JP2946355B2 - Fuel property detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel property detecting device for an engine which detects volatility of fuel from fluctuations in engine rotation.

[0002]

2. Description of the Related Art In recent years, low volatile fuels have been sold for engine fuels, especially gasoline. When fuels having different fuel properties are supplied to the engine and burned, various control characteristics are improved. It is necessary to correct for changes in fuel properties.

[0003] That is, when a heavy fuel with low volatility is supplied, various control characteristics that have been set corresponding to the normal fuel up to that time, especially when the engine temperature is low and the vehicle is running at a cold time, the fuel consumption is low. Evaporation and atomization are reduced, resulting in poor running performance. On the other hand, if the determination of the fuel property based on the volatility of the fuel is made, the increase in fuel during the cold operation is corrected based on the detection of the fuel property so as to be increased by a predetermined amount. Can be improved.

Therefore, conventionally, for detecting and determining the fuel properties such as the volatility of the fuel, for example, Japanese Unexamined Patent Publication No. Sho 62-28
As seen in Japanese Patent No. 8335, the fuel property is detected and determined based on the in-cylinder pressure detected by the pressure sensor based on the difference in combustion speed, that is, the pressure rise, in combustion in the cylinder between heavy fuel and normal fuel. Such techniques are known.

[0005] Further, since the air-fuel ratio decreases during acceleration with low-volatility fuel, it is conceivable to determine the fuel properties by detecting the air-fuel ratio with an air-fuel ratio sensor.

[0006]

However, in the above-described system in which the volatility of the fuel is detected from the fluctuation characteristic of the in-cylinder pressure of the engine, it is necessary to separately provide a pressure sensor. It is disadvantageous in terms of cost. Also,
If the fuel volatility is determined from the change in the air-fuel ratio at the time of acceleration, the detection cannot be determined before traveling, and a decrease in traveling performance until the detection is unavoidable.

On the other hand, it is preferable to detect the volatility of the fuel by using a signal from an existing sensor such as a fluctuation in engine speed. In this case, it is necessary to detect and determine the fuel immediately after starting the engine. It is preferable because the amount of vaporization by heating due to the ambient temperature is small and the true volatility of the fuel can be detected.However, this engine speed fluctuates according to various conditions, Unless the engine rotation fluctuation based on the difference and the rotation fluctuation due to other factors are discriminated, it is difficult to perform highly accurate detection.

That is, when a change in fuel volatility is detected and determined from the characteristic of decreasing engine rotation, an alternator corresponding to an increase in the driving load of a compressor for an air conditioner, the driving load of an oil pump for power steering, and the electric load. When an external load such as a torque converter load acts due to an increase in the driving load of the automatic transmission and a shift to a driving range such as the D range of the automatic transmission, the engine rotation also decreases, and the rotation decreases due to a decrease in volatility. There is a possibility that identification cannot be performed and erroneous detection may occur.

In view of the above circumstances, the present invention provides an engine fuel property detecting device for preventing the occurrence of erroneous detection due to the operation of an external load in detecting and determining the volatility of fuel from the characteristic of decreasing engine rotation. It is intended to provide.

[0010]

In order to achieve the above-mentioned object, an engine fuel property detecting apparatus according to the present invention, as shown in FIG. 1, has a basic structure as shown in FIG. A rotation detecting means A is provided, and a signal from the engine rotation detecting means A is output to a fuel property detecting means B. The fuel property detecting means B detects the volatility of the fuel based on the fluctuation of the engine rotation. Further, the engine E is provided with an external load C whose driving load acting on the engine E is increased by its operation, and an external load detecting means D for detecting an operation state of the external load C is provided. A prohibition means H is provided which receives the signal of the external load detection means D and prohibits the fuel property detection means B from detecting the fuel volatility when the external load C is in the operating state.

The external load C includes driving loads such as a compressor for an air conditioner, an oil pump for power steering, an alternator, and an automatic transmission.

[0012]

In the fuel property detecting device as described above, when the external load is operating, the detection of fuel volatility is prohibited even if other fuel volatility detecting conditions are satisfied. This prevents erroneous detection of volatility due to rotation reduction due to operation of an external load,
It is possible to perform an accurate control corresponding to the volatility based on the detection of the fuel property with high accuracy.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is an overall configuration diagram of an engine provided with the fuel property detection device of one embodiment.

An intake port 4 and an exhaust port 5 communicate with each other in a combustion chamber 3 variably formed above the piston 2 of the engine body 1, and the opening is opened at predetermined timing by an intake valve 6 and an exhaust valve 7. Is opened and closed.

An intake passage 8 connected to the intake port 4
An air flow sensor 11 for detecting the amount of intake air from the upstream side and a throttle valve 12 are interposed, and a downstream portion of a surge tank 13 is formed to be branched into each cylinder, and an injector 14 for injecting and supplying fuel is provided here. Have been.

A bypass air passage 15 is formed in the intake passage 8 so as to bypass the throttle valve 12 and to be connected to the upper and lower intake passages 8. A control valve 16 for adjusting the amount of air is interposed. Further, an ignition plug 17 is provided facing the combustion chamber 3, and a discharge voltage is supplied to the ignition plug 17 via an ignition coil 18 and a distributor 19 to adjust the ignition timing.

A control signal is output from the controller 20 to the ignition coil 18 and the control valve 16 in the bypass air passage 15 to perform ignition timing control and bypass air control. Further, the fuel injection control of the injector 14 is performed according to the operation state by the control signal from the controller 20.

The controller 20 includes a rotation signal for detecting the engine speed from the distributor 19, an intake air amount signal from the air flow sensor 11, an engine water temperature signal from the water temperature sensor 22, and a throttle valve 12 for detecting the operating state. A signal from an idle switch 23 that operates in a fully closed state, a signal from a shift sensor 24 that detects neutral of the transmission (in the case of a manual transmission), a signal from a starter switch 25 that starts a starter, and an external load Signal of the air conditioner switch 27, the signal of the power steering switch 28 according to the operation of the power steering, the signal of the electric load switch 29, the range position signal from the inhibitor switch 30 (in the case of an automatic transmission) Are input.

Further, the controller 20 has a function of the fuel property detecting means B for detecting a signal related to the volatility of the fuel from a decrease in the engine speed during a predetermined period immediately after the engine is started. It has a function of a prohibiting means H for judging the operation state of the load and prohibiting the detection of fuel volatility when the external load is operating.

In the fuel injection control by the controller 20, when it is detected that the fuel used is a heavy fuel having low volatility at the time of starting the engine, the fuel supply amount in a cold state (warm-up increase) is increased. It is configured to perform a correction control that increases and decreases as the engine water temperature rises, and a correction that increases the acceleration increase during acceleration.

More specifically, the determination of the fuel property is performed by detecting a change in the engine speed after a cold start, and a time chart thereof will be described with reference to FIG. In order to start the engine, start the starter motor at point a and start cranking, the engine speed starts to rise, ignites the fuel and further rises when it reaches a complete explosion state, and after the start, it decreases once The process proceeds to the engine speed (target value No) corresponding to the engine water temperature, the throttle opening, and the like.

In the state of decrease from the point b, the heavy fuel has a low fuel volatility as compared with the normal fuel, and the decrease speed is high in accordance with the lean air-fuel ratio. If the number of rotations falls below the set number of revolutions Nd or less after a predetermined time t has elapsed, it is determined that heavy fuel is being supplied. Further, even if the speed of decrease of the rotational speed is lower than the above condition, the engine rotational speed is not lower than the lower limit rotational speed N
If it is lower than 3, it is determined that the supply is heavy fuel.

The processing of the controller 20 will be described with reference to the flowcharts of FIGS. FIG. 4 shows a fuel property determination routine.
At step 1, various signals are read, and at steps S2 to S7, it is determined whether a fuel property detection condition for determining fuel volatility is satisfied.

First, in step S2, the starter switch 25
It is determined whether it is within a predetermined time (approximately 60 seconds) since the switch was turned on. Outside this period, there is a possibility that there is a rotation fluctuation accompanying a load fluctuation corresponding to a change in the operating state, and the possibility of false detection will increase. Therefore, volatile detection is performed only during this period.

In step S3, it is determined whether or not the engine coolant temperature Tw is in a cold state within a predetermined range Ta to Tb. The lower limit temperature Ta is about 0 ° C. In a temperature lower than this temperature, the combustion state is unstable, and even with normal fuel, the rotation speed decreases, and the possibility of erroneous detection increases. On the other hand, the upper limit temperature Tb is about 40-
At 60 ° C, when the engine is warm starting above this temperature, the fuel is warmed and vaporized, and the vaporization difference between heavy fuel and normal fuel is small.
In addition, since the amount of increase in fuel is small and even with normal fuel, the rotation decrease after the engine rotation is increased is large and the possibility of erroneous detection is large, the volatility detection is performed only in the predetermined range Ta to Tb.

Further, in step S4, the starter switch
It is determined whether the starter is operating and cranking is on during 25, and during this cranking, even if the engine is started, the rotation speed may be low and may be lower than the lower limit rotation speed N3, Avoid volatile detection.

Next, step S5 determines whether or not the throttle valve 12 is fully closed, and step S6 determines whether or not the throttle valve 12 is in a neutral state. Volatility is detected when the throttle valve 12 is fully closed and in neutral when there is a possibility of erroneously determining a decrease in rotation at the time of starting or shifting.

On the other hand, in step S7, it is determined whether or not the external load is operating in the ON state by the air conditioner switch 27, the power steering switch 28, the electric load switch 29, the inhibitor switch.
The operation state of the external load is determined by the signal of 30 when the compressor for the air conditioner is operating and the driving load is operating, and the driving load of the oil pump for power steering is controlled according to the steering operation. Is acting, when the driving load of the alternator corresponding to the increase of the electric load such as the lighting of the head lamp is increasing,
In addition, when the torque converter load is acting due to the shift of the automatic transmission to the driving range such as the D range, etc., when the external load is acting, the rotation is reduced and the possibility of erroneous detection is large. From volatility detection.

When the above fuel property detection condition is satisfied, determination of volatility is performed in steps S8 to S17.
First, in step S8, the engine speed N is set to 1250 rpm (N
c) Determine whether or not: This judgment is YES
, At step S9, the previous engine speed Ni-
Determine if 1 is higher than 1250 rpm. This determination is also YES, and when the engine speed N becomes 1250 rpm or less for the first time, a predetermined time (for example, 2 seconds) is set to the timer t in step S10.

Thereafter, in response to a decrease in the engine speed N, the process proceeds to step S11 with a NO determination in step S9, the timer t is decremented, and the timer t is decremented in step S12.
Is determined to be 0. If the determination in step S12 is YES and the predetermined time has elapsed, it is determined in step S13 whether or not the engine speed has decreased to 1000 rpm (Nd) or less. Since the rotation speed has decreased to a predetermined value or more during the time t, it is determined that the fuel volatility is low, and step S15 is performed.
The fuel flag G is set to 1 to perform heavy determination. On the other hand, if the fuel pressure has not decreased to 1000 rpm or less even after the elapse of the predetermined time t, it is determined that the fuel volatility is not low, and the fuel flag G is set to 0 in step S16.

If the engine speed N at the predetermined time t decreases, the engine speed N itself becomes the lower limit speed N3 at step S14 even if it is not determined that the fuel is heavy.
If it is determined that the fuel has dropped below (for example, 500 rpm), it is determined that the fuel is heavy and the fuel flag G is set to 1 in step S15.

When the heaviness judgment is completed, step S17
Sets the determination completion flag F to 1 and terminates this routine based on the determination in step S18. Until that time, the detection is continued with a NO determination in step S18.

Next, in the fuel control routine of FIG. 5, after the control is started, various signals are read in step S21, and the basic injection amount Tp is calculated in step S22 based on the signals.
The basic injection amount Tp is a fuel amount corresponding to the intake charge amount obtained by dividing the intake air amount by the engine speed and multiplying the result.

Then, at step S23, the fuel flag G is set.
Is set to 1 or not, and if the volatility of the fuel set to 1 is low, the warm-up increase coefficient Cw is set to the warm-up increase coefficient Cw1 for heavy fuel in step S24. In the case of normal fuel whose fuel flag G has been reset to 0, the warm-up increase coefficient Cw is set to the warm-up increase coefficient Cw2 for normal fuel in step S25. As shown in FIG. 6, the warm-up increasing coefficients Cw1 and Cw2 are set in correspondence with the engine coolant temperature Tw, and the correction coefficient Cw increases as the coolant temperature decreases in a cold state of about 60 ° C. or lower.
That is, the fuel increase is set to be large, and the warm-up increase coefficient Cw1 for heavy fuel is set to be larger than the warm-up increase coefficient Cw2 for normal fuel, and the fuel increase is performed in a state where the fuel volatility is low. To make it bigger.

Step S26 is for judging the acceleration state from a change in the throttle opening and the like. When accelerating at a predetermined value or more, it is judged in step S27 whether the fuel flag G is set to 1 or not. When the volatility of the fuel set to is low, the acceleration increase coefficient C is determined in step S28.
While acc is set to the acceleration increase coefficient Cacc1 for heavy fuel, if the normal fuel is reset to 0, the acceleration increase coefficient Cacc is set to the acceleration increase coefficient Cacc2 for normal fuel in step S29. Further, if the determination in step S26 is NO and the vehicle is not accelerating, the acceleration increase coefficient Cacc is set to 0 in step S30. The acceleration increase coefficient Cacc1 for heavy fuel is the warm-up increase coefficient Cacc2 for normal fuel.
It is set to a larger value to compensate for lean air-fuel ratio during acceleration due to low volatility.

Step S31 is for calculating other correction amounts Ce such as a feedback correction value and a learning value.
The final injection pulse T is calculated in step S32 based on the correction amount Ce, the basic injection amount Tp, the warm-up increasing coefficient Cw, and the acceleration increasing coefficient Cacc, and the result is output to the injector 14 in step S33 to obtain the predetermined amount. This is to execute fuel injection.

According to the above-described operation, the external load is activated when the fuel property is detected in the determination of the volatility of the fuel from the decrease characteristic of the engine speed within a predetermined period after the cold start. If this is the case, the detection of volatility is prohibited to prevent erroneous detection, and the volatility is not detected under other conditions such as a decrease in the number of revolutions not caused by fuel volatility. Thus, the fuel property can be detected with high reliability and the warm-up amount and the acceleration amount can be corrected based on the detected fuel property, thereby ensuring good traveling performance.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of a fuel property detection device for an engine of the present invention.

FIG. 2 is a schematic configuration diagram of an engine including a fuel property detection device according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing an example of a change in engine speed at the time of fuel property detection.

FIG. 4 is a flowchart of a main part for explaining a heavy-weight determination process of the controller.

FIG. 5 is a main part flowchart for explaining a fuel control process of a controller.

FIG. 6 is a characteristic diagram showing setting characteristics of a warm-up increase correction coefficient;

[Explanation of symbols]

 1 Engine body 8 Intake passage 12 Throttle valve 20 Controller A Engine rotation detecting means B Fuel property detecting means D External load detecting means H Prohibiting means

Claims (1)

(57) [Claims] 1. A fuel property comprising: engine rotation detecting means for detecting a change in engine speed; and fuel property detecting means for detecting volatility of fuel based on a decrease in engine speed based on a signal from the engine speed detecting means. An external load detecting means for detecting an operation state of an external load acting on an engine, receiving a signal from the external load detection means, and detecting a fuel by the fuel property detecting means when the external load is in an operation state. A fuel property detecting device provided with a prohibiting means for prohibiting detection of volatility of the fuel.