Fuel injection controller for internal combustion engine, and engine including the same

Abstract

In a fuel injection controller, a first throttle opening TH0 is defined at a specific time P2. The P2 is a specific time later than the peak value of an intake pipe internal pressure PB of a previous cycle. In the cycle, P3 is a specific time that is set immediately before the calculation of the injection time. A second throttle opening TH2 is defined at P3. The fuel injection controller corrects a fuel injection amount based on variation in correction time ta0 at the first throttle opening TH0 to correction time ta1 at the second throttle opening TH1. The time P2 is later than time P1, which is the peak value of the intake pipe internal pressure of the previous cycle. Accordingly, the fuel injection amount correction is completely unaffected or only slightly affected by the intake pipe internal pressure, thus ensuring close-to-ideal correction.

Claims

1. A fuel injection controller for an engine, said fuel injection controller comprising: a basic fuel injection amount calculator which calculates a basic fuel injection amount for a fuel injector to be drawn in an intake stroke of a current cycle based on an engine rotary speed from an engine rotary speed sensor and an intake pipe internal pressure PB from a pressure sensor in an intake stroke of a previous cycle; a fuel injection amount corrector which makes a correction to the basic fuel injection amount based on variations in a first throttle opening TH0; and a second throttle opening TH1, which occurs immediately before the calculation of the basic fuel injection amount, wherein the first throttle opening TH0 occurs before the second throttle opening TH1; wherein the fuel injection amount corrector makes the correction to the basic fuel injection amount using the first throttle opening TH0, which is set to one of the throttle opening at and after the maximum lift of an intake valve in the intake stroke of the previous cycle, wherein the intake pipe internal pressure PB of the previous cycle takes on a peak value of the intake pipe internal pressure PB, wherein the first throttle opening TH0 is set to a time later than the peak value of the intake pipe internal pressure PB, and wherein when fuel is injected twice per cycle of the engine: a first fuel injection amount including the basic fuel injection amount and said correction to the basic fuel injection amount is a first injection conducted at an early stage of the intake stroke of the current cycle or at a stage earlier than the intake stroke, and the fuel injector further performs a second injection later than the first injection and during the intake stroke of the current cycle; a second fuel injection amount for the second injection is determined based on variations in the second throttle opening TH1, and a third throttle opening TH2 which is defined subsequent to the second throttle opening TH1; and the third throttle opening TH2 is one of a throttle opening at and before the maximum lift of the intake valve.

2. The fuel injection controller of claim 1, wherein the first throttle opening TH0 is set to the throttle opening at or after the full closing of the intake valve in the previous cycle.

3. The fuel injection controller of claim 2, wherein when fuel is injected twice per cycle of the engine: a first fuel injection amount including the basic fuel injection amount and said correction to the basic fuel injection amount is a first injection conducted at an early stage of the intake stroke of the current cycle or at a stage earlier than the intake stroke, and a fuel injector further performs a second injection later than the first injection and during the intake stroke of the current cycle; a second fuel injection amount for the second injection is determined based on variations in the second throttle opening TH1, and a third throttle opening TH2 which is defined subsequent to the second throttle opening TH1; and the third throttle opening TH2 is one of a throttle opening at and before the maximum lift of the intake valve.

4. The fuel injection controller of claim 1, wherein when fuel is injected twice per cycle of the engine: a first fuel injection amount including the basic fuel injection amount and said correction to the basic fuel injection amount is a first injection conducted at an early stage of the intake stroke of the current cycle or at a stage earlier than the intake stroke, and the fuel injector further performs a second injection later than the first injection and during the intake stroke of the current cycle; in the first injection, the intake pipe internal pressure PB in the intake stroke of the previous cycle takes on the peak value of the intake pipe internal pressure; a second fuel injection amount for the second injection is determined based on variations in the second throttle opening TH1, and third throttle opening TH2 which is defined subsequent to the second throttle opening TH1; and the third throttle opening TH2 is one of the throttle opening at and before the peak value of the intake pipe internal pressure PB.

5. The fuel injection controller of claim 1, wherein one of a common throttle opening map Mp and a formula is used for determining said correction to the first fuel injection amount in the first injection, and a correction to the second fuel injection amount for the second injection.

6. The fuel injection controller of claim 4, wherein one of a common throttle opening map Mp and a formula is used for determining said correction to the first fuel injection amount in the first injection, and a correction to the second fuel injection amount for the second injection.

7. An internal combustion engine, comprising a basic fuel injection amount calculator which calculates a basic fuel injection amount for a fuel injector to be drawn in an intake stroke of a current cycle based on an engine rotary speed from an engine rotary speed sensor and an intake pipe internal pressure PB from a pressure sensor in an intake stroke of a previous cycle; and a fuel injection amount corrector which makes a correction to the basic fuel injection amount based on variations in a first throttle opening TH0; and a second throttle opening TH1, which occurs immediately before the calculation of the basic fuel injection amount, wherein the first throttle opening TH0 occurs before the second throttle opening TH1; and wherein the fuel injection amount corrector makes the correction to the basic fuel amount using the first throttle opening TH0, which is set to one of the throttle opening at and after the maximum lift of an intake valve in the intake stroke of the previous cycle, wherein the intake pipe internal pressure PB of the previous cycle takes on a peak value of the intake pipe internal pressure PB, wherein the first throttle opening TH0 is set to a time later than the peak value of the intake pipe internal pressure PB, and wherein when fuel is injected twice per cycle of the engine: a first fuel injection amount including the basic fuel injection amount and said correction to the basic fuel injection amount is a first injection conducted at an early stage of the intake stroke of the current cycle or at a stage earlier than the intake stroke, and the fuel injector further performs a second injection later than the first injection and during the intake stroke of the current cycle; a second fuel injection amount for the second injection is determined based on variations in the second throttle opening TH1, and a third throttle opening TH2 which is defined subsequent to the second throttle opening TH1; and the third throttle opening TH2 is one of a throttle opening at and before the maximum lift of the intake valve.

8. The internal combustion engine according to claim 7, wherein the first throttle opening TH0 is set to the throttle opening at or after the full closing of the intake valve in the previous cycle.

9. An internal combustion engine comprising an intake pipe; a throttle valve including a throttle sensor which measures a throttle opening in said intake pipe; a pressure sensor which senses an intake pipe internal pressure in said intake pipe; a pulse sensor which calculates an engine rotary speed; a fuel injector arranged in the intake pipe; and a fuel injection controller operatively connected to the fuel injector, the throttle valve, the pressure sensor and the pulse sensor; said fuel injection controller comprising: a basic fuel injection amount calculator which calculates a basic fuel injection amount to be drawn in an intake stroke of a current cycle based on an engine rotary speed and an intake pipe internal pressure PB in an intake stroke of a previous cycle; a fuel injection amount corrector which makes a correction to the basic fuel injection amount based on variations in a first throttle opening TH0 and a second throttle opening TH1, which occurs immediately before the calculation of the basic fuel injection amount; wherein the first throttle opening TH0 occurs before the second throttle opening TH1, wherein the intake pipe internal pressure PB of the previous cycle takes on a peak value of the intake pipe internal pressure PB, and wherein the first throttle opening TH0 is set to a time later than the peak value of the intake pipe internal pressure PB, and wherein when fuel is injected twice per cycle of the engine: a first fuel injection amount including the basic fuel injection amount and said correction to the basic fuel injection amount is a first injection conducted at an early stage of the intake stroke of the current cycle or at a stage earlier than the intake stroke, and the fuel injector further performs a second injection later than the first injection and during the intake stroke of the current cycle; a second fuel injection amount for the second injection is determined based on variations in the second throttle opening TH1, and a third throttle opening TH2 which is defined subsequent to the second throttle opening TH1; and the third throttle opening TH2 is one of a throttle opening at and before the maximum lift of the intake valve.

10. The internal combustion engine according to claim 9, wherein the first throttle opening TH0 is set to the throttle opening at or after the full closing of the intake valve in the previous cycle.

11. The internal combustion engine according to claim 9, wherein one of a common throttle opening map Mp and a formula is used for determining said correction to the first fuel injection amount in the first injection, and a correction to the second fuel injection amount for the second injection.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a basic configuration diagram of an engine including a fuel injection controller according to the present invention.

(2) FIG. 2 is a timing chart describing fuel injection control.

(3) FIG. 3 is an enlarged view of area 3 in FIG. 2.

(4) FIG. 4 is a diagram describing an embodiment of fuel injection control.

(5) FIG. 5 is a diagram describing another embodiment of fuel injection control.

(6) FIG. 6 is a diagram illustrating an example of a throttle opening map used in the present invention.

(7) FIG. 7 is a diagram describing still another embodiment of fuel injection control.

(8) FIG. 8 is a diagram describing still another embodiment of fuel injection control.

(9) FIG. 9 is a diagram describing still another embodiment of fuel injection control.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

(10) An illustrative embodiment of the present invention will be described hereinafter in detail with reference to the accompanying drawings. Throughout this description, relative terms like “upper”, “lower”, “above”, “below”, “front”, “back”, and the like are used in reference to a vantage point of an operator of the vehicle, seated on the driver's seat and facing forward. It should be understood that these terms are used for purposes of illustration, and are not intended to limit the invention.

(11) The fuel injection control according to the first aspect of the present invention will be described based primarily on FIG. 2. Similarly, the second aspect of the present invention will be described based on FIG. 4, the third aspect based on FIG. 6, the fourth aspect based on FIG. 7, the fifth aspect based on FIG. 8, and the sixth aspect based on FIG. 9.

Illustrative Embodiments

(12) As illustrated in FIG. 1, an engine 10 includes a cylinder block 11 and a piston 12 arranged in the cylinder block 11. The engine 10 further includes, in a crankcase 13, a pulse sensor 15 which measures the rotary speed (i.e., engine rotary speed) of a crankshaft 14. The engine 10 still further includes an intake valve 17 and an exhaust valve 18 in a cylinder head 16. The engine 10 further includes an intake pipe 19 having a throttle valve 21, an injector 22, and a pressure sensor 23 arranged in this order therein along the flow of introduced air. Further, the engine 10 includes a fuel injection controller 24.

(13) The fuel injection controller 24 obtains information about an engine rotary speed Ne from the pulse sensor 15 and a throttle opening TH from the throttle valve 21. The fuel injection controller 24 further obtains an intake pipe internal pressure PB from the pressure sensor 23. The fuel injection controller 24 controls the injector 22 based on various inputs, e.g., an engine rotary speed Ne, a throttle opening TH and an intake pipe internal pressure PB.

(14) The fuel injection controller 24 includes a basic fuel injection amount calculator 25. The basic fuel injection amount calculator 25 calculates a basic fuel injection amount based on the engine rotary speed Ne and the intake pipe internal pressure PB in the intake stroke of a previous cycle. The fuel injection controller 24 also includes a fuel injection amount corrector 26.

(15) The fuel injection amount corrector 26 corrects the basic fuel injection amount based on variations in two factors. One of these two factors is a throttle opening immediately before the calculation of the basic fuel injection amount. This throttle opening is denoted by TH1. The other of these two factors is a throttle opening in a specified timing before then. This throttle opening is denoted by TH0.

(16) A detailed description of the action of the fuel injection controller 24 is discussed below based on FIG. 2.

(17) In FIG. 2, (a) illustrates an absolute stage and a relative injection stage, one on top of the other, that are determined based on a pulse input from the pulse sensor; (b) illustrates an opening range of the intake valve; (c) illustrates an opening range of the exhaust valve; (d) illustrates calculation periods of injection time; (e) illustrates closed (non-injection) and open (injection) periods of the injector; (f) illustrates an example of change in the throttle opening TH; and (g) illustrates an example of change in the intake pipe internal pressure PB.

(18) The intake valve protrudes the most into the combustion chamber while the intake valve shown in (b) is open (equivalent to the intake stroke) as illustrated in (f). That is, the intake valve reaches the maximum lift. This moment will be hereinafter referred to as ‘the maximum lift of the intake valve.’

(19) Further, the piston moves down in the intake stroke. As a result, the intake pipe internal pressure PB is sucked by the piston, causing the intake pipe internal pressure PB to decline. This brings the intake pipe internal pressure PB down to the minimum level near the center of the intake stroke as illustrated in (g). This moment will be hereinafter referred to as ‘the peak intake pipe internal pressure.’ The peak intake pipe internal pressure tends to occur slightly after the maximum lift of the intake valve.

(20) In the injection time calculation shown in (d), the fuel injection controller 24 shown in FIG. 1 calculates the corrected injection.

(21) As illustrated in FIG. 3, an enlarged view of area 3 in FIG. 2, the corrected injection time is calculated by adding a variation to or subtracting it from the basic fuel injection time. A detailed description will be given below of this calculation with reference to FIG. 3 onward. It may be noted that the internal diameter of the injection hole of the injector is constant. Therefore, the injection amount is approximately proportional to the injection time. Consequently, the term ‘injection time’ can be replaced by the term ‘injection amount’ and vice versa. Practically, when the valve closes from an open position or opens from a closed position, the flow rate will change. Therefore, the time and the amount do not precisely agree, which requires separate correction. However, a description thereof is omitted here.

(22) The basic fuel injection time (amount) is calculated by the basic fuel injection amount calculator 25 based on the engine rotary speed and the peak value of the intake pipe internal pressure PB of the previous cycle.

(23) In FIG. 4, the peak value of the intake pipe internal pressure PB of the previous cycle is the intake pipe internal pressure represented by point P1.

(24) It should be noted, however, that because the intake pipe internal pressure PB of the previous cycle is used, this pressure is probably slightly different from the intake pipe internal pressure in the current cycle. Therefore, this pressure must be corrected.

(25) For this reason, in FIG. 4, at intake pipe internal pressure P2, the throttle opening is TH0. Again, in FIG. 4, P2 is a specific time later than the peak value of the intake pipe internal pressure PB of the previous cycle (e.g., P1).

(26) Further, P3 is a specific point that is set immediately before the calculation of the injection time shown by a rectangle filled with diagonal lines. At the intake pipe internal pressure P3, the throttle opening is TH1.

(27) In this manner, the throttle openings TH1 and TH0 are defined.

(28) FIG. 5 is a diagram illustrating a throttle opening map. The fuel injection amount corrector 26 (FIG. 1) reads a correction time ta0 for the throttle opening TH0 using a throttle opening map Mp (or a formula (including approximation formula)), thus finding a correction time ta1 for the throttle opening TH1. Then, the fuel injection amount corrector 26 acknowledges the change in correction time (ta0 to ta1) as a variation.

(29) The corrected injection time as shown in FIG. 3, i.e., the fuel injection amount, is determined from two factors. One of these two factors is the basic fuel injection time calculated by the basic fuel injection amount calculator 25 (FIG. 1). The other of these two factors is the variation determined by the fuel injection amount corrector 26 (FIG. 1). As a result, fuel is injected only for this period of time.

(30) In FIG. 4, the prior art used the value at point P0 as TH0. However, this causes the change in throttle opening to significantly affect the intake pipe internal pressure shown in (g) (FIG. 4). As a result, the correction is likely to deviate excessively from the ideal one. In contrast, according to the present invention, the correction is completely unaffected or only slightly affected by the intake pipe internal pressure, if affected at all, thus ensuring close-to-ideal correction.

(31) A description will be given of modification examples of FIG. 4 with reference to FIGS. 6 and 7 in this order.

(32) TH0 is the throttle opening when the intake valve closes in the previous cycle (point P4) as illustrated in FIG. 6. FIGS. 6 and 7 are identical to FIGS. 4 and 5 in all other respects. Therefore, the identical description thereof is omitted.

(33) It may be noted that point P4 may be later than the position shown in FIG. 6, i.e., later than the closing of the intake valve. It is more preferred that the point P4 should be immediately after the closing of the intake valve.

(34) As compared to FIG. 4, the intake pipe internal pressure remains completely unaffected by the change in throttle opening afterwards due to the closing of the intake valve as illustrated in FIG. 6. This is advantageous in that the variation can be readily brought close to the ideal one.

(35) In FIG. 7, throttle opening TH1 is set again to the throttle opening immediately before the calculation of the basic injection amount (point P3). On the other hand, TH0 is set to the throttle opening at or after the maximum lift of the intake valve of the engine (point P5).

(36) Then, the basic fuel injection amount is corrected based on variations for throttle openings TH0 and TH1.

(37) In FIG. 7, the correction is partially affected by the change in intake pipe internal pressure, but not as much as in the prior art (in which the correction is totally affected by the change in intake pipe internal pressure because the throttle opening TH0 is set to the throttle opening at point P0).

(38) The present invention as described above is suitable for application to engines that inject fuel once per cycle.

(39) A description will be given next of an example in which fuel is injected twice per cycle.

(40) As illustrated in (e) of FIG. 8, a first injection is conducted at an early stage of the intake stroke or at a stage prior to the intake stroke. A second injection is conducted later than the first injection and during the intake stroke.

(41) In the first injection, the peak value of the intake pipe internal pressure PB of the previous cycle, i.e., PB at point P1, is used as the intake pipe internal pressure PB thereof, as with FIGS. 4 to 7.

(42) Then, TH1 is set to the throttle opening immediately before the calculation of the basic injection amount (point P3) in the correction for the first injection, as with FIG. 7. On the other hand, TH0 is set to the throttle opening at or after the maximum lift of the intake valve of the engine (point P5).

(43) Then, the basic fuel injection amount is corrected based on variations for TH0 and TH1 using the throttle opening map Mp shown in FIG. 5.

(44) Further, point P6 is set to a time at or before the peak value of the intake pipe internal pressure. Then, the throttle opening at point P6 is defined as TH2. Then, the correction amount for the second injection is found based on variations for TH1 and TH2 using the throttle opening map Mp shown in FIG. 5.

(45) It is even better if point P6 is located immediately before the peak value of the intake pipe internal pressure (PB).

(46) A modification example of FIG. 8 will be described with reference to FIG. 9.

(47) In FIG. 9, the first injection is conducted at an early stage of the intake stroke or at a stage prior to the intake stroke, and the second injection is conducted later than the first injection and during the intake stroke, as with FIG. 8.

(48) In the first injection, the peak value of the intake pipe internal pressure PB of the previous cycle, i.e., PB at point P1, is used as the intake pipe internal pressure PB thereof, as with FIG. 8 (i.e., as with FIGS. 4 to 7).

(49) Then, TH1 is set to the throttle opening immediately before the calculation of the basic injection amount (point P3) in the correction for the first injection, as with FIG. 7. On the other hand, TH0 is set to the throttle opening at or after the maximum lift of the intake valve of the engine (point P5).

(50) Then, the basic fuel injection amount is corrected based on variations for TH0 and TH1 using the throttle opening map Mp shown in FIG. 5.

(51) Further, point P7 is set to a time at or before the maximum lift of the intake valve. Then, the throttle opening at point P7 is defined as TH2. Then, the injection amount for the second injection is obtained as a variation (ta2−ta1) for TH1 and TH2 using the throttle opening map Mp shown in FIG. 5.

(52) It is even better if point P7 is located immediately before the maximum lift.

(53) As described above, a common throttle opening map Mp (FIG. 5) is used in the correction for the first injection and the determination for the second injection. Sharing a throttle opening map halves the cost of map preparation as compared to separate preparation of correction maps for the first and second injections. Further, this requires only half of the memory capacity to store the throttle opening map, thus contributing to a reduced cost of a storage section.

INDUSTRIAL APPLICABILITY

(54) The present invention is suitable for application to an engine having an injector.

(55) Although the present invention has been described herein with respect to a number of specific illustrative embodiments, the foregoing description is intended to illustrate, rather than to limit the invention. Those skilled in the art will realize that many modifications of the illustrative embodiment could be made which would be operable. All such modifications, which are within the scope of the claims, are intended to be within the scope and spirit of the present invention.

DESCRIPTION OF REFERENCE SYMBOLS

(56) 10: Engine, 15: Pulse sensor, 17: Intake valve, 21: Throttle valve, 22: Injector, 23: Pressure sensor, 24: Fuel injection controller, 25: Basic fuel injection amount calculator, 26: Fuel injection amount corrector, Ne: Engine rotary speed, PB: Intake pipe internal pressure, TH, TH1: Throttle openings, TH0: Throttle opening before TH1, TH2: Throttle opening after TH1, Mp: Throttle opening map.