JPH0993397A - Original reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the effect to a stepping motor in the case of collision of tips of recording paper in the case where tips of recording paper collide with a 2nd carrier roller, an angular velocity speed of the stepping motor is affected to provide effect onto a read image. SOLUTION: A motor drive section 59 drives a stepping motor 56 by a signal of a predetermined 1st drive frequency and a 1st carrier 52 carries an original 50. After the original 50 is caught by the 2nd carrier rollers 54, a motor drive section 59 drives the stepping motor 56 with a signal of a predetermined 2nd drive frequency higher than the 1st drive frequency after the elapse of a prescribed time to reduce the fluctuation in the load of the 2nd carrier rollers 54 due to collision of tips of the original 50.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet scan type document reading apparatus, and more particularly to preventing deterioration of read image quality when a document is conveyed at high speed.

[0002]

2. Description of the Related Art A facsimile apparatus has a document reading device as an essential component. As this document reading apparatus, there are a book scanner method and a sheet scanner method. In particular, there are many document reading devices that employ a sheet scanner method among document reading devices that are used in facsimile machines.

In the case of an original reading apparatus adopting a sheet scanner system, since it is necessary to read the original intermittently, it is necessary to use a synchronous motor as a drive source for the first roller and the second roller for conveying the original. . As a synchronous motor, an open loop control stepping motor is often used because of its cost and ease of handling.

A document reading apparatus using a stepping motor has a stepping motor 56 as shown in FIG.
The first transport roller 52 and the second transport roller 54 are rotated by the driving force from the. The first transport roller 52 transports the document 50 toward the scanner 51, and the scanner 51 starts reading the document 50 at the time when the leading end of the document 50 is transported directly above the scanner 51. The first transport roller 52 transports the document 50 read by the scanner 51 to the second transport roller 54 located behind the scanner 51. The second carrying roller 54 carries the document 50 carried by the first carrying roller 52 to the outside of the document reading device or the like.

[0005]

However, there is a demand for higher document reading speed, and when the speed of document transportation is increased, the leading edge of the recording paper collides with the second transport roller, causing the second transport roller to move. When the recording paper is pinched, the load of the second transport roller may fluctuate, and the rotation of the second transport roller may be disturbed. This rotation disturbance affects the stepping motor that is the drive source of the second transport roller, and affects the motor angular velocity of the stepping motor as shown in FIG. The influence of the stepping motor on the motor angular velocity also influences the movement of the rotating first conveying roller by obtaining the driving force from the stepping motor. When the movements of the first transport roller and the second transport roller are affected, the quality of the read image is also affected, and fluctuations in the read image or breaks in fine lines may occur.

The present invention has been made to solve the above disadvantages, and an object thereof is to prevent deterioration of the quality of a read image when a document is conveyed at a high speed.

[0007]

In a document reading apparatus according to the present invention, a stepping motor is driven by a signal of a predetermined first driving frequency when a document is conveyed by a first conveying roller,
A sheet scanner using a stepping motor that drives the stepping motor with a signal of a second driving frequency that is higher than the first driving frequency after a predetermined time has passed after the document is caught by the second conveying roller. In a facsimile apparatus equipped with a system type document reading unit, the document transport speed when the leading edge of the document enters the second transport roller is made slower than the document transport speed by the second transport roller to reduce the fluctuation amount of the load of the second transport roller. To do.

Further, in the document reading apparatus, at the time of document transportation by the first transport roller, the stepping motor is driven by a signal of a predetermined first drive current value, the document is pinched by the second transport roller, and then, in advance. After a lapse of a predetermined period of time, the stepping motor is driven by a signal of a second drive current value which is lower than the first drive current value, and a second step in a facsimile apparatus equipped with a sheet scanner type document reading section using a stepping motor. The influence of the fluctuation of the load of the second conveyance roller is reduced by increasing the conveyance torque when the leading edge of the document enters the conveyance roller.

Further, in the original reading device, when the original is conveyed by the first conveying roller, the stepping motor is driven by a signal of a predetermined first driving voltage, and the original is pinched by the second conveying roller and then predetermined. After a certain period of time, the stepping motor is driven by a signal of a predetermined second driving voltage lower than the first driving voltage, and the stepping motor is used as a second conveyance roller in a facsimile apparatus including a sheet scanner type document reading unit. The influence of the fluctuation of the load of the second conveying roller is reduced by increasing the conveying torque when the leading edge of the document enters.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a document reading apparatus used in, for example, a facsimile machine, and in a sheet scanner type image reading apparatus for feeding a document at high speed, the document collides with a feeding roller. The influence on the carrying roller is reduced and the deterioration of the read image quality is prevented.

The document reading device includes, for example, a scanner for reading a document, a first transport roller for transporting the document in front of the scanner, a first upper roller for sandwiching the document with the first transport roller, and a first transport roller for transporting the document behind the scanner. The second upper roller that sandwiches the original with the two conveying rollers and the second conveying roller, the stepping motor that generates the driving force of the first conveying roller and the second conveying roller, and the driving force of the stepping motor is transmitted to the first conveying roller. A first drive transmission section, a second drive transmission section that transmits the driving force of the stepping motor to the second conveyance roller, a motor drive section that drives the stepping motor, and a light that detects whether or not there is a document directly above the scanner. It has a sensor.

The first transport roller and the second transport roller rotate by the driving force transmitted via the first drive transmission unit and the second drive transmission unit, respectively. The first conveyance roller conveys the document toward the scanner, and when the optical sensor detects that the front end of the document has been conveyed to directly above the scanner, the scanner starts reading the document. The first transport roller transports the document to the second transport roller located behind the scanner. The second transport roller transports the document transported from the first transport roller to the outside of the document reading device.

The stepping motor is rotated by a pulse signal from the motor driving section. The motor drive unit has, for example, a frequency switching unit, a frequency storage unit, and a pulse signal generation unit. The frequency switching unit switches the frequency of the driving signal of the stepping motor generated by the pulse signal generating unit between the first driving frequency and the second driving frequency stored in the frequency storage unit in advance. When a document is conveyed, the pulse signal generation unit is instructed to generate a signal of the first drive frequency, and, for example, after a certain time has elapsed after the optical sensor detects that the leading edge of the document has been conveyed right above the scanner. The pulse signal generator is instructed to generate a signal of the second drive frequency. Here, the above-mentioned fixed time is the angular velocity hunting of the stepping motor at the time of load fluctuation during the time until the leading edge of the document reaches the second transport roller, which is obtained from the document transport speed and the distance from the scanner to the second transport roller. It is the convergence time.

The frequency storage unit stores the first drive frequency and the second drive frequency. Here, the first drive frequency and the second drive frequency are within a range that does not hinder the conveyance of the original,
Moreover, the second drive frequency is higher than the first drive frequency and is within the range that secures the required document transportation speed.
When driven by the signal of the first drive frequency, the rotation speed of the stepping motor is slower than when driven by the signal of the second drive frequency.

The pulse signal generating section generates a signal of the first driving frequency or the second driving frequency stored in the frequency storage section according to the signal from the frequency switching section. As a result, when the document is conveyed by the first conveying roller, the stepping motor is driven and driven with a relatively high torque, and after the document is pinched by the second conveying roller, the stepping motor is moved to the first position after a predetermined time has elapsed. The original is conveyed at a high speed by driving at a predetermined second driving frequency higher than the driving frequency.

When the rotation of the stepping motor is controlled by the magnitude of the current value, the motor drive section has, for example, a current value switching section, a current value storage section and a pulse signal generating section. The current value switching unit switches the current value of the drive signal of the stepping motor generated by the pulse signal generation unit between the first drive current value and the second drive current value stored in the current value storage unit in advance. When the original is conveyed by one conveying roller, the pulse signal generator is instructed to generate the signal of the first drive current value, and the optical sensor detects that the leading edge of the original has been conveyed right above the scanner. After that, when a certain time has elapsed, the pulse signal generator is instructed to generate a signal having the second drive current value. The current value storage unit stores the first drive current value and the second drive current value. Here, the first drive current value and the second drive current value are within a range that does not hinder the conveyance of the document, the second drive current value is lower than the first drive current value, and the signal of the first drive current value is The driving torque of the stepping motor is greater when driven by the second drive current value than when driven by.

The pulse signal generating section generates a signal of the first drive current value or the second drive current value stored in the current value storage section according to the signal from the switching section. As a result, when the document is conveyed by the first conveying roller, the stepping motor is driven and driven with a relatively high torque, and after the document is pinched by the second conveying roller, the stepping motor is moved to the first position after a predetermined time has elapsed. The driving is performed at a predetermined second driving current value lower than the driving current value.

When the rotation of the stepping motor is controlled by the voltage level, the motor driving section has, for example, a voltage switching section, a voltage storage section and a pulse signal generating section. The voltage switching unit switches the voltage of the drive signal of the stepping motor generated by the pulse signal generation unit between the first drive voltage and the second drive voltage stored in the voltage storage unit in advance,
When the original is conveyed by the first conveying roller, the pulse signal generator is instructed to generate the signal of the first drive voltage, and the optical sensor detects that the leading end of the original has been conveyed right above the scanner, for example. After that, the pulse signal generation unit is instructed to generate the signal of the second drive voltage when a predetermined time has elapsed. The voltage storage unit stores the first drive voltage and the second drive voltage. Here, when the first drive voltage and the second drive voltage are within a range that does not hinder the conveyance of the document, the second drive voltage is lower than the first drive voltage, and the second drive voltage is driven by the signal of the first drive voltage. The rotation torque of the stepping motor is larger than that when driven by the signal of the second drive voltage.

The pulse signal generating section generates a signal of the first drive voltage or the second drive voltage stored in the voltage storage section according to the signal from the voltage switching section. As a result, when the document is conveyed by the first conveying roller, the stepping motor is driven and driven with a relatively high torque, and after the document is pinched by the second conveying roller, the stepping motor is moved to the first position after a predetermined time has elapsed. It is driven by a predetermined second drive voltage lower than the drive voltage.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a facsimile apparatus incorporating a document reading apparatus as an embodiment of the present invention. As shown in the figure, the facsimile machine includes an MPU1, a ROM2,
RAM 3, DMA controller 4, reading scanning unit 5, reading processing unit 6, recording scanning unit 7, recording processing unit 8, line memory 9, line memory control unit 10, information compression / decompression unit 11, panel unit 12, for panel unit. An interface 13, a mechanism control unit 14, an interface 15 for the mechanism control unit, a network control unit 16, a communication control unit 17, and a modem 18 are provided.
At the time of facsimile transmission, the MPU 1 sends the image information read by the reading scanning unit 5 to the line memory 9 via the reading processing unit 6 and temporarily stores it in the line memory 9. MPU
Reference numeral 1 indicates that the information compression / decompression unit 11 removes the redundancy according to the mode while reading the image information from the line memory 9, and RA
Accumulate in M3. The MPU 1 uses the RAM 3 as a transmission buffer and sends image information to the modem 18 via the communication control unit 17. The modem 18 modulates the image information signal and sends the image information by facsimile via the network control unit 16. Conversely, when receiving a facsimile, the image information signal received from the line via the network control unit 16 is demodulated by the modem 18 and stored in the RAM 3 via the communication control unit 17.
The MPU 1 sends the image information stored in the RAM 3 to the information compression / decompression unit 11. The information compression / restoration unit 11 restores the image information and sends it to the line memory 9. The line memory 9 temporarily stores the image information from the information compression / decompression unit 11, and then sends it to the recording / scanning unit 7 via the recording processing unit 8 for reproduction.

The facsimile device includes a sheet scanner type document reading device as the reading scanning unit 5. The document reading device includes a scanner 51, a first transport roller 52, a first upper roller 53, and a second transport roller 5 as shown in FIG.
4, a second upper roller 55, a stepping motor 56, a first drive transmission unit 57, a second drive transmission unit 58, a motor drive unit 59, and an optical sensor 60. The scanner 51 is composed of, for example, an image sensor such as a CCD, and reads the document 50 line by line in order. The first transport roller 52 is located in front of the scanner 51, and together with the first upper roller 53, the document 50.
Are transported in the direction of the second transport roller 54. The first upper roller 53 and the first transport roller 52 sandwich the document 50 and transport the document. The second conveyance roller 54 is located behind the scanner 51 and conveys the document 50 toward the outside of the reading / scanning unit.
The second upper roller 55 and the second transport roller 54 together with the original 50
Hold the original to transport the original. The stepping motor 56 generates a driving force for the first transport roller 52 and the second transport roller 54. The first drive transmission unit 57 is the stepping motor 5
The driving force of 6 is transmitted to the first transport roller 52. The second drive transmission unit 58 transmits the driving force of the stepping motor 56 to the second transport roller 54. The motor drive unit 59 drives the stepping motor 56. The optical sensor 60 is the scanner 5
It is detected whether or not the document 50 is directly above 1.

The motor drive section 59 has a frequency storage section 61, a frequency switching section 62 and a pulse signal generating section 63 as shown in FIG. The frequency storage unit 61 stores in advance the first drive frequency and the second drive frequency as the frequency of the pulse signal for driving the stepping motor 59. Here, the second drive frequency is higher than the first drive frequency. The frequency switching unit 62 switches the frequency of the pulse signal for driving the stepping motor 59 generated by the pulse signal generation unit 63 between the first driving frequency and the second driving frequency stored in the frequency storage unit 61 in advance. The pulse signal generation unit 63 generates a pulse signal of the first drive frequency or the second drive frequency according to the instruction from the frequency switching unit 62. Here, since the second drive frequency is higher than the first drive frequency, the rotation of the stepping motor 56 is faster when driven by the signal of the second drive frequency than when driven by the signal of the second drive frequency. .

A document conveying operation when a document is read by the facsimile apparatus having the above configuration will be described with reference to the flowchart of FIG.

When a document reading instruction is input from the panel section 12, the facsimile apparatus checks whether or not the document 50 is located at the document feeding start position on the document hopper (not shown) or the like (step S1), and then on the document hopper or the like. If the original 50 is present, the original reading device is instructed to read the original. The frequency switching unit 62 of the document reading apparatus instructs the pulse signal generation unit 63 to output a pulse signal of a low frequency to the stepping motor 56.
Instruct to drive. When the pulse signal generation unit 63 receives the above instruction from the frequency switching unit 62, it reads the low first driving frequency from the frequency storage unit 61 and outputs a pulse signal of the first driving frequency to the stepping motor 56, The driving of the stepping motor 56 is started (step S2). The rotational force of the stepping motor 56 is transmitted to the first transport roller 52 via the first drive transmission portion 57. When the first conveyance roller 52 rotates to convey the original 50, and the optical sensor 60 detects that the leading end of the original reaches just above the scanner (step S3), the frequency switching unit 62 causes the frequency switching unit 62 to perform a predetermined time. To set the internal timer 64 (step S4). Here, the above-mentioned fixed time is the angular velocity hunting of the stepping motor at the time of load fluctuation during the time until the leading edge of the document reaches the second transport roller, which is obtained from the document transport speed and the distance from the scanner to the second transport roller. It is the convergence time, and the angular velocity hunting time of the stepping motor 56 at the time of load fluctuation is α
Then, (from the position of the sensor 60, the second drive roller 54
Distance) / (conveyance speed of the recording paper 50 when the first drive frequency is used) + α.

When the internal timer 64 counts the above-mentioned fixed time (step S5), the frequency switching section 62 instructs the pulse signal generating section 63 to drive the stepping motor 56 with a pulse signal of high frequency, and the pulse signal is generated. The signal generator 63 reads the second driving frequency having a high frequency from the frequency storage 61, outputs a pulse signal of the second driving frequency to the stepping motor 56, and changes the rotation speed of the stepping motor 56 (step S6). . Here, the variation amount of the load of the second conveying roller 54 due to the original 50 colliding with the second conveying roller 54 is proportional to the speed at which the leading end of the original 50 collides with the second conveying roller 54. The leading end of the original 50 is placed on the second transport roller 5
By lowering the conveying speed of the document 50 until it collides with the sheet 4, the amount of load fluctuation can be reduced, and the unevenness in the feeding of the document 50 is reduced to improve the quality of the read image.

The frequency switching unit 62 is a pulse signal generating unit 63.
On the other hand, after instructing to drive the stepping motor 56 with a high-frequency pulse signal, when the optical sensor 60 detects the rear end of the document 50 (step S7), a predetermined discharge time is designated and the operation is performed again. The internal timer 64 is set (step S8). Here, the discharge time is the time until the leading edge of the document reaches the second transport roller, which is obtained from the document transport speed and the distance from the scanner to the second transport roller (from the position of the sensor 60 to the second drive). Roller 54
(Distance to position) / (conveying speed of the recording paper 50 when the second drive frequency is used).

When the internal timer 64 counts the discharge time (step S9), the frequency switching section 62 instructs the pulse signal generating section 63 to stop the generation of the pulse signal. When the pulse generator 63 receives the above instruction, the generation of the pulse signal is stopped, the stepping motor 56 is stopped, and the next document 50 is prepared for conveyance (step S1).
0).

In the above embodiment, the case where the frequency of the pulse signal for driving the stepping motor 56 is changed to change the conveying speed of the document 50 has been described. However, the current value of the pulse signal for driving the stepping motor 56 is changed to change the motor torque. You may make it shine. Stepping motor 5
FIG. 5 shows the configuration of the motor drive unit when the current value of the pulse signal for driving 6 is changed.

As shown in the figure, the motor driving section 59a has a current value storage section 61a, a current value switching section 62a and a pulse signal generating section 63a. The current value storage unit 61a stores in advance the first drive current value and the second drive current value as the current value of the pulse signal for driving the stepping motor 59. Here, the second drive current value is lower than the first drive current value. The current value switching unit 62a is arranged between the first drive current value and the second drive current value, which are stored in the current value storage unit 61a in advance, as the current value of the pulse signal for driving the stepping motor 59 generated by the pulse signal generation unit 63a. Switch with. Pulse signal generator 63
a generates a pulse signal of the first drive current value or the second drive current value according to the instruction from the current value switching unit 62a. Here, since the second drive current value is lower than the first drive current value, the torque T1 when driven by the signal of the first drive current value is driven by the signal of the second drive current value as shown in FIG. Is larger than the torque T2 in the case of

A document conveying operation when a document is read by the facsimile apparatus having the above configuration will be described with reference to the flowchart of FIG.

When a document reading instruction is input from the panel section 12, the facsimile machine checks whether or not the document 50 is present on the document hopper (not shown) or the like as described above (step S11). Instructs the document reading device to read the document. Current value switching unit 62 of the document reading device
a instructs the pulse signal generation unit 63a to drive the stepping motor 56 with a pulse signal having a high current value, and the pulse signal generation unit 63a outputs from the current value storage unit 61a a first drive current having a high current value. The value is read, the pulse signal of the first drive current value is output to the stepping motor 56, and the driving of the stepping motor 56 is started (step S12). The rotational force of the stepping motor 56 is transmitted to the first conveyance roller 52 via the first drive transmission portion 57, and the original 50 is conveyed by the rotation of the first conveyance roller 52. When the optical sensor 60 detects that the leading end of the document 50 reaches directly above the scanner 60 (step S1).
3), the current value switching unit 62a sets a predetermined fixed time and sets the internal timer 64a (step S1).
4). Here, the above-mentioned fixed time is (distance from the position of the sensor 60 to the position of the second drive roller 54) / (conveying speed of the recording paper 50 when the first drive current value is used) + α, as described above. I want it.

When the internal timer 64a counts the fixed time (step S15), the current value switching section 62a sends the stepping motor 56 a pulse signal of the second driving current value which is a low current value to the pulse signal generating section 63a. The pulse signal generator 63a reads the second drive current value from the current value storage 61a, outputs the pulse signal of the second drive current value to the stepping motor 56, and outputs the pulse signal to the stepping motor 56. The rotation torque of is changed (step S16). Here, since the higher the current value is, the higher the rotation torque of the stepping motor 56 is, the rotation torque of the stepping motor 56 is high until the original 50 collides with the second conveyance roller 54, and the driving unevenness of the stepping motor 56 can be reduced. The quality of the read image is high.

The current value switching section 62a is a pulse signal generating section 6
3a is instructed to drive the stepping motor 56 with a pulse signal having a low current value, and then the optical sensor 60
Detects the trailing edge of the document 50 (step S17),
A predetermined discharge time is designated and the internal timer 64a is set again (step S18). Here, the discharge time is obtained by (distance from the position of the sensor 60 to the position of the second drive roller 54) / (conveying speed of the recording paper 50 when the second drive current value is used), as described above. .

When the internal timer 64a counts the discharge time (step S19), the current value switching section 62a instructs the pulse signal generating section 63a to stop the generation of the pulse signal, and the pulse generating section 63 causes the pulse generating section 63 to stop. The generation of the pulse signal is stopped and the stepping motor 56 is stopped (step S20).

Although the motor torque is changed by changing the current value of the pulse signal for driving the stepping motor 56 in the above embodiment, the motor torque is changed by changing the voltage of the pulse signal for driving the stepping motor 56. May be. FIG. 8 shows the configuration of the motor drive unit when the current value of the pulse signal for driving the stepping motor 56 is changed.

As shown in the figure, the motor driving section 59b has a voltage storage section 61b, a voltage switching section 62b and a pulse signal generating section 63b. The voltage storage unit 61b stores in advance the first drive voltage and the second drive voltage as the voltage of the pulse signal for driving the stepping motor 59. Here, the second drive voltage is lower than the first drive voltage. The voltage switching unit 62b includes a stepping motor 59 generated by the pulse signal generating unit 63b.
The voltage of the pulse signal for driving the
Switching between the first drive voltage and the second drive voltage stored in. The pulse signal generation unit 63b generates a pulse signal of the first drive voltage or the second drive voltage according to the instruction from the voltage switching unit 62b. Here, since the second drive voltage is lower than the first drive voltage, the torque T3 when driven by the signal of the first drive voltage is the torque when driven by the signal of the second drive voltage as shown in FIG. Greater than T4.

A document conveying operation when a document is read by the facsimile apparatus having the above configuration will be described with reference to the flowchart of FIG.

When a document reading instruction is input from the panel section 12, the facsimile apparatus checks whether or not the document 50 is present on the document hopper (not shown) or the like (step S21), and if there is the document 50, as described above. Instructs the document reading device to read the document. Voltage switching unit 62b of the document reading device
Instructs the pulse signal generator 63b to drive the stepping motor 56 with a pulse signal having a high current value, and the pulse signal generator 63b reads the first drive voltage, which is a high voltage, from the voltage storage 61b, The pulse signal of the first drive voltage is output to the stepping motor 56 to start driving the stepping motor 56 (step S22). The rotational force of the stepping motor 56 is transmitted to the first transport roller 52 via the first drive transmission portion 57,
When the original 50 is conveyed by the rotation of the first conveying roller 52, and the optical sensor 60 detects that the front end of the original 50 has reached directly above the scanner 60 (step S23), the voltage switching unit 62b has a predetermined constant value. Internal timer 6 by specifying the time
4 is set (step S24). Here, the above-mentioned fixed time is obtained by (distance from the position of the sensor 60 to the position of the second drive roller 54) / (conveying speed of the recording paper 50 when the first drive voltage is used) + α, as described above. .

When the internal timer 64b counts the fixed time (step S25), the voltage switching section 62b drives the stepping motor 56 with the pulse signal of the second driving voltage which is a low voltage to the pulse signal generating section 63b. The pulse signal generator 63b causes the voltage storage unit 61b to
The second driving voltage is read from the stepping motor 56, the pulse signal of the second driving voltage is output to the stepping motor 56, and the rotational torque of the stepping motor 56 is changed (step S2).
6). Here, the higher the voltage, the stepping motor 56
Since the rotation torque of the second conveyance roller 5 is high,
The rotation torque of the stepping motor 56 is high until it collides with No. 4, the driving unevenness of the stepping motor 56 can be reduced, and the quality of the read image is improved.

The voltage switching section 62b is a pulse signal generating section 63.
When the optical sensor 60 detects the trailing edge of the document 50 (step S27) after instructing b to drive the stepping motor 56 with a low-voltage pulse signal (step S27), a predetermined discharge time is designated. The internal timer 64a is set again (step S28). Here, the discharge time is obtained by (distance from the position of the sensor 60 to the position of the second drive roller 54) / (conveyance speed of the recording paper 50 when the second drive voltage is used), as described above.

When the internal timer 64b counts the discharge time (step S29), the voltage switching section 62b instructs the pulse signal generating section 63b to stop the generation of the pulse signal, and the pulse generating section 63b outputs the pulse. The generation of the signal is stopped and the stepping motor 56 is stopped (step S30).

The timer 64 may be provided outside the motor drive unit 59 as shown in the configuration diagram of FIG. 11 for switching the frequency.

[0043]

As described above, according to the present invention, the stepping motor is driven by the signal of the predetermined first driving frequency when the original is conveyed by the first conveying roller, and the original is caught by the second conveying roller. After that, when a predetermined period of time elapses, the stepping motor is driven by a signal of a predetermined second driving frequency higher than the first driving frequency. It is possible to reduce the variation amount of the load of the second transport roller by making the document transport speed at the time of the leading end of the second transport roller lower than the document transport speed by the second transport roller.

Further, since the document conveying speed when the leading end of the document is projected into the second conveying roller is set to be slower than the document conveying speed by the second conveying roller, unevenness in feeding of the document is reduced and the quality of the read image is improved. In addition, noise and the like can be reduced.

When the original is conveyed by the first conveying roller, the stepping motor is driven by a signal of a predetermined first drive current value, and the original is pinched by the second conveying roller, and then a predetermined time elapses. Then, since the stepping motor is driven by the signal of the predetermined second driving current value lower than the first driving current value, the leading end portion of the document is projected into the second conveying roller in the facsimile device having the sheet scanner type document reading unit. At this time, the original carrying torque can be made larger than the original carrying torque by the second carrying roller to reduce the fluctuation amount of the load of the second carrying roller.

When the document is conveyed by the first conveying roller, the stepping motor is driven by a signal of a predetermined first driving voltage, and after the original is pinched by the second conveying roller, a predetermined time elapses. Since the stepping motor is driven by the signal of the predetermined second driving voltage lower than the first driving voltage, the original when the leading edge of the original enters the second conveying roller in the facsimile apparatus having the sheet scanner type original reading unit The conveyance torque can be made larger than the torque when the second conveyance roller conveys the document, and the amount of change in the load of the second conveyance roller can be reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a facsimile machine.

FIG. 2 is a configuration diagram of a document reading device.

FIG. 3 is a configuration diagram of a motor drive unit.

FIG. 4 is a flowchart showing an operation of the document reading apparatus.

FIG. 5 is a configuration diagram of a motor drive unit when a current value is switched.

FIG. 6 is a waveform diagram showing the relationship between current value and torque.

FIG. 7 is a flowchart showing an operation of the document reading apparatus when switching a current value.

FIG. 8 is a configuration diagram of a motor drive unit when a voltage is switched.

FIG. 9 is a waveform diagram showing the relationship between voltage and torque.

FIG. 10 is a flowchart showing the operation of the document reading apparatus when the voltage is switched.

FIG. 11 is a configuration diagram of a motor drive unit when a timer is provided outside the motor drive unit.

FIG. 12 is a configuration diagram of a conventional document reading apparatus.

FIG. 13 is a waveform diagram showing changes in angular velocity.

[Explanation of symbols]

 50 Original Document 51 Scanner 52 First Conveying Roller 54 Second Conveying Roller 56 Stepping Motor 59 Motor Driving Section 59a Motor Driving Section 59b Motor Driving Section 60 Optical Sensor 61 Frequency Storage Section 61a Current Value Storage Section 61b Voltage Storage Section 62 Frequency Switching Section 62a Current value switching unit 62b Voltage switching unit 63 Pulse signal generating unit 63a Pulse signal generating unit 63b Pulse signal generating unit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location H04N 1/00 108 H04N 1/00 108M

Claims (3)

[Claims] 1. A first conveyance roller which is driven by a driving force from a stepping motor, and a second conveyance roller, which conveys an original in the scanner direction by the first conveyance roller and is positioned behind the scanner after the original is read by the scanner. In a sheet-scanner-type document reading apparatus in which a document is conveyed by two conveyance rollers, when a document is conveyed by the first conveyance roller, a stepping motor is driven by a signal of a predetermined first driving frequency, and a document is sandwiched by a second conveyance roller. An original reading device characterized in that, after a predetermined period of time has elapsed after driving, the stepping motor is driven by a signal of a predetermined second drive frequency higher than the first drive frequency. 2. A first conveyance roller driven by a driving force from a stepping motor, and a second conveyance roller, wherein the first conveyance roller conveys an original in the scanner direction, and the original is positioned behind the scanner after the original is read by the scanner. In a sheet scanner type document reading apparatus that conveys a document by two conveyance rollers, when a document is conveyed by the first conveyance roller, a stepping motor is driven by a signal of a predetermined first drive current value, and the second conveyance roller conveys the document. An original reading device characterized by driving a stepping motor with a signal of a predetermined second drive current value lower than the first drive current value when a predetermined time has passed after the insertion. 3. A first conveyance roller driven by a driving force from a stepping motor and a second conveyance roller, wherein the first conveyance roller conveys an original in the scanner direction, and the original is positioned behind the scanner after the original is read by the scanner. In a sheet-scanner-type document reading apparatus that conveys a document by two conveyance rollers, when a document is conveyed by a first conveyance roller, a stepping motor is driven by a signal of a predetermined first drive voltage, and a document is separated by a second conveyance roller. An original reading apparatus, characterized in that, after a predetermined time has elapsed after driving, the stepping motor is driven by a signal of a predetermined second drive voltage lower than the first drive voltage.