JPH01134375A - Image forming device - Google Patents

Abstract

PURPOSE:To stop an optical system accurately at its home position at all times by applying a brake during return movement at timing corresponding to a moving load in an image read area. CONSTITUTION:A encoder 62 consisting of 1st and 2nd sensors 66a and 66b composed of slit disks, photocouplers, etc., is coupled directly with the shaft of a motor 61 which drives an unshown traveling optical system and when a motor rotates at a prescribed speed, pulses P1 and P2 which are 90 deg. out of phase with each other are generated. Then those pulses are supplied to a rotating direction detecting circuit 68 to detect the rotating direction and while its output is supplied to a microcomputer 69, the output pulse P2 of the sensor 66b is applied directly to the computer 69. The output pulse P1 of the sensor 66a is compared in terms of phase by a phase comparator 70 with a reference pulse and an obtained error signal is inputted to the computer 69 through a filter 73 and an A/D converter 74; and a pulse-width modulated signal from the computer is applied to a motor driving circuit 75 to determine the brake timing.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to image forming apparatuses such as electronic copying machines and printers, and particularly relates to braking of optical systems.

Figure 9 schematically shows the outline of a general electronic copying machine, in which (1) is a photosensitive drum that rotates at a constant speed, and the drum (1) is made of a material such as aluminum. It is formed by depositing, for example, a selenium-based photoreceptor material on the surface of a drum base made of. Around the drum (1), there are a main charging section (2), an exposure section (3), an LED for partial image erasing (5), a developing section (6), and a transfer section (7) along the rotation direction of the drum (1).
1 separation section (8), cleaning section (10), static elimination section (1
1) are provided in this order. The charging section (2) has a charge wire (2b) made of a thin tungsten wire disposed inside a U-shaped case (2a) and brought close to the surface of the photoreceptor drum (1) along the axial direction of the drum. . A voltage of approximately 5 to 6 kV is normally applied to this charge wire (2b), and the surface of the photoreceptor drum (1) is charged to approximately 600 to 800 V by this voltage.

L E D (5) is used when it is desired to erase a portion of the latent image, and is not normally used. The developing section (6) uses a stirring roller (14) to stir toner and carrier (iron powder) supplied from a hopper (12) via a toner replenishing roller (13) consisting of a sponge roller or the like. A developer consisting of carrier and toner is supplied to the surface of (15). The photosensitive drum (1)
deposits toner on its surface in accordance with the electrostatic latent image. This forms a visible image. The toner that has formed this developed image is transferred to the paper fed through the registration rollers (16) at the transfer section (7). Release the electrostatic attraction between the paper and the paper and transfer the transferred paper to the drum (1).
It serves to separate from Transfer part (7) and separation part (8
) are each equipped with a charge wire (7b) (8b).

After the paper is separated, the drum surface is cleaned by the cleaning section (1
At step 0), the toner is wiped off by a blade (17) made of a rubber material, and then at the next static eliminator (11), the charge on the surface is removed by receiving light from a static eliminator lamp (18).

(19) is an exposure lamp (20) and an elliptical reflector (21),
This illumination unit includes an auxiliary reflecting plate (22) and a first reflecting mirror (23), and moves to the right in the figure at a speed V when scanning an original (24). (25) is the second.
A mirror unit equipped with third reflecting mirrors (26) and (27), which moves to the right in the figure at a speed of V/2 when scanning a document (24), and always keeps the optical path length relative to the photoreceptor drum (1) constant. These illumination unit (19) and mirror unit I-(25), which serve to hold the vehicle in place, constitute a traveling optical system (28). (29) shows the frame of the electronic copying machine, (30) the contact glass, (31)
(32) is the original holding member (31)
It is a cushioning body made of sponge etc. attached to the inner surface of the

After the light emitted from the exposure lamp (20) is reflected by the original (24), it passes through Surin I- (33) and passes through the first. Second. After being bent at right angles at the third reflecting mirrors (23), (26), and (27), they reach the exposure section (3) via a fixed lens (34) and a fixed fourth reflecting mirror (35).

(36) (37) (38) are the traveling optical system (28);
), a home PI (photointerrupter) for detecting the home position, a brake timing PI, and a paper feed timing PI, which are fixedly installed in sequence along the traveling path of the vehicle, and a shielding piece (39) provided in the illumination unit of the traveling optical system. react to. The home P I (36) is for displaying the reference position of the traveling optical system (28), and the brake P r (37) is for applying a brake to the traveling optical system (28). Timing P I (38) is for determining the timing for conveying the transfer paper from the registration roller (16) to the photosensitive drum (1) side.

FIG. 1O is a partially exploded perspective view specifically showing the traveling optical system (28) and its related parts. In the same figure, (4
3) is a first lamp having a lighting unit (19) shown in FIG.
The moving frame (44) is a second moving frame having a mirror unit (25), and these moving frames (43) (44)
is slidably fitted to the rod (45) at one end thereof. The drive wire (46) is connected to the metal fitting (47) and the screw (48) on the one end side of the first moving frame (43).
It is fixed by (49). In addition, the second moving frame (44
A pulley (50) is attached to the one end side of the wire (46), and the wire (46) is wound one turn around the pulley (50). The wire (46) is connected to the fixed part (51) (5
2) Between the pulleys (50) (53) (54) (55
) (56).

The pulley (55) is attached to a motor shaft (not shown) and functions as a driving pulley. The pulley (54) is connected to the wire (46
) is responsible for giving Tenshiran. Pulley (53)
The shaft (56) is fixed to the main body of the copying apparatus. By moving the wire, the first. The second moving frames (43) and (44) perform reciprocating movement in the (F) direction. (57) and (58) are fixing means for fixing the end of the rod (45) to the main body of the copying machine. (59) is the first and second moving frame (43) (
44) A rail that slidably supports the other end.

(60) is a fixedly arranged PI for forced return shown in FIG. 9, and is a shielding piece (
39). 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 device. Therefore, the forced return P I (60) is provided only for safety purposes.

The traveling optical system (28) moves to the right from the home P I (36) as a starting point, and the paper feed timing P [(3B)
The transfer paper is conveyed from the registration roller (16) toward the photosensitive drum (1). 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 the brake timing P I
When reaching (37), the brake is applied and the home P I
Stop at (36). Thereafter, the same operation is repeated.

In the above configuration, brake timing PI (37)
There is also a conventional example in which the brake timing is specified by a timer counter without providing a brake timing.

■ tries to do "°. As mentioned above, the brake timing during the return operation in the conventional example is done by the output of the brake timing PI, or
Alternatively, the brake timing position is determined by the output of a timer count, but in both cases the brake timing position is fixed.

However, if the moving load of the travel optical system changes due to dirt on the rod (45) or rail (59), the braking capacity will change relatively, so the fixed braking timing described above will not allow you to stop at the home position accurately. There will be no such thing.

The present invention has been made in view of these points, and provides an image forming apparatus that can accurately stop an optical system at a home position even when the moving load of the optical system changes. The purpose is to

In order to achieve the above-mentioned object of reading a document, the present invention starts by starting an optical system for reading a document from a home position and after reaching a predetermined speed.
A motor for driving the optical system and a signal corresponding to the speed of the motor are operated so as to run through the image reading area at the predetermined speed, then return at a predetermined point and return to the home position again. a phase comparator that compares the output of the encoder with a reference value and outputs an error signal; and a phase comparator that controls a motor drive circuit and that outputs an error signal based on the output of the phase comparator when traveling in the image reading area. and a control circuit for supplying a control signal to the motor drive circuit, the image forming apparatus comprising a braking control means for controlling braking based on signal data dependent on an output of the phase comparator when traveling in the image reading area. The configuration is as follows.

With this configuration, the brake during return movement is applied at a timing based on the moving load in the image reading area, so even if the moving load changes, the optical system can always be accurately stopped at the home position. be able to.

The embodiment shown in the drawings will be described below. In FIG. 1, (61) is a motor for driving the traveling optical system (28), and (62) is an encoder that outputs pulses according to the rotation of the motor (61)'. As shown in FIG. 3, this encoder (62) consists of a slit disk (64) fixed to a motor shaft (63) and a motor frame (6
5) and a sensor (66) attached to it. The sensor (66) is composed of a photocoupler or the like, and generates a pulse every time the slit (67) formed on the slit disk (64) passes. The sensor (66) is a first
The first. It consists of a second sensor (66a) (66b), and a pulse (P
I) Generate (Pt). Furthermore, these pulses (PI
)(Pffi) are generated at a rate of 400 per revolution of the motor when the motor has a specified rotational speed.

The first of these. The output pulses (P + ) (P z) of the second sensors (66a) (66b) are given to a rotation direction detection circuit (68) to determine whether the rotation is in the forward direction or in the reverse direction. The discrimination output is processed by a microcomputer (hereinafter referred to as “
microcontroller) (69).

On the other hand, the output pulse (Pt) of the second sensor (66b)
is also given directly to the microcomputer (69). In this case, the output pulse (Pl) of the first sensor (66a) may be supplied to the microcomputer (69) instead of the output pulse (P2) of the second sensor (66b). The microcomputer (69) integrates the output pulses (P2) of the second sensor (66b) using a counter to monitor the current position of the traveling optical system (28) (Figs. 9 and 10) and also calculates the current speed. It is determined from the repetition period of the pulse.

The output pulse (P, ) of the first sensor (66a) is phase-compared with a reference pulse in a phase comparator (70). The reference pulse is provided from a pulse oscillator (71) via a frequency divider (72).The error signal is output from a six-phase comparator (70) and is sequentially passed through a low-pass filter (73) and an A/D converter (74).
It is taken into the microcomputer (69) through. Microcomputer (
69) provides 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, during that time, the encoder (62) and phase comparator (7
0), a microcomputer (69), and a drive circuit (75) form a PLL loop, and the rotational speed of the motor (61) is controlled so that the error signal becomes zero. As a result, the optical system (28) is maintained at a constant speed while traveling in the image reading area. At this time, signal data dependent on the phase error signal is held in the microcomputer (69) and is used to determine the brake timing as described later. The motor drive circuit (75) is connected to a DC power source (
77) connected to four transistors (Ql) to (G
4). The control signal given to the bases of these transistors (Q,) to (G4) is a PWM signal given from the microcomputer (69). When the motor (61) is rotated forward, the transistor (+11
) (G4) is on, transistor (Qz) ([1s
) turns off and current (It) flows, and when inverting, transistor CQt) (Ql) turns on, transistor (I) (G4) turns off and current (I2) flows in the opposite direction.
) flows. When applying the brake during reversal, the same current (1+) flows as during forward rotation.

Here, when the traveling optical system (28) scans a document, it moves to the right in FIG. 9, and 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) passes through the forward rising portion (A) and enters the constant speed region (B).
There are image reading areas (G1) to (G2). At the return position (R), the motor (61) receives a positive current (
Since a current (I z) in the opposite direction is supplied instead of I1), the motor (61) rapidly reverses and the traveling optical system (28
) is in the return movement state. Here, in order to correctly stop the traveling optical system (28) at the home position (H), the brake timing, that is, the brake point must be set correctly.

This brake point (therefore, brake timing) is set as follows in this embodiment.

First, as mentioned earlier, when the traveling optical system (28) is traveling between the image reading areas (G, line (76) in response to the error signal from the comparator (70).
) outputs a PWM signal as shown in FIG. However, unless there is a value exceeding a predetermined darkness value, the overall average is taken, and the brake point shown in FIG. 4 is set based on the average value. At this time, if the moving load is large on average, the return characteristic will be (RT I ), and if the moving load is small to the average value, the return characteristic will be (RTg), so the appropriate braking point in each case is (BP , ), (
Bh). Note that the calculation of the brake point is performed by the microcomputer (69) based on the average value.

The brake timing determined as described above is reflected in the control signal given from the microcomputer (69) to the motor drive circuit (75). That is, during the return movement, the second
The timing of switching from the state where the reverse direction current (I2) is flowing to the state where the forward direction current (11) is flowing is executed by the brake point.

Instead of monitoring the duty of the PWM signal described above, the magnitude of the current (I1) that is the output of the drive circuit (75) may be monitored to form signal data for brake timing. When doing so, the current value is A/D converted and provided to the microcomputer (69).

Further, instead of the PWM signal, the signal data may be formed by monitoring a digital signal input from the A/D converter (74) to the microcomputer (69).

Next, the flowchart of FIG. 6 showing the operation of checking the moving load and calculating its average data, and the flowchart of FIG. 7 showing the operation of deriving the brake point will be explained.

First, in FIG. 6, in step (Ill), the traveling optical system (2
Determine whether or not 8) is forward running, and NO.

If so, proceed to (I7) and end the flow, but YES
If so, in (112) it is determined whether the traveling optical system (28) is in the image reading area (G1) to (at). Here, if NO, skip to (I7) and select YES.
If so, the process goes to (113) and the duty of the PWM signal is stored in the memory one by one. Then, in (I4), it is checked whether or not there is a large difference between the stored values.

Specifically, this check is performed by checking whether any of the duties exceeds a predetermined darkness value. Here, if it is determined that there is a large difference (there is something that exceeds the dark value), a flag to that effect is set in (16). If it is determined that there is no significant difference, the average value of all the stored duty values is calculated at (+15) and the operation flow ends.

On the other hand, in the operation flow shown in FIG. 7, it is determined in step (K1) whether the traveling optical system (28) has reached a predetermined distance. Here, the predetermined distance refers to point (J) in Fig. 4. When the traveling optical system (28) reaches point (J), the next (K2)
) to check whether the flag is set. This flag is the flag set at step (I6) in FIG. 6 described above. If the flag is not set, a brake start point that matches the average value is calculated using (K,). If the flag is set, the process proceeds to (K4) where a slow return is instructed and an abnormality sign is displayed on the display means.

At this time, maintenance-free operation can be expected if a mechanism is provided to drop oil droplets or the like on the rod (45) or rail (59) on which the traveling optical system (28) slides. the above(
After I3) and (K4), the return operation starts at (K,), and the operation flow ends at (K,).

FIG. 8 shows that the return time can be shortened with this configuration. In other words, in the conventional case, even when the load is heavy, the brakes are applied quickly by the uniformly determined brake point (BPo), and the low speed constant speed region (T, ) before the home position becomes longer, resulting in a lower overall return. Although the time is longer, in this configuration, the point at which the brake is applied is late as shown in (BP), so the vehicle enters a low constant speed region just before the home position, and the time in this constant speed region (i't) is short. , the overall return time is shortened.

In the above embodiments, the PLL loop operates only in the image reading area, but it goes without saying that the PLL loop may also operate during the return operation.

The present invention is applicable not only to an image forming apparatus having an optical system of the mirror scan type described above, but also to an image forming apparatus whose optical system uses a document table moving type.

According to the present invention, even if the rods and rails that make up the travel path for the optical system become dirty and the moving load becomes heavy, appropriate braking control can be performed accordingly. Therefore, it becomes possible to accurately stop the optical system at the home position.

Further, in an image forming apparatus that performs a low constant speed return before the home position in the return operation, the constant speed return time can be shortened, and the overall return time can be shortened in general.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram of an image forming apparatus embodying the present invention, FIG. 2 is a detailed diagram of a part thereof, FIG. 3 is a schematic diagram of a part of the apparatus, and FIGS. 4 and 5. is an explanatory diagram, FIGS. 6 and 7 are flowcharts of the operation, and FIG. 8 is an explanatory diagram. FIG. 9 is a schematic diagram showing an outline of a conventional electronic copying machine, and FIG. 10 is an exploded perspective view of its main parts. (28) - Traveling optical system, (61) - Motor. (62)...-Encoder, (69)...-Microcomputer. (70) - Phase comparator, (75) - Motor drive circuit. (BP) (BPI) (BP-brake point. Applicant: Mita Kogyo Co., Ltd. Figure 5 Figure 61"!! Figure 7

Claims (5)

[Claims] (1) The optical system for reading the document starts from the home position, reaches a predetermined speed, travels through the image reading area at the predetermined speed, and then returns at a predetermined point and returns to the home position again. In order to operate the optical system, the motor includes a motor for driving the optical system, an encoder that outputs a signal corresponding to the speed of the motor, a phase comparator that compares the output of the encoder with a reference value and outputs an error signal, and a motor for driving the optical system. An image forming apparatus comprising: a control circuit that controls a drive circuit and provides a control signal based on an output of the phase comparator to the motor drive circuit when traveling in the image reading area;
An image forming apparatus comprising: a braking control means for controlling braking based on signal data dependent on the output of the phase comparator when traveling in the image reading area. (2) The image forming apparatus according to claim 1, wherein the optical system is a traveling optical system of a mirror scan type. (3) The image forming apparatus according to claim 1, wherein the signal data is a duty of a pulse width modulation signal as a control signal output from the control circuit. (4) The image forming apparatus according to claim 1, wherein the signal data is a current value of the motor drive circuit. (5) The image forming apparatus according to claim 1, wherein the control circuit is a microcomputer, and the braking control means is a functional means formed within the microcomputer.