JPH0668663B2 - Blackboard copier - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to an image forming apparatus for forming (forming) an image of characters and the like written on a movable sheet-shaped member.

[Prior Art] A writable and erasable board sheet is wound up by winding rollers provided at both ends of the board sheet, and characters written on the board sheet are irradiated with light from a light source to reflect light from an image. An image forming apparatus has been proposed which exposes a photosensitive drum via a mirror, a lens and the like.

In such an image forming apparatus, a motor is used to drive the winding roller and the rewinding roller for winding or rewinding the board sheet. In particular, the take-up roller is rotated at a constant speed by controlling the motor, and the board sheet is moved by the take-up roller that rotates at a constant speed.

[Problems of conventional technology]

Therefore, in the image forming apparatus that winds the board sheet as described above, the board sheet is wound on the take-up roller by rotating the take-up roller at a constant speed. Since the radius of is increased by the thickness of one board sheet, the winding roller gradually increases in diameter. Therefore, as the number of board sheets wound around the winding roller increases, the moving speed of the board sheets increases. Therefore, when the board sheet whose moving speed gradually increases is irradiated with light and the reflected light is exposed to, for example, the photoconductor to form an image on the transfer sheet, only the moving direction (vertical magnification direction) of the board sheet is gradually increased. It becomes a compressed image. That is,
Since the magnification in the direction orthogonal to the board sheet movement direction (horizontal magnification direction) is constant regardless of the board sheet movement speed determined by the optical system, an image compressed only in the vertical magnification direction with respect to the horizontal magnification direction Becomes

Since the size of the transfer paper is smaller than the copy surface of the board sheet, a certain reduction (for example, 5: 1) is performed to form an image. The reduction ratio in the lateral magnification direction is determined by the position of the lens provided on the optical path of the reflected light. The reduction ratio in the lateral magnification direction is conventionally determined by the reduction ratio in the lateral magnification direction and the reduction ratio in the vertical magnification direction determined by the moving speed of the board sheet. The position (reference position) on the board sheet at which is coincident with is set to the image formation (copy) start position or the copy end position.
So for example on a board sheet the same diameter (length 5
If three circles of A ') are drawn, and the reference position is set to the copy start position, the lateral magnification of the circle near the copy start position is shown on the transfer paper as shown in FIG. 2 (a). A circular shape having a length in the direction A'and a length in the longitudinal magnification direction A'which are almost the same length. However, the length A in the vertical magnification direction is reduced (A → B → C) toward the end of the copy, and the circle near the copy end position becomes an ellipse that is vertically long.

Further, when the reference position is set to the copy end position, the circle on the transfer paper near the copy start position with respect to the set length A ′ in the lateral magnification direction as shown in FIG. The length D in the vertical magnification direction is extremely long, and the length in the vertical magnification direction is reduced toward the end of the copy (D → E → A), and the circle near the copy end position becomes a nearly normal circle. Therefore, in the case of FIG. 9A, a vertically long ellipse is copied near the copy end position of the transfer paper, and in the case of FIG. 9B, the horizontally long ellipse is near the copy start position of the transfer paper. Will be copied to.

[Object of the Invention]

In view of the above-mentioned conventional drawbacks, the present invention sets the reference position substantially at the center of the board sheet, thereby making it possible to form an image on transfer paper or the like without deforming the image drawn on the board sheet. An object is to provide a forming device.

[Main points of the invention]

In order to achieve the above object, the present invention is an optical system in which an image on a writing-erasable display member is moved by rotating a roll that winds up the display member so that the image-forming surface is slit-exposed. In the blackboard copier having the above, the rotation of the roll is controlled so that the longitudinal magnification determined by the moving speed of the display member matches the lateral magnification determined by the optical system at approximately the center of the image area of the display member. It is characterized by having a control means for controlling.

Example of Invention

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

The present embodiment will be described using a so-called blackboard copier, which is capable of copying an ordinary manuscript together with an image on a board sheet.

FIG. 3 is a perspective view showing the overall construction of the blackboard-copier of the embodiment of the present invention. In the figure, the blackboard copier is composed of a board unit 1 and a copying unit 2.
Is composed of a frame 1a, a board sheet 3, and a board operating section 4, and has a board optical system and a winding device for the board sheet 3 inside. The copy section 2 is provided with a document table and an operation section at the upper part, and is mounted so as to be movable back and forth on a rail 5a provided on the copy machine table 5.

When a normal document is placed and copied, the copy unit 2 is not shown.
When the image on the board sheet 3 is copied, the copying section 2 is moved backward as shown in FIG. 3 so that the reflected light of the image on the board sheet 3 is input to the copying section 2. used.

Next, the structure of the board unit 1 will be described with reference to FIG. The winding device includes a winding roller 35, a rewinding roller 36, and a feeding roller 37.
It is composed of a to 37d etc. The board sheet 3 wound many times around the rewinding roller 36 is wound around the winding roller 35 via the feed rollers 37a to 37d. The winding speed at this time is controlled so as to coincide with the center of the copy area of the board sheet 3 by the control described later. Rewinding is done by the take-up roller 35
The board sheet 3 wound on the sheet is reversely fed to the feed roller.
It is carried out by winding the film onto the rewinding roller 36 via 37a to 37d. Also, the board sheet 3 is the backup board 38
Is also kept parallel.

In addition, the blackboard optical system is a fluorescent lamp 39, a first mirror 40, a second mirror
41, the blackboard lens 42, etc., and the feed roller 37 described above.
Fluorescent light 3 on the board sheet 3 formed in a plane between a and 37b
9 light irradiation is performed.

FIG. 5 shows the reflected light from the board sheet 3 when the light from the fluorescent lamp 39 is applied to the board sheet 3 on which characters and figures are drawn.
It shows 32 optical paths.

As shown in the figure, the reflected light 32 is bent 90 degrees by the first mirror 40 that is arranged at an angle of 45 degrees with respect to the reflected light 32, and further bent downward by 90 degrees by the second mirror 41. The photosensitive drum 11 in the copying section 2 is exposed through the blackboard lens 42.

On the other hand, the size of the display surface (copying surface) of the board sheet 3 is vertical.
It is composed of 920 mm and 1,300 mm in width. For example, if you use A4 size as transfer paper, A4 size is 210 mm x 297 mm,
Therefore, the magnification is 210/920 = 0.228. In this case, if the distance from the light irradiation surface of the board sheet 3 to the blackboard lens 42 is a and the distance from the blackboard lens 42 to the photoconductor drum 11 is b, the blackboard is placed at a position where b / a = 0.228. A lens 42 is arranged.

In this embodiment, the distance a is 1400 mm, the distance b is 319.3 mm, and the blackboard lens 42 is provided at this position.

Further, the vertical magnification is determined by the speed ratio between the moving speed of the board sheet 3 and the process speed of the copying section 2 (the peripheral surface speed of the photosensitive drum 11 due to the rotation of the photosensitive drum 11). The process speed of this embodiment is set to 120 mm / s,
Considering that the aforementioned magnification is 0.228 times, the moving speed of the board sheet 3 is set to 526 mm / s (120 / 0.228). Moreover, the moving speed of the board sheet 3 of 526 mm / s is the speed of the time H when the center of the copy area of the board sheet 3 passes the position where the fluorescent lamp 39 irradiates the light as shown in FIG. 1 (a). Is set to match.

In the image forming apparatus configured as described above, the winding of the board sheet 3, which is a main part of the present invention, is performed by the winding motor provided on the shaft of the winding roller 35 of the board sheet 3. Therefore, the board sheet 3 starts to move when the winding motor starts to be driven, and after a time T, the board sheet 3 rotates at a constant speed. On the other hand, the moving speed V of the board sheet 3 is V = π · D · N / 60, where D is the diameter of the winding roller 35 and N is the number of revolutions per minute of the winding motor rotating at a constant speed. .

However, since the board sheet 3 is wound around the take-up roller 35 once every time the take-up roller 35 makes one rotation, the moving speed V of the board sheet 3 is taken n times with the thickness of the board sheet being t. Then, V = π (D + 2nt) N / 60, and the moving speed V of the board sheet 3 gradually increases.

However, in the image forming apparatus of the present embodiment, when the center of the copy area of the board sheet 3 passes the exposure position of the fluorescent lamp 39, the moving speed V of the board sheet 3 coincides with the lateral magnification of 0.228 times 526 mm / s. Therefore, as shown in FIG. 1B, a circle having a length A'in the longitudinal magnification direction and a length A'in the lateral magnification direction is formed at approximately the center position H'on the transfer paper. be able to.

Therefore, as compared with the case where the reference position is set at the copy start position or the copy end position as in the conventional example shown in FIGS. (For example, when copying a circle, the length in the vertical magnification direction is slightly longer than A, and the length in the vertical magnification direction F,
Alternatively, a circle having a length G in the longitudinal magnification direction that is slightly shorter than A can be obtained.

Next, a more specific example of the movement control of the board sheet 3 of the present invention will be described below.

In this embodiment, the motor for rotating the take-up roller 35 is rotationally controlled to match the vertical magnification and the horizontal magnification at the center of the copy area. Moreover, in this embodiment, if the board sheet 3 is composed of, for example, five pages, the vertical magnification and the horizontal magnification are made to coincide with each other in the center of the copy area for each page.

FIG. 6 is a control circuit diagram of the motor 44 that drives the take-up roller 35. In the figure, an encoder 43 is attached to a rotation shaft of a motor 44, detects a rotation signal of the motor 44, and uses the rotation signal as a frequency signal a to detect a phase comparator 45.
Output to. Further, the phase comparator 45 receives a frequency signal b from a voltage control oscillator (hereinafter referred to as VCO) 46, and the VCO 46 has a speed setting circuit 47 described later.
The phase comparator outputs the signal b of the frequency corresponding to the voltage value selected and input for each page of the board sheet 3 set by
Output to 45.

The phase comparator 45 detects the difference between the phase angle of the rotation signal a and the phase angle of the signal b, and when the phase of the rotation signal a is behind the phase of the signal b, it outputs a high signal and the phase of the signal b. Also, when the phase of the rotation signal a is advanced, the low signal is output to the integration circuit 48 as the signal c. When the phase of the signal b matches the phase of the rotation signal a, the output of the phase comparator 45 is high impedance. The integrating circuit 48 smoothes the signal c and further outputs the DC signal d amplified based on the set value of the gain adjusting resistor 48a to the adding circuit 49.

A voltage for generating the minimum torque required for driving the take-up roller 35, which is adjusted by the variable resistor 50a, is input from the reference voltage generator 50 to the adder circuit 49. The signal d is added (combined) to and output as the signal f to the comparison circuit 51. A triangular wave signal g for pulse width modulation is input from the triangular wave generator 52 to the comparison circuit 51, and the comparison circuit 51 performs pulse width modulation using the triangular wave signal g on the signal f input from the adder circuit 49 and the motor 44 To the motor 44, and the rotation speed of the motor 44 is controlled by this signal h.

The control circuit of FIG. 1 forms a closed loop in which a signal is transmitted from the encoder 43 to the motor 44 via the phase comparator 45, the integrating circuit 48, the adding circuit 49, and the comparing circuit 51, and the encoder is rotated by the motor 44. It is a PLL loop. The gain adjustment is performed when the waveform of the signal c is converted into the DC signal d by changing the gain adjustment resistor 48a that is a resistor that determines the loop gain.

The setting of the gain adjusting resistor 48a is set to a sub-control state where the control power is not so strong that the diameter of the winding roller 35 becomes thicker and the rotation speed of the winding motor decreases as the load of the winding motor increases. .

On the other hand, the speed setting circuit 47 connected to the VCO 46 has a resistor R ₁ ,
The other end is composed of four sets of series circuits connected to the variable resistor VRa. Each series circuit consists of a variable resistor, a resistor and a switch. The other end of the resistor R ₁ is grounded and the variable resistor VRa
A reference voltage is applied to the other end of the. These four sets of series circuits correspond to the first to fourth pages of the five pages formed on the board sheet 3, and the variable resistance VR
The series circuit of ₁ and resistor R ₂ and switch SW ₁ corresponds to the first page of board sheet 3 and corresponds to variable resistor VR ₂ and resistor R ₃ and switch SW ₂
The series circuit of corresponds to the second page of the board sheet 3. Similarly, the series circuit of the variable resistance VR ₃ , the resistance R _4, and the switch SW _{3 and} the series circuit of the variable resistance VR ₄ , the resistance R _5, and the switch SW ₄ are respectively. Corresponds to the third and fourth pages of board sheet 3. For example, one of the board sheet 3 by closing the switch SW ₁
A page is selected by a control circuit (not shown),
At the connection point between the resistor R ₁ and the variable resistor VR ₁ , a voltage is generated by dividing the reference voltage by the series circuit of the variable resistors VR ₁ , VRa, and the resistor R ₂ and the resistor R _1, and this voltage is the speed setting circuit. VCO4 as output of 47
Output to 6. Similarly, when the switch SW ₂ is closed, the second page of the board sheet 3 is selected by the control circuit (not shown), and the reference voltage is the variable resistance VR.
A voltage divided by the series circuit of ₂ , VRa and resistor R ₃ and resistor R ₁ is generated at the connection point between resistor R ₁ and variable resistor VR _2, and this voltage is V
Output to CO46. Similarly, when the switches SW ₃ and SW ₄ are closed, the third and fourth pages of the board sheet 3 are selected and the reference voltage is applied to the connection point between the resistor R ₁ and the variable resistors VR ₃ and VR _4. A voltage that is divided is generated. Where resistance R ₂ , R
_{Since 3} , R ₄ and R ₅ have different resistance values, the voltage value output to the VCO 46 is different depending on each page of the board sheet 3. This output voltage is applied to each rotation signal a such that the speed becomes constant at the center of each page.
It is the voltage generated from the VCO at the same frequency as the frequency.

With the circuit configuration as described above, when the load torque increases when the image on the board sheet 3 is copied, that is, when the board sheet 3 is wound around the take-up roller 35 a large number of times,
As shown in the figure, the rotation speed of the drive motor decreases (in this figure, the rotation speed decreases in all areas with respect to the increase of the load torque of the motor 44, but the area used for speed control of the board seat 3). Is the area indicated by the sub-control area at the same time.) Therefore, in the image area of the first page on the board sheet 3, the number of rotations at the beginning and the end of the first page of the take-up roller 35 increases as the load increases. Decrease, curve J in Figure 8
As shown in, the moving speed of the board sheet 3 hardly changes in the image area of the first page of the board sheet 3. On the other hand, also on the fourth page of the board sheet 3, the rotation speed of the drive motor decreases as the load increases at the beginning and the end of the fourth page, and as shown by the curve K in FIG.
There is almost no change in the movement speed of. Moreover, at time H "passing through the center of the configured page in each of the board sheet 3, the resistance R ₂ of the speed setting circuit 47 as the moving speed of the board sheet 3 matches, R _3, R _4, R _{Since 5} is set, the image on the left side of the time H ″ (the first half of each page of the board sheet 3) is enlarged or the image on the right side of the time E (the latter half of each page of the board sheet 3) is reduced. Can be minimized.

The motor 44 used in the above embodiment may be a pulse motor, a DC motor, or the like. Further, in the present embodiment, the reflected light from the board sheet 3 is received by the photosensitive drum 11, but the photoelectric conversion is not limited to the photosensitive drum 11, and photoelectric conversion is performed using, for example, a CCD (charge coupled device) as a light receiving element. Needless to say, it may be used in a digital image forming apparatus that outputs the data after it is output by a printer.

〔The invention's effect〕

As described in detail above, according to the present invention, when an image on a board sheet is formed on a transfer sheet or the like, the lateral magnification set by the optical system lens and the longitudinal magnification determined by the moving speed of the board sheet match. By setting the point approximately at the center of the board sheet, it is possible to obtain an image with less distortion at both ends of the copy area on the board sheet.

[Brief description of drawings]

FIG. 1 (a) is a moving speed characteristic diagram of a board sheet, FIG. 1 (b) is a configuration diagram of a copied image on a transfer sheet, and FIGS. 2 (a) and 2 (b) are conventional copied images on a transfer sheet. Configuration diagram, FIG. 3 is a perspective view of the image forming apparatus of the present invention, FIG. 4 is a configuration diagram of a board portion, FIG. 5 is an optical path explanatory diagram of the board portion, and FIG. 6 is another embodiment of the present invention. Fig. 7 is a motor control circuit diagram of the image forming apparatus, Fig. 7 is a characteristic diagram showing the number of rotations of the motor with respect to load torque, and Fig. 8 is a moving speed characteristic diagram of the board sheet. 1 …… Board part, 2 …… Copier part, 3 …… Board sheet, 32 …… Optical path, 35 …… Take-up roller, 42 …… Blackboard lens, 43 …… Encoder, 44 …… Motor, 45 …… Phase comparator, 46 …… VCO, 47 …… Speed setting circuit, 48 …… Integrator circuit, 49 …… Adding circuit, 50 …… Reference voltage generator, 51 …… Comparison circuit, 52 …… Triangular wave generator.

Continuation of front page (56) Reference JP-A-51-85725 (JP, A) JP-A-51-92626 (JP, A) JP-A-59-171695 (JP, A) JP-A-59-212866 (JP , A) JP 60-164770 (JP, A) JP 61-94798 (JP, A) Actual opening 50-140451 (JP, U) Actual opening 55-41900 (JP, U) Actual opening 61-74487 (JP, U) JP-B 56-40341 (JP, B2) JP-B 56-40342 (JP, B2) JP-B 57-18169 (JP, B2) JP-B 2-60187 (JP, B2) Actual Public Flat 2-45876 (JP, Y2) Actual Public Flat 3-39798 (JP, Y2) Actual Public Flat 3-14675 (JP, Y2) Actual Public Flat 5-40529 (JP, Y2)

Claims (1)

[Claims] 1. A blackboard copying machine having an optical system in which an image on a writable and erasable display member is moved by rotating a roll that winds the display member to expose the image on an image forming surface by slit exposure. A control means for controlling the rotation of the roll so that the vertical magnification determined by the moving speed of the display member matches the lateral magnification determined by the optical system at substantially the center of the image area of the display member. A blackboard copying machine characterized by.