JP2871252B2 - Ink jet recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

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

2. Description of the Related Art FIG. 2 shows the configuration of a general ink jet recording apparatus. Various types of ink supply methods for an ink jet recording apparatus have been proposed. FIG. 2 shows one of them.
The ink is supplied to the recording head 24 on the carriage 23 via the. In the case of such an ink supply type ink jet recording apparatus, the pressure (water head value [mmH2O]) of the ink on the supply system side applied to the head is generally set to the negative pressure side. That is, the ink supply container 21 is installed at a position lower than the recording head 24. In such an ink supply mechanism, a pressure fluctuation occurs in the ink in the supply tube due to the bending movement of the supply tube 22 accompanying the reciprocating movement of the carriage 23, and the pressure fluctuation is transmitted to the inside of the recording head 24, whereby the ink is supplied. The occurrence of a phenomenon that hinders stable ejection has been recognized. This is because the ink pressure increases due to the pressure fluctuation, and when the pressure becomes positive, unnecessary ink splatters from the ink ejection port. In addition, when the ink pressure becomes lower than the allowable negative pressure, the ink is ejected. It is considered that the ejection of air from the outlet causes a discharge failure. Further, pressure fluctuations due to the reciprocating motion of the carriage 23 also occur in the ink supply path inside the recording head 24, and the same problem has been observed. Here, since the head value is generally set on the negative pressure side, it is relatively easy to prevent the phenomenon of positive pressure from occurring. However, with the recent increase in the response frequency of the recording head, the reciprocating speed of the carriage has also been increased, so that the pressure fluctuation has inevitably increased. It is difficult to prevent. In particular, when the acceleration of the carriage is large, there is a risk that ink ejection may be impaired. Further, since the ink pressure decreases as the ink in the ink supply container is consumed, there is a possibility that the ink ejection may be impaired even when the remaining amount of ink is small. As a solution to such a problem, as shown in Japanese Patent Application Laid-Open No. Sho 58-94473, there is a configuration in which a supply tube is branched to the left and right to absorb pressure fluctuations. is not. Therefore, in the related art, by performing acceleration / deceleration control of the carriage so as to always keep the acceleration below a certain value, ink ejection failure due to pressure fluctuation is prevented. FIG. 3 shows a block diagram of the ink jet recording apparatus. CPU based on print data from host device 4
A series of printing operations such as carriage motor drive, head drive, and paper feed motor drive are performed from 1 through the I / O unit 13. The carriage motor 8 is constituted by a DC motor. The carriage motor 8 is driven by the carriage motor drive unit 6 and the current limiting unit 31, and the speed information is fed back by the encoder 7 to be controlled at a predetermined speed. Here, the current limiter 31 is set to a current value that suppresses the acceleration of the carriage to a certain value or less. FIG. 4 shows the carriage motor driving unit 6 and the current limiting unit 31.
1 shows a circuit configuration. With such a configuration, conventionally, the generated current of the carriage motor is suppressed by limiting the current supplied to the carriage motor, the acceleration during the acceleration and deceleration of the carriage is set to a certain value or less, and the fluctuation of the water head value due to the reciprocating motion is reduced. To prevent ink ejection failure.

However, in the control method for constantly suppressing the acceleration of the carriage as described above, since the acceleration and deceleration are performed over a long time, the time required for printing becomes long. The present invention has been made to solve the above-described problem, and an object of the present invention is to provide an ink jet recording apparatus capable of obtaining a stable ink ejection without lowering a printing speed as much as possible.

According to the present invention, there is provided a carriage on which a recording head for ejecting ink droplets is mounted, a carriage driving means for driving the carriage, an ink supply container provided outside the carriage, An ink jet recording apparatus comprising: an ink supply path for supplying ink contained in an ink supply container to the recording head; and an ink remaining amount detection unit that detects an ink remaining amount in the ink supply container. , The acceleration / deceleration of the carriage,
It is characterized in that it is changed according to the detection result of the ink remaining amount detecting means. Further, according to the present invention, the acceleration / deceleration of the carriage is reduced as the remaining amount of ink in the ink supply container decreases.

When the detection result of the ink remaining amount detecting means is higher than a predetermined value, scanning is performed by increasing the acceleration of the carriage in order to increase the printing speed, and only when the detection result of the ink remaining amount is lower than the predetermined value. By gently performing acceleration and deceleration during carriage scanning to suppress pressure fluctuations,
Ink ejection failure due to negative pressure can be prevented.

The present invention will be described below in detail with reference to examples. FIG. 1 is a block diagram showing one embodiment of the present invention.
Reference numeral 1 denotes a CPU as a control unit of the printer, which is provided with a ROM 2 for storing a control program and the like and a RAM 3 for temporarily storing various data. Print data from the host device 4 is sent to the CPU 1 via an I / F unit (interface unit) 5. The CPU 1 controls a series of printing operations such as carriage motor drive, head drive, and paper feed motor drive according to print data. The current value of the carriage motor 8 of the DC motor driven by the carriage motor drive unit 6 is determined by the current limit value switching unit 10, and the current is limited by the current limit unit 9. The carriage speed is controlled by feeding back speed information by the encoder 7. FIG. 5 shows a carriage motor drive circuit including a current limit value switching unit 10, a current limit unit 9, and a carriage motor drive unit 6. The carriage motor drive circuit of the present invention is different from the conventional one (FIG. 4) in that a current limit switching unit 10 including a transistor Q8 capable of selecting a current limit value in two stages is added. Two steps (Vrf1, Vr
The reference voltage Vrf can be set to f2). Transistor Q
8 is an ON state, a voltage Vrf1 obtained by dividing Vp by Ra and a combined resistance Rbc of Rb and Rc becomes a reference voltage, and when the transistor Q8 is in an OFF state,
A voltage Vrf2 obtained by dividing Vp by Ra and Rb becomes a reference voltage (Vrf1 <Vrf2). The current limiting unit 9
The detection voltage Vdt at the current detection resistor R1 and the reference voltage Vrf
Are compared by the operational amplifier OP1 and the circuit configuration is controlled by the transistor Q5. Assuming that the current flowing through the carriage motor 8 is I, the current is limited by I = (Vp−Vrf) / R1. That is, the current value of the carriage motor 8 can be changed by changing the reference voltage Vrf.
The carriage motor drive unit 6 includes transistors Q1 to Q4
H-type bridge circuit consisting of
The carriage motor is rotated forward or backward by changing the current supply direction according to the OFF state. Specifically, when the current limit value is set to 3 A and 1.5 A and the carriage motor is driven by the drive circuit of FIG. 5, the change in the speed of the carriage and the change in the current value are shown in FIGS.
1 and shown in FIG. The ink pressure fluctuation due to the carriage reciprocation at this time is ± 30 to 50 when the current limit value is 3A.
mmH2O, when the current limit value is 1.5 A, ± 10
20 mmH2O. Next, the relationship between the remaining amount of ink in the ink supply container and the water head value will be described. FIG. 6 is a diagram showing the relationship between the remaining amount of ink in the ink supply container and the water head value. The head value in FIG. 6 is the hydrostatic head value at the ink supply container opening. In the printer of this embodiment, the installation position of the recording head is 90 mm above the ink supply container opening. Therefore, the head value for the recording head is 90 m from the value in FIG.
It is a value obtained by subtracting mH2O. The water head usable for the recording head is -20 to -220 mmH2O (+70 to -130 mmH2O in terms of the ink supply container opening). You need to reserve a value. As can be seen from FIG. 6, in order to maintain a usable water head value when the amount of remaining ink is small, the amount of ink pressure fluctuation due to the reciprocating movement of the carriage must be reduced. Therefore, it is necessary to detect the remaining amount of ink by the remaining ink amount detecting unit 11. 7 and 8 are diagrams illustrating the structure of the remaining ink amount detection unit 11 and the operation of detecting the remaining amount of ink. 7 in FIG.
Is an ink supply container, 71 is a remaining amount detection lever, 72 is an ink bag, and 12 is a micro switch. When the amount of ink in the ink bag 72 is equal to or more than a predetermined value, the remaining amount detection lever 71 is separated from the microswitch 12 as shown in FIG. When the remaining amount of ink reaches a predetermined amount, the micro switch 12 is turned on as shown in FIG. 8, and the remaining amount is detected. In this embodiment, the predetermined value of the ink remaining amount is set to 12 g. At this time,
As shown in FIG. 6, the head value of the ink supply container opening is +20 to
−80 mmH2O, and even if the fluctuation of the ink pressure due to the reciprocating motion of the carriage adds ± 50 mmH2O in the water head value, it is +70 to −130 mmH2O, and the allowable range for ink ejection can be secured. When it is detected that the ink has been consumed and the remaining ink amount has become equal to or less than the predetermined value by the remaining ink amount detecting unit 12, the CPU 1 changes the level of the control terminal (terminal E in FIG. 5) of the current limit value switching unit 10. Is performed, and the current limit value (1.5 in the present embodiment) is such that the acceleration during the acceleration and deceleration of the carriage becomes small.
A) is set. At this time, the printing time is longer than the case where the remaining ink amount is not detected, but the fluctuation of the ink pressure due to the reciprocating motion of the carriage is ± 20 in the head value.
Since it is suppressed to mmH2O, the water head value is -60 to -130 mmH2O in a range from point a to point b (ink end detection point—7 g in this embodiment) in FIG. 6, and an allowable range for ink ejection can be secured. . As described above, the acceleration during the acceleration and deceleration of the carriage is set to a large value to perform high-throughput printing until the remaining amount of ink becomes equal to or less than the predetermined value. The acceleration at the time of acceleration / deceleration of the carriage is controlled to suppress the fluctuation of the ink pressure due to the above. This has made it possible to realize an ink jet recording apparatus free from ink ejection failure. In the present embodiment, the method for detecting the remaining amount of ink employs a method of detecting the displacement of the ink bag in accordance with the consumption of ink with a microswitch.However, the allowable head value of the recording head, the amount of ink in the ink supply container, The detection element and the detection method may have other configurations in consideration of the usage efficiency, the component price, the detection accuracy, and the like. Further, in the present embodiment, a DC motor is used as the carriage motor, and the acceleration during acceleration / deceleration is controlled by switching the current limit value. Further, even when a stepping motor is used as the carriage motor, a similar effect can be obtained by switching the slow-up and slow-down time tables.

As described above, according to the present invention,
Since the ink remaining amount is detected by a simple configuration and the drive current of the carriage is changed according to the ink remaining amount, it is possible to adjust the fluctuation of the ink pressure due to the reciprocation of the carriage. And a highly reliable printer can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a structural diagram of an ink jet recording apparatus.

FIG. 3 is a block diagram showing a conventional example.

FIG. 4 is a circuit diagram of a conventional carriage motor drive circuit.

FIG. 5 is a carriage motor drive circuit diagram of one embodiment of the present invention.

FIG. 6 is a diagram illustrating the relationship between the remaining amount of ink in an ink supply container and ink pressure.

FIG. 7 is a structural diagram of an ink supply container according to an embodiment of the present invention.

FIG. 8 is a diagram illustrating detection of the remaining amount of ink in one embodiment of the present invention.

FIG. 9 is a diagram for explaining the operation of the carriage when the acceleration / deceleration is large.

FIG. 10 is a diagram illustrating a current supplied to a carriage motor in the example of FIG. 9;

FIG. 11 is a diagram for explaining the operation of the carriage when the acceleration / deceleration is small.

FIG. 12 is a diagram showing a current supplied to a carriage motor in the example of FIG. 11;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 CPU 2 ROM 3 RAM 4 Host device 5 I / F unit 6 Carriage motor drive unit 7 Encoder 8 Carriage motor 9 Current limit unit 10 Current limit value switching unit 11 Ink end detection unit 12 Ink remaining amount detection unit 13 I / O unit Reference Signs List 21 Ink supply container 22 Supply tube 23 Carriage 24 Recording head 25 Platen 31 Current limiter 71 Remaining amount detection lever 72 Ink bag Q1 to Q8 Transistor R1 to R15 Resistance element Ra to Re Resistance element OP1 Operational amplifier D1 to D5 Diode

Claims (2)

(57) [Claims] A carriage on which a recording head for ejecting ink droplets is mounted; a carriage driving unit for driving the carriage; an ink supply container provided outside the carriage; and ink contained in the ink supply container. An ink supply path for supplying the ink to the recording head; and an ink remaining amount detecting unit for detecting an ink remaining amount in the ink supply container. An ink jet recording apparatus, which changes according to a detection result of a remaining amount detecting unit. 2. The ink jet recording apparatus according to claim 1, wherein the acceleration / deceleration of the carriage is reduced as the remaining amount of ink in the ink supply container decreases.