JP2002201997A - Fuel properties determining device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine a cetane value of the used fuel with high accuracy with a comparatively simple constitution. SOLUTION: An engine is cranked by a starter motor (S2), a cranking engine speed is unified (S3, S4), then the fuel injection is started, and a temperature Tw of the cooling water in starting is detected (S5). Then the complete explosion is determined (S6) at a time when the engine speed Ne reaches a predetermined engine speed LSNe, and a time from the start of the fuel injection to the complete explosion is detected as a time TSTART necessary for the starting (S7). The cetane value of the fuel is determined in reference to a predetermined map on the basis of the time TSTART necessary for starting and the cooling water temperature Tw in starting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for determining fuel properties of an internal combustion engine, particularly, a cetane number.

[0002]

2. Description of the Related Art As a conventional example, for example, Japanese Utility Model 3-45
No. 181 discloses a known cetane number sensor. The purpose of this conventional example is to determine the cetane number of the supplied fuel and inject the fuel at a timing according to the determined value because the cetane number of the fuel on the market varies and stable operation cannot be performed. is there.

[0003] Regarding the method of determining the cetane number, it is assumed that there is a proportional relationship between the viscosity of the fuel and the cetane number. Equipped with a mechanism for measuring
Further, the viscosity measurement result is corrected based on the measurement result of the temperature measuring means to determine the cetane number.

Another conventional example is disclosed in, for example,
There is a diesel engine combustion control device of No. 107820. In this conventional example, the ignition timing detecting means by the in-cylinder pressure sensor is provided, and when the target ignition timing and the actual ignition timing are different due to the variation of the cetane number of the fuel in the market, the ignition timing is set as the target ignition timing. Injection timing and EG
It changes the R ratio and the like.

[0005]

However, in the conventional cetane number determination method as disclosed in Japanese Utility Model Publication No. 3-45181, a complicated mechanism is required for measuring the viscosity of the fuel. , The productivity is degraded, and the cost is inevitable. Furthermore, if a fuel having no correlation between viscosity and cetane number is introduced into the market in the future, its function will not be exhibited. Further, when the vehicle is tilted, it is assumed that the friction of the viscosity measuring mechanism itself in the fuel tank changes, and it is difficult to measure the viscosity accurately.

In a combustion control apparatus for a diesel engine as disclosed in Japanese Patent Application Laid-Open No. H11-107820, the cetane number is determined based on the difference between the actual ignition timing and the target ignition timing. Is difficult to determine accurately, and because the in-cylinder pressure sensor is used as the actual ignition timing detecting means, an increase in cost is inevitable.

In view of such circumstances, the present invention provides a fuel property (cetane number) judging device for an internal combustion engine capable of judging the cetane number of a fuel used with a relatively simple structure and with high accuracy. The purpose is to provide.

[0008]

The research conducted by the present inventors has revealed that there is a close relationship between the temperature of the engine at the time of starting and the time required for starting, and the cetane number of the fuel used. And you. Therefore, in the invention of claim 1, means for detecting the temperature of the engine at the time of start, means for detecting the time required for the start, and the means for detecting the temperature of the engine at the time of the start and the time required for the start Means for determining the cetane number of the fuel being used, to constitute a fuel property determination device for an internal combustion engine.

According to a second aspect of the present invention, in the first aspect of the invention, the means for detecting the temperature of the engine at the time of starting includes:
As the temperature of the engine, any one of an engine cooling water temperature, an engine oil temperature, and a combustion chamber temperature is detected. According to a third aspect of the present invention, in the first or second aspect of the present invention, the means for detecting the time required for starting the engine is cranked by an external device (cranking device) before starting fuel injection at the time of starting. Thereafter, the time from the start of fuel injection to the complete explosion of the engine is detected as the time required for starting. In this case, the complete explosion may be determined when the engine speed becomes equal to or higher than a predetermined speed as in the invention of claim 4.

According to a fifth aspect of the present invention, in accordance with the third or fourth aspect, the cranking speed of the engine is made constant before fuel injection is started. According to a sixth aspect of the present invention, in the fifth aspect of the invention, there is provided a cranking speed stabilizing control means for controlling a cranking speed of the engine by the starter motor as the external device within a predetermined speed range. And

According to a seventh aspect of the present invention, in the hybrid vehicle according to the fifth aspect of the present invention, in the hybrid vehicle, an electric motor directly connected to a crankshaft of the engine is used as the external device, and the cranking speed of the engine is kept constant. It is characterized by. According to an eighth aspect of the present invention, in the first to fourth aspects of the present invention, there is provided a means for detecting a cranking rotational speed of the engine, wherein the means for determining the cetane number includes the detected engine temperature at the time of starting and the starting The cetane number of the fuel being used is determined in accordance with the time required for and the cranking rotation speed.

[0012]

According to the first aspect of the present invention, the cetane number of the fuel used is determined in accordance with the temperature of the engine at the time of starting and the time required for starting. It can be detected accurately. That is, since the research conducted by the present inventors has revealed that there is a close relationship between the temperature of the engine at the time of start and the time required for the start and the cetane number of the used fuel, it has been clarified that this relationship is used. By determining the cetane number, it is possible to suppress the cost for providing a complicated viscosity measurement mechanism and an in-cylinder pressure sensor as in the related art, and it is also possible to eliminate the measurement error as described above, thereby improving the cetane number determination accuracy. Becomes Thereby, combustion control according to the cetane number can be performed, and combustion stability and exhaust performance can be improved.

According to the second aspect of the present invention, it is possible to accurately determine the cetane number at low cost by detecting the temperature of the engine cooling water, the temperature of the engine oil, the temperature of the combustion chamber, and the like as the temperature of the engine at the time of starting. Becomes According to the invention of claim 3, after the engine is cranked by the external device before starting the fuel injection at the time of starting, the time from the start of the fuel injection to the complete explosion of the engine is the time required for the starting. , The determination accuracy of the cetane number is improved.

According to the fourth aspect of the present invention, it is determined that a complete explosion has occurred when the engine speed is equal to or higher than a predetermined speed.
In particular, a device for judging the complete explosion is unnecessary, and the cetane number can be judged at low cost. According to the invention of claim 5,
By keeping the cranking speed of the engine constant before starting the fuel injection, it is possible to prevent the accuracy of the determination of the cetane number from being deteriorated due to the change in the cranking speed, thereby improving the accuracy of the determination of the cetane number.

According to the sixth aspect of the present invention, by performing the cranking rotation speed stabilization control for controlling the cranking rotation speed of the engine by the starter motor as the external device within a predetermined rotation speed range, the normal engine At
The cranking speed of the engine can be kept constant, and the deterioration of the cetane number determination accuracy due to the change in the cranking speed can be prevented, and the cetane number determination accuracy can be improved.

According to the seventh aspect of the present invention, since the present invention is applied to a hybrid vehicle, that is, a vehicle in which an engine can be driven by a large motor, the cranking rotation speed of the engine at the time of starting can be easily made constant. , The determination of the cetane number can be realized with low cost and high accuracy. According to the invention of claim 8, the actual cranking speed of the engine is detected, and in addition to the temperature of the engine at the time of starting, the time required for starting,
Since the cetane number of the fuel used is determined according to the cranking rotation speed, even if the cranking rotation speed is not fixed,
The cetane number can be accurately determined.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system configuration diagram of a vehicular internal combustion engine (here, a compression ignition type diesel engine) showing a first embodiment of the present invention. In the engine 1, air taken in from an intake pipe 2 is supercharged by a turbocharger 3 (intake compressor), cooled by an intercooler 4 by running wind, and passed through a throttle valve 5 for enhancing gas flow. , From the intake valve 6 into the combustion chamber 7. Fuel is directly injected from the fuel injection valve 8 into the combustion chamber 7. The air that has flowed into the combustion chamber 7 and the injected fuel burn here by compression ignition, and the exhaust gas flows out of the exhaust valve 9 to the exhaust pipe 10.

A part of the exhaust gas flowing to the exhaust pipe 10 is EG
The gas is returned to the intake side by the R pipe 11 as EGR gas. The EGR pipe 11 is provided with an EGR cooler 12 for cooling EGR gas with engine cooling water.
An EGR valve 13 for controlling the EGR flow rate is provided.
The remainder of the exhaust gas passes through the turbocharger 3 (exhaust turbine), is purified through the catalyst device 14, and is then discharged outside the vehicle.

Starting (cranking) of the engine 1
Is supplied to the starter motor 15 so that the motor 1
5 by rotating the crankshaft 16. Engine control unit (ECU)
20), a crank angle sensor 21 for detecting the rotational position of the crankshaft 16 and the engine speed Ne for controlling the engine 1 and an engine coolant temperature T
Signals are input from a water temperature sensor 22 for detecting w, an accelerator sensor 23 for detecting an accelerator opening, an engine start switch 24, and the like.

Based on these input signals, the ECU 20 issues a fuel injection command signal for controlling the fuel injection timing and injection amount to the fuel injection valve 8, an opening command signal to the EGR valve 13, and a signal to the starter motor 15. It outputs drive signals and the like. Further, according to the present invention, the ECU 20 can determine the property (cetane number) of the fuel used and simultaneously reflect the control at the time of starting, and reflect the property in various controls. The starting control including the price determination will be described below.

FIG. 2 is a flowchart of the start-up control including the determination of the cetane number of the used fuel executed by the ECU 20. In S1, the engine start switch 24 is turned on.
Or OFF. If it is OFF, the starter motor 15 is turned off in S9, and this routine is terminated.
If it is ON, the process proceeds to S2.

In S2, the starter motor 15 is energized,
Start cranking. Then, in step S3, the cranking rotation speed (engine rotation speed) Ne is controlled within a predetermined rotation speed range (lower limit value) by controlling the supply current to the starter motor 15 by general PID control or the like as cranking rotation speed stabilization control. (LSM or more, HSM or less), the engine speed Ne detected based on the signal of the crank angle sensor 21 is read in S4, and it is determined whether or not the engine speed Ne is within a predetermined speed range. As a result, when the rotation speed is not within the predetermined rotation speed range, the rotation speed control in S3 is continued, and when it is determined that the rotation speed is within the predetermined rotation speed range, the process proceeds to S5. This part corresponds to cranking speed stabilization control means.

In S5, a timer for measuring the time required for starting is started. At the same time, fuel injection is started. At the same time, the engine cooling water temperature Tw at the time of starting is read from the signal of the water temperature sensor 22. This part corresponds to a means for detecting the engine temperature at the time of starting. Then, S6
The engine speed Ne detected based on the signal of the crank angle sensor 21 is read in to determine whether or not the engine speed Ne is equal to or higher than a predetermined speed LSNe corresponding to a complete explosion. If not, the count-up by the timer is continued, and when the rotation speed becomes equal to or more than the predetermined rotation speed LSNe, it is determined that the explosion is complete, and the process proceeds to S7.

In S7, the timer is stopped and the timer value at this time is substituted into TSTART to obtain the time TSTART required for starting (the time from the start of fuel injection to the complete explosion of the engine) TSTART. . This part corresponds to a means for detecting the time required for starting. Finally, in S8, the cetane number STN of the fuel used is determined from the time TSTART required for starting and the engine coolant temperature Tw at the start with reference to the cetane number determination map shown in FIG. Read, and this routine ends. This part corresponds to the cetane number determining means.

Here, as is clear from the cetane number determination map of FIG. 3, the shorter the time TSTART required for starting is, the larger the cetane number STN is, and if the time TSTART required for starting is constant, Cooling water temperature T at startup
As w is lower, the cetane number STN is determined to be larger. As described above, the cetane number of the fuel supplied to the fuel tank can be accurately determined before the operation of the engine is started, and the combustion control based on the injection timing and the EGR rate according to the cetane number can be performed. Performance and exhaust performance can be improved.

In this embodiment, a normal engine-driven vehicle is taken as an example. However, in a hybrid vehicle in which a relatively large electric motor is directly connected to a crankshaft,
Since the electric motor can perform stable cranking at the time of starting, the cetane number can be accurately determined without performing the special cranking rotation speed stabilizing control (S3).

Next, a second embodiment of the present invention will be described. In the present embodiment, the system configuration is the same as that of the first embodiment (FIG. 1), and the starting control including the cetane number determination of the used fuel is performed according to the flowchart of FIG. 4, and the flowchart of FIG. 4 will be described. I do. S21
Then, the engine start switch 24 is turned ON or OFF.
Is determined. If it is OFF, the starter motor 15 is turned off in S29, and this routine ends. If it is ON, the process proceeds to S22.

In step S22, the starter motor 15 is energized to start cranking. Thereafter, in S23, a timer for measuring the time required for the start is started. At the same time, fuel injection is started. At the same time,
The engine cooling water temperature Tw at the time of starting is read from the signal of the water temperature sensor 22. This part corresponds to a means for detecting the engine temperature at the time of starting. At the same time, the engine speed Ne detected based on the signal of the crank angle sensor 21 is read as the engine cranking speed Nc at the start of fuel injection (Nc ← Ne). This part corresponds to cranking rotation speed detecting means.

Then, in S24, the engine speed Ne detected based on the signal of the crank angle sensor 21 is read, and the engine speed Ne becomes equal to the predetermined engine speed L corresponding to the complete explosion.
SNe is determined to be equal to or greater than a predetermined rotational speed LSN.
If it has not reached e, the count-up by the timer is continued, and if it exceeds the predetermined rotational speed LSNe, it is determined that the explosion is complete, and the routine proceeds to S25.

In S25, the timer is stopped, and the timer value at this time is substituted into TSTART, whereby
The time required for starting (the time from the start of fuel injection to the complete explosion of the engine) TSTART is obtained. This part corresponds to a means for detecting the time required for starting. In the next step S26, as shown in FIG.
A map is selected from a plurality of cetane number STN determination maps prepared in advance for each of the maps according to the value of Nc read in S26.

In the last step S27, the time TS required for starting
From TART and the engine cooling water temperature Tw at the time of starting, S
The cetane number STN of the used fuel is read with reference to the map selected in 26, and this routine ends. This part corresponds to the cetane number determining means. Here, if the time TSTART required for the start and the coolant temperature Tw at the time of the start are the same, the cetane number STN is determined to be larger as the cranking speed Nc is lower.

According to the present embodiment, since the map for determining the cetane number is provided for each engine cranking rotation speed at the time of starting, the stabilization control of the cranking rotation speed is performed, and a large engine driving device is used. Or the like, the cetane number can be accurately determined without maintaining the engine cranking rotational speed constant, so that the present invention can be applied to a normal vehicle without increasing the cost.

In the above embodiment, the engine cooling water temperature detected by the most common water temperature sensor is used as the engine temperature at the time of starting. However, the engine oil temperature, the combustion chamber temperature, and the like are used. You may. The engine oil temperature can be detected by a generally equipped oil temperature sensor, and the combustion chamber temperature can be detected when a wall temperature sensor is provided on the combustion chamber wall or when a combustion gas temperature detection sensor is provided in the combustion chamber. In addition, these can be detected.

Since the time required for starting may change due to deterioration of the battery, etc., the determination value of the cetane number may be corrected depending on the state of the battery (open-circuit voltage or the like), or the state of the battery may be improved in a good state. The determination condition may be set so that only the cetane number is determined.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of an engine showing a first embodiment of the present invention.

FIG. 2 is a flowchart of start-up control including cetane number determination of fuel used.

FIG. 3 is a diagram showing a map for determining cetane number.

FIG. 4 is a flowchart showing a second embodiment of the present invention.

FIG. 5 is a diagram showing a cetane number determination map according to a second embodiment.

[Explanation of symbols]

 Reference Signs List 1 engine 2 intake pipe 7 combustion chamber 8 fuel injection valve 10 exhaust pipe 11 EGR pipe 13 EGR valve 15 starter motor 20 ECU 21 crank angle sensor 22 water temperature sensor 24 engine start switch

Claims (8)

[Claims] 1. A means for detecting the temperature of the engine at the time of starting, a means for detecting the time required for the starting, and the detected temperature of the engine at the time of starting and the time required for the starting.
Means for determining the cetane number of the fuel being used. 2. The means for detecting the temperature of the engine at the time of starting detects any one of an engine cooling water temperature, an engine oil temperature, and a combustion chamber temperature as the engine temperature. Item 3. The fuel property determination device for an internal combustion engine according to Item 1. 3. A means for detecting a time required for the starting,
After starting the fuel injection at the start, the engine is cranked by an external device, and the time from the start of the fuel injection to the complete explosion of the engine is detected as the time required for the start. The fuel property determination device for an internal combustion engine according to claim 1 or 2. 4. The fuel property judging device for an internal combustion engine according to claim 3, wherein a complete explosion is judged when the engine speed becomes equal to or higher than a predetermined speed. 5. The engine according to claim 3, wherein the cranking speed of the engine is made constant before fuel injection is started.
5. The fuel property determination device for an internal combustion engine according to claim 4. 6. An internal combustion engine according to claim 5, further comprising a cranking speed stabilization control means for controlling a cranking speed of the engine by a starter motor as said external device within a predetermined speed range. Fuel property determination device. 7. The internal combustion engine according to claim 5, wherein an electric motor directly connected to a crankshaft of the engine is used as the external device to stabilize the cranking speed of the engine. Fuel property determination device. 8. A means for detecting the cranking speed of the engine, wherein the means for determining the cetane number includes the detected engine temperature at the time of starting, the time required for starting, and the cranking speed. The fuel property judging device for an internal combustion engine according to any one of claims 1 to 4, wherein the cetane number of the fuel used is judged accordingly.