JPH04250061A - Ink jet print head - Google Patents

Abstract

PURPOSE:To maintain an ink temperature at a constant value and to improve picture quality and save a power by providing a heat generating means for controlling temperature to the lower part of a heat energy applying means, in a device to apply heat energy on ink to discharge ink drops and record a picture. CONSTITUTION:A print head 1 is formed such that an opposite base plate 3 is joined with a heater base plate 2, a plurality of flow passages 4 are formed therebetween, and a plurality of nozzles 5 are disposed to the opening end of each ink flow passage 4. In this case, a heater 16 for controlling temperature is disposed on a base plate 15 of the heater base plate 2 and in a position facing the tip side of the ink flow passage 4. Meanwhile, a plurality of heaters 19 for generating bubbles are disposed on an insulating layer 18 of the base plate 15 and in a position facing the heater 16. By generating heat by means of the heater 19, ink in the ink flow passage 4 is heated to generate bubbles and ink drops are discharged through a nozzle 5. In this case, through control of a heat generating amount of the heater 16, an ink temperature is maintained at a constant value.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a print head for an ink jet printer, and more particularly to a print head used in an ink jet printer that records an image by at least heating ink and ejecting it in accordance with image information. It is something.

0002

2. Description of the Related Art Conventionally, in the above-mentioned ink jet printers, since images are recorded using ink droplets, it is known that characteristics such as the diameter of recorded dots vary greatly depending on the physical properties of the ink. Further, physical properties of ink, such as viscosity, generally vary greatly depending on its temperature. It is therefore clear that the recording characteristics of an inkjet printer are highly dependent on the temperature of the ink, that is, the temperature of the printhead containing the ink.

For this reason, conventional ink jet printers are equipped with means for controlling the temperature of the ink in order to keep the temperature of the ink within the print head constant and enable stable recording. The most common temperature control device used in this inkjet printer is, for example, as disclosed in JP-A-60-198247, as shown in FIGS. 17 and 18. A temperature detection means 102 and a heating means 103 are provided at the base end of the print head mounting member 101 to which the temperature detection means 100 is attached, and energy given to the heating means 103 is provided so that the temperature detected by the temperature detection means 102 is constant. Some devices are configured to be controlled by a power control circuit 104.

[0004] Further, as a temperature control device used in the above-mentioned inkjet printer, for example, Japanese Patent Laid-Open No. 61-15
As disclosed in Japanese Patent Application No. 8459, a separate heater is provided near the ink sub-tank that supplies ink to the print head, the temperature is detected by a temperature detection means, and the ink is controlled at a stage before being supplied to the print head. Some are designed to maintain a constant temperature.

[0005]

However, the above-mentioned prior art has the following problems. That is, in the case of the former temperature control device, the temperature detection means 102
Since the energy given to the heating means 103 is controlled by the power control circuit 104 so that the temperature detected by the heating means 103 is constant, the control is simple. but,
If the print head 100 records an image by heating ink and ejecting it as ink droplets according to image information, the ink is heated as the image is recorded, so the print head 100 temperature increases. Then, the temperature rise of the print head 100 is
Since the temperature is detected by the temperature detecting means 102 which is separate from the print head 100, there is a time delay in detecting the temperature by the temperature detecting means 102 with respect to the temperature rise of the print head 100. Therefore, as shown in FIG. 19, the print head 100 repeats a cycle in which the temperature near the heater for ejecting ink droplets rapidly increases during the print cycle and rapidly decreases during the pause cycle, thereby maintaining the print head 100 at a constant temperature. The problem was that it was difficult to control.

In the latter case, the temperature of the ink supplied to the print head is controlled at a constant level in the ink sub-tank before being supplied to the print head, so There is a problem that there is a short-term and rapid temperature change near the heater, and it is not possible to follow the temperature change near the heater for ejecting ink droplets. Another problem is that a large amount of electric power is required to heat the ink sub-tank to a constant level in advance.

[0007]

[Means for Solving the Problems] Therefore, the present invention has been made to solve the problems of the above-mentioned prior art.
The purpose of this is to be able to maintain the ink inside the print head at a constant temperature, enable high-quality image recording, have low power consumption, be able to follow short-term temperature changes, and have a simple structure. The purpose of the present invention is to provide an inkjet print head.

That is, the present invention provides an ink jet print head that records an image by ejecting ink droplets by applying thermal energy to the ink according to image information by at least a thermal energy applying means.
A heat generating means for temperature control is disposed below the thermal energy applying means.

[0009] The electric power applied to the heat generating means for temperature control is controlled in accordance with the electric power applied to the thermal energy applying means, for example.

[0010] Furthermore, the heat generating means for temperature control is arranged, for example, in a layered manner below the thermal energy applying means.

Furthermore, the heating means for controlling the temperature is configured to include, for example, a heating wire embedded in the lower layer of the thermal energy applying means.

0012

[Operation] In this invention, since the heat generating means for temperature control is disposed below the heat energy applying means, the heat generating means for temperature control is arranged in accordance with the amount of heat generated by the heat energy applying means. By controlling the amount of heat generated, the temperature of the ink within the inkjet printhead can be maintained constant.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below based on the illustrated embodiments. FIG. 3 shows an embodiment of an inkjet print head according to the present invention.

In the figure, 1 is a print head;
This print head 1, as shown in FIGS. 4 to 6,
By bonding the counter substrate 3 onto the heater substrate 2, a plurality of ink passages 4, 4, etc., which are individually divided and formed between both substrates 2, 3, are provided, and the ink passages 4, 4,... It has a plurality of nozzles 5, 5, . . . formed by open ends. Further, an ink sub-tank 6 having a large capacity is joined to the base end portions of both the substrates 2 and 3, and this ink sub-tank 6 is communicated with each ink flow path 4, 4, . . . . Further, on the back side of the heater board 2, a heat sink 7 is provided for discharging heat generated from the heater board 2 to the outside.
are joined.

As shown in FIG. 7, the print head 1 is positioned by a pin (not shown) on a head mounting member 9a attached to a convex portion 9 protruding from the upper surface of the carriage 8 via a heat sink 7. It is fixed in place with screws. Further, the carriage 8 is slidably held by two rods 10, 10 fixedly arranged in the horizontal direction, and the print head 1 can be moved in the horizontal direction in accordance with the image recording operation. .

[0016] The print head 1 also includes a PWB.
An electric signal is applied via a (printed circuit board) 11, and the PWB 11 is fixed to the side surface of the heat sink 7 on the same side as the print head 1. Wire bonding 1 is used between the print head 1 and the PWB 11.
2, the PWB 11 and a drive circuit (not shown) are connected by flexible cables 13, respectively. Ink is supplied to the print head 1 through a flexible tube 14 from an ink reservoir (not shown).

By the way, in this embodiment, a heat generating means for temperature control is arranged below the thermal energy applying means for applying at least thermal energy to the ink according to image information.

That is, as shown in FIGS. 1 and 2, the heater substrate 2 of the print head 1 includes a substrate 15 made of a Si wafer or the like. A heater 16 for temperature control is laminated at a position corresponding to the tip side of 4. The temperature control heater 16 is formed in a band shape having a predetermined width parallel to the tip edge of the print head 1, and the temperature control heater 16 is provided at both ends of the temperature control heater 16.
Electrodes 17, 17 for supplying current are connected. Furthermore, an insulating layer 18 is laminated over the entire surface of the substrate 15 on which the temperature control heater 16 and the electrodes 17, 17 are formed.

Bubble generation heaters 19, 19 are provided on the insulating layer 18 at positions corresponding to the temperature control heater 16.
... are formed. Heater 1 for generating this bubble
9, 19... are ink flow paths 4, 4, as shown in FIG.
The ink channels 4, 4... are formed by being divided into individual parts along the longitudinal direction so as to be located within the ink channels 4, 4.... A common electrode 20 is connected to the tips of the plurality of bubble generation heaters 19, 19..., and a control electrode 21 is connected to the base ends of the plurality of bubble generation heaters 19, 19...
, 21... are individually connected. Then, by energizing the control electrodes 21, 21, . . . according to the image information, the bubble generation heater 19 connected to the energized control electrode 21 generates heat.

Furthermore, as described above, the insulating layer 1 is provided with bubble generation heaters 19, 19... and electrodes 20, 21.
An insulating protective layer 22 is uniformly laminated on top of the insulating protective layer 22 .

The inkjet print head 1 configured as described above is connected to the bubble generation heaters 19, 19 via the flexible cable 13 and the control electrodes 21, 21...
By applying a voltage to ... according to the image signal, the bubble generation heaters 19, 19... are caused to generate heat. Then, the ink in the ink channels 4, 4... is heated according to the image signal to generate bubbles and ink droplets are ejected from the nozzles 5, 5..., and the print head 1 is moved horizontally by the carriage 8. By doing so, the back side is the platen 18.
It is configured to record an image on recording paper 19 supported by.

In this embodiment, the bubble generation heater 19
, 19... By controlling the amount of heat generated by the temperature control heater 16 according to the amount of heat generated by the inkjet print head 1, the temperature of the ink in the inkjet print head 1 is maintained constant.

Now, the time average energy applied to the bubble generation heaters 19, 19... is Ea, and the temperature control heater 1
6 is the time average energy applied to Eb, and the time average energy that steadily flows from the heater board 2 to the heat sink 7 is Ec.
If the time-average energy used to generate bubbles is Ed, and the time-average energy carried away by ejected ink droplets is Ee, then in steady state, Ea+Eb=Ec+Ed+Ee (1)
This relationship holds true.

[0024] Here, Ec is almost a constant, and Ea, E
Since d and Ee depend on the number n of ink droplets, the energy to be applied to the temperature control heater 16 can be calculated as follows by modifying the above equation (1): Eb=n×Const1+Const2 (
2) is given by the relational expression. Here, Const1
and Const2 are constants that depend on the print head 1, ink, etc.

[0025] Therefore, Const1 and Const
By determining the constant 2 in advance and applying energy based on equation (2) to the temperature control heater 16,
The temperature near the bubble generation heaters 19, 19, ie, the temperature of the ink used to record an image, is kept almost constant. In other words, the temperature of the ink near the bubble generation heaters 19, 19, . . . can be kept almost constant without providing any particular temperature sensor.

FIG. 8 shows a control circuit for an ink jet print head according to this embodiment.

In the figure, 25 is a buffer memory that stores image information sent from the main body of the inkjet printer, and 26 is the number n of dots per line of image information.
A dot number counting circuit 27 counts the above Const1.
a first setting switch 28 for setting the value of digitally;
is Cons set by the first setting switch to the number n of dots counted by the dot number counting circuit 26.
A multiplier for multiplying the value of t1, 29 a second setting switch for setting the value of Const2, and 30 an addition for adding the calculation result of the multiplier 28 and the value of Const2 set by the second setting switch 29. 31 is an adder 30
a D/A converter 32 that converts the addition result into an analog value;
1 is a drive control circuit that controls power supplied to the temperature control heater 16 based on the D/A converter 31, and 16 is a temperature control heater provided in the print head 1.

With the above configuration, in the ink jet print head according to this embodiment, the temperature of the ink within the print head is controlled as follows. That is,
The inkjet print head 1 generates heat in the ink channels 4, 4, etc., as shown in FIG. A bubble B is generated in the ink, and ink droplets are ejected from the nozzles 5, 5, . . . to record an image.

At this time, the image information sent from the inkjet printer main body is temporarily stored in the buffer memory 25, and the number of dots of the image information stored in the buffer memory 25 changes every scan. It is counted by the dot counting circuit 26. The number n of dots counted by the dot counting circuit 26 is multiplied by the value Const1 set by the first setting switch by the multiplier 28. This multiplied value (n×Const1
) is added by the adder 30 to the value of Const2 set by the second setting switch 29.

After that, the value (Eb=n×Const1+Const2) added by the adder 30 is D
- It is converted into an analog value by the A converter 31, and the drive control circuit 32 supplies a predetermined power to the temperature control heater 16 of the print head 1 according to the value Eb converted into the analog value.

In this way, the drive circuit 32 supplies the temperature control heater 16 with a predetermined electric power Eb (=n×Const1
+Const2). Moreover, the electric power Eb supplied to the temperature control heater 16 is
are the time average energy Ea applied to the bubble generation heaters 19, 19..., the time average energy Ec that steadily flows from the heater board 2 to the heat sink 7, and the time average energy Ed used for bubble generation. As shown in the above equation (1), the time average energy Ee carried away by the ink droplet is Ea+Eb=Ec+Ed+Ee (1)
The following relationship holds true, Ec is almost constant, and Ea,
Ed, Ee depend on the number n of ink drops.

Therefore, the electric power Eb supplied to the temperature control heater 16 is calculated as n×C as shown in equation (2).
By setting the value onst1+Const2, the time average energy (Ea+Eb) supplied to the print head 1 given by the left side of equation (1) above, and (
1) The time average energy consumed by the print head 1 (Ec+Ed+Ee) given by the right side of the equation can be made equal.

Therefore, even if the power applied to the bubble generation heaters 19, 19, . . . of the print head 1 changes as shown in FIG. By changing the temperature as shown in FIG. 10, the temperature of the ink near the bubble generation heaters 19, 19, . . . of the print head 1 can be maintained almost constant as shown in FIG. Note that if temperature control is not performed, the temperature of the ink near the bubble generation heaters 19, 19, . . . of the print head 1 changes significantly, as shown in FIG.

[0034] Therefore, since an image can be recorded while the physical properties of the ink used for image recording in the print head 1 are kept almost constant, high quality image recording is possible. Further, since the temperature control heater 16 is supplied with electric power corresponding to the electric power applied to the bubble generation heaters 19, 19..., the electric power supplied to the temperature control heater 16 is Since only a value that compensates for the thermal energy generated from ... is required, power consumption is small. Furthermore, since the temperature control heater 16 is arranged below the bubble generation heaters 19, 19..., it can immediately compensate for the thermal energy generated from the bubble generation heaters 19, 19... It can follow changes and has a simple structure.

FIG. 13 shows another embodiment of the present invention, in which the same parts as in the previous embodiment are given the same reference numerals. Instead of providing one temperature control heater for each bubble generation heater, the temperature control heater is divided into a plurality of parts.

That is, the temperature control heaters 16, 1
6... are set so that one temperature control heater 16 corresponds to a plurality of bubble generation heaters. These temperature control heaters 16, 16, .
It is designed to be independently driven by 6 etc.

In such a case, the temperature control heater 16
, 16... can be made to generate heat according to the heat generation area of the bubble generation heater, so even if the bubble generation heater generates heat only in one part, the temperature control heaters 16, 16... in other areas can be heated. By supplying electricity to the ink, the temperature of the ink in the entire area can be maintained approximately constant.

The rest of the structure and operation are the same as those of the previous embodiment, so their explanation will be omitted.

FIGS. 14 to 16 show still other embodiments of the present invention, and the same parts as in the above embodiments are denoted by the same reference numerals.The embodiment shown in FIG. , as in the above embodiment, the temperature control heater 16
Rather than forming the temperature control heater 16 by laminating them on the substrate, the substrate is etched to form a groove, and the temperature control heater 16 is embedded in the groove of the substrate.

Furthermore, in the embodiment shown in FIG. 15, the temperature control heater 16 is not formed by laminating it on the substrate as in the previous embodiment, but is instead embedded in the substrate. It is composed of

Furthermore, in the embodiment shown in FIG. 16, the temperature control heater 16 is not formed by laminating the temperature control heater 16 on the substrate as in the previous embodiment, but is formed by embedding the temperature control heater 16 in the substrate. It is made of a plurality of heating wires such as nichrome wires.

The rest of the structure and operation are the same as those of the previous embodiment, so their explanation will be omitted.

[0043]

[Effects of the Invention] The present invention has the above-described structure and operation, and it is possible to maintain the ink inside the print head at a constant temperature, and it is possible to record high-quality images, consume less power, and short-term. It is possible to provide an inkjet print head that can follow temperature changes and has a simple structure.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of an embodiment of an inkjet print head according to the present invention.

FIG. 2 is a plan view showing an embodiment of an inkjet print head according to the present invention.

FIG. 3 is a perspective view showing the inkjet print head.

FIG. 4 is a sectional view showing the same inkjet print head.

FIG. 5 is a plan view showing the same inkjet print head.

FIG. 6 is a side view showing the same inkjet print head.

FIG. 7 is a perspective view showing how the inkjet print head is attached.

FIG. 8 is a block diagram showing a control circuit.

FIG. 9 is a graph showing the power applied to the bubble generation heater.

FIG. 10 is a graph showing power applied to a temperature control heater.

FIG. 11 is a graph showing the temperature of the print head.

FIG. 12 is a graph showing the temperature of the print head without temperature control.

FIG. 13 is a plan view of main parts showing another embodiment of the invention.

FIG. 14 is a sectional view of a main part showing still another embodiment of the present invention.

FIG. 15 is a sectional view of a main part showing still another embodiment of the present invention.

FIG. 16 is a sectional view of a main part showing still another embodiment of the present invention.

FIG. 17 is a configuration diagram showing an inkjet recording apparatus to which a conventional temperature control device is applied.

FIG. 18 is a configuration diagram showing an inkjet recording apparatus to which a conventional temperature control device is applied.

FIG. 19 is a graph showing the operation of a conventional device.

[Explanation of symbols]

1 Print head 4 Ink flow path 5 Nozzle 16 Temperature control heater 19 Heater for bubble generation 32 Drive control circuit

Claims (4)

[Claims] 1. An inkjet print head that records an image by ejecting ink droplets by applying thermal energy to the ink according to image information by at least a thermal energy applying means, wherein a lower part of the thermal energy applying means is provided. , an inkjet print head characterized by disposing a heat generating means for temperature control. 2. The ink jet print head according to claim 1, wherein the electric power applied to the heat generating means for temperature control is controlled in accordance with the electric power applied to the thermal energy applying means. 3. The ink jet print head according to claim 1, wherein the heat generating means for temperature control is arranged in a layered manner on a lower layer of the thermal energy applying means. 4. The ink jet print head according to claim 1, wherein the heat generating means for temperature control comprises a heating wire embedded in a lower layer of the thermal energy applying means.