JP5392240B2 - Fuel property determination device - Google Patents

Description

  The present invention relates to a fuel property determination device that determines the fuel property of fuel supplied to an engine.

  2. Description of the Related Art Conventionally, a technique for automatically determining a fuel property related to volatility of fuel supplied to an engine and utilizing it for engine fuel injection control is known. In general, the volatility of heavy fuel containing a large amount of heavy components is lower than that of standard fuel, and the ratio of fuel adhering to the intake port or intake valve is large. On the other hand, in the case of a light fuel with a low content of heavy components, the volatility is high and the rate of fuel adhesion is small. Therefore, by correcting the fuel injection amount in accordance with such characteristics, it becomes possible to accurately control the combustion state in the engine. For example, Patent Document 1 describes what determines the current fuel property based on vehicle acceleration / deceleration information, air-fuel ratio information, and the latest determination fuel property.

Japanese Patent Application Laid-Open No. 6-200806

  By the way, in the case of heavy fuel, there is a tendency that the amount of fuel volatilization from the intake port decreases during acceleration of the vehicle and the air-fuel ratio tends to become lean. However, immediately before the acceleration operation, the engine load is low and the negative pressure in the intake port is sufficiently ensured. Since the ratio of the volatilized fuel in the intake air is high, the degree of leaning is difficult to increase. Therefore, there is a problem that it is difficult to accurately determine the fuel property due to the difference in air-fuel ratio from the case where standard fuel is used.

One of the purposes of this case was created in view of the above-described problems, and is to accurately grasp the properties of fuel supplied to the engine.
The present invention is not limited to this purpose, and is a function and effect derived from each configuration shown in the embodiments for carrying out the invention described later, and other effects of the present invention are to obtain a function and effect that cannot be obtained by conventional techniques. Can be positioned.

(1) The fuel property determination device disclosed herein includes air-fuel ratio detection means for detecting the exhaust air-fuel ratio of the engine, and opening amount detection means for detecting the opening amount of the throttle valve of the engine. And determining means for determining a fuel property of the fuel supplied to the engine based on the exhaust air / fuel ratio detected by the air / fuel ratio detecting means when the opening amount detected by the opening amount detecting means is decreased. Prepare.
Further, a determination value calculating means for adding or subtracting a predetermined value to a determination value corresponding to the fuel property according to the exhaust air / fuel ratio detected by the air / fuel ratio detection means, and a determination value calculating means Fuel property determining means for determining the fuel property based on the determination value.
The determination value calculating means adds the predetermined value to the determination value when the exhaust air-fuel ratio is less than a first threshold value, and a second value where the exhaust air-fuel ratio is larger than the first threshold value. When the value is equal to or greater than the threshold value, the predetermined value is subtracted from the determination value.

  In addition, based on the exhaust air-fuel ratio, an index value that correlates with the fuel properties such as volatility and evaporation rate of the fuel, a ratio and a ratio of heavy components contained in the fuel, and the like may be determined. In other words, the “fuel properties” referred to in this case includes the volatility of the fuel and various properties related to volatility. Specific examples of judgment targets by the judgment means include the fuel's severity, volatility, The content or content rate of the quality component, the evaporation rate of the fuel, and the like.

(2) In addition, a water temperature detection unit that detects a cooling water temperature of the engine is provided, and the determination value calculation unit includes at least the first threshold value and the temperature according to the cooling water temperature detected by the water temperature detection unit. It is preferable to change one of the second threshold values.
( 3 ) Moreover, it is preferable that the said determination means determines the said fuel property based on the magnitude | size of the rich peak of the said exhaust air-fuel ratio which generate | occur | produces with the reduction | decrease of the said opening amount.
( 4 ) Further, a change amount calculating means for calculating a change amount of the opening amount when the throttle valve is closed, and a change rate calculation for calculating a change rate per unit time of the opening amount when the throttle valve is closed. Start condition determination for determining success or failure of a start condition for determining the fuel property based on the change amount calculated by the means and the change amount calculation means and the change rate calculated by the change rate calculation means Means. In this case, it is preferable that the determination unit determines the fuel property when the start condition is satisfied by the determination unit.

According to the disclosed fuel property determination device, it is possible to increase the proportion of the volatile fuel component contained in the exhaust air / fuel ratio by using the negative pressure in the port by the determination based on the exhaust air / fuel ratio when the throttle valve is closed. it can. Thereby, the air-fuel ratio fluctuation due to the fuel property becomes clear, and the fuel property can be accurately determined. In addition, the amount of unburned hydrocarbons from the engine at the time of starting can be reduced by appropriately controlling the amount of fuel at the time of starting by heavy fuel determination.
Further, by determining the fuel property based on the determination value corresponding to the fuel property, it is possible to reduce the influence of temporary exhaust air-fuel ratio fluctuations, errors, etc., and to accurately determine the fuel property. . Furthermore, when adding or subtracting the determination value, the range from the first threshold value to the second threshold value functions as a dead zone, so that the fuel property determination accuracy can be further improved.

It is a figure which illustrates the block structure of the fuel property determination apparatus which concerns on one Embodiment, and the structure of the engine to which this fuel property determination apparatus was applied. It is a graph which illustrates the variation | change_quantity and variation | change_rate of the throttle opening calculated by this fuel property determination apparatus. It is a graph which illustrates the conditions for judging fuel properties with this fuel property judging device. It is a graph which illustrates the relationship between the threshold value for rich peak determination set with this fuel property determination apparatus, and cooling water temperature. It is an example of the flowchart of control implemented by this fuel property determination apparatus. It is a graph which illustrates the fluctuation | variation of the exhaust air fuel ratio of the engine to which this fuel property determination apparatus was applied, engine speed, volumetric efficiency, and throttle opening.

  A fuel property determination apparatus will be described with reference to the drawings. Note that the embodiment described below is merely an example, and there is no intention to exclude various modifications and technical applications that are not explicitly described in the following embodiment.

[1. Device configuration]
The fuel property determination device of the present embodiment is applied to the on-vehicle gasoline engine 10 (hereinafter simply referred to as the engine 10) shown in FIG. Here, one of the cylinders (cylinders) provided in the multi-cylinder engine 10 is shown. A piston 16 connected to a crankshaft 17 via a connecting rod is fitted in the cylinder 15 so as to be slidable back and forth. The connecting rod is a link member that converts the reciprocating motion of the piston 16 into the rotational motion of the crankshaft 17.

  An intake port 11 and an exhaust port 12 are connected to the top surface of the combustion chamber on the cylinder head side. An intake valve 13 is provided at the inlet of the intake port 11, and an exhaust valve 14 is provided at the inlet of the exhaust port 12. The intake port 11 and the combustion chamber are communicated or closed by opening and closing the intake valve 13, and the exhaust port 12 and the combustion chamber are communicated or blocked by opening and closing the exhaust valve 14. The upper ends of the intake valve 13 and the exhaust valve 14 are respectively connected to a rocker shaft (not shown), and are individually reciprocated in the vertical direction by the rocker shaft swinging.

  A fuel supply injector 18 is provided inside the intake port 11. The amount of fuel injected from the injector 18 and the injection timing thereof are controlled by an engine ECU 20 described later.

A throttle valve 9 (ETV, Electric Throttle Valve), a throttle position sensor 6 and an air flow sensor 7 (AFS, Air Flow Sensor) are provided in the intake passage upstream of the injector 18. The throttle valve 9 is an electronically controlled throttle valve for changing the intake amount of air introduced into the cylinder 15 by changing its opening. The throttle position sensor 6 is a sensor with a built-in variable resistor corresponding to the throttle opening T of the throttle valve 9. Since the information on the output current value (or output voltage value) of the throttle position sensor 6 varies according to the throttle opening degree T, the throttle opening degree T is grasped based on this. Information output from the throttle position sensor 6 is transmitted to the engine ECU 20.
The air flow sensor 7 is a sensor that detects an intake air flow rate Q introduced into the cylinder 15. The throttle opening degree T and the intake air flow rate Q detected here are transmitted to an engine ECU 20 described later.

  On the other hand, an air-fuel ratio sensor 4 (for example, an oxygen concentration sensor or LAFS) is provided in the exhaust passage connected to the exhaust port 12. The air-fuel ratio sensor 4 detects information (for example, oxygen concentration, HC concentration, etc.) corresponding to the exhaust air-fuel ratio of the engine 10, and the information detected here is also transmitted to the engine ECU 20. Note that the attachment position of the air-fuel ratio sensor 4 may be in the exhaust manifold of the engine 10 or in the exhaust passage on the downstream side. In the case of a vehicle in which a catalyst device is interposed on the exhaust passage, it is preferable that the vehicle is provided upstream of the catalyst device in order to ascertain an accurate exhaust air-fuel ratio.

The engine 10 is provided with a crank angle sensor 8 that detects an angle θ _CR of the crankshaft. Information on the crankshaft angle θ _CR detected by the crank angle sensor 8 is transmitted to an engine ECU 20 described later. The engine speed Ne can be grasped from the amount of change in the angle θ _CR per unit time. Therefore, the crank angle sensor 8 has a function as means for detecting the engine speed Ne of the engine 10. The engine speed Ne may be calculated by the engine ECU 20 based on the crankshaft angle θ _CR detected by the crank angle sensor 8 or may be calculated inside the crank angle sensor 8.

  A water temperature sensor 5 having a characteristic that the resistance value changes according to the temperature W of the engine coolant is provided at an arbitrary position of the engine 10. Since the information of the output current value (or output voltage value) of the water temperature sensor 5 varies according to the temperature W, the temperature W is grasped based on this. Information output from the water temperature sensor 5 is transmitted to the engine ECU 20.

[2. Control configuration]
The engine ECU 20 (Engine-Electronic Control Unit) is an electronic control device that comprehensively manages the fuel injection amount and ignition timing supplied to each cylinder including the cylinder 15 shown in FIG. For example, it is configured as an LSI device or an embedded electronic device in which a microprocessor, ROM, RAM, etc. are integrated. Hereinafter, the heavy determination control for determining the fuel property (for example, the heavy degree) based on the exhaust air-fuel ratio of the engine 10 will be described.

  The engine ECU 20 is provided with a detection unit 1, a calculation unit 2, and a determination unit 3 as software or hardware that realizes a function for performing heavy determination control.

[2-1. Detection unit]
The detection unit 1 detects various types of information used for heavy determination control, and is provided with an exhaust air-fuel ratio detection unit 1a, a water temperature detection unit 1b, and a throttle opening amount detection unit 1c.

  The exhaust air-fuel ratio detection unit 1a (air-fuel ratio detection means) detects or calculates the exhaust air-fuel ratio of the exhaust discharged from the cylinder 15 based on the information detected by the air-fuel ratio sensor 4, and detects the rich peak R or It is to calculate. The exhaust air / fuel ratio detection unit 1a is provided with a temporary memory (not shown) (for example, DRAM, SRAM, etc.), which not only constantly grasps the latest exhaust air / fuel ratio but also the latest fixed time (for example, several seconds to several hundreds). The exhaust air / fuel ratio in milliseconds) is stored. The rich peak R here means the value of the minimum exhaust air-fuel ratio (peak top exhaust air-fuel ratio) when the exhaust air-fuel ratio temporarily becomes rich during vehicle deceleration. The rich peak R is the smallest value of the exhaust air / fuel ratio within a predetermined time before and after the time when the change in the decreasing direction of the throttle opening T is completed.

  The water temperature detection unit 1b (water temperature detection means) detects or calculates the temperature W (cooling water temperature) of the engine cooling water based on information transmitted from the water temperature sensor 5. Similarly, the throttle opening amount detection unit 1c (opening amount detection means) detects or calculates the throttle opening T based on the information detected by the throttle position sensor 6. The exhaust air / fuel ratio, rich peak R, temperature W, and throttle opening T detected or calculated by the detector 1 are transmitted to the calculator 2.

  The information may be detected or calculated outside the engine ECU 20. For example, the configuration may be such that the temperature W of the engine coolant is directly detected by the water temperature sensor 5, or the main body that detects the exhaust air / fuel ratio may be the air / fuel ratio sensor 4.

[2-2. Calculation unit]
The calculation unit 2 performs a calculation related to heavy determination control, and includes a change amount calculation unit 2a, a change rate calculation unit 2b, and a point calculation unit 2c.

The change amount calculator 2a (change amount calculator) calculates the change amount of the throttle opening T. Here, as shown in FIG. 2, the opening degree change from the throttle opening degree T starts changing until the change is completed throttle opening change amount T _D (hereinafter simply referred to as a variation T _D ). For example, if the state where the change in the throttle opening T is within a preset minute range, such as before time t _A or after time t _B in FIG. the amount T _D will exit from one stable state corresponding to the total amount of the throttle opening T is changed between up to the next stable state. Accordingly, there may be a case where the change rate of the throttle opening T changes in the middle.

The sign of the variation T _D which is calculated, the amount of change is positive in the decreasing direction of the throttle opening degree T, the negative variation in the increasing direction of the throttle opening T. Note that the change amount calculation unit 2a may calculate only the change amount of the throttle opening T when the throttle valve 9 is closed.
The change rate calculation unit 2b (change rate calculation means) calculates a change rate (amount of change per predetermined time) of the throttle opening T. Here, as shown in FIG. 2, the gradient with time change of the throttle opening T (that is, the slope of the graph) is calculated as the throttle opening change rate T _V (hereinafter simply referred to as the change rate T _V ). The sign of the change rate T _V that is calculated is reduced during gradient is positive in the throttle opening degree T, the negative gradient during increase of the throttle opening T.

Predetermined time according to the operation of the change rate T _V here, it may be a preset time may be the time that is set according to the engine RPM Ne. For example, it is conceivable that the number of intakes within the predetermined time is made equal by setting the predetermined time shorter as the engine speed Ne is higher. In this case, the rate of change T _V can also be regarded as corresponding to the rate of change of the exhaust air-fuel ratio at the same number of intakes.

In the stable state in FIG. 2, the rate of change T _V is close to 0, and the rate of change T _V is calculated as a positive value from time t _A to time t _B. Change rate T _V, for example, a positive value when the depression returning operation of the accelerator pedal is made by the driver, the stepping back operation that value as an abrupt increases. Conversely, when the accelerator pedal is depressed, the value becomes negative, and the value decreases as the depression becomes more rapid. The change rate calculating portion 2b may now be calculated only change rate T _V of the throttle opening T during closing of the throttle valve 9.

  The point calculator 2c (determination value calculator) calculates a determination point P (determination value) corresponding to the fuel property when the determination unit 3 described later determines that the fuel is heavy fuel. is there. The determination point P is an index value indicating that the larger the value, the higher the possibility that the fuel property is heavy, and the smaller the value, the lower the possibility that the fuel property is heavy fuel. In this embodiment, it is not determined whether the fuel property is heavy by only one determination, but the determination is repeated a plurality of times, and the determination point P is increased or decreased each time. The fuel properties are judged based on the above. A specific method of adding / subtracting the determination point P will be described later.

  The point calculation unit 2c is a non-volatile backup memory (for example, ROM, FRAM, etc.) for storing the determination point P regardless of the on / off state of the power source (ignition switch) of the vehicle on which the engine 10 is mounted. Flash memory). Thereby, even when fuel is supplied or replenished or after the engine 10 is restarted, the calculated value of the determination point P is maintained.

[2-3. Judgment unit]
The determination unit 3 (determination means) performs determination control related to heavy determination control, and includes a start condition determination unit 3a and a fuel property determination unit 3b.
The start condition determination unit 3a (start condition determination means) determines the start condition for the heavy determination control. In the present embodiment, the fuel property is determined based on the exhaust air / fuel ratio when both of the following conditions 1 and 2 are satisfied.
Condition 1. 1. When the throttle valve 9 is closed (when the throttle opening T is decreased). The value of the change amount T _D and the rate of change T _V be a predetermined condition is satisfied

It can be considered that the above conditions 1 and 2 are simultaneously determined using a map as shown in FIG. 3, for example. In this case, when the point on the plane coordinate system in which the value of the change amount T _D is the x coordinate and the value of the change rate T _V is the y coordinate is located within the determination region in FIG. It is assumed that the condition is satisfied. As shown in FIG. 3, the determination area is set to a quadrant in which both the change amount T _D and the change rate T _V are positive. Further, the larger the change amount T _D, the smaller the change rate T _V is included in the determination region, or the larger the change rate T _V , the smaller the change amount T _D is included in the determination region. As described above, a boundary line between the determination area and the non-determination area is set.

In addition, the success or failure of the above conditions 1 and 2 may be determined only by calculation without using the map as shown in FIG. For example, the amount of change T _D and the rate of change T _V There are both positive, and their multiplication values start condition of heavy determination control when a predetermined value or more is to be established. Alternatively, by preparing a numerical map that is stored the lower limit value of the rate of change T _V the starting condition of the heavy determination control for each variation T _D is established in advance, the actual amount of change T _D and changes the numerical map it is conceivable to determine the starting conditions of heavy determination control by using the rate T _V.

Here, the significance of setting the start condition of the heavy determination control will be described.
In general, when a low-volatile fuel having a higher content of heavier components than a standard fuel is used, the exhaust air-fuel ratio becomes lean during acceleration operation (for example, when the accelerator pedal is depressed). However, it has been pointed out that it is difficult to accurately detect the degree of leanness of the exhaust air-fuel ratio for the following reasons.

Reason 1. Immediately before the acceleration operation, the engine 10 is often in a state of low load and a negative pressure in the intake port 11 is ensured. High fuel ratio.
Reason 2 During acceleration, there is a so-called “intake delay” from when the throttle opening T changes until the intake air actually flows into the cylinder 15, and this “intake delay” time is used to change the throttle opening T. Since the correction of the fuel injection amount is performed based on this, the air-fuel ratio in the cylinder 15 is easily optimized, and as a result, the increase range of the exhaust air-fuel ratio is reduced.

Therefore, it is difficult to grasp the lean tendency derived from the fuel properties from the exhaust air-fuel ratio at the time of acceleration operation. On the other hand, if a deceleration operation (for example, an accelerator pedal depressing operation) is performed in a state where the engine 10 is heavily loaded and the amount of fuel adhering to the intake port 11 is relatively large, the negative pressure in the intake port 11 is reduced. Rises and the adhering fuel rapidly vaporizes, and accordingly, the exhaust air-fuel ratio becomes rich. The degree of enrichment at this time increases as the throttle valve 9 closes rapidly. Therefore, in the present embodiment, “when the throttle valve 9 is closed” is identified by the condition 1, and further, the state where the change amount T _D and the change rate T _V are somewhat large is identified by the condition 2. As a result, the fuel property is determined by referring to the exhaust air / fuel ratio detected in a state where the enrichment tendency derived from the fuel property is easily identified, rather than referring to all exhaust air / fuel ratios.

  The fuel property determination unit 3b (fuel property determination means) has two types of functions. The first function is to tentatively determine whether or not the fuel supplied into the cylinder 15 is heavy fuel when the conditions 1 and 2 are satisfied in the start condition determination unit 3a, and based on the tentative determination result. This is a function for causing the point calculation unit 2c to calculate the determination point P. The second function is a function of making a final fuel property determination based on the determination point P calculated by the point calculation unit 2c.

First, the first function will be described. The fuel property determination unit 3b calculates a rich peak determination threshold value used for calculating the determination point P from the engine cooling water temperature W detected or calculated by the water temperature detection unit 1b. In the present embodiment, two types of threshold values, the first threshold value J _{FUELRP_AF1} and the second threshold value J _{FUELRP_AF2} , are used. Both the first threshold value J _{FUELRP_AF1} and the second threshold value J _{FUELRP_AF2} are set to be smaller (to the rich side) as the water temperature W is lower, and set to a larger value (to the lean side) as the water temperature W is higher. On the other hand, at the same water temperature W, the first threshold value J _{FUELRP_AF1} is set to a value smaller than the second threshold value J _{FUELRP_AF2} .

For example, as shown in FIG. 4, each value may be set so that the difference between the first threshold value J _{FUELRP_AF1} and the second threshold value J _{FUELRP_AF2} becomes a constant value regardless of the water temperature W. If the water temperature W is controlled to be in the range of less than the predetermined upper limit temperature W _A by a cooling device such as a radiator, not shown, a first threshold J _{FUELRP_AF1} and second threshold J _{FUELRP_AF2} also limit the water temperature W Set it within the range of _A or less. The value of the upper limit temperature W _A in the first threshold J _{FUELRP_AF1} and second threshold J _{FUELRP_AF2} is set to the size of the rich side than the exhaust air-fuel ratio of stoichiometric.

The first threshold value J _{FUELRP_AF1} determines whether the magnitude of the rich peak R detected or calculated by the exhaust air / fuel ratio detection unit 1a is the rich peak R when the low-volatile fuel is used. For the threshold. On the other hand, the second threshold value J _{FUELRP_AF2} is a threshold value for determining whether or not the magnitude of the rich peak R is the rich peak R when a standard fuel is used.

The fuel property determination unit 3b compares the value of the rich peak R detected or calculated by the exhaust air / fuel ratio detection unit 1a with the above threshold value, and the value of the rich peak R is determined from the first threshold value J _{FUELRP_AF1} . If the value is smaller, it is temporarily determined that the fuel is likely to be heavy fuel. On the other hand, when the value of the rich peak R is larger than the second threshold value J _{FUELRP_AF2} , it is temporarily determined that the fuel is likely to be a standard fuel (not a heavy fuel). The temporary determination result here is transmitted to the point calculation unit 2c.

In response to this, the point calculation unit 2c calculates the determination point P. First, when there is a high possibility that the fuel is heavy fuel, a predetermined value (for example, 1) is added to the determination point P at that time, and the determination point P is increased. For example, the initial value of the determination point P is P = 0, and the value range is 0 ≦ P ≦ predetermined point P ₀ . On the other hand, when there is a high possibility that the fuel is a standard fuel, a predetermined value (for example, 1) is subtracted from the determination point P at that time, and the determination point P is decreased. The point calculation unit 2c repeatedly performs such calculation every time a temporary determination is transmitted from the fuel property determination unit 3b.

  Here, if we focus on the number of times that it is determined that the fuel is likely to be heavy fuel and the number of times that it is determined that the fuel is likely to be standard fuel, the former is more than the latter Otherwise, the value of the determination point P will not continue to increase. Therefore, the influence of irregular fluctuation, disturbance, noise, etc. of the rich peak R that does not depend on the fuel property is suppressed, and the accuracy of determining the fuel property is improved.

Next, the second function will be described. The fuel property determination unit 3b determines that the fuel is heavy fuel when the determination point P calculated by the point calculation unit 2c is equal to or higher than a predetermined point P ₀ set in advance, and starts the engine 10 ( (Next start)) Various parameters for fuel control immediately after start, acceleration / deceleration increase / decrease amount at cold start, etc. are changed. For example, control is performed such that the fuel injection amount at the time of acceleration is increased or the fuel injection amount immediately after starting is increased as compared with the case where standard fuel is used. The determination result here may be transmitted to the point calculation unit 2c and stored in the nonvolatile backup memory.

[3. flowchart]
FIG. 5 illustrates a flowchart relating to heavy determination control executed by the engine ECU 20. It is repeatedly performed at a predetermined cycle inside the engine ECU 20.
In Step A10, the crankshaft angle θ _CR is detected by the crank angle sensor 8, and the engine speed Ne is acquired. The engine speed Ne acquired here is transmitted to the change rate calculation unit 2b. In step A20, the information detected by the water temperature sensor 5 is transmitted to the engine ECU 20, and the water temperature W of the engine cooling water is acquired by the water temperature detection unit 1b. The water temperature W acquired here is transmitted to the start condition determination unit 3a. In the subsequent step A30, information detected by the throttle position sensor 6 is transmitted to the engine ECU 20, and the throttle opening degree detector 1c acquires the throttle opening degree T.

In step A40, the rate of change T _V of the throttle opening T is computed in the change rate calculating section 2b. Change rate T _V is calculated as a change amount of the throttle opening T within a predetermined time period. Further, the predetermined time relating to this calculation may be set according to the engine speed Ne calculated in step A10, or a preset time may be set.
In step A50, the amount of change T _D of the throttle opening T is computed in the change amount calculating unit 2a. Variation T _D is calculated as the opening amount of change up to the re-stable state from the time when the throttle opening T is escaped the stable state begins to change. Step A40 and the change rate T _V and the change amount T _D calculated in step A50 is transmitted to the start condition determining section 3a.

In step A60, the start condition determination unit 3a determines whether or not the conditions 1 and 2 are satisfied. Here, using a map as shown in FIG. 3, it is determined whether or not the point whose coordinates are defined by the change amount T _D and the change rate T _V is located in the determination region. Here, if the position is within the determination area, the condition 1 and the condition 2 are satisfied, so the process proceeds to step A70, and if the position is not located, the flow is terminated.

In step A70, the first threshold value J _{FUELRP_AF1} and the second threshold value J _{FUELRP_AF2} are set based on the water temperature W acquired by the water temperature detection unit 1b in the fuel property determination unit 3b. In the subsequent step A80, the rich peak R is detected by the exhaust air-fuel ratio detection unit 1a. In step A90, the fuel property determination unit 3b determines whether or not the rich peak R is smaller than the first threshold value J _{FUELRP_AF1} . Here, if R <J _{FUELRP_AF1,} it is temporarily determined that the fuel is highly likely to be heavy fuel, and the process proceeds to step A100. In step A100, the point calculation unit 2c increments the determination point P (P + 1 is substituted for P), and the process proceeds to step A110. If R <J _{FUELRP_AF1} is not satisfied in step A90, step A100 is skipped and the process proceeds to step A110.

In Step A110, the fuel property determination unit 3b determines whether or not the rich peak R is greater than the second threshold value J _{FUELRP_AF2} . Here, when R> J _{FUELRP_AF2,} it is temporarily determined that the fuel is highly likely to be a standard fuel, and the process proceeds to step A120. In step A120, the determination point P is decremented in the point calculation unit 2c (P-1 is substituted for P), and the process proceeds to step A130. If R> J _{FUELRP_AF2} is not satisfied in step A110, step A120 is skipped and the process proceeds to step A130.

From the determination conditions in step A90 and step A110, when J _{FUELRP_AF1} ≦ R ≦ J _{FUELRP_AF2} , the determination point P is maintained at the same value without changing. Accordingly, the range of the first threshold value J _{FUELRP_AF1} or more and the second threshold value J _{FUELRP_AF2} or less functions as a dead zone of the rich peak R where the addition / subtraction of the determination point P is not performed.
At step A130, the fuel property determination unit 3b, input point P is equal to or a predetermined point P ₀ or not is determined. Here, when P ≧ P ₀ , the process proceeds to step A140, and it is determined that the fuel is heavy fuel. In this case, various parameters for fuel control, the fuel injection amount, and the like are changed so as to match the fuel properties, and the fuel amount injected from the injector 18 and the injection timing are controlled. On the other hand, if P <P ₀ in step A130, the process proceeds to step A150, where it is determined that the fuel is not a heavy fuel (a standard fuel), and the fuel is controlled in accordance with the standard fuel. Is done.

[4. Action]
FIG. 6 illustrates fluctuations in the exhaust air / fuel ratio, the engine speed Ne, the volume efficiency Ec, and the throttle opening T when the accelerator pedal is depressed back in a vehicle equipped with the engine 10. When the accelerator pedal is depressed again at time t ₁ , the throttle opening T begins to deviate from the stable state and begins to change in a decreasing direction, and the change rate calculating unit 2b calculates the change rate T _V. Further, after the time t ₁ , the engine speed Ne and the volume efficiency Ec also gradually decrease.

When stepping return operation of the accelerator pedal at time t ₂ is completed, the throttle opening T is again stable state, the amount of change T _D at variation calculating section 1a is calculated. At this time, the start condition determination unit 3a determines the start condition of the heavy determination control. Wherein a change amount T _D and the rate of change T _V condition 1, when satisfying the condition 2, the rich peak R before and after the time t ₂ is detected in the exhaust gas air-fuel ratio detecting unit 1a.

Here, when the fuel is heavy fuel, the negative pressure in the intake port 11 rises and the attached fuel is rapidly vaporized. Therefore, as shown by the solid line in FIG. 6, the exhaust air-fuel ratio becomes greatly rich, and the value of the rich peak R becomes R ₁ . Note that the value of the rich peak R increases as the throttle valve 9 closes rapidly. On the other hand, in the case of a standard fuel, since the amount of attached fuel in the intake port 11 is smaller than that of heavy fuel, the degree of enrichment of the exhaust air-fuel ratio is small as shown by the broken line in FIG. Therefore, the value of the rich peak R becomes R ₂ (lean side) larger than R ₁ .

In the fuel property determination unit 3b, the first threshold J _{FUELRP_AF1} and second threshold J _{FUELRP_AF2} is set based on the coolant temperature W of the engine coolant, these thresholds J _{FUELRP_AF1,} J _{FUELRP_AF2} and rich peak R The value is compared. In the case of a standard fuel, since the value R ₂ of the rich peak R is relatively small, the determination point P does not increase at least. Therefore, it is determined that the fuel is not a heavy fuel (a standard fuel).

On the other hand, when the fuel is heavy fuel, since the value R ₁ of the rich peak R is relatively large, the determination point P does not decrease at least. If R ₁ > J _{FUELRP_AF1} , it is temporarily determined that the fuel is likely to be heavy fuel, and the determination point P is incremented. After repeating this temporary determination, it is determined that the fuel is a heavy fuel only when the determination point P becomes P ≧ P ₀ , and the fuel is controlled according to the fuel properties.

[5. effect]
As described above, in the above-described fuel property determination device, the determination based on the exhaust air / fuel ratio when the throttle valve 9 is closed is performed as defined in the condition 1. As a result, the ratio of the volatile fuel component contained in the exhaust air / fuel ratio can be increased by utilizing the negative pressure in the intake port 11, and the variation in the air / fuel ratio due to the fuel properties becomes clear. Fuel properties such as quality can be accurately determined.

  Further, when heavy fuel is used, drivability can be ensured by performing fuel control that matches the fuel properties. On the other hand, when standard fuel is used, control can be performed without assuming heavy fuel. For example, it is not necessary to increase the fuel injection amount immediately after the engine 10 is started. Therefore, it is possible to optimize the fuel consumption, improve the fuel consumption, and improve the exhaust performance. For example, the amount of unburned hydrocarbons (HC) contained in the exhaust discharged from the engine 10 at the start can be reduced.

Further, in the fuel property determination device described above, the point calculation unit 2c includes a nonvolatile backup memory for storing the determination point P. Thereby, for example, even when the engine 10 is stopped and fuel is supplied, the determination point P before the fuel supply can be held and used for determination of the fuel property after refueling. Can do.
Even if heavy fuel is supplied to a vehicle that uses standard fuel, the standard fuel remains in the fuel line when the engine 10 is started immediately thereafter. Corresponding fuel control is not immediately required. In this sense, storing the determination point P regardless of the on / off state of the vehicle power supply (ignition switch) implements fuel control that matches the fuel properties that are actually supplied to the engine 10. It is reasonable in that it becomes possible. For example, the fuel property can be determined more accurately compared to a method for determining the property of the fuel stored in the fuel tank.

Further, in the above-described fuel property determination device, determination based on the rich peak R detected by the exhaust air / fuel ratio detection unit 1a is performed. Thereby, the degree of volatilization of the fuel can be clearly observed, and the fuel property can be accurately determined.
Further, in the fuel property determination device described above, the fuel property is determined with reference to the exhaust air / fuel ratio detected in a state in which the enrichment tendency derived from the fuel property is easily identified as defined in Condition 2. . That is, the start condition of the heavy determination control is determined based on the change amount T _D and the change rate T _V of the throttle opening. Thereby, the detection accuracy of the exhaust air-fuel ratio can be improved, and erroneous determination can be prevented. Therefore, further improvement in the determination accuracy of the fuel property can be expected.

In the above-described fuel property determination device, the fuel property is determined using the determination point P instead of determining the fuel property by a single determination. As a result, the influence of temporary exhaust air-fuel ratio fluctuations, errors, and the like can be reduced, and the fuel property can be accurately determined.
Further, in the above-described fuel property determination device, when the determination point P is _added or subtracted, a range from the first threshold value J _{FUELRP_AF1} to the second threshold value J _{FUELRP_AF2} is made to function as a dead zone of the rich peak R. Thereby, the influence of the irregular fluctuation | variation of the rich peak R which does not depend on fuel properties, disturbance, noise, etc. can be suppressed, and the determination accuracy of fuel properties can be further improved.

Further, in the above-described fuel property determination device, the first threshold value J _{FUELRP_AF1} and the second threshold value J _{FUELRP_AF2} are set in accordance with the engine coolant temperature W. As described above, by changing the reference for addition / subtraction of the determination point P according to the coolant temperature, the fuel property can be accurately determined in consideration of the temperature condition.
[6. Modifications etc.]
Regardless of the embodiment described above, various modifications can be made without departing from the spirit of the invention. Each structure of this embodiment can be selected as needed, or may be combined appropriately.

  In the above-described embodiment, the configuration in which the predetermined value is added to or subtracted from the determination point P in accordance with the content of the provisional determination is exemplified. However, the predetermined value to be added and the predetermined value to be subtracted are set to different values. Is also possible. For example, if the predetermined value at the time of addition of the determination point P is set larger than the predetermined value at the time of subtraction, it can be easily determined that the fuel is heavy fuel. In this case, it is possible to speed up the switching of the fuel control when changing the fuel properties from the standard fuel to the heavy fuel, and the setting is made with emphasis on drivability. On the other hand, if the predetermined value at the time of addition of the determination point P is set smaller than the predetermined value at the time of subtraction, it is difficult to determine that the fuel is heavy fuel (more carefully determine that it is heavy fuel). Can do. In this case, it is possible to speed up the switching of the fuel control when changing the fuel properties from heavy fuel to standard fuel, and the setting is focused on fuel consumption and exhaust performance.

Further, in the above-described embodiment, the description has been given of determining that the fuel is heavy fuel when the determination point P becomes equal to or higher than the predetermined point P ₀ set in advance. However, the predetermined point P ₀ is not necessarily a fixed value. Need not be. For example, the predetermined point P ₀ may be appropriately set according to various parameters related to the operating state of the engine 10 (engine speed Ne, outside air temperature, intake pressure, exhaust pressure, exhaust temperature, vehicle travel distance, etc.). .

  Further, in the above-described embodiment, the example of determining the size of the rich peak R using two types of threshold values is exemplified, but the size of the rich peak R is described in detail using a larger number of threshold values. It is also possible to judge. For example, if the amount of addition of the determination point P is increased as the size of the rich peak R is increased, the determination as to whether or not the fuel is heavy fuel can be determined more quickly.

  Moreover, in the above-mentioned embodiment, although what determines whether a fuel property is heavy was illustrated, it is also considered that the fuel property is determined by subdividing the determination content. For example, instead of dividing the fuel properties into standard and heavy ones, the fuel volatility (low volatility, medium volatility, high volatility, etc.) based on the size of the rich peak R It is also possible to evaluate an index value that correlates with the degree of heavyness of the fuel, such as the degree of easiness), the evaporation rate, the ratio and ratio of the heavy components contained in the fuel. In this case, the fuel property can be grasped more accurately, and the controllability of the engine 10 can be improved.

  In the above-described embodiment, the gasoline engine 10 is assumed. However, the application target of the fuel property determination device is not limited to this, and can be applied to a diesel engine. Further, the heavy determination control in the fuel property determination device can be performed even in a warm state (a state other than when the engine 10 is cold-started), and is implemented / not performed according to the engine coolant temperature W. There is no need to switch implementations.

1 Detection Unit 1a Exhaust Air / Fuel Ratio Detection Unit (Air / Fuel Ratio Detection Unit)
1b Water temperature detection part (water temperature detection means)
1c Throttle opening amount detection unit (opening amount detection means)
2 calculating part 2a change amount calculating part (change amount calculating means)
2b Change rate calculation unit (change rate calculation means)
2c Point calculation unit (judgment value calculation means)
3 determination part (determination means)
3a Start condition determination unit (start condition determination means)
3b Fuel property determination unit (fuel property determination means)
4 Air-fuel ratio sensor 5 Water temperature sensor 6 Throttle position sensor 20 Engine ECU

Claims (4)

Air-fuel ratio detection means for detecting the exhaust air-fuel ratio of the engine;
An opening amount detecting means for detecting an opening amount of the throttle valve of the engine;
Determination means for determining the fuel property of the fuel supplied to the engine based on the exhaust air-fuel ratio detected by the air-fuel ratio detection means when the opening amount detected by the opening amount detection means decreases;
Determination value calculating means for adding or subtracting a predetermined value to a determination value corresponding to the fuel property according to the exhaust air / fuel ratio detected by the air / fuel ratio detection means;
Fuel property determination means for determining the fuel property based on the determination value calculated by the determination value calculation means,
The determination value calculating means adds the predetermined value to the determination value when the exhaust air-fuel ratio is less than a first threshold value, and a second value where the exhaust air-fuel ratio is larger than the first threshold value. The fuel property determination device, wherein the predetermined value is subtracted from the determination value when the value is equal to or greater than a threshold value . Water temperature detecting means for detecting the cooling water temperature of the engine,
The determination value calculating means changes at least one of the first threshold value and the second threshold value according to the cooling water temperature detected by the water temperature detecting means. The fuel property judging device according to claim 1 . 3. The fuel property according to claim 1, wherein the determination unit determines the fuel property based on a rich peak size of the exhaust air-fuel ratio generated as the opening amount decreases. Judgment device. A change amount calculating means for calculating a change amount of the opening amount when the throttle valve is closed;
Change rate calculating means for calculating a change rate per unit time of the opening amount when the throttle valve is closed;
Start condition determining means for determining success or failure of a start condition for determining the fuel property based on the change amount calculated by the change amount calculating means and the change rate calculated by the change rate calculating means; With
The fuel property determination device according to claim 1, wherein the determination unit determines the fuel property when the start condition is satisfied by the start condition determination unit.

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