Image forming device

Abstract

To provide an image forming device capable of eliminating probability of generation of supply failure caused by overlapped sending because of increased adsorption force between a plurality of sheets through electrification.SOLUTION: An image forming device is provided with: an image forming part forming images on sheets; a resin tray rotatably provided at a side surface of a device body including the image forming part and having a tray surface on which sheets are loaded; a sheet feeding part feeding the sheets loaded on the tray surface toward the image forming part; a blowing part sending air to the sheets loaded on the tray surface and the tray surface; and a control part making the air flowing part send air every time the sheet feeding part feeds the specific number of sheets irrespective of information on sheets fed by the sheet feeding part.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus for forming a sheet image. [Background technology]

[0002] In a conventional image forming apparatus, a manual feed unit is attached to the side of the image forming apparatus. The manual feed unit is adapted to handle sheets of sizes that cannot be set in the cassette feed unit provided at the bottom of the image forming apparatus (e.g., long paper, non-standard size, and small size paper). It is also adapted to handle high-rigidity thick paper that cannot be conveyed due to the large conveyance resistance received from the guide when conveying the sheet. In other words, it is adapted to handle a wide variety of media.

[0003] Among the wide variety of media, coated paper has a smooth surface and is therefore capable of producing high-quality deliverables, with excellent photographic and color reproducibility. In recent years, there has been a demand for continuous feeding of coated paper to improve the productivity of equipment. However, because coated paper has a smooth surface, sheets of the paper adhere strongly to each other, making it difficult to easily separate the sheets.

[0004] Therefore, Patent Document 1 discloses a configuration in which a fan, which is an air blowing means, is provided on the manual feed tray, and air is blown onto multiple coated sheets of paper before feeding begins, separating the sheets and reducing the adhesive force between the sheets. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2006-256819 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in Patent Document 1, when the manual feed tray is made of resin, the surface of the manual feed tray increases in static charge due to friction between sheets when the sheets are fed and separated, regardless of whether the sheets are coated paper or not. In particular, charging due to friction during feeding is likely to occur in a low-temperature, low-humidity environment. As a result, the adhesive force between multiple sheets due to charging increases, and there is a risk of feeding failure due to multiple feeding.

[0007] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide an image forming apparatus capable of reducing the occurrence of sheet feeding failures due to double feeding of sheets. [Means for solving the problem]

[0008] One aspect of the present invention for solving the above problems is characterized by comprising an image forming unit that forms an image on a sheet, a resin tray that is rotatably arranged on a side of a device main body including the image forming unit and has a tray surface on which a sheet is placed, a feeding unit that feeds a sheet placed on the tray surface toward the image forming unit, a blower unit that blows air to the sheet placed on the tray surface and to the tray surface, and a control unit that causes the blower unit to blow air to the sheet placed on the tray surface and to the tray surface each time the feeding unit feeds a predetermined number of sheets, regardless of information about the sheets fed by the feeding unit. Effect of the Invention

[0009] According to the present invention, it is possible to reduce occurrence of feeding failures caused by double feeding of sheets. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view of an image forming apparatus according to a first embodiment of the present invention. [Diagram 2] FIG. 1 is a top view of a manual feed tray according to a first embodiment. [Diagram 3] 1 is a cross-sectional view of a manual feed tray according to a first embodiment. [Figure 4] FIG. 1 is a control block diagram of a fan provided in a manual feed tray according to a first embodiment. [Diagram 5]Change in surface potential on the tray surface of the manual feed tray according to the first embodiment (without fan blowing) [Figure 6] Change in surface potential of sheets loaded on a manual feed tray according to the first embodiment (without fan blowing) [Figure 7] Change in surface potential on the tray surface of the manual feed tray according to the first embodiment (with fan blowing every 4 sheets) [Figure 8] Change in surface potential on the tray surface of the manual feed tray according to the second embodiment (with fan blowing for each sheet) [Figure 9] Flowchart of sheet feeding control according to the second embodiment [Figure 10] Change in surface potential on the tray surface of the manual feed tray according to the third embodiment (with fan blowing for each sheet) [Figure 11] FIG. 11 is a control block diagram of a fan provided in a feed tray according to a fourth embodiment (not grounded). [Figure 12] Voltage when static electricity is applied according to the fourth embodiment (without grounding) [Figure 13] FIG. 13 is a control block diagram of a fan provided in a feed tray according to a fourth embodiment (with grounding). [Figure 14] Voltage when static electricity is applied in embodiment 4 (with ground) [Figure 15] 11 is a cross-sectional view of a manual feed tray according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment according to the present disclosure will be described with reference to the drawings. In this disclosure, the term "image forming apparatus" refers to an apparatus that forms an image on a sheet as a recording material. Image forming apparatuses include printers, copiers, multifunction machines, commercial printing machines, etc.

[0012] [Embodiment 1] <Image forming device> 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus according to a first embodiment. The image forming apparatus 100 is a laser beam printer that uses an electrophotographic process. The image forming apparatus 100 can form and output a full-color or monochrome image on a sheet S based on image data. As the sheet S, various sheets of different sizes and materials can be used, including paper such as plain paper and thick paper, sheet materials with surface treatments such as plastic film, cloth, and coated paper, and sheet materials with special shapes such as envelopes and index paper.

[0013] 1, image forming apparatus 100 is provided with an operation unit 127 for operating the operation of the apparatus at the top of image forming apparatus 100. Then, in the middle of image forming apparatus 100, image forming unit 150 for forming images and control unit 146 for controlling the operation of the entire apparatus are provided. Furthermore, in the bottom of image forming apparatus 100, a feeding unit for feeding sheets to the image forming unit is provided.

[0014] The operation unit 127 is provided with a liquid crystal panel 128. The liquid crystal panel 128 transmits and receives control signals to and from a main controller 146, which is a control unit, via a liquid crystal panel control line 129. The liquid crystal panel 128 displays information such as the state of the device and sheet settings in response to the above-mentioned control signals from the main controller 146. In addition to displaying the above-mentioned information as a user interface, the liquid crystal panel 128 often also functions as a touch panel. While touching the liquid crystal panel 128, the user performs, for example, sheet size settings for the manual feed unit in accordance with the information displayed on the liquid crystal panel 128. The information set by the user on the liquid crystal panel 128 is transmitted to the main controller 146 via the liquid crystal panel control line 129.

[0015] The image forming unit 150, which is an example of an image forming means, includes a photoconductor 109, a primary charger 111, a potential sensor 112, an exposure unit 121, a developing unit 122, a transfer unit 108, a cleaner 107, and a fixing unit 113 for forming an image. The primary charger 111 uniformly charges the surface of the photoconductor 109. The photoconductor 109, the surface of which is uniformly charged by the primary charger, is exposed by the exposure unit 121 in response to an image signal, and an electrostatic latent image corresponding to the image signal is formed. The developing unit 122 develops the electrostatic latent image to form a toner image on the surface of the photoconductor 109. The potential sensor 112 is provided between an exposure position by the exposure unit 121 and a development position by the developing unit 122 in order to measure the potential of the electrostatic latent image. The toner image formed on the surface of the photoconductor 109 is transferred to a sheet 110 fed from a feed cassette 120 by the transfer unit 108. After the toner image is transferred to the sheet 110, residual toner remaining on the photoconductor 109 is collected by a cleaner 107. The toner image is fixed to the sheet 110 with the transferred toner image by a fixing device 113. The sheet with the fixed toner image is discharged onto a discharge tray. Through this series of image processing operations, a product with a printed image is obtained.

[0016] The feeding section includes a feeding cassette 120 that stores the sheets 110 for feeding the sheets 110. The feeding section includes a feeding roller 119a, which is a pickup roller that feeds the sheets 110 stored in the feeding cassette 120. The feeding section further includes a separation roller pair consisting of a feed roller 119b and a retard roller 119c, as a separation conveying section for separating the sheets 110 sent out from the pickup roller 119a. The retard roller 119c applies a frictional force to the sheet in the nip portion between the feed roller 119b and the sheet in the direction opposite to the feeding direction, thereby allowing only one sheet in contact with the feed roller 119b to pass through the nip portion. This allows the feeding section to separate and feed a single sheet.

[0017] The sheet separated and fed to the feeding cassette 120 is conveyed to the registration rollers 118 via the conveying rollers 117 that convey the sheet. The registration rollers 118 adjust the timing of conveying the sheet toward the transfer unit 108. At the same time, the leading edge of the sheet is abutted against the registration rollers 118 to form a flexure in the sheet, thereby correcting the skew of the leading edge of the sheet. Thereafter, the toner image is transferred onto the sheet conveyed to the transfer unit 108 as described above, the sheet is conveyed to the fixing device 113, and is discharged onto the discharge tray. The sheet is conveyed by this series of conveying process operations.

[0018] The image forming process and the transport process are linked to each other, so that the sheets stacked on the feed section undergo image formation, and the product with the image printed thereon is discharged onto the discharge tray.

[0019] In order to carry out the above-mentioned image forming process operation and transport process operation, the image forming apparatus is provided with a controller 146 which is a control section, and various operations of the entire image forming apparatus are controlled by the controller.

[0020] In the conveying process operation, a plurality of sensors 101, 102, 103, 104, 105, and 106 are provided on the conveying path along which the sheet 110 is conveyed. A first sensor 104, a second sensor 105, and a third sensor 106 are arranged at predetermined intervals along the conveying direction of the sheet 110. In addition, stepping motors 114 and 116 and DC brush motors 115 and 132 are provided to provide rotational drive to various conveying rollers. Drive is transmitted to the feed roller 109 by the DC brush motor 115, to the conveying rollers by the stepping motor 116, and to the registration rollers by the stepping motor 114. The operations of the sensors that detect the sheet and the motors that transmit rotational drive to the rollers that convey the sheet are controlled by a controller 146.

[0021] Specifically, when starting a sheet feeding operation, the controller 146 detects the presence or absence of the sheet 110 in the feed cassette 120 by the sheet presence / absence sensor 103. When the controller determines that the sheet 110 is present in the feed cassette 120, the controller starts feeding the sheet 110 stored in the feed cassette 120 by the feed roller 119. The controller rotates the DC brush motor 115 to drive the feed roller 119, and the feed roller 119 transports the sheets 110 one by one from the feed cassette 120 toward the transport roller 117.

[0022] The first sensor 104 and the second sensor 105 are provided between the feed roller 119 and the conveying roller 117 on the conveying path, and detect whether the sheet 110 has passed a detection position on the conveying path from the feed roller 119 to the conveying roller 117. Similarly, the third sensor 106 is provided between the conveying roller 117 and the registration roller 118 on the conveying path, and detects whether the sheet 110 has passed a detection position on the conveying path from the conveying roller 117 to the registration roller 118.

[0023] When the sheet 110 is detected by the third sensor 106, the controller drives the stepping motor 114 to rotate the registration roller 118 after a predetermined time. This predetermined time is for correcting the skew of the leading edge of the sheet described above, and the leading edge of the sheet is abutted against the nip of the registration 118 to form a flexure in the sheet. Thereafter, the timing at which the registration roller 118 conveys the sheet 110 to the transfer unit 108 is adjusted according to the timing at which the toner image formed on the photoconductor 109 is conveyed to the transfer unit 108. As a result, the sheet 110 and the toner image formed on the photoconductor 109 pass through the transfer unit 108 while overlapping, and the toner image is transferred.

[0024] The discharge tray sensor 101 is provided above the discharge tray 123 and detects whether the sheet 110 has been discharged onto the discharge tray 123. Even in a low power consumption mode in which no job is generated for a certain period of time and low power consumption is maintained, the sensor has a mechanism for quickly detecting whether a user has accessed a discharged sheet and removed it from the discharge tray. In the low power consumption mode, if a sheet is removed from the discharge tray 123, the user may perform some operation on the device, so the device returns from the low power consumption mode to the normal standby state.

[0025] The cassette detection sensor 102 detects when the user pulls out the cassette 120 from the apparatus when, for example, refilling the sheets 110. Like the discharge tray sensor 101, the cassette detection sensor 102 has a mechanism for quickly detecting this even in a low power consumption mode in which no job is generated for a certain period of time and low power consumption is maintained.

[0026] The sensors 101, 102, 103, 104, 105, and 106 are each configured with a photointerrupter, for example. In this case, the sensors 101, 102, 103, 104, 105, and 106 each include a light emitting unit (for example, an LED (Light Emitting Diode)) and a light receiving unit (for example, a phototransistor) that receives light emitted from the light emitting unit. The sheet 110 presses a shield provided at a detection position on the conveying path to block the light path between the LED and the phototransistor, and the sensors 101, 102, 103, 104, 105, and 106 can detect the presence or absence of the sheet 110. However, the configuration of the sensors 101, 102, 103, 104, 105, and 106 is not limited to this, as long as the sensors detect the sheet 110 conveyed / discharged on the conveying path at the detection position, or detect the presence or absence of a cassette. For example, the LED and the phototransistor may be disposed opposite each other across the transport path, and the optical path may be blocked when the sheet 110 passes through the transport path. Alternatively, the light from the LED may be reflected by the sheet 110 on the transport path, forming an optical path to the phototransistor.

[0027] The DC brush motor 132 is used to transport a constant amount of toner, to be used for forming a toner image on the photoconductor 109, from a toner supply container set by the user to the developing device 122.

[0028] <Manual feed section> The manual feed section in Fig. 1 is provided on the side of the image forming apparatus, and a manual feed tray 124 on which a sheet is placed is rotatable relative to the apparatus body including the image forming section. In other words, the manual feed tray 124 is provided so as to be openable and closable relative to the apparatus body. Note that Fig. 1 illustrates the manual feed tray in an open position.

[0029] The manual feed section will be described with reference to Figures 2, 3, and 4. Figure 2 is a top view of manual paper tray 124, and Figure 3 is a cross-sectional view of manual paper tray 124. Figure 4 is a control block diagram focusing on control board unit 133 for a fan provided in the manual tray.

[0030] The sheets placed on the manual feed tray 124, like the sheets stored in the feed cassette 120, are transported to the conveying roller 107 by a pair of separation rollers consisting of a feed roller 149a, which is a pickup roller, and a feed roller 149b and a retard roller 149c, which serve as a separation conveying section for separating the sheets sent out from the pickup roller 149a.

[0031] As shown in FIG. 2 and FIG. 3, the tray surface of the manual feed tray 124 on which the sheet is placed is made of a resin material. In consideration of the strength of the tray, PC+ABS is generally used as the resin material, and is also adopted in this embodiment. In addition, a side regulating plate 125 that regulates the position of both side ends of the sheet 140 in the width direction, a fan 138 that is a blowing unit that blows air to the sheet, and a manual feed tray control board unit 133 that controls the fan 138 are provided. Furthermore, a fan control power line 142 and a fan control control signal line 143 for executing control are connected to a main controller 146 (not shown) from the manual feed tray control board unit 133. In addition, the manual feed sheet presence sensor 126 is a sensor for detecting whether a sheet is present on the manual feed tray. The detection signal of the sensor 126 is managed by a processor that executes a predetermined program in the main controller.

[0032] Fan 138 is attached to manual feed tray 124, and air generated by the fan is blown to the sheets through holes in slits 135, 136, and 137 formed in the surface of manual feed tray 124. The slits are made up of slits 135b, 136b, and 137b which are hidden by sheet 140 in Fig. 2, and slits 135a, 136a, and 137a which are not hidden by sheet 140. A member such as a mesh net or sponge with small holes may be attached to slits 135b, 136b, and 137b to prevent foreign objects from falling in.

[0033] The slits 135, 136, and 137 are arranged at different positions in the conveying direction so that air can be blown to the sheet even when the size of the sheet 140 in the conveying direction is different. The duct 139 shown in FIG. 3 is for guiding the air from the fan 138 to the slits 135, 136, and 137, as well as to the periphery of the tray surface of the manual feed tray 124. The air passing through the slits 135, 136, and 137 is blown to the sheets loaded on the tray, reducing the adhesion between the sheets. In the embodiment, when the sheets to be fed are coated paper, the surface properties of the sheets are smooth, so that the adhesion between the sheets is large. Therefore, when feeding coated paper, air blowing processing by the fan 138 is required.

[0034] 4 is a control block diagram centered on manual feed tray control board unit 133. Main controller 146 is connected to fan control unit 141 in manual feed tray control board unit 133, fan control power line 142, and fan control control signal line 143. Fan control unit 141 controls ON / OFF of fan power supply 134 for driving fan 138 according to the state of fan control control signal line 143 from main controller 146. Although a DC power supply such as +12V or 24V is usually used for fan control power line 142, in this proposal, a variable power supply voltage is supplied since it is required to control the number of revolutions of the fan. A detailed internal circuit of fan control unit 141 will be described later.

[0035] <Surface potential of manual feed tray and sheets> FIG. 5 shows the change in surface potential on the manual feed tray when sheets 140 are continuously fed in the conveying direction. In the measurement of FIG. 5, A4R size plain paper was used. When the trailing edge of the fed sheet is conveyed from the manual feed tray to the image forming apparatus, the value is measured by applying a laser beam of a surface potential meter to a surface potential measurement position (tray surface of the manual feed tray) 148. In addition to the laser type, there are also types of surface potential meters that generate and detect induced charges from electrified charges, and the potential indication changes depending on the type of these surface potential meters and the measurement environment such as humidity. For this reason, the surface potential voltage value used in this embodiment is a value for explaining the relativity measured under specific conditions.

[0036] The horizontal axis indicates the elapsed time, and the vertical axis indicates the surface potential value on the tray surface. As shown in Fig. 5, the surface potential gradually increases from the first sheet, and the amount of change in the surface potential decreases as the sixth, seventh, and eighth sheets are fed, but the potential itself continues to increase. Fig. 6 shows the transition of the value of the surface potential meter at the surface potential measurement position (paper surface) 147 on the sheet when A4R-sized plain paper similar to that in Fig. 5 is fed continuously. As in Fig. 5, it was found that the surface potential on the sheet increases as the number of sheets fed increases.

[0037] As shown in Fig. 5 and Fig. 6, an increase in the surface potential means an increase in the amount of charge on the surface of the sheet or the manual feed tray. This causes overlapping sheets to stick together due to electrostatic force. The sticking of sheets together due to electrostatic force causes feeding problems in the image forming apparatus, such as multiple feeding, and leads to reduced downtime due to jamming. Furthermore, an increase in the amount of charge on the manual feed tray itself may cause electrostatic discharge to be applied to the electrical circuit of the manual feed tray control board unit 133. In other words, unless measures are taken against electrostatic discharge in the electrical circuit of the manual feed tray control board unit 133, the electrical circuit may be destroyed.

[0038] Therefore, in this embodiment, as shown in Fig. 7, the fan 138 is used to blow air after every predetermined number of sheets (for example, every four sheets) to feed the sheets. Fig. 7 shows the transition of the surface potential value after the fan 138 is rotated to suppress the amount of electrostatic charge on the manual feed tray surface and the sheets after four sheets are discharged for the A4R plain paper fed in Figs. 4 and 5. That is, when the aforementioned sensor 104 detects the rear end of the fourth sheet, and before starting to feed the fifth sheet, the main controller 146 causes the fan 138 to blow air using the fan control signal 143. Thereafter, the fan 138 stops blowing air, and the fifth sheet is fed.

[0039] By controlling the fan 138 and the sheet feeding in this way, the surface potential of the tray surface is reduced. By reducing the surface potential of the tray surface, the sticking of sheets due to static electricity is also reduced. In other words, it is possible to reduce the occurrence of double sheet feeding and to suppress the occurrence of paper jams. Furthermore, reducing the surface potential of the tray surface makes it possible to reduce the application of static electricity to the electric circuit of the manual feed tray control board unit 133 housed inside the tray.

[0040] In this embodiment, fan 138 is rotated to blow air after the trailing edge of the fourth sheet is detected. However, by taking into consideration environmental factors such as humidity and setting the number of sheets to be fed in advance, it is possible to incorporate controls to prevent unnecessary fan rotation and increased power consumption, and to suppress noise caused by fan operation. In addition, the paper type and size of sheets 140 on manual feed tray 124 can be registered in advance by a user's operation on liquid crystal panel 128 in Fig. 1, and the fan can be driven under preset optimal driving conditions, such as the driving time and the number of sheets to drive after.

[0041] [Embodiment 2] In the first embodiment, the sheets are fed by blowing air by the fan 138 for every group of multiple sheets (four sheets), whereas in the second embodiment, the sheets are fed by blowing air by the fan 138 for each individual sheet.

[0042] FIG. 8 shows the transition of the surface potential on the tray surface of the manual feed tray when the fan 138 blows air every time a sheet is fed. The sensor 104 detects the trailing edge of the sheet being fed, and the main controller 146 rotates the fan 138 with the fan control signal 143. The main controller 146 predetermines the driving period of the fan 138 from before to after the sensor 104 detects the leading edge of the next sheet, and controls the rotation / non-rotation of the fan 138. The wind from the fan is intermittently blown onto the sheet 140 or the tray surface of the manual feed tray 124 for each sheet, so that the amount of charge can be kept low. Also, as in the first embodiment, when the sheet is fed while the fan is driven, the sheet is fed while being skewed, so the rotation by the fan 138 is stopped when the sheet 140 starts to be fed.

[0043] 9 is an example of a process flow preprogrammed by the controller 146. After the start of conveyance of the manually-fed sheet S1, when the sensor 104 detects the trailing edge of the sheet S3, the fan control signal line 143 controls the fan control section 141 in the manual feed tray control board unit 133 to drive the fan S4. Thereafter, it is determined in S5 whether Tmsec has elapsed, and if Tmsec has elapsed, the fan control signal line 143 stops the fan rotation in S6. This process flow is repeated for each number of sheets until the manually-fed sheet conveyance in S2 is completed. In addition, the aforementioned Tmsec uses an overflow function of a hardware timer in the processor, making it possible to control the ON and OFF of the fan 138 by only detecting the trailing edge of the manually-fed sheet without placing too much of a load on the processor's program processing.

[0044] As shown in the above-mentioned second embodiment, the surface potential of the tray surface is reduced by controlling the fan 138 and the sheet feeding. By reducing the surface potential of the tray surface, the adhesion between sheets due to static electricity is also reduced. In other words, it is possible to reduce the occurrence of double sheet feeding and to suppress the occurrence of paper jams. Furthermore, reducing the surface potential of the tray surface makes it possible to reduce the application of static electricity to the electric circuit of the manual feed tray control board unit 133 housed inside the tray.

[0045] [Embodiment 3] In the first and second embodiments, the fan 138 blows air based on the number of sheets to be fed, whereas in the third embodiment, the fan 138 blows air on each sheet to be fed, and then the fan's air volume is controlled.

[0046] 10 shows an example of the transition of the surface potential when the air volume of the fan is further reduced during the drive of the fan in the control of driving and stopping the fan 138 for each sheet in FIG. 9. In the fan control in FIG. 9, the air volume during the drive of the fan 138 is set to 100% as a first air volume, whereas in this embodiment, the air volume is reduced from 100% to N% of the second air volume. That is, in order to reduce the adhesive force of the sheet by the fan 138, the fan is driven at 100% when the sheet is coated paper, whereas the fan is driven at N% when the sheet is other than coated paper (plain paper). By setting the surface potential of the tray surface to N%, the amount of charge on the sheet is reduced, although the surface potential of the tray surface is higher than that at 100%,.

[0047] This makes it possible to reduce the airflow rate of fan 138, and the operating noise of fan 138 can be reduced compared to embodiment 2. Also, power consumption can be reduced compared to the method of embodiment 2. The airflow rate of the fan can be easily reduced by lowering the fan power supply voltage of fan control power line 142 from main controller 146. It is necessary to measure the relationship between the power supply voltage and airflow rate of fan 138 in advance, and further determine the range of N% airflow rate at which the surface potential can be controlled to a specific value or less by correlating it with the transition of the surface potential of the manual feed tray.

[0048] As shown in the above-described third embodiment, the surface potential of the tray surface is reduced by controlling the fan 138 and the sheet feeding. The reduction in the surface potential of the tray surface also reduces the adhesion of sheets to each other due to static electricity. In other words, it is possible to reduce the occurrence of double sheet feeding and to suppress the occurrence of paper jams. Furthermore, reducing the surface potential of the tray surface makes it possible to reduce the application of static electricity to the electric circuit of the manual feed tray control board unit 133 housed inside the tray.

[0049] [Embodiment 4] In the fourth embodiment, the bundle of wires 134 of the electric components housed in the tray is grounded via the tray surface side as shown in Fig. 15. In the first to third embodiments, the bundle of wires of the electric components is not grounded, particularly to the tray surface side as shown in Fig. 4. This makes it possible in this embodiment to suppress the occurrence of short circuits due to static electricity in the electric components.

[0050] FIG. 11 shows a detailed internal circuit of the fan control unit 141 in FIG. 4. The power supply from the main controller 146 via the fan control power line 142 and the fan ON / OFF control via the fan control signal line 143 have been described above. The fan control unit 141 has a mechanical or semiconductor switch inside and controls the power supply to the downstream fan 138. In this embodiment, the fan 138 is equipped with a two-phase brushless motor. The fan rotates by driving the drive current of the two-phase winding alternately for each phase using MOSFETs or bipolar transistors by a sequencer. Reference numeral 134 denotes a fan control line 134 connected to the fan 138 from within the manual feed tray control board unit 133, and is composed of a power line and a GND line for the fan 138.

[0051] FIG. 12 considers damage caused when the electric charge on the manual feed tray is applied as static electricity to the fan power line 134 or GND line of the fan 138. The drive voltage of the two-phase brushless fan in FIG. 11 is driven alternately as the A-phase drive voltage and the B-phase drive voltage in FIG. 12. When static electricity is applied to the fan power line 134, the power supply voltage itself jumps up for an instant and becomes unstable as shown by static electricity application A and static electricity application B of the fan power line 134 voltage in FIG. 11. If static electricity is applied at the time of switching between the A-phase and B-phase during fan driving, the application of static electricity is superimposed on the period T8 during which the diode current in the fan control unit 141 in FIG. 11 flows in reverse recovery current when the diode current is off, and there is a possibility that the reverse recovery current will flow more. For example, during the reverse recovery current period, due to the characteristics of the semiconductor, a high voltage is applied instantaneously and the inside of the semiconductor is in a high concentration of carriers (electrons and holes), which causes carrier bias as in avalanche breakdown, resulting in concentrated losses and destruction of the diode.

[0052] Therefore, in FIG. 13, in order to prevent the breakdown described in FIG. 12, a diode 144, a capacitor 145, and the like are added to the circuit in FIG. 12. By adding the diode 144, the diode 144 compensates for the reverse recovery current during the reverse recovery period as shown in FIG. 14, shortening the reverse recovery period T9 and reducing the reverse recovery current. When static electricity is superimposed during the reverse recovery period, the possibility of breakdown of the diode in the fan control unit 141 described above in FIG. 12 is reduced. Furthermore, by adding the capacitor 145, even if static electricity is applied to the power supply or GND line of the fan power supply line 134, a common mode voltage is applied, making it difficult for voltage fluctuations caused by the influence of static electricity to occur extremely between the power supply and GND. Furthermore, by adding the capacitor 145, the diode in the fan control unit 141 can be a diode with almost no reverse recovery period, such as a Schottky barrier diode, in addition to a high-voltage rectifier diode.

[0053] 15, manual tray control board unit 133 having the configuration shown in Fig. 14 as a countermeasure against destruction due to application of static electricity is disposed inside manual tray unit 124, and fan control wire 134 (power wire, GND wire) is actively brought into contact with the resin manual tray. Even if the charge on the resin manual tray causes insulation breakdown in the physical lead wire coating of fan control wire 134 and is applied as static electricity to the internal lead wire, fan control unit 141 inside manual tray unit 124 will not be destroyed. Improving the static electricity resistance of the electric circuit of the fan drive unit and bringing it into contact with a molded member that is easily charged is a very effective countermeasure against static electricity.

[0054] As explained above, a fan installed inside the manual feed tray unit for the purpose of handling the manually fed sheets is used, and air is blown onto the plastic manual feed tray and the sheets after each desired number of sheets is conveyed. This makes it possible to control the amount of static electricity on the manual feed tray and the sheets, and to prevent feeding problems such as double feeding. Furthermore, by strengthening the electrostatic damage resistance of the electric circuit in the internal electrical unit and actively bringing the lead wires connected to the strengthened electric circuit into contact with the plastic manual feed tray to promote the discharge of static electricity, a measure to prevent electrostatic damage to the internal electrical unit due to static electricity on the manual feed tray is achieved. [Explanation of symbols]

[0055] 150 Image forming section 124 Manual feed tray 138 Fan (blower) 146 Main controller (control unit) 149 Feeding roller (feeding section)

Claims

1. an image forming unit that forms an image on a sheet; a resin tray that is rotatably provided on a side surface of a main body of the apparatus including the image forming unit and has a tray surface on which a sheet is placed; a feeding section that feeds a sheet placed on the tray surface toward the image forming section; A blower that blows air onto the sheet placed on the tray surface and onto the tray surface; a control unit that causes the blower unit to blow air every time the feeding unit feeds a predetermined number of sheets, regardless of information about the sheets to be fed by the feeding unit; 1. An image forming apparatus comprising:

2. The control unit starts feeding of the sheet by the feeding unit in a state where the blowing unit stops blowing air.

2. The image forming apparatus according to claim 1,

3. The control unit is capable of adjusting the amount of air blown by the blower unit, When the sheet placed on the tray is a coated paper, the blower blows air at a first air volume, and when the sheet placed on the tray is a sheet other than a coated paper, the blower blows air at a second air volume smaller than the first air volume.

2. The image forming apparatus according to claim 1,

4. The predetermined number is one, 2. The image forming apparatus according to claim 1, wherein the control unit controls the blower unit to blow air every time the feed unit feeds one sheet.

Images