JP5665517B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that detects the thickness and basis weight of a sheet on which image formation is performed.

  Conventionally, an image forming apparatus such as an ink jet printer, a copying machine, or a laser beam printer automatically detects the thickness and basis weight (weight per unit area) of a recording material on which an image is formed. Image forming conditions such as transfer conditions and fixing conditions are changed.

  Patent Document 1 discloses a transmitter that transmits ultrasonic waves to a sheet, a receiver that receives ultrasonic waves transmitted from the transmitter and passed through the sheet, and a detection that determines the type of the sheet from the reception result of the receiver. An ultrasonic sheet detection mechanism (ultrasonic sensor unit) including means is disclosed.

JP 2006-293144 A

  Here, in order to detect a sheet on a conveyance path for conveying one sheet, a pair of transmitter and receiver is required. For this reason, in an apparatus having a plurality of conveyance paths, when detecting sheets of a plurality of conveyance paths by the ultrasonic sheet detection mechanism, the same number of transmitters and receivers as the conveyance paths are required, which reduces the size and cost of the apparatus. It will be harmful.

  Therefore, a configuration in which a sheet is detected by one transmitter and receiver at a location where a plurality of conveyance paths in the apparatus merge downstream in the conveyance direction to form one conveyance path is conceivable. However, in recent years, the size of the apparatus has been reduced, and a portion where a plurality of conveyance paths merge to form one conveyance path may be immediately before an image forming unit where an image is formed on a sheet (immediately before a registration roller). Many. In such a case, since the distance for conveying the sheet from the detection of the sheet until the arrival at the image forming unit is short, the sheet arrives at the image forming unit in a short time after the sheet is detected by the ultrasonic sheet detection mechanism. For this reason, for example, there is a possibility that only a part of the image forming conditions can cope with the change according to the sheet detection, such as the transfer condition cannot be changed because the change of the transfer condition is not in time for the arrival of the sheet. is there.

  In view of the above problems, an object of the present invention is to detect a sheet conveyed through a plurality of conveyance paths by using as few transmitters and receivers as possible.

The present invention transmits an ultrasonic wave toward a recording material conveyed through the first conveyance path and the second conveyance path, and a first conveyance path and a second conveyance path through which the recording material conveyed to the image forming unit passes. A receiving means for receiving the ultrasonic wave transmitted from the transmitting means and passing through the recording material, and outputting a signal corresponding to the received ultrasonic wave, based on the signal output from the receiving means An image forming apparatus for controlling image forming conditions for forming an image on a recording material, the image forming apparatus having a reflecting portion disposed between the first transport path and the second transport path, wherein the transmitting means is the first transport section. A transmitter disposed opposite to the reflecting portion across the conveyance path, wherein the receiving means is a receiver disposed opposite to the reflecting portion across the second conveyance path; There, ultrasound which the transmitter is transmitting at the reflecting portion passes through the first conveyance path Isa is characterized by reaching to the receiver through the second conveyance path.

  According to the present invention, a sheet conveyed on a plurality of conveyance paths can be detected with as few transmitters and receivers as possible.

1 is a schematic cross-sectional view showing an overall configuration of an image forming apparatus. The schematic sectional drawing of an ultrasonic sensor unit. The schematic sectional drawing which shows arrangement | positioning of an ultrasonic sensor unit. (A) The figure which shows the state in which the sheet | seat is conveyed in a cassette conveyance path, (b) The figure which shows the state in which the sheet | seat is conveyed in a multi conveyance path.

<First Embodiment>
(Image forming device)
The image forming apparatus of this embodiment will be described. First, the overall configuration of the image forming apparatus will be described. FIG. 1 is a schematic cross-sectional view showing the overall configuration of the image forming apparatus 100.

  The color laser printer 100 shown in FIG. 1 includes four photosensitive drums 1 (1a, 1b, 1c, 1d). Around each photosensitive drum 1, charging means 2 (2a, 2b, 2c, 2d) for uniformly charging the surface of the photosensitive drum 1, and a laser beam is irradiated on the photosensitive drum 1 based on image information. An exposure means 3 for forming an electrostatic latent image, a developing means 4 (4a, 4b, 4c, 4d) for developing toner images by attaching toner to the electrostatic latent image, and a toner image on the photosensitive drum 1 Transfer means 12 (12a, 12b, 12c, 12d) for transferring to the intermediate transfer material 5 (intermediate transfer belt), and cleaning means 23 (23a, 23b, for removing post-transfer toner remaining on the surface of the photosensitive drum 1 after transfer. 23c, 23d) and the like are provided.

  The exposure unit 3 is arranged vertically below the process cartridges 7a, 7b, 7c, and 7d, and performs exposure based on the image signal to the photosensitive drums 1a, 1b, 1c, and 1d. Each of the developing units 4a, 4b, 4c, and 4d includes a toner storage unit that stores toner of each color of yellow (Y), magenta (M), cyan (C), and black (Bk), a developing roller, and the like.

  With the above configuration, the photosensitive drums 1a, 1b, 1c, and 1d are charged to a predetermined negative potential by the charging rollers 2a, 2b, 2c, and 2d, and then electrostatic latent images are formed by the scanner unit 3, respectively. The This electrostatic latent image is reversed and developed by the developing units 4a, 4b, 4c, and 4d, and negative toner is attached to form Y, M, C, and Bk toner images, respectively.

  In the intermediate transfer belt unit 5, the intermediate transfer belt 5 is stretched around a driving roller 10 and a tension roller 11, and the tension roller 11 is tensioned. Further, primary transfer rollers 12a, 12b, 12c, and 12d are disposed inside the intermediate transfer belt 5 so as to face the respective photosensitive drums 1a, 1b, 1c, and 1d, and transfer bias is provided by a bias applying unit (not shown). Is applied.

  The toner images formed on the photosensitive drums 1a, 1b, 1c, and 1d are sequentially intermediated from the toner images on the photosensitive drum 1a by applying a positive bias to the primary transfer rollers 12a, 12b, 12c, and 12d. Primary transfer is performed on the transfer belt 5, and the four color toner images are conveyed to the secondary transfer unit 15 in a state where they overlap each other.

  On the other hand, the cassette feeding device has a paper feed roller 8 for feeding the sheet S from within the paper feed cassette 24 for storing the sheet (recording material) S. The sheets S stored in the paper feed cassette 24 are pressed against the cassette paper feed roller 8, separated one by one by the separation pad 9 (friction piece separation method), and conveyed to the cassette conveyance path 30.

  Further, the image forming apparatus 100 is provided with a multi paper feeder in addition to the cassette paper feeder. The sheets S stacked on the multi-feed tray 29 are pressed against the multi-feed roller 27, separated one by one by the separation pad 28, and conveyed to the multi-conveying path 31. The multi-sheet feeder can feed and convey various sheets S different in material, weight per unit area (basis weight), size, and the like as compared with the cassette sheet feeder.

  The cassette conveyance path 30 and the multi-conveyance path 31 merge at a conveyance path junction 21 immediately before the registration roller pair 17 downstream in the sheet conveyance direction to form one conveyance path. The sheet S conveyed from the cassette feeding device or the multi-sheet feeding device is conveyed to the registration roller pair 17 and the secondary transfer unit 15 through the conveyance path.

  By applying a positive bias to the secondary transfer roller 18, the four color toner images on the intermediate transfer belt 5 are secondarily transferred onto the sheet S conveyed to the secondary transfer unit 15. The sheet S is conveyed from the secondary transfer unit 15 to a fixing nip formed by a cylindrical fixing belt 14a and a pressure roller 14b of the fixing unit 14 as a fixing unit, and is formed on the sheet by applying heat and pressure. The toner image thus formed is fixed on the sheet. The fixed sheet S is discharged to a discharge tray 20 by a discharge roller pair 19.

(Ultrasonic sensor unit)
Next, the ultrasonic sensor unit will be described. FIG. 2 is a schematic sectional view of the ultrasonic sensor unit. The ultrasonic sensor unit includes a transmitter 40 and a receiver 41 with a conveyance path for conveying the sheet S interposed therebetween.

  The transmitter (transmitting means) 40 has a transmitting driver (not shown), and a voltage is applied to the piezoelectric element 45a supported on the substrate 44a by the transmitting driver to vibrate the piezoelectric element 45a, and the piezoelectric element 45a vibrates. Is transmitted to the metal plate 46a to vibrate the metal plate 46a. Next, the vibration of the metal plate 46a is transmitted to the cone 47a which is a resonator, and the cone 47a is vibrated. The vibration applied to the cone 47a is converted into air vibration (ultrasonic wave), and the ultrasonic wave 42 of the central axis X1 is output from the cone 47a. The output ultrasonic wave 42 is directed by a cylindrical guide 43a formed of a material having high acoustic impedance, and is output from the transmitter 40 toward the sheet S.

  The ultrasonic wave 42 output from the transmitter 40 reaches the sheet S and vibrates the sheet S. The ultrasonic wave 42 output via the sheet S is collected by a cylindrical guide 43b of a receiver (receiving means) 41, and gives vibration to a cone 47b which is a vibrator. The vibration applied to the cone 47b is transmitted to the piezoelectric element 45b supported by the metal plate 46b and the substrate 44b. The piezoelectric element 45b converts the received vibration into a voltage and outputs a signal to a reception driver (not shown).

  Since the rate at which ultrasonic waves pass through the sheet S (transmittance) is proportional to the logarithm of the weight per unit area (basis weight), the basis weight of the sheet S is determined by the voltage value of vibration received by the piezoelectric element 45b. It becomes possible to discriminate. Specifically, the voltage value of the received signal is small for a sheet with a large basis weight, and the voltage value of the received signal is large for a sheet with a small basis weight.

  In the image forming apparatus of the present embodiment, the fixing temperature and the conveyance speed at the fixing unit 14 are used as image forming conditions for forming an image on the sheet S by the image forming unit based on the output corresponding to the basis weight of the determined sheet S. In addition, control is performed to change the transfer bias and the conveyance speed in the secondary transfer unit 15. In this embodiment, the basis weight of the sheet S is detected by the ultrasonic sensor unit, and the sheet S is positioned upstream of the conveyance path merging unit 21 in order to control the transfer bias and the conveyance speed in the secondary transfer unit 15. Detect by position. This is because the conveyance distance of the sheet S from the conveyance path merging unit 21 to the secondary transfer unit 15 is short, so that the basis weight detection result of the sheet S is fed back to the transfer bias and conveyance speed in the secondary transfer unit 15. This is to make it possible to earn more time.

  Next, the ultrasonic sensor unit of this embodiment will be described with reference to FIGS. FIG. 3 is a schematic cross-sectional view showing the arrangement of the ultrasonic sensor unit. There is a cassette conveyance path 30 that conveys the sheet material fed from the cassette sheet feeder to the conveyance path junction 21, and is formed by a cassette conveyance guide 33 and an inner conveyance guide 32. Further, there is a multi-conveying path 31 that conveys the sheet material fed from the multi-sheet feeding device to the conveying path joining unit 21, and is formed by a multi-conveying guide 35 and an inner conveying guide 32.

  The two conveyance paths are provided with holes (32a, 32b, 33a, 35a) through which ultrasonic waves pass, a transmitter 40 is provided facing the hole 33a, and a receiver 41 is provided facing the hole 35a. ing. Between the cassette conveyance path 30 and the multi conveyance path 31, a reflector 50 that reflects ultrasonic waves is disposed at a position facing the holes 32a and 32b.

  The transmitter 40 is disposed at a position facing the reflection plate 50 with the cassette conveyance path 30 interposed therebetween, and the receiver 41 is disposed at a position opposed to the reflection plate 50 with the multi conveyance path 31 interposed therebetween. The transmitter is arranged so that the central axis X1 of the ultrasonic wave emitted from the transmitter 40 is substantially orthogonal to the surface of the sheet S conveyed through the cassette conveyance path 30, emitted from the transmitter 40 and reflected by the reflecting plate 50. The reflection plate 50 is disposed so that the center axis X2 of the ultrasonic wave that is made is substantially orthogonal to the surface of the sheet S that is conveyed through the multi-conveyance path 31. The reflecting plate 50 is made of a material having a high acoustic impedance, such as iron, in order to reflect the applied ultrasonic wave 42 at the interface between the air and the reflecting plate.

  Next, a method for detecting the type of sheet material passing through the two conveyance paths will be described. 4A is a diagram illustrating a state in which the sheet S is being conveyed in the cassette conveyance path 30, and FIG. 4B is a diagram illustrating a state in which the sheet S is being conveyed in the multi-conveyance path 31.

  When the sheet S is conveyed in the cassette conveyance path 30, as shown in FIG. 4A, the ultrasonic wave 42 output from the transmitter 40 passes through the hole 33 a vacated in the cassette conveyance guide 33. Thus, the cassette conveying path 30 is vibrated at right angles to the sheet S being conveyed. The ultrasonic wave 42 output via the vibrated sheet S passes through the hole 32 a vacated in the inner conveyance guide 32 and reaches the reflection plate 50. The ultrasonic wave 42 that has reached the reflection plate 50 is reflected by the reflection plate 50, passes through the hole 32 a of the inner conveyance guide and the hole 34 a of the multi-conveyance guide, and is received by the receiver 41 of the ultrasonic sensor.

  When the sheet S is conveyed in the multi-conveyance path 31, as shown in FIG. 4B, the ultrasonic wave 42 output from the transmitter 40 is converted into the cassette conveyance guide hole 33a and the inner conveyance guide hole 32a. And reaches the reflector 50. The ultrasonic wave 42 that has reached the reflection plate 50 is reflected by the reflection plate 50, passes through the hole 32a of the inner conveyance guide, and vibrates by hitting the multi conveyance path 31 at right angles to the sheet S being conveyed. The ultrasonic wave 42 output through the vibrated sheet S passes through the hole 34a of the multi-conveyance guide and is received by the receiver 41 of the ultrasonic sensor.

  The receiver 41 converts the received ultrasonic wave 42 into a voltage by the piezoelectric element 45 and determines the basis weight of the sheet material S based on the magnitude of the received voltage value. When it is determined that the basis weight of the sheet material S is large, the applied bias in the secondary transfer unit 15 is increased, the fixing temperature in the fixing unit 14 is increased, or the conveyance speed of the sheet material is decreased. Prevents transfer failure and fixing failure. If it is determined that the basis weight of the sheet material is small, the bias applied to the secondary transfer unit 15 is reduced, the fixing temperature is lowered to prevent the occurrence of transfer failure and fixing failure, and wasted energy. Or reduce consumption.

  Note that the positional relationship between the transmitter 40 and the receiver 41 of the ultrasonic sensor may be reversed.

  As described above, in the present embodiment, by using the reflection plate 50, it is possible to detect a sheet conveyed through two conveyance paths by a pair of transmitter and receiver. Here, since one metal plate which is a reflecting plate is relatively inexpensive for one set of transmitter and receiver, the cost can be reduced compared to using two sets of transmitter and receiver. . Compared with the case where two sets of transmitters and receivers are arranged, the space occupied by one set of transmitters and receivers and the reflector can be reduced, and the apparatus can be downsized. It becomes possible.

  In addition, by arranging the reflecting plate, it is possible to apply ultrasonic waves to the sheet passing through any conveyance path at a substantially right angle to the sheet surface. That is, the central axis X1 of the ultrasonic wave emitted from the transmitter 40 is substantially perpendicular to the surface of the sheet S conveyed through the cassette conveyance path 30, and the ultrasonic wave emitted from the transmitter 40 and reflected by the reflecting plate 50. The central axis X <b> 2 is substantially perpendicular to the surface of the sheet S conveyed through the multi-conveyance path 31.

  When the ultrasonic wave is applied to the sheet S at a substantially right angle in this way, the sheet S flutters (change in the angle at which the sheet is conveyed or change in the position perpendicular to the sheet conveyance surface). The effect on the received ultrasound is reduced. That is, by applying ultrasonic waves at right angles to the sheet material, it becomes insensitive to changes in the position and posture of the sheet material, and variations in the output of the receiver due to flapping of the sheet can be reduced.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 8 Cassette feed roller 9 Cassette separation pad 14 Fixing part 15 Secondary transfer part 17 Registration roller 21 Conveyance path merge part 24 Paper feed cassette 27 Multi paper feed roller 28 Multi paper feed pad 29 Multi separation tray 30 Cassette transport Path 31 Multi-transport path 32 Inner transport guide 33 Cassette transport guide 35 Multi-transport guide 40 Transmitter 41 Receiver 42 Ultrasonic 43 Guide 44 Sensor substrate 45 Piezoelectric element 46 Metal plate 47 Cone

Claims (12)

A first conveyance path and a second conveyance path through which a recording material conveyed to the image forming unit passes;
Transmitting means for transmitting ultrasonic waves toward the recording material transported through the first transport path and the second transport path;
One receiving means for receiving the ultrasonic wave transmitted from the transmitting means and passing through the recording material, and outputting a signal corresponding to the received ultrasonic wave;
An image forming apparatus that controls image forming conditions for forming an image on a recording material based on a signal output from the receiving unit,
A reflective portion disposed between the first transport path and the second transport path;
The transmitting means is a transmitter disposed opposite to the reflecting portion across the first transport path, and the receiving means is disposed opposite to the reflecting portion across the second transport path. One receiver,
The ultrasonic wave transmitted from the transmitter passes through the first transport path, is reflected by the reflecting portion , passes through the second transport path, and reaches the receiver. The central axis of the ultrasonic wave transmitted from the transmitter intersects the recording material conveyed through the first conveyance path ,
The central axis of the ultrasonic wave that is transmitted from the transmitter , passes through the first transport path, and is reflected by the reflecting portion intersects the recording material transported through the second transport path. Item 2. The image forming apparatus according to Item 1. The ultrasonic wave transmitted from the transmitter hits the recording material conveyed through the first conveyance path at a right angle,
The ultrasonic wave that is transmitted from the transmitter, passes through the first transport path, and is reflected by the reflecting portion strikes a recording material transported through the second transport path at a right angle. Image forming apparatus. The reflective portion is an image forming apparatus according to any one of claims 1 to 3, characterized in that a metal plate. A first conveyance guide member that forms the first conveyance path; and a second conveyance guide member that forms the second conveyance path, wherein the first conveyance guide member is an ultrasonic wave transmitted from the transmitter. The second transport guide member includes a second hole through which the ultrasonic wave transmitted from the transmitter and reflected by the reflecting portion passes, and the second transport guide member has a first hole in the first transport path. 5. The image formation according to claim 1, wherein a conveyance direction of the recording material at a position intersects with a conveyance direction of the recording material at the position of the second hole in the second conveyance path. apparatus. A conveyance path merging portion where a portion of the first conveyance path on the downstream side in the recording material conveyance direction from the first hole and a portion of the second conveyance path on the downstream side in the recording material conveyance direction are merged; 6. The image forming apparatus according to claim 5, further comprising: A first stacking unit for stacking the recording material; and a second stacking unit different from the first stacking unit for stacking the recording material, wherein the recording material stacked on the first stacking unit is the first stacking unit. 2. The recording material that is transported to the image forming unit through a transport path, and the recording material stacked on the second stacking unit is transported to the image forming unit through the second transport path. The image forming apparatus according to claim 6. The image forming apparatus according to claim 7, wherein the first stacking unit is disposed below the image forming unit. The image forming apparatus according to claim 8, wherein the second stacking unit is disposed at a position shifted from the first stacking unit with respect to the horizontal direction. The image according to claim 1, wherein the image forming unit includes a transfer unit that transfers a toner image onto a recording material, and the image forming condition is a transfer bias in the transfer unit. Forming equipment. 11. The image forming unit includes a fixing unit that heats a recording material to fix a toner image on the recording material, and the image forming condition is a fixing temperature in the fixing unit. The image forming apparatus according to one item. The image forming apparatus according to claim 1, wherein the image forming condition is a conveyance speed of a recording material .

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