Patent Grant
9733218
The present application claims priority to and incorporates by reference the entire contents of Japanese Patent Application No. 2014-054213 filed in Japan on Mar. 17, 2014.
1. Field of the Invention
The present invention relates to a sheet conveying device, an image forming apparatus, and a method of determining whether multi-feed has occurred.
2. Description of the Related Art
Techniques of determining whether or not multi-feed of sheets has occurred (hereinafter, “multi-feed determination”) based on difference in amount (e.g., an amount of attenuation) of an ultrasonic wave between before and after passing through a sheet(s) being conveyed are conventionally known. Meanwhile, the difference in amount of the ultrasonic wave largely depends not only on the factor of the sheet but also on the factor other than the factor of the sheet. Accordingly, devices (devices that make multi-feed determination) undesirably vary from each other in the difference in amount of the ultrasonic wave, which leads to a false multi-feed determination.
Examples of the factor of the sheet include basic weight of the sheet. Examples of the factor other than the sheet include variation in timing of sending an ultrasonic wave by a sending sensor, variation in timing of receiving an ultrasonic wave by a receiving sensor, variation in arrangement of the sending sensor and the receiving sensor, and device-to-device environmental variation (e.g., variation in the temperature, the humidity, or the like).
A technique of adjusting an amplification factor of an amplifier circuit of a signal output by a receiving sensor receiving a ultrasonic wave is disclosed in, for example, Japanese Laid-open Patent Application No. 2006-312527. According to the technique disclosed in Japanese Laid-open Patent Application No. 2006-312527, device-to-device variation in the difference in amount of the ultrasonic wave can be adjusted, and occurrence of false multi-feed determination can be reduced.
However, such a conventional technique as that described above that adjusts variation in the difference in amount of the ultrasonic wave by using an amplification factor of an amplifier circuit is disadvantageous in that noise filtering characteristics of the amplifier circuit are also undesirably changed, undesirably causing oscillation of an operational amplifier or the like to occur. As a corollary to this, multi-feed determination will fail. For this reason, such a conventional technique as that described above is susceptible to improvement in accuracy of multi-feed determination.
In light of the foregoing, there is a need for a sheet conveying device, an image forming apparatus, and a multi-feed determination method with improved accuracy of multi-feed determination.
It is an object of the present invention to at least partially solve the problems in the conventional technology.
A sheet conveying device includes: a sending unit configured to send an ultrasonic wave; a receiving unit positioned to face the sending unit across a conveyance path, along which a sheet is conveyed, and configured to receive a first ultrasonic wave, the first ultrasonic wave being an ultrasonic wave sent from the sending unit and passed through the sheet, and output a first voltage corresponding to the first ultrasonic wave; an adjusting unit configured to adjust the first voltage into an adjusted first voltage according to a setting; an amplification unit configured to amplify the adjusted first voltage by a preset amplification factor for multi-feed determination into an amplified first voltage; and a determining unit configured to determine whether or not multi-feed of the sheet has occurred based on the amplified first voltage.
A method determines whether or not multi-feed has occurred. The method includes: sending an ultrasonic wave; receiving including receiving the ultrasonic wave passed through a sheet conveyed along a conveyance path and outputting a voltage corresponding to the ultrasonic wave; adjusting the voltage into an adjusted voltage according to a setting; amplifying the adjusted voltage by a preset amplification factor for multi-feed determination into an amplified voltage; and determining whether or not multi-feed of the sheet has occurred based on the amplified voltage.
The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings.
Exemplary embodiments of the present invention are described in detail below with reference to the accompanying drawings. The sheet conveying device described in each embodiment may be applied to an image forming apparatus such as an MFP (multifunction peripheral), a copier, a printer, a scanner, or a facsimile. An MFP is an apparatus having at least two of a copier function, a printer function, a scanner function, and a facsimile function.
A stack of a plurality of sheets is housed in the sheet feeding tray 102. The pickup roller 104 is in contact with an uppermost sheet P of the sheets in the sheet feeding tray 102. The pickup roller 104 rotates counterclockwise, thereby picking up the sheet P with which the pickup roller 104 is in contact.
The sheet feeding rollers 106a and 106b rotate counterclockwise and clockwise, respectively, thereby feeding the sheet P picked up by the pickup roller 104 to the conveyance rollers 110a and 110b along the conveyance path 108.
The conveyance rollers 110a and 110b rotate clockwise and counterclockwise, respectively, thereby further conveying the sheet P fed from the sheet feeding rollers 106a and 106b along the conveyance path 108.
The sending sensor 112 and the receiving sensor 114 are positioned to face each other across the conveyance path 108. The sending sensor 112 is a sensor that sends an ultrasonic wave. The receiving sensor 114 is a sensor that receives the ultrasonic wave sent from the sending sensor 112. If the ultrasonic wave passes through the sheet P, the ultrasonic wave is attenuated by the sheet P and then received by the receiving sensor 114. The thus-received ultrasonic wave is used in various determinations including determination as to whether or not multi-feed has occurred (hereinafter, “multi-feed determination”) and determination as to whether or not a failure has occurred (hereinafter, “failure determination”).
The sheet P delivered by the conveyance rollers 110a and 110b passes through a position of the sending sensor 112 and the receiving sensor 114. Thereafter, an image is transferred onto the sheet P by an image forming unit (not shown). Hence, the image is formed (printed) on the sheet P.
The sending sensor 112 is the sensor that sends an ultrasonic wave.
The receiving sensor 114 is the sensor that receives the ultrasonic wave sent from the sending sensor 112 and converts the received ultrasonic wave into a voltage representing the ultrasonic wave.
The adjusting unit 130 is a circuit that adjusts the voltage, into which the ultrasonic wave is converted by the receiving sensor 114, according to setting of the adjusting unit 130 adjusted by the adjustment control unit 140.
The adjustment control unit 140 is a circuit that adjusts the setting of the adjusting unit 130 and determines whether or not at least any one of the sending sensor 112, the receiving sensor 114, and the adjusting unit 130 has failed by utilizing adjustment of the setting.
The amplification unit 150 is a circuit that amplifies the voltage adjusted by the adjusting unit 130 by a preset amplification factor for multi-feed determination (hereinafter, the “preset multi-feed-determining amplification factor”).
The determining unit 160 is a circuit that determines, based on the voltage amplified by the amplification unit 150, whether or not multi-feed of sheets has occurred and whether or not at least one of the adjusting unit 130 and the amplification unit 150 has failed.
Note that elements of the electrical structure of the sheet conveying device 100 are not necessarily limited to those described above. For example, a detector circuit may be interposed between the amplification unit 150 and the determining unit 160.
How the sheet conveying device 100 operates is specifically described below. Hereinafter, it is assumed that there are the following device-to-device (device: the sheet conveying device 100) variations. Relative to a value of an ultrasonic wave sent by the sending sensor 112, a value of the ultrasonic wave received by the receiving sensor 114 is attenuated by the factor other than the sheet by approximately 15 decibels (dB) at maximum in some devices, while the same is amplified by approximately 15 dB at maximum in some other devices. The same is attenuated by the factor of the sheet in a range from approximately 37 dB to approximately 55 dB.
In short, the discussion below is based on the assumption that the device-to-device variation in the value of the ultrasonic wave received by the receiving sensor 114 caused by the factor other than the factor of the sheet is 30 dB; the same caused by the factor of the sheet is 18 dB. However, this is not a restrictive assumption.
An adjustment operation applied to the setting of the adjusting unit 130 is described below with reference to
Meanwhile, the adjustment operation is performed in a state where no sheet is conveyed by the sheet conveying device 100. For example, the adjustment operation may be performed before factory shipment or during maintenance of the sending sensor 112, the receiving sensor 114, and/or the like. In short, the adjustment operation is performed before a user performs a job, such as a print job, that uses a sheet.
The receiving sensor 114 receives an ultrasonic wave (an example of “second ultrasonic wave”) sent from the sending sensor 112 and reaching the receiving sensor 114 without passing through a sheet, converts the received ultrasonic wave into a voltage (an example of “second voltage”) representing the ultrasonic wave, and outputs the voltage to the adjusting unit 130.
Thereafter, the adjustment control unit 140 determines whether or not the output value, which is the value of the voltage output from the adjusting unit 130, is equal to or higher than a first reference value (S101). More specifically, the adjusting unit 130 adjusts the voltage according to default setting of the adjusting unit 130 and outputs the value of the adjusted voltage at S101.
The first reference value is, for example, a voltage value obtained by subtracting, from the voltage value representing the ultrasonic wave sent from the sending sensor 112, a voltage value corresponding to a maximum amount of attenuation of the ultrasonic wave possibly caused by the factor other than the factor of the sheet until when the ultrasonic wave is received by the receiving sensor 114.
In the embodiment, it is assumed that the ultrasonic wave is attenuated by the factor other than the factor of the sheet by 15 dB at maximum. Accordingly, the first reference value can be obtained by subtracting a voltage value corresponding to 15 dB from the voltage value representing the ultrasonic wave sent from the sending sensor 112.
If the output value of the adjusting unit 130 is lower than the first reference value (No at S101), the adjustment control unit 140 determines that at least any one of the sending sensor 112, the receiving sensor 114, and the adjusting unit 130 has failed (S103).
For example, when the output value of the adjusting unit 130 is an output value 201 which is lower than the first reference value as illustrated in
More specifically, the adjustment control unit 140 determines that a failure such as an inactive state of the sending sensor 112, an inactive state of the receiving sensor 114, a decrease in sensitivity (such as system sensitivity, impedance, or impulse responsivity) of the receiving sensor 114, or a failure of an adjustment circuit has occurred, and sends a notification of the failure to a control unit (not shown) or the like so that the failure is displayed on a display unit (not shown) or the like.
On the other hand, if the output value of the adjusting unit 130 is equal to or higher than the first reference value (Yes at S101), the adjustment control unit 140 determines whether or not the output value of the adjusting unit 130 is lower than a second reference value (S105).
The second reference value is, for example, a voltage value within a range between the first reference value and a voltage value obtained by subtracting, from the voltage value representing the ultrasonic wave sent from the sending sensor 112, a voltage value corresponding to a minimum amount of attenuation of the ultrasonic wave possibly caused by the factor other than the factor of the sheet until when the ultrasonic wave is received by the receiving sensor 114.
In the embodiment, it is assumed that the ultrasonic wave is amplified by the factor other than the factor of the sheet by 15 dB at maximum. Accordingly, the second reference value can be obtained as a voltage value in a range between the first reference value and a voltage value obtained by adding the voltage value corresponding to 15 dB to the voltage value representing the ultrasonic wave sent from the sending sensor 112. In short, the second reference value is a voltage value in a range of 30 dB from the first reference value. In the example described above, a value obtained by adding a voltage value corresponding 1 dB to the first reference value is used as the second reference value. However, the second reference value is not limited thereto.
If the output value of the adjusting unit 130 is equal to or higher than the second reference value (No at S105), the adjustment control unit 140 determines whether or not the adjusting unit 130 can decrease the voltage fed from the receiving sensor 114 or, in other words, whether or not it is possible to adjust the setting of the adjusting unit 130 so as to decrease the voltage (S107).
Here, the adjustment control unit 140 is capable of causing the adjusting unit 130 to decrease the voltage by adjusting the setting of the adjusting unit 130 to setting different from the default setting. In the embodiment, the variation of the voltage representing the ultrasonic wave caused by the factor other than the factor of the sheet is within a voltage range corresponding to a 30-dB range. Accordingly, the adjustment control unit 140 can cause the adjusting unit 130 to decrease the voltage by a value corresponding to 30 dB, which is adjustment limit, at maximum. Note that the adjusting unit 30 is structurally capable of decreasing the voltage by a value corresponding to 30 dB or higher; the adjustment control unit 130 is structurally capable of causing the adjusting unit 130 to decrease the voltage by a value corresponding to 30 dB or higher.
If the adjusting unit 130 cannot decrease the voltage fed from the receiving sensor 114 (No at S107) or, more specifically, the adjusting unit 130 cannot deliver an output value lower than the second reference value because the setting of the adjusting unit 130 is at the adjustment limit of the adjustment control unit 140 and therefore the adjusting unit 130 cannot decrease the voltage any more, the adjustment control unit 140 determines that at least any one of the sending sensor 112, the receiving sensor 114, and the adjusting unit 130 has failed (S109).
For example, when, in a condition where the setting of the adjusting unit 130 does not allow a further decrease in the voltage, the output value of the adjusting unit 130 is an output value 202 which is higher than the second reference value as illustrated in
More specifically, the adjustment control unit 140 determines that a failure such as an overvoltage in a drive circuit of the sending sensor 112, a condition in which the sensitivity (such as the system sensitivity, the impedance, or the impulse response) of the receiving sensor 114 are high and out of standard, disconnection of a connector of the receiving sensor 114, or breakage of a harness of the receiving sensor 114 has occurred, and sends a notification of the failure to the control unit (not shown) or the like so that the failure is displayed on the display unit (not shown) or the like.
On the other hand, if the adjusting unit 130 can decrease the voltage fed from the receiving sensor 114 (Yes at S107), the adjustment control unit 140 adjusts the setting of the adjusting unit 130 and causes the adjusting unit 130 to decrease the voltage fed from the receiving sensor 114 (S111). Thereafter, processing goes back to S105.
At S105, if the output value of the adjusting unit 130 is lower than the second reference value (Yes at S105) or, in other words, when the output value of the adjusting unit 130 is an output value 203 as illustrated in
In short, the adjustment control unit 140 performs the adjustment operation of adjusting the setting of the adjusting unit 130 so that the voltage adjusted by the adjusting unit 130 falls within the range from the first reference value, inclusive, and the second reference value, exclusive. If the adjustment control unit 140 cannot adjust the setting of the adjusting unit 130 in the above-described manner, the adjustment control unit 140 determines that at least any one of the sending sensor 112, the receiving sensor 114, and the adjusting unit 130 has failed.
A method for adjusting, by the adjusting control unit 140, the setting of the adjusting unit 130 is described below with reference to
Referring to the example illustrated in
The adjusting unit 130 includes a step-down circuit including external resistors R1 to Rn and switches SW1 to SWn. The adjusting unit 130 can change a combined resistance value of the external resistors R1 to Rn by switching on/off the switches SW1 to SWn.
More specifically, the adjustment control unit 140 adjusts the setting of the adjusting unit 130 by switching on/off the switches SW1 to SWn so that a value of the voltage divided by the impedance of the resistor 121 and the combined resistance value of the external resistors R1 to Rn falls within the range from the first reference value, inclusive, and the second reference value, exclusive.
In the embodiment, it is assumed that the switches SW1 to SWn are all off in the default setting. Decreasing the voltage by 30 dB can be performed by switching on a predetermined number of the switches SW1 to SWn.
Accordingly, in the embodiment, the adjustment control unit 140 switches on the switches SW1 to SWn one by one so that the output value of the adjusting unit 130 achieves the first reference value and causes the adjusting unit 130 to maintain a state of the switches SW1 to SWn at which the output value of the adjusting unit 130 achieves the first reference value. If the output value of the adjusting unit 130 should be lower than the second reference value in a state where all the switches SW1 to SWn are off or if the output value of the adjusting unit 130 should be equal to or higher than the second reference value in a state where the predetermined number of the switches SW1 to SWn are on, the adjustment control unit 140 determines that at least any one of the sending sensor 112, the receiving sensor 114, and the adjusting unit 130 has failed.
The determination as to whether the voltage value is equal to or higher than the first reference value and equal to or lower than the second reference value may be made using a comparator, an analog-to-digital (AD) converter, or the like. The determination may be made either by the adjusting unit 130 or by the adjustment control unit 140.
An operation for determining whether or not multi-feed has occurred (hereinafter, “multi-feed determination operation”) is described below. Note that the multi-feed determination operation is performed after the above-described adjustment operation. For example, the multi-feed determination operation may be performed when a user performs a job, such as a print job, that uses a sheet.
The receiving sensor 114 receives an ultrasonic wave (an example of “first ultrasonic wave”) sent from the sending sensor 112 and passed through one sheet or, in a case of multi-feed, two or more sheets, converts the received ultrasonic wave into a voltage (an example of “first voltage”) representing the ultrasonic wave, and outputs the voltage to the adjusting unit 130.
Thereafter, the adjusting unit 130 adjusts the voltage, into which the ultrasonic wave is converted by the receiving sensor 114, into an adjusted voltage according to the setting adjusted by the adjustment control unit 140 and outputs the adjusted voltage to the amplification unit 150. The output value of the adjusting unit 130 has thus undergone adjustment that smoothes out device-to-device (device: the sheet conveying device 100) variation in the value of the ultrasonic wave caused by the factor other than the factor of the sheet.
Thereafter, the amplification unit 150 amplifies the voltage adjusted by the adjusting unit 130 by the preset multi-feed-determining amplification factor and outputs the amplified voltage to the determining unit 160.
The preset multi-feed-determining amplification factor is an amplification factor for amplifying a voltage value obtained by subtracting, from the value of the voltage adjusted by the adjusting unit 130, a voltage value corresponding to a maximum amount of attenuation of the ultrasonic wave possibly caused by the factor of the single sheet from when the ultrasonic wave is sent from the sending sensor 112 until when the ultrasonic wave is received by the receiving sensor 114 to an upper-limit output value of the amplification unit 150 or higher.
However, the preset multi-feed-determining amplification factor is smaller than an amplification factor for amplifying a voltage value obtained by subtracting, from the value of the voltage adjusted by the adjusting unit 130, a voltage value corresponding to a minimum amount of attenuation of the ultrasonic wave possibly caused by the factor of two sheets when the ultrasonic wave is sent from the sending sensor 112 until when the ultrasonic wave is received by the receiving sensor 114 to the upper-limit output value of the amplification unit 150.
In the embodiment, the value of the voltage adjusted by the adjusting unit 130 is a voltage value obtained by subtracting, from the voltage value representing the ultrasonic wave sent from the sending sensor 112, a voltage value corresponding to a maximum amount of attenuation of the ultrasonic wave possibly caused by the factor other than the factor of the sheet until when the ultrasonic wave is received by the receiving sensor 114.
Accordingly, in the embodiment, the preset multi-feed-determining amplification factor is an amplification factor for amplifying a voltage, into which an ultrasonic wave sent from the sending sensor 112 and received by the receiving sensor 114 after passing through one sheet in a condition where both the factor other than the factor of the sheet and the factor of the sheet maximize the amount of attenuation is converted by the receiving sensor 114, to the upper-limit output value of the amplification unit 150.
It should be noted that, in the embodiment, the preset multi-feed-determining amplification factor is smaller than an amplification factor for amplifying a voltage, into which an ultrasonic wave sent from the sending sensor 112 and received by the receiving sensor 114 after passing through two sheets in a condition where both the factor other than the factor of the sheet and the factor of the sheet minimize the amount of attenuation is converted by the receiving sensor 114, to the upper-limit output value of the amplification unit 150.
Thereafter, the determining unit 160 determines whether or not multi-feed of the sheets has occurred based on the voltage amplified by the amplification unit 150.
More specifically, the determining unit 160 compares a value derived from the voltage amplified by the amplification unit 150 with a value derived from the upper-limit output value. The value derived from the amplified voltage may be either the amplified voltage itself or an integral of the amplified voltage. The value derived from the upper-limit output value may be either the upper-limit output value itself or an integral of the upper-limit output value.
The determining unit 160 determines that multi-feed has not occurred if the value derived from the voltage amplified by the amplification unit 150 is equal to or higher than the value derived from the upper-limit output value. The reason therefor is described below. The preset multi-feed-determining amplification factor of the embodiment is the amplification factor for amplifying the voltage representing the ultrasonic wave sent from the sending sensor 114 to the upper-limit output value of the amplification unit 150 even in the condition where both the factor of the single-sheet and the factor other than the factor of the sheet maximize the amount of attenuation. Accordingly, when multi-feed has not occurred (i.e., the number of sheets is one), the value of the voltage amplified by the amplification unit 150 should be equal to or higher than the upper-limit output value without exception.
On the other hand, the determining unit 160 determines that multi-feed has occurred if the value derived from the voltage amplified by the amplification unit 150 is lower than the value derived from the upper-limit output value. The reason therefor is described below. The preset multi-feed-determining amplification factor of the embodiment is the amplification factor that is insufficient to amplify the voltage representing the ultrasonic wave sent from the sending sensor 114 to the upper-limit output value of the amplification unit 150 even in the condition where both the factor of the two sheets and the factor other than the factor of the sheet minimize the amount of attenuation. Accordingly, when multi-feed has occurred (i.e., the number of sheets is two or more), the value of the voltage amplified by the amplification unit 150 should be lower than the upper-limit output value without exception.
An operation for determining whether or not a failure has occurred (hereinafter, “failure determination operation”) is described below with reference to
The receiving sensor 114 receives an ultrasonic wave (an example of “third ultrasonic wave”) sent from the sending sensor 112 and reaching the receiving sensor 114 without passing through a sheet, converts the received ultrasonic wave into a voltage (an example of “third voltage”) representing the ultrasonic wave, and outputs the voltage to the adjusting unit 130.
Thereafter, the adjusting unit 130 adjusts the voltage, into which the ultrasonic wave is converted by the receiving sensor 114, according to the setting adjusted by the adjustment control unit 140 and outputs the adjusted voltage to the amplification unit 150 (S201). More specifically, at S201, the adjusting unit 130 adjusts (decreases) the voltage, into which the ultrasonic wave is converted by the receiving sensor 114, to a voltage value obtained by subtracting, from the value of the voltage adjusted according to the setting adjusted by the adjusting control unit 140 through the adjustment operation, a voltage value corresponding to a maximum amount of attenuation of the ultrasonic wave possibly caused by the factor of the single sheet from when the ultrasonic wave is sent from the sending sensor 112 until when the ultrasonic wave is received by the receiving sensor 114, and outputs the thus-adjusted voltage value to the amplification unit 150. It is assumed that the setting for adjusting the voltage, into which the ultrasonic wave is converted by the receiving sensor 114, to such a voltage value as that described above have been configured in advance by the adjustment control unit 140.
The operation described above causes the adjusting unit 130 to output a value that is to be output in a condition where the factor of the single sheet maximizes the amount of attenuation of the ultrasonic wave received by the receiving sensor 114. As a result, because the determining unit 160 can make a pseudo determination that multi-feed has occurred, the determining unit 160 can make the failure determination.
Thereafter, the amplification unit 150 amplifies the voltage adjusted by the adjusting unit 130 by the preset multi-feed-determining amplification factor and outputs the amplified voltage to the determining unit 160.
Thereafter, the determining unit 160 compares a value derived from the voltage amplified by the amplification unit 150 with a value derived from the upper-limit output value. The determining unit 160 determines that multi-feed has not occurred if the value derived from the voltage amplified by the amplification unit 150 is equal to or higher than the value derived from the upper-limit output value, but determines that multi-feed has occurred if the value is lower than the value derived from the upper-limit output value (S203).
As described above, the adjusting unit 130 outputs the value that is to be output in the condition where the factor of the single sheet maximizes the amount of attenuation of the ultrasonic wave received by the receiving sensor 114. Accordingly, the result of determination made by the determining unit 160 should be that multi-feed has not occurred without exception. If the result of determination made by the determining unit 160 should be that multi-feed has occurred (No at S203), the determining unit 160 determines that at least any one of the adjusting unit 130, the amplification unit 150, and the determining unit 160 has failed (S205), and sends a notification of the failure to the control unit (not shown) or the like so that the failure is displayed on the display unit (not shown) or the like.
Meanwhile, conditions of the sending sensor 112 and the receiving sensor 114 remain the same as those in the adjustment operation. Because failure determination of the sending sensor 112 and the receiving sensor 114 has been made at the adjustment operation, repeated failure determination is omitted from S203.
On the other hand, if the result of determination made by the determining unit 160 is that multi-feed has not occurred (Yes at S203), the receiving sensor 114 receives an ultrasonic wave (an example of “fourth ultrasonic wave”) sent from the sending sensor 112 and reaching the receiving sensor 114 without passing through a sheet, converts the received ultrasonic wave into a voltage (an example of “fourth voltage”) representing the ultrasonic wave, and outputs the voltage to the adjusting unit 130.
Thereafter, the adjusting unit 130 adjusts the voltage, into which the ultrasonic wave is converted by the receiving sensor 114, according to the setting adjusted by the adjustment control unit 140 and outputs the adjusted voltage to the amplification unit 150 (S207). More specifically, at S207, the adjusting unit 130 adjusts (decreases) the voltage, into which the ultrasonic wave is converted by the receiving sensor 114, to a voltage value obtained by subtracting, from the value of the voltage adjusted according to the setting adjusted by the adjusting control unit 140 through the adjustment operation, a voltage value corresponding to a minimum amount of attenuation of the ultrasonic wave possibly caused by the factor of the two sheets from when the ultrasonic wave is sent from the sending sensor 112 until when the ultrasonic wave is received by the receiving sensor 114, and outputs the thus-adjusted voltage value to the amplification unit 150. It is assumed that the setting for adjusting the voltage, into which the ultrasonic wave is converted by the receiving sensor 114, to such a voltage value as that described above has been configured by the adjustment control unit 140 after S203.
The adjustment described above causes the adjusting unit 130 to output a value that is to be output in a condition where the factor of the two sheets minimizes the amount of attenuation of the ultrasonic wave received by the receiving sensor 114. Accordingly, because the determining unit 160 can make a pseudo determination that multi-feed has occurred, the determining unit 160 can make the failure determination.
Thereafter, the amplification unit 150 amplifies the voltage adjusted by the adjusting unit 130 by the preset multi-feed-determining amplification factor and outputs the amplified voltage to the determining unit 160.
Thereafter, the determining unit 160 compares a value derived from the voltage amplified by the amplification unit 150 with a value derived from the upper-limit output value. The determining unit 160 determines that multi-feed has not occurred if the value derived from the voltage amplified by the amplification unit 150 is equal to or higher than the value derived from the upper-limit output value, but determines that multi-feed has occurred if the value is lower than the value derived from the upper-limit output value (S209).
As described above, the adjusting unit 130 outputs the value that is to be output in the condition where the factor of the two sheets minimizes the amount of attenuation of the ultrasonic wave received by the receiving sensor 114. Accordingly, the result of determination made by the determining unit 160 should be that multi-feed has occurred without exception. If the result of determination made by the determining unit 160 should be that multi-feed has not occurred (No at S209), the determining unit 160 determines that at least any one of the adjusting unit 130, the amplification unit 150, and the determining unit 160 has failed (S211), and sends a notification of the failure to the control unit (not shown) or the like so that the failure is displayed on the display unit (not shown) or the like. Examples of failure of the amplification unit 150 include anomalous origination from an operational amplifier.
Meanwhile, conditions of the sending sensor 112 and the receiving sensor 114 remain the same as those in the adjustment operation. Because failure determination of the sending sensor 112 and the receiving sensor 114 has been made at the adjustment operation, repeated failure determination is omitted from S209.
On the other hand, if the result of determination made by the determining unit 160 is that multi-feed has occurred (Yes at S209), the determining unit 160 determines that the adjusting unit 130, the amplification unit 150, and the determining unit 160 are normal (S213).
Thereafter, the adjustment control unit 140 brings the setting of the adjusting unit 130 back to the setting adjusted in the adjustment operation.
As described above, according to the embodiment, because the adjusting unit 130 adjusts variation in the ultrasonic wave caused by the factor other than the factor of the sheet, the amplification unit 150 can use a fixed amplification factor. Accordingly, according to the embodiment, an undesirable situation that characteristics of a noise filter in the amplification unit 150 are changed or undesirable oscillation of the operational amplifier that would otherwise occur in multi-feed determination can be prevented. As a result, accuracy in multi-feed determination can be further increased.
According to the embodiment, variation in the ultrasonic wave caused by the factor other than the factor of the sheet is adjusted using the adjusting unit 130 by adjusting the setting of the adjusting unit 130. Accordingly, even if the sending sensor 112, the receiving sensor 114, or the like is replaced after shipment of the sheet conveying device 100 and positional relationship has changed from before the replacement, variation in ultrasonic wave caused by the factor other than the factor of the sheet can be reduced by adjusting the setting of the adjusting unit 130.
According to the embodiment, the setting of the adjusting unit 130 is adjusted in a state where no sheet is conveyed by the sheet conveying device 100, in contrast to the technique disclosed in Japanese Laid-open Patent Application No. 2006-312527 in which the amplification factor is adjusted during sheet conveyance. Accordingly, enhancing productivity of printed matter and the like can also be achieved.
According to the embodiment, whether or not a failure has occurred in elements upstream of the adjusting unit 130 can be determined by adjusting the setting of the adjusting unit 130. Accordingly, considerable reduction in time required to locate a position where a failure has occurred can be achieved.
According to the embodiment, whether or not a failure has occurred in elements downstream of the adjusting unit 130 can be determined by performing the failure determination operation of making a pseudo determination that multi-feed has occurred after the adjustment operation that adjusts the setting of the adjusting unit 130. Accordingly, considerable reduction in time required to locate a position where a failure has occurred can be achieved.
Modifications
The embodiment may be modified so that the adjustment operation is performed in the following manner. The adjustment control unit 140 adjusts the voltage adjusted by the adjusting unit 130 simply to a voltage within the range from the first reference value, inclusive, to the second reference value, exclusive rather than adjusting the output voltage of the adjusting unit 130 to the predetermined voltage value within the range.
In this case, the preset multi-feed-determining amplification factor is preferably an amplification factor for amplifying a voltage, into which an ultrasonic wave sent from the sending sensor 112 and received by the receiving sensor 114 after passing through one sheet in a condition where both the factor other than the factor of the sheet and the factor of the sheet maximize the amount of attenuation is converted by the receiving sensor 114, to the upper-limit output value of the amplification unit 150 and is smaller than an amplification factor for amplifying a voltage, into which an ultrasonic wave sent from the sending sensor 112 and received by the receiving sensor 114 after passing through two sheets in a condition where both the factor other than the factor of the sheet and the factor of the sheet minimize the amount of attenuation is converted by the receiving sensor 114, to the upper-limit output value of the amplification unit 150.
The embodiment may be modified to use the first reference value and the second reference value described below which differ from those of the embodiment. The second reference value of the modification is a voltage value obtained by subtracting, from the voltage value representing the ultrasonic wave sent from the sending sensor 112, a voltage value corresponding to a minimum amount of attenuation of the ultrasonic wave possibly caused by the factor other than the factor of the sheet in the period until when the ultrasonic wave is received by the receiving sensor 114. The first reference value of the modification is a voltage value within a range between the second reference value and a voltage value obtained by subtracting, from the voltage value representing the ultrasonic wave sent from the sending sensor 112, a voltage value corresponding to a maximum amount of attenuation of the ultrasonic wave possibly caused by the factor other than the factor of the sheet until when the ultrasonic wave is received by the receiving sensor 114. In this case, the adjustment control unit 140 may preferably adjust the setting of the adjusting unit 130 by increasing the voltage rather than decreasing the voltage by setting the first reference value after setting the second reference value in contrast to the embodiment in which the first reference value is set before the second reference value.
Hardware Configuration
The controller 910 includes a CPU (central processing unit) 911, an NB (north bridge) 913, a system memory (MEM-P) 912, an SB (south bridge) 914, a local memory (MEM-C) 917, an ASIC (application specific integrated circuit) 916, an HDD (hard disk drive) 918, and an AGP (accelerated graphics port) bus 915. The AGP bus 915 connects between the NB 913 and the ASIC 916. The MEM-P 912 includes a ROM (read only memory) 912a and a RAM (random access memory) 912b.
The CPU 911 provides overall control of the image forming apparatus 900 and includes a chipset made up of the NB 913, the MEM-P 912, and the SB 914. The CPU 911 is connected to other equipment via the chipset.
The NB 913 that bridges the CPU 911 to the MEM-P 912, the SB 914, and the AGP bus 915 includes a PCI master, an AGP target, and a memory controller that controls writing and reading to and from the MEM-P 912.
The MEM-P 912 is a system memory for use as a memory for storing program instructions and data, a memory into which program instructions and data are to be loaded, a memory for printer buffer, and the like, and includes the ROM 912a and the RAM 912b. The ROM 912a is a read only memory for use as the memory for storing program instructions and data. The RAM 912b is a writable and readable memory for use as the memory into which program instructions and data are to be loaded, the memory for printer buffer, and the like.
The SB 914 bridges the NB 913 to a PCI device and a peripheral device. This SB 914 is connected to the NB 913 via the PCI bus. A network I/F (interface) and the like can also be connected to the PCI bus.
The ASIC 916 is an IC (integrated circuit) for image processing and includes hardware elements for the image processing. The ASIC 916 serves as a bridge that connects the AGP bus 915, the PCI bus, the HDD 918, and the MEM-C 917 to each other. This ASIC 916 includes a PCI target and an AGP master, an ARB (arbiter) serving as the core of the ASIC 916, a memory controller that controls the MEM-C 917, a plurality of DMACs (direct memory access controllers) that perform image data rotation and the like by hardware logic or the like, and a PCI unit that transfers data to and from the engine unit 960 via the PCI bus. An FCU (facsimile control unit) 930, a USB (universal serial bus) 940, and an IEEE 1394 (the Institute of Electrical and Electronics Engineers 1394) I/F 950 are connected to the ASIC 916 via the PCI bus. The operating-and-display unit 920 is directly connected to the ASIC 916.
The MEM-C 917 is a local memory for use as an image buffer for the copier function and a code buffer. The HDD 918 is storage for storing image data, program instructions, font data, and forms.
The AGP bus 915 is a bus interface for a graphics accelerator card introduced to speed up graphics operations. The AGP bus 915 allows direct access to the MEM-P 912 with a high throughput, thereby speeding up operations related to the graphic accelerator card.
According to an embodiment, accuracy in multi-feed determination can be increased.
Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.
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