JPH045454A - Cooling device for internal combustion engine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a cooling device for an internal combustion engine, and particularly to a technique useful in a supercharged internal combustion engine.

<Prior Art> In an internal combustion engine with an exhaust turbo supercharger, the exhaust temperature may rise excessively during high-load operation, causing thermal damage to the exhaust valve, exhaust manifold, or the turbine of the supercharger.

For this reason, in the past, high-load operating ranges (for example, 60
00r, p, m, etc.) The target air-fuel ratio is set to be excessively rich (richer than the maximum output air-fuel ratio) to cool the combustion chamber with fuel and lower the exhaust temperature. I have to. Here, the target air-fuel ratio is set so that the exhaust gas temperature becomes equal to or lower than a predetermined value during steady continuous operation.

<Problem to be solved by the invention> However, since the exhaust system has a large heat mass, the increase in exhaust temperature, which is a problem during steady continuous operation, can also be caused by transient engine operating conditions (during acceleration) and high load operation. This is not a problem when the air-fuel ratio enters the air, but on the contrary, the air-fuel ratio becomes too low, leading to a deterioration in fuel efficiency and deterioration in exhaust properties (in particular, an increase in CO emissions).

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a cooling device for an internal combustion engine that can improve fuel efficiency and exhaust properties while suppressing a rise in exhaust system temperature in a high-load operating range. .

<Means for Solving the Problems> Therefore, in claim 1, the present invention includes an ignition timing control means A that sets the ignition timing based on the engine operating state, and a set ignition timing control means A, as shown by the solid line in FIG. A drive control means C for controlling the drive of the spark plug B based on the timing, an engine load detection means for detecting the engine load, and a temperature for detecting a state related to the engine cooling temperature or the cooling water temperature. a detection means E; a heat generation amount setting means F for setting the amount of heat generation in the combustion chamber using at least the detected engine load as a parameter; a basic exhaust system temperature setting means G for setting a basic exhaust system temperature; an exhaust system temperature estimating means H for estimating the exhaust system temperature based on the set heat generation amount and the basic exhaust system temperature; An advance amount setting means I that sets an ignition timing advance amount to lower the exhaust system temperature based on the system temperature, and an ignition timing adjuster that corrects the set ignition timing based on the set ignition timing advance amount. A timing correction means (■) is provided.

Further, in claim 2, in addition to claim 1, the fuel increase correction amount is set to reduce the exhaust system temperature based on the estimated exhaust system temperature as shown by the broken line in FIG. The setting means includes an increase correction means for increasing the fuel supply amount based on the set fuel increase correction amount, and a drive control means N for driving and controlling the fuel supply means M based on the increased fuel supply amount. I tried to prepare for this.

<Operation> In this manner, in claim 1, the heat generation amount is set based on the engine load as at least a parameter, and the basic exhaust system temperature is set based on the cooling water temperature or a state related thereto. The exhaust system temperature is estimated, and the ignition timing is advanced to reduce the exhaust system temperature.

Furthermore, in the second aspect, in addition to the ignition timing control of the first aspect, the amount of fuel is increased based on the estimated exhaust system temperature, thereby also reducing the exhaust system temperature.

<Example> An example of the present invention will be described below based on FIGS. 2 to 6.

In Fig. 2, an intake passage 2 near the intake port of the engine 1
An electromagnetic fuel injection valve 3 as a fuel supply means is attached to the wall, and fuel is supplied under pressure to the fuel injection valve 3 from a fuel pump (not shown). The fuel injection valve 3 is opened by a drive pulse signal from the control device 4, and injects fuel into the intake passage 2.

A compressor 6 of an exhaust turbo supercharger 5 is interposed in the intake passage 2, and a turbine 7 is connected to the compressor 6.
is interposed in the exhaust passage 8.

Then, by rotationally driving the turbine 7 using exhaust energy, the compressor 6 pressurizes intake air and supplies it to the combustion chamber.

An ignition plug 9 is provided in the combustion chamber of the engine 1. A high voltage generated by the ignition coil 1o is applied to the ignition plug 7 via the distributor 11 based on an ignition signal from the control device 4, thereby igniting a spark and burning the fuel.

The control device 4 includes a CPU, ROM, and RAM.

It is equipped with a microcomputer including an A/D converter and an input/output interface, and controls the fuel injection valve 3 and the spark plug 9 based on signals from various sensors.

The distributor 11 includes a crank angle sensor 12.
The crank angle sensor 12 outputs a reference signal (for example, every 180 degrees of crank angle in a four-cylinder engine) and a position signal (for example, every 2 degrees of crank angle) to the control device 4. Here, the engine rotational speed can be detected by measuring the number of input position signals per unit time or the input cycle of the reference signal.

An oxygen sensor 13 is provided in the exhaust passage 8, and the oxygen sensor 13 detects the air-fuel ratio by detecting the oxygen concentration in the exhaust gas. Here, the output voltage of the oxygen sensor 13 suddenly changes around the stoichiometric air-fuel ratio. Further, a hot wire air flow meter 14 as an engine load detection means for detecting the intake air flow rate and a water temperature sensor 15 for detecting the cooling water temperature of the engine 1 are provided, and these detection signals are input to the control device 4. Ru.

A battery is connected to the control device 4 via an engine key switch 17 as an operating power source and for detecting power supply voltage.

The CPU of the control device 4 operates according to the flowcharts shown in FIGS. 3 to 7, and controls the fuel injection valve 3 and the spark plug 9.
and control the drive.

Here, the control device 4 (particularly the CPU) has an ignition timing setting means, a drive control means, a heat generation amount setting means, a basic exhaust system temperature setting means, an exhaust system temperature estimation means, an ignition timing correction means, and an increase correction amount setting means. and an increase correction means.

Next, the operation will be explained according to the flowcharts shown in FIGS. 3 to 7. The routine shown in the flowchart in Figure 3 is 10.
m5e (executed every time period.

First, fuel injection control will be explained.

In Sl, the crank angle sensor 12. Reads various signals from the oxygen sensor 13, air flow meter 14, etc.

In S2, a basic injection amount TP (=KQ/N; is a constant) is calculated based on the detected intake air flow 11Q and engine rotational speed N.

In S3, various correction coefficients C0EF are set using the following equations.

C0EF=1 + water temperature increase correction coefficient 10 air-fuel ratio correction coefficient 10 increase correction coefficient for starting and after starting 10 increase coefficient after idling 10 acceleration reduction correction coefficient The air-fuel ratio is set to be the stoichiometric air-fuel ratio in the normal operating range, and the maximum output air-fuel ratio is set to be richer than the stoichiometric air-fuel ratio in the high-load operating range.

In S4, a voltage correction numerator s is set based on the voltage value of the battery 16. This is to prevent fluctuations in the injection amount of the fuel injection valve 3 due to fluctuations in battery voltage.

In S5, the air-fuel ratio feedback correction coefficient α set by the routine shown in the flowchart of FIG.
Load.

In S6, the fuel increase correction coefficient K for cooling is set by the routine shown in the flowchart of FIG. 7, which will be described later.
Load HOT.

In S7, the fuel injection amount T8 is calculated using the following equation.

T, -T, XC0EFXαXKHOT+TSS8,
The calculated fuel injection amount T is sent to the output register. As a result, a signal with a pulse width corresponding to the fuel injection amount T is output to the fuel injection valve 3, and fuel injection is performed.

Next, the feedback control determination routine will be explained according to the flowchart of FIG. Here, the feedhack control of the air-fuel ratio is performed in a low/medium speed rotation and low/medium load operating range, and is stopped in a high rotation or high load operating range.

In the Sll, a comparison load (T, ) is calculated from the map based on the engine rotational speed. This comparison load is set so that it decreases as the engine rotation speed increases.

In step 312, it is determined whether the actual load (Tp) is less than or equal to the comparative load.
If it is in the medium load operating range, the process advances to S13, and if NO, that is, if it is in the high rotation or high load operating range, the process advances to 314.

In 313, the delay timer is reset to the initial value, and then the process advances to S17.

In S14, the delay timer starts counting.

In S15, it is determined whether the count value of the delay timer has exceeded a predetermined value, and when YES, that is, when the predetermined value has passed since the transition to the high rotation or high load operating range, the feedback control is stopped. The process advances to step 318, and when the answer is No, the process advances to step S16.

In S16, the engine rotation speed is set to a predetermined value (for example, 3800r
, p, m, ) or more, and if YES, proceed to S18 to stop the feedback control and NO.
If so, the process advances to S17.

In S17, the air-fuel ratio flag is set to 1 to perform feedback control.

At 318, the air-fuel ratio flag is set to O to stop feedback control.

The air-fuel ratio flag set in this manner is stored in the RAM.

Next, the setting routine for the air-fuel ratio feedback correction coefficient α will be explained according to the fifth flowchart.

At 521, it is determined whether the air-fuel ratio flap knob is 1 or not, and Y
If ES, the process proceeds to S22 to perform feedback control, and if NO, the process proceeds to S30 to stop the feed hack control.

In S22, the output voltage of the oxygen sensor 13 is read.

In S23, the read output voltage and the basis of the stoichiometric air-fuel ratio are calculated. By comparing the S voltage, it is determined whether the actual air-fuel ratio is richer than the stoichiometric air-fuel ratio. If YES, that is, rich, the process proceeds to S24, and if NO, that is, lean, the process proceeds to S27.

In S24, it is determined whether or not this is the first time that the actual air-fuel ratio is reversed from lean to rich. If YES, the process proceeds to S25; if NO, the process proceeds to S26.

In S25, a new air-fuel ratio feedbank correction coefficient α is set by subtracting the proportional bone P from the air-fuel ratio feedbank correction coefficient α set in the previous routine.

In S26, a new air-fuel ratio feedbank correction coefficient α is set by eliminating the integral I from the air-fuel ratio feedback correction coefficient α set in the previous routine.

In this way, the air-fuel ratio feedback correction coefficient α is set so that the air-fuel ratio is rapidly made leaner by the proportional amount P during the first inversion, and thereafter the air-fuel ratio is gradually made leaner by the integral amount I.

At 327, it is determined whether or not this is the first time that the actual air-fuel ratio has changed from rich to lean. If YES, the process advances to 32B, and if NO, the process advances to S29.

In 328, a new air-fuel ratio feedbank correction coefficient α is set by subtracting the proportional bone P from the air-fuel ratio feedback correction coefficient α set in the previous routine.

In S29, a new air-fuel ratio feedback correction coefficient α is set by subtracting the integral I from the air-fuel ratio feedback correction coefficient α set in the previous routine.

In this way, the air-fuel ratio feedback correction coefficient α is set so that the air-fuel ratio is rapidly enriched during the first inversion, and thereafter the air-fuel ratio is gradually enriched.

In S30, the air-fuel ratio feedback correction coefficient α is clamped to a predetermined value (for example, 1), and the feedback control is stopped.

Next, ignition timing control will be explained according to the routine shown in the flowchart of FIG.

At 331, the detection signal of the crank angle sensor 12 is read.

In S32, the basic ignition timing ADV is searched from the map based on the detected engine speed and engine load (for example, basic injection amount).

At step 333, the cooling ignition timing advance amount KADV set in the injection routine shown in FIG. 7, which will be described later, is read.

In S34, the basic ignition timing ADV and the ignition timing advance amount KADV are added to obtain the ignition timing.

At the ignition timing determined in this way, an ignition signal is output to the ignition coil 10 to cause the ignition plug 9 to ignite via the distributor 11.

Next, the fuel increase correction coefficient KHOT and the ignition timing advance angle IK
The ADV routine will be explained according to the flowchart of FIG.

In S41, various signals from the air flow meter 14, water temperature sensor 15, etc. are read.

At step 342, the amount of heat in the combustion chamber is searched from the map based on the detected intake air flow rate and engine rotational speed. The heat generation amount H is set to increase as the intake air flow rate increases, and is also set to increase as the engine rotation speed increases.

In S43, the reference exhaust system temperature T is determined based on the detected cooling water temperature. is set to increase as the cooling water temperature increases.

In S44, the exhaust system temperature T is calculated and estimated using the following equation.

T = T o + (HX K ) / nK is a coefficient for converting the amount of heat into temperature, and n is the heat capacity from the combustion chamber to the exhaust system, which is determined experimentally.

At step 335, a fuel increase correction coefficient KHOT for lowering the exhaust temperature is searched from the map based on the estimated exhaust system temperature T. This KHOT is set to be larger than I and to become larger as the exhaust system temperature becomes higher.

In S36, based on the estimated exhaust system temperature T, the ignition timing advance amount KADV for lowering the exhaust gas temperature is searched from the map. The ignition timing advance amount KADV is set to advance as the exhaust system temperature increases.

The fuel increase correction coefficient KHOT set in this way is used in the routine shown in the flowchart in Fig. 3 to increase the fuel amount (air-fuel ratio to be less than the maximum output air-fuel ratio).
will be held. Further, the ignition timing advance angle KADV is used in the routine shown in the flowchart of FIG. 6, and even if the ignition timing is advanced, the exhaust temperature is lowered and the exhaust system temperature is lowered.

As explained above, based on the amount of heat generation determined from the intake air flow rate and engine rotational speed, and the basic exhaust system temperature determined from the cooling water temperature, the fuel injection amount increase is corrected and the ignition timing is advanced. As a result, even if steady continuous operation is performed in a high load range, the air-fuel ratio is adjusted to the normal range, the combustion chamber is cooled, and the rise in exhaust system temperature can be suppressed, and the exhaust system temperature can also be reduced by advancing the ignition timing. can be suppressed. Therefore, thermal damage to the engine and exhaust turbocharger can be prevented and durability can be improved.

In addition, when entering a transient high-load operation range, the amount of heat HEt
Since the increase in exhaust system temperature can also be suppressed, the ignition timing advance amount KADV and the fuel increase correction coefficient KHO
T becomes small, and the increase in fuel amount for cooling can be suppressed.

Therefore, it is possible to improve the output during acceleration operation, and to suppress deterioration of exhaust properties and fuel efficiency. In particular, since the exhaust system temperature is lowered by increasing the amount of fuel, ignition timing, and advancing the ignition timing, it is possible to suppress the increase in fuel amount, suppress deterioration of exhaust characteristics and fuel efficiency, and suppress the amount of advance, thereby preventing knocking. can be prevented from occurring.

Note that the engine load includes throttle valve opening, intake negative pressure, and the like.

<Effects of the Invention> As explained above, the present invention has the following features in claim 1:
After determining the heat generation amount using at least the engine load as a parameter and determining the basic exhaust system temperature from the cooling water temperature or related conditions, the exhaust system temperature is estimated, and the ignition timing for cooling is determined based on this exhaust system temperature. By advancing the angle, it is possible to improve the durability during continuous high-load operation as in the conventional example, while improving the output, exhaust properties, and fuel efficiency during transient operation. Further, in the second aspect, the ignition timing advance control and the fuel increase control are performed to lower the exhaust system temperature, so that it is possible to suppress the occurrence of knocking and to suppress the deterioration of the exhaust properties and fuel efficiency.

[Brief explanation of the drawing]

FIG. 1 is a diagram corresponding to claims of the present invention, FIG. 2 is a configuration diagram showing an embodiment of the present invention, and FIGS. 3 to 7 are flowcharts of the same. 1... Engine 3... Fuel injection valve 4... Control device 5... Exhaust turbo supercharger 9... Spark plug
12...Crank angle sensor 13...Oxygen sensor 14...Air flow meter 15...Water temperature sensor Patent applicant Japan Electronics Co., Ltd. Agent Patent attorney Fujio Sasashima No. 4Uy' Figure 6, Figure 7 figure

Claims (2)

[Claims] (1) Detecting engine load in an internal combustion engine that includes an ignition timing setting device that sets the ignition timing based on the engine operating state, and a drive control device that drives and controls the spark plug based on the set ignition timing. engine load detection means; temperature detection means for detecting a state related to the engine cooling temperature or cooling water temperature; and heat generation amount setting means for setting the heat generation amount in the combustion chamber using at least the detected engine load as a parameter. and basic exhaust system temperature setting means for setting a basic exhaust system temperature based on the detected cooling water temperature or a state related to the cooling water temperature, and based on the set heat generation amount and the basic exhaust system temperature. an exhaust system temperature estimating means for estimating the exhaust system temperature based on the estimated exhaust system temperature; an advance amount setting means for setting an ignition timing advance amount in order to lower the exhaust system temperature based on the estimated exhaust system temperature; A cooling device for an internal combustion engine, comprising: ignition timing correction means for correcting the set ignition timing based on an ignition timing advance amount. (2) Increase correction amount setting means for setting a fuel increase correction amount to lower the exhaust system temperature based on the estimated exhaust system temperature, and increase correction amount of fuel supply based on the set fuel increase correction amount. 2. The cooling system for an internal combustion engine according to claim 1, further comprising: an increase correction means for increasing the fuel supply amount; and a drive control means for driving and controlling the fuel supply means based on the increased fuel supply amount.