JPH04250060A - Temperature control device for ink jet recording device - Google Patents

Abstract

PURPOSE:To provide a temperature control device for an ink jet recording device which enables holding a printing head temperature at a constant value without being influenced by a difference in the calorific value of a printing head owing to a printing pattern and enables execution of recording of a picture of high quality. CONSTITUTION:A temperature control device comprises a number of dots counting means to count the number of dots printed by a printing head during a given time, a printing head mounting means to mount the printing head, a heat generating element for controlling temperature disposed in the vicinity of the printing head of the printing head mounting member, and a control means to control energy applied on the heat generating element for controlling temperature based on a counting value obtained by the number of dots counting means.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature control device for an inkjet recording device, and in particular is used in an inkjet recording device that records an image by at least heating ink and ejecting it in accordance with image information. This invention relates to a temperature control device.

0002

2. Description of the Related Art Conventionally, in the above-mentioned ink jet recording apparatus, 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. Therefore, it is clear that the recording characteristics of an inkjet recording apparatus largely depend on the temperature of the ink, that is, the temperature of the print head containing the ink.

[0003] For this reason, in conventional ink jet recording apparatuses, a temperature control device is used to keep the temperature of the print head constant and enable stable recording. As shown in FIGS. 9 and 10, the most common temperature control device used in this inkjet recording apparatus is installed at the base end of a print head mounting member 101 with a print head 100 attached to the tip. , temperature detection means 10
2 and a heating means 103, the heating means 103 is provided so that the temperature detected by the temperature detecting means 102 is constant.
Some devices are configured so that the energy given to the device is controlled by a power control circuit 104.

0004

However, the above-mentioned prior art has the following problems. That is, in the case of the temperature control device described above, the heating means 1 is controlled so that the temperature detected by the temperature detection means 102 is constant.
Since the energy given to 03 is controlled by the power control circuit 104, control is simple. However, when 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 printing The temperature of head 100 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 0.00, 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. 11, the print head 100 has a temperature difference between its internal temperature and the temperature detected by the temperature detection means 102, and the print head 100
There was a problem in that it was difficult to control 0 to a constant temperature.

In order to solve this problem, it is necessary to reduce the temperature difference between the temperature inside the print head 100 and the temperature detected by the temperature detection means 102. Therefore, it is also possible to provide the temperature detection means 102 inside the print head 100. However, with such means, although the temperature inside the print head 100 can be correctly detected by the temperature detection means 102, there is a delay in heat conduction from the heating means 103 to the print head 100. Therefore, even if the heating means 103 controls the heating after the temperature detecting means 102 detects a temperature change, the heating control may not be completed in time as shown in FIG. 12, and in some cases, thermal oscillation may occur. Therefore, a new problem arises in that sufficient control becomes impossible.

[0006]

[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 make it possible to maintain the print head at a constant temperature without being affected by differences in print head heat generation depending on the print pattern, and to maintain the temperature of the inkjet recording device that enables high-quality image recording. The purpose is to provide a control device.

That is, the invention described in claim 1 of the present invention includes a print head that records an image by ejecting ink droplets by applying at least thermal energy to the ink according to image information. A temperature control device for an inkjet recording device, comprising: a dot number counting means for counting the number of dots printed by the print head within a predetermined time; a print head mounting member for mounting the print head; and a print head mounting member for mounting the print head. It is configured to have a heating element for temperature control disposed near the print head, and a control means for controlling the energy applied to the heating element for temperature control based on the count value by the dot number counting means. .

[0008] The time range in which the number of printed dots is counted by the dot number counting means is set, for example, to one scanning time of the print head.

[0009] Furthermore, the invention described in claim 3 of the present invention is provided with a print head that records an image by ejecting ink droplets by applying at least thermal energy to the ink according to image information. A temperature control device for an inkjet recording device, comprising: an ambient temperature detection means for detecting the ambient temperature of the print head; a dot number counting means for counting the number of dots printed by the print head within a predetermined time; a print head mounting member for mounting, a heating element for temperature control disposed near the print head of the print head mounting member, and the ambient temperature of the print head detected by the ambient temperature detection means and the dot number count. and a control means for controlling the energy applied to the temperature control heating element based on the count value by the means.

The maximum number of print dots that can be printed by one scan of the print head is M, the count value by the dot number counting means is N, and the ambient temperature of the print head detected by the ambient temperature detection means is Ts. In this case, the energy E applied to the temperature control heating element within one scan time of the print head is, for example, E=C1×(Ts-T)×(C2-N/M)C1, C2
:Almost satisfies the constant relationship, and the value of constant C2 is 0.5<
It is set so that C2<2.

[0011]

[Operation] The invention as set forth in claim 1 of the present invention includes: a dot number counting means for counting the number of dots printed by the print head within a predetermined time; and a print head mounting member for mounting the print head. , a heating element for temperature control disposed near the print head of the print head mounting member, and a control means for controlling energy applied to the heating element for temperature control based on the count value by the dot number counting means. It is configured to have. Therefore, by controlling the energy applied to the heating element for temperature control by the control means according to the number of dots printed within a predetermined time that determines the amount of heat generated by the print head, The temperature of the mounting member can be set to a predetermined temperature. Therefore, by controlling the amount of thermal energy that flows from the print head to the print head mounting member with the print head mounting member set at a predetermined temperature, the temperature of the print head can be maintained substantially constant.

[0012] In the invention described in claim 3 of this invention, in addition to the above configuration, an ambient temperature detection means for detecting the ambient temperature of the print head is provided, so that it is possible to cope with changes in the environmental temperature. This makes it possible to maintain a constant temperature of the print head with higher precision.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on the illustrated embodiments.

FIGS. 2 to 4 are schematic configuration diagrams showing an inkjet recording apparatus to which the temperature control device for an inkjet recording apparatus according to the present invention is applied.

In the figure, 1 is a print head, and this print head 1 has a heat storage layer 3, a heat generation layer 4, and a protective layer 5 laminated in this order on a Si wafer 2, as shown in FIGS. 5 and 6. The heating element substrate 6 and the Si wafer 7 are provided with nozzles 8, 8...
It is constructed by bonding a counter substrate 9 with a groove formed therein.

As shown in FIG. 2, the print head 1 has the following features:
It is attached to one side of the print head mounting member 10,
The print head mounting member 10 has a rectangular shape that is thicker and larger than the print head 1. Further, the print head mounting member 10 is fixed to a convex portion 12 projecting from the upper surface of a carriage 11 made of aluminum or the like at a position away from the print head 1 with screws, while being positioned with a pin (not shown). The carriage 11 is slidably held by two rods 13, 13 fixedly arranged in the horizontal direction. Note that the carriage 11 is provided with a large number of fins (not shown) in order to enhance the heat dissipation effect.
is formed.

Further, an electric signal is applied to the print head 1 via a PWB (printed circuit board) 14, and the PWB 14 is connected to a side surface of the print head mounting member 10 on the same side as the print head 1. is fixed to. The print head 1 and the PWB 14 are connected by wire bonding 15, and the PWB 14 and a drive circuit (not shown) are connected by a flexible cable 16. Ink is supplied to the print head 1 through a flexible tube 17 from an ink reservoir (not shown).

By the way, in this embodiment, an ambient temperature detection means for detecting the ambient temperature of the print head, a dot number counting means for counting the number of dots printed by the print head within a predetermined time, and a a print head mounting member for attaching the print head; a heating element for temperature control disposed near the print head of the print head mounting member;
and a control means for controlling the energy applied to the temperature control heating element based on the ambient temperature of the print head detected by the ambient temperature detection means and the value counted by the dot number counting means. There is.

That is, as shown in FIG. 1, a first thermistor 20 as an ambient temperature detection element for detecting the ambient temperature of the print head 1 is arranged around the print head 1 of the ink jet recording apparatus. ing.

Further, as shown in FIG. 2, the print head 1 has a print head mounting member 10 at the tip of a print head mounting member 10 made of aluminum or the like, which is thicker and larger than the print head 1 as described above and has a rectangular shape on the side. However, the print head 1 is attached using a highly thermally conductive adhesive (e.g.
This is done by adhering and fixing using a silver particle-dispersed epoxy adhesive.

Furthermore, a silicon rubber heater 21 as a heating element for temperature control is fixed to the back surface of the print head 1 of the print head mounting member 10 with screws. Further, as shown in FIG. 4, a second thermistor 22 as a temperature detection element is embedded in the back side of the PWB 14 of the print head mounting member 10 in order to set the preheating temperature of the print head 1 and prevent overheating. ing.

FIG. 1 shows a control circuit in one embodiment of a temperature control device for an inkjet recording apparatus according to the present invention.

In the figure, 23 is a host machine that outputs print data for image recording, 24 is a printer buffer that temporarily stores the print data output from the host machine 23, and 25 is one line from the printer buffer 24. 22 is a second thermistor provided near the print head 1, and 21 is a silicon rubber provided near the print head 1. The heater 26 is a dot number counting circuit 20 that counts the number of printed dots of one line of print data output from the printer buffer 24.
27 is a first thermistor that detects the temperature around the print head 1; 27 is a surrounding temperature detection circuit that detects the temperature around the inkjet recording device detected by the first thermistor 20; 28 is this surrounding temperature detection circuit 27. An A/D conversion circuit 29 converts the output value from the dot number counting circuit 26 into a digital signal, and 29 is the output of the dot number counting circuit 26 and the A/D conversion circuit 28.
a look-up table (hereinafter referred to as LUT) consisting of a ROM etc. that sets the power supplied to the silicon rubber heater 21 to a predetermined value based on the output from the silicon rubber heater 21;
30 is a D/A conversion circuit that converts the output value from the LUT 29 into an analog signal, and 31 is the D/A conversion circuit 30.
This is a heating element drive circuit that drives the silicon rubber heater 21 based on the value output for each line.

By the way, the inkjet recording apparatus described above applies an image signal to the print head 1 via the flexible cable 16 or the like, and heats the ink in the print head 1 by causing the heat generating layer 4 to generate heat in accordance with the image signal. This bubble causes ink droplets to be ejected from the nozzles 8, 8, . configured to record images.

In this manner, thermal energy corresponding to print data is applied to the print head 1 by the heat generating layer 4 during printing. That is, thermal energy corresponding to the product of the number of dots of print data and the energy required to print one dot is applied to the print head 1 within the carriage scanning time of one line. A part of this thermal energy is lost along with the ink droplets during printing, but most of it remains in the print head 1 and becomes the main factor that changes the temperature of the print head 1.

The thermal energy remaining in the print head 1 flows from the print head 1 to the print head mounting member 10, and
Further, it flows from the print head mounting member 10 into the carriage 11 . This thermal energy flow is directed to the print head mounting member 1.
0, and when the temperature of the print head mounting member 10 is relatively high, the thermal energy flowing from the print head 1 to the print head mounting member 10 is small, and the temperature of the print head mounting member 10 is relatively high. If it is low,
More heat energy flows into it.

Therefore, by controlling the temperature of the print head mounting member 10 in advance according to the amount of thermal energy flowing in, the temperature change in the print head 1 caused by the amount of energy supplied to the print head 1 can be suppressed to a small level. This makes it possible to stably control the temperature. That is, the number of dots detected by the dot number counting circuit 26 corresponds to the amount of thermal energy supplied to the print head 1 when performing the next carriage scan. Therefore, by controlling the temperature of the print head mounting member 10 according to the number of dots detected by the dot number counting circuit 26, it is possible to stably control the temperature of the print head 1. The temperature control of the print head mounting member 10 is as follows:
This is done by controlling the power supplied to the silicon rubber heater 21.

The power supplied to the silicon rubber heater 21 is set by the dot number counting circuit 2 as shown in FIG.
In addition to the number of dots detected by 6, the ambient temperature detection circuit 27 is also taken into consideration. This is because the ambient temperature of the print head 1 is also a factor that determines the temperature of the print head mounting member 10. However, in an environment where the ambient temperature of the print head 1 is substantially constant, there is no need to consider the ambient temperature of the print head 1.

As described above, the power to be supplied to the silicon rubber heater 21 is set by the LUT 29 to which the output of the dot number counting circuit 26 and the output of the ambient temperature detection circuit 27 are input. The algorithm for stably controlling the temperature of the print head 1 is to set the printing rate in one scan of the print head 1 as R, that is, the maximum number of print dots that can be printed as M, and the number of detected print dots as N. Then, the printing rate R is N/M
is given by Further, when the ambient temperature of the print head 1 detected by the ambient temperature detection circuit 27 is T and the set temperature of the print head 1 is Ts, the energy E applied to the silicon rubber heater 21 within one head scanning time is
It was found that E=C1×(Ts−T)×(C2−N/M) (1). Here, C1 and C2 are constants.

The constants C1 and C2 are values specific to the print head 1 and the recording apparatus. Since the printing rate N/M changes from 0 to 1, it is desirable that C2>1 for sufficient control. Furthermore, since there are few images where the entire surface is black (N/M=1), C2>0.5 may be sufficient in practice. here,
If the energy E is negative as a result of the calculation, the energy E applied to the silicon rubber heater 21 is set to zero.

On the other hand, the energy Es required to maintain the print head 1 at a preset temperature Ts is approximately Es=C
Since it is given by 1×C2(Ts-T), the print head 1
In order to avoid excessive heating, it is desirable that the constant C2 be as small as possible, and in practice it is desirable that C2<2. Here, the print head 1 is heated to a preset temperature Ts.
Since the energy Es required to maintain the temperature changes depending on whether the carriage 11 is scanning or not, the warm-up time, etc., the energy E applied to the silicon rubber heater 21 also varies depending on whether the carriage 11 is scanning or not, the warm-up time, etc. It is desirable to control.

In this manner, the energy E given by equation (1) is calculated in advance for each printing rate N/M, and the value obtained by this calculation is stored in the LUT 29 as a digital value.

It goes without saying that the energy E to be applied to the silicon rubber heater 21 may be determined by arithmetic processing by the CPU without using the LUT, but it is also possible to perform more detailed nonlinear control tailored to each print head 1. To do this, it is more convenient to use an LUT.

In the above configuration, the temperature control device for the inkjet recording apparatus according to this embodiment controls the temperature of the print head in the following manner. That is, as shown in FIG. 1, in the inkjet recording apparatus, the heating element drive circuit 31 supplies power to the silicon rubber heater 21 so that the output of the second thermistor 22 becomes a predetermined value when the power is turned on and when not printing. The temperature of the print head 1 is quickly preheated to the set temperature Ts. Furthermore, ink is supplied to the print head 1 through a flexible tube 17 from an ink reservoir (not shown). Note that the ambient temperature of the print head 1 is detected by the first thermistor 20, and the ambient temperature detection circuit 27
The signal is detected by the A/D conversion circuit 28 and converted into a digital signal by the A/D conversion circuit 28.

[0035] In order to record an image using the inkjet recording apparatus, the print data output from the host machine 23 is once recorded in the printer buffer 24. The print data once stored in the printer buffer 24 is transferred to the head drive circuit 25 and the flexible cable 1.
6, etc., to the print head 1. Then, the ink in the print head 1 is heated by the heat generating layer 4 that generates heat according to the image signal to generate bubbles, and the bubbles cause ink droplets to be ejected from the nozzles 8, 8, . . . as shown in FIG. By moving the print head 1 in the horizontal direction by a carriage 11, an image is recorded on a recording paper 19 whose back side is supported by a platen 18.

At this time, the print data outputted from the host machine 23 and once recorded in the printer buffer 24 as described above is outputted line by line to the dot number counting circuit 26 as shown in FIG. The dot number counting circuit 26 counts the number of printed dots of one line of print data. The number of printed dots of this counted print data is 4bi
It is sent to the LUT 29 as a digital value of ts. Further, the ambient temperature of the print head 1 detected by the first thermistor 20 and detected by the ambient temperature detection circuit 27 is also input to this LUT 29 as a 4-bit digital value via the A/D conversion circuit 28. .

[0037] Then, the LUT 29 consisting of ROM etc.
A value corresponding to the value of energy E stored in advance based on the above equation (1) is output as an 8-bit digital value. The digital value output from this LUT29 is D.
After being converted into an analog value by the A conversion circuit 30, it is output to the heating element drive circuit 31. The heating element drive circuit 31 supplies a predetermined power E to the silicon rubber heater 21 based on an analog value set based on the printing rate and the like.

The power supplied to the silicon rubber heater 21 is controlled before the start of the carriage scan for recording the print data used to control the power, or every time the next print data is input after the previous carriage scan is completed. It will be done.

As described above, since the configuration is such that the power supplied to the silicon rubber heater 21 is controlled prior to carriage scanning, the print head 1 is controlled as shown in FIG.
temperature fluctuations are reduced, and recording characteristics are kept stable. Note that when temperature control is not performed, the temperature fluctuation of the print head 1 is large as shown in FIG.

By the way, in the print head 1 of this embodiment,
It is experimentally known that the size of the print dot increases by approximately 1% in diameter for every 1°C increase in the temperature of the print head 1. It is desirable to control temperature fluctuations to within ±5°C.

[0041] Therefore, the present inventor conducted an experiment to confirm the effect of this example.

As a comparative example, when printing a solid black image with a width of A3 size using a conventional device, print head 1
Due to the temperature increase due to heat accumulation, the size of the printed dots became approximately 20% larger than usual just before the end of scanning, which caused a change in density.

On the other hand, when the apparatus of this example was used, the variation in the size of printed dots was less than ±3%, and good recording with small density changes was achieved.

In the above embodiment, the case where the power supplied to the silicon rubber heater 21 was controlled based on the number of dots printed in one carriage scan was explained, but the time range on which the control is based is Of course, the range is not limited to one carriage scan, but may be over multiple carriage scans, or may be a range in which one carriage scan is divided into a plurality of areas. Further, in the case of a line head that does not perform carriage scanning, control can be performed based on the number of dots printed in a predetermined number of lines from the line currently being printed.

In addition, in a print head such as a line head that has a wide printing width and the temperature distribution in the direction of arrangement of multi-nozzles cannot be ignored, the dot number counting circuit 2 is used for each arbitrary printing width.
6・Heating element drive circuit 31・Silicon rubber heater 21
By dividing the temperature into a plurality of parts and controlling each print width independently, more uniform temperature control can be achieved.

Furthermore, when printing by the print head 1 uses thermal energy to express gradations, the number of printing dots N
It is necessary to perform control by taking not only the gradation level into account, but also the gradation level. In this case, the maximum gradation level is 1, the non-printing area is 0, and the sum of the gradation levels of all dots in one scan of the print head 1 is used instead of the number N of printing dots. Accurate temperature control becomes possible.

[0047]

[Effects of the Invention] This invention has the above-described structure and operation, and it is possible to maintain the print head at a constant temperature without being affected by the difference in heat generation amount of the print head depending on the print pattern, resulting in high image quality. It is possible to provide a temperature control device for an inkjet recording device that is capable of recording images of

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a temperature control device for an inkjet recording apparatus according to the present invention.

FIG. 2 is a perspective view showing the inkjet recording apparatus.

FIG. 3 is a side view showing the same inkjet recording apparatus.

FIG. 4 is a cross-sectional view showing the mounting portion of the print head.

FIG. 5 is a perspective view showing the print head.

FIG. 6 is a sectional view of a main part of the print head.

FIG. 7 is a graph showing the operation of this embodiment.

FIG. 8 is a graph showing the temperature change of the print head when temperature control is not performed.

FIG. 9 is a configuration diagram showing an inkjet recording apparatus to which a conventional temperature control device is applied.

FIG. 10 is a configuration diagram showing an inkjet recording apparatus to which a conventional temperature control device is applied.

FIG. 11 is a graph showing the operation of a conventional device.

FIG. 12 is a graph showing the operation of a conventional device.

[Explanation of symbols]

1 Print head 10 Print head mounting member 20 First thermistor 21 Silicon rubber heater, 24 Printer buffer 25 Head drive circuit 26 Dot number counting circuit 29 LUT 31 Heating element drive circuit

Claims (4)

[Claims] 1. A temperature control device for an inkjet recording apparatus comprising a print head that records an image by ejecting ink droplets by applying at least thermal energy to the ink according to image information, wherein a dot number counting means for counting the number of dots printed within a predetermined time; a print head mounting member for mounting the print head; and a heat generating unit for temperature control disposed near the print head of the print head mounting member. 1. A temperature control device for an inkjet recording apparatus, comprising: an element; and a control means for controlling energy applied to the heating element for temperature control based on a count value by the dot number counting means. 2. Temperature control of an inkjet recording apparatus according to claim 1, wherein the time range for counting the number of printed dots by the dot number counting means is one scan time of the print head. Device. 3. A temperature control device for an inkjet recording apparatus comprising a printhead that records an image by ejecting ink droplets by applying at least thermal energy to the ink according to image information, comprising: ambient temperature detection means for detecting ambient temperature; dot number counting means for counting the number of dots printed by the print head within a predetermined time; a print head mounting member for mounting the print head; and the print head mounting member. A heating element for temperature control disposed near the print head of the member, and a heating element for temperature control based on the ambient temperature of the print head detected by the ambient temperature detection means and the count value by the dot number counting means. 1. A temperature control device for an inkjet recording apparatus, comprising a control means for controlling applied energy. 4. The maximum number of print dots that can be printed by one scan of the print head is M, the count value by the dot number counting means is N, and the ambient temperature of the print head detected by the ambient temperature detection means. When is Ts,
The energy E applied to the temperature control heating element within one scanning time of the print head almost satisfies the relationship E=C1×(Ts-T)×(C2-N/M) (provided that C1 , C2 is a constant), and the value of constant C2 is set to 0.5<C2<2.