JP4692370B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device applied to an internal combustion engine capable of making valve opening characteristics of two intake valves provided for one cylinder different from each other.

  In order to improve combustion of an internal combustion engine, a valve drive device is known in which a swirl flow is generated in a cylinder by providing a lift amount difference between two intake valves provided for one cylinder. (For example, Patent Document 1 and Patent Document 2).

JP-A-6-280528 JP-A-11-287139

  In an internal combustion engine in which the valve driving device described in these documents is incorporated, a flow rate difference is generated between the intake air flow rate flowing through one intake valve side and the intake air flow rate flowing through the other intake valve side. A swirl flow is generated. However, when such a flow rate difference occurs, the air-fuel ratio of the air-fuel mixture containing the fuel injected into the intake passage is different between one side and the other side, so that it is introduced into the cylinder. The air-fuel ratio of the air-fuel mixture becomes uneven. The non-uniformity of the air-fuel ratio is promoted as the flow rate difference increases. Therefore, although the swirl flow is strengthened by the increase in the flow rate difference, the deterioration of combustion is induced instead. In particular, in a lean burn engine in which the air-fuel ratio is set leaner than the stoichiometric air-fuel ratio, nitrogen oxide (NOx ) May increase.

  Therefore, the present invention can suppress the deterioration of combustion even when a flow rate difference occurs between the intake flow rate flowing through one intake valve side provided in one cylinder and the intake flow rate flowing through the other intake valve side. An object of the present invention is to provide a control device for an internal combustion engine.

The control device for an internal combustion engine according to the present invention is provided with an intake passage having two openings for one cylinder of the internal combustion engine, and one opening at each opening of the intake passage so that each opening can be opened and closed. Two intake valves, valve drive means capable of opening and closing each of the two intake valves so that the opening characteristics of the two intake valves are different from each other, and a cylinder for injecting fuel into the cylinder An internal injection valve, an in-cylinder injection valve that injects fuel into the intake passage, an in-cylinder injection amount that should inject fuel to be injected per cycle from the in-cylinder injection valve, and the out-of-cylinder injection valve Fuel is injected from at least one of the in-cylinder injection valve and the out-of-cylinder injection valve based on a calculation result of the injection amount calculation means to be distributed to the in-cylinder injection amount to be injected and the calculation result of the injection amount calculation means Fuel injection control means, and the injection amount In the state in which the two intake valves are driven by the valve driving means so that the valve opening characteristics of the two intake valves are different from each other, the outlet means has a flow rate of intake air flowing through one intake valve side and the other intake valve. as the proportion of the in-cylinder injection quantity in accordance with the intake air flow rate difference is large Kunar given as the difference between the intake flow rate through the intake valve side is gradually increased, the in-cylinder injection fuel to be injected per cycle The above-described problem is solved by distributing the amount to the amount of in-cylinder injection (claim 1).

  According to this control device, when a difference in intake flow rate occurs between two intake valves, the proportion of the in-cylinder injection amount increases as the flow rate difference increases. In other words, the proportion of the in-cylinder injection amount decreases as the flow rate difference increases. Therefore, even if non-uniformity occurs between the air-fuel ratio on one side and the air-fuel ratio on the other side due to the difference in intake air flow rate between the two intake valves, the non-uniformity is The influence on the air-fuel mixture can be kept smaller than when all of the fuel to be injected per cycle is distributed to the in-cylinder injection amount. Thereby, the combustion deterioration accompanying generation | occurrence | production of an intake flow rate difference can be suppressed.

  The control apparatus according to the present invention further includes an acquisition unit that acquires the intake flow rate difference or at least one physical quantity correlated with the intake flow rate difference, and the injection amount calculation unit is smaller when the acquisition result of the acquisition unit is large. In comparison, the fuel to be injected per cycle may be distributed between the in-cylinder injection amount and the in-cylinder injection amount so that the ratio of the in-cylinder injection amount becomes larger (Claim 2). The acquisition of the intake flow rate difference may be acquired directly based on the detection result of the detection means capable of detecting the flow rate on at least one intake valve side, estimated from other physical quantities obtained directly, or You may acquire a flow volume difference from the other physical quantity obtained by estimation.

  When the intake flow rate difference is indirectly acquired by estimation or the like, the acquisition means uses the intake flow rate that flows through one intake valve side based on the intake valve flow characteristics of the intake valve. The flow rate may be estimated based on the valve opening characteristics of the intake valve, and the intake flow rate difference may be acquired based on the estimation result. Further, in this case, the valve driving means is configured so that at least one of an operating angle, a maximum lift amount and a phase can be made different for the two intake valves as the valve opening characteristics. The acquisition means can also estimate an intake flow rate flowing through one intake valve side and an intake flow rate flowing through the other intake valve side, respectively, based on at least one of an operating angle, a maximum lift amount, and a phase. Item 4). In these aspects, if the operating state of the valve drive means can be grasped, it is not necessary to install a detection means such as a sensor in order to acquire a physical quantity, and thus an increase in cost can be suppressed.

  Further, the acquisition means according to the present invention may acquire a physical quantity correlated with the intake flow rate difference instead of acquiring the intake flow rate difference. As the physical quantity correlated with the intake flow rate difference, a pressure difference between one intake valve side and the other intake valve side can be exemplified, but in addition, the acquisition means can use the two intake valves as the correlated physical quantity. The valve operating angle difference may be acquired (Claim 5), or the maximum lift amount difference between the two intake valves may be acquired (Claim 6).

  As described above, according to the present invention, when a difference in intake flow rate occurs between two intake valves, the proportion of the in-cylinder injection amount increases as the flow rate difference increases. Since the influence on the air-fuel mixture in the cylinder is suppressed to a small extent due to the non-uniformity of the air-fuel ratio between and the combustion deterioration due to the occurrence of the intake flow rate difference.

(First form)
FIG. 1 shows a main part of an internal combustion engine to which a control device of the present invention is applied. The internal combustion engine 1 is configured as an in-line four-cylinder spark ignition internal combustion engine in which four cylinders 2 (only one is shown in the figure) are arranged in one direction. Each cylinder 2 is provided with an intake passage 3 and an exhaust passage 4. A piston 5 connected to a crankshaft (not shown) via a connecting rod 6 is inserted into each cylinder 2 in a state where it can reciprocate. Each cylinder 2 is provided with a spark plug (not shown) substantially on the center line of the cylinder 2 so that its electrode portion protrudes.

  FIG. 2 schematically shows the internal combustion engine 1 of FIG. 1 from above. As shown in FIG. 2, the intake passage 3 includes an intake port 30 provided for each cylinder 2. The intake port 30 is branched into two passages 30a and 30b before connection to the cylinder 2, and each passage 30a. , 30b are connected to an opening 31 that opens to the cylinder 2. That is, the intake passage 3 has two openings 31 for one cylinder 2. Each opening 31 is provided with one intake valve 7 for opening and closing the opening 31, that is, two intake valves 7 for one cylinder 2. Each intake valve 7 is provided with an electromagnetic drive device 8 for opening and closing the intake valve 7. The electromagnetic driving device 8 is a well-known device that can freely set the valve opening characteristics of each intake valve 7, that is, the operating angle, the lift amount, the phase, and the like. In FIG. 1, only the intake valve 7 and the electromagnetic drive device 8 positioned on the near side in the direction orthogonal to the paper surface are illustrated. The exhaust passage 4 has an exhaust port 40 provided for each cylinder 2, and the exhaust port 40 is provided with an exhaust valve 11 for opening and closing the exhaust port 40. The exhaust valve 11 is driven to open and close by a known valve mechanism 12 whose valve opening characteristic is fixed by a cam 12a.

  As shown in FIG. 1, the electromagnetic drive device 8 includes a housing 80 formed in a cylindrical shape. In the housing 80, two electromagnets 81 and 82 formed in a ring shape are attached to a valve stem. They are provided so as to face each other with the body plunger 83 interposed therebetween and to be separated from each other. Two valve springs 84 are provided in the hollow portions of the electromagnets 81 and 82 so as to sandwich the plunger 83 so as to urge the plunger 83 to a neutral position (a position where the intake valve 7 has an intermediate opening). For this reason, the upward force of FIG. 1 acts on the plunger 83 by the excitation of the electromagnet 81, the valve nose is pressed against the valve seat 9, and the intake valve 7 is closed. On the other hand, due to the excitation of the electromagnet 82, a downward force in FIG. 1 acts on the plunger 83, the valve nose is separated from the valve seat 9, and the intake valve 7 is opened. By adjusting the excitation current supplied to these electromagnets 81 and 82, each intake valve 7 is driven to open and close with a desired valve opening characteristic.

  Fuel supply to each cylinder 2 is performed by the in-cylinder injection valve 15 and the out-cylinder injection valve 16. As shown in FIG. 2, the in-cylinder injection valve 15 is configured to inject fuel directly into the cylinder 2, and the injected fuel spray f <b> 1 spreads in a fan shape toward the center of the cylinder 2. ing. On the other hand, the in-cylinder injection valve 16 is configured to inject fuel into the intake port 30 (intake passage 3), and the injected fuel spray f2 is directed to each of the passages 30a and 30b. .

  The operations of the electromagnetic drive device 8, the in-cylinder injection valve 15, and the out-cylinder injection valve 16 are controlled by an engine control unit (ECU) 20 for properly controlling the internal combustion engine 1. The ECU 20 is a computer provided with peripheral devices such as a microprocessor and storage means such as ROM and RAM necessary for its operation. As sensors connected to the ECU 20, as shown in FIG. 1, there are a crank angle sensor 21 that outputs a signal corresponding to the engine rotational speed (rotation speed) Ne and an air flow meter 22 that outputs a signal corresponding to the intake air flow rate Ga. is there. The illustration of other various sensors is omitted. The ECU 20 makes the opening characteristics of the intake valves 7 different from each other in accordance with the necessity of the generation of the swirl flow in the cylinder 2 and the demand for the strength, and the intake flow rate on the one intake valve 7 side and the other intake valve 7 Each electromagnetic driving device 8 is controlled so that a flow rate difference is generated between the intake air flow rate on the seventh side. As a result, a swirl flow Fsw is generated in the cylinder 2 as shown in FIG. In this control, when the generation of the swirl flow is not necessary, the valve opening characteristics of the intake valves 7 are the same, and when the generation of the swirl flow is required, an intake flow rate difference corresponding to the required swirl ratio is generated. The valve opening characteristics of the intake valves 7 are made different from each other.

  There are various variations in the valve opening characteristics that the ECU 20 makes different in order to change the intake flow rate difference. In this embodiment, a lift difference (maximum lift amount difference) is provided in the maximum lift amount of the two intake valves 7. ing. Other valve opening characteristics, i.e., operating angle and phase, are the same for the two intake valves 7. In this embodiment, the maximum lift amount of the intake valve 7 on one side (upper side in FIG. 2) is made constant, and the maximum lift amount of the other intake valve 7 is reduced by two stages, so that the lift difference between the two intake valves 7 is reduced. Is realized with a large form and a form with a small lift difference.

  FIG. 3 is a flowchart showing an example of a control routine of fuel injection control executed by the ECU 20 in connection with the gist of the present invention. The program of this routine is stored in advance in the ROM of the ECU 20, read out in a timely manner, and repeatedly executed at predetermined intervals. As shown in FIG. 3, the ECU 20 first acquires the engine speed of the internal combustion engine 1 with reference to the output signal of the crank angle sensor 21 in step S1. Next, in step S2, the intake air amount is acquired with reference to the output signal of the air flow meter 22. Next, in step S3, the target fuel injection amount Q is set according to the operating state of the internal combustion engine 1. The target fuel injection amount Q is the fuel to be injected per cycle. Specifically, the target fuel injection amount Q is set based on the engine speed and the intake air amount acquired in step S1 and step S2 so that combustion at a predetermined air-fuel ratio (for example, the theoretical air-fuel ratio) is realized. To do. The setting can be realized, for example, by storing a map that gives the target fuel injection amount Q with the engine speed and the intake air amount as variables in the ROM of the ECU 20 and referring to the map.

  Next, in step S4, a ratio (blowing ratio) a [%] of the injection amount of the in-cylinder injection valve 15 to the target fuel injection amount Q is set. The blowing ratio a is set between 0% and 100% depending on the operating state of the internal combustion engine 1. That is, when the blowing rate a is 0%, fuel is not injected from the in-cylinder injection valve 15, and fuel is injected only from the out-cylinder injection valve 16. On the other hand, when the blowing rate a is 100%, the fuel is injected only from the in-cylinder injection valve 15 and the fuel is not injected from the out-cylinder injection valve 16.

  In the subsequent step S5, the lift difference between the two intake valves 7 is acquired, and the presence or absence of the lift difference is determined. If there is a lift difference, the process proceeds to step S6. If there is no lift difference, the process proceeds to step S9. move on. This lift difference can be obtained from the indicated value for the electromagnetic drive device 8 calculated in another routine. In Step S6, it is determined whether or not the lift difference is large. If the lift difference is large, the process proceeds to Step S7, the blowing rate a is reset, and the process proceeds to Step S9. If the lift difference is not large, That is, if the lift difference is small, the process proceeds to step S8, the blowing rate a is reset, and the process proceeds to step S9. The resetting ratio a in step S7 and step S8 is reset by substituting predetermined values aL and aS (aS <aL) prepared in advance so as to correspond to the magnitude of the lift difference into the variable a. Realize.

  In step S9, an injection amount (in-cylinder injection amount) qc to be injected from the in-cylinder injection valve 15 is calculated based on the blowing rate a set in the above process. The in-cylinder injection amount qc is obtained by multiplying the target fuel injection amount Q by a / 100. Next, in step S10, an injection amount (out-cylinder injection amount) qp to be injected from the in-cylinder injection valve 16 is calculated. The in-cylinder injection amount qp is obtained by multiplying the target fuel injection amount Q by (1-a / 100). In step S11, the in-cylinder injection amount qc of fuel is injected from the in-cylinder injection valve 15 and the in-cylinder injection amount qp of fuel is injected from the in-cylinder injection valve 16, respectively.

  According to the above routine, the predetermined value aL used for resetting the blowing rate a in step S7 is larger than the predetermined value aS in step S8. Therefore, when the lift difference is large, the ratio of the in-cylinder injection amount to be injected from the in-cylinder injection valve is larger than when the lift difference is small. The larger the lift difference, the larger the flow rate difference between the two intake valves 7. Therefore, as the flow rate difference between the two intake valves 7 increases, the ratio of the in-cylinder injection amount increases, and the cylinder is caused by the non-uniformity of the air-fuel ratio between one intake valve 7 side and the other intake valve 7 side. The influence on the air-fuel mixture in 2 is kept small.

(Second form)
Next, a second embodiment of the present invention will be described. This form is the same as the first form except for the control content performed by the ECU 20. 1 and 2 are appropriately referred to for the configuration of the internal combustion engine 1 and the like. In this embodiment, an operating angle difference is provided as the valve opening characteristic that the ECU 20 makes different in order to change the intake flow rate difference. The lift difference and phase may be the same for the two intake valves 7, or a maximum lift amount difference may be provided in conjunction with the operating angle difference.

  FIG. 4 is a flowchart showing an example of a control routine according to the second embodiment. In this figure, the processes common to those in FIG. When the blow ratio a is set in step S4, the operating angle difference between the two intake valves 7 is acquired in subsequent step S21, and the presence / absence of the operating angle difference is determined. This operating angle difference can be obtained from the indicated value for the electromagnetic drive device 8 calculated in another routine. If there is no working angle difference, the process proceeds to step S9. If there is a working angle difference, the process proceeds to step S22, the blowing rate a is reset, and the process proceeds to step S9. This resetting is realized by substituting a predetermined value aR, which is set to a larger value as the operating angle difference becomes larger, into the variable a. For example, as shown in FIG. 5, the predetermined value aR can be realized by preparing a map that gives the predetermined value aR with the operating angle difference as a variable, and referring to the map.

  According to the above routine, the predetermined value aR used for resetting the blowing rate a in step S22 is set to a larger value as the operating angle difference is larger. Therefore, when the operating angle difference is large, the ratio of the in-cylinder injection amount to be injected from the in-cylinder injection valve 15 is larger than when the operating angle difference is small. The greater the difference in operating angle, the greater the difference in flow rate between the two intake valves 7. Therefore, as the flow rate difference between the two intake valves 7 increases, the ratio of the in-cylinder injection amount increases, and the cylinder is caused by the non-uniformity of the air-fuel ratio between one intake valve 7 side and the other intake valve 7 side. The influence on the air-fuel mixture in 2 is kept small.

(Third form)
Next, the 3rd form of this invention is demonstrated. This form is the same as the first form except for the control content performed by the ECU 20. 1 and 2 are appropriately referred to for the configuration of the internal combustion engine 1 and the like. In this embodiment, the intake flow rate flowing on one side and the intake flow rate on the other side are respectively estimated from the valve opening characteristics of the two intake valves 7, and the intake flow rate difference is acquired from the estimation result. . FIG. 6 is a flowchart showing an example of a control routine according to the third embodiment. In this figure, the processes common to the third are assigned the same reference numerals, and redundant description is omitted.

  When the air-blowing rate a is set in step S4, it is determined in subsequent step S31 whether or not the valve opening characteristics of the two intake valves 7 are the same. This determination can be realized based on an instruction value for the electromagnetic driving device 8 calculated in another routine. If the valve opening characteristics are the same, the process proceeds to step S9, and if not, the process proceeds to step S32. In step S32, the intake flow rate flowing through each intake valve 7 side is estimated. This estimation is performed based on the valve opening characteristics of each intake valve 7. This estimation method depends on the control contents for the electromagnetic drive device 8. For example, when the ECU 20 changes the operating angle difference and the maximum lift amount difference so as to be linked with each other in order to change the intake flow rate difference, and further changes the phase, as shown in FIG. This estimation can be realized by preparing a map that gives the intake air flow rate with each phase as a variable and referring to the map. Unlike the control contents for the electromagnetic driving device 8 described above, it is the case where only the lift difference is given and the working angle and phase are not changed as in the first embodiment, or the maximum lift amount, working angle and phase are all changed. However, the intake amount on the side of each intake valve 7 can also be estimated based on at least one of the maximum lift amount, the operating angle, and the phase. The estimation can be realized by preparing a map that gives the intake air flow rate using at least one of these as a variable.

  Next, in step S33, an intake flow rate difference between the two intake valves 7 is calculated from the estimation result in step S32. Next, in step S34, the blowing rate a is reset, and the process proceeds to step S9. This resetting is realized by substituting a predetermined value aQ, which is set to a larger value as the intake flow rate difference becomes larger, into the variable a. For example, as shown in FIG. 8, the predetermined value aQ can be realized by preparing a map that gives the predetermined value aQ using the intake flow rate difference as a variable and referring to the map.

  According to the above routine, the predetermined value aQ used for resetting the blowing rate a in step S34 is set to a larger value as the intake flow rate difference is larger. Therefore, when the intake flow rate difference is large, the proportion of the in-cylinder injection amount to be injected from the in-cylinder injection valve 15 is larger than when the intake flow rate difference is small. Therefore, the influence on the air-fuel mixture in the cylinder 2 due to the non-uniformity of the air-fuel ratio between the one intake valve 7 side and the other intake valve 7 side is suppressed to a small level.

  In each of the above embodiments, the electromagnetic driving device 8 and the ECU 20 constitute the valve driving means according to the present invention. The ECU 20 executes step S4, step S7 to step S10 in FIG. 3 and then executes step S4, step S22, step S9 and step S10 in FIG. 4 to thereby execute step S4, step S34 and step S9 in FIG. And by executing step S10, the ECU 20 functions as the fuel injection amount calculating means according to the present invention. Moreover, when ECU20 performs step S11 of FIG.3, FIG4 and FIG.6, ECU20 functions as a fuel-injection control means which concerns on this invention. Further, by executing step S5 in FIG. 3, the ECU 20 executes step S21 in FIG. 4, and by executing step S32 and step S33 in FIG. 6, the ECU 20 functions as an acquisition unit according to the present invention. To do.

  However, the present invention is not limited to the above embodiments, and can be implemented in various forms. The valve driving means may be realized by any configuration as long as the valve opening characteristics between the two intake valves can be made different from each other so that a difference in intake flow rate can be given. Therefore, the present invention is not limited to the form of FIG. 1 in which the intake valve 7 is driven to open and close by the electromagnetic drive device 8. Further, in the third embodiment, in order to obtain the difference in intake flow rate, the intake flow rate on one intake valve side and the intake flow rate on the other intake valve side are estimated, but a flow rate sensor that can directly detect these is used. It may be provided to implement the present invention. Further, a differential pressure sensor capable of detecting a differential pressure between one and the other may be provided, and the intake flow rate difference may be calculated from the detection result.

The figure which showed the principal part of the internal combustion engine to which the control apparatus of this invention was applied. The figure which showed the internal combustion engine of FIG. 1 typically from the information. The flowchart which showed an example of the control routine which concerns on a 1st form. The flowchart which showed an example of the control routine which concerns on a 2nd form. The figure which showed an example of the map which gives predetermined value aR by making a working angle difference into a variable. The flowchart which showed an example of the control routine which concerns on a 3rd form. The figure which showed an example of the map which gives each intake air flow volume by making each of an operating angle and a phase into a variable. The figure which showed an example of the map which gives predetermined value aQ by making intake air flow rate difference into a variable.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder 3 Intake passage 7 Intake valve 8 Electromagnetic drive device (valve drive means)
15 In-cylinder injection valve 16 Out-cylinder injection valve 20 ECU (fuel injection amount calculation means, fuel injection control means, acquisition means)
31 opening

Claims (6)

An intake passage having two openings for one cylinder of the internal combustion engine, two intake valves provided in each opening of the intake passage, each opening and closing each opening, and the two Valve driving means capable of opening and closing each of the two intake valves so that the valve opening characteristics of the intake valves are different from each other, an in-cylinder injection valve for injecting fuel into the cylinder, and an intake passage An in-cylinder injection valve that injects fuel, and an in-cylinder injection amount that should be injected from the in-cylinder injection valve and an out-cylinder injection amount that should be injected from the in-cylinder injection valve. A fuel injection control unit that injects fuel from at least one of the in-cylinder injection valve and the out-cylinder injection valve based on a calculation result of the injection amount calculation unit;
The injection amount calculation means is an intake air flow rate that flows on one intake valve side in a state where the two intake valves are driven by the valve drive means so that the valve opening characteristics of the two intake valves are different from each other. and as the ratio of the in-cylinder injection quantity in accordance with the intake air flow rate difference is large Kunar given as the difference between the intake flow rate through the other intake valve side is gradually increased, the fuel to be injected per cycle A control device for an internal combustion engine, which distributes between an in-cylinder injection amount and the in-cylinder injection amount.   The apparatus further comprises acquisition means for acquiring the intake flow rate difference or at least one physical quantity correlated therewith, and the injection amount calculation means is configured to determine the in-cylinder injection amount when the acquisition result of the acquisition means is large compared to when the acquisition result is small. 2. The control device for an internal combustion engine according to claim 1, wherein the fuel to be injected per cycle is distributed between the in-cylinder injection amount and the out-cylinder injection amount so that the ratio of the fuel injection is increased.   The acquisition means estimates the intake flow rate flowing through one intake valve side based on the valve opening characteristic of the intake valve, and estimates the intake flow rate flowing through the other intake valve side based on the valve opening characteristic of the intake valve. 3. The control apparatus for an internal combustion engine according to claim 2, wherein the intake flow rate difference is acquired based on the estimation result. The valve driving means is configured such that at least one of an operating angle, a maximum lift amount, and a phase can be made different from each other for the two intake valves as the valve opening characteristic,
The acquisition means estimates an intake flow rate flowing through one intake valve side and an intake flow rate flowing through the other intake valve side based on at least one of a working angle, a maximum lift amount, and a phase, respectively. Item 4. The control device for an internal combustion engine according to Item 3.   The control device for an internal combustion engine according to claim 2, wherein the acquisition unit acquires a difference in operating angle between the two intake valves as the correlated physical quantity.   The control device for an internal combustion engine according to claim 2, wherein the acquisition means acquires a maximum lift amount difference between the two intake valves as the correlated physical quantity.

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