JP2007032437A - Cylinder injection internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cylinder injection internal combustion engine capable of selectively using a plurality of types of fuel spray forms depending on the purpose. <P>SOLUTION: The internal combustion engine 1 comprises a first fuel injection valve 11 for injecting into a cylinder 2 hollow cone spray 21 spreading in a hollow conical shape in relation to a center line CL of the cylinder 2, and a second fuel injection valve 12 for injecting into the cylinder 2 fan spray 22 spreading in a fan shape in relation to the direction of intersecting the center line CL. When the load of the engine exceeds a predetermined level, the operation of each of the first fuel injection valve 11 and the second fuel injection valve 12 is controlled so that the hollow cone spray 21 is injected in an intake stroke and the fan spray 22 is injected in a compression stroke following the intake stroke. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a direct injection internal combustion engine that injects fuel spray into a cylinder.

  As an in-cylinder injection type internal combustion engine, when the engine speed is high and the load is high, fuel injection into the cylinder is divided into an intake stroke and a compression stroke, and the division ratio is determined based on the engine speed and There is known one that changes according to the load level and corrects the ignition timing (Patent Document 1). In some cases, fuel injection is divided into an intake stroke and a compression stroke when the engine load is high, and stratified combustion is realized by performing fuel injection only in the compression stroke when the load is low (patent) Reference 2).

Japanese Unexamined Patent Publication No. 2000-240492 JP 2001-248482 A

  In general, fuel injection in the compression stroke is performed for the purpose of forming an air-fuel mixture having a high concentration locally, while fuel injection in the intake stroke is performed for the purpose of forming a homogeneous air-fuel mixture in the cylinder. The There are fuel spray forms suitable for these purposes, and a fuel spray form suitable for one is not necessarily suitable for the other. The internal combustion engine described above performs fuel injection by dividing it into an intake stroke and a compression stroke. However, since the form of the fuel spray is fixed, it is not possible to blow the fuel spray suitable for each stroke.

  Accordingly, an object of the present invention is to provide a cylinder injection type internal combustion engine that can spray a plurality of types of fuel sprays according to the purpose.

  The in-cylinder injection internal combustion engine of the present invention intersects the first fuel injection valve capable of injecting the first fuel spray spreading in a hollow conical shape into the cylinder with respect to the direction of the center line of the cylinder, and the center line. A fuel that controls the operation of each of the second fuel injection valve capable of injecting the second fuel spray spreading in a fan shape into the cylinder, and the first fuel injection valve and the second fuel injection valve. By providing the injection control means, the above-described problem is solved.

  According to the present invention, the first fuel spray that spreads in a hollow conical shape with respect to the direction of the center line of the cylinder and the second fuel spray that spreads in a fan shape with respect to the direction intersecting the center line of the cylinder are blown according to the purpose. be able to. The first fuel spray is a spray form that can promote the homogeneity of the air-fuel mixture in the cylinder, and the second fuel spray is a spray form that can promote the formation of a locally high-concentration air-fuel mixture. For this reason, the fuel injection control means controls the operations of the first fuel injection valve and the second fuel injection valve, whereby two types of fuel sprays can be sprayed according to the purpose.

  In the in-cylinder internal combustion engine of the present invention, there is no limitation on the purpose of separating two types of fuel spray. For example, when the engine load exceeds a predetermined level, the fuel injection control means injects the first fuel spray in the intake stroke and injects the second fuel spray in the compression stroke following the intake stroke. As described above, the operations of the first fuel injection valve and the second fuel injection valve may be controlled (claim 2). According to this aspect, the first fuel spray is injected in the intake stroke, whereby the homogeneity of the air-fuel mixture is promoted, while the second fuel spray is injected in the compression stroke. The disturbance is promoted and the combustion is promoted, so that the occurrence of knocking is suppressed. In the case of the internal combustion engine of this aspect, knocking is more likely to occur as the engine speed is lower. Therefore, the fuel injection control means has a ratio of the injection amount in the compression stroke to the injection amount in the intake stroke. You may control each operation | movement of a said 1st fuel injection valve and a said 2nd fuel injection valve so that it may become so large that a number is low (Claim 3). Thereby, the occurrence of knocking can be reliably suppressed.

  The fuel injection control means is configured to inject the first fuel spray in an intake stroke when the load is equal to or lower than the predetermined level and to perform homogeneous combustion, and the intake stroke The operation of each of the first fuel injection valve and the second fuel injection valve may be controlled so that the injection of the second fuel spray is prohibited in the compression stroke that follows (Claim 4). . In this case, since the first fuel spray is injected in the intake stroke, a homogeneous air-fuel mixture can be formed in the cylinder, so that homogeneous combustion can be realized effectively.

  Further, the fuel injection control means is configured such that when the load is equal to or lower than the predetermined level and weak stratified combustion is to be performed, the first fuel spray is injected in the intake stroke, and the compression stroke follows the intake stroke. The operations of the first fuel injection valve and the second fuel injection valve may be controlled so that the first fuel spray or the second fuel spray is injected. . In this case, the first fuel spray or the second fuel spray is injected in the intake stroke to improve the homogeneity of the air-fuel mixture, and the second fuel spray is injected in the compression stroke to promote combustion. Therefore, it is possible to effectively realize weak stratified combustion. In this case, the stratification degree of the air-fuel mixture can be changed by appropriately adjusting the ratio of the fuel injection amount in the compression stroke to the fuel injection amount in the intake stroke. For example, in order to increase the stratification degree, the ratio of the fuel injection amount in the compression stroke to the fuel injection amount in the intake stroke may be increased.

  In the in-cylinder injection internal combustion engine of the present invention, a catalyst provided in the exhaust passage for purifying harmful substances in the exhaust, and an ignition timing retardation for retarding the ignition timing within a period in which the catalyst needs to be heated. And the fuel injection control means is configured to inject the first fuel spray in the intake stroke while the ignition timing retarding means retards the ignition timing, and to perform compression following the intake stroke. Each operation of the first fuel injection valve and the second fuel injection valve may be controlled so that the second fuel spray is injected in a stroke. According to this aspect, the first fuel spray is injected in the intake stroke and the second fuel spray is injected in the compression stroke while the ignition timing is controlled to be retarded by the ignition timing control means. Therefore, it is possible to form an air-fuel mixture having a high concentration in the vicinity of the spark plug and a low concentration and a homogeneous mixture in other regions. Thereby, the temperature of the catalyst can be effectively increased.

  As described above, according to the present invention, the first fuel injection valve capable of injecting the first fuel spray spreading in a hollow conical shape with respect to the direction of the center line of the cylinder into the cylinder, the center line of the cylinder, A second fuel injection valve capable of injecting into the cylinder a second fuel spray that spreads in a fan shape in the intersecting direction, and the operation of these fuel injection valves is controlled by the fuel injection control means, Two types of fuel sprays having different forms can be sprayed according to the purpose.

(First embodiment)
FIG. 1 shows a main part of an internal combustion engine according to an embodiment of the present invention. The internal combustion engine 1 is an in-cylinder spark ignition internal combustion engine that directly injects fuel into a cylinder. The internal combustion engine 1 includes a cylinder 2 and a piston 3 that reciprocates in the cylinder 2 and has a cavity 2a formed on the top surface. Have. An intake passage 4 and an exhaust passage 5 are connected to the cylinder 2. The intake passage 4 is provided with an intake valve 6 for opening and closing the intake passage 4, and the exhaust passage 5 is provided with an exhaust valve 7 for opening and closing the intake passage 6. A catalyst 8 for purifying harmful substances in the exhaust is provided in the exhaust passage 5 on the downstream side of the exhaust valve 7. The catalyst 8 is configured as a well-known three-way catalyst.

  The internal combustion engine 1 is adjacent to the first fuel injection valve 11 disposed so as to face the upper portion of the cylinder 2, the second fuel injection valve 12 disposed so as to face the side portion of the cylinder 2, and the first fuel injection valve 11. The spark plug 13 is arranged in the same manner. Each of the first fuel injection valve 11 and the second fuel injection valve 12 is supplied with fuel pumped by a supply pump (not shown), and the spark plug 13 is provided with a distributor (not shown) and the like. Necessary electric power is supplied via. The first fuel injection valve 11 is configured to be able to inject a hollow cone spray (first fuel spray) 21 that spreads in a hollow cone shape in the direction of the center line CL of the cylinder 2. On the other hand, the second fuel injection valve 12 is configured to be able to inject fan spray (second fuel spray) 22 that spreads in a fan shape in the direction intersecting the center line CL of the cylinder 2.

  As shown in FIG. 2A, the first fuel injection valve 11 has a structure of an outer valve, and a ring-shaped slit 15 having a predetermined width is formed by the forward and backward movement of the valve body 14. By injecting fuel from the slit 15, the hollow cone spray 21 shown in FIG. 2B is formed. By appropriately setting the dimension of the slit 15, the spread angle θ1 of the holocon spray 21 is set to a desired size. On the other hand, as shown in FIG. 3A, a flat slit 16 is formed in the nozzle portion 12 a provided at the tip of the second fuel injection valve 12, and fuel is injected from this slit 16. As a result, the fan spray 22 shown in FIG. 3B is formed. Each dimension in the width and thickness direction of the slit 16 is appropriately set, and the fan spray spread angle θ2 is set to a desired size.

  As shown in FIG. 1, the first fuel injection valve 11, the second fuel injection valve 12, and the spark plug 13 are connected to an engine control unit (ECU) 30. The ECU 30 is a known computer that controls the internal combustion engine 1 to an appropriate operating state with reference to output signals of various sensors, and includes a microprocessor and peripheral devices such as a RAM and a ROM necessary for its operation. Various sensors connected to the ECU 30 include a crank angle sensor 31 that outputs a signal corresponding to the crank angle (position) of the internal combustion engine 1, an air flow meter 32 that outputs a signal corresponding to the intake air amount, and a number of other sensors. Although a sensor is connected, illustration of a sensor not directly related to the gist of the present invention is omitted.

  4 and 5 show an example of a control routine repeatedly executed by the ECU 30 at predetermined intervals. FIG. 4 shows a main routine, and FIG. 5 shows a fuel injection control routine defined in step S5 of FIG. ing. As shown in FIG. 4, the ECU 30 acquires the operating state of the internal combustion engine 1 in step S1. The operating state acquired in step S1 includes an engine speed (rotation speed) Ne of the internal combustion engine 1 and an intake air amount Ga as a parameter representing the load. The engine speed Ne can be obtained from the output signal of the crank angle sensor 31, and the intake air amount Ga can be obtained from the output signal of the air flow meter 32. Next, in step S2, a target air-fuel ratio (target air-fuel ratio) is set based on the operating state acquired in step S1. Next, the fuel injection amount Q corresponding to the air-fuel ratio set in step S2 is calculated. The calculation of the fuel injection amount Q can be realized by storing a map with the intake air amount Ga and the engine speed Ne as variables in advance in the ROM of the ECU 30 and referring to this map.

  Next, ECU30 selects the combustion mode according to the driving | running state of the internal combustion engine 1 by step S4. The combustion mode of the internal combustion engine 1 includes a homogeneous combustion mode in which homogeneous combustion is to be performed, a stratified combustion mode in which stratified combustion is to be performed, and a weak stratified combustion mode in which weak stratified combustion is to be performed. Next, in step S5, fuel injection control, which will be described later, is executed. Next, in step S6, the ECU 30 supplies power to the spark plug 13 so that the air-fuel mixture in the cylinder 2 is ignited at a predetermined time, and this routine is executed. Finish.

  FIG. 5 is a flowchart illustrating an example of a control routine for fuel injection control. First, in step S51, the ECU 30 determines whether or not the load of the internal combustion engine 1 is high with reference to the output signal of the air flow meter 32. Whether or not the load is high can be determined by whether or not the load exceeds a predetermined upper limit (predetermined level). This upper limit value is set in consideration of the possibility of knocking. For example, when the internal combustion engine 1 is at full load, it is determined in step S51 that the load is high. If it is determined in step S51 that the load is high, the process proceeds to step S52, where the fuel injection amount Q obtained in step S3 of FIG. 4 is divided into fuel injection in the intake stroke and fuel injection in the compression stroke. Determine the ratio. This division ratio may be unchanged or may be changed according to the operating state of the internal combustion engine 1.

  For example, a map for calculating the division ratio shown in FIG. 6 may be stored in advance in the ROM of the ECU 30, and the division ratio may be obtained with reference to this map. According to this map, the division ratio is set so that the ratio of the injection amount in the compression stroke to the injection amount in the intake stroke increases as the engine speed Ne decreases. As the engine speed Ne is lower, knocking is more likely to occur. Thus, the occurrence of knocking can be reliably prevented by changing the division ratio in this way.

  Next, the ECU 30 injects the hollow cone spray 21 from the first fuel injection valve 11 in the intake stroke based on the division ratio determined in step S52 (step S53), and further in the compression stroke following the intake stroke, the second fuel. The fan spray 22 is injected from the injection valve 12 (step S54). The injection period in each stroke may be set as appropriate. For example, as shown in FIG. 7, the injection period T1 by the first fuel injection valve 11 is set substantially at the center of the intake stroke, and on the other hand, by the second fuel injection valve 12 The injection period T2 may be set so as to be biased toward the compression top dead center. By performing the above fuel injection, as shown in FIG. 8 (a), the hollow cone spray 21 injected in the intake stroke is diffused and vaporized entirely in the cylinder 2, and the cylinder 2 is caused by this vaporization latent heat. The air-fuel mixture inside is cooled, so that the occurrence of knocking is suppressed. On the other hand, as shown in FIG. 8 (b), the fan spray 22 is wound up along the wall surface of the cavity 3 a of the piston 3 that moves upward and is guided to the vicinity of the spark plug 13. This increases turbulence in the cylinder and promotes combustion.

  If it is determined in step S51 that the load is not high, the process proceeds to step S55 to determine whether the load is light. Whether or not the load is light is determined by whether or not the load is equal to or lower than a predetermined lower limit value. If it is not a light load, the process proceeds to step S56, and if it is a light load, the process proceeds to step 63. In step S56, it is determined whether or not the target air-fuel ratio set in step S2 of FIG. 4 is lean, that is, whether or not the target air-fuel ratio is more air than the stoichiometric air-fuel ratio. If the target air-fuel ratio is lean, the process proceeds to step S57, and if not, the process proceeds to step S65. In step S57, it is determined whether or not the combustion mode selected in step S4 in FIG. 4 is the homogeneous combustion mode. If the combustion mode is the homogeneous combustion mode, the process proceeds to step S58, and the first fuel injection valve 11 performs the hollow cone from the first fuel injection valve in the intake stroke. Spray 21 is sprayed (see FIG. 8A). In this case, fuel is injected only in the intake stroke without dividing the fuel injection into the intake stroke and the compression stroke. In other words, the injection of the fan spray 22 from the second fuel injection valve 12 in the compression stroke is prohibited. As a result, a homogeneous air-fuel mixture is formed in the cylinder 2 and so-called homogeneous lean combustion is realized.

  In step S59, it is determined whether or not the combustion mode selected in step S4 of FIG. 4 is the weak stratified combustion mode. If the combustion mode is the weak stratified combustion mode, the process proceeds to step S60, and if not, the process proceeds to step S65. move on. In step S60, a division ratio for dividing the fuel injection amount Q obtained in step S3 of FIG. 4 into the fuel injection in the intake stroke and the fuel injection in the compression stroke is determined. This division ratio may be unchanged, or the division ratio may be changed according to the degree of stratification to be realized. This stratification means the contrast of the air-fuel mixture in the cylinder 2. For example, a map for calculating the division ratio shown in FIG. 9 may be stored in the ROM of the ECU 30, and the division ratio may be obtained with reference to this map. According to this map, since the division ratio is set so that the ratio of the injection amount in the compression stroke to the injection amount in the intake stroke increases as the stratification degree increases, a desired stratification degree can be realized.

  Next, the ECU 30 injects the hollow cone spray 21 from the first fuel injection valve 11 in the intake stroke based on the division ratio determined in step S60 (step S61), and further in the compression stroke following the intake stroke, the second fuel. The fan spray 22 is injected from the injection valve 12 (step S62). By executing step S61 and step S62, so-called stratified lean combustion in which a high-concentration air-fuel mixture locally exists while the air-fuel ratio of the air-fuel mixture in the cylinder 2 is lean as a whole can be realized. In step S62, the same effect can be obtained by injecting the holocorn spray 21 from the first fuel injection valve 11 in the compression stroke instead of the fan spray 22 from the second fuel injection valve.

  In step S63, it is determined whether the combustion mode is the stratified combustion mode. If it is not the stratified combustion mode, the process proceeds to step S65. On the other hand, in the case of the stratified combustion mode, the process proceeds to step S64, and the holocorn spray 21 is injected from the first fuel injection valve 11 in the compression stroke. As a result, as shown in FIG. 10, the skirt portion of the holocorn spray 21 is wound up in a direction away from the center line CL of the cylinder 2, and a high-concentration air-fuel mixture is introduced in the vicinity of the spark plug 13. Spray-guided combustion is realized when light load is applied and stratified combustion is to be realized. In step S65, normal fuel injection control is executed. The form of fuel injection in normal fuel injection control may be set as appropriate. For example, if the combustion mode selected in step S4 in FIG. 4 is the homogeneous combustion mode, the holographic cone 21 is injected from the first fuel injection valve 11 in the intake stroke, and if the selected mode is the stratified combustion mode, The fan spray 22 may be injected from the second fuel injection valve 12.

  In the above embodiment, the ECU 30 functions as the fuel injection control means of the present invention by executing the control routine shown in FIG.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. In this embodiment, the present invention is applied when the internal combustion engine 1 is started. Since the configuration of the internal combustion engine 1 and its peripheral devices is the same as that of the first embodiment, a duplicate description is omitted. FIG. 11 is a flowchart showing a control routine executed by the ECU 30. First, the ECU 30 executes start control of the internal combustion engine 1 in step S11. This start control is well known to start the internal combustion engine 1 by starting cranking after an ignition switch (not shown) is turned on. Next, in step S12, the necessity of raising the temperature of the catalyst 8 is determined. This necessity can be determined based on various parameters such as the cooling water temperature of the internal combustion engine 1, the bed temperature of the catalyst 8, and the elapsed time after the internal combustion engine 1 is stopped.

  If it is not necessary to raise the temperature of the catalyst 8, the subsequent processing is skipped and the routine is terminated. On the other hand, when the temperature of the catalyst 8 needs to be increased, the temperature of the catalyst 8 is increased by repeatedly executing steps S13 to S15 until it is determined in step S16 that the end condition is satisfied. That is, the hollow cone spray 21 is injected from the first fuel injection valve 11 in the intake stroke (step S13), and the fan spray 22 is injected from the second fuel injection valve 12 in the subsequent compression stroke (step S14). Then, the ignition timing of the internal combustion engine 1 is retarded (step S15). Therefore, this form of fuel injection is repeatedly executed while the ignition timing is controlled to be retarded. The division ratio for dividing the fuel injection amount between the intake stroke and the compression stroke may be unchanged or may be changed according to the operating state of the internal combustion engine 1. Further, the retard amount of the ignition timing may be set as appropriate. The termination condition of step S16 may be appropriately set such that the temperature of the catalyst 8 can be determined to be unnecessary, such as when the cooling water temperature of the internal combustion engine 1 or the bed temperature of the catalyst 8 exceeds a predetermined level.

  By executing the control of FIG. 11, it is possible to form a gas mixture having a high concentration in the vicinity of the spark plug 13 and a low concentration and a homogeneous mixture in other regions. Thereby, the temperature of the catalyst 8 can be raised effectively. 11 is executed as a fuel injection control means of the present invention, and step S15 of FIG. 11 is executed so that the ECU 30 performs the ignition timing of the present invention. Each functions as a retarding means.

  The present invention is not limited to the above embodiment, and can be implemented in various forms within the scope of the gist of the present invention. For example, the fan spray 22 may be formed so as to spread in a fan shape with respect to a direction orthogonal to the direction of the center line CL of the cylinder 2. Further, the flat direction of the fan spray 22 is not limited, and may be flattened in the horizontal direction of the cylinder 2 as in the above-described embodiment, or may be flattened in the vertical direction of the cylinder 2. Further, the arrangement positions of the first fuel injection valve 11 and the second fuel injection valve 12 are not limited to the illustrated form, and they may be arranged at appropriate positions as long as the holocon spray and the fan spray of the present invention can be injected.

The figure which showed the principal part of the internal combustion engine which concerns on embodiment of this invention. It is explanatory drawing which shows a 1st fuel injection valve and a spray form, (a) shows the front-end | tip part of a 1st fuel injection valve, (b) shows the form of the holo-cone spray injected from a 1st fuel injection valve. It is explanatory drawing which shows a 2nd fuel injection valve and a spray form, (a) shows the front-end | tip part of a 2nd fuel injection valve, (b) shows the form of the fan spray injected from a 2nd fuel injection valve. The flowchart which shows an example of the control routine which ECU performs. 5 is a flowchart showing an example of a control routine of fuel injection control defined in FIG. Explanatory drawing which shows an example of the map for calculating a division ratio. Explanatory drawing explaining the fuel-injection period in each stroke of an intake stroke and a compression stroke. It is explanatory drawing which shows the state of fuel injection, (a) shows the state which the 1st fuel injection valve injected the holocorn spray in the intake stroke, (b) showed the 2nd fuel injection valve in the compression stroke injected the fan spray. Indicates the state. Explanatory drawing which shows an example of the map for calculating a division ratio. Explanatory drawing which shows the state which the 1st fuel injection valve injected the holocorn spray in the compression stroke. The flowchart which shows an example of the control routine which concerns on 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder 8 Catalyst 11 1st fuel injection valve (1st fuel injection valve)
12 Second fuel injection valve (second fuel injection valve)
21 Holocorn spray (first fuel spray)
22 Fan spray (second fuel spray)
30 ECU (fuel injection control means, ignition timing retarding means)

Claims (6)

  A first fuel injection valve capable of injecting into the cylinder a first fuel spray that spreads in a hollow conical shape with respect to the direction of the center line of the cylinder, and a second fuel spray that expands in a fan shape with respect to the direction intersecting the center line Comprising: a second fuel injection valve capable of injecting fuel into the cylinder; and fuel injection control means for controlling the operations of the first fuel injection valve and the second fuel injection valve. An in-cylinder injection internal combustion engine.   When the engine load exceeds a predetermined level, the fuel injection control means injects the first fuel spray in the intake stroke and injects the second fuel spray in the compression stroke following the intake stroke. The in-cylinder injection internal combustion engine according to claim 1, wherein each operation of the first fuel injection valve and the second fuel injection valve is controlled.   The fuel injection control means is configured so that the ratio of the injection amount in the compression stroke to the injection amount in the intake stroke becomes larger as the engine speed is lower, the first fuel injection valve and the second fuel injection valve. 3. The direct injection internal combustion engine according to claim 2, wherein each operation is controlled.   The fuel injection control means is configured to inject the first fuel spray in an intake stroke and perform the second in a compression stroke following the intake stroke when the load is equal to or less than the predetermined level and homogeneous combustion is to be performed. 4. The in-cylinder injection according to claim 2, wherein the operation of each of the first fuel injection valve and the second fuel injection valve is controlled so that injection of the fuel spray is prohibited. 5. Internal combustion engine.   When the load is less than the predetermined level and weak stratified combustion is to be performed, the fuel injection control means is configured to inject the first fuel spray in the intake stroke and perform the first injection in the compression stroke following the intake stroke. The operation of each of the first fuel injection valve and the second fuel injection valve is controlled so that one fuel spray or the second fuel spray is injected. The cylinder injection internal combustion engine described in 1. A catalyst provided in the exhaust passage for purifying harmful substances in the exhaust, and ignition timing retarding means for retarding the ignition timing within a period in which the catalyst needs to be heated;
The fuel injection control means is configured to inject the first fuel spray in the intake stroke while the ignition timing retarding means retards the ignition timing, and in the compression stroke following the intake stroke, 2. The direct injection internal combustion engine according to claim 1, wherein operations of the first fuel injection valve and the second fuel injection valve are controlled so that fuel spray is injected.

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