JPH04355152A - Ink jet recording apparatus - Google Patents

Abstract

PURPOSE:To prevent the drying in a cap in the cap open state due to printing operation by changing the number of flashing pulses corresponding to environmental humidity. CONSTITUTION:First and second thermisters 1,2 are respectively attached to the outside of a cap 3 and the interior lined with a water absorbing material 4 thereof to measure atmospheric temp. (t1) and the temp. (t2) of the water absorbing material 4. The humidity of environment is measured on the basis of the temps. t1, t2 to calculate the number of flashing pulses necessary for the cap 3 to hold proper moisture in the calculated humidity environment. Since the cap 3 always receives the supply of proper moisture even at an open time by the flashing operation corresponding to the number of flashing pulses, the thickening of the ink remaining in the cap or the re-adhesion of thickened ink to a nozzle surface is prevented.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus.

0002

BACKGROUND OF THE INVENTION The viscosity of ink in ink jet recording changes greatly with changes in temperature, which affects the amount of ink that adheres to the nozzle surface of a print head and the ink drying time, causing disturbances in recording quality. On the other hand, since the operating temperature of an inkjet recording device generally ranges over a wide range from 0° C. to 40° C., a cap mechanism is provided that tightly contacts the nozzle surface of the print head when the print head is not in operation.

This capping mechanism is used for a capping operation to prevent the nozzle surface from excessively drying, and for a cleaning operation to suction and remove ink adhering to the nozzle surface and thickened ink inside the head, and is used for inkjet recording. Guarantees uniform recording quality of the device.

[0004] Furthermore, when continuous printing continues for more than a certain time, in order to discharge the ink that has thickened in the less frequently used nozzles, the ink is discharged from the nozzle in a place that is not involved in printing, such as outside the printing area. The viscosity of the ink inside the head nozzle is maintained constant by the flushing operation of ejecting droplets.

[0005]

[Problems to be Solved by the Invention] As described above, the cap mechanism and flushing operation are important in an inkjet recording device, but during printing, the inner surface of the cap is in a standby state open to the outside air. If printing continues for a long time, the moisture inside the cap will continue to evaporate, leaving the cap in a very dry state. As a result, the ink remaining in the cap increases in viscosity, and the thickened ink adheres to the nozzle surface during the next cap operation, causing a decrease in recording quality and, in the worst case, clogging of the nozzle.

An object of the present invention is to provide an inkjet recording device that eliminates the above-mentioned drawbacks and has improved environmental resistance.

[0007]

[Means for Solving the Problems] The inkjet recording apparatus of the present invention includes a drive mechanism that ejects ink droplets from a print head in response to a print command, and a cap mechanism that closely contacts the print head when the print head is inactive. an inkjet recording device having a first temperature detection means on the outside of the cap mechanism, and a second temperature detection means on the inside of the cap mechanism.
temperature detecting means, a water absorbing material in close contact with the second temperature detecting means, and a difference between the temperature detected by the first temperature detecting means and the temperature detected by the second temperature detecting means. It is characterized by having a flushing operation that changes according to

[0008]

[Operation] According to the present invention, it is possible to change the amount of ink discharged in the flushing operation according to the temperature difference detected by the first temperature detection means and the second temperature detection means, thereby preventing drying inside the cap. This can prevent the residual ink from increasing in viscosity and the thickened ink from re-adhering to the nozzle surface.

[0009]

[Embodiment] The embodiment shown in the drawings will be explained below.

FIG. 1 shows the structure of the cap mechanism in this embodiment. Print head 1100 is movable in direction A. The cap 3 is attached to the tip of the cap frame 5, and has an ink suction port 13 open. The ink suction port 13 communicates with an ink discharge tube 10 connected to the rear end of the cap frame 5. During the cleaning operation, the cap 3 protects the print head 100.
The ink that is brought into close contact with the nozzle surface of the ink suction port 13 and sucked from the ink suction port 13 is discharged from the ink discharge tube 10. The cap frame 5 has a single gear 7 and is attached to the cap frame support 6 by a cap frame attachment shaft 9.

When the single gear 7 is rotated by the cap opening/closing motor 8, the cap frame 5 moves in a circle around the cap frame mounting shaft 9. This causes the cap to open and close. Note that the print head 10
In order to improve the adhesion between the cap 3 and the cap 3, the cap 3 is made of an elastic material such as rubber.

The first thermistor 1 is attached to the cap frame 5
It is attached to the upper part of the cap 3 and used as a means for detecting the temperature of the outside air near the cap 3. A resistance value of the first thermistor 1 corresponding to the temperature near the cap 3 is output to the first terminal 11 .

The water absorbing material 4 is attached so as to cover the entire inner surface of the cap 3 with a uniform thickness. The second thermistor 2 is placed closely between the water absorbent material 4 and the inner surface of the cap 3, and is used as a means for detecting the temperature of the surface of the water absorbent material 4. A resistance value of the second thermistor 2 corresponding to the temperature of the surface of the water absorbing material 4 is outputted to the second terminal 12 .

[0014] Here, the first and second temperature detection means are not limited to thermistors, but may also be thermocouples or the like.

The operation of this embodiment will be explained below with reference to FIGS. 2 and 3.

FIG. 2 is a block diagram showing control of the flushing operation. The first terminal 11 and the second terminal 12 are connected to a first data converter 14 and a second data converter 15, respectively. The first data converter 14 outputs first temperature data 16 (t1) corresponding to the resistance value of the first thermistor 1 appearing at the first terminal 11.

Similarly, the second data converter 15 outputs second temperature data 17 (t2) corresponding to the resistance value of the second thermistor 2 appearing at the second terminal 12. At this time, t1 indicates the outside air temperature near the cap 3, and t2 indicates the temperature on the surface of the water absorbing material 4.

Since the cap 3 is open to the outside air during printing, the water contained in the ink evaporates from the surface of the water-absorbing material 4, and t2 takes a lower value than t1. Since t1 and t2 correspond to the dry bulb temperature and wet bulb temperature, respectively, in the psychrometer, the humidity of the outside air in which the cap 3 is placed can be measured from t1 and the temperature difference between t1 and t2.

Based on t1 and t2, the CPU 18 measures the humidity of the environment in which the present inkjet recording apparatus is placed, and adjusts the amount of humidity necessary for the cap 3 to retain an appropriate amount of moisture in the determined humidity environment. The number of flushing pulses, 19, is output to the nozzle control section 21. If the printing state continues for a specified time or more, the CPU 18 outputs a flushing execution command 20. In response to this, the head control unit 22 interrupts the printing operation and moves the head to a position in front of the cap 3. On the other hand, after the head 100 moves to the front of the cap 3, the nozzle control unit 21 performs jetting from all nozzles for the number of flushing pulses, which is 19. Through this flushing operation, the cap 3 is replenished with ink and can maintain an appropriate amount of moisture.

FIG. 3 is a diagram showing the number of flushing pulses depending on the humidity environment determined from t1 and t2. For the sake of simplicity, the humidity region is divided into three, and the number of flushing pulses per fixed time (19) required for the cap 3 to retain an appropriate amount of moisture in each humidity environment is set. T.L.
, TH indicate the lower and upper limits of the guaranteed operation temperature of the present inkjet recording apparatus. Δt indicates the temperature difference between t1 and t2. Further, HL and HH represent area boundary humidity. The humidity regions I, II, and III indicate lower humidity, that is, dryness.

[0021] If the value of Δt when the first thermistor 1 takes the value of a certain temperature t1 is ΔtIII, it is determined that the environmental humidity is high because the humidity region is III,
The number of flushing pulses is 19, which is the lowest number of 10 pulses/3.
Takes a value of 0 seconds. Similarly, the values of Δt are ΔtII, ΔtI
In this case, the humidity ranges are II and I, respectively, and the number of flushing pulses 19 takes values of 20 pulses/30 seconds and 40 pulses/30 seconds, depending on the respective environmental humidity.

In this example, assuming that the amount of water that evaporates from the water absorbing material 4 per hour at a certain humidity is constant, the number of flushing pulses 19 necessary for the cap 3 to retain an appropriate amount of water is converted to per 30 seconds. expressing. As mentioned above, the flushing operation is executed when the printing state continues for a specified period of time or more, so it must be converted into a unit of specified period. If this specified time is set to 30 seconds, the number of pulses can be used as is as the number of flushing pulses 19.

The function of determining the number of flushing pulses 19 from t1 and t2 is performed by software (for example, t
1 and t2, access to a data table, etc.), or hardware such as a logic circuit.

As described above, since the number of flushing pulses 19 changes, the higher the environmental humidity is, the lower the number of flushing pulses is, and the lower the environmental humidity is, the higher the flushing pulse number 19 is, so that the cap 3 can retain an appropriate amount of moisture even in the open state. Therefore, even if there is ink remaining inside the cap, the ink will not thicken due to drying and the thickened ink will not re-adhere to the nozzle surface. Since the cap itself can be prevented from hardening due to drying, the functionality of the cap can be guaranteed for a long period of time. Furthermore, since the ink consumption is the minimum necessary in the environment humidity, the proportion of ink consumption due to flushing operations can also be reduced.

Since the environmental humidity rarely changes rapidly, it is not necessary to measure t1 and t2 and to obtain the number of flushing pulses 19 frequently. It is sufficient to perform this operation for the next flushing operation after the flushing operation is completed, and in practice, it is acceptable even after several flushing operations, so it has almost no effect on the throughput of the inkjet recording device. .

[0026]

Effects of the Invention As explained above, according to the cap mechanism and flushing operation of the inkjet recording apparatus of the present invention, the amount of ink ejected during flushing changes depending on the humidity of the usage environment, and the cap is always fixed even when released. Since an appropriate amount of moisture is supplied, the ink remaining inside the cap will not thicken or the thickened ink will not re-adhere to the nozzle surface, and the environmental resistance of the inkjet recording device can be improved.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing one embodiment of the configuration of a cap mechanism of an inkjet recording apparatus according to the present invention.

FIG. 2 is a block diagram showing control of a flushing operation using two temperature data.

FIG. 3 is a graph illustrating how to determine the number of flushing pulses depending on the humidity environment from two temperature data.

[Explanation of symbols]

1 First thermistor 2 Second thermistor 3 Cap 4 Water absorbing material 5 Cap frame 6 Cap frame support 7 Single gear 8 Cap opening/closing motor 9 Cap frame mounting shaft 10 Ink discharge tube 11 First terminal 12 Second terminal 13 Ink inlet 14 Data conversion section 15 Data conversion section 16 Temperature data (t1) 17 Temperature data (t2) 18 CPU 19 Number of flushing pulses 20 Flushing execution command 21 Nozzle control section 22 Head control section

Claims (1)

[Claims] 1. An inkjet recording apparatus comprising: a drive mechanism that ejects ink droplets from a print head in response to a print command; and a cap mechanism that is in close contact with the print head when the print head is inactive; A first temperature detection means is provided on the outside, a second temperature detection means is provided on the inside of the cap mechanism, and a water absorbing material is provided in close contact with the second temperature detection means, and the first temperature detection means is detected. An inkjet recording apparatus characterized by having a flushing operation that changes depending on the difference between the temperature detected by the second temperature detection means and the temperature detected by the second temperature detection means.