Image forming apparatus

Abstract

Provided is an image forming apparatus capable of shortening the time required for printing by 1-line amount at the time of divided printing. A printer divides a plurality of heating elements into M1 blocks, and causes the heating elements to heat at different timings for each block. In a case where the number of heating elements capable of being simultaneously energized among the plurality of heating elements is set to N1, and a prescribed number smaller than N1 is set to N2, one high-current block having a number p (p satisfies N2 < p ≤ N1) of heating elements and a low-current block having a number q (q satisfies q ≤ N2) of heating elements are included in the M1 blocks. In a case where the first block is the high-current block, at least one of the blocks other than the first block and the M1th block becomes the low-current block.

Description

Technical Field

[0001] This invention relates to an image forming apparatus. Background Technology

[0002] An image forming apparatus is known to use a thermal header with multiple heating elements to print onto a printing medium. In the thermal header, heating elements of one row of the image to be formed are arranged in the main scanning direction. The image forming apparatus drives the thermal header by heating the multiple heating elements by passing an electric current through them.

[0003] In the case of forming a single-line image, there is a requirement to suppress the current consumed simultaneously by the thermal contact wire. Methods for suppressing this current include the first method, the second method, and the third method, as shown below.

[0004] In the first method, the multiple heating elements of the thermal lead are divided into multiple blocks. The image forming apparatus heats the heating elements for each block in a time-divided manner. Hereinafter, printing performed using the first method will be referred to as "segmented printing." In the second method, based on the electrical power consumed when printing lines up to the current time point, the average electrical power for printing one line at the current time point is determined, within a predetermined upper limit of electrical power (see Patent Document 1). Hereinafter, printing performed using the second method will be referred to as "feedback printing." In the third method, the current for printing lines up to the current time point is predetermined based on the constraints of the power supply's overcurrent protection circuit (OCP). Hereinafter, printing performed using the third method will be referred to as "feedforward printing."

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2019-199072 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] In split printing, printing one line at a time is divided into multiple operations, thus increasing the time required for printing one line at a time compared to printing one line at a time. Furthermore, when split printing and feedforward printing are used together, if the time required for printing one line at a time increases due to split printing, the timing for determining the average power consumption via feedforward printing becomes later. In this case, the printing time for one line at a time in split printing may exceed the OCP constraint. Therefore, using split printing and feedforward printing together is advisable.

[0010] However, if only split printing and advance feeding printing are used together, when the current is determined in accordance with the constraint of OCP, the performance of the power supply cannot be utilized to the maximum extent, and the time required for printing one line of data cannot be shortened in some cases.

[0011] An object of the present invention is to provide an image forming apparatus capable of shortening the time required for printing one line of data during split printing.

[0012] Means for Solving the Problem

[0013] The image forming apparatus of the present invention performs printing based on print data, and is characterized by comprising: a thermal head including a plurality of heating elements arranged in a main scanning direction, each of which generates heat when energized, and forms an image on a print target by causing the plurality of heating elements to generate heat while moving relatively to the print target in a sub-scanning direction; and a control unit configured to perform a first line printing process for printing one line extending in the main scanning direction, the first line printing process comprising: a splitting process of splitting selected R heating elements into M blocks including a first block to an M-th block, wherein the number R is a natural number larger than a natural number obtained by adding the number q to the number p, and M is a natural number of 3 or more; and a heating process of performing printing of the first line by causing the M blocks to generate heat at different timings in an order from the first block to the M-th block, wherein when the maximum number of heating elements among the plurality of heating elements that can be energized simultaneously is denoted as N1, and a predetermined natural number smaller than N1 is denoted as N2, the M blocks include at least one high-current block having p energized heating elements (p is any natural number satisfying N2 < p ≤ N1) and at least one low-current block having q energized heating elements (q is any natural number satisfying q ≤ N2), when the first block is the high-current block, at least one of the blocks other than the M-th block among the M blocks is the low-current block, and when the first block is the low-current block, at least one of the blocks other than the M-th block among the M blocks is the high-current block.

[0014] The image forming apparatus splits the plurality of heating elements included in the thermal head into M blocks, and causes the heating elements to generate heat at different timings for each block, thereby performing printing of one line of data. Here, the M blocks include a low-current block and a high-current block having different numbers of heating elements. The number of heating elements included in the high-current block is larger than the number of heating elements included in the low-current block. Therefore, compared with a case where printing is performed in a state where the plurality of heating elements are split such that all blocks are low-current blocks, the time required for printing can be shortened. Therefore, when the image forming apparatus splits a plurality of heating elements into blocks for printing, it can shorten the time required for printing one line of data.

[0015] In this invention, the current value when N1 heating elements are simultaneously energized can be based on a first current value, which is the maximum permissible current value in the image forming apparatus. The image forming apparatus can maximize the number of heating elements in the high-current block within its permissible range. In this case, the image forming apparatus can minimize the number of blocks when multiple heating elements are divided into M blocks within its permissible range. Therefore, the image forming apparatus can minimize the time required for printing one line.

[0016] In this invention, the current value when simultaneously energizing N2 heating elements can be based on a second current value, which is the maximum current value allowed in the overcurrent protection circuit of the power supply of the image forming apparatus. This reduces the possibility of damage to the overcurrent protection circuit when current is supplied to heating elements with low current blocks.

[0017] In this invention, the first time during which current can be simultaneously supplied to the heating element of the high-current block can be shorter than the second time, which is the longest time during which current can be continuously supplied at the second current value in the overcurrent protection circuit. When current is supplied to the heating element included in the high-current block, the possibility of damage to the image forming apparatus can be reduced. Furthermore, when current is supplied to the heating element of the low-current block, the possibility of damage to the overcurrent protection circuit can be reduced.

[0018] In this invention, the control unit may be further configured to perform a second line printing process, which prints a first line extending in the main scanning direction. The second line printing process includes: a segmentation process, which divides the selected R heating elements into S blocks consisting of a first block to an S-th block, where the number R is a natural number larger than the natural number obtained by multiplying the number q by the number (S-1), and S is a natural number greater than 3; and a heating process, which prints the line by heating the S blocks at different timings, where the number of energized heating elements contained in each of the first to (S-1)-th blocks of the S blocks is q. The control unit is configured to execute: a determination process, which of the first line printing process and the second line printing process should be executed in order to print the line to be printed; and an execution process, which executes the process that was determined to be executed in the determination process in the first line printing process and the second line printing process to be executed in order to print the line to be printed. The image forming apparatus can switch between printing a first line of print processing that divides the image into M blocks containing high-current blocks and low-current blocks, and printing a second line of print processing that divides the image into S blocks, each containing an equal number of energized heating elements, and then print the image. Attached Figure Description

[0019] Figure 1 This is a 3D image of printer 1.

[0020] Figure 2 This is an exploded 3D view of printer 1.

[0021] Figure 3 It is Figure 1 The sectional view shown when viewed from the direction of the arrow along line AA.

[0022] Figure 4 This is a block diagram showing the electrical structure of printer 1 and battery unit 10.

[0023] Figure 5 This is a coordinate graph used to illustrate the first example of split printing.

[0024] Figure 6 This is a coordinate graph used to illustrate the second example of split printing.

[0025] Figure 7 This is a coordinate graph used to illustrate the third example of split printing.

[0026] Figure 8 This is a coordinate graph used to illustrate the fourth example of split printing.

[0027] Figure 9 This is the flowchart for the main processing.

[0028] Figure 10 This is the flowchart for the first segmentation and printing process.

[0029] Figure 11 This is the flowchart for the second segmentation printing process (second example).

[0030] Figure 12 This is the flowchart for the second segmentation printing process (the third example). Detailed Implementation

[0031] <Summary of Printer 1>

[0032] A printer 1 according to an embodiment of the present invention will be described with reference to the accompanying drawings. Hereinafter, Figure 1 The lower left, upper right, upper left, lower right, upper and lower, and lower sides are respectively set as the front, back, left, right, upper and lower sides of printer 1.

[0033] Figure 1 The printer 1 shown is capable of printing images onto medium D based on printing data. Medium D is not limited to a specific medium, but may be, for example, sheet or roll, and in this embodiment, thermal paper.

[0034] Printer 1 includes a housing 2. Housing 2 is rectangular in shape and is longer in the left-right direction than in the front-back and top-bottom directions. A [missing information - likely a component or part] is fitted to the lower rear of housing 2. Figure 2 The battery unit 10 is shown. When the battery unit 10 is installed in the printer 1, it supplies power to the printer 1. An input section 96 is provided near the left end of the upper surface of the housing 2. The input section 96 includes multiple buttons. A USB port 95A is provided on the right side of the housing. A connector for connecting a USB cable can be connected to the USB port 95A.

[0035] like Figure 1 and Figure 2 As shown, the housing 2 includes a lower cover 21, an upper cover 22, and an opening / closing cover 23. The lower cover 21 is plate-shaped and extends in the front-back and left-right directions. The lower cover 21 forms the lower part of the housing 2. The upper cover 22 opens downward and is assembled to the upper side of the lower cover 21. An opening 221 is formed in the upper cover 22. The opening 221 opens on the front surface and the upper surface of the upper cover 22. The opening 221 extends from the center in the vertical direction to the upper end in the front surface of the upper cover 22. The opening 221 extends from the front end to the center in the front-back direction in the upper surface of the upper cover 22. The opening 221 extends from near the left end to near the right end in the upper cover 22. Hereinafter, the end of the rear end of the specified opening 221 in the upper cover 22 will be referred to as "opening end 223", and the end of the lower end of the specified opening 221 in the upper cover 22 will be referred to as "opening end 224".

[0036] The opening / closing cover 23 is plate-shaped and includes a first portion 231 and a second portion 232. The first portion 231 extends in the front-back and left-right directions. The second portion 232 extends downward from the front end of the first portion 231 and extends in the left-right direction. The opening / closing cover 23 fits into the opening 221. The rear end 233 of the first portion 231 is supported by the upper cover 22 and is rotatable. Therefore, the opening / closing cover 23 can open and close the opening 221 by swinging about the rear end 233 of the first portion 231 as an axis.

[0037] The following, such as Figure 1 As shown, the explanation is based on the state where the opening 221 of the cover 23 is closed. In this case, the rear end 233 of the first part 231 faces the opening end 223 of the upper cover 22 with a gap in the front-to-back direction. Moreover, the lower end 234 of the second part 232 faces the opening end 224 of the upper cover 22 with a gap in the vertical direction.

[0038] An insertion port 24 is formed on the upper surface of the housing 2. The insertion port 24 is an opening defined by the opening end 223 of the upper cover 22 and the rear end 233 of the opening and closing cover 23. The medium D is supplied into the housing 2 through the insertion port 24.

[0039] A discharge port 25 is formed on the front surface of the housing 2. The discharge port 25 is an opening defined by the opening end 224 of the upper cover 22 and the lower end 234 of the opening and closing cover 23. After the medium D is printed inside the housing 2, it is discharged from the discharge port 25 to the outside of the housing 2.

[0040] like Figure 2 , Figure 3 As shown, printer 1 includes a head unit 4. The head unit 4 is housed within housing 2 and includes a support plate 5, an impression roller 6, a thermal head 7, and a heat sink 8. The support plate 5 includes a lower plate 51, a left plate 52, and a right plate 53. The lower plate 51 is rectangular in top view and is longer in the left-right direction than in the front-back direction. The lower plate 51 is fixed to the upper surface of the lower cover 21. The left plate 52 extends upward from the left end of the lower plate 51 and extends in the front-back direction. The right plate 53 extends upward from the right end of the lower plate 51 and extends in the front-back direction. The left plate 52 and the right plate 53 face each other in the left-right direction.

[0041] The impression roller 6 is located at the front oblique upper part inside the housing 2 (see reference). Figure 3 The impression roller 6 extends in the left-right direction. It has a cylindrical portion 61 and a shaft 62. The cylindrical portion 61 is an elastic body made of rubber or the like. The shaft 62 passes through the cylindrical portion 61, and the cylindrical portion 61 is fixed to the shaft 62. The left end 621 of the shaft 62 is supported by a left plate 52. The right end 622 of the shaft 62 is supported by a right plate 53. The impression roller 6 is capable of rotating about the axis C of the shaft 62.

[0042] The impression roller 6 is connected to the motor 69 via gear 691, etc. The motor 69 is fixed to the lower rear part on the right surface of the left plate 52. The gear 691 is supported by the left plate 52 on the left side. The motor 69 drives the impression roller 6 to rotate via gear 691.

[0043] like Figure 3 As shown, the axis C of shaft 62 functions as the rotation center C of impression roller 6. The rotation center C of impression roller 6 extends in the left-right direction through the center of shaft 62. Impression roller 6 transports medium D in the transport direction by rotating around the rotation center C. The transport direction is the direction in which the impression roller 6 transports medium D, and is orthogonal to the left-right direction. In this embodiment, the transport direction extends obliquely upward and obliquely downward. Hereinafter, the obliquely upward direction in the transport direction is referred to as the upstream side, and the obliquely downward direction in the forward direction is referred to as the downstream side. The direction orthogonal to the left-right direction and the transport direction is referred to as the opposing direction. The path through which the medium D transported in the transport direction passes is referred to as the "transport path R".

[0044] The thermal head 7 is located below the impression roller 6. When the medium D is transported in the transport direction by the rotation of the impression roller 6, the thermal head 7 moves relative to the medium D in the transport direction. For example... Figure 2 As shown, the thermal head 7 is a wire-type head, comprising a substrate 71, a glaze layer 72, multiple heating elements 73, and a driver IC 74 (see reference). Figure 3 ).

[0045] The substrate 71 extends in the left-right direction and the transport direction orthogonal to the opposing direction. A glaze layer 72 and a plurality of heating elements 73 are disposed on the front-facing obliquely upward surface of the substrate 71 (hereinafter referred to as the "front side"). The glaze layer 72 protrudes upward from the front side. The glaze layer 72 extends in the left-right direction from near the left end to near the right end of the substrate 71. The glaze layer 72 serves as a base for fixing the plurality of heating elements 73 to the substrate 71. The plurality of heating elements 73 are fixed to the glaze layer 72 and arranged in the left-right direction. Each of the plurality of heating elements 73 is heated by energizing it. The plurality of heating elements 73 contact the medium D pressed onto the front side by the impression roller 6, and printing onto the medium D is performed by heating. The driver IC 74 energizes the plurality of heating elements 73 based on printing data, selectively heating them.

[0046] like Figure 3 As shown, the heat sink 8 contacts the side of the substrate 71 opposite to the front side (hereinafter referred to as the "back side"), supporting the substrate 71. The heat sink 8 is plate-shaped and releases heat generated by the heating of multiple heating elements 73. A compression coil spring 41 is disposed inside the housing 2. The upper end of the compression coil spring 41 contacts the lower surface of the heat sink 8, applying an upward force to the heat sink 8. Through the force of the compression coil spring 41, the thermal head 7 is pressed against the impression roller 6.

[0047] like Figure 2 , Figure 3 As shown, the defining member 3 is located upstream of the multiple heating elements 73 of the thermistor head 7 in the transport direction, inside the housing 2 below the insertion port 24. The defining member 3 is plate-shaped, extends in the left-right direction, and extends forward and downward from the opening end 223 of the upper cover 22. The defining member 3 defines the transport path R of the medium D.

[0048] <Electrical structure of printer 1 and battery unit 10>

[0049] Reference Figure 4 The electrical structure of printer 1 and battery unit 10 will be described below. Printer 1 includes CPU 91, RAM 92, flash memory 93, EEPROM 94, communication unit 95, input unit 96, motor 69, impression roller 6, driver IC 74, and thermal printhead 7. CPU 91 controls printer 1. CPU 91 is electrically connected to RAM 92, flash memory 93, EEPROM 94, communication unit 95, input unit 96, motor 69, and driver IC 74.

[0050] RAM 92 stores various variables and other temporary data. Flash memory 93 stores the program and printing data executed by CPU 91 to control printer 1. EEPROM 94 stores various setting information.

[0051] The communication unit 95 is used for connecting to the USB port 95A (see reference). Figure 1 The controller communicates with external devices via a USB cable. The motor 69 drives the impression roller 6 to rotate. The driver IC 74 applies voltage to multiple heating elements 73 of the thermal head 7, selectively energizing and heating them.

[0052] The battery unit 10 includes a control circuit 11 and an overcurrent protection circuit (OCP) 12. Although details are described later, the control circuit 11 is used to control the overcurrent protection circuit 12, which is used to protect the battery unit 10 from overcurrent.

[0053] <Summary of the printing action>

[0054] Printer 1 selectively energizes multiple heating elements 73 of the thermal head 7. Heat energy is applied to the portions of the medium D that are in contact with the energized heating elements 73. A predetermined time (referred to as "energizing time T") elapses after the energizing time has elapsed for the heating elements 73. P ” (refer to Figures 5-8))), a pixel is formed at a portion in the medium D that is in contact with the energized heating element 73. Accordingly, the printer 1 forms a plurality of pixel columns arranged in one column corresponding to the arrangement of the plurality of heating elements 73. The pixel column is referred to as a "row".

[0055] The printer 1 intermittently performs energization to the plurality of heating elements 73 a plurality of times while rotating the platen roller 6 by a motor 69 to convey the medium D to the downstream side in the conveying direction. As a result, a plurality of rows arranged in a direction orthogonal to the arrangement direction of pixels in one row of image are formed on the medium D. The plurality of rows constitute shading on the medium D depending on the presence or absence of formation of each pixel, thereby forming a printed image such as characters and images.

[0056] The above operation is referred to as a "printing operation". The arrangement direction of pixels in one row of image formed on the medium D by the printing operation is defined as the "main scanning direction". In addition, a direction orthogonal to the main scanning direction, which is the arrangement direction of the plurality of rows, is defined as the "sub-scanning direction".

[0057] <Summary of Divided Printing>

[0058] The larger the number of pixels included in one row of image, the larger the number of the plurality of heating elements 73 that are energized to print the row, so the total amount of current energized to the thermal head 7 (hereinafter referred to as "total head current I A ") has a larger value. In contrast, the maximum value of the total head current I A is restricted by the following conditions (a) and (b). (a) is the maximum current value allowable in the printer 1 (hereinafter referred to as "first current value I1"). (b) is the maximum current value allowable in the overcurrent protection circuit 12 of the battery unit 10 (hereinafter referred to as "second current value I2").

[0059] The first current value I1 is the maximum current value allowable for various devices included in the printer 1. Specific examples of the various devices include the battery unit 10, a power circuit for stepping down / boosting the voltage of the battery unit 10 and supplying the voltage to the thermal head 7 and the like, the thermal head 7, a resistor connected to a power line, a capacitor, a filter, and the like. The first current value I1 is larger than the second current value I2 (I1>I2).

[0060] The maximum time during which energization with a current of the first current value I1 can be continuously performed in the printer 1 is referred to as "first time T1". The maximum time during which energization with a current of the second current value I2 can be continuously performed in the overcurrent protection circuit is referred to as "second time T2". The first time T1 is shorter than the second time T2 (T1<T2). The energization time T P is shorter than the first time T1 and the second time T2 (T1>T P , T2>TP ).

[0061] In the following description, the quantities N1, N2, p and q are defined. When N1 of the plurality of heating elements 73 of the thermal head 7 are energized, the total head current I A has a value of a first current value I1. When N2 of the plurality of heating elements 73 of the thermal head 7 are energized, the total head current I A has a value of a second current value I2.

[0062] p is any quantity satisfying the condition N2 < p ≤ N1. q is any quantity satisfying the condition q ≤ N2. In the present embodiment, it is premised that the condition p = N1 and the condition q = N2 are satisfied.

[0063] When the number of the plurality of energized heating elements 73 (hereinafter referred to as "effective dots") is large, the printer 1 does not energize many heating elements 73 at one time. More specifically, when the number of heating elements 73 to be energized for printing one line of image exceeds a predetermined number, the printer 1 divides the plurality of heating elements 73 into a plurality of blocks. The predetermined number is q when a first divided printing process described later ( Figure 10 ) is performed, and is p when a second divided printing process described later ( Figure 11 , 12 ) is performed. The printer 1 prints one line of image by energizing the plurality of heating elements 73 in a time-division manner multiple times for each divided block. Printing performed by this method is referred to as "divided printing".

[0064] Referring to Figures 5-8 , the total head current I A and the number of energized heating elements 73 during execution of divided printing will be described. In Figures 5-8 , for ease of explanation, it is premised that a one-line image is printed by energizing all of the plurality of heating elements 73 included in the thermal head 7. Each block B obtained by dividing the plurality of heating elements 73 is sequentially referred to as "first block B(1)", "second block B(2)", ... starting from the first energized block. In Figures 5-8 , the number of the plurality of heating elements 73 included in each of the plurality of blocks B is different.

[0065] In Figure 5 the first example shown, the plurality of heating elements 73 are divided such that the number of heating elements 73 included in each block B is q, so that a total number M' of blocks B are formed. It should be noted that M' is a natural number of 3 or more. In this case, since q heating elements 73 are energized, the total head current I in each block B AThe value becomes the second current value I2. It should be noted that in the M′ block B (M′), there is a number of heating elements 73, s0 (=x mod q), corresponding to the remainder when the total number x of the plurality of heating elements 73 is divided by the quantity q. In the first example, the effective number of points (the number of energized heating elements 73) is a natural number larger than the natural number obtained by multiplying the quantity q by (M′-1).

[0066] In such Figure 5 In the case where multiple heating elements 73 are divided as shown and segmented printing is performed, the total head current I in each of the first block B(1) to the M′-1th block B(M′-1) is... A The value of I2 always becomes the second current value. Therefore, printer 1 can supply a total head current I to the thermal head 7. A Segment printing is performed under condition (b) where the value of is always within the allowable range of OCP. Hereinafter, the segment printing illustrated in the first example, which divides multiple heating elements 73 into equal parts, will be referred to as the "first segment printing".

[0067] It should be noted that, in Figure 5 In the diagram, the histogram represents the contact between each block B and its adjacent blocks B. However, in reality, there is a gap between the time when each block B is energized and the time when the next block B is energized. Therefore, the total head current I... A The time during which the value of the second current value I2 is not sustained during the energizing time T P That's all. Regarding... Figures 6-8 The same applies.

[0068] On the other hand, Figures 6-8 In the example shown, multiple heating elements 73 are divided into blocks B consisting of p heating elements 73 and q heating elements 73. The total head current I in block B consisting of p heating elements 73 is... A The value becomes the first current value I1. On the other hand, the total head current I in block B, which is composed of heating elements 73 of quantity q, is... A The value becomes the second current value I2. Hereinafter, the block B composed of p heating elements 73 will be referred to as "high current block B". H The block B, consisting of q heating elements 73, is called "low-current block B". L ".

[0069] exist Figure 6 In the second example shown, multiple heating elements 73 are divided into blocks B totaling M1. The first block B(1), the third block B(3)...the M1-2th block B(M1-2) is a high-current block B. HThe second block B(2), the fourth block B(4)...the M1-1th block B(M1-1) is a low-current block B. L High current block B H and low current block B L They are alternately energized. Block B (M1) contains heating elements 73 of a quantity s1 calculated using the following formula. Wherein, high-current block B... H The quantity is denoted as CH1, and the low current block B is... L The quantity is denoted as CL1.

[0070] s1=x-((p×CH1)+(q×CL1))

[0071] exist Figure 7 In the third example shown, multiple heating elements 73 are divided into blocks B totaling M2. The first block B(1), the second block B(2), the fourth block B(4), the fifth block B(5), ... the M2-1th block B (M2-1) is a high-current block B. H The third block B(3), the sixth block B(6), ... are low-current blocks B. L High current block B H and low current block B L High current block B H High current block B H Low current block B L High current block B H High current block B H Low current block B L … are energized in sequence. Block B (M2) contains heating elements 73 of a quantity s2 calculated using the following formula. Wherein, high-current block B… H The quantity is denoted as CH2, and the low current block B is... L The quantity is denoted as CL2.

[0072] s² = x - ((p × CH²) + (q × CL²))

[0073] exist Figure 8 In the fourth example shown, multiple heating elements 73 are divided into blocks B totaling M3. The first block B(1), the third block B(3)...the M1-2th block B(M3-2) are low-current blocks B. L The second block B(2), the fourth block B(4)...the M3-1th block B(M3-1) is a high-current block B. H Low current block B L and high current block B H They are alternately energized. Block B (M3) contains heating elements 73 of a quantity s3 calculated using the following formula. Wherein, high-current block B... H The quantity is denoted as CH3, and the low current block B is...L The quantity is denoted as CL3.

[0074] s3=x-((p×CH3)+(q×CL3))

[0075] Hereinafter, M1, M2, and M3 will be collectively referred to as "M". It should be noted that M is a natural number greater than 3.

[0076] That is, in the second example (see example 2) Figure 6 ) and the third case (refer to Figure 7 In that case, the first block B(1) is the high-current block B. H In the case that at least one of the blocks B, excluding the first block B(1) and the Mth block B(M), becomes a low-current block B. L On the other hand, in cases like the fourth example (see...) Figure 8 In that case, the first block B(1) is the low-current block B. L In the case that at least one of the blocks B, excluding the first block B(1) and the Mth block B(M), becomes a high-current block B. H Because block B contains at least one high-current block B. H and at least one low current block B L Therefore, the effective number of points (the number of heating elements 73 that generate heat for printing one line) in the case of these segmented printings becomes a natural number larger than the natural number obtained by adding the number q to the number p.

[0077] In such Figures 6-8 When multiple heating elements 73 are divided as shown and segmented printing is performed, the total head current I when each block B is energized is... A The value must be at least below the first current value I1. Additionally, the energizing time T for energizing the heating element 73 of each block B... P It is shorter than the first time T1. Therefore, printer 1 can supply a total head current I to the thermal head 7. A Split printing is performed under condition (a) that the value is always within the allowable range of printer 1. Additionally, Figures 6-8 The total number M of blocks B in the second to fourth examples shown is greater than... Figure 5 In the first example shown, the total number of blocks B, M′, is small (M′>M). Therefore, by dividing and printing based on blocks B as shown in the second to fourth examples, printer 1 can shorten the time required to complete printing an image up to one line.

[0078] The following examples, from the second to the fourth, illustrate the segmented printing process where multiple heating elements 73 are divided into high-current blocks B. H and low current block B L The segmented printing is called "second segmented printing".

[0079] <Main Processor>

[0080] Reference Figures 9-12 The main processing will now be explained. When a start instruction for starting the printing operation by specifying a printable image is input via the communication unit 95 and the input unit 96, the CPU 91 reads and executes the program stored in the flash memory 93 to start the main processing.

[0081] like Figure 9 As shown, firstly, the CPU 91 reads and obtains printing data (S1) from the flash memory 93 for printing the print image specified by the start instruction input via the communication unit 95 and the input unit 96. The printing data contains information indicating the pixel columns of each of the multiple rows contained in the print image. Hereinafter, it is assumed that the print image contains a total of K rows. Each of the K rows is referred to as "first row", "second row"... "Kth row" in the order they are printed.

[0082] Next, CPU91 reads from EEPROM94 and performs the first segmentation printing (see reference). Figure 5 ) and the second segmentation printing (refer to) Figures 6-8 Which of the following settings is being configured (S3)? If the CPU91 determines, based on the acquired setting information, that the first segmentation printing should be performed (S5: Yes), it executes the first segmentation printing process (see reference). Figure 10 (S7). Details of the first segmentation printing process will be described later. On the other hand, if the CPU91 determines, based on the acquired setting information, that a second segmentation printing should be performed (S5: No), it executes the second segmentation printing process (see [reference]). Figure 11 or Figure 12 (S9). Details of the second segmentation printing process will be described later. After the first or second segmentation printing process is completed, CPU91 terminates the main processing.

[0083] <First Segment Printing Process>

[0084] Reference Figure 10 The first segmentation printing process will be explained. This first segmentation printing process corresponds to the first example of segmentation printing (see reference...). Figure 5 CPU91 initializes the variable k stored in RAM92 by setting it to 1 (S11). CPU91 initializes the variable k by setting it to 1 through S1 (refer to S11). Figure 9 The total number of rows K contained in the printed image is determined by processing the printed data.

[0085] CPU91 calculates the number (valid points) of the multiple heating elements 73 that are energized when printing the k-th line based on the print data (S15). CPU91 determines whether split printing is required when printing the k-th line based on the calculated valid points (S17). If the calculated valid points are greater than the quantity q, CPU91 determines that split printing is required (S17: Yes).

[0086] CPU 91 initializes the variable m stored in RAM 92 by setting it to 1 (S19). CPU 91 extracts q heating elements 73 from the plurality of heating elements 73 energized for printing the k-th row and allocates them as heating elements 73 included in the m-th block B(m) (S21). CPU 91 heats up the plurality of heating elements 73 allocated to the m-th block B(m) by energizing them (S23), and executes the printing of the portion of the image in the k-th row corresponding to the m-th block B(m). CPU 91 then proceeds to S25.

[0087] CPU 91 determines whether all of the multiple heating elements 73 energized for printing the k-th row have been allocated to block B through the processing in S21 (S25). In other words, in S25, CPU 91 determines whether all of the multiple heating elements 73 energized for printing the k-th row have been energized. If there are any heating elements 73 that have not been allocated to block B (S25: No), CPU 91 updates the variable m by incrementing it by 1 (S27). CPU 91 returns the processing to S21. CPU 91 extracts q heating elements 73 from the multiple heating elements 73 energized for printing the k-th row that have not been allocated to block B. CPU 91 allocates the extracted q heating elements 73 as heating elements 73 included in the m-th block B(m) based on the updated variable m (S21). CPU 91 heats up the multiple heating elements 73 allocated to the m-th block B(m) by energizing them (S23), and executes the printing of the portion of the k-th row corresponding to the m-th block B(m).

[0088] Based on the above, for the multiple heating elements 73 energized for printing the k-th row, each q element is equally divided and allocated to block B. Furthermore, by heating the heating elements 73 at different timings for each block B, the k-th row is printed onto the medium D (see reference). Figure 5 ).

[0089] If the CPU91 determines that all the multiple heating elements 73 energized for printing the k-th row have been allocated to a certain block (S25: Yes), it checks whether the total number K of rows in the printed image is consistent with the variable k (S29). If the CPU91 finds that the variable k is less than the total number K (S29: No), it increments the variable k by 1 to update it (S31), and returns the process to S15. The CPU91 repeats the processing of S15 to S27 based on the updated variable k.

[0090] If CPU91 determines that the total number of rows K in the printed image matches the variable k (S29: Yes), it ends the first segmentation printing process and returns the process to the main process (see [reference]). Figure 9 ).

[0091] On the other hand, in the process of S17, if the calculated number of valid points is less than or equal to q, the CPU91 determines that split printing is unnecessary (S17: No). In this case, the CPU91 heats up all the multiple heating elements 73 that are energized for printing the k-th row (S23) and executes the printing of the k-th row. Since the CPU91 heats up all the multiple heating elements 73 included in the k-th row (S25: Yes), the process proceeds to S29. The processes of S29 and S31 are the same as when split printing is determined to be necessary, so their explanation is omitted.

[0092] <Second Segmentation Printing Process>

[0093] Reference Figure 11 and Figure 12 The second segmentation printing process will be explained. Figure 11 The second segmentation printing process shown corresponds to the second example of segmentation printing (see reference). Figure 6 ). Figure 12 The second segmentation printing process shown corresponds to the third example of segmentation printing (see reference). Figure 7 CPU 91 reads and obtains setting information from EEPROM 94 indicating which second segmentation printing process to perform. Based on the read setting information, CPU 91 selectively executes... Figure 11 or Figure 12 Any second segmentation printing process. Hereinafter, for processes identical to the first segmentation printing process, the same reference numerals will be used, and descriptions will be omitted.

[0094] <Second Segmentation Printing Process (Second Example)>

[0095] like Figure 11As shown, CPU91 determines whether split printing is needed when printing the k-th line based on the number of multiple heating elements 73 energized during printing (the number of valid points) (S17). If the calculated number of valid points is greater than the number p, CPU91 determines that split printing is needed (S17: Yes).

[0096] CPU91 initializes the variable m stored in RAM92 by setting it to 1 (S19). CPU91 calculates the remainder when the variable m is divided by 2 (S51). CPU91 determines whether the calculated remainder is 1 (S53).

[0097] If the CPU91 determines that the remainder is 1 (S53: Yes), it extracts p heating elements 73 from the multiple heating elements 73 that are powered on for printing the k-th row. The CPU91 allocates the extracted heating elements 73 as heating elements 73 included in the m-th block B(m) (S55). Since the m-th block B(m) contains p heating elements 73, the m-th block B(m) corresponds to the high-current block B. H .

[0098] If the CPU91 determines that the remainder is not 1 (S53: No), it extracts q heating elements 73 from the multiple heating elements 73 that are powered on for printing the k-th row. The CPU91 allocates the extracted heating elements 73 as heating elements 73 included in the m-th block B(m) (S57). Since the m-th block B(m) contains q heating elements 73, the m-th block B(m) corresponds to the low-current block B. L .

[0099] CPU91 heats up the multiple heating elements 73 assigned to the m-th block B(m) by energizing them (S23), and executes the printing of the portion of the image in the k-th row corresponding to the m-th block B(m). CPU91 then proceeds to S25.

[0100] By updating variable m while performing the above processing, the multiple heating elements 73 energized for printing the k-th line are divided into high-current blocks B. H (Block 1 (1), Block 3 (3), Block 5 (5)...) and low current block B L (Second block B(2), fourth block B(4), sixth block B(6)...). Additionally, through high-current block B... H Includes heating element 73 and low current block B L The included heating element 73 heats up alternately, and the k-th row is formed into the medium D (refer to...). Figure 6 ).

[0101] If CPU91 determines that the total number of rows K in the printed image matches the variable k (S29: Yes), it ends the second segmentation printing process and returns the process to the main process (see [reference]). Figure 9 ).

[0102] <Second Segmentation Printing Process (Fourth Example)>

[0103] By changing Figure 11 Part of the processing (S55, S57) can perform the fourth example of segmented printing (see reference). Figure 8 The second segmentation printing process corresponds to the following. Details are as follows. When the CPU91 determines that the remainder is 1 (S53: Yes), it extracts q heating elements 73 from the multiple heating elements 73 that are energized for printing the k-th row. The CPU91 allocates the extracted heating elements 73 as heating elements 73 included in the m-th block B(m) (S55). Since the m-th block B(m) contains q heating elements 73, the m-th block B(m) corresponds to the low-current block B. L On the other hand, if the CPU 91 determines that the remainder is not 1 (S53: No), it extracts p heating elements 73 from the multiple heating elements 73 that are powered on for printing the k-th row. The CPU 91 allocates the extracted heating elements 73 as heating elements 73 included in the m-th block B(m) (S57). Since the m-th block B(m) contains p heating elements 73, the m-th block B(m) corresponds to the high-current block B. H .

[0104] By updating variable m while performing the above processing, the multiple heating elements 73 energized for printing line k are divided into low-current blocks B. L (Block 1 (1), Block 3 (3), Block 5 (5)...) and high-current block B H (Second block B(2), fourth block B(4), sixth block B(6)...). Additionally, through low-current block B... L Includes heating element 73 and high current block B H The included heating element 73 heats up alternately, and the k-th row is formed into the medium D (refer to...). Figure 8 ).

[0105] <Second Segmentation Printing Process (Third Example)>

[0106] exist Figure 12 In the second segmentation printing process shown, with Figure 11 The second segmentation printing process is different. CPU91 calculates the remainder when the variable m is divided by 3 (S61). CPU91 determines whether the calculated remainder is 1 or 2 (S63).

[0107] If the CPU91 determines that the remainder is 1 or 2 (S63: Yes), it extracts p heating elements 73 from the multiple heating elements 73 that are powered on for printing the k-th row. The CPU91 allocates the extracted heating elements 73 as heating elements 73 included in the m-th block B(m) (S65). Since the m-th block B(m) contains p heating elements 73, the m-th block B(m) corresponds to the high-current block B. H .

[0108] If the CPU91 determines that the remainder is neither 1 nor 2 (S63: No), it extracts q heating elements 73 from the plurality of heating elements 73 energized for printing the k-th row. The CPU91 allocates the extracted heating elements 73 as heating elements 73 included in the m-th block B(m) (S67). Since the m-th block B(m) contains q heating elements 73, the m-th block B(m) corresponds to the low-current block B. L .

[0109] CPU91 heats up the multiple heating elements 73 assigned to the m-th block B(m) by energizing them (S23), and executes the printing of the portion of the image in the k-th row corresponding to the m-th block B(m). CPU91 then proceeds to S25.

[0110] By updating variable m while performing the above processing, the multiple heating elements 73 energized for printing the k-th line are divided into high-current blocks B. H (Block 1 (1), Block 2 (2), Block 4 (4), Block 5 (5)...) and low current block B L (Third block B(3), sixth block B(6)...). Additionally, through high-current block B... H Includes heating element 73 and low current block B L The included heating element 73 generates heat, and the k-th row is formed into the medium D (refer to...). Figure 7 ).

[0111] <Function and Effects of This Implementation Method>

[0112] Printer 1 divides the multiple heating elements 73 contained in the thermal head 7 into blocks B totaling M, and heats the heating elements 73 at different timings for each block B, thereby printing a single line of image. Here, the blocks B containing a different number of heating elements 73 are high-current blocks B in the total M blocks. H and low current block B L (Refer to Figures 6-8 High current block B H The number of heating elements 73 contained is p, which is higher than that of low current block B. Lthe number q of heating elements 73 comprised therein is larger (p>q). Therefore, compared with the case where printing is performed in a state where a plurality of heating elements 73 are divided such that all blocks B are low-current blocks B L (see Figure 5 ), the time required for printing can be shortened. Therefore, when the printer 1 performs divided printing in which a plurality of heating elements 73 are divided into blocks B for printing, the time required for printing one line of an image can be shortened.

[0113] high-current block B H the number p of the plurality of heating elements 73 comprised therein is equal to the number N1 in the above embodiment. Here, when power is supplied to N1 heating elements 73, the total head current I A has a value of a first current value I1. The first current value I1 is the maximum current value allowed in the printer 1 (see (a)). Therefore, the printer 1 can maximize the number of heating elements 73 in the high-current block B H within the allowable range of the printer 1. In this case, the printer 1 can minimize the number of divisions within the allowable range of the printer 1 when the plurality of heating elements 73 are divided into a total number M of blocks B. Therefore, the printer 1 can maximize the shortening of the time required for printing one line.

[0114] low-current block B L the number q of the plurality of heating elements 73 comprised therein is equal to the number N2 in the above embodiment. Here, when power is supplied to N2 heating elements 73, the total head current I A has a value of a second current value I2. The second current value I2 is the maximum current value allowed in OCP (see (b)). Therefore, when current is supplied to the heating elements 73 of the low-current block B L , the printer 1 can reduce the possibility of OCP damage.

[0115] the first time T1 during which power can be supplied to the heating elements 73 of the high-current block B H is shorter than the second time T2, which is the maximum time that power can be continuously supplied at the second current value I 2进行 in OCP (T1<T2). Therefore, even when current is supplied to the heating elements 73 of the high-current block B H , the printer 1 can reduce the possibility of OCP damage.

[0116] it should be noted that the energization time T for the plurality of heating elements 73 required for printing on the medium D P is shorter than the first time T1 and the second time T2 (T1>T P , T2>T P ). Therefore, when the printer 1 supplies current to the high-current block BH When the heating elements 73 contained therein are energized, the possibility of damage to various devices of the printer 1 can be reduced. In addition, when the printer 1 energizes the low-current block B L when the heating elements 73 therein are energized, the possibility of OCP damage can be reduced.

[0117] The printer 1 can perform printing while switching between the first divided printing process (refer to Figure 10 ) and the second divided printing process (refer to Figure 11 , Figure 12 ), wherein the first divided printing process is a process of dividing into a total number M' of blocks B each having the same number of heating elements 73 to perform printing, and the second divided printing process is a process of dividing into a total number M of blocks B including high-current blocks B H and low-current blocks B L to perform printing.

[0118] <Modified Example>

[0119] The present invention is not limited to the above-described embodiments, and various modifications can be made. The number p of the plurality of heating elements 73 contained in the high-current block B H is not limited to being the same as the number N1, and can be changed within a range satisfying the condition N2 < p ≤ N1. The number q of the plurality of heating elements 73 contained in the low-current block B L is not limited to being the same as the number N2, and can be changed within a range satisfying the condition q ≤ N2. In the case of printing an image of one line, the respective number and printing order of the high-current blocks B H and the low-current blocks B L are not limited to the above-described embodiments, and can be appropriately changed. For example, the plurality of heating elements 73 energized for printing the k-th line can also be divided into high-current blocks B H (first block B(1), fourth block B(4), ...) and low-current blocks B L (second block B(2), third block B(3), fifth block B(5), sixth block B(6), ...).

[0120] The number N1 is not limited to the number of heating elements 73 that are energized when the value of the total head current I A becomes the first current value I1. For example, the number N1 can also be the number of heating elements 73 that are energized when the value of the total head current I A becomes the rated current set for the printer 1.

[0121] The number N2 is not limited to the number of heating elements 73 that are energized when the value of the total head current I A becomes the second current value I2. For example, the number N2 can also be the number of heating elements 73 when the total head current IA The value becomes the number of heating elements 73 energized when the rated current is set for the battery unit 10.

[0122] <Other>

[0123] Printer 1 is an example of the "image forming apparatus" of the present invention. Medium D is an example of the "printing object" of the present invention. CPU 91 is an example of the "control unit" of the present invention. The processing of S9 is an example of the "first line printing processing" of the present invention. The processing of S55, S57, S65, and S67 is an example of the "segmentation processing in the first line printing processing" of the present invention. The effective number of dots is an example of the "selected R heating elements" of the present invention. The processing of S23 in the second segmented printing processing is an example of the "heating processing in the first line printing processing" of the present invention. The processing of S7 is an example of the "second line printing processing" of the present invention. The processing of S21 is an example of the "segmentation processing in the second line printing processing" of the present invention. The processing of S23 in the first segmented printing processing is an example of the "heating processing in the second line printing processing" of the present invention. The total number of blocks M′ in the first segmented printing processing is an example of "S blocks" of the present invention. The processing of S5 is an example of the "determination processing" of the present invention. The processing of S7 and S9 is an example of the "execution processing" of the present invention.

[0124] Explanation of reference numerals in the attached figures

[0125] 1: Printer, 7: Thermal head, 10: Battery unit, 73: Heating element, 91: CPU.

Claims

1. An image forming apparatus for printing based on print data, characterized in that, Comprising: a thermal head including a plurality of heating elements arranged in a main scanning direction, each of which generates heat when energized, the thermal head forming an image on a printing target by causing the plurality of heating elements to generate heat while relatively moving relative to the printing target in a sub-scanning direction; and a control unit configured to perform a first-line printing process, the first-line printing process performing printing of one line extending in the main scanning direction, the first-line printing process comprising: a dividing process of dividing selected R heating elements into M blocks consisting of a first block to an M-th block, wherein the number R is a natural number larger than a natural number obtained by adding the number q to the number p, and M is a natural number of 3 or more; and a heating process of performing the printing of the one line by causing the M blocks to generate heat at different timings in an order from the first block to the M-th block, wherein when the maximum number of heating elements among the plurality of heating elements that can be energized simultaneously is denoted as N1, and a predetermined natural number smaller than N1 is denoted as N2, the M blocks include at least one high-current block in which the number of energized heating elements is p and at least one low-current block in which the number of energized heating elements is q, p is any natural number satisfying N2 < p ≤ N1, and q is any natural number satisfying q ≤ N2, when the first block is the high-current block, at least one of the blocks among the M blocks other than the M-th block is the low-current block, when the first block is the low-current block, at least one of the blocks among the M blocks other than the M-th block is the high-current block.

2. The image forming apparatus according to claim 1, wherein a current value obtained when N1 heating elements are energized simultaneously is a value based on a first current value, and the first current value is a maximum current value allowed in the image forming apparatus.

3. The image forming apparatus according to claim 1 or 2, wherein a current value obtained when N2 heating elements are energized simultaneously is a value based on a second current value, and the second current value is a maximum current value allowed in an overcurrent protection circuit of a power supply of the image forming apparatus.

4. The image forming apparatus according to claim 3, wherein a first time period during which the heating elements of the high-current block can be energized simultaneously is shorter than a second time period, and the second time period is a maximum time period during which energization at the second current value can be continuously performed in the overcurrent protection circuit.

5. The image forming apparatus according to claim 1 or 2, wherein the control unit is further configured to perform a second-line printing process, the second-line printing process performing printing of one line extending in the main scanning direction, the second-line printing process comprising: a dividing process of dividing the selected R heating elements into S blocks consisting of a first block to an S-th block, wherein the number R is a natural number larger than a natural number obtained by multiplying the number q by the number (S-1), and S is a natural number of 3 or more; and a heating process of performing the printing of the one line by causing the S blocks to generate heat at different timings, The number of energized heating elements contained in each of the first to (S-1)th blocks of the S blocks is q. The control unit is configured to execute: The decision process determines whether to execute the first line printing process or the second line printing process in order to print the first line that is the target of printing; and The process is executed, and the first line printing process and the second line printing process are executed according to a certain process that is determined to be executed in the determination process, and the line that is the printing object is printed.

6. The image forming apparatus according to claim 3, characterized in that, The control unit is further configured to perform a second line printing process, which prints one line extending in the main scanning direction. The second line printing process includes: The segmentation process divides the selected R heating elements into S blocks, consisting of the first to the Sth blocks. The number R is a natural number larger than the natural number obtained by multiplying the number q by the number (S-1), and S is a natural number greater than 3. The printing of the 1st line is achieved by heating the S blocks at different time intervals. The number of energized heating elements contained in each of the first to (S-1)th blocks of the S blocks is q. The control unit is configured to execute: The decision process determines whether to execute the first line printing process or the second line printing process in order to print the first line that is the target of printing; and The process is executed, and the first line printing process and the second line printing process are executed according to a certain process that is determined to be executed in the determination process, and the line that is the printing object is printed.

7. The image forming apparatus according to claim 4, characterized in that, The control unit is further configured to perform a second line printing process, which prints one line extending in the main scanning direction. The second line printing process includes: The segmentation process divides the selected R heating elements into S blocks, consisting of the first to the Sth blocks. The number R is a natural number larger than the natural number obtained by multiplying the number q by the number (S-1), and S is a natural number greater than 3. The printing of the 1st line is achieved by heating the S blocks at different time intervals. The number of energized heating elements contained in each of the first to (S-1)th blocks of the S blocks is q. The control unit is configured to execute: The decision process determines whether to execute the first line printing process or the second line printing process in order to print the first line that is the target of printing; and The process is executed, and the first line printing process and the second line printing process are executed according to a certain process that is determined to be executed in the determination process, and the line that is the printing object is printed.

Images