JP2022189085A - Detection device - Google Patents

Abstract

To provide a detection device capable of reducing the decrease in the accuracy of adjusting the amount of light emitted from a light-emitting unit.SOLUTION: A phototransistor 38 receives light emitted by a light-emitting diode 37. A controller 58 adjusts the light emission of the light-emitting diode 37 so that the light-reception adjustment voltage corresponding to the light-reception voltage of the phototransistor 38 is a value within a target adjustment range including the target adjustment value in a state where paper is between the light-emitting diode 37 and the phototransistor 38. The controller 58 sets, as the target adjustment range, a predetermined range of width equal to or greater than the light-reception adjustment change amount including the target adjustment value on the basis of the light-reception adjustment change, which is the amount of change in the light-reception adjustment voltage when the light emission of the light-emitting diode 37 is changed by the minimum unit amount in a state where paper is between the light-emitting diode 37 and the phototransistor 38.SELECTED DRAWING: Figure 2

Description

The present invention relates to a detection device for detecting an object to be detected such as paper.

2. Description of the Related Art In a printing apparatus, an optical sensor is used to detect paper being conveyed. Further, the amount of emitted light is adjusted in order to adjust the sensitivity of such sensors (see Patent Document 1).

Specifically, the input voltage to the controller corresponding to the amount of light received by the light-receiving unit is set to a value within the target adjustment range including the target adjustment value while the paper is between the light-emitting unit and the light-receiving unit of the sensor. A controller adjusts the amount of light emitted by the light emitting unit.

In such sensitivity adjustment, the amount of change in the input voltage to the controller when the light emission amount of the light emitting unit is changed by one step in the adjustment resolution is too large, so the input voltage falls within the target adjustment range. In some cases, it may not be possible to adjust the amount of light emitted.

On the other hand, if the target adjustment range is set sufficiently large, it is possible to adjust the amount of light emission so that the input voltage to the controller has a value within the target adjustment range.

JP-A-7-30398

However, if the target adjustment range is set too large, even if the amount of light emission can be adjusted so that the input voltage to the controller falls within the target adjustment range, the input voltage will not reach the target adjustment value. The deviation becomes large, and there is a possibility that the adjustment accuracy of the light emission amount is lowered.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a detection device capable of reducing the decrease in accuracy of adjusting the amount of light emitted from a light emitting unit.

According to one aspect of the present invention, in a state in which a light-emitting portion, a light-receiving portion that receives light emitted by the light-emitting portion, and an object to be detected are between the light-emitting portion and the light-receiving portion, the light-receiving portion a control unit that adjusts the amount of light emitted by the light emitting unit so that the light receiving adjustment voltage corresponding to the light receiving voltage is within a target adjustment range including the target adjustment value, wherein the control unit includes the light emitting unit and the light receiving unit. including the target adjustment value, based on the amount of change in light reception adjustment, which is the amount of change in the light reception adjustment voltage when the light emission amount of the light emitting unit is changed by the minimum unit in a state where an object to be detected is present between A detection device is provided in which a predetermined range having a width equal to or larger than the amount of change in light reception adjustment is set as the target adjustment range.

According to another aspect of the present invention, a light-emitting portion, a light-receiving portion that receives light emitted by the light-emitting portion, a light-receiving load resistor that converts a photocurrent corresponding to the amount of light received by the light-receiving portion into a light-receiving voltage, With an object to be detected between the light emitting unit and the light receiving unit, the light receiving adjustment voltage corresponding to the light receiving voltage converted by the light receiving load resistance is set to a value within the target adjustment range including the target adjustment value. a control unit that adjusts the amount of light emitted by the light emitting unit, wherein the resistance value of the light receiving load resistor minimizes the amount of light emitted by the light emitting unit when an object to be detected is present between the light emitting unit and the light receiving unit. There is provided a detection device characterized in that the amount of change in the light receiving adjustment voltage when changed by a unit amount is set to a value calculated so as to be equal to or greater than a predetermined value within the width of the target adjustment range. be.

According to the detection device of the present invention, it is possible to reduce the deterioration of the adjustment accuracy of the amount of light emitted from the light emitting unit.

1 is a schematic configuration diagram of a printing apparatus provided with a detection device according to a first embodiment; FIG. 1 is a block diagram showing the configuration of a detection device according to a first embodiment; FIG. 3 is a diagram showing circuit configurations of a sheet sensor, a constant current circuit, and a current-voltage converter of the detection device shown in FIG. 2; FIG. 4 is a flowchart of sensitivity adjustment processing; FIG. 10 is a diagram showing changes in light emission current and light reception adjustment voltage in sensitivity adjustment processing; FIG. 10 is a diagram showing changes in the light emission current and the light reception adjustment voltage in the sensitivity adjustment process when the target adjustment range is smaller than the light reception adjustment change amount; FIG. 4 is a diagram showing an example of photoelectric characteristics of a paper sensor; FIG. 5 is a diagram showing an example of distance characteristics between light emission and light reception of a paper sensor; FIG. 4 is an explanatory diagram of discrimination ratios and detection thresholds;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same or equivalent reference numerals are given to the same or equivalent parts and components throughout each drawing.

The embodiments shown below are examples of devices and the like for embodying the technical idea of this invention. are not specific to the following: The technical idea of this invention can be modified in various ways within the scope of claims.

[First embodiment]
FIG. 1 is a schematic configuration diagram of a printing apparatus provided with a detection device according to the first embodiment of the present invention. A path indicated by a thick line in FIG. 1 is a transport path along which the paper W, which is a print medium, is transported. Of the transport paths, the solid line indicates the normal path RC, the one-dot chain line indicates the reverse path RR, the dashed line indicates the discharge path RD, and the two-dot chain lines indicate the external paper feed path RS1 and internal paper feed. It is route RS2. Upstream and downstream in the following description mean upstream and downstream in the conveying route.

As shown in FIG. 1, the printing apparatus 1 includes a paper feeding unit 2, a transport printing unit 3, an upper surface transport unit 4, a paper discharging unit 5, a reversing unit 6, and a housing 7 that accommodates or holds each unit. and

The paper feeding unit 2 feeds the paper W to the transport printing unit 3 . The paper feed unit 2 includes an external paper feed tray 21 , an external paper feed transport section 22 , a plurality of internal paper feed trays 23 , and an internal paper feed transport section 24 .

The external paper feed table 21 is for stacking paper W used for printing. The external paper feed table 21 is installed so that a part thereof is exposed to the outside of the housing 7 .

The external paper feed transport unit 22 takes out the paper W stacked on the external paper feed table 21 and transports the paper W toward the transport print unit 3 along the external paper feed path RS1.

The internal paper feed table 23 is for stacking paper W used for printing. The internal paper feed table 23 is arranged inside the housing 7 .

The internal paper feed transport unit 24 takes out the paper W stacked on the internal paper feed table 23 and transports the paper W toward the transport print unit 3 along the internal paper feed route RS2.

The transport printing unit 3 prints on the paper W while transporting the paper W. As shown in FIG. The transport printing section 3 includes registration rollers 31, a belt platen section 32, a printing section 33, and paper sensors 34A and 34B. Note that the paper sensors 34A and 34B may be collectively described by omitting alphabetic suffixes.

The registration rollers 31 temporarily stop the sheet W conveyed by the sheet feeding section 2 or the reversing section 6 to correct the skew, and then convey the sheet to the belt platen section 32 . The registration rollers 31 are arranged on the normal route RC in the upstream portion of the transport printing section 3 .

The belt platen section 32 conveys the sheet W conveyed by the registration rollers 31 while holding it on the belt.

The printing unit 33 prints an image by ejecting ink onto the paper W conveyed by the belt platen unit 32 . The printing unit 33 includes a plurality of inkjet heads 36 that eject ink.

The paper sensor 34 detects a paper (corresponding to an object to be detected) W to be conveyed. The paper sensor 34 is composed of a light transmission type sensor having a light emitting diode (corresponding to a light emitting section) 37 and a phototransistor (corresponding to a light receiving section) 38 .

The paper sensor 34A is arranged in the vicinity of the upstream side of the confluence point of the external paper feed route RS1, the internal paper feed route RS2, and the reverse route RR, and detects the paper W conveyed through each of these three routes. . The light-emitting diodes 37 of the paper sensor 34A are arranged below the external paper feed path RS1, the internal paper feed path RS2, and the reverse path RR, and emit light upward. The phototransistor 38 of the paper sensor 34A is arranged to face the light emitting diode 37 across the external paper feed path RS1, the internal paper feed path RS2 and the reverse path RR, and receives the light emitted by the light emitting diode 37. FIG.

The paper sensor 34</b>B detects the paper W conveyed from the registration rollers 31 toward the belt platen section 32 . The paper sensor 34B is arranged near the downstream side of the registration roller 31 . The light-emitting diode 37 of the paper sensor 34B is normally arranged below the path RC and emits light upward. The phototransistor 38 of the sheet sensor 34B is arranged to face the light emitting diode 37 across the normal path RC, and receives the light emitted by the light emitting diode 37 .

The upper transport section 4 transports the sheet W transported by the belt platen section 32 to the discharge section 5 or the reversing section 6 along the normal route RC.

The paper discharge unit 5 discharges the printed paper W. As shown in FIG. The paper discharge unit 5 includes a switching unit 41 , a paper discharge transport unit 42 , and a paper discharge tray 43 .

The switching unit 41 switches the conveying route of the paper W between the discharge route RD and the reversing route RR. The switching unit 41 is arranged at a branching point between the discharge route RD and the reversing route RR.

The paper discharge conveying unit 42 conveys the paper W guided to the paper discharge route RD by the switching unit 41 and discharges the paper onto the paper discharge table 43 .

The paper discharge table 43 is for stacking the printed paper W discharged by the paper discharge transport section 42 . The paper discharge table 43 is formed in a tray shape protruding from the housing 7 .

In double-sided printing, the reversing unit 6 reverses the paper W printed on one side while conveying it along the reversing route RR, and re-feeds it to the transport printing unit 3 .

When the printer 1 performs printing, an unprinted paper sheet W is fed from the paper feeding section 2 to the transport printing section 3 . The fed sheet W is sent to the belt platen section 32 by the registration rollers 31 and printed with ink ejected from the inkjet head 36 while being conveyed by the belt platen section 32 . The printed sheet W is conveyed from the belt platen section 32 to the top conveying section 4 .

In the case of single-sided printing, the single-sided printed sheet W conveyed by the upper surface conveying unit 4 is guided from the normal route RC to the discharge route RD by the switching unit 41, and is discharged to the discharge tray 43 by the discharge conveying unit 42. be done.

In the case of double-sided printing, the single-sided printed sheet W transported by the upper transport unit 4 is guided from the normal route RC to the reversing route RR by the switching unit 41, reversed by the reversing unit 6, and re-supplied to the transport printing unit 3. be printed. The re-fed single-sided printed paper W is sent to the belt platen section 32 by the registration rollers 31 in the transport printing section 3 .

Here, since the sheet W with one side printed is reversed by the reversing section 6, it is sent to the belt platen section 32 with the unprinted side facing upward. The unprinted surface of the paper W is printed with ink ejected from the inkjet head 36 while being transported by the belt platen section 32 . The double-sided printed sheet W is conveyed to the discharge section 5 by the upper surface conveying section 4 and discharged to the discharge table 43 in the discharge section 5 .

Next, the detection device will be explained.

FIG. 2 is a block diagram showing the configuration of the detection device according to the first embodiment. FIG. 3 is a diagram showing the circuit configuration of the paper sensor, constant current circuit, and current-voltage converter of the detection device shown in FIG.

As shown in FIG. 2, the detection device 51 includes the paper sensor 34, the D/A converter 52, the constant current circuit 53, the current/voltage converter 54, the voltage amplifier 55, and the A/D converter. A device 56 , a comparator 57 , a controller (corresponding to a control section) 58 , and a memory 59 are provided.

The paper sensor 34 has a light emitting diode 37 and a phototransistor 38 as described above.

The light emitting diode 37 has an anode connected to the power supply Vcc1 and a cathode connected to the collector of the transistor 61 of the constant current circuit 53, which will be described later.

The phototransistor 38 has a collector connected to the power supply Vcc2 and an emitter connected to the ground via a resistor 65 of the current-voltage converter 54, which will be described later. Also, the emitter of the phototransistor 38 is connected to the voltage amplifying section 55 and the comparator 57 .

The D/A converter 52 converts the digital value for indicating the light emission current IF output by the controller 58 into an analog voltage.

The constant current circuit 53 converts the analog voltage input from the D/A converter 52 into a light emitting current IF and supplies the light emitting diode 37 with the light emitting current IF. The constant current circuit 53 includes a transistor 61 , an operational amplifier 62 and resistors 63 and 64 .

The transistor 61 has a collector connected to the cathode of the light emitting diode 37 , an emitter connected to the ground through a resistor 63 , and a base connected to an output terminal of an operational amplifier 62 through a resistor 64 .

A non-inverting input terminal of the operational amplifier 62 is connected to the D/A converter 52 . The inverting input terminal of operational amplifier 62 is connected to the emitter of transistor 61 . The output terminal of operational amplifier 62 is connected to the base of transistor 61 through resistor 64 .

The resistor 63 is connected between the connection point between the emitter of the transistor 61 and the inverting input terminal of the operational amplifier 62 and the ground.

A resistor 64 is connected between the output terminal of the operational amplifier 62 and the base of the transistor 61 .

The current-voltage converter 54 has a resistor 65 (corresponding to a light receiving load resistor), and converts the photocurrent Ic corresponding to the amount of light received by the phototransistor 38 into a light receiving voltage Ve by the resistor 65 . The resistor 65 is connected between the connection point between the emitter of the phototransistor 38, the voltage amplifier 55 and the comparator 57, and the ground.

The voltage amplifier 55 amplifies the received light voltage Ve of the phototransistor 38 and outputs a received light adjustment voltage Vad which is the amplified voltage.

The A/D converter 56 converts the received light adjustment voltage Vad, which is an analog voltage input from the voltage amplifier 55, into a digital value.

Note that the functions of the voltage amplifying section 55 and the A/D converter 56 may be realized by the controller 58 by software.

The comparator 57 compares the light receiving voltage Ve of the phototransistor 38 with the detection threshold Vt, and outputs to the controller 58 a comparison result indicating whether or not the light receiving voltage Ve is greater than the detection threshold Vt. Here, the detection threshold Vt is the light receiving voltage Ve for determining whether or not the paper sensor 34 is detecting the paper W (whether or not the paper W is present between the light emitting diode 37 and the phototransistor 38). is the threshold.

The controller 58 determines whether or not the paper sensor 34 detects the paper W based on the comparison result input from the comparator 57 .

In the sensitivity adjustment process of the paper sensor 34, which will be described later, the controller 58 adjusts the light reception adjustment voltage Vad corresponding to the light reception voltage Ve of the phototransistor 38 in a state where the paper W is between the light emitting diode 37 and the phototransistor 38. The amount of light emitted from the light emitting diode 37 is adjusted so that the value falls within the target adjustment range including the target adjustment value Vd. In this sensitivity adjustment process, the controller 58 changes the light emission amount of the light emitting diode 37 by one step (corresponding to the minimum unit) in the adjustment resolution while the paper W is between the light emitting diode 37 and the phototransistor 38. Based on the light reception adjustment change amount ΔVg, which is the amount of change in the light reception adjustment voltage Vad when the light reception adjustment voltage Vad is changed, a predetermined range of width equal to or greater than the light reception adjustment change amount ΔVg including the target adjustment value Vd is set as the target adjustment range.

The controller 58 may also control the entire printing apparatus 1 . The controller 58 is configured with a CPU and the like.

The memory 59 stores the set value of the light emission current IF obtained by the sensitivity adjustment processing of the paper sensor 34 .

Next, sensitivity adjustment processing of the paper sensor 34 in the detection device 51 will be described.

Here, as a method for adjusting the amount of light emitted from the light emitting diode 37 for adjusting the sensitivity of the paper sensor 34, a binary search method is used. The binary search method is a method of adjusting the amount of light emitted by the light emitting diode 37 so that the amount of light emitted by the light emitting diode 37 is set to half of the previous amount of change so that the light receiving adjustment voltage Vad is within the target adjustment range. . In addition to the binary search method, a method of increasing the light emission amount of the light emitting diode 37 by a predetermined amount or a method of decreasing the light emission amount by a predetermined amount may be used.

The sensitivity adjustment process is performed in a state where a sheet of paper W of a reference sheet type is present between the light emitting diode 37 of the sheet sensor 34 and the phototransistor 38 . The paper W placed between the light emitting diode 37 and the phototransistor 38 in the sensitivity adjustment process is plain paper, for example. By using plain paper for sensitivity adjustment processing, thick paper and thin paper can be detected. Note that sensitivity adjustment processing may be performed for each paper type. Even in this case, the procedure of sensitivity adjustment processing is the same.

FIG. 4 is a flowchart of sensitivity adjustment processing of the paper sensor 34 . In step S1 of FIG. 4, the controller 58 causes the light emitting diode 37 to emit light.

Specifically, the controller 58 outputs to the D/A converter 52 a digital value indicating the light emission current IF set as the light emission current IF at the start of the sensitivity adjustment process. Here, the light emission current IF at the start of the sensitivity adjustment process is set to a value that causes the light emitting diode 37 to emit light in such an amount that the light reception adjustment voltage Vad is sufficiently larger than the upper limit Vup of the target adjustment range.

The D/A converter 52 converts the digital value input from the controller 58 into an analog voltage. The constant current circuit 53 converts the analog voltage input from the D/A converter 52 into a light emitting current IF and supplies the light emitting diode 37 with the light emitting current IF. As a result, the light emitting diode 37 emits light with an amount of light corresponding to the light emission current IF.

The phototransistor 38 receives light emitted by the light emitting diode 37 . The current-voltage converter 54 converts the photocurrent Ic flowing through the phototransistor 38 that receives the light into a light receiving voltage Ve. The voltage amplifying section 55 amplifies the received light voltage Ve input from the current-voltage converting section 54 and outputs the amplified light receiving adjustment voltage Vad to the A/D converter 56 . The A/D converter 56 converts the received light adjustment voltage Vad input from the voltage amplifier 55 into a digital value and outputs this digital value to the controller 58 .

Next, in step S<b>2 , the controller 58 determines whether or not the light reception adjustment voltage Vad is within the target adjustment range based on the digital value input from the A/D converter 56 .

If it is determined that the light reception adjustment voltage Vad is not within the target adjustment range (step S2: NO), the controller 58 changes the value of the light emission current IF in step S3. Here, when the light reception adjustment voltage Vad is larger than the upper limit Vup of the target adjustment range, the controller 58 changes the light emission current IF to a value half the latest value. When the light reception adjustment voltage Vad is smaller than the lower limit Vdn of the target adjustment range, the controller 58 changes the light emission current IF to a value that is twice the most recent value.

When the value of the light emission current IF is changed, the amount of light emitted by the light emitting diode 37 is changed, and thus the light reception adjustment voltage Vad is changed. After step S3, the controller 58 returns to step S2.

When it is determined in step S2 that the light reception adjustment voltage Vad is within the target adjustment range (step S2: YES), in step S4, the controller 58 changes the value of the light emission current IF at that time to the value of the light emission current IF. It is stored in the memory 59 as a set value. This completes the sensitivity adjustment process.

By the sensitivity adjustment processing as described above, as shown in FIG. 5, the light reception adjustment voltage Vad changes according to the change in the light emission current IF, and the light reception adjustment voltage Vad is within the target adjustment range from Vdn to Vup. When it reaches the value, the sensitivity adjustment (adjustment of the light emission amount of the light emitting diode 37) ends.

As described above, the target adjustment range is set to include the target adjustment value Vd as shown in FIG. Specifically, the target adjustment range is set within a range from the lower limit Vdn represented by the following formula (1) to the upper limit Vup represented by the formula (2).

Vdn=Vd-VRng (1)
Vup=Vd+VRng (2)
The adjustment width voltage VRng in equations (1) and (2) indicates the voltage width that defines the target adjustment range. The width of the target adjustment range is 2×VRng.

The adjustment width voltage VRng is set so that the target adjustment range is a predetermined range that is equal to or greater than the above-described light reception adjustment change amount ΔVg and is not excessively larger than the light reception adjustment change amount ΔVg. Specifically, the adjustment width voltage VRng is the target of the light reception adjustment voltage Vad when the target adjustment range is equal to or greater than the aforementioned light reception adjustment change amount ΔVg and the light reception adjustment voltage Vad is within the target adjustment range. The amount of deviation from the adjustment value Vd is set to be within the allowable range. The adjustment width voltage VRng is set, for example, based on experiments.

Here, unlike the present embodiment, when the target adjustment range is smaller than the amount of change in light reception adjustment ΔVg, as shown in FIG. As a result, the light reception adjustment voltage Vad may not be adjusted to a value within the target adjustment range.

On the other hand, in the present embodiment, since the target adjustment range is set as described above, the light reception adjustment voltage Vad can be adjusted to a value within the target adjustment range. Further, it is possible to suppress the amount of deviation of the light reception adjustment voltage Vad from the target adjustment value Vd when the light reception adjustment voltage Vad becomes a value within the target adjustment range.

Next, a method for calculating the light reception adjustment change amount ΔVg will be described.

Elements used to calculate the light reception adjustment change amount ΔVg include the photoelectric characteristics of the paper sensor 34, the distance characteristics between light emission and light reception of the paper sensor 34, the resolution rslDA of the D/A converter 52, and the reference voltage VrfDA of the D/A converter 52. , the constant current circuit constant RE, the resistance value RL of the resistor 65 of the current-voltage converter 54, the amplification factor Gv of the voltage amplifier 55, and the discrimination ratio P.

The photoelectric characteristics of the sheet sensor 34 indicate the relationship between the light emission current IF supplied to the light emitting diode 37 and the photocurrent Ic flowing through the phototransistor 38 . The relationship between the emission current IF and the photocurrent Ic is, for example, as shown in FIG. In the example of FIG. 7, the photoelectric characteristic of the paper sensor 34 is represented by Ic/IF.

In the example of FIG. 7, the light emission current IF and the photocurrent Ic are in a proportional relationship, but if the light emission current IF and the photocurrent Ic are not in a proportional relationship, the photoelectric characteristics are represented by a polynomial.

The characteristic of the distance between light emission and light reception of the paper sensor 34 indicates the relationship between the distance L between light emission and light reception, which is the distance between the light emitting diode 37 and the phototransistor 38 of the paper sensor 34, and the photocurrent Ic.

FIG. 8 is a diagram showing an example of distance characteristics between light emission and light reception of the paper sensor 34. As shown in FIG. A variation ratio y in FIG. 8 indicates a ratio of the value of the photocurrent Ic corresponding to each of the values of the distance L between the light emitting and receiving light to a certain value of the photocurrent Ic. As can be seen from FIG. 8, the photocurrent Ic decreases as the distance L between light emission and light reception increases.

In the example of FIG. 8, the variation ratio y is represented by the following equation (3), which is a cubic equation.

y=a3×L ³ +a2×L ² +a1×L+b (3)
Here, a3, a2, a1, and b are coefficients corresponding to distance characteristics between light emission and light reception.

Note that the order of the variation ratio y may differ depending on the type of paper sensor 34 and the like.

The resolution rslDA and the reference voltage VrfDA of the D/A converter 52 are determined by hardware. For example, in the case of the 8-bit D/A converter 52, the resolution rslDA is 255 steps. The reference voltage VrfDA indicates the width of the analog voltage.

A constant current circuit constant RE is the resistance value of the resistor 63 of the constant current circuit 53 . As shown in the following equation (4), the analog voltage Vi from the D/A converter 52 and the constant current circuit constant RE determine the light emission current IF.

IF=Vi÷RE (4)
The resistance value RL of the resistor 65 of the current-voltage converter 54 determines the light receiving voltage Ve. The light receiving voltage Ve is represented by the following formula (5).

Ve=Ic×RL (5)
The amplification factor Gv of the voltage amplifying section 55 is the ratio between the received light voltage Ve and the received light adjustment voltage Vad. The light reception adjustment voltage Vad is represented by the following formula (6).

Vad=Ve×Gv (6)
The discrimination ratio P is the ratio of the light receiving voltage Ve when there is paper W between the light emitting diode 37 and the phototransistor 38 and the light receiving voltage Ve when there is no paper W between the light emitting diode 37 and the phototransistor 38. is. The discrimination ratio P differs depending on the type of paper W. FIG. Further, the discrimination ratio P is determined by the structure of the paper sensor 34 and the size of the opening for passing light formed in the guide plate for guiding the paper W between the light emitting diode 37 and the phototransistor 38. etc. The discrimination ratio P is obtained by experiments.

From the resolution rslDA of the D/A converter 52, the reference voltage VrfDA, and the constant current circuit constant RE, the light emission current ΔIF for one step in the adjustment resolution of the light emission amount of the light emitting diode 37 is obtained by the following equation (7). Calculated.

ΔIF=VrfDA/RE/rslDA (7)
Based on the photoelectric characteristics (Ic/IF) of the paper sensor 34 described above, the distance characteristics between light emission and reception represented by equation (3), and ΔIF calculated by equation (7), the photocurrent ΔIc corresponding to ΔIF is is calculated by the following formula (8).

ΔIc = (Ic/IF) x (VrfDA/RE/rslDA)
×(a3×L ³ +a2×L ² +a1×L+b) (8)
By multiplying ΔIc by the resistance value RL of the resistor 65 and the amplification factor Gv, the received light voltage corresponding to ΔIF when there is no paper W between the light emitting diode 37 and the phototransistor 38 is obtained from the following equation (9). ΔVe is calculated.

ΔVe=(Ic/IF)×(VrfDA/RE/rslDA)
×(a3×L ³ +a2×L ² +a1×L+b)×RL×Gv (9)
By dividing ΔVe by the discrimination ratio P corresponding to the paper W used in the sensitivity adjustment process, the light reception adjustment change amount ΔVg is calculated by the following equation (10).

ΔVg=(Ic/IF)×(VrfDA/RE/rslDA)
×(a3×L ³ +a2×L ² +a1×L+b)×RL×Gv/P (10)
By arranging the above formula (10), the following formula (11) is obtained.

ΔVg=(Ic/IF)×VrfDA×(a3×L ³ +a2×L ² +a1×L+b)
×RL×Gv÷(RE×rslDA×P) (11)
The controller 58 sets the aforementioned target adjustment range based on the light reception adjustment change amount ΔVg calculated by the above equation (11).

Note that the A/D converter 56 has a high resolution and has a small influence on the amount of change in light reception adjustment ΔVg. Therefore, in the present embodiment, the resolution of the A/D converter 56 is not used to calculate the light reception adjustment change amount ΔVg.

Next, a method for setting the target adjustment value Vd will be described.

The target adjustment value Vd is set so that the light receiving voltage Ve of the phototransistor 38 when the paper W is between the light emitting diode 37 and the phototransistor 38 is a value obtained by dividing the detection threshold value Vt by the square root of the discrimination ratio P. be done. That is, the target adjustment value Vd is a value obtained by dividing the detection threshold value Vt by the square root of the discrimination ratio P and multiplying it by the amplification factor Gv, and is expressed by the following equation (12).

Vd=(Vt/√P)×Gv (12)
Here, the detection threshold Vt is preset for each paper type.

Also, the discrimination ratio P is obtained by experiments as described above. The diagram on the left side of FIG. 9 shows the transition of the light receiving voltage Ve of the phototransistor 38 in this experiment. In this experiment, the ratio of the light receiving voltage Ve when there is paper W between the light emitting diode 37 and the phototransistor 38 to the light receiving voltage Ve when there is no paper W between the light emitting diode 37 and the phototransistor 38 is , is calculated as the discrimination ratio P. In this experiment, the paper W of the same paper type as the paper W used in the sensitivity adjustment process is used.

The diagram on the right side of FIG. 9 shows the transition of the received light voltage Ve when the sheet sensor 34 detects the sheet W after the sensitivity adjustment process. Assuming that the light emission amount of the light emitting diode 37 is adjusted in the sensitivity adjustment process so that the light receiving adjustment voltage Vad becomes equal to the target adjustment value Vd, the target adjustment value Vd is set as described above. 3, the light receiving voltage Ve when the paper W is between the light emitting diode 37 and the phototransistor 38 is a value obtained by dividing the detection threshold value Vt by √P.

In the example of FIG. 9, the phototransistor 38 is saturated when there is no sheet W between the light emitting diode 37 and the phototransistor 38 . A hypothetical voltage in FIG. 9 indicates the received light voltage Ve when the phototransistor 38 is not saturated. As shown in FIG. 9, assuming that the phototransistor 38 is not saturated, the received light voltage Ve when there is no paper W between the light emitting diode 37 and the phototransistor 38 is the detection threshold value Vt multiplied by √P. It has become. That is, the detection threshold Vt is positioned at the center of the discrimination ratio P. As a result, sufficient detection margins and non-detection margins are secured for the detection threshold value Vt, so erroneous detection of the paper W can be reduced.

Here, the paper sensor 34 has a hysteresis, and the leading edge of the paper W is detected when the light receiving voltage Ve becomes lower than the detection threshold value Vt by the minus side of the hysteresis. Further, the trailing edge of the sheet W is detected when the light receiving voltage Ve rises from the detection threshold value Vt by the positive side of the hysteresis. The detection margin is from the light receiving voltage Ve when there is no paper W between the light emitting diode 37 and the phototransistor 38 to the plus side of the hysteresis. The non-detection margin is from the plus side of the hysteresis to the light receiving voltage Ve when there is no paper W between the light emitting diode 37 and the phototransistor 38 when the phototransistor 38 is not saturated.

As described above, in the detection device 51, in the sensitivity adjustment process, the controller 58 sets a predetermined range equal to or greater than the light reception adjustment change amount ΔVg including the target adjustment value Vd as the target adjustment range based on the light reception adjustment change amount ΔVg. set. As a result, the light reception adjustment voltage Vad can be adjusted to a value within the target adjustment range, the target adjustment range is prevented from becoming excessively large with respect to the light reception adjustment voltage Vad, and the light reception adjustment voltage Vad is within the target adjustment range. It is possible to suppress the amount of deviation of the light reception adjustment voltage Vad from the target adjustment value Vd when the value of . Therefore, it is possible to reduce the deterioration of the adjustment accuracy of the light emission amount of the light emitting diode 37 .

In the detection device 51, the controller 58 determines that the light receiving voltage Ve of the phototransistor 38 when the paper W is between the light emitting diode 37 and the phototransistor 38 is the value obtained by dividing the detection threshold value Vt by the square root of the discrimination ratio P. The target adjustment value Vd is set so that In other words, the controller 58 sets the target adjustment value Vd such that the detection threshold Vt is the middle value in the discrimination ratio P. As a result, sufficient detection margins and non-detection margins are secured for the detection threshold value Vt, so erroneous detection of the paper W can be reduced.

[Second embodiment]
Next, a second embodiment, which is a partial modification of the first embodiment described above, will be described.

In the above-described first embodiment, the target adjustment range is set based on the light reception adjustment change amount ΔVg calculated by Equation (11). On the other hand, in the second embodiment, the resistance value RL of the resistor 65 (light receiving load resistance) of the current-voltage converter 54 is calculated so that the amount of change in light reception adjustment ΔVg is equal to or greater than a predetermined value within the width of the target adjustment range. , the resistance value RL is set to this calculated value.

In this case, the light reception adjustment change amount ΔVg is set to a value equal to or less than the width of the preset target adjustment range and equal to or greater than a predetermined value. The light reception adjustment change amount ΔVg is set so that the amount of deviation of the light reception adjustment voltage Vad from the target adjustment value Vd when the light reception adjustment voltage Vad becomes a value within the target adjustment range in the sensitivity adjustment process is within the allowable range. be. The light reception adjustment change amount ΔVg in this case is set, for example, based on an experiment or the like.

The resistance value RL of the resistor 65 is calculated by the following equation (13), which is a modification of the equation (11), using the light reception adjustment change amount ΔVg as a calculation input value.

RL=ΔVg×(RE×rslDA×P)
÷ ((Ic/IF) x VrfDA
×(a3×L ³ +a2×L ² +a1×L+b)×Gv) (13)
As the resistor 65 of the current-voltage converter 54, one having the resistance value RL calculated as described above is used.

Even in this way, as in the first embodiment, it is possible to adjust the light reception adjustment voltage Vad to a value within the target adjustment range, and to prevent the target adjustment range from becoming excessively large with respect to the light reception adjustment voltage Vad. Thus, it is possible to suppress the amount of deviation of the light reception adjustment voltage Vad from the target adjustment value Vd when the light reception adjustment voltage Vad becomes a value within the target adjustment range. Therefore, it is possible to reduce the deterioration of the adjustment accuracy of the light emission amount of the light emitting diode 37 .

The procedure of sensitivity adjustment processing of the paper sensor 34 is the same in the second embodiment as in the first embodiment. Also in the second embodiment, similarly to the first embodiment, the target adjustment value Vd is set such that the detection threshold value Vt is the middle value in the discrimination ratio P.

[Other embodiments]
As noted above, the present invention has been described through first and second embodiments, but the discussion and drawings forming part of this disclosure should not be understood to limit the present invention. Various alternative embodiments, implementations and operational techniques will become apparent to those skilled in the art from this disclosure.

In the first embodiment, some of the elements used to calculate the light reception adjustment change amount ΔVg may be omitted. Also, other factors may be used to calculate the light reception adjustment change amount ΔVg. Also, in the second embodiment, some of the elements used to calculate the resistance value RL of the resistor 65 may be omitted. Also, other factors may be used to calculate the resistance value RL of the resistor 65 .

In the second embodiment, the current-voltage converter 54 has a plurality of switchable resistors 65 each having a different resistance value, and from these plurality of resistors 65, the resistor 65 having the resistance value RL calculated as described above. may be selected by the controller 58 .

Thus, the present invention naturally includes various embodiments and the like not described here. Therefore, the technical scope of the present invention is defined only by the matters specifying the invention according to the valid scope of claims based on the above description.

[Appendix]
This application discloses the following inventions.

(Appendix 1)
a light emitting unit;
a light receiving unit that receives the light emitted by the light emitting unit;
The light emitting unit is adjusted so that the light receiving adjustment voltage corresponding to the light receiving voltage of the light receiving unit is a value within a target adjustment range including a target adjustment value in a state where an object to be detected is present between the light emitting unit and the light receiving unit. A control unit that adjusts the amount of light emission,
The control unit controls light reception adjustment, which is the amount of change in the light reception adjustment voltage when the light emission amount of the light emission unit is changed by a minimum unit in a state where an object to be detected is present between the light emission unit and the light reception unit. A detection device, wherein a predetermined range of a width equal to or larger than the amount of change in light reception adjustment including the target adjustment value is set as the target adjustment range based on the amount of change.

(Appendix 2)
a light emitting unit;
a light receiving unit that receives the light emitted by the light emitting unit;
a light-receiving load resistor that converts a photocurrent corresponding to the amount of light received by the light-receiving unit into a light-receiving voltage;
With an object to be detected between the light emitting unit and the light receiving unit, the light receiving adjustment voltage corresponding to the light receiving voltage converted by the light receiving load resistance is set to a value within the target adjustment range including the target adjustment value. A control unit that adjusts the light emission amount of the light emitting unit,
The resistance value of the light-receiving load resistor is the amount of change in the light-receiving adjustment voltage when the amount of light emitted by the light-emitting unit is changed by a minimum unit in a state where an object to be detected is present between the light-emitting unit and the light-receiving unit. is set to a value calculated so that is equal to or greater than a predetermined value within the width of the target adjustment range.

(Appendix 3)
The control unit
A threshold value of the light receiving voltage of the light receiving unit for determining whether or not there is an object to be detected between the light emitting unit and the light receiving unit and the light receiving voltage of the light receiving unit when there is no object to be detected between the light emitting unit and the light receiving unit. The detection device according to appendix 1 or 2, characterized in that:

1 Printer 34, 34A, 34B Paper Sensor 37 Light Emitting Diode 38 Phototransistor 51 Detector 52 D/A Converter 53 Constant Current Circuit 54 Current Voltage Converter 55 Voltage Amplifier 56 A/D Converter 57 Comparator 58 Controller 59 Memory 61 transistor 62 operational amplifier 63-65 resistor

Claims (3)

a light emitting unit;
a light receiving unit that receives the light emitted by the light emitting unit;
The light emitting unit is adjusted so that the light receiving adjustment voltage corresponding to the light receiving voltage of the light receiving unit is a value within a target adjustment range including a target adjustment value in a state where an object to be detected is present between the light emitting unit and the light receiving unit. A control unit that adjusts the amount of light emission,
The control unit controls light reception adjustment, which is the amount of change in the light reception adjustment voltage when the light emission amount of the light emission unit is changed by a minimum unit in a state where an object to be detected is present between the light emission unit and the light reception unit. A detection device, wherein a predetermined range of a width equal to or larger than the amount of change in light reception adjustment including the target adjustment value is set as the target adjustment range based on the amount of change. a light emitting unit;
a light receiving unit that receives the light emitted by the light emitting unit;
a light-receiving load resistor that converts a photocurrent corresponding to the amount of light received by the light-receiving unit into a light-receiving voltage;
With an object to be detected between the light emitting unit and the light receiving unit, the light receiving adjustment voltage corresponding to the light receiving voltage converted by the light receiving load resistance is set to a value within the target adjustment range including the target adjustment value. A control unit that adjusts the light emission amount of the light emitting unit,
The resistance value of the light-receiving load resistor is the amount of change in the light-receiving adjustment voltage when the amount of light emitted by the light-emitting unit is changed by a minimum unit in a state where an object to be detected is present between the light-emitting unit and the light-receiving unit. is set to a value calculated so that is equal to or greater than a predetermined value within the width of the target adjustment range. The control unit
A threshold value of the light receiving voltage of the light receiving unit for determining whether or not there is an object to be detected between the light emitting unit and the light receiving unit and the light receiving voltage of the light receiving unit when there is no object to be detected between the light emitting unit and the light receiving unit. 3. The detection device according to claim 1 or 2, characterized in that:

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