JP2005156389A - Temperature detection/disconnection detecting circuit, temperature detection/disconnection detection method, and device for controlling internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple temperature detection/disconnection detecting circuit and so forth, which can maintain temperature detection accuracy, which can surely detect disconnection of a temperature sensor, and which does not require reference resistors for detecting disconnections. <P>SOLUTION: A thermistor Rth, the reference resistor R1, and a switch S1 are connected in series. A prescribed voltage is applied by turning on/off the switch S1. A low-pass filter is formed of a capacitor C and a resistor Rs, in parallel with the thermistor Rth is connected to a detection means 2. When the switch S1 is closed, the temperature detection is performed; and when it is opened, the disconnection detection is performed. In performing the detection of the disconnection, the charge of the capacitor C is discharged through the resistor Rs and the thermistor Rth. The end-to-end voltage of the capacitor C is dropped, and it is decided as being normal. When the thermistor Rth or a lead for connecting the thermistor Rth is disconnected, discharge path for the charge of the capacitor C will be lost. The end-to-end voltage of the capacitor C is maintained and is decided as being abnormal; and disconnection detection can be performed, by monitoring the end-to-end voltage of the capacitor C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a temperature detection / detection circuit that detects the temperature of a detection target based on a change in resistance value of the temperature sensor and enables detection of disconnection of the temperature sensor, an internal combustion engine control device including the temperature detection / detection circuit, and The present invention relates to a temperature detection method using a temperature sensor and a disconnection detection method for the temperature sensor.

  As a technique for measuring temperature, it is known to use a thermistor whose resistance value changes in accordance with a temperature change. A thermistor that is a temperature sensor is connected in series with a reference resistance that is so small that the temperature change rate of the resistance value is negligible with respect to the temperature change rate of the thermistor. A voltage is applied to both ends. The temperature around the thermistor can be measured by reading the voltage change at the common connection point between the reference resistor and the thermistor, in other words, the change in resistance value of the thermistor. Examples of the thermistor that is a temperature sensor include NTC (Negative Temperature Coefficient) in which the resistance value decreases as the temperature rises, and PTC (Positive Temperature Coefficient) in which the resistance value increases as the temperature rises. One is being used.

When measuring a part that is relatively high temperature (for example, about 800 degrees Celsius), such as the catalyst temperature of an automobile, the resistance value of the thermistor in the temperature range at that high temperature is several hundred Ω. Generally, it is set to several hundred Ω. By the way, since the thermistor has a high resistance value of several MΩ at room temperature, it is difficult to detect the disconnection of the thermistor by the voltage division ratio between the reference resistance and the thermistor resistance. In order to detect disconnection of a temperature sensor such as a thermistor, for example, the following Patent Documents 1 and 2 have been proposed.
JP-A-11-281499 JP-A-9-88708

  In the techniques disclosed in Patent Documents 1 and 2, a temperature detection reference resistor and a disconnection detection reference resistor are provided, and means for switching the circuit to either side of these reference resistors must be provided. In other words, the circuit configuration becomes complicated.

  The present invention has been made in view of the above-described circumstances, can maintain temperature detection accuracy and can reliably detect a disconnection of a temperature sensor, and can simply eliminate the need for a reference resistor for disconnection detection. An object is to provide a temperature detection / disconnection detection circuit, a temperature detection / disconnection detection method, and an internal combustion engine control device.

  The temperature detection / disconnection detection circuit according to the first aspect of the present invention, which has been made to solve the above-mentioned problems, is connected in series with a temperature sensor whose resistance value changes in accordance with a change in the detected temperature, and the temperature sensor. Voltage dividing means, a power supply that applies a predetermined voltage to the temperature sensor and the voltage dividing means, a switching means that is connected to the power supply and switches whether to apply the predetermined voltage, the temperature sensor, and the voltage dividing A resistance element having one end connected to a common connection point of the means, a capacitor connected to the other end of the resistance element, and detecting the temperature based on the voltage at the common connection point when the predetermined voltage is applied, and the predetermined And detecting means for detecting disconnection of the temperature sensor based on the voltage of the capacitor when the voltage application is cut off.

  According to the present invention having such characteristics, the following effects are obtained when temperature is detected and when disconnection is detected. First, at the time of temperature detection, a predetermined voltage is applied to the temperature sensor and the voltage dividing means by the switching means. When a predetermined voltage is applied, the temperature sensor has a resistance value corresponding to the measurement target. Further, electric charges are accumulated in the capacitor, and the capacitor rises to a voltage determined by the voltage dividing means and the temperature sensor. The resistance element and the capacitor constitute a low-pass filter, and the voltage at the common connection point is read through the low-pass filter. As a result, the temperature is detected by the detecting means. Next, when disconnection is detected, application of the predetermined voltage applied to the temperature sensor and the voltage dividing means is blocked by the switching means. When the application of the predetermined voltage is interrupted, power is not supplied to the temperature sensor and the voltage dividing means, so that the electric charge accumulated in the capacitor is discharged through the resistance element and the temperature sensor. That is, when the temperature sensor is not disconnected, the capacitor charge is discharged through the resistance element and the temperature sensor. As a result, the voltage across the capacitor drops. On the other hand, when the application of the predetermined voltage is interrupted and the temperature sensor is disconnected, the charge of the capacitor loses its discharge path. Thereby, the electric charge of the capacitor is retained, and the voltage across the capacitor does not change. Accordingly, by detecting the voltage of the capacitor, the detection means detects the disconnection of the temperature sensor. According to the present invention, it is possible to accurately detect the temperature without newly providing a reference resistor for detecting disconnection. Moreover, it is possible to reliably detect disconnection of the temperature sensor.

  The temperature detection / disconnection detection circuit according to the present invention, which has been made to solve the above problems, is connected in series to a temperature sensor whose resistance value changes in accordance with a change in the detected temperature, and the temperature sensor. Voltage dividing means, a power supply for applying a predetermined voltage to the temperature sensor and the voltage dividing means, a switching means connected to the power supply and for switching presence / absence of application of the predetermined voltage, and in parallel with the temperature sensor And detecting a temperature based on a voltage at a common connection point of the temperature sensor and the voltage dividing means when the predetermined voltage is applied, and based on the voltage of the capacitor when the predetermined voltage is cut off And detecting means for detecting disconnection of the temperature sensor.

  According to the present invention having such characteristics, the circuit is not limited to the formation of the low-pass filter as in the first aspect of the invention. That is, a circuit in which a capacitor is provided in parallel with the temperature sensor may be used. Even in this case, it is not necessary to newly provide a reference resistor for detecting disconnection, and temperature detection can be performed with high accuracy. Moreover, it is possible to reliably detect disconnection of the temperature sensor.

  A temperature detection / disconnection detection circuit according to a third aspect of the present invention is the temperature detection / disconnection detection circuit according to the first or second aspect, wherein the switching means is a semiconductor element such as a transistor or FET, or a relay. It is characterized by being a switching element having a mechanical contact. According to the present invention having such characteristics, the switching means is constituted by the semiconductor element or the switching element. The switching means can be selected according to the usage pattern.

  A temperature detection / disconnection detection circuit according to a fourth aspect of the present invention is the temperature detection / disconnection detection circuit according to the first or second aspect, wherein the temperature sensor detects whether or not the catalyst temperature of the vehicle is abnormal. In addition, the resistance value of the temperature sensor decreases as the catalyst temperature rises. According to the present invention having such a feature, a circuit capable of detecting the presence or absence of an abnormality in the catalyst temperature of the vehicle is provided.

  A temperature detection / disconnection detection circuit according to a fifth aspect of the present invention is the temperature detection / disconnection detection circuit according to the first or second aspect, wherein the temperature sensor detects whether there is an abnormality in the exhaust temperature of the vehicle. And the resistance value of the temperature sensor decreases as the exhaust gas temperature rises. According to the present invention having such a feature, the circuit can detect whether there is an abnormality in the exhaust temperature of the vehicle.

  An internal combustion engine control device according to a sixth aspect of the present invention for solving the above-mentioned problems is a device for controlling an internal combustion engine of a vehicle, and the temperature detection / control device according to any one of the first to fifth aspects. It is characterized by including a disconnection detection circuit. According to the present invention having such a feature, since the circuit is included, an internal combustion engine control device capable of maintaining temperature detection accuracy and reliably detecting disconnection of the temperature sensor is provided.

  The temperature detection / disconnection detection method of the present invention according to claim 7, which has been made to solve the above-described problem, includes a temperature measurement mode in which a temperature is measured using a temperature sensor whose resistance value changes in accordance with a change in the detected temperature, An abnormality diagnosis mode for diagnosing an abnormality of the temperature sensor, and in the temperature measurement mode, (1) a step of applying a predetermined voltage to the temperature sensor and voltage dividing means connected in series to the temperature sensor And (2) detecting a temperature based on a voltage at a common connection point of the temperature sensor and the voltage dividing means in a state where the predetermined voltage is applied, and in the abnormality diagnosis mode, (3 ) A step of cutting off the application of the predetermined voltage; and (4) a charge accumulated in the temperature measurement mode of a capacitor connected in parallel to the temperature sensor is discharged. Whether to detect, and wherein based on said detection that it has to include a step of determining a disconnection whether the temperature sensor.

  According to the present invention having such characteristics, first, in the temperature measurement mode at the time of temperature detection, when a predetermined voltage is applied to the temperature sensor and the voltage dividing means, the temperature sensor has a resistance value corresponding to the measurement object. Become. When the voltage at the common connection point is read, the temperature is detected. Next, in the abnormality diagnosis mode when disconnection is detected, application of a predetermined voltage applied to the temperature sensor and the voltage dividing means is blocked. When the application of the predetermined voltage is interrupted, power is not supplied to the temperature sensor and the voltage dividing means, so that the capacitor charge accumulated in the temperature measurement mode is discharged through the temperature sensor. That is, when the temperature sensor is not disconnected, the capacitor charge is discharged through the temperature sensor. As a result, the voltage across the capacitor drops. On the other hand, when the application of the predetermined voltage is interrupted and the temperature sensor is disconnected, the charge of the capacitor loses its discharge path. Thereby, the electric charge of the capacitor is retained, and the voltage across the capacitor does not change. Therefore, the disconnection of the temperature sensor is detected by determining whether or not the capacitor is discharged. According to the present invention, it is possible to accurately detect the temperature without newly providing a reference resistor for detecting disconnection. Moreover, it is possible to reliably detect disconnection of the temperature sensor.

  The temperature detection / disconnection detection method according to an eighth aspect of the present invention is the temperature detection / disconnection detection method according to the seventh aspect, wherein the discharge of the charge in (4) is performed by the impedance of the temperature sensor. It is characterized by having been made. According to the present invention having such a feature, when the temperature sensor is not disconnected, the capacitor charge is discharged through the temperature sensor.

  The temperature detection / disconnection detection method according to claim 9 of the present invention is the temperature detection / disconnection detection method according to claim 7 or claim 8, wherein after the completion of the step (3), a predetermined time elapses and the (4 ). According to the present invention having such characteristics, a predetermined time determined by the time constants of the resistance element and the capacitor is taken into consideration. Better disconnection detection can be performed.

  A temperature detection / disconnection detection method according to a tenth aspect of the present invention is the temperature detection / disconnection detection method according to any one of the seventh to ninth aspects, wherein the predetermined voltage application in (3) is interrupted. A semiconductor element such as a transistor or FET, or a switching element having a mechanical contact such as a relay is used. According to the present invention having such characteristics, the semiconductor element or the switching element cuts off the predetermined voltage being applied to the temperature sensor and the voltage dividing means. Either a semiconductor element or a switching element is selected according to the usage pattern.

  The temperature detection / disconnection detection method according to claim 11 of the present invention is the temperature detection / disconnection detection method according to any one of claims 7 to 9, wherein the temperature sensor detects whether there is an abnormality in the catalyst temperature of the vehicle. And the resistance value of the temperature sensor decreases as the catalyst temperature rises. According to the present invention having such a feature, it is possible to detect whether there is an abnormality in the catalyst temperature of the vehicle.

  A temperature detection / disconnection detection method according to a twelfth aspect of the present invention is the temperature detection / disconnection detection method according to any one of the seventh to ninth aspects, wherein the temperature sensor detects whether or not an exhaust temperature of the vehicle is abnormal. In addition, the resistance value of the temperature sensor decreases as the exhaust gas temperature rises. According to the present invention having such characteristics, it is possible to detect whether there is an abnormality in the exhaust temperature of the vehicle.

  According to the present invention, there is an effect that a reference resistance for detecting disconnection can be simplified. In addition, the temperature detection accuracy can be maintained and the disconnection of the temperature sensor can be reliably detected.

Hereinafter, description will be given with reference to the drawings.
First, a system configuration of an ignition type internal combustion engine using gasoline as fuel, provided with the internal combustion engine control device of the present invention including the temperature detection / detection circuit of the present invention, will be described with reference to FIG. FIG. 1 shows the configuration of only one cylinder.

  In FIG. 1, an internal combustion engine 11 includes a combustion chamber 12, an ignition coil 13 disposed in the combustion chamber 12, an intake valve 14 that takes in mixed air in which air and fuel are mixed, and an exhaust valve 15 that performs exhaust after combustion. And is configured. Such an internal combustion engine 11 is provided with a water temperature sensor 17 for detecting the temperature of the engine cooling water 16 and a crank angle sensor 18 for detecting the rotational speed of the engine at the side of the combustion chamber 12. The internal combustion engine control device 19 sequentially detects and detects the operating state.

  The intake system that performs intake to the combustion chamber 12 is linked to the intake pipe 20, the airflow sensor 21 that measures the intake air that is sucked through the air cleaner, and the driver's accelerator pedal operation or the operating state of the internal combustion engine 11. The electronic control throttle valve 22 that is attached to the rotating shaft that rotates and opens and closes to electrically control the intake air amount, a throttle positioning sensor, and the like are provided.

  The flow rate of the intake air measured by the air flow sensor 21 and the throttle positioning sensor and the opening information of the valve portion of the electronic control throttle valve 22 are input to the internal combustion engine control device 19. The opening degree information is used for detection of the operating state of the internal combustion engine 11 and various controls. The internal combustion engine control device 19 is supplied with power from the battery 23. Further, a signal from the ignition key SW24 is input to the internal combustion engine control device 19.

  The fuel system in the system is a fuel tank that stores fuel, a fuel pump that pumps fuel from the fuel tank, a fuel filter that removes dust in the pumped fuel, and the pressure of the pumped fuel is adjusted to a predetermined pressure And a pressure regulator, and an injector (fuel injection device) 26 for injecting fuel into the intake port 25. The injector 26 is attached to the intake port 25. The injector 26 is attached so that its tip faces the intake valve 14.

  The exhaust system in the system includes an exhaust manifold having an exhaust valve 15, an oxygen concentration sensor 27 for detecting the oxygen concentration in the exhaust, an exhaust temperature sensor 28 for detecting the exhaust temperature, and a three-way catalytic converter for purifying the exhaust. 29, a catalyst temperature sensor 30 for detecting the catalyst temperature, a muffler muffler, and the like. The three-way catalytic converter 29 is configured to simultaneously purify NOx, CO, and HC exhausted from the internal combustion engine 11 operated near the stoichiometric air-fuel ratio at a high purification rate.

  The oxygen concentration sensor 27, the exhaust temperature sensor 28, and the catalyst temperature sensor 30 are connected to the internal combustion engine control device 19. The internal combustion engine control device 19 includes a known control circuit and a temperature detection / disconnection detection circuit of the present invention.

  Next, the basic configuration and operation of the temperature detection / disconnection detection circuit of the present invention will be described with reference to FIG. 2 (assuming an example).

  In FIG. 2, reference numeral Rth indicates a thermistor (temperature sensor) having a negative temperature coefficient characteristic. The thermistor Rth is connected to a DC power supply Vcc. A reference resistor R1 and a switch S1 are connected in series between the thermistor Rth and the DC power supply Vcc. The switch S1 is connected to the DC power supply Vcc, and has a function of applying or blocking the voltage of the DC power supply Vcc. The reference resistor R1 is connected between the switch S1 and the thermistor Rth. The reference resistor R1 corresponds to voltage dividing means in the claims, and the switch S1 corresponds to switching means.

  A resistor Rs is connected to a common connection point between the reference resistor R1 and the thermistor Rth. A capacitor C in parallel with the thermistor Rth is connected to the resistor Rs. The resistor Rs and the capacitor C form a low-pass filter, and a detection means 2 for voltage detection is connected to the low-pass filter.

  In the above configuration, when the temperature is detected, the switch S1 is closed, and a predetermined voltage is applied to the thermistor Rth and the reference resistor R1 by the switch S1. When a predetermined voltage is applied, the thermistor Rth has a resistance value corresponding to the measurement target. Further, when a predetermined voltage is applied, electric charge is accumulated in the capacitor C. The capacitor C rises to a voltage determined by the thermistor Rth and the reference resistor R1. In such a state, when the voltage at the common connection point is read through the low-pass filter, the detection unit 2 detects the temperature.

  When the disconnection is detected, the switch S1 is opened, and the application of the predetermined voltage that has been applied to the thermistor Rth and the reference resistor R1 is blocked by the switch S1. When the application of the predetermined voltage is interrupted, power is not supplied to the thermistor Rth and the reference resistor R1, and therefore the electric charge accumulated in the capacitor C is discharged through the resistor Rs and the thermistor Rth. In such a state, when the voltage of the capacitor C is read, the detection means 2 detects disconnection of the thermistor Rth.

  Regarding the above discharge, when the thermistor Rth is not disconnected, the electric charge of the capacitor C is discharged through the resistor Rs and the thermistor Rth. As a result, the voltage across the capacitor C drops. On the other hand, when the application of the predetermined voltage is interrupted and the thermistor Rth is disconnected (or the lead wire connecting the thermistor Rth is disconnected), the charge of the capacitor C loses its discharge path. Thereby, the electric charge of the capacitor C is held, and the voltage across the capacitor C does not change.

  The temperature detection / disconnection detection circuit according to the present invention is configured to detect disconnection by opening / closing the switch S1 and detecting whether or not the capacitor C is discharged.

  The temperature detection / disconnection detection circuit of the present invention is not limited to forming a low-pass filter by the resistor Rs and the capacitor C. That is, as shown in FIG. 3, the capacitor C may be formed in parallel with the thermistor Rth (the temperature detection / disconnection detection circuit of FIG. It is the same as the configuration except for this, and detailed description is omitted). The temperature detection / disconnection detection circuit of the present invention may be any circuit as long as it detects disconnection using charging / discharging of the capacitor C.

  Next, a control device including the temperature detection / disconnection detection circuit of the present invention will be described with reference to FIG. In the following, the internal combustion engine control device for a vehicle will be described as an example. However, the temperature detection / disconnection detection circuit of the present invention is not limited to this and is used for other mobile control devices, for example, gas and generator control devices. It may be included.

  A vehicle such as an automobile has an exhaust temperature sensor, a catalyst temperature sensor, and the like, and is configured to be able to detect an abnormal increase in exhaust temperature or catalyst temperature. Moreover, it is comprised so that a passenger | crew can be alerted by turning on a warning lamp. In addition, the exhaust temperature and the catalyst temperature are lowered to prevent the occurrence of a vehicle fire or a catalyst erosion.

  In FIG. 4, reference numeral 1 denotes an internal combustion engine control device mounted on a vehicle. The internal combustion engine control device 1 controls an internal combustion engine of a vehicle and is configured to be able to play the above role. The internal combustion engine control device 1 includes a known control circuit (not shown) and a temperature detection / disconnection detection circuit of the present invention described below (corresponding to the internal combustion engine control device 19 described above). It shall be).

  For example, one end of the catalyst temperature sensor (or exhaust temperature sensor) Rth is connected to the collector terminal of the PNP transistor T1 with the reference resistor R1 interposed. The other end of the catalyst temperature sensor Rth is grounded. The emitter terminal of the PNP transistor T1 is connected to the DC power supply Vcc. The base terminal of the PNP transistor T1 is connected to detection means 2 (which is a microcomputer and includes a known CPU, memory, etc.) 2 with a resistor R3 interposed therebetween.

  The detection means (microcomputer) 2 is configured to be able to turn on and off the PNP transistor T1 by switching its port output between HIGH and LOW. A transistor protection diode D1 is connected between the collector terminal and the emitter terminal of the PNP transistor T1. A resistor R2 is connected between the emitter terminal and the base terminal. A low-pass filter including a resistor Rs and a capacitor C is connected to a common connection point between the catalyst temperature sensor Rth and the reference resistor R1. The low-pass filter is connected so as to be input to the A / D converter of the detection means (microcomputer) 2.

  As the catalyst temperature sensor Rth, a sensor having a characteristic as shown in FIG. 5, that is, a sensor whose resistance value decreases as the temperature rises is used. By using such a catalyst temperature sensor Rth, in order to accurately measure the temperature within the measurement target temperature range (for example, 600 ° C. to 1000 ° C.), a reference resistor R 1 having a resistance of 330Ω, for example, is used.

  For example, the DC power source Vcc is 5 V, the resistor R2 is 10 kΩ, the resistor R3 is 1 kΩ, the resistor Rs is 10 kΩ, and the capacitor C is 0.1 μF, for example.

  A thermistor that measures a relatively high temperature (for example, 1000 ° C.) has a high resistance value of several MΩ at room temperature, and it is difficult to distinguish between disconnection and non-disconnection based on the partial pressure ratio between the reference resistance R1 and the catalyst temperature sensor Rth. is there. Moreover, it takes a lot of time and effort to set the temperature of the catalyst to around 600 ° C., for example, in order to inspect whether there is a disconnection. Therefore, the internal combustion engine control device 1 turns on the PNP transistor T1 at the time of temperature detection and turns off the PNP transistor T1 at the time of disconnection diagnosis to determine whether or not the capacitor C is discharged. It comes to detect.

  A little more specific explanation. FIG. 6 shows a sequence diagram according to the present method, and FIG. 7 shows a flowchart according to the present method.

  In FIG. 6, when the state of the temperature sensor (catalyst temperature sensor Rth) is normal, when the PNP transistor T1 is turned on, the voltage of the capacitor C is set to the reference resistance R1 by the charging time constant determined by the time constant of the low-pass filter. To a voltage determined by the catalyst temperature sensor Rth. A predetermined time determined by the time constant of the low-pass filter is measured by a temperature measurement weight counter, and when a predetermined time elapses after the PNP transistor T1 is turned on, A / D conversion is performed. This operation is abbreviated as temperature measurement mode.

  Next, disconnection diagnosis will be described. In FIG. 7, when disconnection diagnosis is started (N in step S1), first, the value A / D converted at the end of the temperature measurement mode is held in the memory of the detection means (microcomputer) 2 (step S2). . The above value is abbreviated as TEMP in FIG. Next, when the temperature sensor abnormality diagnosis mode is entered, the PNP transistor T1 is turned off (step S3). The capacitor C that has held the voltage indicating the TEMP uses the resistor Rs and the catalyst temperature sensor Rth as a path and discharges the charge to the path.

  The voltage across the capacitor C decreases due to the discharge of the charge. Here, a predetermined time determined from the discharge time constant is measured by a temperature measurement weight counter (step S4), and the voltage across the capacitor C is A / D converted a predetermined time after the PNP transistor T1 is turned off. Then, the A / D converted value is held in the memory of the detecting means (microcomputer) 2 (step S5). This value is abbreviated as TEMP2.

  Since the difference between the values of TEMP and TEMP2 has a certain value due to the expected discharge of the capacitor C, if the value is equal to or greater than the threshold value (Y in step S6), the detection means (microcomputer) 2) determines that the temperature sensor is normal (step S7), turns on the PNP transistor T1 (step S8), and shifts to normal control.

  On the contrary, if it is below the threshold value (N in step S6), the detection means (microcomputer) 2 determines that the temperature sensor is disconnected (step S9), shifts to the fail safe mode (step S10), and a warning lamp. Is turned on (step S11).

  As described above, at the time of disconnection of the catalyst temperature sensor Rth, it is possible to prevent a vehicle fire or a catalyst melting loss due to an abnormal temperature rise of the catalyst. Therefore, the safety of the vehicle can be ensured.

  In addition, it goes without saying that the present invention can be variously modified without departing from the spirit of the present invention.

  In the above description, the PNP transistor T1 is used. However, instead of this, a semiconductor element such as a switch or FET, or a switching element having a mechanical contact such as a relay may be used. As long as it is possible to switch the presence / absence of a power source applied to the reference resistor R1 and the temperature sensor (catalyst temperature sensor Rth, etc.), any of them may be used.

1 is a system configuration diagram showing an embodiment of an ignition type internal combustion engine provided with an internal combustion engine control device of the present invention including a temperature detection / detection circuit according to the present invention. 1 is a basic configuration diagram of a temperature detection / detection circuit according to the present invention. FIG. FIG. 3 is a basic configuration diagram different from FIG. 2. It is a block diagram which shows one Embodiment of the temperature detection and detection circuit by this invention. It is a figure which shows the characteristic of a temperature sensor. It is a sequence diagram for demonstrating operation | movement of this invention. It is a flowchart for demonstrating operation | movement of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine control apparatus 2 Detection means (microcomputer)
C Capacitor R1 Reference resistance Rth Temperature sensor (catalyst temperature sensor, exhaust temperature sensor)
Rs resistance (resistance element)
S1 switch (switching means)
T1 PNP transistor (switching means)
Vcc DC power supply (power supply)

Claims (12)

A temperature sensor whose resistance value changes in accordance with a change in the detected temperature, a voltage dividing means connected in series to the temperature sensor, a power supply for applying a predetermined voltage to the temperature sensor and the voltage dividing means, A switching unit that is connected to a power source and switches the presence / absence of application of the predetermined voltage, a resistance element having one end connected to a common connection point of the temperature sensor and the voltage dividing unit, and connected to the other end of the resistance element And detecting means for detecting temperature based on the voltage at the common connection point when applying the predetermined voltage and detecting disconnection of the temperature sensor based on the voltage of the capacitor when applying the predetermined voltage is interrupted, A temperature detection / disconnection detection circuit characterized by comprising: A temperature sensor whose resistance value changes in accordance with a change in the detected temperature, a voltage dividing means connected in series to the temperature sensor, a power supply for applying a predetermined voltage to the temperature sensor and the voltage dividing means, A switching unit that is connected to a power source and switches whether or not the predetermined voltage is applied, a capacitor that is connected in parallel to the temperature sensor, and a common connection of the temperature sensor and the voltage dividing unit when the predetermined voltage is applied Temperature detection based on the voltage at the point, and detecting means for detecting disconnection of the temperature sensor based on the voltage of the capacitor when the application of the predetermined voltage is cut off. circuit. In the temperature detection / disconnection detection circuit according to claim 1 or 2,
A temperature detection / disconnection detection circuit, wherein the switching means is a semiconductor element such as a transistor or FET, or a switching element having a mechanical contact such as a relay. In the temperature detection / disconnection detection circuit according to claim 1 or 2,
The temperature sensor is used for detecting whether or not the catalyst temperature of the vehicle is abnormal, and the resistance value of the temperature sensor decreases as the catalyst temperature rises. Detection circuit. In the temperature detection / disconnection detection circuit according to claim 1 or 2,
The temperature sensor is for detecting whether or not the exhaust temperature of the vehicle is abnormal, and the resistance value of the temperature sensor decreases as the exhaust temperature rises. Detection circuit. An apparatus for controlling an internal combustion engine of a vehicle, comprising the temperature detection / disconnection detection circuit according to any one of claims 1 to 5. A temperature measurement mode for measuring the temperature using a temperature sensor whose resistance value changes according to a change in the detected temperature, and an abnormality diagnosis mode for diagnosing an abnormality of the temperature sensor,
In the temperature measurement mode, (1) a step of applying a predetermined voltage to the temperature sensor and a voltage dividing means connected in series to the temperature sensor; and (2) the temperature sensor in a state where the predetermined voltage is applied. And detecting a temperature based on a voltage at a common connection point of the voltage dividing means,
In the abnormality diagnosis mode, (3) the step of cutting off the application of the predetermined voltage, and (4) the charge accumulated in the temperature measurement mode of the capacitor connected in parallel to the temperature sensor is discharged. And detecting whether or not the temperature sensor is disconnected based on the detection. A temperature detection / disconnection detection method characterized by comprising: In the temperature detection / disconnection detection method according to claim 7,
The temperature detection / disconnection detection method according to (4), wherein the electric charge is discharged by an impedance of the temperature sensor. In the temperature detection / disconnection detection method according to claim 7 or claim 8,
A temperature detection / disconnection detection method characterized in that the step (4) is performed after a predetermined time has elapsed after the completion of the step (3). In the temperature detection / disconnection detection method according to any one of claims 7 to 9,
The temperature detection / disconnection detection method according to (3), wherein a semiconductor element such as a transistor or FET, or a switching element having a mechanical contact such as a relay is used to cut off the application of the predetermined voltage. In the temperature detection / disconnection detection method according to any one of claims 7 to 9,
The temperature sensor is used for detecting whether or not the catalyst temperature of the vehicle is abnormal, and the resistance value of the temperature sensor decreases as the catalyst temperature rises. Detection method. In the temperature detection / disconnection detection method according to any one of claims 7 to 9,
The temperature sensor is for detecting whether or not the exhaust temperature of the vehicle is abnormal, and the resistance value of the temperature sensor decreases as the exhaust temperature rises. Detection method.

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