JP2013007793A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain the quality of a latent image by writing an appropriate value in data holding means when a power supply to driving means including the data holding means is resumed after shut down.SOLUTION: A power source voltage supplied from a power source 301 to a laser driver 304 can be instantaneously interrupted for various reasons. Since the instantaneous interruption causes a deletion of performance data stored in a register 307, the laser driver 304 cannot perform as intended when the power source voltage is restored. Coping with the problem, when a memory controller 305 detects an instantaneous interruption, a performance data is written from a non-volatile memory 306 to the register 307. Thereby, the laser driver 304 performs with appropriate performance data resulting in maintaining the quality of a latent image even when the instantaneous interruption occurs.

Description

  The present invention relates to a technique of an image forming apparatus that forms an image by deflecting and scanning a light beam.

  In an electrophotographic image forming apparatus, an electrostatic latent image is formed on a photoreceptor using laser light emitted from a laser light emitting element (LD), and the electrostatic latent image is developed with toner to form an image. Is going. Patent Document 1 discloses an image forming apparatus that forms an electrostatic latent image using a laser light emitting element. The laser driver IC controls the laser light quantity and operation mode. The set value of the amount of light for the laser driver IC has been previously adjusted with a variable resistor installed on the laser control board. The operation mode is set by pulling up or pulling down the terminal of the laser driver IC.

  In recent years, since the laser driver IC has been digitized, the light amount setting value and the operation mode are set in a register as drive data. The laser light emitting element is controlled by the laser driver IC based on the drive data set in the register. As a result, the variable resistor can be eliminated, and the setting contents can be easily controlled from the outside of the laser driver IC through an electric signal.

Japanese Patent No. 3384950

  By the way, an interlock mechanism has been proposed that mechanically cuts off the power supplied to some units such as a laser driver when the door of the image forming apparatus is opened. The reason why the mechanical interlock mechanism is adopted is that the operation accuracy is higher than that of the power interruption mechanism by software. The interlock mechanism cuts off the power of the laser driver IC and the like, but does not cut off the power of the engine controller and the like.

  When the power of the digital laser driver IC is cut off, the set value of the register is deleted. This is because the register is a volatile storage device. If the light amount setting value is deleted from the register during image formation, the laser light emitting element may not be controlled, or control based on the setting value may be performed.

  Therefore, when the door is opened and closed, the engine controller needs to reset the value in the register of the laser driver IC through the communication unit. As shown in Patent Document 1, as the number of laser beams increases, the number of registers for setting the light amount setting value and the like also increases. Such multiple beams increase the time for writing the set value from the engine controller to the register of the laser driver IC. This causes a delay in the printing start time after the door is opened and closed. Although the interlock mechanism is used as an easy-to-understand example, the same problem occurs when the voltage supplied from the commercial power source is unstable.

  Therefore, the present invention maintains the quality of the latent image by writing an appropriate value to the volatile storage means when the supply of power to the drive means including the volatile storage means is interrupted and restarted. Objective.

According to the present invention,
A light emitting means;
Storage means for storing drive data;
Data holding means for holding drive data read from the storage means while the voltage is supplied;
Driving means for driving the light emitting means based on the driving data held in the data holding means;
A power supply for supplying the data holding means and the driving means with a voltage necessary for the data holding means to hold the drive data,
After the voltage has dropped to a value at which the drive data cannot be held in the data holding means, the drive data stored in the storage means is returned to the data holding means in response to the return to the value at which the drive data can be held in the data holding means again. An image forming apparatus is provided in which the holding unit holds the image forming apparatus.

  According to the present invention, the voltage is stored in the storage unit in response to the voltage decreasing to a value that cannot hold the drive data in the data holding unit and then returning to the value that can hold the drive data in the data holding unit again. The data holding means holds the drive data. Therefore, since drive data is written in the data holding unit, the image forming apparatus can maintain the quality of the latent image.

FIG. 2 is a cross-sectional view illustrating the overall configuration of the image forming apparatus. The figure which shows the structure of an optical scanning unit typically. FIG. 2 is a block diagram illustrating a control unit according to the first embodiment. The block diagram which shows the internal structural example of a memory controller. The block diagram which shows the structural example of a power supply voltage monitoring circuit. The figure which shows the standby | waiting period after a power supply voltage resets. The flowchart which showed the process which a control unit performs. The figure which shows the waveform at the time of a power supply interruption. FIG. 6 is a block diagram illustrating a control unit according to a second embodiment. FIG. 9 is a block diagram illustrating a control unit according to a third embodiment.

<Example 1>
[overall structure]
FIG. 1 is a sectional view showing the overall configuration of the image forming apparatus of the present invention. Here, the printer 1 that forms a multicolor image using four color toners of YMCK will be described, but the present invention can also be applied to an image forming apparatus that forms a single color image. According to FIG. 1, four image forming stations are shown, but their basic configuration is the same. The image forming station includes the following units. The photosensitive drum 2 is a so-called image carrier. The charger 3 is a unit that uniformly charges the image carrier. The cleaner 4 is a unit for cleaning the image carrier. The optical scanning unit 5 is a unit that forms a latent image by irradiating the image carrier with light. The developing unit 7 is a unit that develops a latent image with toner to form a toner image. The transfer blade 6 is a unit that primarily transfers the toner image on the image carrier to the intermediate transfer belt 8.

  The intermediate transfer belt 8 is supported by rollers 10, 11, and 22. The cleaner 12 is a unit that cleans the intermediate transfer belt 8. The recording paper S stored in the paper feed cassette 17 is fed to the transport path by the pickup roller 18. The recording sheet S is conveyed by the vertical pass roller 20 and reaches the registration roller 16, and the conveyance timing is adjusted. The toner image conveyed by the intermediate transfer belt 8 is secondarily transferred to the recording paper S by the secondary transfer roller 22. The toner image is fixed on the recording paper S by the fixing unit 26. Thereafter, the recording sheet S is discharged to a discharge tray 25 by a discharge roller 24.

[Configuration of optical scanning unit]
FIG. 2 is a diagram schematically showing the configuration of the optical scanning unit 5. The laser light emitting element 101 is an example of a light emitting unit, and outputs a light beam modulated according to an image signal. The collimator lens 102 converts the light beam emitted from the laser light emitting element 101 into a parallel light beam. The aperture stop 103 restricts the luminous flux of the light beam that passes therethrough. The cylindrical lens 104 has a predetermined refractive power (degree of refraction) only in the sub-scanning direction. The cylindrical lens 104 forms the light beam that has passed through the aperture stop 103 on the reflection surface of the polygon mirror 105 as an elliptical image that is long in the main scanning direction. The polygon mirror 105 is rotated at a constant speed in the direction indicated by the arrow C in the figure by the scanner motor 106, and deflects and scans the laser light imaged on the reflecting surface. The toric lens 107 is an optical element having fθ characteristics, and is an optical component having different refractive indexes in the main scanning direction and the sub-scanning direction. Both the front and back lens surfaces of the toric lens 107 in the main scanning direction are aspherical. The diffractive optical element 108 is an optical component having an fθ characteristic, and is a long diffractive portion having different magnifications in the main scanning direction and the sub-scanning direction. The laser beam detection element 114 is installed at a position corresponding to the outside of the image forming area of the photosensitive drum 2, detects the laser beam reflected by the reflection mirror 113, and outputs a detection signal. This detection signal is used to determine the image writing timing in the main scanning direction.

  On the photosensitive drum 2, the spot of the laser beam moves linearly in parallel with the drum axis by the main scanning by the polygon mirror 105. When a multi-beam laser that emits a plurality of beams is used as the laser light emitting element 101, a belt-like electrostatic latent image having a predetermined width can be formed on the surface of the photosensitive drum 2 by one main scanning. The photosensitive drum 2 is rotationally driven by a drive unit 112 controlled by a control unit 120 such as an engine controller. As a result, the laser beam is scanned in the sub-scanning direction. Note that the surface potential of the photosensitive drum 2 is displaced by the intensity of the irradiated laser beam. The surface potential corresponds to the density of the toner image. Therefore, if the light quantity of the laser beam does not become a desired light quantity, the quality of the latent image and the toner image cannot be maintained at the desired quality.

[Control configuration]
FIG. 3 is a block diagram showing details of the control unit 120. The CPU 303 is an example of a main control unit provided outside the storage control unit, and is a main control unit of the engine controller. The CPU 303 controls a drive unit that drives the photosensitive drum 2, the roller, and the like, and transmits a setting value for performing laser control to the laser driver 304 disposed on the laser driver substrate 300. The laser driver 304 is an example of a driving unit that drives the laser light emitting element 101 based on driving data held in the data holding unit. The register 307 functions as a data holding unit that holds the drive data read from the storage unit while the voltage is supplied. The nonvolatile memory 306 functions as a storage unit that stores drive data.

  According to FIG. 3, a nonvolatile memory 306 which is a nonvolatile storage means on the laser driver substrate 300, a memory controller 305 which transfers drive data from the nonvolatile memory 306 to the register 307 based on an instruction from the CPU 303, and A laser driver 304 for driving the laser light emitting element based on the drive data stored in the register 307 is mounted. These units may be integrated and mounted as a laser driver IC. Thus, the driving means, the storage means, and the control means are mounted on the same substrate or the same IC. On the other hand, the CPU 303 as the main control means is mounted on a board or IC different from the board or IC on which the driving means, the storage means, and the control means are mounted.

  The CPU 303 and the memory controller 305 of the laser driver board 300 communicate with each other by serial communication, for example. Of course, other communication methods may be employed. The CPU 303 transmits a reset signal to the memory controller 305. The nonvolatile memory 306 is, for example, an EEPROM or a flash memory (registered trademark). The nonvolatile memory 306 is an example of a storage unit that holds operation data regarding the operation mode of the driving unit or the light emission of the laser light emitting element 101. Note that the non-volatile memory 306 may be a volatile memory, and in that case, drive data stored in the volatile memory is updated to appropriate data according to the state of the image forming apparatus.

  The laser driver 304 employs a digital control method. The laser driver 304 includes a register 307. The laser driver 304 drives the laser light emitting element 101 according to the operation data written in the register 307. For example, the laser driver 304 controls the current flowing through the laser light emitting element 101 according to the target light amount value (one of the drive data) written in the register 307, and controls the light amount of the laser light to the target light amount. Even when the laser light emitting element 101 does not output laser light, the laser driver 304 performs control so that a constant bias current flows through the laser light emitting element 101.

  The nonvolatile memory 306 stores a maximum current value (APC target value) when adjusting the light amount by APC (auto power control: automatic light amount adjustment). Thereby, it limits so that the light quantity of a laser beam may not exceed an upper limit. The operation data includes, for example, bias current values and data indicating the operation mode of the laser driver 304. These are eigenvalues determined at the time of shipment from the factory and stored in the nonvolatile memory 306. The operation mode includes a mode in which the shading function of the laser driver 304 is used and a mode in which it is not used, a mode in which APC is executed, and a mode in which it is not executed.

  The power source 301 functions as a power source that supplies the data holding unit and the driving unit with a voltage necessary for the data holding unit to hold the driving data. In FIG. 3, the power supplied from the power source 301 to the laser driver substrate 300 passes through the interlock switch 302. The interlock switch 302 is a mechanical switch that is turned off / on in conjunction with opening / closing of a maintenance door 27 provided in the printer 1. The interlock switch 302 cuts off power supplied from the power source to the driving unit and the data holding unit when the door provided in the image forming apparatus is opened, and power from the power source to the driving unit and the data holding unit when the door is closed. It is an example of the interlock means which switches so that it may supply.

  FIG. 4 is a block diagram showing an example of the internal configuration of the memory controller 305. The memory controller 305 functions as a storage control unit. The memory controller 305 monitors the level of the power supply voltage applied to the driving means. The memory controller 305 indicates that the value (level) of the power supply voltage supplied to the register 307 has returned to a value that allows the register 307 to hold data again after the register 307 has dropped to a value that the register 307 cannot hold data. In response to this, the operation data read from the nonvolatile memory 306 is written into the register 307. In other words, the memory controller 305 writes the drive data stored in the nonvolatile memory 306 to the register 307 when the supply of power to the laser driver board 300 including the register 307 is interrupted and restarted. To maintain the quality. Further, when the voltage level of the power supply via the interlock means becomes equal to or lower than the predetermined value and then exceeds the predetermined value again, the memory controller 305 registers the operation data read from the nonvolatile memory 306 in the register 307 provided in the laser driver 304. It functions as a control means for writing to. After the voltage drops to a value that cannot hold the drive data, the drive data stored in the storage means is held in response to the voltage holding the drive data being supplied to the data holding means again. Means hold.

  The power supply voltage monitoring circuit 401 functions as a detection unit that detects a voltage supplied to the register 307. Specifically, the power supply voltage monitoring circuit 401 is a circuit that monitors the level of the voltage applied from the power supply 301 to the laser driver substrate 300 (particularly the laser driver 304) via the interlock switch 302. That is, the power supply voltage monitoring circuit 401 monitors the power supply voltage Vin applied to the power supply 301 on the laser driver substrate 300. The communication command circuit 402 monitors a reset signal (initialization command) from the CPU 303 and a monitoring result from the power supply voltage monitoring circuit 401.

  When the level of the power supply voltage Vin drops below a predetermined value at which either the laser driver 304 or the nonvolatile memory 306 cannot operate and then exceeds the predetermined value again, the communication command A voltage OK signal that is a signal notifying the circuit 402 that the power supply voltage Vin has returned to the normal value is output.

  FIG. 5 is a block diagram illustrating a configuration example of the power supply voltage monitoring circuit 401. The comparison circuit 501 is an example of a comparison circuit that is supplied with power from a power source without using an interlock unit. The memory controller 305 uses the comparison circuit 501 to compare the power supply voltage level with a predetermined value to determine whether or not the power supply voltage level has again exceeded the predetermined value after the power supply voltage level has fallen below the predetermined value. Thus, the memory controller 305 determines whether or not the voltage has dropped to a value at which the register 307 cannot hold the drive data based on the detection result of the power supply voltage monitoring circuit 401 and the register 307 receives the drive data. It functions as a control means for determining whether or not the voltage has returned to a value capable of holding the drive data from a state where the voltage is reduced to a value that cannot be held.

  According to FIG. 5, the comparison circuit 501 is a circuit that operates by being supplied with electric power (voltage Vcc) from the power supply 301 without passing through the interlock switch 302. The power supply voltage Vin supplied to the laser driver substrate 300 via the interlock switch 302 is applied to the non-inverting input terminal of the comparison circuit 501. A reference voltage Vmin corresponding to a predetermined value is applied from the constant voltage source 502 to the inverting input terminal of the comparison circuit 501. The constant voltage source 502 is also a power source that does not depend on whether the interlock switch 302 is on or off. The comparison circuit 501 outputs a high level signal when the power supply voltage Vin exceeds the reference voltage Vmin, and outputs a low level signal when the power supply voltage Vin falls below the reference voltage Vmin. The high level signal is a voltage OK signal. That is, the voltage OK signal is output when the power supply voltage Vin is restored to a normal value.

  The communication command circuit 402 outputs a communication command to the communication circuit 403 only when the reset is released by the CPU 303 and the voltage OK signal is input. The communication circuit 403 includes a timer 404 that starts timing when a communication command is input. That is, the timer 404 is an example of a time measuring unit that starts measuring time when the voltage level of the power source exceeds a predetermined value. The timer 404 may be configured by a counter. When the timer 404 finishes counting the predetermined period (T seconds), the communication circuit 403 reads the operation data from the nonvolatile memory 306 and writes the operation data to the register 307. As shown in FIG. 6, T seconds is the time from the timing t1 at which the power supply voltage Vin returns to the normal value to the timing t2 at which both the laser driver 304 and the nonvolatile memory 306 reach stable operation. As described above, the memory controller 305 waits until the time counted by the timer 404 exceeds a predetermined period (eg, T seconds), and then writes the operation data read from the nonvolatile memory 306 to the register 307 included in the laser driver 304. .

  FIG. 7 is a flowchart showing processing executed by the control unit. In step S <b> 701, the memory controller 305 determines whether the reset is released based on the reset signal transmitted by the CPU 303. When the reset is released, the process proceeds to S702. In S702, the memory controller 305 determines whether the power supply voltage Vin exceeds the reference voltage Vmin. When the power supply voltage Vin exceeds the reference voltage Vmin, the process proceeds to S703. In S703, the memory controller 305 causes the timer 404 to start measuring time. In S704, the memory controller 305 determines whether or not the timer 404 has finished counting T seconds. When the timer 404 finishes counting T seconds, the process proceeds to S705. In step S <b> 705, the memory controller 305 reads operation data from the nonvolatile memory 306 and writes the operation data in the register 307. Accordingly, the laser driver 304 drives the laser light emitting element 101 based on appropriate operation data written in the register 307, so that a latent image of a desired quality is formed on the surface of the photosensitive drum 2.

  By the way, in the above embodiment, the operation data is automatically transferred from the nonvolatile memory 306 to the register 307 when the power supply 301 of the printer 1 starts supplying power. However, if the voltage level supplied by the commercial power supply is unstable or the door 27 is about to open, the interlock switch 302 may react instantaneously and cut off the power supply voltage Vin instantaneously.

  FIG. 8 is a diagram showing a waveform at the time of instantaneous power interruption. In the related technique in which the CPU 303 monitors the power supply voltage Vin by software, there may be a case where the instantaneous interruption of the power supply voltage Vin cannot be detected. As shown in FIG. 8, the CPU 303 cannot detect the instantaneous interruption that occurs in the period between the timings at which the CPU 303 samples the power supply voltage Vin. That is, the operation data transfer from the nonvolatile memory 306 is not executed even though the storage contents of the register 307 are rewritten to the initial values due to the instantaneous interruption of the power supply voltage Vin. Therefore, the abnormal light emission of the laser light emitting element 101 cannot be suppressed, and the quality of the latent image cannot be maintained at a desired quality.

  On the other hand, in this embodiment, since the output of the comparison circuit 501 is interlocked with the instantaneous interruption of the power supply voltage Vin, the operation data is transferred from the nonvolatile memory 306 to the register 307. In this embodiment, the detection speed of the power supply interruption by the memory controller 305 is determined by the response speed of the comparison circuit 501. On the other hand, in the related art, the CPU 303 monitors the level of the power supply voltage Vin by polling according to the firmware. Therefore, it is clear that the configuration of the embodiment can detect a shorter interruption than the configuration of the related art.

  By the way, the operation data stored in the nonvolatile memory 306 is determined at the time of shipment from the factory, such as the APC target value, the bias current setting value, the laser driver 304 operation mode, and the laser current limit value, and is not changed thereafter. It may be data. In particular, a set value determined to protect the laser light emitting element 101 such as a limit value of the laser current is an example of the operation data. On the other hand, a shading value or the like that changes the amount of laser light is set by communication from the CPU 303 so as to change according to use of the printer 1.

  According to this embodiment, when the supply of power to the register 307 provided in the laser driver 304 is interrupted and restarted, the operation data stored in the nonvolatile memory 306 is written into the register 307. In other words, the memory controller 305 transfers the drive data to the nonvolatile memory in response to the voltage of the value that can hold the drive data being supplied again to the register 307 after the voltage drops to a value that cannot hold the drive data. Reading from 306 and writing to the register 307 functions as a control means for holding the drive data in the register 307. Accordingly, an appropriate value is written in the register 307 included in the laser driver 304, so that the image forming apparatus can maintain the quality of the latent image. In particular, the image forming apparatus maintains the quality of the latent image even when the interlock switch 302 is momentarily interrupted by the door 27 or the register 307 is momentarily disabled due to unstable commercial power. become able to. In particular, if a comparison circuit that operates at a higher speed than software is used, even very short interruptions can be detected, so that it is easy to suppress the degradation of the latent image quality. When a power interruption occurs, it is wise to wait for a predetermined period before the laser driver 304 operates stably. Therefore, it is preferable to copy the operation data to the register 307 after the timer finishes measuring the predetermined period.

<Example 2>
In the first embodiment, when the memory controller 305 detects an instantaneous power interruption to the optical scanning unit 5, the operation data is copied from the nonvolatile memory 306 to the register 307 to suppress malfunction of the laser light emitting element 101. However, in an image forming apparatus in which a plurality of operation data are prepared according to the difference in print mode, there are cases where the operation data stored in the nonvolatile memory 306 cannot be directly written into the register 307. In an image forming apparatus that operates at a plurality of different process speeds (eg, 100 mm / s, 200 mm / s), the light amount setting value for 100 mm / s is half of the light amount setting value of 200 mm / s. Therefore, in the second embodiment, an image forming apparatus that returns the operation data to the register 307 after changing the operation data according to the dynamically changed situation is proposed. In the second embodiment, items common to the first embodiment will be omitted to avoid duplication of explanation.

  In the second embodiment, as an easy-to-understand example, a printer 1 that changes the output of the laser light emitting element 101 in conjunction with the process speed will be described. The printer 1 may have a thick paper printing mode in addition to the normal plain paper printing mode. In the thick paper printing mode, the process speed is to be lowered than usual from the viewpoint of toner image fixability. For example, if the output of the laser light emitting element 101 for a process speed of 200 mm / s is 10 mW, the output of the laser light emitting element 101 for a process speed of 100 mm / s is 5 mW. Therefore, when the process speed is changed, the target value of APC must be changed. When changing the operation data of APC, generally, the CPU controller 303 of the engine controller resets the target value of APC corresponding to the process speed to the laser driver board 300. By the way, in recent years, multi-beams have been developed. In the optical scanning unit 5 that emits a plurality of beams, the operation data corresponding to the APC target value corresponding to the number of beams must be transferred from the CPU 303 to the laser driver substrate 300. Since the transfer data is transmitted by serial communication, an increase in operation data directly leads to an increase in transfer time. Example 2 describes a configuration in view of the above.

  FIG. 9 is a block diagram of a control unit according to the second embodiment. Note that the same reference numerals are assigned to the same or similar components as those already described to simplify the description. The computing device 902 is an example of computing means that computes the coefficient received from the CPU 303 and the light amount value of the laser light emitting element 101 among the operation data read from the nonvolatile memory 306 and writes the computation result in the register 307. .

  Here, it is assumed that the APC target value at the time of factory shipment is an APC target value (APCmax) corresponding to the fastest process speed within a settable range. In principle, the APC target value corresponding to the fastest process speed is larger than the APC target value corresponding to a lower process speed. That is, the APC target value (APCmax) corresponding to the fastest process speed is the maximum value.

  The memory controller 305 monitors the power supply voltage Vin applied to the laser driver substrate 300 and the reset signal from the CPU 303. When the reset is released by the reset signal and the power supply voltage Vin exceeds the reference voltage Vmin, the memory controller 305 reads the operation data from the nonvolatile memory 306 and writes it in the cache memory 901. The CPU 303 transmits the coefficient C corresponding to the print mode to the memory controller 305 in advance. The memory controller 305 also writes the coefficient C into the cache memory 901. Here, if the process speed is the fastest, the APC target value is APCmax. Therefore, the coefficient C = 1. The arithmetic unit 902 reads APCmax and coefficient C, which are operation data, from the cache memory 901, multiplies them, and writes the product, which is the multiplication result, in the register 307 of the laser driver 304.

  On the other hand, when the print mode is changed, the CPU 303 transmits the coefficient C corresponding to the changed print mode to the memory controller 305. For example, assuming that the process speed has been reduced from the fastest to half (half speed), the coefficient C = 0.5. The memory controller 305 writes the APC target value read from the nonvolatile memory 306 and the coefficient C received from the CPU 303 to the cache memory 901. The arithmetic device 902 multiplies the APC target value by the coefficient C and writes the multiplication result (APCmax × 0.5) in the register 307.

  According to the second embodiment, it is possible to protect even dynamically changing operation data from instantaneous interruption. Other effects of the second embodiment are as described in the first embodiment. Here, the APC target value is calculated and the calculation result is stored in the register 307 of the laser driver 304. However, the technical idea of the second embodiment can be applied to other operation data such as the current limit value of the laser light-emitting element 101. .

<Example 3>
In the first and second embodiments, it is assumed that operation data determined at the time of shipment from the factory is stored in a nonvolatile memory 306 configured by an EEPROM, a mask ROM that is inexpensive and cannot be additionally written, or the like. By the way, there is operation data that changes as the image forming apparatus is used. Therefore, in the third embodiment, it is proposed to store such operation data in a nonvolatile storage device which can be additionally written and write it in the register 307. For example, in the second embodiment, it is necessary to receive the coefficient C from the CPU 303 because an instantaneous interruption of the power supply voltage Vin occurs. However, in the third embodiment, the memory controller 305 sets the coefficient C when the print mode is changed. It is written in a non-volatile storage device that can be received and recorded. In the third embodiment, since the memory controller 305 reads the coefficient C from the additionally recordable nonvolatile storage device and writes it to the cache memory 901, the number of times the coefficient C is received from the CPU 303 can be reduced. Note that the nonvolatile memory 306 may be configured by a recordable nonvolatile memory such as an EEPROM. However, fixed operation data that is not changed from the time of shipment from the factory is stored in a storage area that is set so that no additional writing is possible, so that it is not overwritten by mistake. The variable operation data may be stored in a dedicated additionally recordable area.

  FIG. 10 is a block diagram illustrating a control unit according to the third embodiment. The nonvolatile memory 306 stores fixed operation data such as APmax described above. The recordable storage device 1001 is a recordable nonvolatile memory and stores variable operation data such as the coefficient C described above. Since the calculation related to the operation data written in the cache memory 901 is the same as that in the second embodiment, the description thereof is omitted.

  In the third embodiment, the non-volatile memory 306 is an example of a first non-volatile storage device that stores operation data determined at the time of factory shipment among operation data. The recordable storage device 1001 is an example of a second nonvolatile storage device that stores operation data set by the main control means. The recordable storage device 1001 will be described as an EEPROM. The non-volatile memory 306 is also described as an EEPROM. However, the non-volatile memory 306 is made unwritable by a peripheral circuit in order to prevent operation data that has not changed after factory shipment from being accidentally erased or overwritten. Of course, the nonvolatile memory 306 may be realized by a mask ROM.

  In addition to the coefficient C, the additionally recordable storage device 1001 may store a light amount setting value that is adjusted according to the usage amount or environment of the photosensitive drum 2, a shading setting value that can be arbitrarily changed by the user, and the like. Each time such operation data is changed, the CPU 303 transmits a change command, the address of the register 307 whose stored contents are to be changed, and the changed operation data to the memory controller 305. When the memory controller 305 receives the change command from the CPU 303, the memory controller 305 enters a state in which the changed operation data is transferred to the recordable storage device 1001. When the memory controller 305 receives the address and the operation data, the memory controller 305 stores the operation data at a corresponding address in the recordable storage device 1001. The operation of the memory controller 305 when the power supply voltage Vin is interrupted is as described in the first and second embodiments.

  According to the third embodiment, since the dynamically changing operation data is held in the recordable nonvolatile storage device provided in the laser driver substrate 300, the recovery time from the instantaneous interruption is shorter than that in the second embodiment. Can be shortened. Other effects of the third embodiment are as described in the first and second embodiments.

Claims (9)

A light emitting means;
Storage means for storing drive data;
Data holding means for holding the drive data read from the storage means while a voltage is supplied;
Drive means for driving the light emitting means based on the drive data held in the data holding means;
A power supply for supplying the data holding means and the driving means with the voltage necessary for the data holding means to hold the driving data;
The voltage is stored in the storage unit in response to the voltage holding unit returning to a value capable of holding the driving data in the data holding unit after the voltage has dropped to a value that cannot hold the driving data in the data holding unit. The image forming apparatus, wherein the data holding unit holds the driving data.   The drive data is stored in response to the voltage being reduced to a value at which the drive data can be held in the data holding unit again after the voltage drops to a value at which the drive data cannot be held in the data holding unit. The image forming apparatus according to claim 1, further comprising a control unit that causes the data holding unit to hold the drive data by reading from the unit and writing to the data holding unit.   The control means further includes detection means for detecting a voltage supplied to the data holding means, and the voltage is set to a value at which the data holding means cannot hold the drive data based on a detection result of the detection means. The voltage is reduced to a value at which the data holding means can hold the drive data from a state where the voltage has dropped to a value at which the data holding means cannot hold the drive data. The image forming apparatus according to claim 2, wherein it is determined whether or not the image has been returned. When the door provided in the image forming apparatus is opened, the power supplied from the power source to the driving unit and the data holding unit is cut off, and when the door is closed, the power source is supplied to the driving unit and the data holding unit. Further having an interlock means for switching to supply power from
The image forming apparatus according to claim 3, wherein the detection unit detects the voltage via the interlock unit.   The control means further includes a comparison circuit to which power is supplied from the power source without going through the interlock means, and the voltage value is compared with a predetermined value by using the comparison circuit. 5. The image forming apparatus according to claim 4, wherein it is determined whether or not the predetermined value is exceeded again after the value becomes less than or equal to a predetermined value. 6. And further comprises time measuring means for starting time measurement when the value of the voltage exceeds the predetermined value,
6. The image forming apparatus according to claim 5, wherein the control unit waits until the time counted by the timing unit exceeds a predetermined period, and then writes the drive data read from the storage unit to the data holding unit. apparatus. Main control means provided outside the control means;
A calculation unit that calculates a coefficient received from the main control unit and a light amount value of the light emitting unit among the drive data read from the storage unit, and writes a calculation result in the data holding unit; The image forming apparatus according to claim 2, wherein the image forming apparatus is an image forming apparatus. The storage means
A first nonvolatile storage device that stores drive data determined at the time of shipment from the factory among the drive data;
The image forming apparatus according to claim 7, further comprising: a second nonvolatile storage device that stores drive data set by the main control unit. The drive means, the storage means, and the control means are mounted on the same substrate or the same IC,
The said main control means is mounted in the board | substrate or IC different from the board | substrate or IC in which the said drive means, the said memory | storage means, and the said control means were mounted, The Claim 7 or 8 characterized by the above-mentioned. Image forming apparatus.

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