JP2637455B2 - Image reading device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus, and more particularly to an image reading apparatus using a pulse motor for driving a load for reading an image.

2. Description of the Related Art Conventionally, there are many apparatuses using a pulse motor as a drive source for driving a load for reading an image. In this case, it is an essential technique to drive the pulse motor by throwing it up. Further, since a large torque is required at the time of driving the load, a system in which constant current driving is performed and a large amount of current flows only during throw-up has already been proposed.

[Problems to be solved by the invention]

However, in the above conventional example, since a large amount of current flows from the initial stage of the throw-up, the torque of the motor is extracted more than necessary, which leads to a rise in the temperature of the motor, and the life of the motor may be reduced. There was a problem.

Further, when the current is reduced in order to suppress the temperature rise and noise of the motor, there is a disadvantage that the motor must have sufficient torque and the cost is high.

[Means and actions to solve the problem]

According to the present invention, by switching the drive current in accordance with the sleed of a pulse motor, it is possible to reduce the temperature rise and noise of the motor, and to drive the motor stably at low cost and cost. It is.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings, taking a copying apparatus embodying the present invention as an example. FIG. 1 is a sectional view of the entire copying apparatus according to the present embodiment. In FIG. 1, the drive system is divided into a main drive system for driving a paper feed unit, a transport unit, a photoconductor, and a fixing unit, and an optical drive system for driving an optical system. An AC synchronous motor 25 is used as the main drive source, and a pulse motor (stepping motor) 26 is used as the optical drive source.

As the paper feeding method, paper feeding from the cassette 23 or paper feeding from the manual feed unit 24 can be selected. When feeding paper from a cassette, the cassette
The state is managed by a switch group 31 for detecting the presence and absence of a switch 23 and a switch group 31 for detecting the size of the cassette and a switch 37 for detecting the presence or absence of paper in the cassette, and when an abnormality is detected by the switch, a display unit to be described later is used. To be displayed. In the case of manual paper feed, the status is managed by a switch 32 for detecting the status of the manual feed guide 24, and when an abnormality is detected, it is displayed on a display unit described later.

The photoreceptor 12 rotates clockwise. Primary charger
The potential charged on the photoreceptor 12 by the exposure unit 13 is exposed at an exposure position, which will be described in detail later, is developed by a development unit 15, and is transferred to a transfer paper sent from a paper supply unit by a transfer unit unit 14. Transcribe After transfer, the photoconductor 12 is cleaned of residual toner by a cleaning unit 38, and
The process of removing the residual potential by the pre-exposure lamp 16 and forming an image again is repeated.

The transfer paper on which the image has been transferred is transported to the fixing unit 21 on the transport belt of the transport unit 20. The fixing unit 21 includes a heat roller 35 'having a surface on which a temperature detecting element (thermistor) 35 is disposed, and a roller which is pressed against the roller and has a resilient surface. The heat roller 3
5 'uses a halogen lamp as a heat source, and the halogen lamp is built in the roller axial direction. The halogen lamp is controlled by a thermistor so that the surface temperature of the heat roller 35 'becomes a predetermined temperature.

The paper that has passed through the fixing unit 21 is discharged from the fixing unit 21 by a discharge roller 22 and is stored on a discharge tray 39.

The paper discharge sensor 34 is a sensor for detecting whether or not the transfer paper has normally passed through the fixing unit 21.

The drive source of the optical drive system is the pulse motor 26 as described above. This driving source will be described later in detail with reference to FIG.
The pulse motor 26 is configured to drive a completely different load by operating the drive switching solenoid 27. One load is a unit constituting the exposure lamp 4 and the first mirror 5, the second mirror 6, and the third mirror 7, and the other load is a unit constituting the zoom lens 8. These loads that do not need to be driven synchronously can be driven by a common drive source.

This apparatus uses a pulse motor 26 of an optical drive unit to control the position of the zoom lens 8 and the multi-stage magnification selection function by controlling the speed of the lamp systems 4 to 7, and also reflects the reflected light of the original placed on the original glass 3 surface. The function of automatically selecting the density by the optical sensor 40 to be detected, the function of automatically selecting the copy magnification (with communication means) by contact with an external device (not shown), and the occurrence of an abnormality such as paper jam Memory back-up function for storing the remaining states, such as the remaining number of sheets, magnification value, abnormal information, etc., the page continuous shooting function by controlling the position of the exposure lamp 4 by the pulse motor 26, and the developing unit 15 A plurality of color images can be formed by replacing the developing unit 15. By providing a switch 36 for detecting the replacement of the developing unit 15, a function for switching control depending on this state is provided. To have. Next, the operation of the present apparatus will be described.

A power cord (not shown) of the apparatus is connected to a predetermined power supply. FIG. 2 shows an operation panel of the present apparatus, which is arranged on the upper surface of FIG. When the I side of the power switch 51 is pressed, power is supplied to the apparatus. At the same time, the power indicator 52 is lit.

In the initial state after the fixing unit 21 is turned on after the power supply of the thermistor 35 is turned on, it detects that the heat roller 35 'has not reached a predetermined temperature, and controls lighting of a fixing heater (not shown) as a heat source. When the power is turned on, the display on the operation panel is set in the standard mode as follows. The number display 59 displays 1, the magnification display 67 displays the same magnification, and the automatic density adjustment display 76
A is turned on.

The display of the start key 56 is displayed in red when the temperature inside the fixing unit has not reached the feasible temperature, and when the temperature reaches the feasible temperature, the display is switched to green and copying operation is enabled. Display that Normally, all other indicators are turned off.

The fixing temperature of the fixing unit 21 depends on the developing unit.
The temperature differs depending on the type of the developing unit 15, and the set temperature is switched by determining the type of the developing unit 15 by a switch 36 provided on the developing unit 15. Further, when the temperature must be lowered from a high state, a means for forcibly cooling by the in-machine cooling FAN 28 is provided to achieve the fixing temperature quickly.

Next, the operation of the optical drive system after the power is turned on will be described. The exposure lamp systems 4 to 7 move the original on the original glass 3 to the first position.
The original is scanned and moved rightward from the left end of the figure, and the original image is moved through the first mirror 5, the second mirror 6, the third mirror 7, the zoom lens 8, the fourth mirror 9, the fifth mirror 10, and the sixth mirror 11. The document exposure on the photoconductor 12 is executed. That is, the movement start point is set to the left end. This position is called the home position (HP). HP
The HP sensor 29 is provided to detect the pressure. If the position of the exposure lamp 4 is not detected by the HP sensor when the power is turned on, the control unit of the one-chip microcomputer shown in FIG. (A known technique is used for the forward / reverse rotation control of the pulse motor). The start of the rotation control will be described with reference to FIG. 5. First, when the drive switching solenoid 27 is in the off state (there is no force b '), the switching gear moves in the direction A by spring pressure. Thus, the output of the pulse motor 26 is connected to the lamp driving gear via the switching gear, and the exposure lamp units 4 to 7 are driven. At the time of this gear connection, when the switching gear and the lamp driving gear are fitted, control is performed such that the rotation speed of the pulse motor 26 is sufficiently reduced.

If exposure units 4-7 are located at HP,
The pulse motor 26 drives the zoom lens unit 8.
That is, the position of the zoom lens before the power is turned on is unknown. As described above, when the power is turned on, the equal magnification value is selected as the standard mode. Therefore, an operation of temporarily returning to the reference position and setting a predetermined position from that point is executed.

The above reference position is the zoom lens home position (Z.
HP). A Z.HP sensor 30 for detecting this position is provided. The operation will be described with reference to FIG.

The drive switching solenoid 27 is turned on. This causes the plunger of the solenoid to move in the direction b. For this reason,
The switching gear moves in the direction B against the spring force by the force b '. By this movement, the fitting of the switching gear and the lamp driving gear is released. By further moving in the direction B, the switching gear engages with the lens driving gear. The rotation control at the time of gear engagement is the same as described above.

The zoom lens 8 has a magnification of 200% when the lens position is near the Z.HP sensor with the Z.HP sensor as a reference position.
Therefore, the position control is performed within a range of a reduction ratio of 50% when moving further to the right.

At the start of driving the zoom lens, the operation is determined as follows depending on the state of Z.HP.

(1) When the position of the zoom lens 8 is detected by the Z.HP sensor.

(1) -1 Move the zoom lens 8 to the right once, move it out of the range where the Z.HP sensor does not detect, and stop.

(1) -2 Move to the left and move a predetermined distance from the point when the Z.HP sensor detects, and stop.

However, if the Z.HP sensor has not detected the position of the zoom lens, execution is started from the operation (1) -2.

The above operation is a control necessary for preventing a set position error due to a backlash of gears.

Thereafter, the zoom lens 8 is moved to the right again, and the zoom lens 8 is moved from the position where the Z.HP sensor is released to a predetermined position.
In other words, in the case of the setting of the standard mode, it moves to the position corresponding to the equal magnification and stops. Thereafter, the drive switching solenoid 27 is turned off. As a result, as described above, the switching gear
It moves in the direction to be fitted with the lamp driving gear. However, for smooth fitting, it is necessary to rotate the switching gear as described above. At this time, the exposure lamp units 4 to 7 are in H.P29. Therefore, pulse motor 2
Numeral 6 rotates the exposure lamp units 4 to 7 in a direction to move them rightward. As a result, the exposure lamp units 4 to 7
Stops rotating at the point in time when it is disengaged from the HP sensor 29 (meaning that the switching gear and the lamp driving gear have been fitted), rotates again in the opposite direction, and stops at a predetermined position after detecting the HP sensor 29.

The initial operation of the optical drive system described above and the fixing unit 21
, The preparation for the copying operation of this apparatus is completed.

Next, a copying operation based on paper feeding from the cassette 23 will be described.

When the copy start key 56 is pressed, the transfer paper size data based on the input signal of the switch group 31 for detecting the cassette size, the number data set by the number key 54, and the magnification selection keys 61, 62, 64, 65, 66 The copying operation starts based on the magnification data and other data from various mode selection means.

When the copy start key 56 is accepted, the display changes from green to red, the numeric key 54, the magnification keys 61, 62, 64, 65, 66
And the like, mode input is prohibited. The main drive motor 25 starts rotating, and the driving force is transmitted to the sheet feed roller 18, the photoconductor 12, the transport unit 20, the fixing unit 21, and the like.

When the copy key 56 is received, the fixing temperature of the fixing unit 21 is switched according to the cassette size data.

At 0.5 sec after the start of rotation of the main drive motor 25, a paper feed solenoid (not shown) is operated, and the paper feed roller 17 is rotated accordingly, and the transfer paper in the cassette 23 is fed out toward the paper feed roller 18. . The transfer paper feed amount of the paper feed roller 17 is controlled by cassette size data. That is, when the transfer paper is larger than the predetermined value, the feed amount is increased. When the transfer paper reaches the paper feed roller 18, the transfer paper is fed to the registration roller 19 by the paper feed roller 18 and stops when the transfer paper arrives. Paper feed roller 18 and registration roller
The manual feed switch 33 disposed between the transfer paper 19 and the printer 19 detects the transfer state of the transfer paper.

At a predetermined timing until the transfer paper is fed on the paper feed path and reaches the registration roller 19, the start of the original scanning by the exposure lamp units 4 to 7 is permitted. At this time, the exposure lamp is at a position detected by the HP sensor 29.
More specifically, at the time of the initial operation or the backward movement of the copy operation, the vehicle stops at a position backward from the position where the HP sensor is detected by a distance corresponding to the selection magnification at that time.

Upon the start of document scanning, the pulse motor 26, which is the optical system drive source, changes the pulse rate in the direction in which the exposure units 4 to 7 move forward (to the right) until the drive pulse rate corresponding to the selected magnification value is reached. Gradually increases (referred to as slow-up control). That is, the moving speed is gradually accelerated and reaches the target speed. Although not particularly shown, the pulse motor drive circuit of the present device employs a constant current control method and a configuration in which the drive current value can be switched to a plurality of stages (two stages in the embodiment) (see FIG. 3). It is selected by the PB4 output signal of the optical drive pulse motor control signal).

In general, the characteristics of the pulse motor are such that the pull-in torque decreases as the pulse rate increases. Therefore, means for switching the constant current set value is provided, and the current value is switched as necessary.

In the present apparatus, the constant current is reduced during a relatively low pulse rate from the start of movement, and control is performed so that the set current value is increased when the speed exceeds a predetermined value. Control is performed to lower the set current value again with the passage of time. This is mainly aimed at preventing noise, temperature rise and step-out phenomenon of the pulse motor.

Next, a method of forming a margin at the leading end of an image and a method of aligning the leading end with a transfer sheet will be described with reference to FIG.

LED as a means to prevent toner adhesion in non-image areas
Although a static elimination means using a light source such as a lamp or a fuse lamp is generally used, this apparatus achieves the same effect by controlling the voltage value of the grid 13 'provided with the primary charging unit 13. This is an important method in the current situation where it is difficult to arrange a plurality of members around the photoconductor due to the miniaturization of the apparatus. The distance e between the exposure point and the grid cannot be set short enough compared to the distance b between the HP sensor 29 and the document abutment position.
In order to form 2 mm, the grid is switched from the L level to a predetermined voltage after a predetermined time corresponding to the magnification selection value from the start of the movement of the exposure lamp 4. That is, when the grid voltage is at the L level, a potential is not charged on the photoreceptor, so that a toner image is not formed, and an image is formed from the timing when the voltage is switched to the predetermined voltage. To form a margin.

Next, regarding the leading edge of the image with the transfer paper, the distance c between the exposure point and the transfer section is shorter than the distance d between the registration roller 19 and the transfer section. Therefore, before the image at the leading end of the document is actually exposed on the photoreceptor 12, it is necessary to re-feed the transfer paper waiting on the above-described registration roller 19 and feed it toward the transfer unit.

In this apparatus, the exposure lamp 4 starts moving and the exposure lamp 4
Is reached by the HP sensor 29 when the vehicle reaches the target speed. The time required for the exposure lamp 4 to reach the edge of the white plate after passing the HP sensor 29 is the value obtained by dividing the value of the distance b + 2 mm by the selected magnification from the timing of passing the HP sensor 29. And this time is x
And

Also, the value obtained by subtracting the time required for the image at the exposure point of the photoconductor 12 to reach the transfer portion from the time from the start of refeeding by the registration roller 19 to the transfer sheet reaching the transfer portion is defined as y. , The time required to feed the transfer paper 2 mm to this y (2 mm
÷ 100mm / s = 0.02sec… Transport speed = 100mm / s) is added.
The above values are calculated by the following equation.

x- (y + 0.02) = Z (sec) In other words, when the registration roller 19 is operated at the timing when the above equation value Z has passed since the passage through the HP sensor 29 and refeeding is performed, the selected magnification is obtained. Accordingly, a transfer paper image having a margin of 2 mm is obtained.

The scanning distance of the exposure units 4 to 7 moves a predetermined distance in accordance with the cassette size data, magnification data, and the like. When the scanning unit reaches the target position, the pulse rate is gradually reduced (referred to as slowdown control), and after stopping, the HP is returned again. Slow-up control and constant speed control are performed in the direction of the sensor 29 to move backward. And HP sensor 2
At the time point when 9 is detected, slowdown control for stopping at the position corresponding to the selected magnification is performed, and the exposure units 4 to 7 are stopped.

The operation of the manual feed copy is started when the manual feed sensor 33 detects the inserted transfer paper. The main drive motor 25 starts rotating, whereby the paper feed roller 18 rotates. Thus, the inserted transfer paper is fed by the paper feed roller 18 toward the registration roller 19.
Also, after a predetermined time from the time when the manual feed sensor 33 detects the transfer sheet, the start of the original scanning by the exposure lamp units 4 to 7 is permitted. Subsequent operations of the exposure lamp system and the leading edge of the transfer paper are the same as those in the case of cassette paper supply, and thus description thereof is omitted. Next, when the time x ′ required for the transfer paper to pass the distance between the manual feed sensor 33 and the transfer portion has elapsed from the time when the rear end of the transfer paper has passed the manual feed sensor 33, the operation of the registration roller 19 is started. Stop. However, if the manual feed sensor 33 detects the next paper while the above x 'is being counted, the registration roller is set when the time required for the transfer paper to pass the distance between the manual feed sensor 33 and the registration roller 19 has elapsed. Stop the operation of 19.

In addition, the control of the scanning distance of the original is also executed by the rear end signal of the transfer paper. The control operation described above is controlled by the one-chip microcomputer shown in FIG. To Q ₁ Figure 3 shows a ROM, and a one-multichip microcomputer of RAM built. FIG. 4 shows the basic configuration of this microcomputer program. The detailed description of FIG. 4 is omitted.

Next, the control operation of the optical system in this embodiment will be described with reference to the flowchart of FIG. This flow chart is executed by the one-chip microcomputer shown in FIG.

First, when the copy start key 56 of the copying apparatus is pressed (S1), the set speed V of the pulse motor is obtained from the set magnification input from the magnification setting keys 61, 62, 64, 65, 66 (S2).

Here, the set speed V is set faster in the reduction mode than in the 1 × mode, and is set slower in the enlargement mode than in the 1 × mode. This is because the rotation speed of the photoconductor 12 is kept constant.

Then starts a pulse motor (S3), smaller it is determined whether than the predetermined speed [nu ₀ setting speed V is (S4). Here, the predetermined speed ν ₀ is the speed at the point where the current is switched during the slow-up. When setting speed V in this S4 is smaller than the predetermined speed [nu ₀ proceeds to S13.

FIG. 8 is a diagram showing the relationship between time t and the speed of the pulse motor, and the relationship between time t and the drive current of the pulse motor.

If it is determined that V <[nu ₀ in S4 is the case of V ₂ of Figure 8. In this case, even Suroatsupu during and Suroatsupu after speed becomes constant at V _2, the driving current i ₂ to the motor is constant.

When the end of the slow-up is determined in S13, the process proceeds to S10, and the optical system is caused to travel a predetermined distance. If it is determined in S11 that the vehicle has traveled a predetermined distance, the process proceeds to S12 and the optical system is moved to a predetermined position (H
・ Return to P).

Next, setting speed V in S4 will be described greater than a predetermined speed [nu _0.

In this case, the speed of the pulse motor in S5, it is determined whether or not exceeds the predetermined speed [nu _0, increasing the the drive current exceeds a predetermined speed [nu _0. Then, in S7 until it is determined Suroatsupu terminated (until V ₁₎ performs Suroatsupu.

When the end of the slow-up is determined, the timer is started in S8. When the timer is a predetermined period of time (t ₀ seconds) has elapsed (S9-
1) The drive current of the pulse motor is reduced (S9-2), and the optical system is caused to travel a predetermined distance in S10. After traveling a predetermined distance (S11)
Returns the optical system to the predetermined position (HP).

FIG. 9 shows a diagram in which a pulse motor drive current switching detection sensor 80 is provided in the scanning path of the optical system.

FIG. 10 is a flowchart showing the control operation of the optical system in the case shown in FIG.

In the flowchart of FIG. 7, the point at which the current is reduced after the set speed V has been reached is a predetermined distance using a timer. In the flowchart of FIG. 10, a marker (flag) provided in the optical system is provided. ) Is detected (the point at which the speed of the optical system is stabilized) to reduce the drive current.

In the flowcharts of FIGS. 7 and 10, the same step numbers perform the same control, and the description thereof will be omitted.

As described above, according to the present embodiment, the drive current to the pulse motor that drives the optical system is changed according to the moving speed of the optical system that changes based on the set magnification. This makes it possible to control the drive current optimally according to the moving speed of the optical system.

Moreover, when the speed exceeds a predetermined speed during the slow-up of the motor, the torque of the motor can be increased by increasing the drive current.

Also, instead of reducing the drive current immediately when the set speed is reached after the end of slow-up,
Alternatively, by reducing the drive current at a point where the speed of the optical system is stabilized by the sensor, the load can be driven by an inexpensive pulse motor without increasing the required torque of the pulse motor too much.

In addition, in the present embodiment, the drive current is reduced as necessary, so that the temperature rise and noise of the motor can be suppressed.

Although the present embodiment has been described by taking a copying apparatus as an example, the present invention can be similarly applied to other image forming apparatuses.

〔The invention's effect〕

As described above, according to the present invention, by switching the drive current in accordance with the speed of the pulse motor, it is possible to suppress the temperature rise and noise of the motor,
The motor can be driven stably at low cost.

[Brief description of the drawings]

FIG. 1 is a view showing a copying apparatus according to an embodiment of the present invention, FIG. 2 is a view showing an operation panel of the apparatus, and FIG. 3 is a one-chip microcomputer for performing all control of the apparatus. FIG. 4 is a diagram showing a basic configuration of a program of the one-chip microcomputer of FIG. 3, FIG. 5 is an explanatory diagram for switching a load driven by a pulse motor, and FIG. 6 is an image 7 and 10 are control flow charts showing the operation of the optical system in the present embodiment, and FIG. 8 is a time chart of the pulse motor. FIG. 9 is a diagram showing an embodiment in which a sensor is provided to detect that the moving speed of the optical system is stabilized. 4 Exposure lamps 5, 6, 7, 8, 9, 10, 11 Mirror 12 Photoconductor 13 Primary charger 14 Transfer unit 15 Developing unit 20 Transport unit 21 Fixing unit 26 Pulse motor 27 Drive switching solenoid 29 H / P sensor 80 Current switching point detection sensor

Continuation of the front page (56) References JP-A-59-202448 (JP, A) JP-A-63-154083 (JP, A) JP-A-63-94453 (JP, U)

Claims (1)

(57) [Claims] 1. A driving means for driving a load for reading an image by a pulse motor, a starting means for starting a pulse motor by a slow-up, and a drive current for the pulse motor when the speed reaches a preset value during the slow-up. An image reading apparatus comprising: a first switching unit; and a second switching unit that switches a drive current when a predetermined time has elapsed after a predetermined speed has been reached.