JP3556351B2 - Image forming device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus in which a plurality of recording heads are arranged to form a wide head unit.
[0002]
[Prior art]
In a conventional image forming apparatus, for example, Japanese Patent Application Laid-Open No. 64-87356 discloses a method in which a positioning hole is provided in a ceramic substrate, and a recording head is fixed to a base member based on the positioning hole. This facilitates positioning between a plurality of recording heads. Further, by using a plurality of recording heads having a small recording width, a head unit having a large recording width can be provided at a high yield and at low cost.
[0003]
Japanese Patent Application Laid-Open No. 4-298355 discloses a method in which a plurality of in-line type thermal heads are shifted in the line direction, and the effective recording areas are arranged so as to overlap by one dot or more. The recording is performed by overlapping one or more dots in the line direction at the portions. For this reason, a gap that is not recorded at the seam of an image does not occur, and a decrease in recording quality can be prevented.
[0004]
FIG. 20A is a diagram illustrating a schematic configuration of a head unit of a conventional image forming apparatus. A head unit 104 includes recording heads 100 and 101, a guide member 102, and an elastic member 103.
[0005]
[Problems to be solved by the invention]
By the way, in the above-described image forming apparatus, the elongation δ1, δ2 of the head unit 104 occurs as shown in FIG. Here, assuming that the distances from the entire reference position to the ends of the recording heads 100 and 101 on the guide member 102 side are L1 and L2, respectively, since L1 << L2, δ1 <δ2, and is shown in FIG. As described above, there is a problem that an image defect occurs at a joint of images.
[0006]
It is known that such expansion and contraction of the head unit 104 occurs not only due to a change in temperature, but also due to a lack of adjustment accuracy with respect to the head unit 104, aging, and the like.
[0007]
The present invention has been made in view of such a problem, and an object of the present invention is to prevent an image defect from occurring at a joint of recording heads without a positional shift between recording heads even when a temperature change occurs. An object of the present invention is to provide a forming apparatus.
[0008]
Another object of the present invention is to provide an image forming apparatus in which a change in image density is unlikely to occur at a seam of recording heads even if a temperature change occurs and a positional deviation occurs between the recording heads.
[0009]
Another object of the present invention is to provide an image forming apparatus in which a change in image density hardly occurs at a seam of recording heads even when a slight difference in characteristics occurs between adjacent recording heads.
[0010]
[Means for Solving the Problems]
To achieve the above objectives,According to a first aspect of the present invention, in a plurality of recording heads each having a plurality of recording members juxtaposed at a fixed interval, a plurality of recording heads arranged such that a part of each recording area overlaps or touches each other. In an image forming apparatus for forming an image by using an image forming apparatus, measuring means for measuring an amount of displacement of an end of a recording area of two adjacent recording heads among a plurality of recording heads, and each recording head measured by the measuring means Calculating means for calculating the density of the recording member in an area where a part of the recording areas of two adjacent recording heads overlap each other, based on the positional deviation amount of the end of the recording area of Correction means for correcting an amount of a recording signal applied to a recording member in an area where a part of the recording area overlaps with each other, according to the density of the recording member. Comprising a.
[0011]
Also,According to a second aspect of the present invention, the point image recording member uses two or more in-line type recording heads arranged at a fixed interval, shifts them in the line direction, and forms a part of a recording area of two adjacent recording heads. Are arranged on a base member and combined with each other so that the recording head has a width wider than a width that can be recorded by the recording head alone, in an image forming apparatus that records a visible image or a latent image. From the means for measuring the displacement of the recording area edges of the two adjacent recording heads and the amount of displacement of the recording area edges of the two recording heads, the recording areas of the two adjacent recording heads partially overlap each other. Means for calculating the density of the point image recording member in the area where it is located, and the density according to the density of the point image recording member in the area where a part of the recording area overlaps each other. Kiihodo, and means for correcting so as to partially reduce significantly the amount of recording signal to be applied to each point image recording member in the area in which overlap each other in the recording area.
[0012]
Also,In a third aspect based on the second aspect, the means for measuring the displacement of the ends of the recording areas of the two adjacent recording heads is provided in one of the recording heads at a portion where the recording areas of the two recording heads overlap. And a position sensor provided on the recording head on which the mark is not provided so as to face the mark.
[0013]
Also,In a fourth aspect based on the second aspect, the means for measuring the displacement of the end of the recording area of the two adjacent recording heads is provided in the two recording heads at a portion where the recording areas of the two recording heads overlap. And a position sensor provided on the base member so as to face the mark.
[0014]
Also,In a fifth aspect based on the second aspect, the means for measuring a displacement of the end of the recording area of two adjacent recording heads, a distortion measuring member provided on the base member, and a base member deformation amount calculating section are provided. And
[0015]
Also,In a sixth aspect based on the second aspect, the means for measuring the displacement of the end portions of the recording areas of the two adjacent recording heads comprises a temperature sensor provided on the base member, a base member deformation amount calculating section, Having.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
1 to 5 are views showing a configuration of a first embodiment of the present invention. FIG. 1 is a diagram showing an overall configuration of the image forming apparatus, FIG. 2 is a perspective view showing an external appearance of the ion head unit, FIG. 3 is a diagram showing a schematic configuration of the ion head unit, and FIG. 5A is an enlarged view of a portion indicated by A in FIG. 5, and FIG. 5 is a diagram showing one line of dots extracted by the ion head.
[0017]
The configuration of the first embodiment includes ion heads 13 and 14 as in-line type recording heads, electrostatic recording paper 11 as a recording medium, and a base member 22 on which the two ion heads 13 and 14 are placed. Guide members 24 and 25 (FIG. 2) as members that oppose the two ion heads 13 and 14, and a compression spring 31 as an elastic member that abuts the two ion heads 13 and 14 against the guide members 24 and 25, respectively. 32 (FIG. 2). As shown in FIG. 4, a large number of circular ion emission ports (point image recording members) 19 are arranged in the ion heads 13 and 14 at regular intervals in a straight line. 61 and 62 (FIG. 3) are formed and correspond to the recording areas of the ion heads 13 and 14.
[0018]
As shown in FIG. 4, a control electrode 201 is provided around the ion emission port 19, and a control signal is individually given to each control electrode 201 through a control line 202, so that each of the ion emission ports 19 is The amount of released ions can be controlled.
[0019]
In FIG. 1, the electrostatic recording paper roll 15 is engaged with a drive source (not shown) that rotates forward and backward. The electrostatic recording paper 11 fed out from the electrostatic recording paper roll 15 reaches the counter electrode 12 via a transport path provided in the apparatus main body.
[0020]
The ion emitting surfaces of the ion heads 13 and 14 are separated from the counter electrode 12 and the electrostatic recording paper 11 by about 1 mm.
Further, a discharger 18 is arranged downstream of the ion heads 13 and 14 at a distance of about 1 mm from the counter electrode 12 and the electrostatic recording paper 11. Further downstream of the static eliminator 18, a developing unit 23 composed of a developing device for developing an electrostatic latent image, a driving roller 20 engaged with a not-shown forward / reverse driving source, A cutter 21 for cutting the recording paper 11 is provided in order.
[0021]
Further, a write control unit 43 for controlling the amount of ions emitted from the ion heads 13 and 14 in accordance with image data 26 given from outside is provided. The write control unit 43 has as many control signal output terminals as the number of ion emission ports 19 provided in the ion heads 13 and 14, and is connected to control lines 202 provided in the ion heads 13 and 14, respectively. I have. The writing control unit 43 controls the conveyance of the electrostatic recording paper 11, controls the developing unit 23, and exchanges data with an external device in addition to the control of the ion heads 13 and 14. The writing control unit 43 includes a CPU, a RAM, a ROM, and the like, and is controlled according to a program stored in the ROM.
[0022]
Here, a method of fixing the above-described two ion heads 13 and 14 to the base member 22 in this embodiment will be described with reference to FIGS.
One end of each of the ion heads 13 and 14 is in contact with guide members 24 and 25 fixed to the base member 22, and compression springs 31 and 32 provided at opposite ends of the ion heads 13 and 14 move in the direction of the guide members 24 and 25. It is imposed. The relative positional relationship between the two ion heads 13 and 14 is determined by the positional relationship between the end faces of the guide members 24 and 25. The guide members 24 and 25 of the present embodiment are formed by the two ion heads 13 and 14. The ion head is provided so as to be in contact with the end of the ion head closer to the seam of each image, that is, the end of the ion head closer to the center of the base member 22. In other words, the two guide members 24 and 25 are arranged near the ends of the recording areas on the side where the recording areas of the two ion heads 13 and 14 are adjacent to each other.
[0023]
The relative positional relationship between the two ion heads 13 and 14 is set such that the recording areas are adjacent to each other at the same interval as the ion emission ports 19 are arranged as shown in FIG. FIG. 5 shows a case where dots formed by the ion head are extracted by one line.
[0024]
Further, the ion heads 13 and 14 are provided with a heater and a temperature control device (both not shown) for keeping the temperature inside the ion heads 13 and 14 constant. This aims at improving the ion output efficiency and stabilizing the ion output.
[0025]
Next, the operation of the first embodiment will be described.
In FIG. 1, image data 26 sent from an external device is stored in a RAM provided in a writing control unit 43. When a recording start command is issued from outside, the drive of the drive source engaged with the electrostatic recording paper roll 15 and the driving roller 20 is started by the writing control unit 43, and the electrostatic recording paper 11 is moved in the direction of the arrow in FIG. At a constant speed. At the same time, the image data 26 is read from the RAM provided in the writing control unit 43, and first, a control signal corresponding to the image data 26 is given to each control electrode 201 of the ion head 13. From each of the plurality of ion emission ports 19 provided in the ion head 13, an amount of ions corresponding to the image data of the corresponding pixel is emitted, and an electrostatic latent image corresponding to the image data 26 is formed on the electrostatic recording paper 11. Formed on As the electrostatic recording paper 11 advances, control signals applied to the ion head 13 are sequentially changed according to image data. When the electrostatic recording paper 11 advances by a distance corresponding to A in FIG. 1 after the recording is started, a control signal corresponding to the image data 26 is also given to the ion head 14 and the formation of the electrostatic latent image is started. Is done.
[0026]
Thereafter, a control signal corresponding to the image data 26 is given to the ion head 14 later than the ion head 13 by a distance corresponding to the path difference indicated by A in FIG. Progresses. When the electrostatic latent image formed by the ion heads 13 and 14 reaches the position of the developing unit 23, the electrostatic latent image comes into contact with the developing solution filled in the developing unit 23 and a visible image having a density corresponding to the potential of the electrostatic latent image. Is formed. As the electrostatic recording paper 11 is conveyed, the formation and development of the latent image progresses, and the final portion of the latent image passes through the developing unit 23. When the development is completed, the electrostatic recording paper 11 is cut by the discharge cutter 21. Then, the electrostatic recording paper 11 on which the visible image is formed is discharged.
[0027]
As described above, the ion heads 13 and 14 are controlled to have a constant temperature higher than room temperature in order to improve the efficiency of ion output. A heat source such as a developer pump is provided in the apparatus. Therefore, if the operation of the apparatus is continued, the temperature inside the apparatus increases, the temperature of the base member 22 fixing the ion heads 13 and 14 also increases, and a dimensional change occurs due to thermal expansion.
[0028]
However, in the present embodiment, the relative positional relationship between the two ion heads 13 and 14 is affected only by one of the base members 22 corresponding to the distance ΔL between the ends of the guide members 24 and 25 shown in FIG. Only the amount of expansion of the part. Here, since ΔL is almost 0, even if the base member 22 is deformed by thermal expansion, the change in the relative positional relationship between the two ion heads 13 and 14 is small, and the image formed by the two ion heads 13 and 14 is small. It is possible to prevent a gap from being formed at the seam.
[0029]
Hereinafter, a modification of the first embodiment will be described with reference to FIG.
In this modification, the surface A of the concave portion 71 and the surface B of the concave portion 81 provided in the base member 22 are used as guide members serving as opposition to each ion head. Protrusions 74 and 84 provided on the ion heads 13 and 14 abut against these guide members serving as opposition. In this modification, since the surfaces A and B coincide with the positions of the recording area ends 73 and 83, it can be considered that ΔL = 0, and the deformation of the base member 22 is caused by the two ion heads 13 and 14. Has no effect on the relative relationship of
[0030]
The elastic member that abuts each of the two ion heads 13 and 14 against the opposition is not limited to the coil spring, but may be another spring such as a leaf spring. Further, a configuration may be employed in which the coil spring is applied and the opposing surface is abutted against the opponent by the pulling force.
[0031]
Next, a second embodiment of the present invention will be described with reference to FIGS.
The configuration of this embodiment includes ion heads 73, 74, and 75 as in-line type recording heads (FIG. 7 shows only 73 and 74), electrostatic recording paper 11 as a recording medium, and two ion heads 73 and 74. 74, a temperature sensor 52 (FIG. 8) provided on the base member 22 as a means for measuring a displacement between ends of recording areas of two adjacent ion heads, and a deformation amount calculation. It comprises a device 55 and a write control unit 43 as means for correcting the signal amount applied to the ion head.
[0032]
The deformation amount calculation device 55 and the write control unit 43 are configured by a CPU, a RAM, a ROM, and the like. According to a program recorded in the ROM, a process of correcting a recording signal to be applied to the ion head, which will be described later, Processing such as drive control, conveyance control of electrostatic recording paper, exchange of image data with an external device, and the like are performed.
[0033]
As shown in FIG. 7, the electrostatic recording paper roll 15 is engaged with a drive source (not shown) that rotates forward and backward. The electrostatic recording paper 11 fed out from the electrostatic recording paper roll 15 reaches the counter electrode 12 via a transport path provided in the apparatus main body.
[0034]
Further, a static eliminator 18 is disposed downstream of the ion heads 73, 74, 75. Further downstream of the static eliminator 18, a developing unit 23 composed of a developing device for developing an electrostatic latent image, a driving roller 20 engaged with a not-shown forward / reverse driving source, A cutter 21 for cutting the recording paper 11 is provided in order.
[0035]
As shown in FIG. 8, the ion heads 73, 74, 75 are arranged such that the recording areas of the two ion heads 73, 74 overlap each other. In this case, as shown in FIG. 9, at a predetermined temperature Ti, the eight ion emission ports 19 (eight dots indicated by hatching) are adjusted so as to overlap from the end of each ion head. This is an initial state. FIG. 9 shows a case where one line of dots formed by the ion head is extracted.
[0036]
Next, the operation of the second embodiment will be described.
At the same time as the conveyance of the electrostatic recording paper 11 is started based on a recording start command from an external device, the formation of a latent image according to the image data 26 is also started by the ion heads 73, 74, and 75. The image data 26 is provided for each pixel and serves as a signal for controlling the amount of ions emitted from the corresponding ion emission port 19. For example, image data corresponding to a portion where the recording areas of the two ion heads 73 and 74 overlap are subjected to a correction process described later, and then applied to both the ion heads 73 and 74.
[0037]
As the electrostatic recording paper 11 is conveyed, the formation and development of the latent image progresses, and the final portion of the latent image passes through the developing unit 23. When the development is completed, the electrostatic recording paper 11 is cut by the paper discharge cutter 21. Then, the electrostatic recording paper 11 on which the image is formed is discharged. The image forming process is the same as that of the first embodiment except for the process of correcting the control signal applied to the ion head.
[0038]
Hereinafter, a data correction method at the time of forming a latent image in a portion where the recording areas of the two ion heads 73 and 74 overlap (B in FIG. 9) will be described with reference to the flowcharts of FIGS.
[0039]
First, the temperature T of the base member 22 is measured by the temperature sensor 52 (Step S101), and sent to the deformation amount calculating device 55. In addition, the number of the temperature sensors provided on the base member 22 and the mounting position are not limited to one as in the present embodiment, and even if a temperature distribution occurs in the base member 22 by providing a plurality of temperature sensors. An accurate deformation amount may be obtained. The deformation amount calculating device 55 calculates the thermal expansion coefficient α of the base member 22 and the distances L1 and L2 from the reference positions of the ion heads 73 and 74 at the initial temperature Ti of the base member 22, which are stored in an internal memory in advance. In combination, the amount of deformation ΔL of the base member 22 (the amount of displacement between the ends of the recording areas of the two adjacent ion heads 73 and 74) is obtained using the following equation (1) (step S102).
[0040]
ΔL = α × (T-Ti) × (L1-L2) (1)
Next, the deformation amount calculating device 55 decomposes the deformation amount ΔL of the base member 22 into an integral multiple of the interval P between the ion emission ports 19 and a shift amount m less than P by using the following equation (2). The shift amount m of the dots smaller than the dot interval is calculated (step S103).
[0041]
ΔL = P × j + m (2)
Here, j is an integer, and is determined as the largest integer j such that m becomes 0 or more.
[0042]
These values of j and m are sent to the write control unit 43 and used for data correction processing.
The write control unit 43 first determines the number N of the ion emission ports 19 overlapping in the initial state (N = 8 in FIG. 12A) and the number j obtained by the equation (2). Then, the number n of the ion discharge ports 19 belonging to the area where the recording areas overlap at the temperature during operation (overlap area) is obtained from the equation (3) using the following equation (3) (step S104).
[0043]
When n = N + 1-j 0 ≦ m ≦ P / 2
When n = N−j P / 2 <m <P (3)
If this is divided into the cases of m = 0, m <P / 2, m = P / 2, and m> P / 2, the results are as shown in FIGS.
[0044]
By using this value, it can be determined whether or not correction processing should be performed on the data of the pixel to be processed (step S105 in FIG. 11). That is, as shown in FIG. 13, two ion heads 73 and 74 in which Na ion emission ports 19 are arranged in total are used, and addresses 1 to Na are sequentially assigned from one end of the linear ion emission ports. In this case, the ion emission ports at addresses (Na-n + 1) to Na of one ion head (ion head 73) and the addresses 1 to n of the other ion head (ion head 74) belong to the overlap region. It becomes.
[0045]
The control signal to the ion emission port 19 in the portion where the recording areas of the ion head overlap is subjected to two types of correction. First, the first correction is a process of weighting an amount for controlling the ion emission amount according to the position of the ion emission port 19 in a portion where the recording areas overlap (overlap area).
[0046]
The weighting process will be described below with reference to FIG.
First, the weight coefficient of each ion emission port 19 is determined by a function of the position of each ion emission port 19 in the overlap region defined by the following equation (4) (step S106).
[0047]
Ws = −i / n + 1 (4)
Here, i is 1 at every position P (one dot) closer to the end of the recording area of the ion head (closer to the outside) at the position of each ion emission port 19 in the area. The position of the ion emission port 19 that increases and belongs to the innermost part of the overlap region (the ion emission port 19 indicated by the Greek letter β in FIG. 14) is set to i = 0. n is the number of the ion emission ports 19 belonging to the overlap region determined by the equation (3). Note that the shape of the function for determining the weight coefficient is not limited to that of the present example, and an appropriate function can be set according to the characteristics of the point image recording member of the ion head. Preferably, a function is used in which the weighting factor decreases as it approaches the end of the recording area of the ion head.
[0048]
Here, assuming that image data to be output to a certain ion emission port 19 is d, the correction processing is represented by the following equation (5).
dc = Ws × d (5)
Since the function of the equation (4) for determining the weighting coefficient Ws is a monotonically decreasing function of the position i, as the position goes outside the overlap region, the function from the ion emission port 19 of the ion head as the overlapped partner becomes larger. Ions are dominant. That is, the ratio of the amount of ions supplied from the ion head 74 to the dots in the region B in FIG. For this reason, the connection of the image to the single recording area of each ion head is performed smoothly, and even if there is a delicate difference in characteristics between the two ion heads, the seam between the two ion heads becomes less noticeable. .
[0049]
Next, the second correction processing will be described.
As described above, when the base member 22 expands and deforms as the temperature rises, the overlapping manner of the ion emission ports in the region B of FIG. 9 changes in the order of FIGS. To go. At this time, the ion emission port density (density of the point image recording member) between the two ion emission ports 19 (between KL in FIG. 12) indicated by the Greek letter β is a function of the period P with respect to ΔL. Changes as shown in FIG. Therefore, except for the cases shown in FIGS. 12A and 12E, the image density in this portion also changes according to the ion emission port density, and a density difference from the single recording area occurs. The seam of the ion head becomes conspicuous.
[0050]
Therefore, a correction according to the value is added to m. That is, when the density of the ion emission ports between the KL is smaller than that of the single recording area (when 0 ≦ m ≦ P / 2), the signal amount applied to the ion head is increased, and conversely, the ion emission between the KLs is increased. When the exit density is higher than that of the single recording area (when P / 2 <m <P), the signal amount applied to the ion emission port 19 is reduced (step S107 in FIG. 11). The same correction is applied to all the ion emission ports 19 belonging to the overlap region. The weight coefficient for correction is a periodic function of the period P, and is represented by the following expression (6) as a function of m obtained by the expression (2).
[0051]
Note that the shape of the function for determining the weight coefficient is not limited to that of this example, and an appropriate function can be set according to the characteristics of the point image recording member of the ion head.
[0052]
Wm = 1 + m / (P × n) When 0 ≦ m ≦ P / 2
Wm = 1− (P−m) / (P × n) When P / 2 <m <P (6)
The signal dt applied to the ion head is obtained by the following equation (7) from the first corrected signal dc obtained by the equation (5) (step S108).
[0053]
dt = Wm × dc (7)
The above processing is performed on all the pixels of the given image data, and an image is output on the electrostatic recording paper (steps S110 to S113).
[0054]
As a result, when the ion emission port density between the KLs is smaller than that of the single recording area (when 0 ≦ m ≦ P / 2), the dots belonging to the overlap area depend on the degree (value of m). Is higher than that of the dots in the single recording area when the same image data is given, and conversely, when the ion emission port density between KL is larger than that in the single recording area (P / 2 < When m <P), the density of the dots belonging to the overlap area is smaller than that of the dots in the single recording area when the same image data is given, according to the degree (value of m).
[0055]
Therefore, even when the base member 22 is deformed due to thermal expansion and the ion emission ports of the two ion heads do not completely overlap (in the case of FIGS. 12B, 12C, and 12D), the overlap region is formed. The change in image density between the two ion heads and the single recording area can be kept small, so that the seam between the two ion heads is less noticeable.
[0056]
FIG. 16 shows a first modification of the above-described second embodiment. Instead of using the temperature sensor 52 and the deformation calculator 55 to determine the amount of displacement between the ends of the recording areas of two adjacent ion heads, a strain gauge 81 serving as a strain measuring member provided on the base member 22 and a deformation calculator. Determined by 55. Since the strain gauge 81 measures the strain of the base member 22, that is, the deformation per unit length, the deformation calculating device 55 calculates the following two equations by calculating the following equation (8). The displacement ΔL of the recording area of the ion head can be obtained.
[0057]
ΔL = e × (L1−L2) (8)
Here, L1 and L2 are distances from the reference positions of the ion heads 73 and 74 at the initial temperature Ti, and e is a strain amount of the base member 22 obtained by the strain gauge 81 due to thermal expansion.
[0058]
FIG. 17 shows a second modification of the above-described second embodiment. In this modified example, instead of obtaining the amount of displacement between the ends of the recording areas of two adjacent ion heads from the temperature sensor 52 and the deformation amount calculation device 55, the line sensor 91 and the ion head 74 provided in the ion head 73 are provided. This is a method of directly obtaining the positional deviation amount ΔL between the recording areas of two adjacent ion heads by using the marked member 95.
[0059]
The mark member 95 is graduated from a plate made of metal or the like, but may be replaced with a portion that can be detected by the line sensor 91 such as an end of an ion head.
FIG. 18 shows a third modification of the second embodiment. In this modified example, instead of obtaining the amount of displacement between the ends of the recording areas of two adjacent ion heads from the temperature sensor 52 and the deformation amount calculating device 55, a line sensor 91 provided on the base member 22 and an ion head 73 are provided. With the mark member 96 provided and the mark member 95 provided on the ion head 74, the positional deviation amount ΔL between the recording areas of two adjacent ion heads is obtained.
[0060]
That is, the amount of displacement between the base member 22 and the ion head 73 is determined from the change in the position of the mark member 96 detected by the line sensor 91, and the amount of displacement between the base member 22 and the ion member 73 is detected from the change in the position of the mark member 95 detected by the line sensor 91. By calculating the positional shift amount of the ion head 74 and the two shift amounts, the shift amount ΔL between the ion head 73 and the ion head 74 can be obtained.
[0061]
Here, the above-described in-line type recording head (ion head) will be described with reference to FIG.
The in-line type recording head is a recording head that can form an image by performing relative movement with respect to a recording medium in only one direction when recording a raster image. For example, a recording head in which a plurality of point image recording members are arranged in a straight line and can record a linear visual image or latent image without changing a relative position with respect to a recording medium. (FIG. 19A).
[0062]
A plurality of recording areas formed by a plurality of point image recording members arranged on a straight line may be provided in one in-line type recording head (FIG. 19C). In addition, as shown in FIG. 19B, by changing the drive timing of the point image recording member, the in-line type recording head moves the recording medium relatively in one direction with respect to the recording head, thereby forming a straight line. It also includes a recording head capable of recording a visible or latent image in a shape.
[0063]
The line direction is a direction perpendicular to the moving direction of the recording medium with respect to the recording head shown in FIG. "A part of the recording areas of the two recording heads overlap each other or the recording areas of the two recording heads are in contact with each other" means that a point image recording member is provided adjacent to the recording areas of the two recording heads. This indicates that the two recording heads are arranged so that an interval larger than the existing interval does not occur.
[0064]
The embodiments described above include the following inventions.
(Configuration 1)
The two in-line type recording heads (13, 14) are shifted in the line direction, and the recording areas of the two recording heads are arranged so that a part of the recording areas overlap each other or the recording areas of the two recording heads are in contact with each other. An image forming apparatus that records a visible image or a latent image on a recording medium having a width wider than the recording head alone can record,
A base member (22) on which the two recording heads are placed;
A member (24, 25, 71, 84) provided on the base member (22) to oppose the two recording heads;
An elastic member (31, 32) for abutting two recording heads against opposition,
The image forming apparatus according to claim 1, wherein the opposition of the recording heads is such that the recording areas of the two recording heads are arranged near the end of the recording area on the side adjacent to each other.
(Corresponding Embodiment of the Invention)
The first embodiment (FIGS. 1 to 5) and its modification (FIG. 6) correspond.
(Action / Effect)
When the apparatus is operated, the temperature of the apparatus increases, and the base member on which the two recording heads are mounted expands. When the base member expands, the positional relationship between the two recording heads mounted thereon changes. However, since the opponents are provided close to each other, even if the base member expands, there is little dimensional change between the two opponents which is a reference for the position of the recording head, and the relative positional relationship between the two recording heads. Can be prevented from greatly changing.
[0065]
Further, since the temperature of the recording head (ion head) is controlled to stabilize the characteristics, a dimensional change due to a temperature change during operation of the apparatus is small. On the other hand, the base member 1) is made of a material having a large coefficient of thermal expansion from the viewpoint of mechanical strength and workability, and 2) is not temperature-controlled. Large expansion and contraction. Therefore, the dimensional change due to expansion and contraction of the base member contributes to the positional relationship between the two heads.
[0066]
As described above, by preventing the dimensional change of the base member from affecting the relative positional relationship between the two recording heads, it is possible to prevent an image defect from occurring at the joint between the two heads. be able to.
(Configuration 2)
A point image recording member (19) uses two or more in-line type recording heads (73, 74, 75) arranged at regular intervals, displaces these in the line direction, and records two adjacent recording heads. By arranging them on the base member (22) so that a part of the areas overlap each other and combining them, a visible image or a latent image can be printed on a recording medium having a width wider than the recording head can record alone. In an image forming apparatus that records
Means (52, 55, 81, 91, 95, 96) for measuring the displacement of the end of the recording area between two adjacent recording heads;
Means for calculating the density of the point image recording member in an area where a part of the recording areas of two adjacent recording heads overlap each other, based on the displacement amount of the recording area end of each recording head (steps S103 and S104). When,
Depending on the density of the point image recording member in the area where a part of the recording area overlaps with each other, the higher the density, the more the point image recording member in the area where the part of the recording area overlaps with each other is added to each point image recording member. Means for correcting so as to greatly reduce the amount of the recording signal (step S107);
An image forming apparatus comprising:
(Corresponding Embodiment of the Invention)
The second embodiment (FIG. 8) and its modifications (FIGS. 16, 17, and 18) correspond to each other.
(Action / Effect)
The recording head forms an image by forming dot rows at regular intervals. If the relative positional relationship between two adjacent print heads changes due to a change in the size of the base member, the dot rows printed by the respective print heads may not completely overlap in a portion where the print areas overlap (FIG. 12). (B), (c), (d)). At this time, the density of the point image recording member in the portion where the recording areas overlap may be larger or smaller than that in the area where the recording areas do not overlap.
[0067]
For this reason, the image density of the portion where the recording areas overlap (area B in FIG. 9) differs from the density of the areas where the recording areas do not overlap (areas A and C in FIG. 9) when the same recording signal is applied. As a result, the seam of the head may be conspicuous.
[0068]
Therefore, the displacement between the ends of the recording areas of two adjacent recording heads is measured by means for measuring the displacement of the ends of the recording areas of two adjacent recording heads. From this value, means for calculating the density of the point image recording member in the portion where the recording areas overlap, examines how the point image recording members of each recording head overlap in the portion where the recording areas of two adjacent recording heads overlap. (FIGS. 12 (a) to 12 (e)), the value of the width (between KL in FIG. 12) of the portion where the recording regions of the two adjacent recording heads overlap is determined, and the point image recording member in the portion where the recording regions overlap is obtained. Calculate the density. On the basis of this, when the density of the point image recording member is increased in a portion where the recording areas of two adjacent recording heads overlap, the recording signal is corrected by the means for correcting the amount of the recording signal applied to each point image recording member. When the density of the point image recording member is low, on the other hand, by adding a correction to increase the recording signal, the image density at the portion where the recording areas overlap when the same recording signal is given is added. Since the difference in image density in a portion where the recording areas do not overlap is reduced, even when the point image recording members of the two recording heads are displaced from each other in a portion where the recording areas of the two adjacent recording heads overlap, the recording heads are shifted. Seams are less noticeable.
(Configuration 3)
The point image recording member (19) uses two or more inline type recording heads (73, 74, 75) arranged at a certain interval, shifts them in the line direction, and records the recording area of two adjacent recording heads. Are arranged on the base member (22) so that a part of them overlaps each other, and by combining them, a visible image or a latent image is recorded on a recording medium having a width wider than the recording head can record alone. In the image forming apparatus,
For each point image recording member belonging to an area where a part of the recording areas of two adjacent recording heads overlap each other, the point image recording member is located at a boundary between an area where the part of the recording area overlaps and an area where the part does not overlap. The recording signal supplied to the point image recording member belonging to an area where a part of the recording area overlaps is corrected to be greatly reduced as the distance of the point image recording member from the boundary increases according to the distance of the point image recording member. An image forming apparatus characterized by comprising means.
(Corresponding Embodiment of the Invention)
The second embodiment (FIG. 8) and its modifications (FIGS. 16, 17, and 18) correspond to each other.
(Action / Effect)
In a region where a part of the recording areas of two adjacent recording heads overlap each other, the two point image recording members belonging to the two recording heads and having a relationship such that the point images to be recorded overlap each other belong to the two recording heads. An image of that pixel is formed. At this time, the correction unit corrects the recording signal so that the recording signal of the recording head becomes more dominant as the recording area approaches an area that does not overlap with the recording area of another recording head, that is, a single recording area.
[0069]
For this reason, the connection of the image to the single recording area of each ion head is smoothly performed from the portion where the recording areas of the two recording heads overlap, and there is a subtle difference in characteristics between the two ion heads. However, the joint between the two ion heads becomes less noticeable.
(Configuration 4)
The means for measuring the displacement of the end of the recording area of the two adjacent recording heads is provided in a portion where the recording areas of the two recording heads overlap.
A mark (95) provided on one of the recording heads,
A position sensor (91) provided on the recording head on which the mark is not provided so as to face the mark,
An image forming apparatus according to Configuration 2, comprising:
(Corresponding Embodiment of the Invention)
A modification (FIG. 17) of the second embodiment corresponds to this.
(Action / Effect)
Since the position of the end of the recording area is measured by directly measuring the relative movement amount of two adjacent recording heads, accurate measurement is possible regardless of the configuration or material of the base member.
(Configuration 5)
The means for measuring the displacement of the end of the recording area of the two adjacent recording heads is provided in a portion where the recording areas of the two recording heads overlap.
Marks (95, 96) provided on the two recording heads,
An image forming apparatus according to Configuration 2, comprising a position sensor (91) provided on the base member so as to face the mark.
(Corresponding Embodiment of the Invention)
A modification (FIG. 18) of the second embodiment corresponds to this.
(effect)
Since the characteristics of the recording head deteriorate due to aging, it is common to replace the recording head periodically. When replacing the recording head, it is not necessary to remove the position sensor to which the signal line for transmitting the position signal and the power supply line are connected, so that the recording head can be easily replaced.
(Configuration 6)
A distortion measuring member (81) provided on a base member, for measuring a displacement of an end portion of a recording area between two adjacent recording heads;
A base member deformation amount calculation unit (55);
An image forming apparatus according to Configuration 2, comprising:
(Corresponding Embodiment of the Invention)
A modification (FIG. 16) of the second embodiment corresponds to this.
(Action / Effect)
By measuring the amount of distortion of the base member by using the distortion measuring member, the displacement of the end of the recording area of the two adjacent recording heads is measured. Therefore, it is necessary to provide a sensor for each adjacent part of the two recording heads. Instead, the position of the end of the recording area of each recording head can be measured with a small number of sensors. Further, since the sensor is small and the sensor is formed of one part, the degree of freedom of the mounting position of the sensor is large.
(Configuration 7)
Means for measuring the displacement between the ends of the recording areas of two adjacent recording heads is as follows:
A temperature sensor (52) provided on the base member;
An image forming apparatus according to Configuration 2, comprising a base member deformation amount calculation unit (55).
(Corresponding Embodiment of the Invention)
The second embodiment corresponds to this.
(Action / Effect)
Based on the temperature of the base member measured by the temperature sensor and the coefficient of thermal expansion of the base member stored in advance, the deformation amount of the base member due to the thermal expansion is calculated in the base member deformation amount calculation unit. The amount of displacement of the end of the recording area of the head is determined. For this reason, measurement can be performed with a smaller number of sensors than the number of parts where two recording heads are adjacent. Further, since the sensor is small and the sensor is formed of one part, the degree of freedom of the mounting position of the sensor is large.
[0070]
【The invention's effect】
According to the first aspect of the present invention, it is possible to provide an image forming apparatus in which there is no displacement between printheads even when a temperature change occurs, and image defects are less likely to occur at seams of printheads.
[0071]
Further, according to the second aspect of the present invention, it is possible to provide an image forming apparatus in which a change in image density hardly occurs at a seam of recording heads even when a temperature change occurs and a positional displacement between the recording heads occurs. .
[0072]
According to the third aspect of the present invention, it is possible to provide an image forming apparatus in which a change in image density hardly occurs at a seam of recording heads even if a slight difference in characteristics occurs between adjacent recording heads. .
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an overall configuration of an image forming apparatus according to a first embodiment.
FIG. 2 is a perspective view showing an external appearance of the ion head unit according to the first embodiment.
FIG. 3 is a diagram showing a schematic configuration of an ion head unit.
FIG. 4 is an enlarged view of a portion indicated by A in FIG. 3;
FIG. 5 is a diagram showing one line of dots formed by the ion head.
FIG. 6 is a diagram showing a modification of the first embodiment.
FIG. 7 is a diagram illustrating an overall configuration of an image forming apparatus according to a second embodiment.
FIG. 8 is a sectional view of an ion head unit according to a second embodiment.
FIG. 9 is an enlarged view of an image in an overlap section.
FIG. 10 is a front part of a flowchart for describing a data correction method when forming a latent image.
FIG. 11 is a rear part of a flowchart for describing a data correction method when forming a latent image.
FIG. 12 is a view showing that two ion heads are relatively separated by deformation of a base member.
FIG. 13 is a diagram for explaining an overlap region of two ion heads.
FIG. 14 is a diagram illustrating a weighting process.
FIG. 15 is a diagram showing a relationship between an ion emission port density and ΔL.
FIG. 16 is a diagram showing a first modification of the second embodiment.
FIG. 17 is a diagram showing a second modification of the second embodiment.
FIG. 18 is a diagram showing a third modification of the second embodiment.
FIG. 19 is a diagram illustrating an in-line type recording head.
FIG. 20 is a diagram for explaining a problem of a conventional image forming apparatus.
[Explanation of symbols]
13, 14 ... ion head, 24, 25 ... guide member, 31, 32 ... compression spring, 61, 62 ... ion emission part.

Claims (6)

In a plurality of recording heads each having a plurality of recording members juxtaposed at a fixed interval, an image is formed by using a plurality of recording heads arranged such that a part of each recording area overlaps or touches each other. In the image forming apparatus,
  Measuring means for measuring the amount of displacement of the ends of the recording areas of two adjacent recording heads among the plurality of recording heads;
  Based on the displacement of the end of the recording area of each recording head measured by the measuring means, the density of the recording member in the area where the recording areas of two adjacent recording heads overlap each other is calculated. Calculating means for calculating
  Correction means for correcting an amount of a recording signal to be applied to the recording member in an area where a part of the recording area overlaps each other, according to the density of the recording member calculated by the calculation means;
  An image forming apparatus comprising: Point image recording member, at a fixed interval, using two or more in-line type recording heads arranged side by side, these are shifted in the line direction, and so that part of the recording areas of two adjacent recording heads overlap each other. By arranging them on the base member and combining them, an image forming apparatus that records a visible image or a latent image on a recording medium having a width wider than the recording head alone can record,
  Means for measuring the displacement of the ends of the recording areas of two adjacent recording heads;
  Means for calculating the density of the point image recording member in an area where a part of the recording areas of two adjacent recording heads overlap each other, from the amount of displacement of the end of the recording area of each recording head;
  Depending on the density of the point image recording member in the area where a part of the recording area overlaps with each other, the higher the density, the more the point image recording member in the area where the part of the recording area overlaps with each other is added to each point image recording member. Means for correcting so as to greatly reduce the amount of the recording signal;
  An image forming apparatus comprising: The means for measuring the displacement of the end of the recording area between two adjacent recording heads is as follows:
  A mark provided on one of the recording heads at a portion where the recording areas of the two recording heads overlap;
  A position sensor provided on the recording head on which the mark is not provided so as to face the mark,
  The image forming apparatus according to claim 2, further comprising: The means for measuring the displacement of the end of the recording area between two adjacent recording heads is as follows:
  A mark provided on the two recording heads at a portion where the recording areas of the two recording heads overlap;
  A position sensor provided on the base member so as to face the mark,
  The image forming apparatus according to claim 2, further comprising: Means for measuring the displacement of the ends of the recording areas of two adjacent recording heads;
  A strain measurement member provided on the base member,
  A base member deformation amount calculation unit,
  The image forming apparatus according to claim 2, further comprising: The means for measuring the displacement of the end of the recording area between two adjacent recording heads is as follows:
  A temperature sensor provided on the base member,
  A base member deformation amount calculation unit,
The image forming apparatus according to claim 2, further comprising:

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