Control device for internal combustion engines

Abstract

To contribute to further reducing mechanical loss in an internal combustion engine comprising a plurality of suction valves for each cylinder.SOLUTION: An internal combustion engine is configured such that a plurality of suction valves is provided in one cylinder, and a maximum lift amount of one suction valve or timing at which the maximum lift amount is taken is made different from a maximum lift amount of another suction valve or timing at which the maximum lift amount is taken. Then, the internal combustion engine is configured such that a spring constant of a spring that elastically biases a valve body of the one suction valve in a closing direction and a spring constant of a spring that elastically biases the valve body of the other suction valve in the closing direction are set to different values.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an internal combustion engine mounted on a vehicle or the like as a power source.

Background Art

[0002] As a four-stroke reciprocating engine, a so-called multi-valve engine in which a plurality of intake ports and intake valves are provided for each cylinder is known (for example, refer to the following patent document).

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As an approach for further improving the output and fuel consumption performance of an internal combustion engine, reduction of mechanical losses associated with opening and closing driving of intake and exhaust valves of a cylinder can be mentioned. In a general multi-valve engine, a plurality of valves mounted on one cylinder are simultaneously pressed by the same number of cam lobes to open these valves. For this reason, the sum of the reaction forces received by the camshaft from the valve springs that elastically bias the valve bodies of each valve in the closing direction increases, and the friction between the tappet (or valve lifter) and the cam lobe also increases.

[0005] Reducing the valve lift (valve opening amount) or the spring constant of the valve spring can decrease the reaction force on the camshaft and reduce friction between the tappet and the cam lobe. However, reducing the valve lift reduces the amount of intake air flowing into the cylinder, and also weakens the in-cylinder flow, especially the tumble flow which is important for mixing air and fuel well, thus negatively impacting the output, fuel efficiency, and emissions of the internal combustion engine. Furthermore, simply reducing the spring constant of the valve spring can lead to another problem: increased susceptibility to resonance.

[0006] The present invention aims to contribute to further reduction of mechanical losses in an internal combustion engine equipped with multiple intake valves for each cylinder. [Means for solving the problem]

[0007] In this invention, one cylinder Multiple intake ports and Multiple intake valves are provided, Furthermore, injectors are installed individually in each of the multiple intake ports, and among the multiple intake valves The timing at which one intake valve reaches its maximum lift amount or maximum lift amount is different from the timing at which the other intake valve reaches its maximum lift amount or maximum lift amount. In addition, the amount of fuel injected from the injector facing the intake port opened and closed by one of the intake valves is made different from the amount of fuel injected from the injector facing the intake port opened and closed by the other intake valve. It constituted an internal combustion engine.

[0008] More preferably, the maximum lift amount of the other intake valve is made smaller than the maximum lift amount of the one intake valve, and the timing at which the other intake valve reaches its maximum lift amount is delayed compared to the timing at which the one intake valve reaches its maximum lift amount. The spring constant of the spring that elastically biases the valve body of the one intake valve in the closing direction and the spring constant of the spring that elastically biases the valve body of the other intake valve in the closing direction may be set to different values. In that case, it is conceivable to set the spring constant of the spring that biases the valve body of the other intake valve to be smaller than the spring constant of the spring that biases the valve body of the first intake valve. [Effects of the Invention]

[0009] According to the present invention, it may be possible to further reduce mechanical losses in an internal combustion engine equipped with multiple intake valves for each cylinder. [Brief explanation of the drawing]

[0010] [Figure 1] A diagram showing a schematic configuration of an internal combustion engine and control device for a vehicle in one embodiment of the present invention. [Figure 2] A perspective view showing the intake valve and intake camshaft of the internal combustion engine of the same embodiment. [Figure 3] A timing diagram illustrating the relationship between the lift amount of one intake valve and that of the other intake valve of a plurality of intake valves in one cylinder of an internal combustion engine of the same embodiment. [Figure 4] A timing diagram illustrating the relationship between the lift amount of one intake valve and that of the other intake valve of a plurality of intake valves in one cylinder of an internal combustion engine of the same embodiment. [Figure 5] A timing diagram illustrating the relationship between the lift amount of one intake valve and that of the other intake valve of a plurality of intake valves in one cylinder of an internal combustion engine of the same embodiment. [Modes for carrying out the invention]

[0011] One embodiment of the present invention will be described with reference to the drawings. Figure 1 shows an overview of the vehicle internal combustion engine in this embodiment. The internal combustion engine in this embodiment is a port injection type 4-stroke spark ignition reciprocating engine and comprises a plurality of cylinders 1 (for example, three cylinders; one of which is shown in Figure 1). Near the intake port of each cylinder 1, an injector 11 is provided for each cylinder 1 to inject fuel toward the intake port. In addition, a spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 generates a spark discharge between its center electrode and ground electrode upon application of an induced voltage generated by the ignition coil. The ignition coil, together with an igniter which is a semiconductor switching element, is integrally built into the coil case.

[0012] The intake passage 3, which supplies intake air, takes in air from the outside and guides it to the intake port of each cylinder 1. The air cleaner 31, the electronic throttle valve 32 which is an intake throttling valve, the surge tank 33, and the intake manifold 34 are arranged on the intake passage 3 in this order from upstream.

[0013] The exhaust passage 4, which discharges exhaust gases, guides the exhaust gases generated as a result of fuel combustion in each cylinder 1 to the outside through the exhaust port of each cylinder 1. An exhaust manifold 42 and a three-way catalytic converter 41 for exhaust gas purification are positioned on this exhaust passage 4.

[0014] The exhaust gas recirculation (EGR) device 2 comprises an external EGR passage 21 connecting the exhaust passage 4 and the intake passage 3, an EGR cooler 22 installed on the EGR passage 21, and an EGR valve 23 that opens and closes the EGR passage 21 and controls the flow rate of EGR gas flowing through the EGR passage 21. The inlet of the EGR passage 21 is connected to a predetermined location downstream of the catalyst 41 in the exhaust passage 4. The outlet of the EGR passage 21 is connected to a predetermined location downstream of the throttle valve 32 in the intake passage 3 (in particular, the surge tank 33 or the intake manifold 34).

[0015] In this embodiment, the Electronic Control Unit (ECU) 0 responsible for controlling the operation of the internal combustion engine is a microcomputer system having a processor, memory, input interface, output interface, etc. The ECU 0 may consist of multiple ECUs or controllers connected to each other via a telecommunication line such as CAN (Controller Area Network).

[0016] The input interface of the ECU0 receives signals such as a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed, a crank angle signal b output from a crank angle sensor that detects the rotation angle of the internal combustion engine's crankshaft and engine speed, an accelerator opening signal c output from a sensor that detects the amount the driver presses the accelerator pedal (accelerator opening, in other words, the required engine torque or engine load rate), an intake air temperature / intake pressure signal d output from a temperature / pressure sensor that detects the intake air temperature and intake pressure in the intake passage 3 connected to cylinder 1 (downstream of the throttle valve 32, particularly the surge tank 33 or intake manifold 34), a coolant temperature signal e output from a coolant temperature sensor that detects the coolant temperature of the internal combustion engine, an acceleration signal f output from an acceleration sensor that detects the vehicle's acceleration or the gradient of the road surface where the vehicle is currently located, a cam angle signal g output from a cam angle sensor at multiple cam angles of the intake camshaft 13 of the internal combustion engine, and signals h output from switches and selector levers (and their associated position sensors) operated by the driver.

[0017] The output interface of the ECU0 outputs an ignition signal i to the igniter associated with the spark plug 12, a fuel injection signal j to the injector 11, an opening operation signal k to the throttle valve 32, an opening operation signal l to the EGR valve 23, and so on.

[0018] The processor of ECU0 interprets and executes the program stored in the memory, calculates the operating parameters, and controls the operation of the internal combustion engine. ECU0 acquires various information a, b, c, d, e, f, g, h necessary for control through the input interface, obtains the engine speed, and estimates the amount of air (fresh air) inhaled into cylinder 1. Then, it determines various operating parameters such as the required fuel injection amount (such that the target air-fuel ratio at the stoichiometric air-fuel ratio or in its vicinity can be achieved) corresponding to the inhaled air amount, the fuel injection timing (including the number of fuel injections for one combustion), the fuel injection pressure, the ignition timing (including the number of ignitions for one combustion), the required EGR rate (or the EGR gas amount, EGR gas partial pressure), etc. ECU0 applies various control signals i, j, k, l corresponding to the operating parameters through the output interface.

[0019] As shown in FIG. 2, the internal combustion engine of the present embodiment includes a plurality of intake ports and intake valves 14 for each cylinder 1. The poppet valve bodies 141, 142 that open and close each intake port are elastically biased in the closing direction, that is, in the direction of seating on the valve seat, by valve springs 143, 144, respectively. The camshaft 13 that drives the intake valve 14 to open and close has as many cam lobes 131, 132 as the intake valve 14 for each cylinder 1 protruding therefrom. When each cam lobe 131, 132 contacts the valve tappet and presses it, the valve bodies 141, 142 of the intake valve 14 are pushed down against the elastic biasing force of the springs 143, 144, and the valve bodies 141, 142 separate from the valve seat, that is, the intake valve 14 opens.

[0020] In the present embodiment, the profiles of the first cam lobe 131 and the second cam lobe 131 that drive the valve bodies 141, 142 of the plurality of intake valves 14 of one cylinder 1 are made different. In other words, when viewed from the axial direction of the camshaft 13 (the direction parallel to the direction in which the central axis of the camshaft 13 extends), the first cam lobe 131 and the second cam lobe 132 do not completely overlap.

[0021] In the example shown in Figure 3, by shifting the central angle of the first cam lobe 131 that drives the first valve body 141 and the central angle of the second cam lobe 132 that drives the second valve body 142 along the rotational direction of the camshaft 13, the timing at which the lift amount of the second valve body 142 (shown by the dashed line) is maximized is delayed by up to 5° CA in terms of crank angle from the timing at which the lift amount of the first valve body 141 (shown by the solid line) is maximized. As a result, the maximum value of the reaction force acting on the camshaft 13 that tries to open both valve bodies 141 and 142 of the intake valve 14 is reduced. Furthermore, by setting the spring constant of the spring 144 that biases the second valve body 142 to be smaller than the spring constant of the spring 143 that biases the first valve body 141, friction between the valve tappet and the cam lobe 132 can be reduced while suppressing the occurrence of resonance.

[0022] In the example shown in Figure 4, the second cam lobe 132 that drives the second valve body 142 is set lower than the first cam lobe 131 that drives the first valve body 141, making the maximum lift amount of the second valve body 142 (shown by the dashed line) smaller than the maximum lift amount of the first valve body 141 (shown by the solid line). The difference between the two is set to 2 mm or less. This reduces the maximum value of the reaction force acting on the camshaft 13 that tries to open both valve bodies 141 and 142 of the intake valve 14. Furthermore, by setting the spring constant of the spring 144 that biases the second valve body 142 to be smaller than the spring constant of the spring 143 that biases the first valve body 141, friction between the valve tappet and the cam lobe 132 can be reduced while suppressing the occurrence of resonance.

[0023] The example shown in Figure 5 is a combination of the examples shown in Figure 3 and Figure 4. As expected, the maximum value of the reaction force acting on the camshaft 13 to push open both valve bodies 141 and 142 of the intake valve 14 is reduced. Furthermore, by setting the spring constant of the spring 144 that biases the second valve body 142 to be smaller than the spring constant of the spring 143 that biases the first valve body 141, it is possible to reduce friction between the valve tappet and the cam lobe 132 while suppressing the occurrence of resonance.

[0024] Furthermore, if injectors 11 are individually installed in multiple intake ports connected to a single cylinder 1, it is also conceivable to reduce the amount of fuel injected from the injector 11 facing the intake port that the second valve body 142 opens and closes, compared to the amount of fuel injected from the injector 11 facing the intake port that the first valve body 141 opens and closes.

[0025] According to this embodiment, it is possible to ensure a sufficient amount of intake air flowing into cylinder 1, effectively generate in-cylinder flow, particularly tumble flow, and further reduce mechanical losses associated with opening and closing the intake valve 14.

[0026] The present invention is not limited to the embodiments described in detail above. The specific configuration of each part can be modified in various ways without departing from the spirit of the present invention. [Explanation of symbols]

[0027] 0...Control Unit (ECU) 1…Cylinder 13…Intake camshaft 131, 132... Cam lobes 14… Valve 141, 142... valve body 143, 144… Valve springs

Claims

[Claim 1] A single cylinder is provided with multiple intake ports and multiple intake valves, and an injector is installed individually in each of these multiple intake ports. The timing at which one of the plurality of intake valves achieves its maximum lift amount or maximum lift amount is different from the timing at which the other intake valve achieves its maximum lift amount, The amount of fuel injected from the injector facing the intake port opened and closed by one of the intake valves is different from the amount of fuel injected from the injector facing the intake port opened and closed by the other intake valve. The maximum lift amount of the other intake valve is made smaller than the maximum lift amount of the one intake valve, and the timing at which the other intake valve reaches its maximum lift amount is delayed compared to the timing at which the one intake valve reaches its maximum lift amount. An internal combustion engine in which the spring constant of the spring that biases the valve body of the other intake valve is set to be smaller than the spring constant of the spring that biases the valve body of the first intake valve.

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