JP5962097B2 - Recording material discrimination sensor and image forming apparatus - Google Patents

Description

  The present invention relates to a recording material discrimination sensor and an image forming apparatus, and in particular, a light emitting element for irradiating a recording material with light, a driving unit for controlling the light emission amount of the light emitting element, and reflection from the recording material. A recording material discrimination sensor comprising: a light receiving element for receiving light or transmitted light; and a discrimination unit for discriminating the type of the recording material based on a light detection signal of the light receiving element, and the recording material discrimination sensor. The present invention relates to an image forming apparatus provided.

  For example, in an image forming apparatus such as MPF (Multi Function Printers), it is known that the quality of a printed image is improved by controlling the temperature of a fixing heater according to the type of recording material. There is an image forming apparatus provided with a recording material discrimination sensor that can discriminate the type of recording material (see, for example, Patent Document 1).

  In Patent Document 1, light is emitted from a light emitting element such as an LED element (Light Emitting Diode) to a recording material, and reflected light and transmitted light from the recording paper are received by a light receiving element such as a phototransistor. A configuration for discriminating a recording material by detecting a difference in received light amount due to the type is disclosed. Japanese Patent Application Laid-Open No. H10-260260 discloses that by performing fixing under an optimal fixing condition corresponding to a recording material, it is possible to obtain an optimal fixed image when using various recording materials.

  Incidentally, it is known that the light emitting characteristics of the light emitting elements and the light receiving characteristics of the light receiving elements vary from part to part. Therefore, calibration is performed in the recording material discrimination sensor. For example, Patent Document 2 discloses the use of a single reference sheet formed by connecting three types of paper pieces having predetermined dimensions, which are plain paper, an OHP (Over Head Projector) sheet, and photo paper. . A configuration is disclosed in which the reference paper is transported to a position facing the paper sensor by a paper feed mechanism, and calibration is sequentially performed on plain paper, an OHP sheet, and photo paper. Thus, Patent Document 2 discloses that speeding up and facilitating calibration of the recording material discrimination sensor is realized.

  A conventional recording material discrimination sensor absorbs and adjusts component variations and the like of a light emitting element and a light receiving element by performing calibration using a reference recording material. For example, when the light emitting element is an LED element, calibration is performed by adjusting the magnitude of the direct current supplied to the LED. This calibration is generally performed at the time of shipment of an image forming apparatus provided with a recording material discrimination sensor.

  However, the light emission characteristics of the light emitting element and the light receiving characteristics of the light receiving element change over time. Further, due to dirt such as paper dust, the intensity of light irradiated on the recording material and the intensity of light incident on the light receiving element may be reduced. When the light detection signal of the light receiving element is lowered due to such a phenomenon, the conventional recording material discrimination sensor has a problem that calibration cannot be performed properly.

  An object of the present invention is to provide a recording material discrimination sensor capable of executing appropriate calibration even when a light detection signal of a light receiving element is lowered.

The recording material discrimination sensor according to the present invention includes a light emitting element for irradiating the recording material with light, a drive unit for controlling the light emission amount of the light emitting element, and the reflected or transmitted light from the recording material. a light receiving element for, in a recording medium determination sensor, comprising: a determination unit, a to determine the type of the recording medium based on the light detection signal of the light receiving element, the light emitting device to increase the current that will be supplied The light emission amount increases accordingly, and the driving unit can switch the light emitting element between direct current driving and pulse driving to emit light, and the determination unit can detect the light irradiation position of the light emitting element. Whether or not the light detection signal of the light receiving element has become a predetermined magnitude at the time of calibration in which the light emission amount of the light emitting element is changed in a state where a reference recording material for calibration is disposed or in a state where nothing is disposed A calibration unit for determining The drive unit, during the calibration, before SL when the said calibrating unit be changed amount of light emitted from the light emitting device does not determine that the light detection signal of the light receiving element becomes the predetermined size of the signal, The light emission amount of the light emitting element is changed by switching between the direct current drive and the pulse drive .

  When the recording material discrimination sensor of the present invention does not obtain a light detection signal of a light receiving element of a predetermined size even when the light emitting element emits light by direct current driving within a predetermined direct current allowable range during calibration, The light emitting element is caused to emit light by pulse driving within a predetermined pulse current allowable value range constituted by a pulse current having a value larger than the direct current allowable value, thereby increasing the light emission amount of the light emitting element. Thereby, the recording material discrimination sensor of the present invention can execute an appropriate calibration even when the light detection signal of the light receiving element is lowered.

It is a block diagram for demonstrating one Example of the recording material discrimination | determination sensor of this invention. FIG. 2 is a schematic configuration diagram for explaining an example of an optical unit of the recording material discrimination sensor in FIG. 1. FIG. 6 is a schematic side view for explaining another example of the optical unit of the recording material discrimination sensor in FIG. 1. FIG. 4 is a schematic perspective view of the optical unit shown in FIG. 3. 3 is a flowchart for explaining an example of an operation at the time of calibration of the recording material discrimination sensor shown in FIG. 1. It is a figure for demonstrating the relationship between the maximum permissible forward current and ambient temperature in a certain LED element. It is a figure for demonstrating the relationship between the electric current application method to the light emitting element at the time of calibration, and an applied electric current. It is a figure for demonstrating an example of the light emission timing of a light emitting element, and the reading timing of the photon detection signal of a light receiving element. It is a schematic block diagram for demonstrating the further another example of the optical unit used for a recording material discrimination | determination sensor. It is a schematic block diagram for demonstrating the further another example of the optical unit used for a recording material discrimination | determination sensor. 1 is a schematic configuration diagram for explaining an embodiment of an image forming apparatus.

  FIG. 1 is a block diagram for explaining an embodiment of the recording material discrimination sensor of the present invention. FIG. 2 is a schematic configuration diagram for explaining an example of the optical unit of this embodiment. FIG. 3 is a schematic side view for explaining another example of the optical unit of the embodiment. FIG. 4 is a schematic perspective view of the optical unit shown in FIG.

First, an example of the optical unit will be described with reference to FIG. The optical unit 1 includes a light emitting element 3, a light receiving element 5, and apertures 7 and 9.
The light emitting element 3 is driven by a direct current, and the amount of light emission increases as the supplied direct current increases. The light emitting element 3 is configured by, for example, an LED element, a semiconductor laser element, or an organic EL (Electro Luminescence) element. In this embodiment, the light emitting element 3 is constituted by an LED element.

  The light receiving element 5 outputs a photocurrent corresponding to the amount of received light as a detection signal. The light receiving element 5 is constituted by, for example, a phototransistor or a photodiode. In this embodiment, the light receiving element 5 is constituted by a P-channel transistor.

The aperture 7 has one hole for correcting the optical axis. The aperture 7 regulates the optical path of the light emitted from the light emitting element 3 to the optical paths L1 and L1 ′.
The reflection member 11 is disposed on the optical path L1 ′. The reflecting member 11 is made of, for example, a white plate. The reflecting member 11 is used instead of the reference recording material at the time of calibration. The reflection member 11 may have any material and shape as long as it can reflect the light from the light emitting element 3. Further, if the reference recording material is used at the time of calibration, the reflecting member 11 may not be provided.

  The recording material 13 is conveyed on the optical path L1 by a recording material conveyance system (not shown). The optical path L1 intersects the surface of the recording material 13 at the optical axis intersection 15. The angle formed by the perpendicular line 17 and the optical path L1 with respect to the surface of the recording material 13 is, for example, 80 degrees.

  The aperture 9 has one hole for correcting the optical axis. The aperture 9 restricts the optical path of the light received by the light receiving element 5 to the optical paths L2 and L2 '. The light reflected at the optical axis intersection 15 is received by the light receiving element 5 through the optical path L2. The angle formed by the perpendicular line 17 and the optical path L2 is, for example, 80 degrees. Therefore, the angle formed by the optical path L1 and the optical path L2 is, for example, 160 degrees. Further, the light reflected by the reflecting member 11 is received by the light receiving element 5 through the optical path L2 '.

  Another example of the optical unit will be described with reference to FIGS. In FIGS. 3 and 4, the same reference numerals are given to portions that perform the same functions as those in FIG. 2. 3 and 4, the illustration of the reflecting member 11 and the optical paths L1 'and L2' is omitted.

  In this optical unit 1, the light receiving element 5 is a flat type unlike the bullet type (see FIG. 2). However, the function of the light receiving element 5 is the same regardless of whether the outer shape is a bullet type or a planar type.

  For example, fixing screw holes 19 and 21 are provided on both sides of the optical unit body 1a made of resin. By providing the fixing screw holes 19 and 21, the gap between the optical unit 1 and the recording material 13 (not shown in FIG. 4) can be adjusted. The emitted light from the light emitting element 3 strikes the recording material 13 at the optical axis intersection 15 through the optical path L1. The light reflected at the optical axis intersection 15 on the recording material 13 enters the light receiving element 5 through the optical path L2.

  The light emitting element 3 is held by a light emitting element holder 23 and fixed to the optical unit main body 1a. The aperture 7 is held in a groove formed in the optical unit main body 1 a so as to restrict the optical path of the light emitted from the light emitting element 3, and is fixed by a guide pin 25. The aperture 9 is held in a groove formed in the optical unit main body 1 a so as to restrict the optical path of light received by the light receiving element 5, and is fixed by a guide pin 27. The light receiving element 5 is held by a light receiving element holder 29 and fixed to the optical unit main body 1a.

An embodiment of the recording material discrimination sensor will be described with reference to FIG.
The recording material discrimination sensor 31 includes the optical unit 1, the reflection member 11, the drive unit 33, and the discrimination unit 35.

  The drive unit 33 is for controlling the light emission amount of the light emitting element 3. The drive unit 33 can emit light by switching the light emitting element 3 between direct current driving and pulse driving. The drive unit 33 includes a current setting circuit 37, a constant current circuit 39, a determination switching circuit 41, a frequency change circuit 43, a duty change circuit 45, and a light emitting element drive circuit 47.

The drive unit 33 is configured to drive the light emitting element 3 by DC driving using a DC current value within a predetermined DC current allowable range or a frequency, a duty ratio, and a pulse current value within a predetermined pulse current allowable range. The light emitting element 3 emits light by the pulse driving used. In this embodiment, the range of the allowable pulse current value is set by fixing the frequency and the duty ratio and changing only the pulse current value. That is, only the pulse current values of the plurality of pulse currents included in the range of allowable pulse current values are different from each other.

  However, in the recording material discrimination sensor of the present invention, the plurality of pulse currents included in the range of the allowable pulse current value may have different frequencies or may have different duty ratios.

  Note that the pulse current included in the range of allowable pulse current values is a value larger than the maximum DC current value included in the range of allowable DC current values (hereinafter, also simply referred to as allowable DC current value). The pulse current value is

  The current setting circuit 37 sets a current value of a direct current or a pulse current applied to the light emitting element 3. The constant current circuit 39 generates a direct current according to the current value set by the current setting circuit 37 as a constant current.

  The determination switching circuit 41 determines whether or not the direct current generated by the constant current circuit 39 is within a predetermined direct current allowable value range or a predetermined pulse current allowable value range. The determination switching circuit 41 switches between direct current driving and pulse driving.

  When the pulse current value is set by the current setting circuit 37, the frequency changing circuit 43 sets the frequency for pulse driving to a certain frequency of, for example, 50 Hz (Hertz) or more. The duty changing circuit 45 sets the duty ratio in pulse driving to 5%, for example.

  The light emitting element drive circuit 47 applies the light emitting element 3 DC constant current or pulse current based on the current value set by the current setting circuit 37 and the DC drive or pulse drive selected by the determination switching circuit 41.

  The light emitted from the light emitting element 3 is applied to the reflecting member 11. The light reflected by the reflecting member 11 is received by the light receiving element 5. A photocurrent (photodetection signal) corresponding to the amount of received light is generated in the light receiving element 5.

  The determination unit 35 is for determining the type of the recording material 13 based on the light detection signal of the light receiving element 5. In addition, the determination unit 35 includes a current-voltage conversion circuit (amplification unit) 49, a recording material determination circuit 51, and a calibration unit 53.

  The current-voltage conversion circuit 49 converts the photocurrent generated in the light receiving element 5 into a voltage. The current-voltage conversion circuit 49 includes an operational amplifier 55, a feedback resistor 57, a filter capacitor 59, and a reference voltage 61. The value of the feedback resistor 57 determines the current-voltage conversion rate. The filter capacitor 59 and the feedback resistor 57 constitute a low-pass filter. The current-voltage conversion circuit 49 is also configured to change the amplification factor of the operational amplifier 55 by increasing the value of the feedback resistor 57.

The output of the operational amplifier 55 that is the output of the current-voltage conversion circuit 49 is input to the recording material discrimination circuit 51 and the calibration unit 53.
The recording material discriminating circuit 51 discriminates the type of the recording material based on the magnitude of the output voltage of the operational amplifier 55.

  The calibration unit 53 determines whether or not the photocurrent of the light receiving element 3 has reached a predetermined magnitude based on the magnitude of the output voltage of the operational amplifier 55 during calibration. At the time of calibration, the reflection member 11 is irradiated with light while the magnitude of the direct current supplied by the drive unit 33 is changed and the light emission amount of the light emitting element 3 is changed.

  The calibration unit 53 includes a received light amount comparison circuit 63 and a reference voltage 65. The output of the operational amplifier 55 is input to the received light amount comparison circuit 63. The reference voltage 65 is set to a voltage value obtained by converting the amount of reflected light when the reflecting member 11 serving as a reference at the time of calibration is used to convert the photocurrent into a voltage by the current-voltage conversion circuit 49.

  The received light amount comparison circuit 63 determines whether or not the magnitude of the output voltage of the operational amplifier 55 matches the reference voltage 65. The determination result of the received light amount comparison circuit 63 is input to the current setting circuit 37 of the drive unit 33. The received light amount comparison circuit 63 may determine whether or not the magnitude of the output voltage of the operational amplifier 55 is within a predetermined voltage range.

  At the time of calibration, first, the light emitting element 3 emits light by direct current drive by the drive unit 33. The output voltage of the operational amplifier 55 and the reference voltage 65 are compared by the received light amount comparison circuit 63. When the output voltage of the operational amplifier 55 does not reach the reference voltage 65, the applied current is increased in a certain step by the current setting circuit 37. Thereby, the current applied to the light emitting element 3 is increased. The light emission amount of the light emitting element 3 increases, and the light reception amount of the light receiving element 5 increases. When the output voltage of the operational amplifier 55 becomes equal to the reference voltage 65, the calibration is completed.

  If the comparison result of the received light amount comparison circuit 63 does not “match” even if the DC current value applied to the light emitting element 3 is increased to the allowable DC current value, the current setting circuit 37 has a pulse larger than the allowable DC current value. Set the current value. The light emitting element 3 such as an LED element cannot flow a direct current exceeding the allowable direct current value. However, if pulse driving is used, the current supplied to the light emitting element 3 can be increased. If the current supplied to the light emitting element 3 increases, the light emission amount of the light emitting element 3 increases.

  The frequency changing circuit 43 sets a predetermined frequency. The duty changing circuit 45 sets a predetermined duty ratio. The judgment switching circuit 41 switches the applied current from a direct current to a pulse current. A pulse waveform configured with the set frequency and duty ratio is current-amplified by the light-emitting element driving circuit 47 and applied to the light-emitting element 3.

  The reflection member 11 is irradiated with the light emitted from the light-emitting element 3 that is pulse-driven. The light reflected by the reflecting member 11 is received by the light receiving element 5. The photocurrent generated in the light receiving element 5 is converted into a voltage by the current-voltage conversion circuit 49. The voltage is compared with the reference voltage 65 by the received light amount comparison circuit 63.

  If the comparison result of the received light amount comparison circuit 63 is “mismatch”, the current setting circuit 37 increases and sets the pulse current value to be applied. First, the frequency set by the frequency conversion circuit 43 is set to a fixed frequency, and the duty ratio of the pulse current is increased by the duty conversion circuit 45. Thereby, the applied pulse current is increased. As the pulse current value increases, the light emission amount of the light emitting element 3 increases, and the light reception amount in the light receiving element 5 and the output voltage of the current-voltage conversion circuit 49 also increase. The output voltage of the current-voltage conversion circuit 49 and the reference voltage 65 are compared by the received light amount comparison circuit 63.

  For example, as long as the comparison result of the received light amount comparison circuit 63 is “mismatch”, the duty ratio is increased and the pulse application current is increased. If the comparison result of the received light amount comparison circuit 63 is still “inconsistent” even if the duty ratio is increased to a certain set value, the frequency is changed by the frequency changing circuit 43 and the duty changing circuit 45 sets the initial duty ratio. A ratio is set.

Based on the set frequency and duty ratio, the changed frequency is fixed, and the duty ratio is sequentially changed until the comparison result of the received light amount comparison circuit 63 becomes “match”. When the comparison result of the received light amount comparison circuit 63 becomes “match”, the calibration is terminated.
Limit values are set for the change widths of the frequency change circuit 43 and the duty change circuit 45. As a result, the light emitting element 3 is prevented from being destroyed.

  After the calibration operation is completed, when the type of the recording material 13 conveyed to the light irradiation position of the light emitting element 3 is determined, the drive unit 33 determines that the comparison result of the received light amount comparison circuit 63 is “match”. The light emitting element 3 is caused to emit light using the driving conditions of the light emitting element 3.

  FIG. 5 is a flowchart for explaining an example of the operation at the time of calibration of the recording material discrimination sensor shown in FIG. This calibration operation will be described with reference to FIGS.

  The initial value direct current is set by the current setting circuit 37 (step S1). It is determined whether the set direct current value is equal to or less than a predetermined direct current allowable value (step S2). When the DC current is less than the allowable value (YES), an initial DC current is applied to the light emitting element 3 by the constant current circuit 39, the determination switching circuit 41, and the light emitting element driving circuit 47. The light emitting element 3 emits light and the reflecting member 11 is irradiated with light. The light receiving element 5 receives the reflected light from the reflecting member 11.

  The current-voltage conversion circuit 49 converts the photocurrent generated in the light receiving element 5 into a voltage. The received light amount comparison circuit 63 compares the converted photocurrent voltage with the reference voltage 65 (step S4). When the comparison result of the received light amount comparison circuit 63 is “match” (YES), the calibration is completed.

  If the comparison result of the received light amount comparison circuit 63 is “mismatch” in step S4 (NO), the current setting circuit 37 determines whether the current applied to the light emitting element 3 is a direct current or a pulse current. (Step S5). When the current is a direct current (YES), the current setting circuit 37 increases the direct current applied to the light emitting element 3 by a certain current step (step S6).

  Returning to step S2, it is determined whether or not the direct current value set in step S6 is equal to or smaller than a predetermined direct current allowable value. If the current is less than the allowable value (YES), the process proceeds to steps S3 and S4. Until it is determined in step S4 that the comparison result of the received light amount comparison circuit 63 is “match”, or until it is determined in step S2 that the set DC current value has exceeded a predetermined DC current allowable value, step S2 To S6 are repeated.

  If it is determined in step S2 that the set DC current value exceeds a predetermined DC current allowable value (NO), the current setting circuit 37 sets a pulse current as a current to be applied to the light emitting element 3 (step S7). . The current setting circuit 37 sets the initial pulse current value, the frequency changing circuit 43 sets the initial frequency, and the duty changing circuit 45 sets the initial duty ratio (step S8). The set pulse current value is larger than the direct current allowable value.

  It is determined whether the set pulse current (pulse current value, frequency, duty ratio) is equal to or less than a predetermined allowable pulse current value (step S9). In this embodiment, since the frequency and the duty ratio are fixed, it is determined whether the pulse current value is a predetermined value or less. When the set pulse current exceeds the allowable pulse current value (NO), a calibration error is displayed (step S10), and the calibration ends. Usually, since the initial pulse current is set to be equal to or less than the allowable pulse current value, the calibration does not end at this stage.

  In step S9, when the set pulse current is equal to or less than a predetermined allowable pulse current value (YES), an initial value pulse current is applied to the light emitting element 3 by the light emitting element driving circuit 47 (step S3). Since the applied pulse current value is larger than the direct current allowable value, the light emission amount of the light emitting element 3 increases. Light emitted from the light emitting element 3 and reflected by the reflecting member 11 is received by the light receiving unit 5.

  In step S4, the current-voltage conversion circuit 49 compares the output voltage of the received light amount comparison circuit 63 with the reference voltage 65. When the comparison result of the received light amount comparison circuit 63 is “match” (YES), the calibration is completed.

  When the comparison result of the received light amount comparison circuit 63 in step S4 is “mismatch” (NO), it is determined in step S5 whether the applied current is a direct current or a pulse current. When it is a pulse current (NO), the current setting circuit 37 increases the pulse current value applied to the light emitting element 3 by a certain current step and sets it (step S11).

  Returning to step S9, it is determined whether the pulse current value set in step S11 is equal to or less than a predetermined allowable pulse current value. If the current is less than the allowable value (YES), the process proceeds to steps S3 and S4. Until it is determined in step S4 that the comparison result of the received light amount comparison circuit 63 is “match”, or in step S10, it is determined that the set pulse current value exceeds the predetermined allowable pulse current value. , S3, S4, S5 and S10 are repeated in that order.

  In step S9, when it is determined that the set pulse current value exceeds the predetermined allowable pulse current value (NO), a calibration error is displayed (step S10), and the calibration ends.

  In this calibration operation, the frequency and duty ratio of the pulse current applied to the light emitting element 3 are fixed, and the pulse current value is changed. However, in the recording material discrimination sensor of the present invention, the method for changing the pulse current is not limited to this. The recording material discrimination sensor of the present invention may change the light emission amount of the light emitting element by changing the pulse current value, frequency or duty ratio, or a combination thereof with respect to the pulse current applied to the light emitting element.

  The maximum allowable forward current of the light emitting element 3 varies depending on the type of product. Further, the maximum allowable forward current of the light emitting element 3 differs depending on whether the applied current is a direct current or a pulse current. Furthermore, when the applied current is a pulse current, the maximum allowable forward current (pulse current value) varies depending on the frequency and the duty ratio.

  FIG. 6 is a diagram for explaining the relationship between the maximum allowable forward current (IF) and the ambient temperature (Ta) in a certain LED element. In FIG. 6, the vertical axis represents the maximum allowable forward current (unit: mA (milliampere)), and the horizontal axis represents ambient temperature (unit: ° C.).

  When the current applied to the LED element is a direct current (DC), the direct current allowable value is allowed to be 50 mA from an ambient temperature of −40 ° C. (point a) to 25 ° C. (point b). The allowable current value gradually decreases from the ambient temperature of 25 ° C. (point b) to the high temperature side. When the ambient temperature is 85 ° C. (point c), the allowable direct current value is 10 mA.

  When the current applied to the LED element is a pulse current with a frequency of 50 Hz and a duty ratio of 5% (Duty = 5%), the allowable pulse current value is from ambient temperature −40 ° C. (point d) to ambient temperature 25 ° C. (point e). ) Is allowed up to 200 mA. From the ambient temperature of 25 ° C. (point e), the allowable current value gradually decreases on the high temperature side. The allowable pulse current at an ambient temperature of 85 ° C. (point f) is 40 mA.

  When the current applied to the LED element is a pulse current with a frequency of 50 Hz and a duty ratio of 20% (Duty = 20%), the allowable pulse current ranges from an ambient temperature of −40 ° C. (g point) to an ambient temperature of 25 ° C. (h point). ) Is allowed up to 105 mA. From the ambient temperature of 25 ° C. (point h), the allowable pulse current gradually decreases on the high temperature side. The allowable pulse current value at an ambient temperature of 85 ° C. (point i) is 20 mA.

  For example, when the operating temperature range of a copying machine equipped with a recording material discrimination sensor is approximately 0 ° C. to 50 ° C., derating at an ambient temperature Ta = 50 ° C. is required. For example, regarding the current allowable value at an ambient temperature of 50 ° C., the direct current (DC) is the maximum direct current allowable value IF_DC50 = 33 mA, and the pulse current (Duty = 20%) is the maximum allowable pulse current IF_P50 = 133 mA.

For example, when 70% of the maximum allowable current value is set as the allowable current value when the LED element is used, the allowable direct current value IFa_DC50 is approximately 33 mA × 0.7 = 23 mA. The allowable pulse current value IFa_P50 (Duty = 5%) is about 133 mA × 0.7 = 93 mA.
Therefore, if the light emitting element is caused to emit light by pulse driving using a current value larger than that during direct current driving, the instantaneous light emission amount of the light emitting element can be increased as compared with direct current driving.

  FIG. 7 is a diagram for explaining the relationship between the method of applying a current to the light emitting element and the applied current during calibration. The vertical axis represents the applied current IFa of the light emitting element, and the horizontal axis represents time.

  The DC drive section (DC) is from time a1 to time b1. At the start of calibration (time a1), a DC current having an initial current value (point j) is applied to the light emitting element. The current value applied to the light emitting element is increased in a certain step, and reaches the direct current allowable value (IFa_DC50) at time b1 (point k).

  The pulse drive section (pulse) is from time b1 to time d1. At time d1, the allowable pulse current value is IFa_P50. A pulse current is applied from the direct current allowable value IFa_DC50 (k point). The pulse current value is increased at the frequency and duty ratio set as initial values. For example, at the pulse current value (point l) at time c1, the comparison result between the output voltage of the operational amplifier 55 and the reference voltage 65 becomes “match” in the received light amount comparison circuit 63, and the calibration is completed (also in FIG. 1). reference.).

  In the above embodiment, the light detection signal of the light receiving element 5 is changed by changing the pulse current while fixing the frequency and duty ratio in the pulse driving of the light emitting element 3, but the present invention is not limited to this. .

  For example, the light detection signal of the light receiving element 5 may be changed by fixing the frequency and the pulse current value and changing the duty ratio. In this case, the duty ratio may be changed from a large value to a small value, or vice versa.

  For example, consider a case where a maximum current allowable value (pulse current value) is 70 mA when a frequency is 50 Hz and a duty ratio is 90% for a light emitting element constituted by a certain LED element. Considering that about 70% of the maximum allowable current value is set as the allowable current value, the pulse current value is set to 50 mA. When the drive unit changes the light emission amount of the light emitting element by pulse driving, the frequency (50 Hz) and the pulse current value (50 mA) are fixed, and the duty ratio is changed within a range of 5% to 90%, for example. The device emits light. The pulse current value (50 mA) here is larger than the maximum DC current value (for example, 20 mA) supplied during DC driving.

  Further, the light detection signal of the light receiving element 5 may be changed by fixing the pulse current value and the duty ratio and changing the frequency. In this case, the frequency may be changed from a large value to a small value, or vice versa.

  For example, consider a case where a maximum current allowable value (pulse current value) is 70 mA when a frequency is 100 Hz and a duty ratio is 50% for a light emitting element constituted by a certain LED element. Considering that about 70% of the maximum allowable current value is set as the allowable current value, the pulse current value is set to 50 mA. When changing the light emission amount of the light emitting element by pulse driving, the driving unit fixes the pulse current value (50 mA) and the duty ratio (50%), and changes the frequency within a range of 20 to 100 Hz, for example. To emit light. The pulse current value (50 mA) here is larger than the maximum DC current value (for example, 20 mA) supplied by DC driving.

Further, regarding pulse driving, pulse driving may be performed by changing a plurality of elements among the elements of frequency, duty ratio, and pulse current value.
However, in the recording material discriminating sensor of the present invention, the pulse current value used for the pulse drive is set to a direct current allowable value (the maximum value supplied by the DC drive) in order to increase the light emission amount of the light emitting element compared to the DC drive. It is set to a value larger than (DC current value).

  Moreover, in the said Example, although direct current drive was performed about the drive method of the light emitting element 3, and pulse drive was performed after that, this invention is not limited to this. The recording material discrimination sensor of the present invention may perform pulse driving first and then perform DC driving.

In the embodiment shown in FIG. 1, the light detection signal of the light receiving element 5 is always acquired. The determination unit 35 may synchronize the timing of reading the light detection signal of the light receiving element 5 with the pulse driving timing when the light emitting element 3 emits light by pulse driving.
For example, a switching circuit for controlling the reading timing of the light detection signal of the light receiving element 5 may be disposed between the light receiving element 5 and the operational amplifier 55.

FIG. 8 is a diagram for explaining an example of a pulse current application waveform (light emission timing) of the light emitting element and a reading timing of the light detection signal of the light receiving element.
The pulse current applied to the light emitting element 3 has a period T (frequency = 1 / T) configured by a current application section Ton and a current zero (no application) section Toff. The duty ratio is defined by Ton / T.

  Application of the pulse current is started at the point t1, and the current is cut off at t2 after Ton. Thereafter, the pulse current starts to be applied again at the point t3 after the Toff interval, and the current is interrupted after the Ton interval. At this time, the average current value applied to the light emitting element 3 is IF_AVE1.

  The fixed frequency means that Ton + Toff = T is constant. A case where the duty ratio is changed while the frequency is fixed will be described. When the duty ratio is an initial value, a current is applied at t1, and the current is interrupted at t2 after Ton. When the duty ratio is increased, the current interruption timing extends from t2 to t2a. If the frequency is constant even when the current is cut off at t2a, the current is applied again at t3. At this time, the average current value applied to the light emitting element 3 is IF_AVE2.

  The reading timing of the light output signal of the light receiving element 5 is performed at a timing delayed by a time Td from the timing of the applied current to the light emitting element 3, that is, the light emitting timing of the light emitting element 3. Here, reading of the optical output signal of the light receiving element 5 is started at time t1 ′ delayed by Td from the time t1 when current application to the light emitting element 3 is started. Further, reading is interrupted after the delay time Td has elapsed from the time t2 when the current to the light emitting element 3 is interrupted, that is, at the time t2 'after the time Ton from the time t1'. Based on the light output signal of the light receiving element 5, the amount of reflected light received from the reflecting member 11 is measured.

  By setting the reading timing, the light emitted from the light emitting element 3 can be reliably received by the light reflected by the reflecting member 11. Furthermore, the influence of disturbance noise can be minimized. If the duty ratio is changed, it can be dealt with by adjusting the reading interruption timing. For example, when the current cutoff timing to the light emitting element 3 is T2a, the reading cutoff timing of the light detection signal of the light receiving element 5 is set to T2a 'after the delay timing Td has elapsed from the time T2a.

  FIG. 9 is a schematic configuration diagram for explaining still another example of the optical unit used in the recording material discrimination sensor. Parts having the same functions as those in FIG.

This optical unit further includes an optical component 67 that extracts a part of the light emitted from the light emitting element 3 as monitor light on the optical path L1, and a second light receiving element 69 that receives the monitor light.
The optical component 67 is constituted by a prism, for example. However, the optical component 67 taken out as monitor light is not limited to a prism.
The second light receiving element 69 outputs a photocurrent corresponding to the amount of received light as a detection signal. The second light receiving element 69 is constituted by, for example, a phototransistor or a photodiode.

The calibration operation of the recording material discrimination sensor using this optical unit will be described with reference to FIG. At the time of calibration, the light detection signal of the second light receiving element 69 is converted into a voltage and amplified by the current / voltage conversion circuit 49 and input to the calibration unit 53. The calibration unit 53 compares the output voltage of the current-voltage conversion circuit 49 with the reference voltage 65 to determine whether or not the light detection signal of the second light receiving element 69 is a signal having a predetermined magnitude. The operation of the drive unit 33 at the time of calibration is the same as that of the embodiment described above.
If this optical unit is used, the recording material discrimination sensor can be calibrated without using the reflecting member 11 (see FIG. 1) or the reference recording material.

  FIG. 10 is a schematic configuration diagram for explaining still another example of the optical unit used in the recording material discrimination sensor. Parts having the same functions as those in FIG.

  In this optical unit, the light emitted from the light emitting element 3 is restricted to the optical path L by the aperture 7. The light that has passed through the aperture 7 passes through the recording paper 13 and enters the light receiving element 5 through the aperture 9. The aperture 9 restricts the light incident on the light receiving element 5 to the optical path L.

  The configuration of the recording material discrimination sensor using this optical unit is the same as the configuration shown in FIG. The recording material discrimination sensor discriminates the type of the recording paper 13 based on the light detection signal of the light receiving element 5 that has received the transmitted light of the recording paper 13.

  In the recording material discrimination sensor for discriminating the type of the recording paper 13 based on the transmitted light of the recording paper 13, the calibration is performed by using a reference recording paper as a reference or in the optical path L (see FIG. 10). It is performed in a state where it is not arranged. The calibration operation is the same as when calibration is performed based on the reflected light.

  In the optical unit shown in FIG. 10, similarly to the optical unit shown in FIG. 9, an optical component that extracts a part of the light emitted from the light emitting element 3 as monitor light in the optical path L, and monitor light And a second light receiving element that receives the light.

FIG. 11 is a schematic configuration diagram for explaining an embodiment of the image forming apparatus.
A recording material conveying means 71 having a plurality of rollers 71a for conveying the recording paper 13 is provided. The recording paper 13 is conveyed by the recording material conveying means 71 in the direction of the white arrow. An image forming unit 73 for forming an image on the recording paper 13 is provided in the middle of the conveyance path of the recording paper 13 conveyed by the recording material conveying unit 71.

  A recording material determination sensor 31 is provided on the upstream side of the image forming position of the image forming unit 73 in the conveyance path of the recording paper 13. The recording material discrimination sensor 31 discriminates the type of the recording paper 13 based on the reflected light from the recording paper 13. The discrimination information of the recording material discrimination sensor 31 is sent to the image forming unit 73. The image forming unit 73 forms an image on the recording paper 13 under appropriate image forming conditions based on the discrimination information from the recording material discrimination sensor 31.

  In this embodiment of the image forming apparatus, the recording material discrimination sensor 31 discriminates the type of the recording paper 13 based on the reflected light from the recording paper 13, but the recording material discrimination sensor detects the transmitted light from the recording paper 13. The type of the recording paper 13 may be determined based on this. Further, the recording material discrimination sensor may discriminate the type of the recording paper 13 based on reflected light and transmitted light from the recording paper 13.

  As mentioned above, although the Example of this invention was described, the numerical value, material, arrangement | positioning, number, etc. in the said Example are examples, This invention is not limited to these, It was described in the claim Various modifications are possible within the scope of the present invention.

  The recording material discrimination sensor according to the present invention includes a light emitting element for irradiating the recording material with light, a driving unit for controlling the light emission amount of the light emitting element, and the reflected or transmitted light from the recording material. A recording material discriminating sensor comprising: a light receiving element for determining the type of the recording material based on a light detection signal of the light receiving element. In the recording material discrimination sensor according to the present invention, the light emitting element has a light emission amount that increases in accordance with an increase in the supplied direct current. The driving unit can emit light by switching the light emitting element between direct current driving and pulse driving. The discriminating unit is configured to adjust the light of the light receiving element at the time of calibration in which the light emission amount of the light emitting element is changed in a state where a reference recording material for calibration is arranged at a light irradiation position of the light emitting element or nothing is arranged. A calibration unit for determining whether or not the detection signal has a predetermined magnitude is provided. Even if the drive unit changes the amount of light emitted from the light emitting element by direct current drive by changing the direct current value within the range of a predetermined direct current allowable value at the time of the calibration, the calibration unit does not change the light of the light receiving element. When it is not determined that the detection signal is a signal having the predetermined magnitude, the pulse current value and the frequency are within a predetermined pulse current allowable range composed of pulse current values larger than the DC current allowable value. Alternatively, the light emission amount of the light emitting element is changed by pulse driving by changing the duty ratio or a combination thereof.

In the recording material discrimination sensor of the present invention, the drive unit changes the pulse current value while fixing the frequency and the duty ratio when the light emission amount of the light emitting element is changed by the pulse drive during the calibration. Examples include changing the light emission amount of the light emitting element by changing the duty ratio by fixing the current value, changing the frequency by fixing the pulse current value and the duty ratio, or a combination thereof.
As described above, regarding pulse driving, if two elements are fixed and the remaining one element is changed among the three elements of frequency, duty ratio, and pulse current value, the range of allowable pulse current values is designed. Becomes easier.
Further, the configuration in which the duty ratio is changed while fixing the frequency and the pulse current value can reduce the secured calibration time.
Further, the configuration in which the pulse current value and the duty ratio are fixed and the frequency is changed can shorten the calibration time.

In the recording material discrimination sensor of the present invention, at the time of calibration, the drive unit first causes the light emitting element to emit light by the pulse drive, and the calibration even if the light emitting element emits light within the range of the pulse current allowable value. When the unit does not determine that the light detection signal of the light receiving element has become the signal having the predetermined magnitude, the light emitting element may emit light by the DC driving.
In this configuration, for example, when the pulse drive is set in the previous calibration operation, the calibration is completed without shifting to the DC drive by performing the pulse drive first, so that the calibration time is shortened.

Note that the decrease in the amount of light received by the light receiving element due to the deterioration of the light emitting ability of the light emitting element is continuous. On the other hand, for example, when dust or the like enters the optical path of the light emitting element or the light receiving element to temporarily reduce the amount of light received by the light receiving element, and then the dust or the like is removed naturally or artificially, The amount of light received is restored. In this case, even if the calibration operation is first performed by pulse driving, the calibration unit does not determine that the light detection signal of the light receiving element has become a predetermined magnitude at the time of pulse driving. Thereafter, appropriate calibration is performed by switching to direct current drive.
In the recording material discrimination sensor of the present invention, when the light emitting element is caused to emit light during calibration, the order of direct current drive and pulse drive is not limited.

In the recording material discrimination sensor of the present invention, the light receiving element receives reflected light from the recording material. The light receiving element receives light reflected by the light emitting element, and reflects light reflected by the light receiving element. A reflection member that is used in place of the reference recording material at the time of calibration may be arranged in advance at a position where light can be received.
This eliminates the need to use a reference recording material.

The recording material discrimination sensor of the present invention may further include an optical component that extracts a part of light emitted from the light emitting element as monitor light, and a second light receiving element that receives the monitor light, and the calibration unit. In the calibration, it may be determined whether or not the light detection signal of the second light receiving element has become a signal having a predetermined magnitude.
Thus, calibration can be performed based on the light detection signal of the second light receiving element without using the reference recording material and the reflecting member.

In the recording material discrimination sensor of the present invention, the discriminating unit synchronizes the timing of reading the light detection signal of the light receiving element with the pulse driving timing when at least the light emitting element emits light by pulse driving. It may be.
By synchronizing the light emission timing of the light emitting element and the reading timing of the light detection signal of the light receiving element, the noise tolerance is improved.

In the recording material discrimination sensor of the present invention, the discrimination unit includes an amplifying unit that amplifies a signal caused by the photodetection signal of the light receiving element, and the driving unit has the DC current allowable value during the calibration. Even if the light emitting element is caused to emit light by the direct current driving within the range and the pulse driving within the range of the allowable pulse current value, the calibration unit causes the light detection signal of the light receiving element to be a signal having the predetermined magnitude. If it is not determined that the gain has been reached, the amplification factor of the amplifying unit may be increased.
As a result, even when the light detection element emits light by pulse driving, even if the light detection signal of the light receiving element does not become a predetermined magnitude, the calibration operation and the recording material discrimination are performed based on the light detection signal that is amplified more greatly. Operation can be performed.

  The configuration of the amplifying unit is not limited to the configuration of the current-voltage conversion circuit 49 shown in FIG. 1, and any configuration is possible as long as it can amplify a signal resulting from the light detection signal of the light receiving element. Also good.

  The image forming apparatus according to the present invention includes the recording material discrimination sensor according to the present invention. Since the recording material discrimination sensor of the present invention can execute appropriate calibration even when the light detection signal of the light receiving element is lowered, it can also appropriately execute discrimination of the recording material after calibration. As a result, the image forming apparatus of the present invention can realize appropriate image formation according to the type of recording material.

  The image forming apparatus of the present invention includes, for example, a recording material conveying means for conveying recording paper, such as a copying machine, a printer, a multifunction peripheral, and a facsimile, an image forming means for forming an image on the recording paper, and an image Any configuration may be used as long as it includes at least the recording material discrimination sensor of the present invention that discriminates the type of recording paper before the image formation by the forming means.

3 Light-Emitting Element 5 Light-Receiving Element 11 Reflecting Member 31 Recording Material Discriminating Sensor 33 Driving Unit 35 Discriminating Unit 49 Current-Voltage Conversion Circuit (Amplifying Unit)
53 Calibration unit 67 Optical component 69 Second light receiving element

JP 2006-023288 A JP 2004-338339 A

Claims (9)

A light emitting element for irradiating light to the recording material, a drive unit for controlling the light emission amount of the light emitting element, a light receiving element for receiving reflected light or transmitted light from the recording material, and the light receiving element In a recording material discrimination sensor comprising: a discrimination unit that discriminates the type of the recording material based on the light detection signal of
The light emitting element is intended to emission amount increases with the increase of the current that will be supplied,
The drive unit is capable of emitting light by switching the light emitting element between direct current drive and pulse drive,
The discriminating unit is configured to adjust the light amount of the light receiving element at the time of calibration in which the light emission amount of the light emitting element is changed in a state where a reference recording material for calibration is disposed at a light irradiation position of the light emitting element or in a state where nothing is disposed. A calibration unit for determining whether or not the detection signal has reached a predetermined magnitude;
The drive unit, during the calibration, before SL when the said calibrating unit be changed amount of light emitted from the light emitting device does not determine that the light detection signal of the light receiving element becomes the predetermined size of the signal, A recording material discrimination sensor, wherein the light emission amount of the light emitting element is changed by switching between the direct current drive and the pulse drive . Even if the driving unit changes the light emission amount of the light emitting element by direct current driving by changing the direct current value within a range of a predetermined direct current allowable value at the time of the calibration, the calibration unit does not change the light of the light receiving element. When it is not determined that the detection signal has become the signal having the predetermined magnitude, the pulse current value and the frequency are within a predetermined pulse current allowable range constituted by a pulse current value larger than the DC current allowable value. The recording material discrimination sensor according to claim 1, wherein the light emission amount of the light emitting element is changed by pulse driving by changing a duty ratio or a combination thereof. Even if the driving unit changes the light emission amount of the light emitting element by pulse driving by changing the pulse current value within a range of a predetermined allowable pulse current value during the calibration, the calibration unit does not change the light of the light receiving element. 2. The recording material discrimination sensor according to claim 1, wherein when it is not determined that the detection signal has become the signal having the predetermined magnitude, the light emission amount of the light emitting element is changed by the direct current drive. 3. The drive unit changes the pulse current value by fixing the frequency and the duty ratio when changing the light emission amount of the light emitting element by the pulse drive during the calibration, and the duty ratio is fixed by fixing the frequency and the pulse current value. The recording material discrimination according to any one of claims 1 to 3 , wherein the light emission amount of the light emitting element is changed by changing, changing a frequency while fixing a pulse current value and a duty ratio, or a combination thereof. Sensor. The light receiving element receives reflected light from the recording material,
A reflecting member that is used in place of the reference recording material at the time of calibration is disposed in advance at a position where light can be emitted by the light emitting element and a position where reflected light can be received by the light receiving element. The recording material discrimination sensor according to any one of 1 to 4 . An optical component for extracting a part of light emitted from the light emitting element as monitor light;
A second light receiving element for receiving the monitor light,
The calibration unit, during the calibration, the recording medium discrimination sensors according photodetection signal from claims 1 determines whether it is a predetermined size of the signal to any one of 4 of the second light-receiving element . The determination unit, when the light emitting element emits light by a pulse driving, according to any one of claims 1 6 to be synchronized with the pulse drive timing to the timing for reading said optical detection signal of the light receiving element Recording material discrimination sensor. The discriminating unit includes an amplifying unit that amplifies a signal caused by the light detection signal of the light receiving element, and at the time of the calibration, the driving unit switches between the direct current driving and the pulse driving to emit light from the light emitting element. when a is the calibration unit be changed does not determine that the light detection signal of the light receiving element becomes the predetermined size of the signal, any one of claims 1 to 7 to increase the amplification factor of the amplifying section The recording material discrimination sensor according to one item. An image forming apparatus having a recording medium discrimination sensor according to any one of claims 1 to 8.

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