JPS631536B2 - - 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 temperature-dependent collector current increases as the junction temperature rises, and the collector voltage decreases as shown in FIG. 3a due to the voltage drop across the load resistor _R0 .

On the other hand, when an object with a large heat capacity, such as ice 9, comes into contact with the radiator 6, the contact portion is fixed at 0° C. due to the melting heat of the ice 9, and the heat is absorbed. Therefore, the heat capacity of the detection element as a whole increases and the thermal time constant decreases, so the time it takes for the junction temperature to reach a constant level becomes shorter, and at the same time, the collector voltage of transistor 5 increases as shown in Figure 3b. It becomes constant in a short time. Therefore, the presence or absence of an object can be detected by determining whether the output of the object detection element 1 is a or b shown in FIG. Standard characteristics at various initial voltages when there is no contact are created experimentally or by calculation, and after starting the current flow to the object detection element 1, the characteristics are set at regular intervals, that is, T ₁ , T ₂ , Measure the output voltage at time T ₃ ...T _o ,
The presence or absence of an object can be detected by determining whether the voltage value is within the tolerance of the standard characteristic value. In Figure 3, if the standard characteristic is given by c, at time _T4 , the difference between the output voltage when there is no object and the standard characteristic is ΔV ₁ , and the difference between the output voltage when there is an object and the standard characteristic is ΔV 1. The difference from the standard characteristics is ΔV ₂ . On the other hand, the tolerance standard is set to be sufficiently larger than the possible difference between the characteristics when there is no object and the standard characteristics, and also sufficiently smaller than the difference between the characteristics when there is an object and the standard characteristics at the time of final judgment T _o Must.

The power supply unit 2 activates the object detection element 1 based on the signal S _B from the control circuit 4 at the same time as the start of the detection operation for detecting the presence or absence of an object.
The device controls the application of a constant voltage _Vcc to the object detection element 1 to which the voltage _Vcc is applied.
A collector current determined by R ₁ and R ₂ begins to flow. The A/D converter 3 digitally converts the output of the object detection element 1, that is, the magnitude of the collector voltage of the transistor 5, by a well-known method, and the digitally converted collector voltage value is applied to the control circuit 4 and processed. be done.

The control circuit 4 outputs a signal S _B for controlling the power supply section 2, and further includes a control section 10 having a built-in timer for determining the time interval for measuring the collector voltage of the object detection element 1, and a timer determined by the timer. Time T ₁ ,
An input gate 11 for sampling and inputting the digitally converted collector voltage value at T ₂ , T ₃ ...T _o , and a list of standard characteristics at various initial voltages is stored in advance. When the initial voltage of the collector voltage digitally converted from is input, the RAM 12 searches for a list of standard characteristics corresponding to the initial voltage and sends out the data at each time T ₁ , T ₂ , T ₃ . . . T _o Then, the difference between the data sent from the RAM 12 and the digitally converted collector voltage value inputted through the input gate 11 at each time T ₁ , T ₂ , _{T 3} . and a comparison circuit 13 that compares whether or not the difference is within a predetermined tolerance.

Next, the operation of the control circuit 4 will be explained with reference to the flowchart shown in FIG.

When the control circuit 4 is started, the control section 10 outputs the signal S _B and controls the power supply section 2 to apply the voltage V _cc to the object detection element 1, and furthermore, the input gate 11
is opened and closed to input the digitally converted initial voltage value of the output of the object detection element 1. When the digitally converted initial voltage value is applied to RAM12, the RAM
A standard characteristic corresponding to the applied initial voltage value is searched and extracted from the list of standard characteristics stored in 12. Further, a timer built in the control unit 10 is set with a time to determine the sampling interval for sampling at times T ₁ , T ₂ , T ₃ , . . _{. To} . When the timer times out, the control section 10 opens and closes the input gate 11 again, and applies the digitally converted collector voltage value at time _T1 to the comparator circuit 13 via the input gate 11. On the other hand, comparison circuit 1
3, the data corresponding to time T ₁ of the list of standard characteristics searched and extracted from the RAM 12 is transferred,
Each difference is calculated and compared to see if the difference is within a predetermined tolerance. If the difference between the calculated collector voltage value and the standard characteristic is within the tolerance, then check whether the data in the list just used was the final data, that is, whether it was the data corresponding to time T _o . is determined by the comparison circuit 13.
If it is not the final data, the comparator circuit 13
The data in the list No. 2 is shifted to the next data, that is, the data corresponding to the next time, for example, if it is time _T1 , time _T2 is set, and the timeout timer of the control unit 10 is set again. The same operation is repeated sequentially for times T ₁ , T ₂ , T ₃ . If the difference exceeds the tolerance, it is determined that the collector voltage of the object detection element 1 is as shown in FIG.
Output to _SA . If the presence of an object is detected, there is no need to perform the above operation even if the time T _o has not been reached, and the control unit 10 applies the voltage V _cc from the power supply unit 2 to the object detection element 1 based on the signal S _B. The object detection element 1 waits for a certain period of time to cool down before performing the next detection operation.

Further, if the difference calculated in the comparison circuit 13 continues to be determined to be within the tolerance, and furthermore, the final data, that is, the time T _o, is also determined to be within the tolerance, the collector voltage of the object detection element 1 is It is determined that the characteristics shown in FIG. 3a are true, and therefore the comparator circuit 13 outputs a signal indicating that there is no object as the control signal S _A.
This completes the detection operation, and the control section 10 outputs a signal.
S _B controls the power supply unit 2 to stop applying the voltage V _SS to the object detection element 1, and waits for a certain period of time to cool the object detection element 1 until the next detection operation is performed.
Repeat the same detection operation again. Therefore, the control signal S _A becomes a signal indicating the presence or absence of an object, and this control signal S _A can be used, for example, to flash a warning lamp,
Alternatively, it can be used to control the amount of ice stored in ice makers and the like.

The control circuit 4 that performs such operations may be constructed of a microcomputer, and executes the above-mentioned operations according to a preset program.
In this case, the timer that determines the sampling time T ₁ , T ₂ , T _{3 .} With this program, object detection in ice making machines and the like can be performed comprehensively along with other controls.

As described above, according to the present invention, a mechanically strong object detection element can be used, and the initial voltage of the output of the object detection element is measured, and a predetermined value corresponding to the initial voltage value is determined by experiment or calculation. By searching and extracting the list of standard characteristics obtained from the standard characteristics and comparing that data with the measured values at sampling times T ₁ , T ₂ , T ₃ ...T _o , This allows stable object detection.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a sectional view of an object detection element used in the embodiment shown in FIG. 1, and FIG. 3 is a block diagram showing an object detection element shown in FIG. The characteristic diagram of the detection 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 Tr, 6... Heat sink, 7... Lead, 8...
Sealing part, 9...ice, 10...control unit, 11...input gate, 12...RAM, 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;
a storage means that stores in advance an expected detection voltage value of the detection element at fixed time intervals when no object is in contact with the heat radiator; and a storage means that samples the detection voltage of the detection element at fixed intervals and stores the sampled values. An object detection device comprising a comparison means for comparing the predicted detection voltage value, and outputs a signal indicating the presence of an object when a difference between the sampled value and the predicted detection voltage value is greater than or equal to a predetermined value.