JPH0664390B2 - Image forming device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image forming apparatus that sequentially and selectively uses a plurality of developing devices that store developers of different colors to form a color image.

[Prior art]

For example, in a color copying machine using electrophotography, a developing device using a plurality of different color toners is provided for a single latent image carrier such as a photosensitive drum, and the peripheral surface of the latent image carrier is arranged. In contrast to a structure in which a plurality of developing devices are sequentially arranged, a plurality of developing devices are supported by a rotating body, and by rotating the rotating body, only the developing devices corresponding to the desired color toner are hidden. The applicant of the present invention has proposed a multicolor developing device opposed to the image carrier (Japanese Patent Laid-Open No. 50-9343).
7).

In the latter case, since one developing device always faces the latent image carrier, the peripheral length of the latent image carrier can be minimized.

In such a developing device, an attempt has been made to perform a sequence control so that a predetermined developing device is rotationally moved with respect to the drum at a high speed in accordance with a schedule given in advance and is stopped at an accurate position without impact. However, at times, abnormal operations such as the reverse rotation of the drive motor and the occurrence of overcurrent occur, which not only affects the control of the main body of the image forming apparatus, but also damages the developing device itself, and in the worst case, burnout of the rotary drive motor etc. There is also a risk of causing an accident.

In particular, the developing device is fixed at the time of development for a stable developing operation. Therefore, if an abnormality occurs in the lock mechanism, even if the drive motor is normal, Such problems arise.

〔Purpose〕

The present invention has been made in view of the above problems, and not only an abnormality in the driving of the holding unit that integrally holds a plurality of developing devices but also a locking mechanism for fixing the holding unit to the developing position. It is an object of the present invention to provide an image forming apparatus having a self-diagnosis function that enables an operator to take appropriate measures against such abnormalities.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 7.

FIG. 1 is a cross-sectional view showing an example of an electrophotographic copying machine as an image forming apparatus equipped with a rotationally driven multicolor developing device.

In the figure, the photosensitive drum 1, which is a latent image carrier, rotates in the direction of the arrow. A charger 2, an exposure optical system 3, a developing device 4, a transfer system 5, and a cleaning device 6 are arranged around it. The optical system 3 has a document scanning section 3a and a color separation filter section 3b. The developing device 4 includes a yellow developing device 4Y that uses yellow toner, a magenta developing device 4M that uses magenta toner, a cyan developing device 4C that uses cyan toner, and a black developing device 4B that uses black toner.
have k in one. Each developing device is Japanese Patent Publication No.
As disclosed in Japanese Patent Laid-Open No. 5-20579, the toner is prevented from scattering due to the action of the magnetic field by the magnet roller R, and is detachably held by the rotating body 4a as shown in the drawing and is rotated about the central axis 4b. Replace the developer for the position. In addition, S is a toner stirring screw.

On the other hand, the transfer unit 5 includes a drum 5b having a gripper 5a,
It has a transfer discharger 5c inside thereof.

When forming a full-color image, blue, green, red, and ND color separation optical systems are used, as in conventional copiers.
The color separation is performed by the color filter of No. 3, three colors of yellow, magenta, and cyan, and further black are added, and development is performed by a four-color developing device.

Now, for example, when blue light (exposure) is radiated to the photosensitive drum 1, a latent image is formed on the photosensitive drum 1, and the formed latent image is rotated by the yellow developing device 4Y which is rotationally moved to the developing position at an appropriate timing. A visible image is formed, and this visible image is transferred onto the transfer paper held on the transfer drum 5b by the transfer charger 5c. This transfer paper is supplied from the cassette 7. After the above-described processes from exposure to development are performed on the photosensitive drum 1 after cleaning the photosensitive drum 1, the process is performed by the magenta developing device 4M for green light and the cyan developing device 4C for red light. Transfer is performed. Further, exposure is performed using the ND filter described above, and the black developing device 4 responds to this exposure.
After development by BK, transfer is performed. The transfer material which has completed the transfer step is separated by the separating means 8,
It reaches the tray 10 through the fixing device 9.

FIG. 2 is a perspective view showing a main part of the developing device. Reference numeral 11 denotes a ring-shaped rear side plate which is provided at the rear end portion of the rotating body 4a and has the gear 11a in the peripheral portion. Reference numeral 12 is a rotation driving motor, and a gear 13 fixed to one end of the motor shaft is connected to the gear 11a through gears 14, 15 and 16, and a rotation speed and a position are provided at the other end of the motor shaft. For example, an encoder 17 is provided as a detection unit of the. The detectors for the rotational speed and the position may be separate from each other, but in this embodiment, the speed is detected from the number of pulses output from the rotary encoder 17 per unit time, and the position is detected as the integrated value. Z is a positioning means for ensuring a predetermined stop position of the rotating body 4a, and a stopper plate 18 having a groove 18a and a guide edge 18b is attached to the rear side plate 11. FIG. 2 shows two stopper plates partially broken.

On the other hand, Z1 is a rotating body holding mechanism that engages with the stopper plate 18 (see FIG. 3 for details), and 19 is an L-shaped stopper arm, which is an elongated hole 19a formed in the elbow portion.
The other end of the pin 20, one end of which is fixed to the apparatus body, is inserted therethrough. A roller 22 is rotatably attached to one end of the stopper arm 19 by a stopper pin 21, and a tension coil spring 23 is stretched between the stopper pin 21 and the pin 20. Stopper arm 1
At the other end of 9, a lock solenoid 25 as a holding release means is pivotally mounted by a pin 27 via a connecting member 26, and a spring 28 causes the roller 22 to abut on the periphery of the stopper plate 18. Is urged to.
Reference numeral 29 is a photointerrupter as a detection means for detecting engagement and disengagement of the rotating body 4a and the stopper arm 19, and the photointerrupter 29 is arranged so that light is interrupted according to the movement of the end 24 of the stopper arm 19. Has been done.

To rotate the rotating body 4a, first of all, the lock solenoid 2
It must be rotated after pulling 5 to remove the stopper pin 21 from the groove 18a of the stopper plate 18. In order to stop the rotating body 4a, the stopper plate 1
The magnetic force of the lock solenoid 25 is released before 8 reaches the position of the stopper pin 21. Then, roller 22
Rotates along the arcuate edge of the stopper plate 18 that rotates in the N direction, and engages with the coming engagement groove 18a. Since the stopper plate 18 guides the stopper roller 22 into the engagement groove 18a, a part of the arcuate edge is cut out to form a guide edge 18b. The roller 22 is the engaging groove 18
At the moment of entering a, the stopper arm 19 blocks the optical path of the photo interrupter (lock sensor) 29 attached to the main body, and detects the engagement of the positioning means Z. When moving to the next rotation, first activate the lock solenoid 25,
The stopper arm 19 is rotated around the pin 20 to release the engagement between the engagement groove 18a of the stopper plate 18 and the roller 22. By this operation, the stopper arm 19 that has shielded the photo interrupter 29 is moved to the photo interrupter 2
It can be detected from the optical path of 9 that the engagement between the engagement groove 18a and the roller 22 is released.

FIG. 4 shows a control system. Reference numeral 30 is a driver for driving the rotating body driving motor 12. Reference numeral 31 denotes a rotary body drive control circuit of the developing device 4, which is a vector detection circuit 31.
a, position counter 31b, speed counter 31c, motor control CPU (central processing unit) 31d, home position sensor XO, timer 31f and D / A
It is composed of a converter 31g.

The vector detection circuit 31a inputs the two-phase pulse from the rotary encoder 17 and outputs data regarding the forward and reverse rotation directions of the rotating body 4a. The position counter 31b is an up-down type counter, receives the data regarding the forward and reverse rotation directions from the vector detection circuit 31a and the pulse output from the encoder 17 via the vector detection circuit 31a, and the home position (HP) of the rotating body 4a. ) Is used as a reference to output the rotational movement position data to the motor control CPU 31d. The home position sensor XO is arranged at HP which is a reference position, and inputs a clear signal to the position counter 31b when the rotating body 4a reaches HP.
The timer 31f outputs a signal each time a set time elapses.
This signal is input to the speed counter 31c to clear the speed counter 31c and to control the motor control CPU 31.
Also input to the interrupt terminal INT of d. CPU for motor control
31d thereby executes the interrupt program, and adds the speed data and the position data from the speed counter 31C and the position counter 31b. Based on this data, the motor 12
Is controlled. This timer 31f is a C for motor control
The PU 31d sets and resets.
The speed counter 31c inputs the pulse output from the encoder 17 via the vector detection circuit 31a,
The rotation speed data of the rotating body 4a is transferred to the motor control CPU 31
It is output to d. In addition, a ROM (readonly memory) 31d1 in the CPU 31d for controlling the rotating body drive motor
Is the relationship between the color mode that can be set from single-color copy to four-color copy and the amount of rotation, and the amount of rotation and the speed of rotation when the developing device is moved from the developing position of one color to the developing position of another color. The relationship is stored as a control data table, and this control data table and detected speed data,
The motor 12 is controlled according to the position data.

Reference numeral 32 denotes a control circuit of the main body of the copying machine, which is a sequence controller (not shown), which inputs a signal to the motor control CPU 31d through the I / O port and the load drive circuit to control the motor control CPU 31d.

FIG. 5 shows a circuit which constitutes a part of the driver 30 for controlling the drive of the rotary body driving motor 12 and detects an abnormality of the motor 12. This abnormality detection circuit detects overcurrent to the motor 12 and reverse rotation of the motor 12 as an abnormality. A power source 40 is connected to the motor 12 via a relay 42 and a resistor 43. Resistance 4 depending on the magnitude of the current
The potential difference generated at both ends of 3 is applied between the emitter and the base of the transistor 44, and the transistor 44 is turned on when the value exceeds a specified value. Now, when the transistor 44 is turned on by an overcurrent, its collector output changes from LOW to HIGI, and the signal is input to the motor control CPU 31d via the signal line 45, and the overcurrent is detected. On the other hand, this overcurrent signal is sent from the OR gate 46 to the relay 42 via the buffer 47, and the power supply circuit of the motor 12 is cut off.

On the other hand, the reverse rotation signal of the motor 12 is outputted from the edge trigger D flip-flop 48 as the reverse rotation detecting means which receives the two-phase signal from the rotary encoder 17. That is, as shown in FIG. 6, the encoder 17 outputs a two-phase signal of the advance signal A and the delay signal B having a phase shift of 1/4 cycle, and the former advance signal A is the D terminal of the flip-flop 48. , And the latter signal B is sent to the CK terminal. When the motor 12 rotates in the normal direction and in the reverse direction, the rising edges of the delay signal B as a clock signal with respect to the levels L and H of the advance signal are reversed, and accordingly the level of the output from the terminal of the D flip-flop 48 is also changed. Invert. Therefore, CPU for motor control
31d detects the reverse rotation of the motor 12 when receiving the H level signal from the terminal, and the reverse rotation signal causes the relay 4 to rotate.
2 also operates to cut off the power supply of the motor 12.

Next, the operation will be described based on the flowchart of the motor control CPU 31d shown in FIG.

The motor control CPU 31d includes a copying machine body control circuit 32.
Mode signals M0, M1, which specify a rotational position of the rotating body 4a having a plurality of developing devices by detecting a start signal from
Accept M2 (S-1). Then, the lock solenoid 25 of the positioning means Z is commanded to be turned on (S-2), whereby the engagement between the rotating body 4a and the locking roller 22 of the positioning means Z is released, and the rotating body 4a is in a rotatable state. become. Here, since the rotational movement of the rotating body 4a must be completed within a predetermined time defined in relation to the control of the main body of the copying machine, the predetermined time is set in the timer set in the RAM 31d ₂ for detecting abnormality. Set (S-3). (As will be described later, when the set time of this timer elapses, it will jump to the abnormality processing routine). Then, while performing the error detection (S-4) described later, the lock roller 22 and the rotating body 4
Wait until the engagement with a is completely released (S-6). When the disengagement of the lock roller 22 is confirmed by the photo interrupter 29, the motor 12 is started to start the rotational movement of the rotating body 4a, and the rotational speed is controlled to move to the target developing position (S-7). ). During this time, the position counter 31b determines whether or not the encoder pulse is normal and whether or not the set time of the timer has elapsed, and always performs the error detection described later, and when an error occurs, jumps to the error processing routine ((S -8 to S-10) When the rotating body 4a reaches the target position, the lock solenoid 25 is turned off, the power of the motor 12 is shut off, the timer is reset, and the END signal indicating the end of rotation is sent to the main body control circuit 32. Is output (S-11 ~
S-15). With the above, the movement of the rotating body 4a to the predetermined developing position is completed, and the preparation for the predetermined color development is completed.

Next, the flow of error detection will be described. The motor control CPU 31d uses the overcurrent detection circuit and the reverse rotation detection circuit as shown in FIG. 5 to determine whether an overcurrent is flowing to the motor 12 (S-16) or whether the motor 12 is rotated in the reverse direction.
(S-17) It is determined whether or not these errors are detected, the process jumps to the abnormality processing routine. In the abnormality processing routine, first, the power source of the motor 12 is cut off (S-18), and then the lock solenoid 25 is turned off (S-19) to operate the positioning means Z and stop the rotating body 4a. After that, an error signal composed of, for example, 3 bits as shown in Table 1 is output to the main body control circuit 32 according to the content of the abnormality.
(S-20).

As a result, an abnormality alarm is issued and an abnormality countermeasure is taken. If the motor control CPU 31d is reset (S-2
1), the abnormality processing routine is returned to the regular rotation control routine.

〔effect〕

As described above, according to the present invention, in addition to an abnormality in the driving of the holding unit that integrally holds a plurality of developing devices, an abnormality in the lock mechanism for fixing the holding unit to the developing position A predetermined abnormality process is performed, and then the operator can take an appropriate action.

[Brief description of drawings]

1 to 7 show an embodiment of the present invention, FIG. 1 is a side sectional view of an image forming apparatus, FIG. 2 is a perspective view of a main portion of a developing device, and FIG. 3 is a portion of FIG. FIG. 4 is an enlarged view, FIG. 4 is a block diagram of a control system, FIG. 5 is a circuit diagram for detecting an abnormality of a rotary body drive motor, FIG. 6 is a diagram for explaining signal input of a reverse rotation detecting means, and FIG. 7 is a rotary body control flowchart. Is. 4a ... Rotator 4Y ... (Developer) 4M ... (Developer) 4C ... (Developer) 4BK ... (Developer) 12 ... Rotator driving means 17 ... Rotation presence / absence detecting means (encoder) 31f ... Rotation time detection means (timer) 31d ... Rotation control means 43 ... (Overcurrent detection means) 44 ... (Overcurrent detection means) 48 ... Reverse rotation detection means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akio Ohno 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-51-15445 (JP, A)

Claims (1)

[Claims] 1. An image forming apparatus for sequentially forming a color image by selectively using a plurality of developing devices each storing a developer of a different color, and holding means for integrally holding the plurality of developing devices, The driving means for driving the holding means to selectively move the plurality of developing devices to a predetermined developing position; and a lock mechanism for fixing the holding means at the developing position. First detecting means for detecting whether the means is operating normally, second detecting means for detecting whether the lock mechanism is operating normally, and the first and second detection means According to the detection result by means,
An image forming apparatus comprising: a control unit that performs a predetermined abnormality process.