JP4708594B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus that forms an image on a sheet conveyed by a sheet conveyance mechanism such as a conveyance roller, and more particularly to a technique for adjusting an interval between sheets conveyed continuously.
[0002]
[Prior art]
Conventionally, as this type of image forming apparatus, for example, electrophotographic or electrostatic recording type copying machines, printers, facsimiles, ink jet type printers, facsimiles, and the like are known.
[0003]
Usually, the sheet feeding unit of this type of apparatus includes a pickup roller that pulls out a sheet from a bundle of sheets stacked on a cassette, a tray, or the like, and a feeding roller that introduces the pulled sheet into a conveyance path. The sheets are separated and fed one by one in accordance with the timing of the image forming operation.
[0004]
In such sheet feeding (conveyance) control, particularly when performing image formation continuously on a plurality of sheets, the interval between the trailing edge of the preceding sheet and the leading edge of the succeeding sheet is set. It is important to adjust appropriately. Conventionally, after the leading edge of a sheet pulled out by a pickup roller hits the nip of a stopped pair of feeding rollers, the sheet is fed according to the timing at which the position of the preceding sheet is detected by a sensor or the like provided on the conveyance path. The sheet feeding timing is adjusted by starting the rotation of the feeding roller.
[0005]
[Problems to be solved by the invention]
However, in the case of the prior art as described above, when the sheet is continuously fed, the feeding roller is repeatedly stopped / rotated for each sheet. Therefore, the back of the sheet conveying mechanism including the feeding roller is repeated. Noise may occur due to rush. In addition, when stopping / restarting the motor or the like that drives the sheet conveying mechanism, a larger amount of electric power is required than usual, which increases the cost of power supply components of the apparatus and increases the power consumption.
[0006]
Furthermore, when a stepping motor is used as the motor, the motor may step out due to a rapid speed change such as stop / restart.
[0007]
The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to smoothly and efficiently adjust the sheet interval while minimizing the speed fluctuation of the sheet conveying mechanism. An object of the present invention is to provide an image forming apparatus capable of performing the above.
[0008]
[Means for Solving the Problems]
  In order to achieve the above object, the present invention provides:
  In an image forming apparatus that includes a plurality of sheet conveying mechanisms on a sheet conveying path and forms an image on a sheet conveyed by the sheet conveying mechanism.
  A first sheet conveying mechanism capable of changing a conveying speed;
  A second sheet conveying mechanism that is provided downstream of the first sheet conveying mechanism and conveys the sheet at a constant conveying speed;
  A sensor that is provided in the vicinity of the downstream side of the first sheet conveying mechanism and detects a leading edge and a trailing edge of the sheet being conveyed;
  Measuring means for measuring a time interval between sheets conveyed continuously based on the detection result of the sensor;
  An interval adjusting means for adjusting the sheet interval by controlling the conveying speed of the first sheet conveying mechanism based on the time interval measured by the measuring means;
With,
  Causing the first sheet conveying mechanism to start conveying a sheet at a timing when the sheet interval becomes longer than a target sheet interval;
  The interval adjusting means includes
  A time interval measured by the measuring means;
  A distance that is equal to the distance from the sensor to the vicinity of the second sheet conveyance mechanism and that can convey the sheet at a conveyance speed different from the constant conveyance speed by the first sheet conveyance mechanism is predetermined. From a predetermined distance,
  The conveyance speed of the first sheet conveyance mechanism and the conveyance time during which the sheet is conveyed by the first sheet conveyance mechanism at the conveyance speed are obtained.It is characterized by that.
[0011]
  in frontThe interval adjustment means
  The target time interval between sheets is t0,
  The time interval measured by the measuring means is t,
  The predetermined distance is L,
  A constant transport speed of the second sheet transport mechanism is vp,
If
  The conveyance speed v of the first sheet conveyance mechanism and the conveyance time T during which the sheet is conveyed by the first sheet conveyance mechanism at the conveyance speed v may be obtained by the following equation.
  v = vp * L / {L-vp (t-t0)}
  T = {L−vp (t−t0)} / vp
[0012]
  in frontThe interval adjustment means
  The target time interval between sheets is t0,
  The time interval measured by the measuring means is t,
  The predetermined distance is L,
  A constant transport speed of the second sheet transport mechanism is vp,
If
  The conveyance speed v of the first sheet conveyance mechanism and the conveyance time T during which the sheet is conveyed by the first sheet conveyance mechanism at the conveyance speed v may be obtained by the following equation.
  v = vp * L / {vp (t0-t) + L}
  T = {vp (t0−t) + L} / vp
[0013]
  Further, at this time, the interval adjusting means is configured such that the conveyance speed v obtained by the above formula is lower than the stable operation speed of the first sheet conveyance mechanism.Thus, the first sheet transport mechanism cannot be stably operated.The transport speed v and transport time T are set as follows:Then, the first sheet conveying mechanism is stopped for a time (t0-t).Even better.
  v = 0
  T = t0-t
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Exemplary embodiments of the present invention will be described in detail below with reference to the drawings. Here, an example in which the present invention is applied to an electrophotographic laser beam printer is shown as an example, but the present invention can also be suitably applied to an image forming apparatus such as a copying machine or a laser facsimile, an ink jet image forming apparatus, or the like. .
[0017]
It should be noted that the dimensions, materials, shapes, and relative arrangements of the component parts described in the following embodiments are intended to limit the scope of the present invention only to those unless otherwise specified. is not.
[0018]
(First embodiment)
An image forming apparatus according to a first embodiment of the present invention will be described with reference to FIGS.
[0019]
First, the overall configuration of the image forming apparatus will be described with reference to FIG. FIG. 2 is a schematic cross-sectional view of a laser beam printer 201 which is an image forming apparatus according to the present embodiment.
[0020]
As shown in FIG. 2, the feeding unit of the laser beam printer 201 is further picked up by a cassette 202 for storing a sheet S as a recording material (recording paper), a pickup roller 203 for picking up the sheet S from the cassette 202. And a pair of feeding rollers 204 for introducing the sheet S into the conveyance path.
[0021]
A feeding sensor 205 that is a sensor for detecting the leading and trailing ends of the sheet being conveyed is disposed downstream of the pair of feeding rollers 204, and a sheet S that has been fed is disposed on the downstream side thereof, which will be described later. A conveying roller 206 that conveys up to 208 is disposed. The feeding sensor 205 detects the presence of the sheet at the position by blocking the photo interrupter by the light shielding plate by the contact of the sheet.
[0022]
A registration roller 208 that synchronously conveys the sheet S is disposed downstream of the conveyance roller 206, and a pre-registration sensor 207 that detects the leading edge of the sheet is disposed immediately before the registration roller 208. The configuration of this sensor is the same as that of the feeding sensor 205.
[0023]
An image forming unit 209 that forms an image with a laser beam (one-dot chain line in the drawing) from the laser scanner unit 210 is disposed downstream of the registration roller 208. Further, a fixing device 211 is disposed downstream of the image forming unit 209, and discharge transport rollers 212, 213, 214, and 215 are disposed downstream of the fixing device 211, up to the discharge tray 216. The sheet S is conveyed.
[0024]
As described above, in the present exemplary embodiment, the sheet conveyance mechanisms of the pickup roller 203, the feeding roller pair 204, the conveyance roller 206, the registration roller 208, and the paper discharge conveyance rollers 212, 213, 214, and 215 are arranged on the sheet conveyance path. Then, sheet conveyance is performed by these sheet conveyance mechanisms.
[0025]
The sheet S fed from the cassette 202 at the time of printing is positioned by being abutted against the registration roller 208 by the upstream conveying roller 206 in a state where the rotation of the registration roller 208 is stopped. Then, the image data sent from the external device and the sheet S are started by starting the rotation of the registration roller 208 in synchronization with an image vertical synchronization signal output from an external device (not shown) that supplies image information. The image is printed at a predetermined position on the sheet S. Since the above control is publicly known, detailed description is omitted here.
[0026]
Next, the configuration of the control unit of the image forming apparatus will be described with reference to FIG. FIG. 1 is a control block diagram of the image forming apparatus according to the present embodiment.
[0027]
The laser beam printer 201 has a main control device 101 for controlling the whole. The main control device 101 includes a CPU, a ROM, a RAM, a gate element, and the like, and a main part of control is realized by software written in the ROM.
[0028]
As shown in FIG. 1, the main controller 101 includes a paper interval adjusting unit (interval adjusting unit) 102, a feeding control timer 103, a main motor control unit 104, a paper interval measuring unit (measuring unit) 105, and a feeding motor control. Means 106 and a feeding control means 112 are provided, and the sheet interval adjusting means 102 further includes a conveyance speed calculation means 110 and a conveyance time management means 111.
[0029]
A main motor 107, a feed sensor 205, a feed motor 109, and a pickup solenoid 108 are connected to the main controller 101. As a result, a cassette feeding mechanism including the pickup roller 203, the feeding roller pair 204, and the conveying roller 206 is driven to feed the sheet S set in the cassette 202 to the registration roller 208.
[0030]
Next, the function of each part will be described with reference to FIG. FIG. 3 is an enlarged view of the feeding unit of the image forming apparatus according to the present embodiment.
[0031]
As shown in FIG. 3, in the cassette feeding of the laser beam printer 201, the pickup roller 203 is pressed against the sheet S and rotated to feed the pair of feeding rollers 204. The pickup roller 203 has a rotating shaft that moves up and down by a cam mechanism (not shown) driven by a main motor 107. By driving the pickup solenoid 108, the cam mechanism drives and moves up and down.
[0032]
The pickup roller 203 is rotated by the feeding motor 109. The feed motor 109 also rotates the feed roller pair 204. In the present embodiment, a stepping motor is used as the feeding motor 109.
[0033]
The feed roller pair 204 includes a feed roller 204a and a retard roller 204b. The feeding roller 204a rotates in the direction in which the sheet S is conveyed to the registration roller 208 at the same rotation speed as the pickup roller 203 (equal to a standard sheet conveyance speed vp described later).
[0034]
On the other hand, the retard roller 204b applies a load in the opposite direction to the feeding roller 204a to the lower surface of the sheet S with a torque smaller than that of the feeding roller. Since the friction force between the sheets is weaker than the friction force between the roller surface and the sheet, when the sheets are conveyed to the feeding roller pair 204 with two or more sheets overlapped, only the uppermost sheet is The sheet on the lower surface is fed toward the registration roller by the feeding roller 204a and is sequentially separated by the retard roller 204b and pushed back to the cassette side. When only one sheet is sandwiched between the feeding roller 204a and the retard roller 204b, the retard roller 204b rotates with the feeding roller 204a because the torque is weaker than that of the feeding roller 204a.
[0035]
The feeding control unit 112 feeds the sheet S from the cassette 202 by driving the mechanisms. When the sheets S are continuously fed, the succeeding sheet pick-up timing is managed from the number of driving steps of the feeding motor 109 and the sheet size from the timing when the leading edge of the sheet is detected by the feeding sensor 205. Since these controls are well-known, detailed description is omitted here.
[0036]
Here, as described above, the feeding control unit 112 manages the next pickup timing on the basis of the sheet leading edge detection timing by the feeding sensor 205, but in the present feeding mechanism, the retard is performed as described above. Since the separation method by the roller 204b is adopted, the position of the sheet before pick-up is separated by the separation mechanism from the state where the sheet is normally stored in the cassette 202 (the state where the sheet front end is at the position of PA in FIG. 3). The position of the leading edge varies in the range up to the state where the remaining sheet remains (the state where the leading edge of the sheet is at the position PB in FIG. 3). Therefore, even if the feeding control unit 112 manages the feeding interval with the number of driving steps of the feeding motor 109 based on the sheet leading edge detection timing of the feeding sensor 205 as described above, the distance from PA to PB. The sheet spacing at the time of feeding varies.
[0037]
However, in this laser beam printer, it is necessary to feed sheets to the image forming unit 209 at regular intervals, and for this purpose, it is necessary to control the sheet spacing to be constant before the registration rollers 208.
[0038]
Therefore, the sheet interval adjusting unit 102 according to the present embodiment measures the interval between continuously fed sheets using the feeding sensor 205, and determines the sheet conveyance speed of the feeding roller 204a based on the time interval. Shift control is performed to adjust the interval between continuously fed sheets.
[0039]
First, when the sheet interval at the time of feeding (sheet interval before adjustment) is minimized within the above range of variation, the feeding control unit 112 sets an ideal time interval t0 (in front of the registration roller 208). The pickup roller 203 starts to rotate at a timing equal to the target sheet interval. That is, when the leading edge position of the sheet before feeding is the PB position, the feeding interval (feeding based on the sheet leading edge detection timing of the feeding sensor 205) is set so that the time interval with the preceding sheet becomes t0. The number of drive steps of the feed motor 109) is controlled.
[0040]
In this case, the longest sheet interval at the time of feeding is expressed by the following formula. As is apparent from the equation, the feeding roller 204a starts the conveyance of the subsequent (upstream side) sheet at a timing at which the sheet interval during feeding is always longer than the target sheet interval t0. At this time, the feeding roller 204 a is driven at the same standard sheet conveyance speed as the pickup roller 203 and the conveyance roller 206. In the following formula, vp is a standard sheet conveyance speed, that is, a conveyance speed of the conveyance roller (second sheet conveyance mechanism) 206.
t0 + (distance between PA and PB) / vp
vp: Standard sheet conveyance speed
[0041]
Here, the transport speed calculation unit 110 is configured to feed the feeding roller (first sheet) according to a time interval t from the detection of the trailing edge of the preceding sheet to the detection of the leading edge of the succeeding sheet by the feeding sensor 205 measured by the sheet interval measuring unit 105. The sheet conveyance speed v of the conveyance mechanism) 204a and the conveyance time T at the conveyance speed v are obtained by the following equations.
Transport speed v = vp × L / {L−vp (t−t0)}
Transport time T = {L−vp (t−t0)} / vp
[0042]
Here, L is a distance that is determined in advance as a distance by which the upstream preceding sheet can be conveyed at a conveyance speed faster than the standard sheet conveyance speed vp by the feeding roller 204a. In the present embodiment, the distance L is set to be equal to the distance from the feed sensor 205 to the vicinity of the transport roller 206. More specifically, the distance L is set so as to be a distance obtained by subtracting a predetermined margin (a value considering variation in the conveyance speed) from the distance from the feeding sensor 205 to the nip of the conveyance roller 206. is doing.
[0043]
In the configuration of the laser beam printer, the conveying roller 206 downstream of the feeding roller 204a is driven by a main motor (not shown), and the conveying speed is constant (standard sheet conveying speed vp). Therefore, the sheet can be conveyed at the conveyance speed v by the pair of feeding rollers 204 only until the leading edge of the sheet S reaches the conveyance roller 206. In the present exemplary embodiment, the speed fluctuation of the feeding roller 204a is obtained by obtaining the transport speed v so as to use the entire time from when the leading edge of the sheet S passes the feed sensor 205 to just before reaching the transport roller 206. Can be minimized.
[0044]
FIG. 4 shows a flowchart of the control of the sheet interval adjusting means 102 according to this embodiment.
[0045]
First, when feeding control by the feeding control unit 112 is started in step S401 (hereinafter simply referred to as S401), the process waits until the measurement of the sheet interval time by the sheet interval measuring unit 105 is completed in step S402. When the inter-paper time measurement is completed, the transport speed and time are calculated by the transport speed calculating means 110 based on the above formulas in S403. Thereafter, in step S404, the feeding roller speed is changed from vp to v, and in step S405, the feeding roller speed is held at v for the time T by the transport time management unit. After the elapse of time T, the feeding roller speed is returned to vp in S406, and the paper gap adjustment is completed.
[0046]
As described above, according to the present embodiment, the time interval between continuously conveyed sheets is measured using the feeding sensor 205, and the conveying speed of the feeding roller 204a is determined based on the time interval. Since the sheet interval is adjusted by the control, it is not necessary to stop the feeding roller 204a when a plurality of sheets are continuously conveyed, and an increase in noise and power consumption due to the stop / rotation of the roller is suppressed. In addition, the feed motor 109 can be prevented from stepping out.
[0047]
Further, the conveying speed and conveying time of the feeding roller 204a are obtained based on the distance L from the feeding sensor 205 to the vicinity of the conveying roller 206, and until the leading edge of the sheet passes through the feeding sensor 205 and immediately before reaching the conveying roller 206. Since the sheet interval is adjusted using all of the above time, the speed fluctuation of the feeding roller 204a can be minimized. At this time, by providing the feed sensor 205 in the vicinity of the downstream of the feed roller 204a, the distance L can be ensured to the maximum.
[0048]
Further, the feeding interval is controlled so that the conveyance of the upstream sheet is started at a timing when the sheet interval at the time of feeding always becomes longer than the target sheet interval t0, and the conveying speed and the conveying time are set based on the above equations. By calculating, it is possible to eliminate multiplication and division of negative numbers. In an ordinary 8- to 16-bit microcomputer mounted on an image forming apparatus such as a printer, it is necessary to provide dedicated hardware or to make a program complicated in order to execute multiplication or division of a negative numerical value. Thus, by performing calculations as in the present embodiment, no special hardware is required, and an increase in memory, a delay in processing time, and the like due to complicated programs can be prevented.
[0049]
(Second Embodiment)
In the first embodiment, the feeding control unit 112 is equal to the ideal time interval t0 before the registration roller 208 when the sheet interval at the time of feeding is minimized within the range of variation. The feeding interval is set so that However, according to this processing, the conveyance speed v of the feed roller 204a at the time of paper gap adjustment needs to be faster than the standard speed vp.
[0050]
That is, the conveyance speed v obtained by the arithmetic expression of the first embodiment is v> vp.
[0051]
For this reason, the feeding motor 109 that drives the feeding roller 204a needs to be capable of being driven at a speed higher than the standard speed vp.
[0052]
Therefore, in the present embodiment, the following calculation method is adopted instead of the calculation method of the first embodiment. Since other configurations and operations are the same as those of the first embodiment, detailed description thereof is omitted here.
[0053]
First, when the sheet interval during feeding (sheet interval before adjustment) reaches the maximum within the range of variation, the feeding control unit 112 sets an ideal time interval t0 (target and target) before the registration roller 208. The sheet feeding interval is set to be equal to the sheet spacing.
[0054]
As a result, the conveyance speed v of the feed roller 204a at the time of paper gap adjustment can be set to a speed slower than the standard speed vp.
[0055]
For this reason, the feeding control unit 112 according to the present embodiment is configured so that when the leading edge position of the sheet before feeding is the PA position, the feeding interval (feeding) is set so that the time interval with the preceding sheet becomes t0. The number of driving steps of the feeding motor 109 based on the sheet leading edge detection timing of the feeding sensor 205 is controlled.
[0056]
In this case, the shortest sheet interval at the time of feeding is expressed by the following formula. As is apparent from the equation, the feeding roller 204a starts the conveyance of the subsequent (upstream side) sheet at a timing when the sheet interval during feeding is necessarily shorter than the target sheet interval t0.
t0− (distance between PA and PB) / vp
vp: Standard sheet conveyance speed
[0057]
Here, the transport speed calculation unit 110 is configured to feed the feeding roller (first sheet) according to a time interval t from the detection of the trailing edge of the preceding sheet to the detection of the leading edge of the succeeding sheet by the feeding sensor 205 measured by the sheet interval measuring unit 105. The sheet conveyance speed v of the conveyance mechanism) 204a and the conveyance time T at the conveyance speed v are obtained by the following equations. The definition of the distance L is the same as that in the first embodiment.
Conveyance speed v = vp × L / {vp (t0−t) + L}
Transport time T = {vp (t0−t) + L} / vp
[0058]
With the processing as described above, it is not necessary to prepare a more sophisticated motor for adjusting the paper interval. Needless to say, the present embodiment can provide the same effects as those of the first embodiment.
[0059]
(Third embodiment)
In the second embodiment, the feeding control unit 112 is equal to the ideal time interval t0 before the registration roller 208 when the sheet interval at the time of feeding reaches the maximum within the range of variation. Thus, the feeding interval is set so that the conveying speed of the feeding roller at the time of paper interval adjustment is slower than the standard speed.
[0060]
However, in the actual feeding process, it is also conceivable that the sheet interval during feeding varies more than the assumed variation. In other words, the feeding control unit 112 sets the feeding interval so that the ideal time interval t0 before the registration roller 208 is reached when the sheet interval during feeding becomes the maximum within the range of variation. However, the sheet interval during feeding may actually be larger than t0.
[0061]
Therefore, in this embodiment, the calculation formula for determining the conveyance speed v and the conveyance time T of the feeding roller 204a is switched according to the relationship between the sheet interval during feeding and the ideal sheet interval.
[0062]
In the same manner as in the second embodiment, the feeding control unit 112 according to the present embodiment is positioned in front of the registration roller 208 when the sheet interval at the time of feeding reaches a maximum within an assumed variation range. The feeding interval is set to be an ideal time interval t0.
[0063]
Then, the paper interval adjusting means 102 switches the arithmetic expression as follows by comparing the actually measured time interval t with the target time interval t0. The definition of the distance L is the same as that in the first embodiment.
If t <t0:
Conveyance speed v = vp × L / {vp (t0−t) + L}
Transport time T = {vp (t0−t) + L} / vp
If t> t0:
Transport speed v = vp × L / {L−vp (t−t0)}
Transport time T = {L−vp (t−t0)} / vp
When t = t0:
No adjustment
[0064]
FIG. 5 shows a flowchart of the control of the sheet interval adjusting means 102 according to this embodiment.
[0065]
Steps S501, S502, S505 to S507 are the same processes as steps S401, S402, and S404 to S406 of the first embodiment, respectively, and thus description thereof is omitted here.
[0066]
In the sheet interval adjusting unit 102 of the present embodiment, after the sheet time interval t at the time of feeding is obtained in S502, it is compared with the target time interval t0 in S503, and the feeding roller 204a is determined according to the result. The calculation of the transport speed v and the transport time T is switched as described above.
[0067]
By the processing of the paper gap adjusting unit 102 as described above, appropriate paper gap adjustment can be performed even when unexpected variations occur in the sheet interval during feeding. Needless to say, the present embodiment can provide the same effects as those of the first and second embodiments.
[0068]
(Fourth embodiment)
In the second embodiment, the feeding interval is set so that the conveying speed v of the feeding roller 204a at the time of adjusting the sheet interval can be set to a speed slower than the standard speed vp, and the conveying speed v at the time of adjusting the sheet interval is set. And the conveyance time T is obtained by the following equation.
Conveyance speed v = vp × L / {vp (t0−t) + L}
Transport time T = {vp (t0−t) + L} / vp
[0069]
However, in an actual apparatus, there are cases where the feeding roller 204a cannot be stably operated if the conveyance speed v obtained by the above equation is simply adopted. Specifically, for example, such a problem may occur when the conveyance speed v is a low speed that deviates from the operation guarantee range of the feeding motor 109.
[0070]
Therefore, in the present embodiment, when the conveyance speed v obtained by the above formula is within a range that can be handled by the feeding motor 109, the paper gap adjustment is performed by the method described in the second embodiment. On the other hand, when the conveyance speed v is lower than the speed that cannot be handled by the feeding motor 109, that is, lower than the stable operation speed of the feeding roller 204a, the feeding roller 204a is stopped for the time (t0-t). To perform the process.
[0071]
FIG. 6 shows a flowchart of control of the sheet interval adjusting means 102 according to this embodiment.
[0072]
Steps S601 to S603 are the same processes as steps S401 to S403 in the first embodiment, respectively, and thus description thereof is omitted here.
[0073]
In this embodiment, after obtaining the conveyance speed v for adjusting the sheet interval in S603, it is checked in S604 whether the speed v is a realizable speed. If the speed v is feasible, the same sheet spacing adjustment process as in the second embodiment is performed in S605 and S606. On the other hand, if the speed v cannot be realized, the feeding roller 204a is stopped in S607, and after waiting for a time (t0-t) in S608, the original standard speed vp is restored again in S609.
[0074]
By the processing of the sheet interval adjusting unit 102 as described above, the sheet interval at the time of feeding becomes very small, and even when the adjustment by the deceleration of the feeding roller 204a is in an impossible range, the sheet interval can be adjusted. Become.
[0075]
Note that the processing corresponding to steps S604, S607, and S608 of the present embodiment can be applied to the case of “t <t0” in the third embodiment.
[0076]
【The invention's effect】
As described above, the present invention measures the time interval of continuously conveyed sheets using a sensor, and adjusts the sheet interval by controlling the conveying speed of the first sheet conveying mechanism based on the time interval. Therefore, when conveying multiple sheets continuously, it is possible to suppress noise and power consumption increase due to stop / rotation of the sheet conveying mechanism, and to minimize speed fluctuation of the sheet conveying mechanism, Stable and efficient sheet interval adjustment and sheet conveyance can be performed.
[Brief description of the drawings]
FIG. 1 is a control block diagram of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view of an image forming apparatus according to an embodiment of the present invention.
3 is an enlarged view of a feeding unit of the image forming apparatus in FIG.
FIG. 4 is a flowchart of sheet interval adjustment control according to the first embodiment.
FIG. 5 is a flowchart of sheet interval adjustment control according to the third embodiment.
FIG. 6 is a flowchart of control for adjusting a sheet interval in the fourth embodiment.
[Explanation of symbols]
101 Main controller
102 Paper spacing adjustment means
103 Feed control timer
104 Main motor control means
105 Paper interval measuring means
106 Feed motor control means
107 Main motor
108 Pickup solenoid
109 Feed motor
110 Conveyance speed calculation means
111 Transport time management means
112 Feed control means
201 Laser beam printer
202 cassette
203 Pickup roller
204 Feeding roller pair
204a Feeding roller
204b retard roller
205 Feed sensor
206 Conveying roller
207 Sensor before register
208 Registration roller
209 Image forming unit
210 Laser scanner
211 Fixing device
212, 213, 214, 215 Paper discharge roller
216 Output tray
S sheet

Claims (7)

In an image forming apparatus that includes a plurality of sheet conveying mechanisms on a sheet conveying path and forms an image on a sheet conveyed by the sheet conveying mechanism.
A first sheet conveying mechanism capable of changing a conveying speed;
A second sheet conveying mechanism that is provided downstream of the first sheet conveying mechanism and conveys the sheet at a constant conveying speed;
A sensor that is provided in the vicinity of the downstream side of the first sheet conveying mechanism and detects a leading edge and a trailing edge of the sheet being conveyed;
Measuring means for measuring a time interval between sheets conveyed continuously based on the detection result of the sensor;
An interval adjusting means for adjusting the sheet interval by controlling the conveying speed of the first sheet conveying mechanism based on the time interval measured by the measuring means;
Equipped with a,
Causing the first sheet conveying mechanism to start conveying a sheet at a timing when the sheet interval becomes longer than a target sheet interval;
The interval adjusting means includes
A time interval measured by the measuring means;
A distance that is equal to the distance from the sensor to the vicinity of the second sheet conveyance mechanism and that can convey the sheet at a conveyance speed different from the constant conveyance speed by the first sheet conveyance mechanism is predetermined. From a predetermined distance,
An image forming apparatus comprising Rukoto seek conveying time the sheet at the conveying speed and conveying speed of the first roller unit is conveyed by the first sheet transport mechanism. A cassette for storing sheets;
A pickup roller for feeding sheets from the cassette;
A separation unit composed of a feeding roller and a retard roller for separating the sheet fed from the pickup roller;
With
When it is assumed that the leading edge of the uppermost sheet of the sheets stored in the cassette is at the pressure contact portion between the feeding roller and the retard roller, the interval between the preceding sheet and the preceding sheet is the target sheet interval. The image forming apparatus according to claim 1, wherein the first sheet feeding mechanism is a timing for conveying a sheet. Before Symbol interval adjusting means,
The target time interval between sheets is t0,
The time interval measured by the measuring means is t,
The predetermined distance is L,
A constant transport speed of the second sheet transport mechanism is vp,
If
3. The image according to claim 2, wherein a conveyance speed v of the first sheet conveyance mechanism and a conveyance time T during which the sheet is conveyed by the first sheet conveyance mechanism at the conveyance speed v are obtained by the following expression. Forming equipment.
v = vp * L / {L-vp (t-t0)}
T = {L−vp (t−t0)} / vp In an image forming apparatus that includes a plurality of sheet conveying mechanisms on a sheet conveying path and forms an image on a sheet conveyed by the sheet conveying mechanism.
A first sheet conveying mechanism capable of changing a conveying speed;
A second sheet conveying mechanism that is provided downstream of the first sheet conveying mechanism and conveys the sheet at a constant conveying speed;
A sensor that is provided in the vicinity of the downstream side of the first sheet conveying mechanism and detects a leading edge and a trailing edge of the sheet being conveyed;
Measuring means for measuring a time interval between sheets conveyed continuously based on the detection result of the sensor;
An interval adjusting means for adjusting the sheet interval by controlling the conveying speed of the first sheet conveying mechanism based on the time interval measured by the measuring means;
With
The first sheet conveying mechanism starts conveying the sheet at a timing when the sheet interval becomes shorter than the target sheet interval,
The interval adjusting means includes
A time interval measured by the measuring means;
A distance that is equal to the distance from the sensor to the vicinity of the second sheet conveyance mechanism and that can convey the sheet at a conveyance speed different from the constant conveyance speed by the first sheet conveyance mechanism is predetermined. From a predetermined distance,
An image forming apparatus, wherein a conveyance speed of the first sheet conveyance mechanism and a conveyance time during which the sheet is conveyed by the first sheet conveyance mechanism at the conveyance speed are obtained. A cassette for storing sheets;
A pickup roller for feeding sheets from the cassette;
A separation unit composed of a feeding roller and a retard roller for separating the sheet fed from the pickup roller;
With
The first sheet feeding mechanism is such that when the leading edge of the uppermost sheet of the sheets stored in the cassette is in the cassette, the distance from the preceding sheet is the target sheet distance. The image forming apparatus according to claim 4, wherein the timing of conveying the sheet is a timing. Before Symbol interval adjusting means,
The target time interval between sheets is t0,
The time interval measured by the measuring means is t,
The predetermined distance is L,
A constant transport speed of the second sheet transport mechanism is vp,
If
6. The image according to claim 5 , wherein a conveyance speed v of the first sheet conveyance mechanism and a conveyance time T during which the sheet is conveyed by the first sheet conveyance mechanism at the conveyance speed v are obtained by the following expression. Forming equipment.
v = vp * L / {vp (t0-t) + L}
T = {vp (t0−t) + L} / vp The interval adjusting unit is configured to detect the conveyance speed v and the conveyance speed v when the conveyance speed v obtained by the equation is lower than the stable operation speed of the first sheet conveyance mechanism and the first sheet conveyance mechanism cannot be stably operated. The image forming apparatus according to claim 6 , wherein the conveyance time T is set as follows, and the first sheet conveyance mechanism is stopped for a period of (t0−t).
v = 0
T = t0-t

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