Circuit and Method for Detecting Ink Cartridge Mounting in Ink Jet Recording Apparatus

1. Technical Field

The present invention relates to an ink jet recording apparatus for recording images on a recording medium by discharging ink from an ink cartridge to the recording medium through a nozzle, and more particularly, to a circuit and method for detecting whether an ink cartridge is mounted in an ink jet recording apparatus and the type of ink cartridge mounted in the ink jet recording apparatus.

2. Background Art

Substantial developments have been made in the field of electronic recording technology. Specifically, a wide variety of highly efficient recording systems currently available which are capable of recording characters and images onto a recording medium such as, for example, paper and overhead projection film in a rapid and accurate manner. Thermal ink jet recording systems are particularly popular in this regard primarily because they exhibit various advantages such as, for example high printing speed, low noise, easy color printing, simply construction and low price. The concepts and operational principles of thermal ink jet recording systems are well described, for example, in U.S. Pat. No. 5,138,342 for Ink Jet Cartridge And Ink Jet Recording Apparatus Employing The Same issued to Kurata et al., and U.S. Pat. No. 5,500,664 for Ink Jet Recording Apparatus And Detachably Mountable Ink Jet Cartridge issued to Suzuki et al., all of which are incorporated herein by reference.

In general, an ink jet cartridge is detachably mounted on a recording head carriage assembly which supports a recording head, and traverses the recording head across the width of a recording medium in line recording operation. An ink jet cartridge is typically constructed in an unitary, detachable cartridge which contains an ink container for containing the ink, drop generating structures and electrically connections adapted for electrically coupling a recording head to the ink jet recording apparatus which provides drop generating energy in response to information signals generated by the ink jet recording apparatus. The principle behind this type of ink jet recording apparatus is the generation of the thermal pressure wave the ink container and subsequent emission of ink droplets from the ink container through a plurality of nozzles arranged vertically at a front end of a recording head. The thermal pressure wave is generated by selected heating elements installed in the nozzles, which heat the ink contained within the nozzles until the ink is ejected through an ejection orifice of the nozzles to produce a flying droplet of the ink. The droplet is deposited on the recording medium so that a desired character and image can be formed.

When the ink in the ink container is used up, however, the entire ink jet cartridge including a recording head needs to be replaced. This is required because the ink jet cartridge is typically constructed in a unitary structure regardless of whether such an ink jet cartridge involves a relatively large difference between the period in which the ink in the ink container is used up and the service life of the recording head. Although there has been proposed construction of an ink jet cartridge in which the ink container is detachably mounted to a recording head so as to permit replacement of the ink container and the recording head separately at different times, the ink jet cartridge still needs to be taken out from the ink jet recording apparatus for replacement of an entire ink jet cartridge or an individual part of the ink jet cartridge. Accordingly, it is necessary for the ink jet recording apparatus to be able to efficiently detect whether a new or replaceable ink cartridge is mounted on a recording head carriage for recording characters and images on a recording medium. However, not all ink jet recording systems are capable of efficaciously detecting a replaceable ink cartridge mounted thereon. More often, users tend to throw out the old ink cartridge but forget to mount a new ink cartridge for replacement. In such a situation, the recording operation is performed without the ink container mounted thereon. This, however, is not a desirable situation because air may be introduced into the ink passageway and contribute to the ink ejection failure.

Unfortunately, conventional ink jet recording apparatus requires additional detection pins mounted in the ink cartridge to detect the presence or absence of an ink container or a recording head. For example, U.S. Pat. No. 5,212,502 for Ink Jet Print Head Mounting Mechanism issued to Bowling requires both an ink jet cartridge and a carriage to contain a complementary panel of electrical contacts to determine whether the ink jet cartridge is mounted on the carriage. In Suzuki et al., U.S. Pat. No. 5,500,664 for example, a pair of detection pins are mounted on side surfaces of an ink cartridge holder to detect the presence or absence of an ink container. If additional detection pins are mounted in the ink cartridge, as I have observed however, a railroad is also required to connect the ink cartridge to the detection pins which undesirably increase the number of electrical pins in a connector. Further, even if additional detection pins are required to detect the mounting of a replaceable ink jet cartridge mounted on a carriage, it has also been my observation that the conventional ink jet recording apparatus is still unable to distinguish the type of an ink jet cartridge mounted therein. In other words, the conventional ink jet recording apparatus is only capable of detecting whether an ink cartridge is mounted on a carriage, and is not capable of detecting whether a mounted ink jet cartridge is one is a mono ink cartridge an a color ink cartridge.

Accordingly, it is therefore an object of the present invention to provide an ink cartridge detecting circuit in an ink jet recording apparatus and a method capable of detecting whether an ink cartridge is mounted therein the ink jet recording apparatus without using additional detection pins in the ink cartridge.

It is another object of the invention to provide an ink cartridge detecting circuit in an ink jet recording apparatus and a method capable of detecting the type of an ink cartridge mounted in the ink jet recording apparatus.

These and other objects of the present invention can be achieved by an ink jet recording apparatus constructed to include a driver for driving a corresponding nozzle by applying a driving power supply voltage to a respective heating element. A voltage detector is connected to the heating elements and a voltage terminal, for detecting a voltage level dropped in the driving power supply voltage by means of driving of the heating elements. A controller is operatively connected to the voltage detector and the driver, for driving one or more of the heating elements through the driver and for comparing a voltage level to be detected by the voltage detector with a preset reference voltage level in order to detect whether an ink cartridge is mounted on a carriage of the ink jet recording apparatus. When the detection voltage level is higher than a first reference voltage level, the ink jet recording apparatus determines the ink cartridge has been mounted therein. When the detection voltage level is lower than the first reference voltage level, however, the ink jet recording apparatus determines that the ink cartridge has not been mounted therein.

In addition, if the detection voltage level is higher than the first reference voltage level and is also higher than a second reference voltage level, the ink jet recording apparatus determines that a mounted ink cartridge is a color ink cartridge. If, on the other hand, the detection voltage level is lower than the second reference voltage level, the ink jet recording apparatus determines that a mounted ink cartridge is a mono ink cartridge.

The present invention is more specifically described in the following paragraphs by reference to the drawings attached only by way of example.

A more complete appreciation of the present invention, and many of the attendant advantages thereof, will become readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein:

FIG. 1 illustrates an ink jet recording apparatus constructed to detect the mounting of an ink cartridge according to the principles of the present invention; and

FIG. 2 is a flow chart illustrating an ink cartridge detection implemented by the ink jet recording apparatus according to the present invention.

Referring now to the drawings and particularly to FIG. 1, which illustrates a block construction of an ink jet recording apparatus using a detachable ink cartridge (not shown) having an array of nozzles formed on the top of a recording head capable of detecting the mounting of an ink cartridge according to the present invention. The ink jet recording apparatus includes a driver 100 for driving corresponding nozzles of the recording head by applying a driving power supply voltage Vpp to corresponding heating elements RT1 to RT.sub.N. A voltage detector 102 is connected to the heating elements RT1 to RT.sub.N and a voltage terminal Vpp, for detecting a voltage level dropped in the driving power supply voltage by the driving of the heating elements RT1 to RT.sub.N. A controller 112 is operatively connected to the voltage detector 102 and the driver 100 for driving one or more of the heating elements RT1 to RT.sub.N through the driver 100, and for comparing a voltage level to be detected by the voltage detector 102 with a preset reference voltage level in order to detect whether an ink cartridge is mounted on a carriage of the ink jet recording apparatus.

A plurality of heating elements RT1 to RT.sub.N are mounted to have a one-to-one correspondence to the nozzles of a recording head of an ink cartridge. The heating elements are constructed to heat and discharge the ink within a corresponding nozzle when driven by a driving power supply voltage Vpp. The ink jet cartridge described is a typically unitary construct and detachable cartridge including an ink container for containing the ink, and a recording head. The driver 100 is comprised of a first resistance element R1 connected between the driving power supply voltage Vpp and each corresponding terminal of the heating elements RT1 to RT.sub.N. Transistors Q1 to Q.sub.N are operatively connected to respective heating elements and a ground terminal and serve as switching elements for enabling the controller 112 to control operation of the heating elements RT1 to RT.sub.N in order to heat and force ejection of ink through an ejection orifice of the nozzles to produce a flying droplet of the ink The droplet of ink is deposited on a recording medium so that a desired character and image can be formed.

The driver 100 applies the driving power supply voltage Vpp to the corresponding one of the heating elements RT1 to RT.sub.N by means of signals applied to base terminals of the transistors Q1 to Q.sub.N from a driving controller 108, and then drives the corresponding nozzle of a recording head. A voltage detector 102 comprises a second resistance element R2, a diode D1 which are connected in series between the driving power supply voltage Vpp and a corresponding terminal of the heating elements RT1 to RT.sub.N, and a third resistance element R3 coupled to a coupling node between the second resistance element R2 and the diode D1. The voltage detector 102 detects a voltage level of the driving power supply voltage Vpp dropped by driving of the heating elements RT1 to RT.sub.N.

The controller 112 includes an analog-to-digital converter (hereinafter, called "ADC") 104, a driving controller 108, and a microcomputer 106 operatively connected to both the ADC 104 and the driving controller 108 for controlling the ink cartridge detection as contemplated by the present invention. The driving controller 108 drives the transistors Q1 to Q.sub.N according to data applied from the microcomputer 106. The ADC 104 converts the voltage level input by connecting an input terminal thereof to the coupling node of the second resistance element R2 and the diode D1 through the third resistance element R3, into a digital data having a value corresponding to the voltage level, and then applies the digital data to the microcomputer 106. The microcomputer 106 drives the heating elements RT1 to RT.sub.N by simultaneously turning on all the transistors Q1 to Q.sub.N through the driving controller 108 and compares a value of data output from the ADC 104 with a preset reference voltage level in order to detect whether the ink cartridge is mounted on a carriage of the ink jet recording apparatus.

Turning now to FIG. 2 which is a flow chart illustrating an ink cartridge detection implemented by the ink jet recording apparatus constructed according to a preferred embodiment of the present invention. The preferred embodiment of the present invention will be explained in detail as follows.

First, if at least one or more of the transistors Q1 to Q.sub.N is turned on, a current path is formed where current by the driving power supply voltage Vpp flows to ground from the second resistance element R2 and the diode D2 through the corresponding heating element and transistor. The voltage level at the coupling node between the second resistance element R2 and the diode D1 is lower than when the transistors Q1 to Q.sub.N are all at the "off" state. The voltage level is low in proportion to the number of heating elements RT1 to RT.sub.N and transistors which are at the "on" state and connected thereto. This is because the heating elements having the same resistance value are parallel coupled to each other, so that the greater the number of heating elements RT1 to RT.sub.N are operating, the smaller the synthetic resistance value becomes. Further, the voltage level at the coupling node between the second resistance element R2 and the diode D1 is converted into the digital data having a value corresponding thereto by means of the ADC 104, and then applied to the microcomputer 106.

Accordingly, when all the transistors Q1 to Q.sub.N are turned on simultaneously, the microcomputer 106 determines whether or not the ink cartridge has been mounted on a carriage of the ink jet recording apparatus by detection the change of the data value input from the ADC 104. As previously noted, the present invention is intended to establish as a first reference voltage level V.sub.Th1 the voltage level between the voltage level applied to the ADC 104 through the third resistance element R3 when all the transistors Q1 to Q.sub.N are turned off, and another voltage level applied to the ADC 104 through the third resistance element R3 when only one of the transistors Q1 to Q.sub.N is turned on. Accordingly, when a detection voltage level V.sub.D corresponding to the data value applied from the ADC 104 is higher than the first reference voltage level V.sub.TH1 in the situation when all the transistors Q1 to Q.sub.N are turned on simultaneously, the microcomputer 106 determines that an ink cartridge has not been mounted on a carriage of the ink jet recording apparatus. This is because the heating elements RT1 to RT.sub.N are not operating to apply heat to the ink contained in the ink container even though all of the transistors Q1 to Q.sub.N are turned on simultaneously. Consequently, the detection voltage level V.sub.D is higher than the first reference voltage level V.sub.TH1. If, on the other hand, the detection voltage level V.sub.D is lower than the first reference voltage level V.sub.TH1 in the situation when all the transistors Q1 to Q.sub.N are turned on simultaneously, the microcomputer 106 determines that the ink cartridge has been mounted on a carriage of the ink jet recording apparatus. This is because the heating elements RT1 to RT.sub.N are connected in parallel in order to generate heat and force ejection of ink through an ejection orifice of the nozzles for forming desirable characters and images on a recording medium, when all of the transistors Q1 to Q.sub.N are turned on. Consequently, the detection voltage level V.sub.D is lower than the first reference voltage level V.sub.TH1.

After the ink cartridge has been mounted on a carriage of the ink jet recording apparatus, it is also possible to detect whether a mounted ink cartridge is one of a mono ink cartridge and a color ink cartridge. Generally, the mono ink cartridge has a greater number of nozzles than that of the mono ink cartridge. For example, the mono ink cartridge widely used in the ink jet recording apparatus has fifty to sixty-four nozzles, whereas the color ink cartridge has forty-eight nozzles. Therefore, if the microcomputer 106 simultaneously turns on all the transistors Q1 to Q.sub.N, the detection voltage level V.sub.D is higher when the color ink cartridge has been mounted than when the mono ink cartridge has been mounted. For this reason, the present invention seeks to establish as a second reference voltage level V.sub.TH2 the voltage level between the detection voltage level V.sub.D detected when the microcomputer 106 simultaneously turns on all the transistors Q1 to Q.sub.N for the situation that the mono ink cartridge has been mounted, and another detection voltage level V.sub.D detected when the microcomputer 106 simultaneously turns on all the transistors Q1 to Q.sub.N for the situation that the color ink cartridge has been mounted. For instance, when all the transistors Q1 to Q.sub.N are turned on simultaneously by the microcomputer 106, and if the detection voltage level V.sub.D is lower than the first reference voltage level V.sub.TH1 and but is higher than the second reference voltage level V.sub.TH2, the microcomputer 106 determines that the color ink cartridge has been mounted on a carriage of the ink jet recording apparatus. On the other hand, when all the transistors Q1 to Q.sub.N are turned on simultaneously by the microcomputer 106, and if the detection voltage level V.sub.D is lower than the first reference voltage level V.sub.TH1 and is also lower than the second reference voltage level V.sub.TH2, the microcomputer 106 determines that the mono ink cartridge has been mounted on a carriage of the ink jet recording apparatus.

The above operation will be explained hereinafter with respect to FIG. 2. The microcomputer 106 simultaneously turns on all of the transistors Q1 to Q.sub.N through the driving controller 108 in order to drive all nozzles of a recording head at step 200 when the ink jet recording apparatus including an ink cartridge detecting circuit of FIG. 1 is initialized. Thus, the heating elements RT1 to RT.sub.N are driven at once by application of the driving power supply voltage Vpp thereto through the first resistance element R1. At this time, if the ink cartridge has been mounted on a carriage of the ink jet recording apparatus, the ink within the nozzles is discharged. Further, in order to prevent pollution caused due to the discharged ink, it is desirable that such operation is performed when the ink cartridge is at a capping location.

Is Next, the microcomputer 106 compares, at step 202, the detection voltage level V.sub.D according to the data value applied from the ADC 104 with the first reference voltage level V.sub.TH1. When the detection voltage level V.sub.D is higher than the first reference voltage level V.sub.TH1, the microcomputer 106 recognizes that the ink cartridge has not been mounted and sets a flag to indicate that there is no ink cartridge mounted on a carriage at step 204. The displaying unit 110 then displays a message indicating that there is no ink cartridge. By contrast, when the detection voltage level V.sub.D is lower than the first reference voltage level V.sub.TH1, the microcomputer 106 determines that the ink cartridge has been mounted on a carriage, and then compares, at step 208 the detection voltage level V.sub.D with the second reference voltage level V.sub.TH2 so as to detect the type of ink cartridge mounted on a carriage. At this point, if the detection voltage level V.sub.D is higher than the second reference voltage level V.sub.TH2, the microcomputer 106 determines that the color ink cartridge has been mounted on a carriage and sets a corresponding flag to indicate that a mounted ink cartridge is a color ink cartridge at step 210. The displaying unit 110 then displays a message indicating that a mounted ink cartridge is a color ink cartridge at step 212. If, on the other hand, the detection voltage level V.sub.D is lower than the second reference voltage level V.sub.TH2, microcomputer 106 determines that the mono ink cartridge has been mounted on a carriage and sets a corresponding flag to indicate that a mounted ink cartridge is a mono ink cartridge at step 214. After the flag is set at step 214, the displaying unit 110 then displays a message indicating that a mounted ink cartridge is a mono ink cartridge at step 216. Accordingly, it is possible to drive the nozzle in order to determine the type of ink cartridge mounted on a carriage of an ink jet recording apparatus.

As described above, the present invention advantageously provides a means to efficiently detect not only whether or not an ink cartridge has been mounted on a carriage of an ink jet recording apparatus without using additional detection pins in the ink cartridge, but also to determine the type of ink cartridge mounted on a carriage; that is whether a mounted ink cartridge is one of a color ink cartridge and a mono ink cartridge.

While there have been illustrated and described what are considered to be preferred embodiments of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made, and equivalents may be substituted for elements thereof without departing from the true scope of the present invention. For example, even if a preferred embodiment contemplates the detection of the specific type of ink cartridge mounted on a carriage of an ink jet recording apparatus, it is within the scope of the present invention simply to detect whether an ink cartridge has been mounted or not. If this is the case, it is not necessary to drive at once all the heating elements. That is, only any one of the heating elements may be driven or a plurality of heating elements may be driven in order to detect whether or not the voltage level is more easily dropped under enhancement of the level to be detected. Moreover, it is possible to detect the type of ink cartridge mounted on a carriage of an ink jet recording apparatus without detecting whether the ink cartridge has been mounted or not. In addition, many modifications may be made to adapt a particular situation to the teaching of the present invention without departing from the central scope thereof. Therefore, it is intended that the present invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out the present invention, but that the present invention includes all embodiments falling within the scope of the appended claims.