JP5553049B2 - Valve operating device for internal combustion engine - Google Patents

Description

  The present invention relates to a valve operating apparatus for an internal combustion engine provided with a variable valve operating mechanism capable of changing the opening / closing timing of an intake valve.

  2. Description of the Related Art A variable valve mechanism that changes the opening / closing timing of intake and exhaust valves provided in an internal combustion engine is known. The variable valve mechanism changes the opening / closing timing of the intake valve or the exhaust valve by changing the rotational phase of the camshaft with respect to the crankshaft. Patent Document 1 discloses an apparatus having such a variable valve mechanism that independently controls a plurality of intake valves provided in one cylinder.

  In the valve operating device disclosed in Patent Document 1, the opening / closing timing of a plurality of intake valves is controlled independently, and the opening / closing timing of each intake valve is controlled by changing the phase of a cam provided for each intake valve. doing.

JP 2009-144521 A

  By the way, as the intake and exhaust valves are driven to open, cam torque acts on the camshaft. In the variable valve mechanism, this cam torque acts in a direction that hinders the advance of the cam phase, so the phase change speed at the advance angle decreases, and it takes time to change the phase at the advance angle. On the other hand, the cam torque accompanying the opening operation of the intake / exhaust valve does not disturb the retardation of the cam phase. For this reason, the phase change speed at the time of retardation is not lowered. Therefore, due to the variable valve mechanism, the cam phase change speed differs depending on whether the cam related to the operation of the intake valve is advanced or retarded. For this reason, when changing the phase of the cam, if the difference in cam change speed between when the angle is advanced and when the angle is retarded is not taken into May cause a delay in the closing timing of the intake valve. If such a delay in the closing timing of the intake valve extends until after the bottom dead center of the intake stroke, intake air taken into the cylinder may escape more than necessary, and as a result, the actual compression ratio of the internal combustion engine It may cause a decline and misfire.

  Therefore, in view of the above problems, the present invention provides a valve operating apparatus for an internal combustion engine that suppresses misfire due to a delay in the closing timing of the intake valve.

A valve operating apparatus for an internal combustion engine according to the present invention that solves this problem includes a first intake port and a second intake port that are formed so as to generate different airflows in a cylinder, and a first intake port that opens and closes the first intake port. An opening / closing timing of the first intake valve, the cam shaft having a first cam for opening / closing the intake valve and a second cam for opening / closing the second intake valve for opening / closing the second intake port; And a variable valve section that independently changes the opening and closing timing of the second intake valve, and the variable valve section is configured to operate when the internal combustion engine is operated at a high load. One intake valve is opened before the second intake valve, and when the internal combustion engine is operated at a low load, the second intake valve is opened before the first intake valve. The internal combustion engine is operated at the high load and the low If in a condition to be operated in load interchanged closing sequence of the second intake valve and the first intake valve, the variable valve unit, to switch the opening and closing sequence of the first intake valve and the second intake valve, The first intake valve and the second intake valve are closed at a time when misfire caused by delay in the valve closing timing can be avoided. With this configuration, it is possible to prevent a decrease in the actual compression ratio and to suppress misfire by suppressing a decrease in the in-cylinder air due to the blow-back of the intake air taken into the cylinder.

In the valve operating apparatus for an internal combustion engine, it is the timing which can avoid misfire may be determined based on the rotation speed and the load of the internal combustion engine. The fuel injection amount is changed depending on the rotation speed and load of the internal combustion engine, and the possibility of misfiring also changes. Therefore, the rotation speed and load of the internal combustion engine can be used as determinants of the control target value.

In the valve operating apparatus for an internal combustion engine, the first intake port is a port to generate a strong swirl flow in the combustion chamber, the second intake port is configured as a port to produce a weak swirl flow in the combustion chamber be able to. With this configuration, when the internal combustion engine is operated at a high load, mixing of air and fuel can be promoted and smoke can be reduced. Further, when the internal combustion engine is operated at a low load, generation of HC and CO can be suppressed.

  In the valve operating apparatus for an internal combustion engine, the variable valve operating unit may set the time with a target of an actual compression ratio when misfire can be avoided.

  By providing a control target value for the closing timing of the intake valve, the present invention suppresses a decrease in the in-cylinder air due to the blow back of the intake air taken into the cylinder, and prevents a misfire due to a delay in the closing timing of the intake valve. Can be suppressed.

It is a schematic block diagram of the internal combustion engine in which the valve gear was incorporated. It is a schematic block diagram of a combustion chamber, a 1st intake port, and a 2nd intake port, (a) is a perspective view, (b) is a top view. It is a schematic block diagram of a variable valve mechanism, (a) is a perspective view showing a variable valve mechanism, a first intake valve and a second intake valve, (b) shows the structure of the variable valve mechanism. It is a schematic diagram. It is explanatory drawing which showed the valve lift amount with respect to the crank angle about a 1st intake valve and a 2nd intake valve, Comprising: (a) shows the case where the 1st intake valve is advanced, (b), The case where the second intake valve is advanced is shown. It is explanatory drawing which showed the relationship between the swirl ratio of an internal combustion engine when changing the opening / closing timing of an intake valve, and an actual compression ratio. It is explanatory drawing which showed the intensity | strength of the optimal swirl flow in a combustion chamber corresponding to the load and rotation speed of an internal combustion engine. It is explanatory drawing which showed the intake valve closing time map which calculates an intake valve closing time.

  Hereinafter, an embodiment for carrying out the present invention will be described in detail with reference to the drawings.

  The structure of the valve gear 2 of the internal combustion engine 1 in the Example of this invention is demonstrated. FIG. 1 is a schematic configuration diagram of an internal combustion engine 1 in which a valve gear 2 is incorporated. The internal combustion engine 1 is a compression ignition type internal combustion engine (diesel engine). The valve gear 2 includes a variable valve mechanism 3 and an ECU (Electronic Control Unit) 4 that performs various controls of the internal combustion engine 1. The variable valve mechanism 3 and the ECU 4 function as a variable valve unit.

  The internal combustion engine 1 includes a cylinder block 11, a cylinder head 12, a piston 13, a first intake valve 14a, a second intake valve 14b, two exhaust valves 15a and 15b, and a fuel injection valve 16. . A cylinder 11 a is formed in the cylinder block 11. A piston 13 is accommodated in the cylinder 11a. A cylinder head 12 is fixed to the upper surface of the cylinder block 11. A space surrounded by the cylinder block 11, the cylinder head 12 and the piston 13 is formed as a combustion chamber 10. Further, the cylinder head 12 is provided with a fuel injection valve 16 having an injection hole directed to the combustion chamber 10.

  The cylinder head 12 is formed with a first intake port 121a, a second intake port 121b, and two exhaust ports 122a and 122b. The first intake port 121 a and the second intake port 121 b guide intake air to the combustion chamber 10, and the exhaust ports 122 a and 122 b exhaust exhaust gas from the combustion chamber 10. The first intake valve 14a is provided in the first intake port 121a. The first intake valve 14a opens and closes the first intake port 121a. The second intake valve 14b is provided in the second intake port 121b. The second intake valve 14b opens and closes the second intake port 121b. The exhaust valves 15a and 15b are provided in the exhaust ports 122a and 122b, respectively. The exhaust valves 15a and 15b open and close the exhaust ports 122a and 122b.

Next, the first intake port 121a and the second intake port 121b will be described. FIG. 2 is a schematic configuration diagram of the combustion chamber 10, the first intake port 121a, and the second intake port 121b. 2A is a perspective view of the combustion chamber 10, the first intake port 121a, and the second intake port 121b. FIG. 2B is a plan view of the combustion chamber 10, the first intake port 121a, and the second intake port 121b. FIG. The first intake port 121a and the second intake port 121b are formed so as to generate different airflows in the cylinder. The first intake port 121 a is formed in a shape that guides intake air along the cylinder wall surface of the combustion chamber 10. A tangential port is an example of a shape that guides intake air along the cylinder wall surface of the combustion chamber 10. First intake port 121a is for guiding the intake air along the cylinder wall, to generate a strong swirl flow f ₁ in the combustion chamber 10. As the flow rate flowing through the first intake port 121a increases, the strength of the swirl flow generated in the combustion chamber 10 increases. The second intake port 121b is formed in a spiral shape. An example of a spiral intake port is a helical port. The second intake port 121 _b guides a weak swirl flow f ₂ to the center of the combustion chamber 10. The intake air supplied from the second intake port 121b stays at the center in the combustion chamber 10, and diffusion is suppressed. In the present embodiment, the first intake port 121a functions as a mainstream port, and the second intake port 121b functions as a subordinate port.

  Next, the variable valve mechanism 3 will be described. The variable valve mechanism 3 is a mechanism for controlling the opening / closing operation of the first intake valve 14a and the second intake valve 14b. FIG. 3 is a schematic configuration diagram of the variable valve mechanism 3. 3A is a perspective view showing the variable valve mechanism 3, the first intake valve 14a and the second intake valve 14b, and FIG. 3B is a schematic view showing the structure of the variable valve mechanism 3. As shown in FIG. is there.

  The variable valve mechanism 3 includes a cam shaft 31, a first cam 32, a second cam 33, and a phase change mechanism 34. As shown in FIG. 3B, the camshaft 31 is a double-structured shaft, and includes an external camshaft 31a having the same rotation center line and an internal camshaft 31b. The external camshaft 31a has a hollow structure, and an internal camshaft 31b is inserted into the external camshaft 31a so as to be relatively rotatable. The first cam 32 is provided on the external camshaft 31a. The first cam 32 is provided in correspondence with the first intake valve 14a, and opens and closes the first intake valve 14a. The second cam 33 is provided to be slidable in the circumferential direction on the external cam shaft 31a. The second cam 33 is coupled to the internal camshaft 31b. The second cam 33 is coupled to the internal camshaft 31b and the coupling pin 33a through a long hole provided in the outer camshaft 31a along the circumferential direction. The second cam 33 is provided corresponding to the second intake valve 14b, and opens and closes the second intake valve 14b.

  The phase changing mechanism 34 changes the phases of the external camshaft 31a and the internal camshaft 31b with respect to the phase of the crankshaft (not shown). The phase changing mechanism 34 changes the phase of the internal camshaft 31b with respect to the external camshaft 31a. That is, the phase changing mechanism 34 can advance and retard the opening / closing timing of the first intake valve 14a, and can advance and retard the opening / closing timing of the second intake valve 14b. As a result, the opening / closing timing of the first intake valve 14a and the opening / closing timing of the second intake valve 14b are independently changed.

  FIG. 4 is an explanatory diagram showing the valve lift amount with respect to the crank angle for the first intake valve 14a and the second intake valve 14b. FIG. 4A shows a case where the first intake valve 14a is advanced, and FIG. 4B shows a case where the second intake valve 14b is advanced. The vertical axis in FIG. 4 indicates the valve lift amount, and the horizontal axis indicates the crank angle. The crank angle is 0 (° ATDC) at the top dead center of the intake stroke. Further, the solid line in FIG. 4 indicates the valve lift amount of the first intake valve 14a, and the broken line indicates the valve lift amount of the second intake valve 14b. As shown in FIG. 4, the variable valve mechanism 3 can advance the first intake valve 14a and advance the second intake valve 14b. Similarly, the first intake valve 14a can be retarded and the second intake valve 14b can be retarded. Further, both the first intake valve 14a and the second intake valve 14b can be advanced or retarded simultaneously.

  The ECU 4 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and a well-known digital computer in which input / output ports are connected by a bidirectional bus, for controlling the internal combustion engine 1. The internal combustion engine 1 is controlled by exchanging signals with various sensors and actuators provided in the engine. In particular, in this embodiment, the ECU 4 is electrically connected to the phase change mechanism 34 and controls the phase change mechanism 34 based on the operating state of the internal combustion engine 1 obtained from various sensors. That is, the opening / closing operation and the opening / closing timing of the first intake valve 14a and the second intake valve 14b by the variable valve mechanism 3 are controlled by the ECU 4.

  As described above, when the first intake valve 14a and the second intake valve 14b are opened by the opening / closing control of the first intake valve 14a and the second intake valve 14b, the first intake port 121a and the second intake port 121b are connected. Thus, intake air is supplied into the combustion chamber 10.

Next, features of control related to the opening / closing operation of the intake valve in the present embodiment will be described. First, the swirl flow in the combustion chamber 10 will be described. FIG. 6 is an explanatory diagram showing the optimal swirl flow strength in the combustion chamber 10 corresponding to the load and the rotational speed of the internal combustion engine 1. The vertical axis in FIG. 6 indicates the load of the internal combustion engine 1, and the horizontal axis indicates the rotational speed of the crankshaft. As shown in FIG. 6 , when the load of the internal combustion engine 1 is low, it is required to reduce the strength of the swirl flow to suppress spray diffusion and suppress HC and CO. On the contrary, when the load of the internal combustion engine 1 is high, it is required to increase the strength of the swirl flow to promote the mixing of the fuel spray and the air, perform uniform combustion, and suppress the smoke.

By the way, the airflow formed in the combustion chamber 10 by the intake air is governed by the airflow from the port side opened earlier. Therefore, when the first intake valve 14a is opened before the second intake valve 14b is by a gas stream supplied from the first intake port 121a, a strong swirl flow f ₁ in the combustion chamber 10 is formed Is done. Conversely, when the second intake valve 14b is opened before the first intake valve 14a is the air flow supplied from the second intake port 121b, a weak swirl flow f ₂ is the combustion chamber 10 is formed Is done. Therefore, the valve gear 2 controls the opening / closing timing of the first intake valve 14a and the second intake valve 14b according to the characteristics of the air flow required in the combustion chamber 10.

FIG. 5 is an explanatory diagram showing the relationship between the swirl ratio of the internal combustion engine 1 and the actual compression ratio when the opening / closing timing of the intake valve is changed. The vertical axis in FIG. 5 indicates the swirl ratio, and the horizontal axis indicates the actual compression ratio. The relationship between the swirl ratio and the actual compression ratio advances in the direction of arrow A shown in FIG. 5 as the intake air supplied from the first intake port 121a dominates the air flow in the combustion chamber 10. That is, as the opening / closing timing of the first intake valve 14a advances from the opening / closing timing of the second intake valve 14b, the swirl flow is strengthened and the actual compression ratio decreases. On the contrary, the relationship between the swirl ratio and the actual compression ratio advances in the direction indicated by the arrow B shown in FIG. 5 as the intake air supplied from the second intake port 121b dominates the airflow in the combustion chamber 10. That is, as the opening / closing timing of the second intake valve 14b is advanced from the opening / closing timing of the first intake valve 14a, the generation of the swirl flow is suppressed.

  Therefore, from the relationship of FIG. 5 described above, the valve gear 2 advances the opening / closing timing of the first intake valve 14a from the opening / closing timing of the second intake valve 14b as the operating state of the internal combustion engine 1 becomes higher load. Strengthen the swirl style. On the contrary, the valve operating apparatus 2 advances the opening / closing timing of the second intake valve 14b from the opening / closing timing of the first intake valve 14a and suppresses the generation of the swirl flow as the operating state of the internal combustion engine 1 becomes lighter. .

  When the internal combustion engine 1 is operated, the operating state of the internal combustion engine 1 always fluctuates. That is, the operating state of the internal combustion engine 1 includes a case where the engine is operated at a low load and a case where the engine is operated at a high load. Therefore, in order to appropriately control the air flow in the combustion chamber 10, the valve gear 2 needs to perform a process of switching the opening / closing order of the first intake valve 14a and the second intake valve 14b (partial region). As described above, the process of switching the opening / closing order of the first intake valve 14a and the second intake valve 14b is realized by the operation of switching the phases of the first cam 32 and the second cam 33. However, when the phases of the two cams are switched, the cam that changes the phase in the advance direction receives a reaction force from the intake valve, and the phase change speed is delayed. If the closing timing of the intake valve becomes too late due to this delay, the air sucked into the cylinder blows back to the intake port, so that the amount of air in the combustion chamber 10 decreases and causes misfire.

  In response to this phenomenon, the valve gear 2 closes the first intake valve 14a and the second intake valve 14b at a time when misfire caused by a delay in the valve closing time can be avoided. More specifically, the valve gear 2 sets the intake valve closing timing (IVC) corresponding to the load and rotation speed of the internal combustion engine 1 as a control target value. This control target value is selected from a period in which misfire caused by delay in the closing timing of the first intake valve 14a or the second intake valve 14b can be avoided. The valve gear 2 closes the retarded intake valve earlier than the set control target value, and prevents the retarded intake valve from opening earlier than the advanced intake valve. The opening / closing timing of the first intake valve 14a and the second intake valve 14b is determined and controlled. Here, the retarded intake valve indicates an intake valve with a later valve lift timing.

  In this embodiment, the control target value of the intake valve closing timing is calculated and set from the intake valve closing timing map shown in FIG. The vertical axis in FIG. 7 indicates the load of the internal combustion engine 1, and the horizontal axis indicates the rotational speed. In the map of FIG. 7, the closer to the origin, the closer to the bottom dead center (BDC), the closer the intake valve closing timing is to the bottom dead center (BDC), and the farther from the origin, the farther from the bottom dead center (BDC). Yes. The intake valve closing timing map is created from experiments and calculations performed in advance. In the valve gear 2, the control target value of the intake valve closing timing may be the latest timing at which misfire caused by the delay of the intake valve closing timing can be avoided.

  The lower the rotation speed of the internal combustion engine 1 is, the smaller the fuel injection amount and the easier the misfire. For this reason, as shown in the intake valve closing timing map, the target value of the intake valve closing timing is brought close to the bottom dead center. Thereby, the reduction | decrease of the intake air in the combustion chamber 10 is suppressed, and the fall of an actual compression ratio is suppressed. As a result, misfire is suppressed and drivability is prevented from deteriorating. On the other hand, at high rotation and high load with low possibility of misfire, the target value of the intake valve closing timing is delayed to reduce pump loss and improve thermal efficiency.

  The valve gear 2 may be controlled to maintain the actual compression ratio of the internal combustion engine 1 at a predetermined value or higher when the opening / closing order of the first intake valve 14a and the second intake valve 14b is switched. The predetermined value in this case is the value of the actual compression ratio when misfire can be avoided. The valve gear 2 sets the intake valve closing timing with the target of the actual compression ratio when the misfire can be avoided under the control of the ECU 4.

  In this embodiment, the operation of the variable valve mechanism provided in the diesel engine is established. Focusing on the fact that the operations of a plurality of intake valves provided for one combustion chamber influence each other, the plurality of intake valves are coordinated and controlled in consideration of their operating states. The valve gear 2 of the internal combustion engine 1 of the present embodiment suppresses a decrease in in-cylinder air due to blow-back of intake air taken into the combustion chamber 10, prevents a decrease in actual compression ratio, and suppresses misfire. it can.

  The above-described embodiments are merely examples for carrying out the present invention, and the present invention is not limited thereto. Various modifications of these embodiments are within the scope of the present invention. It is apparent from the above description that various other embodiments are possible within the scope. For example, the phase changing mechanism 34 is not limited to the configuration described in the embodiment, and the driving method may be any of a hydraulic type, an electric type, and a mechanical type.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Valve operating apparatus 3 Variable valve mechanism (a part of variable valve part)
4 ECU (part of variable valve)
DESCRIPTION OF SYMBOLS 10 Combustion chamber 14a 1st intake valve 14b 2nd intake valve 31 Cam shaft 32 1st cam 33 2nd cam 121a 1st intake port 121b 2nd intake port

Claims (4)

A first intake port and a second intake port formed to generate different airflows in the cylinder;
A cam shaft provided with a first cam for opening / closing the first intake valve for opening / closing the first intake port and a second cam for opening / closing the second intake valve for opening / closing the second intake port; A variable valve operating portion that independently changes the opening / closing timing of the first intake valve and the opening / closing timing of the second intake valve;
With
The variable valve section opens the first intake valve before the second intake valve when the internal combustion engine is operated at a high load, and the internal combustion engine is operated at a low load. A state in which the internal combustion engine is operated at the high load and a state in which the internal combustion engine is operated at the low load, by opening the second intake valve prior to the first intake valve. In order to change the opening and closing order of the first intake valve and the second intake valve,
When the opening and closing order of the first intake valve and the second intake valve is exchanged, the variable valve section is configured to prevent the misfire caused by the delay of the valve closing timing and the first intake valve and the second intake valve. A valve operating apparatus for an internal combustion engine, wherein the valve is closed. Misfire can be avoided for the time, the rotational speed of the internal combustion engine, and a valve operating system for an internal combustion engine according to claim 1 which is determined based on the load. The first intake port is a port that generates a strong swirl flow in the combustion chamber,
Valve operating system for an internal combustion engine according to claim 1 or 2, wherein said second intake port is characterized by a port to produce a weak swirl flow in the combustion chamber.   The valve operating device for an internal combustion engine according to any one of claims 1 to 3, wherein the variable valve operating portion sets the timing with a target of an actual compression ratio when misfire can be avoided.

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