JP2012232828A - Detection device of end position, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that the detection accuracy of an end position of a recording material varies depending on a rotation angle of a crank arm when the crank arm is used to detect the end position of the recording material.SOLUTION: The twice resolution is used in an area where the detection accuracy is reduced and the normal resolution is used in an area where the detection accuracy is good, in response to a step number of a motor. The detection accuracy is thereby improved and the number of a timer interrupt caused by a CPU 201 is also made to be necessary minimum. Even a detection device of the end position in a crank arm system can detects the end position of the recording material P accurately.

Description

  The present invention relates to a recording material end position detecting device for detecting the end position of a recording material, and an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine including the end position detecting device.

  In a conventional image forming apparatus, a recording material is fed from a paper feed cassette to an image forming unit by a feed roller and conveyed. The recording material to be transported is transported by various effects such as the difference in outer diameter of the transport roller, the difference in transport speed due to wear with the transport roller, and the friction resistance between the transport guide that guides the recording material and the recording material. In some cases, the sheet is conveyed in an oblique state (hereinafter also referred to as skew). When the recording material is conveyed while being skewed and the toner image on the photosensitive drum is transferred to the recording material, the image is printed in an oblique state with respect to the recording material. Therefore, in the image forming apparatus, in order to prevent the skew of the recording material, a shutter member is provided on the registration roller pair and the conveying roller pair so that the recording material front ends are brought into contact with each other, and the recording material front ends are aligned. There is one that suppresses the skew by conveying it to the surface. However, the configuration in which the leading edge of the recording material is abutted to suppress the skew is effective in the direction parallel to the recording material conveyance direction, but the positional deviation cannot be suppressed in the direction orthogonal to the recording material conveyance direction. In the double-sided printing configuration, since the recording material that has passed through the fixing portion on the first side contracts due to heat and pressure of the fixing portion, the recording material size on the second side becomes smaller than the recording material size on the first side. In some cases, the end position parallel to the transport direction differs.

  Therefore, in order to cope with the positional deviation in the direction orthogonal to the recording material conveyance direction, there is a configuration in which a recording material end position parallel to the recording material conveyance direction is detected. As a configuration for detecting the recording material end position, Patent Document 1 discloses a position where the photo interrupter is moved across the recording material in a direction orthogonal to the conveyance direction of the recording material, and the recording material blocks light from the reference position. The end position of the recording material is detected by the distance up to. A method of correcting a shift between the recording material and the image by relatively matching the position of the recording material and the image forming position is disclosed.

JP-A-9-124187

  As described in the prior art, the end position of the recording material can be detected based on how much the sensor has moved from the reference position. However, in order to detect the end position of the recording material, the moving distance from the reference position Had to get. For this reason, when detecting the end position of the recording material, the sensor is first moved to a position where the reference position is detected, and the end position of the recording material is detected after detecting the reference position. . For this reason, in order to detect the end position of the recording material, it is necessary to move the sensor in two directions: driving in the direction to move the sensor to the reference position, and moving to the end position of the recording material. That is, a dedicated drive source and a member for switching the drive are required, which causes a cost increase.

  Therefore, a crank arm can be used to detect the end position of the recording material without using a dedicated drive source or member for reciprocating the sensor. However, when the end position of the recording material is detected using the crank arm, there is a problem that the detection accuracy of the end position of the recording material varies depending on the rotation angle of the crank arm.

  The invention according to the present application has been made in view of the above situation, and an object of the present invention is to accurately detect the end position of a recording material even in an end position detection apparatus using a crank arm.

  To achieve the above object, the present invention provides a rotating member that is rotatably supported and rotated by driving from a driving unit, and a sensor unit that is connected to the rotating member and reciprocates when the rotating member rotates. A recording material detection sensor that is mounted on the sensor unit and detects the presence or absence of the recording material, and the recording material detection sensor detects the recording material while the sensor unit is reciprocating as the rotating member rotates. If there is no recording material by the recording material detection sensor while the sensor unit is reciprocating while the rotation member rotates, or the rotation member rotates during the period when it is detected that there is Based on the rotation angle of the rotation member during the detection period, the recording material detection sensor detects the edge of the recording material on the side orthogonal to the recording material conveyance direction. And, a control means for calculating a position where the recording material is conveyed, said control means, the resolution in detecting a rotational speed of said rotary member is rotated, be controlled in accordance with the state of the drive unit It is characterized by.

  According to the configuration of the present invention, it is possible to accurately detect the end position of the recording material even in the end position detecting device using the crank arm.

The figure which shows the structure of the recording material edge position detection device The figure which shows operation control of a recording material edge part position detection apparatus The figure which shows the state which has detected the edge part position of a recording material Graph showing recording material detection sensor output value and crank arm rotation angle The figure which shows the mode of a motion of the sensor unit 110, and the change of the rotation angle of a crank arm A graph showing the relationship between the rotation angle of the crank arm 102 and the amount of movement of the sensor unit 110 in the linear direction Table showing the amount of movement per step of the sensor unit 6 is a flowchart showing a method for eliminating variations in detection accuracy of recording materials in the first embodiment. The figure which shows two excitation phase signals in the two-phase excitation system of a stepping motor The figure which shows the step number of the stepping motor in 1st Embodiment, and the timing of timer interruption 6 is a flowchart showing a method for eliminating variations in detection accuracy of recording materials in the first embodiment. The figure which shows the step number of the stepping motor in 2nd Embodiment, and the timing of a timer interruption Schematic configuration diagram of an image forming apparatus Flow chart for adjusting the main scan writing position when forming an image for single-sided printing Schematic configuration diagram of an image forming apparatus Flowchart for adjusting the main scan writing position when forming images for duplex printing

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments are not necessarily essential to the solving means of all inventions in combination of features described in what is not, also embodiments to limit the scope of the appended claims.

(First embodiment)
FIG. 1 is a diagram showing a configuration of a recording material edge position detection apparatus according to the first embodiment. The recording material end position detecting device has a crank arm 102 as a rotating member that is rotatably supported around a crankshaft 101 as a center of rotation. Here, the crank arm 102 is configured in a disc shape, but may be configured in a rod-shaped link member. One end of the connecting link 104 is rotatably connected to the crank arm 102 at a connecting portion 103 on the crank arm 102. A sensor unit 110 is connected to a connection portion 105 that is the other end of the connection link 104. The crank arm 102 is rotated by a crank arm driving unit (not shown). The sensor unit 110 is configured to reciprocate on a straight line connecting the crankshaft 101 and the connecting portion 105. The sensor unit 110 includes a light emitting unit 111 and a light receiving unit 112 of a recording material detection sensor. The light emitting unit 111 and the light receiving unit 112 of the recording material detection sensor are combined to form a recording material detection sensor. As the crank arm 102 rotates once, the sensor unit 110 reciprocates once.

  Here, the light emitting unit 111 and the light receiving unit 112 are opposed to detect the presence or absence of a recording material as a transmission type recording material detection sensor. However, the light emitting unit 111 and the light receiving unit 112 are arranged on the same surface. It is also possible to detect the presence or absence of a recording material as a reflective recording material detection sensor.

  When there is no obstacle between the light emitting unit 111 and the light receiving unit 112 of the recording material detection sensor, the light receiving unit 112 can receive light from the light emitting unit 111. When the recording material P between the light emitting portion 111 and the light receiving portion 112 is present, the light from the light emitting portion 111 is blocked by the recording material P, the light receiving unit 112 can not receive light. Accordingly, the recording material detection sensor can detect whether or not the recording material P exists on the optical path between the light emitting unit 111 and the light receiving unit 112. Further, the end of the recording material P can be detected by detecting the output of the light receiving unit 112 and detecting the change point of the output which means switching of the presence or absence of the recording material P.

  Next, a method for obtaining the distance from the crankshaft 101 to the connecting portion 105 of the sensor unit 110 will be described. As shown in FIG. 1, the distance between the crankshaft 101 and the connecting portion 103, that is, the rotation radius of the crank arm is R, and the length of the connecting link 104 is L. Further, an angle formed by a straight line 122 connecting the crankshaft 101 and the connecting portion 105 and a straight line 123 connecting the crankshaft 101 and the connecting portion 103 is θ [rad] (hereinafter referred to as “crank arm angle”). And At this time, if the distance from the crankshaft 101 to the connecting portion 105 is X, the distance X can be expressed by the following equation.

Therefore, if the crank arm angle θ is obtained, the position of the sensor unit can be obtained. While rotating the crank arm 102 to reciprocate the sensor unit 110, the output value of the recording material detection sensor is detected, and the crank arm angle Φ when the end of the recording material P is detected is obtained from the crankshaft 101. The distance to the end position of the recording material P can be calculated.

  FIG. 2 is an example of a block diagram illustrating operation control of the recording material edge position detection device. The CPU 201 is connected to the light emitting unit 111 and the light receiving unit 112 of the recording material detection sensor 110 and detects the output of the light receiving unit 112 when the light emitting unit 111 is turned on. When there is no recording material P between the light emitting unit 111 and the light receiving unit 112, the output value of the light receiving unit is increased and the output value is detected as High. When the recording material P is between the light emitting unit 111 and the light receiving unit 112, the output value of the light receiving unit 112 is reduced by being shielded by the recording material P, and the output value is detected as Low.

  Further, the CPU 201 controls the driving of the crank arm driving unit 230, and the crank arm 102 rotates by the driving force from the crank arm driving unit 230. The crank arm driving unit 230 is a motor such as a stepping motor and a control circuit, and can perform angle control and speed control based on a signal from the CPU 201. The CPU 201 can calculate the rotation angle of the crank arm 102 by a control signal sent to the crank arm driving unit 230. For example, since the number of drive pulses when the stepping motor rotates once is determined, the rotation angle of the stepping motor can be calculated by counting the number of drive pulses of the stepping motor with the CPU 201. If the driving force is transmitted from the stepping motor to the crank arm 102 directly or via a gear or the like, the rotation angle of the crank arm 102 can be calculated based on the angle and gear ratio of the stepping motor. .

  FIG. 3 is a diagram showing a state where the end position of the recording material is detected. The recording material P is conveyed in the direction of the arrow 320. The recording material end position detection device is arranged so that the sensor unit 110 reciprocates in the direction of an arrow 322 perpendicular to the conveyance direction of the recording material P. The crank arm 102 is supported by the crankshaft 101 and rotates in the direction of the arrow 321. The crank arm 102 can also rotate in the direction opposite to the arrow 321. The crank arm 102 rotates in one direction while detecting the end position of the recording material.

  As the crank arm 102 is rotated by the crank arm drive unit, the sensor unit 110 reciprocates in the direction of the arrow 322. If the recording material P on the optical path between the light emitting portion 111 of the recording material detection sensor light receiving portion 112 is present, the output of the recording material detection sensor becomes High (hereinafter, referred to as "no recording material"). If there is the recording material P and the light emitting portion 111 of the recording material detection sensor in the optical path of the light receiving portion 112, the output of the recording material detection sensor becomes Low (hereinafter, referred to also as "having a recording material"). When the sensor output changes from High to Low or from Low to High, it can be said that the end of the recording material P exists on the optical path of the light emitting unit 111 and the light receiving unit 112 of the recording material detection sensor. Therefore, by arranging and reciprocating the sensor unit so that the optical paths of the light emitting unit 111 and the light receiving unit 112 of the recording material detection sensor pass through the end of the recording material, the recording material parallel to the conveyance direction of the recording material can be obtained. The end position can be detected. When the end position of the recording material P is detected, the recording material P may be transported or stopped.

  FIG. 4 is a graph showing the output value of the recording material detection sensor and the rotation angle of the crank arm. As described above, when the output value of the recording material detection sensor is High, there is no recording material, and when the output value is Low, the recording material is present. The horizontal axis indicates the rotation angle of the crank arm. The rotation angle of the crank arm during the period when the output value of the recording material detection sensor is High is φ. Here, as an example, since the crank arm driving unit uses a stepping motor, the rotation angle φ of the crank arm in a predetermined period can be calculated by the CPU 201. In this way, the rotation angle φ of the crank arm is calculated during the period when the output value of the recording material detection sensor is High.

  Next, a method for obtaining the end position of the recording material from the rotation angle φ of the crank arm will be described. FIG. 5 shows the movement of the sensor unit 110 and the change in the rotation angle of the crank arm when time (a), (b), (c) elapses. FIG. 5A shows a state where there is no paper and no paper, and FIG. 5B shows a state where the link member 104 overlaps a straight line 122 connecting the crankshaft 101 and the connecting portion 105. 5 (c) shows a state where there is paper from no paper. As shown in FIG. 5A, when the crankshaft 101 and the connecting portion 103 are connected when the output value of the light receiving portion 112 is switched from Low to High, a straight line 131 is obtained. On the other hand, as shown in FIG. 5C, a straight line 132 is formed when the crankshaft 101 and the connecting portion 103 are connected when the output value of the light receiving portion 112 switches from High to Low. Due to the geometric relationship of the crank mechanism, the straight line 131 and the straight line 123 are symmetrical about the straight line 122. Accordingly, the output value of the light receiving section 112 of the recording material detection sensor is the rotation angle φ of the crank arm when it is High, equal to the angle formed by the straight line 131 and the line 123 shown in FIG. 5 (c). The rotation angle φ can be calculated by the CPU, and the bisector of the rotation angle φ becomes a straight line 122. Therefore, as shown in FIG. 5C, it can be seen that θ is an angle half of φ.

The distance from the crankshaft 101 to the end of the recording material P can be obtained from the equations (1) and (2).

  As described above, when the CPU calculates the angle φ at which the crank arm rotates while the light receiving unit 112 detects the absence of the recording material, the end position of the recording material P can be calculated. The end position of the recording material P can also be calculated by calculating the angle at which the crank arm rotates while the light receiving unit 112 detects the presence of the recording material.

  Next, the relationship between the rotation angle of the crank arm 102 and the movement amount of the sensor unit 110 in the linear direction will be described. FIG. 6 is a graph showing the rotation angle θ of the crank arm on the horizontal axis and the position of the sensor unit 110 on the vertical axis. In the configuration described with reference to FIG. 1, the rotation radius R of the crank arm is 3 mm, the length L of the link member is 9 mm, and the position of the sensor unit 110 is calculated based on the formula (1) and plotted.

  On the horizontal axis, an axis indicating the number of steps is placed together with an axis indicating the rotation angle θ. This is because a stepping motor is used as a motor for driving the crank arm, and the number of steps of the stepping motor corresponds to the rotation angle. In the present embodiment, the number of steps when the stepping motor is driven by the two-phase excitation method is 84 steps, and the sensor unit 110 is configured to reciprocate once, that is, θ is 360 degrees (2π [rad]). . In the graph, the position X of the sensor unit 110 at each step number from 0 to 84 is plotted. Since the angle 360 degrees corresponds to 84 steps, the angle per step is 360 ÷ 84 = 4.3 degrees. Therefore, the graph shows how the sensor unit position changes every time the crank arm rotates 4.3 degrees.

  The circled areas indicated by 601, 603, and 605 in FIG. 6 are densely plotted, indicating that the amount of movement of the sensor unit per step is small. On the other hand, the area surrounded by circles 602 and 604 in FIG. 6 has a rough plot, indicating that the amount of movement of the sensor unit per step is large. The specific data indicating the value of the movement amount per step of the sensor unit depending on the position of the sensor unit 110 is shown in the table of FIG. Data rightmost column in the table of FIG. 7, the value of the position of the sensor unit 110 in the step number, a data taking the difference between the position of the sensor unit 110 at the step number of the previous one. That is, the data indicates how much the sensor unit 110 moves in one step. From this table, it can be seen that when the amount of movement in one step is small, it is 0.01 mm, and when it is large, it is 0.24 mm.

  When the CPU detects the rotation angle of the crank arm at the detection timing as the resolution of one step unit shown in this table, even when the same one step is detected, the actual movement amount of the sensor unit 110 is 0.01 mm. There is a variation between 0.24 mm and 0.24 mm. This variation results in variation in detection accuracy of the end position of the recording material P. That is, the areas surrounded by circles 601, 603, and 605 in FIG. 6 are areas with high detection accuracy because the movement amount of the sensor unit 110 is small. On the other hand, the areas surrounded by circles 602 and 604 in FIG. 6 are areas with low detection accuracy because the amount of movement of the sensor unit 110 is large. Thus, it can be seen that the detection accuracy of the recording material P changes depending on the position of the sensor unit 110.

  A method for eliminating the variation in the detection accuracy of the recording material will be described based on the flowchart of FIG. In step S101, the CPU 201 waits for the crank arm rotation angle θ to become 0 degrees. The position at which the rotation angle θ of the crank arm is 0 degree is calculated by the CPU 201 while the light receiving unit 112 detects the absence of the recording material as described with reference to FIG. Then, the position where the calculated rotation angle φ is equally divided corresponds to 0 degree of the rotation angle θ. The CPU 201 calculates the rotation angle φ by one rotation of the first crank arm, and can detect the position where the rotation angle θ becomes 0 degree at the time of the next rotation of the crank arm.

  In step S102, the CPU 201 sets the number of steps to 0 when the rotation angle θ becomes 0 degrees. In step S103, the CPU 201 increments the step number by one each time the step of the excitation pattern for the stepping motor is advanced. As a result, the CPU 201 can detect the rotation angle θ of the crank arm based on the number of steps. In step S104, the CPU 201 determines whether the number of steps of the stepping motor is in the range of “10 to 37” or “48 to 75”. The number of steps and "10-37" are you set the range of "48 to 75", the movement amount per one step of the sensor unit 110, i.e. the detection accuracy of the edge position of the recording material P 0.10mm This is because the area that exceeds the range is selected. Here, the predetermined amount is set to 0.10 mm, but this range is an example in the present embodiment, and the range of the number of steps can be appropriately set according to the detection accuracy of the end position. If it is determined in step S104 that the number of steps is within the set area, in step S105, the CPU 201 sets the resolution of the sensor unit 110 to twice the normal resolution. On the other hand, when it is determined in S104 that the number of steps is not within the set area, in S106, the CPU 201 sets the resolution of the sensor unit 110 to the normal resolution.

  Here, the double resolution and the normal resolution will be described with reference to FIGS. 9 and 10. FIG. 9 shows two excitation phase signals in the two-phase excitation method of the stepping motor. Reference numeral 901 denotes an A phase signal, and reference numeral 902 denotes a B phase signal. CPU201 If the two-phase excitation driving the stepping motor to generate a timer interrupt at a timing indicated by arrows 903, will switch the level of the A-phase signal and the B-phase signal at this timing. In the case of 1-2 phase excitation driving, the CPU 201 generates a timer interrupt at the timing indicated by an arrow 904, and switches a current control signal (not shown) in addition to the A phase signal and the B phase signal at this timing. . The 1-2 phase excitation drive indicated by 904 has twice as many interrupt timings as the two phase excitation drive indicated by 903. That is, an interrupt is generated at a timing half of the timing 903 and the timing 903. Note that, as indicated by 905, the W1-2 phase excitation drive has an interrupt timing that is twice as high as that of the 1-2 phase excitation drive indicated by 904. The excitation drive described here is an example in the present embodiment, and the timing of the timer interruption can be arbitrarily set according to the detection accuracy of the end position of the recording material P to be obtained.

  With the normal resolution described above, the rotation angle θ of the crank arm is detected at the timing of 903, and the end position of the recording material P is detected. If the detection is performed at this timing, the sensor unit movement amount per step shown in the table of FIG. 7 becomes the detection accuracy of the end position of the recording material P. On the other hand, the double resolution means that the rotation angle θ of the crank arm is detected at the timing of 904 and the end position of the recording material P is detected. When detection is performed at this timing, the end position of the recording material can be detected with a movement amount that is approximately half of the movement amount of the sensor unit per step shown in the table of FIG. Therefore, the end position of the recording material P can be detected with twice the normal accuracy.

  When switching between normal resolution and double resolution, even if the sensor unit continues to be driven at a constant speed without actually switching the excitation method of the stepping motor from 2-phase excitation to 1-2-phase excitation, It is possible to achieve the same resolution. The CPU 201 only needs to generate the timer interrupt at the timing of 903 when detecting the timer interrupt at the normal resolution and generate the timer interrupt at the timing of 904 only when detecting the timer interrupt at the double resolution. 904 A-phase signal 901 and the B-phase signal 902 and the current control signal at a timing (not shown) once the two to change, that is, so as to change at the same timing as the timing of the 903. In this way, even if the stepping motor continues to be driven by the two-phase excitation method, the end of the recording material P is switched by switching the timer interrupt generated by the CPU 201 to 903 or 904 according to the rotation angle of the crank arm. The position detection accuracy can be switched. FIG. 10 shows the number of steps of the stepping motor and the timing of timer interruption. In a section where the detection accuracy of the end position of the recording material P is high, a timer interrupt is generated at a normal resolution timing, and in a section where the detection accuracy of the end position of the recording material P is low, the timing is doubled. It can be seen that a timer interrupt is generated. Thereby, even in a period when the detection accuracy in one step is low, the detection accuracy can be improved by increasing the timing of the timer interruption.

  In step S <b> 107, the CPU 201 determines whether the sensor unit 110 detects the end of the recording material P. Until the end is detected, the CPU 201 switches between the normal resolution and the double resolution by switching the generation timing of the timer interrupt according to the rotation angle θ of the crank arm as shown in FIG. . When the sensor unit 110 detects the edge of the recording material P, in S108, the CPU 201 obtains the rotation angle θ and calculates the paper edge position of the recording material P from Expression (1). The rotation angle θ is detected with either normal resolution or twice the normal resolution, and the value of the end position is also detected with accuracy according to the resolution. In the present embodiment, as an example, a double resolution is used in an area where the detection accuracy exceeds 0.10 mm. Therefore, since the double resolution is used for the area where the detection accuracy is lowered and the normal resolution is used for the area where the detection accuracy is originally good, the detection accuracy is improved and the number of timer interrupts generated by the CPU 201 is minimized. It can also be limited.

  In this way, even with a crank arm type end position detection device, it is possible to accurately detect the end position of the recording material P, and an end position detection device that achieves both low cost and improved accuracy is provided. Can be provided. In the present embodiment, whether or not the detection accuracy exceeds 0.10 mm is used as a reference for determining whether to switch resolution. However, the detection accuracy is not limited to 0.10 mm. For example, an amount by which a significant difference is recognized in the human visual level may be used as a reference. In general, in offset printing, a printing resolution in which a visual acuity of 1.0 is standard resolution of the human eye is determined. In many cases, the offset printed matter is printed at a resolution of 175 lines, that is, 350 dpi. Even if the end position is detected with an accuracy exceeding this resolution, there is almost no difference in human vision. Therefore, 350 dpi, that is, 0.072 mm may be used as a reference.

  Further, it may be determined on the basis of an amount determined by tolerances such as the shape, size, and assembly accuracy of the end position detection device. Even if the resolution is increased by the CPU 201 and the detection accuracy is increased, if there is a so-called mechanical variation caused by tolerances such as shape, dimensions, and assembly accuracy, this variation amount will be used as the final edge position detection accuracy. Affect. Therefore, the timing for switching the resolution may be set according to variations determined by tolerances such as the shape, dimensions, and assembly accuracy of the end position detection device. For example, if the mechanical variation amount is 0.05 mm, the reference for determining the resolution switching by the CPU 201 may be 0.05 mm, which is the same as the mechanical variation amount, or twice as accurate as the mechanical variation amount. It is good also as good 0.025 mm.

(Second Embodiment)
In the first embodiment, a moving amount per step of the sensor unit 110, that is, a resolution that is higher than the normal resolution is used only in an area where the detection accuracy exceeds 0.10 mm, In other areas, normal resolution was used. However, there is an area exceeding 0.20 mm in an area exceeding 0.10 mm. Specifically, the number of steps ranges from 19 to 31 and from 54 to 66. In this range, even if the resolution is doubled, the detection accuracy exceeds 0.10 mm. Therefore, in this embodiment, even if this resolution is doubled, the resolution is set to four times the normal resolution in the range where the detection accuracy exceeds 0.10 mm. This is shown in FIG.

  It is 0.24 mm even where the amount of movement per step of the sensor unit 110 is the largest. Therefore, if the end position is detected using four times the resolution, it can be detected with a detection accuracy of 0.10 mm or less. As a result, the detection accuracy can be reduced to 0.01 mm or less in all areas from 0 step to 84 steps, that is, the crank arm rotation angle θ from 0 degrees to 360 degrees. Note that, as indicated by reference numeral 905 in FIG. 9, the CPU 201 generates a timer interrupt at the excitation timing when the stepping motor excitation method is the W1-2 phase excitation method, as indicated by reference numeral 905 in FIG. The rotation angle θ of the crank arm may be detected by counting the number of steps at this time.

  Control in the present embodiment will be described with reference to the flowchart of FIG. Note that the same processes as those in the flowchart of FIG. 8 described in the first embodiment are denoted by the same reference numerals and description thereof is omitted. S101 to S108 are the same as those in FIG. In step S401, the CPU 201 determines whether the number of steps of the stepping motor is in the range of “19 to 31” or “54 to 66”. The reason why the number of steps is set in this range is to determine whether or not the amount of movement of the sensor unit 110 per step, that is, the detection accuracy of the end position exceeds 0.20 mm. If it is determined in step S401 that the number of steps is within the set area, the CPU 201 sets the resolution of the sensor unit 110 to four times the normal resolution in step S402. On the other hand, if it is determined in step S401 that the number of steps is not within the set area, in step S105, the resolution is doubled as usual, as in the first embodiment. The following control is the same as that described in the first embodiment.

  As described above, in the present embodiment, the resolution is normally selected from three resolutions of two or four times according to the moving position of the sensor unit 110, and the end position of the recording material P is detected. I made it. Therefore, a detection accuracy of 0.10 mm or less can be realized over the entire rotation angle of the crank arm. Furthermore, since the number of interrupts of the CPU 201 for realizing the detection accuracy of 0.10 mm is set to be as small as possible, the cost of the CPU can be reduced. Therefore, it is possible to accurately detect the end position of the recording material P even with a crank arm type end position detecting apparatus, and to provide an end position detecting apparatus that achieves both low cost and improved accuracy. be able to. It should be noted that the resolution may be set not only in three steps of 2 times and 4 times but also in 4 steps and 5 steps. Further, the resolution magnification is not limited to 2 times or 4 times, and any magnification such as 4 times or 8 times may be set. The excitation method of the stepping motor is not limited to two-phase excitation, 1-2 phase excitation, and W1-2 phase excitation, and may be 2W1-2 phase excitation, 4W1-2 phase excitation, or the like.

(Third embodiment)
In the first embodiment and the second embodiment, the recording material edge position detection device has been described. In the present embodiment, an image forming apparatus provided with a recording material edge position detection device will be described. FIG. 13 is a schematic configuration diagram of an image forming apparatus equipped with the recording material edge position detection device shown in the first or second embodiment. In the present embodiment, a laser printer (hereinafter referred to as an “image forming apparatus”) as an example of an image forming apparatus will be described as an example. It doesn't matter.

  The image forming apparatus 20 includes a drum-type electrophotographic photosensitive member (hereinafter also referred to as “photosensitive drum”) 1 as an image carrier. The photosensitive drum 1 is rotatably supported and is driven at a predetermined process speed in the direction of the arrow R1 by a driving unit (not shown). Around the photosensitive drum 1, a charging roller 2, an exposure device 3, a developing device 4, a transfer roller 5, and a cleaning device 7 are sequentially arranged along the rotation direction. A paper feed cassette 21 that stores the recording material P is disposed below the image forming apparatus 20. Further, the recording material P sheet feeding roller 11 in order along the conveying path of the conveying rollers 8, the recording material edge position detecting device 100, the top sensor 9, the conveyance guide 10, a fixing device 6, the transport rollers 12, discharge rollers 13 A paper discharge tray 14 is disposed.

  Next, the operation of the image forming apparatus having the above configuration will be described. The photosensitive drum 1 driven in the direction of the arrow R1 by a driving unit (not shown) is uniformly charged to a predetermined polarity and a predetermined potential by the charging roller 2. Photosensitive drum 1 after the charging, exposure based on image information by an exposure device 3 consisting of a laser scanner or the like is performed with respect to the surface, an electrostatic latent image is formed charge of the exposed portion is removed. The operation of the exposure apparatus 3 is controlled by the CPU 201. The electrostatic latent image is developed by the developing device 4. The developing device 4 includes a developing roller 41, and a developing bias is applied to the developing roller 41 so that toner is attached to the electrostatic latent image on the photosensitive drum 1 and developed (visualized) as a toner image.

  The toner image is transferred to the recording material P by the transfer roller 5. The recording material P is housed in a paper feed cassette 21, fed by a paper feed roller 11, transported by a transport roller 8, and the photosensitive drum 1 through a recording material end position detection device 100 and a top sensor 9. And a transfer nip between the transfer roller 5 and the transfer roller 5. At this time, the leading edge of the recording material P is detected by the top sensor 9 and is synchronized with the toner image on the photosensitive drum 1. A transfer bias is applied to the transfer roller 5, whereby the toner image on the photosensitive drum 1 is transferred to a predetermined position on the recording material P. The recording material P carrying the unfixed toner image on the surface by the transfer is transported to the fixing device 6 along the transport guide 10, and the unfixed toner image is heated and pressurized to be fixed on the surface of the recording material P. When the toner image is fixed, the recording material P is transported by the transport roller 12 and discharged onto the paper discharge tray 14 by the paper discharge roller 13. When an image is formed on the second surface of the recording material P, a part of the recording material P (tip portion) is once discharged to the outside of the image forming device, and then the rotation direction of the FD discharge roller 13 is switched. Switch-back is performed and the sheet is fed to the double-sided roller and re-feed roller 51 in the double-sided conveyance path. The recording material P, which has been reversed upside down in this way, is again fed to the photosensitive drum 1 by the registration rollers 8 and printing on the second surface of the recording material P is performed.

  FIG. 14 is a flowchart for adjusting the main scanning writing position during image formation for single-sided printing. In step S201, the CPU 201 waits for printing to start. When printing is started, in step S <b> 202, the CPU 201 feeds the recording material P from the cassette 10 with the paper feed roller 11, and transports the recording material P with the registration roller 8. In step S <b> 203, the CPU 201 determines whether the top sensor 9 has detected the leading edge of the recording material P. When the leading edge of the recording material P is detected, in step S204, the CPU 201 starts driving the motor 17, and the recording material edge position detection device 100 detects the edge position parallel to the recording material conveyance direction and records it in the CPU 201. Send material edge position information. In step S <b> 205, the CPU 201 determines the adjustment amount of the image writing position in the direction (main scanning direction) orthogonal to the conveyance direction of the recording material P based on the information on the recording material end position. In step S <b> 206, the CPU 201 adjusts the image writing position in the main scanning direction of the exposure unit 3 to form an image after a predetermined time from the timing when the top sensor 9 detects the leading edge of the recording material P. In step S <b> 207, the CPU 201 discharges the image-formed recording material P to the paper discharge tray 14.

  In this embodiment, the recording material edge position detection device 100 is disposed between the registration roller 8 and the top sensor 9. However, the invention is not limited to this arrangement, on the conveyance path of the recording material, before the exposure means 3 starts the exposure to the photosensitive drum 1, a recording material at a timing can be adjusted in the main scanning writing position Any position may be used as long as the end position can be detected.

  As described above, in the image forming apparatus provided with the recording material edge position detection device, even when a positional deviation with respect to the direction orthogonal to the conveyance direction of the recording material P occurs, the recording material is adjusted by adjusting the image writing position. The image shift with respect to P can be reduced. Further, the number of times of detecting the end position of the recording material may be one time or a plurality of times. It is also possible to detect the skew of the recording material by performing detection a plurality of times. Even when the skew of the recording material is detected, the positional deviation between the recording material and the image can be reduced by adjusting the image writing position in the main scanning direction.

  Next, an image forming apparatus provided with a recording material edge position detection device in a double-sided conveyance path will be described with reference to FIG. In addition, about the structure similar to previous FIG. 13, the same code | symbol is attached | subjected and description is abbreviate | omitted. A double-sided sensor 15 detects the recording material P conveyed through the double-sided conveyance path. Reference numeral 17 denotes a motor which is a drive source of the recording material edge position detection device 100. The motor 17 also serves as a drive source for the duplex roller 16 and the refeed roller 51 in the duplex conveyance path.

  FIG. 16 is a flowchart for adjusting the image writing position in the main scanning direction at the time of image formation of double-sided printing according to the present embodiment. In this configuration, the image writing position is adjusted on the second surface of the recording material P after the first surface is printed. The same steps as those in the flowchart of FIG. 14 are denoted by the same reference numerals, and the description thereof is omitted.

  In step S301, the CPU 201 determines whether the current image formation command is duplex printing. If the printing is not duplex printing, the recording material P on which the image is formed on the first side is discharged to a discharge tray. If the printing is duplex printing, the CPU 201 waits for the reversal timing of the recording material P in S302. At the reversal timing, in S303, the CPU 201 reversely drives the FD paper discharge roller 13 to convey the recording material P to the double-sided conveyance path. In step S <b> 304, the CPU 201 determines whether the double-sided sensor 15 has detected the leading edge of the recording material P. When the recording material P is detected, in step S305, the CPU 201 causes the recording material end position detection device 100 to detect an end position parallel to the conveyance direction of the recording material and send information on the recording material end position.

  In step S <b> 306, the CPU 201 determines the correction amount of the image writing position in the direction orthogonal to the conveyance direction of the recording material P (main scanning direction) based on the information on the recording material edge position detected by the recording material edge position detection device. decide. Note that the driving of the recording material edge position detecting device 100 is not necessary because the motor 17 is already driven to convey the recording material P. Further, the acceleration / deceleration control of the motor 17 may be performed while the recording material P is being conveyed on both sides. At this time, the rotational speed of the crank arm in the recording material end position detection device 100 is also accelerated and decelerated simultaneously. However, since the rotation angle of the crank arm is detected by the number of steps, the rotation angle of the crank arm is correctly detected regardless of the speed of the motor, and the end position of the recording material P is detected. It can be performed.

  In step S <b> 307, the CPU 201 determines whether the top sensor 9 has detected the recording material P conveyed toward the registration roller again by the re-feed roller 51. When the top sensor 9 detects the leading edge of the recording material P, in step S308, the CPU 201 adjusts the image writing position in the main scanning direction of the exposure unit 3 and forms an image after a predetermined time from the timing when the leading edge of the recording material is detected.

  As described above, the recording material edge position detection device 100 is arranged in the double-sided conveyance path, the edge position of the recording material P conveyed on both sides is detected, and the writing position is corrected using the result. it can. In addition, the motor 17 serving as a driving source of the recording material end position detecting device 100 is also used as a driving source for conveying the recording material P. In general, there is a large difference in required step resolution between a motor used for conveying the recording material P and a motor that operates the sensor unit as in the present embodiment. Therefore, if the motor is simply used, the accuracy of the end position detection by the sensor unit may not be improved. However, as in this embodiment, by performing control so as to increase the resolution in accordance with the amount of movement of the sensor unit in one step of the motor, it is possible to increase the detection accuracy that varies depending on the motor step. Moreover, it becomes possible to detect the end position of the recording material P with high accuracy, and it is possible to provide an end position detecting device that achieves both low cost and improved accuracy.

DESCRIPTION OF SYMBOLS 100 Recording material edge part position detection apparatus 101 Crankshaft 102 Crank arm 103 Connection part 104 Connection link 105 Connection part 110 Sensor unit 111 Light emission part 112 Light reception part 201 CPU
230 Crank arm drive part P Recording material

Claims (17)

A rotating member that is rotatably supported and rotated by driving from the driving unit;
A sensor unit that is connected to the rotating member and reciprocates as the rotating member rotates;
A recording material detection sensor mounted on the sensor unit for detecting the presence or absence of a recording material;
While the sensor unit is reciprocating as the rotating member rotates, the rotation angle of the rotating member rotated during the period when the recording material detection sensor detects that the recording material is present, or the rotating member The recording material detection sensor detects that there is no recording material while the sensor unit is reciprocating due to rotation of the recording material. Based on the rotation angle of the rotation member, the end of the recording material is detected. Having a control means for detecting the position;
The recording material end position detecting apparatus, wherein the control means controls detection timing according to a rotation angle of the rotating member. A connecting link connecting the rotating member and the sensor unit;
The recording material end position detection apparatus according to claim 1, wherein the rotating member is connected to one end of the connecting link, and a sensor unit is connected to the other end of the connecting link.   3. The recording material end portion according to claim 2, wherein the recording material detection sensor reciprocates on a straight line connecting a connection portion between the sensor unit and the connecting link and a rotation center of the rotating member. Position detection device.   2. The recording material end position detection apparatus according to claim 1, wherein the driving unit is a stepping motor.   5. The recording material end position detection apparatus according to claim 4, wherein the control means controls detection timing according to the number of steps of the stepping motor.   6. The recording material according to claim 4, wherein the control means controls to increase the detection timing when the movement amount of the sensor unit in one step of the stepping motor exceeds a predetermined amount. End position detection device.   The driving force of a stepping motor, the sensor unit and the other member and the recording material edge position detecting device according to any one of claims 4 to 6, characterized in that it is combined with.   2. The recording material according to claim 1, wherein the driving unit drives the rotating member to rotate in one direction when the recording material end sensor detects the position of the recording material edge. 3. End position detection device.   Each time the rotating member makes one revolution, the sensor unit makes one reciprocation, and the sensor unit makes one reciprocation, so that the recording material detection sensor detects that there is a recording material, or the recording material detection. 2. The recording material end position detection apparatus according to claim 1, wherein a period during which the recording material is detected to be absent by a sensor is detected.   The rotation angle of rotation of the rotating member during the period when the recording material detection sensor detects that the recording material is present, or the rotation member rotates during the period of time when the recording material detection sensor detects that there is no recording material. a rotation angle based on the bisecting angle, characterized in that said recording material detection sensor detects the end of the recording material of the side perpendicular to the conveying direction of the recording material, and calculates the position where the recording material is conveyed The recording material end position detection device according to claim 1. The angle obtained by dividing the rotation angle of the rotation member into two equal parts during the period when the recording material detection sensor detects that there is a recording material is θ,
R is the distance from the rotation center of the rotating member to the connecting portion between the rotating member and the connecting link;
When the distance from the connecting portion between the rotating member and the connecting link to the connecting portion between the connecting link and the sensor unit is L,
The distance X from the rotation center of the rotating member to the connecting portion between the connecting link and the sensor unit when the recording material detection sensor detects the end of the recording material on the side orthogonal to the recording material conveyance direction is:

The recording material end position detection apparatus according to claim 10, wherein the recording material end position detection apparatus can detect the recording material end position detection apparatus.   The recording material end position detection apparatus according to claim 1, wherein the rotating member is a crank arm. Image forming means for forming an image on a recording material;
A rotating member that is rotatably supported and rotated by driving from the driving unit;
A sensor unit connected to the rotating member;
In an image forming apparatus having a recording material detection sensor mounted on the sensor unit and detecting the presence or absence of a recording material,
While the sensor unit is reciprocating as the rotating member rotates, the rotation angle of the rotating member rotated during the period when the recording material detection sensor detects that the recording material is present, or the rotating member The recording material detection sensor detects that there is no recording material while the sensor unit is reciprocating due to rotation of the recording material. Based on the rotation angle of the rotation member, the end of the recording material is detected. Control means for detecting the position and adjusting the image writing position by the image forming means according to the detected end position of the recording material;
The image forming apparatus, wherein the control unit controls a detection timing according to a rotation angle of the rotating member.   The image forming apparatus according to claim 13, wherein the driving unit is a stepping motor.   The image forming apparatus according to claim 14, wherein the control unit controls detection timing according to the number of steps of the stepping motor.   16. The image formation according to claim 14, wherein the control unit controls the detection timing to be increased when a movement amount of the sensor unit in one step of the stepping motor exceeds a predetermined amount. apparatus. The image forming apparatus according to claim 14, wherein the driving force from the stepping motor is shared by the sensor unit and another member.