JPH034343Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heater operation display device for an air dryer for an automobile.

Braking devices that use air pressure are the mainstream for large vehicles, and in recent years, air dryers have been installed between the air compressor and the air reservoir to improve the operational stability of this type of braking device. There are many models that absorb moisture in the air and supply dry air from an air reservoir to the braking system. This air dryer has an automatic discharge valve that opens and closes based on signal pressure from an air compressor governor that controls the load on the air compressor, and is designed to automatically discharge absorbed moisture. In order to prevent the discharge valve from freezing in cold weather, it has a built-in heater with a bimetal switch that automatically turns on when the internal water temperature drops below a certain temperature, and displays the operating switch and its operation in the driver's cab etc. The heater is equipped with a pilot lamp to enable operation and confirmation of the operation of the heater.
It is designed to maintain normal operation of the air dryer.

However, in the conventional heater operating circuit, as shown in FIG. 1, a pilot lamp 4 is connected in series to a battery 1 via a key switch 2 and an air dryer operating switch 3. The bimetal switch 5 and the heater 6 are connected in series, and a heater circuit 7 having a larger current capacity is connected in parallel with the pilot lamp energizing circuit side, which turns on and off the bimetal switch 5, that is, energizes the heater 6. Regardless of the de-energized state, the pilot lamp 4 would light up when the operating switch 3 was turned on. For this reason, there was a problem in that the heater circuit 7 was disturbed, such as a disconnection of the heater 6, and the pilot lamp 4 was turned on as if the heater 6 was operating even though no heating was being performed.

In addition, as a matter related to this invention,
There are publications such as No. 156237.

This idea was made in view of the above circumstances.
It is an object of the present invention to solve the conventional problems by providing a circuit configuration that operates a display means only when the heater is in an energized state.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

In FIG. 2 showing the first embodiment of the present invention, 1
1 is a battery, 12 is a key switch, and 13 is an operating switch for operating the heater circuit of the air dryer. This operating switch 13 includes a bimetal switch 14 provided inside the air dryer and a heater 1.
A heater circuit 16 in which 5 and 5 are connected in series is directly connected. Further, a pilot lamp 17 for displaying the operating state of the heater 15 is connected in parallel to the heater circuit 16 and in series with the operating switch 13. In this embodiment, the contact portion 18A of the reed switch 18 is connected between the operating switch 13 and the pilot lamp 17, and the excitation coil portion 18B of the reed switch 18 is connected in parallel with the pilot lamp 17 and directly with the heater circuit 16. Connected to the example.

In such a configuration, if the bimetallic switch 14 is on when the operating switch 13 is turned on, the heater 15 is energized and heating starts. At this time, current also flows through the excitation coil portion 18B of the reed switch 18, the contact portion 18A closes, the pilot lamp 17 lights up, and it can be confirmed that the heater 15 is energized.

On the other hand, when the bimetal switch 14 is off or no current is flowing to the heater 15 due to a disconnection of the heater 15, no current flows to the excitation coil portion 18B of the reed switch 18, and its contact portion 18A is not excited. Since it is turned off, the pilot lamp 17 does not light up. In this way, the pilot lamp 17 is turned on or off depending on whether or not the heater 15 is energized, so the conventional problem of the pilot lamp 17 being lit even when the heater is not energized can be solved, and the heater The operating status of the device can be accurately displayed.

In the above example, a reed switch was used, but
A transistor can also be used as shown in FIG. That is, the emitter and base of the PNP transistor 20 are connected between the operating switch 13 and the bimetal switch 14, and the collector is connected to the pilot lamp 17. Further, a resistor 21 is inserted between the emitter and the base. Note that a diode may be inserted in place of the resistor 21.

According to this configuration, when no current flows through the heater 15, no base current flows through the transistor 20 and the transistor 20 becomes non-conductive, so the pilot lamp 17 does not light up, but the heater 15 remains energized. At times, a base current flows through the transistor 20 and the transistor 20 becomes conductive, so that the pilot lamp 17 lights up. Therefore, as in the first embodiment, the operating state of the heater 15 can be accurately displayed.

Further, FIGS. 4 and 5 each show a device using a thermistor whose resistance changes depending on the ambient temperature.

In these embodiments, a thermistor 30 is arranged near the heater 15 so that the resistance value decreases as the ambient temperature rises, and the resistance change of the thermistor 30 turns on and off the transistor to turn on or off the pilot lamp 17. FIG. 4 shows an example in which an NPN type transistor 31 is used as the transistor, and FIG. 5 shows an example in which a PNP type transistor 32 is used as the transistor.

In these cases, when current flows through the heater 15 and it is in a heat generating state, the resistance value of the thermistor 30 is low and the base currents of the transistors 31 and 32 flow, turning the transistors 31 and 32 on, respectively.
Pilot lamp 17 lights up. On the other hand, when the heater 15 is not in a heat generating state, the resistance value of the thermistor 30 is high and almost no base current flows through the transistors 31 and 32, so the transistors 31 and 32 are turned off, so the pilot lamp 17 does not light up.

As described above, according to the present invention, current flows to the indicator light only when the heater is energized, indicating that the heater is operating, so even when no current is flowing to the heater when the heater circuit is operating, It is possible to eliminate the problem of the indicator light lighting up, and it is possible to accurately display whether or not the heater circuit is operating normally.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional heater operation display device.
2 to 5 are circuit diagrams showing each embodiment of the heater operation display device according to the present invention. 13... Operating switch, 14... Bimetal switch, 15... Heater, 17... Pilot lamp, 18... Reed switch, 20... Transistor, 30... Thermistor, 31, 32... Transistor.

Claims (1)

[Scope of utility model registration request] A heater operation display device for displaying the operating state of a heater circuit with a large current capacity built into an air dryer for an automobile, including means for detecting whether or not the heater circuit is energized; 1. A heater operation display device for an air dryer for an automobile, comprising: a display means connected in parallel with a heater circuit that displays the operation of the heater circuit only when a state is detected.