JP5200783B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that forms an image by ejecting ink droplets onto a recording member, and more particularly to an image forming apparatus that can accurately move an ink head to a maintaining unit.

  In an ink jet recording apparatus that records an image on paper by ejecting ink droplets while scanning the ink head in a direction perpendicular to the paper conveyance direction, the ink head, a guide rod that guides the carriage on which the ink head is mounted, and the like The mounting accuracy of various parts greatly affects the print quality. For example, if the gap between the ink head and the paper changes in the main scanning direction, the landing position of the ink droplets changes and the print quality deteriorates. On the other hand, tightening the process to maintain the mounting accuracy results in an increase in cost. In view of this, an ink jet recording apparatus has been proposed in which a holding portion that holds both end portions of a guide rod that guides a carriage on a side plate includes two adjuster members whose eccentric directions are orthogonal to each other (see, for example, Patent Document 1). In the ink jet recording apparatus described in Patent Document 1, the gap between the ink head and the sheet is rotated by rotating one of the two adjuster members, and the angle between the carriage moving direction and the sheet conveying direction when the other is rotated. Changes so that the dimensions in two directions can be adjusted after the guide rod is installed.

  By the way, in the ink jet recording apparatus, it is necessary to perform a maintenance operation in order to keep the head surface in a good state. Specifically, when a good meniscus (liquid bridge) is broken by leaving it for a long time without discharging ink, the ink in the nozzle is sucked and the nozzle surface is wiped with a wiper. In order to obtain the maximum effect of the maintenance operation, the positional accuracy of the head and the maintenance unit is important. The same applies to the capping performed to maintain the meniscus of the nozzle surface during the non-ejection period. That is, it is required to maintain the positional accuracy between components not only when ejecting ink droplets but also in the maintenance unit.

  Simple measures include increasing the size of the cap member relative to the head surface, and increasing the width and movement of the wiper. However, this is optimal because the machine becomes larger, downtime and cost increase. It is not a measure.

  In order to maintain the position of the ink head in the maintenance unit, an ink jet recording apparatus in which a detection sensor for the origin position is provided in the maintenance unit has been proposed (for example, see Patent Document 2). FIG. 21A shows the structure of an ink jet recording apparatus provided with an origin position detection sensor. When the sensor cutting plate integrated with the carriage blocks the origin position detection sensor, the output signal from the origin position detection sensor changes, and the home position can be detected.

As a technique for detecting the home position, a method of hitting a carriage against a frame or the like is known. However, it is known that a motor load increases and an impact sound is generated. In view of this, a technique has been proposed in which the home position is identified without abutting the carriage against a frame or the like from a state in which the carriage movement position (absolute position) is unknown (see, for example, Patent Document 3). FIG. 21B is a structural diagram of the ink jet recording apparatus described in Patent Document 3. The first detected part M1 and the second detected part M2 are arranged with a predetermined interval (L), and the main scanning direction width of the first detected part M1 and the second detected part M2 The width in the main scanning direction is relatively different (L1> L2). The first detected portion M1 is arranged so that it can be detected by the PW sensor even when the carriage is at the outermost end on one side of the reciprocating region in the main scanning direction. The second detected part M2 is configured such that the carriage stop position matches the home position in a state where the detection position of the PW sensor in the main scanning direction matches the center position of the second detected part M2 in the main scanning direction. Placed in.
JP-A-9-99603 JP 2002-127390 A JP 2006-192632 A

  However, in the ink jet recording apparatus described in Patent Document 2, since the sensor cutting plate and the origin position detection sensor are aligned at only one point, the sensor cutting plate may be caused by remaining paper, a user's finger, a sensor failure, or the like. There is a risk of false detection. If an error is detected, the maintenance operation starts at a place completely different from the maintenance unit.

  Further, in the ink jet recording apparatus described in Patent Document 3, the position of the carriage on which the head is mounted is not detected, but the position of the head in the maintenance unit is not always accurate. There is a problem. In addition, since the position cannot be determined unless the carriage is moved to two detection units, it takes time to detect the position.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that can accurately detect the position of an ink head in a maintenance unit.

In view of the above problems, the present invention, ink droplets ejected from the nozzle surface, the ink head having a lower convex portion protruding below the carriage bottom, equipped with a plurality of the ink head, to the lower convex portion Adjacent, a carriage having a tapered rib protruding below the bottom surface of the carriage, an electric motor for moving the carriage guided by a guide rod, and a function of the nozzle surface during standby while the carriage waits at a reference position An image forming apparatus that forms an image by ejecting ink droplets onto a recording member, and the carriage is disposed in the direction of the maintaining unit. When moved, the detection means for detecting distance information with respect to two or more ink heads, and the distance information is acquired in time series and obtained by the end of the ink head. And reference position determining means for determining a signal waveform detection means for obtaining a signal waveform including a feature, the reference position based on a signal waveform including a feature appearing in an end portion of the lower convex portion is, the corresponding to the tapered rib Carriage height detecting means for detecting the height of the carriage from a part of the signal waveform .

  An image forming apparatus that can accurately detect the position of the ink head in the maintenance unit can be provided.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 shows an example of a perspective view of the structure of the main part of the inkjet recording apparatus 100. A known structure can be used for the main part of the inkjet recording apparatus 100.

  The ink head 11 is disposed in the carriage 21. The ink head 11 in the carriage 21 is bonded and fixed with a UV adhesive or the like, or pressed and fixed with a spring or the like, and the ink head 11 in the carriage 21 is fixed with high accuracy.

  The carriage 21 has a through hole, and the guide lot 13 that stretches both ends of the inkjet recording apparatus 100 passes through the through hole to hold the carriage 21. A part of the carriage 21 is always in contact with the guide rail 16 so as to be biased, so that the posture of the carriage 21 is kept constant. By maintaining this attitude with high accuracy, the distance between the ink head 11 and the recording member (hereinafter simply referred to as paper) is kept uniform regardless of the position in the main scanning direction, and variations in ink landing positions are suppressed. .

  The carriage 21 is connected to the timing belt 14. When the timing belt 14 rotates through a pulley applied to the main scanning motor 18, the carriage 21 is guided by the guide rod 13 and performs a linear motion in a direction (main scanning direction) perpendicular to the paper transport direction. During linear movement, a pulse signal printed on a linear scale (not shown) is read by an encoder sensor (not shown) 22 fixed on the carriage 21 to detect the position of the carriage 21 and from the ink head 11 at a predetermined timing. Ink droplets are ejected.

  On the other hand, the sheet is conveyed by rotating the sheet conveying belt 17 by the sub-scanning motor 19. The sheet conveying belt 17 is stretched between the conveying roller and the tension roller, and the conveying belt rotates in conjunction with the rotation of the sub-scanning motor 19. At this time, the rotational position of the sub-scanning motor 19 is detected by a wheel encoder 20 fixed to the rotation shaft of the transport roller, and the sub-scanning motor 19 is controlled based on a detection signal of the wheel encoder 20.

  FIG. 2 is a cross-sectional view of a joint portion between the carriage 21 and the maintenance unit 12, and FIG. 3 is a front view thereof. Five ink heads 11 are mounted on the carriage 21. For example, C (cyan), M (magenta), Y (yellow), K (black), and K (pigment black) ink droplets are ejected from each ink head 11. In FIG. 2, ink droplets are ejected in the thickness direction of the paper surface (from the back to the front), and in FIG. 3, the ink droplets are ejected downward in the vertical direction.

  The ink droplet ejection mechanism of the ink head 11 includes a piezoelectric actuator such as a piezoelectric element, a thermal actuator that utilizes a phase change caused by liquid film boiling using an electrothermal transducer such as a heating resistor, and a metal phase caused by a temperature change. Pressure generating means for generating pressure for ejecting droplets is applied, such as a shape memory alloy actuator using change and an electrostatic actuator using electrostatic force.

  Even when the maintenance unit 12 is left without ejecting ink droplets, the maintenance unit 12 performs a maintenance operation for maintaining the state of the nozzle opening of the ink head 11, for example, suction of ink in the nozzle, wiping of the nozzle surface with a wiper. , Prevent drying, etc. The ink jet recording apparatus 100 of the present embodiment improves the positional accuracy of the ink head 11 and the maintenance unit 12 in order to obtain the maximum effect of the maintenance operation.

  The rubber cap 12a is capped so that the nozzle surface of the ink head 11 is not dried while the ink head 11 is maintained by the maintenance unit 12. The suction cap 12b is provided in the rubber cap 12a, and comes close to the suction cap 12b and the ink head 11 by capping. The rubber cap 12a is connected to a suction pump, and the ink in the ink head 11 can be sucked by operating the suction pump after capping the ink head 11 with the rubber cap 12a.

  The wiper 12c wipes off the nozzle surface after the suction operation. When the carriage 21 is moved linearly, the wiper 12c and the nozzle surface of the ink head 11 come into contact with each other, and the nozzle surface is wiped off.

  The arrangement of the ink heads 11 shown in the figure is unique to the model, and the number of ink heads 11 and the shape of the maintenance unit 12 are not limited.

  FIG. 4 shows an example of a hardware configuration diagram of the inkjet recording apparatus 100. 4 that are the same as those shown in FIGS. 1 to 3 are marked with the same symbols and descriptions of them will be omitted. The ink jet recording apparatus 100 is controlled by a controller 29. The controller 29 is connected to a main scanning motor 18, a sub scanning motor 19, an encoder sensor 22, a transmissive optical sensor 23, an ink head 11, a USB I / F 10, a power supply 24, and the like via a bus. A motor driver 25, a timer 26, a ROM 27, a RAM 28, and an ink head driving driver 31 are connected.

  Although the transmissive optical sensor 23 will be described in detail later, the transmissive optical sensor 23 can detect the position of the ink head 11 with high accuracy, and can control the position of the ink head 11 in the maintenance unit 12 with high accuracy. To do.

  The USB I / F 10 is an interface connected to, for example, a personal computer (PC) that transmits print data using a USB cable. When printing execution is input by the application software executed on the PC, the printing condition is transmitted together with the printing data, and the controller 29 prints the printing data on a sheet as will be described later according to the printing condition. The print data may be developed into bitmap data by the printer driver on the PC side or may be developed on the ink jet recording apparatus 100 side, but either may be used in the present embodiment.

  The power supply 24 supplies power to the ink jet recording apparatus 100, converts an AC voltage supplied from a commercial power supply into predetermined DC power, and generates a rated current / voltage for the ink jet recording apparatus 100.

  The motor driver 25 is an IC that controls the current flowing through the main scanning motor 18 and the sub scanning motor 19 driven by a DC motor, a step motor, or the like. Although there is only one motor driver 25 in the figure, it is disposed in each of the main scanning motor 18 and the sub-scanning motor 19. The motor driver 25 causes the current having the determined current value to flow in a predetermined direction or generates a pulse signal in accordance with a control signal from the controller 29, and also controls on / off of the current. The main scanning motor 18 and the sub-scanning motor 19 are controlled by sensing that detects the position in the paper transport direction and the position of the ink head 11 in the main scanning direction.

  The timer 26 counts down the set time or generates and outputs a clock signal. Each unit connected to the bus by the timer 26 can be synchronized. The time measured by the timer 26 is used when detecting the position of the ink head 11.

  The ROM 27 stores a file in which various programs 30 and standard patterns 32 are registered, and the CPU of the controller 29 executes the program 30 stored in the ROM 27 to execute the main scanning motor 18, the sub scanning motor 19, and the ink head. 11 is controlled. Further, the CPU 30 executes the program 30 to accurately detect the position of the ink head 11 in the maintenance unit 12. The standard pattern 32 will be described later.

  The RAM 28 is a working memory that temporarily expands the program 30 and data. In this embodiment, it is used when storing a signal (sensor output pattern) output from the transmissive optical sensor 23.

  The controller 29 is a form of a computer having a CPU, an ASIC (Application Specific Integrated Circuit), an input / output interface, and the like, and controls the main scanning motor 18, the sub scanning motor 19 and the ink head 11 when printing data is printed. Then, an image is formed on the paper based on the print data.

  The controller 29 performs image processing suitable for an ink jet method such as dither processing on the print data expressed in gradation by bitmap data. Then, the size of the ink droplet is determined for each color ink according to the pixel value corresponding to the print data. When the discharge amount is 3 levels (small, medium, large), it is only necessary to indicate 4 states for each nozzle, including the case of no discharge, so a 2-bit signal is generated for each ink droplet (pixel dot). To do. These signals are rearranged in an order appropriate to the scanning speed of the ink head 11 in the main scanning direction and the response speed of the ink head 11.

  The ink head drive driver 31 generates a drive waveform for controlling ejection of ink droplets by the ink head 11. The ink head drive driver 31 receives the signal generated by the controller 29, reads the drive waveform pattern data stored in the ROM 27 corresponding to the signal, and generates a drive waveform corresponding to the signal corresponding to one row in the main scanning direction. Generate. Then, the ink head drive driver 31 selectively applies a drive waveform to the pressure generating means of the ink head 11 and discharges ink from the ink discharge port of the ink head 11.

  The controller 29 moves the paper in the transport direction, moves the ink head 11 intermittently according to the width of the print medium, and forms an image on the paper by alternately repeating the transport of the paper and the ejection of ink droplets. .

  In this embodiment, the maintenance unit 12 is provided with a transmissive optical sensor 23 that detects the passage of each ink head 11, and the transmissive optical sensor 23 detects the passage of each ink head 11 to generate a sensor output pattern. . When it is determined that the sensor output pattern matches the pre-stored standard pattern 32, the carriage reference position of the carriage 21 is determined by setting the end face of the ink head 11 that has passed last as a starting point. The carriage reference position is called a home position and is a standby position in the maintenance unit 12.

  That is, since the end face of the ink head 11 is detected based on whether or not the sensor output patterns formed corresponding to the positions of the plurality of ink heads match, the ink head 11 may be erroneously detected by the remaining paper or the user's finger. There is no. For this reason, the end face of the ink head 11 can be detected accurately, and the position of the ink head 11 in the maintenance unit 12 can be determined with high accuracy.

  FIG. 5 is an example of a diagram schematically illustrating the transmissive optical sensor 23. As described above, the carriage 21 moves in parallel with the guide rod 13, and the maintenance unit 12 that maintains the ink head 11 is also disposed on the locus. FIG. 5 is a top view, in which the nozzle surface of the ink head 11 is disposed downward in the thickness direction of the paper surface, and the maintenance unit 12 is disposed upward in the thickness direction of the paper surface.

  The transmissive optical sensor 23 includes a light emitting unit 23a and a light receiving unit 23b, and light emitted from the light emitting unit 23a is received by the light receiving unit 23b. In order to improve the positional accuracy, the smaller the light beam emitted from the light emitting unit 23a, the better. Therefore, the light emitting unit 23a has, for example, a laser diode, and the light receiving unit 23b has a photodiode that converts laser light into an electric machine. A light source having a relatively large luminous flux may be used for the light emitting unit 23a, and the area of the light receiving unit 23b may be reduced.

  The light emitting unit 23 a and the light receiving unit 23 b are arranged to face each other so as to be orthogonal to the moving direction of the carriage 21. That is, the optical path connecting the light emitting unit 23 a and the light receiving unit 23 b is orthogonal to the moving direction of the carriage 21. Since the light receiving unit 23b and the light emitting unit 23a are orthogonal to the ink ejection direction, the risk of contamination of the detection surface due to ink mist can be reduced. In addition, since the arrangement is performed across the carriage 21, the arrangement accuracy of the transmissive optical sensor 23 is important. In addition, it is not necessary that the light receiving unit 23b is simply arranged on the optical path exiting from the light emitting unit 23a, but the perpendicularity to the carriage movement direction (= longitudinal direction of the guide rod 13) is important.

  The transmissive optical sensor 23 protrudes closer to the front side in the thickness direction of the paper surface than the surface of the maintenance unit 12 with the rubber cap. Each ink head 11 passes through the space formed by the protruding light emitting portion 23a and light receiving portion 23b. Since the nozzle surfaces of the ink heads 11 protrude from the bottom surface of the carriage, the transmissive optical sensor 23 can detect the passage of each ink head 11.

  In FIG. 5, the transmissive optical sensor 23 is disposed slightly to the left of the center of the maintenance unit 12, but the position of the transmissive optical sensor 23 is slightly to the left of the right of the center of the maintenance unit 12. I just need it. This is because if two ink heads 11 can be detected, a sensor output pattern can be generated. More preferably, it is provided at the left end of the maintenance unit 12 so that all the ink heads 11 (in this case, five) can be detected.

  FIG. 6 shows an example of a functional block diagram of the ink jet recording apparatus 100 of the present embodiment. The sensor pattern detection unit 33, the sensor pattern comparison unit 34, the starting point position determination unit 35, and the carriage reference position determination unit 36 are realized by the CPU of the controller 29 executing the program 30 or by an ASIC.

  The sensor pattern detection unit 33 generates a sensor output pattern described below based on a signal output from the transmissive optical sensor 23. The sensor pattern comparison unit 34 compares the sensor output pattern with the standard pattern 32 and determines whether or not they match. The starting position determination unit 35 determines the position of the carriage 21 when the end of the ink head 11 has finally passed as the starting position. This starting point position is acquired by an encoder sensor 22 that detects a passing pulse of a linear scale. The carriage reference position determining unit 36 determines a position moved by a predetermined distance A from the starting position as a carriage reference position in the maintenance unit 12. Maintenance work such as capping of the nozzle surface is performed at this carriage reference position.

  FIGS. 7A to 7D are examples of diagrams illustrating the sensor output patterns generated by the sensor pattern detection unit 33 in time series. 7A to 7D show the relationship between the position of the ink head 11 and the position of the transmissive optical sensor 23, and the right figure shows the sensor output of the transmissive optical sensor 23 at that time. The sensor output in FIG. 7 is a binary signal when the ink head 11 is not shielded (transmits) between the light emitting part 23a and the light receiving part 23b of the transmissive optical sensor 23 and when it is shielded. . When transmitting, the sensor output may be zero.

  As shown in FIG. 7A, even if the carriage 21 reaches before the maintenance unit 12, the sensor output shows a transmission state until the ink head 11 shields the transmission optical sensor 23. Next, as shown in FIG. 7B, when the optical path is blocked by the rightmost ink head 11 (hereinafter, referred to as the first to fifth ink heads 11 in order from the closest to the maintenance unit 12). The sensor output changes from the “transmission” state to the “shielding” state.

  Further, when the carriage 21 moves, the rightmost ink head 11a comes out of the optical path and changes from the “shielded” state to the “transmitted” state. Further, when the carriage 21 further moves to the right and the optical path is shielded again by the second ink head 11b from the right, the sensor output is changed from the “transmission” state to the “shielding” state.

  Therefore, when there are five ink heads 11, sensor output patterns having a total of five shielding states are formed. A change in the sensor output pattern (a change of 90 degrees in the figure) when transitioning from the shielding state to the transmission state or from the shielding state to the transmission state indicates the end of the ink head 11 (corresponding to the characteristic part of the claims) ).

  FIG. 8 shows an example of a sensor output pattern. The sensor pattern detection unit 33 plots the transmission state and the shielding state against time or distance (linear scale pulse) to generate a sensor output pattern.

  As shown in the figure, five shielding states corresponding to the ink head 11 are formed. A comparison between the sensor output pattern and the standard pattern 32 stored in the ROM 27 will be described.

  The X axis of the sensor output pattern indicates a time or linear scale pulse, and the Y axis indicates an output (for example, voltage). When the X axis is time, there is no need to acquire pulses, so the system becomes easier and the cost increase can be further suppressed. On the other hand, in order to be directly affected by the speed fluctuation of the carriage 21, the constant speed (no or little rotation unevenness) of the carriage 21 that moves linearly is required.

  On the other hand, in the case of measurement by linear scale pulse conversion, accurate measurement can be performed without being influenced by the carriage speed, but the configuration and control become complicated and the cost increases. Therefore, it can be technically realized by using either one. The X axis of the standard pattern 32 is the same as the sensor output pattern.

  The arrangement (positional relationship) of the ink heads 11 on the carriage 21 is fixed and arranged at a predetermined interval. Whether all the ink heads 11 are equally spaced or whether some of them are different depends on the model. The example shown in FIG. 8 is an example in which five ink heads 11 are arranged at equal intervals.

  The sensor pattern comparison unit 34 compares the sensor output pattern with the standard pattern 32. Since the sensor output may vary due to deterioration or the like, the “transmission” state and the “shielding” state of the sensor output pattern may be normalized to predetermined values such as “1” and “0”, respectively. There is a pattern matching method as a comparison method, but since the sensor output is a binary signal, the method of comparing the number of pulses in the five shielding states and the four transmission states with those of the standard pattern 32 is also a processing load. It is preferable because it is small.

  It is assumed that the number of shielded pulses obtained by the rightmost ink head 11 is k1, the number of transmitted pulses obtained by the distance between the rightmost ink head 11a and the second ink head 11b from the right is m1,. As shown in the figure, since the number of pulses corresponding to the standard pattern 32 is also stored, the number of each pulse is compared.

  “K1 and f1”, “k2 and f2”, “k3 and f3”, “k4 and f4”, “k5 and f5”, “m1 and g1”, “m2 and g2”, “m3 and g3”, “m4 And g4 ”are compared, and the sensor pattern comparison unit 34 determines that the sensor output pattern and the standard pattern 32 match if all match.

  When comparing by pattern matching, the sensor output pattern is developed into a bitmap having the same resolution as that of the standard pattern, and the correspondence with the most matching pixel value is obtained while shifting the correspondence for each pixel.

  When the carriage 21 moves and finally matches up to “k5 and f5”, the position of the carriage 21 at the time of matching is the starting position. In FIG. 8, the left end of the distance A is the starting position, and the position of the carriage 21 immediately after the end of the leftmost ink head 11 passes through the transmissive optical sensor 23 is shown.

  It is known how much the carriage 21 is moved from the starting position to reach the carriage reference position, that is, the distance A. The carriage reference position determination unit 36 moves the ink head 11 to the maintenance unit 12 accurately by counting the linear scale pulse from the starting position and moving it by the distance A. After the movement is completed, the maintenance unit 12 starts a maintenance operation or performs a capping operation.

  FIG. 9 is an example of a flowchart illustrating a procedure by which the inkjet recording apparatus 100 of the present embodiment moves the carriage 21 to the carriage reference position. In FIG. 9, it is assumed that the sensor output pattern is generated by a method of counting linear scale pulses. The flowchart of FIG. 9 starts when the carriage 21 is moved to the maintenance unit 12, for example.

  First, the carriage 21 starts moving in the direction of the maintenance unit 12 (S10). Then, acquisition of the sensor output is started according to the light received by the light receiving unit 23b of the transmissive optical sensor 23 (S20).

  The sensor pattern detection unit 33 starts counting the pulses of the linear scale while monitoring the sensor output of the transmission optical sensor 23 (S30). When all of the ink heads 11 have passed through the optical sensor or a predetermined time has elapsed, acquisition of the sensor output pattern is completed (S40).

  Next, the sensor pattern comparison unit 34 compares the sensor output pattern with the standard pattern 32 stored in the ROM 27 and determines whether or not they match (S50).

  If they do not match (No in S60), the sensor pattern comparison unit 34 determines whether or not the prescribed number of retries has been exceeded (S110). If the number of retries has been exceeded (Yes in S110), the sensor pattern comparison unit 34 An error message is displayed on a display unit such as a liquid crystal display (S120). When there is no display section, a warning lamp is turned on. When connected to a PC, an error message is displayed on the PC display.

  If the number of retries has not been exceeded (No in S110), the controller 29 moves the carriage 21 in the opposite direction (image forming area direction) to detect the sensor output pattern again (S100). When the rightmost ink head 11 passes through the transmissive optical sensor 23, the carriage 21 starts to move again toward the maintenance unit 12, so that the sensor output pattern output unit detects the sensor output pattern again.

  When the sensor output pattern matches the standard pattern 32 stored in the ROM 27 (Yes in S60), the starting position determining unit 35 determines the starting position, and the carriage reference position determining unit 36 determines the position of the distance A therefrom as the carriage reference. The position is determined (S70).

  The controller 29 moves the carriage 21 to the carriage reference position (S80). As a result, maintenance work is possible, so that the maintenance unit 12 performs capping or the like on the ink head 11 (S90).

  As described above, since the ink jet recording apparatus 100 according to the present embodiment directly detects the position of the ink head 11 with the sensor fixed to the maintenance unit 12, the cap or wiper in the maintenance unit 12, the ink head 11, and the like. Relative position accuracy can be improved. Even if a paper having a conveyance failure or a user's hand is erroneously detected as the ink head 11, the carriage reference position is not determined unless the sensor output pattern matches the standard pattern 32, and thus misalignment occurs due to erroneous detection. There is no.

  In this embodiment, an ink jet recording apparatus 100 that can detect the distance (the height of the carriage 21) between the carriage 21 and the maintenance unit 12 at the carriage reference position using the sensor output of the transmission optical sensor 23 will be described. .

  FIG. 10 is an example of a diagram schematically illustrating the transmission optical sensor 23 of the present embodiment. 10, the same parts as those in FIG. 5 are denoted by the same reference numerals, and the description thereof is omitted. The carriage 21 of this embodiment includes a tapered rib 41 at the end in the main scanning direction. The taper rib 41 is a substantially triangular rib that becomes thinner as it moves away from the carriage 21 in the paper direction. The height of the taper rib 41 may be the same as or higher than that of the ink head 11.

  The taper rib 41 blocks the optical path of the transmissive optical sensor 23 similarly to the ink head 11. Therefore, a sensor output pattern in which one more shielding state is formed than in the first embodiment is obtained.

  By providing the taper rib 41 in this way, the height of the carriage 21 can be detected. As shown in FIG. 11A, the distance that the tip end portion (paper side) of the taper rib 41 shields the transmissive optical sensor 23 is shorter than the distance that the carriage side shields the transmissive optical sensor 23. Whether the tip end of the taper rib 41 passes or the carriage side passes depends on the height of the carriage 21. Therefore, the height of the carriage 21 can be detected by detecting the distance that the tapered rib 41 passes through the transmission optical sensor 23.

  FIG. 11B shows an example of a functional block diagram of the inkjet recording apparatus 100 of the present embodiment. In FIG. 11B, the same parts as those in FIG. In this embodiment, a carriage position detection unit is included, and the carriage position detection unit detects the height of the carriage 21 based on the distance (linear scale pulse) that the tapered rib 41 passes through the transmission optical sensor 23.

  In this embodiment, a map 38 in which the relationship between the “number of pulses and the carriage height” is registered is stored in the ROM 27. Therefore, if the number of pulses by the taper rib 41 is detected, the carriage height can be read from the map 38.

  FIG. 12 shows an example of a sensor output pattern. The sensor pattern detection unit 33 continues the movement of the carriage 21 after the last (fifth) ink head 11 e is detected, and measures the “shielding time” of the taper rib 41. The longer the shielding time is, the longer the distance between the nozzle surface and the maintenance unit is. On the contrary, the shorter the shielding time is, the closer the distance between the nozzle and the maintenance unit is.

  In FIG. 12, since the rightmost shielding state is due to the taper rib 41, the carriage height detection unit 37 reads the carriage height from the map 38 based on the distance L shielded by the taper rib 41.

  FIG. 13 is an example of a flowchart illustrating a procedure in which the inkjet recording apparatus 100 according to the present embodiment moves the carriage 21 to the carriage reference position and detects the carriage height. In FIG. 13, the description of the same steps as those in FIG. 9 is omitted. When moving to the carriage reference position in step S80, the distance L shielded by the taper rib 41 is detected. In step S85, the carriage height detection unit 37 detects the carriage height (S85).

  The ink jet recording apparatus 100 according to the present embodiment can detect the “distance between the nozzle, the sheet conveying apparatus, and the maintenance unit”, which is an important dimension in the ink jet recording apparatus 100. Based on this dimension, for example, the print quality can be improved by correcting the ink ejection timing.

  In the first and second embodiments, the sensor output pattern when the carriage 21 moves in one direction (direction approaching the maintenance unit 12) is detected. In this embodiment, the sensor output pattern when the carriage 21 moves in both directions is detected. To detect.

  The carriage 21 is held by penetrating a through hole in the guide lot 13, but the carriage 21 and the guide rod 13 need a backlash (gap) for linear movement. The backlash enables a smooth linear motion, but due to backlash, the carriage 21 swings (yaws) according to the motion direction. That is, the axis of the carriage 21 parallel to the guide rod 13 in a stationary state forms an angle with the guide rod 13 in the forward path (for example, the direction approaching the maintenance unit 12), and in the reverse direction on the backward path (the reverse direction). Make.

  Therefore, since the carriage reference position detected in the forward path is also expected to include some errors, it is more preferable to determine the carriage reference position in the forward path and the return path. Therefore, in this embodiment, the sensor output pattern is measured by moving the carriage 21 in both the forward and backward directions.

The functional block diagram is the same as in the first or second embodiment, but in this embodiment, the sensor output pattern of the return path is stored in the ROM 27 in advance. The sensor pattern comparison unit 34 determines that the sensor output patterns match when both the sensor output patterns of the forward path and the return path match.
Further, the starting point position determination unit 35 of the present embodiment stores the starting point position of the forward path and the starting point position of the return path, and determines the average as the starting position. Then, the carriage reference position determination unit 36 moves the carriage 21 that is separated from the starting position by the distance A to the carriage reference position.

  FIG. 14 is an example of a flowchart showing a procedure for moving the carriage 21 to the carriage reference position by the inkjet recording apparatus 100 of the present embodiment. FIG. 14 shows only steps different from those in FIG.

  First, the carriage 21 starts moving in the direction of the maintenance unit 12 (S10). Then, sensor output is started according to the light received by the light receiving unit 23b of the transmissive optical sensor 23 (S20A).

  The sensor pattern detection unit 33 starts counting the pulses of the linear scale while monitoring the sensor output in the forward path (S30A). When all of the ink heads 11 pass through the optical sensor or when a predetermined time has elapsed, the acquisition of the sensor output pattern of the forward path is completed (S40A).

  Here, the controller 29 starts moving the carriage 21 in the backward direction. And sensor output is started according to the light which the light-receiving part 23b of the transmissive optical sensor 23 received (S20B).

  The sensor pattern detection unit 33 starts counting the pulses of the linear scale while monitoring the sensor output in the return path (S30B). When all of the ink heads 11 have passed the optical sensor or a predetermined time has elapsed, the acquisition of the sensor output pattern for the return path is completed (S40B). Thus, the sensor output patterns of the forward path and the return path are detected (S40). Subsequent processing is the same as that shown in FIG.

  According to the present embodiment, it is possible to remove the tilt component of the ink head 11 by swinging (yawing) the carriage 21, and it is possible to determine a more accurate carriage reference position. Therefore, the relative positional accuracy between the cap or wiper in the maintenance unit 12 and the ink head 11 can be improved as compared with the first embodiment.

  In the first to third embodiments, the ink head 11 protruding from the bottom surface of the carriage 21 is detected by the transmission optical sensor 23. However, when the protrusion amount from the carriage 21 is not sufficient, the position of the ink head 11 is determined by the transmission optical sensor. 23 can be assumed to be difficult to detect. Therefore, it is preferable to provide a protrusion for detecting the position by the transmission optical sensor 23 integrally with the ink head 11.

  FIG. 15 shows an example of a perspective view of the ink head 11 and the transmission optical sensor 23 of the present embodiment. The ink head 11 is provided with a protrusion having a length that protrudes to the outside of the carriage 21. The protruding portion passes between the light emitting portion 23a and the light receiving portion 23b as the carriage 21 moves in the main scanning direction. Also in this embodiment, the transmission optical sensor 23 is provided in the maintenance unit 12 or integrally with the maintenance unit 12, and the carriage reference position can be determined by a predetermined distance A from the starting position.

  According to the present embodiment, the same effects as in the first to third embodiments can be achieved at a lower cost with a smaller number of parts. Further, the condition of the ink head 11 can be detected under more suitable conditions.

  In the first to fourth embodiments, the position of the ink head 11 is detected by the transmission optical sensor 23, but in the present embodiment, the position of the ink head 11 is detected by the head position detection sensor 42. The point that the sensor output pattern is compared with the standard pattern 32 is the same as in the first to fourth embodiments.

  FIG. 16 is an example of a diagram that schematically illustrates detection of the ink head 11 by the head position detection sensor 42. 16A shows a front view, and FIG. 16B shows a side view. In order to maintain the performance of the ink head 11, the maintenance unit 12 and the carriage 21 are disposed at positions facing the head surface in the carriage 21. The functional block diagram is the same as FIG. 6 of the first embodiment.

  The head position detection sensor 42 is disposed in the maintenance unit 12 so as to face the head surface. The head position detection sensor 42 is a reflective sensor, a distance detection sensor, or the like. In the case of the reflection type sensor, the light emitting unit and the light receiving unit are integrally provided, and the distance to the ink head 11 or the carriage 21 is detected based on the time until the light (laser) emitted from the light emitting unit is detected by the light receiving unit. . Further, for example, the slit light is obliquely projected to photograph a stripe pattern on the carriage 21, and the shape and position of the ink head 11 are detected by applying a known triangulation principle from the interval of the stripe pattern. Also good. In the case of a distance detection sensor, for example, the position of the ink head 11 is detected based on the time it takes for an ultrasonic wave to be reflected and returned to the ink head 11 or the carriage 21.

  When the carriage 21 is caused to wait on the maintenance unit 12, the controller 29 moves the carriage 21 at a constant speed, and the sensor pattern detection unit 33 detects the output of the head position detection sensor 42 and the pulse of the linear scale 44.

  FIGS. 17A to 17C are examples of diagrams illustrating the sensor output patterns generated by the sensor pattern detection unit 33 in time series. 17A to 17C show the relationship between the position of the ink head 11 and the position of the head position detection sensor 42, and the right figure shows the sensor output of the head position detection sensor 42 at that time.

  FIG. 17 shows a case where the value output from the head position detection sensor 42 becomes higher as the distance is shorter. As shown in the figure, the output of the head position detection sensor 42 also shows a peak as many as the number of ink heads 11. The reason why the output does not become a perfect pulse is that it is affected by the boundary between the ink head 11 and the carriage 21. Therefore, unlike Example 1, it is not a binary signal when not shielded (transmits) and when shielded.

  As shown in FIG. 17A, when the carriage 21 reaches the maintenance unit 12 and the first ink head 11a passes just above the head position detection sensor 42, the output of the head position detection sensor 42 is also the first. Shows the peak.

  Next, as shown in FIG. 17B, when the third ink head 11c passes right above the head position detection sensor 42, the output of the head position detection sensor 42 also shows three peaks. Further, when the last fifth ink head 11e passes right above the head position detection sensor 42, the output of the head position detection sensor 42 also shows five peaks. In this embodiment, since the intervals between the ink heads 11 are not equal, the peaks of the output of the head position detection sensor 42 are not equal.

  Therefore, when there are five ink heads 11, a total of five peaks are obtained. The sensor pattern detection unit 33 plots the sensor output with respect to time or distance (pulse of the linear scale 44) to generate a sensor output pattern.

  FIG. 18 shows an example of the relationship between the finally detected pulse and the output of the head position detection sensor 42. The sensor pattern comparison unit 34 compares the sensor output pattern acquired by the head position detection sensor 42 with the standard pattern 32 stored in the ROM 27 in advance, and determines whether or not they match. Also in the present embodiment, whether or not they match can be determined by comparing pattern matching and the number of pulses of each peak and trough with the standard pattern 32. In the present embodiment, the boundary between the ink head 11 and the carriage 21 may not be clear, so whether or not they match is determined more gently than in the first to fourth embodiments.

  If they match, the starting position determination unit 35 determines the carriage position when the end of the last (fifth) ink head 11e is detected as the starting position. A position moved by a distance A from the starting position is a carriage reference position.

  Incidentally, if the output value of the head position detection sensor 42 is inclined, it is difficult to detect the end of the ink head 11. Therefore, a threshold value is set, and the starting position of the carriage 21 is determined from the pulse of the linear scale 44 at the location where the output of the head position detection sensor 42 is below the threshold value.

  The threshold value is an intermediate value between the output value when the ink head 11 is not detected and the output value when the ink head 11 is detected, or the output value of the head position detection sensor 42 is in a detection steady state (a state where the output value is almost constant after the peak). ) Is the output value at the time. Since the output value of the latter detection steady state can be determined if the first peak is obtained, the fifth peak can be determined from, for example, the average of the four peaks so far. In FIG. 18, an intermediate value between the output value in the undetected state and the output value in the detected state is used. Therefore, the starting point position determination unit 35 determines the starting point position from the number of pulses when the fifth peak is equal to or less than the threshold value.

  The carriage reference position determining unit 36 determines a position moved by a predetermined distance A from the starting position as a carriage reference position in the maintenance unit 12. Maintenance work such as capping of the nozzle surface is performed at this carriage reference position.

  In this embodiment, the procedure for the inkjet recording apparatus 100 to move the carriage 21 to the carriage reference position is the same as that in FIG.

  As described above, since the ink jet recording apparatus 100 according to the present embodiment directly detects the position of the ink head 11 with the sensor fixed to the maintenance unit 12, the cap or wiper in the maintenance unit 12, the ink head 11, and the like. Relative position accuracy can be improved.

  In this embodiment, the height information of the carriage 21 is obtained from the sensor output pattern. For example, since the peak peak corresponds to the height of the nozzle surface and the valley corresponds to the height of the carriage 21, the carriage height can be obtained from the output value of the peak valley. Thus, it is not necessary to provide the taper rib 41.

  In the fifth embodiment, the starting position is determined as it is based on the number of pulses when the fifth peak is equal to or less than the threshold value. However, in this embodiment, the ink jet recording apparatus 100 that corrects the starting position and calculates a more accurate starting position. Will be described.

  The actual distance between the ink heads 11 can be known in advance. For example, as shown in FIG. 16, if the distance from the first (rightmost) ink head 11a to the next ink head 11b is X, for example, X can be measured. In the present embodiment, it is assumed that only the interval from the third ink head 11c to the fourth ink head 11d is Y, and all others are the interval X. The intervals X and Y are stored in the ROM 27 in advance.

  Since the peak interval of the sensor output pattern should also be X or Y, a value obtained by subtracting X or Y from the interval between peaks may be an error of the head position detection sensor 42. Therefore, the accuracy of the starting position can be improved by correcting this error.

Specific correction will be described with reference to FIG. As shown in FIG. 19, when the intervals between peaks are L1 to L4, respectively.
L1 '= L1-X
L2 '= L2-X
L4 '= L4-Y
L3 ′ = L3-X
Each of these is an error. Any one of them may be used, but since an average error can be obtained by using the average of L1 ′ to L4 ′, the average E of L1 ′ to L4 ′ is used as the error.

  The reference position determining means corrects the starting position with an average E. When the average E is positive, the distances L1 to L4 between the peaks obtained from the sensor output pattern are larger than the actual size. Therefore, the reference position of the carriage 21 is corrected to the left side. Correct the position to the right.

  FIG. 20 is an example of a flowchart of a procedure for moving the carriage 21 to the carriage reference position by the inkjet recording apparatus 100 of the present embodiment. The procedure of FIG. 20 is the same as that of Example 5 except step S75.

  That is, after determining the starting position (S70), the starting position determining means calculates the average E of L1 'to L4' from the intervals L1 to L4 between the peaks and the actual distances X and Y, and corrects the starting position. (S75).

  The carriage reference position determining means determines the position moved by the distance A from the corrected starting position as the carriage reference position (S80).

  In the inkjet recording apparatus 100 of the present embodiment, a more accurate carriage reference position can be determined by correcting the starting position with the actual distances X and Y.

  As described above, the ink jet recording apparatus 100 according to the present embodiment detects the end face of the ink head 11 when the sensor output patterns formed corresponding to the positions of the plurality of ink heads match. There is no possibility that the ink head 11 is erroneously detected by the user's finger. For this reason, the end face of the ink head 11 can be accurately detected, and the position of the ink head 11 in the maintenance unit 12 can be determined with high accuracy.

It is an example of the perspective view of the structure of the principal part of an inkjet recording device. It is an example of sectional drawing of the junction part of a carriage and a maintenance unit. It is an example of the front view of the junction part of a carriage and a maintenance unit. It is an example of the hardware block diagram of an inkjet recording device. It is an example of the figure which illustrates a transmission type optical sensor typically. 1 is an example of a functional block diagram of an ink jet recording apparatus (Example 1). FIG. It is an example of the figure explaining a sensor output pattern in time series. It is a figure which shows an example of a sensor output pattern. FIG. 3 is an example of a flowchart illustrating a procedure for moving the carriage to the carriage reference position by the inkjet recording apparatus (Example 1). (Example 2) which is an example of the figure which illustrates a transmissive | pervious optical sensor typically. It is an example of the figure explaining a taper rib and shielding of an optical path. (Example 2) which is a figure which shows an example of a sensor output pattern. FIG. 9 is an example of a flowchart illustrating a procedure for detecting the carriage height by moving the carriage to the carriage reference position by the inkjet recording apparatus (Example 2). FIG. 10 is an example of a flowchart illustrating a procedure for moving the carriage to the carriage reference position by the inkjet recording apparatus (Example 3). (Example 4) which is an example of the perspective view of an ink head and a transmission optical sensor. (Example 5) which is an example of the figure which illustrates typically the detection of the ink head by a head position detection sensor. (Example 5) which is an example of the figure explaining the sensor output pattern which a sensor pattern detection part produces | generates in time series. (Example 5) which is a figure which shows an example of the relationship between the pulse finally detected and the output of a head position detection sensor. It is an example of the figure explaining correction | amendment of a starting point position. FIG. 16 is an example of a flowchart illustrating a procedure for moving the carriage to the carriage reference position by the inkjet recording apparatus (Example 6). It is a figure which shows an example of the structure of the conventional inkjet recording device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Ink head 12 Maintenance unit 13 Guide rod 16 Guide rail 17 Paper conveyance belt 18 Main scanning motor 19 Sub scanning motor 21 Carriage 23 Transmission type optical sensor 41 Tapered rib 42 Head position detection sensor 100 Inkjet recording apparatus

Claims (9)

The ink droplets ejected from the nozzle surface, the ink head having a lower convex portion protruding below the carriage bottom surface,
A carriage having a plurality of the ink heads and having a taper rib adjacent to the lower convex portion and projecting downward from the bottom surface of the carriage;
An electric motor for moving the carriage guided by the guide rod;
An image forming apparatus configured to form an image by ejecting ink droplets onto a recording member. ,
A detecting means provided in the maintaining means for detecting distance information between two or more ink heads when the carriage is moved in the direction of the maintaining means;
A signal waveform detecting means for acquiring the distance information in time series and acquiring a signal waveform including a characteristic obtained by an end of the ink head;
A reference position determining means for determining the reference position based on a signal waveform including a feature appearing at an end of the lower convex portion ;
Carriage height detecting means for detecting the height of the carriage from a part of the signal waveform corresponding to the tapered rib;
An image forming apparatus comprising: An ink head for ejecting ink droplets from the nozzle surface;
A carriage carrying a plurality of the ink heads;
An electric motor for moving the carriage guided by the guide rod;
An image forming apparatus configured to form an image by ejecting ink droplets onto a recording member. ,
A detecting means provided in the maintaining means for detecting distance information between two or more ink heads when the carriage is moved in the direction of the maintaining means;
A signal waveform detecting means for acquiring the distance information in time series and acquiring a signal waveform including a characteristic obtained by an end of the ink head;
Reference position determining means for determining the reference position based on the signal waveform;
Standard pattern storage means for storing a standard pattern of the signal waveform;
Determination means for determining whether or not the signal waveform and the standard pattern are substantially matched by comparing,
When it is determined that the determination unit substantially matches, the reference position determination unit determines the reference position based on the position of the carriage when substantially matching.
Image forming apparatus characterized by. An ink head for ejecting ink droplets from the nozzle surface;
A carriage carrying a plurality of the ink heads;
An electric motor for moving the carriage guided by the guide rod;
An image forming apparatus configured to form an image by ejecting ink droplets onto a recording member. ,
A detecting means provided in the maintaining means for detecting distance information between two or more ink heads when the carriage is moved in the direction of the maintaining means;
A signal waveform detecting means for acquiring the distance information in time series and acquiring a signal waveform including a characteristic obtained by an end of the ink head;
Reference position determining means for determining the reference position based on the signal waveform;
A linear scale and an encoder sensor for acquiring positional information of the carriage,
The signal waveform detection means detects the signal waveform in association with position information,
The reference position determining means determines a reference position of the carriage based on position information of an end of the ink head detected from the signal waveform ;
An image forming apparatus. The ink head has a lower convex portion protruding below the carriage bottom surface,
The reference position determining means determines the reference position based on a signal waveform including a feature appearing at an end of the downward convex portion;
The image forming apparatus according to claim 2 , wherein the image forming apparatus is an image forming apparatus. The detection means is a transmissive optical sensor;
Detecting the presence or absence of light shielding by the lower convex portion of the ink head;
The image forming apparatus according to claim 1 , wherein the image forming apparatus is an image forming apparatus. When the carriage reciprocates the guide rod,
The detection means detects the distance information on both the outward path and the return path,
The reference position determining means determines the reference position based on the signal waveforms of both the forward path and the return path;
The image forming apparatus according to claim 1 to 5 any one of claims, characterized in that. A protrusion formed integrally with the ink head;
The detection means is a transmission type optical sensor integrated with the maintenance means for optically detecting passage of the protrusion.
The image forming apparatus according to claim 1 , wherein the image forming apparatus is an image forming apparatus. The detection means is a reflective sensor that detects a reflected wave reflected by a detection target;
Detecting the presence or absence of a reflected wave reflected from the ejection surface of the ink head;
The image forming apparatus according to claim 6 any one of claims, characterized in that. The image forming apparatus according to claim 1 , wherein the carriage moves at a constant speed in a main scanning direction when the detecting unit detects an ink head.

Images