Liquid jetting head

Disclosed is a liquid jetting head which can contribute to downsizing. A head unit 20 has two case channels and a driving substrate 28 arranged between inflow openings 35 of the case channels provided on a base surface of the head unit, which is on the opposite side of a nozzle-formed surface of the head unit, in an erect posture with respect to the base surface of the driving substrate 28.

The present invention contains subject matters related to Japanese Patent Application No. 2007-208838 and Japanese Patent Application No. 2008-192198 filed in the Japanese Patent Office on Aug. 10, 2007 and Jul. 25, 2008, respectively, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a liquid jetting head, such as an ink jet-type recording head, and more particularly to a liquid jetting head having a head unit, which is capable of jetting liquid contained in a liquid containing chamber from nozzle orifices by driving pressure generating units, and a driving substrate, which supplies the pressure generating units with a driving signal.

A representative of a liquid jetting head which can jet (discharges) liquid may be an ink jet-type recording head (hereinafter, referred to as recording head) which is mounted in an ink jet-type printer (a kind of liquid jetting apparatus, hereinafter referred to as printer) which performs a record by discharging ink in a liquid state and striking a recording medium (a jetting object), such as recording paper with the ink. Further examples of the liquid jetting head include a color material jetting head used for manufacturing a color filter of a liquid crystal display, an electrode material jetting head used for forming electrodes of an organic electro luminescence display (organic EL display) and a field emission display (FED), and a living organic substance jetting head used for manufacturing a bio-tip (a biochemical element).

The liquid jetting head includes a driving substrate (printed board, circuit board) which receives a driving signal from an apparatus main body and supplies the driving signal to pressure generating units. The driving substrate is provided in a case member. In the liquid jetting head, the driving signal is supplied to each of the pressure generating units from the driving substrate via wiring members having flexibility (hereinafter, referred to as flexible cable), such as tape carrier package (TCP) (refer to seventh page of Patent document 1). Further, a terminal portion which is located at an end of the flexible cable is connected to a terminal portion of the pressure generating unit, and the other terminal portion which is located at the other end of the flexible cable is connected to a substrate terminal portion provided on the driving substrate.

In the structure disclosed in Patent document 1, the pressure generating units (vibrator units) are received in a receiving space formed in the case member, the driving substrate is arranged so as to cover an upper opening of the receiving space while being disposed in parallel with a nozzle formed-surface, and an introducing needle unit is attached to the case member in the state in which an driving substrate is interposed between the case member and the introducing needle unit. That is, the liquid jetting head is structured in a manner such that the driving substrate is provided with a through-hole having a size as large as the flexible cable can pass therethrough and wiring between the driving substrate and the pressure generating unit is accomplished by the flexible cable passing through the through-hole. That is, an end of the flexible cable with the other end connected to the pressure generating unit is connected to the driving substrate by a soldering method in which some solder is pulled to pass through the through-hole and then bent toward a connection terminal formed-surface of the driving substrate.

However, in the case in which the driving substrate is provided with the through-hole, wiring patterns must be formed on the driving substrate so as to detour around the through-hole. For such a reason, a size of the driving substrate in a plan view increases, resulting in a large driving substrate. As a result, a problem, in which the entire volume of the liquid jetting head increases, arises. In these days, line-type heads, in which a plurality of liquid jetting heads are incorporated in a body to jet liquid to a large area at a single time, are put to practical use. Accordingly, it is expected that the liquid jetting head progresses in downsizing when considering application of the line-type head to the liquid jetting head.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a liquid jetting head which can contributes to downsizing.

In order to accomplish such an object of the invention, there is provided a liquid jetting head including a head unit which can jet liquid contained in a liquid containing chamber through a nozzle orifice by operation of a pressure generating unit and a driving substrate which supplies the pressure generating unit with a driving signal, in which the head unit includes a first communication liquid channel which is provided at one end of the head unit and which communicates with the liquid containing chamber and a second communication liquid channel which is provided the other end of the head unit and which communicates with the liquid containing chamber, and in which the driving substrate is arranged between an inflow opening of the first communication liquid channel provided on a base surface which is opposite to a nozzle formed-surface of the head unit and an inflow opening of the second communication liquid channel in an erect posture with respect to the base surface.

With such a structure, the driving substrate is arranged in an erect posture on the base surface between the inflow openings of the first and second communication liquid channels provided on the base surface which is located at the opposite side of the nozzle formed-surface of the head unit. Accordingly, it is possible to reduce the horizontal size of the liquid jetting head regardless of the size of the driving substrate. Moreover, with such a structure, there is no need for a through-hole provided to the driving substrate which allows the flexible cable to pass therethrough. Accordingly, it is possible to reduce the size of the driving substrate. Furthermore, unlike the known structure, with such a structure, there is no need to bend the flexible cable when wiring the flexible cable and the driving substrate. Accordingly, it becomes easy to wire the flexible cable and the driving substrate.

In the structure, it is preferable that the driving substrate be arranged at a center portion of the base surface of the head unit.

According to the structure, the driving substrate is arranged at the center portion. With such a structure, it is possible to suppress fluctuation of lengths of the wirings, each is connected between the driving substrate and each of the pressure generating chambers, for every pressure generating chamber in comparison with the structure in which the driving substrate is arranged at a position other than the center portion, and it is also possible to suppress fluctuation of electric resistances of the wirings. Thanks to such a structure, fluctuation of a voltage of the driving signal which drives the pressure generating unit decreases. As a result, it is possible to reduce the range of fluctuation of the amount of liquid jetted from each nozzle orifice.

Further, thanks to the structure in which the communication liquid channels are arranged at both sides of the driving substrate arranged at the center portion of the base surface, the whole size of the liquid jetting head can be reduced in comparison with a structure in which the communication liquid channels are arranged at any one side of the driving substrate.

Furthermore, since there is no need for a clearance hole, through which the channel passes and which is provided to the wiring substrate like the known structure, it is possible to reduce the chance that a short-circuited state occurs at the time of liquid leakage which is likely to occur.

In the above-mentioned structure, it is preferable that the liquid jetting head include a liquid introducing member equipped with a liquid supply path which takes in liquid from the liquid source and supplies the liquid to the first communication liquid channel and the second communication liquid channel.

In the above-mentioned structure, it is preferable that the liquid introducing member be provided with a substrate holding portion which holds the driving substrate in an erect posture.

In the above-mentioned structure, it is preferable that an introducing portion of the liquid supply path is arranged at a side of the driving substrate in a widthwise direction thereof.

According to the structure, the driving substrate is held in the substrate holding portion of the liquid introducing member and the introducing portion of the liquid supply path is arranged at one side of the driving substrate in a widthwise direction thereof. Accordingly, it is possible to stably arrange the driving substrate in an erect posture and it is possible to adopt a layout in which the driving substrate and the liquid supply path are separated from each while suppressing the increase of the size of the liquid jetting head in a direction perpendicular to the surface of the driving substrate. With such a structure, it becomes possible to reduce the chance of the short-circuited state which is likely to occur.

In the above-mentioned structure, it is preferable that the liquid supply path branch off into a first branch supply path and a second branch supply path, the first branch supply path be provided so as to communicate with the first communication liquid channel which is relatively close to the introducing portion, and the second branch supply path be provided so as to communicate with the second communication liquid channel which is relatively far from the introducing portion while detouring around the driving substrate.

Moreover, in the above-mentioned structure, it is preferable that the first communication liquid channel and the second communication liquid channel be provided so as to communicate with both end portions of the same liquid chamber, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments for practicing the invention will be described with reference to the accompanying drawings. In the following embodiments, various kinds of limitation are given as concrete examples. However, the scope of the invention is not limited to those aspects as long as there is no particular description of the effect that the examples limit the invention in the following explanation. In the embodiments, an ink jet-type recording head (hereinafter, referred to as recording head) is disclosed as an example of a liquid jetting head.

FIG. 1is a plan view showing a structure of a printer1on which a recording head10according to the invention is mounted. The printer1includes a frame2and a platen3arranged in the frame2and is structured in a manner such that recording paper (recording medium or one kind of jetting object, not shown) on the platen is transported by a paper sending roller (not shown) which rotates as a paper sending motor drives. Further, a guide rod4is installed in parallel with the platen3in the frame2. A carriage5which has the recording head10therein is supported by the guide rod4in a pivotable manner. The carriage5is connected to a timing belt9installed between a driving pulley7rotated by operation of a pulse motor6and an idling pulley8installed at the opposite side of the driving pulley7in the frame2. The carriage5is structured so as to reciprocate along the guide rod4in a main scanning direction which is perpendicular to a paper transportation direction by operation of the pulse motor6.

A cartridge holder14, in which an ink cartridge13is detachably mounted, is installed at one side of the frame2. The ink cartridge13is connected to an air pump16via an air tube15and air from the air pump16is supplied into each of the ink cartridges13. As the inside of the ink cartridge13is pressurized by the air, ink is supplied (pneumatic transportation) to the recording head10via an ink supply tube17.

The ink supply tube17is a hollow member, which is flexible and is made of synthetic resin, such as silicon, and an ink channel corresponding to each of the ink cartridges13is formed in the ink supply tube17. A flexible flat cable (FFC)18for transmitting a driving signal from a control portion (now shown) of a main body of the printer1to the recording head10is wired between the main body side of the printer1and the recording head10side.

FIGS. 2 to 8show the structures of the recording head10.FIG. 2is a perspective view of the recording head10,FIG. 3is a front view of the recording head10, andFIG. 4is an exploded perspective view of the recording head10.FIG. 5is a plan view of the recording head10(i.e. head unit20) in a state in which an introducing needle unit21is not attached to the recording head10.FIG. 6is a front view of the recording head in the same state.FIG. 7is a side view of the recording head10in the same state andFIG. 8is a perspective view of the recording head10in the same state.FIG. 9is a sectional view illustrating a main part of the head unit20.

The recording head10in this embodiment includes the head unit20and the introducing needle unit21(one kind of liquid introducing member) as main elements. The head unit20consists of a head case25, a vibrator unit26, a channel unit27, and a driving substrate28.

The head case25is a hollow box-shaped member and has a leading surface (bottom surface) to which the channel unit27is fixed. The vibrator unit26is received in the receiving space12formed in the case, and the driving substrate28and the introducing needle unit21are arranged on the upper surface of the head case25which is opposite to the leading end surface. The upper surface of the head case25is a base surface of the head unit20. Case channels34are formed in the head case25while extending so as to penetrate through the head case25in a height direction of the head case. The case channels34are channels for supplying ink from the introducing needle unit21side to the common ink chambers40(corresponding to the liquid chambers in this invention). The case channels34are provided in a manner such that two rows of case channels34are provided for each common ink chamber40. With this embodiment, the recording head10includes two common ink chambers40corresponding to two sets of nozzle columns (a kind of nozzle group), and therefore the total four rows of case channels34are formed in the case head25. Further, inflow openings35, which are upstream side ends of the case channels34, are formed to protrude from the upper surface of the head case25. The inflow openings35are provided so as to communicate with the ink supply paths51(branch supply paths54) of the introducing needle unit21.

As shown inFIG. 10, of two case channels34corresponding to one common ink chamber40, one case channel, i.e. a first case channel34a(corresponding to a first communication liquid channel in the invention) communicates with the common ink chamber40at one end portion of the head unit20. In greater detail, the first case channel communicates with one end portion of the head unit20, the end being in a lengthwise direction (nozzle column direction) of the common ink chamber40. the other case channel, i.e. a second case channel34b(corresponding to a second communication liquid channel in the invention) communicates with the common chamber40at the other end portion of the common ink chamber40, other than the above-mentioned end portion, in the lengthwise direction of the common ink chamber40. Accordingly, thanks to a structure in which ink is introduced into the common ink chamber40from both side end portions of the common ink chamber in the widthwise direction, as for each of the pressure generating chambers42which communicates with the common ink chamber40, it is possible to reduce loss of ink supply pressure in comparison with a structure in which ink is supplied from only a center portion of the common ink chamber40in the widthwise direction. Therefore, it is possible to equalize jetting characteristics of the pressure generating chambers.

The vibrator unit26includes a plurality of piezoelectric vibrators31(a kind of pressure generating unit) arranged in a comb-teeth form, a flexible cable32(a kind of wiring member) for supplying a driving signal which is output from the driving substrate28to the piezoelectric vibrators31, and a fixing plate33which fixes the piezoelectric vibrators31. The piezoelectric vibrators31are bonded to a flexible surface (vibrating plate38) which sections a portion of the pressure generating chamber42. Each of the piezoelectric vibrator31changes a pressure of ink contained in the pressure generating chamber42by increasing and decreasing a volume of each of the pressure generating chambers42by expanding or contracting itself with the driving signal which is applied. Therefore, it is possible to jet ink from the nozzle orifices43by controlling the pressure fluctuation.

The channel unit27is manufactured by stacking a nozzle-formed substrate36provided with the nozzle orifices43, a channel-formed substrate37which forms ink channels, and a vibrating plate38which seals openings of the channel-formed substrate37and integrating them into a single body. The channel unit27is a unit member which forms a series of ink channels (liquid channels) which extend from the common ink chambers40to the nozzle orifices43by way of ink supplying holes41and the pressure generating chambers42. The pressure generating chambers42branching off from the common ink chamber40are formed so as to correspond to the nozzle orifices43, respectively and structured in a manner such that ink is supplied from the introducing needle unit21side via the case channels34and the common ink chambers40. The channel unit27is bonded to the leading end surface of the head case25in a posture in which the nozzle-formed substrate36faces downward (i.e. faces the platen3side of the printer main body). Accordingly, in the head unit20, the nozzle-formed substrate36becomes a nozzle-formed surface.

The driving substrate28is electrically connected to the substrate terminal portion44(seeFIG. 6) in a manner such that the flexible cable32is connected to the substrate terminal portion44by a soldering method. The driving substrate28is equipped with a connector45which connects the driving substrate28to the FFC18of the printer main body, so that the driving substrate28receives a driving signal from the control portion via the FFC18and supplies the driving signal to the piezoelectric vibrators via the flexible cable32. The flexible cable32has a structure in which wiring patterns made of conductive material, such as copper clad, are formed on the surface of a base film43made of an insulation film, such as polyimide, and portions other than wiring terminals are covered with resist. Accordingly, the wiring which allows the substrate terminal portion44of the driving substrate28and individual terminals of the piezoelectric vibrators to be in an electrically conducted state are provided in a plural number which equals to the number of piezoelectric vibrators.

As shown inFIGS. 5 and 6, the driving substrate28is arranged at the center portion of the upper surface of the head case25in a posture in which the head case25erects with respect to the upper surface of the head case25and rests in parallel with nozzle columns. The driving substrate28is arranged in such a posture at an area between inflow openings38of the first case channel34aand the second case channel34bwhich directly communicate with the same common ink chamber40(a center portion area of the upper surface of the head case25in this embodiment) on the upper surface of head case25. That is, the driving substrate28is disposed in an erect posture with respect to the nozzle-formed surface of the head unit20and the base surface. Accordingly, the driving substrate28is held maintaining such a posture by the introducing needle unit21. This will be described below.

Besides the driving substrate28, the upper surface of the head case25(the base surface of the head unit20) is provided with the introducing needle unit21. The introducing needle unit21includes a base portion47which is formed by a molding method using synthetic resin and has almost the same size as the upper surface of the head case25, a substrate holding portion48which extends upward from a center portion of the base portion47(on an opposite side of the head unit side), and ink introducing portions49(corresponding to introducing portions in the invention) which are provided at both sides of the substrate holding portion48in the base portion47(both sides in a nozzle column direction).

The substrate holding portion48has a box shape which is open at an upper end and a lower end. The inside of the substrate holding portion48is structured so as to receive and hold the driving substrate28. On the inner surface of a wall of the substrate holding portion48which is close to the ink introducing portion49, a fitting rail portion50, having a shape of letter “U” rotated by a quarter angle in a counter clockwise direction, extends in a height direction of the substrate holding portion48(seeFIG. 3). The fitting rail portion50is structured so as to fit to a peripheral boarder of the driving substrate28and functions as a guide when receiving the driving substrate28in the substrate holding portion48and determines a position and a posture of the driving substrate28in the received state. That is, as shown inFIG. 2, in the state in which the driving substrate28is received in and held by the substrate holding portion48, the driving substrate28is arranged in an erect posture with respect to the upper surface of the head case25.

The ink introducing portion49has ink supply paths51(a kind of liquid supply path in the invention), which introduce ink transported from the ink cartridge13via the ink supply tube17by pressure into the head unit20, formed therein. The ink supply path51is provided for each of every color of ink, i.e. each of every common ink chamber40. The ink introducing portion49is arranged at both sides of the substrate holding portion48with respect to the introducing needle unit21, i.e. at sides of the driving substrate28(in a substrate width direction) which is held by the substrate holding portion48. Further, the ink introducing needle53(liquid introducing needle) is attached to an upstream side opening49′ of the ink introducing portion49via a filter52interposed therebetween. The ink introducing needle53is equipped with a self-sealing valve (not shown) which allows ink to be introduced into the ink introducing needle53by adjusting a pressure of ink which is transported from the ink supply tube17.

The ink supply path51provided in the ink introducing portion49branches off into a first branch supply path54aand a second branch supply path54b. These branch supply paths54aand54bare provided so as to correspond to the case channels34aand34b, respectively which communicate with either one of the common ink chambers40. That is, the first branch supply path54acommunicates with the first case channel34alocated close to the corresponding ink introducing portion49(i.e. located under the corresponding ink introducing portion49), and the second branch supply path54bcommunicates with the second case channel34blocated far from the corresponding ink introducing portion49(i.e. located under another ink introducing portion49). The second branch supply path54bis formed to detour around the substrate holding portion48(driving substrate28). With this embodiment, a groove which is horizontally long and sags toward a rear side of the introducing needle unit21is formed at the front side of the introducing unit21and at an upper portion of the base portion47, and the groove functions as part of the second branch supply path54b. InFIGS. 2 and 3, the groove is shown in the open state but the opening of the groove is closed by resin film.

In a similar way, the ink supply path51of the other ink introducing portion49branches off into a first branch supply path54aand a second branch supply path54b. The branch supply paths54aand54bof this ink introducing portion49correspond to the case channels34aand34b, respectively which communicate with the other common ink chamber40. The second branch supply path54bis formed in a manner of detouring around the substrate holding portion48(driving substrate28) on a back side surface of the introducing needle unit21.

In the recording head10having the above-mentioned structure, when ink transported from the ink cartridge13via the ink supply tube17is introduced into the ink supply path51provided in the ink introducing portion49from the ink introducing needle53, some portion of the ink is supplied to the first case channel34avia the first branch supply path54aand the rest of the ink is supplied to the second case channel34bvia the second branch supply path54b. Accordingly, as for each of the common ink chambers40, the corresponding common ink chamber40receives the ink from both of the case channels34aand34bby way of both sides (in a lengthwise direction) thereof.

As described above, in the recording head10, the driving substrate28is arranged between the inflow openings35of the case channels34aand34b, respectively provided on the base surface of the head unit20in an erect posture with respect to the base surface. Accordingly, it is possible to reduce the horizontal plane size of the recording head10, i.e. the size of the recording head10in a direction perpendicular to the nozzle column, regardless of the size of the driving substrate28in comparison with the known structure. As a result, the recording head10according to the invention is suitable for a line-type head in which a plurality of recording heads is incorporated in a body.

Further, since the driving substrate28is arranged at the center portion of the base surface of the head case25, it is possible to suppress lengths of the wirings from the driving substrate28to the piezoelectric vibrators31from being lopsided for every piezoelectric vibrators31and it is possible to suppress fluctuation of electric resistance of the wirings in comparison with a structure in which the driving substrate28is arranged at a position other than the center position of the base surface of the case. For such a reason, it is possible to reduce the range of fluctuation of a voltage of the driving signal for driving the piezoelectric vibrators31, resulting in the decrease of the range of fluctuation of the amount of ink jetted from the nozzle orifices43.

Further, since the case channels34aand34bare arranged at both sides of the driving substrate28arranged at the center portion of the upper surface of the head case25, it is possible to reduce the whole size of the recording head10in comparison with a structure in which the communication liquid channels gather at either one side of the driving substrate28.

Moreover, since an arrangement position of the driving substrate28and an arrangement position of the channels do not overlap in a plan view (on the base surface of the case) like the known structure does, there is no need for a hole of the driving substrate28through which the channel passes. Accordingly, it is possible to reduce the chance of a short-circuited state which is likely to occur when ink leakage happens to occur. Further, there is no need to bend the flexible cable when wiring the flexible cable32and the driving substrate28, the wiring work becomes easy.

Moreover, with this embodiment, the driving substrate28is held in the substrate holding portion48of the introducing needle unit21and the ink introducing portion49is arranged at a side of the driving substrate28(the side in the widthwise direction). Accordingly, it is possible to stably arrange the driving substrate28in an erect posture and it is possible to adopt a layout in which the driving substrate28and the ink supply path51are separated from each other while suppressing the increase of the size of the recording head10in a direction perpendicular to the driving substrate28(the direction perpendicularly intersecting the nozzle column). As a result, it is possible to reduce the chance of a short-circuited state which is likely to occur when ink leakage happens to occur.

Still moreover, with this embodiment, an example of applying the invention to the printer1which is a kind of an off-carriage-type liquid jetting apparatus is disclosed, but the invention can also be applied to an on-carriage-type liquid jetting apparatus.

The invention is not limited to the recording head10which is exemplified above but can be applied to a liquid jetting head mounted in a display manufacturing apparatus, an electrode manufacturing apparatus, a chip manufacturing apparatus, and a micropipette.