Image forming device

Abstract

To secure the reliability of data in a nonvolatile memory without increasing cost and space due to the addition of a cable or the like.SOLUTION: An image forming apparatus includes: a discharge sensor 218 that detects presence or absence of a recording material and outputs a first signal corresponding to a detection result via a SNS signal line; a CPU301 that has a port 301p to which the first signal is input, and determines the presence or absence of the recording material on the basis of the first signal; and a nonvolatile memory 211 having a write-protect function and a WP terminal to which a second signal for switching on or off the write-protect function is input from the CPU301 via the SNS signal line. The CPU301 switches the port 301p from a state where the first signal is input to a state where the second signal is output to output the second signal to the WP terminal via the SNS signal line, disables the write-protect function of the nonvolatile memory 211, and communicates with the nonvolatile memory 211.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus, and more particularly to a write protect function for preventing data from being written to a non-volatile memory mounted in a fixing device of the image forming apparatus. [Background technology]

[0002] Some non-volatile memories have a function called write protect (hereinafter, also referred to as WP) that prohibits writing data to the memory. The write protect function is a function that assigns a dedicated terminal called a WP terminal to the external terminal of the non-volatile memory, and switches between permission and prohibition of writing data to the non-volatile memory according to the voltage level of the WP terminal. Meanwhile, the non-volatile memory is mounted, for example, in a fixing device of an image forming apparatus. In such a case, information related to the fixing device is stored in the non-volatile memory, and the data in the non-volatile memory is used for the purpose of improving the performance of the image forming apparatus (for example, see Patent Document 1). In an image forming apparatus equipped with a non-volatile memory, the data in the non-volatile memory of the fixing device is rewritten according to the usage status of the image forming apparatus. When rewriting data in the non-volatile memory of the fixing device, the write protect is always released, or the write protect function is appropriately switched between enabled and disabled. However, to prevent data in non-volatile memory from being inadvertently rewritten due to external noise, etc., it is advisable to basically keep the write protect function enabled (i.e., prohibit writing) except when rewriting data, in order to increase the reliability of the data in the non-volatile memory. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-305579 Summary of the Invention [Problem to be solved by the invention]

[0004] To switch the write-protect function between enabled and disabled, a signal line for controlling the WP terminal is generally provided. However, depending on the configuration of the image forming apparatus, the non-volatile memory may be laid out behind the fixing device, and it may be necessary to release the write-protection using a connection means such as a cable connecting the board on which the non-volatile memory is mounted and the controller board as an interface. Specifically, adding one cable and connector pin to be connected to the WP terminal may lead to increased costs. Therefore, it is necessary to inexpensively switch the WP terminal of the non-volatile memory between enabled and disabled.

[0005] The present invention has been made under these circumstances, and has an object to ensure the reliability of data within a non-volatile memory without increasing costs or space due to the addition of cables or the like. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the present invention has the following configuration.

[0007] (1) An image forming apparatus having an image forming means for forming an image on a recording material, comprising: a detection means for detecting the presence or absence of a recording material and outputting a first signal according to the detection result via a signal line; a control means having a first terminal to which the first signal is input and judging the presence or absence of a recording material based on the first signal; and a memory unit having a write protect function and a second terminal to which a second signal for switching between enabling and disabling the write protect function from the control means is input via the signal line, wherein the control means switches the first terminal from a state in which the first signal is input to a state in which the second signal is output to the second terminal via the signal line, thereby disabling the write protect function of the memory unit and communicating with the memory unit. Effect of the Invention

[0008] According to the present invention, the reliability of data in a non-volatile memory can be ensured without increasing costs or space due to the addition of cables or the like. [Brief description of the drawings]

[0009] [Figure 1] Schematic diagram of an image forming apparatus according to first and second embodiments [Diagram 2] Schematic diagram of a fixing device according to a first embodiment of the present invention. [Diagram 3] Circuit board connection diagram for Example 1 [Figure 4] Timing chart for printing in Example 1 [Diagram 5] Timing chart when a jam occurs during printing in Example 1 [Figure 6] Timing chart when power is turned on in Example 1 [Figure 7] Timing chart for when a jam occurs when the power is turned on in the first embodiment [Figure 8] Schematic diagram of a fixing device according to a second embodiment of the present invention. [Figure 9] Circuit board connection diagram for Example 2 [Figure 10] Timing chart for printing in Example 2 [Figure 11] Timing chart when full load occurs during printing in Example 2 [Figure 12] Timing chart when power is turned on in Example 2 [Figure 13] Timing chart for Example 2 when a full load occurs when the power is turned on DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings by way of examples. EXAMPLES

[0011] <Image forming device> FIG. 1 shows a schematic diagram of the main parts of an example of an image forming apparatus. The image forming apparatus 1 has an image forming section 2, which is an image forming means for forming an unfixed toner image on recording paper R, which is a recording material (recording paper, paper, or paper, etc.), and a fixing device (image heating device) 100, which is a fixing means for fixing the toner image. The image forming section 2 has an electrophotographic photosensitive drum (hereinafter referred to as drum) 3 that is rotated in the direction of the arrow (clockwise direction), and an unfixed toner image is formed on the drum 3 by a charging device 4, an image exposure device 5, and a developing device 6, which are image forming process means. Then, the toner image formed on the drum 3 is transferred by a transfer device 7 to the recording paper R transported from a paper feed mechanism (not shown). The recording paper R that has passed through the transfer device 7 is separated from the drum 3 and transported to the fixing device 100, where it is heated and pressed, so that the toner image is fixed to the recording paper R as a fixed image. The recording paper R that has left the fixing device 100 is discharged as an image formation product. After the recording paper R is separated, the surface of the drum 3 is cleaned by the cleaning device 8 and the drum 3 is repeatedly used for image formation.

[0012] The image forming device 1 is capable of operating in a print state in which it forms (prints) an image on recording paper R, a standby state in which it can transition to the print state immediately upon receiving a print instruction, and a sleep state in which it consumes less power than the standby state.

[0013] The image forming apparatus 1 also has a door (not shown) for accessing the inside in order to remove the recording paper R when the recording paper R is jammed or to replace toner, etc. The image forming apparatus 1 also has a door sensor (not shown) for detecting whether the door is open or closed. The door sensor outputs, for example, a high level (Hi) when the door is open and a low level (Lo) when the door is closed. The image forming apparatus 1 has a controller board described in FIG. 3, and a CPU is mounted on the controller board. The detection result (Hi or Lo) of the door sensor described above is input to the CPU, and the CPU can determine whether the door is open or closed based on the detection result of the door sensor. The image forming apparatus 1 may be an image forming apparatus of another known configuration, such as a color image forming apparatus.

[0014] <Fixing device> FIG. 2(a) shows a schematic diagram of an example of a fixing device 100. The fixing device 100 has a flexible cylindrical film 202 and a heater 203 that contacts the inner surface of the film 202. The temperature of the heater 203 is detected by a thermistor 205. The fixing device 100 also has a pressure roller 206 that forms a fixing nip portion S together with the heater 203 via the film 202. The heater 203 is held by a holding member 201 made of heat-resistant resin. The holding member 201 also has a guide function for guiding the rotation of the film 202. The stay 204 is provided to apply pressure from a spring (not shown) to the holding member 201, and is made of metal.

[0015] The film 202 may be a single layer film, or a composite film such as PI+PFA coating or SUS+rubber coating. The pressure roller 206 is an elastic roller having a core metal 207 made of iron, aluminum, or the like, and an elastic layer 208 made of silicone rubber or the like. The film 202 is sandwiched and pressed between the pressure roller 206 and heater 203. The area indicated by the double arrows is the fixing nip S formed by the pressure contact.

[0016] The pressure roller 206 is rotated at a predetermined peripheral speed by a fixing drive motor (not shown). This rotation of the pressure roller 206 generates a frictional force between the pressure roller 206 and the outer surface of the film 202 at the fixing nip portion S. This causes a rotational force to act on the film 202, which is rotated while sliding against the heater 203 with pressure. At this time, the holding member 201 also functions as a guide member that guides the inner surface of the film 202, facilitating the rotation of the film 202.

[0017] The memory board 210 is held by the fixing device 100. The memory board 210 has a non-volatile memory 211 as a storage unit, and a photointerrupter 212. The non-volatile memory 211 is a memory that stores information about the fixing device 100, such as the performance and manufacturing lot information of the fixing device 100, during the manufacturing process of the fixing device 100. The photointerrupter 212, together with a flag 214 and a shaft 213, forms a discharge sensor 218 as a detection means. The discharge sensor 218 mainly detects jams (paper jams) in the vicinity of the fixing device 100, for example, jams of the recording paper R after the recording paper R passes through the fixing nip portion S. The discharge sensor 218 may be, for example, a photosensor. When the recording paper R is not touching the flag 214, such as when the image forming apparatus 1 is in a standby state or between sheets during continuous printing, the flag 214 is at a position 217 indicated by a broken line and blocks the photointerrupter 212 from light. Here, the recording paper R is transported from right to left in Fig. 2, which will be referred to as the transport direction hereinafter. On the other hand, when the recording paper R touches the flag 214 (when the recording paper R is jammed during printing, etc.), the recording paper R tilts the flag 214 to the diagonal position in Fig. 2(a), causing the photointerrupter 212 to enter a light-transmitting state.

[0018] FIG. 2B is a view of the discharge sensor 218 from the fixing nip S side, that is, from the right side of FIG. 2A, and shows a state in which the flag 214 is at position 217 in FIG. 2A and blocks the photointerrupter 212 from light. The spring 220 is for returning the flag 214, which has been knocked down by the recording paper R, to position 217. Hereinafter, the state in which the photointerrupter 212 is blocked from light will be referred to as a "paper-out state," and the state in which the photointerrupter 212 is in a light-transmitting state will be referred to as a "paper-present state." In the above configuration, if the paper-out state does not occur at a predetermined timing, for example, if the paper-out state does not occur after the print sequence is completed, the discharge sensor 218 detects the presence of paper and the CPU determines that a jam has occurred. The memory board 210 also has a cable 215, and is connected via a connector 216 to a controller board 300 (see FIG. 3) that is laid out in a location separate from the fixing device 100 in the image forming apparatus 1.

[0019] <Memory board and controller board> The circuit configuration of the memory board 210 and the controller board 300 will be described with reference to FIG. 3. The interface (cable 215) between the memory board 210 and the controller board 300 is composed of SNS, Vcc, SDA, SCL, and GND. Hereinafter, the signal lines used for transmitting and receiving each signal (or voltage) are called the SNS signal line, the Vcc signal line, the SDA signal line, the SCL signal line, and the GND signal line. The SNS signal line is a signal line used for transmitting and receiving the output signal (first signal) of the discharge sensor circuit 304 on the memory board 210. The Vcc signal line is a signal line for the power supply Vcc, which is the power supply for the memory board 210. In the first embodiment, the power supply Vcc is, for example, 3.3 V. The SCL signal line and the SDA signal line are communication lines used for communication between the non-volatile memory 211 on the memory board 210 and the microcomputer (hereinafter referred to as CPU) 301 (control means) on the controller board 300. The communication between the non-volatile memory 211 and the CPU 301 is, for example, I2C communication, etc. The GND communication line is a ground line common to the memory board 210 and the controller board 300, and has the same potential as the housing of the image forming apparatus 1.

[0020] In this example, the non-volatile memory 211 uses BR24G16FVT-3 manufactured by ROHM. This has eight external terminals. Specifically, the non-volatile memory 211 has an A0 terminal, an A1 terminal, an A2 terminal, a GND terminal, a Vcc terminal, and a second terminal, namely, a WP terminal, an SCL terminal, and an SDA terminal. The power supply for the non-volatile memory 211 is input to the Vcc terminal, and the GND terminal is connected to the GND potential. The A0 terminal is an unused terminal, and the A1 terminal and the A2 terminal are terminals for determining a slave address when the non-volatile memory 211 and the CPU 301 perform I2C communication. In the first embodiment, the A0 terminal, the A1 terminal, and the A2 terminal are all connected to GND when used.

[0021] The SCL terminal is a terminal to which a clock is input from the controller board 300. The SDA terminal is a terminal for reading / writing data between the CPU 301 and the non-volatile memory 211 in synchronization with the clock of the SCL terminal. To prevent malfunctions in I2C communication due to external noise or the like, a filter consisting of a resistor 307 and a capacitor 308 is connected to the SCL terminal, and a filter consisting of a resistor 305 and a capacitor 306 is connected to the SDA terminal.

[0022] When the voltage of the WP terminal is at a high level (hereinafter referred to as an H level), the write protection is enabled, and data writing to the non-volatile memory 211 is prohibited. When the voltage of the WP terminal is at a low level (hereinafter referred to as an L level), the write protection is released (disabled), and data writing to the non-volatile memory 211 is permitted. The voltage level of the WP terminal is specified, for example, such that the H level is in the voltage range from Vcc×70% to Vcc, and the L level is in the voltage range from −0.3 V to Vcc×20%.

[0023] The discharge sensor circuit 304 is composed of the above-mentioned photointerrupter 212 and resistor 303. When the recording paper R is in the paper-out state in Fig. 2, the photointerrupter 212 is shielded from light by the flag 214 in Fig. 2, and the phototransistor 212t of the light receiving portion of the photointerrupter 212 becomes non-conductive. On the other hand, when the recording paper R is in the paper-present state, the light shielding by the flag 214 is released from the photointerrupter 212, and the phototransistor 212t of the light receiving portion of the photointerrupter 212 becomes transparent, and the phototransistor 212t of the light receiving portion of the photointerrupter 212 becomes conductive.

[0024] The output of the photo interrupter 212, that is, the SNS signal, is pulled up by the resistor 302 on the controller board 300 and input to the I / O port which is the first terminal of the CPU 301 (hereinafter also referred to as port 301p). When the photo transistor 212t of the light receiving part of the photo interrupter 212 is non-conductive, a high (H) voltage level, and when it is conductive, a low (L) voltage level is input to the port 301p of the CPU 301. Therefore, the CPU 301 can determine whether the recording paper R is in the discharge sensor 218 part, that is, the presence or absence of the recording paper R.

[0025] On the other hand, in the first embodiment, the SNS signal line is connected to the WP terminal of the non-volatile memory 211. Therefore, the SNS signal line has a configuration that combines the function of transmitting the detection result of the discharge sensor 218 and the function of switching the effective / invalid state of the write protection of the non-volatile memory 211. Therefore, compared with the case where these two functions are performed using separate signal lines, one signal line can be reduced. By sharing the signal (signal line) in this way, the voltage of the WP terminal will change according to the detection result of the discharge sensor 218. How the SNS signal changes on the actual sequence of the image forming apparatus 1 is shown in the time charts of FIGS. 4 to 7 and will be described below.

[0026] <Transition of SNS signal> (When printing is performed normally) FIG. 4 shows a flow that starts from a sleep state, prints three sheets, goes into standby, and goes back to sleep. Although FIG. 4 shows the number of sheets printed as three, this is not limited to this. FIG. 4 shows the states of the image forming apparatus 1 (sleep, prints three sheets, standby) in (i), and the power supply Vcc (3.3V, 0V) of the non-volatile memory 211 in (ii). (iii) shows the SNS signal (high (Hi), low (Lo)). The SNS signal also shows the level of the WP terminal of the non-volatile memory 211. (iv) shows the input / output (input, output) of the SNS signal port (port 301p) of the CPU 301, and (v) shows the state of memory data of the non-volatile memory 211 (power off (data retention), write-protected state, write-protected state). (vi) shows the I2C communication state of the non-volatile memory 211 (communication stopped, communication). The horizontal axis shows time, and 401 to 410 show each timing (time). First, in the sleep state, the power supply Vcc is 0 V, the SNS signal is at a low level, and the SNS signal port is at an input. At this time, the power supply Vcc of the non-volatile memory 211 is off at 0 V, so memory data is held and I2C communication is not performed.

[0027] At time 401, the image forming apparatus 1 is restored from the sleep state by a print command from the user, and the power supply Vcc rises to 3.3 V. The SNS signal rises to Hi level on the assumption that the discharge sensor 218 is in a paper-free state, i.e., the photointerrupter 212 is in a light-shielded state. At this time, the WP terminal is also Hi, so the memory data is in a write-protected state. Printing starts, and when the recording paper R flips the flag 214 of the discharge sensor 218 at time 402, the photointerrupter 212 becomes light-transmitting, the SNS signal (WP terminal) becomes Lo, and the write-protection of the memory data is released. When the first sheet of recording paper R passes through the discharge sensor 218 at time 403, the SNS signal (WP terminal) becomes Hi, and the memory data is in a write-protected state, which is maintained until the second sheet of recording paper R reaches the discharge sensor 218 at time 404. After time 404, the same process as for the first sheet is performed, and printing ends at time 407 when the third sheet of recording paper R passes through the discharge sensor 218. In this way, when the discharge sensor 218 detects that the recording paper R is "present," the write protect function of the WP terminal is released.

[0028] After time 407, image forming apparatus 1 goes into standby state, and the SNS signal (WP terminal) goes Hi. When writing the number of prints or the like to non-volatile memory 211, CPU 301 switches SNS signal port 301p from input to output, outputs a Lo-level signal (second signal), releases write protection, and performs I2C communication (time 408).

[0029] Here, when a signal is input from the discharge sensor 218, the CPU 301 sets the SNS signal port to an input state. Meanwhile, the CPU 301 switches the SNS signal port from input to output and performs the following operation. That is, the CPU 301 outputs a signal to the WP terminal of the non-volatile memory 211 using the SNS signal line, and switches the write protect function from enabled (prohibited) to disabled (released). When the operation using the SNS signal line, in other words, the communication with the non-volatile memory 211, ends, the CPU 301 switches the SNS signal port from output to input. If printing has been performed normally, the discharge sensor 218 has not detected the recording paper R at this timing, and as a result, the WP terminal of the non-volatile memory 211 becomes enabled again.

[0030] At time 409 when the communication ends, CPU 301 switches the SNS signal from output to input, and the SNS signal becomes Hi again, entering the write-protect state. At time 410, image forming apparatus 1 enters the sleep state, the power supply Vcc is turned off at 0 V, the power supply of non-volatile memory 211 is turned off, and the memory data is retained. Also, I2C communication is stopped.

[0031] Although the write protection of the non-volatile memory 211 is released for a certain period of time during printing (the period when paper is present) as described above, the risk of unnecessary rewriting of memory data is low for the following two reasons. The first is that the time during which printing is taking place and the recording paper R is passing the discharge sensor 218 is only a very small proportion of the product life of the image forming apparatus 1. The second is that during the above-mentioned period, there is an increased possibility of external noise or malfunction of the image forming apparatus 1, such as the rotation of the motor or the supply of a large current to the fixing device 100. For this reason, by designing the device so that no communication is performed during that period ("communication stopped" until time 408 in FIG. 4(vi)), the risk of data corruption during writing can be reduced.

[0032] (If a jam occurs during printing) Next, a case where a jam occurs during printing will be described with reference to Fig. 5. (i) to (vi) in Fig. 5 are graphs similar to (i) to (vi) in Fig. 4, and the description will be omitted. Also, time 501 to time 511 indicate each timing. (vii) in Fig. 5 shows the detection result of a door sensor (not shown), which is at a high level (Hi) when the door (not shown) is open and at a low level (Lo) when the door is closed.

[0033] 4 up to time 506 is omitted because it is the same as up to time 406 in Fig. 4. Printing of the third sheet begins at time 506, and originally, at time 507, recording sheet R passes the discharge sensor 218, the photointerrupter 212 enters a light-shielded state, and the SNS signal should become Hi. However, due to some abnormality such as skewing of recording sheet R or the presence of a foreign object, recording sheet R stops with flag 214 tilted, and the SNS signal remains Lo.

[0034] When the CPU 301 detects the Lo state of the SNS signal at time 507, it determines that a jam has occurred at the discharge sensor 218. It is assumed that the CPU 301 can determine the timing at which the rear end of the recording sheet R will pass the discharge sensor 218 while the recording sheet R is being transported normally, based on the transport speed of the recording sheet R, the length of the recording sheet R in the transport direction, etc. At this time, the CPU 301 does not switch the SNS signal port from input to output, which is normally performed between time 408 and time 409 (see FIG. 4) after printing is completed, and does not communicate with the non-volatile memory 211.

[0035] While a jam occurs, the SNS signal is Lo, meaning that the write protection of the memory data is released (time 507 to time 508 in (v)). During the period when this SNS signal Lo is input to the CPU 301, communication with the non-volatile memory 211 is not performed ("communication stopped" in (vi)). When a jam occurs, situations are likely to occur where external noise is generated, such as when a user accesses the inside of the image forming apparatus 1 or when static electricity is generated when removing the jammed recording paper R (hereinafter referred to as jammed paper). For this reason, when a jam occurs, the CPU 301 does not communicate with the non-volatile memory 211, thereby reducing the risk of data corruption due to writing.

[0036] At time 508, the door of image forming apparatus 1 is opened and the jammed paper is removed. At this time, the door sensor (not shown) is Hi, and the SNS signal is "indefinite" since it fluctuates depending on the behavior of the jammed paper. At time 509, processing such as removing the jammed paper is completed, the door is closed, the door sensor goes Lo, and post-print processing after jam clearance is performed until time 510, when the apparatus enters standby mode. At time 511, the apparatus transitions to sleep mode and the power to non-volatile memory 211 is turned off.

[0037] 5, no communication is made after time 510 when post-jam processing is completed (see (vi)), but depending on the content of the communication, communication may take place between time 510 and time 511. During this period, jams occur less frequently, and the communication content is assumed to be the number of sheets printed by fixing device 100, and the number of sheets printed only needs to be known approximately when fixing device 100 is replaced. For this reason, when a jam occurs, data is stored only in memory (not shown) in CPU 301, and is written all at once to non-volatile memory 211 after normal printing has been completed.

[0038] (If the power is turned on normally) Figures 6 and 7 are timing charts when the image forming apparatus 1 is powered on, and (i) to (vi) in Figures 6 and 7 are graphs similar to (i) to (vi) in Figure 4, with times 601 to 605, times 701, and times 702 indicating the respective timings. Figure 6 shows the case when the power is turned on in a normal state, and Figure 7 shows the case when the power is turned on in a state where a jam has occurred.

[0039] At time 601, the user turns on the power supply of the image forming apparatus 1, the power supply Vcc becomes 3.3V, the SNS signal becomes Hi, and then the power supply start-up process (starting various motors, scanners, and the fixing device 100, checking sensors, etc.) is performed. During this process, the number of prints, the serial number of the fixing device 100, etc. are read from the non-volatile memory 211 to the CPU 301 from time 602 to time 603. Therefore, at time 602, the CPU 301 switches the SNS signal port from input to output and outputs Lo (iv), releases the write protection of the non-volatile memory 211 (iii), and communication is performed (vi). After the communication is completed at time 603, the CPU 301 switches the SNS signal port 301p from output to input, and the non-volatile memory 211 becomes write-protected. The start-up process is completed at time 604, the image forming apparatus 1 goes into a standby state, and at time 605, it goes into a sleep state.

[0040] (When the power is turned on in a jammed state) 7, when the power is turned on in a state where a jam occurs at the discharge sensor 218, the SNS signal is Lo, indicating that paper is present, after the power is turned on at time 701, and the CPU 301 detects a jam at the discharge sensor 218 at time 702 (JAM detection). As a result, an error occurs in the image forming apparatus 1, the start-up process is stopped (error stop), and the error is notified to the operation panel or the like (not shown). The switching of the SNS signal port from input to output, which was performed from time 602 to time 603 in FIG. 6, and the read process of the non-volatile memory 211 are not performed. This makes it possible to reduce the risk of a read error of memory data in the non-volatile memory 211 or garbled memory data due to external noise or a malfunction of the image forming apparatus 1, for example, even if a jam is cleared. If a jam is cleared after an error stop, the flow is the same as that after time 508 in FIG. 5.

[0041] With the above-mentioned configuration, it is possible to reduce the number of signal lines by one, while ensuring the reliability of data in the non-volatile memory, and to reduce the cost and space of the image forming apparatus. In the first embodiment, the discharge sensor 218 is provided after passing through the fixing nip S, but the position of the discharge sensor 218 is not limited thereto, and it may be provided, for example, before passing through the fixing nip S. In addition, the SNS signal is configured to be Lo when paper is present and Hi when paper is absent, but the logic may be reversed. In that case, care should be taken to ensure that there is no discrepancy with the logic of the WP terminal of the non-volatile memory 211. Furthermore, the present invention is applicable to any type of non-volatile memory as long as it has a write-protect function.

[0042] As described above, according to the first embodiment, the reliability of data in the non-volatile memory can be ensured without increasing costs or space due to the addition of cables or the like. EXAMPLES

[0043] The image forming unit 2 of the image forming apparatus of the second embodiment is the same as that of the first embodiment, so the same reference numerals are used and the description is omitted. FIG. 8 shows the configuration of the fixing device 250 and the discharge unit of the second embodiment. The configuration of the film 202 and the pressure roller 206 is the same as that of the first embodiment, so the description is omitted. The discharge sensor 218 in the first embodiment is omitted because it does not have a distinctive configuration in the second embodiment, but is generally placed at a position after passing through the fixing nip portion S. The memory board 810 is connected to the full load detection board 820 via a cable 815, and is further connected to the controller board 900 via a cable 816 and a connector 831. The memory board 810 has a non-volatile memory 211 that stores information about the fixing device 250, such as the performance of the fixing device 250 and the manufacturing lot.

[0044] <Detection of full discharge tray> After passing through the fixing nip portion S, the recording paper R passes through a paper guide 817 and a pair of discharge rollers 818, and is discharged to a discharge tray 819, which is a stacking portion. The full-load sensor 840 is composed of a shaft 824, a full-load detection flag 823, and a photo interrupter 830. The full-load sensor 840 is used to detect whether the recording paper P on the discharge tray 819 is full. Note that a full-load state corresponds to the presence of paper in the first embodiment, and a state that is not full corresponds to the absence of paper in the first embodiment. When there is only a small amount of recording paper P on the discharge tray 819, the full-load detection flag 823 is at position 822a indicated by the dashed line in the full-load sensor 840, which causes the photo interrupter 830 to be in a light-shielded state. On the other hand, when multiple sheets of recording paper P are stacked on the discharge tray 819 and the discharge tray 819 is in a fully loaded state, such as the topmost recording paper P (hereinafter referred to as stacked paper 821), the fully loaded detection flag 823 moves to position 822b indicated by a solid line, and the photo interrupter 830 enters a light-transmitting state. Hereinafter, this state will be referred to as a fully loaded detection state. When the recording paper P on the discharge tray 819, including the stacked paper 821, is removed, the fully loaded detection flag 823 moves to position 822a again, the photo interrupter 830 enters a light-shielding state, and the fully loaded detection state is released. The light-shielding state and light-transmitting state (full loaded detection state) of the photo interrupter 830 are sent to the controller board 900 by a signal, and the controller board 900 determines whether the discharge tray 819 is fully loaded or not.

[0045] <Memory board, full load detection board, controller board> 9 shows a connection diagram of the memory board 810, the full-load detection board 820, and the controller board 900. In the second embodiment, due to the arrangement of the boards in the image forming apparatus, the full-load detection board 820 plays the role of a relay board that relays the memory board 810 and the controller board 900, but the memory board 810 and the full-load detection board 820 do not necessarily need to be separate boards. The cables 815 and 816 are composed of SNS, Vcc, SDA, SCL, and GND, as in the first embodiment. Hereinafter, the signal lines used for transmitting and receiving each signal (or voltage) are referred to as the SNS signal line, the Vcc signal line, the SDA signal line, the SCL signal line, and the GND signal line.

[0046] Since each terminal of the nonvolatile memory 811 of the memory substrate 810 is similar to that of the nonvolatile memory 211 of the first embodiment, the same reference numerals are used and the description is omitted. Note that a filter consisting of a resistor 907 and a capacitor 908 corresponding to the filter consisting of the resistor 307 and the capacitor 308 of the first embodiment (see FIG. 3) is connected to the SCL terminal. Also, a filter consisting of a resistor 905 and a capacitor 906 corresponding to the filter consisting of the resistor 305 and the capacitor 306 of the first embodiment (see FIG. 3) is connected to the SDA terminal.

[0047] The full-load sensor circuit 904 is composed of a photointerrupter 830 and a resistor 903. When the discharge tray 819 in FIG. 8 is not in a full-load state and the full-load detection flag 823 is at position 822a, the photointerrupter 830 is shielded from light by the full-load detection flag 823. This makes the phototransistor 830t of the light receiving portion of the photointerrupter 830 non-conductive. On the other hand, when the discharge tray 819 is in a full-load state and the full-load detection flag 823 is at position 822b, the light shielding by the full-load detection flag 823 is released from the photointerrupter 830 and the photointerrupter 830 becomes transparent. This makes the phototransistor 830t of the light receiving portion of the photointerrupter 830 conductive.

[0048] The output of the photointerrupter 830, i.e., the SNS signal, is pulled up by a resistor 902 on the controller board 900 and input to the I / O port (hereinafter also referred to as port 901p) of the microcomputer (hereinafter referred to as CPU) 901. When the phototransistor 830t in the light-receiving part of the photointerrupter 830 is non-conductive, a high (H) voltage level is input to the I / O port of the CPU 901, and when it is conductive, a low (L) voltage level is input. Thereby, the CPU 901 can detect whether the recording paper P on the discharge tray 819 is full.

[0049] On the other hand, the SNS signal line is also connected to the WP terminal of the non-volatile memory 211, and is configured to be used in common for the function of the full-load sensor 840 and the write protection function of the non-volatile memory 211. For this reason, one signal line can be reduced compared with the case where these two functions are performed by separate signals.

[0050] <Transition of SNS signal> (When the discharge tray does not become full during continuous printing) The time charts of FIGS. 10 to 13 show how the SNS signal transitions on the sequence of an actual image forming apparatus. Note that (i) to (vi) in FIGS. 10 to 13 are the same graphs as (i) to (vi) in FIG. 4 of the first embodiment. Times 11 to 15, times 21 to 25, times 31 to 35, and times 41 and 42 indicate each timing. FIG. 10 shows a flow starting from the sleep state, transitioning to continuous printing, standby, and then to sleep again. The items in FIG. 10 show the state of the image forming apparatus, Vcc, the SNS signal, the input / output of the SNS signal port (port 901p), the state of the memory data of the non-volatile memory 211, and the I2C communication state of the non-volatile memory 211 from the top.

[0051] First, in an image forming apparatus in a sleep state, the power supply Vcc is 0V, the SNS signal is at low level (Lo), and the SNS signal port of the CPU 901 is an input. At this time, the power supply Vcc of the non-volatile memory 211 is 0V and off, so memory data is retained and I2C communication is not performed (communication is stopped). At time 11, the apparatus returns from the sleep state in response to a print instruction from the user, and the power supply Vcc rises to 3.3V. The SNS signal rises to H level assuming that the full load sensor 840 is not in a full load state, i.e., that the photointerrupter 830 is in a light-shielded state, and the WP terminal is Hi, so the memory data is in a protected state.

[0052] At time 12, continuous printing ends and the image forming apparatus enters a standby state. When writing the number of prints and the like to the non-volatile memory 811, for example, the CPU 901 outputs a low-level signal to the SNS signal port at time 13, releases write protection, and performs I2C communication. At time 14 when communication ends, the CPU 901 switches the SNS signal port from output to input, and the SNS signal goes Hi again, returning to the write-protected state.

[0053] At time 15, the image forming apparatus goes into a sleep state, the power supply Vcc is turned off at 0 V, the power supply to the non-volatile memory 811 is turned off, and the memory data is retained. Through the above process, the non-volatile memory 811 is in a write-protect state or in a power-off state except when data is being written to the non-volatile memory 811. This makes it possible to reduce the risk that data stored in the non-volatile memory 811 will be inadvertently rewritten due to external noise or a malfunction of the image forming apparatus.

[0054] (When the output tray becomes full during continuous printing) Next, a case where the discharge tray 819 becomes full of recording paper P during continuous printing will be described with reference to Fig. 11. After continuous printing is started at time 21, when the discharge tray 819 becomes full at time 22, the full-load detection flag 823 becomes position 822b in Fig. 8, the photointerrupter 830 becomes light-transmitting, and the SNS signal transitions from Hi to Lo. This causes the CPU 901 to determine that the discharge tray 819 has become full (discharge full). At this time, the switching of the SNS signal port from input to output and the communication with the non-volatile memory 211, which should be performed from time 13 to time 14 when the continuous printing in Fig. 10 ends, are not performed in Fig. 11.

[0055] During the full load detection state, the SNS signal is Lo, i.e. the write protect function of the non-volatile memory 811 is released, but during the period when the SNS signal is input to the CPU 901 at a low level, no communication with the non-volatile memory 211 is performed. During the full load detection state, a situation is likely to occur in which external noise such as static electricity is generated when the user accesses the image forming apparatus, for example by removing recording paper P including the stacked paper 821. For this reason, by not performing communication during this period, the risk of memory data becoming corrupted can be reduced.

[0056] At time 23, the user begins removing the stack of papers 821, etc., and at time 24, the user completes removing the stack of papers 821, etc. from the output tray 819, and the device enters a standby state. Note that between time 23 and time 24, the SNS signal becomes "undefined" because it varies depending on the behavior of the stack of papers 821, etc. When the stack of papers 821, etc. is removed at time 24, the full load detection flag 823 returns to position 822a, the photointerrupter 830 becomes light-shielded, the SNS signal goes high, and the non-volatile memory 811 enters a write-protected state. At time 25, the device enters a sleep state, and the power to the non-volatile memory 211 is turned off.

[0057] (When the power is turned on when the output tray 819 is not full) Figures 12 and 13 are timing charts when the image forming apparatus is powered on. Figure 12 shows the normal state, and Figure 13 shows the case when the power is turned on with full load detected. Figure 12 is the same as the timing chart of Figure 6, and the power is turned on at time 31, and at time 32 the CPU 901 switches the SNS signal port from input to output, releases write protection, reads non-volatile memory 811, and ends communication at time 33. The image forming apparatus ends start-up processing at time 34 and enters a standby state, and transitions from standby to sleep at time 35. Other explanations are omitted.

[0058] (When the power is turned on with the output tray 819 fully loaded) When the power is turned on in the state where the discharge tray 819 in FIG. 13 is fully loaded, the CPU 901 detects the discharge tray 819 being fully loaded at time 42 because the SNS signal is at a low level indicating a fully loaded state after the power is turned on at time 41. Therefore, an error occurs in the image forming apparatus, the start-up process is stopped (error stop), and the error is notified on the operation panel or the like (not shown). Therefore, in FIG. 13, the switching of the SNS signal port from input to output, which was performed from time 32 to time 33 in FIG. 12, and the read process of the non-volatile memory 211 are not performed. This makes it possible to reduce the risk of inadvertent data rewriting due to external noise or malfunction of the image forming apparatus. If the process of removing the stacked paper 821, etc. is performed after the error stop, the error is released, and the same flow as that from time 23 onwards in FIG. 11 is carried out.

[0059] With the above-mentioned configuration, it is possible to reduce the number of signal lines by one, while ensuring the reliability of the data inside the non-volatile memory 811, and to reduce the cost and space of the image forming apparatus. In the second embodiment, the SNS signal is configured to be Lo in the fully loaded state and Hi in the stackable state (not fully loaded state), but the reverse logic may be used. In that case, care should be taken not to mismatch (be consistent) with the logic of the WP terminal of the non-volatile memory 811. In the second embodiment, the detection result of the fully loaded sensor circuit 904 is used as the SNS signal, but this sensor is not limited to this sensor, and any sensor that is on the conveyance path of the recording paper R and switches between Hi and Lo depending on the state of the recording paper R may be used. Furthermore, any type of non-volatile memory is applicable to the present invention as long as it has a write-protect function.

[0060] As described above, according to the second embodiment, the reliability of data in the non-volatile memory can be ensured without increasing costs or space due to the addition of cables or the like. [Explanation of symbols]

[0061] 2 Image forming section 211 Non-volatile memory 218 Emission sensor 301 Microcomputer (CPU) 301p port

Claims

1. An image forming apparatus including an image forming unit for forming an image on a recording material, a detection means for detecting the presence or absence of a recording material and outputting a first signal according to the detection result via a signal line; a control means having a first terminal to which the first signal is input and determining the presence or absence of a recording material based on the first signal; a storage unit having a write protect function and having a second terminal to which a second signal for switching between enabling and disabling the write protect function is input from the control means via the signal line; Equipped with The control means switches the first terminal from a state in which the first signal is input to a state in which the second signal is output, outputs the second signal to the second terminal via the signal line, disables the write protect function of the memory unit, and communicates with the memory unit, characterized in that the image forming apparatus.

2. the storage unit disables the write protect function when the detection means detects the presence of the recording material, 2. The image forming apparatus according to claim 1, wherein the control unit stops communication with the storage unit when the detection unit detects the presence of the recording material.

3. The image forming apparatus according to claim 1, characterized in that the control means switches the first terminal from a state in which the second signal is output to a state in which the first signal is input when communication with the memory unit is completed, thereby enabling the write protect function.

4. a fixing unit that fixes unfixed toner formed on a recording material by the image forming unit, the detection unit is a sensor used to determine whether or not a recording material jam has occurred in the vicinity of the fixing unit, the storage unit stores information related to the fixing unit, The image forming apparatus according to claim 1, characterized in that when the control means determines that the jam has occurred based on the detection result of the sensor, the control means does not switch the first terminal from a state in which the first signal is input to a state in which the second signal is output, and stops communication with the memory unit.

5. a fixing unit for fixing the unfixed toner formed on the recording material by the image forming unit; a stacking section for stacking the recording material on which the toner has been fixed by the fixing means; Equipped with the detection means is a sensor used to determine whether the recording materials loaded on the stacking section are fully loaded or not, the storage unit stores information related to the fixing unit, The image forming apparatus according to claim 1, characterized in that when the control means determines that the stacking section is fully loaded based on the detection result of the sensor, it does not switch the first terminal from a state in which the first signal is input to a state in which the second signal is output, and stops communication with the memory section.

6. 6. The image forming apparatus according to claim 4, wherein the sensor is a photosensor.

Images