JP2007245484A - Pressure adjusting chamber, recording head having the same, and ink jet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple structure and low cost capable of drawing out the function of a pressure regulation chamber to the maximum in a pressure regulation chamber using an elastic deformation member provided for adjusting a gas pressure in a container. There are provided an elastic member, a recording head having a pressure adjusting chamber using the elastic member, and an ink jet recording apparatus having the recording head.
A pressure adjusting chamber for adjusting a gas pressure in a container has at least one elastically deformable member whose volume can be changed according to the gas pressure, and an opening having a substantially circular shape. In an elastically deformable member having two substantially flat surfaces on the outer peripheral surface before deformation, and these two surfaces are connected in a substantially symmetrical arrangement via a curved surface portion at a tip portion opposite to the opening. The inner wall side of the ridge line portion of the outer surface shape is provided with a thick wall portion that is thicker than the other thickness of the elastically deformable member.
[Selection] Figure 1

Description

  The present invention relates to a recording head that performs recording by discharging ink, and an ink jet recording apparatus having the recording head, and more particularly, to adjustment of a negative pressure generated in a liquid chamber in the ink jet recording head during an ink discharging operation. .

  Among recording methods such as printers, inkjet recording methods that form characters and images on the recording medium by ejecting ink from nozzles (nozzles) are low-noise, non-impact recording methods that provide high-density and high-speed recording operations. In recent years, it has been widely adopted.

  A general ink jet recording apparatus includes an ink jet recording head, means for driving a carriage on which the ink jet recording head is mounted, means for transporting a recording medium, and control means for controlling these. A device that performs a recording operation while moving the carriage is called a serial type. On the other hand, one that performs a recording operation only by transporting a recording medium without moving the inkjet recording head is called a line type. In a line-type ink jet recording apparatus, an ink jet recording head has a large number of nozzles arranged over the entire width of the recording medium.

  The ink jet recording head has energy generating means for generating energy for discharging given to the ink in the nozzle in order to discharge ink droplets from the nozzle. As an energy generation means, one using an electromechanical transducer element such as a piezo element, one using an electrothermal transducer element such as a heating resistor, or converting electromagnetic waves such as radio waves or lasers into mechanical vibration or heat. There are those using electromagnetic wave mechanical transducer elements, electromagnetic wave heat transducer elements, and the like. Among them, the method of ejecting ink droplets using thermal energy can perform high-resolution recording because the nozzles can be arranged with high density. In particular, an ink jet recording head using an electrothermal transducer element as an energy generating element is easier to miniaturize than one using an electromechanical transducer element, and further advances and reliability in recent semiconductor manufacturing fields. By fully utilizing the advantages of applying IC technology and micromachining technology with remarkable improvement, there is an advantage that high-density mounting is easy and manufacturing cost can be reduced.

  As a method of supplying ink to the ink jet recording head, a so-called head tank integrated method in which an ink tank for storing ink is integrated with the ink jet recording head, a so-called tube supply method in which the ink tank and the ink jet recording head are connected by a tube, and The ink tank and the ink jet recording head are provided separately, and if necessary, the ink jet recording head is moved to the position of the ink tank to connect them, so that ink is supplied from the ink tank to the ink jet recording head. There is a method.

  If the capacity of the ink tank is increased in order to reduce the frequency of ink tank replacement, the weight of the ink tank increases. Therefore, in the serial type ink jet recording apparatus, considering that the weight applied to the carriage increases, the head The tank integrated system is not preferable. Therefore, a serial type ink jet recording apparatus using a large capacity ink tank often employs a tube supply system or a pit-in system. In particular, since the pit-in method needs to stop the recording operation during the ink supply, a tube supply method capable of continuous recording for a long time is often employed.

  The ink supply system of the tube supply type ink jet recording apparatus will be described below with reference to FIG.

  The ink supply system shown in FIG. 14 is connected to the supply unit 305 via a main tank 304 that stores the ink 309 therein, a supply unit 305 to which the main tank 304 is detachably mounted, and a supply tube 306. A recording head 301.

  The supply unit 305 has an ink chamber 305f therein. The ink chamber 305f is opened to the atmosphere through the atmosphere port 305g, and is connected to the supply tube 306 at the bottom of the ink chamber 305f. The supply unit 305 is fixed with a hollow ink supply needle 305a and an air introduction needle 305b each having a lower end located in the ink chamber 305f and an upper end protruding from the upper surface of the supply unit 305. The lower end of the ink supply needle 305a is at a position lower than the lower end of the air introduction needle 305b.

  The main tank 304 has two connector portions composed of rubber plugs or the like for sealing the inside of the main tank 304 at the bottom, and the main tank 304 alone has a sealing structure. When the main tank 304 is attached to the supply unit 305, the ink supply needle 305a and the air introduction needle 305b are attached so as to penetrate the connector portion and enter the main tank 304, respectively. Since the position of the lower end of the ink supply needle 305b and the position of the lower end of the air introduction needle 305b are set as described above, the ink in the main tank 304 is supplied to the ink chamber 305f via the ink supply needle 305a. The air is introduced into the main tank 304 via the air introduction needle 305b so as to compensate for the decrease in the pressure in the main tank 304 due to the above. When the ink is supplied into the ink chamber 305f to the position where the lower end of the air introduction needle 305b is immersed in the ink, the air is not introduced into the main tank 304. Therefore, the ink is supplied from the main tank 304 to the ink chamber 305f. Stops.

  The recording head 301 includes a sub tank unit 301b that stores a certain amount of ink as an ink storage unit, an ink discharge unit 301g in which a plurality of nozzles that discharge ink are arranged, and a flow that connects the sub tank unit 301b and the ink discharge unit 301g. Road 301f. In the ink ejection part 301g, the opening surface of the nozzle faces downward, and the ink is ejected downward. The energy generating means described above is provided in each nozzle of the ink discharge portion 301g. The sub tank portion 301b is located above the ink discharge portion 301g, and the supply tube 306 is connected to the sub tank portion 301b. A filter 301c having a fine mesh structure is attached between the sub tank portion 301b and the flow path 301f in order to prevent nozzle clogging caused by fine foreign matter in the ink entering the ink discharge portion 301g. It has been.

  The area of the filter 301c is set so that the pressure loss due to ink is less than the allowable value. The pressure loss in the filter 301c increases as the mesh of the filter 301c becomes finer and the flow rate of ink passing through the filter 301c increases. Conversely, the area of the filter 301c is inversely proportional. In recent high-speed, multi-nozzle, small-dot recording heads, the pressure loss tends to increase. Therefore, the area of the filter 301c is made as large as possible to suppress an increase in pressure loss.

  An elastic member 321 whose outer shape is a substantially rectangular parallelepiped is formed on the upper surface of the recording head 301 in order to form a pressure adjusting chamber 322 that absorbs a sudden pressure change in the sub tank portion 301b and adjusts the pressure in the sub tank portion 301b. Is attached. The pressure adjustment chamber 322 communicates only with the inside of the sub tank portion 301b through an opening 301d formed in the upper wall portion of the recording head 301. When the elastic member 321 is deformed in accordance with the change in the pressure in the sub tank portion 301b, the volume of the pressure adjusting chamber 322 is changed so that the pressure change in the sub tank portion 301b is absorbed. The cross-sectional shape of the elastic member 321 in the direction parallel to the top surface of the recording head 301 is approximately the same as or smaller than the top surface of the recording head 301. Therefore, a certain height is required to secure a necessary volume of the pressure adjustment chamber 322.

  Since the nozzles of the ink discharge unit 301g are open to the atmosphere and the opening surfaces of the nozzles are arranged facing downward, the inside of the recording head 301 is arranged to prevent ink leakage from the nozzles. It must be kept at negative pressure. On the other hand, if the negative pressure is too large, air enters the nozzle and ink cannot be ejected from the nozzle. Therefore, in order to set the inside of the recording head 301 to an appropriate negative pressure state, the recording head 301 is set such that the position of the opening surface of the nozzle is higher than the liquid level of the ink in the ink chamber 305f by the height H. And the inside of the recording head 301 is maintained at a negative pressure of a head differential of height H. As a result, the nozzle is kept in a state of being filled with ink while a meniscus is formed on the opening surface.

  Ink is ejected from the nozzles by pushing out the ink in the nozzles by driving the energy generating means. After ink ejection, the nozzle is filled with ink by capillary force. During the recording operation, the ejection of ink from the nozzles and the filling of the ink into the nozzles are repeated, and the ink is sucked up from the ink chamber 305f as needed through the supply tube 306.

  When the ink in the ink chamber 305f is sucked up by the recording head 301 and the liquid level of the ink in the ink chamber 305f becomes lower than the lower end of the air introduction needle 305b, the atmosphere enters the main tank 304 via the air introduction needle 305b. As a result, the ink in the main tank 304 is supplied to the ink chamber 305f, and the lower end of the air introduction needle 305b is immersed in the ink in the ink chamber 305f again. While repeating these behaviors, the ink in the main tank 304 is supplied to the recording head 301 as the ink is ejected from the recording head 301.

  By the way, in the sub tank portion 301b of the recording head 301, air that has penetrated through the resin material such as the supply tube 306 and air dissolved in the ink gradually accumulate. In order to discharge excess air accumulated in the sub tank portion 301b, an exhaust tube 310a connected to the exhaust pump 310c is connected to the sub tank portion 301b. However, as described above, in order to keep the inside of the recording head 301 at a moderate negative pressure state, the exhaust tube 310a is provided with the valve 310b. By opening the valve 310b only during the exhaust operation, the inside of the recording head 301 is large. It is trying not to become atmospheric pressure.

  In order to remove ink thickeners in the ink discharge part 301g or when air dissolved in the ink of the ink discharge part 301g is accumulated to form bubbles. In the ink jet recording apparatus, a recovery unit 307 is generally provided. The recovery unit 307 includes a cap 307a for capping the nozzle opening surface of the recording head 301, and a suction pump 307c to which the cap 307b is connected, and the suction pump 307c with the nozzle opening surface capped by the cap 307a. And the ink in the recording head 301 is forcibly sucked to remove the ink thickener and excess bubbles from the ink discharge portion 301g.

  In this suction recovery operation, if the ink flow rate is high, ink thickeners and excess bubbles can be effectively removed. Therefore, in order to increase the ink flow rate in the flow channel 301f, The cross-sectional area is reduced. On the other hand, as described above, since the cross-sectional area of the filter 301c is set as large as possible, the flow path has a shape with a reduced cross-sectional area under the filter 301c.

  As described above, the conventional ink supply system has been described by taking the tube supply method as an example. However, the head integrated method and the pit-in method also differ only in the structure related to the ink supply path from the ink tank to the recording head. The structure below the filter is basically the same as the tube supply system.

  On the other hand, in a general color inkjet recording apparatus, a color is formed on a recording medium by subtractive color mixing using cyan ink, magenta ink, and yellow ink. Furthermore, in order to improve the color developability of the image, in addition to the above three primary colors, ink for enhancing gradation such as black ink, light cyan ink, light magenta ink, light yellow ink, red ink, green Ink for expanding the color reproduction range such as ink, blue ink, orange ink, violet ink and the like is used. Therefore, the ink jet recording head has a configuration of one color ink droplet ejecting section in one head, or in the case of color, one head has a configuration of plural color ink droplet ejecting sections, and this head is mounted on the ink jet recording apparatus. Color recording is realized with this. Therefore, when the recording head 301 shown in FIG. 14 is for color, each of the ink ejection part 301g, the flow path 301f, the sub tank part 301b, and the pressure adjustment chamber 322 corresponds to the number of ink colors. A plurality of recording heads 301 are provided in parallel.

For example, Patent Document 1 and Patent Document 2 can be cited as conventional examples.
Japanese Patent Laid-Open No. 2002-1988 JP 2005-103858 A

  However, when the elastic member 321 is attached so as to provide the pressure adjusting chamber 322 for the sub tank portion 301b in the recording head 301 as in the ink supply system shown in FIG. 14, in order to ensure the maximum volume of the elastic member 321. It is desirable that the rectangular shape is a rectangular parallelepiped. However, in the case of the rectangular parallelepiped shape, when the atmospheric pressure in the elastic member 321 becomes negative, the deformed shape of the elastic member 321 is not stable because the surface of the contracting rectangular parallelepiped is not always constant. For this reason, since the deformed shape of the elastic member 321 changes irregularly, the relationship between the reduced air volume in the elastic member 321 and the negative pressure in the pressure adjusting chamber 322 becomes unstable.

  This will be described with reference to FIG. However, since the numerical values of the X axis and the Y axis are one example, the content of the present invention is not limited to these numerical values.

  In FIG. 8, a straight line A is a case where the reduced air volume in the elastic member 321 and the negative pressure in the pressure adjusting chamber 322 show an ideal relationship. That is, when the volume in the elastic member 321 decreases, a negative pressure in the pressure adjusting chamber 322 is generated at that rate, and a correlation is established. In this case, when the negative pressure in the pressure adjustment chamber 322 decreases, the volume in the elastic member 321 increases accordingly. Thus, when the amount of change in the internal volume of the elastic member 321 and the negative pressure in the pressure adjustment chamber 322 are in a hysteresis relationship, the response of the pressure adjustment chamber 322 to the change in the pressure in the sub-tank portion 301b is always stable. Thus, the ink supply state to the ink discharge unit 301g is also stabilized, and thus the print image is less affected.

  However, when the elastic member 321 becomes difficult to contract at a point in time when the elastic member 321 is deformed, the negative pressure in the pressure adjusting chamber 322 increases rapidly as indicated by the curve B. As a result, the supply of ink to the ink discharge unit 301g cannot keep up with the ink consumption due to printing, and the print density may be adversely affected. For example, the negative pressure in the pressure adjustment chamber 322 may decrease. There is a need to refrain from ejecting ink from the ink ejection part 301g until it decreases. If this is ignored and the temperature rises further, air from the atmosphere enters the nozzles of the ink ejection part 301g, resulting in a non-ejection state where ink is not ejected from the nozzles.

  If the elastic member 321 becomes unstable because it becomes difficult to contract from a certain point in time, the negative pressure in the pressure adjusting chamber 322 becomes unstable in the section I as shown by the curve C. In Section II, the negative pressure rises rapidly. In such a case, the supply of ink to the ink discharge unit 301g becomes unstable, the printed image is disturbed, and finally the discharge state is not achieved. Since the elastic member 321 having such characteristics does not necessarily increase the volume in the elastic member 321 when the negative pressure in the pressure adjusting chamber 322 decreases, the elastic member 321 does not respond to changes in the pressure in the sub tank portion 301b. Responsiveness will not be stable.

  Further, as a further problem of the rectangular parallelepiped elastic member 321, there is a phenomenon that when the inside of the elastic member 321 is in a pressurized state, it interferes with the adjacent elastic member 321.

  An object of the present invention is to provide a compact and simple structure capable of maximizing the functions of a pressure adjusting chamber in a pressure adjusting chamber using an elastically deformable member provided for adjusting a gas pressure in a container. Another object of the present invention is to provide a low-cost elastic member, a recording head having a pressure adjusting chamber using the elastic member, and an ink jet recording apparatus having the recording head.

  In order to achieve the above object, in the present invention, the elastic member 321 may be selected so that the straight line A or the curve D close to the property of the straight line A is obtained. The elastic member is to provide an elastic member having the property of, for example, the straight line A or the curve D in FIG. 8, that is, an elastic member having stable hysteresis. Therefore, according to the present invention, the pressure adjusting chamber for adjusting the gas pressure in the container has at least one elastically deformable member whose volume can be changed according to the gas pressure, and this shape is a single substantially circular opening. Elastic deformation in which the surface and the outer peripheral surface have two surfaces that are substantially flat before deformation, and the two surfaces are connected in a substantially symmetrical arrangement via a curved surface at the tip on the opposite side of the opening. In the member, the inner surface side of the ridge line portion of the outer surface shape is provided with a thick wall portion thicker than the other thickness of the elastically deformable member. Specifically, a rib shape is preferable.

  As a next invention, a tank portion in which a plurality of ink storage portions for individually storing ink is formed, and recording is performed by ejecting ink supplied from the ink storage portion, each corresponding to each ink storage portion. The ink discharge section and the tank section are attached so as to form a plurality of pressure adjustment chambers corresponding to the respective ink storage sections so as to adjust the pressure in the ink storage section. A recording head having a plurality of elastically deforming portions has a substantially circular opening portion and two substantially flat surfaces on the outer peripheral surface before deformation, and these two surfaces are open. In the elastically deforming part connected in a substantially symmetrical arrangement via the curved surface part at the tip part opposite to the part, the inner wall side of the ridge line part of the outer surface shape has a thick wall part thicker than the other thickness of the elastically deforming member. It is characterized by providing. Specifically, a rib shape is preferable.

  In the above-described invention, in the recording head having the tank portion in which the plurality of ink storage portions are formed, the plurality of elastic deformation portions that are attached to the upper portion of the tank portion and form the respective pressure adjustment chambers are, for example, the elastic deformation portions. The shape of the bottom surface on the ink storage portion side is circular, and each elastic deformation portion has two substantially flat surfaces on the outer peripheral surface before deformation, and these two surfaces are the ink storage portion of the elastic deformation portion. It can be made into the shape (what is called a "hat hat" shape) connected with the front-end | tip part on the opposite side through the curved surface part. Furthermore, when the elastic deformation portion is deformed by making the inner surface side of the ridge line portion of the outer surface portion of such an elastic deformation portion shape thicker than the other thickness of the elastic deformation member, specifically, a rib shape. In addition, since the deformation always starts to be crushed from two surfaces, the deformation state is particularly stable. As a result, the time for deformation each time becomes constant, and the responsiveness of the function of the pressure adjusting chamber is stabilized. Accordingly, in the recording head configured to adjust the pressure in the plurality of ink storage units arranged in parallel to store the ink to be supplied to the plurality of ink ejection units, by using each pressure adjustment chamber whose volume can be changed, each pressure The function of the adjustment chamber is stabilized and the function can be maximized.

  In addition, an ink jet recording apparatus of the present invention includes a carriage mounted with the recording head having any one of the above-described configurations and reciprocatingly moved on a straight line, and a recording medium that receives ink ejected from the ink ejection unit of the recording head. Conveying means for conveying the sheet in a direction orthogonal to the moving direction of the carriage.

  Since the above-described ink jet recording apparatus is equipped with a compact recording head as described above, the ink jet recording apparatus main body is also compact, which is desirable for the user as a product. The cost of the ink jet recording apparatus can be reduced.

  As described above, according to the present invention, in the pressure adjusting chamber having at least one elastically deforming portion whose volume can be changed according to the gas pressure so as to adjust the gas pressure in the container, the shape of the elastically deforming portion is uniform. It is composed of two substantially circular openings and two substantially flat surfaces on the outer peripheral surface before being deformed, and these two surfaces are connected via a curved surface portion at the tip opposite to the opening. By having such a shape, it is possible to stabilize the function of the pressure adjusting chamber and to maximize the function. Further, in a recording head having a pressure adjusting chamber employing this elastic deformation portion, in the above arrangement of elastic deformation portions, when the bottom shape of the elastic deformation portion is circular, a narrow ink storage portion or a width Since the diameter of the bottom surface of the elastically deformable portion can be increased even with respect to the ink storage portion where the ink storage is restricted, the tank portion having a plurality of ink storage portions can be stored compactly, and the recording head can be made compact Accordingly, there is an effect that the main body of the ink jet recording apparatus is also made compact. Further, since the bottom surface of the elastically deforming portion can be made large as described above, the possibility is widened even when searching for the shape of the elastically deforming portion that can maximize the function of the pressure adjusting chamber.

  Since the ink jet recording apparatus of the present invention is equipped with a compact recording head as described above, the ink jet recording apparatus main body is also compact, which is desirable for the user as a product. The cost of the ink jet recording apparatus can be reduced.

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view showing a schematic configuration of an ink jet recording apparatus according to an embodiment of the present invention.

  The ink jet recording apparatus shown in FIG. 1 repeats the reciprocating movement (main scanning) of the recording head 201 and the conveyance (sub scanning) of recording sheets S such as general recording paper, special paper, and OHP film at a predetermined pitch. In a serial type recording apparatus that forms characters, symbols, images, and the like by selectively ejecting ink from the recording head 201 in synchronization with these movements and attaching the ink to the recording sheet S as a recording medium. is there.

  In FIG. 1, a recording head 201 is detachably mounted on a carriage 202 that is slidably supported by two guide rails and is reciprocated on a straight line along a guide rail by a driving means such as a motor (not shown). ing. The recording sheet S that receives ink ejected from the ink ejection section of the recording head 201 is opposed to the ink ejection surface of the recording head 201 by a conveyance roller 203 that is a conveyance means, and the distance from the ink ejection surface is constant. So that the carriage 202 is moved in a direction intersecting with the moving direction of the carriage 202 (for example, an arrow A direction which is an orthogonal direction).

  The recording head 201 includes a plurality of nozzle rows for ejecting different colors of ink as a plurality of ink ejection units. A plurality of independent main tanks 204 are detachably attached to the ink supply unit 205 corresponding to the color of ink ejected from the recording head 201. The ink supply unit 205 and the recording head 201 are connected to each other by a plurality of ink supply tubes 206 corresponding to the colors of the ink, and the main tank 204 is mounted on the ink supply unit 205 so that the ink is stored in the main tank 204. Each color ink can be independently supplied to each nozzle row of the recording head 201.

  A recovery unit 207 is disposed so as to face the ink ejection surface of the recording head 201 in a non-recording area that is within the reciprocal movement range of the recording head 201 and outside the passing range of the recording sheet S. Yes. The recovery unit 207 includes a cap unit for capping the ink ejection surface of the recording head 201, a suction mechanism for forcibly sucking ink from the recording head 201 with the ink ejection port surface capped, and contamination of the ink ejection surface. And a cleaning blade for wiping off. The suction operation described above is performed by the recovery unit 207 prior to the recording operation of the ink jet recording apparatus.

  As a result, when the ink jet recording apparatus is operated after being left for a long period of time, the recovery unit 207 sucks the high-density ink present at the bottom of the main tank 204, and in actual recording, the ink is stirred and the density is increased. However, stable ink is used. Therefore, even if the ink jet recording apparatus is not used for a long period of time, for example, the pigment component in the ink and the resin fine particles for improving the fixing property to the recording sheet S are settled at the bottom of the ink tank 204, It is possible to satisfactorily form a high-quality image with a stable concentration of these pigment components and resin fine particles.

  Here, a serial type ink jet recording apparatus has been described as an example. However, a line type ink jet recording head in which a nozzle array is provided over the entire width in the width direction of the recording medium is used as long as the recording head has suction means. The present invention can also be applied to an inkjet recording apparatus to be mounted.

  FIG. 2 is a sectional side view of the recording head 201 mounted on the carriage 202 shown in FIG. FIG. 3 is an exploded perspective view showing a part of the recording head 201. FIG. 4 is a perspective view of the recording head 201 in a state before the head substrate is attached to the front surface of the recording head 201. FIG. 5 is a perspective view of an embodiment showing an elastic member, a pressing member, and a sub tank cover provided in the recording head 201. 5A is a perspective view of the elastic member and the pressing member, FIG. 5B is an exploded perspective view, and FIG. 5C is a state in which a plurality of elastic members are attached to the sub tank cover by the pressing member and mounting screws. FIG. FIG. 6 is a plan view showing an arrangement of a plurality of sub tanks in the recording head 201. FIG. 7 is a plan view showing a state in which the elastic member and the sub tank cover are attached to the head main body.

  The shape of the recording head 201 of the present embodiment is composed of approximately six surfaces including an upper surface 40, a lower surface 41, a front surface 42, a rear surface 43, a right side surface and a left side surface, and is integrally formed except for the upper surface 40 side. In addition, the recording head 201 of the present embodiment is capable of discharging six colors of ink, and each color of ink is drawn from the main tank 204 via the needle of a needle holding member connected to the needle receiving portion 23 for each color. As shown in FIG. 6, it is configured to be supplied into each of the six sub tanks 36 formed as ink storage portions by being partitioned by the partition 50 of the head body 3. The ink supplied to the sub tank 36 is temporarily stored in the ink reservoir 21 through the filter 5 for removing impurities (foreign matter) in the ink and filtering the ink. Then, it flows into the liquid chamber 20 through the communication portion 37 and the flow path 6. The ink that has flowed into the liquid chamber 20 is shown in FIG. 4 due to foaming energy generated by an electrothermal transducer (not shown) that converts electrical energy supplied from the heater board 26 provided on the lower surface 41 into thermal energy. Are discharged from a plurality of discharge ports 29 arranged in parallel for each color. The heater board 26 is provided with a plurality of ink discharge portions each composed of a nozzle row corresponding to each color of ink, that is, corresponding to each sub-tank 36, and the tip of each nozzle serves as a discharge port 29 as a heater. An opening is formed on the surface of the board 26.

  Above the plurality of sub-tanks 36, the sub-tank 36 is formed of an elastic member 10 such as rubber that is an elastically deforming portion communicating with the inside of the sub-tank 36 by an air hole 38 formed as an opening in the sub-tank lid 9. A plurality of pressure adjusting chambers 8 for absorbing a sudden pressure change are provided corresponding to each sub tank 36. In the present embodiment, a plurality of individual elastic members 10 corresponding to the respective sub tanks 36 are used so as to form a plurality of pressure adjusting chambers 8. However, a shape in which they are integrated, that is, a plurality of elastic deformation portions. The plurality of pressure adjusting chambers 8 may be formed using an elastic member having a shape. The shape of each elastic member 10 is a dome shape, and the volume of the pressure adjusting chamber 8, which is a space surrounded by the elastic member 10, varies with the deformation of the elastic member 10 according to the pressure in the sub tank 36. As a result, the pressure in the sub tank 36 is adjusted as will be described later.

  Therefore, the tank portion is constituted by the wall portion for forming the plurality of sub tanks 36 in the head main body 3 and the sub tank lid 9. Therefore, the inside of the tank part is divided into six sub tanks 36 by the five partition walls 50, and a plurality of elastic members 10 are provided on the upper wall part of the tank part, that is, the sub tank cover 9 so as to cover the air holes 38. It is attached.

  In order to protect the elastic member 10, the sub tank cover 7 is attached above the elastic member 10. The sub tank cover 7 includes a rib 15 formed integrally with the sub tank cover 7 so as to extend from the front surface 42 toward the rear surface 43 of the recording head 201, and the sub tank cover 7 so as to extend in a direction intersecting the rib 15. And a reinforcing rib 14 formed integrally. The rib 15 has a function of increasing the rigidity of the recording head 201 in the front-rear direction from the front surface 42 toward the rear surface 43 together with the partition 50 that partitions the sub tank 36, the ink reservoir 21, the flow path 6, and the liquid chamber 20 for each color. Further, the rigidity in the left-right direction, which is the direction perpendicular to the side surface of the recording head 201, is ensured by the reinforcing ribs 14 of the sub tank cover 7 and the sub tank lid 9.

  As shown in FIG. 3 and FIGS. 5 (a) to 5 (b), each elastic member 10 includes the sub tank lid 9 and the plurality of elastic members 10 so that the plurality of elastic members 10 are pressed against the sub tank lid 9 by the pressing member 11. Are attached to the sub-tank lid 9 by means of mounting screws 12. As shown in FIG. 3, the sub-tank lid 9 assembled with the plurality of elastic members 10 is inserted into the recess 3 a of the head main body 3, whereby a plurality of sub-tanks 36 are formed in the recording head 201. Has been. As shown in FIG. 6, a plurality of partition walls 50 are formed in the head body 3 so that the plurality of sub tanks 36 are arranged in parallel, and the shape of each sub tank 36 is a rectangular parallelepiped shape extending long in a direction orthogonal to the arrangement direction. It has become. A plurality of air holes 38 corresponding to each sub tank 36 are formed in the sub tank lid 9, and each air hole 38 communicates with the corresponding sub tank 36. The plurality of air holes 38 are arranged in a staggered manner so that the plurality of elastic members 10 are arranged in the arrangement direction of the sub-tanks 36 and in the direction orthogonal to or intersecting with the arrangement direction, as will be described later with reference to FIG. Has been.

  The partition wall 50 is integrally formed with the main body of the cartridge 3 so as to connect the front surface 42 and the rear surface 43. Further, since the longitudinal direction of the partition wall 50 is substantially orthogonal to the scanning direction of the carriage 202, the ink oscillation in the sub tank 36 or the liquid chamber 20 due to vibration during the scanning of the carriage 202 is minimized. be able to.

  A head substrate 35 is attached to the front surface 42 of the recording head 201, which is the opposite surface of the rear surface 43 where the needle receiving portion 23 is provided, and which is the back surface side when the recording apparatus main body is installed. A plurality of electrodes 4 that are electrically connected by being pressed against the plurality of electrodes provided on the carriage 202 are provided on the head substrate 35 as shown in FIG. The head substrate 35 is electrically connected to the heater board 26 by the flexible substrate 16 as shown in FIG.

  Next, the operation of the pressure adjustment chamber 8 will be described in detail.

  The pressure adjustment chamber 8 is a chamber whose volume is reduced as the internal negative pressure increases. When the pressure adjustment chamber 8 is constituted by the elastic member 10 as in the present embodiment, the elastic member 10 is a rubber material. Etc. are preferably used. Further, in addition to the elastic member 10, a combination of a plastic sheet and a spring may be used. The volume of the pressure adjusting chamber 8 is set according to the environmental temperature in which the recording head 201 is used, the volume of the sub tank 36, and the like. In this embodiment, it is about 0.5 ml.

  When the pressure adjusting chamber 8 is not provided, the pressure in the sub tank 36 directly receives resistance due to pressure loss when ink passes through the main tank 204, the ink supply unit 205, and the ink supply tube 206. Therefore, in the case of so-called high duty discharge in which ink is discharged at a high ratio with respect to the total number of nozzles, for example, ink is discharged from all nozzles of the recording head 201, the discharged ink is supplied to the recording head 201. Ink becomes insufficient and the negative pressure rises rapidly. If the negative pressure in the nozzle of the recording head 201 exceeds a limit value of −200 mmAq (about −2.027 kPa: where the specific gravity of ink is equal to the specific gravity of water), ejection becomes unstable and printing is disturbed. This is inconvenient for image formation.

  In the serial type recording apparatus as in the present embodiment, there is a state in which the ejection of ink is interrupted when the carriage 202 (see FIG. 1) is reversed even in image formation with high duty ejection. By utilizing this, the pressure adjusting chamber 8 reduces the volume during ink discharge to alleviate the negative pressure rising time in the sub-tank 36, and increases the amount of ink supplied through the ink supply tube 206 during reversal. It plays a role like a capacitor.

  For example, if the rate of change in negative pressure with respect to the reduction in the volume of the pressure adjusting chamber 8 is K = −1.013 kPa / ml and the volume of the sub tank 36 is Vs = 2 ml, the ink supplied to the ejected ink is Consider a case where ΔV = 0.05 ml is insufficient. In this case, if there is no pressure adjusting chamber 8, the change in the negative pressure in the sub-tank 36 is ΔP = Vs / (Vs + ΔV) −1 = −2.471 kPa based on the principle of “PV = constant”, and the limit value described above is obtained. Since it exceeds, discharge becomes unstable. On the other hand, when the pressure adjusting chamber 8 is provided, ΔP = K × ΔV = −0.051 kPa, which suppresses an increase in negative pressure and enables stable discharge.

  Further, when the recording head 201 is not used for a long time with the ink discharge port face capped by the cap portion of the recovery unit 207, depending on the temperature, the sub-tank 36 may be subject to thermal expansion or increase in vapor pressure. The pressure in 36 increases. As a result, ink leaks from the nozzles of the recording head 201, or the ink is pushed back to the ink tank 204 to be cut off from the ink in the sub tank 36.

  In such a case, the volume of the pressure adjustment chamber 8 is expanded by the action of the elastic member 10 to absorb the thermal expansion of the gas in the sub tank 36 and the increase in vapor pressure. Thereafter, before opening the cap portion of the recovery unit 207, the negative pressure in the sub-tank 36 is usually reduced by forcibly sucking ink from the recording head 201 with the ink discharge port surface capped. Return to value. This makes it possible to ensure stable printing.

  As described above, the pressure adjustment chamber 8 stabilizes ink ejection and suppresses the influence of pressure loss in the ink supply path from the main tank 204 to the recording head 201. Therefore, by adjusting the material of the pressure adjustment chamber 8, the ink supply tube 206 driven by the carriage 202 can also be used with a small diameter, which can contribute to reducing the load of movement of the carriage 202. Become.

  Next, the shape of the elastic member 10 will be described in detail. FIG. 9A is a side view showing the shape of a comparative example of the elastic member 10, and FIG. 9B is a top view of the elastic member 10. FIG. 10A is a side view showing the shape of a comparative example of the elastic member 10, and FIG. 10B is a top view of the elastic member 10. FIG. 11A is a side view showing the shape of a comparative example of the elastic member 10, and FIG. 11B is a top view of the elastic member 10. 12A is a side view showing the shape of a conventional example of the elastic member 10, FIG. 12B is a front view of the elastic member 10, and FIG. 12C is a top view of the elastic member 10. FIG. 13A is a side view showing the shape of one embodiment of the elastic member 10, FIG. 13B is a front view of the elastic member 10, and FIG. 13C is a top view of the elastic member 10. .

  In order to make the recording head 201 compact, it is preferable that the shape is a rectangular parallelepiped in order to secure a necessary volume of the pressure adjusting chamber 8. However, as described above, it is difficult to obtain a stable negative pressure characteristic with a rectangular parallelepiped shape.

  Next, it is possible to secure a large volume as in the comparative example shown in FIG. 10. The shape of the elastic member 90 is cylindrical, and the shape of the tip of the elastic member 90 is a hemispherical shape. The “shape” shape. As described above, when there is no flat surface on the outer peripheral surface of the elastic member 90, the position of the first collapse is not constant, and the shape of the collapse is not constant, so the negative pressure characteristic of the pressure adjusting chamber is stable. do not do. This is because the inner surface of the “dome-shaped” elastic member 90 is constituted by a concave surface other than the opening, and is not easily pulled when viewed from the inner surface. Therefore, it does not easily collapse to the inner surface unless there is any “trigger” such as “thinner thickness is thinner than others” or “creased”. It is considered that the above-mentioned phenomenon occurs because this “trigger” varies depending on the case.

  In order to improve it, it is to provide a hollow or a plane in a part like the elastic member 91 shown in FIG. 11 or 92 shown in FIG. With this shape, the elastic members 91 and 92 can always start to be deformed from a specific location.

  However, the reduction deformation is constant, but is not necessarily constant when the pressure inside the pressure adjusting chamber 8 rises. This is because there are many places that are easy to extrude when viewed from the inside.

  Therefore, as shown in FIG. 12A, FIG. 12B, FIG. 12C, and the like, the shape of the bottom surface of the elastic member 10 on the sub tank lid 9 side, that is, the opening is the above-described shape of the pressure adjusting chamber 8. It has a circular shape to maximize the functions. The elastic member 10 has two flat surfaces that are bilaterally symmetrical with respect to a straight line that passes through the center of the bottom surface of the elastic member 10 when viewed from the top surface so that the cross-sectional area of the pressure adjusting chamber 8 decreases upward from the bottom surface. The elastic member 10 extends upward from the sub tank lid 9 so that the elastic member 10 has the outer peripheral surface 10a. The two flat surfaces 10a are flat in a state before the elastic member 10 is deformed, and are connected via a tip portion 10b extending on a straight line parallel to the bottom surface of the elastic member 10. That is, the elastic member 10 has a so-called “hat” shape before deformation, and the surface of the tip portion 10b is a curved surface. Accordingly, the two flat surfaces 10a form the same angle as the bottom surface of the elastic member 10, and the distance between the flat surfaces 10a gradually decreases upward from the bottom surface side of the elastic member 10 to the tip portion 10b. ing. The length in the longitudinal direction parallel to the bottom surface of the elastic member 10 at the distal end portion 10b may be substantially the same as the diameter of the bottom surface, or may be larger than the diameter, but larger than the diameter. This makes it possible to increase the volume of the pressure adjusting chamber 8.

  In the elastic member 10 having such a shape, when the elastic member 10 is deformed so that the volume of the pressure adjusting chamber 8 is reduced, the substantially central portions of the flat surfaces 10a are recessed from the flat surface 10a so as to approach each other. Will go. At this time, since the elastic member 10 has the two flat surfaces 10a on the outer peripheral surface, the elastic member 10 is surely crushed from the flat surface 10a. At this time, in order to surely collapse the flat surface 10a, if the thick wall portion is provided around the flat surface 10a, that is, on the back surface side of the ridge line portion (inside the elastic member 10), the elastic member 10 The shape to be crushed is substantially constant, and the shape to be restored by providing the flat surface 10a substantially symmetrically about the tip 10b is also substantially constant, so that the negative pressure characteristic of the pressure adjusting chamber 8 is stable. Will do.

  In the present embodiment, the elastic member 10 having such a shape that the negative pressure characteristic of the pressure adjusting chamber 8 is stabilized can be attached to the sub tank lid 9 while ensuring a sufficient volume of the pressure adjusting chamber 8. In addition, the plurality of elastic members 10 are arranged not only in the arrangement direction of the sub tanks 36 but also in a direction intersecting with the arrangement direction. That is, the pressure regulation chamber 8 on the sub tank 36 is divided in each of the arrangement direction of the sub tanks 36 and the direction intersecting the arrangement direction. Such an arrangement of the elastic members 10 allows each elastic member 10 to be disposed over at least two sub-tanks 36. As a result, each sub-tank 35 having a narrow width or each sub-tank 36 having a limited width is provided. In contrast, the diameter of the bottom surface of the elastic member 10 can be made larger. In order to realize such an arrangement of the elastic members 10, the air holes 38 are arranged in a staggered manner as shown in FIGS. 6 and 7. The shape of each air hole 38 is preferably a half-moon shape because each elastic member 10 straddles the upper part of the two sub tanks 36.

  In FIG. 7, the elastic members 10 are arranged so that the distal end portions 10 b of the elastic members 10 are perpendicular to the arrangement direction of the sub tanks 36. On the other hand, when the length of the tip portion 10b is made larger than the diameter of the bottom surface of the elastic member 10 to increase the volume of the elastic member 10, each tip as shown in FIGS. The portion 10b may be inclined with respect to the arrangement direction of the sub tanks 36. Depending on the positional relationship between the elastic member 10 and the mounting screw 12, the angle of each tip 10b with respect to the arrangement direction of the sub tanks 36 may be set so that the mounting screw 12 can be easily tightened. In the example shown in FIG. 7, the elastic members 10 are arranged so that the attachment screws 12 can be easily attached.

  The shape of the elastic member 10 is not limited to those shown in FIGS. 3, 5, and 9. The elastic member 10 may have any shape as long as the deformation of the elastic member 10 is stable and the deformation is constant and the above function of the pressure adjusting chamber 8 is sufficiently extracted. Further, the size of the elastic member 10 may be appropriately determined according to the configuration of the recording head 201 and the configuration of the ink supply system.

  In the configuration in which the elastic members 10 are arranged in both the direction in which the sub tanks 36 are arranged and the direction intersecting the arrangement direction as described above, even if the width of each sub tank 36 is narrow, the negative pressure characteristics of the pressure adjusting chamber 8 are reduced. Can be provided corresponding to each sub-tank 36. Therefore, the recording head 201 having the plurality of sub tanks 36 can be accommodated in a compact manner, and the function of the pressure adjustment chamber 8 can be maximized. Further, as the recording head 201 is made compact, the main body of the ink jet recording apparatus becomes compact, which is desirable for the user as a product. In addition, the cost of the recording head 201 and the ink jet recording apparatus can be reduced.

1 is a perspective view illustrating a schematic configuration of an ink jet recording apparatus according to an embodiment of the present invention. FIG. 2 is a side sectional view of a recording head mounted on a carriage shown in FIG. 1. FIG. 3 is a perspective view showing a part of the recording head in an exploded manner. FIG. 3 is a perspective view of the recording head in a state before the head substrate is attached to the front surface of the recording head. FIG. 5 is a perspective view showing an elastic member, a pressing member, and a sub tank cover provided in the recording head. FIG. 4 is a plan view showing an arrangement of a plurality of sub tanks in the recording head. It is a top view which shows the state which attached the elastic member and the sub tank cover to the head main body. It is a graph for demonstrating the characteristic of the elastic member attached to the pressure regulation chamber. 6A and 6B are a side view and a top view illustrating a comparative example shape of an elastic member provided in the recording head. It is the side view and top view which show the comparative example of the elastic member shown by FIG. It is the side view and top view which show the comparative example of the elastic member shown by FIG. FIG. 6 is a side view, a front view, and a top view showing a conventional shape of an elastic member provided in a recording head. FIG. 4 is a side view, a front view, and a top view showing an embodiment of an elastic member provided in the recording head. It is a figure which shows typically the ink supply system of the conventional inkjet recording device of a tube supply system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Head main body 3a Concave part 4 Electrode 5 Filter 6 Flow path 7 Sub tank cover 8 Pressure adjustment chamber 9 Sub tank cover 10, 90, 91, 92 Elastic member 10a Flat surface 10b Tip part 11 Holding member 12 Mounting screw 14 Reinforcement rib 15 Rib 16 Flexible Substrate 20 Liquid chamber 21 Ink reservoir 23 Needle receiving portion 26 Heater board 29 Discharge port 35 Head substrate 36 Sub tank 37 Communication portion 38 Air hole 40 Upper surface 41 Lower surface 42 Front surface 43 Rear surface 50 Partition wall 60 Thick wall portion 201 Recording head 202 Carriage 203 Transport roller 204 Main tank 205 Ink supply unit 206 Ink supply tube 207 Recovery unit S Recording sheet

Claims (4)

The pressure adjustment chamber that adjusts the gas pressure in the container has at least one elastic deformation member whose volume can be changed according to the gas pressure, and this shape is deformed into one substantially circular opening and outer peripheral surface. In the elastic deformation member having two surfaces that are substantially flat in the previous state, and these two surfaces are connected in a substantially symmetrical arrangement through the curved surface portion at the tip portion opposite to the opening portion,
A pressure adjusting chamber, wherein a thick wall portion thicker than the other thickness of the elastically deforming member is provided on an inner surface side of a ridge line portion of an outer surface shape.   The pressure adjusting chamber according to claim 1, wherein the thick wall portion has a rib shape. A tank portion formed with a plurality of ink storage portions for individually storing ink, recording by discharging ink supplied from the ink storage portion, and a plurality of ink discharge portions each corresponding to each ink storage portion; A plurality of elastic deformation portions attached to the tank portion so as to form a plurality of pressure adjustment chambers corresponding to the respective ink storage portions so as to adjust the pressure in the ink storage portion so that the volume can be changed according to the pressure. A recording head having a substantially circular shape and two substantially flat surfaces on the outer peripheral surface before deformation, and these two surfaces are opposite to the opening. In the elastically deforming part connected in a substantially symmetrical arrangement through the curved surface part at the tip part on the side,
A recording head characterized in that a thick wall portion thicker than the other thickness of the elastically deformable member is provided on the inner surface side of the ridge line portion of the outer surface shape.   The recording head according to claim 3, wherein the thick wall portion has a rib shape.

Images