JP2004156541A - Internal combustion engine having variable compression ratio mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology to cope with the increase of the wet quantity on a piston crown portion in the state of the high compression ratio. <P>SOLUTION: An air flow control valve control circuit 32 increases turbulence of the air intake flow into a combustion chamber by reducing the opening of an air flow control valve 61 when the compression ratio is high, and mitigates the increase of the wet quantity on a piston crown portion thereby. Turbulence of the air intake flow can be increased by reducing the lift of an air intake valve 41 or by the angle of delay of the valve opening time of the air intake valve 41 in place of the adjustment of the opening of the air flow control valve 61. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an internal combustion engine having a variable compression ratio mechanism.
[0002]
[Prior art]
DESCRIPTION OF RELATED ART Conventionally, the internal combustion engine which has the variable compression ratio mechanism which can change a compression ratio is known (for example, patent documents 1-4).
[0003]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2000-54873 [Patent Document 2]
JP-A-63-18142 [Patent Document 3]
JP-A-7-208220 [Patent Document 4]
JP-A-63-120820
Generally, the higher the compression ratio, the better the thermal efficiency and thus the better the fuel efficiency, but the more the knocking tends to occur. Therefore, when the load of the internal combustion engine is small, the possibility of knocking is low. Therefore, by setting a high compression ratio, fuel efficiency can be improved. On the other hand, when the load is large, knocking is prevented by setting the compression ratio low.
[0005]
[Problems to be solved by the invention]
It is known that when a high compression ratio is set in such an internal combustion engine, the amount of fuel (wet amount) adhering to the piston top surface increases. The reason is that at a high compression ratio, the distance between the top surface of the piston at the top dead center and the cylinder head becomes small, and the fuel particles sucked from the intake port or directly injected into the combustion chamber become It is presumed that this is because it easily adheres to the top surface. An increase in the wet amount at the top of the piston is not preferable because combustion deteriorates. However, conventionally, there has not been enough devised to cope with an increase in the wet amount at the top of the piston in a high compression ratio state.
[0006]
The present invention has been made to solve the above-mentioned conventional problems, and has as its object to provide a technique for coping with an increase in the wet amount of the piston top in a high compression ratio state.
[0007]
[Means for Solving the Problems and Their Functions and Effects]
In order to achieve at least a part of the above object, an internal combustion engine of the present invention includes:
A cylinder and a piston constituting a combustion chamber;
A variable compression ratio mechanism capable of changing the compression ratio of the combustion chamber,
Air flow changing means capable of changing a turbulence state of the intake air flow to the combustion chamber according to the index value indicating the compression ratio,
Is provided.
[0008]
In this internal combustion engine, since the turbulence state of the intake air flow to the combustion chamber can be changed according to the index value indicating the compression ratio, it is possible to prevent an increase in the wet amount at the top of the piston in the high compression ratio state.
[0009]
It is preferable that the airflow changing unit increases turbulence of the intake airflow to the combustion chamber when the compression ratio is larger than a first determination value.
[0010]
Further, the airflow changing means may be configured to reduce the turbulence of the intake air to the combustion chamber when the compression ratio is larger than a first judgment value and the load ratio of the internal combustion engine is smaller than a second judgment value. Preferably, it is increased.
[0011]
When the compression ratio is low and the load factor is low, the wet amount at the top of the piston tends to increase. In this case, if the turbulence of the intake air flow is increased, this tendency can be alleviated.
[0012]
The airflow changing means may include an airflow control mechanism provided in an intake pipe for guiding intake air to the combustion chamber and capable of changing a flow path resistance of the intake pipe. Further, the airflow control mechanism may include an adjustment valve whose opening can be adjusted. Further, the combustion chamber has two intake ports, an intake pipe for guiding intake air to the combustion chamber includes two branch pipes connected to the two intake ports, and the regulating valve includes the two branch ports. It may be provided on only one of the tubes.
[0013]
With such an airflow control mechanism, the turbulence of the intake air flow to the combustion chamber can be easily increased.
[0014]
Alternatively, the airflow changing means may include an intake valve control mechanism capable of changing at least one of a lift amount of an intake valve of the combustion chamber and a timing of a valve opening period. For example, the intake valve control mechanism may increase the turbulence of the intake flow to the combustion chamber by reducing the lift amount of the intake valve. Further, the intake valve control mechanism may increase turbulence of the intake flow to the combustion chamber by delaying a timing of a valve opening period of the intake valve.
[0015]
By using such an intake valve control mechanism, the turbulence of the intake flow to the combustion chamber can be easily increased.
[0016]
Note that the present invention can be realized in various aspects, for example, an internal combustion engine, a control method of the internal combustion engine, a computer program for realizing the control method, a recording medium storing the computer program, It can be realized in the form of a data signal including the computer program and embodied in a carrier wave.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
A. First embodiment:
Next, embodiments of the present invention will be described based on examples. FIG. 1A is a conceptual diagram showing a configuration of an internal combustion engine 10 as a first embodiment of the present invention. The internal combustion engine 10 has a combustion chamber including a cylinder 20 and a piston 21. The cylinder head 22 is provided with a spark plug 51, an intake valve 41, and an exhaust valve.
[0018]
As shown in FIG. 1B, the internal combustion engine 10 has two intake ports 111 and 112 and two exhaust ports 121 and 122. Two branch pipes 101 and 102 of the intake pipe 100 are connected to the intake ports 111 and 112, respectively. The first branch pipe 101 is provided with an airflow control valve 61. The airflow control valve 61 is a control valve whose opening can be adjusted, and has a function of increasing the turbulence of the intake air introduced into the combustion chamber when the opening is small.
[0019]
The piston 21 is connected to the connecting rod 23. The connecting rod 23 has a configuration in which first and second connecting rod members 231 and 233 are connected by a connection pin 232, and can be bent at the connection portion. The upper end of the first connecting rod member 231 is connected to the piston 21 by the piston pin 24, and the lower end of the second connecting rod member 233 is connected to the crank 11. The lower end of the first connecting rod member 231 is further connected to a control rod 26 by a connecting pin 25. The other end of the control rod 26 is connected to a control shaft 27 provided on the periphery of a rotatable control disk 28. The control shaft 27 is installed parallel to the center axis 29 at a position eccentric from the center axis 29 of the control disk 28. Therefore, when the control disk 28 is rotated around the central axis 29, the control shaft 27 revolves around the central axis 29. The control disk 28 is provided with a rotation position sensor 33 for detecting the rotation position of the disk 28.
[0020]
The variable compression ratio control circuit 31 provided in the ECU (Electronic Control Unit) 30 uses the drive unit 34 to position the control shaft 27 in the section from the approximately 3 o'clock position to the approximately 6 o'clock position. Thereby, the degree of bending of the connecting rod 23 can be adjusted. When the degree of bending of the connecting rod 23 changes, the positions of the top dead center and the bottom dead center of the piston 21 in the cylinder 20 also change. Therefore, the compression ratio of the combustion chamber can be changed by adjusting the degree of bending of the connecting rod 23. As can be understood from this description, the connecting rod 23, the control rod 26, the control disk 28, the variable compression ratio control circuit 31, and the drive unit 34 constitute a variable compression ratio mechanism as a whole.
[0021]
This variable compression ratio mechanism is the same as that disclosed in JP-A-2000-54873 disclosed by the present applicant. However, any other mechanism can be adopted as the variable compression ratio mechanism.
[0022]
The ECU 30 further includes an airflow control valve control circuit 32 for controlling the opening of the airflow control valve 61. The ECU 30 is supplied with signals indicating various parameters such as an engine speed, a throttle opening (accelerator pedal depression amount), an intake air amount, a cylinder cooling water temperature, and the like from various sensors. The ECU 30 controls the compression ratio and the opening of the airflow control valve according to these various parameters.
[0023]
FIG. 2 is a flowchart showing a control procedure of the engine according to the first embodiment of the present invention. In step S1, the ECU 30 detects an operating state of the engine such as an engine speed, a throttle opening, an intake air amount, and a coolant temperature of a cylinder. In step S2, the variable compression ratio control circuit 31 calculates a target value of the compression ratio CR appropriate for the operating state of the engine detected in step S1. This calculation can be realized using, for example, a map or a lookup table that receives a combination of values of a plurality of parameters that define the operating state and outputs a target value of the compression ratio. In step S3, the variable compression ratio control circuit 31 rotates the control disk 28 while monitoring the detection signal of the rotation position sensor 33, and sets the compression ratio to a target value.
[0024]
In step S4, the airflow control valve control circuit 32 calculates the load ratio LR corresponding to the current compression ratio CR, and compares this value LR with the determination value α in step S5. Here, the load factor LR means the ratio of the actual air intake amount to the maximum air capacity in the combustion chamber. Since the maximum air capacity in the combustion chamber is equal to the capacity of the combustion chamber when the piston is at the bottom dead center, the maximum air capacity is determined by the compression ratio. The smaller the compression ratio, the larger the value. The actual air intake amount is measured by an air flow meter (not shown).
[0025]
When the value of the load ratio LR is larger than the determination value α (when the compression ratio is small), there is little possibility that the deterioration of the combustion due to the increase in the wet amount at the top of the piston is small, so the opening degree of the airflow control valve 61 is increased. It is set (step S6). For example, in step S6, it is preferable to set the airflow control valve 61 to 100% opening. On the other hand, when the value of the load factor LR is smaller than the determination value α (when the compression ratio is large), there is a possibility that combustion may deteriorate due to an increase in the wet amount at the top of the piston. A small value is set to increase the turbulence of the intake air flow introduced into the combustion chamber (step S7). As shown in FIG. 1 (B), the airflow control valve 61 is provided only in one of the two branch pipes 101 and 102 for guiding intake air to the combustion chamber. By doing so, the balance of the amount of intake air introduced from the two branch pipes 101 and 102 is lost. As a result, compared to the case where the opening degree of the airflow control valve 61 is large, the turbulence of the intake flow in the combustion chamber becomes large, and the wet amount at the top of the piston can be reduced.
[0026]
When the opening of the airflow control valve 61 is reduced, the turbulence itself of the intake air in the branch pipe 101 provided with the airflow control valve 61 also increases. Therefore, even if the airflow control valve 61 is provided in both of the two branch pipes 101 and 102, it is possible to increase the turbulence of the intake air flow by reducing the opening degree of the airflow control valve 61. In this case, the airflow control valve 61 is preferably provided near the intake port 111 of the cylinder head 22. For example, it is preferable to provide the airflow control valve 61 at a position within 10 times the diameter D of the branch pipe 101 connected to the intake port 111 from the intake port 111, and within 5 times the diameter D of the branch pipe 101. More preferably, it is provided at a distance. However, providing the airflow control valve 61 only in one of the two branch pipes 101 and 102 is more effective in increasing the turbulence of the intake flow.
[0027]
In step S7, the ECU 30 corrects the opening of the throttle valve (not shown) in accordance with the opening of the airflow control valve 61, and adjusts the intake air amount.
[0028]
As described above, in the first embodiment, when the load ratio LR is smaller than the determination value α (that is, when the compression ratio is high), the opening degree of the airflow control valve 61 is reduced to increase the turbulence of the intake flow. As a result, it is possible to alleviate an increase in the wet amount at the top of the piston due to an increase in the compression ratio.
[0029]
Since the load ratio LR depends on the compression ratio CR, the value of the load ratio LR can be considered as an index value indicating the compression ratio. Note that the control in FIG. 2 can be performed using the compression ratio CR instead of the load ratio LR.
[0030]
B. Second embodiment:
FIG. 3 is a flowchart showing a control procedure of the engine according to the second embodiment of the present invention. The difference from the first embodiment is only step S5a, and the other procedures and the configuration of the engine are the same as those of the first embodiment.
[0031]
In step S5a of the second embodiment, the first condition that the value of the load ratio LR is smaller than the first determination value α and the second condition that the value of the compression ratio CR is larger than the second determination value β. It is determined whether the conditions are simultaneously satisfied. When both of these conditions are satisfied, there is a high possibility that combustion will deteriorate due to an increase in the wet amount at the top of the piston, so the opening of the airflow control valve 61 is set small (step S7). On the other hand, when one of the two conditions is not satisfied, the opening of the airflow control valve 61 is set to a large value. The reason is that when the compression ratio is high and the load ratio is low, the wet amount at the top of the piston tends to increase. Further, when the wet amount is not excessively large, setting the opening degree of the airflow control valve 61 as large as possible can reduce the pump loss and improve the fuel efficiency.
[0032]
Appropriate values of the determination values α and β change according to the intake air temperature, the cooling water temperature of the cylinder, the engine speed, and the like. Therefore, the values of the determination values α and β are preferably changed according to these parameters.
[0033]
As described above, in the first and second embodiments, the turbulence of the intake air flow is increased when the compression ratio CR is high. Therefore, the increase in the wet amount at the top of the piston due to the increase in the compression ratio is moderated. It is possible to prevent deterioration of combustion.
[0034]
C. Third embodiment:
FIG. 4 is a conceptual diagram illustrating a configuration of an internal combustion engine 10a according to a third embodiment of the present invention. This internal combustion engine 10a has a configuration in which a variable valve lift mechanism 71, a spool valve 72, and a hydraulic pump 73 are provided instead of the airflow control valve 61 of FIG. Further, the ECU 30a includes a valve lift control circuit 70 instead of the airflow control valve control circuit 32. Other configurations are the same as those of the first embodiment.
[0035]
The valve lift control circuit 70 can change the lift amount of the intake valve 41 set by the variable valve lift mechanism 71 by switching the spool valve 72. Since such mechanisms 71 and 72 are well known, detailed description will be omitted.
[0036]
FIG. 5 is a flowchart showing a control procedure of the engine in the third embodiment. The only difference from the first embodiment is steps S6a and S7a. That is, in the third embodiment, when the load is low and the compression ratio is high, the lift amount of the intake valve 41 is reduced to increase the turbulence of the intake flow, thereby preventing the wet amount at the top of the piston from increasing. (Step S7a). That is, when the lift amount of the intake valve 41 is reduced, the gap between the intake port of the cylinder head and the intake valve 41 is reduced, so that the turbulence of the intake flow in the combustion chamber increases. When the lift amount of the intake valve 41 is reduced, the flow path resistance of the intake pipe increases. Therefore, the opening of the throttle valve is increased in step S8. Note that step S5 in FIG. 5 can be replaced with step S5a in FIG.
[0037]
In this way, by reducing the lift amount of the intake valve 41, the turbulence of the intake air flow can be increased, and an increase in the wet amount at the top of the piston can be prevented.
[0038]
D. Fourth embodiment:
FIG. 6 is a conceptual diagram illustrating a configuration of an internal combustion engine 10b according to a fourth embodiment of the present invention. The internal combustion engine 10b has a configuration in which a variable valve timing mechanism 81, a spool valve 82, and a hydraulic pump 83 are provided instead of the components 71 to 73 for adjusting the valve lift in FIG. Further, the ECU 30b includes a valve timing control circuit 80 instead of the valve lift control circuit 70. Other configurations are the same as those of the above-described second embodiment.
[0039]
The valve timing control circuit 80 can change the valve opening timing of the intake valve 41 set by the variable valve timing mechanism 81 by switching the spool valve 82. Since such mechanisms 81 and 82 are well known, detailed description will be omitted.
[0040]
FIG. 7 is a flowchart illustrating an engine control procedure according to the fourth embodiment. The only difference from the third embodiment shown in FIG. 5 is steps S6b and S7b. That is, in the fourth embodiment, the first valve timing control map M1 is used when the load is low and the compression ratio is low (step S6b), and the second valve timing control map M2 is used when the load is low and the compression ratio is high. (Step S7b). These maps M1 and M2 are maps for determining the timing of opening the intake valve 41 in accordance with the engine speed, the throttle opening, the intake air amount, the cooling water temperature of the cylinder, and the like. In the second valve timing control map M2 used at a low load and a high compression ratio, the opening period of the intake valve 41 is delayed compared to the first map M1.
[0041]
FIG. 8 is an explanatory diagram showing an example of the valve timing retarding in the fourth embodiment. In this example, when the load factor LR is greater than the determination value α, the valve opening has started before the top dead center TDC of the piston. The whole is retarded. Specifically, at the retarded valve opening timing, the intake valve 41 opens later than the top dead center TDC of the piston. If the intake valve 41 is opened later than the top dead center TDC, fresh air is introduced after a negative pressure is generated in the combustion chamber, so that the turbulence of the intake flow in the combustion chamber becomes larger. There is. If the valve closing timing is later than the bottom dead center BDC, as in the example of FIG. ) Is more preferable because the turbulence of the intake air flow in the combustion chamber is further increased.
[0042]
Thus, by delaying the opening period of the intake valve 41, the turbulence of the intake air flow can be increased to prevent the wet amount at the top of the piston from increasing.
[0043]
Note that the opening degree adjustment of the airflow control valve 61 used in the first embodiment, the lift amount adjustment of the intake valve 41 used in the third embodiment, and the valve opening period adjustment of the intake valve 41 used in the fourth embodiment. It is also possible to employ a combination of some of the above.
[0044]
E. FIG. Modification:
The present invention is not limited to the above-described examples and embodiments, but can be implemented in various modes without departing from the gist of the invention, and for example, the following modifications are possible.
[0045]
E1. Modification 1
In the first embodiment, the turbulence of the intake air flow is adjusted by using the air flow control valve 61. However, another mechanism that changes the flow path resistance of the intake pipe may be used instead. Yes, for example, a variable orifice can be used.
[0046]
Further, the mechanisms 71 to 73 for adjusting the lift amount of the intake valve 41 and the mechanisms 81 to 83 for adjusting the valve opening timing are merely examples, and other various configurations can be adopted. For example, as the intake valve 41, a motor-operated valve that can arbitrarily adjust the lift amount and the valve opening timing can be used.
[0047]
As can be understood from these descriptions, the present invention only needs to include airflow changing means capable of changing the turbulence state of the intake air flow to the combustion chamber in accordance with the index value indicating the compression ratio. As the index value indicating the compression ratio, various parameters such as the compression ratio itself and the load ratio can be used.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing a configuration of an internal combustion engine 10 according to a first embodiment.
FIG. 2 is a flowchart showing an engine control procedure in the first embodiment.
FIG. 3 is a flowchart illustrating an engine control procedure according to a second embodiment.
FIG. 4 is a conceptual diagram showing a configuration of an internal combustion engine 10a according to a third embodiment.
FIG. 5 is a flowchart illustrating an engine control procedure according to a third embodiment.
FIG. 6 is a conceptual diagram showing a configuration of an internal combustion engine 10b according to a fourth embodiment.
FIG. 7 is a flowchart illustrating an engine control procedure according to a fourth embodiment.
FIG. 8 is an explanatory diagram showing an example of retarding valve timing in a fourth embodiment.
[Explanation of symbols]
Reference Signs List 10 internal combustion engine 11 crank 20 cylinder 21 piston 22 cylinder head 23 connecting rod 24 piston pin 25 connecting pin 26 control rod 27 control shaft 28 control disk 29 central shaft 30 ECU
31 Variable compression ratio control circuit 32 Air flow control valve control circuit 33 Rotational position sensor 34 Drive unit 41 Intake valve 42 Exhaust valve 51 Spark plug 61 Air flow control valve 70 Valve lift control circuit 71 Variable valve Lift mechanism 72 Spool valve 73 Hydraulic pump 80 Valve timing control circuit 81 Variable valve timing mechanism 82 Spool valve 83 Hydraulic pump 100 Intake pipes 101 and 102 Branch pipes 111 and 112 Intake ports 121 and 122 Exhaust ports 231 and 233 Connecting rod member 232 Connection pin

Claims (9)

An internal combustion engine,
A cylinder and a piston constituting a combustion chamber;
A variable compression ratio mechanism capable of changing the compression ratio of the combustion chamber,
Air flow changing means capable of changing a turbulence state of the intake air flow to the combustion chamber according to the index value indicating the compression ratio,
An internal combustion engine comprising: The internal combustion engine according to claim 1,
The internal combustion engine, wherein the airflow changing means increases turbulence of an intake air flow to the combustion chamber when a compression ratio is larger than a first determination value. The internal combustion engine according to claim 1,
The airflow changing means increases the turbulence of the intake air to the combustion chamber when the compression ratio is larger than a first judgment value and the load factor of the internal combustion engine is smaller than a second judgment value. , Internal combustion engine. The internal combustion engine according to any one of claims 1 to 3, wherein
The internal combustion engine includes an airflow control mechanism provided in an intake pipe that guides intake air to the combustion chamber and that can change a flow path resistance of the intake pipe. The internal combustion engine according to claim 4, wherein
The internal combustion engine, wherein the airflow control mechanism includes an adjustment valve whose opening is adjustable. The internal combustion engine according to claim 5, wherein
The combustion chamber has two intake ports, and an intake pipe that guides intake air to the combustion chamber includes two branch pipes connected to the two intake ports,
The internal combustion engine, wherein the regulating valve is provided in only one of the two branch pipes. The internal combustion engine according to any one of claims 1 to 3, wherein
The internal combustion engine, wherein the airflow changing means includes an intake valve control mechanism capable of changing at least one of a lift amount of an intake valve of the combustion chamber and a timing of a valve opening period. The internal combustion engine according to claim 7, wherein
The internal combustion engine, wherein the intake valve control mechanism increases turbulence of an intake flow to the combustion chamber by reducing a lift amount of the intake valve. The internal combustion engine according to claim 7, wherein
The internal combustion engine, wherein the intake valve control mechanism increases turbulence of an intake flow to the combustion chamber by delaying a timing of an opening period of the intake valve.

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