JPS5862062A - Multiple nozzle head - Google Patents

Abstract

PURPOSE:To obtain the multiple nozzle head; wherein flow paths which yield a pressure loss proprotional to the square of a flow speed are provided in the parts of supplying paths that guide ink to a pressuring chamber; and which applies the pressure that is smaller than the pressure applied at the selected time when the half selection is performed and performs the multiplex driving. CONSTITUTION:An example of a four nozzle head is illustrated. In actual cases, however, present invention can be applied to the multiple nozzle head having about 2,000 nozzles. The ink flow paths such as nozzles 3 and pressurizing chambers 2 are formed in the head. Flow paths 13 comprising abruplty expanded parts 11 of the flow paths 13 comprising abruptly expanded parts 11 of the flow paths and abruptly shrunk parts 12 when they are observed from the side of the pressurizing chambers 2, are provided in the parts of supply paths 4. In an equivalent circuit diagram illustrating the head, resistance Rs in the supply path is varied by a volume speed Us of the ink that flows the position. The decrease in the volume speed on the nozzle side is more conspicous than the rate of decrease in pressure phi. When the flow path whose pressure loss is varied in proportion to the square of the flow speed is provided, the flow speed at the time of selection can be made twice the flow speed when the half selection is performed. Thus the speed of the ink droplets can be made fast.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ink-on-demand type inkjet printer, and relates to a multi-nozzle head that is capable of multiplex driving in 1%.

The present inventor has already proposed a multi-nozzle head capable of multiplex drive as shown in FIG. This consists of base 11 and pressurized chamber 2. Nozzle 3. A supply channel 4 etc. is carved and a diaphragm 5 is placed on the top surface.
Glue and press 11 element 6X.

6Y is provided, and the number of wires and drivers are reduced by multiplex driving the EE11 element 6 in X and Y. 1 and 7 are ink, and 8 is an ink container. - FIG. 2 shows an equivalent rotation for explaining the head of FIG. 1, where the pressure ′j1. o
Compliance of the vibration system consisting of the Fi piezoelectric pedestal 6 and the diaphragm 5 *Resistance of the Ftn nozzle 5, resistance of the Fs supply path 4* U n *Us of the nozzle 5. This is the volume velocity of ink that collapses the supply channel 4. In an actual head, the inertance of the nozzle 3 and the supply path 4 and the compliance due to the compressibility of the ink in the pressurizing chamber 2 cannot be ignored, so FIG. 2 is not strictly correct.

[In FIG. 1, when M7J of the piezoelectric elements 6M and 6Y is driven, the ink 7 in the pressurizing chamber 2 is ejected from the nozzle A5.

When only one of the piezoelectric elements 6x and ti6Y is driven (in the case of half selection in multiplex island motion), it can be considered that half the pressure is applied to the piezoelectric element 6 on average as when both are driven.

In 112WA, O, Rn, and Pg can be regarded as constant regardless of the volume velocity of the ink flowing there, so when the pressure ψ is halved, tyn and Us are halved.

Therefore, the nozzle volume velocity IF U n tj when half-selected
It becomes half of the volume velocity in the case of selection. When the ink drops, the momentum decreases due to the surface tension of the ink before it becomes an ink droplet and flies out. Therefore, when the ink without velocity is ejected, it is drawn back into the nozzle without causing any damage. If this limit speed is, for example, 1 rn/lx, it is necessary to set the ink droplet speed when 1 is selected to be less than or equal to 2 m/s.

It is an object of the present invention to further improve the head shown in Figure 1 and provide an inkjet head with improved ink droplet velocity during selection.

A plan view of a head according to an embodiment of the present invention is shown in FIG. 3. Although this example shows a head with only four nozzles, it can actually be applied to a multi-nozzle head with about 2000 nozzles. 1 on the head
Nozzle 3 similar to Figure 11. An ink flow path such as a pressurizing chamber 2 is formed.

The piezoelectric elements are Xl, X2. Yl, l of Y2.

Each Y is a matrix of 2. Looking at the example of $1154, there is a channel 15 provided with a channel rapidly widening section 11 and a rapidly contracting center section 12.

The head loss h1 in the rapidly expanding section 11 is h, m ζ (O 嘗 / 2 g
) ・・・ ・・・ ■ζ 1 = ξ [
1-(A1/Mu-ro) ] Meeting -・
... ■However, 1 in ξ. The cross-sectional area of the mu tltF path 4,
Mu$: Breakage of sweat passage 13 [1υ: Finished velocity of flow passage 4 1g: Acceleration of gravity.

The loss of water ii h s in the sudden condensation region 12 can be expressed as h-1ζ cloud (ol/2g) . . . ■ -.

Here, the loss coefficient ζ嘗 is a constant determined by M11, and is, for example, 125 in ζS when M*/Am=α5.

Also, from the formula ■, if M1/M■-α5, then ζ1 snow (L25
becomes.

Therefore, when the sum of the head losses in the rapidly expanding section 11 and the rapidly decreasing section 12 is -α5, h = h *
+ h *−15(υ”/2g)−·■ is given.

An equidistant circuit for explaining the 3M head is shown in Fig. 4. What differs from Fig. 92 is that the resistance R- of the supply path is simulated by the volume velocity 1'Ua that can be crossed there. This is because it is the sum of the pressure drop F8ij on the supply side, the pressure drop proportional to the velocity in the supply path 4 and the flow path 15, and the pressure drop that occurs in the rapid expansion section 11 and the sudden contraction center section 12, as shown by the formula (2).

tp e wm Rso Us + K
U s meeting pot Φ... ■
However,: proportionality constant * ReO: can be expressed as the flow path resistance of the supply path 4 and the flow path 15. On the other hand, macroscopically, it contributes to 19se++Rs*Us -----・-■, so it can be expressed as Rs = 1Flso + KUs ·----- from [F]. Therefore, as the pressure V decreases and the volumetric stray electricity US decreases as the body bends, P- of equation 1 also decreases. Therefore, compared to the nozzle resistance Fr, the proportion of the amount that escapes after the supply side resistance Fts decreases increases. In the end, the volumetric velocity of the nozzle was significantly reduced by more than the rate at which the pressure ψ was reduced.

As you can see from the above explanation, by providing a flow path on the supply side in which the pressure loss changes in proportion to the square of the flow velocity,
! The flow velocity at the time of turning can be made lower than the flow velocity at the time of selection, and conversely, the flow velocity at the time of selection can be made faster.

The tMs diagram shows other @U goods shapes used in the present invention, (
a) It uses the loss due to elbow 20, and the water loss is 1
1he is hθ for one elbow is ζe(0172g
) ・・・・・・■ Set p to 1199 in ζθ.

In addition, (b) a beam 21 is provided in the middle of the Vi finished connection 4.

(c), (a) Fluid diode 2 in fill path 4
2.2.5 is provided to obtain a pressure loss proportional to the square of the flow path and to improve the efficiency of ink ejection. (C) is a combination of a sudden expansion in cross section and a narrow tube, and (d) is due to the merging of Fi branch 1.

As can be seen from the above explanation, 1.According to the present invention, by providing a flow path in the supply 11 in which the pressure changes in proportion to the square of the flow velocity, the flow velocity when selected is twice the speed when half selected. The speed of ink droplets can be increased.

The present invention is a printer, a plotter, and a factor Z.

Can be widely applied to copiers, etc.

In addition to the multiplex drive head shown in FIG. 11 of the present invention, the present invention is also used in each Hinoki multi-nozzle head that selectively ejects ink by driving two piezoelectric elements.

According to the present invention, one piezoelectric element is disposed in one pressurizing chamber, and the piezoelectric element is also used when driven by an electric matrix, such as in the case of V-2V multiplex driving of liquid crystal.

4 A simplified example of the drawings, Tomohana Figure 1 shows a multiplex drive head to which the present invention can be applied, Figure 2 shows a schematic equivalent circuit for explaining the physical properties of the head in Figure 1, and Figure 3 Apply the present invention to the head shown in Figure 1! Flat-meter diagram of the improved head.

Figure 4: Fi chick Figure 5: Equivalent circuit of the head, Figure 5 is 1
It is a figure which shows the other Example of fl# abbreviation of this invention.

2... Pressure chamber 3... Nozzle 4
...-# Ship route 11... Rapidly expanding section 1
2 ・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・············・・・・・・・・・・・・・・・・・・・・・···························・Figure 2, Figure 3, 4th cause (O) (C) (b) 5th cause

Claims (1)

[Claims] A flow path that generates a pressure loss proportional to the square of the flow rate is provided in a part of the inter-supply path that leads ink from the ink container to the pressurizing chamber, and a pressure that is slightly smaller than the applied pressure when selecting 1 is applied when selecting medium. A multi-nozzle head characterized by seven multiplex drives.