JP4065869B2 - Cooling system control device for internal combustion engine - Google Patents

Description

  The present invention relates to an improvement of a cooling system control device for controlling the cooling water temperature of a water-cooled engine mounted on a vehicle.

Needless to say, improvement of fuel consumption and reduction of exhaust gas are important issues for vehicles equipped with an internal combustion engine (hereinafter referred to as an engine). There are various methods for improving the fuel consumption of the engine / reducing the gas. Among the techniques that have been studied in the past, there are those that control the cooling water temperature of the engine. The purpose of this control is to maintain the cooling water temperature within an appropriate range. Generally, increasing the cooling water temperature raises the engine oil temperature and lowers the engine friction, thereby reducing the engine load. This reduces fuel consumption and reduces fuel consumption and exhaust gas.
Regarding the relationship between engine temperature (cooling water temperature) and fuel consumption, various papers have been published in the past, so a detailed explanation here will be omitted, but the average water temperature of the engine cooling water during driving will increase. Along with this, it is known that the average oil temperature also increases, and as a result, the mode fuel efficiency improves. Changes in engine oil friction are the main factors that improve fuel efficiency. The higher the oil temperature, the lower the engine oil friction. Therefore, controlling the water temperature at as high a temperature as possible is effective in improving fuel efficiency. However, if the water temperature is too high, there will be unfavorable aspects such as the life of the oil and the accelerated wear of the various parts of the engine, so there is a need for more precise control so that the proper temperature is not exceeded. Yes.

  As is well known, until several years ago, the engine water temperature was generally controlled by the flow rate of cooling water passing through the engine by a valve (so-called thermo valve) that was opened and closed mechanically by a thermostat installed at the cooling water outlet. It was controlled by adjusting. However, it is difficult to say that the target temperature needs to be changed depending on the engine status, control accuracy, response delay, reliability, etc. You need something that you can control with. For such a purpose, Patent Document 1 discloses an engine cooling system water temperature control device in which a thermo valve is electrically operated, and the rotational speed of the electric water pump and the electric thermo valve are set according to the deviation between the target water temperature and the actual water temperature. What controls the water temperature by adjusting the opening is disclosed.

Recently, as an inexpensive and reliable method for detecting engine water temperature, a water temperature sensor using a thermistor has been used in combination with a digital control device such as a microcomputer. The resistance value of the thermistor varies with changes in water temperature, but its characteristics are not linear with respect to temperature. Although the characteristics of the thermistor will be described in detail in the description of the first embodiment, the resistance value decreases as the measurement temperature increases, and the change in resistance value (Δr / Δt) with respect to the unit temperature change is the environmental temperature of the vehicle, for example In the range of about −30 ° C. to 120 ° C., the lower the temperature, the larger the temperature, and the smaller the temperature, and the difference reaches several times. For this reason, as the water temperature increases, the voltage change with respect to the temperature change decreases. From the viewpoint of accurately controlling the engine temperature particularly at a high temperature, there is a problem that the sensitivity to the temperature decreases at an essential high temperature.
Furthermore, as another problem, there is a demand for using a digital control device mounted on a vehicle with as few bits as possible from the viewpoint of economy. Since the output voltage of the sensor corresponding to 1 bit is constant, when it is configured to obtain a practically suitable detection resolution of 0 ° C. or less and 0.1 ° C. or less, about 90 ° C. (about 5 minutes at 90 ° C.) 1) At 120 ° C., there arises a problem that only a detection resolution of about 1 ° C. (about 1/10) can be obtained.

  In order to help understanding of the harmful effects caused by the reduction in detection resolution, FIG. 11 shows a time chart of control value change when water temperature feedback control is performed on the target water temperature using the water temperature sensor having the above characteristics. . FIG. 11A shows a case where the target water temperature is 90 ° C., and FIG. 11B shows a case where the target water temperature is 100 ° C. In each figure, the horizontal axis represents time, and the vertical axis represents water temperature. For the water temperature line 20 detected by the water temperature sensor (thermistor) used for control, the actual water temperature line 21 detected by a temperature sensor (not used for water temperature feedback control) with sufficiently fine water temperature detection accuracy prepared separately for observation is used. Show. In the feedback control at 90 ° C, the water temperature is controlled with an accuracy of ± 0.5 ° C at the actual water temperature relative to the target water temperature, but at 100 ° C, the water temperature is controlled with an accuracy of ± 1 ° C with respect to the target water temperature. Is called. Thus, the followability to the target water temperature cannot be made smaller than the control resolution (hereinafter also simply referred to as resolution) combining the sensor and the digital control device, and a steady deviation exceeding the resolution always occurs. .

In addition, there are the following problems at the time of transition where the engine load changes suddenly. Since the change in the water temperature can be detected only within the range of resolution, there is a problem that when an early change in the water temperature occurs, a control response delay with respect to the target water temperature occurs, and the deviation between the target water temperature and the actual water temperature becomes even larger. In steady operation where the engine heat generation and radiator heat dissipation are stable, the actual water temperature tends to be stable with respect to the target water temperature, but in transient conditions the engine heat generation and radiator heat dissipation change, so the actual water temperature is the target water temperature. It is difficult to stabilize. At higher temperatures, the combined resolution of the water temperature sensor and digital controller becomes coarser. Therefore, even in such a transient state, the higher the temperature, the longer the time until the control water temperature follows the target water temperature, and the controllability of the water temperature. There was a problem that would get worse.
JP 2001-32714 A

Since the conventional control device for the cooling system of the internal combustion engine is configured as described above, it has the following problems.
Thermistors used as water temperature sensors are difficult to replace with other ones because of their reliability, but their characteristics are non-linear and the lower the water temperature, the larger the change in resistance value (change in output voltage) with temperature change. Change in value (change in output voltage) is reduced. Also, since the digital control device used for vehicle control can cope with the entire temperature range of the environment, the voltage value corresponding to 1 bit cannot be made very small, and a predetermined resolution can be obtained near 0 ° C. With such a configuration, there was a problem that only a detection resolution of about 1/5 was obtained at 90 ° C. and about 1/10 of a detection resolution at 120 ° C.
As a result, a large steady-state deviation always occurs at the target high temperature. For safety reasons, the target water temperature is set lower with a margin for the engine limit water temperature, but the controllability of the water temperature is poor. In such a case, a large margin must be taken, and the degree of improvement in fuel consumption is reduced against the request to increase the control water temperature as much as possible in order to further increase the degree of improvement in fuel consumption. In addition, if the margin is too small to meet the water temperature control accuracy, there is a problem that the engine may reach the limit water temperature and destroy the engine.

  The present invention eliminates the above-mentioned problems and provides a cooling system control device for an internal combustion engine that can control the temperature with high accuracy even when the temperature of the cooling water is high, while using a thermistor temperature sensor and a digital control device with a small number of bits. The purpose is to obtain.

A control device for a cooling system of an internal combustion engine of the present invention includes an electric adjustment valve that controls a cooling water flow rate of a water-cooled internal combustion engine,
A temperature sensor using a thermistor that detects the coolant temperature and outputs a voltage signal;
Water temperature determining means for determining whether or not the water temperature is equal to or higher than a predetermined temperature and outputting a result;
A first calculating means for calculating the water temperature with a first resolution by referring to a first table stored in advance from the output voltage of the temperature sensor when the output of the water temperature determining means is not equal to or higher than the predetermined temperature;
A first calculating means for calculating the water temperature with a first resolution by referring to a first table stored in advance from the output voltage of the temperature sensor when the output of the water temperature determining means is not equal to or higher than the predetermined temperature;
A plurality of attenuating means having a known attenuation rate for generating a plurality of different attenuating voltage signals from the output voltage of the temperature sensor when the output of the water temperature determining means is equal to or higher than the predetermined temperature ;
A plurality of A / D terminals having the same number of bits, taking different ones of the plurality of attenuated voltage signals from the respective A / D terminals, and calculating a sum of the plurality of attenuated voltage signals; Is divided by the sum of the attenuation rates of the plurality of attenuation means to obtain an original output voltage, and the cooling water temperature is determined with a second resolution by referring to a first table stored in advance from the obtained output voltage. Second computing means including a digital control device for obtaining
An electronic control device is provided for controlling the water flow rate by controlling the electric adjustment valve based on a deviation between the calculated water temperature and a separately provided target temperature, thereby controlling the water temperature.

  The control system for the cooling system of the internal combustion engine according to the present invention uses a thermistor that does not provide sufficient linearity as a temperature sensor, and uses a digital control device with a small number of bits. The effect that the control can be performed with the same resolution as the low temperature range is obtained.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described. FIG. 1 shows the configuration of a control system for a cooling system of an internal combustion engine according to the present invention. A water pump 202 for circulating the cooling water to an engine (internal combustion engine) 201 and heat radiation of the cooling water are performed. The radiator 203 and a heater core 204 that exchanges heat for taking heat for heating the vehicle interior from the cooling water are connected to each other by a pipe 13 (not shown). In the middle of the pipe 13, an adjustment valve 205 (which is an electric adjustment valve according to the present invention) for adjusting the amount of water circulating from the engine 201 to the radiator 203, the cooling water discharged from the engine 201 and the radiator 203 radiates heat. There is a bypass passage 206 in which the cooling water whose temperature has been lowered is mixed and recirculated to the water pump 202. The radiator 203 is provided with a radiator fan 208 for blowing air, and the radiator fan 208 is provided with a radiator fan controller 209 for driving a motor of the radiator fan. A coolant temperature sensor 103 for detecting the coolant temperature of the engine coolant is attached to a coolant circulation path (not shown) near the coolant outlet of the engine 201.
Signals from the above-described sensors attached to the engine 201 and other various sensors (not shown) are used to detect engine input information, perform control calculations, and control an actuator (not shown) related to driving of the vehicle (also referred to as an ECU). Has been entered. An electronic control unit (ECU) 101 controls the internal combustion engine such as ignition control and fuel injection control of the engine 201 and also controls the cooling water temperature of the present invention.
Note that the connection order of the water pump 202, the regulating valve 205, and other parts to the engine 201 may vary depending on the automobile manufacturer. Here, for convenience of explanation of the present invention, one type is shown as an example. Yes, it is not limited to the format of FIG.

FIG. 2 shows a water temperature sensor and a temperature detection part, among various control systems provided in the ECU 101. A microcomputer 102 is mounted in the ECU 101. A signal from the water temperature sensor 103 is input to the first A / D terminal 105 of the microcomputer 102 via the input circuit 104. A thermistor type water temperature sensor 103 is used, and a voltage is applied from a power source 10 through a sufficiently large resistor 11. Alternatively, a constant current may be supplied from a constant current circuit (not shown). The resistance value of the water temperature sensor changes according to the change of the cooling water temperature.
FIG. 3 is a graph 13 showing resistance value change characteristics of the thermistor type water temperature sensor 103, where the horizontal axis indicates the water temperature and the vertical axis indicates the resistance value of the water temperature sensor 103. The water temperature detection range of the water temperature sensor 103 is a range where the cooling water temperature is about −30 ° C. to 120 ° C., and the resistance value decreases as the water temperature increases. The amount of change in the resistance value with respect to the unit temperature change is larger as the water temperature is lower, and the change in the resistance value with respect to the unit temperature change is less at high temperatures.

FIG. 4 shows the temperature detection resolution 14 of the sensor relative to the water temperature from the characteristic 13 of FIG. In the figure, the horizontal axis represents the water temperature, and the vertical axis represents the temperature detection resolution. The detection resolution of the first A / D terminal 105 of the microcomputer 102 used in the ECU 101 is about 10 bits. For this reason, the water temperature sensor 103 has a detection resolution of 0.1 ° C. or less at around −30 ° C. to 0 ° C., but a detection resolution of about 0.5 ° C. at 90 ° C. and about 1 ° C. at 120 ° C. .
When a predetermined current is passed from the power source 10 to the water temperature sensor 103 through a sufficiently large resistor 11, the voltage of the first A / D terminal 105 is detected and compared with a table (not shown) stored in advance or predetermined. The water temperature can be obtained by performing the calculation. An amplifier circuit 106 is connected to the input circuit 104. The amplifying circuit 106 (analog amplifying means according to the present invention) has an analog amplifier that amplifies the output voltage of the water temperature sensor 103 by, for example, four times (a digital signal that has sufficiently high bit resolution is necessary for digital). The output of the amplifier circuit 106 is input to the second A / D terminal 107. The quadruple signal 13B is indicated by a dotted line in FIG. 3 for comparison. However, the characteristic 13 in FIG. 3 is a characteristic of the resistance value, and strictly speaking, is different from the voltage. However, if the resistance value of the resistor 11 is sufficiently larger than the resistance value of the thermistor, the resistance characteristic can be regarded as the same as the voltage characteristic. Here, the amplification factor of the amplifier is not limited to 4 times, but is preferably about 3 to 6 times.
As a result, the signal from the first A / D terminal 105 is one time that of the water temperature sensor 103 (hereinafter referred to as signal A for convenience of explanation), and the signal from the second A / D terminal 107 is four times that from the water temperature sensor 103 (hereinafter referred to as signal A). For convenience of explanation, the signal B) is input to the microcomputer 102.

Next, the operation of water temperature control using the water temperature sensor detection circuit of FIG. 2 will be described with reference to the flowchart of FIG.
ECU 101 detects the operating state of engine 201 in step S301. That is, the engine speed (referred to as NE) is calculated from a crank signal sensor (not shown) and the like, and the charging efficiency is calculated from the signal of an intake air sensor (not shown) and the NE.
In step S302, the signal A of the water temperature sensor 103 input to the first A / D terminal 105 is detected. In step S303, the characteristic line shown in 13 of FIG. The water temperature A is calculated with reference to the table (stored in advance). Step S302 is the first calculation means according to the present invention.
In step S304, a target water temperature (referred to as WT) is calculated from the operating state (including at least charging efficiency) of the engine 201 calculated in step S301.
In step S305, it is determined whether the current water temperature A calculated in step S303 is set in advance or is equal to or higher than a predetermined water temperature WT1 set as described later from the target temperature WT obtained in step S304. The water temperature WT1 is preferably set to a temperature that is about 10 ° C. lower than the target temperature WT, for example. However, since the target temperature varies depending on operating conditions, it is set to a specific water temperature that is, for example, 0 ° C. or more and below the target temperature. May be. The determination in step S305 is performed by the water temperature determination means referred to in the present invention.

If negative (N) in step S305, the process proceeds to step S306. Here, the current water temperature A is lower than the target water temperature WT, and a deviation (ΔWT) from the target water temperature is calculated. Here, the reason why the signal B is not used is that the water temperature detection resolution can be obtained even with the water temperature sensor voltage value A that is not amplified four times because the temperature is low, and the amplified water temperature sensor voltage value B because the water temperature sensor output voltage is high. This is because there is a possibility that the detection voltage range of the second A / D terminal 107 is exceeded.
In step S307, using the deviation ΔWT calculated in step S306, the opening of the adjustment valve 205 is calculated in order to perform water temperature feedback control.
The calculation method of the target opening is shown below.
θ = Kp • ΔWT + Ki • ΣΔWT + Kd • dΔWT + θi (1)
here,
θ: Adjustable valve target opening ΔWT: Water temperature deviation (deviation between target water temperature and current water temperature)
ΣΔWT: Water temperature deviation integral value
dΔWT: Water temperature deviation differential value
Kp: proportional gain
Ki: integral gain
Kd; differential gain θi; initial opening of adjusting valve When the water temperature is equal to or lower than the predetermined water temperature WT1, feedback control of the water temperature is performed using the water temperature sensor output signal A that has not been amplified. The flow in FIG. 5 is repeatedly executed.

If the determination in step S305 is affirmative (Y), the water temperature is high and the detection resolution of the water temperature sensor is insufficient for the water temperature sensor voltage value A. Therefore, the process proceeds to step S308 and water temperature detection processing is performed.
In step S308, the water temperature sensor voltage value B amplified by the amplifier circuit 106 in FIG. 2 is read. In step S309, the characteristic line shown in 13B in FIG. 3 is rewritten and stored in a table in advance by the voltage value B detected in step S308. The water temperature is calculated with reference to the second table. Since the amplification circuit 106 amplifies the voltage value four times, if the resolution of the second A / D terminal 107 of the microcomputer 102 is 10 bits, a detection resolution substantially equivalent to 12 bits can be obtained.
In step S310, a deviation (ΔWT) from the target water temperature WT is calculated based on the water temperature B calculated in step S309. Thereafter, the process proceeds to step S307, and the target opening degree of the adjustment valve 205 is calculated. The way of calculation is as shown in the equation (1).
The temperature calculation in steps S308 to S310 is the second calculation means in the present invention.

  As described above, according to the first embodiment, the water temperature is detected by the amplified voltage obtained by amplifying the output voltage of the water temperature sensor 103 in the water temperature high temperature range where the detection resolution of the water temperature sensor 103 is deteriorated. The detection resolution of the sensor can be maintained well. Therefore, when performing the water temperature control on the target water temperature WT, the deviation between the target water temperature and the current water temperature when the temperature control is in a steady state can be reduced. Moreover, since the water temperature detection resolution is improved, fluctuations in the water temperature can be detected quickly, and the control deviation during the transition with respect to the target water temperature can be reduced. In addition, since the deviation from the target water temperature can be reduced, when setting the engine temperature, the margin with the engine limit water temperature can be set small, and a higher target water temperature can be set. Therefore, fuel consumption characteristics can be further improved.

Embodiment 2. FIG.
In the first embodiment, in order to improve the water temperature detection resolution at high temperature, the water temperature is detected by a signal obtained by amplifying the output voltage of the water temperature sensor 103. Other methods will be described below.
Since the configuration of the engine cooling system of the second embodiment is the same as that of FIG. FIG. 6 shows the configuration of the detection part of the water temperature sensor 103 in the ECU 101. Since the configuration of FIG. 6 is simpler than the configuration of FIG. 2 of the first embodiment (there is no amplifier 106 and second A / D terminal 107), the description thereof is omitted. In this embodiment, only the detection circuit of the normal water temperature sensor 103 is used to improve the water temperature detection resolution. The method will be described with reference to the flowchart of FIG. FIG. 7 is a routine that is periodically executed to calculate the water temperature. For example, processing is performed every 6.25 ms.

In step S401, it is determined whether the detected water temperature is equal to or higher than a predetermined value at the previous water temperature calculation timing. In the case of negative in step S401, the water temperature is low and the water temperature detection resolution can be secured, and the process proceeds to step S410 in order to perform a normal water temperature detection process.
In step S410, the water temperature sensor voltage value Vwt is read.
In step S411, the water temperature is calculated using the water temperature sensor voltage value Vwt detected in step S410.

If affirmative in step S401, the process proceeds to step S402.
In step S402, the counter value is incremented to N + 1 in order to count the number of routine executions.
In step S403, the water temperature sensor voltage value Vwt is read.
In step S404, the water temperature sensor voltage value Vwt read in step S403 is added to the sum ΣVwt of the water temperature sensor voltage values.
In step S405, it is confirmed whether or not the number of routine executions counted in step S402 has become 16. Since this routine performs processing every 6.25 ms, it is 100 ms after 16 routine executions. If affirmative, the process proceeds to step S406.
In step S406, an average value Vwt_ave of the water temperature sensor voltage value Vwt detected 16 times in the past 100 ms is calculated.
In step S407, the water temperature is calculated from the average value Vwt_ave of the water temperature sensor voltage value calculated in step S406 using a voltage / water temperature reading table (second table) stored in advance.
Since the water temperature calculated here is an average value of 16 sensor voltage detections, the water temperature detection resolution is 16 times the resolution of the water temperature obtained by one calculation. Since the resolution of the first A / D terminal 105 is 10 bits, the water temperature can be detected with an apparent resolution of 14 bits.
In step S408, the sum ΣVwt of the water temperature sensor voltage values is cleared.
In step S409, the counter value N is cleared.
In the case of negative in step S405, it is not the timing for calculating the average value, so the processing is ended as it is and the next cycle is started.
The process of repeating steps S401 to S407 is one of the second calculation means in the present invention.

Thus, in this embodiment, the water temperature detection resolution in the ECU 101 is improved by detecting the voltage value of the water temperature sensor 103 a plurality of times and using the average value at a high water temperature when the detection resolution of the water temperature sensor 103 is lowered. Can be made. By improving the detection resolution of the water temperature, an effect can be obtained for improving the fuel consumption as in the first embodiment.
In the first embodiment, the output temperature of the water temperature sensor 103 is amplified to improve the water temperature detection resolution. However, in this method, the water temperature detection range is narrowed. In the second embodiment, the output voltage of the water temperature sensor 103 is measured a plurality of times and the water temperature is detected based on the average value, so that the water temperature detection resolution can be improved over the entire water temperature detection range of the water temperature sensor. Therefore, the water temperature detection resolution can be improved over a wide area.
In the above description, the averaging count is 16, but it goes without saying that it may be changed as appropriate.

Embodiment 3 FIG.
In FIG. 7, the voltage value of the water temperature sensor is averaged, and the water temperature is detected by the voltage value average value. However, the flow shown in FIG. 8 may be adopted.
In FIG. 8, steps S401, 402, 403 and steps S410, 411 are the same as step S with the same reference numerals in the flow of FIG.
In step S504, the water temperature (WT) is obtained by referring to the first table based on the water temperature sensor voltage value Vwt detected in step S503.
In step S505, the water temperature WT calculated in step S504 is added to the sum ΣWT of water temperatures.
In step S506, it is confirmed whether the routine execution count has reached 16. Since this routine performs processing every 6.25 ms, it is 100 ms after 16 routine executions.
If affirmative, the process proceeds to step S507.
In step S507, the average value (WT # ave) of the water temperature (WT) calculated 16 times in 100 ms.
Is calculated.
Since the water temperature calculated here is an average value of 16 times of water temperature calculation, the water temperature detection resolution is 16 times. Since the resolution of the A / D terminal 105 is 10 bits, the water temperature can be detected with an apparent resolution of 14 bits.
In step S508, the sum of water temperatures (ΣWT) is cleared.
In step S509, the counter value is cleared.
The process described above is also one of the second calculation means in the present invention.
If the result in Step S506 is negative, it is not the timing for calculating the water temperature, so the processing is performed as it is.
End the process.

  In the third embodiment, after calculating the water temperature first, the water temperature is averaged to improve the water temperature detection resolution. However, the water temperature sensor output voltage described in the second embodiment is averaged. In the same manner as the method, the fuel efficiency improvement effect can be obtained by improving the water temperature detection resolution.

Embodiment 4 FIG.
Another embodiment for improving the water temperature detection resolution will be described. FIG. 9 is a configuration diagram illustrating a detection portion of the water temperature sensor 103 of the ECU 101 according to the fourth embodiment. Since the same reference numerals as those in FIG. 2 of the first embodiment are the same, detailed description thereof is omitted.
In the figure, the signal voltage of the input circuit 104 is divided by resistors R1, R2, R3, and R4 connected in series. This dividing circuit is a plurality of attenuation means according to the present invention. The divided signal voltages are input to the third A / D terminal 602, the fourth A / D terminal 603, and the fifth A / D terminal 604, respectively, at the points divided by these resistors. Each of these terminals has the same number of bits.
The operation of water temperature detection by the water temperature sensor detection circuit of FIG. 9 will be described using the flowchart of FIG.
Step S401 is the same as step S401 in FIG. 7 of the second embodiment, and thus a description thereof is omitted. However, it is determined whether or not the water temperature is equal to or higher than a predetermined value. If affirmative, the process proceeds to step S702.

In step S702, the water temperature sensor voltage value is read. The detection voltage at the first A / D terminal 105 is Vwt,
K1 = (R2 + R3 + R4) / (R1 + R2 + R3 + R4)
K2 = (R3 + R4) / (R1 + R2 + R3 + R4)
K3 = (R4) / (R1 + R2 + R3 + R4)
The detection voltage at the 3rd A / D terminal 602 is K1 · Vwt.
The detection voltage at the 4th A / D terminal 603 is K2 · Vwt.
The detection voltage at the fifth A / D terminal 604 is K3 · Vwt.
In step S703, the sum of read voltages at the A / D terminal is calculated.
ΣVwt = Vwt + K1, Vwt + K2, Vwt + K3, Vwt
= (1 + K1 + K2 + K3) ・ Vwt
From the above formula, using this method, the output resolution of the water temperature sensor is (1 + K1 + K2 + K3) times.
In step S704, the water temperature is calculated using the sum of the read voltages calculated in step S703.
Of course, Vwt is calculated as Vwt = ΣVwt / (1 + K1 + K2 + K3), and the water temperature is read from a table indicating the relationship between the voltage stored in advance and the water temperature.
Since the output resolution of the water temperature sensor is (1 + K1 + K2 + K3) times, the water temperature detection resolution can also be (1 + K1 + K2 + K3) times, and the water temperature detection resolution at high temperatures can be increased. Can be secured.

In the case of negative in S701, the water temperature is low and the water temperature detection resolution can be secured, and the process proceeds to S705 to perform the normal water temperature detection processing.
In S705, the water temperature sensor voltage value (Vwt) is read.
In S706, the water temperature is calculated using the water temperature sensor voltage value (Vwt) detected in S705.

  As described above, also in the present embodiment, since the water temperature detection resolution at the time of high water temperature can be improved, the effect of improving the fuel consumption can be obtained as in the above-described embodiment.

  The cooling system control device for an internal combustion engine of the present invention has been described as an engine mounted on a vehicle, but is not limited to this, and can be applied to various engines of ships and aircraft.

1 is a system configuration diagram of a cooling system control device for an internal combustion engine according to a first embodiment of the present invention. It is a block diagram of the water temperature detection part of the electronic controller (ECU) of FIG. It is temperature / resistance characteristic explanatory drawing of the water temperature sensor of FIG. It is temperature / detection resolution characteristic explanatory drawing of the water temperature sensor of FIG. It is a flowchart explaining the water temperature detection operation | movement of FIG. It is a block diagram of the water temperature detection part of the electronic controller (ECU) used for the cooling system control apparatus of the internal combustion engine of Embodiment 2 of this invention. It is a flowchart explaining the water temperature detection operation | movement by ECU of FIG. It is a flowchart explaining the water temperature detection operation | movement of the electronic control apparatus by Embodiment 3 of this invention. It is a block diagram of the water temperature detection part of the electronic controller (ECU) used for the cooling system control apparatus of the internal combustion engine by Embodiment 4 of this invention. It is a flowchart explaining the water temperature detection operation | movement by ECU of FIG. It is the chart which showed the behavior at the time of performing water temperature feedback control using the thermistor water temperature sensor.

Explanation of symbols

101 electronic control unit (ECU), 102 microcomputer, 103 water temperature sensor,
104 input circuit, 105 first A / D terminal, 106 amplifier circuit,
107 2nd A / D terminal,
201 engine, 202 water pump, 203 radiator,
204 Regulating valve, 206 Bypass waterway,
602 3rd A / D terminal, 603 4th A / D terminal, 604 5th A / D terminal.

Claims (2)

An electric regulating valve for controlling the cooling water flow rate of the water-cooled internal combustion engine,
A temperature sensor using a thermistor that detects the coolant temperature and outputs a voltage signal;
Water temperature determining means for determining whether or not the water temperature is equal to or higher than a predetermined temperature and outputting a result;
A first calculating means for calculating the water temperature with a first resolution by referring to a first table stored in advance from the output voltage of the temperature sensor when the output of the water temperature determining means is not equal to or higher than the predetermined temperature;
A plurality of attenuating means having a known attenuation rate for generating a plurality of different attenuating voltage signals from the output voltage of the temperature sensor when the output of the water temperature determining means is equal to or higher than the predetermined temperature ;
A plurality of A / D terminals having the same number of bits, taking different ones of the plurality of attenuated voltage signals from the respective A / D terminals, and calculating a sum of the plurality of attenuated voltage signals; Is divided by the sum of the attenuation rates of the plurality of attenuation means to obtain an original output voltage, and the cooling water temperature is determined with a second resolution by referring to a first table stored in advance from the obtained output voltage. Second computing means including a digital control device for obtaining
An electronic control device is provided that controls the electric control valve based on a deviation between the calculated water temperature and a separately provided target temperature to control the cooling water flow rate, thereby controlling the water temperature. A cooling system control device for an internal combustion engine. 2. The cooling system control apparatus for an internal combustion engine according to claim 1, wherein the predetermined temperature determined by the water temperature determination means is not less than 0 ° C. and not more than the target temperature .

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