JPH0731364B2 - Image forming device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electronic copying machine or a printer.

2. Description of the Related Art FIG. 9 schematically shows an outline of a general electronic copying machine. (1) is a photosensitive drum that rotates at a constant speed, and the drum (1) is made of a material such as aluminum. For example, a selenium-based photosensitive material is vapor-deposited on the surface of the formed drum substrate. Around the drum (1), along the rotation direction thereof, a main charging portion (2), an exposure portion (3), an LED (5) for partial image erasing, a developing portion (6), a transfer portion (7). ，
The separation section (8), the cleaning section (10), and the static elimination section (11) are provided in this order. In the charging section (2), a charge wire (2b) made of a tungsten thin wire arranged in a U-shaped case (2a) is brought close to the surface of the photosensitive drum (1) along the axial direction of the drum. . A voltage of about 5 to 6 kv is usually applied to the charge wire (2b), and the surface of the photosensitive drum (1) is charged to about 600 to 800v by the voltage.

The LED (5) is used when it is desired to erase a part of the latent image and is not normally used. The developing section (6) stirs the toner and the carrier (iron powder) replenished from the hopper (12) through the toner replenishing roller (13) such as a sponge roller with the stirring roller (14),
A developer consisting of carrier and toner is supplied to the surface of the developing roller (15). The photosensitive drum (1) adheres toner to its surface according to the electrostatic latent image. This forms a visible image. The toner on which this visible image is formed is transferred to the sheet fed through the registration roller (16) to the transfer section (7).
Is transcribed by. The separating portion (8) serves to separate the transfer agent paper from the drum (1) by releasing an electrostatic attraction state between the drum (1) and the paper by throwing an AC electric field on the drum surface. The transfer part (7) and the separation part (8) are provided with charge wires (7b) and (8b), respectively.

After separating the paper, clean the drum surface (1
In (0), the blade (17) made of a rubber material receives the toner wiping action, and in the next charge removing portion (11), the light from the charge removing lamp (18) is received to remove the surface charge.

Reference numeral (19) is an illumination unit having an exposure lamp (20), an elliptical reflection plate (21), an auxiliary reflection plate (22), and a first reflection mirror (23). When scanning a document (24), it is in the right direction in the figure. To speed v. Reference numeral (25) is a mirror unit including second and third reflection mirrors (26) and (27),
During scanning in 4), it moves to the right in the figure at a speed of v / 2, and serves to keep the optical path length to the photosensitive drum (1) always constant. The illumination unit (19) and the mirror unit (25) form a traveling optical system (28). (29) shows a frame of an electronic copying machine, (30) shows contact glass, (31) shows a document holding member, and (32) shows a cushioning body made of sponge or the like mounted on the inner surface of the document holding member (31). Is. The light emitted from the exposure lamp (20) is reflected by the original (24), then passes through the slit (33) and is bent at right angles by the first, second and third reflection mirrors (23) (26) (27). After that, it reaches the exposure section (3) through the fixed lens (34) and the fixed fourth reflecting mirror (35).

(36) (37) (38) are home PIs for home position detection, which are sequentially fixedly installed along the traveling path of the traveling optical system (28).
(Photointerrupter), brake timing PI, and paper feed timing PI, which respond to the shield piece (39) provided in the illumination unit of the traveling optical system. The home PI (36) shows the reference position of the traveling optical system (28) and brakes.
PI (37) is for braking the traveling optical system (28), and the paper feed timing PI (38) is the timing for transferring the transfer sheet from the registration roller (16) to the photosensitive drum (1) side. It is for taking.

FIG. 10 is a partially exploded perspective view specifically showing the traveling optical system (28) and its related parts. In the figure, (43) is a first moving frame having the lighting unit (19) shown in FIG. 1,
Reference numeral (44) is a second moving frame having a mirror unit (25), and these moving frames (43) and (44) are slidably fitted to the rod bar (45) at one end thereof. The drive wire (46) is fixed to the one end side of the first moving frame (43) by the metal fitting (47) and the screws (48) (49). A pulley (50) is attached to the one end side of the second moving frame (44), and the wire (46) is wound around the pulley (50) for one turn. The wire (46) is mounted between the fixed parts (51) and (52) by the pulleys (50) (53) (54) (55) (5).
6) Suspended through. The pulley (55) is mounted on a motor shaft (not shown) and functions as a driving pulley. The pulley (54) serves to apply tension to the wire (46). The shafts of the pulleys (53) (56) are fixed to the copying machine main body. By moving the wire, the first and second moving frames (43)
(44) reciprocates in the (F) direction. (57) and (58) are fixing means for fixing the ends of the rod bar (45) to the main body of the copying machine. (59) is a rail that slidably supports the other ends of the first and second moving frames (43, 44).

Reference numeral (60) is a fixedly arranged PI for forced return, which is also shown in FIG. 9, and reacts with the shield piece (39) of the optical system (28). Generally, the return operation of the traveling optical system (28) is automatically performed when the count value of the timer counter reaches the timer value set in the registration timer according to the copy size selected on the operation panel of the electronic copying apparatus. Therefore, the PI for forced return is
(60) is provided only for safety.

The traveling optical system (28) moves to the right from the home PI (36) as a starting point, and conveys the transfer sheet from the registration roller (16) to the photosensitive drum (1) at the sheet feed timing PI (38). . When the count value of the timer counter reaches the timer value corresponding to the copy size set via the keys on the operation panel (not shown), the traveling optical system (28) returns and reaches the brake timing PI (37). Brakes are applied and stop at home PI (36). After that, the same operation is repeated.

In the above-described configuration, there is a conventional example in which the brake timing PI (37) is not provided and the brake timing is designated by the timer counter.

Problems to be Solved by the Invention By the way, the moving load of the traveling optical system is extremely increased due to aged or sudden dirt generated on the above-mentioned traveling path constituting members such as the rod bar (45) and the rail (59). In such a case, if the normal traveling operation is forcibly continued, the traveling optical system and the traveling path will be damaged.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of preventing such a damage accident.

Means for Solving the Problems In order to achieve the above object, according to the present invention, an optical system for reading an original image starts at a home position to reach a predetermined speed, and then an image reading area is read and moved in the image reading area at the predetermined speed. Then, in order to return to the home position again after returning at a predetermined point, a motor for driving the optical system, an encoder that outputs a signal corresponding to the speed of the motor, and an encoder A phase comparator that outputs an error signal by comparing the output with a reference value and a motor drive circuit are controlled, and a control signal based on the output of the phase comparator when the image reading area of the image reading area is running is provided to the motor drive circuit. In the image forming apparatus including a control circuit for controlling the image reading area, a signal dependent on the output of the phase comparator during image reading traveling in the image reading area is Determination means for determining whether or not a predetermined threshold is exceeded, and means for applying a special measure to the movement of the optical system based on the output of the determination means by the determination signal when the signal exceeds the threshold When the signal does not exceed the threshold value, a braking control means for setting the brake timing at the time of return based on the average value of the signal during the image reading traveling is provided.

According to such a configuration, an abnormality in the moving load is detected while the optical system is traveling in the image reading area, the detection result is reflected when the optical system returns, and appropriate measures are taken. That is, if no abnormality is detected, the braking control means operates so as to properly stop the optical system at the home position. Is given priority, and when the optical system returns, special measures such as low speed return, abnormal sign display, and dropping oil drops on the traveling path are taken.

Embodiments Embodiments shown in the drawings will be described below. The following embodiments also describe the braking control when no abnormality is detected.

In FIG. 1, (61) is a motor for driving the traveling optical system (28), and (62) is an encoder for outputting a pulse according to the rotation of the motor (61). As shown in FIG. 3, the encoder (62) is composed of a slit disk (64) fixed to the motor shaft (63) and a sensor (66) attached to the motor frame (65). The sensor (66) is composed of a photo coupler or the like, and generates a pulse each time it passes through the slit (67) formed in the slit disk (64). The sensor (66) is composed of first and second sensors (66a) (66b) arranged at different positions as shown in FIG. 1, and has a phase difference of 90 ° with each other at a specified rotation speed of the motor. Generate the resulting pulse (P ₁ ) (P ₂ ). It should be noted that these pulses (P ₁ ) (P ₂ ) are generated at a rate of 400 per one rotation of the motor at the specified rotation speed of the motor. Output pulse (P ₁ ) of these first and second sensors (66a) (66b)
(P ₂ ) is given to the rotation direction detection circuit (68), and it is determined whether the rotation is in the forward direction or in the reverse direction. The discrimination output is given to a microcomputer (hereinafter referred to as "microcomputer") (69).

On the other hand, the output pulse (P ₂ ) of the second sensor (66b) is also directly given to the microcomputer (69). In this case, the output pulse (P ₁ ) of the first sensor (66a) may be supplied to the microcomputer (69) instead of the output pulse (P ₂ ) of the second sensor (66b). The microcomputer (69) integrates the output pulse (P ₂ ) of the second sensor (66b) with a counter, and the traveling optical system (2
8) Monitor the current position (Figs. 9 and 10) and determine the current velocity from the pulse repetition period.

The output pulse (P ₁ ) of the first sensor (66a) is applied to the phase comparator (7
In 0), the phase is compared with the reference pulse. The reference pulse is given from the pulse oscillator (71) through the frequency divider (72). The error signal output from the phase comparator (70) is sequentially passed through the low-pass filter (73) and A / D converter (74) to the microcomputer (69).
Is taken into. The microcomputer (69) gives a PWM (pulse width modulation) signal to the motor drive circuit (75) based on this error signal only while the traveling optical system (28) is traveling in the image reading area. Therefore, the encoder (62),
A PLL loop is formed by the phase comparator (70), the microcomputer (69), and the drive circuit (75), and the rotation speed of the motor (61) is controlled so that the error signal becomes zero. As a result, the optical system (28) is kept at a constant speed while the image reading area is running. At this time, the signal data depending on the phase error signal is held in the microcomputer (69) and used for determining the brake timing as described later. The motor drive circuit (75) is composed of four transistors (Q ₁ ) to (Q ₄ ) connected to a DC power supply (77) as shown in FIG. And these transistors (Q ₁ ) ~
The control signal given to the base of (Q ₄ ) is a microcomputer (69).
This is the PWM signal given from. When rotating the motor (61) forward, the transistors (Q ₁ ) (Q ₄ ) are on, the transistors (Q ₁ ) (Q ₃ ) are off, and the current (I ₁ ) flows,
When reversing, the transistor (Q ₂ ) (Q ₃ ) is on,
The transistors (Q ₁ ) (Q ₄ ) are turned off and the reverse current (I ₂ ) flows. When the brake is applied during reverse rotation, the same current (I ₁ ) as during normal rotation flows.

Here, when the traveling optical system (28) scans a document, it moves to the right in FIG. 9, but this direction is called "forward" and the opposite direction is called "return".

Now, in FIG. 4, the traveling optical system (28) started from the home position (H) enters the constant velocity region (b) through the forward rising portion (a), and the image reading is performed in this constant velocity region (b). Areas (G ₁ ) to (G ₂ ) exist. At the return position (R), the motor (61) is supplied with the reverse current (I ₂ ) instead of the forward current (I ₁ ), so that the motor (61) is rapidly reversed and the traveling optical system ( 28) is in the return movement state. Here, in order to correctly stop the traveling optical system (28) to the home position (H), the brake timing,
That is, the braking point must be set correctly.

This brake point (hence brake timing) is set as follows in this embodiment. First, the microcomputer (69) is given through the A / D converter (74) when the traveling optical system (28) is traveling in the image reading areas (G ₁ ) to (G ₂ ) as described above. A PWM signal as shown in FIG. 5 is output to the line (76) in response to the error signal from the phase comparator (70). In the present embodiment, the duty B of this PWM signal is output.
Paying attention to the fact that / A changes depending on the moving load, the value of the duty B / A is checked step by step, and unless there is a value that exceeds a predetermined threshold value, the entire average is taken and the fourth value is calculated based on the average value. The brake points shown in the figure are set. At this time, if the moving load is large on average, the return characteristic is (RT ₁ ), and if the moving load is smaller than the average value, the return characteristic is (RT ₂ ). Therefore, in each case, the appropriate braking point is ( BP ₁ ), (B
P ₂ ). The calculation of the brake point is performed by the microcomputer (69) based on the average value.

The braking timing determined as described above is reflected in the control signal given from the microcomputer (69) to the motor drive circuit (75). That is, the brake point executes the timing at which the reverse current (I ₂ ) shown in FIG. ₂ is switched to the forward current (I ₁ ) during the return movement.

Instead of monitoring the duty of the PWM signal described above, the magnitude of the current (I ₁ ) that is the output of the drive circuit (75) may be monitored to form the signal data for brake timing. When doing so, the current value is A / D converted and given to the microcomputer (69). Further, instead of the PWM signal, a digital signal input from the A / D converter (74) to the microcomputer (69) may be monitored to form the signal data.

Next, the flow chart of FIG. 6 showing the checking operation of the moving load and the flow chart of FIG.

First, in FIG. 6, in step (# 1), the traveling optical system (28)
Is forward driving, and if NO, then (#
Proceed to 7) to end the flow, but if YES (# 2)
In the traveling optical system (28) the image reading area (G ₁ )
(G ₂ ) is determined. Here, if NO ((#
Skip to 7), and if YES, proceed to (# 3) and store the duty of the PWM signal in the memory one by one. And (#
In 4), it is checked whether or not there is a large difference between the stored values. Specifically, this check is performed by checking whether or not one of the duties exceeds a predetermined threshold value. Here, if it is determined that there is a large difference (some exceed the threshold), (# 6)
Then set a flag to that effect. If it is determined that there is no large difference, the average value of all the duty values stored in (# 5) is calculated and the operation flow is ended.

On the other hand, in the operation flow of FIG. 7, it is determined in step (K ₁ ) whether the traveling optical system (28) has reached a predetermined distance. Here, the predetermined distance refers to point (J) in FIG. When the traveling optical system (28) has reached the point (J), it is checked at the next (K ₂ ) whether or not the flag is set. This flag is a flag that is set in step (# 6) of FIG. 6 described above. If the flag is not set, the brake start point that matches the average value is calculated in (K ₃ ). If the flag is set, proceed to (K ₄ ) and instruct the action to be taken in case of an abnormality. Examples of this measure include instructing slow return and displaying an abnormal sign on the display means.
Instead of this, if a mechanism for dropping oil drops or the like is provided on the rod rod (45) or the rail (59) on which the traveling optical system (28) slides and drops the oil drops, maintenance-free operation can be expected. Further, as a measure, the return operation may be stopped and only the abnormality may be displayed to have maintenance.
After the (K ₃₎ (K ₄₎ are both initiate a return operation at (K _5), and ends the operation flow (K _6).

FIG. 8 shows that the return time can be shortened when no abnormality is detected. That is, in the conventional case, even if the load is heavy, the brake point (BP
_{Due to 0} ), the brake is applied quickly and the low-speed constant velocity area (T ₁ ) in front of the home position becomes longer, and the overall return time becomes longer. However, in the above configuration, the point where the brake is applied is slow as in (BP). , Just before the home position, the vehicle enters the low-speed constant speed area, and the time in this constant speed area (T ₂ ) is short, and the return time is shortened as a whole.

In the above-described embodiment, when the traveling load is large and the flag is set during traveling in the image reading area in the forward direction, the image reading area is allowed to travel as it is without immediately taking the above-mentioned measures, and thereafter, When the measures are taken, at least the paper which is about to be copied is completely copied.

The present invention can be applied not only to the mirror scan type optical system described above, but also to an image forming apparatus in which the optical system is a document table moving type.

EFFECTS OF THE INVENTION As described above, according to the present invention, when the traveling load abnormally increases due to the contamination of the traveling path constituent members of the optical system, it is detected and appropriate measures are taken. Damage to the road can be prevented, and the optical system can be properly stopped at the home position when the moving load is not abnormally increased. Has the effect of

[Brief description of drawings]

FIG. 1 is a block circuit diagram of an image forming apparatus embodying the present invention, FIG. 2 is a detailed view of a part thereof, and FIG. 3 is a schematic view of a part of the same apparatus, FIGS. 4 and 5. Is an explanatory diagram, FIGS. 6 and 7 are flowcharts of operations, and FIG. 8 is an explanatory diagram. FIG. 9 is a schematic view showing the outline of a conventional electronic copying machine, and FIG. 10 is an exploded perspective view of the main part thereof. (28) …… Running optical system, (45) …… Rod rod, (59)…
… Rail, 61 …… Motor, (62) …… Encoder, (6
9) …… Microcomputer, (70) …… Phase comparator, (75) ……
Motor drive circuit.

Claims (7)

[Claims] 1. An optical system for reading a manuscript image starts from a home position to reach a predetermined speed, then image-reads and runs in an image reading area at the predetermined speed, and then returns at a predetermined point to return to the home position. For driving the optical system, an encoder for outputting a signal corresponding to the speed of the motor, and a phase for outputting an error signal by comparing the output of the encoder with a reference value. An image forming apparatus comprising: a comparator; and a control circuit which controls a motor drive circuit and gives a control signal based on the output of the phase comparator to the motor drive circuit during image reading traveling in the image reading area. Determining means for determining whether or not the signal dependent on the output of the phase comparator during image reading traveling in the reading area exceeds a predetermined threshold value; Means for applying a special treatment to the movement of the optical system based on the output of the judging means by the judgment signal when the signal exceeds the threshold value, and when the signal does not exceed the threshold value while the image reading is running. And a braking control means for setting a brake timing at the time of return based on the average value of the signal in the image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the optical system is a mirror scan type traveling optical system. 3. The image forming apparatus according to claim 1, wherein the special treatment is to return the optical system at a low speed. 4. The image forming apparatus according to claim 1 or 2, wherein the special treatment is to return the optical system at a low speed and to output an abnormal sign. 5. The image forming apparatus according to claim 1 or 2, wherein the special treatment is to drop an oil drop on a traveling path forming member of the optical system. 6. The image forming apparatus according to claim 5, wherein the traveling path constituting member is a rod rod into which the moving frame of the optical system is slidably fitted. 7. The image forming apparatus according to claim 5, wherein the traveling path constituting member is a rail for slidably pointing a moving frame of the optical system.