JPH0284A - Heating type fixing device - Google Patents

Abstract

PURPOSE:To detect whether or not fixation is defective instantaneously and securely by comparing the optical density of a toner picture formed on a recording medium with a predetermined value after a recording medium passes a heater. CONSTITUTION:A 1st photosensor 1 is provided on the exit side of the heater 2 and a photodetection part detects light which is emitted by an internal light emission part and reflected by a sheet S to detect the optical density of a density detection mark on the sheet S having already passed the heater 2. Then the toner picture on the sheet S is heated with radiant heat and fixed on the sheet S. Further, a 2nd photosensor 3 provided on the entrance side of the heater 2 and detects the optical density of the density detection mark before the fixation of the sheet S. Then detecting circuits 4 and 5 detect the outputs of the sensors 1 and 2 and a comparing circuit 6 compare their outputs with each other, thereby generating an alarm unless the output reaches a standard optical density difference.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a heating type fixing device used, for example, in an electrophotographic printer or an electrostatic recording printer.

(2) Background of the technology Electrophotographic or electrostatic recording printers have excellent print quality and speed, and are extremely quiet, making them particularly suitable as output printers for office computers. It is replacing the traditional stamping type line printer.

For example, in an electrophotographic printer, a photosensitive plate is charged to give it photosensitivity, the photosensitive plate is irradiated with light corresponding to an electrical signal to create an electrostatic latent image, and the latent image is developed with toner. The transferred toner image is transferred onto a recording medium (hereinafter simply referred to as a sheet), and the transferred toner image is fixed by a fixing device.

This fixing device is roughly classified into a heating type and a pressure fixing type, and the heating type includes a heat roller type, an open type, and a radiation type represented by a flash type.

(3) Problems with the conventional technology In these fixing devices, there is excessive supply of toner in the developing section, fluctuations in the heating temperature in the heating type, and uneven pressure force due to uneven sheet thickness in the pressure type. Poor fixing occurs from time to time.

Furthermore, the toners used in these devices have different characteristics, so the brand of toner to be used is specified depending on the model, and if a different toner is used, normal fixing will not normally be performed.

However, in recent years, not only printers but also copiers, faxes, etc.
As devices that use toner are rapidly becoming more popular, the possibility of poor fixing due to the use of unspecified toner is greatly increasing.

For this reason, for example, as shown in Japanese Utility Model Application Publication No. 55-12206, a white roller is provided so as to come into contact with the surface of the sheet after passing through a heating type fixing device, and whether or not toner has adhered to this white roller is determined. There is a device configured to detect fixing failure of a heating type fixing device by detecting it with an optical sensor.

However, in such a heating type fixing device, it is necessary to provide a white roller, resulting in a problem that the configuration becomes complicated.

(4) Purpose of the Invention The present invention was made in order to deal with such circumstances, and its purpose is to provide a heating type fixing device that can immediately and reliably detect fixing defects with a simple configuration. It's about doing.

(5) Structure of the invention And, this object is to provide a heating type fixing device that heats and fixes a toner image transferred onto a recording medium using a heater, in which a toner image formed on the recording medium after passing through the heater. This is achieved by a heating type fixing device characterized by comprising means for detecting fixing failure of the toner image depending on whether the optical density of the toner image is a predetermined value or not.

That is, the present invention makes it possible to detect fixing failure with a simple configuration by effectively utilizing the relationship described below with reference to FIG.

Hereinafter, a case of a radiation type fixing device will be explained as an example.

Figure 1 shows the relationship between the amount of heat used to fix the toner image and the density of the toner image. This is the optical density of the toner image measured.

As the amount of heat absorbed by the toner image increases, the toner begins to melt from the surface, and the surface tension of the melted toner attracts adjacent unmelted toner, resulting in partial exposure of the sheet, which reduces the density. decreases once, d
+.

When the amount of absorbed heat further increases, the toner is melted over the entire surface, and then the toner in the lower layer in contact with the sheet is melted and begins to penetrate into the sheet, and the density of the toner image reaches the maximum value d2.

When the toner image density, that is, the optical density from dl to d2 is divided into four stages and the adhesion force of the toner to the dot is observed, the results are as follows.

(2) is a stage in which a portion of the surface layer of the toner is melted and a portion of the sheet is exposed, and therefore, the toner has almost no adhesion to the sheet and is therefore easily peeled off.

In case (2), only the surface layer of the toner was melted, but not all of the lower layers were melted, so the adhesion was weak and it was easy to peel off due to friction.

In case (2), even the toner in the lower layer in contact with the sheet melts and a portion of it penetrates into the sheet, so a relatively strong adhesive force is generated between the sheet and the toner, making it difficult to peel off easily due to friction.

In case (2), the toner permeates the entire surface of the sheet, so at least the permeated toner cannot be removed by friction.

That is, in the present invention, the optical density of the toner image on the sheet after passing through the heating type fixing device is measured based on the relationship between the above-mentioned adhesion force of the toner to the sheet and the optical density measured by the optical sensor. This is to check the adhesion of the toner to the sheet, that is, the fixability.

(6) Embodiment FIG. 1 is a block diagram for explaining an embodiment of a heating type fixing device according to the present invention.

A first photo sensor 1 is provided on the exit side of the heater 2, which will be described later, and has a built-in light emitting part and a light receiving part, and detects the light emitted from the light emitting part and reflected from the sheet S. 2
2 is a heater for detecting the optical density of the density detection mark provided on the sheet S after passing through the sheet S;
The toner image on the sheet S is heated by radiant heat and the toner image is fixed on the sheet S. 3 is a second photo sensor, which is provided on the inlet side of the heater 2, and is connected to the sheet +
4 is a first detection circuit that measures the output of the first photo sensor 1; 5 is a second detection circuit; can be,
6 is a comparison circuit that measures the output of the second photo sensor 3, stores a standard optical density difference in advance, and compares the difference between the output of the first detection circuit 4 and the output of the second detection circuit 5. seek,
This difference is compared with the standard optical density difference, and if the standard print density difference is not reached, an alarm signal is generated.

In the above configuration, the value of the standard optical density difference stored in advance in the comparator circuit 6 is set based on the value approximately at the center of the level 2 described in FIG. 1 above.

Further, as illustrated in FIG. 3, the density detection mark M is provided outside the printing range (indicated by a chain line) of the sheet S.

In the above embodiment, the optical density of the toner image before fixing and after fixing was measured at the inlet and outlet sides of the heater 2, respectively. However, it is not always necessary to measure the optical density of the toner image before fixing. There isn't.

Further, an optical density detection mark scraping mechanism whose main component is a rotating brush is provided after the heater 2, and the optical density of the optical density detection mark after passing through the scraping mechanism is measured by the first photo sensor 1. This makes it possible to further improve the effects of this embodiment.

(7) As described in detail of the invention, according to the present invention, it is possible to obtain a heating type fixing device that can immediately and reliably detect fixing defects with a simple configuration and prevent fixing defects from occurring again.

Ward 1

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the amount of heat absorbed by a toner image and the optical density of the toner image, FIG. 2 is a block diagram illustrating an embodiment of a heating type fixing device according to the present invention, and FIG. FIG. 3 is a diagram illustrating recording positions of optical density detection marks in FIG. In the figure, 1 is the first photo sensor, 2 is the heater, and 3 is the second photo sensor.
4 is a first detection circuit, 5 is a second detection circuit, and 6 is a comparison circuit. (i, Yusu

Claims (1)

[Scope of Claims] In a heating type fixing device that heats and fixes a toner image transferred onto a recording medium using a heater, the optical density of the toner image formed on the recording medium after passing through the heater is A heating type fixing device, comprising means for detecting fixing failure of the toner image depending on whether or not the value is a predetermined value.