JPS63206773A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent defective image formation by prohibiting the image formation when a source voltage is below a reference value and releasing the prohibition of the image formation when the source voltage and heater temp. respectively increases to prescribed values or above. CONSTITUTION:Copying with a copying machine is prohibited under the control of a microcomputer 55 when the source voltage to the copying machine drops to the prescribed level or below. The prohibition condition of the copying is released on condition that the temp. of a fixing heater 31 of a fixing device 28 is in excess of a reference level when the source voltage returned to the prescribed level.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to image forming devices such as copying machines and printers, and particularly to problems such as paper jams, poor toner fixation, and
This is to prevent defective image formation due to image defects or the like.

[Prior Art 1] Conventionally, proposals have been made to reduce the adverse effects of a drop in power supply voltage on copying operations in electrophotographic processes.

FIG. 6 is a graph showing the temperature of the toner constant wear heater when performing multi-copy (copying a large number of sheets) when the WIIi voltage drops.

As shown in the figure, when multi-copy is started (T-ta
), when the power supply voltage is lowered, the temperature of the heat roller falls below the lower limit temperature at which defective fixing, low-temperature offset, etc. do not occur.

This is because when the power supply voltage decreases, it is not possible to supply the heater with a current value sufficient to compensate for the temperature drop in the constant toner deposition heater caused by the copying paper taking away the amount of heat.

Therefore, when the power supply voltage drops, the amount of heat absorbed by the copy paper is reduced (in order to limit the number of copies per unit time, and to prevent toner fixation failure)
-121480).

In addition, in consideration of the fact that the light intensity of the exposure device that exposes and scans the document decreases when the lightning voltage decreases, the power supply to the fixing heater, which consumes a large amount of power, is cut off to reduce the level of decrease in the power supply voltage. It is attempted to suppress the reduction in the amount of light of the exposure apparatus by reducing the amount of light even by a minute (Japanese Patent Application Laid-open No. 135878/1983).

[Problems to be Solved by the Invention] However, even if the number of copies per unit time is limited when the power supply voltage drops, for example, the torque of the main motor that drives the photoreceptor drum etc. will be reduced, Poor rotation may cause image defects or paper jams. Further, even if the number of close-up images per medium time is controlled, toner fixation failure may occur.

On the other hand, in order to maintain the level of voltage supplied to the optical device,
Cutting off the power supply to the fixing heater is only possible for a very short period of time because the temperature of the fixing heater decreases, resulting in poor toner adhesion, low-temperature offset, and the like.

That is, if the power supply voltage drops below a predetermined level,
There are limits to the measures taken for each individual device that constitutes a copying machine, and it is difficult to complete normal copying operations.

The present invention has been devised in view of the above circumstances, and provides an image forming apparatus that prevents defective image formation from occurring due to a drop in power supply voltage.

Means for Solving Problems] An image forming apparatus according to the present invention includes: an image forming means that forms an image by heating and fixing a toner image on a sheet of paper using a heater; and a temperature detecting means that detects the temperature of the heater. and a detection means for detecting the level of the 'am voltage supplied to the image forming means; and when the power supply voltage level is below a reference value, it instructs the image forming means to prohibit image formation, and the power supply voltage is The image forming apparatus is characterized by comprising a control means for canceling the image formation prohibition when the level and the heater temperature each reach a predetermined value or higher.

[Example 1] Hereinafter, taking the case where the image forming device is a copying machine as an example, Attachment R
4. Examples will be described with reference to the drawings.

FIG. 1 schematically shows a copying machine according to this embodiment.

Approximately at the center of the copying machine body, a photoreceptor drum 1 that can be rotated counterclockwise by a main motor M1 (AC synchronous motor) is arranged, and around it are a main eraser lamp 2) and a sub charger 3. , supply eraser lamp 4, main charging charge t5, J1i1 image device t
6, transfer charge 177, copy paper separation charger 8,
A blade type cleaning device ff19 is provided. The photoreceptor drum 1 has a photoreceptor layer provided on its surface.
This photoreceptor is charged with #IIs by passing through the eraser lamp 2.4 and the charger 3.5, and receives image exposure from the optical system 10.

The optical system 10 starts from below the original glass 16.
6 and a document holder 30, and is configured to be able to scan the original image of the original placed between the original document holder 30 and the original document holder 30. ing.

The light source and the movable mirror 11 are arranged at a speed of 1 (V/m
) (where m: copy magnification), and the movable mirror 12.13 is driven by a DC motor M3 so as to move leftward at a speed of (V/2 m). As the optical system scans the original image, the photosensitive drum receives image exposure and forms an electrostatic latent image. Further, toner is attached to the static latent image in the developing device W6. Note that when changing the copying magnification, the lens 14 is moved on the optical axis by the stepping motor M4, and the mirror 15 is also moved and oscillated.

On the other hand, there are paper feed rollers 21 on the left side of the copying machine body.
．． A paper feed section 20122 equipped with a roller pair 23, a timing roller pair 26, a conveyor belt 27,
, the fixing device 28, and the discharge port-ra pair 29 constitute a copy paper conveyance path.

Here, the timing roller pair 26 sends out the copy paper conveyed from the paper feed section with its leading edge aligned with the toner image forming area formed on the photoreceptor drum.

The sent copy paper is transferred by the transfer charger 7.
The toner image is transferred, peeled off from the surface of the photoreceptor drum 1 by the separation charger 8, passed through the conveyor belt 27, and then melted and fixed by the fixing device 28. After that, the toner image is transferred to the machine by the discharge roller pair 29. is discharged outside.

(Description of the operation panel) An operation panel 100 as shown in FIG. 2 is installed on the upper front of the copying machine, and the operation panel 100 includes a print start key 102 for starting the copy operation In addition to numeric keys 110 to 119 for entering the number of sheets, known key switches and the like are provided. Further, the round LED 103 is a warning indicator light that lights up when the power supply voltage falls below a predetermined level.

(Description of the control circuit of the copying machine) The copying machine described above has a plurality of C
Controlled by PLI, each CPU communicates with each other as necessary. Among these, the feature of the present invention is that i! l1jIll is processed by the first CPU. Further, the other processes in the CPU are well known and will not be explained unless specifically required.

FIG. 3 is a circuit configuration diagram showing a power supply voltage abnormality detection processing circuit according to this embodiment.

As shown in FIG. 3, the circuit includes a single-phase AC power source 1, an AC drive circuit 3 that drives the toner constant wear heater 31 and the main motor M1, and a DC control circuit 5 that controls the AC drive circuit 3. and a power supply voltage detection circuit 7.

In the AC drive circuit 3, the SSR (solid state relay) 32 controls the energization to the toner constant deposition heater (lamp) 31 built in the fixing device M2B at 1111ID.
At the same time, the 5SR 33 controls energization of the AC synchronous motor M1 that rotationally drives the photoreceptor drum 1.

Further, the DC control circuit 5 stably supplies DC 5V.
It is composed of a C power supply 50 and a one-chip microcomputer 55 (incorporating a first CPU) having a built-in A/D converter that receives DC power from the DC power supply.

Note that the AC power supplied to the DC power supply 50 is
The voltage is lowered by a transformer 4.

The power supply voltage detection circuit 7 divides the voltage converted into low-voltage direct current by the transformer 70 and the rectifier 71 using resistors N73 and N74 to obtain a voltage at a predetermined level.

- E one-chip microcomputer 55 (hereinafter referred to as one-chip microcomputer 55) is mall! While performing the pressure detection process, the fixing heater lamp 31 is controlled via the 5SR32 so that the temperature of the toner constant mounting heater of the W mounting W128 is maintained at a predetermined value. Also, 5
The synchronous motor M1 is started and stopped via the SR33.

Here is the analog input port A of the one-chip microcontroller 55.
Nφ is connected to the voltage dividing point of the power supply detection circuit 7, and
The analog input boat AN1 is connected to a thermistor that detects the decline of the heat roller (fixing heater) of the constant W device. Furthermore, the output port PAφ is connected to the 5SR32 via the driver rc, and the output port PA 1 is connected to the 5SR32 via the driver rc.
It is connected to 5SR33 via a driver IC. In addition, the output boat PA2 outputs the LED1 via the driver rc.
It is connected to the lighting circuit of 03.

FIG. 4 is a flowchart showing an outline of the processing of the i-th CPU. As shown in FIG. 4, when the power is turned on, the first CPLI initializes internal registers, various timers, etc., initializes them (S3), and starts an internal timer that defines the time for one routine (S5). Next, the power supply voltage detection process is performed (87), and then the copy operation starts.
Q3! ! ! Input processing (S9) and output processing (81)
1) is performed, and when the timer ends (813), the process returns to S5. Incidentally, the above S9 and S11 are well known, so the explanation thereof will be omitted.

FIG. 5 is a flowchart showing details of the power supply voltage detection process (S7). First, analog signal input capo 1
The voltage level input to ~ANφ is A/D converted to detect the power supply voltage level (S101). still,? When outputting the t2 source voltage voltage level, known methods such as peak level detection and area (integral value) detection can be used.

Next, the detected value is compared with a predetermined level (S103).

When the detected value is less than the predetermined level, flag 2 is set to "1" (8105). This flag 2 is used to perform processing when the power supply voltage returns to a predetermined level later. Next, it is determined whether a copying operation is in progress (S107). Here, the term "during a copying operation" refers to the period from when the copying operation is started by inputting the print start key 102, etc. until the copying on the - side of the copying paper is completed. Note that whether or not a copying operation is in progress is not limited to the above case, and can be determined from the viewpoint of whether or not a defective copy is generated, as will be described later. Further, whether or not a copying operation is in progress is determined based on transmissions from other CPUs (8105).

If copying is in progress, copy stop processing is performed (810
9). The copy stop process is executed in order to prevent the copying paper currently being copied from remaining in the copying machine, which would require the effort to remove the paper, or to prevent paper jams from occurring when the copying prohibition is canceled. Furthermore, it is possible to prevent defective copies from occurring due to interruption of a copying operation currently being executed. That is, in this embodiment, for a copy sheet that is in the middle of being copied, the copying operation is completed and the copied paper is discharged from the machine. Moreover, when the power supply voltage level is less than a predetermined level, the LED 103, which is a warning indicator light, is turned on (8113). In addition to lighting up the LED 103, a copy stop message may be transmitted to another CPU 1 or a connected external IIA device through communication.

On the other hand, when copying is not in progress (5107), processing is performed to place the copying machine in copy prohibition (standby state) so that copying is not performed on a new copying paper surface (8111). Here, copy prohibition refers to a state in which a new copying operation is not started. For example, when copying is prohibited, input from the print start key 102 is not accepted by the CPU.

When it is determined in step 5103 that the detected value exceeds a predetermined level, it is determined whether the flag 2 is "1" (8115). Further, when the flag 2 is 1'', it is determined whether the temperature of the heat roller of the fixing device (toner constant fixing temperature) exceeds the reference level (8117).
. The temperature of the heat roller is determined by A/D converting the input voltage of the analog input port AN1 connected to the toner constant temperature detection thermistor, and comparing it with a reference level by software in the first CPU. Further, the reference value for comparison is set based on whether toner fixation failure, offset, etc. occur.

5119 only when the power supply voltage exceeds the predetermined level, flag 2 is "1", and the constant W temperature exceeds the reference level.
The processes from 5123 to 5123 are executed. That is, when the power supply voltage drops, the copy prohibition is canceled only after the power supply voltage recovers to a predetermined level or higher and the fixing temperature also recovers to a reference level or higher (8119), and the warning display LED 103 is turned off (8119).
121), and sets flag 2 to "O" (8123). or,
If the fixing temperature is below the reference level and flag 2 is 0”,
That is, if the power supply voltage does not drop, the process returns to the main routine.

In the above embodiment, when the 'RWA voltage supplied to the copying machine falls below a predetermined level, the copying machine is placed in a copy inhibited state (standby state). For this reason, image defects and dots may occur due to insufficient torque or step-out of the AC synchronous motor for driving the photoreceptor drum due to the power supply voltage, or a decrease in the light amount of the exposure means, or a decrease in the current supplied to the toner constant wear e-tater. This will prevent defective copies such as poor fixing and paper jams.

Further, when the power supply voltage returns to a predetermined level, the copy inhibited state is canceled on the condition that the temperature of the heat roller (fixing heater) exceeds the reference level. Therefore, if the temperature of the heat roller is below the reference level due to a drop in the power supply voltage, etc., copying will not be restarted, thereby preventing defective copies due to toner fixation failure and low-temperature offset.

In this embodiment, when comparing the amount of power supply voltage drop Δv1 that causes a defective copy with the amount of power supply voltage drop ΔV2 that causes a non-maskable auto-reset on the microcomputer, ΔV1<ΔV2. Therefore, the above processing becomes possible.

(Reference to Other Embodiments) In the above embodiment, the copy prohibition is executed by processing to prevent the start of a new copy operation, and also performs copy stop processing to prevent copying paper from being copied.
The copying operation is understood as a series of operations from scanning the original to heating and fixing the toner image on the copy paper. However, since the copy prohibition and copy stop processing is performed to prevent defective copies from occurring, it is possible to define the contents of the copying operation from this perspective, and the toner image is transferred and heated to be fixed on the paper surface. This can be considered a "copying operation". For this reason, for example, by the timing roller pair 26,
Based on the point in time when the copy paper is carried out to the photosensitive drum 1 side, it may be determined that copying is not in progress before that time, and that copying is in progress after that point. In this case, for example, it is determined whether or not copying is in progress based on the time point at which a known timing clutch-on signal is output.

[Effects of the Invention] As described above, according to the present invention, defective image formation when the power supply voltage drops below a reference value is prevented by prohibiting image formation. Also, when the power supply voltage exceeds a predetermined value, the image formation prohibition is canceled on the condition that the toner constant wear heater is at a predetermined value or higher. For this reason, conventionally,
A defective image formation that could occur even if measures against power supply voltage fluctuations are taken for each individual device constituting the image forming means is not performed. Further, when image formation is not prohibited, toner fixation failure, low temperature offset, etc., due to a decrease in the N source voltage do not occur.

[Brief explanation of the drawing]

FIG. 1 is a sectional view schematically showing a copying machine according to this embodiment. FIG. 2 is a front view of the operation panel of the copying machine according to this embodiment. Figure 3 shows the ti of the M9 aircraft according to this example.
It is a circuit block diagram of a tm marsh pressure abnormal pressure abnormality detection processing circuit. FIG. 4 is a flowchart showing an outline of the processing of the 10th PCI. FIG. 5 is a flowchart showing details of the power supply voltage detection process (S7). FIG. 6 is a graph showing the fixing temperature of the fixing device when performing multi-copying when the power supply voltage drops. 28... Fixing device 55... One-chip microcomputer patent applicant Minolta Camera Co., Ltd. agent Patent attorney
Hirodo Okawa Patent Attorney Akio Maruyama Figure 3 Figure 4 Figure 5

Claims (2)

[Claims] (1) An image forming means that forms an image by heating and fixing a toner image on paper using a heater, a temperature detecting means that detects the temperature of the heater, and a level of power supply voltage supplied to the image forming means. a detection means for detecting, when the power supply voltage level is below a reference value, instructing the image forming means to prohibit image formation, and when the power supply voltage level and the heater temperature each exceed a predetermined value; , a control means for canceling the prohibition of image formation, and an image forming apparatus comprising: . (2) An image forming apparatus according to claim 1, wherein the image forming means forms an image by an electrophotographic process.