JP2524042Y2 - Paper skew detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an apparatus for detecting skew of a sheet.

[Conventional technology]

As is well known, a page printer or the like prints on a sheet cut to a predetermined size such as a B5 plate, an A4 plate, or a B4 plate. In this case, since the paper is not provided with a paper feed hole as in the case of continuous paper, skew during transportation (skew) becomes a problem.

Therefore, as shown in JP-A-57-131652,
A skew detection device that detects a difference in the passage timing of the leading edge of the sheet by a pair of sensors arranged in a direction perpendicular to the sheet conveying direction, and determines that skew has occurred if the difference is equal to or greater than an allowable value, or As shown in Japanese Patent Application Laid-Open No. 57-8173, a difference in the passage timing of the trailing edge of the paper is detected by two sensors arranged in both directions of the paper transport direction and a direction perpendicular thereto, and the difference is an allowable value. If it is above, a skew detection method that determines that skew has occurred, and further, as shown in JP-A-56-88041,
There is known a skew detection mechanism that detects a difference between the required times of passage of one side and the other side in the transport direction by two sensors arranged at right angles to the paper transport direction, and determines the presence or absence of skew based on the difference. . Further, as shown in Japanese Utility Model Application Laid-Open No. 59-57429, a pair of sensors are arranged in a direction perpendicular to the paper conveyance direction, and a skew is determined based on a difference in paper detection timing between these sensors. There is known a skew detecting device which varies an allowable value for determining a skew according to the skew.

[Problems to be solved by the invention]

However, in any case, since it is assumed that the mounting position of the sensor exactly matches the designed position, there is a problem that a detection error occurs when the mounting error of the sensor or the manufacturing accuracy is poor.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sheet skew detection device capable of detecting the presence or absence of skew with high accuracy even if there is an error in mounting a sensor for detecting a sheet.

[Means for solving the problem]

In order to achieve the above object, the present invention provides first and second sheet detecting means which are disposed at a right angle to a sheet conveying direction to detect a sheet to be conveyed,
Detection timing determination means for determining which of the paper detection means of the first and second paper detection means is earlier in paper detection timing, and paper detection timing of the first paper detection means by the detection timing determination means being earlier. If the first sheet detecting means detects the leading edge of the sheet, the second sheet is counted up.
A predetermined clock signal is counted until the leading edge of the sheet is detected by the sheet detecting means, and if the detecting timing determining means determines that the sheet detecting timing of the second sheet detecting means is early, the countdown state is performed. Up / down counting means for counting a predetermined clock signal from when the leading edge of the sheet is detected by the second sheet detecting means to when the leading edge of the sheet is detected by the first sheet detecting means; The initial value of the down-counting means is set to zero and the sheet is conveyed in a normal state without skew, and a value obtained by reversing the sign of the count value of the up-down counting means at this time is set as the initial value of the up-down counting means. Setting means for comparing the count value of the up / down counting means with a predetermined allowable skew value when the sheet is conveyed, Characterized by comprising a comparison means for detecting the presence or absence.

[Action]

First, the initial value of the up / down counting means is set to zero, and the sheet is conveyed in a normal state without skew, and a value obtained by reversing the sign of the count value of the up / down counting means at this time is set as the initial value of the up / down counting means. I do.

When the sheet is conveyed in this state, a true skew value of the sheet in which the mounting position errors of the first and second sheet detecting units are offset is obtained from the count value of the up / down counting unit.

Therefore, the presence or absence of skew of the paper can be detected with high accuracy by comparing the count value of the up / down counting means with a predetermined allowable skew value.

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of the present invention, in which two paper sensors 1A and 1B, a timing determination circuit, an up / down counter 3, an offset value setting circuit 4, a count value monitor 5,
It comprises a comparator 6 and a monitoring light emitting diode 7.

The paper sensors 1A and 1B are arranged at predetermined intervals in a direction perpendicular to the transport direction of the paper 10, and when the paper 10 passes, as shown in FIGS. The sheet detection signals PDa and PDb of “1” are output continuously during this period.
These signals PDa and PDb are input to the timing determination circuit 2. When these signals are input, the determination circuit 2 detects which signal has become "1" first, and according to the timing, the signal is up-down. It outputs a count control signal CCS for controlling the counter 3 to an up-count state or a down-count state. For example, when the sheet detection timing of the sensor 1A is early, the count control signal CC of "0" as shown in FIG.
S is output, and when the sheet detection timing of the sensor 1B is earlier, a count control signal CCS of “1” is output to control the count down state.

Further, the timing determination circuit 2 calculates the logical sum and the exclusive logical sum of the output signals PDa and PDb of the sensors 1A and 1B, and sends the logical sum signal to the up / down counter 3 for the load signal of the offset value.
It outputs as an LD, and outputs an exclusive OR signal as a start / stop signal ST / STP of the up / down counter 3.

When the count control signal CCS is “0”, the up-down counter 3 is in an up-count operation state, and when the count control signal CCS is “1”, it is in a down-count operation state, and counts the clock signal φ input from the clock oscillator 8. , 1B, while the sheet 10 is not detected, the load signal LD (FIG. 2 (c)) of "0" is input from the timing determination circuit 2, and the offset value setting circuit is provided by the load signal LD. 4 is taken as the initial value of the count operation, and while the start / stop signal ST / STP is "1", that is, as shown in FIG. While the output signal is being output, the clock signal φ is counted up or down.

Here, assuming that the offset value set in the setting circuit 4 is “0”, the counter 3 outputs two sensors.
The count value Q corresponding to the difference between the sheet detection timings 1A and 1B is obtained. However, the count value Q in this case also includes an error component of an error in the mounting position of the sensors 1A and 1B.

In this embodiment, in order to cancel this error component, the offset value is set to “0”, and the sheet 10 is transported in a normal state without skew. Then, a count value ΔQ corresponding to an error in the mounting position of the two sensors 1A and 1B is obtained from the up-down counter 3. Therefore, the count value ΔQ is set in the offset value setting circuit 4. Specifically, the setting switch group 40 of a plurality of bits is set and operated to “1” or “0” corresponding to the count value ΔQ,
The set signal is inverted by the exclusive OR gate group 41 and input to the offset input of the counter 3 as an offset value “−ΔQ”. The most significant bit of the switch group 40 sets the polarity of the offset value. In this embodiment, the switch corresponding to the most significant bit is set to "1". In this case, the offset value “−ΔQ” can be set in the offset value setting circuit 4 by setting and operating the switches of the other bits except the most significant bit of the switch group 40 in accordance with the out value ΔQ. The offset value “−ΔQ” set in the offset value setting circuit 4
Is actually taken into the counter 3 by the load signal LD output from the timing determination circuit 2 when the sheet is actually conveyed to the sheet. Will be done.

As a result, when the sheet 10 is conveyed in a normal state, the count value Q of the counter 3 becomes "0", and the component of the mounting error between the two sensors 1A and 1B is canceled. However, when the sheet 10 is conveyed in the skew state, the counter 3
Is a value corresponding to the skew amount. That is, when the skew amount is S, in a skew state in which the paper detection timing of the sensor 1A is advanced, the count value Q of the counter 3 becomes Q = S−ΔQ, and conversely, the paper detection timing of the sensor 1B is advanced. In a skew state, Q = −S−ΔQ.

As a result, the counter 3 obtains a count value Q corresponding to the true skew amount that does not include the mounting error component of the sensors 1A and 1B.

The count value Q becomes a positive or negative value according to the direction of the skew. When the count value Q is negative, the count value Q is inverted by the inverting circuit 9 and input to the count value monitor 5 and the comparator 6.

The count value monitor 5 numerically displays the skew amount of the paper 10. On the other hand, the comparator 6 calculates the allowable value of the skew amount ± Δ
S is compared with the count value Q, and when Q> ± ΔS, it is determined that the skew amount has exceeded the allowable value, and the paper feed error signal EM
Is output.

The monitoring light emitting diode 7 is a count control signal.
Lights up only when the paper detection timing of the sensor 1A is advanced by the CCS.

As described above, in the present embodiment, when determining the presence or absence of skew based on the difference between the sheet detection timings of the two sensors, the count initial value of the counter 3 is set so that the mounting error component of the two sensors is canceled. Therefore, a signal corresponding to the true skew amount of the paper 10 is obtained. Therefore, even if there is an installation error between the two sensors, a detection error does not occur, and high-precision skew detection is possible. In other words, there is an advantage that the mounting accuracy of the two sensors 1A and 1B can be reduced, and the manufacture becomes easy.

[Effect of the invention]

As described above, in the present invention, the offset value corresponding to the mounting error between the two detection means is set in advance for the up / down counting means for counting the difference between the paper detection timings of the two paper detection means, and then the paper detection is performed. Since the difference between the timings is counted, the presence or absence of skew can be detected with high accuracy even if there is an attachment error between the two detecting means. Further, the mounting accuracy of the two sheet detecting means can be reduced, and the effect of facilitating manufacture can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is an input / output signal waveform diagram of each part of the embodiment. 1A, 1B: paper sensor, 2: timing determination circuit, 3
... Up / down counter, 4 ... Offset value setting circuit, 5 ... Monitor display, 6 ... Comparator, 7 ...
... Light emitting diode, 8 ... Clock oscillator, 9 ... Inverting circuit.

Claims (1)

(57) [Scope of request for utility model registration] A first and a second sheet detecting means for detecting a sheet to be conveyed, the first and second sheets being spaced apart in a direction perpendicular to the sheet conveying direction;
Paper detection means, detection timing determination means for determining which of the first and second paper detection means the paper detection timing is earlier, and the first detection means If it is determined that the paper detection timing of the paper detection means is early, the count is up, and the first paper detection means detects the leading edge of the paper, and then the second paper detection means detects the leading edge of the paper. A predetermined clock signal is counted until the time is reached, and if the detection timing determination means determines that the paper detection timing of the second paper detection means is early, the countdown state is set, and the second paper detection means detects the paper count. An up-down card that counts a predetermined clock signal from when the leading edge of the sheet is detected until the first sheet detecting means detects the leading edge of the sheet. The paper is transported in a normal state with no skew by setting the initial value of the up / down counting means to zero, and a value obtained by reversing the sign of the count value of the up / down counting means at this time is used as the up / down counting means. Setting means for setting the initial value of the sheet, and comparing means for detecting the presence or absence of skew of the sheet by comparing the count value of the up / down counting means with a predetermined allowable skew value when the sheet is conveyed. Paper skew detector.