JPS6361605B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting the remaining amount of recording liquid such as ink in an ink jet recording apparatus. The ink reservoir of an inkjet recording apparatus will be explained below as an example.

In an inkjet recording device, the ink reservoir is generally located inside the device, and the remaining amount of ink cannot be monitored. If you drive the ink jet head when it is out of ink, not only will air bubbles get mixed into the pressure chamber, making it impossible to eject ink, but it will also have an adverse effect on the ink jet head itself as it is being driven dry, which will cause problems when filling the ink next time. This will result in unnecessary maintenance.

Conventionally, the remaining amount of ink has been mainly detected by detecting the liquid level in an ink reservoir. However, the method of detecting the remaining amount of ink by detecting the position of the liquid level can only be detected when the ink reservoir is always fixed. Furthermore, since the liquid surface is in contact with the outside air, gas dissolves into the ink. For example, in the case of an ink jet head that uses an electromechanical transducer, the dissolved gas regenerates within the pressure chamber, resulting in unstable or impossible ink discharge. It's easier to get into an irritated state. Furthermore, if the liquid surface is in contact with the outside air, dust in the outside air will dissolve into the ink, causing nozzles in the ink jet head to become clogged.

The present invention detects the remaining amount of ink when the ink in the ink reservoir is isolated from the outside air and the liquid level does not need to be constant, for example, when the ink reservoir is in the shape of a thin flexible bag. It also provides a means to do so.

The present invention is characterized in that a temperature measuring resistor is installed within the ink reservoir. An embodiment of the present invention will be described in detail below.

A resistance temperature detector is a substance whose resistance value changes significantly with temperature changes. In general, materials with a positive temperature coefficient include nickel, platinum, copper, etc., and materials with a negative temperature coefficient include metal oxides. The present invention utilizes this temperature measuring resistor to detect the remaining amount of ink. A resistance thermometer is originally used to measure temperature as a resistance thermometer, but in the present invention, it is possible to use a temperature measurement device that includes a resistance thermometer, which has the function of temperature measurement and is desired to keep the value as low as possible when measuring temperature. The feature is that the self-heating of the element system is used in reverse. An embodiment of the invention is shown in FIGS. 1 and 2. FIG. 1 shows a state where the ink 8 is filled, and FIG. 2 shows a state where the remaining amount of the ink 8 is low. The temperature measuring element 3 has a temperature measuring resistor 1 and a lead wire 2 inside, and is installed in ink 8 filled in a flexible ink bag 4 that blocks the outside air and ink. 5 is an ink inlet/outlet, and 6 is an opening provided in the ink reservoir protective case 7. Now power supply 9
When a more constant voltage is applied to the temperature measuring element 3, the temperature measuring element 3 generates Joule heat and self-heats. Generally, the amount of heat generated in the lead wire 2 is greater than the amount of heat generated in the resistance temperature detector 1, and the amount of heating can be adjusted by appropriately selecting the material, length and diameter of the lead wire 2, or adjusting the amount of heat generated by the lead wire 2. A resistor is provided in 2 and the resistance value is used. Now, in the state where the ink 8 is filled as shown in FIG. Its own temperature remains balanced and hardly changes. The current value flowing through the temperature measuring element 3 at this time is measured by the current detection device 10, and the current value at this time is used as a reference value. Next, as shown in FIG. 2, when the ink 8 is running low, there is almost no ink 8 around the temperature measuring element 3;
The temperature of the temperature measuring element 3 itself rises due to self-heating, and the resistance value of the temperature measuring resistor 1 changes. Therefore, the current value changes, and the remaining amount of ink 8 can be determined from that value.

FIG. 3 shows the relationship between the amount of ink and the current value when nickel, which has a positive and large temperature coefficient, is used as the resistance temperature detector 1. Since the resistance of nickel increases as the temperature increases, the current value decreases. If the current value A when the ink amount B requires ink replenishment is checked in advance, an alarm can be issued based on that value. A feature of this remaining ink amount detecting device is that the state in which the amount of ink is decreasing can be continuously determined based on the current value, which is largely different from other remaining ink amount detecting devices. Further, as a method of detecting the remaining amount of ink, it is also possible to check the characteristic value of the current value. Since the graph of the current value is a curve, its differential value also changes with the amount of ink. The feature of this method is that it is more stable against changes in ambient temperature than the method of examining the current value itself.

Next, FIG. 4 shows the relationship between the amount of ink and the current value when a metal oxide having a large negative temperature coefficient is used as the resistance temperature detector 1. In the case of metal oxides, the resistance decreases as the temperature increases, so the current value increases. In this case, as in FIG. 3, the amount of ink can be determined from the change in current value.

As explained above, the present invention is capable of disposing a self-heating temperature measuring element having a temperature measuring resistor in an ink reservoir, and capturing the temperature change of the temperature measuring element itself, which changes with the amount of ink, as a current change. The characteristic ink remaining amount detection device has the following effects.

(1) The ink liquid level is not exposed to the outside air. That is, it is possible to detect the amount of ink in an ink reservoir where the ink level is not constant.

(2) Since the state of decrease in ink can be continuously detected as a change in current value, it is also possible to know the amount of ink used.

[Brief explanation of drawings]

FIGS. 1 and 2 are block diagrams showing an embodiment of the liquid remaining amount detection device according to the present invention, and FIGS. 3 and 4 show resistance temperature sensors having positive and negative temperature coefficients as temperature measuring elements, respectively. FIG. 3 is a diagram showing the relationship between the amount of ink and the current value when used. DESCRIPTION OF SYMBOLS 1... Measuring resistor, 2... Lead wire, 3... Temperature measuring element, 4... Ink reservoir, 5... Ink inlet/outlet, 6... Opening, 7... Ink reservoir protective case, 8... Ink, 9...power supply, 10...current detection device.

Claims (1)

[Claims] 1. A resistance temperature detector connected to a heating means is arranged in a liquid storage container made of a flexible bag that blocks the outside air and liquid so that it is always present in the liquid, and the resistance temperature sensor is arranged to correspond to the amount of the liquid. A liquid remaining amount detection device that detects, as a change in current value, a resistance value of the temperature-measuring resistor that changes in accordance with a heat capacity of the liquid that changes.