JPH0239791B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a toner density suitable for application to an apparatus that forms an electrostatic latent image on an electrostatic recording medium, visualizes the latent image with toner, and prints on paper. Regarding control method.

Recently, this type of device uses multiple detection means to measure matters related to toner concentration, such as the image density printed on paper, the toner density in the developer, and the number of prints. Proposals have been made to improve the reliability of the control by controlling the toner density based on the signal from the detection means. However, in the past, the signals from these detection means were processed independently regardless of the reliability of the signal, so if even one detection means with low reliability caused an abnormality, the other detection means Even if the toner is normal, the timing of toner replenishment is significantly delayed, resulting in a situation where proper concentration control becomes impossible.

Accordingly, the present invention provides an apparatus that visualizes an electrostatic latent image on an image carrier using toner and transfers it onto a sheet of paper, in which signals from two or more different detection means capable of detecting matters related to toner density are used. To provide a toner density control method that eliminates the above-mentioned drawbacks by converting the values into common printing parameters and integrating them all at once, comparing the integrated value with a reference value, and issuing a toner replenishment instruction. The purpose is to

Hereinafter, the present invention will be specifically explained based on an embodiment shown in the drawings.

As shown in FIG. 1, the printing device 1 has a latent image forming drum 2, which is an electrostatic recording medium, which is rotated in the direction of arrow A. Around the drum 2, there is a charger 3, which will be described later. An electrode 5, a developing device 6, a transfer device 7, a static eliminator 9, and a cleaner 10, which constitute a detection means, are provided. The developing device 6 has a magnetic brush roll 6b rotated in the B direction in a container 6a, and a developer 6c consisting of a carrier and toner.
Furthermore, a toner concentration detector 11 for measuring the toner concentration in the developer 6c is installed in the container 6a. Note that the developing machine 6 includes a toner replenishing device 1.
2 is provided. Also, the transfer machine 7 has paper 1.
3 is wrapped around the paper 13, and the transfer device 7 can convey the paper 13 in the C direction at the same speed as the drum 2. Furthermore, the transfer device 7 carries an image for measuring the print density printed on the paper. A concentration detector 15 is provided. As shown in FIG. 2, a processing circuit 17 constituting the toner density control section 14 is connected to the detection means such as the electrode 5, the toner density detector 11, and the image density detector 15. is connected to the conversion circuit 18. The toner replenishing device 12 is connected to the conversion circuit 18 via an addition circuit 19 and a comparator 20, and a reference setting circuit 21 is connected to the comparator 20.

Since the printing device 1 has the above-described configuration, the latent image forming drum 2, which is rotationally driven in the direction A, is uniformly charged by the charger 3 and then selectively charged dot by dot by the electrode 5. is removed and an electrostatic latent image is formed on the drum 2. Next, a developer 6c is supplied to the drum 2 by the rotating magnetic brush roll 6b of the developing device 6, and the latent image on the drum 2 is visualized by the toner in the developer 6c. The visualized image is transferred by the transfer device 7 onto a sheet 13 that is conveyed in the C direction. On the other hand, the drum 2 is de-charged by the static eliminator 9, and the cleaner 10
The remaining toner is scraped off and cleaned.
Prepare for the next print. At this time, the processing circuit 17 counts the number of dots from which the charge has been removed from the electrode 5, that is, the number of printed dots, and also counts the number of printed dots from the toner concentration detector 11.
The toner density in the developer 6c is measured by the image density detector 15, and the image density on the paper 13 is further measured by the image density detector 15. The circuit 17 accepts the measurement results as they are.
Alternatively, it is subjected to a certain process and outputted to the conversion circuit 18 in synchronization with a timing pulse TP of a certain period. (In the case of this embodiment, as shown in FIG. 3, the processing circuit 17 receives a signal S1 having a pulse width T corresponding to the number of printed dots in one cycle of the pulse TP, and detects when the toner concentration has fallen below a certain value. (The conversion circuit 18 outputs a pulse signal S2 of a constant width when the print density is detected to be below a certain value, and outputs a pulse signal S3 of a constant width when the print density is detected to be below a certain value.) , S2, and S3, convert them into common printing parameters, and add them to the addition circuit 1.
Output to 9. (For example, the conversion circuit 18 uses the number N of printing dots obtained from the pulse width T of the signal S1 as a reference printing parameter, and converts the number of printing dots
Each pulse is evaluated as M dots, and one pulse of signal S3 is evaluated as one dot, and each time signals S2 and S3 are input, equivalent dot numbers M and L are calculated as signals S2' and S
3' to the circuit 19. ) Each signal S1, S for printing parameters in the conversion circuit 18
2. The evaluation of S3 is given high when the reliability of the detection means is high, and low when it is low. In this way, each signal S converted to the same printing parameter
1', S2', and S3' are input to the adder circuit 19 for each timing pulse TP, and the circuit 19 integrates all these signals at once and outputs the integrated value K to the comparator 20. On the other hand, the timing for replenishing toner is sent to the basic setting circuit 21 by signals S1', S2', S
The reference value KS is set by the same printing parameter as 3', and therefore the comparator 20 compares the reference value KS from the setting circuit 21 and the integrated value K from the adder circuit 19, and determines that K≧KS. In this case, it is determined that the time to replenish toner has arrived, and a signal S6 is output to the toner replenishing device 12. Device 1
2 is driven by the signal S6 to replenish toner into the container 6a, and as a result, the toner concentration in the developer 6c is always maintained within an appropriate range. It should be noted that signals from detection means with low reliability among the detection means are given only a low evaluation when converted into printing parameters by the conversion circuit 18, and therefore have a small influence on the integrated value K. Even if an abnormality occurs in such a detection means, as long as other highly reliable detection means are normal, the toner replenishment timing, and therefore the toner concentration, will not be significantly disturbed.

In the above embodiment, the signals S1', S2', and S3' from the conversion circuit 18 were added together and compared with the reference value KS, but as shown in FIG. An addition/comparison circuit 22 is connected to add signals S1', S2', and S3' individually, and the signals S1', S2', and S3' from each detection means are integrated and their ratio (integration ratio) is calculated. , the ratio when each detection means is normally operating (standard ratio)
Compare with. As long as each detection means is operating normally, the integration ratio and the reference ratio of each signal S1', S2', and S3' approximately match, but if a failure occurs in even one of the detection means, the integration ratio and the reference ratio will change. Since it changes greatly, abnormalities in each detection means can be immediately detected. Further, if each detection means is operating normally, other failures can be detected by comparing the integrated ratio and the reference ratio. (For example, when the toner density is normal and the print density is low, the integrated ratio of the signals S2' and S3' varies with respect to the reference ratio, so it is possible to discover a failure such as deterioration of the developer 6c. ) In the above-mentioned embodiment, the detection means includes the electrode 5, the toner density detector 11, and the image density detector 15.
Although the case has been described in which the detection means is composed of two or more detection means, it goes without saying that two or more detection means may be used as long as they can detect matters related to toner concentration.

As explained above, according to the present invention, the electrode 5, the toner density detector 11, the image density detector 15
Signals S1, S2, S3 from multiple detection means such as
After converting into a common printing parameter, it is integrated all at once, and the toner replenishment timing is determined based on the integrated value K. Therefore, each signal S1, S2, and S3 can be evaluated according to the reliability of the detection means. Therefore, even if some unreliable detection means malfunctions, the toner replenishment timing will not be significantly disrupted, and toner density control can be performed favorably.

[Brief explanation of drawings]

FIG. 1 is a side view showing an example of a printing device to which the present invention is applied, FIG. 2 is a block diagram of a toner density control section in the printing device shown in FIG. 1, and FIG. 3 shows the operation of each part in FIG. The time chart shown in FIG. 4 is a block diagram showing another example of the toner density control section. 1... Device (printing device), 2... Electrostatic recording medium (latent image forming drum), 5... Detection means (electrode), 1
1...detection means (toner concentration detector), 13...
Paper, 15...Detection means (image density detector), S
1, S2, S3...signal, K...integrated value.

Claims (1)

[Scope of Claims] 1. In a device that visualizes an electrostatic latent image on an image carrier using toner and transfers it onto a sheet of paper, a method of detecting information from two or more different detection means capable of detecting matters related to toner concentration is provided. A toner density control method characterized by converting signals into common printing parameters and integrating them all at once, and comparing the integrated value with a reference value to issue a toner replenishment instruction.