JP2000122487A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To previously prevent the erroneous detection of an error caused when AC input is unexpectedly interrupted in an image forming device. SOLUTION: A power source unit 10 applies the voltages of 24 V and 5 V to a control unit 30 based on the AC input. The voltage 5 V is used for driving the first electric loads, i.e., CPU 31 and ASIC 35, etc., and the voltage 24 V is used for driving the second electric loads (electric machine device), i.e., clutch 51, solenoid 52, and motor 53, etc. The unit 10 has a zerocross signal generating circuit 12 detecting the zerocross of the AC input, and the CPU 31 detects the AC input interruption based on the zerocross signal. In the case of the detection of the AC input interruption, the second electric load which is not used at that time among the second electric loads is forcibly driven.

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 such as an electrophotographic copying machine, and more particularly to a method for coping with an unexpected interruption of an AC input.

[0002]

2. Description of the Related Art An image forming apparatus such as a copying machine usually includes a power supply unit for transforming, rectifying, and smoothing an AC input to generate a plurality of different DC voltages. The DC voltage is, for example, a relatively low voltage VL (5 V) for driving an electric circuit including a CPU and a relatively high voltage V for driving an electromechanical device such as a clutch, a solenoid, and a motor.
H (24 V).

[0003]

Such a power supply unit, due to its structure, includes a relatively large-capacity capacitor for storing electric charge, and when the AC input is cut off for some reason, the electric charge is lost. It takes a predetermined time until the output voltages of VH and VL become 0 after discharging. In addition, there is a difference between VH and VL at that time. Therefore, even after the AC input is cut off, the CP using the VL as the input voltage is used.
ICs such as U and ASIC continue to operate for a while.

Various error detection means are provided in the image forming apparatus. When an unexpected AC input disconnection such as opening of a front door or disconnection of a power plug occurs during power-on, particularly during copying operation. In some cases, an error may be erroneously detected before the voltage becomes zero. Such errors persist after a return, depending on the type,
Some things cannot be canceled without the help of a service person.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus having a new function capable of preventing the occurrence of such a trouble when the AC input is interrupted.

[0006]

An image forming apparatus according to the present invention includes a first DC voltage obtained based on an AC input;
A power supply unit for outputting a second DC voltage higher than the first DC voltage, a first electric load including a CPU driven by the first DC voltage, and a second DC voltage An AC input disconnection detecting means for detecting an AC input disconnection, and when the AC input disconnection is detected by the AC input disconnection detecting means, the charge stored in the capacitor. And forced discharge means for forcibly discharging the charged electric charge.

As a result, the electric charge stored in the capacitor of the power supply unit decreases rapidly, and as a result, the first
In addition, the second DC voltage is also rapidly reduced, thereby preventing the occurrence of the above-described error detection error.

[0008] The forced discharging means may be constituted by means for forcibly driving an electric load controlled by the second DC voltage. This eliminates the need for special new components for forced discharge.

The AC input disconnection detecting means includes, for example, a zero cross signal generating means for detecting a zero cross of the AC input to generate a zero cross signal, a means for periodically counting the zero cross signal, and a reference clock. Means for measuring the time after the count value of the zero-cross signal is cleared to zero, and determining that the measured time has become larger than a predetermined value before the count value of the zero-cross signal reaches a predetermined value. Means.

As the zero-cross signal generating means, a means conventionally used for detecting the frequency of the AC input can be used.

The first electric load includes a CPU and an integrated circuit, and the second electric load includes an electromechanical device.

The electric load to be forcibly driven is preferably a load which is in an unused state at that time.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram of control hardware of a copying machine as an image forming apparatus to which the present invention is applied.

In FIG. 1, 24V and 5V from AC input
A power supply unit 10 for generating two types of output voltages; a heater drive circuit 20 driven by an AC voltage passing through the power supply unit 10; a fixing heater 21 whose energization is controlled by the heater drive circuit 20; Unit 1
A control unit 30 that receives 24V and 5V voltages from 0 as operating voltages and controls the heater drive circuit 20 and the like.
A clutch (CL) 51, a solenoid (SL) 52, and a motor (M) 53, which are electromechanical devices controlled by the control unit 30, and an operation unit 40 that provides an interface between the control unit 30 and a user. Is shown. Although not shown, the operation unit 40 includes various operation keys and a display unit.

As is well known, the power supply unit 10 transforms, rectifies, and smoothes an AC input to generate DC voltages of 24 V and 5 V. The voltage output circuit has a relatively large-capacity capacitor 11. In the present embodiment,
The power supply unit 10 has a zero cross signal generation circuit 12 that detects a zero cross of the AC input voltage and generates a zero cross signal (pulse signal). This zero cross signal is used as an interrupt signal of the CPU 31 described later.

The control unit 30 includes a CPU 31 for controlling the entire copying machine (image exposure, development, fixing, paper feeding, etc.), a memory 32 for storing an operation program of the CPU 31 and various data, and a periodic interruption. An ASIC (Application) that operates under the control of the CPU 31 and generates an error and controls a control target and detects an error.
Specific Integrated Circuit) 35. In the memory 32, a zero-cross counter 321 updated by program control by the CPU 31, a zero-cross time counter 322, a time T323, and a zero-cross disconnection flag 3
24 memory areas are provided. The function of each of these memory areas will be described later.

The object to be controlled in the copying machine is a fixing heater 2.
There are various types such as a document illumination lamp, a document / paper transport system, etc. other than 1, but here, the fixing heater 21 is shown as a representative one thereof.

The operation of this embodiment will be described below with reference to various flowcharts.

First, when the power of the copying machine is turned on, FIG.
As shown in FIG.
Starts zero-cross monitoring (S11). Next, an idle routine is entered (S12). Details of the idle routine will be described later with reference to FIG.

In the zero-cross monitoring start process, as shown in FIG.
1), the count n of the zero-cross counter 321 and the count t of the zero-cross time counter 322 are cleared to zero (S22). Further, the count of the number of times of zero crossing is started by permitting the zero cross interrupt by the zero cross signal, and the time measurement of the timer 34 is started by permitting the timer interrupt (S2).
3).

In this embodiment, the timer 34 is set to 2 ms
A timer interrupt is generated for the CPU 31 every ec. Each time this timer interrupt occurs, the CPU 31
Is a zero-crossing time counter 322, as shown in FIG.
Is incremented (+1 increment) (S31).

On the other hand, a zero-cross signal is also used as an interrupt signal for the CPU 31. FIG. 6 shows the timing relationship between the timer interrupt and the interrupt by the zero-cross signal (hereinafter referred to as a zero-cross interrupt).

When a zero-cross interrupt occurs, the CPU 31
As shown in FIG. 5, first, the zero-crossing frequency counter 32
1 is incremented (S41), and it is checked whether the value n has reached a predetermined value N (S42). If the count value n has not reached N, the zero-cross interrupt processing is terminated, and if it has reached, the processing of step S43 is performed. That is, the current value t of the zero-crossing time counter 322 is read and saved in a variable T (323 in the memory 32). Thereafter, both the zero-cross time counter 322 and the zero-cross counter 321 are cleared to zero, and the counting of the zero-cross signal and the time measurement by the timer are started again.

Next, referring to FIG. 7, step S12 in FIG.
The idle routine will be described in detail.

In this idle routine, the normal error processing S58, key processing S59, display processing S60, copy start processing S60, etc. of the copying machine are performed in parallel with the processing S100 when the AC input is cut off.

Before describing the details of the AC input disconnection process S100, a normal process of the copying machine will be described. Although not shown in the flowchart of FIG. 2, the CPU 31 initializes an optical unit (not shown) for exposing a document and turns on the fixing heater 21 by turning on the fixing heater 21 when the power is turned on. Key control for image formation.

When the operation mode key is operated to change the copy mode, the CPU 31 performs a display process S in accordance with the operation.
The display of the operation unit 40 is switched by 60, and when the magnification is changed, the magnification setting operation control of the optical unit is also performed.

In the copy start process S61, as shown in FIG. 8, it is checked whether or not the copy start key of the operation section 40 has been pressed (S81), and if so, a copy routine is started (S82).

In this copy routine, as shown in FIG. 9, a scanner process for scanning a document (S91),
The sheet feeding process (S92) for feeding the sheet from the sheet feeding unit in accordance with the copy mode set by 0 (S92) and the heater control (S93) for controlling the fixing heater 21 are repeated until the copying is completed (S94).

The occurrence of various errors is monitored, and when an error occurs, necessary error processing S58 (FIG. 7) is performed. That is, as shown in FIG. 10, when an error based on the hardware detection unit is detected (S71, Yes), the copying operation is stopped and all output signals are turned off (S7).
2). Even if a detection error by hardware does not occur, other error processing is performed here (S73).
The other error processing is an error detected by software, for example, when the rotation signal of the main motor is not detected even when the main motor is turned on, or when the temperature of the fixing device exceeds a predetermined temperature.

Next, the details of the AC input disconnection process S100 will be described.

Returning to FIG. 7, first, the CPU 31 determines the value of the variable t obtained in the preceding zero-cross interrupt processing (FIG. 5), that is, the timer count value T by the number of times of zero-cross detection N
To calculate the generation cycle H of the zero-cross signal (S
51). In a normal state, the value of H is 10 msec when the AC input frequency is 50 Hz, and 8.3 msec when the frequency is 60 Hz. The CPU 31 controls the phase of the output voltage of the original illumination lamp and the fixing heater based on the obtained cycle H. If the cycle H is out of the standard, the CPU 31
Determines that there is a zero-cross signal error (one of the other errors in S73), and displays that fact on the operation unit 40. For example, if the standard of the cycle is ± 30%, the allowable range of the value of the cycle H is 10 ± 3 msec when the AC input is 50 Hz.
In the case of c and 60 Hz, it becomes 8.3 ± 2.5 msec.

If the AC input to the power supply unit is interrupted due to the opening of the front door or the disconnection of the outlet plug during the above operation, since the electric charge remains in the capacitor 11 of the voltage output circuit of the power supply unit, the AC input is A state may occur in which the control unit operates for a while while being disconnected. At this time, even if the AC input is cut off, the CPU 31 attempts to control the temperature of the fixing heater 21 and determines that an error has occurred because the power supply to the fixing heater 21 is not actually performed. An abnormal state such as an error may occur. This error corresponds to the hardware detection error described in step S71 of FIG.

Such an error is a false detection. In order to prevent this, the CPU 31 determines that the timer count value t has become larger than a large value (predetermined value P) before the zero-cross detection number n reaches a predetermined N times (S52, Yes). It is determined that the zero-cross signal has been disconnected, and the zero-cross disconnection determination flag is set to 1 (S53).

As described above, since the zero-cross interruption is determined by checking the count value t before the count value n reaches N, the value of N is maintained even after the AC input is interrupted.
Etc. are small enough to guarantee that they are operating. However, in order to stabilize the value of the period H, it is desirable that the value of N is not too small. Therefore, the value of N may be determined by comprehensively considering these conditions, the frequency of the AC input, the characteristics of the power supply unit 10 in the actual copying machine, and the like. In this example, N = 10.

Subsequent to step S53, an unused electrical load (especially, an electromechanical device having relatively large power consumption) at that time is checked, and the unused electrical load is forcibly driven (S54). . For example, when the optical unit is not operating, an ON signal is sent to the optical motor (M) and the optical unit cooling fan, and when the sheet feeding unit is not operating, an ON signal is sent to force the power consumption. I do. As a result, charges are rapidly discharged from the capacitor 11 of the power supply unit 10. As a result, the voltage (24 V and 5 V) supplied to the control unit 30 decreases rapidly,
The operation of the U31 itself and other ICs is stopped, and erroneous error detection is eliminated.

If the cycle H is equal to or less than the value P in step S52, if the zero-cross break determination flag is 1 (S55, Yes), the electric load is turned off (S56), and the zero-cross break determination is performed. Return the flag to 0 (S
57). This is a measure to be taken when the vehicle returns from the abnormal state.

Although the preferred embodiment of the present invention has been described above, various modifications and changes can be made without departing from the scope of the claims. For example, the detection of the AC input disconnection is performed based on the zero-cross signal of the AC input, but any means may be used as long as the AC input disconnection can be immediately detected.

[0040]

According to the present invention, it is possible to prevent the occurrence of erroneous error detection accompanying an unexpected interruption of AC input in an image forming apparatus. Further, no new hardware is required for that purpose, and the present invention can be realized using existing hardware.

[0041]

[Brief description of the drawings]

FIG. 1 is a block diagram of control hardware of a copying machine as an image forming apparatus to which the present invention is applied.

FIG. 2 is a flowchart of a process when the power of the copying machine shown in FIG. 1 is turned on.

FIG. 3 is a flowchart showing details of step S11 in FIG. 2;

FIG. 4 is a flowchart showing a timer interrupt process in the copying machine of FIG. 1;

FIG. 5 is a flowchart showing a zero-cross interruption process in the copying machine of FIG. 1;

FIG. 6 is a timing chart showing the relationship between a timer interrupt and a zero-cross interrupt.

FIG. 7 is a flowchart showing details of an idle routine S12 of FIG. 2;

FIG. 8 is a flowchart showing details of a copy start process of FIG. 7;

FIG. 9 is a flowchart showing details of a copy routine started by a copy routine start process S82 in FIG. 8;

FIG. 10 is a flowchart showing details of error processing S58 in FIG. 7;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Power supply unit, 11 ... Capacitor, 12 ... Zero cross signal generation circuit, 20 ... Heater drive circuit, 21 ... Fixing heater, 30 ... Control unit, 31 ... CPU,
32 ... memory, 34 ... timer, 35 ... ASIC, 40 ...
Operating part, 51 ... clutch, 52 ... solenoid, 53 ... motor.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masatoshi Tanabe 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H027 DA01 ED04 ED08 ED17 EE04 EK05 ZA01 ZA09 5H410 CC03 DD02 DD03 DD05 EB05 EB25 FF03 FF22 LL04 LL18 9A001 BB06 HH23 LZ01

Claims (5)

[Claims] 1. A power supply unit for outputting a first DC voltage obtained based on an AC input and a second DC voltage higher than the first DC voltage, and a built-in power supply unit for accumulating electric charges. An image forming apparatus comprising: a capacitor; a first electric load including a CPU driven by the first DC voltage; and a second electric load driven by the second DC voltage. AC input disconnection detecting means for detecting disconnection, and forced discharging means for forcibly discharging the electric charge accumulated in the capacitor when the AC input disconnection is detected by the AC input disconnection detecting means. Characteristic image forming apparatus. 2. An image forming apparatus according to claim 1, wherein said forced discharge means includes means for forcibly driving an electric load controlled by said second DC voltage. 3. The AC input disconnection detecting means detects a zero cross of the AC input and generates a zero cross signal, a means for periodically counting the zero cross signal, and a reference clock. Means for measuring the time after the count value of the zero-cross signal is cleared to zero, and determining that the measured time has become larger than a predetermined value before the count value of the zero-cross signal reaches a predetermined value. 2. The image forming apparatus according to claim 1, further comprising: 4. The image forming apparatus according to claim 2, wherein said first electric load includes a CPU and an integrated circuit, and said second electric load includes an electromechanical device. 5. The image forming apparatus according to claim 1, wherein the electric load to be forcibly driven is a load which is in an unused state at that time.