JP2886606B2 - Image processing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus that processes an image, and more particularly, to a mechanism that includes a motor inside the apparatus and controls a feedback of the rotation. To an image processing apparatus.

2. Description of the Related Art Laser printers have been widely used to print image information output from word processors and computers. Many of such laser printers include a photoconductor (hereinafter simply referred to as a photoconductor drum) such as a photoconductor drum or a photoconductor belt for writing image information as optical information. The photosensitive drum is charged first, and then optical information is written using a laser beam to form an electrostatic latent image. The electrostatic latent image is developed by a developing device, and a toner image is formed on a photoconductor. This toner image is transferred to recording paper. The recording paper is fixed by a fixing device such as a heat roll, and is carried out to a paper discharge tray.

In such a laser printer, a laser beam is scanned one line at a time in the axial direction of the photosensitive drum (main scanning) by a polygon mirror (rotating polygon mirror), while the photosensitive drum is rotated in a predetermined direction (sub-scanning direction). To form an electrostatic latent image. Therefore, in the state where the formation of the electrostatic latent image is performed, the photosensitive drum must rotate at a specified speed in the sub-scanning direction and at a constant speed in order to equalize the pitch of each line.

For this purpose, the photoconductor drum driving motor increases its rotation speed at the start of rotation of the photoconductor drum, and when the rotation speed reaches a predetermined value, the constant speed control is performed at the specified speed described above. Speed feedback is provided. In order to perform this feedback, the rotation speed of the motor for driving the photosensitive drum is detected by an encoder. That is, the motor is controlled so that the speed detected by the encoder becomes an expected value, whereby the constant speed control of the photosensitive drum is performed.

FIG. 12 illustrates the principle of such a constant speed control in a conventional image processing apparatus. The encoder 211 is connected to, for example, a photosensitive drum driving motor 212 and outputs an AC waveform 213 having a frequency proportional to the rotation speed of the motor 212 based on the same principle as that of a generator. The AC waveform 213 is appropriately amplified by an amplifier 214, and the result is binarized by a binarization circuit 215. The pulse signal 216 thus obtained is input to the speed control circuit 217, and the rotation speed of the motor 212 is detected.

FIG. 13 shows details of the speed control circuit. The speed control circuit 217 includes a CPU (Central Processing Unit) 221. The CPU 221 is connected to the ROM 223 and the RAM 22 via the bus 222.
4, 16-bit timer 225, 8-bit PWM circuit 226 and I / O
Connected to port 227.

Here, the ROM 223 is a read-only memory that stores programs for the CPU 221 to perform various controls. RA
M224 is a random access memory for temporarily storing various data. The 16-bit timer 225 is a circuit that sequentially counts 16-bit data in synchronization with a clock (not shown).

FIG. 14 shows a periodic change in the count value of the 16-bit timer. The 16-bit timer 225 counts up one by one from the minimum value MIN (O), and the maximum value MAX
When (OFFFFH) is counted, counting is again started one by one from the minimum value MIN.

Returning to FIG. 13, the description will be continued. Various input / output devices are connected to the I / O port 227, and the above-described pulse signal 216 is also input from here, and the CPU 221 operates at the time of its startup.
The count value (hereinafter, referred to as a capture value) of the 16-bit timer 225 is read and stored in a capture register 225A in the 16-bit timer 225. Further, an interrupt is generated for the CPU 221 at the time of the rise. In this interrupt processing, the CPU 221 calculates the difference between the count value previously written to the register in the 16-bit timer 225 and the current count value, calculates the result, determines the power to be supplied, and determines the 8-bit PWM. Send to circuit 226.

Now, suppose that the previous count value was the value C _N in FIG. 14, and the current count value is the value C _{N + 1} . In this case, the motor 212 rotates at a lower speed as the difference _CD increases, and the motor 212 rotates at a higher speed as the difference CD decreases.

8-bit PWM circuit 226 varies the threshold for the count value of the 8-bit timer built in accordance with the integration of the difference C _D and C _D, to generate a PWM signal 229.

FIG. 15 illustrates the principle of generating a PWM signal.
FIG. 9A shows a periodic change in the count value of the 8-bit timer when counting at a certain clock. Similar to the 16-bit timer shown in FIG. 14, the count value is the minimum value MIN (O ) To the maximum value MAX (OFFH) at regular intervals. The count value of the 8-bit timer is compared by a dashed line 231 in the figure as an example, and a pulse signal that sets a section having a larger count value to the H (high) level and the other to the L (low) level Occurs when the 15th
It looks like Figure b. When a comparison is made, for example, with a dashed line 232 as a threshold higher than the one-dot chain line 231, the resulting pulse signal is as shown in FIG. By comparing the sawtooth wave represented by the count value with an arbitrary value,
A PWM signal having a pulse width corresponding to the magnitude of the value is generated.

The PWM signal 229 output from the 8-bit PWM circuit 226 is appropriately amplified by the amplifier 234 and supplied to the motor drive circuit 235 to drive the motor 212. That is, the DC drive motor 212 is supplied with a pulse signal that is turned on and off at a certain voltage, and the rotation speed is controlled according to the pulse width.

[Problem to be Solved by the Invention] The curve shown by a solid line in FIG. 16 represents ideal speed control in such an image processing apparatus. In the figure, the vertical axis represents the rotation speed of the photosensitive drum driven by a motor, for example, and the horizontal axis represents the elapsed time. When driving of the motor 212 from where the time t ₀ is started, initially the motor 212 is driven at full power, will linearly increase the rotation speed. Then from the time the speed control circuit 217 described in FIG. 13 has reached a certain low speed V ₁ than the final velocity V _2, the speed of the motor 212 while the speed control circuit 217 changes the pulse width is constant Start such control.

However, in the image processing apparatus, noise may be superimposed on the AC waveform 213 output from the encoder 211 shown in FIG. 12 due to a discharge or a variety of causes generated in a high voltage generating portion in the apparatus. In such a case, the binarization circuit 215 may binarize even a noise portion.

FIG. 17 is for explaining the state of the pulse signal after binarization in this case. FIG. 7A shows the pulse signal 216A in a state where no noise is generated. In FIG. 2B, a “whiskers” 241 due to noise are generated in some of the pulses.

When such noise occurs, the count value is written to the capture register 225A at the rising edge of each waveform such as noise. As a result, the difference in the count value becomes smaller in the portion where noise occurs,
Even if the rotation speed of the motor 212 is low, the speed becomes apparently high. Therefore, so that would detect a higher speed than the speed V ₁ at a much lower rate V ₃ than the speed V _1, for example, FIG. 16. In such a case, as indicated by the chain line in this FIG. 16, so that feedback control is performed from the actual time of the speed V _3. As a result, the speed varies greatly overshoot would occur, the time to converge to the final velocity V ₂ will be prolonged.

Moreover, the voltage width of the AC waveform 213 output from the encoder 211 is smaller as the motor rotates at a lower speed.
Therefore, malfunctions due to noise as described above are more likely to occur as the motor rotates at a lower speed.
There is a problem that the adverse effects of overshoot are more likely to occur.

Accordingly, a first object of the present invention is to provide an image processing apparatus capable of stably controlling the speed of an internal mechanism by a motor even when noise occurs.

A second object of the present invention is to provide an image processing apparatus capable of accurately performing a wide speed control of an internal mechanism by a motor.

[Means for Solving the Problems] In the invention described in claim 1, for example, a DC motor for moving the surface of a photoconductor such as a photoconductor drum or a photoconductor belt, a drive circuit for driving the DC motor, An encoder that outputs a pulse signal at a cycle corresponding to the rotation speed of the DC motor, a counter that counts a clock signal, and a cycle monitor that monitors whether the cycle of the pulse signal output from the encoder is shorter than a predetermined cycle. Means for storing the count value of the counter at the time when the pulse signal is generated when the period monitoring means does not determine that the period is shorter than the predetermined period, while the period monitoring means is shorter than the predetermined period. When it is determined that the current count value of the counter is invalid, the memory that stores the previous count value as the current count value and the drive of the DC motor A speed discriminating means for discriminating the rotational speed of the DC motor by calculating a difference between count values which are successively written to the memory after a pulse signal has been generated a predetermined number of times or more from the start of operation is provided in the image processing apparatus.

Then, the count value is not adopted until the pulse signal is generated a predetermined number of times or more from the start of the driving of the DC motor, and whether the cycle of the pulse signal output from the encoder is shorter than the predetermined cycle is monitored. If the period monitoring means does not determine that the period is shorter than the predetermined period, the count value of the counter at the time when the pulse signal is generated is stored. Otherwise, the current count value of the counter is invalidated. As a result, the previous count value is stored as the current count value, and the first object is achieved except for unstable elements.

According to the second aspect of the present invention, for example, a DC motor for moving the surface of a photoreceptor such as a photoreceptor drum or a photoreceptor belt, a drive circuit for driving the DC motor, and a cycle corresponding to the rotation speed of the DC motor An encoder that outputs a pulse signal, a counter that counts a clock signal, a period monitoring unit that monitors whether a period of the pulse signal output from the encoder is shorter than a predetermined period, and the period monitoring unit includes: While the count value of the counter at the time when the pulse signal is generated is not determined to be shorter than the predetermined cycle, the count value of the counter is stored when the cycle monitoring unit determines that the cycle is shorter than the predetermined cycle. A memory that invalidates the value and stores the previous count value as the current count value, and after a predetermined time has elapsed from the start of driving the DC motor. Taking the difference of the count value to be written to successive in the memory is and a speed determining means in the image processing apparatus for determining the rotational speed of the DC motor.

Then, while not determining the count value until a predetermined time has elapsed from the start of driving the DC motor, monitoring whether the cycle of the pulse signal output from the encoder is shorter than the predetermined cycle, If the period monitoring means does not determine that the period is shorter than the predetermined period, the count value of the counter at the time when the pulse signal is generated is stored. By storing the count value as the current count value, the above-described first object is achieved except for unstable elements.

According to the third aspect of the present invention, for example, a DC motor for moving the surface of a photoconductor such as a photoconductor drum or a photoconductor belt, a drive circuit for driving the DC motor, and a cycle corresponding to the rotation speed of the DC motor , A first counter that counts a clock signal at a relatively long cycle, a second counter that counts a clock signal at a relatively short cycle, and both counters that generate a pulse signal The image processing apparatus includes a capture register for storing the count values of the first and second counters, and speed determination means for determining the rotation speed of the DC motor based on the count values of the first and second counters stored in the capture registers. Let it.

Then, by using the counter of the two cycles, the above-described second object is achieved in correspondence with a wide range of speed control of the motor.

"Example" Hereinafter, the present invention will be described in detail with reference to examples. In addition,
In this embodiment and the modified example, the counter and the timer are used in the same meaning.

FIG. 2 shows an image processing apparatus of the present embodiment constituted by a laser printer and an image scanner.

A laser printer 11 serving as an image recording device in the image processing device includes a laser scanning device 12. The laser scanning device 12 includes a semiconductor laser 13 that modulates and outputs laser light in accordance with an image signal. The laser beam emitted from the semiconductor laser 13 enters a polygon mirror (rotating polygon mirror) 14 and is deflected according to the rotation. After passing through the fθ lens 15, the deflected laser beam has its traveling direction changed by mirrors 16 and 17, and is output from the laser scanning device 12.

Below the laser scanning device 12, a photosensitive drum 19 that rotates at a constant speed is arranged. The laser beam output from the laser scanning device 12 repeatedly scans a predetermined exposure position 21 of the photosensitive drum 19 in the axial direction, that is, the main scanning direction. A charging corotron 22 is disposed slightly before the exposure position 21 so as to face the photoconductor drum 19, so that the surface of the photoconductor drum 21 is uniformly charged. By irradiating the charged photosensitive drum 21 with a laser beam, an electrostatic latent image corresponding to image information is formed on the drum surface. This electrostatic latent image is developed by the developing device 24 on the drum surface downstream of the exposure position. In the developing device 24, a developing roll 25 for magnetically raising toner to develop an electrostatic latent image,
Components such as a toner supply mechanism 26 for supplying the toner in the cartridge to the developing roll 25 are arranged. A predetermined developing bias is applied to the developing device 24.

The toner image formed by the development of the developing device 24 is transferred to the transfer corotron 28 by the rotation of the photosensitive drum 19.
To the position opposite to, where the recording paper (plain paper)
Will be transferred electrostatically to The charge corotron 22 and the transfer corotron 28 used in this embodiment have a structure in which a single corotron wire is stretched between the ground and a voltage application terminal.

Next, the recording paper transport path will be briefly described. Recording paper (not shown) is provided in a three-stage cassette tray 31-1 to 31-
3 are stacked. Crescent rolls 32-1 to 32-3 each having a half-moon shape are arranged slightly above these cassette trays 31-1 to 31-3. These half-moon rolls 32-1 to 32-3 are selectively driven in accordance with the type of the selected cassette tray 31, so that one type of recording paper sent out is supplied to a predetermined type. The paper is transported to the location of the transport roll 33 via the path. In this laser printer, the recording paper is sent out using the half-moon rolls 32-1 to 32-3. However, other feeding means such as a retard roll may be used instead.

The fed recording paper advances along the path shown by the broken line by the transport roll 33, and stops the advance once it reaches the leading end of the registration roll. Thereafter, the electromagnetic clutch (not shown) starts rotation of the registration roll 34 in synchronization with the rotation position of the photosensitive drum 19, and the recording paper starts to be stably conveyed at a constant speed. Thus, the recording paper passes between the photosensitive drum 19 and the transfer corotron 28 at a desired timing. Only at the time of this passage, the transfer corotron 28 discharges, whereby the toner image on the photosensitive drum 19 is electrostatically attracted toward the transfer corotron 28, and the toner image is transferred onto the recording paper. . The recording paper on which the transfer has been performed is neutralized from the back surface thereof by a static eliminator (not shown) arranged downstream of the transfer corotron 28, and is separated from the drum surface. After the peeled recording paper is transported on a transport path of a predetermined length to release the tension,
It is carried to a fixing device comprising a pair of a heat roll 6 and a pressure roll 8. In the fixing device, the recording paper passes between a heat roll 6 and a pressure roll 8 which are nipped with a predetermined width. At this time, the side of the recording paper on which the toner image has been transferred is the heat roll 6 side, and the pressure roll 8 presses the recording paper against the heat roll 6 to enable efficient heat transfer. Heat roll 6, at the time when the recording paper as previously described has been reached is controlled such that the second set temperature S ₂ of the high temperature side, a first set of low-temperature side at a given point in addition to this It is controlled so that the temperature S _1. While being controlled to the second predetermined temperature S _2,
The toner image on the recording paper is heat-fixed to the paper surface.

At the exit side of the fixing device, a switching valve 38 for switching the conveyance path of the recording paper after fixing is provided. This switching valve
By the switching operation of 38, the recording paper after fixing goes straight as it is and is discharged in the first discharge direction 39, or is transported in the device in a reverse U-shape and is substantially in the opposite direction to the first discharge direction 39. Second
In the discharge direction 41 of the laser printer 11. The reason why two types of discharge directions can be selected in this way is to enable selection of discharge with the recording surface facing up or discharge with the recording surface down. When the second ejection direction 41 is selected and the recording surface is ejected with the recording surface facing down, printed sheets one by one can be stapled by the stapler in the ejection order.

By the way, the toner image not transferred to the recording paper is
It is removed from the drum surface by a cleaning device 43 arranged further downstream of the transfer corotron 28.
The cleaning device 43 includes a blade 44 for scraping toner from the drum surface, and a rotating body 45 for retracting toner particles accumulated under the blade 44 to a rear storage location.
Is arranged.

On the other hand, an image scanner 52 is connected to the laser printer 11 via a cable 51. Image scanner 52
Is a device for reading the image information of the original 54 placed on the platen glass 53. An openable and closable platen cover 55 for holding a document 54 is arranged on the upper portion of the main body of the image scanner 52. Further, inside the apparatus main body, a scanner 58 is reciprocally mounted on a rail 57 arranged in parallel with the platen glass 53 and in the longitudinal direction thereof. The scanner 58 will be described later (FIG. 1).
It is driven by a scanner motor.
In the scanner 58, a lamp 61 for illuminating a reading portion of the original 54, an optical lens 62 for converging the reflected light of the original 54, and a one-dimensional lens disposed at a position where an optical image is formed by the optical lens An image sensor 63 is provided. The image information read by the one-dimensional image sensor 63 is
The image data is input to an image processing circuit to be described later in the image scanner 52, and after being subjected to processing such as binarization and dither processing, the data is supplied to the laser printer 11 via the cable 51.

1. Outline of Circuit Configuration FIG. 1 shows an outline of respective circuit portions of a laser printer and an image scanner in such an image processing apparatus.

The laser printer 11 has a CPU (central processing unit) 81 mounted thereon. The CPU 81 is connected to the following units via a bus 82 such as a data bus, and performs general control of the laser printer in addition to control of the surface temperature of the heat roll.

(A) ROM 83: a read-only memory storing programs for performing various controls of the laser printer.

(B) RAM 84: a random access memory for temporarily storing various data.

(C) Operation panel 85: A panel for performing various operations.

(D) Communication control unit 86: connected to a host computer (not shown) or the image scanner 52 of this embodiment via a cable 51, to receive data for printing and exchange data for control. .

(E) Image memory 88: Stores data for printing.

(F) Main motor drive circuit 89: a drive circuit of a main motor 91 for driving the photosensitive drum 19, the heat roll 6, or various rollers for conveying the recording paper of the laser printer.

(G) ROS motor drive circuit 92: a drive circuit for the ROS motor 93 that drives the polygon mirror 14.

(H) Fixing control circuit 94: a circuit for controlling the energization of the heater 95 built in the heat roll 6.

(I) High-voltage power supply control circuit 96: A circuit for generating high-voltage power supplies and applying these to the corotrons such as the charge corotron 22 and the developing electrodes 97.

(G) Signal input circuit 98: Processes signals supplied from various signal sources such as a temperature sensor 99 for measuring the surface temperature of the heat roll 6 and an encoder 101 for measuring the rotation speed of the main motor 91, and processes the signals on the bus 82. It is a circuit for sending out.

(L) Solenoid excitation circuit 102: A circuit for controlling the excitation of the solenoid 103 for controlling the switching of the switching valve 38 (FIG. 2).

(Ii) Clutch drive circuit 105: a circuit that controls the drive of the clutch 106 for controlling the rotation of the rollers on the transport path.

(C) Speed control circuit 107: a circuit that supplies data for speed control to a main motor drive circuit 89 for driving the main motor 91. Note that the speed control circuit 107 of the present embodiment
Although the basic circuit part is the same as the conventional speed control circuit shown in FIG. 13, it does not have its own CPU, ROM or RAM, and shares parts such as the CPU 81 in the laser printer 11. It is configured.

The image scanner 52 has its own CPU 111. The CPU 111 is connected to the following units via a bus 112.

(A) ROM 113: a read-only memory storing a program for controlling the operation of the image scanner.

(B) RAM 114: a random access memory for temporarily storing various data.

(C) Operation panel 115: A panel for performing an operation for reading a document.

(D) Communication control unit 116: is connected to the laser printer 11 via the cable 51, and supplies data for printing to the printer.

(E) Scanner motor drive circuit 117: a drive circuit for the scanner motor 118 that drives the scanner 58.

(F) Lamp lighting circuit 119: a drive circuit for lighting the lamp 61.

(G) Image processing circuit 121: a circuit that processes image information read by the one-dimensional image sensor 63 and passes the result to the communication control unit 86.

(H) Signal input circuit 122: a circuit for inputting a pulse signal from the encoder 123 for detecting the rotation state of the scanner motor 118.

(I) Speed control circuit 124: a circuit that inputs a pulse signal from the encoder 123 and controls the speed of the scanner motor 118. The circuit configuration is basically the same as that of the speed control circuit 107 in the laser printer 11.

Circuit for Preventing Malfunction FIG. 3 shows control at the start of rotation of the main motor in the image processing apparatus having the above-described configuration. The CPU 81 monitors the point in time when the start of driving of the main motor 91 is instructed to rotate the photosensitive drum 19 (step in FIG. 3). When the start of driving of the main motor 91 is instructed (Y), the 8-bit PWM circuit
Instructs the PWM signal 229 to be output and outputs the main motor 91
Is set to be driven at full power (step). Next, a first mode is set as a mode for motor control (step).

Table 1 below shows the contents of the three modes for mode control.

When the image processing apparatus is set to the first mode, the CPU 81 clears the count value C of the rising interrupt counter (step). Here, the rising interrupt counter counts a pulse signal output from the encoder 101 when the main motor 91 rises, and when the pulse signal reaches a predetermined value, determines that the pulse signal thereafter becomes valid and makes the speed control circuit 107 valid. Is a counter to give to This is provided to prevent a malfunction of speed control due to noise or the like when the main motor 91 starts up. The rising interrupt counter is configured by allocating a predetermined area of the RAM 84.

After clearing the rising interrupt counter, the CPU 81 enables the interrupt processing by the encoder 101 and ends the control (END).

FIG. 4 shows how the main motor is controlled after the control shown in FIG. 3 is completed. Under this control, the CPU 81 reads out data in a predetermined area of the RAM 84 and first checks the currently set mode (step in FIG. 4). If the first mode is set (step; Y), full power is output (step), the count value C of the rising interrupt counter is incremented by 1 (step), and the count value C It is checked whether or not the value of “10” is greater than “10” (step). This is to eliminate the influence of noise at the initial rotation of the main motor 91 as described above. In place of such control, interrupts are prohibited for a predetermined time from the start of rotation of the main motor 91, and after a certain time has elapsed, a capture value is read, saved in the RAM 84, and interrupts are enabled. Is also possible.

When the count value C of the rising interrupt counter becomes "10" or more in the step of FIG. 4 (Y), the CPU 81 changes the first mode to the second mode (step). And
The captured value of the encoder at that time is read (step), and this is written in a dedicated area of the RAM 84 (step). For this purpose, the speed control circuit 107 is provided with a 16-bit timer 225 as shown in FIG.

On the other hand, when the CPU 81 determines that the mode is the second mode (step Y in FIG. 4), the CPU 81 controls the main motor drive circuit 89 to drive the main motor 91 at full power (step S4). ). Then, the capture value at this time is read (step). CPU81
Calculates the period from when the previous interrupt was made to when this interrupt was made (step).

The calculated period is compared with a target value (step). Here, the target value is a period that corresponds to a certain low speed V ₁ than the rotation speed V ₂ of the main motor 91 corresponding to the set speed of the photosensitive drum 19 (see FIG. 16). That is, when the rotational speed as a result of the main motor 91 is driven at full power to reach the velocity V ₁ (step;
Y), the CPU 81 rewrites the mode from the second mode to the third mode (step), and rewrites the capture value of the encoder 101 (step).

On the other hand, if it is determined that the target value has not been reached in the comparison of the cycles in the steps (N), the capture value of the encoder 101 is read again when the next interrupt occurs, and the cycle is calculated. Will be performed.

Finally, if neither the first mode nor the second mode (step; N, step; N), that is, if the device is in the third mode
A description will be given of the case where the mode is set. This third
In the mode, feedback control is performed as control after reaching the speed V ₁ in Figure 16. That is, CP
When there is an interrupt due to the rise of the pulse signal from the encoder 101, the U81 reads the capture value of the encoder 101 (step). Then, the difference between this and the previous capture value is calculated to calculate the period (step).

When Motoma' the period, width of the pulse signal for setting the rotational speed V ₂ in Figure 16 is determined by the speed control circuit 107 (step), this is the main motor drive circuit
Supplied to 89 (step). Thereafter, the process proceeds to the step, where the capture value of the encoder 101 is rewritten, and the process is restarted from the step at the next encoder rising interrupt. That is, the photoreceptor drum 19 is rotated at a constant speed by repeatedly performing the control after the step.

Prevention of Error in Period Calculation As described above, in the image processing apparatus of this embodiment, the photosensitive drum 19 provided in the laser printer 11 uses the pulse signal output from the encoder 101 to generate the period of the pulse signal. Is calculated (step in FIG. 4). However, at a relatively low speed, this period from the rise of the pulse signal to the next rise is one of the values of the 16-bit timer 225 (FIG. 13) of the present embodiment.
It may be longer than the count period of the cycle.

The problem at such a low speed will be described with reference to FIG. FIG. 7A shows a temporal change of the count value of the 16-bit timer 225. The time from the minimum value MIN (O) of the count value to the next maximum value MAX (OFFFFH) corresponds to one cycle T.

FIG. 9B shows an example of a state of generation of a pulse signal when the main motor 91 starts up to some extent. And capture value A ₂ based on the captured value A ₁ and the next rising based on the rise in some point in the pulse signal is generated within one period T on the time axis. Therefore, it is possible to obtain a difference using these values A ₁ and A ₂ .

However, when the generation cycle of the pulse signal as shown in FIG c is longer than the 1 period T, only the captured value A ₃ and capture value A ₄ based on the next rising based on rising at the time in the pulse signal Then, it becomes impossible to check how much the count value has changed. Therefore, the two determined capture values A ₃ and A ₄
Is calculated as a value within one cycle, correct speed control cannot be performed.

In order to avoid such a problem, the clock cycle used for the 16-bit timer 225 may be made slower than before or a counter having a larger number of bits may be used. However, in this case, there is a problem that fine speed control becomes impossible, and the use of a special counter greatly increases the price of the apparatus.

Therefore, in the image processing apparatus of this embodiment, the main motor 91
The method employs a method capable of performing a wide range of advanced speed control from the time when the control signal rises to the time when the feedback control is performed.

FIG. 6 shows a main part of a speed control circuit enabling such control.

The speed control circuit 107 includes a divide-by-4 circuit 132 that divides the frequency of the clock signal 131 supplied to the 16-bit timer 225 by 4. The clock signal 133 output by dividing the frequency by 4 from the divide-by-4 circuit 132 is supplied to another 16-bit timer 134. When a pulse signal is supplied from the encoder 101 shown in FIG. 1, the count values of these two 16-bit timers 225 and 134 are read.

FIG. 7 shows the principle of calculating the speed by the speed control circuit using two 16-bit timers of the present embodiment. FIG. 5A is similar to FIG. 5A, and is a 16-bit timer.
225 represents a change in the cycle of the count value. When a pulse signal as shown in FIG. 7c arrives,
As described above, the difference between the two captured values A ₃ and A ₄ cannot be obtained.

FIG. 7B shows a period change of the count value of the 16-bit timer 134 that counts the clock signal divided by 4. Since the count cycle of the timer 134 is 4T, it is longer than the cycle of the pulse signal shown in FIG. 7c. Therefore, it is possible to determine how many cycles of the 16-bit timer 225 the captured time interval corresponds to, based on the two capture values B ₃ and B ₄ due to the rise of these pulse signals. Therefore, a substantial difference between these count values can be accurately calculated using this data and the two capture values A ₃ and A ₄ .

Of course, the frequency division ratio may be appropriately set to another value according to the width of the speed control in the image processing apparatus, or a timer or counter having another cycle may be separately prepared. The measurement using the two types of counters may be performed only when the rotation speed of the main motor 91 is low.
After that, the measurement may be performed using only the high-speed counter.

Further, in a section in which the accuracy of the speed control is not particularly required, the cycle of the clock signal is expanded only in that section.
By making the resolution of the timer such as the 16-bit timer 225 rough, the overflow of the timer can be prevented, and the period measurement can be performed correctly.

Control of Image Scanner The speed control of the main motor 91 in the laser printer 11 of the image processing apparatus has been described above. Next, the speed control of the scanner motor 118 arranged in the image scanner 52 of the image processing apparatus will be described. Do.

The scanner 58 shown in FIG. 2 reciprocates on the rail 57, and a scanner motor 118 is used as a driving source thereof. The difference between the control of the scanner motor 118 and that of the main motor 91 of the laser printer 11 is as follows.

(I) Since only the scanner 58 is driven, the photosensitive drum 19
The load is smaller than that of the main motor 91 which drives the heat roller 6 or the various rollers for transporting the recording paper, so that the scanner motor 118 is small and has low power.

(Ii) The moving speed of the scanner 58 during the forward movement is quite low.

FIG. 8 shows how the scanner reciprocates. In this figure, the vertical axis represents the speed of the scanner 58,
The + direction is the forward speed, and the-direction is the backward speed. Scanner 58 from the time t _A to t _B is moved forward, the reading of the time the document 54 (see FIG. 2) is performed. Times of Day
Although backward is performed for from t _B to return the scanner 58 to the home position, the first half rapid backward movement is performed in, to accurately control the stop position from the time t _C which has reached the point where almost approaching the home position Therefore, the speed becomes extremely low, and control for stopping is performed.

Due to the above-described characteristics, for example, even in the case where the rail 57 has a slight obstacle, the scanner motor 118 easily stops before reaching the specified position, especially in the control stage for stopping. Although the same speed control as that of the main motor 91 in the laser printer 11 is performed for the scanner motor 118 of this embodiment, it is generally difficult to drive the scanner motor 118 that has been stopped once due to a load. Therefore, in the image scanner 52 of the present embodiment, measures are taken to restart the drive when the scanner motor 118 stops at a position where it should not stop.

FIG. 9 shows the state of such control. When the CPU 111 instructs the scanner motor drive circuit 117 to start the scanner motor 118 (step in FIG. 9;
Y), the monitoring timer is started (step). Here the monitoring timer, which is formed using the RAM114 and clock signals, is set from 1.5 times the period of the pulse signal corresponding to the lowest speed is controlled to two times the time t _1.

After the watchdog timer is started, CPU 111 may interrupt depending on whether (step), whether the measurement time t of the timer exceeds the time t ₁ (step) and pulse signals were made the stop control of the image scanner 52 by an operator or the like It monitors whether it has been done (step).

When the stop control of the image scanner 52 is performed (Step; Y), the CPU 111 controls the scanner motor driving circuit 117 to stop driving the scanner motor 118 (Step). When an interruption is performed (step; Y), that is, when the rotation of the scanner motor 118 is started, the monitoring timer is preset (step),
Returning to the step again, the monitoring control is performed. That is, after the scanner motor 118 starts to rotate smoothly, the occurrence of a motor stop is monitored while presetting a monitoring timer every time an interrupt is performed.

On the other hand, if the measurement time t of the timer exceeds the time t ₁ at step will be stopped at (Y), when the rotation of the scanner motor 118 is non-stop control. In such a case, an increase in the driving power of the scanner motor 118 is instructed to the scanner motor driving circuit 117 (step). As a result, the scanner motor 118 is powered up, for example, by increasing the applied voltage.

In this state, when an interrupt occurs due to the arrival of the pulse signal from the encoder 123 (Step; Y), the driving power of the scanner motor 118 is returned to the original specified value (Step). Then, the monitoring timer is preset (step), and the process returns to the step again to perform the monitoring control.

Contrastingly, if the interruption even after the lapse of time t ₂ from the power-up is performed of the scanner motor 118 is not performed (step; Y), it is forced reboot of the scanner motor 118 by the power-up It turned out that the CPU
111 stops driving of the scanner motor 118 (step) and causes the operation panel 115 to display an error (step).

"Modifications" Although the drive control of the motor in the image processing apparatus of the present embodiment has been described above, the present invention is not limited to these, and various modifications are possible.

First Modified Example For example, with respect to the control of the main motor 91, in the embodiment, as shown in the step of FIG. At the start, the influence of noise at the beginning of rotation was removed. In a first modification,
The same noise removal is performed as control of the interrupt processing.

FIG. 10 shows such control at the beginning of rotation of the main motor. In this modification, when there is an interrupt, the CPU 81 loads the current capture value into a predetermined area of the RAM 84 (step in FIG. 9), and then reads the previous capture value (step). Then, the difference D between the two is calculated (step).

When the difference D is obtained, the CPU 81 compares this with the comparison value E (step). Comparison value E in this example is half the value of the difference corresponding to the final velocity V ₂ of the motor 212 in FIG. 16. Such a value indicates that the motor 212 is rotating at a speed much higher than the normal speed, and it can be inferred that an abnormal situation such as generation of noise occurs.

If the difference D is larger than the comparison value E (Y), it is assumed that such a danger has not occurred, and the previous capture value is replaced with the value captured in the current step (step). That is, the current capture value is written to the corresponding area of the RAM 84. Then, the driving of the main motor 91 is controlled based on the difference D.

On the other hand, if the difference is equal to or smaller than the comparison value E in the step (N), the captured value captured this time is not used, and the control performed last time for the main motor 91 is instructed. (Step).
That is, when noise occurs, malfunction due to this is avoided.

Second Modification In the embodiment, as shown in FIG. 7, two 16-bit timers 225 and 134 are used, and the clock signal used for one of the 16-bit timers 225 is divided by 4 and the other 16-bit timer is used. 13
The use of No. 4 prevented the occurrence of errors when the interval between arrivals of the pulse signal was long.

In the second modified example, unlike this, the overflow of the timer is detected, and the occurrence of the same error is prevented by using this.

FIG. 11 shows the basic configuration of a circuit for this purpose. The pulse signal output from the encoder 101 shown in FIG.
In addition to being directly used for the interrupt processing of the CPU 81, the delay circuit 153
After being delayed by a predetermined time, the signal is supplied to the reset terminals R of both the 16-bit timer 225 and the overflow detection circuit 161. At this point, the 16-bit timer 225 resets its timing operation, and starts the timing operation in synchronization with the clock signal. The overflow detection circuit 161 is a 16-bit timer 2
This circuit detects an overflow of 25. When an overflow occurs, the detection result is held and the content is reset at the same timing as the 16-bit timer 225.

When a pulse signal arrives at this circuit, the CPU 81 is interrupted, and at the same time, a control signal for reading the contents is supplied to both the 16-bit timer 225 and the overflow detection circuit 161. As a result, the 16-bit timer 225 stores the current count value 162 in the RAM 84 as a capture value. The overflow detection circuit 161 also stores overflow presence / absence data 163 indicating whether the 16-bit timer 225 has overflowed in the RAM 84 as overflow capture data. After such a storing operation is completed, the contents of the 16-bit timer 225 and the overflow detection circuit 161 are reset as described above.

Therefore, in the circuit of the second modification, even when a pulse signal arrives at a cycle longer than one cycle of the 16-bit timer 225 and less than two cycles, the count value of the 16-bit timer 225 is checked by checking the RAM 84 for overflow. Can be correctly obtained.

Note that in the embodiment, the speed control circuits 107 and 124 have their own CPUs.
Although it is described that the speed control circuit is not provided, such a speed control circuit may be configured using a CPU in which a counter such as a 16-bit timer is integrally configured with a pulse width control circuit such as an 8-bit PWM circuit. Of course.

[Effects of the Invention] As described above, according to the first aspect of the present invention, an encoder that outputs a pulse signal at a cycle corresponding to the rotation speed of the DC motor is used, and from the start of driving the DC motor for image processing. Since the rotation speed of the DC motor is determined based on the difference between the count values that are successively written to the memory after the pulse signal has been generated a predetermined number of times or more, a large amount of noise can be cut when the DC motor starts to be driven.
Also, it is monitored whether or not the period of the pulse signal output from the encoder is shorter than a predetermined period. If the period monitoring means does not determine that the period is shorter than the predetermined period, the time at which the pulse signal is generated is determined. While the count value of the counter is stored, in other cases the current count value of the counter is invalidated and the previous count value is stored as the current count value. It is possible to stabilize the speed control of the motor used in the device.

According to the second aspect of the present invention, an encoder that outputs a pulse signal at a cycle corresponding to the rotation speed of the DC motor is used, and the memory is successively stored in the memory after a lapse of a predetermined time from the start of driving of the DC motor for image processing. Since the rotational speed of the DC motor is determined based on the difference between the written count values, it is possible to cut a large amount of noise when the DC motor starts driving. Also, it is monitored whether or not the period of the pulse signal output from the encoder is shorter than a predetermined period. If the period monitoring means does not determine that the period is shorter than the predetermined period, the time at which the pulse signal is generated is determined. While the count value of the counter is stored, in other cases the current count value of the counter is invalidated and the previous count value is stored as the current count value. It is possible to stabilize the speed control of the motor used in the device.

According to the third aspect of the present invention, an encoder that outputs a pulse signal at a cycle corresponding to the rotation speed of the DC motor is used, a first counter that counts a clock signal at a relatively long cycle, Since the second counter that counts in a relatively short cycle is provided, the rotation speed of the DC motor can be determined over a wide range based on the count values of the first and second counters.
There is an advantage that the speed control of the motor can be stabilized over a wide range.

[Brief description of the drawings]

1 to 9 are diagrams for explaining an image processing apparatus according to an embodiment of the present invention. FIG. 1 is a block diagram showing a main part of a circuit configuration of the image processing apparatus, and FIG. FIG. 3 is a flow chart showing control at the start of rotation of the main motor in the image processing apparatus. FIG. 4 is a flowchart showing control of the main motor after the control shown in FIG. 3 is completed. FIG. 5 is a waveform diagram for explaining a problem at the time of low-speed control of the motor, and FIG. 6 is a speed control circuit which enables a wide range of speed control using two 16-bit timers. Block diagram showing the main part of
The figure shows various waveform diagrams for explaining the principle of speed calculation of the speed control circuit using these two 16-bit timers. FIG. 8 is a characteristic diagram showing the state of reciprocating movement of the scanner. FIG. 10 is a flowchart showing a control flow for enabling restarting of the scanner motor when the main motor is rotated, FIG. 10 is a flowchart showing a control at an initial rotation of the main motor in the first modification, and FIG. FIG. 12 is a block diagram showing a principle configuration of a circuit for detecting an overflow in a modification to prevent occurrence of a speed detection error, FIG. 12 is a block diagram showing a principle of constant speed control in a conventional image processing apparatus, and FIG.
FIG. 13 is a block diagram showing a main part of a conventional speed control circuit.
Fig. 14 is an explanatory diagram showing the periodic change of the count value of the 16-bit timer, Fig. 15 is a timing diagram showing the principle of generation of the PWM signal, and Fig. 16 is the ideal speed control and the overspeed in image processing. FIG. 17 is an explanatory diagram showing both shot examples, and FIG. 17 is various waveform diagrams for explaining the state of the pulse signal after binarization when noise occurs. 11… Laser printer, 52… Image scanner, 58… Scanner, 81, 111… CPU, 83, 113… ROM, 84, 114… RAM, 89 …… Main motor drive circuit, 91 …… Main Motor, 98, 122 ... signal input circuit, 101, 123 ... encoder, 107, 124 ... speed control circuit, 117 ... scanner motor drive circuit, 118 ... scanner motor, 131, 133 ... clock signal, 132 …… 4 divider circuit, 134, 225… 16 bit timer, 161… Overflow detection circuit, 226 …… 8 bit PWM circuit.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H02P 5/00-5/26 H02P 7/00-7/34 H04N 1/00 G03G 15/00 B41J 3 / 00

Claims (5)

(57) [Claims] A DC motor for image processing; a driving circuit for driving the DC motor; an encoder for outputting a pulse signal at a cycle corresponding to a rotation speed of the DC motor; a counter for counting a clock signal; Cycle monitoring means for monitoring whether the cycle of the pulse signal output from the encoder is shorter than a predetermined cycle; and if the cycle monitoring means does not determine that the pulse signal is shorter than the predetermined cycle, the pulse signal is While the count value of the counter at the time of occurrence is stored, when the cycle monitoring means determines that the cycle is shorter than the predetermined cycle, the current count value of the counter is invalidated and the previous count value is stored as the current count value. After the pulse signal is generated a predetermined number of times or more from the start of driving the DC motor, the memory is sequentially written into the memory. The image processing apparatus characterized by comprising a speed determining means for determining the rotational speed of the DC motor takes the difference between the count value that. 2. A DC motor for image processing, a driving circuit for driving the DC motor, an encoder for outputting a pulse signal at a period corresponding to a rotation speed of the DC motor, a counter for counting a clock signal, Cycle monitoring means for monitoring whether the cycle of the pulse signal output from the encoder is shorter than a predetermined cycle; and if the cycle monitoring means does not determine that the pulse signal is shorter than the predetermined cycle, the pulse signal is While the count value of the counter at the time of occurrence is stored, when the cycle monitoring means determines that the cycle is shorter than the predetermined cycle, the current count value of the counter is invalidated and the previous count value is stored as the current count value. A memory, and a difference between the count values sequentially written to the memory after a predetermined time has elapsed from the start of driving of the DC motor. Taken image processing apparatus characterized by comprising a speed determining means for determining the rotational speed of the DC motor. 3. A DC motor for image processing, a drive circuit for driving the DC motor, an encoder for outputting a pulse signal at a cycle corresponding to the rotation speed of the DC motor, and a clock signal at a relatively long cycle. A first counter that counts, a second counter that counts a clock signal at a relatively short cycle, a memory that stores count values of both counters at the time when the pulse signal is generated, and a memory that stores the count value. A speed discriminating unit for discriminating a rotation speed of the DC motor based on count values of the first and second counters. 4. A counter for counting the number of pulse signals output from an encoder at the start of driving of the DC motor, and based on a pulse signal output from the encoder after the counter has counted a predetermined number. The image processing apparatus according to claim 1, further comprising a speed determination unit configured to determine a rotation speed of the DC motor. 5. An image processing apparatus according to claim 1, further comprising a resolution changing means for setting the resolution of said counter at a lower speed when said DC motor is driven at a lower speed than in other cases. .