JPH02305309A - Catalyst temperature alarm for vehicle - Google Patents

Abstract

PURPOSE:To surely detect the disconnection of a signal line or the like connected to a thermistor by generating an alarm through judgement of unsteady state when detected catalyst temperature is lower by not less than a predetermined temperature than estimated catalyst temperature predicted by a temperature estimating means. CONSTITUTION:A temperature detecting signal through a thermistor TH for detecting the temperature of catalyst which is built in an engine exhaust gas part is inputted to an MPU 7 through an A/D converter 3. When the detected temperature of catalyst is not lower than predetermined temperature TS1, a discriminating signal of H level is outputted to turn a transistor TR on and light an alarm lamp LT. The output signal of an engine intake air quantity sensor 5 is inputted to the MPU 7 through the A/D converter 3 and the temperature of catalyst is estimated based on the quantity of intake air. When the discriminated temperature is less than a predetermined valve and the estimated temperature is not lower than a predetermined value, the alarm lamp LT is lighted by judging an unsteady state.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a catalyst temperature warning device for a vehicle that detects and gives an alarm by detecting the temperature of a catalyst for purifying exhaust gas from a vehicle engine. It is something.

(Prior Art) In recent years, various catalysts have been incorporated into engine exhaust sections to purify exhaust gas discharged from vehicle engines.

When a catalyst incorporated in the engine exhaust section rises above a predetermined temperature due to high-temperature exhaust gas, it is necessary to detect this and issue an alarm.

FIG. 3 is a circuit diagram of such a conventional vehicle catalyst temperature warning device.

In FIG. 3, the thermistor TH is installed close to a catalyst incorporated in the engine exhaust section, and its resistance R1 decreases as the temperature of the catalyst increases.

A resistor R2 is connected in parallel with this resistor Rt, and a resistor Rt,
The divided voltage Vt of the combined resistance of R2 and the resistor R is applied to the inverting input of the comparator OPA as a catalyst temperature detection signal.

On the other hand, a predetermined reference voltage Vs is applied to the non-inverting input terminal of the comparator OPA. When the resistance Rte of the thermistor TH decreases due to the temperature rise of the catalyst, and the value of the temperature detection signal Vt falls below the reference voltage Vs, the comparator OPA outputs an H level signal. This turns on the transistor TR, lights up the alarm lamp LT, and warns that the situation is unsteady.

(Problems to be Solved by the Invention) However, in the temperature characteristics of the thermistor TH as a temperature sensor, the resistance R1 exhibits a very large value when the detected temperature is low.

Therefore, if there is a break in the thermistor TH or a break in the signal line connected to the inverting input terminal of the comparator OPA, the human resistance to the inverting input terminal of the comparator OPA becomes infinite, as if the catalyst temperature were low. It is set to the same state as in the previous case. Therefore, under such conditions, abnormalities in the temperature of the catalyst could not be properly detected. Furthermore, it is difficult to distinguish the disconnection of the thermistor TH because the temperature characteristic of the thermistor TH is such that the resistance value becomes extremely large when the detection temperature is low.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a catalyst temperature alarm device for a vehicle that can reliably detect an abnormality when a signal line or the like connected to a thermistor is disconnected.

[Structure of the Invention] (Means for Solving the Problems) To achieve the above object, the present invention provides a catalyst temperature alarm device for a vehicle that detects the temperature of a catalyst related to cleaning exhaust gas from an engine. temperature estimating means for estimating the temperature of the catalyst based on the engine intake air amount;
The apparatus further includes an alarm means for warning that the temperature is unsteady when the temperature detected by the temperature detection means is not high and the temperature estimated by the temperature estimation means is high.

(Function) The present invention has a temperature estimating means for estimating the temperature of the catalyst in addition to a temperature detecting means for detecting the temperature of a catalyst related to cleaning exhaust gas from the engine. The temperature rise of the catalyst is proportional to the average amount of heat generated by the engine, and the average amount of heat generated by the engine is proportional to the average amount of air intake by the engine. Therefore, the average air intake amount of the engine is calculated, and the temperature of the catalyst is estimated based on the calculation result. Furthermore, if the temperature detected by the temperature detection means is not high, but the temperature estimated by the temperature estimation means is high, a warning is issued to the effect that the system is unsteady.

Therefore, if a failure of the temperature detection means or a break in the signal line connected to the temperature detection means occurs, the abnormality can be reliably detected.

(Example) Hereinafter, an example according to the present invention will be described in detail with reference to the drawings.

First, the configuration will be explained with reference to FIG.

The constant voltage power supply 1 is connected to a battery (not shown), receives power from the battery, and outputs a constant voltage Vo. Resistors R1 and R2 are connected in series between this constant voltage power supply 1 and ground. The connection point between the resistors R1 and R2 is connected to the input terminal P1 of the A/D converter 3. Further, a thermistor TH is connected in parallel to the resistor R2. The thermistor TH is installed close to a catalyst incorporated in the engine exhaust section, and its resistance Rt decreases as the temperature of the catalyst increases. Conversely, the resistance R1 of the thermistor TH increases as the temperature of the catalyst decreases. That is, the thermistor TH detects the temperature of the catalyst installed in the engine exhaust section, and changes the resistance Rt according to the detected temperature.

The engine intake air amount sensor (hereinafter abbreviated as sensor) 5 is provided at the air intake port of the engine, and detects the average value of the amount of air taken in by sampling at predetermined time intervals, and generates an intake amount detection signal in the form of an analog amount. Output. Further, the sensor 5 may be configured to output a moving average value of a predetermined number of sampled values as an inhalation amount detection signal.

The A/D converter 3 is connected to the sensor 5 via a terminal P2, and inputs the intake amount detection signal. The A/D converter 3 converts the temperature detection signal input through the terminal P1 and the intake amount detection signal input through the terminal P2 into digital signals, respectively.

The microcomputer (hereinafter abbreviated as MPU) 7 is A/
It is connected to the D conversion path 3 and receives the temperature detection signal and intake amount detection signal from the A/D converter 3. The MPU 7 has a temperature estimation means for estimating the temperature of the catalyst based on the intake amount detection signal.

That is, the average value of the temperature rise of the engine exhaust section in which the catalyst is incorporated is proportional to the average amount of heat generated by the engine, and the average amount of heat generated by the engine is proportional to the average value of the amount of air taken in. Therefore, the temperature TLh of the catalyst can be calculated based on the following (1).

Tth=Kx [average value of intake air amount] (1) where K is a coefficient. If it is determined that the temperature is higher than the predetermined temperature 181, an H level determination signal is output.

Furthermore, if the temperature determined by the temperature determining means is low, for example, below a predetermined temperature Ts2 (Ts2 < Ts+), and the temperature estimated by the temperature estimating means is high, for example, temperature 181 or higher, the MPU 7 becomes unsteady. It has an unsteady determination means for determining that.

When this unsteady state determination means determines that it is unsteady, H
Outputs a level judgment signal.

The A/D converter 3 and the MPU 7 constitute an arithmetic processing section 9.

Output terminal P3 of MPU7 is connected to ground via resistors R7 and R8. Further, the output terminal P3 is connected to the base of the transistor TR via a resistor R7, and the collector of the transistor TR is connected to the alarm lamp LT. Therefore, the transistor TR is turned on based on the H level signal from the temperature determining means or unsteady determining means built in the MPU 7, and the alarm lamp LT is turned on to issue an alarm.

Next, the operation of the embodiment shown in FIG. 1 will be explained.

The signal voltage Vt of the temperature detection signal input to the input terminal P1 of the A/D converter 3 is determined by the thermistor T as shown in equation (2).
It changes depending on the resistance Rt of H.

tXR2 This temperature detection signal of signal voltage Vt is converted into a digital signal by the A/D converter 3 and sent to the MPU 7.

In the MPU 7, the temperature determining means determines the temperature of the catalyst based on the temperature detection signal, and the temperature of the catalyst is determined to be a predetermined temperature 1.
If it is determined that the value is 81 or more, an H level determination signal is output. This turns on the transistor TR and lights up the alarm lamp LT to issue an alarm.

Next, a description will be given of temperature detection of the catalyst in a state where the signal line between the thermistor TH and the A/D converter 3 is disconnected at the location indicated by the X mark in FIG.

As shown in FIG. 2, a divided voltage Vt (1) of resistors R and R2 is input to the input terminal P1.

R1+R2 The temperature corresponding to this divided voltage Vt○ is set to be below a predetermined temperature Ts2, and the temperature determination means of the MPU 7 determines that the temperature based on the divided voltage ■to is low and sets it to L level. Outputs the signal.

On the other hand, the temperature estimating means of the MPU 7 estimates the temperature of the catalyst based on the intake amount detection signal from the sensor 5, and when the average value of the intake air amount is equal to or higher than a predetermined value, the temperature of the catalyst is determined to be a predetermined value. It is estimated that the temperature is equal to or higher than Ts1.

As described above, when the temperature determined by the temperature determining means is low, for example, below the predetermined temperature TS2, and the temperature estimated by the temperature estimating means is high, for example, above the predetermined temperature Ts1, the unsteady determining means determines that the unsteady state is unsteady. It determines that this is the case and outputs an H level determination signal. As a result, the transistor TR turns on and the alarm lamp LT lights up to issue an alarm.

Next, another embodiment of the present invention will be described with reference to FIG.

The embodiment shown in FIG. 2 uses an operational amplifier OP as a temperature estimation means for estimating the catalyst temperature based on the engine intake air amount.
This operational amplifier OPB and a resistor Rt
l, RI2, and capacitor c.

It is characterized by forming an exponential weighting (=I) averaging circuit to estimate the catalyst temperature with high precision.

The temperature detecting means formed by the thermistor TH and the comparator OPA is the same as the example shown in FIG. 3, so the same reference numerals are given and detailed explanation is omitted.

The sensor 5 is connected via a resistor R1+ to the inverting input terminal of an operational amplifier OPB, and the output terminal of the operational amplifier OPB is connected back to the inverting input terminal via a resistor R12.

A capacitor C1 is connected in parallel to this resistor RI2. Further, the output terminal of the operational amplifier OPB is connected to the inverting input terminal of the comparator OPC via a resistor RI4.

A non-inverting input terminal of the comparator OPC is connected to the thermistor TH, and receives a temperature detection signal from the thermistor TH.

In the embodiment configured as above, the temperature estimating means, that is, the operational amplifier OPB, estimates the temperature of the catalyst with high accuracy based on the intake amount detection signal from the sensor 5, and when the estimated temperature rises, the operational amplifier OPB outputs the temperature. signal level decreases. Therefore, the inverting input terminal of the comparator OPC receives the estimated signal vb, which decreases as the estimated temperature of the catalyst increases.
is given.

On the other hand, the temperature detection signal from the thermistor TH is input to the non-inverting input terminal of the comparator OPC, and the thermistor T
When a failure occurs in H, for example, a disconnection occurs at the location marked with X in the figure, the divided voltage vtO of resistors R1 and R2 is input as shown in equation (3).

When the value of the estimated signal vb is lower than the divided voltage Vto, that is, when the estimated temperature of the catalyst is higher than the predetermined temperature, the comparator OPC outputs an H level signal, turns on the transistor TR, and turns on the alarm lamp. Turn on the LT to issue an alarm.

As described above, the embodiment shown in FIG. 2 can reliably issue a warning when a failure occurs in the thermistor TH.

[Effects of the Invention] As explained above, according to the present invention, if the catalyst temperature detected by the temperature detection means is lower than the catalyst temperature estimated by the temperature estimation means by a predetermined temperature amount, an unsteady state is detected. Since the system is designed to issue a warning that this is the case, an unsteady state can be reliably detected even if a signal line or the like connected to the thermistor is disconnected.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, FIG. 2 is a circuit diagram showing another embodiment of the invention, and FIG. 3 is a circuit diagram showing a conventional example. 5... Engine intake air amount sensor 7... Microcomputer TH... Thermistor OPB... Operational amplifier opc... Comparator

Claims (1)

[Scope of Claims] Temperature detection means for detecting the temperature of a catalyst related to purification of exhaust gas from an engine; temperature estimation means for estimating the temperature of the catalyst based on the amount of engine intake air; and by the temperature detection means. 1. A catalyst temperature warning device for a vehicle, comprising warning means for issuing an alarm when the detected temperature is lower than the temperature estimated by the temperature estimation means by a predetermined temperature or more.