JP2005084388A - Image input device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image input device preventing the lowering of reading accuracy by reducing the blur of an original platen caused by the volatilization of lubricant with which space between the rotary shaft member and the bearing member of a motor is filled. <P>SOLUTION: The image input device is equipped with the transparent original platen on which an original is placed, a carriage on which a scanning means is mounted and which moves back and forth in a subscanning direction in parallel with the board surface of the original platen, the motor having the rotary shaft member energized to be rotated and the bearing member rotatably supporting the rotary shaft member, installed on an opposite side to the original in a state where the original platen is put in between and generating driving force for driving the carriage in the subscanning direction, and the lubricant with which the space between the rotary shaft member and the bearing member is filled, which lubricates the rotary shaft member and the bearing member and whose volatilization temperature is higher than the heat generation temperature of the motor. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image input device.

  Conventionally, as an image input device equipped with an image sensor, for example, an optical reduction type image input device that forms an optical image of an original on a scanning line on an image sensor using an optical system such as a lens or a mirror, and an original on a scanning line A close-contact type image input apparatus that directly forms an optical image on an image sensor is known. In the case of the contact type image input apparatus, the optical path from the original to the image sensor can be shortened. Therefore, the image input device can be made thin, and the installation volume of the image input device can be reduced.

  However, if the image input device is made thin like a contact type image input device, the distance between the document table on which the document is placed and various components housed in the image input device is reduced. Further, when the internal volume of the image input device is reduced, it is necessary to devise the arrangement of various components housed inside. For example, in the case of a conventional optical reduction type image input device, a motor that generates power for driving a carriage in which an image sensor is accommodated is installed on the outer side in the sub-scanning direction than the carriage. On the other hand, in a thin image input apparatus, the motor may be installed in the vicinity of the center of the carriage in the sub-scanning direction, that is, below the document table, with a sufficient surrounding volume.

  The lubricant filled between the rotating shaft member of the motor and the bearing member that supports the rotating shaft member may volatilize when heated by the operation of the motor. As described above, the motor is installed below the document table, and the distance between the document table and the motor is small. For this reason, the lubricant volatilizes due to the heat generated by the motor and easily adheres to the document table. As a result, there is a problem that the document table is clouded and the reading accuracy of the document is lowered.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image input device that reduces fogging of a document table due to volatilization of a lubricant filled between a rotating shaft member and a bearing member of a motor, and prevents a decrease in reading accuracy. There is.

  An image input apparatus according to the present invention rotates by energizing a transparent document table on which a document is placed, a carriage on which scanning means is mounted, and reciprocating in the sub-scanning direction in parallel with the surface of the document table. A rotating shaft member that rotates, and a bearing member that rotatably supports the rotating shaft member, and is disposed on the opposite side of the document with the document table interposed therebetween, and generates a driving force that drives the carriage in the sub-scanning direction. A motor, and a lubricant that is filled between the rotating shaft member and the bearing member, lubricates the rotating shaft member and the bearing member, and has a volatilization temperature higher than a heat generation temperature of the motor. Features. The lubricant has a volatilization temperature higher than the heat generation temperature of the motor. Therefore, even if the motor generates heat during operation, the volatilization of the lubricant is prevented. Thus, the volatilized lubricant does not adhere to the document table, and fogging of the document table is reduced. Therefore, even when the motor is installed close to the document table, it is possible to prevent the reading accuracy from being lowered.

  In the image input apparatus according to the present invention, the power supplied to the motor is set to a value at which the heat generation temperature of the motor is smaller than the volatilization temperature of the lubricant. By reducing the power supplied to the motor, the heat generation of the motor is suppressed. Therefore, volatilization of the lubricant that has entered the heat generating portion of the motor is prevented. Therefore, even when the motor is installed close to the document table, it is possible to prevent the reading accuracy from being lowered.

  Furthermore, the image input apparatus according to the present invention is characterized in that the viscosity of the lubricant is set to a value that prevents the motor from entering the heat generating portion. When the viscosity of the lubricant is low, the lubricant easily penetrates into the heat generation part of the motor, and the lubricant is likely to volatilize. Therefore, setting the viscosity of the lubricant prevents the lubricant from entering the heat generating part of the motor. Therefore, even when the motor is installed close to the document table, it is possible to prevent the reading accuracy from being lowered.

Furthermore, in the image input device according to the present invention, the viscosity of the lubricant is 60 mm ² / s or more at 40 ° C. Note that 1 mm ² / s = 1 cSt (centistokes). By defining the viscosity, the lubricant can be prevented from entering the heat generating portion of the motor. Therefore, even when the motor is installed close to the document table, it is possible to prevent the reading accuracy from being lowered.
Furthermore, the bearing member is an impregnated bearing impregnated with the lubricant. Therefore, it is not necessary to supply lubricant to the bearing member. Therefore, the life of the rotating shaft member and the bearing member can be extended.

Hereinafter, an example showing an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing a positional relationship between a motor 20 and a document table 11 in a so-called flatbed image scanner 10 to which an image input apparatus according to an embodiment of the present invention is applied. FIG. FIG. 2 is a schematic view of internal components of the image scanner 10 according to an embodiment of the present invention as viewed from the document table 11 side. FIG. 3 is a block diagram of the image scanner 10.

  The housing 12 is formed in a box shape with an upper opening, and supports the document table 11 on the opening side. The document table 11 is formed of a transparent plate such as a generally rectangular glass plate. For example, a document 13 such as a photograph or a printed document can be placed on the surface of the document table 11. The carriage 30 accommodates a CIS (Contact Image Sensor) 31 as scanning means. In the present embodiment, the distance between the carriage 30 and the document table 11 is reduced by using the CIS 31 as the scanning unit. Therefore, the thickness of the housing 12 is reduced. Accordingly, the distance between the motor 20 installed in the housing 12 and the document table 11 is also reduced.

  The CIS 31 includes a light source unit 32 and a linear image sensor 33. The light source unit 32 includes an LED (light emitting diode) that emits light of a specific color as a light source. The light source unit 32 includes an LED that emits red light for reading a color image, an LED that emits green light, and an LED that emits blue light. The light source unit 32 has a plurality of LEDs for each color. A light guide (not shown) for guiding the emitted light to the document table 11 side is attached to the light source section 32 composed of each LED. A light guide (not shown) is formed of a light transmissive member such as glass.

  The linear image sensor 33 includes a plurality of light receiving elements arranged in a straight line, a MOS transistor switch, and the like. An optical system that forms an image of light from the original 13 on the light receiving element is provided on the side of the original platen 11 of the light receiving element (not shown). The optical system includes, for example, a lens and is installed corresponding to each of the light receiving elements. The optical system forms an optical image of the original 13 on the scanning line on the linear image sensor 33 at the same magnification as the original 13. The linear image sensor 33 scans the optical image on the scanning line formed by the optical system, and outputs an electrical signal correlated with the density of the optical image. Thereby, the linear image sensor 33 converts an optical image into an image signal. The linear image sensor 33 accumulates a charge obtained by photoelectric conversion of light in a predetermined wavelength region such as visible light, infrared light, or ultraviolet light in a light receiving element such as a photodiode for a certain period of time. The linear image sensor 33 outputs the electric charge accumulated for a certain period of time using an MOS transistor switch as an electric signal corresponding to the amount of light received for each light receiving element.

  The carriage 30 that accommodates the CIS 31 is supported by the guide rod 34 and is moved in parallel with the surface of the document table 11 by the sub-scanning drive unit 40. As a result, the carriage 30 carries the CIS 31 in parallel with the surface of the document table 11. The sub-scanning drive unit 40 includes a motor 20, a gear train, a pulley 41, a pulley 42, and a belt 43. The motor 20 generates a driving force for driving the carriage 30 when energized. The gear train includes a gear 44, a gear 45, and a gear 46, and reduces the rotational driving force generated from the motor 20 and transmits it to the pulley 41. The pulley 41 is configured integrally with the gear. Both ends of the belt 43 are supported by a pulley 41 and a pulley 42, respectively. The pulley 41 is rotated by the driving force transmitted from the motor 20 via the gear train. Due to the rotation of the pulley 41, the belt 43 whose other end is supported by the pulley 42 circulates between the pulley 41 and the pulley 42. The carriage 30 is provided with a meshing portion 35 that meshes with the belt 43. When the belt 43 and the meshing portion 35 mesh with each other, the carriage 30 is pulled in the sub-scanning direction by the rotating belt 43. As the carriage 30 moves in the sub-scanning direction, the scanning line for scanning the original 13 moves, and a two-dimensional image can be scanned.

  The main scanning drive unit 14 is a circuit that performs drive control of the linear image sensor 33, and is a circuit that controls the on / off of the MOS transistor switch and the reading of charges accumulated in the light receiving element. An AFE (Analog Front End) unit 15 serving as an image processing unit includes an analog signal processing unit, an A / D converter, and the like. The analog signal processing unit subjects the analog image signal output from the CIS 31 to signal processing such as amplification and noise reduction processing, and outputs the result. The A / D converter quantizes the image signal output from the analog signal processing unit into digital image data of a digital representation having a predetermined bit length, and outputs the digital image data.

  The digital image processing unit 16 performs processes such as gamma correction, interpolation of defective pixels by a pixel interpolation method, shading correction, and sharpening of an image signal on the digital image data output from the AFE unit 15. Note that the various processes described above performed by the digital image processing unit 16 may be replaced with processes performed by a computer program executed by the control unit 50. The digital image data subjected to various processes by the digital image processing unit 16 is transferred to a personal computer or the like via an interface (not shown).

  The control unit 50 includes a CPU 51, a ROM 52, and a RAM 53. The CPU 51 executes a computer program stored in the ROM 52 and controls each unit of the image scanner 10. The ROM 52 is a memory that stores a computer program executed by the CPU 51 and various data. The RAM 53 is a memory that temporarily stores programs and various data.

Next, the motor 20 will be described in detail.
As shown in FIG. 1, the motor 20 is installed inside the housing 12 below the document table 11. The motor 20 has a shaft 21 as a rotating shaft member that rotates when energized. The shaft 21 has a pinion 22 at one end. The pinion 22 meshes with a gear 44 that forms a gear train. The shaft 21 is provided with a rotor 23 in the axial direction. The rotor 23 faces the stator 25 installed inside the case 24. As the motor 20, a stepping motor is used that holds the angle until the rotor 23 rotates by a certain angle by inputting a pulse and the pulse is input again. For example, a DC motor may be used as the motor 20. The motor 20 is connected to a motor control circuit (not shown) of the sub-scan driving unit 40. When a stepping motor is used, pulsed power corresponding to a predetermined rotation angle is input to the motor 20 from the motor control circuit.

  The shaft 21 is rotatably supported by bearing members 26 at two axial positions. The bearing member 26 supports the shaft 21 at both ends in the axial direction of the case 24 through which the shaft 21 penetrates. The bearing member 26 rotatably supports the shaft 21 by sliding with the shaft 21. The bearing member 26 is made of, for example, a porous material and is impregnated with a lubricant. That is, in the case of the present embodiment, the bearing member 26 is an impregnated bearing. Thereby, the lubricant is filled between the shaft 21 and the bearing member 26, and the space between the shaft 21 and the bearing member 26 is lubricated by the lubricant. As the lubricant, for example, machine oil or grease is used.

  In the case of the image scanner 10 using the CIS 31, the distance D from the end of the shaft 21 of the motor 20 to the document table 11 is small as shown in FIG. In the present embodiment, the distance D from the end of the shaft 21 on the side of the document table 11 to the end of the document table 11 on the side of the motor 20 is about 20 mm. By energizing the motor 20, the temperature of the motor 20 including the case 24 rises. For example, in the case of a stepping motor, since the stator 25 is energized, the stator 25 and the case 24 in which the stator 25 is installed generate heat. The heat generated in the case 24 is transmitted to the bearing member 26 installed in the case 24, and the bearing member 26 also generates heat. Further, since the shaft 21 and the bearing member 26 slide, heat is generated due to friction between the shaft 21 and the bearing member 26.

  As the lubricant that lubricates between the shaft 21 and the bearing member 26, a lubricant whose volatilization temperature is higher than the temperature of the motor 20 that generates heat by the operation of the motor 20 is used. Thus, even when the lubricant is heated by the operation of the motor 20, the lubricant is prevented from volatilizing. The lubricant volatilizes when heated with the operation of the motor 20. Therefore, it is effective to reduce the heat generation of the motor 20 in order to prevent the volatilization of the lubricant. The motor 20 generates heat when energized, and the amount of generated heat correlates with the current value. Therefore, in the case of the present embodiment, the electric power supplied to the motor 20 is set to a current of 125 mA when the voltage is 24V. Thereby, the heat generation of the motor 20 is reduced, and the temperature of the motor 20 due to the operation becomes lower than the volatilization temperature of the lubricant. As a result, the volatilization of the lubricant is prevented.

It is also effective to prevent the lubricant filled between the shaft 21 and the bearing member 26 from entering the heat generating portion of the motor 20 in order to prevent the lubricant from volatilizing. Therefore, in this embodiment, the viscosity of the lubricant is regulated to prevent the lubricant from entering the heat generating portion of the motor 20. By increasing the viscosity, the fluidity of the lubricant is lowered, and the lubricant is prevented from entering the heat generating portion of the motor 20. In the case of this example, the viscosity of the lubricant is set to 60 mm ² / s or more at 40 ° C. When the viscosity of the lubricant is smaller than 60 mm ² / s (40 ° C.), the fluidity of the lubricant is increased. As a result, the penetration of the lubricant into the heat generating part of the motor 20 increases.

According to the embodiment of the present invention described above, the physical properties of the lubricant that lubricates the shaft 21 and the bearing member 26 are defined. That is, the volatilization temperature of the lubricant is set higher than the heat generation temperature when the motor 20 is operated, and the viscosity of the lubricant is set to 60 mm ² / s (40 ° C.) or more. Further, in order to reduce the heat generation of the motor 20 itself, the power supplied to the motor 20 is set to 24V-125 mA. Thereby, the heat generation of the motor 20 is reduced and volatilization of the lubricant is prevented. As a result, even if the housing 12 is made thin by using the CIS 31 as in this embodiment and the distance between the motor 20 and the document table 11 is reduced, the volatilized lubricant is prevented from adhering to the document table 11. Thus, the occurrence of fogging of the document table 11 is prevented. Therefore, it is possible to achieve both reduction in thickness of the image scanner 10 and prevention of reduction in reading accuracy of the document 13.

  In one embodiment of the present invention, an impregnated bearing impregnated with a lubricant is used as the bearing member 26. Therefore, it is not necessary to supply lubricant to the bearing member 26. Therefore, the maintenance of the motor 20 can be facilitated and the life of the shaft 21 and the bearing member 26 can be extended.

  In the embodiment of the present invention described above, an example in which the image input device is applied to a flatbed image scanner has been described. However, the present invention is not limited to an image scanner as long as it is an image input device that optically reads a document, such as a copying machine, a facsimile machine, or a multifunction machine. In the present invention, an example in which the CIS, which is a contact image sensor, is applied as the scanning unit of the image input apparatus has been described. However, for example, a lens reduction type image sensor that inputs an optical image to the image sensor using a lens, a mirror, or the like. May be applied.

1 is a schematic diagram illustrating an image scanner according to an embodiment of the present invention. 1 is a schematic diagram showing an internal configuration of an image scanner according to an embodiment of the present invention. 1 is a block diagram of an image scanner according to an embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Image scanner (image input device), 11 Document stand, 13 Document, 20 Motor, 21 Shaft (rotary shaft member), 26 Bearing member, 30 Carriage, 31 CIS (scanning means)

Claims (5)

A transparent platen on which the document is placed;
A carriage mounted with scanning means and reciprocating in the sub-scanning direction in parallel with the platen surface of the document table;
A rotating shaft member that rotates when energized and a bearing member that rotatably supports the rotating shaft member are installed on the opposite side of the document with the document table interposed therebetween, and drive the carriage in the sub-scanning direction. A motor that generates driving force;
Filled between the rotary shaft member and the bearing member, lubricates the rotary shaft member and the bearing member, a lubricant having a volatilization temperature higher than the heat generation temperature of the motor,
An image input device comprising:   The image input apparatus according to claim 1, wherein the electric power supplied to the motor is set to a value at which a heat generation temperature of the motor is smaller than a volatilization temperature of the lubricant.   The image input device according to claim 1, wherein the viscosity of the lubricant is set to a value that prevents the motor from entering the heat generating portion. The image input apparatus according to claim 3, wherein the viscosity of the lubricant is 60 mm ² / s or more at 40 ° C.   The image input device according to claim 1, wherein the bearing member is an impregnated bearing impregnated with the lubricant.

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