JPH0783733A - Device for detecting presence or absence of powder - Google Patents

Abstract

PURPOSE:To detect the presence or absence of powder around a heat generating source and temperature sensor by detecting the radiant heat or conducted heat from a heat generating source with the temperature sensor. CONSTITUTION:The temperature of a resistance temperature sensor 2 which detects radiant heat or conducted heat from a heater 1 which is a heat generating source through a medium relies upon the medium in which the heater 1 and sensor 2 are placed. When the ambient temperature changes, the temperature of the sensor 2 changes, but, when a bridge circuit is constituted of a temperature compensating resistance temperature sensor 4 and resistors 5 and 6, the balance of the bridge circuit is not lost by the change, and the detection of the presence or absence of powder is not affected. When the case where the heater 1 and sensor 2 are placed in the air is used as a reference, it can be detected that powder exists in the circumference of the heater 1 and sensor 2 from the variation of the resistance value of the sensor 2, because the temperature of the sensor 2 changes when the heater 1 and sensor 2 are placed in the powder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting the presence or absence of powder.

[0002]

2. Description of the Related Art As a device for detecting the presence or absence of powder, that is, a device for detecting that the stored powder has fallen below a certain level, a piezoelectric vibration type or capacitance type device has been conventionally known.

[0003]

The conventional piezoelectric vibration type or capacitance type powder presence / absence detection device is disadvantageous in that it is expensive and has a short life and is restricted in the mounting posture and the mounting place. was there.

An object of the present invention is to provide a device which has a simple structure and is inexpensive and which can detect the presence or absence of powder.

[0005]

According to the present invention, the temperature of a resistance temperature sensor (hereinafter, referred to as a detection sensor) for detecting radiant heat from a heat source or conduction heat via a medium is determined by the heat source and the detection sensor. The presence or absence of powder around the detection sensor is detected by the change in resistance value accompanying the temperature change of the detection sensor by utilizing the dependence of the medium on which it is placed, and there is no restriction on the mounting posture or the mounting location. The resistance temperature sensor used for the detection sensor is inexpensive and has a long life.

[0006]

FIG. 1 is a diagram showing the principle of the present invention. The temperature of the detection sensor 2 that detects radiant heat from the heater 1 which is a heat source or conduction heat through the medium depends on the medium on which the heater 1 and the detection sensor 2 are placed if the ambient temperature is constant. When the heater 1 and the detection sensor 2 are placed in the air as a reference, the temperature of the detection sensor 2 changes when the heater 1 and the detection sensor 2 are placed on the powder 3, The presence of the powder 3 around the heater 1 and the detection sensor 2 can be detected from the change in the resistance value of the sensor 2.

When the temperature of the detection sensor 2 rises or falls as compared with the state without the powder 3 depending on the thermal conductivity of the powder 3 or the presence or absence of stirring, etc., but there is the powder 3 to be detected. In addition, it is only necessary to obtain in advance that the temperature of the detection sensor 2 relatively rises or falls relative to the state where the powder 3 does not exist.

When the ambient temperature changes, the temperature of the detection sensor 2 changes, but if the temperature compensation resistance temperature sensor 4, the resistors 5 and 6 and the bridge circuit are formed as shown in FIG. The change does not disturb the balance of the bridge circuit and does not affect the powder detection.

[0009]

[Embodiment 1] FIG. 3 shows a circuit of a powder presence / absence detection device using a resistance temperature sensor for detecting radiation or conduction heat from a heat source according to the present invention as a presence / absence detection sensor. A sensor 2, a temperature compensating resistance temperature sensor 4, and a bridge circuit composed of resistors 5 and 6, and the other circuits are composed of a differential amplifier 7 serving as a signal conversion unit, a comparator 8 and a heater 1 serving as a heat source. .
The resistance temperature sensor 2 and the temperature compensation resistance temperature sensor 4, which are detection sensors, are platinum thin film temperature sensors of 500Ω.

FIG. 4 shows an embodiment of the presence / absence detection apparatus according to the present invention. FIG. 4A is a plan view of the presence / absence detection apparatus.
(B) is a side view and (C) is a bottom view. The detection sensor 2 and the heat-shrinkable tube 11 in which the column 10 protruding from the box-shaped resin mold case 9 is covered with the heat-shrinkable tube 11
The temperature compensating resistance temperature sensor 4 and the heater 1 covered with are attached. Inside the case, a printed circuit board 12 in which a circuit including a differential amplifier electrically connected to each sensor is formed is housed and filled with resin 13. The lead wire 14 guided from the printed circuit board 12 is taken out from the side surface of the case and supplies power and output signals from the outside.

As shown in FIG. 5, the powder presence / absence detection device 15 according to the present invention is attached to the storage box 16 with screws 17, and the flour 18 as the powder to be detected is put in the heater 1
It was operated by supplying 1 W of electric power. At an ambient temperature of 24 ° C,
When the detection sensor 2 is changed from being immersed in the flour 18 to being exposed, the temperature of the detection sensor 2 shows 32 ° C. when the flour 18 is present, and is 6 ° C. from the temperature of 26 ° C. when there is no flour 18. ℃ went up. The output signal of the presence / absence detection device for powder is from the voltage generated by the temperature difference between the detection sensor 2 and the temperature compensation resistance temperature sensor 4 from the H level with the flour 18 to the state without the flour 18, as shown in FIG. L
Inverted to the level, the presence or absence could be detected.

[0012]

According to the present invention, the presence / absence of powder is detected by installing a powder presence / absence detection device, which uses a resistance temperature sensor for detecting radiation or conduction heat from a heat source as a detection sensor, in a powder storage box. (1) The structure of the powder presence / absence detection device is simple and inexpensive. (2) The platinum thin film temperature sensor as a detection sensor is inexpensive, has a long life, and is stable. (3) Since the portion in contact with the powder is covered with the resin, the influence on the powder is small. (4) There are no restrictions on the mounting posture or the mounting location. It is possible to obtain an effect that the conventional device does not have.

[Brief description of drawings]

1 shows the principle of the device according to the invention.

FIG. 2 is a circuit diagram showing temperature compensation of a detection sensor according to the present invention.

FIG. 3 is a circuit diagram of a device according to the present invention.

FIG. 4A is a plan view showing an embodiment according to the present invention,
(B) is a side view and (C) is a bottom view.

FIG. 5 is a sectional view of the storage box showing a mounting state of the powder presence / absence detection device.

FIG. 6 is a level change of the powder and an output signal when the powder presence / absence detection device according to the present invention is operated.

[Explanation of symbols]

 1 Heater 2 Resistance Temperature Sensor (Detection Sensor) 3 Powder 4 Temperature Compensation Resistance Temperature Sensor 5 Resistor 6 Resistance 7 Differential Amplifier 8 Comparator 9 Mold Case 10 Support 11 Heat Shrink Tube 12 Printed Circuit Board 13 Resin 14 Lead Wire 15 Powder Presence detection device 16 Storage box 17 Screw 18 Wheat flour

Claims (1)

[Claims] 1. A heat source and two resistance temperature sensors are used. One resistance temperature sensor is a temperature sensor for detecting radiation or conduction heat from the heat source, and the other resistance temperature sensor is for the heat source. An apparatus for detecting the presence or absence of powder, which is configured for temperature compensation of a resistance temperature sensor for detecting radiation or conduction heat of the powder.