JPS5862342A - Method to estimate temperature of cooling water in engine - Google Patents

Abstract

PURPOSE:To obtain proper controls in engine when the temperature of water cannot be detected by some abnormality by gradually increasing the supply of fuel and estimating the temperature of water at the time of perfect ignition according to a characteristic curve between the supply amount of fuel and the temperature of water on the basis of the supply amount at the time of perfect ignition. CONSTITUTION:When 0.5> A-point voltage V> 4.5, a water-temperature detecting circuit 1 is considered to be abnormal, and an injection pulse width Ti is gradually increased as time elapses by a computing circuit 16 until a perfect ignition is detected by a perfect ignition detector 14 on the basis of a signal from a revolution detecting unit 5. When the perfect ignition detector 14 is on, the pulse width Ti is fixed and inputted into a water-temperature estimator 17, and the temperature of water is estimated according to a characteristic curve and memorized in a memory 4. For this estimation, since the generated amount of heat is proportional to an integrated number of revolutions before cooling water is circulated to a radiator, the integrated number of revolutions is obtained by the water-temperature detector 17 for estimating the increased value of the water temperature, and this result is added to the water temperature at the time of perfect ignition for estimating the water temperature during driving. On the basis of this estimated value, the pulse width Ti is computed by the computing circuit 16.

Description

[Detailed Description of the Invention] This invention provides a method for detecting engine cooling water temperature when an abnormality occurs in the normal cooling water temperature detection circuit etc. that detects the engine cooling water temperature and the actual cooling water temperature cannot be detected. This article relates to a method for estimating cooling water temperature from a system.

Conventional engine cooling water detection device (for example, there is a line as shown in Figure 1. In the figure) is a thermistor-type engine cooling water temperature sensor, which detects the ambient temperature (i.e., cooling water temperature). When the voltage changes, the resistance value changes.The voltage dividing resistor It of the power supply voltage Vcc.

The voltage at the connection point A between
■, When the temperature is 120℃, 】■ is shown respectively.

This voltage is applied to A/D (Analog-Digital) converter 2
A/I) is converted and the digital value is sent to CPU3.
The control program reads the control program and calculates and outputs various engine control parameters (for example, fuel supply amount, ignition timing, etc.) based on the control program and constants stored in the memory 4.

In this conventional cooling water temperature detection device, if an abnormality such as a short or disconnection occurs in the cooling water temperature sensor 1 or its wiring harness or other cooling water detection circuit, the voltage at point A will be 0 in the case of a short, In case of disconnection, resistor R1
and the maximum divided voltage Vmax determined by R2,
The actual cooling water temperature cannot be detected and shows extremely high or low values. Therefore, if an abnormality occurs in the cooling water temperature detection circuit, that is, if the voltage at point A shows 0.5 V or less or 4.5 V or more, the actual cooling water temperature will be No matter how much it is, CP (
, J3 assumes that the cooling water temperature is 80°C) and performs the necessary processing.

For this reason, with conventional cooling water temperature detection devices, if an abnormality occurs in the cooling water temperature detection circuit, various controls of the engine are performed based on values that are different from the actual cooling water temperature. It is inappropriate and inaccurate, and has problems such as inability to start in cold weather and poor drivability during warm-up.

This invention was made by focusing on the conventional problems, and is designed to estimate the cooling water temperature from another system when the cooling water temperature detection circuit fails. When starting the engine, the amount of fuel supplied is gradually increased from the minimum value, and the cooling water temperature at the time of complete explosion is estimated from the fuel supply amount, and the temperature during engine operation after complete explosion is estimated. The purpose of the present invention is to solve the above problem by estimating the cooling water temperature from the cumulative fuel supply door or the cumulative rotational speed of the engine after complete explosion, and finding a value close to the actual cooling water temperature.

Below 1. This invention will be explained based on the drawings.

FIG. 2 is a block diagram showing an embodiment of a device for realizing the engine cooling water temperature estimation method of the present invention.

In the figure, in addition to the conventional device shown in FIG.
A rotation detection device 5 that emits a signal every revolution of the engine, a starter motor switch 6 that turns the starter motor on and off, a fuel injection valve 7 that injects fuel into each cylinder, a rotation detection device 5 and a starter motor switch 6. an input/output control circuit 8 that inputs signals etc. and outputs drive signals etc. for the fuel injection valve 7;
The temperature sensor determining circuit 9 determines whether the output value of the cooling water temperature sensor 1 is normal or not, and operates the input/output control circuit 8.

FIG. 3 shows a block diagram of the temperature sensor discrimination circuit 9 of FIG. 2. In the figure, the voltage at point A is
with reference voltages of 0.5 V and 4.5 V, respectively.
The output of one comparator 10 is compared with the NOT circuit 1.
2, the NOT circuit 12 and the other comparator 11
The output of is input to the OR circuit 13. Therefore, 01(1
Output terminal I3 of circuit 13, that is, temperature discrimination circuit 9
From this, when the A point voltage is within 0.5 V to 4.5 V, a low signal (this indicates that the cooling water temperature detection circuit before A point is normal), but when the A point voltage is 0. If the voltage is below .5V or above 4.5V, a high signal (indicating an abnormality) is output, and it is determined whether the cooling water temperature detection circuit is normal or not.

FIG. 4 shows a detailed block diagram of the main part CQ of FIG. In the figure, reference numeral 14 denotes a complete explosion detector for the engine, which receives a signal from the rotation detection device 5 and detects whether or not the engine has completely exploded at the time of startup. When the engine part completely explodes, the rotation speed suddenly increases, so the increase rate of the rotation speed must be set to a predetermined value (for example, 200 rpm7).
80 msec = 2500 rpm/sec) or more, the complete explosion detector 14 outputs a high signal.

15 is a timer, which is reset (set to 0) when the starter motor and tasinochi are turned on.

When the starter motor switch is on and the output of the complete explosion detector 14 is low (off), the arithmetic circuit 16 sets the fuel injection pulse width T1 (therefore, the fuel supply amount) to the timer 15 according to the characteristics shown in FIG. Depending on the value, gradually increase the amount from the minimum value. Then, when the engine completes explosion and the complete explosion detector 14 outputs a high signal, the fuel injection pulse width is fixed at that time.

As shown in FIG. 6, generally speaking, the engine cooling water temperature Tw and the fuel injection pulse width Ti (i.e. fuel supply amount) required for the fuel to explode and the engine to rotate at that temperature Tw
There is a certain relationship between the upper limit value and the lower limit value E in the figure. That is, the lower Tw is, the larger Ti is, and the Filw
is high (T1 decreases as Tw becomes approximately 6)
Above 0° C., T1 becomes a minimum constant value. Therefore, at the point where the output of the complete explosion detector 14 becomes high, the water temperature estimator 17 calculates the cooling water temperature Tw based on the value of the fixed fuel injection pulse width T1 of the arithmetic circuit 16 based on the characteristics shown in FIG. is estimated and this estimated value is stored in the memory 4.

In addition, the engine cooling water temperature after a complete explosion will be approximately proportional to the amount of heat generated by the engine if the cooling water temperature is low and the thermostand is closed, and therefore the cooling water does not circulate between the engine and the radiator. It continues to rise.

The amount of heat generated is approximately proportional to the cumulative rotational speed of the engine.

For this reason, the water temperature estimator 17 estimates the minus part of the cooling water temperature from the cumulative rotational speed obtained from the rotation signal of the rotation detection device 5, and adds this increase to the estimated cooling water temperature at the time of complete explosion. estimates the cooling water temperature during operation and stores it in memory 4.
We will change the contents of

In FIG. 4, 18 is a register that temporarily stores the output (fuel injection pulse width Ti) of the arithmetic circuit 16, and 19 is a register that inputs a signal from the rotation detection device 5 to activate the fuel injection valve 7 every time the engine rotates once. a reference pulse generator that generates a reference pulse for opening the valve; 20 a clock that generates a clock signal; 2;
1 is a counter that counts the clock signal when the reference pulse generator 19 is reset (set to 0) by the reference pulse, and n is a comparator that compares the fuel injection pulse width Ti of the register 18 with the count of the counter 2. , after the reference pulse is input, the count reaches the fuel injection pulse width 1゛1.
While Ti is smaller, the transistor T is turned off and the fuel injection valve 7 is opened, and from the time when Ti = Ti is reached, the transistor T is turned on and the fuel injection valve 7 is closed. Note that N is an engine speed signal and Q is an intake air amount signal.

Next, the effect will be explained.

In FIG. 2, when the power to each element of the device is turned on, the temperature sensor discrimination circuit 9 first turns on the cooling water temperature sensor 1.
Check the output value, that is, the voltage at point A, and check if it is 0.5~
If the voltage is between 4.5 V and there is no abnormality in the cooling water temperature detection circuit, the voltage value is used to perform various normal engine controls.

However, if the voltage at point A is 0.5 V or less or 4.5 V or more, it is assumed that there is an abnormality (short circuit or disconnection) in the cooling water temperature detection circuit such as the cooling water temperature sensor 1 and its wiring harness. The following control is performed.

When starter motor switch 6 is turned on, timer 15
is reset (to 0) and starts operating. At the same time, the complete explosion detector 14 detects whether or not the engine has completely exploded from the engine rotation signal from the rotation detector 5, and outputs a low signal (off) while the engine is not completely exploded.

While the complete explosion detector 14 is off, the calculation circuit 16 calculates and outputs the fuel injection pulse width Ti (therefore, the fuel supply amount) according to the characteristics shown in FIG. 5 in accordance with the output of the timer 15.

This Ti is temporarily stored in the register 18 (Fig. 7 (1)
)) ). On the other hand, when the reference pulse generator 19 also generates a reference signal for each revolution of the engine (Fig. 7(a)), the counter 21 is reset and the clock signal from the clock input starts to be counted (Fig. 7(a)). At the same time, the transistor T is turned off via the comparator 22, the fuel injection valve 7 is opened, and fuel injection begins.

Rero (Figure 7(d)). The value of counter 21 is register 1
The fuel injection valve 7 continues to open while the value of the counter 21 is smaller than Ti of 8, and when the value of the counter 21 becomes equal to Ti, the comparator ρ turns on the transistor T and the fuel injection valve 7 closes. Therefore, fuel is supplied according to the fuel injection pulse width 1゛i calculated by the calculation circuit 16 according to the characteristics shown in FIG. .

While the engine does not completely explode, the fuel injection pulse width Ti gradually increases with the passage of time, and the amount of fuel supplied is gradually increased.

When the engine completes a complete explosion and the output of the complete explosion detector 14 turns on,
The fuel injection pulse width Ti, which is the output of the arithmetic circuit 16, is fixed and input to the water temperature estimator 17.

The water temperature estimator 17 estimates the cooling water temperature Tw at the time of complete explosion from the Ti, according to the characteristics shown in FIG. 6, and stores this estimated value in the memory 4.

The engine cooling water temperature after a complete explosion is estimated as follows. In general, the cooling water temperature of an engine that continues to operate after a complete explosion is low and the thermostat is closed, so while the cooling water is not circulating between the engine and the radiator, the engine's heat generation It increases almost in proportion to the amount. The amount of heat generated is proportional to the cumulative rotational speed of the engine. Therefore, after a complete explosion, the water temperature estimator 17 calculates the cumulative rotational speed from the rotation signal from the rotation detection device 5, and from this the increase in the cooling water temperature after the complete explosion can be estimated. By adding this increase to the above-mentioned cooling water temperature at the time of complete explosion, the cooling water temperature during operation can be estimated. This estimated value is stored in the memory 4 instead of the previous estimated value, and based on this new estimated value, the calculation circuit 16 calculates and outputs the fuel injection pulse width Ti, and uses this Ti to fuel the fuel in the same manner as described above. supply.

During operation after a complete explosion, as the amount of heat generated increases, the cumulative rotational speed increases, and therefore the cooling water temperature rises, the fuel injection pulse width increases as shown in Figure 6. 1 is gradually reduced. Then, when the estimated cooling water temperature reaches 80°C (this 80°C is the thermostat ON/OFF setting temperature), the estimated temperature is fixed at 80°C. From J1 onwards, arithmetic circuit 1
6 inputs N (engine speed), Q (intake air amount) and the values in the memory 4, calculates a fuel injection pulse width that matches the operating conditions, and controls the fuel injection area.

The determination may be made from the integrated value of the fuel injection pulse width, that is, the integrated value of the fuel supply amount. Or, less accurately,
It is also possible to estimate the amount of heat generation from the elapsed time after the complete explosion and determine the amount of increase in the cooling water temperature.

As explained above, according to the present invention, when an abnormality in the cooling water temperature detection circuit is detected, the engine starting operation is started from the minimum fuel supply amount, and the fuel supply amount is gradually increased. Then, the engine cooling water temperature at the time of a complete explosion is estimated from the fuel supply amount at the time of a complete explosion, and the increase in the cooling water temperature after a complete explosion is calculated as the cumulative fuel supply amount at the time of a complete explosion. Or, since it is estimated from the cumulative rotation speed, even when an abnormality occurs in the cooling water temperature detection circuit, various controls of the engine can be appropriately and accurately performed based on the estimated temperature that is close to the actual cooling water temperature. The effect is that starting performance in cold weather is improved and drivability is maintained during warm-up.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional engine cooling water temperature detection device, FIG. 2 is a block diagram of a device for realizing the engine cooling water temperature estimation method of the present invention, and FIG. 3 is a block diagram of a conventional engine cooling water temperature detection device. A block diagram of the sensor discrimination circuit, Figure 4 is the main part C of Figure 2.
Figure 5 is a characteristic diagram of timer value and fuel injection pulse width, Figure 6 is a characteristic diagram of cooling water temperature and fuel injection pulse required for engine rotation [IJ characteristic diagram, Figure 7 is a diagram of characteristics of fuel injection pulse width] It is a time chart for explaining fuel injection valve control. ]...Cooling water temperature sensor, 3...CI) U, 4.
・・Memory, 5・Rotation detection device, 6・
...Starter motor switch, 7...Fuel injection valve, 9
... Temperature sensor discrimination circuit, ]4 ... Complete explosion detector, 1
5...Timer, 16...Arithmetic circuit, 1
7...Water temperature estimator, 18...Register, 19
゛...Reference pulse generator, 21...Counter, 22
...Comparator. Patent amount/Applicant Nissan Motor Co., Ltd. Patent application agent Megumi Yamamoto - 2 figures, 3 figures, 6 figures

Claims (1)

[Claims] (1) When an abnormality occurs in the cooling water temperature detection circuit, etc. and the actual cooling water temperature cannot be detected, start the engine by setting the amount of fuel supplied to the engine to the minimum value, and then Gradually increase the supply amount, and from the fuel supply amount at the time of complete engine explosion, estimate the cooling water temperature at the time of complete explosion according to the characteristic curve between fuel supply amount and cooling''/:Q temperature. A method for estimating engine cooling water temperature, characterized by: '(2) Estimating the increase in engine cooling water temperature after complete explosion from the cumulative amount of fuel supplied to the engine or the cumulative engine rotational speed after complete explosion. A method according to claim 1, characterized in that: