JPH0525104B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exposure apparatus such as an electronic copying machine that uses a fluorescent lamp as an exposure light source.

(Prior Art) An electronic copying machine exposes a charged drum to light according to document information, and then forms a toner visible image on an electrostatic latent image formed on the drum surface. This is a device that transfers images onto copy paper.

FIG. 2 is a diagram showing an example of the conventional configuration of such an electronic copying machine. When the operator presses a copy start button (not shown), the illustrated device begins a copy operation. The photosensitive drum 1, which is rotating in the direction of the arrow, is cleaned by a blade in the cleaning section 2, after which the residual toner on the photosensitive drum is scraped off by a blade, and then corona discharge is applied to the surface of the photosensitive drum 1 by a charging electrode 3, so that a positive charge is applied to the surface of the photosensitive drum 1. The entire surface is charged. A charge erasing section 4 erases unnecessary portions of the charges charged by the charging electrode 3.

On the other hand, an exposure unit 6 whose on/off control is controlled by a fluorescent lamp lighting circuit 5 irradiates light onto a document 8 placed on a document table 7, and the reflected light is transmitted through a self-cleaning lens (an example of a light transmitting body). (manufactured by Nippon Sheet Glass Co., Ltd.) 9 and irradiates the photosensitive drum 1.
Here, when the document table 7 is horizontally moved in the direction of the arrow in the figure, the image information on the document 8 is focused by the self-occurring lens 9 and sequentially irradiated onto the photosensitive drum 1.
As a result, the unnecessary portion (area corresponding to a non-image area) is charged and erased by the charge erasing section 4, and an electrostatic latent image of the document image information is sequentially formed on the charged area of the photosensitive drum surface where an image is to be formed. It is formed. The electrostatic latent image formed on the surface of the photosensitive drum 1 is converted into a visible image by adsorption of toner in the subsequent developing section 10. The toner image on the surface of the photosensitive drum is transferred to a copy paper in a transfer section 11, and the copy paper that is in close contact with the photosensitive drum 1 is separated. The separated copy paper is sent to the fixing roller 13 via the conveyance mechanism 12, and the copy paper is heated and pressurized by the fixing roller 13 to fuse the toner on the copy paper to the copy paper, and the copying operation is completed. finish.

By the way, as the light source 20 used in the exposure section 6, a fluorescent lamp as shown in FIG. 3 is normally used. In FIG. 3, A is a perspective view, and B is a sectional view taken along the line A-A'. In the figure, 21
22 is a pin, 22 is a base, 23 is a heater formed surrounding the fluorescent tube 24, and 25 is a heat generating portion of the heater 23. The heat generating portion 25 may be attached around the fluorescent tube 24 as shown in FIG. 2, for example, and may be further fixed thereon with a heat shrink tube (not shown) or the like. Alternatively, there are cases where the tube is simply attached to the surface of the fluorescent tube without using a heat shrink tube. Reference numerals 26 and 27 are electrodes for applying current to the heater 23, 28 is a reflective film/fluorescent film, and 29 is an opening (aperture). Heater 23 is fluorescent tube 2
4 is provided to quickly increase the temperature of the tube wall.

The relationship between the tube wall temperature and the amount of emitted light of a fluorescent lamp constructed in this manner is shown in FIG. 4. In the figure, the horizontal axis shows the fluorescent tube wall temperature, and the vertical axis shows the amount of emitted light. Here, the temperature of the tube wall of the fluorescent lamp reaches the predetermined reference value t ₀ within the warm-up time of the fixing heater provided in the fixing roller 13, and the amount of emitted light reaches L ₀ . This results in accurate exposure and accurate copying of the image.

By the way, if we pay attention to the relationship between the fluorescent lamp, the tube wall temperature, and the amount of emitted light in Figure 4, we can see that the amount of emitted light depends on the tube wall temperature at t ₁
The maximum Lmax is reached when the tube wall temperature becomes higher than t1, and when the tube wall temperature becomes higher than _t1 , it tends to decrease, and the tube wall temperature reaches
If the maximum value is exceeded, the amount of light will decrease to less than _L0 required for proper exposure. That is, the tube wall temperature is t
If the maximum value is exceeded, the amount of light will be insufficient and accurate copying of images will become impossible.

(Problems to be Solved by the Invention) In order to solve the above-described insufficient light amount when the tube wall temperature exceeds t max, conventionally, the tube wall temperature of the fluorescent lamp is increased as shown by the broken line in FIG. Fluorescent lamps were used because they produced a sufficient amount of light even though they were expensive. For this reason, a fluorescent lamp and a lighting circuit that emit a large amount of light are required, which is one of the causes of increased costs.
Furthermore, even if the temperature of the tube wall of the fluorescent lamp became extremely high, it could not be detected because no temperature detection means was provided.

The present invention has been made in view of these points, and its purpose is to realize an exposure apparatus that at least turns off the lighting of the fluorescent lamp as an abnormality when the tube wall temperature of the fluorescent lamp becomes too high. It's about doing.

(Means for Solving the Problems) The present invention, which solves the above-mentioned problems, is an exposure device that obtains image information by irradiating the surface of a document with a fluorescent lamp. a light amount detection sensor that is set in advance so that when the threshold value is exceeded, the amount of light emitted from the fluorescent lamp is equal to or less than a light amount reference value necessary for appropriate exposure, and which detects the amount of light from the fluorescent lamp; a fluorescent lamp lighting control circuit that controls lighting of the fluorescent lamp by controlling energy supplied to the fluorescent lamp based on the output of the light amount detection sensor; Although the circuit controls the supplied energy so that the light amount of the fluorescent lamp maintains at least the light amount reference value necessary for the appropriate exposure, the light amount of the fluorescent lamp becomes less than the light amount reference value. , and when the amount of light emitted from the fluorescent lamp shows a tendency to decrease over time, at least the lighting of the fluorescent lamp is turned off.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. Components that are the same as those in FIG. 2 are designated by the same numbers. In the figure, 31 is a light amount detection sensor that detects the amount of light emitted from the fluorescent lamp 20, and 32 is a fluorescent lamp lighting control circuit that receives the output of the light amount detection sensor 31 and controls the on/off of energization to the fluorescent lamp 20. be. The fluorescent lamp lighting control circuit 32 is configured to turn off the lighting of the fluorescent lamp 20 if the amount of light from the fluorescent lamp 20 is less than the above-mentioned L ₀ and the amount of light is decreasing. The operation of the device configured as described above will be explained as follows.

When the power of the electronic copying machine is turned on, the fixing heater (not shown) in the fixing roller 13 and the fluorescent lamp 2 are turned on.
0 and the fluorescent lamp heater 23 (see FIG. 3) are started to be energized. As a result, the tube wall of the fluorescent lamp gradually rises due to self-heating due to the energization and heat generation from the heat generating portion 25 due to the energization of the heater 23. As the temperature of the tube wall increases, the amount of light emitted from the fluorescent tube through the aperture portion 29 also increases accordingly, as shown in FIG. The light amount detection sensor 31 detects the amount of light from the fluorescent lamp 20 and applies its output to the fluorescent lamp lighting control circuit 32. Then, the fluorescent lamp lighting control circuit 32 controls the amount of light of the fluorescent lamp 20 to be L ₀
It is detected whether the amount of light is decreasing or increasing. That is, if the light amount is less than L ₀ and the light amount is increasing, it can be determined that the tube wall temperature of the fluorescent lamp is less than t ₀ , and if the light amount is more than L ₀ and the light amount is increasing, the tube wall temperature is t ₀ . If it can be determined that the temperature is between t ₁ and the light amount is more than L ₀ and the light amount is decreasing, the tube wall temperature can be determined to be between t ₁ and t max, and if the light amount is less than L ₀ and the light amount is decreasing. is the tube wall temperature t
It can be determined that there is an abnormality if it is above max. When an abnormality in the tube wall temperature is detected in this way, the power supply to the fluorescent lamp 20 is stopped and the lighting of the fluorescent lamp 20 is turned off.

Regarding fluorescent lamp replacement when abnormal lighting occurs, if the abnormality occurs continuously, or if it occurs more than a certain number of times within one replacement, replacement or repair is required as an abnormality in the fluorescent lamp, heater, or control circuit. So,
Stop the copy operation.

Next, a method for detecting that the amount of light from a fluorescent lamp tends to decrease will be described in detail. for example,
When the light amount of a fluorescent lamp is controlled by PWM (pulse width modulation) modulation, the relationship between the duty and the amount of emitted light (i.e., luminous efficiency) is expressed as
The result will be as shown in the figure. In the figure, the vertical axis is the amount of emitted light, and the horizontal axis is the duty (%). The figure shows three types of light emission characteristics using tube wall temperatures t ₁ , t ₂ , and t ₃ as parameters. The magnitude relationship of the tube wall temperature is t ₁ <t ₂ <t ₃ , where t ₂ is the tube wall temperature at which the luminous efficiency of the fluorescent lamp is maximum. As shown in the figure, the luminous efficiency decreases whether the tube wall temperature is higher or lower than _t2 .

FIG. 6 is a diagram showing the relationship between the fluorescent lamp tube wall temperature and the amount of emitted light. In the figure, the vertical axis is the amount of emitted light, and the horizontal axis is the fluorescent tube wall temperature. t ₁ , t ₂ , and t ₃ on the horizontal axis are the same as those in FIG. 5. L ₀ on the vertical axis is the aforementioned light amount reference value. From FIG. 6, the following can be seen. In other words, when trying to control the amount of emitted light to the reference value L ₀ , if the amount of emitted light is less than the reference value L ₀ , if the tube wall temperature is less than t ₂ , the tube wall temperature will rise over time and the emission will be interrupted. The duty decreases with time as the efficiency improves, and above t ₂ the duty increases with the passage of time as the tube wall temperature increases and the luminous efficiency decreases.

Therefore, the duty value is sampled at fixed time intervals, and whether the value increases or decreases indicates whether the temperature of the tube wall is above t ₂ or below t ₂ .
That is, when the duty value increases, the temperature of the tube wall is above _t2 , and when the duty value decreases, the temperature of the tube wall is below _t2 . Therefore, the amount of light emitted from the fluorescent lamp 20 is constantly monitored by the light amount detection sensor 31, and when the amount of emitted light falls below the reference value _L0 and the duty value increases, it can be said that the amount of emitted light tends to decrease. If it is found that the amount of emitted light is decreasing, it indicates that the tube wall temperature is becoming higher than t ₂ (state of t ₃ ), that is, the tube has entered a dangerous state. Therefore, in this case,
As described above, the fluorescent lamp 20 is turned off.

With this configuration, an abnormal rise in tube wall temperature can be prevented, and the fluorescent lamp and lighting circuit can be made smaller, resulting in cost reduction.

Meanwhile, during this time, the fixing heater also generates heat and becomes ready for fixing. When fusing is possible, the electronic copying machine's READY lamp lights up to notify the operator that copying is possible, but as mentioned above, an abnormally high tube wall temperature is detected. A message indicating that copying is not possible is displayed until a certain period of time has elapsed, and a message that copying is possible is displayed after the specified period of time has elapsed. When the operator presses the copy button with copy enabled in this way,
The fluorescent lamp lighting control circuit 32 starts energizing the fluorescent lamp 20 again, and performs the copying operation in the manner described with reference to FIG. Note that during the copying operation, the amount of light emitted from the fluorescent lamp 20 is controlled to be constant. Once,
After the power supply to the fluorescent lamp 20 is stopped, the temperature of the fluorescent lamp tube wall hardly decreases and is maintained at approximately _t0 , partly because the external heater 23 is constantly energized. Therefore, when the operator presses the copy button,
When the fluorescent lamp 20 starts to be energized, the amount of emitted light quickly reaches the reference value L ₀ and provides a sufficient amount of light.

In addition, in the above explanation, we have explained the case where the abnormally high temperature of the tube wall is detected and the energization to the fluorescent lamp is stopped, but the energization to the tube wall heater and the fixing heater can also be stopped if necessary. This can reduce power consumption.

Additionally, if a certain document is being scanned when it is determined that the fluorescent lamp is abnormal, the fluorescent lamp is kept on during the scanning until the copying operation is completed, and the fluorescent lamp is turned off when the scanning is completed. Preferably, the light lamp is turned off and the next scan is not performed.

In addition, in the above explanation, the case where the tube wall temperature of the fluorescent lamp is indirectly detected based on the output of the light amount detection sensor has been explained, but it is also possible to directly detect the tube wall temperature of the fluorescent lamp using the temperature detection sensor. A similar effect can also be obtained by detecting it.

Further, in the above description, the case of an exposure device used in an electronic copying machine has been described, but the present invention is also effective for other image reading devices and image forming devices.

(Effects of the Invention) As explained in detail above, according to the present invention,
It is possible to realize an exposure apparatus that at least turns off the lighting of the fluorescent lamp as an abnormality when the tube wall temperature of the fluorescent lamp becomes too high.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
The figure shows an example of the conventional configuration of an electronic copying machine, Figure 3 shows an example of the configuration of a fluorescent lamp, Figure 4 shows the light emission characteristics of a fluorescent lamp, and Figure 5 shows an example of the configuration of a fluorescent lamp. FIG. 6 is a diagram showing the relationship between the duty and the amount of emitted light, and FIG. 6 is a diagram showing the relationship between the fluorescent tube wall temperature and the amount of emitted light. 1...Photosensitive drum, 2...Cleaning section, 3
... Charged electrode, 4 ... Charge erasing section, 5 ... Fluorescent lamp lighting circuit, 6 ... Exposure section, 7 ... Document table, 8 ... Document, 9 ... Self-cleaning lens, 10 ... Development section , 11... transfer section, 12... transport mechanism, 13...
... Fixing roller, 20 ... Fluorescent lamp, 31 ... Light amount detection sensor, 32 ... Fluorescent lamp lighting control circuit.

Claims (1)

[Scope of Claims] 1. An exposure device for obtaining image information by irradiating a document surface with a fluorescent lamp, in which when the tube wall temperature of the fluorescent lamp exceeds an abnormally high temperature threshold, the luminescence of the fluorescent lamp is stopped. The light amount is set in advance to be less than the light amount reference value necessary for proper exposure, and there is also a light amount detection sensor that detects the light amount of the fluorescent lamp, and a light amount detection sensor that detects the light amount of the fluorescent lamp and adjusts the amount of light to the fluorescent lamp based on the output of the light amount detection sensor. The fluorescent lamp lighting control circuit is provided with a fluorescent lamp lighting control circuit that controls lighting of the fluorescent lamp by controlling supply energy, and the fluorescent lamp lighting control circuit is configured such that the light amount of the fluorescent lamp is at least equal to the appropriate exposure. Even though the supplied energy is controlled to maintain the necessary light intensity reference value, the light intensity of the fluorescent lamp becomes less than the light intensity reference value, and the light emission of the fluorescent lamp decreases over time. An exposure apparatus characterized in that when the amount of light shows a decreasing tendency, at least the lighting of the fluorescent lamp is turned off.