JP2788905B2 - Paper detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet detecting device for detecting the presence or absence of a printing sheet used in a dot serial printer or the like.

[0002]

2. Description of the Related Art Conventionally, as this type of paper detecting apparatus,
For example, there is one described in JP-A-03-234696. FIG. 7 is a block diagram of a sheet detecting device disclosed in the publication. 7, reference numeral 101 denotes a printing paper 10
2, an A / D converter 103 for converting an analog signal output from the photo sensor 101 into a digital signal, and a microprocessor unit 104 for reading the digital data to determine the presence or absence of the sheet 102 ( MPU). 106 is MP
A non-volatile memory which performs writing and reading by the U104 and retains data internally even when the power is turned off. Numerals 105 and 107 denote first and second voltage setting switches for notifying the MPU 104 of digital data reading timing. It is. As the paper detection photo sensor 101, a transmission type photo sensor is used.

Next, the operation of the apparatus shown in FIG. 7 will be described. First, the paper 1 is supplied to the photo sensor 101 for detecting the printing paper.
02 is not set. In this state, since the efficiency of transmitting light to the light emitting portion of the sheet detection photosensor 101 is good, the amount of current flowing through the transistor on the light receiving side increases, and the analog input voltage to the A / D converter 103 increases. The A / D converter 103 converts a high analog voltage into digital data and supplies the digital data to the MPU 104. In this state, when the first voltage setting switch 105 is turned on, the MPU 104 reads the digital data from the A / D converter 103 and writes this data to the nonvolatile memory 106 as a voltage level when there is no printing paper.

[0006] Next, the sheet 102 is brought into a state where the sheet 102 is applied to the sheet detection photosensor 101. In this state, the transmission efficiency of light from the light-emitting portion to the light-receiving portion of the paper detection photosensor 101 is reduced by half for thin paper that passes light halfway, and almost zero for thick paper. In any case, the value of the current flowing through the transistor on the light receiving side becomes smaller than that in the above-mentioned paper absence state, so that the A / D converter 103 converts this low analog input voltage into digital data and supplies it to the MPU 104. In this state, when the second voltage setting switch 107 is turned on, the MPU 104 reads the digital data from the A / D converter 103 and writes this data to the nonvolatile memory 106 as a voltage level when paper is present. An intermediate value between the two data written in the above procedure is set as a threshold level for determining the presence or absence of a sheet.

[0005]

In the conventional paper detection method, a reflection type photosensor is used, the reflected light from the platen is detected as a paperless level, and a threshold value for detecting the presence or absence of a paper is set based on the detected light. When setting, there is a problem that it is determined that there is paper even though there is actually no paper, and it is not possible to correctly detect the absence of paper. That is, the platen of the dot serial printer is usually made of rubber, and if it is hit with a print head, the surface of the rubber is deteriorated.
Therefore, the amount of reflected light of the reflective photo sensor increases,
At this time, since the direction changes in the direction of the threshold value for determining the presence of paper, there is a problem that the presence of paper is erroneously detected. The change in the reflected light of the platen varies depending on the position of the platen, and the variation is strongly affected by the print position of the print data used by the user. However, there is a problem that erroneous detection is likely to occur at a position where the change of the reflected light is large.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a paper detecting apparatus capable of preventing erroneous detection of a paper and accurately detecting the presence or absence of a paper in view of the above conventional problems. .

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to have a sensor for detecting reflected light from a sheet, and to detect the presence or absence of a sheet by comparing the output of the sensor with a predetermined threshold value. A sheet detecting device for detecting a position on the platen serving as a buffer material of the print head where the amount of printing is the largest, a unit for reading the output of the sensor at the detected position, and a reference to the obtained output value of the sensor. Means for setting the threshold value as described above.

[0008]

Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows the first embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of the embodiment. In FIG. 1, a print data creation means 1 creates print data such as dot data and an output position of the dot data based on transmission data from a host device 9, and sends the print data to a printer mechanism control means 7 and a print amount calculation means 2. Output. The print amount calculating means 2 includes a dot string check section 21 and a horizontal print amount adding section 22. The dot string check section 21 refers to the print information created by the print data creating means 1 and checks the horizontal direction of the platen. The print amount at each position is determined as 1 when the print head is output and 0 when not output, and the horizontal print amount adder 22 updates the contents of the platen print amount memory 3 according to the result. The platen printing amount memory 3 is a table storing the total value of the printing amount at each position in the horizontal direction of the platen, and a non-volatile memory is used so as not to be erased even when the power is turned off.

The print amount search means 4 is provided between the platen print amount memory 3 and the threshold value setting means 5, searches the maximum value of the print amount in the platen print amount memory 3, and displays the maximum value and the platen indicating the maximum value. Threshold value setting means 5
Notify. The threshold setting means 5 includes a sensor position control unit 5
1, a sensor reading unit 52 and a threshold setting unit 53, which perform control to set the comparison voltage 12 of the comparator 6 based on information from the maximum printing amount search unit 4. The comparison voltage 12 is set on the basis of the output voltage value of the reflective photosensor 8 at the horizontal position of the platen 13 where the printing amount has the maximum value, as described later in detail. The reflection type photo sensor 8 is mounted on the lateral feed mechanism 15 and moves in the left-right direction to logarithmically convert the reflected light of the object into a voltage value. The comparator 6 compares the output of the reflection type photosensor 8 with the comparison voltage 12, and outputs a logical value 1 to the printer mechanism control means 7 when the comparison voltage 12 is low and a logical value 0 when the comparison voltage 12 is high. I do. The printer mechanism controller 7 determines that there is paper when the logical value is 1, and that there is no paper when the logical value is 0.

The print head 10 uses an electromagnet as a driving force.
The paper 16 is arranged between the platen 13 and the paper 16. Further, a ribbon 11 coated with ink is arranged between the paper 16 and the print head 10. By outputting a pin on the ribbon 11, the ink adheres to the paper 16 and printing is performed. The platen 13 is a cylindrical roller made of rubber and has a function of feeding the paper 16 in the front-rear direction by frictional force and a function as a buffer material for pins of the print head 10. The print range 14 is a range on the platen 13 where the pins of the print head 10 are output, and is indicated by diagonal lines for explanation. The printer mechanism control means 7 controls the printer mechanisms such as the horizontal feed mechanism 15 and the print head 10 according to the print information created by the print data creation means 1, and performs printing on the paper 16. The horizontal feed mechanism 15 is a mechanism that mounts the print head 10 and the reflective photosensor 8 and moves the print head 10 in the left-right direction.

Next, the operation of this embodiment will be described with reference to FIG. In FIG. 2, first, the print data creation means 1
Then, print information is created based on the data transmitted from the host device 9 (S1). The dot line check unit 21 calculates the print amount of each dot line in one printing from the print information, and updates the platen print amount memory 3 by the horizontal print amount adding unit 22 (S2, S3). Since the platen print amount memory 3 is a non-volatile memory with a limited number of times of writing, the timing of actually writing the memory is such that the obtained print amount is stored in the volatile memory to some extent, and the stored print amount is It is desirable to take measures such as writing to the non-volatile memory when the standard is reached.

Next, the print amount searching means 4 searches the maximum value of the print amount in the platen print amount memory 3 to obtain a position P on the print range 14 where the print amount is maximum (S4). Also, it is checked whether the paper 16 is set in the printer (S5). If the paper 16 is set, the comparison voltage 12 is not changed (S6). When the paper 16 is not set, the reflection type photosensor 8 is moved to the position P obtained by the print amount search unit 4 by the sensor position control unit 51, and the reflection type photosensor 8 at the position P is read by the sensor reading unit 52. Is read, and the threshold setting unit 53 sets the comparison voltage 12 of the comparator 6 on the basis of the read value (S
7).

In this embodiment, the comparison voltage 12 is determined only at the position where the printing amount indicates the maximum value. However, a plurality of upper positions having a large printing amount on the platen are detected, and the plurality of positions are detected. It is better to obtain the comparison voltage 12 from the output value of the reflection type photosensor 8 at the step S1. That is, it is desirable to read the output values of the photosensor 8 at a plurality of positions where the print amount is large, and to set the comparison voltage 12 based on the output values of the positions where deterioration has progressed most. The printer mechanism control means 7 executes printing within the range where the paper 16 is set while monitoring the output result of the comparator 6 (S8).

Next, a method of setting the comparison voltage by the threshold value setting means 5 will be described. FIG. 3 is a diagram showing changes in the print amount and the output voltage of the reflective photosensor 8 at the left and right positions of the print range 14. Each position in the left-right direction is 0 on the leftmost side, and 1, 2, 3,. . . Assigned to n. In FIG. 3, n = 9 for explanation. First, state 1 is an initial state, and since printing has never been performed, all outputs of the reflective photosensor 8 at each printing position indicate the value of X0. In state 1, the threshold value setting unit 5 sets the value of X2 (= X0 + Z) as the voltage value of the comparison voltage 12. Here, Z is a value that can sufficiently cope with a change in the output of the reflective photosensor 8 due to the deterioration of the printing surface until the comparison voltage 12 is set next time.

State 2 shows the print amount and the output result of the reflection type photosensor 8 when used for T-time printing from state 1, and the threshold value setting means 5 reflects the light to the print position 3 where the print amount is the largest. The photosensor 8 is moved. Printing position 3
In the position of, the output of the reflection type photosensor 8 indicates the voltage value X1, so the threshold value setting means 5 sets the comparison voltage 12
Is set to the value of X4 (= X1 + Z).
Next, state 3 shows the print amount and the output result of the reflection type photosensor 8 when printing is further performed for T time from state 2, and the print amount shows the maximum value at print positions 3 and 7. in this case,
The print amount search means 4 compares the print amounts before and after each print position. As a result, in state 3, the print density near the print position 7 is high. Notifies that the printing amount is maximum. The threshold value setting means 5 moves the reflection type photosensor 8 to the position of the printing position 7. At the position of the printing position 7, the output of the reflection type photosensor 8 indicates the voltage value X3, so the value of X6 (= X3 + Z) is set as the value of the comparison voltage 12.

In this embodiment, the position where the deterioration of the printing surface of the platen is most advanced is determined as the position indicating the maximum value of the printing amount in the horizontal position on the platen, and the output value of the reflection type photo sensor at that position is obtained. , The threshold value for identifying the presence / absence of paper is set, so that the presence / absence of paper can be accurately detected without determining that paper is absent even if the platen has deteriorated. In addition, the position with the largest printing amount on the platen is set as the position with the largest deterioration, and the position with the largest deterioration is detected based on the total value of the printing amounts accumulated in the memory. Can be detected.

Next, a second embodiment of the present invention will be described. FIG. 4 is a block diagram showing the configuration of the present embodiment. In the present embodiment, first, the print amount calculation unit 2 in FIG.
, A dot check unit 23 and a print surface print amount addition unit 24 are provided instead of the dot row check unit 21 and the horizontal print amount addition unit 22. Further, a rotation position control unit 54 is provided in the threshold value setting unit 5, and the rotation position control unit 54 is connected to the platen rotation position control unit 17.

Although the platen printing amount memory 3 stores only the printing amount in the horizontal direction with respect to the printing range 14 in the first embodiment, in the present embodiment, the printing range 14 is considered as one surface, The print amount at the position of the two-dimensional coordinates in the direction is stored. The dot check unit 23 sets the position of the dot to be output in one printing to 1 and the position of the dot not to be output to 0, and the print surface print amount adding unit 24 stores the platen print amount memory 3 corresponding to each coordinate position of the print range 14. The result of the dot check unit 23 is added to the table position. The platen rotation position control means 17 uses an encoder or the like to set an arbitrary position in the rotation direction of the platen 13 as the origin, and along the paper feed direction in units of vertical printing resolution, 1, 2, 3,. . . N is assigned so that the vertical position of the print range 14 can be managed as a result. Other configurations are the same as those in FIG.

Next, the operation of this embodiment will be described with reference to FIG. Note that the operations of the print data creation unit 1 and the printer mechanism control unit 7 in S1 and S9 in FIG. 5 are the same as the operations in S1 and S8 in the first embodiment, and a description thereof will be omitted. In the first embodiment, the deterioration of the print surface in the vertical direction is treated as the same, but in the present embodiment, the deterioration of the print surface is managed by two-dimensional coordinates as follows.
First, after the print information is created in S1, the dot check unit 23 calculates the print amount (1 or 0) of each dot in one printing from the print information created by the print data creation unit 1.
Is updated, and the contents of the platen print amount memory 3 are updated by the print surface print amount adder 24 (S2, S3). Next, the print amount searching means 4 searches the maximum value of the print amount in the platen print amount memory 3, and obtains the coordinates Q on the print range 14 where the print amount is maximum (S4).

Subsequently, it is checked whether the paper 16 is set in the printer (S5). If the paper 16 is set, the comparison voltage 12 is not changed (S6).
When the paper 16 is not set, the reflection type photosensor 8 is moved by the sensor position control unit 51 to the lateral position of the coordinate Q obtained by the print amount search unit 4, and the platen 13 is moved by the rotation position control unit 54. The rotation is controlled so that the vertical position of the coordinate Q comes to the position of the reflective photosensor 8 (S7). Thereafter, the output voltage of the reflective photosensor 8 at the coordinate Q is read by the sensor reading section 52, and the threshold voltage setting section 53 sets the comparison voltage 12 of the comparator 6 based on the read value (S).
8). In this embodiment, as in the first embodiment, a plurality of upper positions with a large print amount on the platen may be detected, and a threshold value may be set based on sensor outputs at the plurality of positions.

Next, a method of setting a threshold value according to the present embodiment will be described with reference to FIG. FIG. 6 is a diagram showing a change in the print amount at the two-dimensional coordinate position of the print range 14. Each position in the left-right direction is 0 on the leftmost side, and 1, 2, 3,. . . Assigned to n. Similarly, the origin of the platen rotation position control means 17 is set to 0 for each position in the vertical direction, and 1, 2, 2
3. . . Assigned to N. Here, n =
9, N = 9. In FIG. 6, first, state 1 is an initial state, and since printing has never been performed, the print amount at each print position is all zero. At this time, if the output of the reflective photosensor 8 indicates the value of X0, the threshold value setting means 5 sets the value of the comparison voltage 12 to X
2 (= X0 + Z) is set. Here, Z is a value that can sufficiently cope with a change in the output of the reflective photosensor 8 due to the deterioration of the printing surface until the comparison voltage 12 is set next time.

Next, state 2 is the print amount when used for T-time printing from state 1, and the threshold value setting means 5 sets the reflection type photosensor at the position of the coordinate (3, 3) where the print amount is the largest. The lateral feed mechanism 15 and the platen 13 are operated so that the position 8 comes. Assuming that the output of the reflection type photosensor 8 indicates the voltage value X1 at the position of the coordinates (3, 3), the comparison voltage 12
Is set as the value of X4 (= X1 + Z). State 3
Indicates the print amount and the output result of the reflection type photosensor 8 when used for T-time printing further from the state 2, and the print amount shows the maximum value at the coordinates (3, 3) and (7, 7).

When there are a plurality of positions having a large print amount, the print amount searching means 4 compares the print amounts around the respective coordinates. In this case, as is clear from FIG. 6, in the state 3, the coordinates (7,
7) Since the peripheral printing density is high, the threshold setting means 5 notifies the coordinates (7, 7) that the printing amount is the maximum. The threshold value setting means 5 operates the traversing mechanism 15 and the platen 13 so that the reflective photosensor 8 comes to the position of the coordinates (7, 7). Assuming that the output of the reflection type photosensor 8 indicates the voltage value X3 at the position of the coordinates (7, 7), the value of X6 (= X3 + Z) is set as the value of the comparison voltage 12.

In this embodiment, the position where the deterioration of the printing surface of the platen is most advanced is determined from the two-dimensional coordinate position of the platen surface, and the presence or absence of paper is determined based on the output value of the reflection type photosensor at that position. Since the discrimination threshold is set, the position where the deterioration of the platen is most advanced can be accurately detected, and the detection accuracy of the sheet can be further improved as compared with the first embodiment.

[0025]

As described above, according to the present invention, the position where the printing amount on the platen is the largest is detected, and the threshold value is set based on the sensor output at that position. This eliminates the possibility of erroneously detecting that there is a sheet even though there is no sheet, and has the effect of accurately detecting the presence or absence of a sheet.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the embodiment of FIG.

FIG. 3 is a diagram for explaining a method of setting a threshold value in the embodiment of FIG.

FIG. 4 is a block diagram showing a second embodiment of the present invention.

FIG. 5 is a flowchart showing an operation of the embodiment of FIG. 4;

FIG. 6 is a diagram for explaining a method for setting a threshold value in the embodiment of FIG. 4;

FIG. 7 is a circuit diagram showing a conventional sheet detection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Print data creation means 2 Print amount calculation means 3 Platen print amount memory 4 Print amount search means 5 Threshold value setting means 6 Comparator 7 Printer mechanism control means 8 Reflective photo sensor 10 Print head 11 Ink ribbon 13 Platen 15 Lateral feed mechanism 16 paper

Claims (4)

(57) [Claims] 1. A sheet detecting device having a sensor for detecting reflected light from a sheet and comparing the output of the sensor with a predetermined threshold value to detect the presence or absence of a sheet. Means for detecting the position of the largest print amount on the platen, means for reading the output of the sensor at the detected position, and means for setting the threshold value based on the output value of the obtained sensor. A sheet detection device comprising: 2. The sheet detecting apparatus according to claim 1, wherein said position detecting means includes means for accumulating a total print amount at a position in a lateral direction of said platen, and said platen is searched by searching said accumulating means. A sheet detection device that detects a position where the amount of printing is the largest in the horizontal direction. 3. The sheet detecting apparatus according to claim 1, wherein said position detecting means includes means for accumulating a total print amount at each of two-dimensional coordinate positions in a horizontal direction and a vertical direction of said platen, A sheet detecting device for detecting a position with the largest print amount among two-dimensional coordinate positions of a platen by searching a storage unit. 4. The sheet detecting device according to claim 1, wherein said position detecting means detects a plurality of upper positions having a large print amount on said platen, and detects a plurality of obtained positions. A sheet detecting device for setting a threshold value from a sensor output.