JPS628178A - Electrophotographic recording device - Google Patents

Abstract

PURPOSE:To perform fine toner concentration control according to variation in the black/white rate of a original and a variety of original sizes by detecting the amount of toner on a drum, converting an obtained analog signal into a digital signal, and varying the amount of toner on the basis of the value. CONSTITUTION:For example, the reference value of toner concentration is 1.9V and continuous recording of original size A3 is carried out while the black/ white rate is >=5%. In this case, the input of an A/D converter 3 is 2.4-2.5V and the output is at level 8. A decision circuit 4 decides that and turns on a driving circuit 5 for three seconds, so a motor is driven for three seconds to supply a developing device with toner by an amount corresponding to the driving time. Then when continuous recording of original size A4 is carried out while the black/white rate is 2-3%, the input of the A/D converter 3 becomes about 2.0-1.9V and the output level of the A/D conveter 3 becomes three; and the driving circuit 5 is turned on for 0.5sec, thereby supplying toner to the developing device correspondingly. When the input of the A/D converter 3 is <=1.9V, no toner is supplied.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an electrophotographic recording device.

[Conventional technology]

Control of toner density in conventional electrophotographic recording apparatuses has been performed based on the amount of toner on a photoreceptor drum. In other words, the amount of toner developed on the surface of the photoreceptor drum is measured, and based on the measured amount, if the amount of toner is higher than an arbitrarily set standard level, the toner is replenished into the developing device. First, when the amount of toner is less than a reference level, the toner concentration is controlled so that a certain amount of toner is replenished into the developing device to keep the toner concentration in the developing device constant.

In addition, there is also a device that changes the amount of toner supplied depending on the size of the recording paper.

[Problem that the invention seeks to solve]

In the conventional recording apparatus described above, when the toner replenishment amount is set assuming a normal original with a black-and-white ratio of about 51 as a reference level, when originals with many black areas are continuously recorded, The amount of replenishment cannot keep up with the amount of consumption, and the toner density gradually becomes lower than the initial target □, resulting in the density of the recorded image becoming thinner.Conversely, the amount of toner replenishment is assumed to be an original with a high black rate. When a document with a low black rate is continuously recorded when the setting is set, there is a drawback that toner is oversupplied and the density of the recorded image greatly fluctuates.

In addition, even in a method that changes the amount of toner replenishment depending on the size of the recording paper, if it is specified that a fixed amount of toner must be replenished for each size of recording paper, the same drawback as mentioned above will occur. occurs.

[Means for solving problems]

The electrophotographic recording device of the present invention includes a sensor that measures the amount of toner developed on a photoreceptor drum and converts it into an analog signal, and an A/D converter that converts this analog signal into a digital signal. The developing device has means for controlling the amount of toner to be supplied to the developing device based on the digital signal.

Since the output level of the A/D converter varies in proportion to the black and white ratio of the original, it is possible to set in advance the drive time of the motor to supplement toner to the developer, for example, in accordance with this output level. This enables fine-grained control of the amount of toner replenished in response to continuous recording of documents with many black areas, or conversely, continuous recording of documents with large black areas. is possible.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of essential parts of an embodiment of an electrophotographic recording apparatus of the present invention.

A reflective deafness sensor 1 detects the amount of toner on the drum and outputs an analog signal. Amplification circuit 2Fi amplifies this analog signal. A/D converter 8i1t) converts the amplified analog signal representing the amount of toner into an 8-bit digital value with 8 levels. The determination circuit 4 is constituted by a microprocessor, reads the digital value converted into one of eight levels, and determines the on-time of the drive circuit 50. The drive circuit 5 is turned on for the ON time determined by the determination circuit 4, and drives a motor etc. to replenish toner to the developing device.

Table 1 shows the input of the A/D converter 8 and the corresponding A/D converter 8.
It shows the output level of the D converter 8 and the time for turning on the drive circuit 5.

Table 1 Next, the operation of this embodiment will be explained. It is assumed that the reference value of toner density is 1.9v. Now, assume that documents of A8 size and black and white ratios of 51 or more have been continuously recorded.

In this case, the input to the A/D converter 80 is approximately 2.4 to 2.5V, and the output is level 8.The 0 judgment circuit number judges this and turns on the drive circuit 5 for only 8 seconds. As a result, the motor is driven for 8 seconds, and the developing device is replenished with an amount of toner commensurate with this driving time. Next, it is assumed that documents of A4 size and a black and white ratio of 2 to 8 are consecutively recorded. and the input of the A/D converter 8 is 2.0 to 1.
．． The voltage is about 9V, and the output level of the A/D converter 8 reaches 8V. The drive circuit 5 is 0. ! It is turned on for only s seconds, and the corresponding amount of toner is replenished into the developing device. Further, when the input to the A/D converter 8 is 1.9V or less, toner is not replenished.

Note that the drive circuit 6 may have a time set by the number of pulses, although this differs depending on the toner replenishment mechanism.Although a microprocessor is used in the determination circuit 4 in this embodiment, it can be easily replaced with hardware. The circuit may be assembled using only hardware.

〔Effect of the invention〕

As explained above, the present invention detects the amount of toner on the drum, converts the obtained analog signal into a digital signal, and changes the amount of toner based on that value. Even if the size changes, the toner density can be controlled in a correspondingly fine manner.

[Brief explanation of drawings]

FIG. 1 is a block diagram of essential parts of an embodiment of an electrophotographic recording apparatus of the present invention. DESCRIPTION OF SYMBOLS 1... Reflection type sensor, 2... Amplification circuit, 8... A/D converter, 4... Judgment circuit, 5... Drive circuit.

Claims (1)

[Scope of Claims] An electrophotographic recording device includes: a sensor that detects the amount of toner developed on a photoreceptor drum and outputs an analog signal; and an A/D converter that converts the analog signal into a digital signal. . A photographic recording apparatus, comprising means for controlling the amount of toner to be supplied to the developing device based on the digital signal.