JPH0241031B2 - TONAAHOKYUSEIGYOKAIRO - Google Patents

Description

[Detailed description of the invention]

[Overview] A toner replenishment system installed in an electrophotographic recording device that monitors toner marks for measuring toner density formed on the photoconductor separately from recorded information and controls the toner density of the developer in the developing device. The control circuit improves control accuracy by changing control conditions depending on the type of recording paper. [Industrial Field of Application] The present invention relates to an improvement in a toner replenishment control circuit provided in an electrophotographic recording apparatus using a two-component developer. FIG. 3 is a schematic diagram of an electrophotographic printing apparatus (laser printer) that uses a laser as a light source for exposure. 2 is a charger that imparts photosensitivity to the surface of the photosensitive drum 1 by corona discharge; 3 is a charger that applies a laser beam modulated by recorded information to the surface of the photosensitive drum 1 that has been imparted with photosensitivity; An exposure device 4 irradiates a beam to create an electrostatic latent image of recorded information;
4a is a toner hopper that stores toner for replenishment; 4b is a toner replenishment roller; 4c is a developer reservoir; It is a transfer device that transfers images to In the developing device 4, development is performed by electrostatically adhering the charged toner to the electrostatic latent image on the surface of the photosensitive drum 1. Since the toner is charged, it is generally called a carrier. It is used in the form of a mixture with iron powder, etc. (this mixture is referred to as a two-component developer or simply a developer), and the triboelectrification that occurs when this is stirred is utilized. The ratio of toner in the developer (toner concentration) is generally based on about 2%, but since only the toner is consumed during printing, the toner concentration will decrease if left as is. For this reason, an electrophotographic recording device that uses a two-component developer is provided with a toner replenishment control circuit, which replenishes toner to the developer reservoir 4c according to the density of the toner mark formed on the photosensitive drum 1. Control is being carried out for this purpose. At this time, it is desirable to minimize fluctuations in the toner concentration within the developer reservoir 4c. [Prior Art] FIG. 4 is a block diagram of a conventional example of a toner replenishment control circuit, and FIG. 5 shows a timing chart of signals in each part thereof. In FIG. 4, reference numeral 11 denotes a reference density generating section that generates a reference value of toner density, and the reference density setting section 12 selects, for example, "normal", "dark", "thin", etc.
One of the three types of reference values is set, and the amount of electricity Vn corresponding to the set type is generated. Reference numeral 13 denotes a density detection unit that detects the density of a toner mark formed outside the recording area at the end of the photosensitive drum by development, and the detected value is obtained as an amount of electricity Vm. 14 is under the control of the control section 15, and by comparing the detection value Vm detected by the concentration detection section 13 with the reference value Vn generated by the reference concentration generation section 11,
This is a density determination unit that determines whether or not the density of a toner mark is appropriate, and performs a comparison determination as follows and sends out a determination signal Se in accordance with the determination result. The control unit 15 simultaneously sends to the density determination unit 14 a verification period signal Sa and a determination control signal Sd of a certain time length _T1 representing the toner mark verification validity period, and then when a certain period of time ΔT has elapsed, the mark determination period is determined. A determination period signal Sb of a constant time length T ₂ that specifies . The detection value is detected during the period when the verification period signal Sa is output.
When Vm exceeds the reference value Vn, the concentration determining section 14 sends out the detection signal Sc during that time, and the detection signal Sc
As a result, the sending of the determination control signal Sd is stopped.
Note that if the detection signal Sc is not sent,
The determination control signal Sd is stopped at the same time as the verification period signal Sa. The concentration determination unit 14 sends out a determination signal Se as a logical product of the determination period signal Sb and the determination control signal Sd. A counting section 16 counts the judgment signal Se sent out by the concentration judgment section 14. Reference numeral 17 denotes a count value determining section, which sends out a toner replenishment signal when the count value in the counter section 16 reaches a predetermined number n, and at the same time, the count value of the counter section 16 is reset to zero by the toner replenishment signal. When the toner replenishment signal is sent as described above, the toner replenishment roller 4b provided in the developing device 4 rotates, and a certain amount of toner is replenished from the toner hopper 4a to the developer reservoir 4c. The toner mark is placed on the photosensitive drum 1 page by page, with the leading edge of the recording paper 6 (perforation in the case of continuous recording paper) as the home position (base point).
It is formed at a predetermined distance, for example, 1 inch, from the home position above, and the verification period signal Sa, determination period signal Sb, and determination control signal Sd from the control unit 15 to the verification unit 14 are also sent from the leading edge of the recording paper. Performed as a home position. [Problems to be Solved by the Invention] In the toner replenishment control circuit configured as described above, the count value determination unit 17 determines whether the count value in the counting unit 16 reaches a constant value, for example, 7, regardless of the size of the recording paper used. When this occurs, a toner replenishment signal is sent. Normally, the recording paper used in electrophotographic recording devices has a length of 3.5 inches and 4 to 14 mm in 0.5 inch increments.
There is a record sheet that is inch long. However, when using 14-inch long recording paper, as in the case of using 3.5-inch long recording paper, toner is not replenished unless the counted value in the counting unit 16 reaches, for example, 7 times. . On the other hand, it takes, for example, 10 to 30 seconds for the toner concentration inside the developing device 4 to become uniform after the toner is replenished and for the effect to appear on the toner mark. Therefore, when using short recording sheets,
There is a problem of excessive toner replenishment, and when long recording paper is used, there is a problem that toner replenishment cannot keep up. In addition, by forming toner marks for each predetermined paper transport amount (rotation angle amount of the rotating drum),
It is also possible to make toner supply independent of the paper length. However, this toner mark is used to set the paper's home position (print start position), and if this is made to correspond to the paper transport amount, the toner mark formation position will differ for each paper. Become. For this reason, a separate circuit for forming a mark for home position adjustment is required, resulting in a problem that the circuit configuration becomes complicated. Therefore, an object of the present invention is to prevent excessive or insufficient supply of toner caused by the type or length of recording paper used. [Means for solving the problem] Figure 1 is a block diagram of the principle of the present invention.
In addition to the same reference numerals as those of the conventional example explained in the drawings, 18 is a criterion selection section that selects the criterion used for verification in the count value determination section 17 according to the type of recording paper. [Operation] That is, the judgment criterion selection section 18 selects the judgment criterion number N as illustrated in the following table according to the type of recording paper, that is, the paper length, and the count value judgment section 17 selects, for example, 3.5. In the case of inch-long recording paper, when the count value of the counting section 16 reaches 24,
Further, in the case of a 14-inch long recording paper, when the number reaches 6, a toner replenishment signal is sent.

〔Effect of the invention〕

As described above, according to the present invention, toner replenishment control can be performed according to the type of recording paper, that is, the paper length, so that fluctuations in toner concentration in the developer reservoir can be reduced and recording quality can be improved. Can be done.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the principle of the present invention, Fig. 2 is a block diagram of an embodiment, Fig. 3 is a schematic diagram of an electrophotographic printing device, Fig. 4 is a block diagram of a conventional example, and Fig. 5 is a conventional one. It is an explanatory diagram of an example. In the figure, 13 is a concentration detection section, 14 is a concentration determination section,
16 is a counting section, 17 is a count value judgment section, 18 is a criterion selection section, 18a is a paper length setting section, and 18b is a conversion table.

Claims (1)

[Claims] 1. Toner marks, which are density control marks, are formed on the image carrier in page units of recording paper by development.
a density detection unit 13 that detects the density of the toner marks; and a detection value Vm detected by the density detection unit 13.
a density determination unit 14 that compares the value with a reference value Vn and sends a determination signal indicating that the density is light when Vm<Vn;
a counting unit 16 that counts the number of times the density determining unit 14 has sent out a determination signal; and a count determining unit 17 that compares the counted value in the counting unit 16 with a determination standard and sends out a toner replenishment signal according to the verification result. A toner replenishment control circuit comprising: a determination criterion selection section 18 that selects a determination criterion used for comparison in the count value determination section 17 according to the type of recording paper.