JPH0729419B2 - Recording device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus, and more particularly to a recording apparatus including a plurality of heating elements as recording elements in a recording head.

[Conventional technology]

As a recording device of this type, for example, by energizing a heating element provided in a minute nozzle for ejecting ink to generate heat, a rapid volume change that occurs during heating of ink around the heating element to bubbling occurs. 2. Description of the Related Art Some ink jet recording apparatuses that perform recording by ejecting ink droplets from ejection ports by using a head having a large number of nozzles arranged in a predetermined direction. In such an ink jet recording apparatus, generally, a so-called divided drive system is adopted in which the nozzles are divided into groups for each predetermined number and the heating elements are driven for each group.

This is an effective method for reducing the size of the head drive power source and power source components such as the power connector flexible cable and reducing the number of components. In addition, the ink jet head power source requires a very small variation in voltage value and fine adjustment of the voltage value in order to perform stable ejection in consideration of the characteristics of the heating element and ink. Therefore, it is not preferable to increase the capacity of the power supply, and the above method is effective in avoiding this.

FIG. 5 shows a structural example of a main part of a conventional ink jet recording apparatus based on such a division drive system. Here, 1 is an inkjet head unit, which has, for example, 32 nozzles, and these are divided into four groups from a first group to a fourth group, for example, with eight nozzles as one unit. In recording, these groups are driven in group units in an appropriate order. Reference numeral 2 is a head drive unit having a head drive element provided corresponding to each nozzle. Here, as the head drive element, a general NPN type transistor with Darlington connection is used.

Reference numeral 4 denotes a divisional drive control unit having four stages of flip-flops 9. As shown in FIG. 6, any one of the output signals Q1 'to Q4' for each group is sequentially supplied during one cycle of the clock signal CK. Is output. Reference numeral 3 is a drive control unit for controlling the head drive unit 2, and has an AND gate provided corresponding to each head drive element. Each AND gate is
It has two input terminals and a drive control signal from the split drive control unit.
It accepts the recording signal for each dot from the CPU, etc. For example, the AND gate 3 corresponding to the first group receives the drive control signal Q1 'and any one of the recording signals Dot Datal-8.

[Problems to be solved by the invention]

In such a conventional ink jet recording apparatus, in the division drive control unit 4, as shown in FIG. 6, the drive control signal for one group is turned off and at the same time the drive control signal for the next group is turned on. There is.

However, as shown in FIG. 7, the output of the head drive element is slightly delayed with respect to the input when the output is off due to its characteristics (see FIG. 8). Simultaneous drive (energization) between groups to be sequentially driven. Will occur,
The maximum value of the current VH from the power supply will appear at this point.

That is, in the conventional split drive control unit, simultaneous energization occurs, so that it is necessary to design each unit based on the current value at this time. This leads to an increase in the size of the current source and other components, which is larger than the case where only one group is energized, and therefore the advantages of the split drive method in terms of size, reliability, and price. It is hard to say that is what makes the most of it.

[Means for solving problems]

SUMMARY OF THE INVENTION It is an object of the present invention to solve such a conventional problem and to make the most of the advantages of the split drive method, thereby providing a highly reliable, compact and inexpensive recording apparatus. .

Therefore, in the present invention, a recording head having a plurality of heat generating elements, a drive unit for driving the plurality of heat generating elements, and the plurality of heat generating elements are grouped into a plurality of groups having at least one heat generating element that can be simultaneously driven. In a recording apparatus having a division drive control unit that divides and controls the drive unit so as to sequentially select and drive the plurality of groups, the division drive control unit is configured to drive the next group after one group is driven. Before the group is driven, the driving is controlled so as not to be driven for a predetermined period according to at least the switching characteristic of the driving unit.

[Action]

According to the above configuration, the next group is not driven for a predetermined period according to the switching characteristic of the driving unit, and thus the two groups that should be sequentially driven are not simultaneously driven. The supplied energy required for driving can be reduced.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail and specifically with reference to the drawings.

FIG. 1 shows an example of the configuration of the inkjet recording apparatus of the present invention. Here, 11, 12, 13 and 14 are an inkjet head unit, a head drive unit, a drive control unit and a division drive control unit, respectively, which will be described later with reference to FIG.

Reference numeral 15 is a timer unit for supplying a clock signal CK for division drive to the division drive control unit 14, and 16 is a control unit composed of a CPU and its peripheral LSI, etc., and a drive signal for each dot according to recording information. Is output as a recording signal Dot Data. 17
Is a power supply unit for energizing the heating elements arranged in the nozzles of the inkjet head unit 11, and 18 is a latch unit for latching the recording signal Dot Data from the control unit 16 and supplying it to the drive control unit 13.

FIG. 2 shows a detailed configuration example of each unit 11-14. Here, the inkjet head unit 1 has a heating element 14A inside.
And a plurality of these nozzles, each of which is a unit of the first group to the n-th group.
The group is divided into several groups.
Then, at the time of recording, these groups are driven group by group in an appropriate order. In this example, the inkjet head 1 is composed of 32 nozzle groups, and these nozzle groups are divided into four groups (first group to fourth group) of eight nozzles each.

The head drive unit 12 has a group of head drive elements 12A configured by connecting NPN transistors in Darlington connection.
The drive control unit 13 uses the recording signal Dot Data from the latch unit 18.
Is a circuit for outputting to the head drive unit 12 in synchronization with the timing of the drive control signals Q1 to Q4 of the division drive control unit 14, and any one of the drive control signals Q1 to Q4 and the recording signal Dot Data.
It has a group of AND gates 13A receiving any one of 1 to 32. That is, for example, the uppermost AND gate 13A belonging to the group corresponding to the first group receives the drive control signal Q1 and the recording signal Dot Data1 and outputs the recording signal Dot Data1 only when the drive control signal Q1 is on. It is supplied to the corresponding head drive element 12A of the head drive unit 12.

The division drive control unit 14 is configured by using four stages of flip-flops 19, and generates a signal for sequentially driving the first to fourth groups according to the input of the clock signal CK, and a clock signal CK. Inverter 21 for inverting
And a group of AND gates 22 that receive the output of the flip-flop 19 and the inverted output of the inverter 21 to generate the drive control signals Q1 to Q4.

FIG. 3 shows the generation timing of the drive control signals Q1 to Q4,
The operation of the split drive control unit 14 will be described with reference to this figure.

The feature of this example is that the clock signal supplied from the timer unit 15 is
The point is that the output inhibition time τ is provided between the output signals of the shift register 29 when the CK is turned on. The width of the output inhibition time τ is determined by the width of the on time of the clock signal CK, and the drive time (energization time) of the head is determined by the off time τ ₁ of the clock signal CK.

Note that the value of τ is the drive element used in the head drive unit 12,
That is, the turn-on time (τon in FIG. 8), turn-off time (τf in FIG. 8), storage time (τstg in FIG. 8), etc. of the Darlington-connected NPN transistor can be appropriately determined according to the switching characteristics. That is,
The value of τ is equal to or larger than the sum of the turn-off time τf and the storage time τstg minus τon in the turn-on time, so that the first group and the second group 2 are energized at the same time in FIG. 2, for example. Can be prevented.

FIG. 4 shows the current value supplied from the head power supply unit 17 when recording is performed by supplying the signals Q1 to Q4 as described above.
That is, according to this example, since the division drive is performed in consideration of various characteristics of the head drive element 13B, a large current unlike the conventional case is not required, and the current waveform changes from the state shown in FIG. The situation is dramatically improved as shown in Fig. 4.

As described above, according to the present example, the circuit configuration is simply changed or added to the conventional example shown in FIG. 5, and the ratings of the components used in the power supply circuit are changed only by slightly changing the timing of the clock signal CK. The capacity can be reduced, a sufficient effect can be obtained in terms of price, reliability, etc., and the advantages of the split drive method can be maximized.

In the above example, the case where 32 heating elements are divided into 4 by 8 and sequentially driven has been described, but it goes without saying that the number of heating elements and the number of divisions are arbitrary and desired. For example, by setting the number of bits of the shift register of the division control unit to an arbitrary number, division driving can be performed with an arbitrary number.

Also, from the switching characteristics of the driving element (Darlington connected transistor), the turn-on time and the turn-off time are treated as canceling each other, and the output inhibition time (τ in FIG. 3) is considered to be equal to or longer than the storage time by considering only the storage time. May be

Further, the present invention is not limited to the configurations shown in FIGS. 1 and 2, and includes, for example, the drive control unit 13, the division drive control unit 14, the data latch unit 18, and the timer unit 15 shown in FIG. A gate array or the like may be used as one unit.

〔The invention's effect〕

As described above, according to the present invention, it is possible to realize the inkjet recording apparatus which is capable of maximizing the advantages of the divided drive system, is highly reliable, is small in size, and is inexpensive.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of the ink jet recording apparatus of the present invention, FIG. 2 is a circuit diagram showing a configuration example of a main part of the ink jet recording apparatus shown in FIG. 1, and FIG. 3 is a heating element in this example. 4 is a timing chart showing an example of the generation timing of the divided drive control signal of FIG. 4, FIG. 4 is a waveform chart showing the waveform of the current supplied to the head by the drive as shown in FIG. 3, and FIG. 5 is the main part of the conventional ink jet recording apparatus. FIG. 6 is a timing chart for explaining a conventional split drive system, FIG. 7 is a waveform diagram showing a waveform of current supplied to a head by the conventional drive system, and FIG. 8 is a Darlington connection. FIG. 4 is a diagram for explaining switching characteristics of the NPN transistor. 1,11 ...... Inkjet head unit, 2,12 ...... Head drive part, 3,13 ...... Drive control part, 4,14 ...... Split drive control part, 9,19 ...... Flip-flop, 11A ...... Heating element , 12A ... Head drive element, 13A ... AND gate, 21 ... Inverter, 22 ... AND gate, Q1 to Q4, Q1 'to Q4' ... Drive control signal, Dot Data1 to 8 ... Recording signal, CK , CK ′ …… Clock signal.

Claims (3)

[Claims] 1. A recording head having a plurality of heating elements, driving means for driving the plurality of heating elements, and the plurality of heating elements divided into a plurality of groups having at least one heating element capable of being driven simultaneously. Then, in a recording apparatus having a division drive control means for controlling the drive means so as to sequentially select and drive the plurality of groups, the division drive control means is configured such that after one group is driven, the next group is driven. The recording apparatus is controlled so that the drive is not performed for a predetermined period at least according to the switching characteristic of the drive unit before the drive. 2. The recording apparatus according to claim 1, wherein the predetermined period is a time obtained by subtracting a turn-off time from a time obtained by adding a turn-off time of the driving means and an accumulation time. Recording device. 3. The recording apparatus according to claim 1 or 2, wherein the recording head ejects ink by a heating element.