JP5418331B2 - Droplet discharge apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a droplet discharge apparatus and an image forming apparatus provided with a recording head that discharges a liquid to form various patterns.

For example, as an image forming apparatus such as a printer, a facsimile machine, a copying machine, a plotter, and a complex machine of these, an ink jet type (liquid discharge recording type) image forming apparatus using a recording head for discharging ink droplets is known.
This ink jet type image forming apparatus means that ink droplets are transported from a recording head (not limited to paper, including OHP, etc., and ink droplets, other liquids, etc. can be attached, It is ejected onto a recording medium or recording medium, recording paper, recording paper, etc.) to form an image (recording, printing, printing, and printing are also used synonymously). .

  In this specification, “image forming apparatus” means an apparatus that forms an image by discharging liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, or the like. In addition, “image formation” not only applies an image having a meaning such as a character or a figure to a medium, but also applies an image having no meaning such as a pattern to the medium (simply applying a droplet). It also means landing on the medium. “Ink” is not limited to ink, but is used as a general term for all liquids capable of image formation, such as recording liquid, fixing processing liquid, and liquid. DNA samples, resists, pattern materials and the like are also included.

In such an ink jet image forming apparatus, it is necessary to stably supply ink in order to discharge ink reliably.
Here, in the off-carriage method in which the recording head and the ink cartridge are separated, the cartridge and the recording head are directly connected via a supply path. For this reason, when the pressure of the ink to be fed is small, the ink supply is not in time for the ejection of the recording head due to the pressure loss of the supply path (including the filter), resulting in ejection failure.

  For this reason, a technique is known in which a pump is provided in a tube connecting the recording head and the ink cartridge, a bypass path is connected to the upstream side and the downstream side of the pump, and a valve is interposed in the bypass path to cover pressure loss. It has been.

  Patent Document 1 discloses an ink supply path including a pump having a liquid feeding function by pressurization between an ink cartridge and a recording head, in parallel with the supply path, in order to improve ink pressure feeding efficiency. A configuration in which a supply detour having a valve mechanism for opening and closing is provided is disclosed. The ink supply bypass is used as an ink supply path when the recording head ejects ink, and a valve mechanism provided in the bypass is a control mechanism that selectively opens and closes the ink supply bypass.

  However, in the ink supply method in which a valve is provided in the above-described bypass path to cover the pressure loss, and in the above-described Patent Document 1, it is necessary to appropriately control the valve provided in the bypass path to maintain a desired pressure. For this reason, when applying to an image forming apparatus using a plurality of types of inks having different colors, it is required to control the valve and the pump for each color type of the ink. There was a problem that required complex control.

  The present invention has been made in view of such a situation, and even when a plurality of inks having different colors are used, the pump can be easily supplied without complicating the pumping amount according to the amount of ink consumed. Accordingly, it is an object of the present invention to provide a liquid droplet ejection apparatus and an image forming apparatus capable of maintaining a negative pressure in a recording head appropriately without causing refill shortage by a single pump control.

  In order to achieve such an object, a liquid droplet ejection apparatus according to the present invention includes a recording head having a nozzle for ejecting liquid droplets, a liquid tank that stores liquid to be supplied to the recording head, and supplies liquid to the recording head. The first flow path, the second flow path communicating with the liquid tank, the first flow path and the second flow path are communicated, and the internal flow is determined according to the flow rate of the liquid flowing through the first flow path. A liquid discharge surface of the recording head, comprising: a pressure adjusting valve whose path resistance changes; and a third flow path branched from the second flow path and connected to the pressure adjusting valve via a liquid feed pump. Is arranged at a position higher than the liquid level in the liquid tank, and the negative pressure of the recording head is maintained by the water head difference between the recording head and the liquid tank, and the pressure adjusting valve is housed in the housing and the housing, A valve body that moves according to the flow rate of the liquid flowing through the first flow path; The ding is disposed between the upper end connected to the first flow path, the lower end connected to the second flow path, and the upper end and the lower end, and the third flow path is connected The valve body has an axial shape, and has an upper portion disposed opposite to the upper end of the housing, a lower portion disposed opposite to the lower end of the housing, and a smaller diameter than the upper and lower portions. And is provided at the upper part of the valve body, and communicates the second flow path and the third flow path with the first flow path in the housing. It has a through hole and a protrusion provided on the outer periphery side of the through hole at the upper part of the valve body and projecting in the direction of movement of the valve body in the housing. It has an opening of the same shape as the protrusion, and the protrusion is open even when the valve body moves in the housing. The liquid that is pressurized by the liquid feed pump of the third flow path and pumped into the housing through the lateral hole passes only through the through hole provided in the upper part of the valve body. Then, it flows out to the first flow path.

  An image forming apparatus according to the present invention is the above-described liquid droplet ejection apparatus according to the present invention, wherein the liquid is ink.

  As described above, according to the present invention, even when a plurality of inks having different colors are used, a simple and single pump can be used without complicating the pumping amount according to the amount of ink consumed. By the control, the negative pressure in the recording head can be appropriately maintained without causing refill shortage.

It is a figure which shows the structural example of the inkjet printer as embodiment of this invention. It is a figure which shows the ink supply system in this embodiment. It is a figure for demonstrating the basic operation | movement principle of a flow-path resistance variable unit. FIG. 3 is a diagram showing a change in pressure of the recording head. It is sectional drawing of the flow-path resistance variable unit 83 as the 1st Embodiment of this invention. It is an expanded sectional view of the V section of Drawing 5 (c). FIG. 6 is an enlarged cross-sectional view of a V portion in FIG. 5C, showing a state where ink flows into the protrusion accommodating portion 201. It is a partial expanded sectional view which shows the structural example which added the air release port to 1st Embodiment. It is a partial expanded sectional view which shows the structural example which added the ink position detection apparatus to 1st Embodiment. It is sectional drawing of the flow-path resistance variable unit 83 as the 2nd Embodiment of this invention. It is an expanded sectional view of the W section of Drawing 10 (c). It is a partial expanded sectional view which shows the structural example which added the air release port to 2nd Embodiment. It is sectional drawing of the flow-path resistance variable unit 83 as the 3rd Embodiment of this invention. It is an expanded sectional view of the X section of Drawing 13 (c). It is sectional drawing of the flow-path resistance variable unit 83 as the 4th Embodiment of this invention. It is an enlarged view of the Y section of FIG. It is a partial expanded sectional view which shows another structural example of 4th Embodiment. It is a partial expanded sectional view which shows the 5th Embodiment of this invention.

  Next, an embodiment in which a droplet discharge device and an image forming apparatus according to the present invention are applied to an ink jet printer will be described in detail with reference to the drawings.

First, an outline of the present embodiment will be described.
The present embodiment has the following characteristics when the liquid in the cartridge is supplied to the recording head.
In this embodiment, a valve is provided between the cartridge and the recording head and a pump is provided so as to bypass the valve, and the pump is always in an ON state. The valve body (movable member) inside the valve moves according to the discharge flow rate of the recording head, and this movement reduces the gap between the valve body and the side wall in the housing, and the pressure is supplied from the liquid feed pump. Ink pressure increases. As a result, the pressure loss occurring in the supply path in the recording head direction is covered. Since it has such a feature, it is characterized by not requiring complicated pump control or a control mechanism.

Next, the configuration of the present embodiment will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing an ink jet printer as an embodiment of the present invention. 1A shows a front view of the ink jet printer, FIG. 1B shows a right side view, and FIG. 1C shows a plan view.

  The ink jet printer shown in FIG. 1 holds a carriage 120 slidably in a main scanning direction (guide rod longitudinal direction) by a guide rod 122 and a guide rail 128 which are guide members horizontally mounted on left and right side plates 123L and 123R. ing. The carriage 120 is moved and scanned in the longitudinal direction (main scanning direction) of the guide rod 122 by a main scanning motor and a timing belt (not shown).

  On the carriage 120, the recording heads 1 that eject ink droplets of a plurality of colors (for example, yellow, cyan, magenta, black, etc.) are arranged in a direction crossing the main scanning direction, and the ink droplet ejection direction is downward. It is attached towards. The recording head 1 is of a thermal type that obtains a discharge pressure by ink film boiling. There are various types of recording heads, such as those that use a piezoelectric element to deform the diaphragm or deform the diaphragm with an electrostatic force to obtain the discharge pressure. can do.

  A head tank 101 having an ink chamber for temporarily storing ink to be ejected is integrally connected to the upper portion of the recording head 1. The term “integrated” as used herein includes that the recording head 1 and the head tank 101 are connected by a tube, a pipe, or the like, and both are mounted on the carriage together. A liquid supply tube 16 is connected to the head tank 101, and the other end of the liquid supply tube 16 is connected to a cartridge holder 77 that is stationary on the main body. An ink cartridge 76, a pump unit 80, and a pressure control unit 81 are connected to the cartridge holder 77. As can be seen from FIG. 1, the pressure control unit 81 is disposed on the upper part of the ink cartridge 76, and includes a variable flow path resistance unit 83 inside.

Next, the ink supply system in the present embodiment will be described with reference to FIG.
FIG. 2 is a schematic diagram of an ink supply system in which the pressure control unit 81 and the pump unit 80 are connected in the present embodiment.

  The liquid supply tube 16 communicates with the ink cartridge 76 via the pressure control unit 81. The ink cartridge 76 is provided with an air communication portion 45, and the air communication portion 45 has a serpentine structure with a small inner diameter to suppress ink drying. The atmosphere communication portion 45 is not limited to a serpentine structure, and may have any configuration as long as drying can be suppressed. In addition, when ink or liquid that is resistant to drying is used, the air communication portion 45 does not have to have a drying suppression structure.

  By the way, the liquid surface in the ink cartridge 76 is disposed at a position (h) lower than the ink ejection surface 100 of the recording head 1. As a result, in a state where the ink is filled in the entire ink supply path, the recording head 1 is held at a negative pressure due to the water head difference h between the liquid levels of the recording head 1 and the ink cartridge 76. Can be discharged stably.

  The recording head 1 also prevents moisture drying when ink is not ejected, and at the same time removes bubbles in the recording head 1 and sucks ink in the recording head 1 when the nozzles are clogged. A cap 50 is provided. When the ink in the recording head 1 is sucked, the cap 50 is capped on the ink discharge surface 100 of the recording head 1, and the ink is guided to the waste liquid storage unit 52 by the suction pump 51. In addition, although the cap 50 uses both for moisturizing and for suction, you may comprise the cap which made each role independent. Further, the sucked ink may be returned to the ink cartridge 76 instead of the waste liquid storage unit 52.

  Further, the cap 50 may serve not only as a suction operation but also as an idle discharge receiver from the recording head 1. The wiper blade 71 is attached to the wiping unit 70, and the wiper blade 71 wipes the ink ejection surface 100 of the recording head 1 after maintenance, thereby adjusting the meniscus of the nozzle surface.

Next, the operation principle of the variable flow path resistance unit will be described with reference to FIG.
FIG. 3 shows a basic operating principle in an example of the variable flow path resistance unit 83 in the pressure control unit 81. Here, how the flow path resistance variable unit 83 changes the flow path resistance will be described.

The variable flow path resistance unit 83 includes a housing 40 and a movable valve (movable member) 88. A lateral hole 86 c is formed on the side surface of the housing 40, and the liquid feed pump 78 shown in FIG. 2 is connected to the lateral hole 86 c via the supply path 17. The liquid feed flow rate of the liquid feed pump 78 is larger than the maximum discharge flow rate of the recording head 1.
The movable valve 88 has an axial shape and is composed of at least three elements: an upper part 88t, a central part 88m, and a lower part 88b, and the diameter of the central part 88m is smaller than that of the lower part 88b. A through hole 84 is provided in the movable valve upper portion 88t.

  The movable valve 88 is movable inside the housing 40, and takes the form shown in FIG. 3 (a), FIG. 3 (b), or an intermediate state depending on the state of the internal flow. FIG. 3A shows the state of the variable flow path resistance unit 83 when the recording head 1 is stopped. In this state, the movable valve 88 is on the side of the port 86 b that is the lower end portion of the housing 40. This is because the gap Gb between the housing 40 and the movable valve lower portion 88b is larger than the through hole 84 formed in the housing 40 and the movable valve upper portion 88t, and beyond the port 86a that is the upper end portion of the housing 40. This is because there are the tube 16 and the filter 109 having a large fluid resistance as shown in FIG.

  As a result, the ink sent by the pump indicated by the arrow Qa flows easily, that is, flows to the port 86b side (in the direction of arrow A) where the fluid resistance is small, so that the movable valve lower portion 88b is forced to the port 86b side by the ink flow. Receive. In this state, even if the liquid feed pump 78 in the pump unit 80 continues to operate without stopping, the ink flows through the supply tubes 18 and 17 via the liquid feed pump 78 as shown by the arrow α in FIG. Only by circulation, the pressure of the pressurized ink is not applied to the recording head 1. In other words, when the ejection flow rate of the recording head 1 is small or non-ejection, the movable valve 88 moves in the direction of the port 86b, and the ink flow produced from the pump unit 80 can be released to the port 86b side. To do.

  FIG. 3B shows the state of the variable flow path resistance unit 83 under the condition that the recording head 1 is discharging. Since the gap Gt between the housing 40 and the movable valve upper portion 88t is made narrow, the fluid resistance is smaller in the through hole 84. Therefore, the ink discharged from the head passes through the through hole 84 as indicated by the arrow Qh. At this time, the ink flowing to the port 86 a side causes a pressure loss due to passing through the through hole 84. That is, the pressure of the ink passing through the through hole 84 and flowing on the port 86a side is smaller than the pressure of the ink flowing through the movable valve 88m. Due to this pressure difference, the movable valve upper portion 88t receives a force on the port 86a side. This force is greater than the force received on the port 86b side from the ink flowing on the port 86b side (arrow A direction) (because the pressure difference on the port 86a side> the pressure difference on the port 86b side). Therefore, the movable valve 88 moves to the port 86a side.

When the movable valve 88 moves to the port 86a side, the movable valve lower portion 88b overlaps the small diameter portion 400 of the housing 40, and the gap between the housing 40 and the movable valve lower portion 88b is smaller than the gap Gb in FIG. Gb ′ and the fluid resistance increases. This fluid resistance increases in proportion to the amount of movement of the movable valve 88 relative to the port 86a. That is, if the movable valve 88 moves to the port 86a side, the fluid resistance of the gap Gb ′ increases with the amount of movement. As the fluid resistance of the gap Gb ′ increases, the pressure difference of the ink flowing in the direction of the port 86b (arrow A direction) increases accordingly (because it is determined by pressure difference = fluid resistance × flow rate). Therefore, when the movable valve 88 moves toward the port 86a, the pressure difference of the gap Gb ′ catches up with the pressure difference (constant) due to the through hole 84.
From the pressure difference and the area ratio of the movable valve upper portion 88t and the movable valve lower portion 88b, the force received by the movable valve 88 on the port 86a side and the force received on the port 86b side at a certain point in the housing 40 are balanced. Thus, the movable valve 88 stops.

  By the way, when the fluid resistance of the gap Gb ′ is increased, the ink supplied by the liquid feeding pump 78 is less likely to flow in the direction of the port 86b (arrow A direction), and the pressure of the ink supplied from the liquid feeding pump 78 is movable. It increases within the valve 88 (because the maximum discharge flow rate of the recording head 1 <the supply flow rate of the liquid feed pump). The ink whose pressure has increased passes through the through hole 84 and flows toward the recording head 1. That is, the pressure of the ink supplied by the liquid feed pump 78 increases in the fluid resistance variable unit 83 and flows in the direction of the recording head 1, so that the pressure loss generated in the liquid supply tube 16 and the filter can be covered. I mean.

  When the discharge flow rate of the recording head 1 is small, the movable valve 88 is balanced in an intermediate state between FIGS. 3A and 3B according to the discharge flow rate.

  By repeating the above operation, the supply system can supply a stable pressure without causing refill shortage in the ink supply to the recording head 1 in the water head difference supply. In addition, this supply system has any flow rate that the recording head 1 can have, regardless of whether it is composed of different types of ink represented by yellow (Y), cyan (C), magenta (M), and black (Bk). Even when discharging, the control operation of the pump is the same.

  FIG. 4 shows the pressure change of the recording head 1 in this supply system. The vertical axis represents the pressure in the liquid chamber of the recording head 1, and the horizontal axis represents time. The pressure indicated by this pressure change is the gauge pressure, and the origin is the atmospheric pressure.

  The pressure of the recording head 1 increases when the liquid feed pump 78 is driven (step S1). This is because the pressure of the liquid feed pump 78 has propagated to the liquid chamber of the recording head 1 through the supply path. When the recording head 1 starts ejection (step S2), the pressure once decreases due to the inertia of the ink (P1), and then reaches a stable region. A difference between the pressure in the stable region and the pressure in the atmospheric pressure is ΔP. When the ejection of the recording head 1 is stopped (step S3), the pressure once rises due to the inertia of the ink (P2). Finally, when the liquid feed pump 78 is stopped (step S4), the pressure returns to the initial state. In this graph, the discharge is continuously performed from the recording head 1.

  By the way, according to the investigation by the present inventors, it is known that the pressure ΔP of the recording head 1 varies from the target value due to the dimensional variation of the movable valve 88 in the supply system. Specifically, the negative pressure value ΔP in the recording head varies with the dimensional variation of the through hole 84 of the movable valve upper portion 88t and the fitting size between the movable valve upper portion 88t and the housing 40, that is, the variation of the gap Gt in FIG. , Will vary from the target value. In order to prevent this, there is a measure such as mounting a pipe having high dimensional accuracy in the through hole with respect to the dimensional variation of the through hole. However, the variation of the gap Gt that is the fitting size of the upper part of the valve body and the housing is There is no easy solution. In particular, when the gap Gt becomes large due to dimensional variation, the amount of ink flowing between the gaps increases and the target pressure ΔP varies.

  In view of such a problem, in each of the embodiments of the present invention, the ink flowing inside the movable valve only passes through the through hole 84 in order to maintain a negative pressure by simple pump control without causing insufficient refill. Since the configuration is such that it flows, the variation of the gap Gt, which is the fitting dimension between the movable valve upper portion 88t and the housing 40, is ignored, and the configuration allows the ink flowing through the gap Gt not to be considered. Each of these embodiments will be described later.

  As described above, according to the embodiments of the present invention, in the image forming apparatus, the negative pressure in the recording head can be appropriately maintained by simple pump control, and a valve necessary for producing the effect is provided. It is possible to eliminate the influence of dimensional variation of the body.

  In each embodiment of the present invention, the reason why the negative pressure can be maintained by simple pump control without causing insufficient refill will be described.

  In each embodiment of the present invention, a valve having a characteristic that fluid resistance changes depending on the flow direction and flow rate of the liquid flowing inside is provided between the cartridge and the recording head. This valve is comprised from the housing and the valve body. The valve body has a shaft shape, and the shaft diameter at the center is smaller than the upper and lower parts. A through hole is provided in the upper part of the valve body.

  The valve body is movable inside the housing and moves up and down according to the flow inside, that is, the discharge flow rate of the recording head. When the valve body is at the bottom dead center, a gap is formed between the lower part of the valve body and the side wall of the housing. However, when the valve body is raised, the gap between the side wall of the housing and the lower part of the valve body is reduced.

  In the housing, a horizontal hole is formed in the central portion of the valve body, and a liquid feed pump attached so as to bypass the valve is connected to this hole. The liquid feeding pump is always in a liquid feeding state, and when the liquid is not discharged from the recording head, the valve body is at the bottom dead center, so that the gap with the housing side wall is large. Therefore, the flow of the liquid from the liquid feeding pump repeats the circulation of passing through the lower part of the valve body and returning to the liquid feeding pump again.

  When the liquid is discharged from the recording head, the valve body rises due to the pressure difference, and the gap with the housing side wall becomes small. Therefore, the liquid pressurized from the liquid feed pump is supplied to the recording head through the through hole in the upper part of the valve body. At this time, the pressure loss in the supply path is covered by pressurization of the liquid feed pump. When the recording head stops discharging, the liquid does not flow through the through hole but flows in the lower direction of the valve body, and the valve body moves to the bottom dead center. As a result, the liquid passes through the lower part of the valve body, returns to the liquid feed pump again, and repeats circulation, so that a shortage of refill can be prevented by simple pump control.

  Next, the reason why each embodiment of the present invention is not affected by the dimensional variation of the valve body will be described.

  In each embodiment of the present invention, a through hole is provided in the upper part of the valve body, and a protruding portion directed in the moving direction (upstream side or downstream side) within the housing of the valve body is formed outside the through hole. The housing is provided with a circular opening through which a protrusion provided on the valve body passes, and a cavity is provided at the tip of the hole. Even if the valve body rises from the bottom dead center due to the valve body protrusion and the circular opening, the protrusion is always in a closed state with the housing, and has a large fluid resistance. Therefore, even if there is a gap between the valve body and the side wall of the housing due to dimensional variation between the valve body and the housing, the flow of the liquid flowing inside the valve is hindered by a large resistance between the protrusion and the housing. Further, even if the liquid passes through the resistance portion between the projection and the housing, the liquid only stays in the cavity ahead, and the liquid does not flow into the gap between the valve body and the housing side wall.

  Accordingly, the liquid pressurized from the liquid feed pump passes only through the through hole in the upper part of the valve body and does not pass through the gap between the valve body and the housing side wall. Even if a gap fits and the liquid passes through only the through hole, it is not affected by dimensional variations.

Next, a technical problem caused by the variation in valve body dimensions will be described.
According to the inventor's investigation results, in a system that compensates for the lack of refill with a valve and a pump, the dimensional accuracy of the through hole in the upper part of the valve body and the fitting dimensional precision of the upper part of the valve body and the housing vary, and accordingly the recording head It is known that the negative pressure value of the inside will vary from the target value.
In order to prevent this problem, there are measures such as mounting a pipe in the through hole for dimensional variation of the through hole, but there is no easy way to deal with variations in the fitting size between the upper part of the valve body and the housing. It is necessary to limit as much as possible.

  In view of such a problem, in each embodiment of the present invention, as a supply system that maintains a negative pressure by simple pump control without causing refill shortage, the liquid flowing inside the valve body flows only through the through hole. Therefore, the variation of the fitting size between the upper part of the valve body and the housing can be ignored.

[First Embodiment]
Next, a first embodiment of the present invention will be described. FIG. 5 is a cross-sectional view of the variable flow path resistance unit 83 according to the first embodiment of the present invention. FIG. 5A shows the flow path resistance variable unit 83 in a state where the recording head 1 is not ejecting and the liquid feed pump 78 is driven. Since the ink supplied from the liquid feed pump 78 flows only to the port 86b (lower end) side, the movable valve 88 receives a force on the port 86b side and stops on the port 86b side. The movable valve 88 shown in this figure has a configuration in which a through hole 84 is provided in the upper portion 88t and a projection 95 is provided on the outer peripheral port 86b side.

  The housing 202 is formed by opening an opening 210 in the same shape as the protrusion 95 so as to penetrate the protrusion 95 of the movable valve 88t. When the movable valve 88 is attached to the housing 202, the protrusion 95 is It protrudes from 202. The protrusion accommodating portion 201 is provided so as to be connected to the opening 210 having the same shape as the protrusion 95 so that the protrusion 95 protruding from the housing 202 of the movable valve 88t can be accommodated therein. It has become. The housing cap 200 is configured to cap the housing 202 and cover the movable valve 88.

  Note that the protrusion 95 is not limited to the outer peripheral edge of the movable valve upper portion 88t, and may be disposed anywhere as long as it is in the outer peripheral direction with respect to the through hole 84 and the opening 210 is formed in the housing 202 accordingly. . Further, from the viewpoint of assembly, it is desirable that the protrusion accommodating portion 201 and the housing cap 200 are configured as separate members from the housing 202. Similarly, in order to attach the protrusion accommodating portion 201, the lateral hole portion 86 c is preferably a separate member with respect to the housing 202. The housing cap 200 in FIG. 5 has a tapered shape toward the port 86a (upper end) side, but is not limited to this shape, and may be any shape as long as it can be connected to the liquid supply tube 16. .

  FIG. 5B is a diagram illustrating the moment when the recording head 1 starts ejection. The ink supplied from the liquid feed pump 78 flows out to the arrow B side. At this time, the gap T is small because the movable valve upper portion 88t is on the port 86b side, and the fluid resistance is also high. For this reason, the ink flowing in the direction of arrow B does not flow through the gap T and the protrusion, but passes through the through hole 84.

  FIG. 5C shows the variable flow path resistance unit 83 in a state where the recording head 1 continues to discharge from FIG. 5B. The movable valve 88 receives a force on the port 86a side due to a pressure difference from the ink that has passed through the through hole 84, and moves in that direction. The movable valve 88 is balanced at a certain position. At that time, it is desirable that the protruding portion 95 has such a length as to close the opening 210 wherever the balanced position is, that is, at the most port 86a side. Further, the projection length may be any length as long as the movable valve 88t can be closed regardless of the position.

  When the movable valve 88 is raised, the gap T in FIG. 5B is widened. However, since the protrusion 95 always closes the opening 210, the ink hardly flows in the direction of the protrusion accommodating portion. Further, even if the ink flows into the protrusion accommodating portion 201, it is received by the cavity 211 formed inside. In order to describe the ink flow in the opening 210 and the features of this embodiment in detail, the V portion shown in FIG.

  FIG. 6 shows the flow of ink when the portion V in FIG. 5C, that is, the protrusion accommodating portion 201 and the protrusion 95 in FIG. 5 is enlarged, and the movable valve 88 moves to the port 86a side. Yes. FIG. 6A is an enlarged view when the recording head 1 is not ejected.

  Since the gap T is small as described above, the fluid resistance is large, and the protrusion 95 closes the opening 210 and the housing 202, so that the gap Gt_in formed between them is a large fluid resistance. Therefore, the ink passes through the through hole 84 without passing through the gap T.

  FIG. 6B shows the ink flow when the movable valve moves to the port 86a side. Compared with FIG. 6A, the gap T is widened, but since the projection 95 always closes the opening 210 and the housing 202, the large fluid resistance of the gap Gt_in is constant regardless of the position of the movable valve. . Accordingly, the ink flows in the direction of the through hole 84. However, when the pressure of the ink supplied from the liquid feed pump 78 increases, the ink flows in the direction of the housing 202 and the protrusion accommodating portion 201 (direction d1), but the amount is small because of the resistance of the gap Gt_in. , Accumulated in the protrusion accommodating portion 201. Since the accumulated ink 300 is not in communication with the port 86a side, the ink 300 does not pass through the gap Gt.

  In addition, since the protrusion accommodating part 201 stores a small amount of ink, it is desirable that the volume of the internal cavity 211 is large. Therefore, the port 86b may have a depth. Further, the shape of the cavity 211 in the protrusion accommodating portion 201 is not limited to the shape shown in the figure, and may be a groove in which the protrusion portion 95 is accommodated. Further, when the ink in the cavity 211 has accumulated, it is possible to replace the protrusion accommodating portion 201 with another member as described above.

  FIG. 7 shows a state in which the portion V in FIG. 5C, that is, the protrusion accommodating portion 201 and the protrusion 95 in FIG. 5 is enlarged, and the ink that has passed through the through hole 84 toward the port 86 a flows into the protrusion accommodating portion 201. Show.

  When the movable valve 88 moves to the port 86a side, the pressure in the cavity 211 becomes relatively smaller than the ink on the port 86a side. As a result, as shown by the arrow d2, the ink flows through the gap 211 through the gap Gt. Even in this state, the ink 300 accumulated in the cavity portion 211 does not communicate with the ink inside the housing 202, and therefore does not flow through the gap T and into the housing 202.

  As described above, according to the present embodiment, even when the gap Gt varies in size and is close to the clearance fit, the flow flows in the movable valve 88 of the variable flow resistance unit 83 regardless of the variation. The ink can be configured to flow mainly through the through hole 84. For this reason, even if the gap Gt between the housing 202 or the housing cap 200 and the movable valve upper portion 88t varies, it is possible to control the stable pressure ΔP in FIG. 4 by ensuring the inner diameter of the through hole. Therefore, the effect of this invention is great.

Thus, according to the above-described embodiment, the negative pressure in the recording head can be appropriately maintained by simple pump control without being affected by the dimensional variation of the valve body.
For this reason, even when applied to an image forming apparatus that uses a plurality of inks of different colors, the pump feed amount is not complicated according to the ink consumption, and simple and single pump control is performed. Therefore, the negative pressure in the recording head can be appropriately maintained without causing refill shortage.

Next, a configuration in which an atmosphere opening is added to the first embodiment will be described with reference to FIG.
FIG. 8 is an enlarged view of the projection accommodating portion 201 and the projection portion 95 shown in FIG. 6, in which an atmosphere opening port (atmospheric communication hole) 400 is added.

  Since the hollow portion 211 of the protrusion accommodating portion 201 shown in FIGS. 6 to 7 is sealed, the pressure changes due to the movement of the movable valve 88. In particular, when the internal pressure becomes negative, positive pressure ink is drawn. Therefore, as shown in FIG. 8, the atmosphere opening port 400 may be provided in the cavity portion 211 so that the interior of the cavity portion 211 can always be maintained at atmospheric pressure.

  In the configuration example shown in FIG. 8, since the inside of the cavity 211 is maintained at atmospheric pressure, ink is not drawn into the cavity 211 even if the movable valve 88 moves. Therefore, the amount of ink flowing from the movable valve 88 in the direction of arrow d1 can be reduced, and the amount of ink flowing from the port 86a side in the direction of arrow d2 can also be reduced.

  It is desirable that the atmosphere opening 400 has a serpentine structure with a small inner diameter in order to prevent ink in the flow path resistance variable unit 83 from evaporating. In order to prevent the ink 300 accumulated in the cavity 211 from leaking out from the atmosphere opening port 400, it is desirable that the atmosphere opening port 400 be installed at a position as high as possible (in the direction of the arrow Z) from the bottom of the protrusion accommodating unit 201. . Further, the installation position of the atmosphere opening port 400 may be freely changed according to the installation direction of the flow path resistance variable unit 83, but it is desirable to install it at a position where the ink 300 accumulated in the cavity 211 is difficult to leak out.

  Next, a configuration example in which the ink position detection device is added to the first embodiment will be described with reference to FIG. FIG. 9 shows a configuration example in which the protrusion accommodating portion 201 is provided with a photosensor 450 for detecting the liquid level position of the ink 300 accumulated in the hollow portion 211.

  When the liquid surface position of the ink 300 accumulated in the cavity 211 rises, the ink may leak from the atmosphere opening port 400. Therefore, the photo sensor 450 is attached to the hollow portion 211 in the protrusion accommodating portion 201, and when the light transmittance becomes a predetermined threshold value or less, it is determined that the ink 300 has accumulated near the atmosphere opening 400. If the remaining amount of ink remaining detected by the photosensor is equal to or lower than a predetermined threshold, the flow path resistance can be determined by notifying the user that the remaining amount is lower than the threshold and replacing the protrusion accommodating portion 201. The variable unit 83 can be used for a long time.

  Note that the photosensor is used as a means for adjusting the liquid level position of the ink 300 accumulated in the cavity 211. However, the present invention is not limited to this, and any detection means may be used as long as the liquid level position can be detected. . Further, it is possible to obtain how many inks are experimentally printed without using the liquid level detecting means, and how much ink is accumulated in the cavity 211, and based on the result, the replacement timing of the protrusion accommodating portion 201 is predicted. good.

[Second Embodiment]
Next, a second embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 10 is a sectional view of the flow path resistance variable unit 83 according to the second embodiment of the present invention.

The movable valve 88 shown in FIG. 10 has a configuration in which a through hole 84 is provided in the upper portion 88t, and a protrusion 95 is provided on the outer peripheral port 86a side, that is, on the opposite side to the configuration example of FIG. Further, the housing cap 200 is formed by opening the opening 204 in the same shape as the protruding portion 95 so as to penetrate the protruding portion 95 of the movable valve 88 t, and when the housing cap 200 is attached to the movable valve 88. The protruding portion 95 protrudes from the housing cap 200.
Further, the housing cap 200 is configured to cap the housing 202 and cover the movable valve 88. The protrusion accommodating portion 205 is provided so as to be connected to the opening 204 having the same shape as the protrusion 95 so that the protrusion 95 protruding from the housing cap 200 of the movable valve 88t can be accommodated therein, and the inside thereof is hollow. It has become.

  Note that the protrusion 95 is not limited to the outer peripheral edge of the movable valve upper portion 88t, and is located in the outer peripheral direction with respect to the through hole 84. As long as the opening 204 is formed in the housing cap 200, the protrusion 95 is disposed anywhere. good. In addition, it is desirable that the protrusion accommodating portion 205 and the housing cap 200 are configured as separate members from the housing 202. Similarly, in order to attach the protruding portion accommodating portion 205, it is desirable that the lateral hole portion 86 c is a separate member with respect to the housing 202.

  FIG. 10A shows the flow path resistance variable unit 83 in a state where the recording head 1 is non-ejection and the liquid feed pump 78 is driven. Since the recording head 1 is not ejected, there is no flow on the port 86a side, so that ink flows in the direction of arrow A.

  FIG. 10B is a diagram illustrating the moment when the recording head 1 starts ejection. The ink supplied from the liquid feed pump 78 flows out to the arrow B side. At this time, the gap T is small because the movable valve upper portion 88t is on the port 86b side, and the fluid resistance is also high. Further, since there is a fluid resistance of the gap Gt, the ink passes through the through hole 84 and flows toward the port 86a.

FIG. 10C shows the variable flow path resistance unit 83 in a state where the recording head 1 continues to discharge from FIG. 10B. The movable valve 88 receives a force on the port 86a side due to a pressure difference from the ink that has passed through the through hole 84, moves in that direction, and balances at a certain position.
It is desirable that the protrusion 95 has such a length as to close the housing cap 200 and the opening 204 regardless of where the movable valve 88 is balanced. Further, the projection length may be any length as long as the housing cap 200 and the opening 204 can be closed regardless of the position of the movable valve 88.

  When the movable valve 88 moves to the balanced position from the state of FIG. 10B, the gap T widens as shown in FIG. 10C, but the protrusion 95 always closes the opening 204. Is difficult to flow in the direction of the protrusion accommodating portion. In order to explain the ink flow in the opening 204 in detail, the W portion shown in FIG.

  FIG. 11 shows the flow of ink when the movable portion 88 moves toward the port 86a by enlarging the W portion in FIG. 10C, that is, around the protrusion 95 in FIG. FIG. 11A is an enlarged view when the movable valve 88 is on the port 86b side, and FIG. 11B is an enlarged view when the movable valve 88 moves toward the port 86a.

  In the state of FIG. 11A, since the gap T shown in FIG. 10 is small, the fluid resistance is large and there is a fluid resistance of the gap Gt. Furthermore, since the projection 95 closes the housing cap 200, there is also a fluid resistance of the gap G_out between them. Therefore, the ink supplied from the liquid feed pump 78 passes through the through hole 84 without advancing the fluid resistance of the gap T, gap Gt, and gap G_out.

  In the state of FIG. 11B, the gap T is wider than that of FIG. 11A, but the protrusion 95 always closes the housing cap 200, so the fluid resistance of the gap Gt_out depends on the position of the movable valve. It is constant. Similarly, there is a fluid resistance of the gap Gt. Therefore, even if the movable valve 88 moves in the direction of the port 86a, the ink flows in the direction of the through hole 84.

  However, depending on the position of the movable valve, the pressure of the ink supplied from the liquid feeding pump 78 may increase, the ink pressure is high, the fitting size of the gap Gt, and the fitting of the protrusion 95 and the housing cap 200. When the dimension is large, the ink flows in the direction of the protrusion accommodating portion 205 (the direction of the arrow d3). At this time, even if the fitting size is large, the amount of ink flowing in the direction of the arrow d3 is small because of the fluid resistance of the gap Gt and the gap G_out. Further, even when the ink reaches the protrusion accommodating portion, it is accumulated in the cavity portion 206 that is inclined toward the port 86b with respect to the outer peripheral direction. By accumulating the ink in the outer circumferential direction, the ink 300 accumulated inside the cavity portion 206 is accumulated at a position away from the gap G_out. Therefore, if the amount of the ink 300 accumulated in the cavity portion 206 does not reach a certain position, the ink 300 accumulates from the gap G_out. Ink does not flow. Accordingly, it is desirable that the cavity 206 is inclined toward the port 86b with respect to the outer peripheral direction.

  Further, since the protrusion accommodating portion 205 stores a small amount of ink, it is desirable that the volume of the internal cavity 206 is large. For this reason, the protrusion accommodating portion 205 may have a depth on the port 86b side. Further, the shape of the cavity 206 in the protrusion accommodating portion 205 is not limited to the shape shown in the figure, and may be a groove in which the protrusion 95 is accommodated. Further, when the ink in the cavity 206 has accumulated, it is possible to replace the protrusion accommodating portion 205 with another member as described above.

  When the movable valve 88 moves to the port 86a side, the pressure in the cavity 206 becomes relatively higher than the ink on the port 86a side. For this reason, the ink that has passed through the through hole 84 does not enter the cavity portion 206, thereby preventing the ink from flowing into the cavity portion 206.

  As described above, according to the present embodiment, even if the gap Gt and the valve body upper portion 88t have different dimensions and both are close to the clearance fit, the flow resistance variable unit 83 of the flow resistance variable unit 83 is not affected by the variation. The ink flowing in the movable valve 88 can be configured to mainly flow through the through hole 84.

  Further, as compared with the configuration of the first embodiment shown in FIG. 5, since the projection 95 is provided on the port 86a side, the fluid resistance when the ink flows in the direction of the cavity 205 can be increased. . Therefore, it is more difficult for the ink to flow into the protrusion accommodating portion than in the configuration shown in FIG. 5 where the protrusion 95 is in the port 86b direction. Therefore, even if the flow resistance unit 83 can be used for a long time and the gap Gt between the housing cap 200 or the housing 202 and the movable valve upper portion 88t varies, the stability of FIG. Since the pressure ΔP can be controlled, the effect of the present invention is great.

  Next, a configuration in which an atmosphere opening is added to the second embodiment will be described with reference to FIG. FIG. 12 is a diagram illustrating a configuration example in which the atmosphere opening 400 is provided to the protrusion accommodating portion 205.

  As in the first embodiment described above with reference to FIG. 8, the cavity 206 of the protrusion accommodating portion 205 is sealed, so that when the movable valve 88 moves in the direction of the port 86 a, the inside is pressurized and the movable valve 88 is It can be inferred that they are pushed back when moving in the direction of the port 86a. In order to prevent this, an atmosphere opening port 400 communicating with the atmosphere may be provided in the cavity portion 206 so that the inside of the cavity portion 211 can always be maintained at atmospheric pressure.

  It is desirable that the atmosphere opening 400 has a serpentine structure with a small inner diameter in order to prevent ink in the flow path resistance variable unit 83 from evaporating. In order to prevent the ink 300 accumulated in the cavity 206 from leaking out from the atmosphere opening port 400, it is desirable that the atmosphere opening port 400 be installed as high as possible from the bottom of the protrusion accommodating portion 201. Further, the installation position of the atmosphere opening port 400 may be freely changed depending on the installation direction of the flow path resistance variable unit 83, but it is desirable to install it at a position where the ink 300 accumulated in the cavity 211 is difficult to leak out. In addition, in order to prevent ink collected in the cavity 206 from leaking out from the atmosphere opening port 400, it is desirable to replace the protrusion accommodating unit 205 when the ink 300 has accumulated to a height near the atmosphere opening port 400. Further, in order to detect how high the ink 300 is accumulated in the cavity 206, a photo sensor (not shown) may be attached to the protrusion accommodating portion 205 to detect.

[Third Embodiment]
Next, a third embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 13 is a cross-sectional view of the variable flow path resistance unit 83 according to the third embodiment of the present invention.

The movable valve 88 shown in FIG. 13 has a configuration in which a through hole 84 is provided in an upper portion 88t, and a protruding portion 95t is provided on the outer peripheral port 86a side, and a protruding portion 95b is provided on the port 86b side. The housing cap 200 is formed by opening an opening 204 in the same shape as the projection 95t so as to penetrate the projection 95t. When the housing cap 200 is attached to the movable valve 88, the projection 95t is a housing. It protrudes from the cap 200.
Further, the housing cap 200 is configured to cap the housing 202 and cover the movable valve 88.

The port 86a side protrusion accommodating portion 205 is provided so as to be connected to the opening 204 having the same shape as the protrusion 95 so that the protrusion 95t protruding from the housing cap 200 of the movable valve 88t can be accommodated therein. The interior is hollow.
The housing 202 has an opening 210 having the same shape as the protrusion 95b so as to penetrate the protrusion 95b. When the movable valve 88 is on the port 86b side, the protrusion 95b protrudes. The port 86b-side protrusion accommodating portion 201 is provided so as to be connected to the opening 210 having the same shape as the protrusion 95b so that the protrusion 95b protruding from the housing 202 of the movable valve 88b can be accommodated therein. is there.

  Here, the protruding portion 95t is not limited to the outer peripheral edge of the movable valve upper portion 88t, and is located in the outer peripheral direction from the through hole 84. If the housing cap 200 and the opening 204 are formed accordingly, the protruding portion 95t is disposed anywhere. May be. Similarly, the protrusion 95b may be disposed anywhere as long as the housing 202 and the opening 210 are formed in the outer peripheral direction from the through hole 84. Further, it is desirable that the port 86 a side protrusion accommodating portion 205, the port 86 b side protrusion accommodating portion 201, and the housing cap 200 are configured as separate members from the housing 202. Further, in order to attach the port 86 b side protrusion accommodating portion 201, the lateral hole portion 86 c is preferably a separate member with respect to the housing 202.

  FIG. 13A shows the flow path resistance variable unit 83 in a state where the recording head 1 is non-ejection and the liquid feed pump 78 is driven. Since the recording head 1 is not ejected, there is no flow on the port 86a side, so that ink flows in the direction of arrow A.

  FIG. 13B is a diagram illustrating the moment when the recording head 1 starts ejection. The ink supplied from the liquid feed pump 78 flows out to the arrow B side. At this time, the gap T is small because the movable valve upper portion 88t is on the port 86b side, and the fluid resistance is also high. Therefore, immediately after the recording head 1 starts discharging, the ink passes through the through hole 84 and hardly flows in the gap T direction.

  FIG. 13C shows the variable flow path resistance unit 83 in a state where the recording head 1 continues to discharge from FIG. 13B. The movable valve 88 receives a force toward the port 86a due to the pressure difference with the ink that has passed through the through hole 84, and balances at a certain position.

  Here, it is desirable that the protrusion 95t has such a length as to close the housing cap 200 and the opening 204 no matter where the movable valve 88 is balanced. Similarly, it is desirable that the protrusion 95b has a length that always closes the housing 202 and the opening 210 no matter where the movable valve 88 is balanced. Further, the protrusions 95t and 95b may have any protrusion length as long as the opening 204, 210 can be closed regardless of the position of the movable valve 88.

  The gap T in FIG. 13C widens when the movable valve 88 moves to a balanced position. However, since the projection 95b closes the opening 210, the fluid resistance created in the closed state is large, and the ink Is difficult to flow in the direction of the protrusion accommodating portion. Further, even if ink flowing on the port 86 a side flows into the port 86 a side protrusion accommodating portion 201, the ink is stored in the port 86 a side protrusion accommodating portion 205. In other words, the ink that has passed through each of the protrusions 95t and 95b is distributed and stored in the respective protrusion accommodating parts. In order to describe the above-described ink flow in detail, the X portion shown in FIG.

  FIG. 14 shows the flow of ink when the portion X in FIG. 13C, that is, around the protrusions 95b and 95t in FIG. 13, is enlarged and the movable valve 88 moves toward the port 86a. 14A is an enlarged view when the movable valve 88 is on the port 86b side, and FIGS. 14B and 14C are enlarged views when the movable valve 88 moves in the direction of the port 86a. is there.

  In the state of FIG. 14A, since the gap T is small, the fluid resistance is large, and the protrusion 95b closes the housing 202, so that there is a fluid resistance in the gap Gt_in between them. Therefore, the ink supplied from the liquid feed pump 78 is difficult to flow in the direction of the gap T and the gap Gt_in and passes through the through hole 84.

  In the state of FIG. 14B, the gap T is wider than that of FIG. 14A, but the protrusion 95b always closes the housing 202, so the fluid resistance of the gap Gt_out is independent of the position of the movable valve. It is constant. Therefore, even if the movable valve 88 moves in the direction of the port 86a, the ink flows in the direction of the through hole 84. However, depending on the position of the movable valve, the pressure of the ink supplied from the liquid feeding pump 78 may increase, the ink pressure is high, the fitting size of the protrusion 95b and the housing 202 is large, and the gap Gt_in is wide. The ink flows into the port 86b side protrusion accommodating portion 201 indicated by the arrow d1. Even if the ink flows in the direction of the arrow d1, the amount of ink flowing into the port 86b side protrusion accommodating portion 201 is small because of the fluid resistance of the gap Gt_in. Even if the ink reaches the port 86b side protrusion accommodating portion, the ink is accumulated in the cavity portion 211.

  Here, since the port 86b side protrusion accommodating portion 201 stores a small amount of ink 300, it is desirable that the volume of the internal cavity 211 is large. For this reason, the port 86b side protrusion accommodating portion 201 is located on the port 86b side. There may be depth. Further, the shape of the cavity 211 in the port 86b side protrusion accommodating portion 201 is not limited to the shape shown in the figure, and may be a groove in which the protrusion portion 95b is accommodated. Further, when the ink in the hollow portion 211 has accumulated, the port 86b side protrusion accommodating portion 201 can be replaced with another member. Further, since the accumulated ink 300 is not in communication with the port 86a side, the ink 300 does not pass through the gap Gt.

  The ink on the port 86 a side that has passed through the through hole 84 is guided into the liquid supply tube 16 by the ejection of the recording head 1. However, if the inner diameter of the through hole 84 is large and the pressure loss generated when the ink supplied from the liquid feed pump 78 passes through the through hole 84 is small, the pressure of the ink on the port 86a side is large, thereby causing a gap. It can be estimated that the gas passes through G_out and flows into the port 86a-side protrusion accommodating portion 205.

  FIG. 14C shows a state where ink has flowed in this way. The ink 301 that has flowed in is collected in the outer circumferential direction of the cavity portion 206 in the port 86 a side protrusion accommodating portion 205. Since the ink 301 collected in the outer circumferential direction accumulates at a position away from the gap G_out, if the amount of the ink 301 accumulated in the cavity 206 does not reach a certain point, the ink passes from the gap G_out through the gap Gt, There is no flow up to the 86b side protrusion accommodating portion 201. Accordingly, it is desirable that the cavity 206 is inclined toward the port 86b with respect to the outer peripheral direction.

  In this way, the ink supplied from the liquid feed pump 78 mainly passes through the through hole 84 and flows to the recording head 1. However, when the pressure of the ink is large and the protrusion is a clearance fit, the ink passes through the gaps Gt_in to G_out and is stored in each protrusion accommodating part. That is, before and after passing through the through hole 84, the ink is stored in another independent place.

  As described above, according to the present embodiment, even when the gap Gt and the valve body upper portion 88t have different dimensions and both are close to the clearance fit, the movable valve of the variable flow path resistance unit 83 can be used regardless of the variation. The ink flowing in 88 can flow mainly through the through hole 84.

  Further, since the ink can be stored in another independent place before and after passing through the through hole 84, the frequency of replacing the protrusion accommodating portion is reduced, and the flow resistance unit 83 is used for a long time. The stable pressure ΔP shown in FIG. 4 can be controlled by the inner diameter of the through hole. Therefore, the effect of this invention is great.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 15 is a cross-sectional view of the variable flow path resistance unit 83 according to the third embodiment of the present invention.

  FIG. 15 shows a cross section of the variable flow path resistance unit 83 in a state where the recording head 1 is not ejecting and the liquid feed pump 78 is driven. The movable valve 88 has a configuration in which a through hole 84 is provided in the upper portion 88t, and a protrusion 95 is provided on the outer peripheral port 86b side. The housing 202 is formed by opening an opening 210 in the same shape as the protrusion 95 so as to penetrate the protrusion 95 of the movable valve 88t. When the movable valve 88 is attached to the housing 202, the protrusion 95 is It protrudes from 202.

  The protrusion accommodating portion 201 is provided so as to be connected to the opening 210 having the same shape as the protrusion 95 so that the protrusion 95 protruding from the housing 202 of the movable valve 88t can be accommodated therein. It has become. The housing cap 200 can be capped from above the housing 202 to cover the movable valve 88.

Further, the elastic member 250 is attached to the gap between the opening 210 and the protruding portion 95.
As described above, it is desirable that the protrusion accommodating portion 201 and the housing cap 200 are configured as separate members from the housing 202 from the viewpoint of assembly. Similarly, in order to attach the protrusion accommodating portion 201, the lateral hole portion 86 c is preferably a separate member with respect to the housing 202. The elastic member 250 attached to the gap between the opening 210 and the protrusion 95 is attached in order to suppress the ink supplied from the liquid feed pump 78 from flowing into the protrusion accommodating part 201. In order to explain the details, the Y portion shown in FIG.

  FIG. 16A is an enlarged view of the Y portion in FIG. 15, that is, the periphery of the protrusion 95 in FIG. FIG. 16B shows a front view and a plan view of the opening 210 to which the elastic member 250 is attached.

  FIG. 16A shows a state in which the recording head 1 is in the ejection state and the movable valve 88 has moved to the port 86a side. The elastic member 250 is attached to the surface of the part including at least the opening 210, and acts to narrow the gap Gt_in. Therefore, it is possible to prevent the pressure of the ink supplied from the liquid feed pump 78 from increasing and flowing in the direction of the arrow d1.

  If the frictional resistance of the elastic member 250 on the side surface 255 on the protruding portion 95 side is large, the operation of the movable valve 88 is hindered and the function of the variable flow path resistance unit 83 is not fulfilled. Therefore, it is desirable that the side surface 255 has a low frictional resistance and is smooth. If the inner diameter of the elastic member 250 is smaller than the protrusion 95, the movable valve 88 is inserted into the elastic member 250 and may not move. Therefore, the inner diameter of the elastic member 250 is desirably larger than the outer diameter of the protrusion 95.

  In the present embodiment, the protrusion 95 is formed in the direction of the port 86b, and the elastic member 250 is attached to the surface around the opening 210 so as to correspond to the direction. However, as shown in FIG. A protrusion may be formed on the 86a side, and the elastic member 250 may be formed on the housing cap so as to correspond thereto. Similarly, as shown in FIG. 13, even when the protrusions are formed in the port 86a side direction and the port 86b side direction, the structure in which the elastic member 250 is formed in the protrusion housing part so as to correspond thereto. good.

Next, another configuration example of the fourth embodiment will be described with reference to FIG.
FIG. 17 is another embodiment of the elastic member shown in FIG.

  The elastic member 251 shown in FIG. 17 has a circular blade shape and is attached only to the surface of the opening 210. Since the elastic member 251 has a blade shape, the area in contact with the movable valve 88 is small, and the frictional resistance generated in the movable valve 88 is small. Therefore, the movement of the movable valve 88 is not hindered.

  Furthermore, it becomes resistance when ink flows through the gap T in the direction of the arrow d1. Accordingly, the ink does not flow in the direction of the arrow d1 but flows in the direction of the through hole 84 and does not accumulate in the protrusion accommodating portion 201. Therefore, there is no need to replace the protrusion accommodating portion 201, and the flow resistance variable unit 83 can be used for a long period of time, so the effect of the present invention is great.

  The number of the circular blade-shaped elastic members 251 is not limited to two, and may be any number as long as the movement of the movable valve 88 is not hindered. Also, as shown in FIG. 10, when a projection is formed on the port 86a side, a circular blade-shaped elastic member 251 may be formed on the housing cap so as to correspond thereto. Similarly, as shown in FIG. 13, even when the protrusions are formed in the port 86a side direction and the port 86b side direction, a circular blade-shaped elastic member 251 is formed in the protrusion accommodating portion so as to correspond thereto. The structure which is made may be sufficient.

[Fifth Embodiment]
Next, a fifth embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 18 shows an enlarged view around the protrusion 95 in the fifth embodiment of the present invention.

  FIG. 18 shows a state in which the recording head 1 is in the ejection state and the movable valve 88 has moved to the port 86a side. In addition, a plurality of convex portions 260 are formed on the surface of the protruding portion 95 to provide resistance to the flow, and increase the flow resistance of the flow path that flows through the convex portion 260 surface to the hollow portion 211 in the protruding portion receiving portion 201. It is the composition which makes it. For this reason, even if the pressure of the ink supplied from the liquid feed pump 78 increases, it becomes difficult for the ink to flow in the direction of the arrow d1. Therefore, it is possible to prevent ink from flowing in the direction of the through hole 84 without flowing in the direction of the arrow d1 and collecting in the protrusion accommodating portion 201.

In addition, the shape of the convex portion is not limited to a circle, and any configuration such as a square may be used as long as the fluid resistance is increased. Is desirable. Further, the interval between the convex portions may be any interval as long as it has an effect of increasing fluid resistance.
Further, even when a protrusion is formed on the port 86a side as shown in FIG. 10 or when the protrusion is formed on both the port 86a side and the port 86b side as shown in FIG. In order to correspond to this, it is desirable that convex portions are formed in the respective protruding portions.

[About each embodiment]
Each of the above-described embodiments is a preferred embodiment of the present invention, and the present invention is not limited to this, and various modifications can be made based on the technical idea of the present invention.

  For example, the supply system according to each embodiment described above can be applied regardless of the type of ink. The liquid feed pump 78 shown in each embodiment may be any type of pump as long as ink can be fed.

DESCRIPTION OF SYMBOLS 1 Recording head 16 Liquid supply tube 76 Ink cartridge 80 Pump unit 81 Pressure control unit 83 Flow path resistance variable unit 84 Through-hole 86a Downstream side port 86b Upstream side port 86c Horizontal hole part 88 Movable valve 95 Protrusion part 200 Housing cap 201, 205 Protrusion Housing portion 202 Housing 204, 210 Opening

JP 2004-351845 A

Claims (12)

A recording head having nozzles for discharging droplets;
A liquid tank for storing liquid to be supplied to the recording head;
A first flow path for supplying the liquid to the recording head;
A second flow path communicating with the liquid tank;
A pressure regulating valve that connects the first flow path and the second flow path, and an internal flow path resistance changes according to a flow rate of the liquid flowing through the first flow path;
A third flow path branched from the second flow path and connected to the pressure regulating valve via a liquid feed pump;
With
The droplet discharge surface of the recording head is disposed at a position higher than the liquid surface in the liquid tank, and the negative pressure of the recording head is maintained due to a water head difference between the recording head and the liquid tank.
The pressure regulating valve has a housing and a valve body that is accommodated in the housing and moves according to a flow rate of the liquid flowing through the first flow path,
The housing is disposed between an upper end connected to the first flow path, a lower end connected to the second flow path, the upper end and the lower end, and the third A horizontal hole to which the flow path is connected,
The valve body has an axial shape, an upper part disposed to face the upper end part of the housing, a lower part disposed to face the lower end part of the housing, and more than the upper part and the lower part A central portion that is formed in a small diameter and is disposed to face the lateral hole of the housing, and is provided on the upper portion of the valve body, and the second flow path and the third flow path in the housing, and the A through hole that communicates with the first flow path, and a protrusion that is provided on the outer periphery side of the through hole at the upper portion of the valve body and protrudes in the moving direction of the valve body in the housing And
The housing has an opening having the same shape as the protruding portion through which the protruding portion can pass, and the protruding portion can always block the opening even when the valve body moves in the housing. By having the length, the liquid pressurized by the liquid feeding pump of the third flow path and pumped into the housing through the lateral hole is only the through hole provided in the upper part of the valve body. And a liquid discharge device which flows out to the first flow path.   The droplet discharge according to claim 1, wherein a gap between the lower portion of the valve body and a side wall in the housing is reduced as the valve body moves toward the upper end side. apparatus.   3. The droplet discharge according to claim 1, wherein the protrusion is provided on the valve body so as to protrude toward one or both of the first flow path side and the second flow path side. 4. apparatus.   4. The droplet discharge device according to claim 1, wherein the housing includes a protrusion accommodating portion that accommodates the protrusion protruding beyond the opening. 5.   The droplet discharge device according to claim 4, wherein an atmospheric communication hole communicating with the atmosphere is formed in the protrusion accommodating portion.   The droplet discharge device according to claim 5, wherein the air communication hole is provided at an upper position in a gravity direction with respect to a bottom portion of the protrusion accommodating portion.   The liquid droplet ejection apparatus according to claim 4, further comprising a liquid surface position detecting unit that detects a liquid surface position of the liquid accumulated in the protrusion accommodating portion.   8. The method according to claim 4, wherein the protrusion accommodating portion has a shape inclined from the first flow channel direction toward the second flow channel direction. 9. Droplet discharge device.   The liquid droplet ejection apparatus according to claim 4, wherein the protrusion accommodating portion is provided to be detachable from the container.   The liquid droplet ejection apparatus according to claim 1, wherein an elastic member that blocks the flow of the liquid is provided on a surface of the opening.   11. The liquid droplet ejection apparatus according to claim 1, wherein a convex portion that increases flow path resistance on the surface of the protruding portion is formed on the surface of the protruding portion. The droplet discharge device according to any one of claims 1 to 11 is an image forming device,
An image forming apparatus, wherein the liquid is ink.

Images