JPS631537B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an object detection device in which the heat capacity of a detection element changes when it comes into contact with an object, and digitally processes the voltage that fluctuates depending on the change to detect the presence or absence of an object. Regarding.

Generally when you need to detect the presence or absence of an object,
For example, in an ice maker, it is detected whether ice has reached a certain level in the ice storage compartment using a photoelectric element or a mechanical thermometer. As a result, there was a danger that frost could build up or the mechanical contacts could freeze, causing malfunctions.

In addition, semiconductor technology and electronics technology have advanced in recent years, and LSIs or microcomputers have been put into practical use and are used in a variety of fields. For example, it is used to control the temperature or power of air conditioners, refrigerators, case boxes, ice makers, etc., but the function of detecting and controlling the amount of ice in an object, such as an ice machine, is also used for temperature control and power control. It is desirable to perform comprehensive control using an LSI or microcomputer along with power control, etc.

The present invention has been made in view of the above points, and provides a novel object detection device that is completely different from conventional object detection devices. The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, in which 1 is an object detection element, 2 is a power supply section, and 3 is an A/D
Converter 4 is a control circuit.

The object detection element 1 includes an NPN type transistor 5,
Load resistor connected to collector of transistor 5
It consists of R ₀ and dividing resistors R ₁ and R ₂ connected between the base and the collector and between the base and the emitter, respectively, and takes out the collector voltage of the transistor 5 as an output. This transistor 5 is the second
As shown in the figure, a heat sink 6 having good thermal conductivity, for example made of aluminum, is thermally bonded and fixed at one end into a closed pipe, and a lead 7 is connected to the heat sink 6.
It extends to the other end and is hermetically sealed with a sealing portion 8. When nothing is in contact with the heatsink 6, the heat generated in the junction by the collector current flowing through the transistor 5 is transferred to the transistor 5.
Heat is radiated according to a thermal time constant determined by the thermal resistance and heat capacity of itself and the heat radiator 6, and the temperature of the junction increases until the heat generation and heat radiation are balanced. Therefore, the collector current, which has temperature dependence, increases as the junction temperature rises, and the collector voltage gradually decreases as the voltage drops across the load resistor _R0 , and becomes constant when heat generation and heat radiation are balanced. Become. However, a certain power supply voltage V _cc is determined depending on the initial state such as the ambient temperature, that is, the voltage V _cc
When a power supply voltage V _cc is applied to the object detection element 1 such that the amount of heat generated by the collector current flowing due to the current is slightly larger than the amount of heat radiated from the radiator 6,
The output voltage, ie, the collector voltage, decreases rapidly until the thermal time constant of the object detection element 1 itself described above, but then decreases linearly.
Figure 3a shows its characteristics.

On the other hand, when an object with a large heat capacity, such as ice 9, is in contact with the radiator 6, the contact area is fixed at 0°C due to the melting heat of the ice 9, and the heat is absorbed, so the amount of heat released is less than the amount of heat generated. The collector voltage becomes a constant voltage in a short time as shown in FIG. 3b. Therefore, the difference between when objects are in contact and when they are not in contact becomes larger as time passes.

The power supply unit 2 is controlled by the signal S _B from the control circuit 4, and supplies a predetermined power supply voltage V _cc1 to check the initial state of the object detection element 1 at the same time as the object detection operation starts. Furthermore, a power supply voltage _Vcc2 of a magnitude corresponding to the content of the signal S _B is applied to the object detection element 1. The A/D converter 3 converts the output of the object detection element 1, that is, the collector voltage of the transistor 5, into a 4-bit or 8-bit digital signal using a well-known method, and the digitally converted collector voltage is It is applied to the control circuit 4.

The control circuit 4 outputs a signal S _B to control the power supply section 2, and further includes a control section 10 having a built-in timer that determines times _T1 and _T2 for measuring the collector voltage of the object detection element 1, and a control section 10. The input gate 11 inputs the digitally converted collector voltage value in the initial state and at times _T1 and _T2 determined by the timer, and the collector voltage input in the initial state. Calculate the voltage value such that the output of the object detection element 1 changes linearly depending on the value as described above, and further predict the collector voltage at time _T2 from the collector voltage value input at time _T1 . Arithmetic circuit 1 that calculates and stores voltage values
2, the collector voltage value input at time T ₂ and the expected voltage value calculated by the arithmetic circuit 12 are compared,
A comparison circuit that determines whether or not the difference is within a predetermined tolerance range, and outputs a signal to the control signal S _A indicating that there is no object if it is within the tolerance, and that there is an object if it is outside the tolerance. It consists of 13.

Next, the operation will be explained with reference to the flowchart shown in FIG.

When the control circuit 4 is started, the control section 11 of the control circuit 4 outputs a signal S _B with predetermined contents for measuring the initial state, and the power supply section 2 follows the contents of the signal S _B. Voltage magnitude power supply voltage
_Vcc1 is applied to the object detection element 1. Next, control section 1
0 opens and closes the input gate 11, and the collector voltage generated by the power supply voltage _Vcc1 (voltage _Vc1 at time O in FIG. 3) is digitally converted and sent to the arithmetic circuit 12.
is applied to The arithmetic circuit 12 is a power source for obtaining an initial voltage value (voltage V _c2 in FIG. 3) at which the characteristic of the object detection element 1 becomes linear when there is no object, based on the digitally converted collector voltage value V _c1 . The voltage V _cc2 is calculated and the result is sent to the control unit 10. The control unit 10 generates a signal according to the calculated voltage _Vcc2 .
In order to output S _B to the power supply unit 10, the power supply voltage _Vcc2 is applied from the power supply unit 10 to the object detection element 1, and the collector voltage becomes _Vc2 . At this time, a timer built in the control section 10 is set to time out at time _T1 . The time T ₁ is approximately equal to or slightly larger than the thermal time constant determined by the transistor 5, heat sink 6, etc. shown in FIG.
That is, it is set at the boundary between the curved changing part and the linear changing part. When the timer times out at time _T1 , the control unit 10 opens and closes the input gate 11 again, and the digitally converted collector voltage value at time _T1 is applied to the arithmetic circuit 12, and the arithmetic circuit 12 Based on the voltage value, time is calculated using a pre-stored linear equation of a straight line.
Calculate the expected collector voltage value at T ₂ ,
Memorize the result. Further, the timer of the control section 11 is set again so as to time out at the next time _T2 , and at the time _T2 , the control section 10 opens and closes the input gate 11, and the digitally converted collector voltage value at the time _T2 is set. is applied to the comparator circuit 13 via the input gate 11, and the expected collector voltage value calculated and stored at time _T1 is applied to the comparator circuit from the arithmetic circuit 12, and the two are compared. i.e. the calculated voltage value and the actual time T ₂
The difference between the measured collector voltage value and the measured collector voltage value is calculated, and it is determined whether the difference is within a predetermined tolerance. As shown in Fig. 3, if the theoretical collector voltage calculated by the arithmetic circuit 12 is denoted by C, the difference when the object is not in contact is △V ₁ , and the difference when the object is in contact is △V 1. The difference is △V ₂ . Therefore, the presence or absence of an object can be determined by appropriately setting the tolerance between ΔV ₁ and ΔV ₂ . In this way, if the difference is within the tolerance, the comparison circuit 13
outputs a signal indicating that there is no object to the control signal S _A ,
If it is outside the tolerance, the object presence signal is sent to the control signal S _A
Output to. When the determination of the presence or absence of an object is completed, the control unit 10 stops applying voltage from the power supply unit 2 to the object detection element 1 based on the signal S _B , waits for a certain period of time until the object detection element 1 cools down, and then starts the next detection operation. Move to. By repeating the above operations, objects can be detected at regular intervals.

According to the operation of the control circuit 4, the output of the object detection element 1 at the initial stage is measured, the voltage value to be applied is calculated, and the collector voltage value at time _T1 is changed from the collector voltage value at time _T2 to the voltage value to be applied. Object detection is performed by predicting the collector voltage value at a given time and comparing it with the actual collector voltage value. It is capable of detecting objects. Furthermore, the control circuit 1 can be configured with a microcomputer, and the above-described operations can be executed using a preset program. In this case, the operating time and standby time of the timer can be controlled comprehensively along with object detection by executing another program, such as a temperature control or power control program. Furthermore, since the object detection element 1 uses the pipe-shaped heat sink 6, it can be mechanically strong.

As described above, according to the present invention, a detection element with mechanical strength can be used, and objects can be detected reliably without being affected by ambient temperature, making it highly useful for ice making machines, etc. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a cross-sectional view of an object detection element used in the embodiment shown in FIG. 1, and FIG. 3 is an object detection device shown in FIG. 2. The characteristic diagram of the element and FIG. 4 are flowcharts showing the operation. 1...Object detection element, 2...Power supply unit, 3...
A/D converter, 4... Control circuit, 5... Transistor, 6... Heatsink, 7... Lead, 8... Sealing part, 9... Ice, 10... Control unit, 11... Input Gate, 12...Arithmetic circuit, 13...Comparison circuit.

Claims (1)

[Claims] 1. A power supply unit that supplies a power supply voltage, a semiconductor element having a PN junction, and a semiconductor element that is fixed so as to be thermally coupled and installed at a position where an object to be detected is in contact with the semiconductor element, and a current is caused to flow through the semiconductor element. a detection element comprising a heat radiator for dissipating heat generated by the above, and outputting a detection voltage according to a temperature rise of the PN junction when the power supply voltage is supplied;
and a control circuit to which the output of the detection element is applied and which controls the power supply section, the control circuit supplies a predetermined power supply voltage to the detection element, and detects the detection at the start of the supply. Read the detection voltage of the element, calculate a power supply voltage at which the characteristic of the detection voltage with respect to time when there is no object is linear based on the detection voltage, and then supply the calculated power supply voltage to the detection element. An object detection device characterized in that the predicted detection voltage value calculated based on the linear characteristic is compared with the actual detection voltage value from the detection element to detect the presence or absence of an object.