JP2002365860A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which is capable of rapidly forming normal images even when the light quantity of a fluorescent lamp is below a regulated value. SOLUTION: This image forming device has an image carrying member, an electrification control member for controlling electrification of this image carrying member, a developer carrying member for supplying a developer to the image carrying member, development control means for controlling the potential to be impressed to the developer carrying member, the fluorescent lamp 8 for illuminating an original, a light quantity detecting circuit (light quantity detecting means) 19 for detecting the light quantity of the fluorescent lamp 8 and a light quantity control circuit (light quantity control means) 20 for controlling the light quantity of the fluorescent lamp 8 from the detected light quantity of the light detecting circuit 19. When the detected light quantity by the light quantity detecting circuit 19 is below the reference light quantity necessary for the illumination of the original in image forming operation, the provisional light quantity value lower than the reference light quantity is set and state light quantity control circuit 20 is controlled in accordance with the provisional light quantity value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using a fluorescent lamp as a light source for exposing a document.

[0002]

2. Description of the Related Art A halogen lamp or a fluorescent lamp is often used as a light source for illuminating a document in an image forming apparatus such as a copying machine. Among them, the fluorescent lamp has advantages such as low heat generation and high efficiency. However, since the amount of light changes depending on the temperature of the fluorescent lamp at that time, it is necessary to stabilize this. That is, for example, the amount of light of the fluorescent lamp when continuously lit while changing the ambient temperature changes as shown in FIG. 1 according to the temperature of the tube wall at that time, so that the light of the fluorescent lamp is detected by the light receiving element. However, it is necessary to stabilize the output by changing the tube current and the like by a comparison circuit and a control circuit.

However, when the temperature of the fluorescent lamp is low immediately after lighting, even though the copying operation itself is possible, the amount of light is too small. Failure often occurred.
For this reason, in a conventional copying machine, even when the copying machine is not used by inserting a heater in the vicinity of the fluorescent lamp, the fluorescent lamp is preheated, or a high power heater is used as the heater. The power supply switch is turned on, and the tube wall temperature of the fluorescent lamp is raised as quickly as possible within seconds or minutes.

[0004]

However, such a method has the following drawbacks, and the above problem cannot be said to be sufficiently solved.

[0005] First, in the method of preheating the fluorescent lamp, it is necessary to energize it at night or on holidays, which consumes a large amount of electric power. Also, with this method, if the main power of the copier installation location is turned off or if you forget to plug in the outlet, preheating is not performed, so if you copy suddenly, the amount of light will be insufficient and many images will be black Will be. Furthermore, recently, copiers have been reduced in size and weight, and have become easier to carry, and are often used immediately after transportation and transportation. It is necessary to wait until the light amount of the fluorescent lamp reaches the required light amount.

On the other hand, the method of quickly raising the temperature of the fluorescent lamp requires a high-power heater as a heater, and therefore, it is necessary to securely take a safety measure or incorporate a temperature control means. As a result, the copying machine becomes large, complicated, and expensive.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an image forming apparatus capable of rapidly performing normal image formation even when the amount of fluorescent light is equal to or less than a prescribed value. It is in.

[0008]

In order to achieve the above object, the present invention provides an image carrier, a charging member for charging the image carrier, charging control means for controlling charging of the charging member,
A developing carrier for supplying a developer to the image carrier, a developing control unit for controlling a potential applied to the developing carrier, a fluorescent lamp for illuminating a document, and a light amount for detecting a light amount of the fluorescent lamp In an image forming apparatus having a detection unit and a light amount value control unit that controls the light amount of the fluorescent lamp based on the light amount detected by the light amount detection unit, the amount of light detected by the light amount detection unit during image forming operation is a reference required for document illumination. When the light quantity is equal to or less than the light quantity, a provisional light quantity value lower than the reference light quantity is set, and the light quantity value control means is controlled based on the provisional light quantity value.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<First Embodiment> FIG. 2 is a sectional view of a copying machine according to the present invention.
Is a corona discharger, 3 is a short-focus optical element array, 4 is a developing device, 5 is a transfer corona discharger, and 6 is a cleaning device. In the developing device 4, reference numeral 4a denotes a hopper, and 4b denotes a developing sleeve for supplying the toner 4c to the photosensitive drum 1.

Reference numeral 7 denotes a document table, 8 denotes a fluorescent lamp as an exposure lamp, 9 denotes a support frame of the fluorescent lamp 8, 10 denotes a light receiving element such as a photodiode, and the light receiving element 10 denotes a window 9 of the support frame 9.
It is arranged in a part. 11 is a paper feed tray for supplying the transfer paper, 12 is a transfer roller of the transfer paper, 13 is a timing roller, 14 is a separator of the transfer paper after the transfer,
Reference numeral 15 denotes a transfer path of the transfer sheet, 16 denotes a fixing device, 17 denotes a transfer sheet discharge roller, and 18 denotes a discharge tray. With this configuration, the photosensitive drum 1 is uniformly charged to a predetermined polarity by the corona discharger 2.

On the other hand, the fluorescent lamp 8 illuminates the original on the original table 7, and the reflected light is exposed on the photosensitive drum 1 via the optical element array 3, where a latent image is formed. The formed latent image is developed by a developing device 4, and the developed image is transferred by a transfer corona discharger 5 in a transfer section.

On the other hand, the transfer paper is transported from a paper feed tray 11 to a transfer section by transport rollers 12 and timing rollers 13, where the developed image is transferred. Then, the transfer paper having completed the transfer is separated by the separation charger 14, sent to the fixing device 16 via the transport path 15, and fixed to the developed image, and then sent out to the paper output tray 18.

FIG. 3 shows the light receiving element (photodiode).
FIG. 2 is a block diagram showing a configuration of a control device for controlling the light amount of the fluorescent lamp 8 and the driving of the device in accordance with the light amount detected by 10.

In FIG. 3, reference numeral 10 denotes the light receiving element for detecting the light amount of the fluorescent lamp 8, reference numeral 19 denotes a light amount detecting circuit for amplifying the signal of the light receiving element 10 to generate a light amount signal, and reference numeral 20 denotes a light amount signal which is stabilized at a reference light amount. The light amount control circuit 20 controls the light amount of the fluorescent lamp as described above.
When the detected light amount does not reach the reference light amount due to the low temperature, the fluorescent lamp 8 is turned on at the maximum current. When the temperature of the fluorescent lamp 8 becomes high or rises and the light amount required for exposure is obtained. Is a circuit for controlling the fluorescent lamp current in a feedback manner to keep the light quantity of the fluorescent lamp 8 constant. Reference numeral 21 denotes a device drive control circuit for inputting a control signal of the fluorescent lamp 8 to start an operation (copy operation) of the copying machine, and reference numeral 8 denotes the fluorescent lamp.

Next, the operation will be described.

When an operator who desires the copying operation turns on a copy switch (not shown), the fluorescent lamp 8 is energized and turned on, the light receiving element 10 detects the light amount, and the light amount detecting circuit 19 outputs this detection signal. Signal. This light quantity signal is compared with a preset reference light quantity in the light quantity control circuit 20. When the light quantity signal does not reach the reference light quantity, the fluorescent lamp 8 is turned on at the maximum current, and when the light quantity signal reaches the reference light quantity. Feeds back the amount of fluorescent light
The current is controlled so that the light amount of the light is maintained at the reference light amount.

As shown in FIG. 5, the copy switch is turned on.
When the temperature of the fluorescent lamp 8 at the time point t0 is low and has not reached a temperature sufficient to obtain the reference light amount a, the light amount control circuit 2
0 inputs the light amount signal to turn on the fluorescent lamp 8 at its maximum current. When the light amount of the fluorescent lamp 8 reaches the reference light amount a at a time t1 after being turned on for a certain period of time, the apparatus drive control circuit 21 inputs the above light amount signal to enable a copy operation to be started. The light amount control circuit 20 also receives this light amount signal and performs feedback control of the fluorescent lamp lighting current to keep the light amount of the fluorescent lamp 8 constant (reference light amount a).

On the other hand, as shown in FIG. 6, the temperature of the fluorescent lamp 8 at the time t0 when the copy switch is turned on is preheated,
Alternatively, when the outside light temperature is high and the reference light amount a has already been obtained, there is no preheating process of the fluorescent lamp 8 and the copying operation can be started immediately. Further, the light quantity of the fluorescent lamp 8 is also feedback-controlled from the time point t0.

FIG. 4 is a flowchart showing the flow of the above operation. FIG. 7 is a flowchart showing an embodiment of the present invention.

In general, in a copying machine, it is necessary to stabilize the temperature of the fixing device and the light amount of the fluorescent lamp before starting the copying operation. That is, warm-up is often required before the copy operation starts.

However, in a surf fixing device using an endless belt-shaped fixing film, which is used recently, warming-up is hardly required. Therefore, only a fluorescent lamp may need to be warmed up at a low temperature.

The present embodiment takes such circumstances into consideration. Normal control is sufficient when the reference light amount has reached the light amount of the fluorescent lamp 8 turned on by the copy switch ON. Then, the copying operation is started, a provisional light amount value lower than the reference light amount value is set according to the fluorescent light amount at the time of forming the latent image, the light amount control of the fluorescent lamp 8 is performed with the provisional light amount value, and the charging potential of the photosensitive drum 1 is And the application voltage of the developing sleeve 4b is controlled in accordance with the provisional light amount value so as to compensate for the contrast reduction of the latent image due to the insufficient light amount so as to obtain the optimum image.

In the normal fluorescent light quantity of the present embodiment,
The drum potential (Vd) of the black portion of the document is -700 V, the drum potential (V1) of the white portion is -150 V, and the DC voltage (Vdc) applied to the developing sleeve 4b when the density adjustment switch is at the center is -350V. The potential difference between V1 and Vdc is 2
By setting to 00V, an optimal copy image without fog can be obtained.

However, when the fluorescent lamp light amount is low, the Vd potential hardly changes, but the V1 potential changes. Therefore, when the fluorescent lamp light amount is equal to or less than the reference light amount value in normal use, the V1 potential is changed from the fluorescent lamp light amount. After calculation, the Vdc potential is changed so that the potential difference between V1 and Vdc becomes 200V. V
By changing the dc potential, the potential difference between Vd and Vdc is reduced. However, in the case of a black character on a white background which is commonly used, the density of the black character may slightly decrease. Can be taken.
Incidentally, when the Vd potential fluctuates due to the amount of the fluorescent lamp, it may be adjusted by the applied voltage of the corona discharger 2.

As described above, according to the present embodiment, the light amount of the fluorescent lamp is detected immediately before the copying operation is started, and even when the light amount does not reach the preset reference light amount, the light amount is determined by the provisional light amount value. Since the copying operation is started under the control, the copying operation of the copying machine becomes possible regardless of the presence or absence of the preheating or the rapid heating means. With a character image as a general document, even a low-contrast latent image has sufficient reproducibility, and many copied images do not hinder practical use. In the case of a document requiring a normal latent image contrast, a mode changeover switch may be set, and the copying operation may be waited until the light amount of the fluorescent lamp reaches the reference light amount value by the mode changeover.

Second Embodiment Next, a second embodiment of the present invention will be described.

In this embodiment, even when the light amount of the fluorescent lamp turned on by the copy switch ON does not reach the reference light amount, the copying operation is started and the charging potential of the photosensitive drum and the developing potential are adjusted according to the change in the fluorescent light amount. Control the voltage applied to the sleeve.
Since the light intensity of the fluorescent lamp increases as the temperature rises when the fluorescent lamp is turned on, the latent image due to insufficient light intensity is controlled by controlling the charging potential of the photosensitive drum and the voltage applied to the developing sleeve in accordance with the change in the light amount that increases during the copying operation. In order to obtain the optimum image by compensating for the decrease in contrast.

When the light intensity of the fluorescent lamp is equal to or less than the reference light intensity during normal use, V1 and Vd are adjusted in accordance with the changing light intensity of the fluorescent lamp.
The Vdc potential is changed so that the potential difference of c becomes 200V. Also, when the light amount of the fluorescent lamp reaches the reference light amount value during the copying operation, it is preferable to control the light amount of the fluorescent lamp with the reference light amount value.

As described above, in the present embodiment,
The light amount of the fluorescent lamp during the copying operation is detected, and the developing bias Vdc and the drum charging voltage that match the light amount of the latent image are variably output. Since the copying operation is started even when the fluorescent lamp light amount has not reached the preset reference light amount, the copying operation of the copying machine becomes possible irrespective of the presence or absence of the preheating or rapid heating means.

In a character image, which is a general original, a copied image, even a low-contrast latent image, poses no practical problem. In the case of a document requiring a normal latent image contrast, the copy operation may be made to wait until the light amount of the fluorescent lamp reaches the reference light amount value by mode switching.

[0032]

As is apparent from the above description, according to the present invention, an image carrier, a charging member for charging the image carrier, charging control means for controlling charging of the charging member, A developing carrier for supplying a developer to the image carrier, a developing control unit for controlling a potential applied to the developing carrier, a fluorescent lamp for illuminating a document, and a light amount detection for detecting a light amount of the fluorescent lamp Means for controlling the amount of light of the fluorescent lamp based on the amount of light detected by the amount of light detected by the amount of light detected by the amount of light detected by the amount of light from the fluorescent light. When the light amount is below, a provisional light amount value lower than the reference light amount is set, and the light amount value control means is controlled based on the provisional light amount value. Do it quickly Doo is an effect that it can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a time-dependent characteristic curve using a temperature of a fluorescent lamp light quantity as a parameter.

FIG. 2 is a cross-sectional view of the image forming apparatus (copier) according to the present invention.

FIG. 3 is a block diagram illustrating a configuration of a control device of the image forming apparatus (copier) according to the present invention.

4 is a flowchart showing an operation of the control device shown in FIG.

FIG. 5 is a diagram illustrating rising characteristics of a fluorescent lamp in the image forming apparatus (copying machine) illustrated in FIG. 2;

FIG. 6 is a diagram illustrating rising characteristics of a fluorescent lamp in the image forming apparatus (copier) illustrated in FIG. 2;

FIG. 7 is a flowchart showing the operation of the control device of the image forming apparatus (copier) according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum (image carrier) 2 Corona discharger (charging member) 4 Developing device 4b Developing sleeve (developing carrier) 8 Fluorescent lamp 10 Light receiving element 19 Light quantity detection circuit (light quantity detection means) 20 Light quantity control circuit 21 Device drive control circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G06T 1/00 430 G03G 15/04 120 H04N 1/04 101 F-term (Reference) 2H027 DA07 DE02 DE07 EA01 EA05 EB03 EC06 EC19 EF09 EH10 EK03 EK11 EK19 FA37 FB06 FB07 2H076 AA58 DA04 DA17 DA22 EA21 5B047 AA01 BA02 BC11 CA19 CB03 CB04 5C072 AA05 BA20 CA04 CA10 CA14 FB27 LA02 XA01

Claims (4)

[Claims] An image bearing member, a charging member for charging the image bearing member, charging control means for controlling charging of the charging member,
A developing carrier for supplying a developer to the image carrier, a developing control unit for controlling a potential applied to the developing carrier, a fluorescent lamp for illuminating a document, and a light amount for detecting a light amount of the fluorescent lamp In an image forming apparatus having a detecting unit and a light amount value control unit for controlling the light amount of the fluorescent lamp based on the detected light amount of the light amount detecting unit, a light amount detected by the light amount detecting unit during an image forming operation is a reference necessary for document illumination. An image forming apparatus comprising: setting a temporary light amount value lower than the reference light amount when the light amount is equal to or less than the light amount; and controlling the light amount value control unit based on the temporary light amount value. 2. An image forming operation, wherein the control value of at least one of the charging control unit and the development control unit is changed according to the light amount control value of the light amount value control unit at the provisional light amount value. The image forming apparatus according to claim 1. 3. The image forming apparatus according to claim 1, wherein the light amount detected by said light amount detecting means is equal to or less than a reference light amount necessary for illuminating the document. 2. The image forming apparatus according to claim 1, wherein at least one of the control values is changed. 4. When the amount of light detected by the light amount detecting means during the image forming operation is equal to or less than a reference light amount required for document illumination, the charging control means and the developing control means according to the light amount detected by the light amount detecting means. 4. An image forming apparatus according to claim 2, further comprising means for selecting a method of changing a control value of the image forming apparatus and a method of stopping the image forming operation until the detected light amount reaches a reference value. .