JPH0634111Y2 - Wire dot print head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to the structure of a wire dot print head used in an impact printer, and particularly to a wire dot print head having a temperature detecting element for detecting the temperature of a coil inside. Concerning the structure of.

(Prior Art) Various types of wire dot print heads have been conventionally implemented, but a temperature detection element for detecting the temperature of the coil is provided inside the head, and based on the output signal of this temperature detection element. It has been proposed to prevent burning of the coil by controlling printing so that the temperature of the coil does not rise above a predetermined temperature. A print head of this type will be described below with reference to FIG. FIG. 5 is a sectional view showing the structure of a conventional dot print head.

In FIG. 5, reference numeral 1 is a print wire, the base of which is fixed to the tip of the armature 2. The armature 2 is fixed to the tip of the leaf spring 3 for biasing, and the base of the leaf spring 3 is sandwiched between the magnetic spacer 4 and the hinge plate 5 and fixed. A permanent magnet 6 is disposed below the hinge plate 5, and a base 7 made of a magnetic material is disposed below the permanent magnet 6.
Are arranged. Further, a yoke 8 is provided above the spacer 4.
Are arranged.

The cores 9 are arranged below the armatures 2,
A coil 10 is wound around the core 9. An embedding ring 12 is arranged substantially in the center of the head 11, and a thermistor 13 as a temperature detecting element is arranged in a hole formed in the center of the embedding ring 12. The embedded ring 12 is made of a metal having high heat conductivity. A filler 14 is filled between the embedded ring 12 and the coil 10 and between the coil 10 and the base 7, and the filler 14 serves to fix the coil 10, the embedded ring 12 and the thermistor 13 together. Since it has high heat conductivity, it has a function of transferring the heat generated in the coil 10 to the embedded ring 12 and the thermistor 13.

A bobbin guide 16 is provided at the bottom of the base 7 via a packing 15.
, And a printed wiring board 17 is also attached to the lower part of the printed wiring board 17 via a packing 15. Although not shown, the coil 10 and the thermistor 13 are connected to the printed wiring board 17
It is connected to the.

Next, the operation will be described.

When not printing, the magnetic flux generated by the permanent magnet 6 is the base 7, core
It is formed between 9, armature 2, yoke 8, spacer 4, leaf spring 3, hinge plate 5 and permanent magnet 6, and the magnetic flux attracts the armature 2 to the core 9. At this time, the leaf spring 3 bends and stores a spring force. When printing is performed, the coil 10 wound around the core 9 is energized. As a result, the magnetic flux generated by the permanent magnet 6 is canceled and the armature 2
There is no suction force to suck. As a result, the spring force stored in the leaf spring 3 drives the armature 2 in the direction of arrow A shown in FIG. As a result, the print wire 1 is also driven in the same direction through the wire guide 18 and protrudes above the print head 11. By this projecting operation, printing is performed on a sheet (not shown) via an ink ribbon (not shown). Printing wire 1
After printing, the armature 2 is returned in the direction opposite to the arrow A direction after printing, and the energization of the coil 10 is stopped, so that the armature 2 is attracted to the core 9 by the re-formed magnetic flux, and one printing operation is completed.

When the coil 10 is energized, heat is generated in the coil 10,
This heat is transmitted to the thermistor 13 via the filler 14 and the embedding ring 12. The thermistor 13 has a preset detection temperature, and when the preset temperature is reached, control such as stopping the energization of the coil 10 for a certain period of time is performed. And wait for the coil temperature to drop. By doing so, the temperature of the coil can be prevented from exceeding a certain temperature, and therefore burning of the coil can be prevented.

(Problems to be solved by the invention) However, in the above-mentioned conventional device, the heat of the coil is transmitted to the thermistor through the filler, the embedding ring, and the air, so that the temperature detected by the thermistor does not follow the temperature of the coil. Poor throughput (execution CPS during continuous printing)
There was a problem that (Character Per Second) decreased. This will be described with reference to FIG. Sixth
The figure is a graph showing the coil temperature and the thermistor temperature in the conventional device.

FIG. 6 shows the measurement results of the coil temperature and the thermistor temperature when JIS JIS level 1 kanji was continuously printed for 1 hour.
The coil temperature and the thermistor temperature are values read from the respective resistance values. Regarding the temperature detected by the thermistor, the coil temperature is 180 ℃ when continuously printing JIS 1st level Chinese characters.
It was set not to exceed the above. The thermistor detection temperature is a temperature that triggers the energization of the coil to be stopped when the thermistor detects this temperature and to resume energization to the coil when the coil is cooled and the thermistor detects this temperature again. . The temperature detected by the thermistor should be set within the heat resistant temperature (180 ° C) in consideration of variations in the thermal resistance of the filler, the embedding ring, and the air present in the middle where heat is transferred from the coil to the thermistor.
(° C) is set to the lowest temperature detected by the thermistor. In the case of FIG. 6, this temperature is 120 ° C.
As a result, even when the thermistor reaches 120 ° C, the coil temperature may not necessarily reach 180 ° C or a temperature close to it (for example, point B shown in Fig. 6). Stop and go to sleep.
Therefore, the pause time is relatively long with respect to the printing time, and the throughput is reduced.

The present invention has been made in view of the above problems, and an object thereof is to provide a dot print head with improved throughput by improving the followability of the thermistor temperature with respect to the coil temperature.

(Means for Solving the Problem) Means taken for solving the above problem is to provide a positioning member for positioning the temperature detecting element for detecting the temperature of the coil by bringing the temperature detecting element into contact with the coil.

(Operation) The operation of the present invention based on the above configuration will be described.

By providing the positioning member, the temperature detecting element is always in contact with the coil. Therefore, the heat of the coil, which is generated by being energized, is directly transmitted to the temperature detecting element, and the followability of the temperature of the temperature detecting element to the coil temperature is improved. As a result, the temperature detected by the temperature detecting element can be set so that the coil temperature is close to the heat resistant temperature, and the throughput is improved.

(Embodiment) An embodiment according to the present invention will be described below with reference to the drawings.
Note that elements common to the drawings are given the same reference numerals.

FIG. 1 is a sectional view showing an essential part of an embodiment of the present invention, FIG. 2 is a perspective view showing an embedding ring of the embodiment, and FIG. 3 is a plan view of an essential part of the embodiment of the present invention. .

In FIG. 1, the core 9 is the coil 10 as in the conventional example.
It is wound around. The core 9 and the coil 10 are arranged on the base 21. Below the base 21, a hinge plate 23 and a printed wiring board 17 are attached via a packing 22. The coil 10 is connected to a printed wiring board 17 as shown in the figure.

As shown in FIG. 3, an embedding ring 24 is arranged at the center of the core 9 and the coil 10 arranged in an annular shape. The embedding ring 24 is formed of a member having a high heat conductivity, and as shown in FIG. 3, grooves 25 are formed on the four sides thereof, and an insertion portion 24a is formed on the lower end thereof. A thermistor 13 as a temperature detecting element for detecting the temperature of the coil 10 is arranged at a position facing the groove 25. The thermistor 13 is in contact with the coil 10. As shown in FIG. 1, the thermistor 13
Are connected to the printed wiring board 17 by conductors, for example copper wires 26. The embedded ring 24 is inserted into an insertion hole 27 formed in the base 7, packing 22, and hinge plate 23, and in particular, the insertion portion 24a at the lower end thereof is fixed in position by being inserted into the insertion hole of the hinge plate 23. ing. The embedded ring 24 is inserted into the insertion hole 27 to urge the copper wire 26 of the thermistor 13 toward the coil 10 to bring the thermistor 13 into contact with the coil 10. Other structures are similar to those of the conventional example.

Next, the operation of the embodiment having the above structure will be described. The printing operation is similar to that of the conventional example, and therefore its explanation is omitted. Here, the coil temperature control operation will be described.

When a current is applied to the coil 10 to drive the printing wire for printing, the coil 10 generates heat and its temperature rises. The temperature of the coil 10 in contact with the thermistor 13 is directly transmitted to the thermistor 13. The temperature of the coil 10 which the thermistor 13 is not in contact with is transmitted to the nearby thermistor 13 via the air and the embedded ring 24.

FIG. 4 is a graph showing the coil temperature and the thermistor temperature in the example. Similar to the graph shown in the conventional example, this graph shows the measurement results of the coil temperature and the thermistor temperature when JIS 1st level Chinese characters were continuously printed for 1 hour. The coil temperature and the thermistor temperature are read from the respective resistance values, and particularly the thermistor temperature is a value read as a total resistance value in which four thermistors are connected in parallel. Also in the case of this embodiment, the upper temperature limit of the coil is set to 180 ° C., and the coil temperature is controlled so as not to rise any higher.

As can be seen from this graph, the followability of the thermistor temperature with respect to the coil temperature is improved, and the coil temperature is
That is, the thermistor detection temperature for stopping energization of the coil when the temperature approaches 180 ° C. is also set to a relatively high temperature. Therefore, the coil can be energized until the temperature of the coil approaches the heat-resistant temperature very closely, and as a result, the throughput is increased. By the way, by the above measurement, a result that the throughput is improved by about 7% as compared with the measurement result of the conventional example was obtained.

Although four thermistors are provided as the temperature detecting elements in the present embodiment, the number of thermistors is not limited to this. By further increasing the number of thermistors and bringing them into contact with the coils, the followability of the thermistor temperature with respect to the coil temperature can be further improved.

(Effect of the Invention) As described in detail above, according to the present invention, since the temperature detecting element is brought into contact with the coil by the embedded ring,
The followability of the temperature of the temperature detection element with respect to the coil temperature is improved, and as a result, the effect of preventing the coil from burning and improving the throughput is obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing an essential part of an embodiment of the present invention, FIG. 2 is a perspective view showing an embedding ring of the embodiment, and FIG. 3 is a plan view of an essential part of an embodiment of the present invention. FIG. 4 is a graph showing the coil temperature and the thermistor temperature in the embodiment, FIG. 5 is a sectional view showing the structure of a conventional print head, and FIG. 6 is a graph showing the conventional coil temperature and the thermistor temperature. 9: core, 10: coil, 13: thermistor, 24: embedded ring.

Claims (1)

[Scope of utility model registration request] 1. An output signal of a temperature detecting element for detecting a temperature of a coil while energizing a coil wound around a core arranged in an annular shape facing an armature to drive a print wire fixed to the armature. A wire dot print head in which control is performed to lower the coil temperature on the basis of the wire dot print head, characterized in that a positioning member is provided for positioning the temperature detecting element in contact with the coil.