JP2001304028A - Cooling device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cooling device for internal combustion engine wherein a water temperature is controlled so as to control knocking for suppressing deterioration of fuel consumption to the maximum extent by considering the deterioration of fuel consumption caused by a phase lag of an ignition timing together with the deterioration of fuel consumption caused by reduction of the water temperature. SOLUTION: This cooling device is provided with means for detecting an operating region of the internal combustion engine, a target water temperature value map wherein a target water temperature value TW of cooling water in the internal combustion engine is set beforehand corresponding to the operating region, means for controlling the temperature of cooling water in the internal combustion engine on the basis of the operating region which is detected and the target water temperature map, means for detecting knocking strength IKN of the internal combustion engine, means for controlling the ignition timing of the internal combustion engine by deciding the phase lag amount of the ignition timing from a basic ignition timing on the basis the knocking strength which is detected, and means for correcting the target water temperature value TW of the present operating region according to the knocking strength IKN which is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling device for an internal combustion engine, and more particularly, to a cooling device that achieves both improvement in fuel efficiency and prevention of knocking.

[0002]

2. Description of the Related Art In a gasoline engine, a gas mixture near a spark plug is ignited by a spark given from the spark plug, and the flame is transmitted to the entire gas mixture to cause gasoline combustion. Knocking is one of the abnormal combustions in that case. Knocking is a phenomenon in which an unburned portion self-ignites without waiting for flame propagation when the pressure becomes abnormally high during the flame propagation. When knocking occurs, the combustion gas oscillates and heat is easily transmitted, and as a result, the engine may be damaged.

[0003] Knocking is closely related to the ignition timing. If the ignition timing is advanced, the maximum combustion pressure increases, and knocking is likely to occur. On the other hand, it is preferable to achieve a high compression ratio in order to increase the thermal efficiency and reduce the fuel consumption rate. Therefore, a control is performed in which a vibration sensor is attached to a cylinder block or the like to advance the ignition timing to near the limit where knocking occurs while detecting occurrence of knocking.

[0004] However, the method of avoiding knocking by retarding the ignition timing causes a decrease in torque, which leads to a deterioration in fuel efficiency. On the other hand, when the temperature of the cooling water of the internal combustion engine is lowered, it is known that knocking is less likely to occur, although the torque is also lowered due to an increase in friction loss and fuel consumption is deteriorated. Therefore, a technique has been proposed for preventing knocking by controlling the water temperature in addition to controlling the ignition timing in an internal combustion engine having a water temperature control mechanism.

For example, Japanese Unexamined Patent Publication No. 10-288138 discloses that, in addition to controlling different cooling water temperatures suitable for respective operating regions of an internal combustion engine and performing ignition timing retard control in accordance with knocking detection, A device that prevents knocking without deteriorating drivability is disclosed.

[0006]

Problems to be Solved by the Invention
According to the device disclosed in Japanese Patent No. 38, not only the ignition timing is retarded, but also the water temperature control according to each operation region is performed, so that the ignition timing retard amount can be suppressed,
Fuel economy does not deteriorate excessively. However, since it only complies with a preset water temperature set value, it is not possible to flexibly respond to an actual operation state, and depending on the operation state, a large ignition timing retard amount is still required, and the fuel consumption deteriorates accordingly. Can not be avoided.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to minimize fuel consumption deterioration in consideration of fuel consumption deterioration due to ignition timing delay and water temperature deterioration. An object of the present invention is to provide a cooling device for an internal combustion engine that realizes water temperature control that enables knocking control.

[0008]

According to a first aspect of the present invention, there is provided an operating region detecting means for detecting an operating region of an internal combustion engine, and an internal combustion engine corresponding to the operating region. A target water temperature map in which a target water temperature value of the cooling water is predetermined, a water temperature control means for controlling the temperature of the cooling water of the internal combustion engine based on the detected operation region and the target water temperature value map, Knocking intensity detecting means for detecting the knocking intensity, ignition timing control means for determining the ignition timing retard amount from the basic ignition timing based on the detected knocking intensity and controlling the ignition timing of the internal combustion engine, A cooling device for an internal combustion engine, comprising: a target water temperature value correction unit configured to correct a target water temperature value in a current operation region according to knocking intensity. In this device, in a situation where the ignition timing retard amount for avoiding knocking becomes large, the knocking can be prevented while suppressing the deterioration of the fuel efficiency by lowering the target water temperature.

Further, according to a second aspect of the present invention, in the cooling device according to the first aspect, the target water temperature value correcting means is configured to output the target water temperature value only when the detected knocking intensity is equal to or higher than a predetermined value. Is corrected. In this device, the target water temperature value is reduced only when the ignition timing retard amount is large, so that excessive water temperature correction is avoided and deterioration of fuel efficiency is prevented.

Further, according to a third aspect of the present invention, in the cooling device according to the first aspect, the target water temperature value correcting means may include a rate of change of a load of the internal combustion engine in addition to the detected knocking intensity. The target water temperature value is corrected according to the above. In this device, when the load change rate is large, the water temperature correction can be suppressed, and excessive water temperature correction for a transient state involving a response delay of the water temperature control is avoided, thereby preventing deterioration of fuel efficiency. .

According to a fourth aspect of the present invention, in the cooling device according to the first aspect, the target water temperature value correction means is provided when the cumulative value of the detected knocking intensity exceeds a predetermined value. To correct the target water temperature value. In this device, the water temperature correction is not performed only by the temporary knocking intensity, and the water temperature correction is performed based on the accumulated value. Therefore, it is possible to perform an appropriate water temperature correction according to the knocking frequency.
Fuel economy is prevented from deteriorating.

According to a fifth aspect of the present invention, in the cooling device according to the first to fourth aspects, the target water temperature value correction means includes a knocking intensity detected by the knocking intensity detection means. Instead, the ignition timing retard amount determined by the ignition timing control means is used as the knocking intensity.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an overall schematic diagram of an electronically controlled internal combustion engine provided with a cooling device according to one embodiment of the present invention. The internal combustion engine 10 includes a cylinder block 12 and a cylinder head 14. A plurality of cylinders 16 extending in the vertical direction are arranged in the cylinder block 12 in parallel in the thickness direction of the drawing, and a piston 18 is housed in each cylinder 16 so as to be able to reciprocate. Between the cylinder block 12 and the cylinder head 14, the upper side of each piston 18 is a combustion chamber 20. In the cylinder head 14,
An intake valve 22 and an exhaust valve 24 are respectively supported so as to be able to reciprocate substantially vertically.

The engine body includes an air cleaner 26, a throttle valve 28, a surge tank 30, an intake manifold 3
An intake passage 34 having two or the like is connected. An injector 36 that injects fuel is attached to the intake manifold 32. Further, a spark plug 38 is attached to the cylinder head 14. At the time of ignition, the high voltage generated by the igniter 40 receiving the ignition signal is supplied to the spark plug 38 via the ignition distributor 42. An exhaust passage 44 is connected to the engine body.

The cooling water in the internal combustion engine 10 is supplied by a water pump 46 through a forward passage 48 to a radiator 50.
After being sent to the side and cooled by the radiator 50, it is returned to the internal combustion engine 10 via the return flow path 52, and is maintained at a predetermined temperature. The radiator 50 is provided with a cooling fan 54, which is driven as needed. A passage switching valve 56 is provided in the middle of the forward passage 48, and a predetermined amount of the cooling water sent out by the water pump 46 is appropriately passed through the bypass passage 58 without passing through the radiator 50. It is returned to the internal combustion engine 10.

The engine 10 is provided with various sensors. Among them, the sensor related to the present invention will be described. A water temperature sensor 60 for detecting the temperature of the cooling water of the engine 10 is attached to the cylinder block 12. The surge tank 30 has an internal pressure (intake pressure P
An intake pressure sensor 62 for detecting M) is attached. The distributor 42 has a crank angle (C
A) a crank reference position sensor 64 that generates a reference position detection pulse at every 720 ° CA
A crank angle sensor 66 for generating a rotation speed detection pulse every 0 ° CA is provided. Further, a knock sensor 68 that detects knocking of the engine 10 as vibration is attached to the cylinder block 12.

Engine electronic control unit (engine ECU) 70
Is a microcomputer system that executes fuel injection control, ignition timing control, water temperature control, and the like. In the ECU 70, as preprocessing for various controls, an intake pressure signal, a coolant temperature signal, and the like are fetched by an AD conversion routine executed at every constant crank rotation angle, and the intake pressure data PM is stored in a predetermined area of an internal memory. , Cooling water temperature data THW and the like. Further, every time a pulse signal from the crank angle sensor 66 is input, the engine speed is calculated from the pulse interval by a routine (not shown), and stored as engine speed data NE in a predetermined area of the internal memory. Further, the change rate of the intake pressure PM is calculated at a constant time period, and the load change rate data Δ
Stored as PM.

FIG. 2 is a diagram showing the operation of monitoring the normal output value of knock sensor 68 to determine the knock determination level.
It is a flowchart which shows the procedure of the knock sensor background processing routine performed by CU70 at a fixed crank angle cycle. First, in step 102, the output SKN of a peak hold circuit provided inside the ECU for holding the peak value of the output of the knock sensor 68 is read. Next, at step 104, the update amount DSBG is calculated by an operation of DSBG ← | SBGO−SKN | / 4. here,
SBGO is the knock sensor background calculated by the previous calculation. The update amount DSBG is obtained by calculating the knock sensor background up to the previous calculation and the current peak value SKN.
Is calculated as 1/4 of the absolute value of the difference from

Next, in steps 106 and 108,
The update amount DSBG is limited so as to be equal to or less than a predetermined upper limit guard value GDSBG. Then, step 110
In steps 112 and 112, the present peak value SKN is compared with the knock sensor background SBGO up to the previous time, and SKN
Are determined, and steps 114, 116 and 118 are determined.
Then, the knock sensor background SBG is updated according to the determination result. That is, when SKN <SBGO, SBG is calculated as SBG ← SBGO + DSBG−α SBGO ≦ SKN <SBGO × 1.5, when SBG ← SBGO + DSBG + αSBGO × 1.5 ≦ SKN, SBG ← SBGO + DSBG. Here, α is an adjustment coefficient for setting the knock sensor background SBG to a value in an appropriate range. In the last step 120, the knock sensor background SBG calculated this time is stored as SBGO in preparation for the next calculation, and this routine ends.

FIG. 3 is a flowchart showing a procedure of an ignition timing control routine executed by the ECU 70 at a constant crank angle cycle based on the output of the knock sensor 68. First, at step 202, the current engine speed N
The basic ignition timing SA according to NE and PM is calculated by referring to a predetermined map based on E and the intake pressure PM. The ignition timing SA is a value calculated by the crank angle in the advance direction from the compression top dead center (ignition advance angle) (° CA-BTDC)
It is.

In step 204, the knock sensor output
The peak value SKN is equal to the background SBG and a predetermined coefficient K.
₁Is determined to be greater than the product of SKN <SBG
× K ₁In the case of
Proceeding to step 206, the ignition timing retard amount RKN is determined in advance.
Predetermined amount A₀Only decrease. On the other hand, SBG × K₁≤
In the case of SKN, it is considered that knocking has occurred, and
Proceeding to step 208, the ignition timing retard amount RKN is determined in advance.
Predetermined amount A₁Only increase.

Next, at step 210, guard processing is performed on the RKN so that the updated value of the ignition timing retard amount RKN falls within a certain range. Finally, at step 212, the ignition timing S obtained at step 202
By reducing A by the retard amount RKN, the effective ignition timing is determined. Thus, when knocking has not occurred, the ignition timing is advanced, while when knocking has occurred, the ignition timing is retarded and knocking is suppressed.

Next, the water temperature control of the present invention will be described in which the fuel consumption is deteriorated due to the ignition timing retard and the fuel temperature is deteriorated due to the decrease in the water temperature. FIG. 4 is a flowchart showing a processing procedure of a water temperature control routine executed in the ECU 70 at a constant crank angle cycle. FIGS. 5 and 6 are maps referred to during the processing of the water temperature control routine. FIG. 5 shows the engine speed NE and the intake pressure P as the engine load.
FIG. 6 shows a map in which the target water temperature TW is predetermined according to M, and FIG. 6 shows a map in which the water temperature decrease amount DT for correcting the target water temperature according to the knocking intensity IKN and the load change rate ΔPM is predetermined. .

First, in step 302, a target water temperature TW corresponding to NE and PM is calculated by referring to the map shown in FIG. 5 based on the current engine speed NE and intake pressure PM. Then, in step 304, it is determined whether the peak value SKN the knock sensor output is greater than the product of the background SBG and a predetermined coefficient K _2. SKN ≦
When the SBG × K _2, since the person who knocking avoiding or not, or even if generated knocking only retarding the ignition timing generator is determined to be advantageous in terms of fuel consumption, the target water temperature This routine ends without performing the correction.

On the other hand, when SBG × K ₂ <SKN,
Since knocking has occurred, and it is determined that avoiding knocking by lowering the water temperature as well as relying only on the retardation of the ignition timing is more advantageous from the viewpoint of fuel efficiency, Target water temperature correction processing is executed. That is, in step 306, the knocking strength IKN is obtained by the calculation of IKN ← SKN / SBG.

Next, in step 308, IKN and ΔKN are determined by referring to the map shown in FIG. 6 based on the calculated knocking intensity IKN and the current load change rate ΔPM.
The water temperature decrease amount DT according to the PM is calculated. In the map of FIG. 6, the water temperature drop amount DT is set to increase as the knocking intensity IKN increases. In addition, considering the load change rate, since the water temperature control generally involves a response delay, it takes some time for the water temperature to reach the target value and its effect appears to avoid knocking. This is to prevent excessive water temperature correction from being performed. Therefore, in the map of FIG. 6, the water temperature decrease amount DT is set to be smaller as ΔPM is larger.

In the last step 310, step 30
The final target water temperature TW is determined by reducing and correcting the target water temperature TW obtained in 2 by the water temperature decrease amount DT. The cooling fan 54 and / or the flow path switching valve 56 are controlled by a separately executed routine so that the coolant temperature THW detected by the coolant temperature sensor 60 is maintained at the target coolant temperature TW. Become.

FIG. 7 is a flowchart showing a processing procedure of a water temperature control routine according to another embodiment. Steps 402 and 404 correspond to steps 302 and 304 in FIG.
And are respectively the same. Then, at step 404, SK
When it is determined that N ≦ SBG × K ₂ , step 40
6, the knocking strength accumulated value AIKN described later is set to 0.
And the routine ends. Step 4
When it is determined in S04 that SBG × K ₂ <SKN, the process proceeds to step 408, and the knocking intensity IKN is calculated as in step 306 of FIG.

Next, at step 410, the cumulative knocking intensity value AIKN is updated by the calculation of AIKN ← AIKN + IKN. Then, in 412, the updated knock intensity cumulative value AIKN it is determined whether more than a predetermined value L _0,
Only when it is exceeded, steps 414 and 416 are executed. Steps 414 and 416 correspond to step 3 in FIG.
08 and 310 respectively. As described above, by performing the water temperature correction based on the accumulated value without performing the water temperature correction only with the temporary knocking intensity, reliability is improved, and appropriate water temperature correction according to the knocking frequency can be realized. .

As described above, by lowering the water temperature by the water temperature control, knocking is less likely to occur, and as a result, in the ignition timing control in FIG. 3, the ignition timing is advanced.

The ignition timing retard amount RKN in the ignition timing control routine of FIG. 3 is a value reflecting the knocking intensity. Therefore, when correcting the target water temperature value, the ignition timing retard amount R determined in the ignition timing control routine is replaced with the peak value SKN of the output of knock sensor 68.
KN can be used as knocking strength. That is, instead of the map shown in FIG. 6, as shown in FIG. 8, the ignition timing retard amount RKN and the load change rate ΔPM
May be set in advance in order to correct the target water temperature in accordance with.

FIG. 9 is a graph showing the effect of the present invention on the water temperature.
Advance angle SA and fuel consumption rate SFC using
(Specific Fuel Consumption) [g / kWh]
FIG. Water temperature is T_TwoThe ignition advance angle is S
A_TwoWhen knocking occurs at_TwoKeep in
The ignition advance angle is SA₁By delaying until
Assuming that knocking can be avoided, the fuel consumption rate is C₁Or
La C_ThreeRise to C _Three-C₁Only the fuel consumption rate gets worse
You. On the other hand, if the ignition advance angle is A_TwoWater temperature while maintaining at_Two
To T₁Knocking can be avoided by lowering
Then, the deterioration of fuel consumption rate is C_Two-C₁Only need, C
_Three-C_TwoOnly the deterioration of the fuel consumption rate will be reduced.
You.

[0034]

As described above, according to the cooling device for an internal combustion engine according to the present invention, fuel economy deterioration is suppressed as much as possible in consideration of fuel economy deterioration due to ignition timing retard and water temperature deterioration. Knocking control is realized.

[Brief description of the drawings]

FIG. 1 is an overall schematic diagram of an electronically controlled internal combustion engine including a cooling device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a procedure of a knock sensor background processing routine executed by an ECU.

FIG. 3 is a flowchart showing a processing procedure of an ignition timing control routine executed by an ECU.

FIG. 4 is a flowchart showing a processing procedure of a water temperature control routine executed by an ECU.

FIG. 5 is a diagram showing a map in which a target water temperature TW is determined in advance according to an engine speed NE and an intake pressure PM as an engine load.

FIG. 6 is a diagram showing a map in which a water temperature decrease amount DT for correcting a target water temperature according to knocking intensity IKN and load change rate ΔPM is predetermined.

FIG. 7 is a flowchart showing a processing procedure of a water temperature control routine according to another embodiment.

FIG. 8 is a diagram showing a map in which a water temperature decrease amount DT for correcting a target water temperature according to an ignition timing retard amount RKN and a load change rate ΔPM is predetermined.

FIG. 9 is a characteristic diagram showing a relationship between an ignition advance angle SA and a fuel consumption rate SFC using a water temperature as a parameter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine 12 ... Cylinder block 14 ... Cylinder head 16 ... Cylinder 18 ... Piston 20 ... Combustion chamber 22 ... Intake valve 24 ... Exhaust valve 26 ... Air cleaner 28 ... Throttle valve 30 ... Surge tank 32 ... Intake manifold 34 ... Intake passage 36 ... Injector 38 ... Spark plug 40 ... Igniter 42 ... Ignition distributor 44 ... Exhaust passage 46 ... Water pump 48 ... Outgoing passage 50 ... Radiator 52 ... Return passage 54 ... Cooling fan 56 ... Flow passage switching valve 58 ... By-pass passage 60 ... water temperature sensor 62 ... intake pressure sensor 64 ... crank reference position sensor 66 ... crank angle sensor 68 ... knock sensor 70 ... engine electronic control unit (engine ECU)

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F02D 45/00 312 F02D 45/00 312Q 345 345B F02P 5/152 F02P 5/15 D 5/153 (72) Inventor Nakagawa Yasuki No. 1 Toyota Town, Toyota City, Aichi Prefecture F-term in Toyota Motor Corporation (reference) 3G022 DA02 EA02 FA01 GA01 GA05 GA07 GA09 GA13 3G084 BA17 BA30 DA02 DA38 EA08 EC02 FA11 FA20 FA25 FA38

Claims (5)

[Claims] An operating region detecting means for detecting an operating region of the internal combustion engine; a target water temperature value map in which a target water temperature value of cooling water for the internal combustion engine is predetermined corresponding to the operating region; Water temperature control means for controlling the temperature of the cooling water of the internal combustion engine based on the target water temperature value map; knocking intensity detection means for detecting the knocking intensity of the internal combustion engine; and a basic ignition timing based on the detected knocking intensity. Ignition timing control means for controlling the ignition timing of the internal combustion engine by determining the ignition timing retard amount of the internal combustion engine; target water temperature value correction means for correcting the target water temperature value of the current operation region according to the detected knocking intensity; A cooling device for an internal combustion engine, comprising: 2. The cooling device for an internal combustion engine according to claim 1, wherein said target water temperature value correction means corrects the target water temperature value only when the detected knocking intensity is equal to or more than a predetermined value. 3. The cooling device for an internal combustion engine according to claim 1, wherein the target water temperature value correction means corrects the target water temperature value in accordance with the detected knocking intensity and a change rate of a load of the internal combustion engine. . 4. The cooling device for an internal combustion engine according to claim 1, wherein the target water temperature value correction means corrects the target water temperature value when the detected cumulative value of the knocking intensity exceeds a predetermined value. 5. The target water temperature value correction means uses an ignition timing retard amount determined by the ignition timing control means as the knocking intensity, instead of the knocking intensity detected by the knocking intensity detection means. Item 1
The cooling device for an internal combustion engine according to any one of claims 1 to 4.