JPH04126254U - Image forming device - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent destruction and malfunction of the integrated circuit of the exposure device due to electrostatic induction from the charger, developer, etc. [Structure] The substrates 28 and 32 on which the light emitting diode array 30 and control IC 34 of the exposure device 50 are mounted are sealed with the head base 22 and the head cover 54 to provide electrostatic shielding.
The shield is grounded, and the boards 28 and 32 are connected to the head base 2.
2 to prevent malfunctions caused by electrostatic induction. When the head base 22 is made of plastic, the head base is placed on the developer side and the head cover is placed on the charger side.
Further, in this case, a conductive plastic or an insulating plastic whose surface is made conductive is used as the head base material. Preferably, the surfaces of the head base and head cover are insulated to prevent destruction due to contact with a charger or developer.

Description

[Detailed explanation of the idea]

0001

[Field of application of idea]

This invention relates to electrophotographic image forming apparatuses, and is particularly applicable to the protection of circuit elements in exposure devices. Regarding protection.

0002

[Prior art]

In an electrophotographic image forming apparatus, high-voltage devices such as a charger and a developing device are installed adjacent to the exposure device. Place the pressure member. With the miniaturization of image forming devices, the connection between the exposure device, charger, and developer is becoming smaller. There is a need to reduce the spacing. The inventors believe that due to this, It has been found that the integrated circuit of the exposure device is destroyed. This situation is shown in FIG.

0003 In the figure, 2 is a photosensitive drum, 4 is a charger, 6 is its charger wire, and 8 is a charger. In the developing device, 10 and 12 are toner holding members. 20 is an exposure device, 22 is a head 24 is a head cover, 26 is a lens array, and 28 is a light emitting diode door. 32 is an external board that controls the light emitting diode array 30. Equipped with C34. 36 is a flexible prism for connecting the boards 28 and 32. This is a component board.

0004 In order to downsize the image forming apparatus, the distance W between the exposure device 20 and the charger 4 is, for example, 1 mm. The distance between the exposure device 20 and the developing device 8 is also set to about 1 mm. One-sided charging A voltage of about 5 to 8 KV is applied to the device 4, and a voltage of about 300 to 400 V is applied to the developing device 8. voltage is applied. The light emitting diode array 30 and control IC 34 used are The chip is usually exposed and is not protected by a package. This not only eliminates packaging costs, but also enables direct wire bonding to the chip. This is to connect directly to the substrates 28 and 32. In this state, charger 4 When high pressure is applied to the developing device 8, the light emitting diode array 30 and the control I Destruction of C34 occurs. Furthermore, even if no damage occurs, malfunctions due to electrostatic induction may occur. arise. According to the inventor's study, the destruction occurred in the light emitting diode array 30 and the control IC 3. This occurs around the ground terminal of No. 4, and this occurs when the charger No. 4 is connected to the earth terminal where discharge current easily flows. This is thought to be due to corona discharge from the developing device 8.

[0005] Destruction due to corona discharge occurs at locations where the substrates 28 and 34 are exposed, for example, as shown in Fig. In the case of arrangement No. 4, it occurs around the exposed control IC 34. Also, as shown in Figure 5, In order to pass the flexible printed circuit board 36, the head cover 38 is deformed and an opening is opened. 40, a discharge occurs through the aperture 40 and destroys the light emitting diode array 30. Ru. Here, regarding the inside of the exposure device 20, destruction of the light emitting diode array 30 will be described. However, if an IC such as a shift register is mounted on the board 28, the shift register will also be damaged. Destroyed.

[0006]

[Problems to be devised]

The challenge of this idea is to prevent the destruction of the light emitting diode array and control IC due to discharge. At the same time, the objective is to facilitate miniaturization of the image forming apparatus. The problem in claim 2 is In addition to this, while using inexpensive plastic for the head base, the above issues were solved. It's about achieving.

[0007]

[Structure of the idea]

This idea is based on the idea that high-voltage components such as a charger and a developer are placed adjacent to the exposure device. In an image forming device using the photo-photography method, an electrostatic shield is installed around the circuit board of the exposure device. The electrostatic shield is grounded. with electrostatic shielding If grounded, the discharge current will flow from the shield to ground, causing the light emitting diode array and It does not flow to circuit elements such as control ICs. As a result, damage to circuit elements is prevented and There is no need to package the circuit elements. Additionally, a grounded electrostatic shield This prevents malfunctions of light emitting diode arrays, control ICs, etc.

[0008] This idea also allows the circuit board of the exposure device to be connected to a grounded metal head cover and a plug. The plastic head base is covered with a metal head cover on the charger side. Connect the exposure device to the charger and developer so that the stick head base appears on the developer side. It is characterized by being placed between the statues. If you do this, the high voltage charger side will have A metal head cover appears, and a plastic head cover is placed on the relatively low voltage charger side. Since the ground appears, it is possible to prevent circuit elements from being destroyed or malfunctioning. Plasti In addition to conductive plastic, the base material of the dock head can be made of inexpensive insulating plastic. If an insulating plastic is used, the surface can be made conductive and the seal can be used. It is preferable to have a code function.

[0009] By the way, if a conductive surface such as a head cover comes into contact with a charger or developer, the circuit will be damaged. The element is destroyed instantly. Therefore, preferably the surface of the head cover or head base to prevent circuit elements from being destroyed due to contact between the exposure device and the charger or developer. Ru.

0010

【Example】

[0011]

[Example 1] FIG. 1 shows an exposure device 50 according to an embodiment. In the figure, 22 is the head base. 54 is a head cover made of metal such as aluminum. It shall be made of metal. The head base 22 and head cover 54 are used as electrostatic shields. , ground. 26 is a lens array, 28 is a circuit board that is a light emitting diode array 3 0 and part of the control IC. 32 is an external board, which is not mounted on the board 28. Equipped with external control IC34. 36 is a flexible cable that connects the boards 28 and 32. It is a printed circuit board. The substrates 28 and 32 are tightly fixed to the metal head base 22. Then, fix the potential on the backside of the board to ground to minimize the effects of electrostatic induction. Ru. In order to prevent discharge from the openings at both ends of the exposure device 50, it is preferable to use the method shown in FIG. Conductive side plates 56 are provided and attached to both ends of the exposure device 50. sa The ID plate 56 is made of conductive synthetic resin, for example, and seals both ends of the exposure device 50. It is used to prevent discharge and also to prevent the intrusion of dust, etc. More side play If the lens array 26 is fixed with the bracket 56, the head base 22 and the head The cover 54 may have a simple elongated shape. For this head The base 22 and head cover 54 can be manufactured easily. In other words, when metal is pulled out, etc. These can be manufactured. Further, the side plate 56 may be a metal head, for example. It is fixed to the head base 22 and grounded via the head base 22.

0012 In addition to metal, the head base 22 and head cover 54 may be made of conductive synthetic material. Resin or the like can also be used, and the material of the electrostatic shield only needs to be conductive. Ma In the embodiment described above, the head cover 54 was modified to shield the external board 32; The shield of the board 32 includes a metal cover separate from the head cover 54, a metal wire mesh, Alternatively, a conductive carbon fiber net, a conductive synthetic resin cover, etc. may be used. Furthermore The shields at both ends of the exposure device 50 do not use the side plates 56, but instead use the head base. 22 and the head cover 54 may be modified to cover both ends.

[0013] FIG. 3 shows how the exposure device 50 is attached. Destruction due to discharge occurs from charger 4. This is mainly due to discharge. However, the boards 28 and 32 are connected to the head base 22. The exposure device 50 is shielded with a cover 54, and conductive side plates 56 are provided at both ends of the exposure device 50. Since the discharge current flows to the shield, the light emitting diode array 30 and the control It does not flow to IC34. In the exposure device 50, the substrates 28 and 32 are sealed with a shield. And there is no discharge through the gap. The charger 4 and developer 8 generate light emitting diodes using high voltage discharge. Not only will it destroy the card array 30 and control IC 34, but it will also destroy these items due to electrostatic induction. malfunction. However, the substrates 28 and 32 were hermetically shielded, By bringing the substrates 28 and 32 into close contact with the head base 22 as a shield, static electricity is reduced. No malfunctions occur due to induction. In addition, in the embodiment, the originally existing head base 22 Since the head cover 54 is transformed into a shield, the shield does not become large and is made of gold. It is durable because it is made of metal.

[0014] Results of destruction of the light emitting diode array 30 and control IC 34 under the conditions shown in Figure 3 are shown in Table 1. In this experiment, the minimum distance between the exposure device and the charger 4 was 1 mm, and the sheet This study investigated how the destruction status of an IC changes depending on the presence or absence of a lead.

[0015]

[Table 1] Changes in IC breakdown voltage depending on shielding conditions Shielding conditions IC breakdown voltage Without shielding with the arrangement shown in Figure 4, the potential of head base charger 4 is 1 to 2 KV 22 and head cover 24 are not grounded , and control IC 34 is destroyed. Using the exposure device shown in Figure 5, ground 22 on the board 28 and the head cover 38 from the head base 3 to 4 KV, and reduce the breakdown voltage of the control IC on the board 28 with the incomplete shield 40 remaining, causing the opening IC to break. Measurement Under the conditions shown in Figure 3, the breakdown starting voltage was measured. IC breakdown did not occur up to 15KV.

[0016]

[Example 2] In Example 1, a metal head base 22 was used. However, the long head base No. 22 is difficult to process and is extremely expensive in metal. Therefore, I decided to use a cheap head base. An example using plastic is shown below. In Figure 6, 62 is a plastic The material is polyphenylene sulfide (PPS) and polycarbonate. Use engineering plastics such as PC. These plastic The normal operating temperature is 100 degrees Celsius or higher, and the temperature inside the image forming device is around several tens of degrees. Not deformed. Of course, other materials such as inexpensive ABS may also be used. most of these Preferably, the material has high resistance to alcohol used for cleaning the lens array 26. It is polyphenylene sulfide. The head base 62 is made of metal or graphite. It may be made conductive by mixing conductive fine particles or conductive fibers such as pyrite or carbon fiber. , conductive plastics are expensive, and because of conductive fine particles and conductive fibers, the surface Smoothness decreases. Furthermore, adding these substances will make injection molding difficult and result in Shape deteriorates. Therefore, the head base 62 is made of, for example, insulating plastic. use

[0017] The exposure device 51 is placed with the metal head cover 54 on the side of the charger 4 as shown in FIG. Then, a plastic head base 62 is placed on the side of the developing device 8 and connected to the high voltage charger 4. Prioritize prevention of damage and malfunction caused by For example, the voltage used for the charger 4 is usually 1~ The developing voltage applied to the developing device 8 is usually about 20 KV, and the maximum is about 5 to 10 KV. It is about 0 to 300V. The inventor made it clear that the exposure device 51 should not come into contact with the developing device 8. If the head base 62 is made of insulating plastic, the light emitting diode array 3 It was confirmed that there would be no damage or malfunction of the 0 or control IC 34.

[0018] In the above explanation, the mounting positions of the exposure registers 50 and 51, charger 4, and developer 8 are correct. It was assumed that these objects would not come into contact with each other. However, the exposure devices 50 and 51 When it comes into contact with the electric appliance 4 or the developing device 8, the light emitting diode array 30 and the control IC 34 are turned off instantly. sometimes destroyed. Such contact may occur, for example, with the exposure registers 50, 51, the charger 4, and the developer. This tends to occur when assembling or adjusting the device 8. Therefore, we downsized the image forming device and installed an exposure device. In order to make the distance between 50, 51 and the charger 4 and developer 8 1 mm or less, Measures must be taken to prevent damage and malfunction caused by contact. For this purpose, as shown in Figure 8, , an insulating coating 64 is applied to the surface of the metal head cover 54. For example, the insulation coating 64 is , pasting insulating tape, applying insulating paint to the surface by electrodeposition, or When the cover 54 is made of Al, an alumite layer is formed by anodizing the Al surface. It should be composed of this.

[0019] For the plastic head base 62, as shown in FIG. A conductive coating 66 is provided on the surface of the stick to serve as an electrostatic shield, and the surface is further coated with a conductive coating 66. The surface may be covered with an insulating coating 68 to protect it from contact with the developing device 8. Insulating coating The method of forming the covering 68 is the same as that described above, and the conductive covering 66 is attached to the head base 6. 2 (on the board 28 side), if the head base 62 itself is insulating. Insulating coating 68 is not required. Also, for the metal head base 22 in FIG. Preferably, the surface is provided with an insulating coating 68.

[0020] The conductive coating 66 may be made of, for example, a non-electroplated film on which a conductive tape such as Al foil is pasted. Gold that forms a conductive coating of Al, Ni, Cu, etc. by It may be constructed by applying a conductive paint containing a large amount of metallic powder. Insulating coating 64 , 68 are preferably provided on the outer surface of the head cover 54 or the head bases 22, 62. However, it may also be provided on the inner surface. The conductive coating 66 is connected to ground and It is preferable to discard the electric field by flowing it to ground.

[0021] In this way, light emitting diode damage caused by contact with the charger 4 or the developer 8 can be prevented. 30 and control IC 34 and prevent malfunction, and attach the exposure devices 50, 51, etc. The light emitting diode array 30 and control The influence on the control IC 34 can be prevented. In addition, conductive coating 66 is made of inexpensive insulating plastic. The surface of the head base 62 is made conductive to serve as an electrostatic shield for the developing device 8. be able to.

[0022] Table 2 shows the performance specifications of the plastic head base 62. The head base used S62 uses polyphenylene sulfide as an engineering plastic. The insulating head base used has a conductive coating 66 and an insulating coating on the surface as shown in Figure 9. 68 were laminated. In addition, the head base of the comparative example is made of simple polyphenylene as a material. The known shape described in Utility Model Publication No. 3-4528 using ruphide plastic It is.

[0023]

[Table 2] Item Example Comparative example Flatness (μm) 50 100~200 Squareness (μm) 100 200 Accuracy of distance from substrate 28 to lens array 26 ±20 ±200~250 Dielectric strength (KV ) 16-20 1-2 Image forming apparatus width (mm) 14 20 *Flatness is measured with a surface roughness meter and represents the flatness of the contact surface of the head base 62 with the substrate 28. * Perpendicularity represents the deviation from the light emitting surface of the light emitting diode array 30 to the left and right at the center of the height of the lens array 26. * Withstand voltage represents the amount of power applied to the charger when the light emitting diode array 30 is damaged by discharge. 4, and is a value when the distance between the exposure device 51 and the charger 4 is about 1 mm.

[0024] As is clear from Table 2, in the Examples, the flatness and perpendicularity were 1/2 to 1/2 that of the Comparative Examples. 4, and also reduce the spacing error between the light emitting diode array 30 and the lens array 26. We succeeded in reducing the amount to about 1/10 of the conventional example. This is the mounting surface of the board 28 By arranging the mounting surface of the lens array 26 at a right angle, the rigidity of the housing 62 is increased and the This is because it prevents damage. Here, polyphenylene sulfide is also used as a comparative example. However, if a resin with lower rigidity is used, the shape accuracy in the comparative example will further decrease. . In the embodiment, even if the head base 62 is made of plastic, it will not work as an image forming apparatus. We were able to obtain sufficient shape accuracy. For example, a light emitting diode array 30 and a lens The required performance is ±50 μm or less for the accuracy of the spacing with the array 26, and ±2 in the example. 0 μm fully satisfies this condition. In contrast, ±200 μm or more in the comparative example. The above does not meet this condition at all. Also, the withstand voltage has been increased to about 10 times that of the comparative example. successfully prevented malfunctions and discharge damage caused by corona discharge from charger 4. did. The voltage used for corona discharge in the charger 4 is usually 10 KV or less, At 16 to 20 KV in the example, discharge damage can be sufficiently prevented. Against this At 1 to 2 KV in the comparative example, the light emitting diode array 30 was damaged due to corona discharge. Breakage occurs frequently.

[0025]

[Effect of the idea]

With this idea, even if high-voltage components such as chargers and developers are placed close together, the exposure device Destruction or malfunction of the light emitting diode array, control IC, etc. can be prevented. Ma If metal is used for the electrostatic shielding member, a strong and compact shield can be created. Furthermore, By sealing the opening of the exposure unit with a shield, you can completely shield static electricity and prevent light emitting diodes from entering. Destruction and malfunction of the door array and control IC can be completely prevented. This idea also includes placing a metal head cover on the high-voltage charger side and a plastic head cover on the side of the high-voltage charger. A low-voltage developer head base is placed on the side of the low-voltage developer, and an inexpensive plastic head base is used. This prevents damage and malfunction of the light emitting diode array and control IC while using the

[Brief explanation of drawings]

[Fig. 1] A cross-sectional view of an exposure device in an image forming apparatus according to an embodiment.

[Fig. 2] Front view of the side plate in the image forming apparatus of the embodiment.

[Fig. 3] Cross-sectional view of main parts of the image forming apparatus of the embodiment

[Fig. 4] Cross-sectional view of main parts of a conventional image forming apparatus

[Fig. 5] A cross-sectional view of an exposure device of a conventional image forming apparatus.

[Figure 6] A cross-sectional view of the exposure device in an example in which the head base is made of plastic.

[Fig. 7] A sectional view of the main parts of the image forming apparatus in an embodiment in which the head base is made of plastic.

[Fig. 8] A sectional view of the main parts of the head cover in the embodiment shown in Fig. 6.

[Fig. 9] A cross-sectional view of the main parts of the head base in the embodiment shown in Fig. 6.

[Explanation of symbols]

2 Photosensitive drum 4 Charger 8 Developing device 22 Head base 26 Lens array 28 Circuit board 30 Light emitting diode array 32 External board 34 Control IC 50,51 Exposure device 54 Head cover 56 Side plate 62 Plastic head base 64 Insulating coating 66 Conductive coating 68 Insulating coating

──────────────────────────────────────────────── ─── Continued from the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location G03G 15/00 103 8004-2H 15/04 120 9122-2H H05K 9/00 A 7128-4E

Claims (2)

[Scope of utility model registration request] Claim 1: In an electrophotographic image forming apparatus in which a high voltage member is arranged adjacent to an exposure device, an electrostatic shield is provided around a circuit board of the exposure device, and the electrostatic shield is grounded. An image forming apparatus characterized by: 2. An electrophotographic image forming apparatus in which a charging device and a developing device are arranged adjacent to an exposure device, comprising: a metal head cover having a circuit board of the exposure device grounded;
The exposure device is disposed between the charging device and the developing device so that the metal head cover appears on the charging device side and the plastic head base appears on the developing device side. , image forming device.