JP6071393B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

As a heating method of a heat fixing device used in an image forming apparatus such as a copying machine, a laser printer, and a facsimile, a heat roller method using a halogen heater or the like as a heat source, and a film heating method using a ceramic heater as a heat source are widely used. . The film heating method has an advantage that the temperature of the fixing device can be increased in a short time because the heat capacity is lower than that of the heat roller method. As a result, the waiting time from standby can be shortened and power can be saved, and the temperature rise in the image forming apparatus main body can be suppressed.
With reference to FIG. 2, a heat fixing device using a film heating method will be described. FIG. 2 is a schematic diagram illustrating a configuration example of the heat fixing device.
Reference numeral 204 denotes a heater based on ceramic. A heating element pattern 205 is formed on the heater 204 and is covered with an electrical insulating layer 206 such as glass. The insulating layer 206 is made as thin as possible in order to improve heat conduction. In general, the heating element pattern 205 is connected to a commercial power source via a switching element such as a triac or a mechanical switching element such as a relay. By controlling the switching element ON / OFF, the heating element pattern 205 is connected to the heating element pattern 205. Electric power is supplied. This ON / OFF control is performed based on the value of the thermistor 207 pressed against the vicinity of the heater 204, for example, the back surface of the heater 204 with a predetermined pressure.
Reference numeral 203 denotes a stay of heat resistant and heat insulating material for fixing and supporting the heater 204. Reference numeral 201 denotes a cylindrical heat-resistant film material (hereinafter referred to as a fixing film), which covers the heater 204 and the stay 203. As the fixing film 201, a single layer film, a composite film such as PI + PFA coating, SUS + rubber coating, or the like is used, and the inner surface of the fixing film 201 has a structure having good conductivity. In FIG. 2, the heater 204 and the fixing film 201 are illustrated in a state where they are separated from each other for easy understanding of the configuration, but actually, the heater 204 (insulating layer 206) is pressed against the inner surface of the fixing film 201. It will be in a hit state.
A pressure roller 208 is an elastic roller in which a heat-resistant elastic layer 210 such as silicone rubber is provided in a roller shape on the outer periphery of a metal core or a metal pipe 209 (hereinafter referred to as a pressure roller shaft). The pressure roller 208 and the heater 204 are pressed against each other with the fixing film 201 interposed therebetween. The pressure roller 208 is rotationally driven in the direction of arrow B at a predetermined peripheral speed by a fixing drive motor (not shown). The rotational force directly acts on the fixing film 201 by the frictional force with the outer surface of the fixing film 201 by the rotational driving of the pressure roller 208, and the fixing film 201 is pressed against and slides on the insulating layer 206 in the direction of arrow C. Driven by rotation. At this time, the stay 203 also functions as a fixing film inner surface guide member and also serves to facilitate the rotation of the fixing film 201. In a state where the rotation of the fixing film 201 due to the rotation of the pressure roller 208 is steady and the temperature of the heater 204 rises to a predetermined level, the image recording paper P onto which the multicolor toner image has been transferred is conveyed in the direction of arrow A. The conveyed image recording paper P is pressed against the pressure roller 208 together with the fixing film 201, whereby the heat of the heater 204 is applied to the image recording paper P through the fixing film 201, and the unfixed image is heated and fixed. Is done.
In order to reduce the size of the heat fixing device, the fixing film 201 and the pressure roller shaft 209 are disposed in the vicinity of a frame ground (hereinafter referred to as FG) of the image forming apparatus.
In the image forming apparatus having the above configuration, when a high voltage and high energy surge such as a common mode induced lightning is applied to the commercial power supply, the surge is applied in the following path. One is the path from the heating element pattern to the FG of the image forming apparatus through the insulating layer and the fixing film, and the other is the FG from the fixing film to the heat-resistant elastic layer of the pressure roller and the pressure roller shaft. Is the route to Actually, between the fixing film and FG with the highest impedance in the above path (
Hereinafter, almost all surge voltage is applied between the gap D) or between the pressure roller shaft and the FG (hereinafter, gap E). At this time, when a discharge occurs in the gap D or the gap E, the place where the surge voltage is applied moves to the insulating layer, and the insulating layer may break down.
In order to solve this problem, it is difficult to discharge by ensuring a large distance between the gap D and the gap E, or by providing a surge protection device such as a varistor between the line to which the commercial power is applied and the FG, The energy is released directly to the FG. Also, in Patent Document 1, the fixing film or the pressure roller shaft is grounded with a resistor, so that the surge energy is quickly absorbed, and it is difficult for the gap D and gap E to discharge, and a high voltage is applied to the insulating layer. A configuration for preventing this is proposed. Further, in Patent Document 2, the fixing film or the pressure roller shaft is grounded by a capacitor, so that the voltage applied to the gap D and the gap E is determined by the amount determined by the capacitance ratio between the capacitance component of the insulating layer and the capacitor. There has been proposed a configuration in which the electric discharge is reduced and the electric discharge is difficult to occur in the air gap D and the air gap E.

JP-A-6-51659 JP 2010-164636 A

However, these configurations and patent documents have the following problems, respectively.
First, a configuration that ensures a large distance between the gap D and the gap E increases the volume of the heat-fixing device, which becomes a barrier to downsizing the device. In addition, a configuration in which a surge protection device is provided between a line to which commercial power is applied and FG is a UL or TUV as a surge protection device.
It is necessary to use parts that have been approved by the safety standards of each country. Further, the configuration of Patent Document 1 is such that even when a surge having energy that cannot be absorbed by the resistor is applied, the gap D is prevented so that the dielectric breakdown of the resistor or the discharge between both terminals of the resistor does not occur. And the distance of the gap E is sufficiently secured. Therefore, it is disadvantageous for downsizing of the apparatus. Further, the configuration of Patent Document 2 is such that the gap D and the gap E do not generate a discharge even when the divided surge voltage exceeds the breakdown voltage between both terminals of the capacitor or the discharge start voltage of the gap D and the gap E. Of sufficient distance. Therefore, similarly to Patent Document 1, it becomes an obstacle to downsizing of the apparatus.

  An object of the present invention is to provide an image forming apparatus capable of preventing dielectric breakdown of an insulating layer in a heat-fixing apparatus at low cost and without increasing the size of the apparatus.

In order to achieve the above object, an image forming apparatus of the present invention includes:
An image forming unit for forming an image on a recording material;
A heater having a heating element that is covered with an insulating layer and generates heat when electric power is supplied from a commercial power supply via a commercial power supply line; and a fixing film that is provided on an outer periphery of the heater and rotates while sliding with the heater And a pressure member pressed against the heater via the fixing film, and sandwiching and conveying the recording material on which an image is formed at a nip portion formed between the fixing film and the pressure member A heat fixing device for heat fixing the image on the recording material,
In an image forming apparatus comprising:
The fixing film has a conductive layer electrically connected to a frame ground on an inner surface that slides with the heater,
The pressure member includes a metal shaft, and an elastic layer provided on an outer periphery of the metal shaft and in contact with the fixing film,
Between the fixing film and the frame ground is a first gap in a direction in which the metal shaft extends, and at least a part of the surge is generated when the surge is applied to the commercial power line. A first gap having a size that forms a first path that flows from the body to the frame ground through the insulating layer, the fixing film, and the first gap;
Between the metal shaft and the frame ground is a second gap in the extending direction of the metal shaft, and at least a part of the surge is generated when the surge is applied to the commercial power line. A second gap having a size from which a second path flowing from the body to the frame ground through the insulating layer, the fixing film, the elastic layer, the metal shaft, and the second gap is formed;
The conductive layer and the commercial power supply line are electrically connected through a surge protection device having an operating voltage higher than a peak voltage of the commercial power supply and lower than a voltage at which the insulating layer breaks down.

  According to the present invention, it is possible to prevent dielectric breakdown of the insulating layer in the heat fixing apparatus without increasing the size of the apparatus at low cost.

1 is a schematic cross-sectional view showing a configuration of an image forming apparatus according to the present invention. Schematic diagram illustrating a configuration example of a heat fixing device Circuit diagram explaining the power supply line to the heater The figure which shows the arrangement | positioning relationship between each member and FG of the heat fixing apparatus in this invention. The circuit diagram which equivalently represented the characteristic of each member of the heat fixing device in the present invention Diagram showing voltage and current waveforms when no varistor is connected and no discharge occurs in the air gap The figure which shows each voltage and current waveform at the time of discharging with a gap without connecting a varistor Diagram showing voltage and current waveforms when a varistor is connected The figure which shows the arrangement | positioning relationship between each member and FG of the heat fixing apparatus in this invention. The circuit diagram which equivalently represented the characteristic of each member of the heat fixing device in the present invention

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be exemplarily described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. That is, it is not intended to limit the scope of the present invention to the following embodiments.

Example 1
With reference to FIG. 1, the configuration of a color image forming apparatus according to an embodiment of the present invention will be described. FIG. 1 is a schematic cross-sectional view illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. In this embodiment, a color image forming apparatus having a plurality of photosensitive drums has been taken up. However, the present invention is not limited to this, and the present invention is also applicable to a monochrome copying machine and printer having a single photosensitive drum. Can do.

  The image forming unit of the image forming apparatus according to the present embodiment is configured to form an image with toner (developer) on an image recording paper (recording material) P by a conventionally known electrophotographic method. That is, each of the charged photoconductors 121, 122, 123, and 124 is irradiated with a laser beam to form an electrostatic latent image, and each has a different color (yellow (Y), magenta (M), cyan (C), black (K)) toner is adhered. In this way, a multicolor toner image is formed by sequentially superimposing the four color single color toner images respectively formed on the photosensitive members 121, 122, 123, and 124 on the intermediate transfer member 125. The image recording paper P fed from the paper feed unit 111 by the paper feed roller 112 and transported along the transport path H is sandwiched between the multi-color toner image formed on the intermediate transfer body 125 and the transfer roller 113 and pressed. Is done. Since a positive bias is applied to the transfer roller 113 by the transfer bias generator 114, a negatively charged multicolor toner image is transferred onto the image recording paper P. Thereafter, the image recording paper P is nipped and conveyed by the heat fixing device 130 at the nip formed between the fixing film and the pressure roller, whereby the multicolor toner image is heated and fixed. It is discharged to the discharge tray 115.

The configuration of the image forming apparatus according to the embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a circuit diagram illustrating a power supply line to the heater. FIG. 4 is a schematic diagram showing an arrangement relationship between each component of the heat fixing apparatus and FG (frame ground) in the first embodiment of the present invention. In addition, the heat fixing apparatus of the present embodiment uses a film heating method,
The configuration is as described above with reference to FIG. Therefore, the description of the overlapping parts is omitted, and the matters not described here are the same as the above description using FIG.

  The heating element pattern 205 formed on the heater 204 is electrically connected to the metal contacts 313a and 313b of the connector 312 with the electrodes 314a and 314b through the conductive patterns 315 and 316, respectively. The electrodes 314a and 314b are connected to the commercial power supply 310 on one side via the triac 308 and the relay 309a and on the other side via the thermo switch 307 and the relay 309b. Here, detachable drawer connectors 311 a and 311 b are used at locations where the heat fixing device 130 is electrically connected to the image forming apparatus 100.

  By controlling ON / OFF of the triac 308, power supply to the heating element pattern 205 is performed. The thermo switch 307 is pressed against the back surface of the heater 204 with a predetermined pressure, and has a function of ensuring safety by interrupting energization when the heater 204 abnormally generates heat.

  The outer periphery of the heater 204 is covered with the fixing film 201, and a pressure roller (pressure member) 208 is pressed through the fixing film 201. When the fixing film 201 comes into contact with the rotating pressure roller 208, the fixing film 201 is driven to rotate by the frictional force and slides on the heater 204 (insulating layer 206). The fixing film 201 employs a conductive SUS film coated with rubber in order to obtain an appropriate heat storage effect while maintaining thermal responsiveness. The pressure roller 208 includes a heat-resistant elastic layer 210 and a pressure roller shaft 209 that is a metal shaft.

  Here, since the resistance value of the recording paper P is extremely reduced in a high temperature and high humidity environment, the current from the commercial power source that flows through the heating element pattern 205 is passed through the insulating layer 206 and the rubber layer of the fixing film 201. In some cases, the transfer bias P flows through the transfer bias generator 114. As a result, the transfer bias may be affected by the commercial power supply, resulting in image unevenness.

  This problem is addressed by the following method. The rubber layer at the end of the fixing film 201 is slightly peeled to expose the SUS portion (conductive layer) 306 on the inner surface, and a charge eliminating needle 302 made of metal hair is brought into contact therewith. The static elimination needle 302 is grounded to the FG 301 of the image forming apparatus via a resistor 303. The resistor 303 is preferably about several MΩ. As a result, the impedance between the SUS part 306 and the FG of the fixing film 201 can be lowered to prevent the current from the commercial power source from flowing out to the transfer bias generator 114.

  Further, in order to stabilize the potential of the pressure roller 208, the pressure roller shaft 209 is also grounded to the FG 301 via the static elimination needle 304 and the resistor 305. The resistor 305 is raised to several hundred MΩ to several GΩ so that the current due to the transfer bias does not flow through the image recording paper P and the resistor 305 to the FG.

  Finally, in order to regulate the voltage applied to the insulating layer 206, a varistor 213 is additionally provided in parallel therewith. The operating voltage of the varistor 213 is 1000 V, which is higher than the peak voltage of the commercial power supply and lower than the dielectric breakdown voltage of the insulating layer.

FIG. 5 is a diagram showing each member of the above-described heat fixing apparatus with an equivalent electronic circuit. When a common mode surge is applied to the commercial power supply 310, it travels through the commercial power supply line 411 of the heat fixing device 130 and reaches the SUS part line 412 on the inner surface of the fixing film via the insulating layer 402 and the varistor 213. After that, it is divided into two hands, and one of them returns to the FG via the gap D (first gap) between the SUS part line 412 and the FG line 415 and the resistor 303 (referred to as a path F (first path) ). The other is first transmitted to the rubber surface line 413 of the fixing film through the fixing film layers 403a and 403b, and further, the pressure roller shaft made of metal through the heat-resistant elastic layers 404a and 404b of the pressure roller in contact therewith. Line 414 is reached. And finally, it returns to FG via the space | gap E (2nd space | gap) and the resistance 305 (it is set as the path | route G (2nd path | route) ). In addition, 410 is a heater, 417a and 417b are Y capacitors, 418a and 418b are X capacitors, and 419 is a common mode choke coil.

  6 to 8, when a common mode induced lightning surge 6 kV is actually applied to the commercial power supply 310, the voltage applied to each location and the waveform of the current flowing through each location will be described. . In the configuration of this embodiment, since the impedance of the path G is higher than that of the path F, the gap D is easier to discharge than the gap E. Therefore, only the waveform of the path F, that is, the voltage and current applied to the insulating layer 402, the voltage and current applied to the gap D, and the current flowing through the varistor 213 were simulated.

  FIG. 6 is a diagram showing a voltage waveform and a current waveform when the varistor 213 is not connected and when the gap D is not discharged. 6A is a diagram illustrating a voltage waveform, and FIG. 6B is an enlarged view of the waveform of FIG. 6A. FIG. 6C is a diagram illustrating a current waveform, and FIG. 6D is an enlarged view of the waveform of FIG. When a lightning surge is applied to the commercial power supply 310, a voltage exceeding 7 kV is applied to the insulating layer 402 and the gap D. The reason why the voltage exceeds 6 kV is that surge current flows into the common mode choke coil 419 and Y capacitors 417a and 417b existing on the circuit, and kickback occurs in the common mode choke coil 419. Further, it can be seen that 90% or more of the applied voltage is applied to the gap D and is hardly applied to the insulating layer 402. It can be seen that the surge energy is gradually lost due to the resistance component of the circuit, and the voltage is also decreasing.

  FIG. 7 is a diagram illustrating a voltage waveform and a current waveform when the varistor 213 is not connected and discharge is performed in the gap D. FIG. FIG. 7A is a diagram illustrating a voltage waveform, and FIG. 7B is an enlarged view of the waveform of FIG. 7A. FIG. 7C shows a current waveform, and FIG. 7D is an enlarged view of the waveform of FIG. 7C. When a lightning surge is applied to the commercial power supply 310, a voltage amplified by circuit kickback is applied to the insulating layer 402 and the gap D. When the voltage exceeds the discharge start voltage of the gap D, a discharge is generated in the gap D, and the voltage applied to the gap D instantaneously decreases to almost zero. At the same time, a large current flows through the gap D and the insulating layer 402, and the capacitive component of the insulating layer 402 is charged. As the battery is charged, the voltage applied to the insulating layer 402 increases. When this voltage exceeds the dielectric breakdown voltage of the insulating layer 402, the dielectric breakdown of the insulating layer 402 occurs. Thereafter, the surge energy resonates with the inductance of the circuit and the capacitance component of the insulating layer 402, but is gradually lost due to the resistance component of the circuit.

  FIG. 8 is a diagram showing a voltage waveform and a current waveform when the varistor 213 is connected. 8A is a diagram illustrating a voltage waveform, and FIG. 8B is an enlarged view of the waveform of FIG. 8A. FIG. 8C is a diagram showing a current waveform, and FIG. 8D is an enlarged view of the waveform of FIG. When a lightning surge is applied to the commercial power supply 310, the voltage is amplified by the kickback of the circuit, and the discharge starts in the gap D before long. At the same time as discharging, a large current flows through the gap D and the insulating layer 402, and is charged to the capacitance component of the insulating layer 402. When the charge voltage exceeds the operating voltage 1000V of the varistor 213, the current flowing in the insulating layer 402 is divided into the varistor 213, and the voltage applied to the insulating layer 402 is maintained at 1000V. Thereafter, the current resonates between the insulating layer 402 and the varistor 213, and the voltage applied to the insulating layer 402 continues to be maintained at 1000V. Therefore, the insulating layer 402 does not break down.

From the above, by installing a varistor in parallel with the insulation layer of the heater, even if a high voltage and high energy surge such as a common mode induced lightning surge is applied to the commercial power supply, the insulation layer will break down. It becomes possible to prevent. An image forming apparatus having this function can be realized at low cost and in a compact manner.

  In this embodiment, an example in which a varistor is used as a surge protection device has been shown. However, other elements may be used as long as they are in an energized state when a predetermined operating voltage is exceeded. It may be used.

(Example 2)
With reference to FIG. 9 and FIG. 10, an image forming apparatus according to Embodiment 2 of the present invention will be described. FIG. 9 is a schematic diagram showing an arrangement relationship between each member of the heat fixing apparatus and FG in Embodiment 2 of the present invention. FIG. 10 is a diagram showing each member of the heat fixing apparatus shown in FIG. 9 by an equivalent electronic circuit. Regarding the image forming apparatus according to the present embodiment, matters that are not particularly described here are the same as those in the first embodiment, and description of portions that are the same as those in the first embodiment is omitted.

  Since the temperature of the surface of the fixing film 201 of the heat fixing device 130 is controlled at a high temperature exceeding 150 ° C., when the image recording paper P is passed, moisture contained in the paper is evaporated and steam is generated. Due to this vapor pressure, a part of the unfixed toner image is blown off in the direction of conveyance A of the image recording paper P, and an image defect called tailing occurs. In order to improve this tailing, a negative bias (hereinafter referred to as a fixing film bias) is applied to the SUS part 306 of the fixing film 201. This fixing film bias is generated by a fixing film bias generator 1003 and supplied to the SUS section line 1012 of the heat fixing device 130 at a contact point 901. Since the fixing film bias is about −1000 V, the resistor 903 plays a role of current limiting. Therefore, the resistor 903 needs to be several tens of MΩ or more.

  On the other hand, as described in the first embodiment, it is necessary to reduce the impedance of the SUS portion line 1012 to the FG to about several MΩ so that the transfer bias is not affected by the commercial power source and causes image unevenness. In this example, a capacitor 906 is provided between the SUS part line 1012 and the FG. The capacitance of the capacitor 906 is determined by the partial pressure with the capacitance value of the insulating layer 206 (= insulating layer 402), and is about 3300 pF. The reason why a capacitor instead of a resistor is provided in 906 is that the potential of the SUS part line 1012 is divided by the fixing bias resistors 903 and 906.

  In order to regulate the voltage applied to the insulating layer 206 (= insulating layer 402), varistors 913a and 913b are additionally provided in parallel therewith, that is, between the commercial power supply line 411 and the fixing film bias line 1012. The operating voltage of the varistors 913a and 913b needs to be higher than the total value of the peak voltage of the commercial power supply and the voltage value of the fixing film bias and lower than the breakdown voltage of the insulating layer. The voltage that satisfies this is 1500 V to 2000 V, and two 820 V are connected in series in consideration of cost.

  When the common mode induced lightning surge 6 kV is actually applied to the commercial power supply 310 with respect to the image forming apparatus having the heat fixing device described above, the voltage applied to each location and the current flowing to each location are 1 is obtained in the same manner as that shown in FIG. As described above, even in the heat fixing device in which the fixing film bias is applied to the SUS portion of the fixing film, the same effect as in the first embodiment can be obtained by additionally arranging two varistors in series with the insulating layer of the heater. It is done. That is, even when a high voltage and high energy surge such as a common mode induced lightning surge is applied to the commercial power supply, it is possible to prevent dielectric breakdown of the insulating layer. An image forming apparatus having this function can be realized at low cost and in a compact manner.

In each of the above-described embodiments, an example in which the present invention is applied to a heat fixing apparatus that heat-fixes an image on a recording material has been described. However, the scope of application of the present invention is not limited thereto. For example, an image heating device for modifying the surface of the recording material, such as polishing the surface of the recording material by heating, an image heating device for assumed attachment, a heating drying device for a heated material, a heating laminating device, etc. The present invention can be widely applied to an apparatus for performing a heat treatment on a heating material.

  In each of the above-described embodiments, configurations combined with each other as much as possible can be adopted.

  DESCRIPTION OF SYMBOLS 100 ... Image forming apparatus 130 ... Heat fixing apparatus 201 ... Fixing film 204 ... Heater 205 ... Heating element pattern 206 ... Insulating layer 208 ... Pressure roller 213 ... Varistor 301 ... FG

Claims (5)

An image forming unit for forming an image on a recording material;
A heater having a heating element that is covered with an insulating layer and generates heat when electric power is supplied from a commercial power supply via a commercial power supply line; and a fixing film that is provided on an outer periphery of the heater and rotates while sliding with the heater And a pressure member pressed against the heater via the fixing film, and sandwiching and conveying the recording material on which an image is formed at a nip portion formed between the fixing film and the pressure member A heat fixing device for heat fixing the image on the recording material,
In an image forming apparatus comprising:
The fixing film has a conductive layer electrically connected to a frame ground on an inner surface that slides with the heater,
The pressure member includes a metal shaft, and an elastic layer provided on an outer periphery of the metal shaft and in contact with the fixing film,
Between the fixing film and the frame ground is a first gap in a direction in which the metal shaft extends, and at least a part of the surge is generated when the surge is applied to the commercial power line. A first gap having a size that forms a first path that flows from the body to the frame ground through the insulating layer, the fixing film, and the first gap;
Between the metal shaft and the frame ground is a second gap in the extending direction of the metal shaft, and at least a part of the surge is generated when the surge is applied to the commercial power line. A second gap having a size from which a second path flowing from the body to the frame ground through the insulating layer, the fixing film, the elastic layer, the metal shaft, and the second gap is formed;
Image formation characterized in that the conductive layer and the commercial power supply line are electrically connected via a surge protection device having an operating voltage higher than a peak voltage of the commercial power supply and lower than a voltage at which the insulating layer breaks down. apparatus.   The image forming apparatus according to claim 1, further comprising a fixing film bias generating unit that applies a voltage to the conductive layer. The operating voltage of the surge protection device is
Higher than the total value of the peak voltage of the commercial power supply and the voltage generated by the fixing film bias generating means,
The image forming apparatus according to claim 2, wherein the insulating layer has a voltage lower than a breakdown voltage. The fixing film has a rubber layer on the outer periphery of the conductive layer,
The conductive layer is peeled off from the end facing the frame ground through the first gap by a predetermined range, and the metal bristles are in contact with the outer peripheral surface from which the rubber layer has been peeled off. , relative to the frame ground, and the metal bristles, resistance or the image forming apparatus according to claim 1 via a capacitor, characterized in that it is electrically connected. The image forming apparatus according to claim 1, wherein the surge protection device is one of a varistor, a thyristor, and an avalanche diode.

Images