JPH0310698Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] This invention relates to a heat dissipation structure for an input/output unit that couples external input/output signals in a programmable controller or the like.

[Prior art and its problems]

As electronic devices become smaller, the input/output units mentioned above are also required to be smaller and more highly integrated. As a result, the amount of heat generated per unit area by internal circuit components increases, and a more effective heat dissipation structure is required. Moreover, when handling electronic equipment,
Electronic equipment must be used with heat dissipation regardless of its mounting form.

The internal electric circuit of the input/output unit described above is
5, in which FIG. 4 shows an input circuit and FIG. 5 shows an output circuit. First, the operation of the input circuit shown in FIG. 4 is such that when the external input contact 11 is turned on, a current flows from the external input signal power source 12, passes through the terminal block 1, is limited by the series resistor 13, and is passed through the photocoupler 14. The current flows to the photodiode, which is the primary side of the photodiode. This current operates the phototransistor on the secondary side of the photocoupler 14, and a signal is applied to the Schmitt circuit 15. This output is sent to an internal circuit P of the control section (not shown) and processed. Indicator light 1 to confirm that input signals are being sent at the same time
6 is lit. The current flowing to the photodiode side of the photocoupler 14 is several mA to several tens of mA, but when this current flows through the series resistor 13, heat is generated in proportion to the time it flows. Since the voltage drop across the photocoupler 14 is small, most of the external signal voltage is applied to this series resistor 13, and as the voltage increases, the amount of heat generated increases. Next, the fifth
Regarding the output circuit shown in the figure, the driver 21 is operated by a signal from the control unit Q (not shown), and the operation indicator light 22 is turned on, and the photocoupler 2
Apply current to the photodiode side of No.3. Voltage V _cc
Since the value of is as low as +5V, the heat generated by this current is minimal. When the phototransistor of the photocoupler is turned on, the base current of the output transistor 26 is supplied from the positive side of the external load power supply 24 through the resistor 25. As a result, transistor 2
6 is turned on to drive the external load 27 via the terminal block 2. Here, since the output current of the photocoupler 23 is minute, a Darlington connection power transistor with a high current amplification factor is used as the transistor 26. The saturation voltage of this transistor is about 1V. Therefore, power is consumed and heat is generated approximately in proportion to the load current of the external load. For this reason, the transistor is attached closely to the heat dissipation fin to improve heat dissipation. The electronic components forming the input circuit and output circuit described above, including components that generate a lot of heat, are mounted on the same printed circuit board to form a circuit. These are then assembled as an input/output unit by covering them with a cover having ventilation slits on the four surrounding sides. A perspective view of the external appearance is shown in FIG. 6, and a cross section taken along the line A-A is shown in FIG. 7. In other words, the input circuit and the output circuit are mounted on the same printed circuit board 3 to achieve multi-point design, and the series resistor 1, which is an electronic component that generates a lot of heat, is mounted on the same printed circuit board 3 as above.
3 and the transistor 26 attached to the heat dissipation fin 27 are arranged on the left and right, and the terminal block 1 on the input circuit side and the terminal block 2 on the output circuit side are arranged at the adjacent ends, that is, on opposite sides of the printed circuit board 3. At the top center there is an input circuit indicator light 16 and an output circuit indicator light 2.
However, since the indicator lights 16 and 22 both have short legs, the sub-printed board 4 is used to lift up the entire display. Therefore, a connecting wire (not shown) is required to connect the sub-printed board 4 and the printed circuit board 3. The printed circuit board 3 mounted as described above is covered with a cover 5 for protection, but this cover 5 is formed so that the heads of the indicator lights 16 and 22 and the terminal blocks 1 and 2 are exposed, and the surrounding Ventilation slits 6 are provided on both sides.

That is, outside air enters the interior through the slit on one side of the cover 5, cools the internal parts that generate a lot of heat, and then is discharged through the slit on the other side. When two input/output units having such a heat dissipation structure are mounted on a basic unit, there are two mounting methods, one as shown in FIG. 8 and the other as shown in FIG. 9. 8th
The figure shows a state in which the terminal blocks 1 and 2 are placed on the basic unit 7 and mounted on the left and right sides. In this case, the air generated inside the cover 5 rises and is discharged from the slit 6 at the top. Cold outside air is sucked in through the slit at the bottom and the cover 5 is naturally ventilated.
Internal cooling takes place. However, when the terminal block is installed vertically as shown in FIG. 9, there is no ventilation slit in the vertical direction of the case, so natural ventilation is not achieved. Although some of the hot air inside the case is exhausted through the slits on both sides, and a small amount of cold outside air is sucked in through the slits on both sides, there is a drawback that the amount of ventilation inside the case is extremely small and ventilation cooling is insufficient.

[Purpose of invention]

The object of this invention is to eliminate the above-mentioned drawbacks and provide a heat dissipation structure that allows effective ventilation cooling regardless of the mounting direction of the input/output unit.

[Key points of the idea]

The main points of this idea are that a recess is provided in the center of the cover, a slit is provided on the side of the recess to ensure a ventilation path, and a gap is created between the terminal block and the printed circuit board and between the terminal block and the cover. This is due to the provision of ventilation channels.

[Example of idea]

Figures 1 to 3 show examples of this invention; Figure 1 is a perspective view of the input/output unit;
This figure is a perspective view of the interior of the input/output unit shown in FIG. 1 with the cover removed, and FIG. 3 is a sectional view taken along the line B--B in FIG. 1. An inverted trapezoidal recess is provided in the center of the cover 50 parallel to the terminal blocks 1 and 2. The indicator lights 16, 22 are directly attached to the printed circuit board 3 so that the heads of the indicator lights 16, 22 (FIG. 2) are exposed from the bottom of the recess. Further, a slit 7 for ventilation is provided on the side surface of the recess. cover 50
As in the conventional structure, ventilation slits 6 are provided on both sides, and ventilation slits 8 are also provided on the sides where the external terminal blocks 1 and 2 are exposed. Also, there is a gap 9 between the bottom of the terminal blocks 1 and 2 and the printed circuit board 3.
a is provided, and a gap 9b is also formed between the upper part of the terminal blocks 1 and 2 and the cover 50 to allow ventilation in both. Ventilation holes 10 are provided in the printed circuit board 3 near the series resistor 13 and the transistor 26, which are heat-generating components, and the heat dissipation fin 27 of the transistor 26 has ventilation holes 27a or slits 27 for ventilation.
b. Even when an input/output unit having such a heat dissipation structure is installed in the direction shown in FIG. 9, the inside of the case 50 is cooled by ventilation in the direction shown by the arrow in FIG. Ru.

[Effect of idea]

In this design, a recess is provided in the center of the cover, a slit is provided on the side of the recess for ventilation, a gap is provided between the terminal block and the printed circuit board, and a gap is provided at the joint between the terminal block and the cover. Since ventilation is also possible in the direction from one terminal block to the other terminal block on the opposite side, ventilation cooling can be performed effectively regardless of whether the input/output unit is installed vertically or horizontally. Furthermore, the recess provided in the cover eliminates the need for a sub-printed board for mounting the indicator light, resulting in cost reduction.

[Brief explanation of drawings]

Figures 1 to 3 show an embodiment of this invention; Figure 1 is a perspective view of the external appearance of the input/output unit;
Figure 2 is a perspective view of the internal appearance of the input/output unit in Figure 1 with the cover removed, and Figure 3 is B-B in Figure 1.
4 is an electric circuit diagram on the input side of the input/output unit, FIG. 5 is an electric circuit diagram on the output side of the same as above, and FIG. 6 is an external perspective view of the input/output unit with a conventional structure.
Figure 7 is a sectional view taken along the line A-A in Figure 6, Figure 8 is an external perspective view of the basic unit with the input/output unit installed horizontally, and Figure 9 is the basic unit with the input/output unit installed vertically. FIG. 1, 2; terminal block, 3; printed circuit board, 6, 7,
8, 27b; slit, 9a, 9b; gap, 1
0; ventilation hole, 27; heat dissipation fin, 50; cover.

Claims (1)

[Scope of utility model registration request] An input unit side terminal block and an output unit side terminal block are placed on opposite sides of a rectangular printed circuit board, and electronic components are mounted on the printed circuit board surrounded by both terminal blocks to connect the input circuit and output. An input with a structure in which a circuit is formed and these are covered with a cover with ventilation slits on both sides except for the terminal block on the input unit side and the terminal block on the output unit side, leaving only the terminal block and the head of the indicator light exposed. In the output unit: A recess parallel to the terminal block is formed approximately in the center of the cover, and ventilation slits are provided around the sides of this recess, and ventilation slits are provided between the bottom of the terminal block and the printed circuit board and between the top of the terminal block and the cover. A heat dissipation structure for an input/output unit, characterized in that a gap is provided, and a ventilation hole or a ventilation slit is provided in a heat dissipation fin of a built-in component.