JPH0727173B2 - 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, and more particularly to braking of an optical system.

2. Description of the Related Art FIG. 6 schematically shows 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 section (2), an exposure section (3), an LED (5) for partial image erasing, a developing section (6), a transfer section (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 800 V 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 unit (6) stirs the toner and the carrier (iron powder) replenished from the hopper (12) via 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 unit (8) serves to separate the transferred sheet from the drum (1) by releasing an electrostatic attraction state between the drum (1) and the sheet 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. 7 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 (4
3) (44) reciprocates in the (F) direction. (57) (5
8) is a fixing means for fixing the end portion of the rod bar (45) to the main body of the copying machine. (59) is the first and second moving frames (43)
It is a rail that slidably supports the other end of (44).

(60) is a fixedly arranged PI for forced return, which is also shown in FIG. 6, 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 As described above, the brake timing during the return operation in the conventional example is performed by the output of the brake timing PI or is determined by the output of the timer counter. Are fixed.

However, if the weight of the traveling optical system changes due to the exchanging of the traveling optical system, or if the moving load changes due to dirt on the rod rod (45) or rail (59), the braking ability will change relatively. With the brake timing of, the vehicle will not stop exactly at the home position.

The present invention has been made in view of the above circumstances, and is an image capable of accurately stopping the traveling optical system at the home position even when the weight or the moving load of the traveling optical system changes. An object is to provide a forming device.

Means for Solving the Problems In order to achieve the above object, in the present invention, an optical system for reading a document image is operated so as to start from a home position, return at a predetermined point, and return to the home position again. ,
An image forming apparatus comprising: a motor for driving the optical system; an encoder that outputs a signal according to the speed of the motor; and a control circuit that gives a control signal to a motor drive circuit based on the output of the encoder. The circuit is configured to have a brake timing determining means for calculating the acceleration of the motor at the time of starting from the home position based on the output of the encoder and determining the brake timing based on the acceleration.

Action With such a configuration, the optical system can accurately stop at the home position. In addition, even if the optical system is exchanged with an optical system of a different weight or the moving load increases due to the contamination of the rod rod, this configuration will not affect the moving load when the optical system starts to move. Since the corresponding brake timing is set, accurate stopping at the home position is realized.

Embodiments Embodiments 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 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 causes a phase difference of 90 ° from each other at a specified rotation speed of the motor. Generate pulse (P ₁ ) (P ₂ ). It should be noted that these sensors (66a) and (66b) generate 400 pulses per one rotation of the motor at the specified rotation speed of the motor. The output pulses (P ₁ ) and (P ₂ ) of the first and second sensors (66a) and (66b) are given to the rotation direction detection circuit (68) to determine whether the rotation is the forward rotation or the reverse rotation. The discrimination output is a microcomputer (hereinafter referred to as "microcomputer") (6
Given to 9).

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. 6 and 7) and determine the current velocity from the pulse repetition period. Further, the brake timing during the return operation is determined as described later.

(70) is a motor drive circuit, and as shown in FIG. 2, four transistors (Q ₁ ) to the DC power source (71) are connected.
(Q ₄ ) The control signal given to the bases of these transistors (Q ₁ ) to (Q ₄ ) is given from the microcomputer (69). When rotating the motor (61) forward, the transistors (Q ₁ ) (Q ₄ ) are on, while the transistors (Q ₂ ) (Q ₃ ) are off, current (I ₁ ) flows. (Q ₂ ) (Q ₃ ) is on, the transistors (Q ₁ ) (Q ₄ ) are 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. 6, 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 area (73) through the forward rising portion (72), and the image reading is performed in this constant velocity area (73). 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 brake point (B) must be set correctly. If the brake is applied at a point (B ₁ ) earlier than the correct brake point (B), the traveling optical system (28) will stop before the home position (H) as shown at (H ₁ ) and conversely the point (B). If the brake is applied later (B ₂ ),
This is because the vehicle will stop at a point past the home position as shown in (H ₂ ).

This brake point (hence brake timing) is set as follows in this embodiment. First, at the time of forward rising, as shown in FIG. 5, the speed (V ₁ ) (V ₂ ) of the motor (61) at at least two points (t ₁ ) (t ₂ ) is changed to the output pulse ( _second ) of the second sensor (66b). Calculated in the microcomputer (69) based on P ₂ ). The velocity in this case may be an angular velocity. Then, speed (V ₁ ) (V ₂ ) and time (t ₁ )
The acceleration (α) of the motor (61) at the time of forward rising is calculated based on (t ₂ ). Then, the brake timing, that is, the brake point (B) is calculated based on the acceleration. This is based on the recognition that the ability of the motor (61) to start the traveling optical system (28) (acceleration × mass) and the ability to stop the traveling optical system (28) have a certain similar relationship. The motor (61) rotates at full power at the time of forward rising, and works at full power at the time of braking.

The braking timing determined as described above is reflected in the control signal given from the microcomputer (69) to the motor drive circuit (70). That is, the timing for switching from the state in which the reverse current (I ₂ ) flows in FIG. 2 to the state in which the forward current (I ₁ ) flows during the return movement is executed by the above-mentioned determined brake timing data. Of.

In the present embodiment, the calculation of the acceleration and the determination of the brake timing described above are configured to be performed for each moving operation of the traveling optical system (28), but it is not always necessary to do so and the traveling optical system (28) It may be performed every predetermined number of movements.

It goes without saying that the present invention can be applied not only to the above-described mirror scan type optical system but also to an image forming apparatus or the like in which the optical system is a document table moving type.

EFFECTS OF THE INVENTION According to the present invention, since the brake timing is set according to the moving load at the time of moving up of the optical system, the conditions are changed when the specifications are changed by exchanging the optical system or when the rod rod is dirty. Even in the case of such a case, there is an effect that an optimum brake timing can be realized and the vehicle can accurately stop at the home position, which is extremely useful.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an image forming apparatus embodying the present invention, FIG. 2 is a partial circuit diagram thereof, FIG. 3 is a partial schematic diagram thereof, and FIGS. 4 and 5 are FIG. FIG. FIG. 6 is a schematic diagram showing an outline of a conventional electronic copying machine,
FIG. 7 is an exploded perspective view of the main part. (28) …… Running optical system, (61) …… Motor, (62) ……
Encoder, (69) …… Microcomputer, (70) …… Motor drive circuit, (H) …… Home position, (B) …… Brake point.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-60-59342 (JP, A) JP-A-58-220138 (JP, A) JP-A-60-262147 (JP, A) JP-A-59- 29238 (JP, A) JP 61-145541 (JP, A) JP 62-178228 (JP, A)

Claims (3)

[Claims] 1. A motor for driving the optical system and a speed of the motor for operating an optical system for reading an original image so as to start from a home position, return at a predetermined point, and return to the home position again. In an image forming apparatus including an encoder that outputs a signal according to the above, and a control circuit that gives a control signal to a motor drive circuit based on the output of the encoder, the control circuit controls the acceleration of the motor at the time of starting from the home position. An image forming apparatus comprising: a brake timing determining unit that calculates a brake timing based on an output of the encoder and determines a brake timing based on the acceleration. 2. The control circuit is composed of a microcomputer, and the brake timing determining means is a functional means formed in the microcomputer. Image forming apparatus. 3. The image forming apparatus according to claim 1, wherein the optical system is a mirror scan type traveling optical system.