JP4867811B2 - Internal combustion engine having a variable valve mechanism - Google Patents

Description

  The present invention relates to an internal combustion engine including a variable valve mechanism.

  Conventionally, for example, Patent Document 1 discloses an internal combustion engine including a variable valve mechanism that can independently change the valve characteristics of two intake valves arranged in the same cylinder. More specifically, in the above-described conventional internal combustion engine, the intake air amount passing through the two intake valves is made different by varying the valve operating characteristics (lift amount, etc.) of the two intake valves under predetermined operating conditions. By making the difference, a swirl is generated in the combustion chamber.

JP 2004-1000055 A

  However, in the above-described conventional technology, no consideration is given to the configuration of the intake port suitable for effectively generating the swirl by making the intake air amounts of the two intake valves different.

  The present invention has been made to solve the above-described problems, and an internal combustion engine that generates a swirl in a cylinder by making the intake air amounts passing through the first intake valve and the second intake valve different from each other. An object of the present invention is to provide an internal combustion engine including a variable valve mechanism that can generate an effective swirl over the entire intake stroke.

The first invention includes a first intake port in which a first intake valve is disposed, a second intake port in which a second intake valve is disposed, valve operating characteristics of the first intake valve, and the A variable valve mechanism that allows the valve characteristics of the second intake valve to be changed independently; and the intake air amount that passes through the first intake valve and the second intake valve is different. An internal combustion engine comprising swirl generating means for generating a swirl in a cylinder by controlling a variable valve mechanism,
The swirl generating means generates the difference in the intake air amount by executing a one-valve early closing control that makes the closing timing of the first intake valve earlier than the closing timing of the second intake valve. There,
The first intake port has a swirl ratio that reaches a peak value when the lift amount of the first intake valve is lower than the full lift amount during the execution of the one-valve early closing control, and When it is the full lift amount, it has a characteristic that the swirl ratio is lower than the peak value ,
The second intake port is more than the lift amount of the second intake valve when the peak value of the swirl ratio arrives at the first intake port during execution of the one-valve early closing control. When the lift amount of the intake valve 2 is high, the peak value of the swirl ratio arrives at the second intake port,
The first intake port is configured as a helical port;
The second intake port is configured as a tangential port;
The first intake valve opens between the initial stage and the middle stage of the intake stroke when the one-valve early closing control is executed .

The second invention is Oite the first inventions, the first intake port and the second intake port, at the time the execution of the single valve early closing control of the first intake valve The swirl generated by the first intake port has a characteristic that the swirl generated by the second intake port is stronger than the swirl generated by the second intake port in a low lift state before the lift amount reaches the full lift amount. It is characterized by.

According to the first aspect of the present invention, when the one-valve early closing control for generating the swirl is executed, the first intake port in which the first intake valve whose closing timing is advanced is arranged is used to perform the intake stroke. It becomes possible to generate a swirl effectively in the initial stage. Then, in the middle and late stages of the intake stroke, it is possible to generate a swirl by using the second intake port, which is the other intake port in which the second intake valve that opens until later is arranged. . As described above, according to the present invention, it is possible to separate the intake port responsible for swirl generation at the initial stage and the mid-late stage of the intake stroke. For this reason, it becomes possible to generate a swirl effectively over the entire intake stroke. Furthermore, according to the present invention, the characteristics of the second intake port can be determined so that a more effective swirl can be generated using the second intake port in the middle and later stages of the intake stroke. Furthermore, according to the present invention, the swirl can be effectively generated by using the first intake port at the initial stage of the intake stroke, and the second intake port can be effectively used at the middle and later stages of the intake stroke. Therefore, it is possible to configure the intake port so that swirl can be generated.

According to the second invention, the intake port can be configured such that the first intake port is responsible for effective swirl generation at the initial stage of the intake stroke. This makes it possible to effectively generate a swirl over the entire intake stroke.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. The system shown in FIG. 1 includes an internal combustion engine 10. The internal combustion engine 10 is a four-cycle diesel engine (compression ignition type internal combustion engine). Each cylinder of the internal combustion engine 10 is provided with an injector 12 that directly injects fuel into the cylinder. The injectors 12 of each cylinder are connected to a common common rail 14. Fuel in a fuel tank (not shown) is pressurized to a predetermined fuel pressure by a supply pump 16, stored in the common rail 14, and supplied from the common rail 14 to each injector 12.

  An exhaust passage 18 of the internal combustion engine 10 is branched by an exhaust manifold 20 and connected to an exhaust port of each cylinder. The internal combustion engine 10 of the present embodiment includes a turbocharger 22. The exhaust passage 18 is connected to the exhaust turbine of the turbocharger 22. Further, an exhaust gas purification device 24 for purifying exhaust gas is provided on the exhaust passage 18 downstream of the turbocharger 22.

  An air cleaner 28 is provided near the inlet of the intake passage 26 of the internal combustion engine 10. The air sucked through the air cleaner 28 is compressed by the intake compressor of the turbocharger 22 and then cooled by the intercooler 30. The intake air that has passed through the intercooler 30 is distributed to the intake port of each cylinder by the intake manifold 32.

  An intake throttle valve 34 is installed between the intercooler 30 and the intake manifold 32. An air flow meter 36 for detecting the intake air amount is installed in the vicinity of the downstream side of the air cleaner 28. An intake pressure sensor 38 that detects the pressure in the intake passage 26 is installed on the downstream side of the intake throttle valve 34.

  The internal combustion engine 10 shown in FIG. 1 is provided with two intake valves 62 and 66 (see FIG. 3) and two exhaust valves (not shown) in each cylinder. The internal combustion engine 10 includes an intake variable valve mechanism 40 that can change the valve characteristics of the intake valves 62 and 66 of each cylinder, and an exhaust variable valve mechanism that can change the valve characteristics of an exhaust valve (not shown). 42. More specifically, the intake variable valve mechanism 40 is a mechanism that can independently change the valve operating characteristics (lift amount, operating angle, closing timing, etc.) of the two intake valves 62 and 66. The intake variable valve mechanism 40 having such a function can be realized by, for example, a variable valve mechanism detailed in International Publication No. WO 2006/025565 A1. For this reason, the detailed description is omitted or simplified here.

  FIG. 2 is a view showing a lift curve of the intake valve realized by the intake variable valve mechanism 40 shown in FIG. In the present embodiment, in the operation region where swirl is required, by controlling the intake variable valve mechanism 40, the closing timing of one intake valve 66 is compared with the other intake valve 62 as shown in FIG. Then, control is performed so that it can be advanced (single valve early closing control). According to such one-valve early closing control, the amount of intake air passing through the two intake valves 62 and 66 can be made different, and thus a swirl can be generated satisfactorily. In the present specification, the intake port whose intake valve lift amount is increased during the one-valve early closing control is referred to as a “mainstream port (second intake port” in the present invention), and The intake port on which the lift amount of the intake valve is lowered is referred to as a “subordinate port (first intake port in the present invention)”.

  The exhaust variable valve mechanism 42 is assumed to have a function of changing the opening / closing timing of the exhaust valve while keeping the lift amount and the operating angle constant. Such a function can be realized, for example, by providing a VVT mechanism (not shown) for controlling the opening / closing timing of the exhaust valve. The intake variable valve mechanism 40 is also provided with such a VVT mechanism (not shown).

  Further, the system of the present embodiment includes an ECU (Electronic Control Unit) 50. In addition to the various sensors described above, the ECU 50 is connected to a crank angle sensor 52 for detecting the engine speed and an accelerator opening sensor 54 for detecting the accelerator opening, and the various actuators described above. Is connected. The ECU 50 controls the operating state of the internal combustion engine 10 by driving each actuator according to a predetermined program based on those sensor signals and information.

[Characteristics of Embodiment 1]
(About characteristics given to each intake port)
The internal combustion engine 10 of the present embodiment is characterized by the configuration of the intake port. More specifically, in the present embodiment, at the time of execution of the one-valve early closing control, the slave port (first intake port) that is the intake port in which the intake valve 66 whose lift amount is reduced is disposed is provided. Has a characteristic that a high swirl ratio can be obtained in a low lift state. More specifically, the subordinate port has a swirl ratio that reaches a peak value when the lift amount of the intake valve 66 is lower than the full lift amount, and is higher than the peak value when the lift amount is the full lift amount. The characteristic that the swirl ratio is lowered (the characteristic of the subordinate A in FIG. 6) is given.

  On the other hand, in the present embodiment, during the execution of the one-valve early closing control, the main flow port (second intake port), which is the intake port in which the intake valve 62 whose lift amount is to be increased, is arranged has a high lift. The characteristic that a high swirl ratio is obtained in the state is given. More specifically, when the lift amount of the intake valve 62 is higher than the lift amount of the intake valve 62 when the peak value of the swirl ratio arrives at the subordinate port, the mainstream port is swirled at the main port. A characteristic (the characteristic of the mainstream A in FIG. 5) that gives the peak value of the ratio is given.

  Further, in addition, the dependent port and the mainstream port of this embodiment are in a low lift state before the lift amount of the intake valve 66 on the dependent port side reaches the full lift amount when the one-valve early closing control is executed. The swirl generated by the subordinate port is given a characteristic that is stronger than the swirl generated by the mainstream port.

(Specific examples of mainstream ports and subordinate ports)
FIG. 3 is a plan view showing an example of the configuration of the intake port 60 that satisfies the characteristics of the mainstream port and the subordinate port as described above. In the example shown in FIG. 3, a main flow port 60 a that is an intake port in which the intake valve 62 whose lift amount is increased when the one-valve early closing control is executed is configured as a tangential port. Such a tangential port basically has a characteristic that a high swirl ratio can be obtained when the intake valve 62 is in a high lift state. More specifically, according to the main flow port 60a configured as described above, the main flow port 60a is along the tangential direction of the cylinder 64, so that the cylinder 64 can be moved during a high lift when the intake air flow rate is relatively large. It is possible to effectively generate a swirl in the cylinder.

  In the example shown in FIG. 3, the dependent port 60b, which is an intake port in which the intake valve 66 whose lift amount is lowered when the one-valve early closing control is executed, is configured as a helical port. In such a helical port, the end on the intake valve 66 side is curved in a spiral shape on the plan view shown in FIG. For this reason, the characteristic that a high swirl ratio is obtained when the intake valve 66 is in a relatively low lift state is given. More specifically, according to the subordinate port 60b configured as described above, the swirl is effectively generated in the cylinder by utilizing the spiral shape of the port itself at the time of low lift with a relatively small intake air flow rate. be able to.

  By adopting the configuration of the intake port 60 of the present embodiment described above (that is, a characteristic in which a high swirl ratio is obtained when the mainstream port 60a is in a high lift state, and the subordinate port 60b is in a low lift state. (Since it has a characteristic that a high swirl ratio is obtained at a certain time), swirl generation using the dependent port 60b is performed in the early stage of the intake stroke, and swirl generation is performed using the mainstream port 60a in the middle and later stages of the intake stroke. In this way, the intake port responsible for swirl generation is separated in the early and middle late stages of the intake stroke. For this reason, it becomes possible to generate a swirl effectively over the entire intake stroke. Such excellent effects will be described in detail with reference to FIGS.

(Effects of the configuration of the intake port of the first embodiment)
FIG. 4 is a diagram illustrating characteristics of samples of the mainstream port and the subordinate port prepared for confirming the effect of the configuration of the intake port 60 according to the first embodiment of the present invention. That is, as shown in FIG. 4, two types of samples called “mainstream A” and “mainstream B” are prepared as mainstream ports, and two subports are also called “subordinate A” and “subordinate B”. Different types of samples are prepared. Incidentally, there is basically a trade-off relationship between the swirl ratio and the flow coefficient of the intake port. That is, basically, when the flow coefficient is increased, the swirl ratio becomes small (the swirl becomes weak), and conversely, when the swirl ratio is increased, the flow coefficient becomes small.

  In “main flow A”, the characteristics of the intake port are determined with emphasis on increasing the swirl ratio rather than the flow coefficient when the intake valve is in a high lift state. In “main flow B”, the characteristics of the intake port are determined with emphasis on increasing the flow coefficient from the swirl ratio when the intake valve is in a high lift state. The flavoring of the port characteristics of the mainstream A and the mainstream B can be realized by appropriately adjusting the shape of the inner wall of the intake port. As an example of the intake port that realizes the mainstream A, the above-described diagram is used. 3 corresponds to the mainstream port 60a. The mainstream B is a sample whose port characteristics are adjusted for comparison with the mainstream port 60a of the present embodiment.

  FIG. 5 is a graph showing swirl and flow coefficient characteristics in the main flow A and the main flow B in relation to the lift amount. As shown in FIG. 5A, the main stream A (black square mark) has a characteristic that a high swirl ratio can be obtained in a high lift state as compared with the main stream B (black rhombus mark). I understand. On the other hand, as shown in FIG. 5B, it can be seen that the main flow B has a characteristic that it is higher in the high lift state than the main flow A in terms of the flow coefficient.

  On the other hand, in FIG. 4, “subordinate A” determines the characteristics of the intake port with emphasis on increasing the swirl ratio rather than the flow coefficient when the intake valve is in the low lift state. “Subordinate B” determines the characteristics of the intake port with emphasis on increasing the flow coefficient over the swirl ratio when the intake valve is in a low lift state. The seasoning of the port characteristics of the subordinate A and subordinate B can also be realized in the same manner as the mainstream A and mainstream B described above. As an example of the intake port that realizes the subordinate A, FIG. The subordinate port 60b shown in FIG. The subordinate B is a sample whose port characteristics are adjusted for comparison with the subordinate port 60b of the present embodiment.

  FIG. 6 is a diagram showing the swirl and flow coefficient characteristics in each of subordinate A and subordinate B in relation to the lift amount. As shown in FIG. 6A, it can be seen that the subordinate A (white circle mark) has a characteristic that a high swirl ratio can be obtained in a low lift state as compared to the subordinate B (white triangle mark). . On the other hand, as shown in FIG. 6B, it can be seen that in terms of flow coefficient, the subordinate B has a characteristic that it is higher in the low lift state than the subordinate A.

  FIG. 7 is a diagram for explaining a combination example of the four samples (mainstream A and the like) used for confirming the effect of the configuration of the intake port 60 according to the first embodiment of the present invention. Here, as shown in FIG. 7, a combination employed in the intake port 60 of the present embodiment, that is, a combination of the mainstream A and the subordinate A is referred to as “specification A”. Further, a combination of the mainstream B and the subordinate B is referred to as “specification B”, and a combination of the mainstream A and the subordinate B is referred to as “specification C”. According to these three specifications A, B, and C, by comparing the specification B and the specification C, it becomes possible to determine the influence of the mainstream port. By comparing the original C, the influence of the dependent port can be determined.

  FIG. 8 is a diagram comparing the swirl ratio during the intake stroke among the above three specifications A, B, and C. From FIG. 8, the mainstream A and the subordinate A are combined even in the initial stage of the intake stroke of 0 to 60 ° CA in the crank angle and in the middle and late stages of the intake stroke in the range of 90 to 180 ° CA of the crank angle. It can be seen that the specification A (port configuration of the present embodiment) can generate the swirl most effectively.

  FIG. 9 is an image diagram for explaining the improvement effect of the swirl generation function by the configuration (specification A) of the intake port according to the first embodiment of the present invention. FIG. 9A shows the operation at the initial stage of the intake stroke. When the one-valve early closing control is executed, the intake valve 66 on the dependent port 60b side is closed earlier than the intake valve 62 on the mainstream port 60a side. For this reason, at the time of execution of the one-valve early closing control, the intake valve 66 on the dependent port 60b side is used only in the low lift region between the initial stage and the middle stage of the intake stroke. In the present embodiment, the subordinate port 60b used in such a manner is an intake port having a high swirl ratio in a low lift state. For this reason, in the initial stage of the intake stroke, it is possible to effectively generate a swirl using the dependent port 60b.

  FIG. 9B shows the operation in the middle and late stages of the intake stroke. When the one-valve early closing control is executed, since only the intake valve 62 on the main flow port 60a side performs the lift operation after the middle stage of the intake stroke, the intake air flows into the cylinder through only the main flow port 60a. In the middle and late stages of such an intake stroke, the intake valve 62 on the mainstream port 60a side frequently uses a high lift region. In the present embodiment, the mainstream port 60a used in such a manner is an intake port having a high swirl ratio in a high lift state. For this reason, in the middle and late stages of the intake stroke, it is possible to effectively generate the swirl using the mainstream port 60a.

  FIG. 10 is a diagram showing the relationship between the flow coefficient (stroke average μσ) and the swirl ratio (stroke average Swirl) in the form of the average value of one intake stroke. More specifically, the waveforms of the respective specifications A, B, and C show the waveforms obtained when the degree of early closing of the intake valve on the dependent port side is changed, and the respective specifications A, B , C, the three points arranged in the horizontal direction in FIG. 10 correspond to the points at the equal close degree.

  According to the experimental results shown in FIG. 10, the configuration (specification A) of the present embodiment can obtain a high swirl ratio without causing a decrease in the flow coefficient as compared with the other specifications B and C. It turns out that it becomes. The reason is that the other specifications B and C are able to secure the same flow coefficient as that of the specification A at the iso-closed degree, but the flow of the two intake ports interferes with each other and the swirl is sufficient. This is probably because the ratio was not obtained.

  In contrast, according to the configuration of the mainstream port 60a and the subordinate port 60b of the present embodiment, a strong swirl can be generated using the subordinate port 60b in the initial stage of the intake stroke, and the middle and late stages of the intake stroke The strong swirl can be generated using the mainstream port 60a in a state where the dependent port 60b whose swirl ratio has exceeded the peak value is closed. That is, as described above, the intake port responsible for swirl generation is separated at the initial stage and the mid-late stage of the intake stroke. Accordingly, it is possible to effectively generate a swirl over the entire intake stroke while avoiding flow interference between the two intake ports. As a result, the trade-off relationship between the swirl ratio and the flow coefficient can be improved.

  FIG. 11 is a diagram showing the relationship between the fuel consumption of the internal combustion engine 10 and the NOx emission amount. As in the system of this embodiment, in a system that generates a swirl by one-valve early closing control of an intake valve, the swirl ratio can be increased as the degree of early closing of the intake valve on the dependent port side is further increased. However, the flow coefficient decreases (the above trade-off relationship). However, according to the configuration of the intake port 60 of the present embodiment described above, since the trade-off relationship can be improved as described above, the flow coefficient is not reduced (that is, the pump loss is deteriorated (fuel consumption is reduced). A sufficient swirl ratio can be secured.

  When the swirl ratio can be sufficiently secured, the mixing of the intake air and the fuel in the cylinder is improved, so that the smoke discharge amount can be suppressed. And it becomes possible to increase the amount of EGR gas by the amount that can suppress the smoke discharge amount. This makes it possible to reduce the NOx emission amount. For this reason, as shown in FIG. 11, it is possible to suitably achieve both improvement in fuel consumption and improvement in exhaust emission performance (reduction in NOx emission).

  By the way, in the first embodiment described above, the “first intake valve”, “second intake valve”, “first intake port”, and “second intake port” in the present invention include: The intake valve 66, the intake valve 62, the slave port, and the main flow port correspond to each other. However, in the present invention, the first and second intake valves and the first and second intake ports are not limited to a configuration in which one is provided for each cylinder. That is, a configuration in which two or more of these first and second intake valves and first and second intake ports are provided in each cylinder may be employed.

  In the first embodiment described above, the “swirl generation means” according to the first aspect of the present invention is realized by the ECU 50 controlling the intake variable valve mechanism 40 so that the one-valve early closing control is executed. ing.

FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. It is a figure which shows the lift curve of the intake valve implement | achieved by the intake variable valve operating mechanism shown in FIG. It is a top view showing an example of the composition of the intake port which satisfies the characteristic of the mainstream port and subordinate port of Embodiment 1 of the present invention. It is a figure which shows the characteristic of each sample of the mainstream port and subordinate port prepared in order to confirm the effect by the structure of the intake port of Embodiment 1 of this invention. It is the figure which represented the characteristic of the swirl in each of the mainstream A and the mainstream B, and the flow coefficient with the lift amount. It is the figure which represented the characteristic of the swirl and flow coefficient in each of subordinate A and subordinate B in relation to the lift amount. It is a figure for demonstrating the example of a combination of four samples (mainstream A etc.) used in order to confirm the effect by the structure of the intake port of Embodiment 1 of this invention. It is the figure which compared the swirl ratio in an intake stroke between said three specifications A, B, and C. FIG. It is an image figure for demonstrating the improvement effect of the swirl production | generation function by the structure (specification A) of the intake port of Embodiment 1 of this invention. It is the figure which represented the relationship between a flow coefficient (stroke average (micro | micron | mu)) and a swirl ratio (stroke average Swirl) in the form of the average value of one intake stroke. It is a figure showing the relationship between the fuel consumption of an internal combustion engine, and NOx discharge | emission amount.

Explanation of symbols

10 Internal combustion engine 18 Exhaust passage 20 Exhaust manifold 26 Intake passage 32 Intake manifold 40 Intake variable valve mechanism 42 Exhaust variable valve mechanism 50 ECU (Electronic Control Unit)
60 Intake port 60a Mainstream port 60b Subordinate port 62 Intake valve (mainstream port side)
64 Cylinder 66 Intake valve (dependent port side)

Claims (2)

The first intake port in which the first intake valve is arranged, the second intake port in which the second intake valve is arranged, the valve operating characteristics of the first intake valve, and the second intake valve A variable valve mechanism that can change the valve characteristics independently, and the variable valve mechanism is controlled so that there is a difference in the amount of intake air that passes through the first intake valve and the second intake valve An internal combustion engine comprising swirl generating means for generating swirl in a cylinder,
The swirl generating means generates the difference in the intake air amount by executing a one-valve early closing control that makes the closing timing of the first intake valve earlier than the closing timing of the second intake valve. There,
The first intake port has a swirl ratio that reaches a peak value when the lift amount of the first intake valve is lower than the full lift amount during the execution of the one-valve early closing control, and When it is the full lift amount, it has a characteristic that the swirl ratio is lower than the peak value ,
The second intake port is more than the lift amount of the second intake valve when the peak value of the swirl ratio arrives at the first intake port during execution of the one-valve early closing control. When the lift amount of the intake valve 2 is high, the peak value of the swirl ratio arrives at the second intake port,
The first intake port is configured as a helical port;
The second intake port is configured as a tangential port;
An internal combustion engine provided with a variable valve mechanism, wherein the first intake valve opens between an initial stage and an intermediate stage of an intake stroke when the one-valve early closing control is executed . The first intake port and the second intake port are in the low lift state before the lift amount of the first intake valve reaches the full lift amount when the one-valve early closing control is executed. an internal combustion engine towards the swirl intake port generates comprises a variable valve mechanism according to claim 1, characterized in that it has a characteristic such that stronger than swirl the second intake port to produce a .

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