JP3627556B2 - Fuel property detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel property detection device, and more particularly to a fuel property detection device that detects fuel property from fluctuations in the rotational speed of an internal combustion engine.
[0002]
[Prior art]
During normal operation of the internal combustion engine, the air-fuel ratio is controlled to the lean side in order to reduce emissions. However, since the fuel is difficult to vaporize during low temperature operation, if the air-fuel ratio is controlled to the lean side, the combustion state becomes unstable and drivability deteriorates. Therefore, conventionally, during low-temperature operation, intake-synchronous injection control that performs fuel injection within the valve opening period of the intake valve, injection amount increase control that increases the fuel injection amount than normal, and idle air amount that increases the idle speed Stabilization of the combustion state is performed by increasing control or ignition timing advance control that advances the ignition timing from the normal time. Hereinafter, the above-described control executed to stabilize the combustion state during low-temperature operation is generically referred to as “combustion stabilization control”.
[0003]
By the way, as a fuel for an internal combustion engine, there is a case where a heavy fuel having a property that is less likely to evaporate than a normal fuel (light fuel) is used. Even when such heavy fuel is used, if the combustion stabilization control is executed under conditions suitable for heavy fuel so that combustion stability during low temperature operation can be ensured, Will increase the emissions in the exhaust gas. Therefore, a control device for an internal combustion engine has been developed that detects fuel properties based on the combustion state of the internal combustion engine and executes combustion stabilization control according to the result.
[0004]
For example, in the fuel property detection device disclosed in JP-A-4-215757, when the engine speed is increased by starting with the ignition switch turned on, and then the engine speed decreases to a predetermined value or less, The fuel property is detected by comparing the engine speed with a reference value.
[0005]
[Problems to be solved by the invention]
In the fuel property detection device disclosed in Japanese Patent Application Laid-Open No. 4-213057, at the time when the engine speed increases at the start and then the engine speed decreases below a predetermined value, the engine speed is less than the reference value. Although the internal combustion engine is sometimes determined to be heavy fuel, the internal combustion engine has variations in oil viscosity, friction, ISC (idle rotational speed control device) air flow, and the like. However, there are cases where the engine speed does not decrease below the reference value, and there is a problem that the detection accuracy of the fuel property is not so good.
[0006]
The present invention has been made in view of the above points, and an object of the present invention is to provide a fuel property detection device that can improve the detection accuracy of the fuel property by gradually decreasing the engine speed immediately after the engine is started. .
[0007]
[Means for Solving the Problems]
The invention according to claim 1 is an engine speed detecting means for detecting the engine speed,
When the engine speed detected by the engine speed detection means becomes equal to or greater than a predetermined value immediately after the engine is started , the ignition timing is gradually retarded to the target retard amount corresponding to the coolant temperature, and the engine speed is increased. Rotational speed reduction means for gradually reducing the number ;
Fuel property detection means for detecting the fuel property by comparing the engine speed detected by the engine speed detection means with a predetermined reference value when retarding the ignition timing to the target retardation amount .
[0008]
In this way, by gradually reducing the engine speed immediately after starting the engine, even if there are variations in the internal combustion engine, with heavy fuel, the engine speed drops below the reference value and the fuel properties can be accurately detected. , the detection accuracy is above improvement.
[0009]
The invention according to claim 2 is the fuel property detection device according to claim 1 ,
After the fuel property is detected by the fuel property detecting means, there is provided a rotation speed reduction stop means for stopping the reduction of the engine speed by the rotation speed reduction means.
[0010]
As described above, after detecting the fuel property, the reduction in the engine speed by the speed reduction means is stopped, so that the engine speed can be prevented from being lowered more than necessary.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a configuration diagram of an embodiment of a system to which a fuel property detection device of the present invention is applied. The system includes an internal combustion engine 10. The internal combustion engine 10 is controlled by the ECU 12. The internal combustion engine includes a cylinder block 14. A cylinder 16 and a water jacket 18 are formed inside the cylinder block 14. A water temperature sensor 19 is disposed in the water jacket 18. The water temperature sensor 19 outputs a signal corresponding to the temperature of the cooling water flowing inside the water jacket 18 (hereinafter referred to as the water temperature THW) to the ECU 12. The ECU 12 detects the water temperature THW based on the output signal of the water temperature sensor 19.
[0012]
A piston 20 is disposed inside the cylinder 16. The piston 20 can slide in the vertical direction in FIG. A cylinder head 22 is fixed to the upper part of the cylinder block 14. An intake port 24 and an exhaust port 26 are formed in the cylinder head 22.
The bottom surface of the cylinder head 22, the top surface of the piston 20, and the side wall of the cylinder 16 define a combustion chamber 28. Both the intake port 24 and the exhaust port 26 described above open to the combustion chamber 28. The tip of the spark plug 30 is exposed in the combustion chamber 28. The spark plug 30 ignites the fuel in the combustion chamber 28 by being supplied with an ignition signal from the ECU 12.
[0013]
The internal combustion engine 10 also includes an intake valve 34 and an exhaust valve 36. The intake valve 34 and the exhaust valve 36 open and close each port by being attached to and detached from valve seats provided at openings of the intake port 24 and the exhaust port 26 to the combustion chamber 28.
An intake manifold 38 communicates with the intake port 24. A fuel injection valve 40 is disposed in the intake manifold 38. The fuel injection valve 40 injects fuel into the intake manifold 38 in accordance with a command signal given from the ECU 12.
[0014]
A surge tank 42 communicates with the upstream side of the intake manifold 38. An intake pipe 44 communicates with the upstream side of the surge tank 42. A throttle valve 46 is disposed in the intake pipe 44. A throttle opening sensor 48 is disposed in the vicinity of the throttle valve 46. The output signal of the throttle opening sensor 48 is supplied to the ECU 12. The ECU 12 detects the throttle opening based on the output signal of the throttle opening sensor 48.
[0015]
An air flow meter 50 communicates with the upstream side of the intake pipe 44. The air flow meter 50 outputs a signal according to the flow rate of air passing through the air flow meter 50 toward the ECU 12. The ECU 12 detects the intake air amount GA of the internal combustion engine 10 based on the output signal of the air flow meter 50. An air cleaner 52 communicates further upstream of the air flow meter 50. Outside air filtered by the air cleaner 52 flows into the intake pipe 44.
[0016]
On the other hand, an exhaust passage 54 communicates with the exhaust port 26 of the internal combustion engine. An O ₂ sensor 56 is disposed in the exhaust passage 54. The O ₂ sensor 56 outputs a signal corresponding to the oxygen concentration contained in the exhaust gas to the ECU 12.
A catalytic converter 58 is disposed downstream of the O ₂ sensor 56 in the exhaust passage 54. The catalytic converter 58 purifies the exhaust gas by adsorbing hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxide (NOX) contained in the exhaust gas. The catalyst converter 58 is provided with a catalyst temperature sensor 60. The catalyst temperature sensor 60 outputs a signal corresponding to the temperature of the catalytic converter 58 (hereinafter referred to as catalyst temperature Tc) to the ECU 12. The ECU 12 detects the catalyst temperature Tc based on the output signal of the catalyst temperature sensor 58.
[0017]
The internal combustion engine 10 is also provided with a crank angle sensor 62. The crank angle sensor 62 outputs a pulse signal to the ECU 12 every time the internal combustion engine 10 rotates by a predetermined crank angle. The ECU 12 detects the rotational speed of the internal combustion engine 10 (hereinafter referred to as engine rotational speed NE) based on the output signal of the crank angle sensor 62.
An idle switch 64 is also connected to the ECU 12. The idle switch 64 is a switch that is turned off when an accelerator operation is being performed, and is turned on when the accelerator operation is released. The ECU 12 determines the presence or absence of an accelerator operation from the on / off state of the idle switch 64.
[0018]
In this system, during normal operation of the internal combustion engine 10, the air-fuel ratio is controlled to the lean side in order to reduce emissions in the exhaust gas. Hereinafter, the above control realized during normal operation of the internal combustion engine 10 is referred to as “normal control”. On the other hand, when the combustion state is expected to be unstable, such as when the internal combustion engine 10 is started at a low temperature, intake synchronous injection that performs fuel injection within the intake valve opening period in order to ensure combustion stability Control, injection amount increase control to increase the fuel injection amount from the normal time, idle air amount increase control to increase the idle speed, or ignition timing advance control to advance the ignition timing from normal time Stabilization is underway. Hereinafter, the above-described control executed to stabilize the combustion state during low-temperature operation is generically referred to as “combustion stabilization control”.
[0019]
Hereinafter, the content of the process which ECU12 performs in one Example of this invention is demonstrated using FIGS.
FIG. 2 is a flowchart of an embodiment of a routine executed by the ECU 12 to set the retard permission flag in the device of the present invention. The routine shown in FIG. 2 and each of the following routines are scheduled interrupt routines that are started at predetermined time intervals, and retarding is permitted at start-up (when the ignition switch is turned on). The flag xacat has been reset to off. When the routine shown in FIG. 2 is started, first, the process of step S10 is executed.
[0020]
In step S10, whether or not the value of the counter ecast that measures the elapsed time immediately after starting the internal combustion engine 10 (after the ignition switch is turned off from on) exceeds a predetermined value a and is less than a predetermined value b. Is determined. The predetermined value a corresponds to, for example, about 1 second, and the predetermined value b corresponds to about several seconds. As a result, when a <ecast <b is satisfied, the process proceeds to step S12. If a <ecast <b is not established, this routine is terminated assuming that the fuel property cannot be detected.
[0021]
In step S12, it is determined whether or not the engine speed NE is equal to or higher than a predetermined speed n (n is about 1000 rpm, for example) and the start-up is completed normally. If the engine speed NE is equal to or greater than the predetermined engine speed n in step S12 and the engine is normally started, the process proceeds to step S14 to retard the ignition timing so as to decrease the engine speed NE. The permission flag xacat is turned on “1”, and the current routine is terminated. If the engine speed NE is less than the predetermined engine speed n and the start has not been completed, the engine speed may be stopped if the engine speed NE is lowered. Therefore, the process proceeds to step S16 in order not to retard the ignition timing. The retard permission flag xacat is turned off “0”, and the current routine is terminated.
[0022]
FIG. 3 is a flowchart of an embodiment of a routine executed by the ECU 12 to calculate the retard amount in the device of the present invention. When the routine shown in FIG. 2 is started, first, the process of step S20 is executed.
In step S20, it is determined whether or not the idle switch 64 is in an on state and an idling state (flag xidle is on). If it is in the idling state, the process proceeds to step S22, and if it is not in the idling state, the current routine is terminated. In step S22, it is determined whether or not the retard angle permission flag xacat is on and the retard angle control is permitted. If the retard permission flag xacat is on, the process proceeds to step S23. If the retard permission flag xacat is off and retard control is not permitted, the current routine is terminated.
[0023]
In step S23, it is determined whether or not the control switching flag F is set to “1”. If the control switching flag F is set to “1”, the current routine is terminated. If the control switching flag F is not set to “1”, the process proceeds to step S24. This step S23 is provided in order to stop the further retard of the ignition timing after the control switching flag F is set to “1” in the determination of the combustion stabilization control. It is possible to prevent the number from decreasing more than necessary.
[0024]
In step S24, the target retardation amount KARTD is determined by referring to the map shown in FIG. 4 based on the water temperature THW detected at the time of starting. In the map shown in FIG. 4, the target retardation amount KARTD is set larger as the water temperature THW is lower, and the ignition timing is retarded as the target retardation amount KARTD is smaller. Thereafter, in step S26, the temporary retardation correction amount teard is decreased by a constant ADEC and gradually changed to the retardation side. The temporary retard correction amount teard and the constant ADEC are absolute values, and the ignition timing is retarded as the temporary retard correction amount teard (or the retard correction amount eard) is smaller.
[0025]
Next, in step S26, it is determined whether or not the temporary retardation correction amount teard is less than or equal to the target retardation amount KARTD. If the temporary retardation correction amount teard is less than or equal to the target retardation amount KARTD, the target retardation amount KARTD is set to the temporary retardation correction amount teard in step S30, and the temporary retardation correction amount teard is not too small. Put the guard on. On the other hand, if the temporary retardation correction amount teard exceeds the target retardation amount KARTD, step S30 is bypassed. Thereafter, in step S32, the temporary retardation correction amount teard is set to the retardation correction amount earrt, and the current routine is terminated.
[0026]
FIG. 5 is a flowchart of an embodiment of a routine executed by the ECU 12 to start the combustion stabilization control in the device of the present invention. When the routine shown in FIG. 5 is started, first, the process of step S40 is executed.
In step S40, it is determined whether or not an elapsed time T after starting the internal combustion engine 10 is equal to or less than a predetermined value a. As a result, if T ≦ a is established, it is next determined in step S42 whether the water temperature THW is less than a predetermined value g. If THW <g is satisfied in step S42, it is determined that the internal combustion engine 10 is in a low temperature start state. In this case, next, in step S44, after the control switching flag F is set to “1”, the current routine is ended.
[0027]
The ECU 12 executes the combustion stabilization control when the control switching flag F is set to “1”. Therefore, according to the above processing, the combustion stabilization control is executed when the internal combustion engine 10 is started at a low temperature, so that good combustion stability in the idle operation state can be obtained.
On the other hand, if a negative determination is made in step S40 or S42, then in step S46, the control switching flag F is set to “0”. When the process of step S46 ends, the process proceeds to step S48.
[0028]
In step S48, it is determined whether or not the intake air amount GA of the internal combustion engine 10 is less than a predetermined value c. In general, the smaller the intake air amount GA, the more likely the combustion becomes unstable. Therefore, if GA <c is satisfied in step S48, it is determined that the combustion may become unstable, and then the process of step S50 is executed. On the other hand, if GA <c is not established in step S48, the current routine is terminated.
[0029]
In step S50, it is determined whether or not the value of a counter ecast that measures the elapsed time immediately after the start of the internal combustion engine 10 is less than a predetermined value d. The predetermined value d is set to a value larger than the predetermined value a. If ecast <d is satisfied in step S50, then the process of step S52 is executed. On the other hand, if ecast <d is not satisfied in step S50, the current routine is terminated.
[0030]
In step S52, it is determined whether or not the water temperature THW is less than a predetermined value e. The predetermined value e is set to a value larger than the predetermined value g. If THW <e is established in step S52, it is determined that the internal combustion engine 10 has not been warmed up, and then the process of step S54 is executed. On the other hand, if THW <e is not established in step S52, the current routine is terminated.
[0031]
In step S54, it is determined whether or not the engine speed NE is less than a predetermined value f. As a result, if NE <f is established, it is determined that the combustion state is unstable, and then in step S56, the control switching flag F is set to “1”, so that the combustion stabilization control is performed. Executed. On the other hand, if NE <f is not established in step S56, the current routine is terminated.
[0032]
According to the routine shown in FIG. 5, when the intake air amount GA is less than c, the elapsed time T after startup is less than d, and the water temperature THW is less than e, the engine speed NE is predetermined. It is determined that the combustion state has become unstable when the value is lower than the value f. In this case, the control switching flag F is set to “1” in step S56 and the combustion stabilization control is executed, so that the combustion state is stabilized.
[0033]
Here, after the internal combustion engine 10 is started, when the engine speed NE shown in FIG. 6 (A) exceeds the predetermined speed n, the ignition timing shown in FIG. 6 (B) is gradually retarded thereafter. For this reason, as shown in FIG. 6A, when the engine speed NE is reduced and the fuel property is heavy fuel, the engine speed NE is reliably reduced below the reference value f and the control switching flag is set. F is set to “1”, combustion stabilization control is executed, and further retard of the ignition timing is stopped. At this time, since the ignition timing is gradually retarded, the possibility of engine stall can be eliminated.
[0034]
Further, since the ignition timing is retarded immediately after starting, the warm-up performance of the catalyst is improved, and the emission in the exhaust gas can be reduced. Further, even if the fuel property is light fuel, the increase in the engine speed immediately after starting is suppressed by the retard of the ignition timing, so that emission in the exhaust gas can be reduced, and noise and vibration can be reduced.
Instead of retarding the ignition timing in the present embodiment, control may be performed to gradually decrease the air amount during idling, and further the warm-up increase value of the fuel injection amount immediately after starting is gradually decreased. Control may be performed.
[0035]
When the predetermined value n used in step S12 and the predetermined value f used in step S54 are the same value, when NE ≧ n in step S12, the ignition timing is further retarded. Therefore, it is not necessary to provide step S23 in FIG.
The ECU 12 and the crank angle sensor 62 correspond to the engine speed detecting means described in the claims, and Steps S40 to S56 correspond to the fuel property detecting means, and Steps S26 to S32 correspond to the engine speed detecting means. Corresponding to the lowering means, steps S22 and S23 correspond to the rotational speed reduction stopping means.
[0036]
【The invention's effect】
As described above , according to the first aspect of the present invention , even if there is a variation in the internal combustion engine by gradually decreasing the engine speed immediately after the engine is started, the engine speed is less than the reference value for heavy fuel. The fuel property can be accurately detected and the detection accuracy is improved.
[0038]
According to the second aspect of the present invention, after the fuel property is detected, the decrease in the engine speed by the engine speed reducing means is stopped, so that the engine speed can be prevented from being reduced more than necessary.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an embodiment of a system to which a fuel property detection device of the present invention is applied.
FIG. 2 is a flowchart of an embodiment of a routine executed by an ECU to set a retard angle permission flag in the present invention.
FIG. 3 is a flowchart of an embodiment of a routine executed by the ECU to calculate a retard amount in the present invention.
FIG. 4 is a diagram showing a map used in the present invention.
FIG. 5 is a flowchart of an embodiment of a routine executed by the ECU to start combustion stabilization control in the present invention.
FIG. 6 is a graph showing changes in engine speed and ignition timing in the present invention.
[Explanation of symbols]
10 Internal combustion engine 12 ECU

Claims (2)

An engine speed detecting means for detecting the engine speed;
When the engine speed detected by the engine speed detection means becomes equal to or greater than a predetermined value immediately after the engine is started , the ignition timing is gradually retarded to a target retard amount corresponding to the coolant temperature to rotate the engine. Rotational speed reduction means for gradually reducing the number ;
Fuel property detection means for detecting the fuel property by comparing the engine speed detected by the engine speed detection means with a predetermined reference value when retarding the ignition timing to the target retardation amount. A fuel property detection device comprising: The fuel property detection device according to claim 1,
After detecting the fuel property by the fuel property detecting means, the engine speed reducing means for stopping the engine speed reduction by the engine speed reducing means is stopped.
A fuel property detection device comprising:

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