JPH055552Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to an exposure control device for a copying machine, and more particularly to an exposure control device that stabilizes the amount of light that changes depending on the temperature of the tube wall of a fluorescent lamp.

2. Description of the Related Art A typical electrophotographic copying machine forms a copy image corresponding to a document on paper through the steps of charging, exposure, development, transfer, and fixing.

In the exposure process, according to an exposure control device using a fluorescent lamp, the light emitted from the fluorescent lamp illuminates the document, and the reflected light causes the electrostatic charge on the photoreceptor to form a predetermined image. An electrostatic latent image is formed on the photoreceptor.

As shown in Figure 5, the amount of light emitted by the fluorescent lamp of this exposure control device changes depending on the tube wall temperature of the fluorescent lamp, so if the tube wall temperature of the fluorescent lamp is too low or too high, the light amount Since the temperature decreases, it is necessary to keep the temperature of the tube wall within a predetermined temperature range.

Problems that the invention aims to solve As described above, with conventional exposure control devices, for example, the amount of light changes depending on the tube wall temperature of a fluorescent lamp.
There is a problem in that the copy density on the copy paper obtained through the exposure, development, and transfer steps varies.

In addition, conventional exposure control devices have been proposed that maintain the tube wall temperature within a predetermined range by attaching a temperature sensor such as a thermistor, a heating device such as a heater, etc. to the tube wall of the fluorescent lamp. However, this conventional exposure control device has the problem of high cost.

An object of the present invention is to solve the above-mentioned problems and eliminate variations in copy density by keeping the amount of light emitted by the fluorescent lamp within a predetermined range during the formal exposure timing.

Means for Solving the Problems The exposure control device for a copying machine of the present invention includes a fluorescent lamp that irradiates an original on a platen glass of the copying machine, a temperature sensor disposed in close contact with the tube wall of the fluorescent lamp, and the temperature sensor. In response to the tube wall temperature signal detected by
The light amount control means controls the amount of power supplied to the fluorescent lamp according to this light amount value signal.

Effect According to the present invention, the tube wall temperature of the fluorescent lamp is detected by a temperature sensor, the light amount value corresponding to this detected temperature is read out from a predetermined light amount map, and the electric power amount corresponding to this light amount value is calculated from the fluorescent lamp. supply to.

For example, as shown in Figure 3, if the tube wall temperature of a fluorescent lamp is 20°C, the amount of light emitted from the fluorescent lamp is approximately 70% of that of normal copying operation, and this state The control means outputs a control signal to the power supply device of the fluorescent lamp to increase the amount of light by 30%.

Embodiments Hereinafter, embodiments of the present invention will be described based on the drawings.

As shown in FIG. 2, the light emitted from the fluorescent lamp 1 is irradiated onto the document 3 on the platen glass 2.
The reflected light passes through a lens 4 and is irradiated onto a photosensitive drum 5. Around fluorescent light 1,
A reflector 6 is provided to focus the light emitted from the fluorescent lamp 1, and a temperature sensor 7 is attached to one end of the tube wall of the fluorescent lamp 1 to detect the tube wall temperature.

FIG. 1 shows a circuit configuration for controlling the power supplied to the fluorescent lamp 1. As shown in FIG. The output signal of the temperature sensor 7 that detects the temperature of the tube wall of the fluorescent lamp 1 is input to the microcomputer 8, and is output to a predetermined value according to a light amount map stored in the microcomputer 8 that represents the relationship between the tube wall temperature of the fluorescent lamp 1 and the amount of light. The light quantity control signal is output to the triac 9.

An AC voltage of 100V is applied between terminals a and b, and the voltage to the stabilizer 10 is turned on and off by turning on and off the triax 9. The ballast 10 is for lighting the fluorescent lamp 1 in a stable light amount, and is controlled by an on/off signal sent from the microcomputer 8 to the gate of a triax 9 as a switch element.

The ROM in the microcomputer 8 stores in advance a light intensity map (for example, the characteristic curve shown in FIG. 3) representing the relationship between the tube wall temperature and the light intensity value of the fluorescent lamp 1, and the light intensity map (for example, the characteristic curve in FIG. 3) is stored in the ROM in the microcomputer 8. A predetermined voltage control signal is output to the terminal 9.

For example, if the tube wall temperature of fluorescent lamp 1 is 20°C, the light intensity of fluorescent lamp 1 is approximately the same as that during normal copying operation.
Since the light intensity is 70%, the microcomputer 8 outputs a control signal to the triax 9 as an on/off signal with a predetermined duty ratio to increase and supply the remaining 30% of the light intensity so that the total light intensity becomes 100%. As a result, the increase/decrease in the amount of light with respect to the tube wall temperature of the fluorescent lamp 1 is corrected to an appropriate value.

FIG. 4 shows a timing chart of the AC voltage applied to the ballast 10. When the tube wall temperature of the fluorescent lamp 1 is 30°C, the reflected light from the fluorescent lamp 1 through the document 3 matches the total light amount during normal copying operation, so the on/off signal with a predetermined basic duty ratio is A signal is applied from the computer 8 to the triax 9. That is, an AC voltage as shown by diagonal lines in FIG. 4 is applied to the ballast 10 via the triax 9.

When the tube wall temperature of the fluorescent lamp 1 is 20°C, the light intensity of the fluorescent lamp 1 is reduced by about 30% compared to when the tube wall temperature is 30°C. The rising phase angle is advanced by a predetermined phase angle, and the corresponding on/off signal is sent from the microcomputer 8 to the triac 9.
Output to.

In this way, the light amount corresponding to the tube wall temperature of the fluorescent lamp 1 is read out from a predetermined light amount map, and based on this light amount value, a predetermined phase angle signal is turned on and off from the microcomputer 8 to the gate of the triax 9. However, the change in the light amount of the fluorescent lamp 1 is set so as to fall within a predetermined range.

In this embodiment, the predetermined alternating current voltage applied to the ballast 10 is turned on and off by the triax 9, but in the present invention, an SCR or other semiconductor switch may be used instead of the triax 9 as a switch element. can.

Effects of the invention As described above, according to the invention, the tube wall temperature of a fluorescent lamp is detected by a temperature sensor, and the exposure amount is controlled based on the characteristic value of the light amount map. It is only necessary to change the characteristic values of the light intensity map for various fluorescent lamps with temperature versus light intensity characteristics, and the same control circuit can be used to control them, increasing design flexibility and making maintenance easier. It becomes simple. In addition, the relationship between tube wall temperature and light intensity is a complex function that is difficult to realize with analog circuits, but by using a light intensity map, the amount of emitted light can be instantly adjusted to the planned light intensity regardless of the tube wall temperature. . Therefore, the exposure amount can be kept within a predetermined range without being influenced by the surrounding environment, especially the tube wall temperature of the fluorescent lamp, and image quality defects due to variations in copy density can be reliably prevented. .

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the present invention. Fig. 2 is a schematic diagram showing the main parts of an embodiment of the invention. Fig. 3 is a diagram showing the relationship between tube wall temperature and light intensity of a fluorescent lamp. FIG. 4 is a timing chart showing the voltage applied to the ballast in one embodiment of the present invention, and FIG. 5 is a graph showing the relationship between tube wall temperature and light amount of a general fluorescent lamp. 1...Fluorescent lamp, 2...Platen glass, 3...
Original, 5...Photosensitive drum, 7...Temperature sensor,
8...Microcomputer, 9...Triack.

Claims (1)

[Scope of utility model registration request] A fluorescent lamp illuminates the document on the platen glass of a copying machine, a temperature sensor is placed closely on the tube wall of the fluorescent lamp, and a light amount value signal is sent to a microcomputer in response to the tube wall temperature signal detected by the temperature sensor. Exposure control for a copying machine, characterized in that the light amount control means reads out a stored map of tube wall temperature versus light amount characteristics of a fluorescent lamp and controls the amount of electric power supplied to the fluorescent lamp according to the light amount value signal. Device.