JP3532355B2 - Lighting device abnormality detection method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting an abnormality in an illumination device in an image forming apparatus such as a copying machine, and more particularly to a method for detecting an abnormality in a light source for illumination.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a document is illuminated by an illuminating light source, and reflected light from the document is imaged on an image forming surface of a photoconductor or the like to form an image of the document on the photoconductor or the like. To form. An image forming process in an image forming apparatus such as a copying machine will be described below with reference to FIG. In FIG. 4, as is well known, the document is set on the contact glass 1, and the illumination light emitted from the illumination light source 2 below the document illuminates the document, and the reflected light from the document is reflected by the first mirror 3a, Second mirror 3b, third mirror 3c, lens 4, fourth mirror 3d, fifth mirror 3e, sixth mirror 3
After passing through f, the photosensitive drum 5 is reached. The light of the document is transmitted through the lens 4 so that the image of the document is formed on the photosensitive drum 5. At that time, the first scanner 6 having the illumination light source 2 and the first mirror 3a scans along the document surface, and the second scanner 7 having the second mirror 3b and the third mirror 3c scans the first surface. Scanner 6
Scans along the surface of the document at a speed half the moving speed thereof, and these scans cycle with the rotation of the photoconductor drum 5, so that the image of the document is formed on the photoconductor drum 5 as an electrostatic latent image. To form. Then, the electrostatic latent image formed on the photoconductor 5 is developed with toner, as is well known, and the toner image is transferred to a sheet and fixed by heating and pressure bonding to form an image on the sheet.

In the image forming process, the illumination light source 2 used in the step of optically scanning the original image is
It is controlled by a circuit as shown in FIG. In FIG. 5, the illumination light source 2 includes a relay 12 capable of interrupting its lighting circuit,
And a bidirectional switch element 13 such as a triac are connected in series to the AC power supply 11. Primary coils of a transformer 15 are connected to both ends of the illumination light source 2. The AC power supply 11 is stepped down by the transformer 15, full-wave rectified by the rectifier 16 and input to the voltage detection circuit 17,
The detection output of the voltage detection circuit 17 is input to the microcomputer 20. On the other hand, a zero-cross circuit 19 is connected to the AC power line.
Is also connected, and the zero-cross signal obtained by the zero-cross circuit 19 is also input to the microcomputer 20. The microcomputer 20 turns on the triac 13 through the trigger circuit 14 based on the detection voltage of the voltage detection circuit 17 by using the zero-cross signal as a basic control timing.
Turn off. As a result, control is performed to make the amount of light emitted from the illumination light source 2 constant.

Under such control, a high power lamp such as a halogen lamp is used as the illumination light source 2. However, this halogen lamp has a large amount of heat generation due to the large power, and when continuously lit for a long time, the heat of the halogen lamp causes high heat in each part of the apparatus, which causes various troubles. For this reason, in the copying machine, the illumination light source 2 is turned on only during the time when the document is scanned, and is turned off during the rest of the time, for example, while the machine is waiting, and also when the scanner finishes scanning the document and returns to the original position to return. I am trying to let you. Further, when an abnormal state such as continuous lighting or erroneous lighting occurs, it is necessary to reliably detect the abnormality and cut off the power supply to the illumination light source 2 in order to eliminate the abnormal state.

As an example of the abnormality detecting method and the power supply cutoff method, a temperature fuse 21 is incorporated in the lighting circuit of the illumination light source 2 as shown in FIG. 5, or the temperature is detected by a thermistor to detect a temperature above a certain level. When the voltage rises, there is a method of forcibly shutting off the lighting circuit. However, these detections and interruptions are the detections and interruptions at the final stage of the abnormal state, and it is desirable to detect and cope with the abnormality before the forced interruption. Therefore, a method of monitoring the lighting state of the lamp by using a light amount detecting means and a microcomputer is adopted. JP 62-
An example is described in Japanese Patent No. 9338. this is,
An original density detecting means is provided outside the circuit as shown in FIG. 5, and an output of the original density detecting means is used to detect an abnormality of the illumination light source. In addition, JP-A-2-109
Japanese Patent No. 038 describes another example of monitoring the lighting state of a lamp. This is to newly provide an optical sensor for detecting the emitted light of the illumination light source in addition to a regulator for controlling the illumination device, and detect an abnormality of the illumination light source using the output from the optical sensor. Further, generally, as shown in FIG. 5, the voltage detected by the voltage detection circuit is indirectly replaced with the light amount of the illumination light source, and when the detected voltage is abnormal, it is determined that the illumination light source is abnormal. There are many things I tried to do. The invention described in Japanese Patent Application Laid-Open No. 2-176772 is an example thereof.

[0006]

However, in the case of monitoring the lighting state of the illumination light source using the detection signal from the document density detecting means, as in the invention described in JP-A-62-9338, The lighting state of the illumination light source can be monitored if the scanner can detect the document density, for example, in the vicinity of the standby position of the scanner. If the scanner cannot detect the document density, the illumination light source can be monitored. When an abnormality occurs in, the abnormality cannot be detected. Further, if an optical sensor for detecting the amount of light is newly provided as in the invention described in Japanese Patent Application Laid-Open No. 2-109038, the provision of this optical sensor will increase the cost as it is.

Further, as in the invention described in Japanese Patent Application Laid-Open No. 2-176772, a method of indirectly replacing the detection voltage by the voltage detection circuit with the light quantity of the illumination light source, and determining the abnormality of the illumination light source by the detection voltage. There are two types of control methods depending on the type of voltage detection circuit. One is a method in which the microcomputer captures the full-wave rectified applied voltage waveform as it is at a certain timing, and the microcomputer calculates the effective value to calculate and output the interval for turning the lamp voltage on and off. The other is a method in which the effective value calculation is performed by the voltage detection circuit and the output is taken in by the microcomputer to turn on / off the lamp voltage. Since the latter includes an effective value arithmetic circuit, the circuit becomes more complicated than the former, but since the microcomputer does not have to perform the effective value calculation, there is an advantage that the processing occupation time of the microcomputer can be shorter than the former.

However, the signals taken in by the microcomputer are completely different between the former and the latter, and the difference is shown in FIG. In contrast to the AC power supply waveform, the waveforms of the trigger circuit are both pulse width modulated (hereinafter referred to as “PW
Signal), the voltage waveform of the illumination light source input to the microcomputer is a part of the AC waveform as shown in A in the case of the circuit that takes in the applied voltage as it is as in the former case. When the voltage detection circuit includes an effective value calculation circuit as in the latter case, the peak and the valley are alternately and gently continuous as shown in B. Due to these differences, the light amount control of the illumination light source differs between the two, and the control also differs when abnormality detection is performed using these signals.

The example shown in Japanese Patent Application Laid-Open No. 2-176772 is suitable for the method of taking in the applied voltage as it is as in the former case, but it is more suitable for the method of taking in the effective value voltage by the circuit as in the latter case. Is not suitable for. The reason is that in the case of RMS voltage, unlike in the case of direct applied voltage, PW
This is because the voltage value is not always off when the M light source for illumination is off. Therefore, JP-A-2-
When the effective value is detected by the method described in Japanese Patent No. 176772, erroneous detection will be caused unless attention is paid to the monitoring timing of the illumination light source off command and the illumination light source voltage.

Therefore, as an effective method when the effective value voltage is used, there is a monitoring method using a timer counter. Once the illumination light source (hereinafter referred to as "lamp") is turned on, it is monitored whether or not continuous lighting is performed for a predetermined time or longer. FIG. 7 shows a control flow for the monitoring. When an interrupt by the zero-cross signal is input,
As a monitoring flow, first, in step S1, it is checked whether the lamp voltage is on. If the lamp voltage is on, the timer count is incremented (added),
If it is off, 0 is substituted. Next, in step S3, it is checked whether the timer count has reached a predetermined count. At this time, if the predetermined value is not reached, the process returns. Further, if it is the predetermined value, it means that the lighting time has exceeded the predetermined time. In the example shown in FIG. 5, the main relay 12 of the AC input unit is cut off in step S5, and the abnormality detection is performed in step S6. Notify the control of the copying machine. This monitoring is performed not only during the copying operation but also during the power-on of the copying machine main body.

However, even if this method is used, the abnormality detection may not work depending on the circuit failure. For example, in FIG. 5, the triac 13 is not completely damaged, but an abnormal condition in which only half a wave is conducted in the lamp input part may occur when the triac 13 is damaged in only one direction and becomes a short circuit state. . At this time, in the monitoring flow shown in FIG. 7, when the voltage of the half wave is turned off, that is, when the lamp voltage drops, it is recognized that the lamp is off in step S1, the timer count is cleared to 0, and the abnormality is detected. It may not work. Then, the lamp 2 continues to be turned on until the thermal fuse 2, which is the final detection means, is broken, and depending on the position of the scanner, the scale and other parts beside the document placing portion may be deformed by heat. Get there.

The present invention has been made in view of the above situation, and the invention according to claim 1 is an image using the voltage detecting means for detecting the effective value voltage across the illumination light source as the light amount detecting means. In the lighting device of the forming apparatus, even if the light amount control circuit fails for some reason and the lighting light source lighting circuit is in a half-wave conduction state, it is possible to reliably detect an abnormal state such as continuous lighting or erroneous lighting of the light source. An object of the present invention is to provide a method for detecting an abnormality in a lighting device.

According to a second aspect of the present invention, in the image forming apparatus such as a copying machine, the illumination light source is turned off during the returning operation of the scanner, and in the high speed image forming apparatus, the illumination light source is turned off during the returning operation of the scanner. Even if it is, the voltage does not become 0 when the effective value voltage is detected, and it may be erroneously determined to be continuous lighting. Therefore, such an erroneous detection method for an illumination device can be prevented. The purpose is to provide.

According to the third aspect of the present invention, the abnormal lighting detection reference is changed between the copying operation and the standby status, and the abnormal lighting detection of the illumination light source during the standby status can be made more reliable. The purpose is to provide a detection method.

[0015]

The invention according to claim 1 is
The control means for controlling the light quantity of the illuminating light source to be constant is used, and the light quantity detecting means of this controlling means has a voltage detecting means for detecting the effective value voltage across the illuminating light source. , It is used not only as a light quantity control means for controlling the light quantity by its output, but also as an abnormality detection means.The monitoring method by this abnormality detection means is to increment the timer by turning on the output voltage for each zero-cross interrupt obtained from the AC power supply The abnormality detection is performed when the timer reaches a predetermined value, and the timer is reset when the output voltage off signal is continuously detected twice or more.

According to the second aspect of the present invention, in the monitoring method by the abnormality detecting means, the reference voltage for determining whether to increment or reset the timer is set higher than the minimum lamp voltage during the scan recovery operation during the copy operation. It is characterized by taking.

According to the third aspect of the present invention, in the monitoring method by the abnormality detecting means, the reference voltage for determining whether to increment or reset the timer is higher than the lamp minimum voltage during the scan recovery operation during the copy operation. However, it is characterized in that it is set to 0 when in standby.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an abnormality detecting method for an illumination device according to the present invention will be described below with reference to the drawings. According to the present invention, in the image forming apparatus such as a copying machine having the image forming process shown in FIG. 4, the illumination light source 2 for optically scanning the original image is as shown in FIG. The voltage detection circuit 17 shown in FIG. 5 is adapted to an image forming apparatus of an effective value detection system. A feature of the present invention is a method of monitoring an abnormal state such as continuous lighting or erroneous lighting of the illumination light source 2.

FIG. 1 shows an example of a monitoring flow of an abnormality detection method for a lighting device according to the present invention. In FIG. 1, when a zero-cross interrupt is first input by a zero-cross signal, the monitoring flow first checks in step S11 whether the lamp voltage is on. If the lamp voltage is on, the timer count is incremented in step S12, and step S1 is performed to support half-wave input.
A check flag is set at 3. When the lamp voltage is off,
In step S15, it is checked whether the half-wave check flag is set. If the flag is set here, it means that the lamp voltage was turned on at the previous zero-cross interrupt, the timer count is incremented in step S16, and the check flag is set in step S17.
Continue monitoring until the next zero-cross interrupt. If the flag is not set in step S15, it means that the lamp voltage was off at the previous zero-cross interrupt, so that the timer count is reset for the first time (step S18).

The subsequent operation is the same as the operation shown in FIG. That is, in step S14, it is checked whether the timer count has reached a predetermined count. At this time, if the predetermined value is not reached, the process returns. If the predetermined value is reached, it means that the lighting time has exceeded the predetermined time. In the example shown in FIG. 5, the main relay 12 of the AC input section is shut off in step S19, and the abnormality detection is performed in step S20. Notify the control of the copying machine.

In contrast to the conventional monitoring flow example shown in FIG. 7,
In the example of the present invention shown in FIG. 1, the timer is not reset even if the lamp voltage off is input by the zero-cross interrupt only once, and the monitoring flow is not recognized as being off unless the lamp voltage off is continuously input. There is. Therefore, even if only the AC half-wave is supplied to the lamp due to a failure of the light quantity control circuit or the like, it is possible to reliably detect the abnormality of the illumination light source.

However, as described above, in the image forming apparatus such as a copying machine, in order to reduce the heat generation of the illumination light source including the high power lamp as much as possible, the lamp is turned off at the time of the returning operation of the scanner. For this reason, if the scanner's returning operation is fast in a machine with a high copying speed, the time during which the lamp voltage effective value is 0 during that returning operation is short, and the lamp voltage effective value is 0 for a short time. It may happen that the next scan operation starts immediately after the error. This state is shown in FIG. In this way, in the case where the scanner's returning operation is fast, step S1 shown in FIG.
If the voltage ON / OFF judgment criterion is set to 0 in 1 and the lamp is actually turned off during the returning operation of the scanner during the copying operation, it is determined that the lamp voltage is ON in step S11 of the monitoring flow. However, if the effective value of the lamp voltage is not 0 more than twice for the zero-cross interrupt,
It is determined that the LEDs are continuously lit, and when a predetermined time has passed, the abnormality detection is activated, resulting in erroneous detection.

In order to eliminate such an erroneous detection, the lamp reference voltage shown in FIG. 2 may be used as the criterion for judging the lamp voltage on / off in step S11. The ramp reference voltage shown in FIG. 2 is set to be larger than the value at which the effective value of the ramp voltage falls completely between one copy operation and the subsequent copy operation in the continuous copy operation. This lamp reference voltage is the minimum scan length of the copier,
In other words, during copying operation when the return time of the scanner is the shortest, by setting the value at which the lamp voltage effective value is the lowest as a guide, it is possible to prevent erroneous detection of continuous lighting. In this case, erroneous detection can be prevented even if the control is performed by changing the reference voltage every time the scan length changes.

As described above, the lamp voltage ON / OFF judgment reference is set higher than the lamp minimum voltage at the time of the scan returning operation during the copying operation, so that the continuous lighting is judged during the copying operation of the high speed machine having a high copying speed. It is possible to prevent false detection. However, as shown in FIG. 2, even if the criteria for turning on / off the lamp voltage during standby is set to a value higher than the minimum lamp voltage during the scan recovery operation, that is, a value other than 0, with respect to this value and below. Will be out of the allowable range for detection. Therefore, it is advisable to separately set the ON / OFF determination reference voltage of the lamp voltage during the copying operation or the standby.

FIG. 3 shows an example in which the ON / OFF judgment reference voltage of the lamp voltage is separately set during the copying operation or the standby. That is, in FIG. 3, before determining whether or not the lamp voltage is on, in step S21, it is checked whether the copying operation is in progress or in standby, and a reference voltage suitable for each is set, and then the on / off determination in step S11 is performed. It is a flow to move to. More specifically, if in standby, the reference voltage is set to 0 in step S22, and if in copy operation, the reference voltage is higher in step S23 than the lamp minimum voltage during scan recovery operation during copy operation. The value is further set to an arbitrary value according to the scan length, and it is determined in step S11 whether or not the lamp voltage is on. As a result, false detection of continuous lighting during copy operation,
It is possible to detect abnormalities without any trouble, such as no detection of erroneous lighting during standby.

[0026]

According to the first aspect of the invention, the image forming apparatus such as a copying machine or the like, in which the light amount detecting means of the light amount controlling means has a voltage detecting circuit of a type for detecting an effective value voltage across the illumination light source. In the illumination device according to claim 1, the voltage detection means is used as a light quantity control means for controlling the light quantity by its output and also as an abnormality detection means, and the monitoring method by the abnormality detection means is a zero cross obtained from an AC power source. The timer is incremented by turning on the output voltage for each interrupt. When the timer reaches a predetermined value, it is detected as an abnormality, and when the output voltage off signal is detected twice or more in succession, the timer is reset. Even if the light intensity control circuit fails for some reason and only half-waves are conducted to the illumination light source input section, the timer function that supports half-wave input Since realized abnormality monitoring method for performing cement, an abnormal condition such as continuous lighting or erroneous lighting of the light source can be reliably detected.

According to the second aspect of the present invention, the on / off reference voltage for abnormality monitoring is not 0 but higher than the lamp minimum voltage during the scan recovery operation during the copy operation. It is possible to prevent erroneous detection of continuous lighting even when the lamp is actually turned off during the scan return operation.

According to the third aspect of the present invention, since the on / off reference voltage for abnormality monitoring is set separately for the copying operation and the standby operation, the lamp is actually turned off during the copying operation. Regardless, it is possible to reliably detect abnormalities such as erroneous detection as continuous lighting, or not detecting this even though it is lit due to a malfunction during standby, but it is not detected. Becomes

[Brief description of drawings]

FIG. 1 is a flowchart showing an embodiment of an abnormality detection method for a lighting device according to the present invention.

FIG. 2 is a waveform diagram showing an example of a lamp voltage change during operation of a copying machine to which the present invention can be applied.

FIG. 3 is a flowchart showing another embodiment of the abnormality detection method for a lighting device according to the present invention.

FIG. 4 is a front view showing an example of an optical system of a copying machine to which the present invention can be applied.

FIG. 5 is a block diagram showing an example of a light amount control circuit of an illumination light source of a copying machine to which the present invention can be applied.

FIG. 6 is a waveform diagram showing the operation of the above light amount control circuit.

FIG. 7 is a flowchart showing an example of a method for detecting an abnormality of a lighting device in a conventional copying machine.

[Explanation of symbols]

2 Lighting light source 11 AC power supply 13 Triacs that constitute the control means 14 Trigger circuit constituting control means 17 Voltage detection means

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Claims (3)

(57) [Claims] 1. A method of detecting an abnormality of an illumination device in an image forming apparatus, comprising: a control means for controlling a constant light quantity of an illumination light source, wherein the light quantity detection means of the control means is effective at both ends of the illumination light source. The voltage detection means for detecting the value voltage is provided, and the voltage detection means is used not only as the light quantity control means for controlling the light quantity by its output but also as the abnormality detection means. Is an error detection when the output voltage is turned on for each zero-cross interrupt obtained from the AC power supply, and when the timer reaches a predetermined value, it is detected as an abnormality, and when an output voltage off signal is detected twice or more in succession. A method for detecting an abnormality in a lighting device, which comprises resetting a timer. 2. The monitoring method by the abnormality detecting means is characterized in that the reference voltage for judging whether to increment or reset the timer is set higher than the lamp minimum voltage at the scan recovery operation during the copy operation. The method for detecting an abnormality of a lighting device according to claim 1. 3. A monitoring method using an abnormality detecting means sets a reference voltage for determining whether to increment or reset a timer higher than a lamp minimum voltage during a scan recovery operation during a copy operation, and during a standby status. The abnormality detection method for a lighting device according to claim 1, wherein the abnormality detection method is set to 0.