 2, wherein the developing device operating time measuring means counts the number of the recording sheets to obtain the developing device operating time.