JPH01306830A - Image reader - Google Patents

Abstract

PURPOSE:To rationally evade a collision between an optical system and a sensor supporting arm by providing the rocking center of the sensor supporting arm on the side of a reference end for aligning original edges and a spring member energizing the center toward a retreat position. CONSTITUTION:The rocking center is provided on the side of the reference end A used for aligning originals and at the position retreating from underneath an original platen glass 16. The title reader is provided with the sensor supporting arm 40 longitudinally equipped with at least one of original discriminating sensors 46-49, a rocking and driving means rocking the sensor supporting arm 40 between the position below the original platen glass 16 and the position retreating therefrom, and the spring member 41 returning the sensor supporting arm 40 to the retreat position when the rocking and driving means is turned off. Since the sensor supporting arm 40 has its rocking center on the side of the reference end and energized by the spring member 41 toward the retreat position, the optical system rocks the sensor supporting arm 40 toward the retreat direction, while moving, to evade the collision which may damage both of them.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image reading device that optically scans a document placed on a document table glass to read a document image, and particularly relates to a device for reading a document image. This invention relates to the improvement of a device that detects document properties such as document size and density prior to document processing.

Conventional Technique ■ When reading a document image, it is necessary to detect the document size and image density in order to set the scanning range and light amount of the optical system.

For example, conventional methods for detecting the size of a document include a method in which a CCD itself for reading an image performs a preliminary scan, and a method in which a sensor for detecting the size of the document is separately provided below the surface of the document placement glass.

However, the method of pre-scanning the COD has the problem that the copying time becomes longer due to the time required for the pre-scanning, and the copying speed becomes slower.Also, in any of the above methods, if the lower surface of the document holding cover is different from the background color of the document, There is a problem in that the size of the document cannot be determined unless it is set aside.

In order to solve these problems, the present applicant has provided an arm equipped with an image size determination sensor so as to be swingable between a position below the document platen glass and a position evacuated from there.
We have devised a technique in which this arm is swung below the document platen glass when the document holding cover is opened, and the document size is detected by a sensor.

By the way, according to the technique of swinging the sensor support arm mentioned above, it is possible to perform a preliminary scan with the optical system as in the conventional technique, or to change the color of the lower surface of the document holding cover to the background color of the document. However, if the sensor support arm is not retracted to the retracted position due to a malfunction in the means for swinging it, or if the reading optical system goes out of control, the optical system and sensor support arm may be damaged. There is a problem in that they collide and one or both of them are damaged.

The present invention solves these problems by rationally selecting the swing center position of the sensor support arm, and by providing a spring member that urges it to the retracted position, thereby ensuring that the sensor support arm does not retract incorrectly. It is an object of the present invention to provide a useful means that can prevent damage caused by a collision even if an optical system runs out of control.

In order to achieve the above-mentioned object of reducing the size of the document, the present invention provides an image reading device that optically scans a document placed on a document platen glass to read the document image. A sensor for document discrimination such as density can be oscillated between a position below the document glass and a position retracted from the document glass, and the center of the swing is at the document alignment reference edge side and a position retracted from the document glass. and the sensor is provided with at least one
at least one sensor support arm provided along the longitudinal direction; a swing drive means for swinging the sensor support arm between a position below the platen glass and a position evacuated therefrom; When the drive means is in the off state,
The sensor support arm is characterized by comprising a spring member that returns the sensor support arm to the retracted position.

Sat-U In copying machines, etc., the reading optical system that reads the original image is
The document image is read by scanning the lower part of the document table glass from one end side to the other end side, and after the reading is completed, it moves back to the one end side.

At this time, one end side is aligned with a reference end side for positioning the edge of the document when setting the document.

In the present invention, since the sensor support arm has its pivot center on this reference end side and is urged to the retracted position by the spring member when retracting, there is no possibility that the sensor support arm will make a retraction error. In the unlikely event that the spring member deteriorates over time,
Even if the optical system goes out of control while the sensor support arm is not completely retracted, the optical system will swing the sensor support arm in the retracting direction while it is moving, avoiding a collision that could cause damage to the two. It will be done.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image reading device according to the present invention will be described below with reference to the accompanying drawings.

[Overall configuration and operation of copying machine]

FIG. 1 shows a copying machine to which the present invention is applied, in which a photosensitive drum 1 is rotatably supported approximately in the center of a copying machine main body 100 in the direction of arrow a in the figure, and an eraser is mounted around the photosensitive drum 1. Lamp 2. Charger 3, other end/inter-image eraser 4.
Developing device6. A transfer charger 7, a separation charger 8, and a cleaning device 9 are arranged in this order. The photoreceptor drum 1 has a photoreceptor layer provided on its surface, and this photoreceptor layer is uniformly charged by passing through the eraser lamp 2 and the charger 3, and then passed through the scanning optical system 10 through the slit section 5. Upon image exposure, an electrostatic latent image is formed on its surface. The other end and inter-image eraser 4 has a plurality of light emitting diodes arranged in the image width direction, and removes unnecessary charges from the surface of the photoreceptor drum 1 during image formation.

The optical system 10 is installed below the document table glass 16 so as to be able to scan the document image, and includes an exposure lamp 17, movable mirrors 11, 12, 13, a lens 14, and a mirror 15. The exposure lamp 17 and the movable mirror 11
moves integrally in the direction indicated by the arrow at a speed of (v/m) (however, 2m: copying magnification) with respect to the circumferential speed V of the photosensitive drum 1 (constant regardless of whether the magnification is the same or variable magnification). , movable mirror 1
2.13 is driven by a scan motor M3 so as to move integrally in the direction indicated by the arrow at a speed of (V/2 m). In addition, when changing the copy magnification, use the stepping motor M.
4, the lens 14 moves on the optical axis and the mirror 15 moves and swings to correct the optical path.
Such a magnification changing mechanism is already known in principle.

Also, regarding control of the scanning speed of the optical system 10,
Control is performed to change the rotational speed of the scan motor M3 according to the copy magnification data, but a detailed explanation of the control method and the like will be omitted.

Copy paper is fed into the machine by an automatic paper feeding mechanism 20 provided on the left side of the copying machine main body 100 in the figure and having upper and lower cassette loading sections, or by a manual paper feeding mechanism 30 provided above it. After being temporarily stopped by the roller pair 21, the toner image is sent to the transfer section in synchronization with the image formed on the surface of the photoreceptor drum 1, the toner image is transferred by the transfer charger 7, and the toner image is transferred to the photoreceptor drum by the separation charger 8. The sheet is separated from the surface of the paper sheet 1 and sent to a fixing device 23 by a conveyor belt 22, where the image is fixed thereon and then discharged onto a paper discharge tray 24. After the transfer, the photosensitive drum 1 is cleaned by a cleaning device 9. The toner and charge remaining on the surface are removed by the eraser 2 in preparation for the next copying process.

Either the automatic paper feed mechanism 20 or the manual paper feed mechanism 30 is selectively used. In case of automatic paper feeding, copy machine 10
The image forming system including the photoreceptor drum 1 is started by operating the print key that starts the copying operation of 0, and when the pre-driving process for the photoreceptor drum 1 is completed, the paper feed roller 25 or 26 is driven and the copy paper is Drive of the optical system 10 is started by a scan start signal outputted as the copy paper is transported, and the copy paper is fed in synchronization with the image forming operation. Although not necessarily one sheet of copy paper, but a plurality of sheets may be pushed out by the rotation of paper feed rollers 25 or 26, only the topmost sheet is sent out by the next-stage sorting mechanism 27, 27'.

In the handling mechanism 27, 27', the upper roller 27a,
27a' is the lower roller 27b in the feeding direction.

27b' is rotationally driven in the push-back direction in the direction of the arrow in the drawing. The second and subsequent sheets of copy paper that are pushed out together with the top layer copy paper by the paper feed roller 25 or 26 are pushed back by the lower rollers 27b and 27b', and only the top layer copy paper is sent to the next intermediate roller pair 28. or 28'
sent towards. The intermediate roller pair 28.28' is
As will be described later, it is associated with the next-stage timing roller pair 21 and its drive is controlled.

On the other hand, in the case of manual paper feeding, when copy paper is inserted from the manual paper insertion slot 32 and the sensor 34 detects this,
The manual feed roller 33 rotates to feed the copy paper into the machine, and at the same time or a little later, the print key 7 is pressed.
Driving of the photoreceptor drum 1 and the like starts in the same manner as in operation 1. Then, the manually fed copy paper is temporarily stopped and on standby at the detection part of the copy paper leading edge detection switch 35, and when the preliminary drive process including rotation of the photosensitive drum 1 is completed, the paper feed roller 33 rotates again. This sends it onto the plane.

In addition, size detection switches 5WII to 5W14 and 5W21 to SW are installed in each cassette mounting portion of the automatic paper feeding mechanism 20.
24 is provided, and the operating state of the switch is changed by the arrangement of protrusions or magnets (not shown) provided on the cassettes 91 and 92 to be loaded, and the size of the loaded copy paper is determined by a 4-bit binary code. It is designed to be determined by

Next, an automatic document feeder 2 is installed at the top of the copying machine main body 100.
00 (hereinafter referred to as ADF). ADF20
0 generally includes a document feeding section 201 that stocks documents and feeds them out one by one, and a conveyor belt 2 that transfers the documents sent to the document feeder 201.
At step 05, the upper surface of the document platen glass 16 is conveyed, and the glass 16
A document transport unit 20 that stops the document at a predetermined position on the surface and feeds the document onto a paper output tray 204 after scanning the document.
It consists of 2. The document conveyance section 202 can be used alone as a manual document conveyance device, and can also be used on the document table glass 16 when mounted on the copying machine main body 100.
It can be opened and closed with respect to the copying machine main body 100 so as to expose the cover, and is used as a normal document holding cover when copying a thick book.

A magnet (not shown) is installed in the copying machine main body 100, and when the document transport section 202 is closed, the magnet is sensed and the switch O8W, which is a reed switch, is turned on, and when opened, the switch O8W is turned off.

This allows detection of opening and closing of the document holding cover.

Also, when this switch O8W is turned on, the ADF200
and the control of the copying machine main body 100 are associated with each other, and the operation mode of the copying machine main body 100 is switched to the ADF mode.

[Original size detection sensor]

In the optical system 10, a long lamp as shown in FIG. A sensor support arm 40 having a shape is arranged. The base end 4Oa side of the sensor support arm 40 is located at the reference end (A in the figure) for aligning documents, and is connected to the copying machine frame 1O1 via a coil spring 41 as shown in FIGS. 3 and 4.
The document platen 16 is swingably supported by a solenoid 42 and is driven to move in and out of a position below the document platen glass 16 .

The coil spring 41 is connected to the base end 40a of the sensor support arm 40.
The upper part of the support bin 46 is inserted and connected to the bearing 45 provided in the outer part. The upper end of the support bin 46 is connected to the copying machine frame 10.
1, and the upper end of a coil spring 41 is fixedly connected to the copying machine frame 101. On the other hand, coil spring 4
The upper end of 1 is latchingly connected to a bearing 45. The winding direction of the coil spring 41 is selected to be the direction shown in the figure, and when the sensor support arm 40 is swung to the detection position shown by the broken line in FIG. 3, the bearing 45 provided thereon causes the coil diameter of the coil spring 41 to be reduced. It will tear in the direction of compression.

Thus, when the sensor support arm 40 is located at the detection position, the coil spring 41 elastically urges the sensor support arm 40 toward the retracted position due to its elastic restoring force (repulsion force). Here, the spring constant of the coil spring 41, the wire diameter,
The average radius, effective number of turns, etc. are selected to appropriate values in consideration of the weight and swing range of the sensor support arm 40. In addition,
During rocking, the coil spring 41 may be moved in the direction in which the coil diameter expands, and the sensor support arm 40 may be returned to the retracted position using the force in the direction in which the coil spring 41 is contracted. Furthermore, a spiral spring may be used instead of the coil spring 41.

If such an embodiment is adopted in which the coil spring 41 is provided and the sensor support arm 40 is returned to the retracted position by the elastic restoring force of the coil spring 41, the solenoid 42 that swings the sensor support arm 40 to the detection position may have a malfunction or disconnection. Even if this occurs, the sensor support arm 40 can be reliably returned to the retracted position.

Now, the details of the connection structure between the solenoid 42 and the sensor support arm 40 are such that one end 43a of the L-shaped crank lever 43, which is pivotally supported around a horizontal axis in the center, is connected to the movable shaft portion 42a of the solenoid 42, and the other end The swing lever 4 has a bottle portion 43b connected to the base end 40a of the sensor support arm 40.
This configuration is such that it is inserted and locked into the elongated hole 44b of No. 4. When the solenoid 42 is not energized, the crank lever 43 stands up as shown by the solid line in FIG. 3, and the sensor support arm 40 swings back to the state shown by the solid line due to the restoring force of the coil spring 41. There is. This return position is located on the original platen glass 1 as shown in FIG. 2 (A) in plan view.
6. This is a position retracted from below to the side. When the solenoid 42 is energized, the sensor support arm 40 swings against the restoring force of the coil spring 41 to the position shown in FIG. . In the position (b), the sensor support arm 40
Since the base end of the sensor support arm 40 contacts the stopper 45, the sensor support arm 40 is held in that position.

Note that the swing angle θ at this time is 30'' in this embodiment.

For example, four sensors 4 are mounted on the sensor support arm 40.
6, 47, 48, and 49 are arranged at predetermined intervals in the longitudinal direction. As shown in FIG. 5, each of the sensors 46 to 49 includes a light emitting element 46a that emits light in an oblique direction and a light receiving element 46b that receives light from above. Therefore, as shown in FIG. 5(A), when there is no original on the document glass 16, the light emitted from the light emitting element 46a passes through the document glass 16, so that the light is incident on the light receiving element 46b. do not. On the other hand, as shown in FIG.
00 is placed, the light emitted from the light emitting element 46a illuminates the document surface directly above the light receiving element 46b. Therefore, diffusely reflected light from the irradiated portion of the document enters the light receiving element 46b. The light receiving element 46b changes to the "L" level upon incidence of this diffusely reflected light. The light emitting element and light receiving element of each of the sensors 46 to 49 are synchronized by a synchronization circuit 50 shown in FIG. 6, so that only the light from the light emitting element is received by the light receiving element.

When the sensor support arm 40 is swung to the position shown in FIG. 2 (b), the document size can be detected from the detection states of the sensors 46 to 49.

The reason for this is explained with reference to FIG. 2. First, when an A5 original is placed vertically on the original platen glass 16 as shown by A5T, all the sensors 46 to 49 are off from the original A5T, so the "H" level is detected. output (see ■ in Table 1).

Next, if you place the B5 original vertically as shown at 85T,
Since only the sensor 48 enters below the document B5T, only the sensor 48 changes to the "L3 level" (see ■ in Table 1).

Next, when an A4 document is placed vertically as indicated by A4T, the sensors 48 and 49 enter below the document A4T, so that the two sensors 4B and 49 change to the "L" level (see ◯ in Table 1).

When a B4 original is placed vertically as shown by B4T, the remaining three sensors except sensor 46 are placed under the original B4T, so only sensor 46 is at the "H" level and the other sensors are at "H" level.
L” level (see ■ in Table 1). Below, the sensor output when an A3 document is placed vertically is shown in [Phase] in Table 1, and B5
The sensor output when the document is placed horizontally is shown in ■ in Table 1.
The sensor output when the document is placed horizontally is as shown in 0 in Table 1.

Note that the sensor output cover patterns shown in ■■, ■~@, [phase], and ■ in the table are patterns that are not found in document size detection.

[Margin below]

Table 1 From the above results, it can be seen that the sensor output patterns differ depending on the document size and whether the document is placed horizontally or vertically. Therefore, it is possible to determine the document size from the output pattern of all the sensors.

[Configuration and operation of control circuit] FIG. 7 shows the control circuit of the copying machine. Main control section 70
Input signals include detection signals from various switches, etc., and key input signals from pressing keys on the operation panel. Specifically, the detection signal is sent to the switches 5W11 to 14.
, 5W21 to 24, an open/close detection signal of the ADF document conveying section 20, and a detection signal of the sensors 46 to 49.

Key human input signals include a print key ON signal, a print number selection key ON signal, and the like. In addition, the main control unit 7
From 0, the main motor M1 and other motors M2. M3・
..., a saw 24142 control type control signal, and a display signal to the display section of the operation panel 72 are output.

FIG. 8 is a main flow showing the copy operation controlled by the control circuit. When the device is started, an internal timer is set in step S1. The internal timer controls one copy operation routine, and control in each process is measured based on this timer. When this timer is set, steps S2 to S5 are advanced and J predetermined processing is performed.

In other words, if there is a key on the operation panel, it can be read.
(S2), detects the size of the original set on the original platen glass, (S3), then performs a copying operation (S4),
At this time, additional processing such as displaying an error message if there is a paper jam is performed (S5).

When all the above processes are completed, the process waits for the time set in the internal timer to elapse (S6), and repeats the processes from 82 to S5 again.

The document size detection process in step S3 is performed automatically by the ADF in the ADF mode, and in a non-ADF mode by swinging the sensor support arm 40 to detect the size of the document placed on the document table glass. This shows both processes. This process is shown in detail in the subroutine shown in FIG. In this subroutine, first, in step s7, it is determined whether the conditions are such that the sensor support arm 40 can be swung below the document table glass (this oscillation is referred to as arm opening in the flowchart). This judgment is performed in steps S71 to S76 shown in the subroutine of FIG. 10. That is, if the device is in the process of copying (S71), a document is sent to the ADF (372) even if the device is not in the process of copying, and the device is in the ADF.
mode (373), and even if the ADF mode is not set, if the document transport section 202 is closed (S74), the arm open flag is set to O. This prohibits arm opening.

On the other hand, when the copying operation is not in progress, the ADF mode is not active, and the document transport section 202 is open, the arm open flag is set to 1, and it is judged that the arm open condition is satisfied.

When this judgment is completed, the program proceeds to step S8.
Proceed to and check the count value of the state counter. The state counter can have seven types of state values from 0" to "6", and the values are rewritten as the program advances through each routine from "0" to "6". “
Each routine 6'' refers to a step group on each multi-branch line branched from step S8. Each routine 0'' to 62 includes steps SIO, S12.S24.'
333.336. S45. S53. S63. It has a processing step of changing the state value of the state counter as follows. When the device is first started, the state value of the state counter is "0", so the program advances through the "0" routine and returns to the main flow. When the program advances to step S8 again, The state value of the state counter is checked, and the routine instructed by the state value is judged. When the routine is finished stepping, it returns to the main flow again and steps through the main flow. When it reaches step S8, The routine specified by the state value of the state counter is judged and the routine is advanced.This operation is repeated thereafter.

Next, each routine from 0" to "6" will be explained.
0'' routine, first clears the data at the time of initial setting (at startup after troubleshooting, at power on, etc.) and the data at the previous detection in step S9, and then clears the data at step S9.
At O, the state counter is set to "13" and the process returns to the main routine.

In the routine 1'', it is determined in step Sll whether the test scan has been completed, and if it has been completed,
Proceeding to step S12, the state counter is set to 2", and if the state counter has not finished yet, the process returns to the main routine without changing the contents of the state counter. Then, the test scan is performed by incrementing the routine to "1" each time. When the test scan is completed, the process advances to step 312 and the state counter is set to 2''. Note that the test scan is a preliminary scan that is performed to check for abnormalities in the optical system at the time of initial setting, for example, when the power is turned on, and when returning after clearing a blockage.

In the routine "2", if the arm release flag is set to "1" in step S21, the process proceeds to step S22, where the arm solenoid 42 is turned on and the sensor support arm 40 is swung below the document table glass 16. Subsequently, in step 323, a timer TA is set to set the time required for the arm 40 to stop after it starts swinging.

Then, in step 324, the state counter is set to "3".
Set to . On the other hand, the flag is set to "1" in step S21.
If it is determined that it is not, the process returns to the main routine without proceeding to steps 822-24.

Therefore, in this case, the program will run routine "2" until the flag is set to "1".

In the routine 3'', it is determined in step S31 whether the arm release flag is set to "1", and the answer is Yes.
In this case, the process advances to step S32 and it is determined whether or not timer TA has timed up. If the time is up, the process advances to step S33 and the counter is set to 4. If the time has not expired yet, return as is.

On the other hand, if it is determined in step 331 that the flag is not "1", in such a case, as explained in the subroutine of FIG. (2) In any of the three cases when the document transport section 202 is closed, the program proceeds to step S34 and turns off the arm solenoid 42.

As a result, the sensor support arm 40 begins to swing toward the retracted position due to the elastic restoring force of the coil spring.

Then, in step S35, the time required for the arm 40 to be retracted to the retracted position is set in the timer TA, and the state counter is set to "5".

In the routine "4", it is determined again in step S41 whether the arm release flag is set to "1", and the flag is set to "1".
1'', the process advances to step S42, and the sensors 46 to 49
The detection signal is taken in, the document size is determined, and the document size data in the memory is updated. Then, after the operator finishes setting the original on the original table glass 16, the operator
When 02 is closed, the flag is set to "0" in the arm open judge routine shown in FIG.
The arm solenoid is turned off, and in step 344, timer T-A is set to the time until the arm is retracted to the retracted position. Thereafter, in step S45, the state counter is set to "5" and the process returns to the main flow. When the arm solenoid 42 is turned off, the sensor support arm 40 begins to swing in the retracting direction due to the elastic restoring force of the coil spring 41.

In the routine "5", the timer T-
A judgment is made as to whether or not the time has expired. When the time has expired, the timer T-B is set in step S52, and the state counter is set to "6" in step S53.
’. The timer T-B is a timer that sets a time for trouble detection, and is set to a predetermined time that allows enough time for the arm to be retracted.

In the routine "6", it is determined in step S61 whether or not the arm has been retracted. This determination can be made by providing a limit switch or an optical detection switch at the retracted position of the arm to confirm the presence of the arm. If the arm does not retreat, step S6
Proceeding to step 4, it is determined whether or not timer T-B has timed up.

If the timer T-B times out while the arm is not retracted, the process proceeds to step S65, where an error is displayed on the operation panel and a process is performed to prohibit the copy operation.

By the way, in this case, if the optical system goes out of control despite the copy prohibition, if the center of swing of the sensor support arm 40 is positioned far from the document alignment reference edge A as shown in FIG. In this case, the tip 40b of the sensor support arm collides with the optical system 10 during scanning of the optical system 10, damaging the optical system 10, the arm 40, or both. However, the sensor support arm 40 of this embodiment Since the center of swing is located on the side of the document alignment reference end A and the sensor support arm 40 is returned to the retracted position by the elastic restoring force of the coil spring 41, the tip 40b of the sensor support arm is moved during scanning by the optical system 10. There will be no collision with the optical system 10 and damage to the optical system 10, the sensor support arm 40, or both. Furthermore, even if the sensor support arm 40 does not return to the retracted position due to deterioration of the coil spring 41 over time, the sensor support arm 40 is moved to the 11th position by the optical system 10 during scanning by the optical system 10.
It will be pushed out in the retreating direction as shown by the arrow in Figure (B), and damage due to collision will be avoided.

Next, in step S61, when the arm is completely retracted before the timer T-B times up, the process proceeds to step S62, where the timer T-B is cleared and step S63
Set the state counter to "2" at Therefore,
Thereafter, each time a new document is sent, the process will start from routine "2".

Incidentally, in the above embodiment, the sensors 46 to 49 are used for determining the document size, but the present invention is not limited to this, and sensors for measuring the image density of the document, for example, may also be used. When measuring image density, the number of sensors may be at least one.

Further, in the above embodiments, the present invention is applied to a copying machine equipped with an ADF, but it goes without saying that the present invention can be applied to a copying machine not equipped with an ADF.

1. As explained above, the image reading device according to the present invention has the swing center of the sensor support arm on the reference end side where the edge of the document is aligned, and a spring member that biases the sensor support arm to the retracted position. With this configuration, for example, even if a failure occurs in the swing drive means for swinging the sensor support arm to the detection position, the sensor support arm can be reliably returned to the retracted position. . In addition, in the unlikely event that a malfunction occurs in the spring member and the sensor support arm does not return to the retracted position, and the optical system scans at this time, or the optical system goes out of control while determining the document size, the optical system Since the sensor support arm can be pushed back to the retracted position, there is an effect that a collision between the optical system and the sensor support arm can be reasonably avoided.

Furthermore, in the event of a failure, the sensor support arm is reliably retracted to the retracted position, so copying operations in manual mode can be continued, improving usability.

[Brief explanation of the drawing]

FIG. 1 is an overall view of a copying machine to which the present invention is applied, FIG. 2 is a plan view showing a sensor support arm, FIG. 3 is a perspective view of the arm, FIG. 4 is a side view of the arm, and FIG. The figure is a diagram explaining the detection principle of the sensor, Figure 6 is a diagram showing the electric circuit of each sensor, Figure 7 is a diagram showing the control circuit of the copying machine, Figure 8 is a diagram showing the main flow of the copying operation, and Figure 9 is a diagram showing the copying machine control circuit. 10 is a flowchart showing the subroutine of the document size detection operation, FIG. 10 is a flowchart showing the subroutine of the arm open judge, and FIGS. 11(a) and 11(b) are diagrams for explaining the present invention in detail. 16... Original table glass, 40... Sensor support arm, 41... Coil spring, 42... Solenoid, 46
~49...Sensor 202...Document transport unit (document holding cover). Patent applicant: Minolta Camera Co., Ltd. Figure 5 Figure 6 Figure 7 Figure 7n Figure 8

Claims (1)

[Claims] (1) In an image reading device that optically scans a document placed on a document platen glass to read the document image, a sensor for determining the document size, image density, etc., and a sensor for determining the position below the document platen glass are used. It is capable of swinging between a position retracted from the original platen glass, the center of swing is provided at a position retracted from below the original platen glass on the document alignment reference edge side, and at least one sensor is provided in the longitudinal direction. a sensor support arm provided along the document table; a swing drive means for swinging the sensor support arm between a position below the platen glass and a position retracted therefrom; and a swing drive means when the swing drive means is turned off. a spring member that returns the sensor support arm to a retracted position when the sensor support arm is in the retracted position.