JP4344201B2 - Print control method - Google Patents

Description

  The present invention relates to a printing control method in a printing system that forms images on both a first surface and a second surface of a web.

  As an image alignment control method between the first side and the second side in the case of forming an image on both sides of a web typified by a continuous belt-like sheet having no feed hole, the following double-sided printing is used. A typical control method will be described with reference to the drawings.

  FIG. 1 shows an example of a printing system capable of duplex printing. In the first printing apparatus P1, an image Im based on the print data is printed on the web W as shown in FIG. 2, and an alignment mark (toner mark) Rm is printed at the top end of each page. And discharged from the printing apparatus P1.

  The web W discharged from the printing apparatus P1 is fed to the second printing apparatus P2 after being reversed by the reversing apparatus T. By reversing the front and back of the web W by the reversing device T, the web surface (first surface) on the side holding the toner mark Rm is opposed to the detection surface of the mark sensor 16 (see FIG. 3). The web surface (second surface) in the state faces the surface of the photosensitive drum 101.

  Here, the page head is virtually set on the photosensitive drum 101 in synchronization with the transmission timing of the web feed control signal (hereinafter referred to as “CPF-N signal”) from the controller 17. Therefore, by controlling the web conveyance speed so that the phase of the CPF-N signal transmission timing from the controller 17 and the timing at which the mark sensor 16 detects the toner mark Rm are matched, the page on the photosensitive drum 101 is controlled. It is possible to match the top and the page top of the web W with high accuracy at the transfer point TP.

  Here, if the photosensitive drum 101 is rotated at a constant speed and only the web conveyance speed is controlled, a speed difference is generated between the web W being conveyed and the photosensitive drum 101, and the photosensitive drum 101 is transferred onto the web W. This causes a problem that the image is disturbed. In addition, the friction between the photosensitive drum 101 and the web W increases, leading to a problem that the life of the photosensitive drum 101 is shortened. Therefore, it is effective to control the conveyance speed of the web W and the rotation speed of the photosensitive drum 101 synchronously.

  In this example, as shown in FIG. 3, the distance from the transfer point TP by the transfer unit 105 to the exposure point EP on the surface of the photosensitive drum 101 is L1, and the web from the transfer point TP to the detection point DP by the mark sensor 16 is used. The distance on the conveyance path is L2. Here, in a state where the web is transported in such a relationship that the page top PP virtually set on the photosensitive drum 101 and the toner mark Rm representing the page top of the web W coincide at the transfer point TP. The toner mark detection timing is defined as “control timing”.

  By the way, regarding the back side printing of the first page at the start of printing, since the operator starts printing after the web W is loaded in advance at a predetermined position of the printing apparatus P2, the front page top position and the back page top position are started. Usually matches.

When the print data for the first page has been formed on the photosensitive drum 101, the printing apparatus receives the first CPF_LEG-P signal from the controller 17 as shown in FIG. When the CPF_LEG-P signal is received, the calculation of the control timing is executed. Here, the calculation of the control timing is performed based on the following concept, for example. That is, in order to make the top of the second page virtually set on the photosensitive drum 101 coincide with the toner mark Rm of the second page of the web W at the transfer point TP, The toner mark Rm needs to be detected when the top of the second page of the second page comes to the position L2 from the transfer point TP. Accordingly, when the time from the reception of the second CPF-N signal to the control timing is t ₁ and the process speed of the printing apparatus is vp, t ₁ is expressed by the following equation.

t ₁ = (L1−L2) / vp (1)
Further, since the data indicating the page head on the photosensitive drum 101 reaches the transfer point TP every one cycle of the CPF-N signal, that is, every CPF length, the control timing thereafter is the CPF length. Every time. From the detection deviation time of the toner mark Rm with respect to this control timing, it is grasped how much the top of the page printed on the back side is deviated from the top of the front page. That is, when the detection timing of the toner mark Rm is later than the control timing, the web conveyance speed and the rotation speed of the photosensitive drum 101 are accelerated, and conversely, when the detection timing of the toner mark Rm is earlier than the control timing, The conveyance speed and the rotation speed of the photosensitive drum 101 are reduced. That is, the web conveyance speed is controlled so that the timing for detecting the toner mark Rm coincides with the control timing.

Here, FIG. 3 shows the page head position on the photosensitive drum surface at the time when the control timing t _{1 has} elapsed after receiving the CPF-N signal of the nth page (n is an integer of 2 or more). The description will be given with reference.

First, when the nth page toner mark Rm is detected when the control timing t _{1 has} elapsed since the receipt of the nth page CPF-N signal, the nth page toner mark Rm to the transfer point TP is detected. Can be expressed as L2. Next, the distance L3 from the page top position of the nth page on the surface of the photosensitive drum 101 to the transfer point TP is the rotational speed (= web conveyance speed) of the photosensitive drum 101 when printing the nth page. When V _n, represented by the following formula.

  Here, considering the condition for the toner mark Rm of the nth page on the web W to coincide with the top of the page of the nth page formed on the surface of the photosensitive drum 101 at the transfer point TP, The relationship between the distance from the toner mark Rm of the nth page on the web W to the transfer point TP and the distance from the top page position of the nth page on the surface of the photosensitive drum 101 to the transfer point TP is the web transport Since the speed and the rotational speed of the photosensitive drum 101 are controlled at the same speed, the distances need to be equal. That is, the relationship L2 = L3 needs to be established.

Hereinafter, the distance L2 in the web transport path from the detection point DP due to the mark sensor 16 to the transfer point TP, the rotation speed V _n of the photosensitive drum at the time of printing the first page n as a parameter, the above equation (2), The relationship of L2 = L3 is verified.
(A) First, when the distance L1 from the exposure point EP to the transfer point TP is equal to the distance L2 from the detection point DP to the transfer point TP by the mark sensor 16 (L2 = L1),

= L2
Therefore, regardless of the rotational speed _{V n} of the photosensitive drum, L3 = L2 is satisfied.
(B) When the distance L1 from the exposure point EP to the transfer point TP is different from the distance L2 from the detection point DP to the transfer point TP by the mark sensor 16 (L2 ≠ L1), When the rotation speed V _n is _equal to the process speed vp, from the equation (2),

Thus, the relationship L3 = L2 is established.
(C) When the distance L1 from the exposure point EP to the transfer point TP is different from the distance L2 from the detection point DP to the transfer point TP by the mark sensor 16 (L2 ≠ L1), the photoconductor for printing the nth page. When the drum rotation speed V _n is different from the process speed vp,

It becomes.

These results, in the above (a), (b), L3 = L2 , and when the in the control timing t ₁ has detected the first page n of the toner mark Rm on the web W, the n-th page of the toner The mark Rm and the top data of the nth page on the surface of the photosensitive drum 101 coincide at the transfer point TP.

On the other hand, in the above (c), since the L3 ≠ L2, at the control timing t _1, also detect the n-th page of the toner mark Rm on the web W, and the toner mark Rm of the n-th page The top data of the nth page on the surface of the photosensitive drum 101 does not coincide at the transfer point TP, and is shifted by the difference between L3 and L2.

Here, the difference between L3 and L2 in the above (c) is considered. Assuming that L3> L2, and calculating from the result of (c) above, the following equation is obtained.

Therefore, the difference between L3 and L2 increases with the difference between L1 and L2. That is, the distance L1 from the exposure point EP to the transfer point TP, the larger the difference between the distance L2 from the detection point DP due to the mark sensor 16 to the transfer point TP, at the control timing t _1, the n-th page on the web W When the toner mark Rm of the eye is detected, the amount of positional deviation between the toner mark Rm of the nth page and the top data of the nth page on the surface of the photosensitive drum 101 becomes large.

  The object of the present invention is to match the image of the first surface even when the distance L1 from the exposure point EP to the transfer point TP and the distance L2 from the detection point DP to the transfer point TP by the mark sensor 16 are greatly different. Another object of the present invention is to provide a print control method capable of accurately printing an image on the second surface.

  The above purpose is to calculate the control timing from the web conveyance speed at the time of receiving the CPF_LEG-P signal issued by the controller at the timing when the end of the print data of each page is exposed to the photosensitive drum. Is achieved.

  According to the present invention, even when the distance from the exposure point to the transfer point and the distance from the detection point by the mark sensor to the transfer point are greatly different, the second surface is made to coincide with the image on the first surface. It is possible to provide a control method capable of accurately printing an image.

  Embodiments of the present invention will be described below with reference to FIGS.

  In the printing apparatus P2 at the time of duplex printing, regarding the back side printing of the first page at the start of printing, the operator starts printing after the web W is loaded in advance at a predetermined position of the printing apparatus P2, so the top of the front page The position and the page top position on the reverse side usually match.

  When the print data for the first page has been formed on the photosensitive drum 101, the printing apparatus receives the first CPF_LEG-P signal from the controller 17 as shown in FIG.

When the time from the reception of the second CPF-N signal to the control timing is t ₁ and the process speed of the printing apparatus is vp, t ₁ is expressed by the following equation.

t ₁ = (L1−L2) / vp (1)
From the detection deviation time of the toner mark Rm with respect to this control timing, it is grasped how much the top of the page printed on the back side is deviated from the top of the front page. That is, when the detection timing of the toner mark Rm is later than the control timing, the web conveyance speed and the rotation speed of the photosensitive drum 101 are accelerated, and conversely, when the detection timing of the toner mark Rm is earlier than the control timing, The conveyance speed and the rotation speed of the photosensitive drum 101 are reduced. That is, the web conveyance speed is controlled so that the timing for detecting the toner mark Rm coincides with the control timing.

Subsequently, the printing apparatus receives a second CPF_LEG signal from the controller 17 at a timing when the print data for the second page is completely formed on the photosensitive drum 101. Here, when the second CPF_LEG signal is received, the timing for detecting the toner mark Rm is deviated from the control timing by the above control, so that the web conveyance speed and the rotation speed of the photosensitive drum 101 are changed. Even during updating, acceleration / deceleration is stopped and the speed at that time is fixed. Then, the control timing according to the web conveyance speed at the time is calculated. Here, when the web conveyance speed at the time of receiving the second CPF_LEG signal is V ₂ and the time from the reception of the third CPF-N signal to the next control timing is t ₂ , t ₂ is obtained by the following equation.

_{t 2 = (L1-L2)} / V 2 ... formula (3)
Then, the toner mark Rm deviation of the detection time to the control timing t _2, to page head surface, grasp whether page head for printing on the back side is how displaced. When a deviation is detected, acceleration / deceleration control is performed on the web conveyance speed and the rotation speed of the photosensitive drum 101. Subsequently, when the third CPF_LEG signal is received, updating of the web conveyance speed and the photosensitive drum 101 rotation speed is stopped, and the speed at that time is fixed. And the control timing according to the speed at the time is calculated.

  Since the above control is applicable to any page being printed, this control will be described below as the case of the nth page.

The printing apparatus receives the CPF_LEG-P signal from the controller 17 at the timing when the print data for the nth page is completely formed on the photosensitive drum 101, so that the web conveyance speed and the rotational speed of the photosensitive drum 101 are determined. Stop acceleration / deceleration and fix at the current speed. Then, the control timing according to the web conveyance speed at the time is calculated. Here, when the web transport speed at the time of receiving the CPF_LEG-P signal of the n-th page (= rotational speed of the photosensitive drum) and _{V n,} receives the (n + 1) th page CPF-N signal The time t _n from the start to the control timing is obtained by the following equation.

_{t n = (L1-L2)} / V n ... formula (4)
for t _n, to grasp the positional deviation amount from the deviation time of the mark detection timing, and controls the web transport speed and the drum speed as described above.

Here, the distance L3 from the leading data of the nth page on the surface of the photosensitive drum to the transfer point TP at the time when the control timing t _{n-1 has} elapsed since the reception of the CPF-N signal of the nth page. Is considered with reference to FIG.
L3 = L1-t _n-1 × V _n-1
Substituting equation (4) into control timing t _n−1 ,
L3 = L1-{(L1-L2) / Vn _-1 } * Vn _-1.
= L2
Thus, the relationship L3 = L2 is established. That is, if the toner mark Rm of the nth page on the web is detected when the control timing t _{n-1 has} elapsed since the receipt of the CPF-N signal of the nth page, the nth page on the web. The toner mark Rm of the eye coincides with the top data of the nth page on the surface of the photosensitive drum at the transfer point TP.

1 is an overall configuration diagram of a printing system. The schematic diagram which shows the positional relationship of the alignment mark. Explanatory drawing of alignment control. The timing chart in a prior art example. The timing chart in the Example of this invention.

Explanation of symbols

W ... Web, P1, P2 ... Printing device, 16 ... Mark detection means,
17 ... Controller.

Claims (2)

A first printing device that forms an image on a first surface of a web that does not have a feed hole, and a second printing device that forms an image on the second surface of the web. The first printing apparatus has mark forming means for forming an alignment mark at a predetermined position on each page of the web, and at least the second printing apparatus has mark detection means for detecting the alignment mark. A time difference between the generation timing of the web feed control signal at every preset period and the generation timing of the mark detection signal generated by the mark detection means by detecting the alignment mark In a printing control method for a printing system, including means for controlling the web conveyance speed to be a predetermined time difference by controlling acceleration / deceleration ,
Each time the control means receives the web feed control signal, the control means calculates the predetermined time difference based on the web conveyance speed at that time after fixing the web conveyance speed at that time. Print control method.   At least the second printing apparatus includes an image carrier that temporarily holds the image, and the control unit synchronously controls the web conveyance speed and the image carrier movement speed. The printing control method according to claim 1.

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