Image forming device

Abstract

To provide an image formation apparatus which can shorten the time required for printing for one line in the time of division-printing.SOLUTION: A printer divides a plurality of heater elements into M1 blocks and makes the heater elements generate heat at different timing for each block. When the number of heater elements that can be electrically conducted simultaneously in the plurality of heater elements is N1, and a prescribed number smaller than N1 is N2, the M1 blocks include one high-current block in which the number of heater elements is p (p is N2<p≤N1) and a low-current block in which the number of heater elements is q (q is q≤N2). When the first block is the high-current block, at least one block excluding the first block and the M1-th block is the low-current block.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] Image forming devices are known that use a thermal line head equipped with multiple heating elements to print on a print medium. In the thermal line head, heating elements for one line of the image to be formed are arranged in the main scanning direction. The image forming device drives the thermal line head by passing an electric current through the heating elements to generate heat.

[0003] There is a demand for reducing the current consumed by the thermal line head when forming an image for one line. The following three methods are known to reduce the current: Method 1, Method 2, and Method 3.

[0004] In a first method, the multiple heating elements of a thermal line head are divided into multiple blocks. The image forming apparatus heats the heating elements for each block in a time-division manner. Hereinafter, printing performed by the first method will be referred to as "divided printing." In a second method, the average amount of power required to print one line at the current time is determined based on the amount of power consumed when the previous line was printed, within a range that does not exceed a predetermined upper limit of power (see Patent Document 1). Hereinafter, printing performed by the second method will be referred to as "feedback printing." In a third method, the current required to print a line after the current time is determined in advance according to the constraints of the power supply's overcurrent protection circuit (OCP). Hereinafter, printing performed by the third method will be referred to as "feedforward printing." [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-199072 Summary of the Invention [Problem to be solved by the invention]

[0006] In the case of divided printing, one line is printed in multiple instalments, so the time required to print one line is longer than when one line is printed all at once. Furthermore, when divided printing and feedback printing are used together, the longer time required to print one line based on divided printing delays the timing at which the average power consumption is determined by feedback printing. In this case, there is a possibility that the OCP constraints will be exceeded when printing one line during divided printing. For this reason, it is considered to use divided printing and feedforward printing together.

[0007] However, if split printing and feedforward printing are simply used together, and the current is determined according to the OCP constraints, the power supply performance cannot be utilized to its full potential, and the time required to print one line may not be reduced.

[0008] An object of the present invention is to provide an image forming apparatus that can reduce the time required to print one line when performing divided printing. [Means for solving the problem]

[0009] The image forming apparatus according to the present invention is an image forming apparatus that performs printing based on print data, and includes a plurality of heating elements arranged in the main scanning direction and each generating heat by being energized, and forms an image on a printing target by generating heat in the plurality of heating elements while relatively moving in the sub-scanning direction with respect to the printing target. A thermal head, and the plurality of heating elements are divided into M blocks (M is an integer of 3 or more), and the heating elements are caused to generate heat in the order of the first block, the second block,... the M block at different timings for each block, thereby performing printing of one line extending in the main scanning direction. A first control means, among the plurality of heating elements, when the number of heating elements that can be energized simultaneously is denoted as N1 and a predetermined number smaller than N1 is denoted as N2, at least one high-current block in which the number of energized heating elements is p (p is any number satisfying N2 < p ≦ N1) and at least one low-current block in which the number of energized heating elements is q (q is any number satisfying q ≦ N2) are included in the M blocks, and when the first block is the high-current block, at least one of the blocks excluding the first block and the M block among the M blocks becomes the low-current block, and when the first block is the low-current block, at least one of the blocks excluding the first block and the M block among the M blocks becomes the high-current block, which is characterized in that.

[0010] The image forming apparatus divides a plurality of heating elements included in the thermal head into M blocks, and performs printing for one line by causing the heating elements to generate heat at different timings for each block. Here, the M blocks include low-current blocks and high-current blocks 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, the time required for printing can be shortened compared to the case where printing is performed in a state where the plurality of heating elements are divided so that all blocks become low-current blocks. Therefore, the image forming apparatus can shorten the time required for printing one line when performing printing by dividing a plurality of heating elements into blocks.

[0011] In the present invention, the current value when N1 heating elements are energized may be a value based on a first current value, which is the maximum current value allowed by the image forming device. The image forming device can maximize the number of heating elements in a high current block within the allowable range of the image forming device. In this case, the image forming device can minimize the number of divisions when multiple heating elements are divided into M blocks within the allowable range of the image forming device. As a result, the image forming device can minimize the time required to print one line.

[0012] In the present invention, the current value when current is passed through the N2 heating elements may be a value based on a second current value, which is the maximum current value allowed by an overcurrent protection circuit of the power supply of the image forming apparatus. The image forming apparatus can reduce the possibility of the overcurrent protection circuit being damaged when current is passed through heating elements in a low current block.

[0013] In the present invention, a first time period during which current can be applied to the heating elements in the high current block may be shorter than a second time period, which is the maximum time period during which the second current value can be continuously applied by the overcurrent protection circuit. The image forming apparatus can reduce the possibility of damage to the image forming apparatus when current is applied to the heating elements included in the high current block. Also, the image forming apparatus can reduce the possibility of damage to the overcurrent protection circuit when current is applied to the heating elements in the low current block.

[0014] In the present invention, the image forming apparatus may further include a second control means that divides the plurality of heating elements equally into S blocks (S is an integer of 3 or more) and prints one line extending in the main scanning direction by causing the heating elements to heat at different times for each block, and a switching means that switches between printing by the first control means and printing by the second control means. The image forming apparatus can perform printing by switching between a printing method in which printing is performed by dividing the image into M blocks including high current blocks and low current blocks, and a printing method in which printing is performed by dividing the image into S blocks, each with an equal number of energized heating elements. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a perspective view of a printer 1. [Figure 2] FIG. 2 is an exploded perspective view of the printer 1. [Figure 3] 2 is a cross-sectional view taken along line AA in FIG. 1, viewed from the direction of the arrow. [Figure 4] 2 is a block diagram showing the electrical configuration of the printer 1. FIG. [Figure 5] 10 is a graph for explaining a first example of divided printing. [Figure 6] 10 is a graph for explaining a second example of divided printing. [Figure 7] 10 is a graph for explaining a third example of divided printing. [Figure 8] 10 is a graph for explaining a fourth example of divided printing. [Figure 9] 10 is a flowchart of a main process. [Figure 10] 10 is a flowchart of a first divided printing process. [Figure 11] 10 is a flowchart of a second divided printing process (second example). [Figure 12] 10 is a flowchart of a second divided printing process (third example). DETAILED DESCRIPTION OF THE INVENTION

[0016] <Printer 1 Overview> A printer 1 according to an embodiment of the present invention will be described with reference to the drawings. Hereinafter, the lower left, upper right, upper left, lower right, upper, and lower in Fig. 1 will be referred to as the front, rear, left, right, upper, and lower of the printer 1, respectively.

[0017] 1 can print an image on a medium D based on print data. The medium D is not limited to a specific medium, but may be, for example, a sheet or roll, and in this embodiment is heat-sensitive cut paper.

[0018] The printer 1 has a case 2. The case 2 is rectangular and is longer left-to-right than it is front-to-back and up-to-down. A battery 10 shown in Figure 2 is attached to the lower rear of the case 2. The battery 10 supplies power to the printer 1. An input unit 96 is provided near the left end of the top surface of the case 2. The input unit 96 includes a number of push buttons. A USB jack 95A is provided on the right side of the case. A USB cable connector can be connected to the USB jack 95A.

[0019] As shown in FIG. 2, the case 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-rear and left-right directions. The lower cover 21 forms the lower part of the case 2. The upper cover 22 opens downward and is attached to the upper side of the lower cover 21. An opening 221 is formed in the upper cover 22. The opening 221 extends from the center in the up-down direction to the upper end on the front surface of the upper cover 22. The opening 221 extends from the front end to the center in the front-rear direction on the upper surface of the upper cover 22. The opening 221 extends from near the left end to near the right end of the upper cover 22. Hereinafter, the end of the upper cover 22 that defines the rear end of the opening 221 will be referred to as the "opening end 223," and the end of the upper cover 22 that defines the lower end of the opening 221 will be referred to as the "opening end 224."

[0020] 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-rear and left-right directions. The second portion 232 extends downward from the front end of the first portion 231 and also extends in the left-right direction. The opening / closing cover 23 fits into the opening 221. A rear end 233 of the first portion 231 is rotatably supported by the upper cover 22. Therefore, the opening / closing cover 23 can open and close the opening 221 by swinging around the rear end 233 of the first portion 231 as an axis.

[0021] The following description will be based on the state in which the opening / closing cover 23 closes the opening 221, as shown in Fig. 1. In this case, the rear end 233 of the first part 231 faces the opening edge 223 of the upper cover 22 in the front-to-rear direction with a gap therebetween. Furthermore, the lower end 234 of the second part 232 faces the opening edge 224 of the upper cover 22 in the up-down direction with a gap therebetween.

[0022] An insertion slot 24 is formed in the top surface of the case 2. The insertion slot 24 is an opening defined by an opening edge 223 of the upper cover 22 and a rear edge 233 of the opening / closing cover 23. The medium D is supplied into the case 2 through the insertion slot 24.

[0023] An outlet 25 is formed in the front surface of the case 2. The outlet 25 is an opening defined by an opening edge 224 of the upper cover 22 and a lower edge 234 of the opening / closing cover 23. After printing on the medium D inside the case 2, it is discharged from the case 2 through the outlet 25.

[0024] As shown in Figures 2 and 3, the printer 1 is equipped with a head unit 4. The head unit 4 is housed in the case 2 and includes a support plate 5, a platen 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 plan view and is longer in the left-right direction than in the front-to-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 also extends in the front-to-back direction. The right plate 53 extends upward from the right end of the lower plate 51 and also extends in the front-to-back direction. The left plate 52 and right plate 53 face each other in the left-to-right direction.

[0025] The platen roller 6 is provided diagonally above and at the front inside the case 2 (see FIG. 3), and extends in the left-right direction. The platen roller 6 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. A left end 621 of the shaft 62 is supported by the left plate 52. A right end 622 of the shaft 62 is supported by the right plate 53. The platen roller 6 can rotate around the shaft 62.

[0026] The platen roller 6 is connected to a motor 69 via a gear 691 and the like. The motor 69 is fixed to the rear lower part on the right surface of the left plate 52. The gear 691 is supported by the left plate 52 on the left side of the left plate 52. When the motor 69 is driven, it rotates the platen roller 6 via the gear 691.

[0027] As shown in FIG. 3, the center of rotation C of the platen roller 6 passes through the center of the shaft 62 and extends in the left-right direction. The platen roller 6 rotates around the center of rotation C to transport the medium D in the transport direction. The transport direction is the direction in which the medium D is transported by the platen roller 6, and is perpendicular to the left-right direction. In this embodiment, the transport direction extends diagonally upward and rearward and diagonally downward and frontward. Hereinafter, the diagonally upward and rearward side of the transport direction will be referred to as the upstream side, and the diagonally downward and frontward side will be referred to as the downstream side. The direction perpendicular to the left-right direction and the transport direction will be referred to as the opposing direction. The path along which the medium D transported in the transport direction passes will be referred to as the "transport path R."

[0028] The thermal head 7 is provided below the platen roller 6. When the medium D is transported in the transport direction by the rotation of the platen roller 6, the thermal head 7 moves in the transport direction relative to the medium D. As shown in FIG. 2, the thermal head 7 is a line head, and includes a substrate 71, a glaze 72, a plurality of heating elements 73, and a driver IC 74 (see FIG. 3).

[0029] The substrate 71 extends in the left-right direction and the transport direction, perpendicular to the facing direction. The glaze 72 and the multiple heating elements 73 are provided on the surface of the substrate 71 facing diagonally upward toward the front (hereinafter referred to as the "front surface"). The glaze 72 protrudes upward from the front surface. The glaze 72 extends in the left-right direction from near the left edge of the substrate 71 to near the right edge. The glaze 72 serves as a base for fixing the multiple heating elements 73 to the substrate 71. The multiple heating elements 73 are fixed to the glaze 72 and aligned in the left-right direction. Each of the multiple heating elements 73 generates heat when energized. The multiple heating elements 73 come into contact with the medium D pressed against the front surface by the platen roller 6, and generate heat to print on the medium D. The driver IC 74 energizes the multiple heating elements 73 based on print data, selectively causing them to generate heat.

[0030] As shown in FIG. 3, the heat sink 8 contacts the surface of the substrate 71 opposite to the front surface (hereinafter referred to as the "rear surface") and supports the substrate 71. The heat sink 8 is plate-shaped and dissipates heat generated by the heat generation of the multiple heating elements 73. The compression coil spring 41 is provided inside the case 2. The upper end of the compression coil spring 41 contacts the lower surface of the heat sink 8 and urges the heat sink 8 upward. The urging force of the compression coil spring 41 presses the thermal head 7 against the platen roller 6.

[0031] 2 and 3, the regulating member 3 is provided upstream in the transport direction from the multiple heat generating elements 73 of the thermal head 7, and is located below the insertion opening 24 inside the case 2. The regulating member 3 is plate-shaped and extends in the left-right direction, and also extends diagonally downward and forward from the opening edge 223 of the upper cover 22. The regulating member 3 regulates the transport path R of the medium D.

[0032] <Electrical configuration> The electrical configuration of the printer 1 will be described with reference to Figure 4. The printer 1 includes a CPU 91, RAM 92, flash memory 93, EEPROM 94, a communication unit 95, an input unit 96, a motor 69, a platen roller 6, a driver IC 74, and a thermal head 7. The CPU 91 controls the printer 1. The CPU 91 is electrically connected to the RAM 92, flash memory 93, EEPROM 94, communication unit 95, input unit 96, motor 69, and driver IC 74.

[0033] The RAM 92 stores temporary data such as various variables. The flash memory 93 stores print data and programs executed by the CPU 91 to control the printer 1. The EEPROM 94 stores various setting information.

[0034] The communication unit 95 is a controller for communicating with external devices via a USB cable connected to a USB jack 95A (see FIG. 1). The motor 69 is capable of rotating the platen roller 6. The driver IC 74 is capable of applying voltage to the multiple heating elements 73 of the thermal head 7 to selectively energize and generate heat.

[0035] <Outline of printing operation> The printer 1 selectively energizes the plurality of heating elements 73 of the thermal head 7. Thermal energy is applied to the portions of the medium D that come into contact with the energized heating elements 73. The energization time for the heating elements 73 is set to a predetermined time ("energization time T P " (see Figures 5 to 8)), pixels are formed on the medium D in the areas that come into contact with the energized heating elements 73. In this way, the printer 1 forms multiple rows of pixels that line up in a line corresponding to the arrangement of the multiple heating elements 73. The row of pixels is called a "line."

[0036] The printer 1 uses the motor 69 to rotate the platen roller 6 to transport the medium D downstream in the transport direction, while intermittently energizing the multiple heating elements 73 multiple times. As a result, multiple lines are formed on the medium D, arranged in a direction perpendicular to the direction in which the pixels in one line of an image are aligned. The multiple lines create shades on the medium D depending on whether or not each pixel is formed, forming a printed image such as characters or an image.

[0037] The above operation is called the "printing operation." The direction in which pixels are arranged in one line of an image formed on the medium D by the printing operation is called the "main scanning direction." Furthermore, the direction in which multiple lines are arranged, which is perpendicular to the main scanning direction, is called the "sub-scanning direction."

[0038] <Overview of split printing> The more pixels included in one line of an image, the more the number of heating elements 73 energized to print this line. Therefore, the total amount of current flowing through the thermal head 7 (hereinafter referred to as the "total head current I A The value of the total head current I A The maximum value of is constrained by the following conditions (a) and (b). (a) The maximum current value allowed in the printer 1 (hereinafter referred to as the “first current value I1”) (b) Circuit for protecting the battery 10 from overcurrent (hereinafter referred to as "Over Current Protection (OCP) circuit"). The maximum current value allowed in this circuit (hereinafter referred to as "second current value I2").

[0039] The first current value I1 is the maximum current value allowed by various devices included in the printer 1. Specific examples of various devices include the battery 10, a power supply circuit for stepping down / stepping up the voltage of the battery 10 and supplying it to the thermal head 7, etc., the thermal head 7, resistors, capacitors, filters, etc. connected to the power line. The first current value I1 is greater than the second current value I2 ((I1 > I2).

[0040] In the printer 1, the maximum time for which the current of the first current value I1 can be continuously energized is referred to as "first time T1". In the overcurrent protection circuit, the maximum time for which the current of the second current value I2 can be continuously energized is referred to as "second time T2". The first time T1 is shorter than the second time T2 (T1 < T2). The energization time T is shorter than both the first time T1 and the second time T2 (T1 > T P and T2 > T P ). P )

[0041] In the following description, numbers N1, N2, p, and q are defined. When N1 of the plurality of heating elements 73 of the thermal head 7 are energized, the value of the total head current I A becomes the first current value I1. When N2 of the plurality of heating elements 73 of the thermal head 7 are energized, the value of the total head current I A becomes the second current value I2.

[0042] p is any number that satisfies the condition N2 < p ≤ N1. q is any number that satisfies the condition q ≤ N2. In this embodiment, it is assumed that the condition p = N1 is satisfied and the condition q = N2 is satisfied.

[0043] When the number of energized heating elements 73 (hereinafter referred to as the "number of on dots") is large, the printer 1 does not energize many heating elements 73 at once. More specifically, when the number of energized heating elements 73 to print one line of an image exceeds q, the printer 1 divides the heating elements 73 into multiple blocks. The printer 1 prints one line of an image by energizing the heating elements 73 in multiple blocks in a time-division manner. Printing performed in this manner is called "divided printing."

[0044] 5 to 8, the total head current I A and the number of energized heating elements 73. For ease of explanation, Figs. 5 to 8 assume that one line of an image is printed by energizing all of the plurality of heating elements 73 included in the thermal head 7. The blocks B into which the plurality of heating elements 73 are divided are referred to as "first block B(1)," "second block B(2)," etc., starting with the block that is energized first. In Figs. 5 to 8, the number of the plurality of heating elements 73 included in each of the plurality of blocks B differs.

[0045] 5, the plurality of heating elements 73 are divided so that the number of heating elements 73 included in each block B is q, and a total number of blocks B is formed. In this case, the total head current I A This value is the second current value I2 because current is passed through the number q of heating elements 73. Note that the M'-th block B(M') includes the number s0 (=x mod q) of heating elements 73, which corresponds to the remainder when the total number x of the heating elements 73 is divided by the number q.

[0046] When the heating elements 73 are divided and divided printing is performed as shown in FIG. 5, the total head current I A The value of the second current value I2 is always the second current value I2. ADivided printing can be performed under condition (b) where the value of is always within the OCP tolerance range. Hereinafter, the divided printing illustrated in the first example, in which the plurality of heating elements 73 are equally divided, will be referred to as "first divided printing."

[0047] In FIG. 5, the bar graph representing each block B is in contact with other adjacent blocks B on the left and right. However, in reality, there is an interval between when each block B is energized and when the next block B is energized. Therefore, the total head current I A The time when the value of the second current value I2 is the current conduction time T P The same applies to Figures 6 to 8.

[0048] 6 to 8, the plurality of heating elements 73 are divided into a block B consisting of p number of heating elements 73 and a block B consisting of q number of heating elements 73. The total head current I A The value of the first current value I1 is the total head current I A The value of this is the second current value I2. Hereinafter, the block B consisting of the number p of heating elements 73 will be referred to as the “high current block B H ", and a block B consisting of the number q of heating elements 73 is called a "low current block B L "

[0049] In the second example shown in FIG. 6, the plurality of heating elements 73 are divided into a total of M1 blocks B. The first block B(1), the third block B(3), the M1-2 block B(M1-2) are high current blocks B. H The second block B(2), the fourth block B(4), the M1-1 block B(M1-1) are low current blocks B L High current block B H and low current block B L The M1-th block B (M1) includes the number s1 of heating elements 73 calculated by the following formula. However, the high current block B H The number of blocks is denoted as CH1, and the low current block BL The number is denoted as CL1. s1=x-((p×CH1)+(q×CL1))

[0050] In the third example shown in FIG. 7, the plurality of heating elements 73 are divided into a total of M2 blocks B. The first block B(1), the second block B(2), the fourth block B(4), the fifth block B(5), ..., the M2-1st block B (M2-1) is a high current block B. H The third block B(3) and 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 The M2-th block B (M2) includes the number s2 of heating elements 73 calculated by the following formula. However, the high current block B H The number of blocks is denoted as CH2, and the low current block B L The number is denoted as CL2. s2=x-((p×CH2)+(q×CL2))

[0051] In the fourth example shown in FIG. 8, the plurality of heating elements 73 are divided into a total of M3 blocks B. The first block B(1), the third block B(3), the M1-2 block B(M3-2) are low current blocks B. L The second block B(2), the fourth block B(4), the M3-1 block B(M3-1) are high current blocks B H Low current block B L and high current block B H The M3-th block B (M3) includes the number s3 of heating elements 73 calculated by the following formula. However, the high current block B H The number of blocks is denoted as CH3, and the low current block B L The number is denoted as CL3. s3=x-((p×CH3)+(q×CL3)) Hereinafter, M1, M2, and M3 will be collectively referred to as "M."

[0052] That is, as in the second example (see FIG. 6) and the third example (see FIG. 7), the first block B(1) is the high current block B H In this case, at least one of the blocks B, excluding the first block B(1) and the Mth block B(M), is a low current block B L On the other hand, as in the fourth example (see FIG. 8), the first block B(1) is the low current block B L In this case, at least one of the blocks B, excluding the first block B(1) and the Mth block B(M), is a high current block B H This becomes:

[0053] When the heating elements 73 are divided into a plurality of blocks and divided printing is performed as shown in FIGS. 6 to 8, the total head current I A The value of is at least equal to or less than the first current value I1. P is shorter than the first time T1. Therefore, the printer 1 has a total head current I A Divided printing can be performed under condition (a) where the value of is always within the tolerance of the printer 1. Furthermore, the total number M of blocks B in the second to fourth examples shown in FIGS. 6 to 8 is smaller than the total number M' of blocks B in the first example shown in FIG. 5 (M' > M). Therefore, by performing divided printing based on blocks B divided using the methods shown in the second to fourth examples, the printer 1 can reduce the time required to complete printing one line of an image.

[0054] In the following, in the division printing exemplified in the second to fourth examples, a plurality of heating elements 73 are arranged in the high current block B H and low current block B L The split printing that divides the page into two parts is called "second split printing."

[0055] <Main processing> The main processing will be described with reference to Figures 9 to 12. The main processing starts when the CPU 91 reads and executes a program stored in the flash memory 93 when a start instruction for starting a printing operation by specifying a predetermined print image is input via the communication unit 95 or the input unit 96.

[0056] As shown in Figure 9, first, the CPU 91 reads and acquires from the flash memory 93 print data for printing a print image specified by a start instruction input via the communication unit 95 or the input unit 96 (S1). The print data includes information indicating the pixel rows of each of the multiple lines included in the print image. Hereinafter, it is assumed that a total of K lines are included in the print image. Each of the K lines will be referred to as the "first line," "second line," ... "Kth line" in the order in which they are printed.

[0057] Next, the CPU 91 reads and acquires from the EEPROM 94 setting information indicating whether first split printing (see FIG. 5) or second split printing (see FIGS. 6 to 8) will be performed (S3). If the CPU 91 determines based on the acquired setting information that first split printing will be performed (S5: YES), it executes a first split printing process (see FIG. 10) (S7). Details of the first split printing process will be described later. On the other hand, if the CPU 91 determines based on the acquired setting information that second split printing will be performed (S5: NO), it executes a second split printing process (see FIG. 11 or 12) (S9). Details of the second split printing process will be described later. After completing the first split printing process or the second split printing process, the CPU 91 terminates the main process.

[0058] <First divided printing process> The first divided printing process will be described with reference to Figure 10. The first divided printing process corresponds to the first example of divided printing (see Figure 5). The CPU 91 initializes the variable k stored in the RAM 92 by setting it to 1 (S11). The CPU 91 identifies the total number K of lines included in the print image based on the print data acquired by the process of S1 (see Figure 9).

[0059] The CPU 91 calculates the number of heating elements 73 (the number of ON dots) to be energized when printing the kth line based on the print data (S15). The CPU 91 determines whether divided printing is necessary when printing the kth line based on the calculated number of ON dots (S17). If the calculated number of ON dots is greater than the number q, the CPU 91 determines that divided printing is necessary (S17: YES).

[0060] The CPU 91 initializes the variable m stored in the RAM 92 by setting it to 1 (S19). The CPU 91 extracts q heating elements 73 from the plurality of heating elements 73 that are energized to print the kth line, and assigns them as heating elements 73 to be included in the mth block B(m) (S21). The CPU 91 energizes the plurality of heating elements 73 assigned to the mth block B(m) to cause them to generate heat (S23), and prints the portion of the kth line image that corresponds to the mth block B(m). The CPU 91 proceeds to S25.

[0061] The CPU 91 determines whether all of the heating elements 73 to be energized for printing the kth line have been assigned to block B by the processing of S21 (S25). If there are any heating elements 73 remaining that have not been assigned to block B (S25: NO), the CPU 91 updates the variable m by adding 1 (S27). The CPU 91 returns the processing to S21. The CPU 91 extracts q heating elements 73 from the heating elements 73 that have not been assigned to block B among the heating elements 73 to be energized for printing the kth line. The CPU 91 assigns the extracted q heating elements 73 as heating elements 73 to be included in the mth block B(m) based on the updated variable m (S21). The CPU 91 energizes the heating elements 73 assigned to the mth block B(m) to generate heat (S23), and prints the portion of the kth line that corresponds to the mth block B(m).

[0062] As a result, the plurality of heating elements 73 energized to print the k-th line are divided into equal parts of q elements each and assigned to the blocks B. Furthermore, the k-th line is printed on the medium D by the heating elements 73 emitting heat at different times for each block B (see FIG. 5).

[0063] When the CPU 91 determines that all of the plurality of heating elements 73 energized to print the kth line have been assigned to any of the blocks (S25: YES), it determines whether the total number K of lines included in the print image matches the variable k (S29). When the CPU 91 determines that the variable k is smaller than the total number K (S29: NO), it updates the variable k by adding 1 (S31) and returns the process to S15. The CPU 91 repeats the processes of S15 to S27 based on the updated variable k.

[0064] When the CPU 91 determines that the total number K of lines included in the print image matches the variable k (S29: YES), it ends the first divided print process and returns the process to the main process (see FIG. 9).

[0065] On the other hand, if the calculated number of ON dots is equal to or less than the number q in the process of S17, the CPU 91 determines that divided printing is not necessary (S17: NO). In this case, the CPU 91 energizes all of the multiple heating elements 73 that are energized to print the kth line, causing them to generate heat (S23), and prints the kth line. Since the CPU 91 has energized all of the multiple heating elements 73 included in the kth line to generate heat (S25: YES), the process proceeds to S29. The processes of S29 and S31 are the same as those when it is determined that divided printing is necessary, so their explanation will be omitted.

[0066] <Second divided printing process> The second divided printing process will be described with reference to Figures 11 and 12. The second divided printing process shown in Figure 11 corresponds to the second example of divided printing (see Figure 6). The second divided printing process shown in Figure 12 corresponds to the third example of divided printing (see Figure 7). The CPU 91 reads and acquires setting information indicating which second divided printing process to perform from the EEPROM 94. Based on the read setting information, the CPU 91 selectively executes either the second divided printing process of Figure 11 or Figure 12. Below, processes that are the same as those in the first divided printing process are assigned the same reference numerals and descriptions thereof will be omitted.

[0067] <Second divided printing process (second example)> 11, the CPU 91 determines whether divided printing is necessary when printing the kth line based on the number of heating elements 73 that are energized when printing the kth line (the number of ON dots) (S17). If the calculated number of ON dots is greater than the number p, the CPU 91 determines that divided printing is necessary (S17: YES).

[0068] The CPU 91 initializes a variable m stored in the RAM 92 by setting it to 1 (S19). The CPU 91 calculates the remainder when the variable m is divided by 2 (S51). The CPU 91 determines whether the calculated remainder is 1 (S53).

[0069] If the CPU 91 determines that the remainder is 1 (S53: YES), it extracts p heating elements 73 from the plurality of heating elements 73 that are energized to print the k-th line. The CPU 91 assigns the extracted heating elements 73 as heating elements 73 to be included in the m-th block B(m) (S55). Since the m-th block B(m) includes p heating elements 73, the m-th block B(m) is a high current block B. H Corresponds to.

[0070] If the CPU 91 determines that the remainder is not 1 (S53: NO), it extracts q heating elements 73 from the plurality of heating elements 73 that are energized to print the k-th line. The CPU 91 assigns the extracted heating elements 73 as heating elements 73 to be included in the m-th block B(m) (S57). Since the m-th block B(m) includes q heating elements 73, the m-th block B(m) is a low-current block B. L Corresponds to.

[0071] The CPU 91 energizes the heating elements 73 assigned to the m-th block B(m) to generate heat (S23), and prints the portion of the image on the k-th line that corresponds to the m-th block B(m). The CPU 91 then proceeds to S25.

[0072] By executing the above process while updating the variable m, the plurality of heating elements 73 to be energized for printing the k-th line are arranged in the high current block B H (1st block B(1), 3rd block B(3), 5th block B(5)...) and low current block B L (2nd block B(2), 4th block B(4), 6th block B(6)...) Also, high current block B H and the heating element 73 included in the low current block B L The k-th line is formed on the medium D by the heating elements 73 included in the k-th line forming element 73 alternately generating heat (see FIG. 6).

[0073] If the CPU 91 determines that the total number K of lines included in the print image matches the variable k (S29: YES), it ends the second divided print process and returns to the main process (see FIG. 9).

[0074] <Second divided printing process (fourth example)> By changing some of the processing in FIG. 11 (S55, S57), it is possible to execute the second divided printing processing corresponding to the fourth example of divided printing (see FIG. 8). The details are as follows: When the CPU 91 determines that the remainder is 1 (S53: YES), it extracts q heating elements 73 from the plurality of heating elements 73 that are energized to print the kth line. The CPU 91 assigns the extracted heating elements 73 as the heating elements 73 to be included in the mth block B(m) (S55). Since the mth block B(m) includes q heating elements 73, the mth block B(m) is a 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 plurality of heating elements 73 that are energized to print the k-th line. The CPU 91 assigns the extracted heating elements 73 as the heating elements 73 to be included in the m-th block B(m) (S57). Since the m-th block B(m) includes p heating elements 73, the m-th block B(m) is a high current block B. H Corresponds to.

[0075] By executing the above process while updating the variable m, the plurality of heating elements 73 to be energized for printing the k-th line are allocated to the low current block B L (1st block B(1), 3rd block B(3), 5th block B(5)...) and high current block B H (2nd block B(2), 4th block B(4), 6th block B(6)...) Also, low current block B L and the high current block B H The k-th line is formed on the medium D by the heating elements 73 included in the k-th line forming element 73 alternately generating heat (see FIG. 8).

[0076] <Second divided printing process (third example)> In the second divided printing process shown in Fig. 12, unlike the second divided printing process shown in Fig. 11, the CPU 91 calculates the remainder when variable m is divided by 3 (S61). The CPU 91 determines whether the calculated remainder is 1 or 2 (S63).

[0077] If the CPU 91 determines that the remainder is 1 or 2 (S63: YES), it extracts p heating elements 73 from the plurality of heating elements 73 that are energized to print the k-th line. The CPU 91 assigns the extracted heating elements 73 as heating elements 73 to be included in the m-th block B(m) (S65). Since the m-th block B(m) includes p heating elements 73, the m-th block B(m) is a high current block B. H Corresponds to.

[0078] If the CPU 91 determines that the remainder is neither 1 nor 2 (S63: NO), it extracts q heating elements 73 from the plurality of heating elements 73 that are energized to print the k-th line. The CPU 91 assigns the extracted heating elements 73 as heating elements 73 to be included in the m-th block B(m) (S67). Since the m-th block B(m) includes q heating elements 73, the m-th block B(m) is a low-current block B. L Corresponds to.

[0079] The CPU 91 energizes the heating elements 73 assigned to the m-th block B(m) to generate heat (S23), and prints the portion of the image on the k-th line that corresponds to the m-th block B(m). The CPU 91 then proceeds to S25.

[0080] By executing the above process while updating the variable m, the plurality of heating elements 73 to be energized for printing the k-th line are arranged in the high current block B H (1st block B(1), 2nd block B(2), 4th block B(4), 5th block B(5)...) and low current block B L (3rd block B(3), 6th block B(6)...) Also, high current block B H and the low current block B L The k-th line is formed on the medium D by the heat generated by the heating elements 73 included therein (see FIG. 7).

[0081] <Actions and Effects of This Embodiment> The printer 1 divides the plurality of heating elements 73 included in the thermal head 7 into a total of M blocks B, and prints one line of an image by heating the heating elements 73 at different timings for each block B. Here, the total number M of blocks B includes high-current blocks B each having a different number of heating elements 73. H and low current block B L (See Figures 6 to 8.) High current block B H The number p of heating elements 73 included in the low current block B L The number of heat generating elements 73 included in the block B is larger than the number q (p>q). L The time required for printing can be reduced compared to when printing is performed with the multiple heating elements 73 divided into blocks B (see FIG. 5). Therefore, the printer 1 can reduce the time required to print one line of an image during divided printing, in which printing is performed by dividing the multiple heating elements 73 into blocks B.

[0082] High Current Block B H The number p of the plurality of heating elements 73 included in the heater element 73 is equal to the number N1 in the above embodiment. Here, when N1 heating elements 73 are energized, the total head current I A The value of this current is the 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 uses the high current block B H The number of heating elements 73 in each line can be maximized within the tolerance of the printer 1. In this case, the printer 1 can minimize the number of divisions, when the multiple heating elements 73 are divided into blocks B of a total number M, within the tolerance of the printer 1. This allows the printer 1 to minimize the time required to print one line.

[0083] Low Current Block B L The number q of the plurality of heating elements 73 included in the head 10 is equal to the number N2 in the above embodiment. Here, when N2 heating elements 73 are energized, the total head current I A The value of the second current value I2 is the maximum current value allowed in the OCP (see (b)). Therefore, the printer 1 uses the low current block B.L When current is applied to the heating element 73 of L , the possibility of OCP damage can be reduced.

[0084] High current block B H The first time T1 during which current can be applied to the heating element 73 of H is shorter than the second time T2 which is the maximum time during which the second current value I2 can be continuously applied by OCP (T1 < T2). Therefore, even when current is applied to the heating element 73 of the high current block B H the printer 1 can reduce the possibility of OCP damage.

[0085] Note 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 current is applied to the heating element 73 included in the high current block B H the printer 1 can reduce the possibility of damage to various devices of the printer 1. Also, when current is applied to the heating element 73 of the low current block B L the printer 1 can reduce the possibility of OCP damage.

[0086] The printer 1 performs a first divided printing process (see FIG. 10) of dividing the printing into blocks B with a total number M' where the number of each heating element 73 is equal, and a second divided printing process (see FIGS. 11 and 12) of dividing the printing into blocks B with a total number M including the high current block B H and the low current block B L and can perform printing while switching between them.

[0087] <Modification example> The present invention is not limited to the above embodiment, and various modifications are possible. The number p of the plurality of heating elements 73 included in the high current block B H is not limited to being the same as the number N_1, and may be changed within the range satisfying the condition N_2 < p ≤ N_1. The low current block B LThe number q of the plurality of heating elements 73 included in the high current block B is not limited to be equal to the number N2, and may be changed within the range that satisfies the condition q≦N2. H and low current block B L The number of the heat generating elements 73 and the order in which they are printed are not limited to the above embodiment and may be changed as appropriate. For example, the heat generating elements 73 that are energized to print the k-th line are the high current block B H (1st block B(1), 4th block B(4)...) and low current block B L (second block B(2), third block B(3), fifth block B(5), sixth block B(6), etc.).

[0088] The number N1 is the total head current I A is not limited to the number of heating elements 73 that are energized when the value of the total head current I A Alternatively, it may be the number of heating elements 73 that are energized when the value of (a) is the rated current set in the printer 1.

[0089] The number N2 is the total head current I A is not limited to the number of heating elements 73 that are energized when the value of the total head current I A Alternatively, the number of heating elements 73 that are energized when the value of (a) is the rated current set for the battery 10 may be used.

[0090] <Other> The printer 1 is an example of an "image forming apparatus" of the present invention. The medium D is an example of a "printing target" of the present invention. The CPU 91 that performs the processing of S9 is an example of a "first control means" of the present invention. The CPU 91 that performs the processing of S5 is an example of a "switching means" of the present invention. The CPU 91 that performs the processing of S7 is an example of a "second control means" of the present invention. [Explanation of symbols]

[0091] 1: Printer 7: Thermal head 10: Battery 73: Heating element 91: CPU

Claims

1. An image forming apparatus that performs printing based on print data, a thermal head that includes a plurality of heating elements that are aligned in a main scanning direction and generate heat when energized, and that forms an image on a printing object by heating the plurality of heating elements while moving relative to the printing object in a sub-scanning direction; a first control means for dividing the plurality of heating elements into M blocks (M is an integer of 3 or more) and printing one line extending in the main scanning direction by causing the heating elements to heat in the order of a first block, a second block, ..., and an Mth block at different timings for each block; Equipped with Of the plurality of heating elements, the number of heating elements that can be energized simultaneously is N １ and N １ A predetermined number smaller than N ２ In this case, the number of energized heating elements in the M blocks is p (p is N ２ < p ≦ N １ and at least one high current block having a number q (where q is q≦N ２ and at least one low current block, When the first block is the high current block, at least one of the M blocks excluding the first block and the Mth block becomes the low current block; When the first block is the low current block, at least one of the M blocks excluding the first block and the Mth block becomes the high current block; N １ a current value when the heating elements are energized is based on a first current value that is a rated current value set in the image forming apparatus, N ２ an image forming apparatus characterized in that the current value when current is passed through the heating elements is a value based on a second current value, which is a rated current value set in a power supply of the image forming apparatus;

2. 2. The image forming apparatus according to claim 1, wherein the first time during which the heating elements of the high current block can be energized is shorter than the second time, which is the maximum time during which the second current value can be continuously supplied by the overcurrent protection circuit of the power supply of the image forming apparatus.

3. a second control means for dividing the plurality of heating elements into S blocks (S is an integer of 3 or more) and causing the heating elements to heat at different timings for each block, thereby printing one line extending in the main scanning direction; 3. The image forming apparatus according to claim 1, further comprising a switching unit that switches between printing by the first control unit and printing by the second control unit.

Images