JP3945064B2 - Combustion state detection device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a combustion state detection device for an internal combustion engine, and more particularly to a combustion state detection device for an internal combustion engine that detects fuel properties from fluctuations in the rotational speed of the 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 from the normal time, or ignition timing than the normal time Stabilization of the combustion state is performed by ignition timing advance control for advancing. 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 combustion state detecting device for an internal combustion engine disclosed in Japanese Patent Laid-Open No. 4-213057, the engine speed increases by starting with the ignition switch turned on, and then the engine speed decreases to a predetermined value or less. At that time, the fuel property is detected by comparing the engine speed with a reference value, and detection is prohibited when an external load is activated to prevent erroneous detection.
[0005]
[Problems to be solved by the invention]
In the combustion state detecting device for an internal combustion engine disclosed in JP-A-4-215757, when the engine speed increases at the time of starting and then the engine speed decreases to a predetermined value or less, the engine speed is a reference. If it is less than the value, it is determined that the fuel is heavy, and this detection is prohibited when an external load is applied. Therefore, the heavy fuel cannot be detected when the external load is applied, and combustion stabilization control cannot be executed. In this case, since the combustion state becomes unstable, there is a problem that idle malfunction occurs or drivability deteriorates.
[0006]
The present invention has been made in view of the above points. Combustion of an internal combustion engine capable of detecting fuel properties when an external load is applied by switching the reference value to a low value when an external load is applied. An object is to provide a state detection device.
[0007]
[Means for Solving the Problems]
The invention according to claim 1 is an engine speed detecting means for detecting the engine speed,
A combustion state detection device for an internal combustion engine, comprising fuel property detection means for detecting the fuel property by comparing the engine speed detected by the engine speed detection means with a reference value,
Have a reference value switching means for switching the reference value to a lower value corresponding to the type of the external load when the external load is applied to the engine,
The reference value switching means determines the external load from the shift position of the shift lever, and switches the reference value with a predetermined delay when the shift position of the shift lever is switched from the drive range to the neutral range.
[0009]
Thus, to determine the external load from the shift position of the shift lever, because the shift position of the shift lever is switched to the reference value by a predetermined delay time when switching from the drive range to the neutral range, good accuracy further The fuel property can be detected.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a block diagram of an embodiment of a system to which a combustion state detecting device for an internal combustion engine 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.
[0011]
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 receiving an ignition signal from the ECU 12.
[0012]
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.
[0013]
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.
[0014]
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.
[0015]
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.
[0016]
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. Further, the ECU 12 has a power steering switch for instructing the on / off signal of the vehicle air conditioner, the shift position (N, D, R, etc.) of the shift lever for automatic (AT) transmission, and the operation of the hydraulic pump of the power steering. And an electric load switch signal for instructing the operation of an alternator (alternator).
[0017]
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 Stabilization of the combustion state is performed by control, injection amount increase control that increases the fuel injection amount from the normal time, 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”.
[0018]
The contents of the process executed by the ECU 12 in the first embodiment of the present invention will be described below with reference to FIGS.
FIG. 2 is a flowchart of a first embodiment of a routine executed by the ECU 12 to start combustion stabilization control in the apparatus of the present invention. The routine shown in FIG. 2 and the routines shown below are all scheduled interrupt routines that are activated at predetermined time intervals. When the routine shown in FIG. 2 is started, first, the process of step S10 is executed.
[0019]
In step S10, it is determined whether or not the shift position of the automatic transmission shift lever is in an N (neutral) range. As a result, if the shift position is in the N range, the process proceeds to step S12, and a predetermined value ENEDNNN is set as the reference rotation speed enddown. On the other hand, if the shift position is not the N range but the D (drive) range or the R (reverse) range, the process proceeds to step S14, and a predetermined value ENEDWND is set as the reference rotation speed enddown. Here, the predetermined value ENEDWNN is a value used as a reference for detecting the fuel property when there is no external load with the shift position in the N range, and the predetermined value ENEDWND is an external load with the shift position in the D range or R range. It is a value that is sometimes used as a reference for detecting the fuel property, and as indicated by a one-dot chain line in FIG.
[0020]
After the execution of steps S12 and S14, the process proceeds to step S16, where it is determined whether or not the engine speed NE based on the output signal of the crank angle sensor 62 is equal to or less than the reference speed enddown. As a result, if NE ≦ endown, the fuel property is heavy fuel, and the process proceeds to step S18, where the process for detecting the rotation reduction, that is, the combustion stabilization control process is executed, and the current routine is terminated. On the other hand, if NE> endowed, the fuel property is light fuel and step S18 is bypassed, and the current routine is terminated.
[0021]
Here, as shown by a two-dot chain line between times t0 and t1 in FIG. 3, when the shift position is in the N range and no external load is applied to the engine, the reference rotation speed enddown for fuel property detection becomes a one-dot chain line. As shown, when the engine speed NE shown by the solid line is equal to or lower than this value ENEDNNN, heavy fuel with an unstable combustion state is detected.
[0022]
When time t1 is passed and the shift position is in the D range and an external load is applied to the engine, the fuel property detection reference rotational speed enddown becomes ENEDWND, which is smaller than ENEDWNN when there is no external load. When the engine speed NE indicated by the solid line is equal to or lower than this value ENEWDND, heavy fuel with an unstable combustion state is detected. For this reason, even when an external load is applied, the fuel property can be accurately detected. Based on this detection result, even when an external load is applied, combustion stabilization control is executed for heavy fuel, so that it is possible to prevent idling malfunction and drivability deterioration.
[0023]
In step S10, in addition to whether or not the shift position is in the N range, it is determined whether or not the air conditioner is activated. If the N range or the air conditioner is not activated, the process proceeds to step S12, and the D range or the air conditioner is activated. In the case of the operation of the conditioner, the process proceeds to step S14, and the reference rotation speed endowd for detecting the fuel property may be set to ENEDWND with respect to the steady increase of the external load due to the operation of the air conditioner. The reference rotation speed endowd for detecting the fuel property for a steady increase in external load may be set to a value different from ENEDWND. As described above, since the reference rotation number (reference value) for fuel property detection is switched according to the type of the external load, the fuel property can be detected with higher accuracy when an external load is applied.
[0024]
Next, the contents of the process executed by the ECU 12 in the second embodiment of the present invention will be described with reference to FIGS.
FIG. 4 is a flowchart of a second embodiment of a routine executed by the ECU 12 to start the combustion stabilization control in the apparatus of the present invention. When the routine shown in FIG. 4 is started, first, the process of step S20 is executed.
[0025]
In step S20, it is determined whether or not the idle switch 64 is in an on state. 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 shift position of the automatic transmission shift lever is in the N range. As a result, if the shift position is in the N range, the process proceeds to step S24. On the other hand, if the shift position is not the N range but the D (drive) range or the R (reverse) range, the process proceeds to step S26, and a predetermined value EENDWND is set to the reference rotational speed enddown.
[0026]
In step S24, it is determined whether or not the value of the accessory drive counter ecaminv is equal to or greater than a predetermined value e. The auxiliary machine drive counter ecaminv counts the time after turning on an auxiliary machine of a type that receives a transient large external load (rush load) when the power steering hydraulic pump or alternator is turned on and then converges. Here, when ecaminv ≧ e, a predetermined value ENEDAMOF is set as the reference rotational speed endedown at step S28, and when ecaminv <e, the predetermined value ENEMONON is set as the reference rotational speed endedown at step S30. Here, the predetermined value ENEDAMOF (= ENEDWNN) is a reference value for detecting fuel properties when there is no external load, and the predetermined value ENEDAMON is a reference for detecting fuel properties when an external load is applied to the auxiliary machine. As shown by a one-dot chain line in FIG. 6, there is a relationship of ENEDAMOF> ENEDAMON.
[0027]
After the execution of steps S26 to S30, the process proceeds to step S32, where it is determined whether or not the engine speed NE based on the output signal of the crank angle sensor 62 is equal to or less than the reference speed enddown. As a result, if NE≤endown, the fuel property is heavy fuel, and the process proceeds to step S34, where the process for detecting the rotation decrease, that is, the combustion stabilization control process is executed, and the current routine is terminated. On the other hand, if NE> endowed, the fuel property is light fuel and step S32 is bypassed, and the current routine is terminated.
[0028]
FIG. 5 is a flowchart of an embodiment of a routine executed by the ECU 12 to operate the auxiliary machine drive counter ecaminv 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, whether or not the power steering switch for instructing the operation of the hydraulic pump of the power steering has changed from off (non-operation) to on (operation) is detected this time and the power steering switch expssw detected this time is ON. The determination is made based on whether or not the power steering switch expresssoff is OFF. If the power steering switch has not changed from OFF to ON, the process proceeds to step S42, and if the power steering switch has changed from OFF to ON, the process proceeds to step S46.
[0029]
In step S42, whether or not the electrical load switch exels detected this time is ON, whether or not the electrical load switch instructing the operation of the alternator (alternator) has changed from off (non-operation) to on (operation) is ON, and The determination is made based on whether or not the previously detected electrical load switch exelso is OFF. If the electrical load switch has not changed from OFF to ON, the process proceeds to step S44, and if the electrical load switch has changed from OFF to ON, the process proceeds to step S46.
[0030]
In step S44, the auxiliary machine drive counter ecaminv is incremented by 1 in order to count the time after the power steering hydraulic pump or alternator changes from non-operation to operation. In step S46, the auxiliary drive counter ecaminv is reset to 0 because the hydraulic pump or alternator of the power steering has changed from non-operation to operation. Thereafter, the current process is terminated.
[0031]
Here, as shown by the two-dotted line from time t0 to t1 in FIG. 6, when the power steering hydraulic pump is inactive (expssw = OFF) and no external load is applied to the engine, the fuel property is detected. As shown by the one-dot chain line, the reference engine speed enedown of the engine is ENEDAMOF, and when the engine speed NE shown by the solid line is equal to or lower than this value ENEDAMOF, the heavy fuel whose combustion state is unstable is detected.
[0032]
When the hydraulic pump of the power steering is activated (expssw = ON) at time t2 and a large external load is transiently applied to the engine and the engine speed NE decreases transiently, the auxiliary machine drive counter ecaminv is 0 as shown by the solid line. After being reset to, it is incremented sequentially. During the period from time t1 to time t2 when the external load is large, the value of the auxiliary machine drive counter ecaminv is equal to or less than the predetermined value e. Therefore, the reference rotational speed enddown of the fuel property detection is ENEMONON as shown by the one-dot chain line, and the external load is It becomes smaller than ENEDAMOF when there is no.
[0033]
When the engine speed NE indicated by the solid line is equal to or lower than this value ENEMONON, heavy fuel with an unstable combustion state is detected. For this reason, even when an external load is applied, the fuel property can be accurately detected. Even when an external load is applied based on the detection result, combustion stabilization control is executed if the fuel is heavy, and it is possible to prevent idle malfunction and deterioration of drivability.
[0034]
By the way, after time t2 when the load converges, the value of the auxiliary drive counter ecaminv exceeds the predetermined value e, so the reference rotation speed endowdown for fuel property detection becomes ENEDAMF as shown by the one-dot chain line.
Note that the reference rotational speed enddown when an external load is applied is set to a predetermined constant value ENEDAMON, but the reference rotational speed enddown can be varied according to the magnitude of the external load.
[0035]
Next, the contents of the process executed by the ECU 12 in the third embodiment of the present invention will be described with reference to FIGS.
FIG. 7 is a flowchart of a third embodiment of a routine executed by the ECU 12 to start combustion stabilization control in the device of the present invention. When the routine shown in FIG. 7 is started, first, the process of step S50 is executed.
[0036]
In step S50, it is determined whether or not the value of the N range counter ecswdn is equal to or greater than a predetermined value b. The N range counter ecswdn counts the time after the shift position of the automatic transmission shift lever changes from the D range to the N range. Here, if ecnswdn ≧ b, a predetermined value EENDWNN is set to the reference rotation speed enddown in step S52, and if ecnswdn <b, the predetermined value EENDWND is set to the reference rotation speed endedo in step S54. As described above, the predetermined value ENEDWNN is a reference value for fuel property detection when there is no external load with the shift position in the N range, and the predetermined value ENEDWND is an external load with the shift position in the D range or R range. This is a reference value for detecting the fuel property when it is applied, and there is a relationship of ENEDWNN> ENEDWND, as shown by a one-dot chain line in FIG.
[0037]
After the execution of steps S52 and S54, the process proceeds to step S56, where it is determined whether or not the engine speed NE based on the output signal of the crank angle sensor 62 is equal to or less than the reference speed enddown. As a result, if NE ≦ endown, the fuel property is heavy fuel, and the process proceeds to step S58, where a process for detecting a reduction in rotation, that is, a combustion stabilization control process is executed, and the current routine is terminated. On the other hand, if NE> endowed, the fuel property is light fuel and step S58 is bypassed, and the current routine is terminated.
[0038]
FIG. 8 is a flowchart of an embodiment of a routine executed by the ECU 12 to operate the N-range counter ecnswdn in the device of the present invention. When the routine shown in FIG. 5 is started, the process of step S60 is first executed.
In step S60, it is determined whether or not the shift position of the automatic transmission shift lever is in the D range. If the shift position is the D range, the process proceeds to step S62, and the N range counter ecnswdn is reset to 0. If the shift position is not in the D range, that is, if it is in the N range, the process proceeds to step S64, and the N range counter ecnswdn is incremented by one. Thereafter, the current process is terminated. For this reason, when the shift position is switched from the D range to the N range, the value of the N range counter ecnswdn is sequentially incremented from 0.
[0039]
Here, as indicated by a two-dot chain line from time t0 to t1 in FIG. 9, when the engine is not in an external load and the shift position is in the N range, the reference rotational speed enddown of the fuel property detection becomes a one-dot chain line. As shown, when the engine speed NE shown by the solid line is equal to or lower than this value ENEDNNN, heavy fuel with an unstable combustion state is detected.
[0040]
When time t1 is passed and the shift position is in the D range and an external load is applied to the engine, the fuel property detection reference rotational speed enddown becomes ENEDWND, which is smaller than ENEDWNN when there is no external load. When the engine speed NE indicated by the solid line is equal to or lower than this value ENEWDND, heavy fuel with an unstable combustion state is detected. For this reason, even when an external load is applied, the fuel property can be accurately detected.
[0041]
Thereafter, when the shift position becomes the N range at time t2, the value of the N range counter ecnswdn is sequentially incremented thereafter, and the value of the N range counter ecnswdn becomes the value b or more at time t3. Therefore, the reference rotation speed endowdown for detecting the fuel property becomes ENEDWNN at time t3 delayed from time t2. This is because, even if the shift position is switched from the D range to the N range, the external load is not reduced immediately but is reduced with a delay. Therefore, the switching of the reference rotational speed enddown is delayed by the time t2-t3 in accordance with this delay. This prevents erroneous detection of the fuel property at time t2-t3. For this reason, it is possible to accurately detect the fuel property, and based on the detection result, the combustion stabilization control is executed if the fuel is heavy, and it is possible to prevent idle malfunction and drivability deterioration.
[0042]
The ECU 12 and the crank angle sensor 62 correspond to the engine speed detection means described in the claims, and steps S16, S32, and S56 correspond to the fuel property detection means, and steps S10 to S14, S22 to S30 and S50 to S54 correspond to the reference value switching means.
[0043]
【The invention's effect】
As described above, a first aspect of the present invention, it has a reference value switching means for switching to a low value corresponding to the reference value the kind of the external load when the external load is applied to the engine,
The reference value switching means determines the external load from the shift position of the shift lever, and switches the reference value with a predetermined delay when the shift position of the shift lever is switched from the drive range to the neutral range.
[0044]
The good urchin, to determine the external load from the shift position of the shift lever, the order shift position of the shift lever switches the reference value by a predetermined delay time when switching from the drive range to the neutral range, good fuel property more accurate Can be detected.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an embodiment of a system to which a combustion state detection apparatus for an internal combustion engine according to the present invention is applied.
FIG. 2 is a flowchart of a first embodiment of a routine executed by an ECU 12 to start combustion stabilization control.
FIG. 3 is a signal timing chart for explaining the first embodiment of the present invention.
FIG. 4 is a flowchart of a second embodiment of a routine executed by the ECU 12 to start firing stabilization control.
FIG. 5 is a flowchart of an embodiment of a routine executed by the ECU 12 to operate an auxiliary machine drive counter ecaminv in the device of the present invention.
FIG. 6 is a signal timing chart for explaining a second embodiment of the present invention.
FIG. 7 is a flowchart of a third embodiment of a routine executed by the ECU 12 to start firing stabilization control.
FIG. 8 is a flowchart of an embodiment of a routine executed by the ECU 12 to operate an N range counter ecnswdn in the device of the present invention.
FIG. 9 is a signal timing chart for explaining a third embodiment of the present invention.
[Explanation of symbols]
10 Internal combustion engine 12 ECU

Claims (1)

An engine speed detecting means for detecting the engine speed;
A combustion state detection device for an internal combustion engine, comprising fuel property detection means for detecting the fuel property by comparing the engine speed detected by the engine speed detection means with a reference value,
Have a reference value switching means for switching the reference value to a lower value corresponding to the type of the external load when the external load is applied to the engine,
The reference value switching means determines the external load from a shift position of a shift lever, and switches the reference value after a predetermined time delay when the shift position of the shift lever is switched from a drive range to a neutral range. A combustion state detection device for an internal combustion engine.

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