JPS61290064A - Ink jet recorder - Google Patents

Abstract

PURPOSE:To enable temperature control to be performed with high accuracy, by providing a heater and a temperature sensor at such positions that the difference between the temperature of the heater and the temperature of an ink at a nozzle outlet becomes substantially equal to the difference between the temperature of the heater and the temperature of the sensor. CONSTITUTION:The sensor 5 is disposed at such a position that Th-Tc= Th-To and therefore Tc=To, where Th is the temperature of a heater part 2, Tc is the temperature of the sensor and To is the temperature of the ink 4 at the nozzle outlet 3, namely, the temperature of the sensor is always equal to the temperature of the ink at the nozzle outlet, irrespective of the environmental temperature, namely, the temperature Ti of inflow of the ink into a ceramic body 1. Electric power applied to the heater is so controlled that the temperature Tc of the sensor 5 is constant irrespective of the variations in the inflow ink temperature Ti. A head body is formed of a ceramic material having favorable thermal conductivity and excellent resistance to corrosion and chemicals, and a heating element and the temperature sensor are disposed in close contact with the surface of the body.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inkjet recording apparatus, and more particularly, to temperature control of ink ejected from nozzles in an inkjet recording apparatus.

The inkjet recording device guides the ink from the ink supply section to a narrow nozzle, and continuously sprays the ink in the form of particles from the opening at the tip of this nozzle.

It allows characters, figures, etc. to be drawn on a recording medium,
In order to perform recording, it is necessary that the frequency of occurrence of ink droplets ejected from a nozzle is stable and that the size of the ink droplets is uniform. However, the properties of the ink are affected by changes in ambient temperature, and in particular, the viscosity of the ink increases as the ambient temperature decreases. When the viscosity of the ink increases in this way, the frequency of ink droplet generation decreases, and the diameter of the ink droplets increases. If the frequency of occurrence or the diameter of ink particles ejected from the nozzle becomes uneven due to the ambient temperature, the characters printed on the recording medium will become unstable and unclear, leading to a lack of reliability in quality. Become. Therefore, conventionally, a heat conductive member is attached to cover the back of the recording head and the ink tube near the head, and a nichrome wire is wrapped around the outer circumference of the heat conductive member and covered with a heat-resistant insulating material. It has been proposed that ink is kept warm by arranging a temperature sensing element in a cavity provided at a position where the ink is heated (Japanese Patent Laid-Open No. 50-4912).
However, since the heat conductive member and the wound nichrome wire did not come into perfect contact with each other, the thermal efficiency was not sufficient, and there were also problems with durability such as breakage of the nichrome wire. In addition, an inkjet recording device has been proposed in which a heater is provided in the head liquid chamber to keep the ink warm (Japanese Patent Application Laid-Open No. 101473/1982), but since the heater is in direct contact with the ink, the ambient temperature When the heating power is low and a large heating power is required, bubbles may be generated, which has the disadvantage that the control temperature range is limited.

■---Five inventions were made in view of the above-mentioned circumstances.
It is an object of the present invention to provide a temperature control device that has good thermal efficiency, excellent durability, and can accurately control the temperature of ink ejected from an inkjet head.

Configuration In order to achieve the above object, the present invention continuously ejects ink droplets from a nozzle, and selectively charges and charges the ink droplets.
An inkjet recording apparatus that performs recording on a recording medium by deflecting the ink includes a heater that heats the ink and a temperature sensor that detects the temperature, and the temperature between the temperature of the heater and the ink temperature at the nozzle exit is determined. The heater and the temperature sensor are installed at positions such that the temperature difference between the temperature of the heater and the temperature of the temperature sensor is approximately equal. Hereinafter, the present invention will be explained based on examples.

FIG. 1 is a cross-sectional configuration diagram of an inkjet head suitable for use in an inkjet recording apparatus according to the present invention. In the figure, 1 is a ceramic body, 2 is a heater that heats the ink, 3 is a nozzle plate, and 4 is an inkjet head. , 5 is a temperature sensor that detects temperature, and as is well known, ink droplets are ejected from a nozzle to print on a recording medium (not shown), and a stable no-satellite area is obtained in particle formation. In order to achieve this, it is necessary to keep the ink temperature within a constant temperature range even when the environmental temperature changes. Therefore, in temperature control, the temperature Tc of the temperature sensor 5 is
The power applied to the heater is controlled so that it remains constant even if the temperature Ti of ink flowing into the heater changes. Therefore, in the present invention, when the environmental temperature, that is, the temperature at which ink flows into the ceramic body 1 is Ti, the temperature of the heater section 2 is Th, the temperature of the sensor 5 is Tc, and the ink temperature at the nozzle exit is To, Th-Tc =Th-To4Tc=:To That is, the sensor is installed at a position where the sensor temperature and the ink temperature at the nozzle outlet are always equal regardless of the environmental temperature.

If this is not done, for example, Ti=5℃, Th=60
℃, Tc=30℃.

If To = 25°C, when T i = 20°C, if Tc = 30°C, Th will be approximately 23°C, and T
o cannot be controlled constant.

FIG. 2 is a diagram showing the temperature between A and B in FIG. 1 when the present invention is implemented. Even if the environmental temperature changes, point C, which has approximately the same temperature as TO, remains almost the same. , if the sensor 5 is placed at this position C, Tc=To
This allows for highly accurate temperature control.

FIG. 3 is a diagram showing the isothermal line a (indicated by a dashed line) of TO. According to this isothermal ia, the above effect can be obtained no matter where the sensor is placed, C or D. In addition, if the above-mentioned helad body 1 is made of a ceramic material, and a heating resistor 2 and a temperature sensor resistor 5 are provided on the surface thereof by thick film printing or the like, and the ceramic in contact with the ink chamber is directly heated by the heating element 2, Heat conduction efficiency and control response are greatly improved. Furthermore, ceramic materials have good corrosion resistance and chemical resistance, and there is no problem of wettability with ink, allowing for good temperature control.

FIG. 4 is a diagram showing an example of a temperature control circuit used in carrying out the present invention, in which the power supply voltage Vcc is divided by the resistor R1 and the resistance of the temperature sensor, and the divided voltage output is used for calculating the voltage follower. In addition to amplifier 10.

The output is compared with a reference voltage V r e f. If the temperature sensor exhibits a negative resistance change characteristic with respect to temperature as shown in FIG.
The output of the operational amplifier 11 becomes L level, the transistor Tr1 is turned off, and when the transistor Tr1 is turned on, a current flows to the heating element and heats the ink.

Effects As is clear from the above description, according to the present invention, the temperature of the temperature sensor and the ink temperature at the head outlet are the same regardless of the environmental temperature, so that highly accurate temperature control can be performed. In addition, the head body is made of a ceramic material with good thermal conductivity, corrosion resistance, and chemical resistance, and the heating element and temperature sensor are provided in close contact with the surface of the ceramic material, resulting in good thermal conductivity.

It is possible to obtain a temperature control device that has high responsiveness, can perform accurate ink temperature control, and has excellent durability without disconnection or deterioration over time.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of a head body used in the inkjet recording apparatus of the present invention, FIG. 2 is a diagram showing the relationship between the installation location of a temperature sensor and temperature, and FIG. FIG. 4 is a diagram showing an example of a temperature control circuit, and FIG. 5 is a diagram showing temperature sensor output characteristics. 1... Head body, 2... Heater, 3... Nozzle plate, 4... Ink, 5... Temperature sensor. Fig. 1 ACB Fig. 4 Fig. 5 □ To the seventh sir # (performance)

Claims (3)

[Claims] (1) In an inkjet recording device that continuously ejects ink droplets from a nozzle and records on a recording medium by selectively charging and deflecting the ink droplets, a heater that heats the ink and a temperature a temperature sensor that detects a temperature difference between the temperature of the heater and the ink temperature at the nozzle outlet;
An inkjet recording apparatus characterized in that the heater and the temperature sensor are installed at positions where the temperature difference between the temperature of the heater and the temperature of the temperature sensor is approximately equal. (2) The head body having the nozzle is made of ceramics, and a heating resistor and a temperature sensor resistor are provided on the surface thereof. Inkjet recording device. (3) The inkjet recording apparatus according to claim (2), wherein a resistor paste is provided on the surface of the ceramic body by thick film printing.