Output Controller for a Dot Printer Head

The present invention relates to an output controller for a doe printer head.

A dot printer is known in which the printing mode can be selected from a plurality of printing modes having different dot densities such as LQ (letter quality), NLQ (near letter quality), Draft, etc. A printing mode of a highest dot density is LQ, and then, NLQ, and Draft follow in order.

In a conventional printer, even if a printing mode can be selected, printing conditions are constant. Therefore, when a printing mode of a high dot density is selected, the number of times of hits of a needle against a platen per unit time is large, which may cause a problem of a high noise level.

A first object of the present invention is to determine the energizing time for a driving coil corresponding to a printing mode selected according to a desired usage.

A second object of the present invention is to keep the noise level low even when the printing mode of the high dot density is selected.

According to the present invention, there is provided an output controller for a dot printer head which prints upon driving a driving coil of a dot printer head by a head driving portion, comprising: an operation unit for selecting a printing mode; a printing mode setting portion for setting the energizing time corresponding to the selected printing mode, being connected to the operation unit; and the energizing time control portion for controlling the energizing time for the driving coil corresponding to the output of the printing mode setting portion.

Therefore, when a printing mode of a high dot density is selected, it is possible to make the printing energy small by making the energizing time period short, and thereby it is made possible to lower the noise level by the arrangement in which the printing mode setting portion is made to output the energizing time data corresponding to the printing mode by selecting the printing mode in operating the operation unit, and based on the energizing time data, the energizing time of the energizing signal, which is output from the head driving portion to the driving coil of the dot printer head is controlled by the energizing time control portion.

Various other objects, features and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood from the following detailed description when considered in connection with the accompanying drawings in which like reference characters designate like or corresponding parts throughout the several views and wherein:

FIG. 1 is a block diagram showing an electronic circuit;

FIG. 2 is a timing chart showing the relation between a head energizing signal and a head driving current when a Draft printing mode is selected;

FIG. 3 is a timing chart showing the relation between a head energizing signal and a head driving current when an LQ printing mode is selected; and

FIG. 4 is a flow chart.

A preferred embodiment according to the present invention will be explained referring to the drawings. As shown in FIG. 1, a bus line connects a control unit 1 composed of a CPU, etc., a printing mode setting portion 3 connected to an operation unit 2 for selecting a printing mode from a plurality of printing modes having different kinds of dot densities such as LQ (letter quality), NLQ (near letter quality) or Draft, a ROM 4 on which program data are written, and a RAM 5 on which variable data are written. A head driving portion 7 is connected to the output side of an energizing time control portion 6 to which printing data from the control unit 1 and an energizing time data set in the printing mode setting portion 3 are to be input, and there is provided a dot printer head 9 having a plurality of driving coils 8 which make needles hit a platen being driven by the head driving portion 7. The energizing time control portion 6 comprises a first timer 10, a second timer 11 and a third timer 12.

In the constitution as described in the above, the operation will be explained referring to a flow chart shown in FIG. 4. When the printing mode is selected from LQ, NSQ, Draft, etc. by operating the operation unit 2, the energizing time which makes the head driving portion 7 output an head energizing signal to the driving coil 8 corresponding to a selected printing mode is set by the printing mode setting portion 3. The energizing time period is set by being divided into a continuous energizing time period Ta, an on-pulse width period Tb in a chopper driving time and an off-pulse width Tc in a chopper driving time as shown in FIGS. 2 and 3, and the continuous energizing time Ta is set in the first timer 10 of the energizing time control portion 6, the on-pulse width Ta in the chopper driving time is set in the second timer 11, and the off-pulse width Tc in the chopper driving time is set in the third timer 12.

On the other hand, the control unit 1 reads out the printing data (dot data) from a character generator in the ROM 4 corresponding to a character code transmitted from a host computer, and outputs the data to the head driving portion 7 through the energizing time control portion 6; in this case, the energizing time period of the head energizing signal which is output to the driving coil 8 from the head driving portion 7 is controlled by the energizing time control portion 6. The first timer 10 of the energizing time control portion 6 counts the continuous energizing time period Ta, the second timer 11 counts the on-pulse width Tb in a chopper driving time period, and the third timer 12 counts the off-pulse width Tc in a chopper driving time period. When these counted values reach the set values, the head driving portion 7 cuts off energizing the driving coil 8.

FIG. 2 is a timing chart showing the relation between the head energizing signal and the head driving current A when the Draft printing mode is selected, and FIG. 3 is a timing chart showing the relation between the head energizing signal and the head driving current A when the LQ printing mode is selected; the noise in a printing time can be decreased by making the printing energy per dot small and by making the energizing time for a printing mode having a high dot density LQ in the printing mode shorter than the energizing time for a Draft printing mode having a low dot density.

According to the present invention as described in the above, in the output controller for the dot printer head which prints upon driving the driving coil of the dot printer head, the operation unit for selecting the printing mode, the printing mode setting portion for setting the energizing time corresponding to the selected printing mode being connected to the operation unit, and the energizing time control portion for controlling the energizing time of the driving coil according to the output of the printing mode setting portion are provided, so that when a printing mode of a high dot density is selected, the printing energy can be reduced by decreasing the energizing time. Consequently the noise level can be lowered, due to an arrangement in which the printing mode setting portion is made to output energizing time data corresponding to the printing mode in selecting the printing mode according to a usage by operating the operation unit, and based on the energizing time data, the energizing time of the head energizing signal which is output from the head driving portion to the driving coil of the dot printer head is controlled by the energizing time control portion.